Process method for producing titanium-doped iron phosphate by one-step method

Abstract

The invention relates to the technical field of preparation of iron phosphate doped with titanium, and particularly discloses a process method for producing titanium-doped iron phosphate by a one-step method, which comprises the following steps: S1, dissolving a titanium dioxide by-product ferrous sulfate in deionized water, detecting the iron content and the titanium content, and supplementing titanyl sulfate or titanium-removed ferrous sulfate according to the target iron-titanium content; s2, adding hydrogen peroxide into the ammonium phosphate solution, and uniformly mixing; s3, air is continuously introduced into the iron-titanium solution, the temperature is increased to 85 + / -2 DEG C, an ammonium phosphate and hydrogen peroxide mixed solution is added, the molar ratio of iron to phosphorus is 0.96 + / -0.01, charging is completed within 30 min, then the temperature is increased to 95 + / -2 DEG C, heat preservation is conducted for 2 h, and air is continuously introduced; s4, after the materials in the system become white from light yellow, continuing to perform heat preservation and filtration, and washing a filter cake after filtration; and S5, drying and calcining the washed filter cake. According to the method, a one-step method is combined with step-by-step continuous oxidation, the problem of high impurity content in the one-step method is solved, compared with a two-step method, the process is simplified, the cost is reduced, and the titanium element utilization rate and the compaction density in the titanium dioxide by-product are also improved.

Description

Technical Field

[0001] This invention relates to the field of titanium-doped iron phosphate preparation technology, specifically a one-step process for producing titanium-doped iron phosphate. Background Technology

[0002] Lithium iron phosphate (LiFePO4) has become the mainstream cathode material for lithium batteries due to its high safety and low cost. Titanium doping is a key modification method to improve its conductivity. The one-step method, a relatively primitive approach to producing anhydrous iron phosphate, involves reaction, washing, and drying. However, it has been phased out due to the high content of magnesium and manganese impurities and the high iron-to-phosphorus ratio in the finished product. The two-step method for preparing iron phosphate involves reaction, washing, a secondary reaction (aging, maturation, or ripening), washing, and drying. However, the two-step process has a long operating cycle and requires multiple repetitions of the reaction and treatment. Patents CN202411798340.3 (A Low-Cost Preparation Method for High-Performance Titanium-Doped Iron Phosphate), CN202510411805.3 (A Method for Doping Iron Phosphate with Titanium), and CN202410572832.4 (A Preparation Method for Battery-Grade Titanium-Doped Iron Phosphate) show that, although the iron phosphate products prepared by combining a two-step process with a titanium doping process can meet the requirements of industrial production for impurities, powder dispersibility, and electrochemical performance, the two-step process has a long operation cycle, requires multiple repeated reactions and treatments, is complex, has high energy consumption, high production costs, and high requirements for raw materials. In addition, it is difficult to avoid the incorporation of impurities during production.

[0003] This invention effectively combines the titanium-doped iron phosphate process with the original one-step process route, and innovatively adopts a step-by-step and continuous oxidation approach. This effectively suppresses the generation of magnesium and manganese impurities. The impurity content and titanium content of the produced titanium-doped anhydrous iron phosphate both meet the current mainstream industry standards, and the titanium doping is uniform. However, the compaction density is higher than that of the two-step method. This invention also improves the utilization rate of titanium elements in titanium dioxide by-products and makes full use of reaction waste heat and air as oxidants, which greatly saves costs. Summary of the Invention

[0004] The purpose of this invention is to provide a one-step process for producing titanium-doped iron phosphate, which solves the problems of high magnesium and manganese impurities in the existing one-step process and long process time and high cost in the two-step process. The result is a simple production process for titanium-doped iron phosphate, with readily available raw materials, fast reaction speed, significantly reduced cost, and product quality that meets industry standards.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows: a one-step process for producing titanium-doped iron phosphate, comprising the following steps: S1 Raw Material Dissolution: Dissolve ferrous sulfate, a byproduct of titanium dioxide, in deionized water, detect the iron and titanium content, and supplement with titanium oxysulfate or ferrous sulfate after removing titanium according to the target iron and titanium content to obtain an iron-titanium solution. Preparation of S2 ammonium phosphate and hydrogen peroxide mixed solution: Add ammonium phosphate solution with pH 2-4 to hydrogen peroxide and mix well to obtain ammonium phosphate and hydrogen peroxide mixed solution, wherein the hydrogen peroxide content meets the requirement that the molar ratio of iron to hydrogen peroxide is 1:0.5; S3 reaction aging: The iron-titanium solution is continuously purged with air and heated to 85±2℃. The ammonium phosphate and hydrogen peroxide mixed solution is added, with an iron-phosphorus molar ratio of 0.96±0.01. The addition is completed within 30 minutes. Then, the temperature is raised to 95±2℃ and kept at that temperature for 2 hours while continuously purging with air. S4 Washing and Filtration: After the material in the system turns from light yellow to white, continue to keep it warm for more than 30 minutes, then filter it and wash the filtered cake with deionized water. S5 Drying and Calcination: The washed filter cake is dried and calcined to obtain titanium-doped anhydrous iron phosphate.

[0006] Furthermore, the ammonium phosphate solution described in S2 is prepared by adjusting the pH to 2.0-4.0 with phosphoric acid and ammonia.

[0007] Furthermore, in S4, the sample is washed with deionized water until the conductivity is below 150 μS / cm.

[0008] Furthermore, the drying temperature in S5 is 100±5℃, the drying time is 10h, the calcination temperature is 600±10℃, and the calcination time is 4h.

[0009] Furthermore, the drying in S5 is performed under negative pressure, and the calcination is carried out in an air atmosphere.

[0010] The beneficial effects of this implementation plan are as follows: 1. Cost reduction: This production process uses a one-step method, and the system temperature reaches 60℃ after the reaction and aging are integrated, which effectively utilizes the heat of reaction and reduces the subsequent heating cost. At the same time, air is used as an oxidant, which reduces the cost of using another oxidant, hydrogen peroxide.

[0011] 2. High product quality: The anhydrous iron phosphate produced by this process has a high iron-to-phosphorus ratio, and the prepared lithium iron phosphate has good electrical properties and high compaction density.

[0012] 3. Improve the utilization rate of titanium: This process effectively utilizes titanium in titanium dioxide by-products, greatly saving raw material costs.

[0013] 4. Low magnesium and manganese impurity content: This process continuously introduces air during the reaction. During the high-temperature aging process, the air gradually oxidizes the residual ferrous iron that was not completely oxidized by the hydrogen peroxide in the previous stage. During the aeration stage, the ferrous iron in the entire process can be oxidized to ferric iron. Since the ksp of ferric phosphate is smaller than that of manganese phosphate and magnesium phosphate, ferric phosphate is easier to precipitate and can preferentially precipitate the finished product, thereby inhibiting the precipitation of magnesium and manganese. The resulting anhydrous ferric phosphate product has a significantly lower magnesium and manganese impurity content compared to the process with discontinuous air introduction. Compared with the two-step method, the magnesium and manganese impurity content is comparable.

[0014] 5. Reduced process time: This process is simple to operate and reacts quickly, greatly saving process time. Attached Figure Description

[0015] Figure 1 This is a flow chart of a one-step process for producing titanium-doped iron phosphate according to the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0017] This invention provides a one-step process for producing titanium-doped iron phosphate, the process flow diagram of which is shown below. Figure 1 As shown, the method includes the following steps: S1 Raw Material Dissolution: Dissolve ferrous sulfate, a byproduct of titanium dioxide, in deionized water, detect the iron and titanium content, and supplement with titanium oxysulfate or ferrous sulfate after removing titanium according to the target iron and titanium content to obtain an iron-titanium solution. Preparation of S2 ammonium phosphate and hydrogen peroxide mixed solution: Add ammonium phosphate solution with pH 2-4 to hydrogen peroxide and mix well to obtain ammonium phosphate and hydrogen peroxide mixed solution, wherein the hydrogen peroxide content meets the requirement that the molar ratio of iron to hydrogen peroxide is 1:0.5; S3 reaction aging: The iron-titanium solution is continuously purged with air and heated to 85±2℃. The ammonium phosphate and hydrogen peroxide mixed solution is added, with an iron-phosphorus molar ratio of 0.96±0.01. The addition is completed within 30 minutes. Then, the temperature is raised to 95±2℃ and kept at that temperature for 2 hours while continuously purging with air. S4 Washing and Filtration: After the material in the system turns from light yellow to white, continue to keep it warm for more than 30 minutes, then filter it and wash the filtered cake with deionized water. S5 Drying and Calcination: The washed filter cake is dried and calcined to obtain titanium-doped anhydrous iron phosphate.

[0018] In the method described in this invention, the ammonium phosphate solution in S2 is prepared by adjusting the pH to 2.0-4.0 with phosphoric acid and ammonia.

[0019] In the method described in this invention, in step S4, the sample is washed with deionized water until the conductivity is below 150 μS / cm.

[0020] In the method described in this invention, the drying temperature in S5 is 100±5℃, the drying time is 10h, the calcination temperature is 600±10℃, and the calcination time is 4h.

[0021] In the method described in this invention, the drying in step S5 is performed under negative pressure, and the calcination is carried out in an air atmosphere.

[0022] The preparation method of the present invention will be described in detail below with reference to specific embodiments: Example 1 S1: 500g of ferrous sulfate, a byproduct of titanium dioxide production, was dissolved in 1250g of deionized water. The iron and titanium contents were then measured. The titanium content was adjusted as needed to obtain an iron-titanium solution. The iron content was 5.1%, and the titanium content was 510mg / kg. 2g of titanium oxysulfate was added and dissolved. After dissolution, the iron content was measured to be 5.07%, and the titanium content was 716mg / kg.

[0023] S2: Preparation of ammonium phosphate: Adjust the pH of 188g of phosphoric acid (85%) to 2.35 with 7% ammonia water, cool it down and then add 100g of hydrogen peroxide (27%) and mix well.

[0024] S3: Use a peristaltic pump to introduce air into the iron-titanium liquid and heat the iron-titanium liquid to 85°C and keep it at that temperature. After the temperature is reached, add a mixture of ammonium phosphate and hydrogen peroxide solution. Add the solution dropwise over 30 minutes. After the addition is complete, set the temperature to 95°C and keep it at that temperature while continuously introducing air.

[0025] S4: After the system changes from pale yellow to white, continue to keep it warm for more than 30 minutes, filter it while it is hot, and wash the filter cake with deionized water until the conductivity is lower than 150 μs / cm.

[0026] S5: After drying the filter cake under negative pressure at 100℃ for 10 hours, calcine it at 600℃ in air for 4 hours to obtain titanium-doped anhydrous ferric phosphate.

[0027] Example 2 S1: 500g of ferrous sulfate, a byproduct of titanium dioxide production, was dissolved in 1250g of deionized water. The iron and titanium contents were then measured. The titanium content was adjusted as needed to obtain an iron-titanium solution. The iron content was 5.12%, and the titanium content was 615mg / kg. 1g of titanium oxysulfate was added and dissolved. After dissolution, the iron content was measured to be 5.06%, and the titanium content was 713mg / kg.

[0028] S2: Preparation of ammonium phosphate: Adjust the pH of 186g of phosphoric acid (85%) to 2.35 with 7% ammonia water, cool it down, and then add 99g of hydrogen peroxide (27%) and mix well.

[0029] S3: Use a peristaltic pump to introduce air into the iron-titanium liquid and heat the iron-titanium liquid to 85°C and keep it at that temperature. After the temperature is reached, add a mixture of ammonium phosphate and hydrogen peroxide solution. Add the solution dropwise over 30 minutes. After the addition is complete, set the temperature to 95°C and keep it at that temperature while continuously introducing air.

[0030] S4: After the system changes from pale yellow to white, continue to keep it warm for more than 30 minutes, filter it while it is hot, and wash the filter cake with deionized water until the conductivity is lower than 150 μs / cm.

[0031] S5: After drying the filter cake under negative pressure at 100℃ for 10 hours, calcine it at 600℃ in air for 4 hours to obtain titanium-doped anhydrous ferric phosphate.

[0032] Example 3 S1: 500g of ferrous sulfate, a byproduct of titanium dioxide production, was dissolved in 1250g of deionized water. The iron and titanium contents were then measured. The titanium content was adjusted as needed to obtain an iron-titanium solution. The iron content was 5.1%, and the titanium content was 815mg / kg. 200g of a titanium-free ferrous sulfate solution with a 5% iron content was weighed and mixed with the solution. After dissolution, the iron content was measured to be 5.07%, and the titanium content was 703mg / kg.

[0033] S2: Preparation of ammonium phosphate: Adjust the pH of 187g phosphoric acid (85%) to 2.35 with 7% ammonia water, cool it down and then add 99g hydrogen peroxide (27%) and mix well.

[0034] S3: Use a peristaltic pump to introduce air into the iron-titanium liquid and heat the iron-titanium liquid to 85°C and keep it at that temperature. After the temperature is reached, add a mixture of ammonium phosphate and hydrogen peroxide solution. Add the solution dropwise over 30 minutes. After the addition is complete, set the temperature to 95°C and keep it at that temperature while continuously introducing air.

[0035] S4: After the system changes from pale yellow to white, continue to keep it warm for more than 30 minutes, filter it while it is hot, and wash the filter cake with deionized water until the conductivity is lower than 150 μs / cm.

[0036] S5: After drying the filter cake under negative pressure at 100℃ for 10 hours, calcine it at 600℃ in air for 4 hours to obtain titanium-doped anhydrous ferric phosphate.

[0037] Comparative Example 1 S1: 500g of ferrous sulfate, a byproduct of titanium dioxide production, was dissolved in 1250g of deionized water, and its iron and titanium contents were measured. The titanium content was adjusted as needed to obtain an iron-titanium solution. The iron content was measured to be 5.1%, and the titanium content was 710mg / kg.

[0038] S2: Preparation of ammonium phosphate: Adjust the pH of 188g of phosphoric acid (85%) to 2.35 with 7% ammonia water, cool it down and then add 120g of hydrogen peroxide (27%) and mix well.

[0039] S3: Heat the iron-titanium liquid to 85℃ and keep it at that temperature. Once the temperature is reached, add the ammonium phosphate and hydrogen peroxide mixed solution. Add the solution dropwise over 30 minutes. After adding the solution, set the temperature to 95℃ and keep it at that temperature.

[0040] S4: After the system changes from pale yellow to white, continue to keep it warm for more than 30 minutes, filter it while it is hot, and wash the filter cake with deionized water until the conductivity is lower than 150 μs / cm.

[0041] S5: After drying the filter cake under negative pressure at 100℃ for 10 hours, calcine it at 600℃ in air for 4 hours to obtain titanium-doped anhydrous ferric phosphate.

[0042] Comparative Example 2 S1: Take 1750g of titanium-free ferrous sulfate solution with an iron content of 5.1%.

[0043] S2: Preparation of ammonium phosphate: Adjust the pH of 190g phosphoric acid (85%) to 2.35 with 7% ammonia water, cool it down and then add 120g hydrogen peroxide (27%) and mix well.

[0044] S3: Heat the titanium-free ferrous sulfate solution to 85°C and keep it at that temperature. Once the temperature is reached, add the ammonium phosphate and hydrogen peroxide mixed solution dropwise over 30 minutes. After the addition is complete, set the temperature to 95°C and keep it at that temperature.

[0045] S4: After the system changes from pale yellow to white, continue to keep it warm for more than 30 minutes, filter it while it is hot, and wash the filter cake with deionized water until the conductivity is lower than 150 μs / cm.

[0046] S5: After drying the filter cake under negative pressure at 100℃ for 10 hours, calcine it at 600℃ in air for 4 hours to obtain anhydrous ferric phosphate.

[0047] Comparative Example 3 S1: Take 1750g of titanium-free ferrous sulfate solution with an iron content of 5.1%.

[0048] S2: Preparation of ammonium phosphate: Adjust the pH of 190g phosphoric acid (85%) to 7 with 7% ammonia water, cool it down and then add 120g hydrogen peroxide (27%) and mix well.

[0049] S3: Heat the titanium-free ferrous sulfate solution to 50°C and keep it at that temperature. Once the temperature is reached, add the ammonium phosphate and hydrogen peroxide mixed solution dropwise over 30 minutes. After adding the solution, stir for 30 minutes.

[0050] S4: After filtering the reaction material, wash the filter cake with deionized water until the conductivity is below 1000 μs / cm.

[0051] S5: The washed filter cake is aged with 0.05 mol / L dilute phosphoric acid and heated to 95℃. After turning white, it is filtered and washed for 30 minutes until the conductivity is below 150 μs / cm.

[0052] S6: After drying the filter cake under negative pressure at 100℃ for 10 hours, calcine it at 600℃ in air for 4 hours to obtain anhydrous ferric phosphate.

[0053] The table below shows the detection results of anhydrous ferric phosphate in Examples 1-3 and Comparative Examples 1-3:

[0054] Results analysis: Examples 1-3 illustrate a one-step process for producing titanium-doped iron phosphate according to the present invention. Comparative Example 1 uses a one-step process, but air is not continuously introduced for oxidation during the reaction stage. Comparative Example 2 is a one-step process without titanium doping, and Comparative Example 3 is a two-step process without titanium doping.

[0055] As can be seen from the above data, the magnesium and manganese impurities in the finished product of Comparative Example 1 are 5-8 times that of the present invention, indicating that the stepwise continuous oxidation of the present invention has a strong inhibitory effect on magnesium and manganese impurities in the one-step method. In addition, the present invention uses air as a partial oxidant, which effectively reduces the amount of hydrogen peroxide used and achieves the purpose of saving costs.

[0056] The anhydrous iron phosphate produced by this invention is comparable to that of Comparative Example 3 in terms of impurities, but the process is simplified and the cost is reduced.

[0057] Compared with Comparative Examples 2 and 3, the lithium iron phosphate prepared by the process of the present invention has a high compaction density of 2.6 g / cm³ due to titanium doping. 3 The battery is approximately 1000 meters thick, meets the standards for power batteries, and has broad application prospects.

[0058] This invention combines the advantages of titanium-doped iron phosphate and the one-step process, performing step-by-step continuous oxidation. It solves the industry problem of high impurities in the one-step process, while the impurity content is not much different from that of the two-step process. However, this invention simplifies the process and reduces costs, and has significant progress.

[0059] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A one-step process for producing titanium-doped iron phosphate, characterized in that, Includes the following steps: S1 Raw Material Dissolution: Dissolve ferrous sulfate, a byproduct of titanium dioxide, in deionized water, detect the iron and titanium content, and supplement with titanium oxysulfate or ferrous sulfate after removing titanium according to the target iron and titanium content to obtain an iron-titanium solution. Preparation of S2 ammonium phosphate and hydrogen peroxide mixed solution: Add ammonium phosphate solution with pH 2-4 to hydrogen peroxide and mix well to obtain ammonium phosphate and hydrogen peroxide mixed solution, wherein the hydrogen peroxide content meets the requirement that the molar ratio of iron to hydrogen peroxide is 1:0.5; S3 reaction aging: The iron-titanium solution is continuously purged with air and heated to 85±2℃. The ammonium phosphate and hydrogen peroxide mixed solution is added, with an iron-phosphorus molar ratio of 0.96±0.

01. The addition is completed within 30 minutes. Then, the temperature is raised to 95±2℃ and kept at that temperature for 2 hours while continuously purging with air. S4 Washing and Filtration: After the material in the system turns from light yellow to white, continue to keep it warm for more than 30 minutes, then filter it and wash the filtered cake with deionized water. S5 Drying and Calcination: The washed filter cake is dried and calcined to obtain titanium-doped anhydrous iron phosphate.

2. The process for producing titanium-doped iron phosphate in a one-step manner according to claim 1, characterized in that: The ammonium phosphate solution described in S2 is prepared by adjusting the pH to 2.0-4.0 with phosphoric acid and ammonia.

3. The process for producing titanium-doped iron phosphate in a one-step manner according to claim 1, characterized in that: S4 is washed with deionized water until the conductivity is below 150 μS / cm.

4. The process for producing titanium-doped iron phosphate in a one-step manner according to claim 1, characterized in that: The drying temperature of S5 is 100±5℃, the drying time is 10h, the calcination temperature is 600±10℃, and the calcination time is 4h.

5. The process for producing titanium-doped iron phosphate in a one-step manner according to claim 1, characterized in that: The drying described in S5 is performed under negative pressure, and the calcination is carried out in an air atmosphere.

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