Desulfurization method of sulfur-containing metal salt, battery-grade metal salt, and preparation method and application thereof

Abstract

The application relates to the technical field of secondary battery positive electrode materials, in particular to a desulfurization method of sulfur-containing metal salt, a battery-grade metal salt and a preparation method and application thereof. The desulfurization method of the sulfur-containing metal salt can effectively reduce the sulfur content in the metal salt, has the advantages of good desulfurization effect, low cost, high repeatability, few by-products and the like. Especially, the S impurity content in the material can be effectively reduced to below 800 ppm, meeting the requirement of 800 ppm sulfur impurity of the battery-grade phosphate or carbonate.

Description

Technical Field

[0001] This invention relates to the field of secondary battery cathode material technology, and more specifically, to a desulfurization method for sulfur-containing metal salts, battery-grade metal salts, their preparation methods, and applications. Background Technology

[0002] In recent years, with the increasing impact of fossil fuels on the Earth's environment, clean energy is being widely used as an alternative. Lithium-ion batteries have gained widespread recognition due to their advantages such as high energy density, light weight and small size, no memory effect, long cycle life, and environmental friendliness.

[0003] Lithium iron phosphate, as an electrode cathode material, has a high reversible charge-discharge specific capacity, and also has advantages such as wide availability of raw materials, low pollution, good safety, and long cycle life. It is currently a relatively ideal cathode material for power and energy storage lithium-ion batteries.

[0004] Building upon this, lithium manganese iron phosphate (LiFe) can further improve compaction density and enhance battery energy density. x Mn 1-x Lithium manganese phosphate (LiFePO4) combines the safety and stability of lithium iron phosphate with the high voltage of lithium manganese phosphate. Like lithium iron phosphate, it has an olivine crystal structure containing both manganese and iron, with an adjustable iron-to-manganese ratio, resulting in excellent structural stability. Even if all lithium ions are released during charging, the structure will not collapse. However, lithium manganese iron phosphate has a dual-voltage plateau, exhibiting some instability.

[0005] The cost of lithium iron phosphate (LFP) raw materials depends on upstream lithium, phosphorus, and iron sources. Different raw material processing routes lead to different cost reduction paths. Lithium carbonate, manganese carbonate, iron phosphate, manganese phosphate, and lithium phosphate, as cathode raw materials for LFP / LFP batteries, can reduce the manufacturing cost of lithium-ion batteries.

[0006] Currently, lithium carbonate, manganese carbonate, manganese phosphate, and lithium phosphate are mostly prepared from ores. The sulfuric acid process is the lowest cost method for preparation. Taking lithium phosphate as an example: the mainstream process for lithium extraction from lithium ore is the sulfuric acid process. After transformation roasting and sulfation roasting, the lithium ore is leached and lime is added to adjust the pH to neutral, which can remove a large number of impurity metal ions. After organic extraction, a pure lithium sulfate solution is obtained. After adding phosphorus to adjust the pH, lithium phosphate is obtained. Since lithium sulfate is coated inside the crystal nucleus during the lithium precipitation process, conventional washing methods cannot completely remove the sulfur impurities.

[0007] Existing patent CN112573546A provides a new method for reducing sulfate content in the direct production of lithium carbonate from lithium sulfate and sodium (potassium) carbonate. It uses "pre-precipitation supplementary impurity removal" as an auxiliary method, "reverse feeding, non-circulating mother liquor" and "high-efficiency desorption", which can reduce the sulfate content of industrial-grade lithium carbonate to 0.03% and increase the main content to 2.5N, and reduce the sulfate content of battery-grade lithium carbonate to 0.010% and stabilize the main content at 3N or even reach the 3.5N limit. The reverse feeding and high-efficiency desorption process used in this scheme is only suitable for desulfurization in the preparation of lithium phosphate from lithium sulfate, and is not suitable for desulfurization of high-sulfur lithium phosphate.

[0008] Existing patent CN102249340A provides a method for preparing manganese sulfate, manganese phosphate, and calcium sulfate. The method involves reacting a pure manganese sulfate solution with a calcium phosphate solution under stirring, filtering the reaction product to obtain a calcium sulfate filter cake and a manganese phosphate filtrate. The manganese phosphate filtrate is then distilled under reduced pressure to obtain a saturated manganese phosphate solution, which is cooled and crystallized to obtain manganese phosphate hydrate. This hydrate is then dried and pulverized to obtain manganese phosphate crystals. The calcium sulfate filter cake is washed, dried, and pulverized to obtain calcium sulfate dihydrate. This method generates a large amount of calcium sulfate as a byproduct during the desulfurization process.

[0009] In view of this, the present invention is hereby proposed. Summary of the Invention

[0010] The primary objective of this invention is to provide a desulfurization method for sulfur-containing metal salts. This method addresses the problems of poor desulfurization effect, high cost, poor versatility, and numerous byproducts in existing technologies, and effectively reduces the sulfur content in phosphates or carbonates prepared by the sulfuric acid method.

[0011] The second objective of this invention is to provide a method for preparing battery-grade metal salts, including a desulfurization method for sulfur-containing metal salts. This method is a method for preparing battery-grade metal salts that can effectively reduce the sulfur content in raw materials.

[0012] A third objective of this invention is to provide a battery-grade metal salt with an S content of less than 800 ppm, which meets the requirement that the sulfur impurity content in battery-grade metal salts is less than 800 ppm.

[0013] The fourth objective of this invention is to provide a lithium-ion battery cathode material. By using the aforementioned battery-grade metal salt as a raw material, the cost of removing impurities from the raw material can be effectively reduced, and the production efficiency of the cathode material can be improved.

[0014] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0015] This invention provides a desulfurization method for sulfur-containing metal salts, comprising the following steps:

[0016] (a) Mix a sulfur-containing metal salt with an organic acid to obtain an acid solution; filter the acid solution to obtain a first clear solution;

[0017] Wherein, the sulfur-containing metal salt includes phosphates and / or carbonates, and the organic acid includes oxalic acid and / or benzoic acid;

[0018] (b) Add a precipitant to the first clear liquid, adjust the pH of the solution to be higher than the pH of the sulfur-containing metal salt precipitate, and filter to obtain battery-grade metal salt and second clear liquid.

[0019] Wherein, when the sulfur-containing metal salt is a phosphate, the precipitant is ammonia; when the sulfur-containing metal salt is a carbonate, the precipitant is a mixture of ammonium carbonate and ammonia.

[0020] Further, in step (a), the phosphate includes at least one of lithium phosphate, manganese phosphate, iron phosphate, cobalt phosphate, titanium phosphate, nickel phosphate, magnesium phosphate, and aluminum phosphate.

[0021] Further, in step (a), the carbonate includes at least one of lithium carbonate, manganese carbonate, cobalt carbonate, and nickel carbonate.

[0022] Further, in step (a), the mass ratio of the sulfur-containing metal salt to the organic acid is 1:1 to 50.

[0023] Further, in step (a), the pH of the solution system is 1 to 5 in the step of mixing the sulfur-containing metal salt with the organic acid.

[0024] Furthermore, in step (a), during the mixing process, the temperature of the solution system is 0–50°C.

[0025] Further, in step (a), the mixing time is 1 to 12 hours.

[0026] Further, in step (b), the mass ratio of the amount of precipitant added to the sulfur-containing metal salt is 1 to 10:1.

[0027] Furthermore, in step (b), during the process of adjusting the pH of the solution, the temperature of the solution system is 20–90°C.

[0028] Further, in step (b), during the process of adjusting the pH of the solution, the solution is stirred at a speed of 200 to 600 rpm.

[0029] Furthermore, in step (b), after the step of adjusting the pH of the solution, an aging process of the crystals is also included.

[0030] Preferably, the aging time is 1 to 12 hours.

[0031] Preferably, during the aging process, the temperature of the solution system is 20–90°C.

[0032] Further, in step (b), the pH of the sulfur-containing metal salt precipitate specifically includes at least one of the following characteristics (1) to (12):

[0033] (1) The pH of lithium phosphate precipitation is ≥5.5, preferably 5.5~10;

[0034] (2) The pH of manganese phosphate precipitation is ≥7, preferably 7-10;

[0035] (3) The pH of the ferric phosphate precipitate is ≥2, preferably 2 to 4;

[0036] (4) The pH of cobalt phosphate precipitation is ≥6, preferably 6 to 9;

[0037] (5) The pH of the titanium phosphate precipitate is ≥5, preferably 5 to 8;

[0038] (6) The pH of the nickel phosphate precipitation is ≥6, preferably 6 to 9;

[0039] (7) The pH of magnesium phosphate precipitation is ≥8, preferably 8 to 10;

[0040] (8) The pH of aluminum phosphate precipitation is ≥4, preferably 4 to 7;

[0041] (9) The pH of lithium carbonate precipitation is ≥9, preferably 9 to 11;

[0042] (10) The pH of the manganese carbonate precipitate is ≥6, preferably 6 to 8;

[0043] (11) The pH of cobalt carbonate precipitation is ≥6, preferably 6 to 8;

[0044] (12) The pH of the nickel carbonate precipitate is ≥8, preferably 8 to 10.

[0045] Further, in step (b), the filtration is thermal filtration; preferably, the temperature of the thermal filtration is 50–90°C.

[0046] Furthermore, the desulfurization method for sulfur-containing metal salts further includes:

[0047] (c) The second clear liquid obtained in step (b) is crystallized and concentrated to obtain an ammonium salt of organic acid. After the ammonium salt of organic acid is deaminated, the organic acid and ammonia are recovered and reused.

[0048] Preferably, the crystallization and concentration specifically include: performing a primary crystallization, followed by a secondary crystallization after concentration.

[0049] More preferably, the temperature for the primary crystallization and / or the secondary crystallization is -5℃ to 5℃, and the time is 2 to 24 hours.

[0050] More preferably, the deamination temperature is 90–140°C and the time is 2–24 hours.

[0051] This invention provides a method for preparing battery-grade metal salts, including a desulfurization method for the sulfur-containing metal salts.

[0052] This invention provides a battery-grade metal salt, which is mainly prepared by the aforementioned method for preparing battery-grade metal salt.

[0053] This invention provides a lithium-ion battery cathode material, which is mainly made from the aforementioned battery-grade metal salt.

[0054] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0055] (1) The desulfurization method for sulfur-containing metal salts provided by the present invention can effectively reduce the sulfur content in phosphates and carbonates, and has the advantages of good desulfurization effect, low cost, high repeatability and few by-products.

[0056] (2) The method for preparing battery-grade metal salts provided by the present invention can effectively reduce the content of sulfur impurities in the material.

[0057] (3) The battery-grade metal salt provided by the present invention has an S content of less than 800 ppm, which meets the requirement that the content of sulfur impurities in battery-grade metal salt is less than 800 ppm.

[0058] (4) The lithium-ion battery cathode material provided by the present invention uses the above-mentioned battery-grade metal salt as raw material, which can effectively reduce the cost of raw material impurity removal and improve the production efficiency of cathode material. Attached Figure Description

[0059] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0060] Figure 1 This is a process flow diagram of the desulfurization method for high-sulfur lithium phosphate provided in Embodiment 1 of the present invention;

[0061] Figure 2 This is a process flow diagram of the desulfurization method for high-sulfur lithium carbonate provided in Embodiment 3 of the present invention. Detailed Implementation

[0062] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0063] In a first aspect, the present invention provides a method for desulfurizing sulfur-containing metal salts, comprising the following steps:

[0064] (a) Mix the sulfur-containing metal salt with an organic acid to obtain an acid solution; filter the acid solution to obtain a first clear solution;

[0065] Among them, sulfur-containing metal salts include phosphates and / or carbonates, and organic acids include oxalic acid and / or benzoic acid;

[0066] (b) Add a precipitant to the first clear liquid to adjust the pH of the solution to be higher than the pH of the sulfur-containing metal salt precipitate, and filter to obtain the battery-grade metal salt and the second clear liquid.

[0067] When the sulfur-containing metal salt is a phosphate, the precipitant is ammonia; when the sulfur-containing metal salt is a carbonate, the precipitant is a mixture of ammonium carbonate and ammonia.

[0068] The desulfurization method for sulfur-containing metal salts provided by this invention employs a specific organic acid for dissolution, followed by recrystallization of the metal salt using a precipitant. The organic acid used in this invention does not introduce new impurity ions, facilitating the acquisition of battery-grade metal salts. During the dissolution process, sulfur impurities in the sulfur-containing metal salt are diluted, and during recrystallization, the sulfur impurities in the crystallized battery-grade metal salt precipitate can be controlled at a very low level (less than 800 ppm), reaching the level of battery-grade raw materials. Furthermore, this method is applicable to the desulfurization processes of various phosphates or carbonates.

[0069] In some embodiments, the sulfur-containing metal salts claimed in this invention refer to phosphates or carbonates with a sulfur content greater than 7000 ppm, or even greater than 10000 ppm. The desulfurization method for sulfur-containing metal salts provided by this invention can reduce the sulfur content of phosphates and / or carbonates to battery-grade levels, even with relatively high sulfur impurity content.

[0070] In some embodiments, the phosphates claimed in this invention include all phosphates suitable for desulfurization by this method, including but not limited to at least one of lithium phosphate, manganese phosphate, iron phosphate, cobalt phosphate, titanium phosphate, nickel phosphate, magnesium phosphate, and aluminum phosphate.

[0071] In some embodiments, the carbonates claimed in this invention include all carbonates suitable for desulfurization by this method, including but not limited to at least one of lithium carbonate, manganese carbonate, cobalt carbonate, and nickel carbonate.

[0072] In some embodiments, in step (a), the amount of organic acid used should be sufficient to completely dissolve the sulfur-containing metal salt to be desulfurized. The mass ratio of the sulfur-containing metal salt to the organic acid is 1:1 to 50, for example, any ratio or a range of any two ratios from 1:1, 1:2, 1:5, 1:8, 1:10, 1:15, 1:18, 1:20, 1:25, 1:30, 1:35, 1:38, 1:40, 1:45, and 1:50. Preferably, the organic acid can be an aqueous solution of organic acid with a mass concentration of 5% to 50%, for example, any one value or a range of any two values ​​from 5%, 10%, 11%, 15%, 17%, 20%, 25%, 30%, 33%, 35%, 38%, 40%, 45%, and 50%.

[0073] In some embodiments, in step (a), the step of mixing the sulfur-containing metal salt with the organic acid, the pH of the solution system is controlled to be 1–5, for example, any one of the values ​​1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or a pH range consisting of any two values. Further, the pH of the solution system can be specifically set according to different metal salts to ensure sufficient dissolution of the sulfur-containing metal salt raw material by the organic acid. Examples include lithium phosphate (pH = 1–4.5), manganese phosphate (pH = 1–3.5), iron phosphate (pH = 1–1.5), cobalt phosphate (pH = 1–4), titanium phosphate (pH = 1–3.5), nickel phosphate (pH = 1–5), magnesium phosphate (pH = 1–5), aluminum phosphate (pH = 1–3.5); lithium carbonate (pH = 1–4.5), manganese carbonate (pH = 1–3.5), cobalt carbonate (pH = 1–4), and nickel carbonate (pH = 1–5).

[0074] In some embodiments, in step (a), the mixing temperature is 0 to 50°C, for example, any one value or a range of any two values ​​among 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, and 50°C; the mixing time is 1 to 12 hours, for example, any one value or a range of any two values ​​among 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, and 12 hours.

[0075] In some embodiments, in step (a), the mass ratio of the precipitant added to the sulfur-containing metal salt is 1 to 10:1, for example, any ratio or a range of any two ratios of 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1.

[0076] In some embodiments, during step (b) of adjusting the pH of the solution, the temperature of the solution system is 20 to 90°C, for example, any one value or a range of any two values ​​among 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, and 90°C.

[0077] In some embodiments, during step (b) of adjusting the pH of the solution, the solution is stirred at a speed of 200 to 600 rpm, for example, any one value or a range of any two values ​​from 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, to 600 rpm.

[0078] In some embodiments, step (b) further includes an aging process of the crystals after adjusting the pH of the solution, during which the metal salt crystals crystallize completely. Further, the aging time is 1–12 hours, for example, any single value or a range of any two values ​​from 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, and 12 hours. During the aging process, the temperature of the solution system is 20–90°C, for example, any single value or a range of any two values ​​from 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, and 90°C.

[0079] In some embodiments, in step (b), adjusting the pH of the solution to be higher than the pH of the sulfur-containing metal salt precipitation process refers to adjusting the pH to be higher than the initial precipitation pH of a specific metal salt. To save on the amount of precipitant used, this specifically refers to a preferred pH range. The initial precipitation pH and preferred range values ​​for each different metal salt are described below:

[0080] (1) The pH of lithium phosphate precipitation is ≥5.5, preferably 5.5 to 10, for example any pH value or a range of any two pH values ​​from 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10.

[0081] (2) The pH of manganese phosphate precipitation is ≥7, preferably 7 to 10, for example any pH value or a range of any two pH values ​​from 7, 7.5, 8, 8.5, 9, 9.5, 10.

[0082] (3) The pH of the ferric phosphate precipitation is ≥2, preferably 2 to 4, for example any pH value of 2, 2.5, 3, 3.5, 4 or a range of any two pH values;

[0083] (4) The pH of cobalt phosphate precipitation is ≥6, preferably 6 to 9, for example any pH value or a range of any two pH values ​​from 6, 6.5, 7, 7.5, 8, 8.5, 9.

[0084] (5) The pH of the titanium phosphate precipitation is ≥5, preferably 5 to 8, for example any pH value or a range of any two pH values ​​from 5, 5.5, 6, 6.5, 7, 7.5, 8.

[0085] (6) The pH of the nickel phosphate precipitation is ≥6, preferably 6 to 9, for example any pH value or a range of any two pH values ​​from 6, 6.5, 7, 7.5, 8, 8.5, 9.

[0086] (7) The pH of magnesium phosphate precipitation is ≥8, preferably 8 to 10, for example any pH value of 8, 8.5, 9, 9.5, 10 or a range of any two pH values;

[0087] (8) The pH of the aluminum phosphate precipitation is ≥4, preferably 4 to 7, for example any pH value or a range of any two pH values ​​from 4, 4.5, 5, 5.5, 6, 6.5, 7.

[0088] (9) The pH of the lithium carbonate precipitation is ≥9, preferably 9 to 11, for example any pH value or a range of any two pH values ​​from 9, 9.5, 10, 10.5, to 11.

[0089] (10) The pH of the manganese carbonate precipitation is ≥6, preferably 6 to 8, for example any pH value or a range of any two pH values ​​from 6, 6.5, 7, 7.5, 8.

[0090] (11) The pH of the cobalt carbonate precipitation is ≥6, preferably 6 to 8, for example any pH value of 6, 6.5, 7, 7.5, 8 or a range of any two pH values;

[0091] (12) The pH of the nickel carbonate precipitate is ≥8, preferably 8 to 10, for example any pH value of 8, 8.5, 9, 9.5, 10 or a range of any two pH values.

[0092] In some embodiments, in step (b), the filtration is specifically performed by hot filtration, primarily to increase the solubility of the metal salt and thus the yield. Simultaneously, it avoids the crystallization of organic acids, such as ammonium oxalate, at low temperatures, which could contaminate the metal salt and reduce its purity. Preferably, the hot filtration temperature is 50–90°C, for example, any one of 50°C, 60°C, 70°C, 80°C, or 90°C, or a range consisting of any two of these values.

[0093] In some embodiments, if the ammonium salt of the organic acid used has very low solubility in water and can be deaminated at a relatively low temperature to convert it into an organic acid and recover ammonia, then the above-mentioned desulfurization method for sulfur-containing metal salts also includes a step of reusing the organic acid and ammonia.

[0094] (c) The second clear liquid obtained in step (b) is crystallized and concentrated to obtain ammonium salts of organic acids. After deammoniation of the ammonium salts of organic acids, the organic acids and ammonia are recovered and reused. The deammoniation decomposition equation is: (NH4)2C2O4→H2C2O4+2NH3↑. The recovered organic acids can be used to dissolve sulfur-containing metal salts. The organic acids are designed as a continuously circulating solvent, which can be recycled through a simple deammoniation process, greatly reducing the amount of organic acids used and thus reducing the cost of desulfurization.

[0095] In some implementations, crystallization and concentration specifically include: performing primary crystallization, followed by secondary crystallization after concentration.

[0096] In some embodiments, after secondary crystallization, the solution portion of the crystallization is removed, and the solution is evaporated and condensed to obtain dilute ammonia water. This dilute ammonia water can be used to absorb the recovered ammonia gas to obtain ammonia water with a higher concentration. This high-concentration ammonia water can be reused as a precipitant to further reduce the cost of desulfurization.

[0097] In some embodiments, primary crystallization and / or secondary crystallization are cryogenic freezing crystallization, with the crystallization temperature being -5°C (minus 5°C) to 5°C, for example, any one value or a range of any two values ​​among -5°C, -4°C, -3°C, -2°C, -1°C, 0°C, 1°C, 2°C, 3°C, 4°C, and 5°C; and the time being 2 to 24 hours, for example, any one value or a range of any two values ​​among 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, and 24 hours.

[0098] In some embodiments, the method provided by the present invention can recover organic acids and ammonia by denitrification at a relatively low temperature. Specifically, the denitrification temperature is 90–140°C, for example, any one value or a range of any two values ​​from 90°C, 100°C, 110°C, 120°C, 125°C, 130°C, 135°C, and 140°C, to ensure complete decomposition; the time is 2–24 hours, for example, any one value or a range of any two values ​​from 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, and 24 hours.

[0099] Secondly, the present invention provides a method for preparing battery-grade metal salts, including the desulfurization method of the sulfur-containing metal salts, which can effectively reduce the sulfur impurity content in the material.

[0100] Thirdly, the present invention provides a battery-grade metal salt, mainly prepared by the aforementioned method for preparing battery-grade metal salts. In this battery-grade metal salt, the sulfur content is less than 800 ppm, meeting the requirement that the sulfur impurity content in battery-grade metal salts be less than 800 ppm.

[0101] Fourthly, the present invention provides a lithium-ion battery cathode material, which is mainly made from the aforementioned battery-grade metal salt, and can effectively reduce the cost of raw material impurity removal and improve the production efficiency of cathode materials.

[0102] In this embodiment of the invention, the content of each element is tested using an inductively coupled plasma spectrometer (ICP).

[0103] Example 1

[0104] This application provides a desulfurization method for lithium phosphate with high sulfur content, such as... Figure 1 As shown, it includes the following steps:

[0105] Step 1: Take 50g of high-sulfur lithium phosphate and grind it into a -74μm powder. The composition of lithium phosphate is shown in Table 1.

[0106] Table 1

[0107]

[0108] Step 2: Add 500g of 11wt% oxalic acid solution to the lithium phosphate from Step 1, adjust the pH to 5.2, and stir rapidly at 25℃ and 600rpm until the lithium phosphate is completely dissolved. The reaction equation is: Li3PO4 + H2C2O4 → Li2C2O4 + LiH2PO4, yielding 550g of the first mixture. The composition of the first mixture is shown in Table 2.

[0109] Table 2

[0110]

[0111] Step 3: Filter the first mixture obtained in Step 2 to obtain a second mixture and a trace amount of solid calcium oxalate precipitate. The composition of the second mixture is shown in Table 3.

[0112] Table 3

[0113]

[0114] Step 4: Add 57g of ammonia (20wt%) to the second mixture from Step 3, adjust the pH to 9, and control the temperature at 80℃ and the stirring speed at 300rpm during the pH adjustment process. Aging for 8 hours at 80℃ until lithium phosphate crystallizes completely. The specific equation is Li2C2O4+LiH2PO4+2NH4OH→Li3PO4+(NH4)2C2O4+2H2O, to obtain the first crystallization mixture.

[0115] Step 5: The first crystallization mixture obtained in Step 4 is subjected to hot filtration at a temperature controlled at 80℃. After filtration, a third mixture and wet-based lithium phosphate solid are obtained. The wet-based lithium phosphate is dried to obtain 45.8g of low-sulfur lithium phosphate solid, with a lithium phosphate recovery rate of 99.7%. The composition of the low-sulfur lithium phosphate solid is shown in Table 4.

[0116] Table 4

[0117]

[0118] It can be seen that the sulfur content in the obtained lithium phosphate decreased from 7347 ppm to 333 ppm, which meets the sulfur impurity requirements for battery-grade lithium phosphate.

[0119] Step 6: Freeze the third mixture obtained in Step 5 at 0°C for 3 hours to obtain the second crystallized mixture. After filtering the second crystallized mixture, the first ammonium oxalate crystals and the fourth mixture are obtained.

[0120] Step 7: Concentrate the four mixtures obtained in Step 6 to 20 wt% to obtain the first concentrate. Freeze the first concentrate at 0°C for 3 hours to obtain the third crystallized mixture. After filtering the third crystallized mixture, obtain the second ammonium oxalate crystals and the fifth mixture.

[0121] Step 8: Mix the first ammonium oxalate crystal from Step 6 and the second ammonium oxalate crystal from Step 7, and place them in an oven at 120℃ for deammoniation treatment. After baking for 8 hours, 52.15 g of solid oxalic acid was obtained. The oxalic acid recovery rate was 94.8%. The ammonia nitrogen content of ammonium oxalate and oxalic acid before and after baking is shown in Table 5.

[0122] Table 5

[0123]

[0124] Step 9: Return the oxalic acid solid obtained in Step 8 to Step 2 for reuse. Prepare 500g of 11wt% oxalic acid solution. When preparing the solution, add 2.84g of fresh oxalic acid solid. This solution can be used to dissolve the next batch of lithium phosphate.

[0125] Step 10: Evaporate and condense the fifth mixture from Step 7 to obtain dilute ammonia water. Use this to absorb the ammonia gas from the decomposition of ammonium oxalate in Step 8, and then prepare 35g of 20wt% concentrated ammonia water. Return the prepared concentrated ammonia water to Step 4 and use it as a precipitant.

[0126] Example 2

[0127] This application provides a desulfurization method for high-sulfur iron phosphate, comprising the following steps:

[0128] Step 1: Take 50g of high sulfur content ferric phosphate and grind it into a -74μm powder. The composition of ferric phosphate is shown in Table 6.

[0129] Table 6

[0130]

[0131] Step 2: Add 500g of 20wt% oxalic acid solution to high-sulfur ferric phosphate, adjust the pH to 1.5, and stir rapidly at 600rpm at 30℃ until the ferric phosphate is completely dissolved, yielding 550g of the first mixture. The composition of the first mixture is shown in Table 7.

[0132] Table 7

[0133]

[0134] Step 3: Filter the first mixture obtained in Step 2 to obtain a second mixture and a trace amount of solid calcium oxalate precipitate. The composition of the second mixture is shown in Table 8.

[0135] Table 8

[0136]

[0137] Step 4: Add 31g of ammonia (20wt%) to the second mixture from Step 3, adjust the pH to 2.8, control the temperature at 60℃ and the stirring speed at 300rpm during the pH adjustment process, age for 6h at 60℃ until the ferric phosphate crystals are completely crystallized, and obtain the first crystallized mixture.

[0138] Step 5: The first crystallization mixture obtained in Step 4 is subjected to hot filtration at a temperature controlled at 80℃. After filtration, a third mixture and wet-based ferric phosphate solid are obtained. The wet-based ferric phosphate is dried to obtain 47.17 g of low-sulfur ferric phosphate solid, with a ferric phosphate recovery rate of 94.34%. The composition of the low-sulfur ferric phosphate solid is shown in Table 9.

[0139] Table 9

[0140]

[0141] It can be seen that the S content in the obtained iron phosphate decreased from 14497.23 ppm to 507.14 ppm, which meets the S impurity requirements for battery-grade iron phosphate.

[0142] Step 6: Freeze the third mixture obtained in step 5 at -2℃ for 3 hours to obtain the second crystallized mixture. After filtering the second crystallized mixture, the first ammonium oxalate crystals and the fourth mixture are obtained.

[0143] Step 7: Concentrate the four mixtures obtained in Step 6 to 15 wt% to obtain the first concentrated solution. Freeze the first concentrated solution at -2℃ for 3 hours to obtain the third crystalline mixture. After filtering the third crystalline mixture, obtain the second ammonium oxalate crystals and the fifth mixture.

[0144] Step 8: Mix the first ammonium oxalate crystal from Step 6 and the second ammonium oxalate crystal from Step 7, and place them in an oven at 130℃ for deammoniation treatment. After baking for 6.5 hours, 94.71 g of solid oxalic acid was obtained. The oxalic acid recovery rate was 94.71%. The ammonia nitrogen content of ammonium oxalate and oxalic acid before and after baking is shown in Table 10.

[0145] Table 10

[0146]

[0147] Step 9: Return the oxalic acid solid obtained in Step 8 to Step 2 for reuse. Prepare 500g of 11wt% oxalic acid solution. When preparing the solution, add 5.29g of fresh oxalic acid solid. This solution can be used to dissolve the next batch of ferric phosphate.

[0148] Step 10: Evaporate and condense the fifth mixture from Step 7 to obtain dilute ammonia water, which is used to absorb the ammonia gas from the decomposition of ammonium oxalate in Step 8, and then prepare 21g of concentrated ammonia water with a concentration of 20wt%. The prepared concentrated ammonia water is returned to Step 4 and used as a precipitant.

[0149] Example 3

[0150] This application provides a desulfurization method for lithium carbonate with high sulfur content, such as... Figure 2 As shown, it includes the following steps:

[0151] Step 1: Take 50g of high-sulfur lithium carbonate and grind it into a -74μm powder. The composition of lithium carbonate is shown in Table 11.

[0152] Table 11

[0153]

[0154] Step 2: Add 500g of 11wt% oxalic acid solution to the lithium carbonate from Step 1, adjust the pH to 5.17, and stir rapidly at 600rpm at 25℃ until the lithium carbonate is completely dissolved. The reaction equation is Li2CO3 + H2C2O4 → Li2C2O4 + H2O + CO2↑, yielding 550g of the first mixture. The composition of the first mixture is shown in Table 12.

[0155] Table 12

[0156]

[0157] Step 3: Filter the first mixture obtained in Step 2 to obtain a second mixture and a trace amount of solid calcium oxalate precipitate. The composition of the second mixture is shown in Table 13.

[0158] Table 13

[0159]

[0160] Step 4: Add 75g of ammonia (20wt%) and 100g of ammonium carbonate to the second mixture from Step 3, adjust the pH to 10, and control the temperature at 80℃ and the stirring speed at 200rpm during the pH adjustment process. Aging is carried out for 8 hours at 80℃ until lithium carbonate crystallizes completely. The specific equation is: Li2C2O4 + (NH4)2CO3 → Li2CO3 + (NH4)2C2O4, to obtain the first crystallization mixture.

[0161] Step 5: The first crystallization mixture obtained in Step 4 is subjected to hot filtration at a temperature controlled at 80℃. After filtration, a third mixture and wet-based lithium carbonate solid are obtained. The wet-based lithium carbonate is dried to obtain 43.21g of low-sulfur lithium carbonate solid, with a lithium carbonate recovery rate of 86.42%. The composition of the low-sulfur lithium carbonate solid is shown in Table 14.

[0162] Table 14

[0163]

[0164] It can be seen that the S content in the obtained lithium carbonate decreased from 10193.01ppm to 707.33ppm, which meets the S impurity requirements for battery-grade lithium carbonate.

[0165] Step 6: Freeze the third mixture obtained in Step 5 at 0°C for 3 hours to obtain the second crystallization mixture. After filtering the second crystallization mixture, the first ammonium oxalate crystals and the fourth mixture are obtained.

[0166] Step 7: Concentrate the four mixtures obtained in Step 6 to 20 wt% to obtain the first concentrated solution. Freeze the first concentrated solution at 0℃ for 3 hours to obtain the third crystalline mixture. After filtering the third crystalline mixture, obtain the second ammonium oxalate crystals and the fifth mixture.

[0167] Step 8: Mix the first ammonium oxalate crystal from Step 6 and the second ammonium oxalate crystal from Step 7, and place them in an oven at 110℃ for deammoniation treatment. After baking for 16 hours, 51.75 g of solid oxalic acid was obtained. The oxalic acid recovery rate was 94.09%. The ammonia nitrogen content of ammonium oxalate and oxalic acid before and after baking is shown in Table 15.

[0168] Table 15

[0169]

[0170] Step 9: Return the oxalic acid solid obtained in Step 8 to Step 2 for reuse. Prepare 500g of 11wt% oxalic acid solution. When preparing the solution, add 3.25g of fresh oxalic acid solid. This solution can be used to dissolve the next batch of lithium carbonate.

[0171] Step 10: Evaporate and condense the fifth mixture from Step 7 to obtain dilute ammonia water. After absorbing the ammonia gas from the decomposition of ammonium oxalate in Step 8, prepare 45g of 20wt% concentrated ammonia water. Return the prepared concentrated ammonia water to Step 4 and use it as a precipitant.

[0172] Example 4

[0173] This application provides a desulfurization process for cathode raw materials in new energy batteries, including the following steps:

[0174] Step 1: Take 50g of high-sulfur lithium carbonate and grind it into a -74μm powder. The composition of lithium carbonate is shown in Table 16.

[0175] Table 16

[0176]

[0177] Step 2: Add 500g of 17wt% benzoic acid solution to high-sulfur lithium carbonate, adjust the pH to 4.95, and stir rapidly at 600rpm at 25℃ until the lithium carbonate is completely dissolved, obtaining 550g of the first mixture. The composition of the first mixture is shown in Table 17.

[0178] Table 17

[0179]

[0180] Step 3: Filter the first mixture from step 2 to obtain a second mixture and trace amounts of calcium benzoate. The composition of the second mixture is shown in Table 18.

[0181] Table 18

[0182]

[0183]

[0184] Step 4: Add 75g of ammonia (20wt%) and 100g of ammonium carbonate to the second mixture described in Step 3, adjust the pH to 10, control the temperature at 80℃ and the stirring speed at 200rpm during the pH adjustment process, and age for 8 hours (aging temperature controlled at 80℃) until lithium carbonate crystallizes completely to obtain the first crystallized mixture.

[0185] Step 5: The first crystallization mixture obtained in Step 4 is subjected to hot filtration at a controlled temperature of 80℃. After filtration, a third mixture and wet-based lithium carbonate solid are obtained. The wet-based lithium carbonate is dried to obtain 43.78g of low-sulfur lithium carbonate solid, with a lithium carbonate recovery rate of 87.53%. The composition of the low-sulfur lithium carbonate solid is shown in Table 19.

[0186] Table 19

[0187]

[0188] As can be seen, the sulfur impurity in lithium carbonate decreased from 11156.74 ppm to 724.21 ppm, meeting the sulfur impurity requirements for battery-grade lithium carbonate.

[0189] Step 6: Freeze the third mixture obtained in Step 5 at 0°C for 3 hours to obtain the second crystallized mixture. After filtering the second crystallized mixture, the first ammonium benzoate crystals and the fourth mixture are obtained.

[0190] Step 7: Concentrate the four mixtures described in Step 6 to 20 wt% to obtain the first concentrated solution. Freeze the first concentrated solution at 0°C for 3 hours to obtain the third crystalline mixture. After filtering the third crystalline mixture, obtain the second ammonium benzoate crystals and the fifth mixture.

[0191] Step 8: Mix the first ammonium benzoate crystal from Step 6 and the second ammonium benzoate crystal from Step 7, and place them in an oven at 110℃ for deammoniation treatment. After baking for 16 hours, 81.6 g of solid benzoic acid was obtained, and the oxalic acid recovery rate was 96.1%. The ammonia nitrogen content of ammonium benzoate and benzoic acid before and after baking is shown in Table 20.

[0192] Table 20

[0193]

[0194]

[0195] Step 9: Return the benzoic acid solid from Step 8 to Step 2 for reuse, and prepare 500g of benzoic acid solution with a concentration of 17wt%. When preparing the solution, add 3.4g of fresh benzoic acid solid for use in the next batch of lithium carbonate dissolution.

[0196] Step 10: Evaporate and condense the fifth mixture from Step 7 to obtain dilute ammonia water, which is used to absorb the ammonia gas from the decomposition of ammonium benzoate in Step 8, and then prepare 45g of 20wt% concentrated ammonia water. The prepared concentrated ammonia water is returned to Step 4 and used as a precipitant.

[0197] Comparative Example 1

[0198] Under the same process conditions, the oxalic acid in Example 1 was replaced with the same mass of acetic acid.

[0199] Step 5 yielded 45.1 g of lithium phosphate solid, with a lithium phosphate recovery rate of 98.2%. The composition of the low-sulfur lithium phosphate solid is shown in Table 21.

[0200] Table 21

[0201]

[0202] After acetic acid dissolves sulfur-containing metal salts, the sulfur impurity in the recrystallized lithium phosphate decreases from 7347 ppm to 396 ppm, meeting the sulfur impurity requirements for battery-grade lithium phosphate.

[0203] However, through steps 6 and 7, the two-stage crystallization process did not yield ammonium acetate crystals, making it impossible to achieve the reuse of organic acid (acetic acid) and ammonia through a simple crystallization process.

[0204] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for desulfurizing sulfur-containing metal salts, characterized in that, Includes the following steps: (a) Mix a sulfur-containing metal salt with an organic acid to obtain an acid solution; filter the acid solution to obtain a first clear solution; Wherein, the sulfur-containing metal salt includes phosphates and / or carbonates, and the organic acid includes oxalic acid and / or benzoic acid; The phosphate includes at least one of lithium phosphate, manganese phosphate, iron phosphate, cobalt phosphate, titanium phosphate, nickel phosphate, magnesium phosphate, and aluminum phosphate. The carbonate includes at least one of lithium carbonate, manganese carbonate, cobalt carbonate, and nickel carbonate; (b) Add a precipitant to the first clear liquid, adjust the pH of the solution to be higher than the pH of the sulfur-containing metal salt precipitate, and filter to obtain battery-grade metal salt and second clear liquid; Wherein, when the sulfur-containing metal salt is a phosphate, the precipitant is ammonia; when the sulfur-containing metal salt is a carbonate, the precipitant is a mixture of ammonium carbonate and ammonia.

2. The desulfurization method for sulfur-containing metal salts according to claim 1, characterized in that, In step (a), at least one of the following features (1) to (4) is included: (1) The mass ratio of the sulfur-containing metal salt to the organic acid is 1:(1~50); (2) In the step of mixing sulfur-containing metal salts with organic acids, the pH of the solution system is 1~5; (3) During the mixing process, the temperature of the solution system is 0~50℃; (4) The mixing time is 1~12h.

3. The desulfurization method for sulfur-containing metal salts according to claim 1, characterized in that, In step (b), at least one of the following features (1) to (3) is included: (1) The mass ratio of the amount of the precipitant added to the sulfur-containing metal salt is (1~10):1; (2) During the process of adjusting the pH of the solution, the temperature of the solution system is 20~90℃; (3) During the process of adjusting the pH of the solution, the solution is stirred at a speed of 200~600 rpm.

4. The desulfurization method for sulfur-containing metal salts according to claim 1, characterized in that, In step (b), after the step of adjusting the pH of the solution, there is also a crystal aging process; the aging time is 1 to 12 hours.

5. The desulfurization method for sulfur-containing metal salts according to claim 4, characterized in that, In step (b), during the aging process, the temperature of the solution system is 20~90℃.

6. The desulfurization method for sulfur-containing metal salts according to claim 1, characterized in that, In step (b), the pH of the sulfur-containing metal salt precipitate comprises at least one of the following characteristics (1) to (12): (1) The pH of lithium phosphate precipitation is ≥5.5; (2) The pH of manganese phosphate precipitation is ≥7; (3) The pH of the ferric phosphate precipitate is ≥2; (4) The pH of cobalt phosphate precipitation is ≥6; (5) The pH of titanium phosphate precipitate is ≥5; (6) Nickel phosphate precipitation occurs at a pH ≥ 6; (7) The pH of magnesium phosphate precipitation is ≥8; (8) The pH of aluminum phosphate precipitation is ≥4; (9) The pH of lithium carbonate precipitation is ≥9; (10) The pH of manganese carbonate precipitation is ≥6; (11) The pH of cobalt carbonate precipitation is ≥6; (12) The pH of nickel carbonate precipitation is ≥8.

7. The desulfurization method for sulfur-containing metal salts according to claim 6, characterized in that, In step (b), the pH of the sulfur-containing metal salt precipitate comprises at least one of the following characteristics (1) to (12): (1) The pH of lithium phosphate precipitation is 5.5~10; (2) The pH of manganese phosphate precipitation is 7-10; (3) The pH of ferric phosphate precipitation is 2-4; (4) The pH of cobalt phosphate precipitation is 6-9; (5) The pH of titanium phosphate precipitation is 5-8; (6) The pH of nickel phosphate precipitation is 6-9; (7) The pH of magnesium phosphate precipitation is 8-10; (8) The pH of aluminum phosphate precipitation is 4~7; (9) The pH of lithium carbonate precipitation is 9-11; (10) The pH of manganese carbonate precipitation is 6-8; (11) The pH of cobalt carbonate precipitation is 6-8; (12) The pH of nickel carbonate precipitation is 8~10.

8. The desulfurization method for sulfur-containing metal salts according to claim 1, characterized in that, In step (b), the filtration is thermal filtration; the temperature of the thermal filtration is 50~90℃.

9. The desulfurization method for sulfur-containing metal salts according to claim 1, characterized in that, Also includes: (c) The second clear liquid obtained in step (b) is crystallized and concentrated to obtain an ammonium salt of organic acid. After the ammonium salt of organic acid is deaminated, the organic acid and ammonia are recovered and reused.

10. The desulfurization method for sulfur-containing metal salts according to claim 9, characterized in that, The crystallization and concentration specifically include: performing primary crystallization, followed by secondary crystallization after concentration.

11. The desulfurization method for sulfur-containing metal salts according to claim 10, characterized in that, The temperature for the primary crystallization and / or the secondary crystallization is -5℃ to 5℃, and the time is 2 to 24 hours.

12. The desulfurization method for sulfur-containing metal salts according to claim 9, characterized in that, The deamination temperature is 90~140℃, and the time is 2~24h.

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