Dry thermal reaction-based method for producing lithium sulfate from waste battery black powder and converting same into lithium hydroxide

Abstract

A dry thermal reaction-based method for producing lithium sulfate from black mass or black powder and converting same into lithium hydroxide, according to one embodiment of the present invention, can produce lithium sulfate and convert same into lithium hydroxide through water leaching and a dry thermal reaction, which uses a sulfate additive. In addition, unlike a conventional secondary battery waste resource recycling process, strong acid and alkaline solutions are not used, and thus environmental pollutants such as waste liquid and waste slurry are not generated, thereby significantly reducing environmental treatment costs. Additionally, lithium recovery efficiency is high due to the high solubility of lithium sulfate (about 27 times that of lithium carbonate). Further, a resource circulation process such as reusing metal sulfate residues, which are process by-products, as a sulfate additive without additional post-treatment, recycling process water (ultrapure water) and recycling generated dust can be implemented.

Description

Method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on dry thermal reaction

[0001] The present invention relates to a method for manufacturing lithium sulfate and converting it into lithium hydroxide, and more specifically, to a method for manufacturing lithium sulfate and converting it into lithium hydroxide from waste battery black powder based on a dry thermal reaction.

[0002] Lithium-ion batteries (LIBs) are widely used as power sources in various applications, such as portable electronic devices, electric vehicles (BEVs, HEVs, PHEVs), E-mobility, and Energy Storage Systems (ESS), due to their high energy density and lightweight characteristics. In particular, the production volume of lithium secondary batteries is increasing rapidly due to the surge in demand for electric vehicles, and consequently, the demand for lithium compounds, which are the main cathode raw materials for LIBs, is also rising. Cathode materials, which are the main components of these secondary batteries, account for a large portion of manufacturing costs and contain expensive metals such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li). Since most of these metals are imported, the recycling industry is becoming active to recover valuable metals from secondary battery waste resources (black powder, waste batteries, wastewater, etc.) generated to ensure product competitiveness and secure raw material supply.

[0003] Conventional wet recycling methods are technologies that use chemical solvents, such as sulfuric acid, hydrochloric acid, and organic solvents, to dissolve, extract, and recover valuable metals. However, they have the disadvantage of generating waste during the process and incurring high equipment costs. Consequently, there is an increasing demand for dry recycling technologies that can increase recycling efficiency while minimizing waste generated during the process and reducing the environmental burden.

[0004] The present invention was conceived to solve the aforementioned problems and provides a method for manufacturing lithium sulfate from waste battery black powder and a method for converting it into lithium hydroxide hydrate, which minimizes waste generated in the production process and reduces resource waste through a recyclable process.

[0005] The technical problems of the present invention are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by a person skilled in the art from the description below.

[0006] To achieve the above technical objective, a method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction according to an embodiment of the present invention comprises the step (S01) of preparing black mass or black powder as a raw material, which includes process by-products derived from waste batteries or generated in a secondary battery cathode active material manufacturing process;

[0007] A step (S02) of performing a dry thermal reaction process to produce a thermal reaction powder separated into lithium sulfate and a metal oxide by mixing the above raw material and a sulfate additive and performing a dry thermal reaction treatment;

[0008] Step (S03) of performing a water leaching process in which the above-mentioned thermal reaction powder is immersed in ultrapure water;

[0009] A first solid-liquid separation step (S04) in which the lithium sulfate is obtained in an aqueous solution state and the metal oxide is obtained as a solid metal oxide cake;

[0010] A lithium sulfate powdering step (S05) in which a portion of the obtained lithium sulfate aqueous solution is evaporated and concentrated to produce lithium sulfate powder;

[0011] A lithium hydroxide conversion step (S06) in which the remainder of the above lithium sulfate aqueous solution undergoes a metal hydroxide addition reaction to produce lithium hydroxide and metal sulfate residues;

[0012] A second solid-liquid separation step (S07) in which the lithium hydroxide is obtained in an aqueous solution state and the metal sulfate residue is obtained in a solid state; and

[0013] The above metal sulfate residue may include a step (S08) of being reused as a sulfate additive in the dry thermal reaction process of step S02.

[0014] The above raw materials may include lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn).

[0015] The above dry thermal reaction treatment step may be performed at a temperature exceeding 600°C under an atmospheric environment.

[0016] The above sulfate additive may include Na2SO4, BaSO4, CaSO4, or a combination of two or more of these.

[0017] The above raw material and the above sulfate additive may be mixed in a weight ratio of 1:0.01 to 1:1.

[0018] The lithium component in the metal oxide produced through the above dry thermal reaction treatment step may be less than 0.1 weight%.

[0019] The recovery rate of lithium through the above dry thermal reaction treatment step can be 97% or higher.

[0020] The above lithium sulfate may be soluble in ultrapure water, and the above metal oxide may not be soluble in ultrapure water.

[0021] The above-mentioned thermoreactive powder and ultrapure water may be mixed in a weight ratio of 1:0.7 to 1:5.

[0022] The recovery rate of lithium through the above water leaching process can be 90% to 97%.

[0023] The lithium component in the metal oxide cake may be less than 0.1 weight%.

[0024] The above lithium sulfate aqueous solution or the above lithium sulfate powder may not contain cobalt (Co), nickel (Ni), and manganese (Mn) components.

[0025] The purity of the above lithium sulfate aqueous solution or the above lithium sulfate powder may be 99% to 99.5% or higher.

[0026] The above metal hydroxide may include NaOH, Ba(OH)2, Ca(OH)2, and combinations of two or more of these.

[0027] The metal component of the above sulfate additive and the metal component of the above metal hydroxide component may be the same.

[0028] The amount of the metal hydroxide added may be in a weight ratio of 0.1 to 0.5 times the weight of the lithium sulfate aqueous solution.

[0029] The above lithium hydroxide aqueous solution or lithium hydroxide powder may not contain cobalt (Co), nickel (Ni), and manganese (Mn) components.

[0030] The metal sulfate residue produced in the above lithium hydroxide conversion step may be reused as is as a sulfate additive in the above S02 step without additional post-treatment, such as neutralization, purification, or wastewater treatment.

[0031] The above metal sulfate residue may include a dry or wet state.

[0032] The ultrapure water remaining after manufacturing lithium hydroxide powder by evaporating and concentrating the above lithium hydroxide aqueous solution can be recycled in step S03.

[0033] The dust generated through the above dry thermal reaction process can be collected by a dust collector and recycled as a raw material for the above S02 step.

[0034] According to the present invention as described above, the method for producing lithium sulfate and converting lithium hydroxide from black mass or black powder based on a dry thermal reaction according to an example of the present invention enables the production of lithium sulfate and conversion into lithium hydroxide through a dry thermal reaction process and a water leaching process utilizing a sulfate additive. Furthermore, unlike conventional secondary battery waste resource recycling processes, strong acid and alkaline solutions are not used, so environmental pollutants such as waste liquid and waste slurry are not generated, thereby significantly reducing environmental treatment costs. In addition, the lithium recovery efficiency is high due to the high solubility of lithium sulfate (approximately 27 times that of lithium carbonate). Moreover, a resource-circulating process can be implemented by reusing metal sulfate residue, a process byproduct, as a sulfate additive without additional post-treatment, recycling process water (ultrapure water), and recycling generated dust.

[0035] The effects of the present invention are not limited to those mentioned above, and include other effects that are clearly understood by a person skilled in the art from the description throughout the specification but are not explicitly mentioned.

[0036] FIG. 1 is a flowchart illustrating a method for producing lithium sulfate and lithium hydroxide from waste battery black powder based on a dry thermal reaction according to one embodiment of the present invention.

[0037] FIG. 2 is a schematic diagram of the equipment and process flow applied to the dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder according to the present invention.

[0038] FIG. 3 shows the thermal reaction temperature of lithium sulfate prepared from waste battery black powder based on a dry thermal reaction according to Example 1 and Comparative Example 1 of the present invention, (a) 700~800 ℃ (Example 1), (b) 600 ℃ (Comparative Example 1), and (c) the X-ray diffraction (XRD) analysis result for the raw material.

[0039] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the attached drawings. However, the present invention is not limited to the embodiments disclosed below but can be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Throughout the specification, the same reference numerals refer to the same components.

[0040] Unless otherwise defined, all terms used herein (including technical and scientific terms) may be used in a meaning commonly understood by those skilled in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise. The terms used herein are for describing embodiments and are not intended to limit the present invention. In this specification, the singular form includes the plural form unless specifically stated otherwise in the text.

[0041] As used in the specification, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, actions, and / or elements to the mentioned components, steps, actions, and / or elements.

[0042]

[0043] Method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on dry thermal reaction

[0044] FIG. 1 is a flowchart illustrating a method for producing lithium sulfate and lithium hydroxide from waste battery black powder based on a dry thermal reaction according to one embodiment of the present invention.

[0045] Referring to FIG. 1, first, a step (S01) of preparing black mass or black powder as a raw material, which is derived from waste batteries or includes process by-products generated in the manufacturing process of a secondary battery positive electrode active material, may be performed.

[0046] The above black mass or black powder may be used as a raw material in the method for manufacturing lithium sulfate and converting lithium hydroxide described below. Here, black mass refers to a mixed material obtained through a process of crushing and separating spent lithium-ion batteries, and may include metallic components such as lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) derived from the cathode material of the lithium-ion battery, and graphite components derived from the anode material. Additionally, black powder refers to a black powdery material derived from the cathode active material of the lithium-ion battery, and may be a more refined form of raw material composed of cathode active material components such as lithium cobalt oxide (LCO) and lithium nickel manganese cobalt oxide (NCM), from which anode components have been removed. In one embodiment, the cathode active material component in the raw material is a lithium nickel manganese cobalt oxide (NCM) component, which may include lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn), but is not limited thereto. Black powder can be obtained not only from the recycling process of waste batteries but also as a byproduct in the cathode active material manufacturing process.

[0047] The above raw materials may contain a trace amount of water. The trace amount of water is intended to enhance the uniformity of the reaction and facilitate efficient heat transfer. When the raw materials and sulfate additives are mixed, the trace amount of water forms a thin water film on the surface, facilitating contact between the reactants and enabling uniform heat distribution, thereby allowing for more efficient selective reaction between lithium and sulfate. Additionally, the formation of oxygen or hydrogen gas through the decomposition of water molecules at high temperatures can improve reactivity by generating oxygen required for the reaction and hydrogen required for reduction. This reaction environment maintains the consistency of the thermal reaction and enhances reactivity, which can ultimately contribute to improving the recovery rate of lithium sulfate. For example, the above raw materials and water may be mixed in a mass ratio of 1:0.05 to 1:0.1, but are not limited thereto.

[0048] A step (S02) of performing a dry thermal reaction process to produce a thermal reaction powder separated into lithium sulfate and metal oxide by mixing the prepared raw material and a sulfate additive and performing a dry thermal reaction treatment can be performed.

[0049] The above dry thermal reaction treatment step involves the raw material (black mass or black powder) and the sulfate additive undergoing a thermal reaction under specific temperature conditions, wherein lithium and sulfate react selectively to form a lithium sulfate phase (Li2SO4 phase) and a metal oxide phase (M x O y A phase (where M is a valuable metal, and x and y are independently any integers) may be formed. Specifically, the metal oxide may include nickel oxide (NiO), manganese oxide (MnO), cobalt oxide (CoO), and at least one selected from these. For example, the dry thermal reaction may be a chemical reaction represented by the following chemical formula 1.

[0050] [Chemical Formula 1]

[0051] Lithium Nickel Manganese Cobalt Oxide (NCM) + AM a (SO4) a→ Li2SO4+ M x O y + AM 2z O z

[0052] In the above chemical formula 1, AM is an alkali metal or alkaline earth metal, for example Na, Ca, or Ba, M is a valuable metal other than lithium, for example Ni, Mn, Co, and at least one selected from these, and x, y, a, and z are independently any integers.

[0053] In one embodiment, the above chemical formula 1 may be one or more chemical reactions selected from the following chemical formulas 2 to 4.

[0054] [Chemical Formula 2]

[0055] Lithium nickel manganese cobalt oxide (NCM) + Na2SO4 → Li2SO4 + M 1 x1 O y1 + Na2O

[0056] [Chemical Formula 3]

[0057] Lithium nickel manganese cobalt oxide (NCM) + CaSO4 → Li2SO4 + M 2 x2 O y2 + CaO

[0058] [Chemical Formula 4]

[0059] Lithium nickel manganese cobalt oxide (NCM) + BaSO4 → Li2SO4 + M 3 x3 O y3 + BaO

[0060] In the above chemical formulas 2 to 4, M 1 , M 2 and M 3 is independently a valuable metal other than lithium, for example Ni, Mn, Co, and at least one selected from these, and x1, x2, x3, y1, y2 and y3 are independently any integers.

[0061]

[0062] The above dry thermal reaction treatment step may be performed under an atmospheric temperature exceeding 600 °C, specifically in a temperature range of 650 to 900 °C, preferably 700 to 850 °C, for several minutes to several hours, preferably 30 minutes to 2 hours. Under these thermal reaction conditions, the sulfate additive allows lithium and sulfate to react selectively, thereby forming a lithium sulfate phase (Li2SO4 phase) and a metal oxide phase (M x O y It is separated into phases, and in particular, the metal on the metal oxide may contain almost no lithium, specifically, the lithium component in the metal oxide may contain less than 0.1 wt%. Within the thermal reaction temperature range, lithium has a higher reactivity with sulfates compared to other metals, such as Ni, Mn, and Co, and can be preferentially converted into the form of lithium sulfate (Li2SO4). Since the generated lithium sulfate forms a thermodynamically stable phase separation with metal oxides such as nickel, cobalt, and manganese, almost no lithium may be dissolved or incorporated into the metal oxide. Due to these selective reactivity and phase separation characteristics of lithium, the residual lithium content in the metal oxide formed through the dry thermal reaction process can be controlled to an extremely low level of less than 0.1 wt%.

[0063] In addition, the lithium sulfate phase (Li2SO4 phase) and the metal oxide phase (M x O yThe phase can be separated due to differences in solubility in water. Specifically, lithium sulfate has a high solubility (approx. 349 g / L), with about 35 g dissolving per 100 g of water at 25°C, whereas the metal oxide exhibits the characteristic of being almost insoluble in water. By utilizing this difference in solubility, in the water leaching process described later, lithium sulfate is selectively dissolved and recovered in an aqueous solution state, while the metal oxide is separated into an insoluble solid state, thereby enabling effective separation of components. By utilizing these differences in physicochemical properties, high-purity lithium sulfate can be recovered without complex chemical treatment.

[0064] Specifically, the above sulfate additive is the chemical formula AM a (SO4) a (wherein AM is an alkali metal or alkaline earth metal, for example, Na, Ca, or Ba, and a is any integer) and, more specifically, may include Na2SO4, BaSO4, CaSO4, or a combination of two or more of these. In this case, the sulfate additive may be in an anhydrous form.

[0065] In particular, the above-mentioned sulfate additive may be a metal sulfate residue generated during the lithium hydroxide conversion process described later, which is recycled directly without additional treatment. This is because the metal sulfate residue (Na2SO4, CaSO4, BaSO4, etc.) generated during the lithium hydroxide conversion process contains the same chemical composition as the sulfate additive used in the initial thermal reaction process; therefore, the metal sulfate residue can be directly reused as an additive in the dry thermal reaction process without the need for separate post-treatment processes such as purification, neutralization, or concentration. Through this, a resource-circulating process can be realized that improves economic efficiency and minimizes waste generation.

[0066] The above raw material and the sulfate additive may be mixed in a weight ratio of 1:0.01 to 1:1. This mixing ratio may be a range in which the stoichiometric reaction between lithium and sulfate effectively occurs, taking into account the lithium content in the raw material. Specifically, the above raw material and the sulfate additive may be mixed in a weight ratio of 1:0.03 to 1:0.7, more specifically in a weight ratio of 1:0.05 to 1:0.5, and in one embodiment, in a weight ratio of 1:0.07. In particular, within this mixing ratio range, the conversion rate of lithium in the raw material to lithium sulfate is maximized, and unnecessary cost increases caused by the use of an excessive amount of additive can be prevented. Furthermore, this mixing ratio facilitates uniform mixing of the powder and heat transfer during the thermal reaction, thereby enabling a stable reaction.

[0067] The lithium content in the metal oxide produced through the above dry thermal reaction treatment step may be less than 0.1 weight%. This low residual lithium content implies that the dry thermal reaction process of the present invention is highly effective for lithium recovery. In particular, since the generated lithium sulfate forms a thermodynamically stable phase separation with metal oxides such as nickel, cobalt, and manganese, there is a high probability that lithium will not be dissolved or incorporated into the metal oxide. Due to this selective reactivity between lithium and sulfate and clear phase separation characteristics, the residual lithium content in the metal oxide can be controlled to an extremely low level of less than 0.1 weight%, which implies that the lithium recovery rate is excellent.

[0068] In particular, through the dry thermal reaction step under the aforementioned conditions, the reaction between lithium and sulfate occurs selectively, while the reaction of metals other than lithium with sulfate can be restricted. This utilizes the thermodynamic property that lithium preferentially reacts with sulfate compared to other valuable metals under specific conditions. This selective reaction allows lithium to be formed into a form of lithium sulfate that is highly soluble in water, while simultaneously maintaining other metals in the form of oxides that are insoluble in water. This facilitates the recovery of lithium in a subsequent water leaching process due to differences in solubility. This reaction selectivity enables the recovery of high-purity lithium compounds without the need for complex separation and purification processes.

[0069] The lithium recovery rate through the above dry thermal reaction treatment step may be 97% or higher, specifically 97% to 99.9%, and 97.19% in one embodiment, but is not limited thereto. This high lithium recovery rate indicates selective reactivity between lithium and sulfate and stable phase separation, which may be superior even compared to conventional wet processes. This high recovery rate can serve as a key factor in ensuring the economic viability of the process.

[0070] The lithium sulfate produced through the above S02 process may be obtained in the form of a hydrate. For example, it may be lithium sulfate monohydrate (Li2SO4·H2O), but is not limited thereto. Lithium sulfate hydrate has superior solubility in water compared to the anhydrous form, which may result in high water leaching efficiency, and forms a stable crystalline phase, making storage and handling easy. However, the form of the hydrate (monohydrate or polyhydrate) may vary depending on process conditions and environment, and this may not affect the quality of the final product.

[0071] The above raw material (black mass or black powder) contains a lithium content of approximately 4.5 to 6.5 weight%, and the production capacity of lithium sulfate that can be manufactured based thereon may be approximately 240 g to 340 g per 1 kg of raw material. Through this, the lithium contained in the raw material can be effectively converted into lithium sulfate.

[0072] Meanwhile, during the above dry thermal reaction process, a portion of the sulfate additive may undergo thermal decomposition to produce an alkali metal compound or an alkaline earth metal compound, which may specifically be at least one selected from Na2O, CaO, BaO, and combinations thereof. A portion of these compounds may be incorporated as impurities into the lithium sulfate. For example, the alkali metal or alkaline earth metal content contained in the lithium sulfate may be controlled to a level of about 1 to 400 ppm relative to the total mass of the lithium sulfate, and in one embodiment, to 300 to 350 ppm for sodium, 100 to 150 ppm for barium, and 1 to 10 ppm for calcium. Impurities at this level may not significantly affect the purity of the final product, the lithium sulfate. Furthermore, since the metal component of the metal hydroxide used in the lithium hydroxide conversion step described later is identical to the metal component of the alkali metal compound or alkaline earth metal compound contained in the lithium sulfate, the impact of these impurities on the final product may be negligible.

[0073] Through the above dry thermal reaction process, thermal reaction powder, steam (pH 7), and dust are generated. Specifically, the main product, the thermal reaction powder, exists in a phase-separated form of lithium sulfate and metal oxide, and is used as a raw material for the subsequent water leaching process. The neutral steam (pH 7) generated during the process has the advantage of having a low environmental burden, unlike the acidic or alkaline steam generated in conventional wet processes. In addition, the generated dust is collected through a dust collector and recycled as a raw material for the dry thermal reaction (S02) stage, thereby minimizing material loss and improving process efficiency. As such, the dry thermal reaction process of the present invention possesses characteristics that are both environmentally friendly and resource-circulating.

[0074]

[0075] Subsequently, a step (S03) of performing a water leaching process in which the above-mentioned thermal reaction powder is immersed in ultrapure water and a first solid-liquid separation step (S04) of obtaining the above-mentioned lithium sulfate in an aqueous solution state and obtaining the above-mentioned metal oxide as a solid metal oxide cake may be performed.

[0076] The water leaching process (S03) and the first solid-liquid separation step (S04) of the present invention utilize the difference in water solubility between lithium sulfate and metal oxides in the thermal reaction powder. Specifically, by utilizing the characteristic that lithium sulfate has high water solubility and dissolves easily in ultrapure water, whereas metal oxides including nickel, cobalt, and manganese are almost insoluble in water, a solid metal oxide cake and lithium sulfate in an aqueous solution can be obtained.

[0077] In the above-mentioned water leaching process, the thermal reaction powder and ultrapure water may be mixed in a weight ratio of 1:1 to 1:5, and a weight ratio of 1:2 or higher may be particularly desirable for smooth stirring. This mixing ratio is optimized considering the solubility of lithium sulfate, and by using a sufficient amount of ultrapure water, complete dissolution of lithium sulfate can be ensured and efficient stirring can be enabled. The water leaching process time may be 1 hour to 5 hours. This may be an optimized time for complete dissolution of lithium sulfate and efficient separation.

[0078] The recovery rate of lithium through the above water leaching process is 90% to 97%, specifically 92.53% to 96.26%, but is not limited thereto.

[0079] The first solid-liquid separation step (S04) described above is a step of physically separating lithium recovered in an aqueous solution phase and metal oxide recovered in a solid phase using a filter. The fact that effective component separation is possible with only this simple physical separation is due to the distinct difference in water solubility between lithium sulfate and metal oxide. That is, lithium sulfate existing in an aqueous solution state and metal oxide existing in an insoluble solid state during the water leaching process can be separated solely through a filtration process using a filter. Compared to conventional wet processes that require complex chemical separation or purification processes, this offers significant advantages in terms of process simplification and cost reduction.

[0080] The lithium component in the metal oxide cake may be less than 0.1 weight%. That is, the components of the metal oxide cake may exclude lithium or contain only a very small amount, while most of the components may include oxides of valuable metals other than lithium, such as manganese (Mn), cobalt (Co), and nickel (Ni). In the dry thermal reaction process described above, lithium is selectively converted into lithium sulfate, and in the subsequent water leaching process, the lithium sulfate is effectively dissolved and separated from the metal oxide, so that only a very small amount of lithium remains in the metal oxide cake, or may not contain any lithium component at all.

[0081]

[0082] Afterwards, a lithium sulfate powdering step (S05) may be performed to produce lithium sulfate powder by evaporating and concentrating a portion of the obtained lithium sulfate aqueous solution.

[0083] Specifically, the lithium sulfate powdering step can produce a lithium sulfate solution concentrated to approximately 70 to 80% by heating the lithium sulfate solution at 100 to 110°C and evaporating it. A portion of the concentrated lithium sulfate solution can be produced into lithium sulfate powder through a lithium sulfate powdering facility. The lithium sulfate powder produced can exhibit very high purity due to the excellent selectivity and separation efficiency of the preceding processes. Specifically, the lithium sulfate powder does not contain valuable metal components such as cobalt (Co), nickel (Ni), and manganese (Mn), and the purity of the lithium sulfate in aqueous solution or powder form can be 99% or higher, specifically a high level of 99% to 99.5%. The remainder of the concentrated lithium sulfate solution can be used in the lithium hydroxide conversion step (S06) described later.

[0084]

[0085] After the above S04 step, a lithium hydroxide conversion step (S06) may be performed in which the remainder of the obtained lithium sulfate aqueous solution undergoes a metal hydroxide addition reaction to produce lithium hydroxide and metal sulfate residues. Through the S06 process, lithium hydroxide and metal sulfate residues are generated through a chemical reaction between lithium sulfate and a metal hydroxide.

[0086] The above lithium hydroxide conversion step may be a chemical reaction represented by the following chemical formula 5.

[0087] [Chemical Formula 5]

[0088] Li2SO4+ NaOH, Ba(OH)2or Ca(OH)2→ LiOH + CaSO4, BaSO4or Na2SO4

[0089] The metal hydroxide mentioned above may include NaOH, Ba(OH)2, Ca(OH)2, and combinations of two or more of these. The metal hydroxide selected for this purpose may be identical to the metal component of the sulfate additive used in the previously performed dry thermal reaction process. For example, it is preferable to use NaOH as the additive in the lithium hydroxide conversion process when Na2SO4 was used as the additive in the dry thermal reaction, Ca(OH)2 when CaSO4 was used, and Ba(OH)2 when BaSO4 was used. This design enables resource circularity by configuring the entire process from the dry thermal reaction to the lithium hydroxide conversion process as a single continuous flow, thereby ensuring that the entire process is closely interconnected and allowing for the direct recycling of by-products. Since the metal component of the sulfate additive used in the dry thermal reaction step is identical to the metal component of the metal hydroxide used in the lithium hydroxide conversion step, the metal sulfate residue generated after the completion of the lithium hydroxide conversion process can be recycled as is. In other words, by selecting a metal hydroxide with a metal component matching the sulfate additive used in the dry thermal reaction process, metal sulfate residues can be repeatedly utilized without a separate treatment process. This maximizes process efficiency and economic viability, and enables the realization of a stable resource-recycling process without additional purification or treatment.

[0090]

[0091] The amount of the metal hydroxide added is 0.5 to 2 weight ratio relative to the weight of the lithium sulfate aqueous solution, the reaction temperature is 120 to 140 ℃, and the reaction time may be 1 to 3 hours.

[0092] The lithium hydroxide produced is generally obtained in the form of a hydrate, and in one embodiment, it may have the form of lithium hydroxide monohydrate (LiOH·H2O).

[0093]

[0094] Subsequently, a second solid-liquid separation step (S07) in which the lithium hydroxide is obtained in an aqueous solution state and the metal sulfate residue is obtained in a solid state, and a lithium hydroxide powdering step in which the lithium hydroxide aqueous solution is evaporated and concentrated to produce lithium hydroxide powder may be performed.

[0095] After the reaction with the hydroxide additive is completed, the reaction solution can be cooled to -10 to 3°C for separation utilizing the difference in solubility between lithium hydroxide and the metal sulfate residue. During this process, ultrapure water can be added while cooling to ensure the complete dissolution of lithium hydroxide. By utilizing the characteristic that the solubility of lithium hydroxide is maintained even at low temperatures, the complete dissolution of lithium hydroxide can be secured by adding ultrapure water while cooling. The cooled solution can be separated into lithium hydroxide (LiOH) in an aqueous state and solid metal sulfate residue (Na2SO4, CaSO4, BaSO4) that precipitates as solubility rapidly decreases with temperature reduction, through solid-liquid separation using a filter. This physical separation method has the advantages of a simple process, low environmental burden, and excellent separation efficiency as it does not require chemical treatment.

[0096] In particular, a step (S08) may be performed in which the metal sulfate residue is reused as a sulfate additive in the dry thermal reaction process of step S02. At this time, the metal sulfate residue generated in the above-described process can be directly reused without separate post-treatment. Recycling such process by-products can realize a resource-circulating process that reduces additive costs and minimizes waste generation.

[0097]

[0098] FIG. 2 is a schematic diagram of the equipment and process flow applied to the dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder according to the present invention.

[0099] Referring to FIG. 2, a dry thermal reaction between the raw material and the sulfate additive takes place in the rotary kiln (1) facility, and the water leaching of the thermal reaction product (powder) proceeds in the water leaching facility (2). Subsequently, the first solid-liquid separation of the lithium sulfate aqueous solution and the metal oxide takes place in the filter press (3), which is the first solid-liquid separation facility, and the conversion to lithium hydroxide through the reaction of the lithium sulfate aqueous solution and the metal hydroxide proceeds in the lithium hydroxide synthesis facility (4). In the second solid-liquid separation facility, the lithium hydroxide and the metal sulfate residue undergo the second solid-liquid separation, and the final product, lithium hydroxide powder, is manufactured in the evaporation concentration facility (6) and the lithium hydroxide powdering facility (7). In particular, the metal sulfate residue generated during the process is used as an additive in the thermal reaction process, the evaporated concentrated water is reused in the water leaching process, and the dust generated in the dry thermal reaction process is also collected by a dust collector and reused as a raw material, thereby enabling a resource-recycling process.

[0100]

[0101] The present invention will be explained in more detail below using examples and experimental examples. However, the following examples and experimental examples are for illustrating the present invention and the scope of the present invention is not limited thereto.

[0102]

[0103] Example 1: Lithium sulfate prepared from waste battery black powder based on dry thermal reaction

[0104] 35 g of black powder, 2.5 g of sulfate additive (Na2SO4), and 2.5 g of distilled water were mixed, and a dry thermal reaction was carried out in a rotary kiln at a temperature of 700 to 800 °C for approximately 0.5 to 2 hours. The reaction was performed in an atmospheric environment, and the heating rate was set to 5 °C / min. As a result of the thermal reaction, lithium was selectively converted into lithium sulfate (Li2SO4), while nickel, cobalt, and manganese were phase-separated into their respective metal oxides. The phase and crystal structure of the resulting thermal reaction powder were confirmed through XRD analysis, and the residual lithium content in the metal oxides was measured to be less than 0.1 wt%. At this time, the lithium recovery rate was 97.19%.

[0105]

[0106] Comparative Example 1: Lithium sulfate produced from waste battery black powder based on dry thermal reaction

[0107] Lithium sulfate was prepared using the same method as in Example 1, except that the thermal reaction temperature was set to 600 ℃.

[0108]

[0109] FIG. 3 shows the thermal reaction temperature of lithium sulfate prepared from waste battery black powder based on a dry thermal reaction according to Example 1 and Comparative Example 1 of the present invention, (a) 700 to 800 ℃ (Example 1), (b) 600 ℃ (Comparative Example 1), and (c) the X-ray diffraction (XRD) analysis result for the raw material.

[0110] Referring to Fig. 3, when the thermal reaction temperature in the dry thermal reaction step is 700–800 °C (Example 1, Fig. 3(a)), clear peaks of CoO, NiO, and Li2SO4 are observed, indicating that lithium is effectively converted into lithium sulfate and other metals exist in oxide form. On the other hand, in the case of Comparative Example 1 (Fig. 3(b)) processed at 600 °C, peaks of lithium complex oxides such as LiCoO2, LiNiO2, and LiMn2O4 are observed, which are similar to the lithium complex oxides of LiNiO, LiCoO, and LiMnO2 identified in the original sample (Fig. 3(c)), indicating that the reaction between lithium and sulfate did not proceed sufficiently at that temperature. This implies that the temperature of 600 °C did not provide sufficient thermal energy for the reaction between lithium and sulfate. Meanwhile, peaks of lithium complex oxides may also be observed when the thermal reaction temperature exceeds 800 °C. Therefore, it may be desirable for the thermal reaction temperature to be 700 to 800 ℃ during the dry thermal reaction step.

[0111]

[0112] Table 1 shows the lithium recovery rate results through the method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction according to one embodiment of the present invention.

[0113] Process Raw material After dry thermal reaction After water leaching Lithium sulfate aqueous solution Lithium hydroxide powder Weight (g) 403 9.6 100 4.891 Li Content (wt%) 4.36 3.7 44 1.4 77 0.288 Li Weight (g) 1.5 26 1.4 83 1.4 77 1.41 Lithium Recovery rate -97.1 996.7 892.43 Remarks Raw material 35g + Sulfate additive 2.5g + H2O 2.5g

[0114]

[0115]

[0116] Referring to Table 1, the lithium recovery rate at each process step is shown, indicating the weight (g), lithium content (weight%), and lithium recovery rate (%) at each process. Starting with a mixed powder of 35 g of raw material (lithium content 4.36 wt%, lithium weight 1.526 g), 2.5 g of sulfate, and 2.5 g of distilled water, after the dry thermal reaction with the addition of sulfate, 39.6 g of the sample showed a lithium content of 3.744 wt% (lithium weight 1.483 g), resulting in a recovery rate of 97.19%. After water leaching, in the aqueous solution state (100 g), a recovery rate of 96.78% was obtained with a lithium content of 1.477 wt% (lithium weight 1.477 g), and in the final powder state of lithium hydroxide powder (4.89 g), a recovery rate of 92.43% was obtained with a lithium content of 0.288 wt% (lithium weight 1.410 g). These results confirm that the process of the present invention maintains a high lithium recovery rate of over 90% at each stage, and in particular, exhibits excellent recovery efficiency of over 97% in the initial dry thermal reaction stage and over 96% in the water leaching stage.

[0117]

[0118] Tables 2 and 3 show the results of analyzing the impurity composition of lithium sulfate powder and lithium hydroxide powder produced through a dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder according to an embodiment of the present invention. (N / D; Not Detected)

[0119] Classification NaBaPSiKCaCuAlCdCo Lithium Sulfate 335ppm 250ppm 213ppm 145ppm 28.8ppm 12.4ppm 13.6ppm 321ppm N / DN / DC rFeMgMoNiPbTiVZn-N / DN / DN / DN / DN / DN / DN / DN / DN / DN / DN / D-

[0120] Classification NaBaPSiKCaCuAlCdCo Lithium Hydroxide 600ppm 128ppm 150ppm 61ppm 6.9ppm 5.4ppm 4.7ppm 162ppm N / DN / DC rFeMgMoNiPbTiVZn-N / DN / DN / DN / DN / DN / DN / DN / DN / DN / DN / DN-

[0121]

[0122]

[0123] Referring to Tables 2 and 3, the lithium content of the lithium sulfate powder was found to be 19.87 wt%, and major impurities such as Na (335 ppm), Ba (250 ppm), P (213 ppm), Si (145 ppm), and Al (321 ppm) were detected, but metal components such as Co, Cr, Fe, Mg, Mo, Ni, Pb, Ti, V, and Zn were not detected. Meanwhile, the final product converted into lithium hydroxide had a lithium content of 19.9 wt%, and contained impurities such as Na (600 ppm), Ba (128 ppm), P (150 ppm), Si (61 ppm), and Al (162 ppm), but metal components such as Co, Cr, Fe, Mg, Mo, Ni, Pb, Ti, V, and Zn were not detected. Through this, it can be confirmed that the lithium sulfate and lithium hydroxide produced through the process according to a preferred example of the present invention are high-purity products that do not contain transition metal impurities such as nickel, cobalt, and manganese.

[0124]

[0125] The embodiments of the present invention described above are merely exemplary, and the scope of protection of the present invention may include various modifications and equivalents therefrom, as understood by those skilled in the art.

[0126]

[0127] [Explanation of the symbol]

[0128] 1: Dry thermal reaction facility (rotary kiln), 2: Water leaching facility, 3: 1st solid-liquid separation facility (filter press), 4: Lithium hydroxide synthesis facility, 5: 2nd solid-liquid separation facility (filter press), 6: Evaporation concentration facility, 7: Lithium hydroxide pulverization facility

Claims

1. A step (S01) of preparing black mass or black powder as a raw material, which includes process by-products derived from waste batteries or generated during the manufacturing process of secondary battery cathode active materials; A step (S02) of performing a dry thermal reaction process to produce a thermal reaction powder separated into lithium sulfate and a metal oxide by mixing the above raw material and a sulfate additive and performing a dry thermal reaction treatment; Step (S03) of performing a water leaching process in which the above-mentioned thermal reaction powder is immersed in ultrapure water; A first solid-liquid separation step (S04) in which the lithium sulfate is obtained in an aqueous solution state and the metal oxide is obtained as a solid metal oxide cake; A lithium sulfate powdering step (S05) in which a portion of the obtained lithium sulfate aqueous solution is evaporated and concentrated to produce lithium sulfate powder; A lithium hydroxide conversion step (S06) in which the remainder of the above lithium sulfate aqueous solution undergoes a metal hydroxide addition reaction to produce lithium hydroxide and metal sulfate residues; A second solid-liquid separation step (S07) in which the lithium hydroxide is obtained in an aqueous solution state and the metal sulfate residue is obtained in a solid state; and A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, comprising the step (S08) in which the metal sulfate residue is reused as a sulfate additive in the dry thermal reaction process of step S02.

2. In Paragraph 1, The above raw materials include lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn), and a method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction.

3. In Paragraph 1, A dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder, wherein the above dry thermal reaction treatment step is performed at a temperature exceeding 600°C under an atmospheric atmosphere.

4. In Paragraph 1, A dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder, wherein the above sulfate additive comprises Na2SO4, BaSO4, CaSO4, or a combination of two or more of these.

5. In Paragraph 1, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, wherein the above raw material and the above sulfate additive are mixed in a weight ratio of 1:0.01 to 1:

1.

6. In Paragraph 1, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, wherein the lithium component in the metal oxide produced through the above dry thermal reaction treatment step is less than 0.1 weight%.

7. In Paragraph 1, A dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder, wherein the lithium recovery rate through the above dry thermal reaction treatment step is 97% or higher.

8. In Paragraph 1, A dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder, wherein the lithium sulfate is soluble in ultrapure water and the metal oxide is not soluble in ultrapure water.

9. In Paragraph 1, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, wherein the above thermal reaction powder and ultrapure water are mixed in a weight ratio of 1:0.7 to 1:

5.

10. In Paragraph 1, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, wherein the lithium recovery rate through the above-mentioned water leaching process is 90% to 97%.

11. In Paragraph 1, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, wherein the lithium component in the metal oxide cake is less than 0.1 weight%.

12. In Paragraph 1, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, wherein the above lithium sulfate aqueous solution or the above lithium sulfate powder does not contain cobalt (Co), nickel (Ni), and manganese (Mn) components.

13. In Paragraph 1, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, wherein the purity of the above lithium sulfate aqueous solution or the above lithium sulfate powder is 99% to 99.5% or higher.

14. In Paragraph 1, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, wherein the metal hydroxide comprises NaOH, Ba(OH)2, Ca(OH)2, and combinations of two or more of these.

15. In Paragraph 1, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, characterized in that the metal component of the sulfate additive and the metal component of the metal hydroxide component are the same.

16. In Paragraph 1, A dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder, wherein the amount of the metal hydroxide added is 0.1 to 0.5 times the weight of the aqueous lithium sulfate solution.

17. In Paragraph 1, A dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder, wherein the above-mentioned lithium hydroxide aqueous solution or lithium hydroxide powder does not contain cobalt (Co), nickel (Ni), and manganese (Mn) components.

18. In Paragraph 1, A dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder, wherein the metal sulfate residue produced in the above lithium hydroxide conversion step is reused as is as a sulfate additive in the above S02 step without additional post-treatment.

19. In Paragraph 18, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, wherein the metal sulfate residue is in a dry or wet state.

20. In Paragraph 1, A dry thermal reaction-based method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder, wherein the lithium hydroxide aqueous solution is evaporated and concentrated to produce lithium hydroxide powder, and the remaining ultrapure water is recycled in step S03.

21. In Paragraph 1, A method for producing lithium sulfate and converting lithium hydroxide from waste battery black powder based on a dry thermal reaction, wherein dust generated through the above dry thermal reaction process is collected by a dust collector and recycled as a raw material for the above S02 step.

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