A lithium aluminum titanium phosphate solid electrolyte material and its preparation method and application

Abstract

The present invention belongs to the technical field of lithium-ion battery materials, and specifically discloses a lithium titanium aluminum phosphate solid electrolyte material, a preparation method thereof, and an application thereof. The preparation method of the lithium titanium aluminum phosphate solid electrolyte material provided by the present invention comprises the following steps: S1. After uniformly mixing a lithium source and a phosphorus source, pre-sintering at 450°C to 550°C for 4h to 6h to obtain a lithium-phosphorus precursor; S2. uniformly mixing a titanium source, an aluminum source, and a lithium-phosphorus precursor, sintering at 850°C to 950°C for 4h to 6h, and refining to obtain a lithium titanium aluminum phosphate solid electrolyte material. In the present invention, a lithium source and a phosphorus source are pre-sintered to obtain a lithium-phosphorus precursor, which can promote the subsequent LATP-generated grains to be more uniform and dispersed, while facilitating a more complete reaction with the titanium / aluminum source during subsequent sintering, reducing the generation of impurities, improving the electrolyte-electrode interface compatibility, and thus improving the electrochemical performance of the material. The present invention is applicable to the field of preparation of lithium-ion batteries and their solid electrolyte materials.

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 and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries are used in various fields of human life due to their high energy density, long cycle life, low production cost, and relatively light weight. However, their safety issues have greatly limited their development in the battery field. To eliminate the safety hazards such as electrolyte leakage, evaporation, and battery short circuits that may be caused by liquid electrolytes in traditional lithium-ion batteries, the industry has turned to the research and development of all-solid-state and semi-solid-state lithium-ion batteries based on solid-state electrolytes. The use of solid-state electrolytes to prepare lithium-ion batteries not only eliminates safety hazards, but also has the advantages of high electrical conductivity and high mechanical strength, good electrochemical and thermal stability, and good compatibility with electrode materials. The battery's specific capacity and cycle efficiency are significantly better than those of traditional lithium-ion batteries.

[0003] LATP (lithium aluminum titanium phosphate) has attracted significant attention in the lithium-ion battery industry due to its wide electrochemical stability window, high chemical stability, air and water stability, low cost, and high ionic conductivity. Currently, LATP is primarily produced using solid-phase or semi-solid-phase synthesis methods, using lithium, aluminum, titanium, and phosphorus sources as raw materials. However, sintering these multi-element mixtures can easily lead to compaction, resulting in large, uncontrollable grain sizes after sintering. Furthermore, the electrochemical performance of the resulting lithium aluminum titanium phosphate material remains to be improved. Therefore, a method for preparing lithium aluminum titanium phosphate solid-state electrolyte materials is needed that can be industrialized and mass-produced while ensuring small, uniform, and dispersed particle sizes and excellent electrochemical performance. Summary of the Invention

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

[0005] To achieve the above-mentioned purpose, the embodiment of the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a lithium aluminum titanium phosphate solid electrolyte material, the preparation method comprising the following steps:

[0007] S1. After the lithium source and phosphorus source are mixed evenly, they are pre-sintered at 450°C~550°C for 4h~6h to obtain a lithium-phosphorus precursor;

[0008] S2. The titanium source, the aluminum source and the lithium-phosphorus precursor are uniformly mixed, sintered at 850° C. to 950° C. for 4 h to 6 h, and refined to obtain a lithium titanium aluminum phosphate solid electrolyte material.

[0009] The preparation method of the lithium titanium aluminum phosphate solid electrolyte material provided by the present invention first obtains a lithium phosphorus precursor with controllable particle size by pre-sintering a lithium source and a phosphorus source. The precursor can promote the subsequent LATP generated grains to be more uniform and dispersed, and at the same time facilitates a more complete reaction with the titanium / aluminum source during subsequent sintering, reduces the generation of impurities and improves the electrolyte-electrode interface compatibility. In addition, since the lithium phosphorus precursor is synthesized in advance, the reaction time for the subsequent generation of LATP can be significantly reduced, from about 10 hours of the original solid phase reaction time to 4 hours to 6 hours in the present invention, and energy consumption is greatly reduced, which not only effectively controls production costs but also improves the quality of the lithium titanium aluminum phosphate solid electrolyte material.

[0010] In traditional multi-element co-blending sintering processes, lightweight elements such as lithium, titanium, and aluminum are prone to uneven mixing due to density differences. The present invention first forms a stable precursor of lithium-phosphorus, effectively preventing the separation of the titanium source from the lightweight elements at high temperatures. During the sintering stage at 850°C to 950°C, the lithium-phosphorus precursor formed by pre-sintering has higher thermal stability than the free lithium source, ensuring the stoichiometric accuracy of the final product. Furthermore, the intermediate phases, such as lithium phosphate, generated by pre-sintering provide a template effect for the formation of the NASICON structure in step S2, resulting in smaller grain sizes than those obtained by the co-blending sintering process, significantly reducing grain boundary resistance, and improving the electrochemical performance of the lithium aluminum titanium phosphate solid electrolyte material.

[0011] 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 the need for 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, thus having a high industrialization prospect.

[0012] Furthermore, the molecular formula of the lithium aluminum titanium phosphate solid electrolyte material is Li 1+x Al x Ti 2-x (PO4)3, where 0.1≤x≤0.5.

[0013] Furthermore, S1 includes dispersing the lithium source in water, adding the phosphorus source, mixing evenly, and then drying. In the present invention, microwave drying is selected.

[0014] In S1, the heating rate of the pre-sintering is 3°C / min to 5°C / min.

[0015] Furthermore, the pre-sintered sample is refined to obtain a lithium-phosphorus precursor with a medium particle size of 1 μm to 10 μm.

[0016] The refinement treatment includes: grinding the pre-sintered sample with a nail disc to obtain a primary particle size precursor; sand grinding the primary particle size precursor to obtain a secondary particle size precursor; drying and air flow crushing the secondary particle size precursor to obtain a lithium phosphorus precursor with a medium particle size of 1μm~10μm.

[0017] During the above-mentioned refinement process, the grinding medium size of the sand mill is controlled to be 0.1mm~0.5mm, and the grinding medium material is selected from alumina or zirconia. In the present invention, zirconia with a grinding medium size of 0.3mm is used as an example for illustration; the sand mill speed is controlled to be 800rmp~1000rmp, the sand milling time is 3h~6h, and the solid content is 25%~40%; the air flow crushing pressure is controlled to be 0.6MPa~0.8MPa, and the classifying wheel frequency is 150Hz~190Hz.

[0018] Furthermore, in S2, the sintering heating rate is 3°C / min to 5°C / min.

[0019] Furthermore, the titanium source includes titanium dioxide.

[0020] Furthermore, 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 dilithium hydrogen phosphate.

[0021] Furthermore, the lithium source includes at least one of lithium hydroxide, lithium oxide, lithium nitrate, lithium acetate, lithium oxalate, lithium citrate or lithium carbonate.

[0022] Furthermore, the aluminum source includes at least one of aluminum oxide, aluminum nitrate, aluminum acetate or aluminum hydroxide.

[0023] Furthermore, the molar ratio of Li in the lithium source to P in the phosphorus source is 1.1:3 to 1.3:3.

[0024] Furthermore, the uniform mixing described in the present invention can be performed by mixing the materials 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.

[0025] In a second aspect, the present invention further provides a lithium aluminum titanium phosphate solid electrolyte material, which is prepared by the preparation method of the lithium aluminum titanium phosphate solid electrolyte material provided in the first aspect.

[0026] The lithium aluminum titanium phosphate solid electrolyte material provided by the present invention has a small and uniform particle size, a more dispersed morphology, and higher ionic conductivity and stability. 50 The diameter is 100nm~600nm and the specific surface area is 25cm 2 / g~60cm 2 / g, and the ionic conductivity is 0.96×10 -4 S / cm~5.32×10 -4 S / cm.

[0027] In a third aspect, 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.

[0028] Compared with conventional lithium-ion batteries, the lithium-ion batteries assembled using the lithium aluminum titanium phosphate solid electrolyte material provided in the second aspect have significantly improved reversible capacity, cycle capacity retention rate, and safety and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is a scanning electron microscope image of LATP solid electrolyte I in Example 1 of the present invention;

[0031] Figure 2 This is a scanning electron microscope image of LATP solid electrolyte II in Example 2 of the present invention;

[0032] Figure 3 This is a scanning electron microscope image of LATP solid electrolyte III in Example 3 of the present invention;

[0033] Figure 4 This is a scanning electron microscope image of LATP solid electrolyte IV in Example 4 of the present invention;

[0034] Figure 5 This is a scanning electron microscope image of LATP solid electrolyte pair I in Comparative Example 1 of the present invention;

[0035] Figure 6 This is a scanning electron microscope image of LATP solid electrolyte pair II in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] Example 1

[0038] This embodiment provides a method for preparing a lithium aluminum titanium phosphate solid electrolyte material, the preparation method comprising the following steps:

[0039] S1. Lithium hydroxide and phosphoric acid were weighed in a Li: P molar ratio of 1.3:3 and placed in 14 times the weight of lithium hydroxide in deionized water and stirred at 800 rpm for 2 h. The solution was then microwave-dried (drying time 30 min, microwave frequency 2200 MHz) to give a lithium-phosphorus mixture.

[0040] The lithium-phosphorus mixture was ground by a nail disc mill, put into a sagger, and placed in a kiln. The temperature was raised to 500° C. at a rate of 3° C. / min and then sintered at the same temperature for 5 h to obtain a lithium-phosphorus precursor raw material.

[0041] The lithium-phosphorus precursor raw material was crushed by a spiked disc mill and prepared into a slurry with a solid content of 30%. The slurry was stirred at 800 rpm for 2 hours in a sand mill and dried in a microwave oven with a microwave frequency of 2200 MHz for 30 minutes. The slurry was crushed again by a spiked disc mill and the crushed material was treated by a three-way air flow mill under a crushing pressure of 0.8 MPa and a classifying wheel frequency of 190 Hz to obtain a lithium-phosphorus precursor with a medium particle size of 8 μm.

[0042] S2. Alumina, titanium dioxide and lithium phosphorus precursor were weighed in a Li:Al:Ti:P molar ratio of 1.3:0.3:1.7:3, the materials were mixed evenly using a mixer and placed in a sagger and sintered at 900 ° C for 4h to obtain agglomerated LATP material;

[0043] The agglomerated LATP material was crushed by a nail disc mill, prepared into a slurry with a solid content of 30%, and then processed by a sand mill at a speed of 1000 rpm and a stirring time of 3 hours;

[0044] The sand-milled slurry was microwave-dried and crushed by a spike disc mill. The crushed material was treated with a three-way air flow 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 I.

[0045] The morphology of LATP solid electrolyte I was tested by scanning electron microscopy. The scanning electron microscopy image of LATP solid electrolyte I is shown in the figure. Figure 1 As shown. Calculation shows that the D 50 The surface area is 120 nm and the specific surface area is 54 m 2 / g.

[0046] Example 2

[0047] This embodiment provides a method for preparing a lithium aluminum titanium phosphate solid electrolyte material, the preparation method comprising the following steps:

[0048] S1. Lithium carbonate and ammonium phosphate were weighed in a Li: P molar ratio of 1.1:3 and placed in deionized water 8 times the weight of lithium carbonate, stirred at 400 rpm for 6 h, and then the solution was microwave-dried (drying time 30 min, microwave frequency 2000 MHz) to obtain a lithium-phosphorus mixture;

[0049] The lithium-phosphorus mixture was ground by a nail disc mill, put into a sagger, and placed in a kiln. The temperature was raised to 450°C at a rate of 5°C / min and then sintered at the same temperature for 6 hours to obtain a lithium-phosphorus precursor raw material.

[0050] The lithium-phosphorus precursor raw material was crushed by a spiked disc mill and prepared into a slurry with a solid content of 25%. The slurry was stirred at a speed of 400 rpm for 6 hours in a sand mill and dried in a microwave oven with a microwave frequency of 2000 MHz for 30 minutes. The slurry was crushed again by a spiked disc mill and the crushed material was treated with a three-way air flow mill under a crushing pressure of 0.6 MPa and a classifying wheel frequency of 170 Hz to obtain a lithium-phosphorus precursor with a medium particle size of 14 μm.

[0051] S2. Aluminum hydroxide, titanium dioxide and lithium phosphorus precursor were weighed in a Li:Al:Ti:P molar ratio of 1.1:0.1:1.9:3, the materials were mixed evenly using a mixer and placed in a sagger and sintered at 850 ° C for 6h to obtain agglomerated LATP material;

[0052] The agglomerated LATP material was crushed by a spiked disc mill to prepare a slurry with a solid content of 35%, which was then processed by a sand mill at a speed of 400 rpm and a stirring time of 6 h.

[0053] The sand-milled slurry was microwave-dried and crushed by a spike disc mill. The crushed material was treated with a three-way air flow mill and crushed under a crushing pressure of 0.6 MPa and a classifying wheel frequency of 170 Hz to obtain a lithium aluminum titanium phosphate solid electrolyte material, which was recorded as LATP solid electrolyte II.

[0054] The morphology of LATP solid electrolyte II was tested using scanning electron microscopy. The scanning electron microscopy image of LATP solid electrolyte II is shown in the figure. Figure 2 As shown. Calculation shows that the D 50 The surface area is 280nm and the specific surface area is 35m 2 / g.

[0055] Example 3

[0056] This embodiment provides a method for preparing a lithium aluminum titanium phosphate solid electrolyte material, the preparation method comprising the following steps:

[0057] S1. Lithium oxide and diammonium phosphate were weighed in a Li:P molar ratio of 1.5:3 and placed in 12 times the weight of lithium oxide in deionized water and stirred at 500 rpm for 5 h. The solution was then microwave-dried (drying time 15 min, microwave frequency 2400 MHz) to give a lithium-phosphorus mixture.

[0058] The lithium-phosphorus mixture was ground by a nail disc mill, put into a sagger, and placed in a kiln. The temperature was raised to 550° C. at a rate of 4° C. / min, and then sintered at the same temperature for 4 h to obtain a lithium-phosphorus precursor raw material.

[0059] The lithium-phosphorus precursor raw material was crushed by a spiked disc mill and prepared into a slurry with a solid content of 35%. The slurry was stirred at a speed of 500 rpm for 5 hours in a sand mill, dried in a microwave oven with a microwave frequency of 2400 MHz for 15 minutes, and crushed again by a spiked disc mill. The crushed material was treated with a three-way air flow mill and crushed under a crushing pressure of 0.8 MPa and a classifying wheel frequency of 190 Hz to obtain a lithium-phosphorus precursor with a medium particle size of 9.6 μm.

[0060] S2. Alumina, titanium dioxide and lithium phosphorus precursor were weighed in a Li:Al:Ti:P molar ratio of 1.5:0.5:1.5:3, the materials were mixed evenly using a mixer and placed in a sagger and sintered at 950 ° C for 4h to obtain agglomerated LATP material;

[0061] The agglomerated LATP material was crushed by a spiked disc mill to prepare a slurry with a solid content of 35%, which was then processed by a sand mill at a speed of 500 rpm and a stirring time of 5 h.

[0062] The sand-milled slurry was microwave-dried and crushed by a spike disc mill. The crushed material was treated with a three-way air flow 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 III.

[0063] The morphology of LATP solid electrolyte III was tested using scanning electron microscopy. The scanning electron microscopy image of LATP solid electrolyte III is shown in the figure below. Figure 3 As shown. Calculation shows that the D 50 The surface area is 700 nm and the specific surface area is 25 m 2 / g.

[0064] Example 4

[0065] This embodiment provides a method for preparing a lithium aluminum titanium phosphate solid electrolyte material, the preparation method comprising the following steps:

[0066] S1. Lithium hydroxide and phosphoric acid were weighed in a Li: P molar ratio of 1.4:3 and placed in 15 times the weight of lithium hydroxide in deionized water and stirred at 600 rpm for 4 h. The solution was then microwave-dried (drying time 20 min, microwave frequency 2300 MHz) to give a lithium-phosphorus mixture.

[0067] The lithium-phosphorus mixture was ground by a nail disc mill, put into a sagger, and placed in a kiln. The temperature was raised to 530° C. at a rate of 5° C. / min, and then sintered at the same temperature for 4.5 h to obtain a lithium-phosphorus precursor raw material.

[0068] The lithium-phosphorus precursor raw material was crushed by a spiked disc mill and prepared into a slurry with a solid content of 35%. The slurry was stirred at a speed of 600 rpm for 4 hours in a sand mill, dried in a microwave oven with a microwave frequency of 2300 MHz for 20 minutes, and crushed again by a spiked disc mill. The crushed material was treated with a three-way air flow mill and crushed under a crushing pressure of 0.8 MPa and a classifying wheel frequency of 180 Hz to obtain a lithium-phosphorus precursor with a medium particle size of 7.9 μm.

[0069] S2. Alumina, titanium dioxide and lithium phosphorus precursor were weighed in a Li:Al:Ti:P molar ratio of 1.4:0.4:1.6:3, the materials were mixed evenly using a mixer and placed in a sagger and sintered at 900 ° C for 4.5h to obtain agglomerated LATP material;

[0070] The agglomerated LATP material was crushed by a spiked disc mill to prepare a slurry with a solid content of 30%, which was then processed by a sand mill at a speed of 600 rpm and a stirring time of 4 h.

[0071] The sand-milled slurry was microwave-dried and crushed by a spike disc mill. The crushed material was treated with a triangular airflow mill and crushed under a crushing pressure of 0.8 MPa and a classifying wheel frequency of 180 Hz to obtain a lithium aluminum titanium phosphate solid electrolyte material, which was recorded as LATP solid electrolyte IV.

[0072] The morphology of LATP solid electrolyte IV was tested using scanning electron microscopy. The scanning electron microscopy image of LATP solid electrolyte IV is shown in the figure. Figure 4 As shown. Calculation shows that the D 50 The surface area is 530 nm and the specific surface area is 28 m 2 / g.

[0073] Comparative Example 1

[0074] This comparative example provides a method for preparing a lithium aluminum titanium phosphate solid electrolyte material. The material ratio of the preparation method is the same as that of Example 1, and no pre-sintering is performed during the preparation process. The preparation method comprises the following steps:

[0075] S1. Lithium hydroxide, phosphoric acid, aluminum oxide, and titanium dioxide were weighed and mixed according to a Li:Al:Ti:P molar ratio of 1.3:0.3:1.7:3 to prepare a slurry with a solid content of 30%. The mixture was mixed using a sand mill and stirred at 800 rpm for 3 hours. The mixed solution was dried in a microwave oven at a microwave frequency of 2200 MHz for 30 minutes, and the dried material was crushed by a pinwheel mill. The material was placed in a sagger and placed in a kiln for sintering at 900°C for 8 hours to obtain agglomerated LATP material.

[0076] S2. The resulting agglomerated LATP material was crushed by a nail disc mill and mixed with a slurry having a solid content of 30% and then processed by a sand mill, wherein the sand mill speed was 1000 rpm and the stirring time was 3h;

[0077] The sand-milled slurry was microwave-dried and crushed by a spike disc mill. The crushed material was treated with a three-way air flow 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 I.

[0078] The morphology of LATP solid electrolyte pair I was tested by scanning electron microscopy. The scanning electron microscopy image of LATP solid electrolyte pair I is shown in the figure. Figure 5 As shown. Calculation shows that LATP solid electrolyte has a great influence on the D 50 The surface area is 1.2 μm and the specific surface area is 15 m 2 / g.

[0079] Comparative Example 2

[0080] This comparative example provides a method for preparing a lithium aluminum titanium phosphate solid electrolyte material. The material ratio of the preparation method is the same as that of Example 1. During the preparation process, the raw materials for pre-sintering in step S1 are replaced by "lithium source and phosphorus source" instead of "titanium source and phosphorus source". The other parameters are the same as those of Example 1. The preparation method is as follows:

[0081] S1. Titanium dioxide and phosphoric acid were weighed in a Ti:P molar ratio of 1.7:3 and placed in deionized water 14 times the weight of titanium dioxide. The mixture was stirred at 800 rpm for 2 h, and then the solution was microwave-dried (drying time 30 min, microwave frequency 2200 MHz) to obtain a phosphorus-titanium mixture.

[0082] The phosphorus-titanium mixture was ground by a nail disc mill, put into a sagger, and placed in a kiln. The temperature was raised to 500°C at a rate of 3°C / min and then sintered at this temperature for 5 hours to obtain a phosphorus-titanium precursor raw material.

[0083] The phosphorus-titanium precursor raw material was crushed by a pinwheel mill and prepared into a slurry with a solid content of 30%. The slurry was stirred at 800 rpm for 2 hours in a sand mill and dried in a microwave oven with a microwave frequency of 2200 MHz for 30 minutes. The slurry was crushed again by a pinwheel mill and the crushed material was treated with a three-way air flow mill. The slurry was crushed under a crushing pressure of 0.8 MPa and a classifying wheel frequency of 190 Hz to obtain a lithium-phosphorus precursor with a medium particle size of 15 μm.

[0084] S2. Lithium hydroxide, aluminum oxide, titanium dioxide and titanium phosphorus precursor were weighed in a Li:Al:Ti:P molar ratio of 1.3:0.3:1.7:3, the materials were mixed evenly using a mixer, and placed in a sagger and sintered at 900 ° C for 4h to obtain agglomerated LATP material;

[0085] The agglomerated LATP material was crushed by a spiked disc mill to prepare a slurry with a solid content of 30%, which was then processed by a sand mill at a speed of 1000 rpm and a stirring time of 3 h.

[0086] The sand-milled slurry was microwave-dried and crushed by a spike disc mill. The crushed material was treated with a triangular 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.

[0087] 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 as follows: Figure 6 As shown. Calculation shows that the LATP solid electrolyte has a D 50 The surface area is 860nm and the specific surface area is 20m 2 / g.

[0088] Effect Examples

[0089] 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 assembled 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: a conductive agent Super P (5%), a binder PVDF (5%), oxalic acid (0.8%) and N-methylpyrrolidone are added to the positive electrode active material and stirred thoroughly, and then the coating roller is used to form a half-cell positive electrode sheet; the LATP solid electrolyte prepared in Examples 1-4 and Comparative Examples 1-2 is pressed into a powder with a thickness of 0.5-1mm and a Φ19mm disc to prepare a solid electrolyte membrane;

[0090] Positive electrode → drop 2uL electrolyte → solid electrolyte membrane → drop 2uL electrolyte → negative electrode lithium sheet, after a certain pressure (10-40MPa) pressing and loading into the button battery shell to make a full solid-state half-cell. 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 and lithium-ion battery pairs I~II.

[0091] The ionic conductivity, reversible capacity, coulombic efficiency and 100-cycle capacity retention rate of the assembled lithium-ion battery were measured using the AC impedance method and the constant current charge and discharge test method.

[0092] Coulombic 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 (25°C).

[0093] The specific test results are shown in Table 1 below.

[0094] Table 1

[0095]

[0096] It can be seen from the data in Table 1 that the ionic conductivity of the lithium aluminum titanium phosphate solid electrolyte material provided by the embodiment of the present invention is 0.96×10 -4 S / cm~5.32×10 -4 The assembled lithium-ion battery has a reversible capacity of 128 mAh / g to 151 mAh / g, a coulombic efficiency of 94.5% to 97.2%, and a capacity retention rate of 83.2% to 88.4% after 100 cycles, demonstrating excellent electrochemical performance.

[0097] From the above, we can also see that the D 50 , specific surface area and ionic conductivity are significantly lower than those of LATP solid electrolyte I. The reason may be that in the traditional multi-element blending sintering process, lightweight elements such as lithium, titanium, and aluminum are prone to uneven mixing due to density differences, and caking is prone to occur during the sintering stage. The final grain size and specific surface area are large, affecting its electrochemical performance. It can be seen from Comparative Example 2 that titanium and phosphorus are more tightly combined than lithium and phosphorus, and the agglomeration phenomenon is more serious. The particle size of the titanium-phosphorus precursor is significantly larger than that of the lithium-phosphorus precursor. The D50 of the solid electrolyte finally obtained is also significantly improved, and the specific surface area is greatly reduced, which is not conducive to the mutual conduction of ions and electrons.

[0098] The present invention first forms a stable precursor of lithium-phosphorus, effectively preventing the separation of the titanium source from the lightweight element at high temperatures. During the sintering stage at 850°C to 950°C, the lithium-phosphorus precursor formed by pre-sintering exhibits higher thermal stability than the free lithium source, ensuring the stoichiometric accuracy of the final product. Furthermore, the lithium phosphate and other intermediate phases generated during pre-sintering provide a template effect in the subsequent sintering process, resulting in smaller grains, significantly reducing grain boundary resistance, and improving the electrochemical performance of the lithium aluminum titanium phosphate solid electrolyte material.

[0099] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection 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 phosphorus source are mixed evenly, they are pre-sintered at 450°C~550°C for 4h~6h to obtain a lithium-phosphorus precursor; S2. The titanium source, the aluminum source and the lithium-phosphorus precursor are uniformly mixed, sintered at 850° C. to 950° C. for 4 h to 6 h, and refined to obtain a lithium titanium aluminum phosphate solid electrolyte material.

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

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

6. The method for preparing the lithium aluminum titanium phosphate solid electrolyte material according to claim 1, wherein: 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, wherein: 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 particles 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 according to claim 8 or 9 in a semi-solid lithium ion battery or a solid lithium ion battery.

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