Method for preparing iron phosphate for batteries and use thereof

Abstract

The application discloses a method for preparing iron phosphate for batteries and application thereof, and relates to the technical field of resource recovery and preparation. The method for preparing the iron phosphate for batteries can be used for treating the anhydrous iron phosphate dust collection material with high water content and incomplete crystal transformation, and utilizes the phosphoric acid aqueous solution to leach the iron phosphate in the iron phosphate dust collection material. 3+ is reduced to Fe 2+ After that, the porous iron phosphate is synthesized by combining a surface dispersing agent and a segmented oxidation aging treatment, and the iron phosphate for batteries is obtained through calcination, so that the recycling of the dust collection material and the recycling of the iron phosphate are realized.

Description

Technical Field

[0001] This disclosure relates to the field of resource recycling technology, and in particular to a method for preparing iron phosphate for batteries and its application. Background Technology

[0002] With the rapid expansion of the new energy industry, the demand for battery materials is increasing year by year. Lithium iron phosphate (LFP) cathode materials are one of the important cathode materials due to their abundant raw material sources, low price, high capacity, and good safety. As an important precursor material for LFP, the chemical composition, structure, morphology, and particle size of iron phosphate largely determine the overall performance of LFP cathode materials.

[0003] Currently, the industrial production process for iron phosphate typically involves wet synthesis to obtain iron phosphate dihydrate. During production, sintering converts the dihydrate to anhydrous iron phosphate, while simultaneously removing as much H2O as possible. However, during sintering, some fine iron phosphate particles are easily drawn away by the blower and enter the bag filter. This results in incomplete sintering, and the particles readily combine with water molecules in the exhaust gas, producing iron phosphate with high water content—commonly known in the industry as iron phosphate dust collector material. Its yield is approximately 3% to 7% of the qualified product. The high water content in iron phosphate affects the Li / P ratio in lithium iron phosphate production, leading to reduced battery capacity and cycle performance. Therefore, iron phosphate with high water content and incomplete crystallization cannot be used as a normal product. Furthermore, the lithium iron phosphate production process requires grinding and crushing the iron phosphate. Some iron phosphate particles are large and difficult to crush, potentially causing clogging in subsequent spraying processes.

[0004] Therefore, it is important to provide a method for preparing ferric phosphate with better sand-milling performance using ferric phosphate dust collectors. Summary of the Invention

[0005] This disclosure aims to at least address one of the technical problems existing in the prior art. To this end, this disclosure proposes a method for preparing iron phosphate for batteries.

[0006] This disclosure also proposes the application of the above method in the recovery of iron phosphate dust.

[0007] A method for preparing iron phosphate for batteries according to a first aspect of this disclosure includes the following steps:

[0008] 1) Prepare a first mixture of ferric phosphate dust and phosphoric acid aqueous solution, leach it, and then perform a first solid-liquid separation to obtain a first liquid phase; prepare a second mixture of the first liquid phase and elemental iron, react it, and then perform a second solid-liquid separation to obtain a second liquid phase;

[0009] The leaching temperature is not higher than 50°C; the molar ratio of phosphorus to elemental iron in the phosphoric acid aqueous solution is 1:1.05~1.2;

[0010] 2) Prepare a third mixture of the second liquid phase and the surface dispersant, and subject the third mixture to a segmented oxidative aging treatment; obtain a solid phase through a third solid-liquid separation; calcine the solid phase to obtain the iron phosphate;

[0011] The surface dispersant includes at least one of cationic surfactants, anionic surfactants, and nonionic surfactants; the cationic surfactant includes quaternary ammonium surfactants; the anionic surfactant includes at least one of sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS); and the nonionic surfactant includes at least one of polyether surfactants and hydroxyl surfactants.

[0012] The number of segments in the segmented oxidation aging treatment is N segments, where N is a positive integer not less than 2;

[0013] The roasting temperature is not lower than 580℃; the roasting time is not lower than 2 hours.

[0014] The method for preparing battery-grade iron phosphate according to this disclosure has at least the following beneficial effects:

[0015] This method for preparing battery-grade iron phosphate can be used to process anhydrous iron phosphate dust with high water content and incomplete crystallization, enabling the recycling of the dust and the recovery of iron phosphate, thus reducing production costs. The iron phosphate in the dust dissolves in the phosphoric acid solution at low temperatures, avoiding spontaneous precipitation caused by excessively high leaching temperatures, which affects product uniformity and results in a product BET < 3. Furthermore, it utilizes elemental iron to consume H+. + At the same time, Fe 3+ Reduced to Fe 2+ By controlling the amount of elemental iron added, the yield of phosphorus (P) was effectively guaranteed, costs were reduced, and the Fe / P imbalance problem in ferric phosphate was avoided. Further, the porosity and milling performance of ferric phosphate were improved by utilizing selected surface dispersants and staged oxidation aging treatment, resulting in the synthesis of porous ferric phosphate. During the first stage of oxidation aging, the surface dispersant helped prevent spontaneous precipitation at high temperatures, thus avoiding the formation of blocky products. The small amount of synthesized ferric phosphate also served as a seed crystal, increasing the precipitation rate. Finally, calcination yielded a qualified ferric phosphate product for batteries.

[0016] According to some embodiments of this disclosure, the ferric phosphate dust is derived from a rotary kiln. By mass percentage, the ferric phosphate dust contains 1%–5% H₂O; 33%–36% Fe; and 18.5%–20.5% P. The content of impurity elements is 0–100 ppm.

[0017] According to some embodiments of this disclosure, the ratio of the ferric phosphate dust collector to the phosphoric acid aqueous solution is 20 g to 200 g: 1 L. For example, it can be 20 g: 1 L, 30 g: 1 L, 40 g: 1 L, 50 g: 1 L, 60 g: 1 L, 70 g: 1 L, 80 g: 1 L, 90 g: 1 L, 100 g: 1 L, 110 g: 1 L, 120 g: 1 L, 130 g: 1 L, 140 g: 1 L, 150 g: 1 L, 160 g: 1 L, 170 g: 1 L, 180 g: 1 L, 190 g: 1 L, or 200 g: 1 L.

[0018] According to some embodiments of this disclosure, the phosphoric acid concentration in the phosphoric acid aqueous solution is 30% to 50%. For example, it can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or 50%, where phosphoric acid concentration refers to the mass percentage concentration of phosphoric acid in the phosphoric acid aqueous solution. If the phosphoric acid concentration is too high, it can easily lead to the spontaneous precipitation of Fe and P elements, affecting the uniformity of the product. If the phosphoric acid concentration is too low, it can easily lead to a decrease in the dissolution rate and amount of elemental iron, affecting production.

[0019] According to some embodiments of this disclosure, the mass ratio of the ferric phosphate dust collector to the elemental iron is 0.06~0.6:1. If the amount of ferric phosphate dust collector is too high, it can easily lead to a lower BET ratio in the product. For example, the ratio can be 0.06:1, 0.08:1, 0.1:1, 0.12:1, 0.14:1, 0.16:1, 0.18:1, 0.2:1, 0.22:1, 0.24:1, 0.26:1, 0.28:1, 0.3:1, 0.32:1, 0.34:1, 0.36:1, 0.38:1, 0.4:1, 0.42:1, 0.46:1, 0.48:1, 0.5:1, 0.52:1, 0.54:1, 0.56:1, 0.58, or 0.6:1.

[0020] According to some embodiments of this disclosure, the elemental iron is derived from at least one of iron sheets and iron powder.

[0021] According to some embodiments of this disclosure, the leaching temperature is 20°C to 50°C. For example, it can be 25°C, 30°C, 35°C, 40°C, 45°C, or 50°C.

[0022] According to some embodiments of this disclosure, the leaching treatment time is no more than 4 hours.

[0023] According to some embodiments of this disclosure, the leaching treatment time is 1.5 h to 4 h. For example, it can be 1.5 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h, or 4 h.

[0024] According to some embodiments of this disclosure, the molar ratio of phosphorus to elemental iron in the phosphoric acid aqueous solution is 1:1.05 to 1.2. For example, it can be 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, 1:1.1, 1:1.11, 1:1.12, 1:1.13, 1:1.14, 1:1.15, 1:1.16, 1:1.17, 1:1.18, 1:1.19, or 1:1.2.

[0025] According to some embodiments of this disclosure, the reaction temperature of the reaction in step 1) is 50°C to 90°C. For example, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C.

[0026] According to some embodiments of this disclosure, the reaction time of the reaction in step 1) is 6 h to 10 h. For example, it can be 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, or 10 h.

[0027] According to some embodiments of this disclosure, the concentration of iron in the second liquid phase is 110 g / L to 240 g / L. For example, it can be 110 g / L, 120 g / L, 130 g / L, 140 g / L, 150 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L, 220 g / L, 230 g / L, or 240 g / L. This facilitates control of the viscosity of the reaction solution, which is beneficial for subsequent reactions and prevents the subsequent product from becoming too dense, resulting in a lower BET (Best Efficacy) level.

[0028] According to some embodiments of this disclosure, the mass ratio of iron to the surface dispersant in the third mixture is 1:0.001~0.005; optionally, the mass ratio of iron to the surface dispersant in the third mixture is 1:0.0014~0.0045. For example, it can be 1:0.0014, 1:0.0016, 1:0.0018, 1:0.002, 1:0.0022, 1:0.0024, 1:0.0026, 1:0.0028, 1:0.003, 1:0.0032, 1:0.0034, 1:0.0036, 1:0.0038, 1:0.004, 1:0.0042, or 1:0.0045.

[0029] According to some embodiments of this disclosure, the quaternary ammonium surfactant contains hydroxyl groups. The quaternary ammonium surfactant includes at least one of SRC-JX-1 and SRC-JX-3.

[0030] According to some embodiments of this disclosure, the polyether surfactant includes PPEA-15.

[0031] According to some embodiments of this disclosure, the hydroxyl surfactant includes SRC-JX-2.

[0032] According to some embodiments of this disclosure, the number of segments in the segmented oxidation aging treatment is 2 to 6. For example, it can be 2, 3, 4, 5, or 6.

[0033] According to some embodiments of this disclosure, the segmented oxidation aging process includes one stage of oxidation aging process to N stages of oxidation aging process;

[0034] Each stage of the segmented oxidation and aging process includes: adding an oxidant and then aging. The aging process in each stage is designed to prevent a decrease in the product's BET (Brightness Equivalent Tolerance) and a reduction in its milling performance.

[0035] According to some embodiments of this disclosure, the oxidant includes at least one selected from hydrogen peroxide, oxygen, ozone, and air. If the oxidant is oxygen, ozone, or air, it can be directly introduced into the third mixture during use.

[0036] According to some embodiments of this disclosure, the oxidant and Fe... 2+ The oxidant is added in excess of 10% to 20%, meaning the total molar amount of the oxidant is equal to the amount of Fe in the third mixture. 2+ The amount of molar amount required for the reaction to complete is 110% to 120%. This ensures oxidation efficiency. For example, it can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%.

[0037] According to some embodiments of this disclosure, the hydrogen peroxide has a mass percentage concentration of 27.5% or higher.

[0038] According to some embodiments of this disclosure, the mass percentage concentration of the hydrogen peroxide is 27.5% to 35%. For example, it can be 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5%, or 35%.

[0039] According to some embodiments of this disclosure, the temperature of the segmented oxidation aging treatment is 50℃~90℃. For example, it can be 50℃, 52℃, 54℃, 56℃, 58℃, 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃, or 90℃.

[0040] According to some embodiments of this disclosure, the first-stage oxidative aging treatment includes adding the oxidant to remove 20% to 50% of the Fe in the third mixture. 2+ Oxidized to Fe 3+ The aging process takes 1 to 6 hours. The remaining multi-stage oxidation aging process includes adding the oxidant to remove the remaining Fe... 2+ Oxidized to Fe 3+ and perform the aforementioned aging treatment. For example: in the aforementioned oxidative aging treatment, Fe... 2+ The total oxidation amount can be 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, or 50%.

[0041] According to some embodiments of this disclosure, the aging time for each oxidation aging treatment is 1 h to 6 h. For example, it can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h, 4 h, 4.2 h, 4.4 h, 4.6 h, 4.8 h, 5 h, 5.2 h, 5.4 h, 5.6 h, 5.8 h, or 6 h.

[0042] According to some embodiments of this disclosure, the segmented oxidation aging process is divided into two segments, including a first-stage oxidation aging process and a second-stage oxidation aging process.

[0043] The first stage of oxidation aging treatment includes adding the oxidant to reduce 20% to 50% of the Fe in the third mixture.2+ Oxidized to Fe 3+ The aging process takes 1 to 6 hours.

[0044] The two-stage oxidation aging process includes continuing to add the oxidant to remove the remaining Fe. 2+ Oxidized to Fe 3+ The aging process takes 1 to 6 hours.

[0045] According to some embodiments of this disclosure, the segmented oxidation aging process is divided into three segments, including a first-stage oxidation aging process, a second-stage oxidation aging process, and a third-stage oxidation aging process.

[0046] The first stage of oxidation aging treatment includes adding the oxidant to reduce 20% to 45% of the Fe in the third mixture. 2+ Oxidized to Fe 3+ The aging process takes 1 to 6 hours.

[0047] The two-stage oxidation aging treatment includes continuing to add the oxidant to reduce 30%~50% of the Fe... 2+ Oxidized to Fe 3+ The aging process takes 1 to 6 hours.

[0048] The three-stage oxidation aging process includes continuing to add the oxidant to remove the remaining Fe. 2+ Oxidized to Fe 3+ The aging process takes 1 to 6 hours.

[0049] According to some embodiments of this disclosure, the total aging time in the segmented oxidation aging process is 3h to 18h. For example, it can be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h, 16h, 16.5h, 17h, 17.5h, or 18h.

[0050] According to some embodiments of this disclosure, the calcination temperature is 580°C to 750°C.

[0051] According to some embodiments of this disclosure, the roasting temperature is 590℃~740℃. For example, it can be 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃ or 740℃.

[0052] According to some embodiments of this disclosure, the roasting time is 2 h to 4 h. For example, it can be 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h, or 4 h.

[0053] According to some embodiments of this disclosure, step 2) further includes a pre-calcination treatment. The pre-calcination treatment includes at least one of washing and drying.

[0054] According to some embodiments of this disclosure, the first solid-liquid separation, the second solid-liquid separation, and the third solid-liquid separation each independently include at least one of filtration, centrifugation, vacuum filtration, and pressure filtration.

[0055] Application of the above-described method according to the second aspect of this disclosure in the recovery of iron phosphate dust.

[0056] Other features and advantages of this disclosure will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing this disclosure. Attached Figure Description

[0057] Figure 1 A flowchart of a method for preparing iron phosphate for batteries;

[0058] Figure 2 The XRD pattern of the iron phosphate dust collector is shown.

[0059] Figure 3 The XRD pattern of anhydrous ferric phosphate prepared in Example 1 is shown below.

[0060] Figure 4A SEM image of anhydrous ferric phosphate prepared in Example 1 (scale bar: 4 micrometers).

[0061] Figure 4B SEM image of anhydrous ferric phosphate prepared in Example 1 (scale bar: 40 micrometers).

[0062] Figure 5 SEM image of ferric phosphate dihydrate prepared in Comparative Example 2 (scale bar is 4 micrometers).

[0063] Figure 6 The particle size distribution diagram is shown for the anhydrous ferric phosphate prepared in Example 1.

[0064] Figure 7 The image shows a cross-sectional SEM image of anhydrous ferric phosphate prepared in Example 1.

[0065] Figure 8 Anhydrous ferric phosphate prepared in Example 1 and Comparative Example 2 were subjected to the same milling conditions. 50The graph showing the change of -t. Detailed Implementation

[0066] The following will describe the concept and technical effects of this disclosure clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of this disclosure.

[0067] Unless otherwise specified, all reagents used are commercially available products.

[0068] In the description of this disclosure, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion, such that a process, method, or product that includes a series of steps or units is not necessarily limited to those steps or units that are expressly listed, but may include other steps or units that are not expressly listed or that are inherent to such processes, methods, or products.

[0069] When a numerical range is disclosed in this disclosure, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed in this disclosure should be understood to include any and all subranges to which they are incorporated.

[0070] The term "not higher than" means less than or equal to, and should be understood to include the number itself.

[0071] The term "not less than" means greater than or equal to, and should be understood to include the number itself.

[0072] Unless otherwise specified, "about" or "around" in this disclosure indicate an allowable error within ±5%.

[0073] In the embodiments of this disclosure, the iron phosphate dust collector material used is sourced from Hunan Bangpu Recycling Technology Co., Ltd.; by mass percentage, the iron phosphate dust collector material contains 3.2% H2O, 35.3% Fe, 20.1% P, and the contents of other impurity elements (such as Ca, Mg, Na, etc.) are all less than 10 ppm.

[0074] The trace element content in the following solutions, ferric phosphate dust, and anhydrous ferric phosphate was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The precipitate was first completely dissolved in an acidic solution before measurement, and the iron content in the solution was determined by potassium dichromate titration. The phosphorus content in the ferric phosphate precipitate was determined by the quinomolybdate-limonene gravimetric method, and the molar ratio of Fe to P was calculated.

[0075] Example 1

[0076] This example provides a method for preparing iron phosphate for batteries, the steps of which are as follows:

[0077] (1) Leaching:

[0078] Ferric phosphate dust collector was mixed with 50% phosphoric acid aqueous solution at a material-to-liquid ratio of 50 g: 1 L and leached at 50℃ for 2 h, achieving a solubility greater than 99%. Solid-liquid separation was performed, and excess iron powder (approximately 1.15 times the molar amount of P in the phosphoric acid aqueous solution, with a mass ratio of ferric phosphate dust collector to iron powder of 0.09:1) was added to the liquid phase. The mixture was reacted at 60℃ for 6 h, filtered, and the leachate was obtained. The leachate was diluted to a Fe concentration of approximately 110 g / L to obtain the reaction solution.

[0079] (2) Ferric phosphate precipitation and crystallization:

[0080] In the multi-stage oxidation aging treatment (multi-stage precipitation), hydrogen peroxide and Fe... 2+ Add 10%–20% excess hydrogen peroxide to ensure oxidation reaction efficiency. In the first-stage, second-stage, and third-stage oxidation aging treatments, the Fe content in the reactants is confirmed by potassium dichromate titration before the aging treatment. 2+ Total oxidation amount.

[0081] (2-1) Add the reaction solution to the reaction vessel, heat it to 90°C, and then add the surface dispersant SDS to obtain a mixed solution.

[0082] The mass ratio of SDS to iron in the reaction solution is 0.001495:1.

[0083] (2-2) First-stage oxidation aging treatment: At 90℃, 30% hydrogen peroxide was added to the mixed solution to control Fe. 2+ The total oxidation amount was 20%, and the temperature was maintained for 3 hours for aging.

[0084] (2-3) Second-stage oxidation aging treatment: At 90℃, continue to add 30% hydrogen peroxide to control Fe 2+ The total oxidation amount was 70%, and the temperature was maintained for 3 hours for aging.

[0085] (2-4) Three-stage oxidation aging treatment: At 90℃, continue to add 30% hydrogen peroxide to control Fe 2+ The total oxidation amount was 100%, and the mixture was aged at this temperature for 3 hours. After the reaction was completed, the mixture was filtered to separate ferric phosphate dihydrate and the filtrate. The filtrate can be used to dilute concentrated phosphoric acid and the leachate.

[0086] (2-5) Sintering: After two-stage countercurrent washing and drying, ferric phosphate dihydrate was calcined at 600℃ for 2 h to obtain anhydrous ferric phosphate.

[0087] Example 2

[0088] This example provides a method for preparing iron phosphate for batteries, the steps of which are as follows:

[0089] (1) Leaching:

[0090] Ferric phosphate dust collector was mixed with 50% phosphoric acid aqueous solution at a material-to-liquid ratio of 50 g: 1 L and leached at 40℃ for 2 h, achieving a solubility greater than 99%. Solid-liquid separation was performed, and excess iron powder (approximately 1.05 times the molar amount of P in the phosphoric acid aqueous solution, with a mass ratio of ferric phosphate dust collector to iron powder of 0.25:1) was added to the liquid phase. The mixture was reacted at 60℃ for 8 h, filtered, and the leachate was obtained. The leachate was diluted to a Fe concentration of approximately 160 g / L to obtain the reaction solution.

[0091] (2) Ferric phosphate precipitation and crystallization:

[0092] In the multi-stage oxidation aging process, hydrogen peroxide and Fe... 2+ Add 10%–20% excess hydrogen peroxide to ensure oxidation reaction efficiency. In the first-stage, second-stage, and third-stage oxidation aging treatments, the Fe content in the reactants is confirmed by potassium dichromate titration before the aging treatment. 2+ Total oxidation amount.

[0093] (2-1) Add the reaction solution to the reaction vessel, heat it to 90°C, and then add the surface dispersant SDBS to obtain a mixed solution.

[0094] The mass ratio of SDBS to iron in the reaction solution is 0.00299:1.

[0095] (2-2) First-stage oxidation aging treatment: At 90℃, 30% hydrogen peroxide was added to the mixed solution to control Fe. 2+ The total oxidation amount was 20%, and the temperature was maintained for 3 hours for aging.

[0096] (2-3) Second-stage oxidation aging treatment: At 90℃, continue to add 30% hydrogen peroxide to control Fe 2+ The total oxidation amount was 60%, and the mixture was kept at a warm temperature for 2 hours.

[0097] (2-4) Three-stage oxidation aging treatment: At 90℃, continue to add 30% hydrogen peroxide to control Fe 2+ The total oxidation amount was 100%, and the mixture was aged at this temperature for 2 hours. After the reaction was completed, the mixture was filtered under pressure to separate ferric phosphate dihydrate and the filtrate. The filtrate can be used to dilute concentrated phosphoric acid and the leachate.

[0098] (2-5) Sintering: After two-stage countercurrent washing and drying, ferric phosphate dihydrate was calcined at 600℃ for 2 h to obtain anhydrous ferric phosphate.

[0099] Example 3

[0100] This example provides a method for preparing iron phosphate for batteries, the steps of which are as follows:

[0101] (1) Leaching:

[0102] Ferric phosphate dust collector was mixed with 50% phosphoric acid aqueous solution at a material-to-liquid ratio of 50 g: 1 L and leached at 40℃ for 4 h, achieving a solubility greater than 99%. Solid-liquid separation was performed, and excess iron powder (approximately 1.10 times the molar amount of P in the phosphoric acid aqueous solution, with a mass ratio of ferric phosphate dust collector to iron powder of 0.45:1) was added to the liquid phase. The mixture was reacted at 60℃ for 8 h, filtered, and the leachate was obtained. The leachate was diluted to a Fe concentration of approximately 160 g / L to obtain the reaction solution.

[0103] (2) Ferric phosphate precipitation and crystallization:

[0104] In the multi-stage oxidation aging process, hydrogen peroxide and Fe... 2+ Add 10%–20% excess hydrogen peroxide to ensure oxidation reaction efficiency. In both the first-stage and second-stage oxidation-aging treatments, the Fe content in the reactants is confirmed by potassium dichromate titration before the aging process. 2+ Total oxidation amount.

[0105] (2-1) Add the reaction solution to the reaction vessel, heat it to 90°C, and then add the surface dispersant PPEA-15 (polyether surface dispersant, provided by Shanghai Sanrui Polymer Materials Co., Ltd.) to obtain a mixed solution.

[0106] The mass ratio of PPEA-15 to iron in the reaction solution is 0.00299:1.

[0107] (2-2) First-stage oxidation aging treatment: At 90℃, 30% hydrogen peroxide was added to the mixed solution to control Fe. 2+ The total oxidation amount was 20%, and the temperature was maintained for 3 hours for aging.

[0108] (2-3) Second-stage oxidation aging treatment: At 90℃, continue to add 30% hydrogen peroxide to control Fe 2+ The total oxidation amount was 100%, and the mixture was aged at this temperature for 6 hours. After the reaction was completed, the mixture was filtered to separate ferric phosphate dihydrate and the filtrate. The filtrate can be used to dilute concentrated phosphoric acid and the leachate.

[0109] (2-4) Sintering: After two-stage countercurrent washing and drying, ferric phosphate dihydrate was calcined at 600℃ for 2 h to obtain anhydrous ferric phosphate.

[0110] Example 4

[0111] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that in step (1), "dilution of the leachate to a Fe concentration of about 110 g / L" is replaced with "dilution of the leachate to a Fe concentration of about 200 g / L".

[0112] Example 5

[0113] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that the heating temperature in step (2-1) is replaced by 85°C instead of 90°C.

[0114] Example 6

[0115] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that in step (2-1), the mass ratio of SDS to iron in the reaction solution is 0.004485:1.

[0116] Example 7

[0117] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that in step (2-1), the surface dispersant SDS is replaced with SRC-JX-1 (a surfactant containing quaternary ammonium and hydroxyl groups, provided by Shanghai Sanrui Polymer Materials Co., Ltd.), and the mass ratio of SRC-JX-1 to iron in the reaction solution is 0.004485:1.

[0118] Example 8

[0119] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that in step (2-1), the surface dispersant SDS is replaced with SRC-JX-2 (a nonionic surfactant containing hydroxyl groups, provided by Shanghai Sanrui Polymer Materials Co., Ltd.), and the mass ratio of SRC-JX-2 to iron in the reaction solution is 0.004485:1.

[0120] Example 9

[0121] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that in step (2-1), the surface dispersant SDS is replaced with SRC-JX-3 (a surfactant containing quaternary ammonium and hydroxyl groups, provided by Shanghai Sanrui Polymer Materials Co., Ltd.), and the mass ratio of SRC-JX-3 to iron in the reaction solution is 0.004485:1.

[0122] Example 10

[0123] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that in step (2-2), the heat preservation aging time for the oxidation aging treatment is replaced by 2 hours instead of 3 hours.

[0124] Example 11

[0125] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that the calcination temperature in steps (2-5) is replaced by 700°C instead of 600°C.

[0126] Comparative Example 1

[0127] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that in step (1), the temperature of the leaching of the phosphoric acid aqueous solution and the iron phosphate dust collector is changed from 50°C to 80°C.

[0128] Comparative Example 2

[0129] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that a surface dispersant is missing in step (2-1).

[0130] Comparative Example 3

[0131] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that: in step (2-1), a surface dispersant is missing; in step (2-3), SDS is added before a second-stage oxidation is performed, wherein the mass ratio of SDS to iron in the reaction solution is 0.001495:1.

[0132] Comparative Example 4

[0133] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that the surface dispersant in step (2-1) is replaced by PEG3000 instead of SDS.

[0134] Comparative Example 5

[0135] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that the surface dispersant in step (2-1) is replaced by citric acid (CA, provided by Sinopharm Chemical Reagent Co., Ltd.).

[0136] Comparative Example 6

[0137] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as in Example 1, except that steps (2-2) to (2-4) are replaced with "adding 30% hydrogen peroxide to the mixed solution to control Fe". 2+Oxidation was complete; after the reaction was finished, pressure filtration was performed to separate ferric phosphate dihydrate and the filtrate.

[0138] Comparative Example 7

[0139] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that in step (2-1), the mass ratio of SDS to iron in the reaction solution is 0.000897:1.

[0140] Comparative Example 8

[0141] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that in step (2-1), the mass ratio of SDS to iron in the reaction solution is 0.00897:1.

[0142] Comparative Example 9

[0143] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that the calcination time in steps (2-5) is replaced by 1 hour instead of 2 hours.

[0144] Comparative Example 10

[0145] This example provides a method for preparing iron phosphate for batteries. The steps are basically the same as those in Example 1, except that the calcination temperature in steps (2-5) is replaced by 500°C instead of 600°C.

[0146] Detection example

[0147] 1. The iron, phosphorus, and other impurity elements in the anhydrous ferric phosphate prepared in Examples 1-11 and Comparative Examples 1-10 were tested, and the results were compared with industry standards to determine whether the products were qualified. The composition, morphology, and particle size of the anhydrous ferric phosphate were characterized using X-ray diffraction (XRD), Malvern 3000 laser particle size analyzer, and scanning electron microscopy (SEM).

[0148] The results are shown in Table 1. Figures 2 to 7 As shown.

[0149] Table 1

[0150]

[0151] The ferric phosphates prepared in Examples 1-11 meet the requirements for anhydrous ferric phosphate in HG / T4701-2021, "Ferric Phosphate for Batteries". The ferric phosphates prepared in Comparative Examples 1-7 all have a specific surface area below 3, which does not meet the requirements, and the ferric phosphate particles exhibit lumpy precipitates. The anhydrous ferric phosphate prepared in Comparative Example 8 has excessively small particle size, is prone to agglomeration, and is difficult to filter. The ferric phosphates prepared in Comparative Examples 9-10 exhibit impurity peaks in their XRD patterns, which does not meet the requirements.

[0152] The methods in Examples 1-11 added a surface dispersant before the staged oxidation and aging treatment, avoiding the formation of blocky crystal seeds in the early stage of crystallization. Combined with the subsequent multi-stage oxidation and aging treatment, the BET and porosity of the product were improved, resulting in anhydrous ferric phosphate with high BET and easy milling. The method in Comparative Example 1 dissolved the ferric phosphate dust material with a phosphoric acid aqueous solution at a high temperature, leading to the direct spontaneous formation of blocky crystal nuclei. Subsequent precipitation and crystallization occurred on this basis, thus failing to produce qualified anhydrous ferric phosphate. If the blocky crystal nuclei were filtered out before subsequent processing, the recovery purpose could not be achieved. The method in Comparative Example 2 lacked a surface dispersant, and direct high-temperature oxidation easily produced blocky crystal nuclei, making it difficult for the subsequent multi-stage oxidation and aging treatment to achieve the desired effect. The method in Comparative Example 3 added a surface dispersant after one stage of oxidation, at which point crystal nuclei had already formed, making it impossible to control crystallization. The surface dispersant PEG3000 used in the method in Comparative Example 4 had excessive viscosity after dissolution, resulting in poor dispersion. The surface dispersant CA used in the method in Comparative Example 5 did not participate in the complexation and adsorption reactions between particles, thus failing to achieve a dispersion effect. The method in Comparative Example 6 lacked multi-stage oxidation aging treatment, leading to rapid crystal nucleus formation and growth, resulting in a low BET value for the product. The method in Comparative Example 7 added too little surface dispersant, resulting in an insufficient ratio between the surface dispersant and the particles, causing some particles to fail to bind and thus failing to achieve the desired effect. The method in Comparative Example 8 added too much surface dispersant, resulting in excessively small particle size. The surface dispersant easily self-binded, leading to particle aggregation and ultimately particle agglomeration. The methods in Comparative Examples 9 and 10 showed incomplete sintering, with XRD revealing the presence of ferric phosphate dihydrate phase.

[0153] 2. The anhydrous ferric phosphate obtained in Examples 1-11 and Comparative Examples 1-10 was tested for its milling performance through batching and milling; the number of milling cycles was recorded during milling. The specific steps are as follows:

[0154] 10 kg of anhydrous ferric phosphate was mixed with 2.52 kg of lithium carbonate, 0.6 kg of glucose, 0.1 kg of superconducting carbon black, and 0.6 kg of PEG1500, and then 25.6 kg of water was added to obtain a slurry. The slurry was first coarsely ground (10 min / batch) using a sand mill (Guangdong Huijing Intelligent Equipment Co., Ltd., horizontal sand mill KNB-S) under the same conditions until particle size D was reached. 50 If the particle size is less than 2 μm, the coarsely ground slurry is then finely ground using a sand mill under the same conditions (10 min / time) until the particle size D is reached. 50 Less than 0.5 μm.

[0155] The results are shown in Table 2.

[0156] Table 2

[0157]

[0158] The iron phosphates prepared in Examples 1-11 have good sand milling performance, while the iron phosphates prepared in Comparative Examples 1-7 have poor sand milling performance.

[0159] 3. The anhydrous ferric phosphate obtained in Example 1 and Comparative Example 2 were mixed with water at a mass ratio of 1:4 to obtain slurry A and slurry B, respectively. Slurry A and slurry B were then milled using a sand mill (Guangdong Huijing Intelligent Equipment Co., Ltd., horizontal sand mill KNB-S) under the same sand milling conditions (10 min / time) until particle size D was reached. 50 Less than 0.5 μm.

[0160] The results are as follows Figure 8 As shown.

[0161] In D 50 Under similar conditions, compared to Comparative Example 2, the anhydrous ferric phosphate prepared in Example 1 yielded a product meeting the requirements in a shorter milling time. This indicates that the formation of bulk crystal nuclei affects the milling performance of anhydrous ferric phosphate.

Claims

1. A method for producing iron phosphate for a battery, characterized by, The method comprises the following steps: 1) preparing a first mixture of iron phosphate dust collection material and aqueous phosphoric acid solution, carrying out leaching treatment, and obtaining a first liquid phase through first solid-liquid separation; preparing a second mixture of the first liquid phase and elemental iron, carrying out reaction, and obtaining a second liquid phase through second solid-liquid separation; The temperature of the leaching treatment is not higher than 50 DEG C; the molar ratio of phosphorus element in the aqueous phosphoric acid solution to the elemental iron is 1:1.05-1.2; 2) preparing a third mixture of the second liquid phase and a surface dispersing agent, and carrying out segmented oxidation aging treatment on the third mixture; carrying out third solid-liquid separation to obtain a solid phase; and calcining the solid phase to obtain the iron phosphate; The surface dispersing agent comprises at least one of a cationic surfactant, an anionic surfactant and a non-ionic surfactant; the cationic surfactant comprises a quaternary ammonium surfactant; the anionic surfactant comprises at least one of SDS and SDBS; and the non-ionic surfactant comprises at least one of a polyether surfactant and a hydroxyl surfactant; The segmented oxidation aging treatment comprises N segments, and N is a positive integer not lower than 2; The segmented oxidation aging treatment comprises one segment of oxidation aging treatment to N segments of oxidation aging treatment; Each segment of oxidation aging treatment comprises adding an oxidizing agent and carrying out aging treatment; The temperature of the segmented oxidation aging treatment is 50 DEG C-90 DEG C; The aging time of each segment of oxidation aging treatment is 1 h-6 h; The temperature of the calcination is not lower than 580 DEG C; and the time of the calcination is not lower than 2 h.

2. The method of claim 1, wherein, The solid-liquid ratio of the iron phosphate dust collection material to the aqueous phosphoric acid solution is 20 g-200 g:1 L; And / or, the mass percentage concentration of phosphoric acid in the aqueous phosphoric acid solution is 30%-50%; And / or, the mass ratio of the iron phosphate dust collection material to the elemental iron is 0.06-0.6:

1.

3. The method of claim 1, wherein, The time of the leaching treatment is not higher than 4 h.

4. The method of claim 1, wherein, The reaction temperature in step 1) is 50 DEG C-90 DEG C; And / or, the reaction time in step 1) is 6 h-10 h.

5. The method of claim 1, wherein, The mass ratio of iron element in the third mixture to the surface dispersing agent is 1:0.0014-0.0045.

6. The method of claim 1, wherein, The oxidizing agent comprises at least one of hydrogen peroxide, oxygen, ozone and air.

7. The method of claim 1, wherein, The one-stage oxidation aging treatment includes adding the oxidizing agent to oxidize 20% to 50% of Fe in the third mixture to Fe 2+ Oxidation to Fe 3+ ; and the remaining multi-stage oxidation aging treatment includes adding the oxidizing agent to oxidize the remaining Fe 2+ Oxidation to Fe 3+ and performing the aging treatment.

8. Application of the method according to any one of claims 1-7 in the recovery of iron phosphate dust collection material.

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