A method for producing lithium phosphate

Abstract

The application discloses a preparation method of lithium phosphate, and belongs to the technical field of automobile lithium ion battery materials. The method comprises the following steps: adding a modified template agent into a phosphoric acid solution, adding a lithium hydroxide aqueous solution after stirring under heating, controlling the end point pH, continuing to heat and stir, filtering, washing, vacuum drying, and thus obtaining lithium phosphate powder; the modified template agent is prepared by reacting Pluronic F127 after being activated by N,N'-carbonyl diimidazole and an amine compound. Compared with the prior art, the lithium phosphate prepared by the method has a narrower particle size distribution and a higher specific surface area, and when used as an electrolyte additive of an automobile lithium battery, the lithium phosphate helps to improve the stability of electrolyte and the cycle life, and when used as a precursor of a positive electrode material, the lithium phosphate can improve the consistency of the electrode material, meets the requirements of a power battery on safety and energy density, and the process condition is mild and easy to be applied in industrialization.

Description

Technical Field

[0001] This invention relates to the field of automotive lithium-ion battery materials technology, and in particular to a method for preparing lithium phosphate. Background Technology

[0002] Lithium phosphate, as an important electrolyte additive and cathode material precursor for lithium-ion batteries, has broad application prospects in the new energy field. Currently, the main methods for preparing lithium phosphate include high-temperature solid-state methods, liquid-phase precipitation methods, and sol-gel methods. High-temperature solid-state methods typically use lithium carbonate and phosphate as raw materials, synthesized through high-temperature calcination under an inert atmosphere. While simple to operate and easy to industrialize, they suffer from defects such as uneven particle size, irregular crystal morphology, and a wide particle size distribution, and the high energy consumption of high-temperature sintering is significant. Liquid-phase precipitation methods directly precipitate lithium phosphate by adding phosphoric acid or phosphate to a lithium-containing solution. The reaction conditions are mild, and the product purity is high. However, conventional liquid-phase methods lack effective control over crystal nucleation and growth processes, resulting in poor controllability of product particle size and morphology. Sol-gel methods can achieve uniform mixing at the molecular level, but the process cycle is long, the cost is high, and industrialization is difficult. In addition, hydrometallurgical processes for recovering lithium phosphate from spent lithium batteries have also attracted attention. However, these methods require multiple steps such as acid leaching and impurity removal, making the process complex and prone to introducing impurities.

[0003] Patent CN119191317A discloses a method for preparing lithium hexafluorophosphate using an organic solvent method under ammonia catalysis. However, its reaction system and process conditions differ significantly from those used in lithium phosphate preparation. The raw materials, such as potassium hexafluorophosphate and lithium hydride, as well as the acetonitrile solvent system, cannot be directly applied to lithium phosphate synthesis. The article "Synthesis and Characterization of Ultrafine Lithium Phosphate by Turbulent Circulation Method" published in the *Journal of Chemical Industry and Engineering* reports a new process for preparing ultrafine lithium phosphate using a co-precipitation method under turbulent circulation. However, its turbulent circulation equipment has a complex structure, requires high process control, and there is still room for further improvement in the specific surface area of ​​the product.

[0004] In summary, existing methods for preparing lithium phosphate generally suffer from problems such as high energy consumption and uneven product particle size in high-temperature solid-phase methods, insufficient crystal growth control and wide particle size distribution in conventional liquid-phase methods, as well as complex and costly specialized equipment. Therefore, developing a preparation method with mild process conditions, simple equipment requirements, and the ability to effectively control the growth and morphology of lithium phosphate crystals has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method for preparing lithium phosphate.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing lithium phosphate is as follows: A modified template agent was added to a phosphoric acid solution, and the mixture was heated and stirred. Then, an aqueous solution of lithium hydroxide was added dropwise while stirring was maintained. When the pH of the system reached 7.5-9, the dropwise addition was stopped, and the mixture was kept warm and stirred. After the reaction was completed, the mixture was filtered, washed, and the filter cake was vacuum dried to obtain lithium phosphate powder. The modified template agent is prepared by dissolving Pluronic F127 in anhydrous toluene, activating it with N,N'-carbonyldiimidazole, removing the solvent by rotary evaporation, dissolving the residue in anhydrous acetonitrile and adding it dropwise to an excess of amine compound, precipitating it by vacuum distillation, and drying it under vacuum.

[0007] Preferably, the lithium phosphate is prepared by the following method, in parts by weight: Add 60-150 parts of a 0.1-1 mol / L phosphoric acid solution to a reaction vessel, add 1-3 parts of a modified template agent, and stir at 100-500 r / min for 5-50 min at 70-95℃. Then, add a 0.5-3 mol / L lithium hydroxide aqueous solution dropwise while maintaining stirring at 100-500 r / min. Stop the dropwise addition when the pH of the system reaches 7.5-9, and continue stirring at the same temperature for 10-90 min. After the reaction is complete, filter the solution and wash it 1-6 times with hot distilled water at 40-70℃. Vacuum dry the filter cake to obtain lithium phosphate powder.

[0008] A further preferred embodiment is the preparation method of the lithium phosphate, in parts by weight: Add 60-150 parts of a 0.1-1 mol / L phosphoric acid solution to a reaction vessel, along with 1-3 parts of a modified template agent and 0.1-0.5 parts of dodecyltrimethylammonium bromide. Stir at 100-500 r / min for 5-50 min at 70-95℃. Then, add a 0.5-3 mol / L lithium hydroxide aqueous solution dropwise while maintaining stirring at 100-500 r / min. Stop the dropwise addition when the pH of the system reaches 7.5-9, and continue stirring at the same temperature for 10-90 min. After the reaction is complete, filter the solution and wash it 1-6 times with hot distilled water at 40-70℃. Vacuum dry the filter cake to obtain lithium phosphate powder.

[0009] The dropping rate is 1-5 mL / min.

[0010] The filter cake vacuum drying is performed by drying the filter cake at 60-85℃ and -0.08 to -0.10 MPa for 1-20 hours.

[0011] The modified template agent is prepared as follows, in parts by weight: Add 5-15 parts of Pluronic F127 to 20-50 parts of anhydrous toluene, add 0.5-4 parts of N,N'-carbonyldiimidazole, treat at room temperature under nitrogen protection for 2-6 hours, and remove the solvent by rotary evaporation; dissolve the residue in 10-40 parts of anhydrous acetonitrile, add dropwise to 30-80 parts of amine compound, treat at 40-70℃ for 2-10 hours, distill under reduced pressure, precipitate the reaction solution with anhydrous diethyl ether, and dry under vacuum at 40-60℃ and -0.08 to -0.10 MPa for 8-16 hours to obtain the modified template agent.

[0012] The rotary evaporator is set at a water bath temperature of 40-50℃, a vacuum degree of -0.08 to -0.095 MPa, a rotation speed of 10-100 rpm, and a evaporation time of 5-40 minutes.

[0013] The vacuum distillation is carried out under conditions of -0.08 to -0.095 MPa and a water bath temperature of 60-80℃ for 20-40 minutes.

[0014] The vacuum drying is performed at 40-60℃ and -0.08 to -0.10 MPa for 8-16 hours.

[0015] The amine compound is at least one of 1,3-propanediamine, 1,2-propanediamine, 1,5-pentanediamine, diethylenetriamine, m-phenylenediamine, and ethylenediamine.

[0016] Preferably, the amine compound is composed of 1,2-propanediamine and m-phenylenediamine in a mass ratio of 0.5-2:0.5-2.

[0017] To address the issues of weak adsorption capacity and limited regulatory effect of conventional template agents on lithium phosphate crystal faces, this invention employs an amino-terminated modification strategy. The terminal hydroxyl group of Pluronic F127 is activated by N,N'-carbonyldiimidazole and then reacted with an amine compound to introduce a nitrogen-containing functional group at the polymer chain end. The hydrogen bonding between the amino hydrogen and phosphate group firmly anchors the template agent to the crystal face, thereby effectively inhibiting excessive grain growth and obtaining lithium phosphate products with significantly reduced particle size and narrowed distribution.

[0018] Furthermore, to address the shortcomings of single amine-modified template agents in terms of the density and balanced regulation of the adsorption layer on the crystal face, this invention further adopts a rigid-flexible chain segment combination strategy, grafting a compact flexible aliphatic diamine and an aromatic diamine containing a rigid benzene ring onto the end of the template agent. Utilizing the synergistic effect of the rigid chain providing a stable adsorption framework and the flexible chain imparting spatial compliance, the template agent forms a more dense and ordered adsorption layer on the crystal face, achieving more balanced regulation of the growth rate of lithium phosphate on each crystal face, and further improving the uniformity of the product.

[0019] Furthermore, the compound modified template agent still has limitations in terms of nucleation site control and spatial confinement ability. To address this, the present invention introduces a cationic quaternary ammonium salt surfactant into the lithium phosphate precipitation system. By utilizing the hydrophobic co-assembly of its hydrophobic tail chain with the hydrophobic chain segment of the modified template agent and the electrostatic enrichment effect of the quaternary ammonium head group on phosphate, a regular composite micelle template is formed through self-assembly. This template constructs a local high-concentration phosphate microregion on the micelle surface and forms a curved confinement effect, thereby enhancing the uniformity of nucleation and guiding the growth of crystal spheres. Ultimately, a regular lithium phosphate powder with smaller particle size and significantly increased specific surface area is obtained.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects: 1) This invention enhances the crystal plane anchoring effect by modifying the template agent with terminal amino groups, resulting in a narrower particle size distribution of the product. When used as an electrolyte for automotive lithium batteries, it helps to improve the uniformity of electrolyte wetting and the consistency of the cell.

[0021] 2) The present invention uses a combination of rigid and flexible segments to make the template agent adsorption layer more dense and orderly, and the product morphology more regular, which can improve the processing fluidity of the cathode material precursor and the uniformity of electrode coating.

[0022] 3) This invention introduces cationic quaternary ammonium salts to construct composite micelles to enhance confined nucleation, which significantly increases the specific surface area. When used as a power battery material, it is beneficial to improve the lithium-ion transport rate and rate performance. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention.

[0024] The specific details of the raw materials used in the embodiments of the present invention are as follows: Pluronic F127, CAS number 9003-11-6, average molecular weight approximately 12,600, purchased from Merck AG, Germany, product number P2443, is a commercially available product.

[0025] PEG-400, CAS No. 25322-68-3, average molecular weight 400, colorless, transparent, viscous liquid, analytical grade, commercially available product.

[0026] Dodecyltrimethylammonium bromide, CAS No. 1119-94-4, purity ≥99.0%, analytical grade, commercially available product.

[0027] N,N'-carbonyldiimidazole, CAS No. 530-62-1, purity ≥98.0%, white or off-white powder, commercially available product.

[0028] 1,3-Propanediamine, CAS No. 109-76-2, purity ≥99.0%, colorless to pale yellow transparent liquid, commercially available product.

[0029] 1,2-Propanediamine, CAS No. 78-90-0, is a colorless, transparent, viscous liquid at room temperature with a purity of ≥99.0%, and is a commercially available product.

[0030] 1,5-Pentanediamine, CAS No. 462-94-2, is a colorless viscous liquid at room temperature with a purity of ≥99.0%, and is a commercially available product.

[0031] Diethylenetriamine, CAS No. 111-40-0, purity ≥99.5%, colorless to pale yellow viscous liquid, commercially available product.

[0032] m-Phenylenediamine, CAS No. 1477-55-0, purity ≥99.0%, colorless and transparent liquid, commercially available product.

[0033] Ethylenediamine, CAS No. 107-15-3, purity ≥99.0%, is a colorless, transparent, viscous liquid, a commercially available product.

[0034] In the embodiments and comparative examples of this invention, all raw materials are commercially available products. Example 1

[0035] A method for preparing lithium phosphate is as follows, in parts by weight: 100 parts of a 0.4 mol / L phosphoric acid solution were added to a reaction vessel, along with 2 parts of a modified template agent. The mixture was stirred at 250 r / min for 20 min at 90 °C. Subsequently, a 1.8 mol / L lithium hydroxide aqueous solution was added dropwise at a rate of 3 mL / min, while maintaining stirring at 250 r / min during the addition. The addition was stopped when the pH of the system reached 8, and the mixture was kept at the same temperature and stirred for another 45 min. After the reaction was completed, the mixture was filtered and washed four times with hot distilled water at 55 °C. The filter cake was then dried under vacuum at 75 °C and -0.09 MPa for 10 h to obtain lithium phosphate powder.

[0036] The modified template agent is prepared as follows, in parts by weight: Ten parts of Pluronic F127 were added to 30 parts of anhydrous toluene, and 1.8 parts of N,N'-carbonyldiimidazole were added. The mixture was treated at room temperature under nitrogen protection for 4 hours. The solvent was removed by rotary evaporation at a water bath temperature of 42℃, a vacuum of -0.09MPa, and a rotation speed of 80rpm for 30 minutes. The residue was dissolved in 20 parts of anhydrous acetonitrile and added dropwise to 50 parts of amine compounds. The mixture was treated at 50℃ for 6 hours and then distilled under reduced pressure at -0.09MPa and a water bath temperature of 70℃ for 30 minutes. The reaction solution was precipitated with anhydrous diethyl ether and dried under vacuum at 50℃ and -0.09MPa for 10 hours to obtain the modified template agent.

[0037] The amine compound is 1,3-propanediamine. Example 2

[0038] The preparation method of lithium phosphate is basically the same as that in Example 1, except that the amine compound in the preparation method of the modified template agent is 1,2-propanediamine. Example 3

[0039] The preparation method of lithium phosphate is basically the same as that in Example 1, except that the amine compound in the preparation method of the modified template agent is 1,5-pentanediamine. Example 4

[0040] The preparation method of lithium phosphate is basically the same as that in Example 1, except that the amine compound in the preparation method of the modified template agent is diethylenetriamine. Example 5

[0041] The preparation method of lithium phosphate is basically the same as that in Example 1, except that the amine compound in the preparation method of the modified template agent is m-phenylenediamine. Example 6

[0042] The preparation method of lithium phosphate is basically the same as that in Example 1, except that the amine compound in the preparation method of the modified template agent is ethylenediamine. Example 7

[0043] The preparation method of lithium phosphate is basically the same as that in Example 1, except that the amine compound in the preparation method of the modified template agent is composed of 1,2-propanediamine and m-phenylenediamine in a mass ratio of 1:1. Example 8

[0044] The preparation method of lithium phosphate is basically the same as that in Example 1, except that the amine compound in the preparation method of the modified template agent is composed of 1,3-propanediamine and 1,2-propanediamine in a mass ratio of 1:1. Example 9

[0045] A method for preparing lithium phosphate is as follows, comprising the following components in parts by weight: 100 parts of a 0.4 mol / L phosphoric acid solution were added to a reaction vessel, along with 1.8 parts of a modified template agent and 0.2 parts of dodecyltrimethylammonium bromide. The mixture was stirred at 250 r / min for 20 min at 90 °C. Subsequently, a 1.8 mol / L lithium hydroxide solution was added dropwise at a rate of 3 mL / min, while maintaining stirring at 250 r / min during the addition. The addition was stopped when the pH of the system reached 8, and the mixture was kept at the same temperature and stirred for another 45 min. After the reaction was completed, the mixture was filtered and washed four times with hot distilled water at 55 °C. The filter cake was then dried under vacuum at 75 °C and -0.09 MPa for 10 h to obtain lithium phosphate powder.

[0046] The preparation method of the modified template agent is the same as in Example 7.

[0047] Comparative Example 1 The preparation method of lithium phosphate is basically the same as that in Example 1, except that the modified template agent is an equal amount of Pluronic F127.

[0048] Comparative Example 2 The preparation method of lithium phosphate is basically the same as that in Example 1, except that the modified template agent is an equal amount of PEG-400.

[0049] Comparative Example 3 A method for preparing lithium phosphate is basically the same as that in Example 1, except that the modified template agent is not added.

[0050] Test Example 1 Particle size distribution test: The particle size distribution of lithium phosphate powder prepared in each example and comparative example was tested using a Malvern Mastersizer 3000 laser particle size analyzer. The specific operation was as follows: 0.10 g of lithium phosphate powder to be tested was weighed and placed in a 50 mL beaker. 50 mL of deionized water was added as the dispersion medium. The beaker was placed in an ultrasonic cleaner and ultrasonically dispersed for 5 minutes at a power of 100 W and a frequency of 40 kHz to obtain a uniform suspension. The laser particle size analyzer was turned on and preheated for 30 minutes. The refractive index of the dispersion medium was set to 1.33, the refractive index of the particles was 1.58, and the absorptivity was 0.01. The above suspension was added dropwise at a stirring pump speed of 2000 r / min until the light-blocking degree reached 8%-12%. After stabilization, the particle size distribution data was recorded, and the D10, D50, and D90 values ​​were read. The particle size distribution span was calculated according to the formula Span=(D90-D10) / D50.

[0051] The test results are shown in Table 1.

[0052] Table 1 Example 1 0.86 2.41 5.28 1.83 Example 2 0.83 2.32 5.05 1.82 Example 3 0.76 2.08 4.42 1.76 Example 4 0.68 1.86 3.82 1.69 Example 5 0.61 1.69 3.28 1.58 Example 6 0.55 1.52 2.85 1.51 Example 7 0.46 1.21 2.02 1.29 Example 8 0.85 2.40 5.21 1.82 Example 9 0.38 0.96 1.51 1.18 Comparative Example 1 1.68 4.95 12.82 2.25 Comparative Example 2 1.92 5.78 15.96 2.43 Comparative Example 3 2.45 8.12 23.55 2.60 Test Example 2 Specific surface area test: The specific surface area of ​​lithium phosphate powder prepared in each example and comparative example was tested using a Micromeritics ASAP2460 fully automated specific surface area and pore size analyzer. The specific operation was as follows: 0.5 g of the lithium phosphate powder to be tested was weighed and placed into a pre-weighed sample tube. The sample tube was then placed in a degassing station at 120°C for vacuum degassing for 4 hours to fully remove adsorbed moisture and gas from the sample surface. After degassing, the sample tube was transferred to the analysis station. Using high-purity nitrogen as the adsorbate at liquid nitrogen temperature (77 K), the amount of nitrogen adsorbed by the sample under different relative pressures was measured, and adsorption-desorption isotherms were obtained. The Brunauer-Emmett-Teller multi-point method was used to calculate the specific surface area of ​​the sample within the relative pressure range of 0.05-0.30. The relevant test data are summarized in Table 2.

[0053] Table 2 Example 1 15.6 Example 2 16.0 Example 3 17.8 Example 4 20.4 Example 5 22.7 Example 6 25.0 Example 7 26.9 Example 8 15.7 Example 9 29.8 Comparative Example 1 8.3 Comparative Example 2 6.1 Comparative Example 3 4.5 In Comparative Example 3, without the addition of a template agent, lithium phosphate crystals grew freely in a homogeneous solution, resulting in unconstrained ion deposition, leading to coarse primary grains and severe secondary agglomeration. In Comparative Example 2, PEG-400 formed weak hydrogen bonds with water only through ether bonds, exhibiting weak adsorption capacity to crystal faces and failing to suppress anisotropic growth. Comparative Example 1 used unmodified Pluronic F127, which provided some steric hindrance, but lacked functional groups that specifically interacted with crystal faces, resulting in reversible physical adsorption and limited regulatory effect. In Examples 1 to 6, the terminal hydroxyl groups of Pluronic F127 were activated with N,N'-carbonyldiimidazole and then reacted with diamines to introduce nitrogen-containing functional groups. The nitrogen atoms could coordinate with lithium ions, and the amino hydrogen could form hydrogen bonds with phosphate groups, firmly anchoring the template agent to the crystal face, effectively delaying solute diffusion and hindering the advancement of growth steps, thereby inhibiting excessive grain growth. Example 6 uses ethylenediamine, which has a shorter carbon chain and a higher density of terminal amino grafts. It provides more anchoring points per unit mass of template agent and has more sufficient crystal surface coverage. Therefore, the product has the smallest particle size and the highest specific surface area.

[0054] Example 7 modifies 1,2-propanediamine by compounding it with m-phenylenediamine. 1,2-Propanediamine is a compact, flexible aliphatic chain with close-spaced amino groups, which can form dense anchor points on the crystal facets. m-Phenylenediamine contains a rigid benzene ring, which forms stable anchor points with a defined geometric orientation after adsorption. The simultaneous grafting of two chains with different rigidity, flexibility, and spatial configurations onto the template agent ends provides a stable framework, while the compact, flexible chain imparts dense anchoring. The synergistic effect makes the adsorption layer of the template agent on the crystal facets more dense and ordered, resulting in a more balanced control of the growth rate on each crystal facet. Therefore, the product uniformity is superior to that of any single amine modification. In Example 8, the compounded 1,3-propanediamine and 1,2-propanediamine are both three-carbon straight-chain diamines with the same carbon chain length, highly homogeneous chemical properties, and spatial configurations. The compounding did not produce effective complementarity of chain segment properties, and the adsorption behavior of the template agent on the crystal facets was not significantly different from that of using a single amine. Therefore, the product performance of Example 8 is basically equivalent to that of Examples 1 and 2, failing to demonstrate a synergistic effect.

[0055] Example 9, based on Example 7, incorporates dodecyltrimethylammonium bromide. The hydrophobic tail chain of dodecyltrimethylammonium bromide embeds into the micelle nucleus formed by the hydrophobic segments of the modified template agent through hydrophobic interactions. The positively charged quaternary ammonium head group extends towards the aqueous phase, self-assembling to form a well-defined composite micelle. The quaternary ammonium head group enriches phosphate groups on the micelle surface through electrostatic interactions, forming locally high-concentration microregions. This allows lithium ions to rapidly nucleate within the confined space after droplet addition, effectively suppressing the particle size inhomogeneity problem of homogeneous nucleation. Simultaneously, the spherical structure of the composite micelle provides a curved confined template for crystal growth, guiding the grains to grow into well-defined spheres along the spherical direction. The synergistic effect of positive and negative charge matching and hydrophobic driving gives Example 9 a stronger spatial confinement and nucleation control capability than Example 7, resulting in a further reduction in product particle size and a significant increase in specific surface area.

Claims

1. A method for preparing lithium phosphate, characterized in that, The method is as follows: A modified template agent was added to a phosphoric acid solution, and the mixture was heated and stirred. Then, an aqueous solution of lithium hydroxide was added dropwise while stirring was maintained. When the pH of the system reached 7.5-9, the dropwise addition was stopped, and the mixture was kept warm and stirred. After the reaction was completed, the mixture was filtered, washed, and the filter cake was vacuum dried to obtain lithium phosphate powder. The modified template agent is prepared by dissolving Pluronic F127 in anhydrous toluene, activating it with N,N'-carbonyldiimidazole, removing the solvent by rotary evaporation, dissolving the residue in anhydrous acetonitrile and adding it dropwise to an excess of amine compound, precipitating it by vacuum distillation, and drying it under vacuum. The amine compound is at least one of 1,3-propanediamine, 1,2-propanediamine, 1,5-pentanediamine, diethylenetriamine, m-phenylenediamine, and ethylenediamine.

2. The method for preparing lithium phosphate as described in claim 1, characterized in that, The method is as follows, by weight: Add 60-150 parts of a 0.1-1 mol / L phosphoric acid solution to a reaction vessel, add 1-3 parts of a modified template agent, and stir at 100-500 r / min for 5-50 min at 70-95℃. Then, add a 0.5-3 mol / L lithium hydroxide aqueous solution dropwise while maintaining stirring at 100-500 r / min. Stop the dropwise addition when the pH of the system reaches 7.5-9, and continue stirring at the same temperature for 10-90 min. After the reaction is complete, filter the solution and wash it 1-6 times with hot distilled water at 40-70℃. Vacuum dry the filter cake to obtain lithium phosphate powder.

3. The method for preparing lithium phosphate as described in claim 1, characterized in that, The method is as follows, by weight: Add 60-150 parts of a 0.1-1 mol / L phosphoric acid solution to a reaction vessel, along with 1-3 parts of a modified template agent and 0.1-0.5 parts of dodecyltrimethylammonium bromide. Stir at 100-500 r / min for 5-50 min at 70-95℃. Then, add a 0.5-3 mol / L lithium hydroxide aqueous solution dropwise while maintaining stirring at 100-500 r / min. Stop the dropwise addition when the pH of the system reaches 7.5-9, and continue stirring at the same temperature for 10-90 min. After the reaction is complete, filter the solution and wash it 1-6 times with hot distilled water at 40-70℃. Vacuum dry the filter cake to obtain lithium phosphate powder.

4. The method for preparing lithium phosphate as described in claim 1, characterized in that, The dropping rate is 1-5 mL / min.

5. The method for preparing lithium phosphate as described in claim 1, characterized in that, The filter cake vacuum drying is performed by drying the filter cake at 60-85℃ and -0.08 to -0.10 MPa for 1-20 hours.

6. The method for preparing lithium phosphate as described in claim 1, characterized in that, The modified template agent is prepared as follows, in parts by weight: Add 5-15 parts of Pluronic F127 to 20-50 parts of anhydrous toluene, add 0.5-4 parts of N,N'-carbonyldiimidazole, treat at room temperature under nitrogen protection for 2-6 hours, and remove the solvent by rotary evaporation; dissolve the residue in 10-40 parts of anhydrous acetonitrile, add dropwise to 30-80 parts of amine compound, treat at 40-70℃ for 2-10 hours, distill under reduced pressure, precipitate the reaction solution with anhydrous diethyl ether, and dry under vacuum at 40-60℃ and -0.08 to -0.10 MPa for 8-16 hours to obtain the modified template agent.

7. The method for preparing lithium phosphate as described in claim 6, characterized in that, The rotary evaporator is set at a water bath temperature of 40-50℃, a vacuum degree of -0.08 to -0.095 MPa, a rotation speed of 10-100 rpm, and a evaporation time of 5-40 minutes.

8. The method for preparing lithium phosphate as described in claim 6, characterized in that, The vacuum distillation is carried out under conditions of -0.08 to -0.095 MPa and a water bath temperature of 60-80℃ for 20-40 minutes.

9. The method for preparing lithium phosphate as described in claim 6, characterized in that, The vacuum drying is performed at 40-60℃ and -0.08 to -0.10 MPa for 8-16 hours.

10. The method for preparing lithium phosphate as described in claim 6, characterized in that, The amine compound is composed of 1,2-propanediamine and m-phenylenediamine in a mass ratio of 0.5-2:0.5-2.