Large-particle-size lithium phosphate material as well as preparation method and application thereof

Abstract

The invention discloses a large-particle-size lithium phosphate material as well as a preparation method and application thereof. The preparation method of the large-particle-size lithium phosphate material comprises the following steps: preparing a lithium source solution, heating half of the lithium source solution to 70-80 DEG C to serve as bottom water, adding a phosphoric acid solution, caustic soda liquid and the rest of the lithium source solution into the bottom water while stirring, adjusting the pH value of the system to 10.5-11 after the addition is completed, and keeping the temperature at 75-80 DEG C to react for 1-2 hours; and filtering and drying reactants to obtain the large-particle-size lithium phosphate. Through innovative flow rate regulation and control and a three-strand parallel flow reaction mode, the technical problems in a traditional lithium phosphate preparation method are successfully solved, and large-particle-size, high-yield and high-efficiency lithium phosphate synthesis under the condition of high-concentration phosphoric acid is realized. The technical scheme provided by the invention has a wide application prospect, and provides effective technical support for industrial production of lithium phosphate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of battery materials, and particularly relates to a large-particle-size lithium phosphate material and a preparation method and application thereof. BACKGROUND

[0002] Lithium iron phosphate (LiFePO4) is an important anode material for lithium batteries, which has excellent thermal stability, long cycle life and low cost, and is widely used in lithium batteries and other electrochemical energy storage devices. Among them, lithium phosphate (Li3PO4) is an important raw material for preparing lithium iron phosphate.

[0003] At present, the preparation methods of lithium phosphate mainly include direct method, coprecipitation method, sol-gel method and solid phase reaction method, etc. Among them, the most common method is to prepare lithium phosphate by chemical reaction of lithium source (such as lithium chloride, lithium hydroxide, etc.) and phosphoric acid source (such as diammonium hydrogen phosphate, phosphoric acid, etc.). However, the existing process still faces the following technical challenges: 1. It is difficult to control the particle size and yield: the existing method has limitations in controlling the particle size and yield of lithium phosphate, and the obtained product particles are generally fine and the amount is low, which is difficult to meet the needs of large-scale industrial application. 2. Low reaction efficiency: In the traditional process, it is difficult to accurately control the feeding rate, temperature and other key parameters of the reactants, resulting in low lithium conversion rate and reaction rate, which affects the quality and yield of the product. Especially in high-concentration phosphoric acid system, due to the complex reaction environment, the reaction rate is slow and the conversion is incomplete. The root cause is that the existing process adopts the method of pre-mixing high-concentration phosphoric acid and lithium-containing solution and then adding liquid alkali, which is easy to generate lithium phosphate precipitate with small particle size and incomplete crystallization. Such precipitate has poor dewatering performance in the process of centrifugation or pressure filtration, and the filter cake has high water content and poor flowability, which is difficult to continuously discharge, and even difficult to directly enter the disc dryer. If forced drying, high-moisture materials are easy to caking, which seriously affects the subsequent screening operation. 3. Complex reaction environment: Most of the existing technologies rely on complex reaction devices and harsh operating conditions, which not only increases the production cost, but also increases the operation difficulty and equipment maintenance burden.

[0004] Therefore, how to effectively control the reaction process under high-concentration phosphoric acid conditions to realize the controllable preparation of large-particle-size and high-yield lithium phosphate is still a difficult problem to be solved in the current technical field. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a large-particle-size lithium phosphate material and a preparation method and application thereof, which solves the technical problems of small particle size and low yield of lithium phosphate in the prior art, and is difficult to meet the needs of industrial production.

[0006] The purpose of the present application is achieved by the following technical solutions: A method for preparing a large-particle-size lithium phosphate material includes the following steps: Prepare a lithium source solution. Take half of the lithium source solution and heat it to 70~80℃ as the bottom water. Under stirring conditions, add the phosphoric acid solution, liquid alkali and the remaining lithium source solution to the bottom water at the same time. After the addition is complete, adjust the pH of the system to 10.5~11 and maintain the reaction at 75~80℃ for 1~2 hours. The reactants were filtered and dried to obtain lithium phosphate with large particle size.

[0007] In this invention, because precipitation occurs simultaneously with the addition of raw materials, the three-stream parallel flow (phosphoric acid solution, liquid alkali, and remaining lithium source solution) maintains the concentration of each reactant ion in the solution system at a consistently low level, thereby significantly reducing local supersaturation. This control strategy is crucial for the synthesis of large-particle-size lithium phosphate. Furthermore, the three-stream parallel flow reaction mode allows for sufficient contact between the lithium source solution, liquid alkali, and phosphoric acid solution in a short time, accelerating the reaction process. This efficient mass transfer method effectively improves the material conversion rate of the reaction while shortening the reaction time, making the lithium phosphate preparation process more efficient and significantly improving reaction efficiency. Based on this, increasing the reaction temperature and stirring frequency can further accelerate the reaction rate, enabling the synthesis of lithium phosphate to achieve high yield, high efficiency, and easy dehydration, thus providing feasibility for large-scale industrial production.

[0008] Preferably, the lithium content in the lithium source solution is 18~20 g / L.

[0009] Preferably, the concentration of the phosphoric acid solution is 75-85%, more preferably 85%.

[0010] Preferably, the concentration of the liquid alkali is 30-35%, more preferably 32%.

[0011] Preferably, the solute in the lithium source solution is at least one selected from lithium hydroxide, lithium carbonate, lithium bicarbonate, and lithium chloride.

[0012] Preferably, the volume ratio of the phosphoric acid solution to the total lithium source solution is 1.15~1.28:16.

[0013] Preferably, in the step of adding phosphoric acid solution, liquid alkali and remaining lithium source solution to the bottom water, the feed flow rate ratio of liquid alkali to phosphoric acid solution is 2.3~2.9:1; the volume ratio of liquid alkali to phosphoric acid solution is 2.3~2.5:1.

[0014] Preferably, in the step of adding phosphoric acid solution, liquid alkali and residual lithium source solution to the bottom water, the feed flow rate ratio of liquid alkali and residual lithium source solution is 4.3~6.5:10; and the volume ratio of liquid alkali and residual lithium source solution is 2.7~3.1:8.

[0015] In this invention, the pH of the reaction system is stabilized between 6 and 10 by adjusting the feed flow rate of the reactants. This mild condition promotes the formation of large-particle lithium phosphate, while precise control of the flow rate further optimizes the crystal growth process.

[0016] Preferably, the stirring rate is 120~300 rpm.

[0017] Preferably, the specific operation of adjusting the pH of the system to 10.5~11 is as follows: the pH of the system is adjusted by adding liquid alkali.

[0018] In this invention, by controlling the feed flow rate of the reactants, the pH of the reaction system is stabilized at 6-10 in the initial stage to promote the directional growth of large-particle lithium phosphate; then the pH is further increased to 10.5-11 to drive the reaction toward complete conversion.

[0019] The above-mentioned method for preparing large-particle-size lithium phosphate materials yields large-particle-size lithium phosphate materials.

[0020] The application of the aforementioned large-particle-size lithium phosphate materials in the preparation of lithium battery cathode materials.

[0021] The lithium phosphate prepared by this invention has a suitable particle size and uniform particle size distribution. Using it as a cathode material for lithium batteries helps to improve its electrochemical performance, especially in terms of charge-discharge efficiency, cycle stability and cycle life.

[0022] Compared with the prior art, the beneficial effects of the present invention include: This invention addresses the technical challenges of poor dehydration performance in the production of lithium phosphate from high-concentration phosphoric acid and insufficient yield from low-concentration raw materials. By controlling the flow rate and employing a three-stream parallel-flow reaction mode, it achieves efficient synthesis of large-particle-size, high-yield lithium phosphate under high-concentration phosphoric acid conditions. This technical solution is simple to operate and precisely controlled, enabling continuous and stable precipitation of easily dehydrated lithium phosphate. It effectively solves the technical problems of small product particle size and difficult dehydration in traditional processes, significantly improving production efficiency and raw material utilization. This invention provides reliable technical support for the industrial continuous production of lithium phosphate and has broad application prospects. Attached Figure Description

[0023] Figure 1 This is a flowchart of the preparation method of the large-particle-size lithium phosphate material described in this invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] Example 1 A method for preparing large-particle-size lithium phosphate material, the specific steps of which are as follows: (1) Prepare a lithium source solution (specifically, a lithium chloride solution with a lithium content of 18 g / L), take 8 mL of the solution. 3 Lithium source solution, at 10m 3 It is added to the reactor at a rate of / h and heated to 80℃ at a speed of 200rpm to serve as bottom water; (2) Maintain a rotation speed of 200 rpm, and simultaneously add 1.15 m of [unspecified substance] to the bottom water. 3 Phosphoric acid solution (85% concentration), 2.7m 3 Liquid alkali (concentration 32%) and 8m 3 The lithium source solution contains a phosphoric acid solution with a flow rate of 1.88 m / s. 3 The flow rate of liquid alkali is 4.4 m / h. 3 / h, the flow rate of the lithium source solution is 10m 3 / h, after which the pH of the solution was measured to be 6.5, 0.4m was added. 3 The system pH was adjusted to 11 with liquid alkali and maintained at 80°C for 1 hour. (3) After the reaction is complete, the reactants are put into the batch tank for mixing, and then put into the centrifuge for dehydration according to the production rhythm. After drying, lithium phosphate product is obtained.

[0026] Example 2 A method for preparing large-particle-size lithium phosphate material, the specific steps of which are as follows: (1) Prepare a lithium source solution (specifically, a lithium chloride solution with a lithium content of 20 g / L), take 8 mL of the solution. 3 Lithium source solution, at 10m 3 It is added to the reactor at a rate of / h and heated to 80℃ at a speed of 200rpm to serve as bottom water; (2) Maintain a rotation speed of 200 rpm, and simultaneously add 1.28 m of [unspecified substance] to the bottom water. 3 Phosphoric acid solution (85% concentration), 3.1m 3 Liquid alkali (concentration 32%) and 8m 3 The lithium source solution contains a phosphoric acid solution with a flow rate of 2.3 m / s. 3 The flow rate of liquid alkali is 6.5 m / h. 3 / h, the flow rate of the lithium source solution is 10m 3 / h, after the addition was complete, the pH of the solution was measured to be 7.5, and 0.35m was added. 3 The system pH was adjusted to 10.8 with liquid alkali and maintained at 80°C for 1 hour. (3) After the reaction is complete, the reactants are put into the batch tank for mixing, and then put into the centrifuge for dehydration according to the production rhythm. After drying, lithium phosphate product is obtained.

[0027] Example 3 A method for preparing large-particle-size lithium phosphate material, the specific steps of which are as follows: (1) Prepare a lithium source solution (specifically, a lithium carbonate solution with a lithium content of 18 g / L), take 8 mL of the solution. 3 Lithium source solution, at 10m 3 It is added to the reactor at a rate of / h and heated to 80℃ at a speed of 200rpm to serve as bottom water; (2) Maintain a rotation speed of 200 rpm, and simultaneously add 1.15 m of [unspecified substance] to the bottom water. 3 Phosphoric acid solution (85% concentration), 2.7m 3 Liquid alkali (concentration 32%) and 8m 3 The lithium source solution contains a phosphoric acid solution with a flow rate of 1.88 m / s. 3 The flow rate of liquid alkali is 4.4 m / h. 3 / h, the flow rate of the lithium source solution is 10m 3 / h, after the addition was complete, the pH of the solution was measured to be 6.6, and 0.38m was added. 3 The system pH was adjusted to 11 with liquid alkali and maintained at 80°C for 1 hour. (3) After the reaction is complete, the reactants are put into the batch tank for mixing, and then put into the centrifuge for dehydration according to the production rhythm. After drying, lithium phosphate product is obtained.

[0028] Example 4 A method for preparing large-particle-size lithium phosphate material, the specific steps of which are as follows: (1) Prepare a lithium source solution (specifically, a lithium carbonate solution with a lithium content of 20 g / L), take 8 mL of the solution. 3 Lithium source solution, at 10m 3 It is added to the reactor at a rate of / h and heated to 80℃ at a speed of 200rpm to serve as bottom water; (2) Maintain a rotation speed of 200 rpm, and simultaneously add 1.28 m of [unspecified substance] to the bottom water. 3 Phosphoric acid solution (85% concentration), 3.1m 3 Liquid alkali (concentration 32%) and 8m 3 The lithium source solution contains a phosphoric acid solution with a flow rate of 2.3 m / s. 3 The flow rate of liquid alkali is 6.5 m / h. 3 / h, the flow rate of the lithium source solution is 10m 3 / h, after which the pH of the solution was measured to be 7.8, 0.35m was added. 3 The system pH was adjusted to 11 with liquid alkali and maintained at 80°C for 1 hour. (3) After the reaction is complete, the reactants are put into the batch tank for mixing, and then put into the centrifuge for dehydration according to the production rhythm. After drying, lithium phosphate product is obtained.

[0029] Comparative Example 1 A method for preparing lithium phosphate material, the specific steps of which are as follows: (1) Prepare a lithium source solution (specifically, a lithium chloride solution with a lithium content of 20 g / L); (2) Maintain a rotation speed of 200 rpm and add 16m of [unclear] into the reactor sequentially. 3 Lithium source solution (flow rate 10m) 3 / h), 1.28m 3 Phosphoric acid solution (concentration 85%, flow rate 5m) 3 / h), heat to 80℃ and then at 5m 3 Add 3.1m at a flow rate of / h. 3 After adding 32% alkali solution, the pH of the solution was measured to be 7.5. 0.35 mg / L was then added. 3 The system pH was adjusted to 10.8 with liquid alkali and maintained at 80°C for 1 hour. (3) After the reaction is complete, the reactants are put into the batch tank for mixing, and then put into the centrifuge for dehydration according to the production rhythm. After drying, lithium phosphate product is obtained.

[0030] The centrifuge dewatering effect of lithium phosphate slurry in the examples and comparative examples was observed, and the particle size of the prepared lithium phosphate product was tested using a Malvern 2000 laser particle size analyzer. The test results are shown in Table 1. It should be noted that the laser particle size analyzer will automatically output a parameter characterizing the particle size uniformity after the test. The smaller the parameter, the more concentrated the particle size.

[0031] Table 1 Test Results

[0032] As shown in Table 1, this invention successfully synthesized large-particle-size lithium phosphate under high-concentration phosphoric acid conditions by controlling the flow rate and employing a three-stream parallel-flow reaction mode. Compared with Comparative Example 1, the lithium phosphate prepared by this invention has a significantly larger particle size and better particle size distribution consistency. The increased particle size and concentrated distribution help to shorten the centrifugal dehydration time and reduce the residual moisture content of the filter cake, thereby improving the dehydration performance of the product.

[0033] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for producing a lithium phosphate material having a large particle size, characterized by, The method comprises the following steps: preparing a lithium source solution, taking half of the lithium source solution and heating it to 70-80 DEG C as a bottom water, adding a phosphoric acid solution, a liquid alkali and the remaining lithium source solution into the bottom water under stirring, adjusting the pH of the system to 10.5-11 after the addition is completed, keeping the reaction at 75-80 DEG C for 1-2 hours; filtering and drying the reaction product to obtain the large-particle-size lithium phosphate.

2. The method for preparing large-particle-size lithium phosphate material according to claim 1, characterized in that, The lithium content in the lithium source solution is 18-20 g / L.

3. The method of claim 1, wherein the lithium phosphate material has a particle size of 1 to 10 μm. The concentration of the phosphoric acid solution is 75-85%; and / or The concentration of the liquid alkali is 30-35%.

4. The method of claim 1 to 3, wherein the lithium phosphate material having a large particle size is prepared by the steps of: The solute of the lithium source solution is at least one of lithium hydroxide, lithium carbonate, lithium bicarbonate and lithium chloride. ​ 5. The method of claim 1, wherein the lithium phosphate material has a particle size of 1 to 100 μm. The volume ratio of the phosphoric acid solution to the total lithium source solution is 1.15-1.28:

16.

6. The method of claim 1, wherein the lithium phosphate material has a particle size of 1 to 100 μm. In the step of adding the phosphoric acid solution, the liquid alkali and the remaining lithium source solution into the bottom water, the feeding flow rate ratio of the liquid alkali to the phosphoric acid solution is 2.3-2.9:1; the volume ratio of the liquid alkali to the phosphoric acid solution is 2.3-2.5:

1.

7. The method of claim 1, wherein the lithium phosphate material has a particle size of 1 to 100 μm. In the step of adding the phosphoric acid solution, the liquid alkali and the remaining lithium source solution into the bottom water, the feeding flow rate ratio of the liquid alkali to the remaining lithium source solution is 4.3-6.5:10; the volume ratio of the liquid alkali to the remaining lithium source solution is 2.7-3.1:

8.

8. The method of claim 1, wherein the lithium phosphate material has a particle size of 1 to 100 μm. The stirring rate is 120-300 rpm; and / or The specific operation of adjusting the pH of the system to 10.5-11 is adjusting the pH of the system by adding the liquid alkali.

9. A lithium phosphate material having a large particle size, characterized in that, The large-particle-size lithium phosphate material is prepared by the method of any one of claims 1-8.

10. The use of the large-particle-size lithium phosphate material of claim 9 in the preparation of a lithium battery cathode material.

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