Method of preparing raw material for lithium iron phosphate positive electrode

Abstract

A method of preparing a raw material for a lithium iron phosphate positive electrode, according to one embodiment, comprises the steps of: extracting valuable metals from a metal oxide-based waste positive electrode material and preparing an extraction residue containing phosphorus as an impurity; adding, to the extraction residue, an iron-containing precipitating agent that forms a precipitate with phosphorus and recovering the precipitate; washing the recovered precipitate and then drying same; and calcining the dried precipitate.

Description

Manufacturing method of raw materials for lithium iron phosphate cathode materials

[0001] The manufacturing method according to the invention relates to a method for manufacturing a raw material for a lithium iron phosphate cathode material, and more specifically, to a method for manufacturing a raw material that can be used in the production of a lithium secondary battery cathode material from an industrial by-product generated during recycling of waste batteries.

[0002] As the global battery market grows explosively, recycling technologies for used batteries are attracting attention. Recycling batteries is the final link in completing the resource-circulating structure of battery production, use, reuse, recycling, and production. It involves extracting materials from used batteries and reusing them in battery production.

[0003] Recycling of waste batteries is divided into a pre-treatment process, which includes the discharge and peeling, crushing, and pulverization processes of waste batteries, and a post-treatment process, which recovers valuable materials (valuable metals, graphite, etc.) from waste battery scrap.

[0004] Among the post-processing processes, wet smelting is a process that can extract valuable metals such as Li, Mn, and Ni that are difficult to recover in dry processes, but it has the disadvantage of generating a large amount of industrial by-products that are simply discarded during the extraction process.

[0005] According to one aspect of the present invention, a method for producing a raw material that can be used in the production of a lithium secondary battery cathode material from a byproduct generated during recycling of waste batteries can be provided.

[0006] The objectives of the present invention are not limited to the above-described scope. Those skilled in the art will have no difficulty understanding the additional objectives of the present invention from the overall content of this specification.

[0007] A method for manufacturing a raw material for a lithium iron phosphate cathode according to the present invention comprises the steps of extracting a valuable metal from a metal oxide waste cathode and preparing an extraction residue containing phosphorus as an impurity; mixing an iron-containing precipitant that combines with phosphorus to form a precipitate with the extraction residue and recovering the precipitate; washing the recovered precipitate with water and then drying it; and calcining the dried precipitate.

[0008] In one specific example, the metal oxide-based waste cathode may contain lithium, nickel, manganese, and cobalt.

[0009] In one specific example, the impurity may be derived from an organophosphate compound used as an extractant in the extraction of valuable metals.

[0010] In one specific example, the extract may contain 1.7 to 3.9 g / L of Li and 0.01 to 0.09 g / L of P on an elemental basis.

[0011] In one specific example, the iron-containing precipitant may be ferric polysulfate.

[0012] In one specific example, based on the weight of elemental reference phosphorus (WP1) contained per 1 L of the extract residue, the iron-containing precipitant may be mixed so that the weight of iron satisfies 8 WP1 to 15 WP1 per 1 L of the extract residue.

[0013] In one specific example, the washing may be performed at 40 to 60°C.

[0014] In one specific example, the washing may be repeated 3 to 5 times.

[0015] In one specific example, the calcination may be performed at 550 to 650°C in an inert atmosphere.

[0016] A manufacturing method according to one specific example can manufacture a raw material that can be used in the production of a lithium iron phosphate cathode material during the recycling process of a waste metal oxide cathode material of a lithium secondary battery.

[0017] A manufacturing method according to one specific example goes beyond recycling by extracting and recovering valuable metals from waste metal oxide-based cathode materials, and also introduces byproducts, which are a major problem in the process of extracting and recovering valuable metals from waste cathode materials, into the virtuous recycling of cathode materials, thereby reducing the cost of raw material supply and waste disposal and suppressing environmental pollution.

[0018] The various advantageous and beneficial effects of the present invention are not limited to the above-described contents, and will be more easily understood in the course of explaining specific embodiments of the present invention.

[0019] FIG. 1 is a scanning electron microscope photograph (FIG. 1(a)) of a raw material for a lithium iron phosphate cathode material manufactured according to one embodiment, an Fe element mapping image (FIG. 1(b)) and a P element mapping image (FIG. 1(c)) using energy dispersive X-ray spectroscopy.

[0020] Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings. However, 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.

[0021] In addition, the embodiments of the present invention are provided to more completely explain the present invention to a person having average knowledge in the relevant technical field.

[0022] The shape and size of elements in the drawing may be exaggerated for clearer explanation.

[0023] In describing the embodiments of the present invention, if a detailed description of a known technology related to the present invention is judged to unnecessarily obscure the gist of the present invention, such detailed description will be omitted. In addition, the terms described below are terms defined in consideration of their functions in the present invention, and these may vary depending on the intention or custom of the user or operator. Therefore, the definitions should be made based on the contents throughout this specification. The terminology used in the detailed description is only for the purpose of describing the embodiments of the present invention and should in no way be limiting. Unless clearly defined otherwise, expressions in the singular form include plural meanings.

[0024] In this description, expressions such as "including" or "having" are intended to indicate certain features, numbers, steps, operations, elements, portions or combinations thereof, and should not be construed to exclude the presence or possibility of one or more other features, numbers, steps, operations, elements, portions or combinations thereof other than those described.

[0025] Unless otherwise specified in the specification of the present invention, the % unit means weight %.

[0026] In the specification of the present invention, an element described as being contained in a solution should be interpreted to mean including ions of the element and / or compounds containing the element (including ionic phases).

[0027] Below, the present invention will be described in detail through each embodiment or example of the present invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may be combined with other embodiments or examples. Therefore, the citation of a claim in the patent claims is only an example of an embodiment, and the technical concept of the present invention should not be interpreted solely as a combination with the cited claim, and combinations with various claims also fall within the scope of the technical concept of the present invention.

[0028] A method for manufacturing a raw material for a lithium iron phosphate cathode according to one embodiment comprises the steps of extracting a valuable metal from a waste metal oxide cathode and preparing an extraction residue containing phosphorus as an impurity; mixing an iron-containing precipitant that combines with phosphorus to form a precipitate with the extraction residue and recovering the precipitate; washing the recovered precipitate with water and then drying it; and calcining the dried precipitate.

[0029] A manufacturing method according to one aspect can manufacture a raw material (precursor) useful for producing lithium secondary battery cathode materials, such as lithium iron phosphate (LFP), from a byproduct obtained by precipitating and removing phosphorus impurities during the process of extracting valuable metals from waste metal oxide-based cathode materials.

[0030] In detail, the waste cathode material may be a waste cathode material of a lithium secondary battery, and may be a metal oxide-based waste cathode material. The metal oxide-based waste cathode material may contain lithium, nickel, cobalt, and manganese. More specifically, the metal oxide-based waste cathode material may be a layered NCM (Ni, Co, Mn) ternary metal oxide containing intercalated lithium. The NCM ternary metal oxide may have a composition commonly used as a lithium secondary battery cathode material, and as a practical example, may have a composition in which the molar ratio of Ni: Co: Mn satisfies x of 0.30 to 0.85: y of 0.05 to 0.35: z of 0.03 to 0.35, and satisfies x + y + z = 1.

[0031] Specifically, the extraction residue may be an extraction residue in which metal is extracted from a sulfuric acid leachate obtained by leaching metal components from the black mass of a spent battery containing a metal oxide-based cathode material using sulfuric acid.

[0032] As a practical example, the sulfuric acid leachate may contain metals (e.g., copper) of the current collector and metal components (e.g., lithium, nickel, manganese, and cobalt) of the metal oxide-based waste cathode material, and the extraction residue may be the residue remaining after valuable metals (e.g., copper, nickel, manganese, and cobalt) other than lithium are extracted and removed from the sulfuric acid leachate. As a more practical example, the raffinate may contain 1.7 to 3.9 g / L of Li and 0.01 to 0.09 g / L of P on an elemental basis, and as an even more practical example, the raffinate may contain 1.7 to 3.9 g / L of Li, 0.01 to 0.09 g / L of P, 31 to 76 g / L of Na, 0.01 to 0.05 g / L of F, 0.01 to 1.50 g / L of Ni, 0.01 to 0.10 g / L of Cl, and 0.02 to 0.20 g / L of K on an elemental basis.

[0033] Elemental phosphorus (P), an impurity in the extractant residue, may originate from the organophosphate compound used as an extractant (extraction solvent) during the extraction of valuable metals. In other words, the phosphorus in the extractant residue may be in the form of phosphoric acid. The organophosphate compound may be any substance commonly used in the solvent extraction of valuable metals such as nickel, manganese, and / or cobalt from sulfuric acid leachates. Practical examples of organophosphate compounds include, but are not limited to, di-2-ethylhexylphosphoric acid (D2EHPA), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC88A), di-2-ethylhexylphosphoric acid, tri-butyl-phosphate (TBP), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester, or mixtures thereof.

[0034] After valuable metals other than lithium (e.g., copper, nickel, manganese, and cobalt) are extracted and removed and an extractant containing phosphorus as an impurity is prepared, a step of adding and mixing an iron-containing precipitant that combines with phosphorus to form a precipitate to the extractant and recovering the formed precipitate can be performed.

[0035] The iron-containing precipitant may be an iron salt that reacts with phosphorus, specifically phosphoric acid, to form a precipitate. Specifically, the iron salt may be a sulfate (e.g., ferrous sulfate), and the ferrous sulfate may be ferrous sulfate, ferrous sulfate hydrate, ferric polysulfate, or a mixture thereof. Ferrous sulfate is advantageous because it forms a precipitate in the form of a compound of phosphoric acid and iron without further contaminating the raffinate residue, which already contains sulfate ions, derived from the sulfuric acid leachate.

[0036] More advantageously, the iron-containing precipitant may contain ferric polysulfate. When ferric polysulfate is used as the iron-containing precipitant, the precipitates coagulate and settle quickly, significantly shortening the precipitation time and facilitating faster solid-liquid separation, thereby reducing the process time by more than 30%, which is advantageous. In this case, the iron content in the ferric polysulfate may be 10 to 25 wt%, but is not necessarily limited thereto.

[0037] The amount of the iron-containing precipitant to be added is sufficient so that the phosphorus (on an elemental basis) contained in the extract residue can be removed in the form of iron phosphate compounds, while preventing an increase in production costs due to excessive addition of the iron-containing precipitant. As a practical example, when the weight of elemental phosphorus contained per 1 L of the extract residue is WP1, the iron-containing precipitant can be added so that the weight of iron satisfies 8 WP1 to 15 WP1, specifically 10 WP1 to 14 WP1, and more specifically 10 WP1 to 12 WP1 per 1 L of the extract residue.

[0038] After an iron-containing precipitant is added and mixed into the extract residue, phosphorus contained in the extract residue can be removed through a precipitation reaction. The precipitation reaction can be performed at a temperature of 20 to 40°C, specifically 20 to 30°C, and more specifically at room temperature. Here, room temperature refers to the temperature of the extract residue in a state where no artificial heat is applied, and can be practically a temperature of approximately 25°C.

[0039] After the precipitation reaction, solid-liquid separation can be performed through precipitation-based filtration. The residue (filtrate) from which phosphorus has been removed and the cake containing the precipitate can be separated and recovered through solid-liquid separation. The residue (filtrate) from which phosphorus has been removed can be utilized in a separate process to recover useful metals contained within the residue. As a non-limiting example, it can be utilized in a lithium recovery process to recover lithium in the form of lithium carbonate.

[0040] The cake containing the sediment may be dried after washing. Specifically, washing may include a step of mixing and stirring the cake and water to prepare a slurry, and a step of recovering the washed sediment by solid-liquid separation.

[0041] During washing, water may be mixed with the cake in an amount of 5 to 20 times, specifically 8 to 12 times, the dry weight of the cake to be washed. In addition, washing may be performed at a temperature of 40 to 60°C. If washing is performed at a temperature below 40°C, there is a risk that the washing effect of impurities adsorbed on the surface of the sediment including iron phosphate compounds may be low, and if it exceeds 60°C, the washing effect may be insignificantly improved, but a large amount of energy may be required, which may increase production costs. The washing temperature may be controlled by adjusting the temperature of the slurry itself or by adjusting the temperature of the water mixed with the cake during the preparation of the slurry. The prepared slurry may be stirred at a speed of 50 to 300 rpm for 10 to 40 minutes using a conventional reaction tank equipped with a stirrer.

[0042] Thereafter, the washed sediment can be separated and recovered from the slurry through conventional solid-liquid separation, such as filtration. Specifically, the solid-liquid separation of the slurry can be performed using a conventional filter press composed of a filter plate and a filter cloth; however, it should be understood that the present invention is not limited by specific filtration conditions or filtration devices.

[0043] Step (i) including mixing and stirring with water, and step (ii) including recovery of the washed precipitate by solid-liquid separation, wherein steps (i) and (ii) of the washing may be repeated 3 to 5 times. By washing in a heated state and repeating the washing, impurities adsorbed on the surface of the iron phosphate compound can be substantially completely removed. After the washing is completed, drying may be performed on the washed precipitate, and the drying may be performed at a temperature of 90 to 110°C, but is not necessarily limited thereto.

[0044] After drying is performed, a step of calcining the dried precipitate may be performed, and a crystalline phase of iron phosphate oxide (FePO4) may be produced by calcining the dried precipitate. The calcination may be performed at a temperature of 550 to 650°C in an inert atmosphere. This calcination temperature is a temperature at which nucleation and growth of iron phosphate oxide crystals occur smoothly while preventing agglomeration (sintering) between particles. The calcination may be performed for 1 to 15 hours, and the inert atmosphere may be, but is not necessarily limited to, an atmosphere of helium, neon, argon, nitrogen, or a mixed gas thereof.

[0045] Iron phosphate oxide produced by calcination can be utilized as a raw material (precursor) for manufacturing lithium iron phosphate (LiFePO4) cathode materials for lithium secondary batteries. This reduces industrial waste generated during the recycling process of metal oxide-based lithium secondary battery cathodes, and creates a virtuous resource cycle in which byproducts from the metal oxide-based cathode material recycling process are used as raw materials (precursors) for phosphate-based cathodes.

[0046] Hereinafter, the present invention will be described in detail through examples. However, it should be noted that the examples described below are intended only to illustrate and concretize the present invention and are not intended to limit the scope of the invention. This is because the scope of the invention is determined by the matters set forth in the patent claims and matters reasonably inferred therefrom.

[0047] The examples presented below are examples in which nickel, cobalt, manganese and copper are extracted from the sulfuric acid leachate obtained by leaching valuable metals (Ni, Co, Li, Mn, Cu, etc.) from the black mass of a spent lithium battery equipped with an NCM ternary cathode material using sulfuric acid, and the remaining extractant is used, and PC88A and D2EHPA are used as organophosphate compounds during the extraction. The extractant contained 2.9 g / L of Li, 0.02 g / L of P, 50.1 g / L of Na, 0.02 g / L of F, 0.03 g / L of Cl, 0.15 g / L of Ni and 0.04 g / L of K on an elemental basis.

[0048] (Example)

[0049] Ferric polysulfate was added and stirred so that 0.24 g of elemental iron was mixed per 1 L of the extract, and then allowed to settle to form a precipitate, which was then filtered to separate and recover the cake and filtrate. The moisture content of the cake was about 25%. Elemental analysis showed that the cake contained 0.12% Ni, 4.01% P, 0.20% Li, 17.2% Fe, and 0.17% F on a weight percent basis.

[0050] The cake separated and recovered from the extractant was mixed with water at 60℃, and the water was mixed in an amount 8 times the weight of the dried cake, stirred at 200 rpm for 30 minutes, and then the solid (precipitate) was separated and recovered using a filter press. This washing process was repeated 4 times. The solid (precipitate) washed 4 times was dried at 105℃. As a result of elemental analysis of the dried solid (precipitate), it was confirmed that it contained less than 0.01% Ni, less than 0.01% Li, and less than 0.01% Na on a weight % basis. This shows that metal components such as nickel, lithium, and sodium are removed by washing with heated water, and the purity is improved to a level that can be used as a raw material for lithium iron phosphate cathode materials.

[0051] Afterwards, the dried solid (sediment) was calcined at 600°C for 10 hours in a nitrogen atmosphere to produce iron phosphate.

[0052] Fig. 1(a) is a scanning electron microscope image of iron phosphate obtained by calcination attached to a carbon tape, Fig. 1(b) is an Fe element mapping image using energy dispersive X-ray spectroscopy in the same area as Fig. 1(a), and Fig. 1(c) is a P element mapping image using energy dispersive X-ray spectroscopy in the same area as Fig. 1(a). As shown in Fig. 1, it can be seen that iron phosphate is produced in the form of fine particles of tens to hundreds of nanometers, and that it has excellent purity and can be used as a precursor for lithium iron phosphate cathode materials.

Claims

1. A step of extracting valuable metals from a metal oxide-based waste cathode material and preparing an extraction residue containing phosphorus as an impurity; A step of mixing an iron-containing precipitant that forms a precipitate by combining with phosphorus with the extracted residue and recovering the precipitate; A step of washing and drying the recovered sediment; and A method for producing a raw material for a lithium iron phosphate cathode material, comprising a step of calcining the dried precipitate.

2. In paragraph 1, A method for producing a raw material for a lithium iron phosphate cathode material, wherein the metal oxide-based waste cathode material contains lithium, nickel, manganese and cobalt.

3. In paragraph 1, A method for manufacturing a raw material for a lithium iron phosphate cathode material, wherein the above impurity is derived from an organic phosphorus compound used as an extractant in the extraction of valuable metals.

4. In paragraph 1, A method for producing a raw material for a lithium iron phosphate cathode material, wherein the above-mentioned extract contains 1.7 to 3.9 g / L of Li and 0.01 to 0.09 g / L of P on an elemental basis.

5. In paragraph 4, A method for manufacturing a raw material for a lithium iron phosphate cathode material, wherein the iron-containing precipitant is ferric sulfate.

6. In paragraph 5, A method for producing a raw material for a lithium iron phosphate cathode material, wherein the iron-containing precipitant is mixed so that the iron weight satisfies 8 WP1 to 15 WP1 per 1 L of the extracted residue, based on the weight of element standard phosphorus contained per 1 L of the extracted residue, WP1.

7. In paragraph 1, A method for producing a raw material for a lithium iron phosphate cathode material, wherein the above washing is performed at 40 to 60°C.

8. In paragraph 7, A method for manufacturing a raw material for a lithium iron phosphate cathode material, wherein the above washing is repeated 3 to 5 times.

9. In paragraph 1, A method for producing a raw material for a lithium iron phosphate cathode material, wherein the above calcination is performed at 550 to 650°C in an inert atmosphere.

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