Nano lithium phosphate and preparation method thereof

Abstract

The invention relates to the technical field of lithium phosphate preparation, in particular to nano lithium phosphate and a preparation method thereof. Comprising the following steps: adding a phosphorus source solution into supersaturated lithium source slurry, carrying out mixing reaction, carrying out solid-liquid separation on a reaction product to obtain a solid phase, and washing and drying the solid phase, the mass concentration of the supersaturated lithium source slurry is 3.7-10% in terms of lithium, and the mass concentration of the phosphorus source solution is 12-25% in terms of phosphorus; the molar ratio of the lithium element to the phosphorus element in the supersaturated lithium source slurry to the phosphorus source solution during the mixed reaction is (2.98-3.03): 1. According to the method, the phosphoric acid solution is added into the supersaturated lithium hydroxide slurry, and the nanoscale lithium phosphate with high purity, high yield, high solid content and relatively small particle size can be prepared by controlling the adding sequence of the acid-base raw materials and regulating and controlling the Li / P value of the system.

Description

Technical Field

[0001] This invention relates to the field of lithium phosphate preparation technology, specifically to a nano-lithium phosphate and its preparation method. Background Technology

[0002] As an important inorganic nanomaterial, lithium phosphate nanoparticles have broad application prospects in lithium-ion batteries, catalysts, ceramic materials, and other fields. In lithium-ion batteries, lithium phosphate can serve as a precursor for cathode materials, and its nanoscale particle size can significantly improve the battery's charge-discharge performance, cycle stability, and rate performance. With the rapid development of industries such as new energy vehicles and portable electronic devices, the demand for high-performance lithium phosphate is increasing, especially for lithium phosphate materials with high purity and nanoscale particle size.

[0003] Currently, lithium phosphate is commonly prepared in industry by extracting lithium from raw materials such as lithium ore, brine, and lithium-containing waste liquid, or by the lithium carbonate acid dissolution and neutralization method. However, these processes have problems such as complex routes, high impurity content in the product, large amount of washing water consumption, difficulty in controlling particle size to obtain nano-sized lithium phosphate, and environmental pollution.

[0004] High-quality nano-lithium phosphate is typically prepared by neutralizing lithium hydroxide monohydrate (or lithium hydroxide) with phosphoric acid. Alternatively, it can be prepared hydrothermally after neutralization. However, current technologies often use low-concentration systems as raw materials, resulting in low single-batch production capacity, low product yield, demanding requirements for reaction equipment, and the generation of large amounts of mother liquor, leading to high downstream water treatment costs and significant challenges for industrialization. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a nano-sized lithium phosphate and its preparation method. This invention involves adding a phosphoric acid solution to a supersaturated lithium hydroxide slurry. By controlling the order of addition of the acid and alkali raw materials and adjusting the Li / P ratio of the system, high-purity, high-yield, high-solid-content, and small-particle-size nano-sized lithium phosphate can be prepared.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing nano-lithium phosphate, comprising: adding a phosphorus source solution to a supersaturated lithium source slurry for mixing and reaction; washing and drying the solid phase obtained after solid-liquid separation of the reaction products; wherein the mass concentration of the supersaturated lithium source slurry is 3.7-10% based on lithium, and the mass concentration of the phosphorus source solution is 12-25% based on phosphorus; and the molar ratio of lithium to phosphorus in the supersaturated lithium source slurry and phosphorus source solution during the mixing reaction is (2.98-3.03):1.

[0007] Preferably, the phosphorus source is selected from one or more of phosphoric acid and lithium dihydrogen phosphate.

[0008] Preferably, the lithium source is lithium hydroxide.

[0009] Preferably, the pH value of the reaction process is 11.5~12.0.

[0010] Preferably, the mixing reaction process is carried out by stirring, and the stirring rate is 200~800 r / min.

[0011] Preferably, the reaction time is 0.5 to 6 hours.

[0012] Preferably, the reaction temperature is 25~80℃.

[0013] Preferably, the drying temperature is 70~120℃.

[0014] Preferably, the drying time is 4 to 12 hours.

[0015] Preferably, the mother liquor after solid-liquid separation of the reaction products and the wash water after solid-phase washing are recycled as dissolving water for phosphorus and lithium sources.

[0016] Secondly, the present invention provides a nano-lithium phosphate product prepared by the above-described preparation method.

[0017] The particle size of the nano-lithium phosphate is 30~65nm.

[0018] The beneficial effects of this invention are: The preparation method of this invention determines the amount of supersaturated lithium source and phosphorus source by the molar ratio of lithium and phosphorus, thereby maintaining the system in a high pH environment. Under this environment, by adding the phosphorus source solution to the supersaturated lithium source slurry, the PO4 in the phosphorus source solution is reduced. 3- With Li in lithium source slurry + This process rapidly generates lithium phosphate nanoparticles through nucleation, eliminating the need for additional impurity removal and concentration steps, thus avoiding excessive impurities and yielding high-purity products. Furthermore, this invention eliminates the need for hydrothermal reactors or microreactors, enabling the preparation of nano-lithium phosphate in conventional reactors. This reduces equipment and operating costs, while also facilitating increased production capacity and industrial scale-up, creating favorable conditions for large-scale industrialization.

[0019] The preparation method described in this invention produces no byproducts, and the mother liquor after solid-liquid separation and the wash water after solid-phase washing are both solutions containing trace amounts of lithium and phosphorus, which can be recycled as phosphorus and lithium source dissolution water. This eliminates the need for downstream water treatment equipment, and the recycling of the mother liquor and wash water reduces water consumption, achieving water recycling and making the process more economical and environmentally friendly.

[0020] Compared with existing products, the nano-lithium phosphate product prepared by this invention has a smaller particle size and higher purity, meeting the requirements for high-performance lithium phosphate products. Attached Figure Description

[0021] Figure 1 Flowchart of the preparation process for nano-lithium phosphate; Figure 2 XRD pattern of the nano-lithium phosphate product prepared in Example 1; Figure 3 The images show the primary particle morphology of the lithium phosphate products prepared in Example 1, Comparative Example 1, and Comparative Example 2. Figure 4 These are morphological images of lithium phosphate products obtained from different treatment groups in Example 2; Figure 5 The image shows the primary particle size distribution of lithium phosphate products obtained from different treatment groups in Example 2. Figure 6 These are morphological images of lithium phosphate products obtained from different treatment groups in Example 3; Figure 7 These are morphological images of lithium phosphate products obtained from different treatment groups in Example 3; Figure 8 The image shows the primary particle size distribution of lithium phosphate products obtained from different treatment groups in Example 3. Figure 9 The image shows the primary particle size distribution of lithium phosphate products obtained from different treatment groups in Example 3. Figure 10 These are morphological images of lithium phosphate products obtained from different treatment groups in Example 4; Figure 11 The image shows the primary particle size distribution of lithium phosphate products obtained from different treatment groups in Example 4. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solution of the invention, the invention will be further described in detail below with reference to specific embodiments.

[0023] Currently, the difficulties in lithium phosphate preparation lie in product purity, product yield, product morphology control, low unit capacity, and wastewater and waste residue treatment. To achieve the preparation of high-purity, high-yield, high-solid-content, and small-particle-size nano-sized lithium phosphate, this invention provides a method for preparing nano-lithium phosphate, comprising: adding a phosphorus source solution to a supersaturated lithium source slurry for mixing and reaction; washing and drying the solid phase obtained after solid-liquid separation of the reaction products; wherein the mass concentration of the supersaturated lithium source slurry is 3.7-10% (calculated as lithium), and the mass concentration of the phosphorus source solution is 12-25% (calculated as phosphorus); during the mixing reaction, the molar ratio of lithium to phosphorus in the supersaturated lithium source slurry and phosphorus source solution is (2.98-3.03):1.

[0024] This invention determines the amount of supersaturated lithium and phosphorus sources used in the reaction process by controlling the molar ratio of lithium and phosphorus, thereby maintaining the system in a high pH environment. Under this environment, by adding the phosphorus source solution to the supersaturated lithium source slurry, the PO4 in the phosphorus source solution is reduced. 3- With Li in lithium source slurry + This process rapidly generates lithium phosphate nanoparticles through nucleation, eliminating the need for additional impurity removal and concentration steps, thus avoiding excessive impurities and yielding high-purity products. Furthermore, this invention eliminates the need for hydrothermal reactors or microreactors, enabling the preparation of nano-lithium phosphate in conventional reactors. This reduces equipment and operating costs, while also facilitating increased production capacity and industrial scale-up, creating favorable conditions for large-scale industrialization.

[0025] The principle of preparing nano-lithium phosphate in this invention is as follows: The following ionization equilibrium and reaction exist in the solution of the system of this invention: H3PO4 = H2PO4 - + H + ; H2PO4 - = HPO4 2- + H + ; HPO4 - = PO4 3- + H + ; H - +OH - = H2O; PO4 3- + 3Li + =Li3PO4↓; LiOH·H2O = Li + + OH - + H2O; Or LiOH = Li + + OH - .

[0026] When the phosphorus source solution is added to the lithium source slurry, the H in the phosphorus source solution... + With OH in lithium source slurry - Rapidly combine to form H2O, combining H3PO4 and H2PO4 - HPO4 2- As the molecules move in the direction of ionization, a large amount of PO4 will rapidly form in the solution. 3- Because lithium phosphate is a sparingly soluble salt, its K... sp Approximately 2.0 × 10-11 Li + With PO4 3- They coexist stably at pH < 5.0. When the solution pH exceeds 5.0, both lithium ions and phosphate ions crystallize out as Li3PO4. The higher the pH, the higher the concentration of lithium ions and phosphate ions, and the faster the crystallization rate. This invention controls the reaction system in a high pH environment by controlling the molar ratio of lithium and phosphorus elements in the supersaturated lithium source slurry and phosphorus source solution. At this pH, lithium ions and phosphate ions crystallize out rapidly in large quantities, bursting into nucleation to obtain nanoscale lithium phosphate. During the crystallization process, OH groups in the system are continuously consumed. - and Li + However, if there is an excess of undissolved LiOH·H2O or LiOH solid in the lithium source slurry, it will continue to dissolve to maintain the high Li content of the system. + The concentration and high pH environment prevent the growth of lithium phosphate single crystals, ultimately resulting in nanoscale lithium phosphate products.

[0027] In some embodiments of the present invention, the molar ratio of lithium to phosphorus in the supersaturated lithium source and phosphorus source is any one of 2.98:1, 3:1, 3.03:1, or a value between both. Exceeding the range defined in this invention will affect the purity, yield, and morphology of the product.

[0028] Existing technologies for preparing lithium phosphate typically use fully dissolved, low-concentration lithium sources, with the Li concentration in the source solution usually controlled below 2.5%, resulting in a product slurry solid content below 10% and low yield per reaction. The supersaturated lithium source slurry of this invention has a mass concentration of 3.7-10% (based on lithium) and the phosphorus source solution has a mass concentration of 12-25% (based on phosphorus). In some embodiments of this invention, the supersaturated lithium source slurry has a mass concentration of any one of 3.7%, 6.9%, or 10% (based on lithium) or a value between two of these; the phosphorus source solution has a mass concentration of any one of 12%, 18%, or 25% (based on phosphorus) or a value between two of these. This allows the product size to be maintained at a small nanometer scale, and the final product slurry solid content reaches 15%-35%, increasing the lithium phosphate production capacity per unit volume by 1.5-4.0 times compared to mainstream processes. Furthermore, if a low-concentration unsaturated lithium source is used, the prepared lithium phosphate product will be large micron-sized particles, which does not meet the product requirements of this invention.

[0029] The phosphorus source described in this invention is selected from one or more of phosphoric acid and lithium dihydrogen phosphate. When the phosphorus source is lithium dihydrogen phosphate, a portion of the lithium source may also be provided.

[0030] The lithium source described in this invention is lithium hydroxide.

[0031] In the neutralization process for preparing lithium phosphate, increasing the solution pH is typically used to improve yield, usually controlled to around 8.5, yet the yield only reaches about 96%. Since the lithium source accounts for about 90% of the raw material cost, improving the Li yield is essential. To improve the yield, this invention controls the pH of the reaction process to 11.5-12.0 by adjusting the molar ratio of lithium and phosphorus in the lithium source slurry and phosphorus source solution, achieving a Li yield of over 99%. In some embodiments of this invention, the pH of the reaction process is any one of 11.5, 11.8, or 12.0, or a value between two of these.

[0032] The mixing reaction process described in this invention employs stirring, with a stirring rate of 200~800 r / min.

[0033] The reaction time described in this invention is 0.5 to 6 hours.

[0034] The reaction temperature described in this invention is 25~80℃. The drying temperature described in this invention is 70~120℃.

[0035] The drying time described in this invention is 4 to 12 hours.

[0036] Existing technologies for preparing lithium phosphate from raw materials require processes such as mother liquor concentration, impurity removal, concentration, and precipitation. This generates waste solids after impurity removal and waste liquid containing sodium sulfate or ammonium sulfate after precipitation. This waste liquid requires additional water treatment equipment and may also produce low-value byproducts such as sodium sulfate, increasing production costs. The preparation method described in this invention produces no byproducts, and both the mother liquor after solid-liquid separation and the wash water after solid-phase washing are solutions containing trace amounts of lithium and phosphorus, which can be recycled as phosphorus and lithium source dissolving water. This offers two advantages: first, it eliminates the need for downstream water treatment equipment; second, the recycling of mother liquor and wash water reduces water consumption. This invention fundamentally solves the problems of wastewater and waste residue, reduces environmental pollution, and has significant socio-economic benefits.

[0037] Secondly, the present invention provides a nano-lithium phosphate product prepared by the above-described preparation method.

[0038] The particle size of the nano-lithium phosphate is 30~65nm.

[0039] Compared with existing products, the nano-lithium phosphate product prepared by this invention has a smaller particle size and higher purity, meeting the requirements for high-performance lithium phosphate products.

[0040] The above is a detailed description of the technical solution of the present invention. The following are embodiments of the present invention.

[0041] Example 1 Preparation of nano-lithium phosphate 1. Selecting raw materials Phosphoric acid was chosen as the phosphorus source, and lithium hydroxide monohydrate was chosen as the lithium source. The raw material specifications are as follows: Table 1. Phosphoric acid index

[0042] Table 2. Lithium hydroxide monohydrate index

[0043] 2. See the process flow diagram. Figure 1 The preparation process includes the following steps: S1. Mix lithium hydroxide monohydrate with water to prepare a slurry, resulting in a supersaturated lithium hydroxide slurry (calculated as Li, with Li accounting for 3.7% by mass in the slurry or solution); prepare phosphoric acid solution (calculated as P, with a mass concentration of 20%); control the amount of supersaturated lithium hydroxide slurry and phosphoric acid solution according to the Li / P ratio of 3.0 (molar ratio); S2. At 25℃, add phosphoric acid solution to supersaturated lithium hydroxide slurry for neutralization reaction, while controlling the stirring speed at 200 r / min, the reaction time at 2 h, the pH of the reaction system at 11.8, and then age for 2.0 hours after mixing. S3. After the reaction is completed, the lithium phosphate precipitate is separated from the reaction mother liquor by centrifugation. The precipitate is washed with deionized water for 2-3 stages to remove the entrained soluble lithium salt. The washed product is dried at 80°C for 6 hours to obtain nano lithium phosphate powder. In this scheme, the lithium yield is 99.43% and the product purity is 99.6%.

[0044] S4. The mother liquor after solid-liquid separation and the wash water after washing in S3 are returned to S1 and recycled as solvents.

[0045] Comparative Example 1: Preparation of lithium nanoparticles using conventional methods S1. Mix lithium hydroxide monohydrate with water to prepare a slurry, resulting in a lithium hydroxide slurry (calculated as Li, with a mass concentration of 0.7%); prepare phosphoric acid solution (calculated as P, with a concentration of 20%); control the amount of supersaturated lithium hydroxide slurry and phosphoric acid solution according to the Li / P ratio of 3.0 (molar ratio); S2. At 25°C, lithium hydroxide slurry is added to phosphoric acid solution while the stirring speed is controlled at 200 r / min. The reaction time is 2 h and the pH of the reaction system is 11.4. After mixing, the mixture is aged for another 2.0 hours. S3. After the reaction is complete, the lithium phosphate precipitate is separated from the mother liquor by centrifugation. The precipitate is then washed 2-3 times with deionized water to remove any entrained soluble lithium salts. The washed product is dried at 80°C for 6 hours to obtain nano-lithium phosphate powder. In this method, the lithium yield is 99.50%, and the product purity is 99.2%.

[0046] Comparative Example 2: Preparation of lithium nanoparticles using conventional methods S1. Mix lithium hydroxide monohydrate with water to prepare a slurry, resulting in a lithium hydroxide slurry (calculated as Li, with a mass concentration of 1.1%); prepare phosphoric acid solution (calculated as P, with a concentration of 20%); control the amount of supersaturated lithium hydroxide slurry and phosphoric acid solution according to the Li / P ratio of 3.0 (molar ratio); S2. At 50℃, add phosphoric acid solution to lithium hydroxide slurry while controlling the stirring speed at 200 r / min, the reaction time is 2 h, the pH of the reaction system is 10.0, and after mixing, it is aged for 3.0 hours. S3. After the reaction is complete, the lithium phosphate precipitate is separated from the reaction mother liquor by centrifugation, pressure, or membrane washing. The precipitate is then washed 2-3 times with deionized water to remove any entrained soluble lithium salts. The washed product is dried at 80°C for 6 hours to obtain nano-lithium phosphate powder. In this process, the lithium yield is 97.26%, and the product purity is 99.1%.

[0047] The products of Example 1 and Comparative Examples 1-2 were tested, and the results are as follows: (1) Product chemical indicators The chemical composition detection data of the products in Example 1 and Comparative Examples 1-2 are shown in Table 3. The phase identification results of the product in Example 1 are shown in Table 3. Figure 2 .

[0048] Table 3. Product Chemical Indicators

[0049] As can be seen, the product prepared in this embodiment is pure-phase lithium phosphate with a purity of 99.6%, which is higher than that of the prior art.

[0050] (2) Product size and shape Table 4. Average size of primary lithium phosphate particles

[0051] It can be seen that the particle size of the product prepared in Example 1 of the present invention is significantly reduced, with an average size of only about 37 nm.

[0052] Figure 3The figures show the primary particle morphology of lithium phosphate products prepared in Example 1, Comparative Example 1, and Comparative Example 2 (scale bar is 300 nm). As can be seen from the figures, Comparative Example 1 and Comparative Example 2 are both rod-shaped particle aggregates. The average size of the micron-sized particles in Comparative Example 1 is 1776 nm, and the particle size in Comparative Example 2 is about 300 nm. In contrast, the primary particles of lithium phosphate prepared by the process of this invention are nano-sized particles with an average primary particle size of 37 nm.

[0053] Example 2: Investigation of Li / P molar ratio 1. Experimental Condition Design Nano-lithium phosphate was prepared according to the method in Example 1. With other parameters kept constant, the Li / P molar ratio was adjusted to investigate the effect of the product prepared under different Li / P molar ratios. The experimental control conditions are shown in Table 5.

[0054] Table 5. Experimental Control Conditions

[0055] 2. Experimental effect test: 2.1 Product purity test Table 6. Product purity under different Li / P conditions

[0056] As shown in Table 6, the Li / P molar ratio has a significant impact on the purity of lithium phosphate products. This is because a lower Li / P ratio may result in the presence of lithium dihydrogen phosphate in the product, thus reducing its purity. When Li / P ≤ 2.95, the product purity is below 99%. Conversely, a higher Li / P ratio may result in the presence of unreacted LiOH, further reducing purity. When Li / P ≥ 3.06, the product purity is below 99%. Therefore, the optimal Li / P molar ratio in the process is 2.98–3.03.

[0057] 2.2 Product Yield Test Table 7. Product yield (in Li) under different Li / P conditions

[0058] As shown in Table 7, the Li / P molar ratio has a significant impact on the Li yield in the reaction. This is because when precipitating Li3PO4, the Li / P ratio is 3:1. When the Li / P ratio of the reaction feed is greater than 3.0, some Li cannot precipitate. When the Li / P ratio is greater than 3.06, the Li recovery rate is only 97.16%. Similarly, when the Li / P ratio is less than 3.0, some PO4 remains in the solution. 3-The inability to settle reduces the yield. Considering all factors, a Li / P ratio of 2.98–3.03 is more suitable.

[0059] 2.3 Product Dimension Measurement Figure 4 The morphology images of lithium phosphate products obtained from different treatment groups (scale bar: 300 nm) show significant differences in primary particle morphology between products with excessively low and high Li / P molar ratios. When Li / P < 2.98 or Li / P > 3.03, the products are all rod-shaped particles. When the Li / P molar ratio is 2.98 ≤ Li / P ≤ 3.03, the primary particles are approximately spherical particles around 50 nm in size. The particle size was measured (see...). Figure 5 It can be seen that within the range of 2.98 ≤ Li / P ≤ 3.03, the primary particle size is small, ranging from 37 to 61 nm. When Li / P = 3.06, the primary particle size reaches 192 nm, and when Li / P = 2.95, it even reaches 422 nm. Therefore, it is necessary to control the Li / P ratio in the reaction feed to regulate the product morphology.

[0060] 2.4 Product slurry solids content test Solid content: The proportion of lithium phosphate solid mass in the material after S2 aging to the total mass of the reactants.

[0061] Table 8. Solid content of the system under different Li / P conditions

[0062] As can be seen from Table 8, the Li / P molar ratio is only a minor adjustment to the material ratio and has little effect on the solid content of the product.

[0063] Example 3: Investigation of Raw Material Concentration 1. Experimental Condition Design Nano-lithium phosphate was prepared according to the method in Example 1. With other parameters kept constant, the concentrations of supersaturated lithium hydroxide slurry and phosphoric acid solution were adjusted to investigate the effect of the product prepared under different raw material concentrations. The experimental control conditions are shown in Table 9.

[0064] Table 9. Experimental Control Conditions

[0065] 2. Experimental effect test: 2.1 Product purity test Table 10. Product purity under different Li concentrations at P=20%

[0066] Table 11. Product purity under different P concentrations (Li=3.70%)

[0067] As can be seen from Tables 10 and 11, the material concentration has no significant effect on the purity of the product. Within the scope of this invention, the purity of the product is above 99.5%.

[0068] 2.2 Product Yield Test Table 12. Product yield (based on Li) under different Li concentrations at P=20%.

[0069] Table 13. Product yield (based on Li) under different P concentrations (Li=3.70%)

[0070] As can be seen from Tables 12 and 13, the lithium yield of the product is not significantly affected by the concentrations of Li and P in the materials. Within the scope defined by this invention, the Li yield is above 99%.

[0071] 2.3 Product Dimension Measurement Figures 6-7 Morphology images of lithium phosphate products obtained from different treatment groups (scale bar is 300 nm). Figures 8-9 This image shows the primary particle size distribution of lithium phosphate products obtained from different treatment groups. Figure 6 and Figure 8 It can be seen that Li concentration has the most significant impact on product morphology and size. When Li concentration < 3.7%, the product morphology is rod-shaped particles. When Li = 0.7%, the primary particle size is 1848 nm, and when Li = 1.1%, the primary particle size is still 276 nm. When Li concentration ≥ 3.7%, nano-sized lithium phosphate particles are obtained. When Li = 3.7 nm, the primary particle size is 37 nm, and when Li = 13%, it is still 39 nm. However, when the Li concentration is 13%, the water content of the prepared LiOH slurry (excluding the water of crystallization in LiOH·H2O) is only about 22%, making the reaction difficult and resulting in poor batch stability. When the Li concentration is 10%, the slurry contains about 40% water (excluding the water of crystallization in LiOH·H2O), thus the slurry has better fluidity, and the product morphology and indicators are more stable. In summary, the Li concentration should be controlled within the range of 3.7% to 10.0%.

[0072] Depend on Figure 7 and Figure 9 It can be seen that the P concentration has little effect on the morphology and size of the product. When the Li concentration is 3.7% and the P concentration is 6%~25%, the product consists of spherical particles of 30~50nm.

[0073] 2.4 Product slurry solids content test Table 14. Solid content of products under different Li concentrations at P=20%

[0074] Table 15. Solid content of products under different P concentrations (Li=3.7%)

[0075] The concentrations of Li and P in the reactants have a significant impact on the solid content of the reaction products, directly affecting the process capacity. Analysis of Tables 14 and 15 shows that, under the condition of P=20%, increasing the Li concentration significantly increases the Li concentration. When Li < 3.7%, the solid content of the reaction products is below 6%; when P < 12%, the solid content is below 15%, resulting in relatively low production efficiency. Even at P=12%, the solid content is still below 15%, but by appropriately increasing the Li concentration, the solid content can reach above 15%. In summary, considering both product morphology and production efficiency, the Li concentration should be controlled between 3.7% and 10%, and the P concentration between 12% and 25%.

[0076] Example 4: Investigation of the order of raw material addition 1. Experimental Condition Design Nano-lithium phosphate was prepared according to the method in Example 1. With other parameters kept constant, the order of raw material addition was changed to investigate the effect of the order of raw material addition on the effect. The experimental design is shown in Table 16.

[0077] Table 16. Experimental Control Conditions

[0078] Note: Treatment group 2 and treatment group 3 are two repeated experiments conducted using the same sample addition method.

[0079] 2. Experimental effect test: 2.1 Product purity test Table 17. Product purity under different sample addition methods

[0080] As shown in Table 17, the purity of lithium phosphate products obtained by the two addition methods is not significantly different, reaching approximately 99.5%. Lithium hydroxide slurry contains a high amount of solids, making it difficult to transport via pipelines. Inaccurate metering during transport may occur, leading to variations in chemical properties between different batches, which hinders industrial scale-up. Therefore, adding phosphoric acid to the lithium hydroxide slurry is more feasible.

[0081] 2.2 Product Yield Test Table 18. Lithium yield of products with different sampling methods

[0082] As can be seen from Table 18, the yield of Li in the reaction is not much different between the two addition methods, both reaching over 99%.

[0083] 2.3 Product Dimension Measurement Figure 10 Morphology images of lithium phosphate products obtained from different treatment groups (scale bar is 300 nm). Figure 11 The diagram shows the primary particle size of lithium iron phosphate products obtained from different treatment groups. It can be seen that the product obtained by adding phosphoric acid to the lithium hydroxide slurry consists of nano- and small particles with a primary particle size of 37 nm. Lithium iron phosphate prepared by adding phosphoric acid to lithium hydroxide slurry may exhibit unstable morphology. The primary particle size of the product in treatment group 2 is around 201 nm, while the primary particle size of treatment group 3, which also uses the same method of adding phosphoric acid to lithium hydroxide slurry, is uneven, with small particles around 288 nm in size, but also containing large particles larger than 1 μm. Therefore, it is determined that adding phosphoric acid to lithium hydroxide slurry can prepare stable nano-sized lithium iron phosphate particles.

[0084] 2.4 Product slurry solids content test Table 19. Solid content of products with different sampling methods

[0085] As can be seen from Table 19, the sampling method has little effect on the solid content of the product. Within the scope of this invention, the solid content of the product is close to about 16.10%.

[0086] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing nanoscale lithium phosphate, characterized by, The preparation method comprises the following steps: The phosphorus source solution is added into the supersaturated lithium source slurry to mix and react, and then the solid phase obtained after the solid-liquid separation of the reaction product is washed and dried to obtain the nano lithium phosphate product.

2. The method for preparing nano-lithium phosphate according to claim 1, characterized in that, The mass concentration of the supersaturated lithium source slurry is 3.7-10% in terms of lithium.

3. The method for preparing nano-lithium phosphate according to claim 1, characterized in that, The mass concentration of the phosphorus source solution is 12-25% in terms of phosphorus.

4. The method of claim 1 to 3, wherein the lithium phosphate nanomaterial is prepared by the following steps: The molar ratio of lithium element to phosphorus element in the supersaturated lithium source slurry and the phosphorus source solution during the mixing and reaction is (2.98-3.03):

1. ​ 5. The method for preparing nano-lithium phosphate according to any one of claims 1 to 3, characterized in that, The phosphorus source is selected from one or more of phosphoric acid and lithium dihydrogen phosphate.

6. The method for preparing nano-lithium phosphate according to any one of claims 1 to 3, characterized in that, The lithium source is lithium hydroxide.

7. The method for preparing nano-lithium phosphate according to any one of claims 1 to 3, characterized in that, The pH value of the reaction process is 11.5-12.

0.

8. The method for preparing nano-lithium phosphate according to any one of claims 1 to 3, characterized in that, The mixing and reaction process adopts stirring, and the stirring rate is 200-800 r / min. The reaction temperature is 25-80℃.

10. The nano-lithium phosphate product of claim 9, wherein, The reaction time is 0.5-6 h. The mother liquor after the solid-liquid separation of the reaction product and the washing water after the washing of the solid phase are recycled as the phosphorus source and the lithium source dissolving water.

9. A nano lithium phosphate product prepared by the preparation method in any one of claims 1-8. The particle size of the nano lithium phosphate product is 30-65 nm.

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