Lithium titanium aluminum phosphate solid electrolyte material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion battery materials, and particularly discloses a lithium titanium aluminum phosphate solid electrolyte material and a preparation method and application thereof. The preparation method of the lithium titanium aluminum phosphate solid electrolyte material provided by the invention comprises the following steps: S1, uniformly mixing a lithium source and a phosphorus source, and presintering at 450-550 DEG C for 4-6 hours to obtain a lithium-phosphorus precursor; and S2, uniformly mixing a titanium source, an aluminum source and the lithium phosphorus precursor, sintering at 850-950 DEG C for 4-6 hours, and refining to obtain the lithium aluminum titanium phosphate solid electrolyte material. The lithium source and the phosphorus source are pre-sintered to prepare the lithium phosphorus precursor, the precursor can promote crystal grains generated by subsequent LATP to be more uniform and dispersed, meanwhile, the precursor is beneficial to more sufficient reaction with a titanium / aluminum source in subsequent sintering, generation of impure phases is reduced, the compatibility of an electrolyte-electrode interface is improved, and then the electrochemical performance of the material is improved. The method is suitable for the field of preparation of lithium ion batteries and solid electrolyte materials thereof.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and relates to a lithium titanium aluminum phosphate solid electrolyte material, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries are applied in various fields of human life due to their advantages such as high energy density, long cycle life, low preparation cost, and relatively light weight. However, their safety issues greatly limit the development of lithium-ion batteries in the battery field. In order to eliminate potential safety hazards such as electrolyte leakage, evaporation, and battery short circuit caused by liquid electrolytes in traditional lithium-ion batteries, the industry has turned to research and development of all-solid-state and semi-solid-state lithium-ion batteries based on solid electrolytes. Preparing lithium-ion batteries using solid electrolytes can not only eliminate safety hazards, but also has advantages such as high conductivity, high mechanical strength, good electrochemical stability and thermal stability, and good compatibility with electrode materials. Moreover, the specific capacity and cycle efficiency of the battery are significantly better than those of traditional lithium-ion batteries.

[0003] LATP (lithium titanium aluminum phosphate) has attracted much attention in the lithium-ion battery industry due to its wide electrochemical stability window, high chemical stability, stability to air and water, low cost, and high ionic conductivity. At present, the industry mainly uses solid-phase synthesis method or semi-solid-phase synthesis method to produce LATP, and the raw materials used are lithium source, aluminum source, titanium source, and phosphorus source. However, when sintering a mixture of multiple elements, agglomeration is likely to occur, and the grain size of the sintered product is large and uncontrollable, and the electrochemical performance of the finally prepared lithium titanium aluminum phosphate material needs to be improved. Therefore, a preparation method for a lithium titanium aluminum phosphate solid electrolyte material that can achieve industrial mass production and ensure small particle size, uniform dispersion, and good electrochemical performance is needed. Summary of the Invention

[0004] Aiming at the deficiencies of the lithium titanium aluminum phosphate solid electrolyte material in the prior art, the present invention improves the preparation method of the existing lithium titanium aluminum phosphate solid electrolyte material. After pre-sintering the lithium source and the phosphorus source to obtain a lithium-phosphorus precursor, and then co-sintering with other elements, a lithium titanium aluminum phosphate solid electrolyte material with small particle size, uniform dispersion, and excellent electrochemical performance is prepared.

[0005] To achieve the above invention purpose, the embodiments of the present invention adopt the following technical solutions: In a first aspect, the present invention provides a preparation method for a lithium titanium aluminum phosphate solid electrolyte material, and the preparation method includes the following steps: S1. After uniformly mixing the lithium source and the phosphorus source, pre-sinter at 450°C to 550°C for 4h to 6h to obtain a lithium-phosphorus precursor; S2. Mix the titanium source, aluminum source and the lithium phosphorus precursor evenly, sinter at 850 °C to 950 °C for 4 h to 6 h, and perform refinement treatment to obtain the lithium titanium aluminum phosphate solid electrolyte material.

[0006] In the preparation method of the lithium titanium aluminum phosphate solid electrolyte material provided by the present invention, first, a lithium phosphorus precursor with controllable particle size is prepared by pre-sintering a lithium source and a phosphorus source. This precursor can promote the grains generated by subsequent LATP to be more uniform and dispersed, and at the same time is conducive to more sufficient reaction with the titanium / aluminum source during subsequent sintering, reducing the generation of impurity phases and improving the electrolyte-electrode interface compatibility. In addition, due to the pre-synthesis of the lithium phosphorus precursor, the reaction time for subsequent generation of LATP can be significantly reduced, from about 10 h of the original solid-phase reaction time to 4 h to 6 h in the present invention, greatly reducing energy consumption. It not only effectively controls the production cost, but also improves the quality of the lithium titanium aluminum phosphate solid electrolyte material.

[0007] In the traditional multi-element co-blending sintering process, light elements such as lithium, titanium, and aluminum are prone to uneven mixing due to density differences. In the present invention, a stable lithium phosphorus precursor is first formed, which can effectively avoid the separation of the titanium source from light elements at high temperatures; in the sintering stage at 850 °C to 950 °C, the pre-sintered lithium phosphorus precursor has higher thermal stability than the free lithium source, ensuring the accuracy of the stoichiometric ratio of the final product. In addition, intermediate phases such as lithium phosphate generated by pre-sintering can provide a template effect for the formation of the NASICON-type structure in step S2, with a smaller grain size than that obtained by the co-blending sintering process, significantly reducing the grain boundary resistance and improving the electrochemical performance of the lithium titanium aluminum phosphate solid electrolyte material.

[0008] The preparation method of the lithium titanium aluminum phosphate solid electrolyte material provided by the present invention can be implemented on the basis of existing equipment without new equipment, significantly reducing energy consumption and production costs, and significantly improving the electrochemical performance and stability of the obtained lithium titanium aluminum phosphate solid electrolyte material. Therefore, it has high industrialization prospects.

[0009] Further, the molecular formula of the lithium titanium aluminum phosphate solid electrolyte material is Li 1+x Al x Ti 2-x (PO 4 ) 3 , where 0.1 ≤ x ≤ 0.5.

[0010] Further, in S1, it includes dispersing the lithium source in water, adding the phosphorus source and mixing evenly, and then drying. In the present invention, microwave drying is selected.

[0011] In S1, the heating rate of the pre-sintering is 3 °C / min to 5 °C / min.

[0012] Further, the pre-sintered sample is refined to obtain a lithium phosphate precursor with a median particle size of 1 μm to 10 μm.

[0013] The refining treatment includes: first coarsely crushing the pre-sintered sample with a nail disk mill to obtain a primary particle size precursor; performing sand milling on the primary particle size precursor to obtain a secondary particle size precursor; drying and air jet crushing the secondary particle size precursor to obtain a lithium phosphate precursor with a median particle size of 1 μm to 10 μm.

[0014] During the above refining treatment process, control the size of the grinding medium for sand milling to be 0.1 mm to 0.5 mm, and the grinding medium material is selected from alumina or zirconia. In the present invention, zirconia with a grinding medium size of 0.3 mm is taken as an example for illustration; control the sand milling speed to be 800 rmp to 1000 rmp, the sand milling time to be 3 h to 6 h, and the solid content to be 25% to 40%; control the air jet crushing pressure to be 0.6 MPa to 0.8 MPa, and the classifier wheel frequency to be 150 Hz to 190 Hz.

[0015] Further, in S2, the heating rate of the sintering is 3 °C / min to 5 °C / min.

[0016] Further, the titanium source includes titanium dioxide.

[0017] Further, the phosphorus source includes at least one of phosphoric acid, metaphosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium phosphate, lithium dihydrogen phosphate, or lithium hydrogen phosphate.

[0018] Further, the lithium source includes at least one of lithium hydroxide, lithium oxide, lithium nitrate, lithium acetate, lithium oxalate, lithium citrate, or lithium carbonate.

[0019] Further, the aluminum source includes at least one of alumina, aluminum nitrate, aluminum acetate, or aluminum hydroxide.

[0020] Further, the molar ratio of Li in the lithium source to P in the phosphorus source is 1.1:3 to 1.3:3.

[0021] Further, in the present invention, the mixing to be uniform can be achieved by mixing in a mixer at a rotation speed of 1000 rpm to 2000 rpm for 3 to 5 times, each time for 10 min to 20 min.

[0022] In a second aspect, the present invention also provides a lithium titanium aluminum phosphate solid electrolyte material, which is prepared by the preparation method of the lithium titanium aluminum phosphate solid electrolyte material provided in the first aspect.

[0023] The lithium titanium aluminum phosphate solid electrolyte material provided by the present invention has fine and uniform particle size, is more dispersed in morphology, and has higher ionic conductivity and stability. Among them, the secondary particles D of the electrolyte material 50with a particle size of 100 nm to 600 nm and a specific surface area of 25 cm 2 / g to 60 cm 2 / g, and an ionic conductivity of 0.96×10 -4 S / cm to 5.32×10 -4 S / cm.

[0024] Thirdly, the present invention provides an application of the lithium aluminum titanium phosphate solid electrolyte material provided in the second aspect in a semi-solid lithium ion battery or a solid lithium ion battery.

[0025] Compared with conventional lithium ion batteries, the lithium ion batteries assembled with the lithium aluminum titanium phosphate solid electrolyte material provided in the second aspect have significantly improved reversible capacity, cycle capacity retention rate and safety stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is the scanning electron microscope image of LATP solid electrolyte I in Example 1 of the present invention; Figure 2 It is the scanning electron microscope image of LATP solid electrolyte II in Example 2 of the present invention; Figure 3 It is the scanning electron microscope image of LATP solid electrolyte III in Example 3 of the present invention; Figure 4 It is the scanning electron microscope image of LATP solid electrolyte IV in Example 4 of the present invention; Figure 5 It is the scanning electron microscope image of LATP solid electrolyte pair I in Comparative Example 1 of the present invention; Figure 6 It is the scanning electron microscope image of LATP solid electrolyte pair II in Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] Example 1 This embodiment provides a preparation method of a lithium aluminum titanium phosphate solid electrolyte material, and the preparation method includes the following steps: S1. Weigh and mix lithium hydroxide and phosphoric acid according to a Li:P molar ratio of 1.3:3, place them in deionized water with a weight 14 times that of lithium hydroxide, stir at a speed of 800 rmp for 2 h, and then microwave-dry the solution (drying time is 30 min, microwave frequency is 2200 MHz) to obtain a lithium-phosphorus mixed material; Crush the above lithium-phosphorus mixed material with a nail disk mill, load it into a sagger and place it in a kiln, heat it to 500 °C at a rate of 3 °C / min and sinter at this temperature for 5 h to obtain a lithium-phosphorus precursor raw material; After crushing the lithium-phosphorus precursor raw material with a nail disk mill, prepare a slurry with a solid content of 30%, stir it with a sand mill at a speed of 800 rmp for 2 h, dry it in a microwave oven with a microwave frequency of 2200 MHz for 30 min, crush it again with a nail disk mill, and process the crushed material with a three-way air classifier mill. Crush it under the conditions of a crushing pressure of 0.8 MPa and a classifier wheel frequency of 190 Hz to obtain a lithium-phosphorus precursor with a median particle size of 8 μm.

[0030] S2. Weigh and mix alumina, titanium dioxide and the lithium-phosphorus precursor according to a Li:Al:Ti:P molar ratio of 1.3:0.3:1.7:3, mix the materials evenly with a mixer, load them into a sagger and place them in a sintering furnace at 900 °C for 4 h to obtain a caked LATP material; Crush the obtained caked LATP material with a nail disk mill, prepare a slurry with a solid content of 30% and then process it with a sand mill, where the sand mill speed is 1000 rmp and the stirring time is 3 h; Microwave-dry the sanded slurry, crush it with a nail disk mill, process the crushed material with a three-way air classifier mill, and crush it under the conditions of a crushing pressure of 0.8 MPa and a classifier wheel frequency of 190 Hz to obtain a lithium aluminum titanium phosphate solid electrolyte material, denoted as LATP solid electrolyte Ⅰ.

[0031] Use a scanning electron microscope to test the morphology of LATP solid electrolyte Ⅰ. The scanning electron microscope image of LATP solid electrolyte Ⅰ is as Figure 1 shown. It can be calculated that the D 50 of LATP solid electrolyte Ⅰ is 120 nm, and the specific surface area is 54 m 2 / g.

[0032] Example 2 This example provides a preparation method of a lithium aluminum titanium phosphate solid electrolyte material. The preparation method includes the following steps: S1. Weigh and mix lithium carbonate and ammonium phosphate according to a Li:P molar ratio of 1.1:3, place them in deionized water with a weight 8 times that of lithium carbonate, stir at a speed of 400 rmp for 6 h, and then microwave-dry the solution (drying time is 30 min, microwave frequency is 2000 MHz) to obtain a lithium-phosphorus mixed material; The above lithium-phosphorus mixed material is pulverized by a nail disk mill, placed in a sagger and then put into a kiln. It is heated to 450 °C at a rate of 5 °C / min and sintered at this temperature for 6 h to obtain a lithium-phosphorus precursor raw material; After the lithium-phosphorus precursor raw material is pulverized by a nail disk mill, it is made into a slurry with a solid content of 25%. The slurry is stirred in a sand mill at a speed of 400 rmp for 6 h and dried in a microwave oven with a microwave frequency of 2000 MHz for 30 min. Then it is pulverized again by a nail disk mill, and the pulverized material is processed by a three-way air classifier mill. It is pulverized under the conditions of a pulverizing pressure of 0.6 MPa and a classifier wheel frequency of 170 Hz, and a lithium-phosphorus precursor with a median particle size of 14 μm is obtained.

[0033] S2. Weigh and mix aluminum hydroxide, titanium dioxide and the lithium-phosphorus precursor according to the molar ratio of Li:Al:Ti:P of 1.1:0.1:1.9:3. Use a mixer to mix the materials evenly, place them in a sagger and sinter at 850 °C for 6 h to obtain a caked LATP material; The obtained caked LATP material is pulverized by a nail disk mill, made into a slurry with a solid content of 35% and then processed by a sand mill. The speed of the sand mill is 400 rmp and the stirring time is 6 h; The milled slurry is dried by microwave and pulverized by a nail disk mill. The pulverized material is processed by a three-way air classifier mill. It is pulverized under the conditions of a pulverizing pressure of 0.6 MPa and a classifier wheel frequency of 170 Hz, and a lithium aluminum titanium phosphate solid electrolyte material, denoted as LATP solid electrolyte II, is obtained.

[0034] The morphology of LATP solid electrolyte II is tested by scanning electron microscopy. The scanning electron micrograph of LATP solid electrolyte II is as Figure 2 shown. It can be calculated that the D 50 of LATP solid electrolyte II is 280 nm and the specific surface area is 35 m 2 / g.

[0035] Example 3 This example provides a preparation method of a lithium aluminum titanium phosphate solid electrolyte material. The preparation method includes the following steps: S1. Weigh and mix lithium oxide and diammonium hydrogen phosphate according to the molar ratio of Li:P of 1.5:3, place them in deionized water with a weight 12 times that of lithium oxide, stir at a speed of 500 rmp for 5 h, and then microwave-dry the solution (the drying time is 15 min and the microwave frequency is 2400 MHz) to obtain a lithium-phosphorus mixed material; The above lithium-phosphorus mixed material is pulverized by a nail disk mill, placed in a sagger and then put into a kiln. It is heated to 550 °C at a rate of 4 °C / min and sintered at this temperature for 4 h to obtain a lithium-phosphorus precursor raw material; After grinding the lithium phosphate precursor raw materials with a nail disk mill, a slurry with a solid content of 35% is prepared, stirred in a sand mill at a speed of 500 rmp for 5 h, dried in a microwave oven with a microwave frequency of 2400 MHz for 15 min, and then ground again by a nail disk mill. The ground material is processed by a three-way air classifier mill and ground under the conditions of a grinding pressure of 0.8 MPa and a classifier wheel frequency of 190 Hz, thus obtaining a lithium phosphate precursor with a median particle size of 9.6 μm.

[0036] S2. Weigh and mix alumina, titanium dioxide, and the lithium phosphate precursor according to the molar ratio of Li:Al:Ti:P of 1.5:0.5:1.5:3. Use a mixer to mix the materials evenly and load them into a crucible, then sinter at 950 °C for 4 h to obtain the agglomerated LATP material. The obtained agglomerated LATP material is ground by a nail disk mill, and after being made into a slurry with a solid content of 35%, it is processed by a sand mill. The speed of the sand mill is 500 rmp and the stirring time is 5 h. The milled slurry is dried by microwave and then ground by a nail disk mill. The ground material is processed by a three-way air classifier mill and ground under the conditions of a grinding pressure of 0.8 MPa and a classifier wheel frequency of 190 Hz, thus obtaining the lithium aluminum titanium phosphate solid electrolyte material, denoted as LATP solid electrolyte III.

[0037] The morphology of LATP solid electrolyte III is tested by scanning electron microscopy. The scanning electron micrograph of LATP solid electrolyte III is as Figure 3 shown. Through calculation, it can be known that the D 50 of LATP solid electrolyte III is 700 nm, and the specific surface area is 25 m 2 / g.

[0038] Example 4 This example provides a preparation method of a lithium aluminum titanium phosphate solid electrolyte material. The preparation method includes the following steps: S1. Weigh and mix lithium hydroxide and phosphoric acid according to the molar ratio of Li:P of 1.4:3, place them in deionized water with a weight 15 times that of lithium hydroxide, stir at a speed of 600 rmp for 4 h, and then microwave-dry the solution (the drying time is 20 min and the microwave frequency is 2300 MHz) to obtain a lithium phosphate mixture. The above lithium phosphate mixture is ground by a nail disk mill, loaded into a crucible, and placed in a kiln furnace. It is heated to 530 °C at a rate of 5 °C / min and sintered at this temperature for 4.5 h to obtain the lithium phosphate precursor raw materials. After grinding the lithium phosphorus precursor raw materials with a nail disk mill, a slurry with a solid content of 35% is prepared, stirred in a sand mill at a speed of 600 rmp for 4 h, dried in a microwave oven with a microwave frequency of 2300 MHz for 20 min, and then ground again by a nail disk mill. The ground material is processed by a three-way air classifier mill and ground under the conditions of a grinding pressure of 0.8 MPa and a classifier wheel frequency of 180 Hz to obtain a lithium phosphorus precursor with a median particle size of 7.9 μm.

[0039] S2. Weigh and mix alumina, titanium dioxide and lithium phosphorus precursor according to the molar ratio of Li:Al:Ti:P of 1.4:0.4:1.6:3, mix the materials evenly with a mixer, and put them into a crucible and sinter at 900 °C for 4.5 h to obtain a caked LATP material. The obtained caked LATP material is ground by a nail disk mill, and after being made into a slurry with a solid content of 30%, it is processed by a sand mill, where the speed of the sand mill is 600 rmp and the stirring time is 4 h. The milled slurry is dried by microwave and then ground by a nail disk mill. The ground material is processed by a three-way air classifier mill and ground under the conditions of a grinding pressure of 0.8 MPa and a classifier wheel frequency of 180 Hz to obtain a lithium aluminum titanium phosphate solid electrolyte material, denoted as LATP solid electrolyte Ⅳ.

[0040] The morphology of LATP solid electrolyte Ⅳ is tested by scanning electron microscopy, and the scanning electron micrograph of LATP solid electrolyte Ⅳ is as Figure 4 shown. It can be calculated that the D 50 of LATP solid electrolyte Ⅳ is 530 nm, and the specific surface area is 28 m 2 / g.

[0041] Comparative Example 1 This comparative example provides a preparation method of a lithium aluminum titanium phosphate solid electrolyte material. In terms of material ratio, this preparation method is the same as that of Example 1, and no pre-sintering is carried out during the preparation process. The preparation method includes the following steps: S1. Weigh and mix lithium hydroxide, phosphoric acid, alumina and titanium dioxide according to the molar ratio of Li:Al:Ti:P of 1.3:0.3:1.7:3 to prepare a slurry with a solid content of 30%. Mix the materials with a sand mill, stir at a speed of 800 rmp for 3 h. The mixed solution is dried in a microwave oven with a microwave frequency of 2200 MHz for 30 min, and the dried material is ground by a nail disk mill. Then it is put into a crucible and placed in a kiln and sintered at 900 °C for 8 h to obtain a caked LATP material.

[0042] S2. The obtained caked LATP material is ground by a nail disk mill, and after being made into a slurry with a solid content of 30%, it is processed by a sand mill, where the speed of the sand mill is 1000 rmp and the stirring time is 3 h. The sanded slurry is dried by microwave and then crushed by a nail disc mill. The crushed material is processed by a three-way air classifier mill and crushed under the conditions of a crushing pressure of 0.8 MPa and a classifier wheel frequency of 190 Hz, thus obtaining the lithium titanium aluminum phosphate solid electrolyte material, denoted as LATP solid electrolyte pair Ⅰ.

[0043] The morphology of LATP solid electrolyte pair Ⅰ is tested by scanning electron microscopy. The scanning electron micrograph of LATP solid electrolyte pair Ⅰ is as Figure 5 shown. It can be calculated that the D 50 of LATP solid electrolyte pair Ⅰ is 1.2 μm, and the specific surface area is 15 m 2 / g.

[0044] Comparative Example 2 This comparative example provides a preparation method of a lithium titanium aluminum phosphate solid electrolyte material. In terms of material ratio, this preparation method is the same as that of Example 1. During the preparation process, the pre-sintered raw materials in step S1 are replaced from "lithium source and phosphorus source" to "titanium source and phosphorus source", and the remaining parameters are the same as those of Example 1. The specific preparation method is as follows: S1. Weigh and mix titanium dioxide and phosphoric acid according to a Ti:P molar ratio of 1.7:3, place them in deionized water with a weight 14 times that of titanium dioxide, stir at a speed of 800 rmp for 2 h, and then dry the solution by microwave (the drying time is 30 min and the microwave frequency is 2200 MHz) to obtain a phosphorus-titanium mixed material; The above phosphorus-titanium mixed material is crushed by a nail disc mill, loaded into a crucible and placed in a kiln, heated to 500 °C at a rate of 3 °C / min and sintered at this temperature for 5 h to obtain a phosphorus-titanium precursor raw material; After the phosphorus-titanium precursor raw material is crushed by a nail disc mill, it is made into a slurry with a solid content of 30%, stirred by a sand mill at a speed of 800 rmp for 2 h, dried in a microwave oven with a microwave frequency of 2200 MHz for 30 min, and then crushed again by a nail disc mill. The above crushed material is processed by a three-way air classifier mill and crushed under the conditions of a crushing pressure of 0.8 MPa and a classifier wheel frequency of 190 Hz, thus obtaining a lithium-phosphorus precursor with a median particle size of 15 μm.

[0045] S2. Weigh and mix lithium hydroxide, aluminum oxide, titanium dioxide and the lithium-phosphorus precursor according to a Li:Al:Ti:P molar ratio of 1.3:0.3:1.7:3, mix the materials evenly by a mixer, and load them into a crucible and sinter at 900 °C for 4 h to obtain a caked LATP material; The obtained caked LATP material is crushed by a nail disc mill, made into a slurry with a solid content of 30% and then processed by a sand mill, where the sand mill speed is 1000 rmp and the stirring time is 3 h; The sand-milled slurry was microwave-dried and crushed by a spike-disk mill. The crushed material was treated by a tripartite airflow mill and crushed under a crushing pressure of 0.8 MPa and a classifying wheel frequency of 190 Hz to obtain a lithium aluminum titanium phosphate solid electrolyte material, which was recorded as LATP solid electrolyte pair II.

[0046] The morphology of LATP solid electrolyte pair II was tested by scanning electron microscopy. The scanning electron microscopy image of LATP solid electrolyte pair II is shown in the figure. Figure 6 As shown. Calculation shows that the LATP solid electrolyte has a D 50 The surface area is 860 nm and the specific surface area is 20 m 2 / g.

[0047] Effect example In order to explore the electrochemical performance and stability of lithium aluminum titanium phosphate solid electrolyte materials prepared by different preparation methods, the present invention assembles the LATP solid electrolytes prepared in Examples 1-4 and Comparative Examples 1-2 into solid-state lithium-ion batteries to examine their practical application effects. The battery assembly process is as follows: add conductive agent Super P (5%), binder PVDF (5%), oxalic acid (0.8%) and N-methylpyrrolidone to the positive electrode active material and stir them thoroughly, and then roll the coating to form a half-cell positive electrode sheet; press the LATP solid electrolyte prepared in Examples 1-4 and Comparative Examples 1-2 into a Φ19mm disc with a thickness of 0.5-1mm to obtain a solid electrolyte membrane; Positive electrode → drop 2uL electrolyte → solid electrolyte membrane → drop 2uL electrolyte → negative electrode lithium sheet, after a certain pressure (10-40MPa), press and put it into the button battery shell to make a full solid-state half-battery. According to the LATP solid electrolyte material selected in the preparation of the solid electrolyte membrane, the assembled batteries are correspondingly recorded as lithium-ion batteries I~IV, lithium-ion battery pairs I~II.

[0048] The ionic conductivity, reversible capacity, coulombic efficiency and 100-cycle capacity retention rate of the lithium-ion battery assembled above were measured according to the AC impedance method and the constant current charge and discharge test method.

[0049] Coulomb efficiency test conditions, reversible capacity test conditions, and 100-cycle capacity retention test conditions: 1.0 C, 3.0-4.5 V, and 100 cycles at room temperature of 25°C.

[0050] The specific test results are shown in Table 1 below.

[0051] Table 1

[0052] As can be seen from the data in Table 1, the ionic conductivity of the lithium titanium aluminum phosphate solid electrolyte material provided by the embodiment of the present invention is 0.96×10 -4 S / cm to 5.32×10 -4 S / cm. The reversible capacity of the lithium-ion battery assembled therefrom is 128 mAh / g to 151 mAh / g, the Coulomb efficiency is 94.5% to 97.2%, and the capacity retention rate after 100 cycles is 83.2% to 88.4%, showing excellent electrochemical performance.

[0053] In summary, it can also be seen that the D 50 , specific surface area, and ionic conductivity of the LATP solid electrolyte pair I and the LATP solid electrolyte pair II are significantly lower than those of the LATP solid electrolyte I. The reason may be that in the traditional multi-element co-mixing and sintering process, light elements such as lithium, titanium, and aluminum are prone to uneven mixing due to density differences, and caking is likely to occur during the sintering stage. Eventually, the obtained grain size and specific surface area are relatively large, affecting their electrochemical performance. It can be seen from Comparative Example 2 that the combination of titanium and phosphorus is more compact than the combination of lithium and phosphorus, and the caking phenomenon is more serious. The median particle size of the phosphorus-titanium precursor is significantly larger than that of the lithium-phosphorus precursor, and the D50 of the finally obtained solid electrolyte is also significantly increased, and the specific surface area is much smaller, which is not conducive to the mutual conduction of ions and electrons.

[0054] In the present invention, a stable lithium-phosphorus precursor is first formed, which can effectively avoid the separation of the titanium source from the light elements at high temperatures; during the sintering stage at 850°C to 950°C, the pre-sintered lithium-phosphorus precursor has higher thermal stability than the free lithium source, ensuring the stoichiometric ratio accuracy of the final product. In addition, intermediate phases such as lithium phosphate generated by pre-sintering can provide a template effect for the next sintering process, resulting in smaller grain sizes, significantly reducing the grain boundary resistance, and improving the electrochemical performance of the lithium titanium aluminum phosphate solid electrolyte material.

[0055] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a lithium aluminum titanium phosphate solid electrolyte material, characterized in that: The preparation method comprises the following steps: S1. After the lithium source and the phosphorus source are uniformly mixed, they are pre-sintered at 450°C~550°C for 4h~6h to obtain a lithium-phosphorus precursor; S2. Evenly mix the titanium source, the aluminum source and the lithium-phosphorus precursor, sinter at 850° C. to 950° C. for 4 h to 6 h, and refine the mixture to obtain a lithium aluminum titanium phosphate solid electrolyte material.

2. The method for preparing the lithium aluminum titanium phosphate solid electrolyte material according to claim 1, characterized in that: The molecular formula of the lithium aluminum titanium phosphate solid electrolyte material is Li 1+x Al x Ti 2-x (PO4)3, where 0<x≤0.

5.

3. The method for preparing the lithium aluminum titanium phosphate solid electrolyte material according to claim 1, characterized in that: In S1, the heating rate of the pre-sintering is 3°C / min-5°C / min.

4. The method for preparing the lithium aluminum titanium phosphate solid electrolyte material according to claim 1, characterized in that: In S1, the median particle size of the lithium phosphorus precursor is 1 μm to 10 μm.

5. The method for preparing the lithium aluminum titanium phosphate solid electrolyte material according to claim 1, characterized in that: In S2, the heating rate of the sintering is 3°C / min~5°C / min.

6. The method for preparing the lithium aluminum titanium phosphate solid electrolyte material according to claim 1, characterized in that: The titanium source comprises at least one of titanium dioxide or titanium citrate; and / or The phosphorus source comprises at least one of phosphoric acid, metaphosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium phosphate, lithium dihydrogen phosphate or dilithium hydrogen phosphate; and / or The lithium source comprises at least one of lithium hydroxide, lithium oxide, lithium nitrate, lithium acetate, lithium oxalate, lithium citrate or lithium carbonate; and / or The aluminum source includes at least one of aluminum oxide, aluminum nitrate, aluminum acetate or aluminum hydroxide.

7. The method for preparing the lithium aluminum titanium phosphate solid electrolyte material according to claim 1, characterized in that: The molar ratio of Li in the lithium source to P in the phosphorus source is 1.1:3 to 1.3:

3.

8. A lithium aluminum titanium phosphate solid electrolyte material, characterized in that: The lithium aluminum titanium phosphate solid electrolyte material is prepared by the preparation method of any one of claims 1 to 7.

9. The lithium aluminum titanium phosphate solid electrolyte material according to claim 8, characterized in that: The secondary particle D of the lithium aluminum titanium phosphate solid electrolyte material 50 100nm~600nm, BET is 25cm 2 / g~60cm 2 / g.

10. Use of the lithium aluminum titanium phosphate solid electrolyte material as claimed in claim 8 or 9 in a semi-solid lithium ion battery or a solid lithium ion battery.

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