Method for producing high-purity lithium carbonate by recovering lithium from scraps of lithium ion secondary battery, and lithium carbonate produced thereby

Abstract

The present invention relates to a method for producing high-purity lithium carbonate by recovering lithium from scraps of a lithium ion secondary battery, and lithium carbonate produced thereby. The present invention may comprise: a step of roasting lithium ion secondary battery scrap powder in a reducing atmosphere; a step of wet-grinding; a step of water leaching while adding carbon dioxide; a step of removing impurities other than lithium by using an ion exchange resin; a step of synthesizing lithium carbonate by pyrolysis; and a step of obtaining solid lithium carbonate by filtering.

Description

Method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap and lithium carbonate produced thereby

[0001] The present invention relates to a method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap through a carbon dioxide leaching process, a purification process using an ion exchange resin, and a thermal decomposition process, and to lithium carbonate produced thereby.

[0002] Lithium-ion secondary batteries are widely used in various fields such as electric vehicles, energy storage systems (ESS), smartphones, satellites, and solar panels. As demand increases, the amount of waste scrap generated during the manufacturing process and used lithium secondary batteries is increasing day by day.

[0003] In particular, the rapid growth of the electric vehicle market has led to a sharp increase in the value of key minerals used in lithium-ion secondary battery cathodes, such as lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn). This has led to intensifying competition for resource acquisition, driven by resource nationalism among resource-rich countries and the internalization of supply chains across each country. Furthermore, global environmental protection trends such as carbon neutrality and strengthened environmental regulations are driving demand for eco-friendly processes, materials, and products, as well as the growing importance of waste reuse and recycling. These trends are also garnering significant attention and projected growth in the waste lithium secondary battery recycling market.

[0004] Among the core minerals of lithium-ion secondary batteries, lithium has seen the greatest increase in value over the past few years. Since cathode materials contain 5-7% lithium, methods for recovering lithium compounds through recycling are attracting much attention and interest.

[0005] Currently, Korea relies entirely on imports for lithium carbonate, a key raw material for lithium-ion secondary batteries. As battery demand grows, recycling key raw materials such as Li, Ni, Co, and Mn becomes essential. Furthermore, in order to respond to resource weaponization by developing countries and protect the global environment, it is an important task for recycling technology to efficiently increase the recovery rate of lithium in a more environmentally friendly manner to secure competitiveness.

[0006] Existing methods for recovering and synthesizing lithium include recovering lithium from waste liquids containing lithium generated during the process of separating nickel, cobalt, and manganese components from lithium-ion secondary battery scrap. These methods recover and synthesize lithium by mixing the waste liquid containing lithium with a diluent and an extractant and then using a solvent and acid. However, these methods involve multiple steps using solvents, diluents, extractants, and acids, and consume large amounts of water and energy, resulting in significant losses in terms of economy and time. Furthermore, most lithium recycling companies produce industrial lithium carbonate with a purity of less than 99.5%, which contains high levels of impurities such as sodium (Na) and sulfur (S) due to the auxiliary materials used in the process.

[0007] Accordingly, after repeated research, the researchers confirmed that by applying a carbon dioxide leaching process and a purification process using an ion exchange resin, lithium carbonate with a purity of 99.5% or higher that can be directly used in the battery manufacturing process can be manufactured, thereby completing the present invention.

[0008] [Prior Art Literature]

[0009] [Patent Document]

[0010] Patent Publication No. 10-2022-0026285 (March 4, 2022)

[0011] Patent Publication No. 10-1682217 (November 28, 2016)

[0012] The present invention aims to provide a method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap, and lithium carbonate produced thereby.

[0013] The first aspect of the present invention for solving the above problem is a method for producing lithium carbonate by recovering lithium from lithium ion secondary battery scrap, comprising: (1) a step of roasting lithium ion secondary battery scrap powder in a reducing atmosphere at 600°C to 1,000°C for 100 to 300 minutes, (2) a step of wet-pulverizing the roasted product at a temperature of 25°C to 30°C, (3) a step of converting first lithium carbonate into lithium bicarbonate by adding carbon dioxide to the wet-pulverized product and leaching it, thereby producing a leached lithium bicarbonate solution in which lithium bicarbonate is dissolved, (4) a step of filtering the leached lithium bicarbonate solution to produce a filtered lithium bicarbonate solution, (5) a step of removing impurities other than lithium by purifying the filtered lithium bicarbonate solution using a polystyrene series ion exchange resin at a flow rate of 5 to 10 liters per hour, thereby producing a purified lithium bicarbonate solution, (6) a step of purified lithium bicarbonate A method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap may be provided, including a step of synthesizing second lithium carbonate by thermal decomposition while stirring lithium bicarbonate in a solution at a temperature of 80 to 100°C at 60 to 400 rpm, and (7) a step of filtering a second lithium carbonate solution containing second lithium carbonate to separate it into solid second lithium carbonate and second lithium carbonate filtrate.

[0014] In this aspect, the second lithium carbonate filtrate can be reused as process water in steps (2) and (3).

[0015] In this aspect, the temperature of the process water can be between 5°C and 45°C.

[0016] In this aspect, the purity of the second lithium carbonate may be 99.5% or higher.

[0017] The second aspect of the present invention may be high-purity lithium carbonate manufactured by the front side.

[0018] According to the present invention, a method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap and lithium carbonate produced thereby can be provided.

[0019] FIG. 1 is a flow chart of a method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap according to one aspect of the present invention.

[0020] FIG. 2 is a graph showing changes in the synthesis efficiency of lithium carbonate according to changes in the temperature of a purified lithium bicarbonate solution according to one aspect of the present invention.

[0021] FIG. 3 is a graph showing the results of XRD analysis of lithium carbonate finally obtained according to one aspect of the present invention.

[0022] Figure 4 is a graph showing the results of XRD analysis of battery-grade lithium carbonate extracted from lithium minerals.

[0023] FIG. 5 is a scanning electron microscope (SEM) image of lithium carbonate finally obtained according to one aspect of the present invention.

[0024] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. The embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided so that the present invention can be more completely described to those with average knowledge in the art. Therefore, the shape and size of elements in the drawings may be exaggerated for clearer description, and elements indicated by the same reference numerals in the drawings are the same elements. In the present invention, the expressions first or second do not denote order or importance, but are simply used to distinguish components.

[0025] The present invention relates to a method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap, and to high-purity lithium carbonate produced thereby.

[0026] FIG. 1 shows a flow chart for synthesizing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap according to an aspect of the present invention. FIG. 2 shows a change in the synthesis efficiency of lithium carbonate according to a change in the temperature of a purified lithium bicarbonate solution according to an aspect of the present invention. FIG. 3 shows the results of an XRD analysis of lithium carbonate finally obtained according to an aspect of the present invention. FIG. 4 shows the results of an XRD analysis of battery-grade lithium carbonate extracted from lithium minerals. FIG. 5 shows a scanning electron microscope (SEM) image of lithium carbonate finally obtained according to an aspect of the present invention.

[0027] The process sequence is explained with reference to Figure 1.

[0028] First, lithium-ion secondary battery scrap powder can be prepared (step a).

[0029] Lithium-ion secondary battery scrap powder may include powder obtained from scrap of lithium-ion secondary batteries discarded after use, as well as powder generated during the production process of lithium-ion secondary battery cathode active materials.

[0030] Lithium-ion secondary battery scrap may be used alone or in combination with lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide (LiNiCoMnO2), lithium manganese oxide (LiMnO2), and lithium iron phosphate (LiFePO4), but is not limited thereto.

[0031] For example, lithium-ion secondary battery scrap powder can be used that essentially contains metals such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li), while also containing impurities such as aluminum (Al), iron (Fe), and copper (Cu) and carbon.

[0032] Specifically, lithium nickel cobalt manganese oxide (LiNi) is used as a lithium-ion secondary battery scrap powder. x Co y Mn 1-x-y Scrap powder containing O2) can be used. The composition of the scrap powder may be 10 to 50 parts by weight of Ni, 5 to 20 parts by weight of Co, 5 to 20 parts by weight of Mn, 2 to 8 parts by weight of Li, 0.5 to 5 parts by weight of Co, 0.5 to 5 parts by weight of Al, 0.5 to 5 parts by weight of Fe, and 0.5 to 5 parts by weight of other impurities, based on 100 parts by weight of the total weight.

[0033]

[0034] Next, the lithium ion secondary battery scrap powder can be mixed with a reducing agent and sintered in a nitrogen atmosphere (step b).

[0035] In the process of manufacturing positive electrode materials for lithium-ion secondary batteries, complex processes such as sintering, addition of carbon and other metal oxides, addition of binder, and thermal bonding are performed to maintain or improve battery characteristics. For this reason, waste positive electrode materials contain various oxide forms of valuable metals and impurities, which can act as an obstacle in recovering valuable metals. To eliminate this obstacle, a reducing agent is added to lithium-ion secondary battery scrap powder and roasting is performed at high temperatures to remove the binder added during positive electrode material manufacturing and reduce the metallic substances combined with oxygen.

[0036] The reaction mechanism of the sintering process is as follows.

[0037] 2LiMeO2+ 2C → Li2CO3+ 2Me + CO2

[0038] Here, Me = Ni, Co, Mn.

[0039] Carbon powder can be used as a reducing agent. Activated carbon can be used as a carbon powder. Activated carbon powder reacts with lithium to maximize lithium recovery.

[0040] In the combustion process, 10 to 50 parts by weight of reducing agent can be mixed with 100 parts by weight of lithium ion secondary battery scrap powder.

[0041] The firing process can utilize either a rotary or non-rotary kiln, but using a rotary kiln is more preferable as it can promote the firing reaction.

[0042] The roasting process can be performed at a temperature of 600°C to 1,000°C for 100 to 300 minutes (isothermal period). During the roasting process, nitrogen (N2) gas can be introduced to maintain a reducing atmosphere. High-temperature roasting promotes binder decomposition, and the scrap powder and reducing agent can react with lithium to maximize the recovery rate.

[0043] After the firing process (isothermal section) is completed, the kiln can be cooled for 300 to 500 minutes. There is no need to maintain a nitrogen atmosphere during the cooling period.

[0044] After this process, the resulting product may contain components such as primary lithium carbonate and metallic substances. The lithium carbonate produced during the process may be referred to as primary lithium carbonate.

[0045]

[0046] Next, the resulting powder obtained in step (b) can be wet-pulverized (step c).

[0047] Wet grinding can produce finer powders during the same grinding time as dry grinding, and because there is no powder scattering or spreading compared to dry grinding, it can improve the environment of the workplace and the working conditions of workers.

[0048] Wet milling can be performed by placing the resulting powder, balls, and solvent into a mill (milling machine) and then milling. 93% alumina (Al2O3) balls can be used. Wet milling can be performed at a temperature of 25°C to 30°C.

[0049] Water (soft water) can be used as a solvent in the initial step. Once the process is complete, the filtrate recovered in step (h) (hereinafter referred to as "process water") can be used in place of water (soft water). Since process water contains some lithium, reusing it in this step can increase the lithium concentration in the water leachate in step (d), thereby enhancing the lithium recovery rate and reducing the amount of wastewater generated.

[0050] By performing this process, the roasted product obtained in step (b) can be transformed into a form easily leached. Specifically, wet milling increases the specific surface area of ​​the roasted product, significantly enhancing the leaching efficiency. Ultimately, this significantly improves the lithium recovery rate.

[0051] The wet grinding result obtained through this process can be subjected to a water leaching process without separate purification or filtration.

[0052]

[0053] Next, the wet grinding result can be subjected to carbon dioxide water leaching to obtain a leaching solution (hereinafter, “leached lithium bicarbonate solution”) (step d) (carbon dioxide water leaching process).

[0054] The carbon dioxide leaching process can be performed by adding water (soft water) and carbon dioxide to the wet grinding result and then stirring it.

[0055] Lithium may be present in the wet-milled product as lithium carbonate (Li2CO3). The solubility of lithium carbonate is approximately 2,300 ppm at room temperature. The lithium carbonate contained in the wet-milled product can be referred to as primary lithium carbonate.

[0056] Adding carbon dioxide (CO2) gas to the wet milling process can convert primary lithium carbonate into lithium hydrogen carbonate (LiHCO3). The solubility of lithium hydrogen carbonate is approximately 10,000 ppm at room temperature. By converting primary lithium carbonate into lithium hydrogen carbonate, a greater amount of lithium can be dissolved in the solvent. If the lithium dissolved in the solvent is subsequently recovered, the lithium recovery rate can be increased.

[0057] Carbon dioxide can be added by aerating the gas. Unreacted carbon dioxide can be captured and reintroduced into the process water. This minimizes carbon dioxide usage.

[0058] Water (soft water) can be used in the initial stage of the carbon dioxide leaching process. Once the manufacturing process is complete, the process water recovered in step (h) can be used instead of water (soft water). Process water may contain some lithium, so reusing it in this step can increase the lithium concentration in the leachate. This can increase the lithium recovery rate and reduce wastewater generation.

[0059] The temperature of the process water recovered in step (h) may be 5°C to 45°C, more preferably 10°C to 40°C. Lithium bicarbonate has high solubility at low temperatures and low solubility at high temperatures. Therefore, in order to dissolve a large amount of lithium in water, the process must be conducted at a low temperature, and the lower the temperature of the process water, the more advantageous it is for producing a high-concentration solution.

[0060] It is preferable that the carbon dioxide leaching process be carried out for a sufficient period of time to ensure that the first lithium carbonate is sufficiently dissolved.

[0061] The reaction mechanism of the carbon dioxide (CO2) leaching process is as follows.

[0062] Li2CO3+ CO2+ H2O → 2LiHCO3

[0063] Lithium bicarbonate may exist in a dissolved state in the leached lithium bicarbonate solution.

[0064]

[0065] Next, the leached lithium bicarbonate solution obtained in step (d) can be filtered to separate solid and liquid, thereby obtaining a filtrate (hereinafter, “filtered lithium bicarbonate solution”) (step e).

[0066] (d) Since the lithium bicarbonate solution obtained in step (d) contains scrap powder, the solid phase and the liquid phase can be separated by filtering it using the Filter Press method. Lithium bicarbonate may exist in a dissolved state in the filtered lithium bicarbonate solution.

[0067]

[0068] Next, the filtered lithium bicarbonate solution obtained in step (e) can be purified using an ion exchange resin to produce a purified solution (hereinafter, “purified lithium bicarbonate solution”) (step f).

[0069] (e) Impurities other than lithium present in the filtered lithium bicarbonate solution obtained in step (e) can be removed using an ion exchange resin to purify it to a purity of 99.5% or higher. By performing this process, high-purity lithium carbonate of 99.5% or higher can be manufactured.

[0070] Polystyrene-based cation exchange resins can be used as ion exchange resins. In this case, 1 liter of resin can process approximately 120 to 150 liters of process water at a flow rate of 5 to 10 liters per hour.

[0071] In general, methods such as co-precipitation, which uses chemicals such as acids or alkalis to adjust the pH, are widely used to remove impurities other than lithium. However, this method requires a lot of chemicals and increases the amount of wastewater generated. In addition, depending on the chemicals used, additional contamination such as sodium (Na) may occur in addition to the target impurities to be removed. To solve these problems and manufacture high-purity battery-grade lithium carbonate, it is necessary to adsorb and remove only the ions of impurities other than lithium. Purification using ion exchange resins simplifies the process by reducing the conventional cleaning step, and the filtrate generated in step (h) can be reused as process water, thereby reducing the amount of wastewater generated and maximizing the lithium recovery rate.

[0072]

[0073] Next, by heating the purified lithium bicarbonate solution obtained in step (f), secondary lithium carbonate can be synthesized through thermal decomposition of lithium bicarbonate (step g).

[0074] Lithium carbonate produced through the thermal decomposition of lithium bicarbonate can be called secondary lithium carbonate. The synthesis reaction mechanism of secondary lithium carbonate through the thermal decomposition of lithium bicarbonate is as follows.

[0075] 2LiHCO3→ Li2CO3+ CO2+ H2O

[0076] The synthesized secondary lithium carbonate can be dissolved in a solvent and exist as a solution, or precipitated and exist as a solid. Through this process, a lithium bicarbonate solution, a secondary lithium carbonate solution, and a solid secondary lithium carbonate can coexist. Considering that a high-purity solid secondary lithium carbonate is formed, this is called a secondary lithium carbonate solution.

[0077] Thermal decomposition can be performed at temperatures ranging from 80 to 100°C. Since the solubility of secondary lithium carbonate decreases at higher temperatures, the process of synthesizing secondary lithium carbonate by thermal decomposition of lithium bicarbonate can increase the recovery rate of secondary lithium carbonate when performed at higher temperatures.

[0078] Referring to Figure 2, it can be seen that the second lithium carbonate synthesis efficiency is low below 70℃, and as the temperature increases, the second lithium carbonate synthesis efficiency increases. It can be confirmed that the synthesis efficiency reaches 100% at 100℃. The synthesis efficiency can be calculated as the ratio of the 'concentration of lithium recoverable at room temperature based on the raw material' to the 'concentration of lithium recovered from the raw material at each temperature'.

[0079] The pyrolysis process can be carried out with stirring, and the stirring speed can be 60 to 400 rpm.

[0080] The second lithium carbonate solution may include a lithium bicarbonate solution, a second lithium carbonate solution, and solid second lithium carbonate.

[0081]

[0082] Next, the second lithium carbonate solution prepared in step (g) can be filtered to obtain a solid second lithium carbonate, and the liquid second lithium carbonate filtrate can be recovered (step h).

[0083] Secondary lithium carbonate can be dried using a dryer to remove moisture, thereby obtaining high-purity battery-grade secondary lithium carbonate with a final purity of 99.5% or higher. The drying temperature can be 100°C to 300°C.

[0084] The second lithium carbonate filtrate can be recovered and reused as process water in steps (c) and (d). Since the filtrate contains some lithium, reusing the filtrate as process water can increase the lithium concentration in the lithium carbonate solution leached in step (d), thereby increasing the lithium recovery rate and reducing the amount of wastewater generated.

[0085]

[0086] Hereinafter, the present invention will be described in detail through examples. However, the present invention is not limited to the examples.

[0087]

[0088] 1. Preparation of lithium-ion secondary battery scrap powder

[0089] Lithium-ion secondary battery scrap was used as powder obtained from spent lithium-ion secondary battery batteries or cells. Table 1 shows the results of component analysis using inductively coupled plasma (ICP-MS) for lithium-ion secondary battery scrap powder.

[0090] ClassificationLiNiCoMnMgCaZnCuFeNaAl(unit)%ppmConcentration3.7425.224.592.06236284113,8051,6505379,828

[0091] 2. Mix with reducing agent and roast

[0092] A mixture of scrap powder and activated carbon was placed in a rotary kiln and subjected to a roasting process at 800±5°C for 200 minutes. After the isothermal section, the roasting product was cooled for approximately 400 minutes. Nitrogen (N2) gas was flowed from the heating section to the isothermal section to maintain a nitrogen atmosphere. The nitrogen flow rate was 50 LPM (Liter Per Minute), and the nitrogen atmosphere was not maintained during the cooling section.

[0093]

[0094] 3. Wet grinding

[0095] The resulting powder, 93% alumina balls, and process water were added to the milling machine and wet ball milled together. The temperature was maintained at 25°C to 30°C, and the process was conducted for 360 minutes.

[0096]

[0097] 4. Carbon dioxide (CO2) leaching and filtration

[0098] The wet grinding product was added with process water at 25°C, and a carbon dioxide leaching process was performed using a stirrer while adding carbon dioxide gas through aeration. By ensuring sufficient leaching, a leached lithium bicarbonate solution was obtained. Afterwards, the solution was filtered using a filter press to obtain a filtered lithium bicarbonate solution. The results of the component analysis of the filtrate are shown in Table 2.

[0099] Table 2 also shows the components of the leaching filtrate obtained by filtering the leaching liquid obtained by the conventional water leaching method (a method of transforming lithium carbonate into lithium chloride or lithium hydroxide with high solubility using hydrochloric acid or sulfuric acid in the wet grinding result (Korean Patent No. 10-1682217)).

[0100] Classification LiNiCoMnMgCaZnCuFeNaAl (unit) ppm (conventional process) 8,6507983081,1109410132,55036 (present invention) 9,610407784325000320

[0101] Referring to Table 2, it can be confirmed that in the case of the carbon dioxide (CO2) water leaching method according to the present invention, the content of impurities in the filtrate is significantly less than in the case of the conventional water leaching method.

[0102]

[0103] 5. Purification using ion exchange resin

[0104] The above filtered lithium bicarbonate solution was purified by passing the target component cations through a polystyrene-based cation exchange resin at a flow rate of 5 to 10 liters per hour, adsorbing them onto the resin. The results of component analysis of the purified lithium bicarbonate solution obtained after purification are shown in Table 3.

[0105] ClassificationLiNiCoMnMgCaZnCuFeNaAl(unit)ppmBefore purification9,610407784325000320After purification9,42000012000300

[0106] Referring to Table 3, it can be confirmed that nickel, cobalt, and manganese, excluding lithium, were removed by more than 99.5%.

[0107]

[0108] 6. Synthesis and filtration of lithium carbonate through thermal decomposition

[0109] Lithium carbonate was synthesized by thermal decomposition of a purified lithium bicarbonate solution while stirring at a temperature of 100°C. The lithium carbonate solution was filtered to separate it into solid lithium carbonate and lithium carbonate filtrate.

[0110] The solid lithium carbonate was dried at a temperature of 130°C to obtain high-purity, battery-grade lithium carbonate.

[0111] Lithium carbonate filtrate can be reused as process water in wet milling and carbon dioxide leaching processes. ICP analysis results for the lithium carbonate filtrate are shown in Table 4.

[0112] ClassificationLiNiCoMnMgCaZnCuFeNaAl(unit)ppmFiltrate2,28000011000250Year-old000000000650

[0113] Referring to Table 4, it can be confirmed that the lithium carbonate filtrate according to the present invention contains lithium and impurity contents at the same level as soft water. Therefore, it is shown that the lithium carbonate filtrate can be used as process water instead of soft water. If the lithium carbonate filtrate is reused as process water, the lithium concentration can be increased during the production of lithium bicarbonate solution, ultimately increasing the lithium recovery rate. In addition, since the wastewater is reused instead of discharged, the amount of wastewater generated can be drastically reduced. Generally, soft water is usually used as process water and then discharged as wastewater.

[0114] Table 5 shows the purity of lithium carbonate manufactured by a conventional process (Korean Patent No. 10-1682217) in which sodium carbonate is added after hydrochloric acid or sulfuric acid leaching to remove residue and synthesize lithium carbonate, and the purity of lithium carbonate manufactured by a carbon dioxide water leaching process according to the present invention.

[0115] ClassificationLi2CO3NiCoMnMgCaZnCuFeNaAlSi(unit)%ppmBattery Spec≥99.53001050205552501030(Conventional process)99.10007545202243320(Invention)99.8000010003008

[0116] Referring to Table 5, it can be confirmed that the purity of lithium carbonate in the conventional process is 99.1%, and in the case of the present invention, the purity of lithium carbonate is 99.8%. The purity specification of lithium carbonate for battery-grade lithium carbonate is stipulated to be 99.5% or higher, and the lithium carbonate according to the present invention satisfies this specification. In addition, it can be confirmed that the levels of major impurities such as Mg, Ca, and Na, which are managed, have been significantly reduced, and all of these meet the battery specifications. Therefore, it can be confirmed that the lithium carbonate manufactured according to the present invention is at a level that can be immediately used as a material for a lithium-ion secondary battery cathode material.

[0117] FIG. 3 shows the XRD analysis results for lithium carbonate finally obtained according to one aspect of the present invention, and FIG. 4 shows the XRD analysis results for battery-grade lithium carbonate extracted from lithium mineral.

[0118] Referring to FIGS. 3 and 4, it can be confirmed that the XRD diffraction peaks for the lithium carbonate finally obtained according to one aspect of the present invention and the battery-grade lithium carbonate extracted from minerals are identical. Therefore, it can be seen that the lithium carbonate manufactured by recovering lithium from lithium-ion secondary battery scrap according to one aspect of the present invention is identical to pure battery-grade lithium carbonate.

[0119] Figure 5 shows a scanning electron microscope (SEM) image of lithium carbonate finally obtained according to one aspect of the present invention.

[0120]

[0121] The terminology used herein is intended to describe specific embodiments and is not intended to limit the invention. Singular expressions should be construed to include plural references unless the context clearly indicates otherwise. Terms such as "comprise" or "have" indicate the presence of features, numbers, steps, operations, components, or combinations thereof described in the specification, but are not intended to exclude them.

[0122] The present invention is not limited to the above-described embodiments and the attached drawings, but is intended to be defined by the appended claims. Therefore, those skilled in the art will appreciate that various substitutions, modifications, and alterations may be made without departing from the technical spirit of the present invention as defined in the claims, and such modifications are also considered to fall within the scope of the present invention.

[0123]

[0124]

[0125]

[0126]

[0127]

Claims

1. A method for producing lithium carbonate by recovering lithium from lithium-ion secondary battery scrap, (1) A process of calcining lithium ion secondary battery scrap powder by maintaining it at 600°C to 1,000°C for 100 to 300 minutes in a reducing atmosphere; (2) A process of wet grinding the roasting result at a temperature of 25℃ to 30℃; (3) A process for converting first lithium carbonate into lithium bicarbonate by adding carbon dioxide to the wet grinding result and leaching it, thereby producing a leached lithium bicarbonate solution in which the lithium bicarbonate is dissolved; (4) A process for producing a filtered lithium bicarbonate solution by filtering the above-mentioned lithium bicarbonate solution; (5) A process for manufacturing a purified lithium bicarbonate solution by removing impurities other than lithium by purifying the filtered lithium bicarbonate solution at a flow rate of 5 to 10 liters per hour using a polystyrene series ion exchange resin; (6) A process for synthesizing second lithium carbonate by thermal decomposition of the lithium bicarbonate in the above purified lithium bicarbonate solution while stirring at 60 to 400 rpm at a temperature of 80 to 100°C; and (7) A process for filtering the second lithium carbonate solution containing the second lithium carbonate to separate it into a solid second lithium carbonate and a second lithium carbonate filtrate. A method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap.

2. In paragraph 1, The above second lithium carbonate filtrate is reused as process water in steps (2) and (3). A method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap.

3. In paragraph 2, The temperature of the above process water is 5℃ to 45℃, A method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap.

4. In paragraph 1, The purity of the above-mentioned second lithium carbonate is 99.5% or more, A method for producing high-purity lithium carbonate by recovering lithium from lithium-ion secondary battery scrap.

5. High-purity lithium carbonate manufactured according to any one of clauses 1 to 4.

Images