Lithium ion solid electrolyte material lithium sodium yttrium phosphate and preparation method and application thereof

Abstract

The present application relates to a kind of lithium ion solid electrolyte material lithium sodium yttrium phosphate and its preparation method and application.The chemical formula of the lithium ion solid electrolyte material lithium sodium yttrium phosphate is Li x Na 7‑ x Y2P7O 24 Wherein x=0-6.0, preferably x=4.

Description

Technical Field

[0001] This invention belongs to the field of battery electrolyte materials technology, specifically relating to a lithium-ion solid electrolyte material, sodium yttrium phosphate, its preparation method, and its application. Background Technology

[0002] High-energy-density lithium-ion batteries have become a research hotspot. Traditional batteries use organic liquid electrolytes, which pose safety hazards such as fire and explosion. One solution is to use solid electrolytes, which have high safety, to replace liquid electrolytes. Solid electrolytes also have advantages such as resistance to dendrite growth and good stability.

[0003] Lithium-ion solid electrolytes mainly include organic solid electrolytes, oxide solid electrolytes, and sulfide solid electrolytes. Among them, oxide solid electrolytes have attracted much attention due to their wide electrochemical window and chemical and electrochemical stability, but they still have problems such as low ionic conductivity (less than 10^-3 S / cm). Existing solid electrolyte materials have approached their theoretical limits after long-term development, and breakthroughs in ionic conductivity require the discovery of new structures.

[0004] Research has found that Na7Y2P7O 24 When it constitutes 30% of a two-phase structure, this structure is rich in monovalent ions and has a near-layered structure, showing potential as a solid electrolyte. However, the inability to synthesize a pure phase makes its performance unmeasurable and unusable. Low-temperature liquid-phase ion exchange methods have been successfully demonstrated to convert sodium-ion conductors into lithium-ion conductors, producing excellent performance. Summary of the Invention

[0005] To address the issue of low ionic conductivity in existing solid-state electrolytes for lithium-ion batteries, this invention aims to provide a novel framework sodium yttrium lithium phosphate material, its preparation method, and its applications. When used as a solid-state electrolyte, this material exhibits a bulk ionic conductivity exceeding 10^-3 S / cm, and the method is simple and easy to implement.

[0006] In a first aspect, the present invention provides a lithium-ion solid electrolyte material, lithium yttrium sodium phosphate, wherein the chemical formula of the lithium-ion solid electrolyte material, lithium yttrium sodium phosphate, is Li. x Na 7-x Y2P7O 24 , where x = 0-6.0, preferably x = 4.

[0007] Preferably, the lithium-ion solid electrolyte material sodium yttrium phosphate has a monoclinic crystal system with space group P2 / c (No. 13) and cell parameters α = γ = 90° and β = 98-105°.

[0008] Secondly, the present invention provides a method for preparing the above-mentioned lithium-ion solid electrolyte material, sodium yttrium phosphate, the preparation method comprising the following steps:

[0009] (1) According to sodium yttrium phosphate Na7Y2P7O 24 Sodium salt, ammonium phosphate, and yttrium oxide raw materials were weighed according to the chemical element stoichiometry and mixed to obtain raw material mixed powder;

[0010] (2) The raw material mixture powder is pre-calcined, then ground, pressed into tablets, and then calcined at high temperature again to obtain precursor powder;

[0011] (3) Dissolve lithium salt in ionic liquid and add precursor powder to stir and heat to react for ion exchange. After washing, centrifugation and drying, the lithium-ion solid electrolyte material sodium yttrium phosphate is obtained.

[0012] Preferably, in step (1), the sodium salt includes at least one of sodium oxide, sodium carbonate, and sodium bicarbonate, and the ammonium phosphate salt includes at least one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

[0013] Preferably, in step (2), the preheating temperature is 250-500℃, the heating rate is 2-10℃ / min, and the holding time is 3-24h.

[0014] Preferably, in step (2), the tablet compression can be carried out by uniaxial cold pressing or cold isostatic pressing, with a pressure of 50-400MPa and a holding time of 3-80min.

[0015] Preferably, in step (2), the high-temperature calcination temperature is 550-650℃, the heating rate is 2-10℃ / min, and the holding time is 8-36h.

[0016] Preferably, in step (3), the lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(difluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)diimide; and the ionic liquid includes at least one of 1-butyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and polyethylene glycol.

[0017] Preferably, in step (3), the molar ratio of the lithium salt to the ionic liquid is (1.5-2.5):1, and the mass ratio of the mixed solution of the lithium salt and the ionic liquid to the precursor powder is (20-30):1.

[0018] Preferably, the stirring and heating reaction is carried out at a temperature of 100-200℃ for 12-36 hours and at a rotation speed of 100-400 rpm.

[0019] Thirdly, the present invention provides an application of the above-mentioned lithium-ion solid electrolyte material in a secondary battery, wherein the secondary battery includes a lithium-ion battery and a sodium-ion battery.

[0020] Beneficial effects

[0021] This invention expands the types of oxide solid electrolytes. The original lithium-ion solid electrolyte materials only included NASICON, LISICON, garnet, perovskite, anti-perovskite, and amorphous structures. Extensive research has continuously improved their ionic conductivity by changing the types and amounts of elements. However, due to the limitations of the framework structure, the improvement of ionic conductivity has reached its limit. Further improvements in ionic conductivity will depend on the generation of new structures. The sodium lithium yttrium phosphate material obtained by the low-temperature liquid-phase ion replacement method in this invention has a bulk ionic conductivity of 4.00 × 10^-3 S / cm, providing a new structure for improving the performance of lithium-ion solid electrolytes. Attached Figure Description

[0022] Figure 1 The precursor material Na7Y2P7O prepared in Example 1 24 Crystal structure diagram;

[0023] Figure 2 The precursor material Na7Y2P7O prepared in Example 1 24 X-ray powder diffraction pattern;

[0024] Figure 3 The lithium-ion solid electrolyte material, sodium yttrium phosphate (Li4Na3Y2P7O), prepared in Example 1. 24 Crystal structure diagram;

[0025] Figure 4 The lithium-ion solid electrolyte material, sodium yttrium phosphate (Li4Na3Y2P7O), prepared in Example 1. 24 Synchrotron radiation X-ray powder diffraction pattern;

[0026] Figure 5 Sodium yttrium phosphate (Li4Na3Y2P7O) is a lithium-ion solid electrolyte material prepared in Example 1. 24 Scanning electron microscope image;

[0027] Figure 6 Sodium yttrium phosphate (Li4Na3Y2P7O) is a lithium-ion solid electrolyte material prepared in Example 2. 24 XRD pattern;

[0028] Figure 7 Sodium yttrium phosphate (Li5Na2Y2P7O) is a lithium-ion solid electrolyte material prepared in Example 3.24 ICP test diagram;

[0029] Figure 8 Sodium yttrium phosphate (Li4Na3Y2P7O) is a lithium-ion solid electrolyte material prepared in Example 1. 24 Conductivity measurement graph;

[0030] Figure 9 Sodium yttrium phosphate (Li5Na2Y2P7O) is a lithium-ion solid electrolyte material prepared in Example 3. 24 The conductivity measurement diagram. Detailed Implementation

[0031] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0032] First, this invention provides a lithium-ion solid electrolyte material, sodium yttrium phosphate. The chemical formula of the sodium yttrium phosphate material can be Li... x Na 7-x Y2P7O 24 Where x = 0-6.0, preferably x = 4. A value that is too large for x will increase the replacement ratio, causing a decrease in ionic conductivity.

[0033] The lithium-ion solid electrolyte material, sodium yttrium phosphate, provided by this invention, features lithium ions occupying low-coordination sites in its structure. Due to charge repulsion and other effects, these lithium ions migrate through low-coordination channels, resulting in a low migration barrier. Furthermore, this electrolyte material, based on a novel framework, achieves rapid lithium-ion conduction due to its skeletal structure similar to the precursor (sodium yttrium phosphate) and the low-coordination lithium-ion migration channels. It exhibits high stability and high ionic conductivity, thus solving the problem of low ionic conductivity in lithium-ion solid electrolytes.

[0034] In some embodiments, the lithium-ion solid electrolyte material sodium yttrium phosphate has a monoclinic crystal system with space group P2 / c (No. 13) and cell parameters α = γ = 90° and β = 98-105°.

[0035] The following is an exemplary description of a method for preparing sodium yttrium phosphate, a lithium-ion solid electrolyte material provided by the present invention. The preparation method may include the following steps:

[0036] (1) According to sodium yttrium phosphate Na7Y2P7O 24 Sodium salt, ammonium phosphate, and yttrium oxide raw materials were weighed according to the chemical element stoichiometry and mixed to obtain raw material mixed powder;

[0037] (2) The raw material mixture powder is pre-calcined, then ground, pressed into tablets, and then calcined at high temperature again to obtain precursor powder;

[0038] (3) Dissolve lithium salt in ionic liquid and add precursor powder to stir and heat to react for ion exchange. After washing, centrifugation and drying, the lithium-ion solid electrolyte material sodium yttrium phosphate is obtained.

[0039] In some embodiments, in step (1), the sodium salt may include at least one of sodium oxide, sodium carbonate, and sodium bicarbonate, and the ammonium phosphate salt may include at least one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

[0040] In some embodiments, in step (1), the raw materials can be mixed by dry ball milling or wet ball milling using a planetary ball mill, with zirconia balls as grinding balls, a ball-to-material ratio of (2-20):1, a ball milling speed of 180-480 rpm, and a ball milling time of 8-36 h; preferably, ethanol, methanol, isopropanol, or propylene glycol can be used as solvents for wet ball milling, and the amount of solvent can be 10-25% of the total mass of the raw materials; after mixing, the raw materials can be dried at a temperature of 50-120°C for 4-36 h.

[0041] In some embodiments, in step (2), the preheating temperature can be 250-500℃, the heating rate can be 2-10℃ / min, and the holding time can be 3-24h.

[0042] Pre-calcination allows the carbon dioxide and ammonia gases that may be generated during the reaction of sodium carbonate and diammonium hydrogen phosphate in the mixed raw materials to volatilize, avoiding poor contact and affecting phase purity during the formation of the high-temperature phase structure. Excessive pre-calcination temperature will lead to partial formation of the sodium yttrium phosphate phase, while excessively low temperature and insufficient holding time will result in incomplete gas volatilization.

[0043] In some embodiments, in step (2), the tablet compression can be carried out by uniaxial cold pressing or cold isostatic pressing, the pressure can be 50-400MPa, and the holding time can be 3-80min.

[0044] In some embodiments, in step (2), the high-temperature calcination temperature can be 550-650℃, the heating rate can be 2-10℃ / min, and the holding time can be 8-36h. If the high-temperature calcination temperature is too low or the holding time is too short, it will result in incomplete phase formation and a non-pure phase; if the calcination temperature is too high, yttrium phosphate will partially precipitate, causing a phase change, and it will also cause the material to completely melt and stick to the container. If the calcination time is too long, yttrium phosphate will also precipitate, affecting the phase purity.

[0045] In some embodiments, in step (3), the lithium salt may include at least one of lithium bis(fluorosulfonyl)imide, lithium bis(difluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)diimide; the ionic liquid may include at least one of 1-butyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and polyethylene glycol.

[0046] In some embodiments, in step (3), the molar ratio of the lithium salt to the ionic liquid can be (1.5-2.5):1; the mass ratio of the mixed solution of the lithium salt and the ionic liquid to the precursor powder can be (20-30):1.

[0047] Ion exchange is essentially driven by concentration gradient. If the proportion of mixed lithium salt is too low, the exchange effect will not be achieved. The solubility of lithium salt in ionic liquids is fixed; if the mixing ratio is too high, it will be difficult to dissolve, and it will easily contaminate the sample during final purification. The mixing ratio with the precursor powder is also limited by the concentration gradient. During the exchange process, Li enters the material, and Na from the material enters the solution, leading to a continuous decrease in the lithium ion concentration gradient between the solution and the powder. Too much precursor powder makes it difficult to maintain the concentration gradient during later exchange stages.

[0048] In some embodiments, in step (3), the temperature of the stirring and heating reaction can be 100-200°C, the time can be 12-36h, and the rotation speed can be 100-400rpm.

[0049] In some embodiments, in step (3), the centrifugation speed can be 2500-7000 rpm and the time can be 2-5 min; the washing solvent can be at least one of ethanol, methanol, isopropanol, and propylene glycol; the drying temperature can be 60-100℃ and the time can be 6-18 h.

[0050] The method for preparing impedance test samples of lithium-ion solid electrolyte material sodium yttrium phosphate provided by the present invention may include the following steps: 0.5-1.5g of electrolyte powder is placed in a tableting mold, the uniaxial pressing pressure is 100-400MPa, the holding time is 5-80min, the thickness is measured after demolding, and the sample is placed in a CR2032 button battery case for measuring ionic conductivity.

[0051] Further, the ionic conductivity test procedure was as follows: The button battery containing the lithium-ion solid electrolyte was tested in a constant temperature chamber at 25°C using an electrochemical workstation at a bias voltage of 10mV and a frequency of 1MHz-1Hz. The data was fitted using Zview software, and the bulk ionic conductivity was found to be 4.00×10^-4S / cm.

[0052] The lithium-ion solid electrolyte material provided by this invention can be applied to secondary batteries, which may include lithium-ion batteries and sodium-ion batteries.

[0053] The lithium-ion solid electrolyte material of this invention is applied to lithium-ion batteries. The negative electrode material can be lithium metal, and the positive electrode material can be a commercially available positive electrode material. It achieves an ionic conductivity of 4.00 × 10⁻⁴ S / cm under a bias voltage of 10 mV and a frequency range of 10 MHz to 1 Hz. Furthermore, the material used in this invention has the advantages of simple preparation process, abundant and inexpensive raw materials, and excellent electrochemical performance, thus showing broad application prospects in energy storage.

[0054] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0055] Example 1

[0056] The lithium-ion solid electrolyte material provided in this embodiment is sodium yttrium phosphate (Li4Na3Y2P7O). 24 The preparation method includes the following steps:

[0057] (1) According to sodium yttrium phosphate Na7Y2P7O 24 Sodium carbonate, yttrium oxide and ammonium dihydrogen phosphate were weighed and mixed according to the chemical element stoichiometry. They were placed in a ball mill jar and 10 ml of ethanol was added. The mixture was wet-milled for 12 h and dried at 60 °C for 12 h to obtain the raw material mixed powder.

[0058] (2) The raw material mixture powder was pre-calcined in a muffle furnace at 400°C for 4 hours. After the reaction was completed, it was naturally cooled to room temperature, ground for 15 minutes, pressed into tablets at 100 MPa for 5 minutes, and then calcined at 600°C for 12 hours. After naturally cooling to room temperature, it was ground for 15 minutes to obtain the precursor material Na7Y2P7O. 24 ;

[0059] (3) 23g of lithium bis(trifluoromethanesulfonyl)imide was dissolved in 40ml of ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt at 60℃. The 2.8 precursor powder was added to the mixed solution. The reaction was carried out in a reactor at 180℃ with stirring at 300rpm for 24h. After the reaction was completed, it was naturally cooled to room temperature. The solid-liquid mixture after the reaction was washed with ethanol. The sample powder was separated by centrifugation. Finally, it was dried at 60℃ for 12h to obtain the lithium-ion solid electrolyte material.

[0060] Example 2

[0061] The lithium-ion solid electrolyte material provided in this embodiment is sodium yttrium phosphate (Li4Na3Y2P7O). 24 The preparation method is the same as in Example 1, with the main difference being:

[0062] In step (2), the tablets are pressed at 150 MPa and calcined at 580 °C;

[0063] In step (3), lithium bis(trifluoromethanesulfonyl)imide is dissolved in an ionic liquid at 80°C; the reaction is carried out in a reactor at 160°C for 18 hours.

[0064] Example 3

[0065] The lithium-ion solid electrolyte material provided in this embodiment is sodium yttrium phosphate (Li5Na2Y2P7O). 24 The preparation method is the same as in Example 1, with the main difference being:

[0066] In step (2), the mixed raw material powder is pre-calcined in a muffle furnace at 350°C;

[0067] In step (3), lithium bis(trifluoromethanesulfonyl)imide is dissolved in 35 ml of ionic liquid at 60 °C, and 3 g of precursor powder is added to the mixed solution; finally, it is dried at 80 °C for 9 h; and the displacement part of step (3) is repeated twice.

[0068] Comparative Example 1

[0069] The preparation method of the lithium-ion solid electrolyte material provided in this comparative example is the same as that in Example 1, with the main difference being:

[0070] In step (2), the tableting and calcination processes are not performed.

[0071] The final impedance test showed a random point, indicating that the material is not an ionic conductor.

[0072] Comparative Example 2

[0073] The preparation method of the lithium-ion solid electrolyte material provided in this embodiment is the same as that in Example 1, with the main difference being:

[0074] In step (3), the replacement process time is reduced to 2 hours.

[0075] The final impedance test showed a random point, indicating that the material is not an ionic conductor.

[0076] Comparative Example 3

[0077] The preparation method of the lithium-ion solid electrolyte material provided in this comparative example is the same as that in Example 1, with the main difference being:

[0078] In step (2), the high-temperature calcination temperature is set to 680℃.

[0079] After being calcined at high temperature, the material completely melts and sticks to the bottom of the crucible, making it difficult to separate and proceed to the next step.

[0080] Comparative Example 4

[0081] The preparation method of the lithium-ion solid electrolyte material provided in this comparative example is the same as that in Example 1, with the main difference being:

[0082] In step (3), the molar ratio of lithium salt to ionic liquid is 0.5:1.

[0083] The final impedance test showed a random point, indicating that the material is not an ionic conductor.

[0084] Figure 1 The precursor material Na7Y2P7O prepared in Example 1 24 The crystal structure diagram is shown. As can be seen from the diagram, each YO7 decahedron (pentagonal bipyramidal) shares an edge with a PO4 tetrahedron, and the five PO4 tetrahedrons share an angle, forming a stable three-dimensional framework structure. The precursor is a monoclinic structure with one secondary axis and four different sodium sites. Among them, Na3 accounts for 1 / 7 of the total sodium content, while the other sodium sites each account for 2 / 7 of the total sodium content.

[0085] Figure 2 The precursor material Na7Y2P7O prepared in Example 1 24 The X-ray powder diffraction pattern shows the successful synthesis of the precursor.

[0086] Figure 3 The lithium-ion solid electrolyte material, sodium yttrium phosphate (Li4Na3Y2P7O), prepared in Example 1. 24 The crystal structure diagram is shown. As can be seen from the diagram, after substitution, the Na0 and Na2 sites in the precursor have been replaced by Li0 and Li2, decreasing from the original six-coordinate to four-coordinate.

[0087] Figure 4The lithium-ion solid electrolyte material, sodium yttrium phosphate (Li4Na3Y2P7O), prepared in Example 1. 24 The synchrotron X-ray powder diffraction pattern is shown in the figure. It can be seen from the figure that the prepared solid electrolyte powder, obtained from the refinement results, is composed of Li₄Na₃Y₂P₇O₄. 24 It also consists of a small amount of YPO4.

[0088] Figure 5 Sodium yttrium phosphate (Li4Na3Y2P7O) is a lithium-ion solid electrolyte material prepared in Example 1. 24 The scanning electron microscope image shows that the material has a layered structure.

[0089] Figure 6 Sodium yttrium phosphate (Li4Na3Y2P7O) is a lithium-ion solid electrolyte material prepared in Example 2. 24 XRD pattern. Figure 6 The middle XRD pattern represents the product after 18 hours of reaction. The figure shows a comparison of the products after 18 hours, 24 hours, and 12 hours. As can be seen from the figure, the overall structure of the product after 18 hours of substitution did not change significantly compared to the product after 24 hours of substitution. However, some precursor peaks were not completely eliminated; for example, the peak at 2Theta = 35° is significantly higher than that of the product after 24 hours of substitution, indicating incomplete substitution.

[0090] Figure 7 Sodium yttrium phosphate (Li5Na2Y2P7O) is a lithium-ion solid electrolyte material prepared in Example 3. 24 ICP test results. The figure shows that the ratio of Na to Y, determined by ICP testing, confirms the material as Li₅Na₂Y₂P₇O. 24 This proportion of materials.

[0091] 0.7g of the electrolyte powder from Example 1 was placed into a 16mm diameter tableting mold, uniaxially compressed at 150MPa for 5 minutes, and the thickness after demolding was measured to be 1.4mm. The powder was then placed into a CR2032 button battery casing for ionic conductivity measurement. The results are as follows: Figure 8 As shown in the figure, the bulk ionic conductivity of the material obtained by fitting is 4.00 × 10^-3 S / cm.

[0092] 0.4 g of the electrolyte powder from Example 3 was placed into a 13 mm diameter tableting mold, uniaxially compressed at 120 MPa for 10 min, and the thickness after demolding was measured to be 1.2 mm. The powder was then placed into a CR2032 button cell casing for ionic conductivity measurement. The results are as follows: Figure 9 As shown in the figure, the bulk ionic conductivity of the material obtained by fitting is 1.12 × 10^-3 S / cm.

[0093] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A lithium-ion solid electrolyte material, sodium yttrium phosphate, characterized in that, The chemical formula of the lithium-ion solid electrolyte material, sodium yttrium phosphate, is Li. x Na 7-x Y2P7O 24 , where x = 0 - 6.0 and x is not 0.

2. The lithium-ion solid electrolyte material, sodium yttrium phosphate, according to claim 1, is characterized in that, x=4。 3. The lithium-ion solid electrolyte material sodium yttrium phosphate according to claim 1, characterized in that, The lithium-ion solid electrolyte material, sodium yttrium phosphate, has a monoclinic crystal system and a space group of [space group number missing]. P2 / c (No.13), with unit cell parameters α=γ=90°, β=98-105°.

4. A method for preparing the lithium-ion solid electrolyte material sodium yttrium phosphate as described in claim 1, characterized in that, The preparation method includes the following steps: (1) According to sodium yttrium phosphate Na7Y2P7O 24 Sodium salt, ammonium phosphate, and yttrium oxide raw materials were weighed according to the chemical element stoichiometry and mixed to obtain raw material mixed powder; (2) The raw material mixture powder is pre-calcined, then ground, pressed into tablets, and then calcined at high temperature again to obtain precursor powder; (3) Dissolve lithium salt in ionic liquid and add precursor powder to stir and heat to react for ion exchange. After washing, centrifugation and drying, the lithium-ion solid electrolyte material sodium yttrium phosphate is obtained.

5. The preparation method according to claim 4, characterized in that, In step (1), the sodium salt includes at least one of sodium oxide, sodium carbonate, and sodium bicarbonate, and the ammonium phosphate salt includes at least one of ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

6. The preparation method according to claim 4, characterized in that, In step (2), the preheating temperature is 250-500℃, the heating rate is 2-10℃ / min, and the holding time is 3-24h.

7. The preparation method according to claim 4, characterized in that, In step (2), the tablet can be pressed by uniaxial cold pressing or cold isostatic pressing, with a pressure of 50-400MPa and a holding time of 3-80min.

8. The preparation method according to claim 4, characterized in that, In step (2), the high-temperature calcination temperature is 550-650℃, the heating rate is 2-10℃ / min, and the holding time is 8-36h.

9. The preparation method according to claim 4, characterized in that, In step (3), the lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(difluoromethanesulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)diimide; the ionic liquid includes at least one of 1-butyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and polyethylene glycol.

10. The preparation method according to claim 4, characterized in that, In step (3), the molar ratio of the lithium salt to the ionic liquid is (1.5-2.5):1, and the mass ratio of the mixed solution of the lithium salt and the ionic liquid to the precursor powder is (20-30):

1. The stirring and heating reaction is carried out at a temperature of 100-200℃ for 12-36 hours and at a speed of 100-400 rpm.

11. The application of the lithium-ion solid electrolyte material sodium yttrium phosphate as described in claim 1 in a secondary battery, characterized in that, The secondary battery includes lithium-ion batteries and sodium-ion batteries.

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