A multi-element doped NASICON solid-state electrolyte, a preparation method and application thereof

Abstract

This invention belongs to the field of sodium metal battery technology, and particularly relates to a multi-element doped NASICON-type Na3Zr2Si2PO4 12 Solid electrolytes, their preparation methods, and applications. The solid electrolyte is Na₃Zr₂Si₂PO₄. 12 Based on Na3Zr2Si2PO 12 The Zr, Si, and P sites are doped with elements A, B, and C, respectively. Element A includes one or more of Ti, Fe, Y, Ca, or Zn; element B includes one or more of Al, Mg, or As; and element C includes one or more of B, Se, or S. This invention induces polyhedral distortion through multi-element doping, thereby further triggering lattice distortion and constructing an amorphous phase to improve the ionic conductivity and interfacial dendrite resistance of the solid electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of sodium metal battery technology, and particularly relates to a multi-element doped NASICON-type solid electrolyte, its preparation method and application. Background Technology

[0002] With increasing demands for safety and cost-effectiveness in energy storage, traditional lithium-ion battery systems urgently need innovation. Solid-state sodium metal batteries combine the high theoretical capacity of sodium metal anodes with the intrinsic stability of solid-state electrolytes (SSEs), exhibiting significant advantages in energy density, power density, environmental adaptability, and safety, making them a promising next-generation battery technology.

[0003] Among various solid electrolyte materials, NASICON-type compounds (general formula Na) are the most common. 1+x Zr2SixP 3-x O 12 Solid-state electrolytes (0 ≤ x ≤ 3) have attracted much attention due to their excellent chemical and electrochemical stability and high ionic conductivity. However, the rigidity of oxide-based solid-state electrolytes leads to insufficient intergranular contact during sintering, resulting in a relatively low material density and significant internal porosity, thus limiting further improvements in ionic conductivity. Furthermore, the contact between the solid-state electrolyte and the sodium metal anode is typically point-contact, with poor interfacial bonding and a limited contact area, easily causing localized current concentrations. This can induce dendrite growth along grain boundaries, affecting the cycle stability and safety of the battery.

[0004] Amorphization is considered an effective approach to improve the ionic conductivity and interfacial compatibility of solid electrolytes. For example, introducing low-valence metal ions into halide or sulfide solid electrolytes can induce the formation of an amorphous phase, thereby simultaneously improving ion transport performance and material stability. Currently, common studies on inducing amorphization in NASICON-type solid electrolytes typically employ the introduction of a single low-valence metal ion (e.g., Mg). 2+ Ca 2+The strategy of doping with various elements (such as ions) can induce lattice distortion to some extent. However, due to the limited variety of doping elements and the limited types and intensities of lattice strain introduced, it often only induces localized and slight structural disorder, making it difficult to achieve a significant and uniform amorphization transformation over a long range. Therefore, there is a bottleneck in the improvement of ionic conductivity. At the same time, the effect of single-element doping on promoting low-temperature densification sintering is also relatively limited. Theoretically, introducing more complex and stronger lattice distortion through multi-element synergistic doping is a better path to overcome the above limitations and achieve deep amorphization. However, this is technically very difficult: First, the co-doping of multiple heterogeneous ions can easily destroy the thermodynamic stability of the NASICON structure, leading to the precipitation of impurity phases during heat treatment, which in turn degrades performance; second, the influence of different ions on sintering kinetics is complex, making it difficult to precisely control the formation of multiphase microstructures while reducing the sintering temperature, thus achieving a balance between high density and high ionic conductivity. Therefore, how to design an effective combination of multi-element components and doping ratios that can induce full amorphization while maintaining the structural integrity of the material matrix and optimizing sintering behavior has always been a technical problem that has not been well solved in this field. Summary of the Invention

[0005] This invention provides a multi-element doped NASICON-type solid electrolyte, its preparation method, and its applications. The core of this application lies in providing an innovative multi-element combined doping scheme. By precisely selecting specific types and valence states of doping elements (such as elements A, B, and C) and controlling their proportions, a synergistic effect is achieved. This design not only effectively accumulates the distortion of polyhedra (such as [ZrO6] octahedrons and [(Si / P)O4] tetrahedra), successfully inducing the generation of a high-content amorphous phase, thereby significantly reducing the sodium ion migration barrier; it also promotes grain fusion and porosity elimination at significantly reduced sintering temperatures, resulting in a high-density electrolyte phase. This ultimately solves the problems of simultaneously improving ionic conductivity and suppressing interfacial dendrites, providing a reliable electrolyte material solution for the practical application of high-performance solid-state sodium metal batteries.

[0006] To achieve the above objectives, the present invention provides a multi-element doped NASICON-type solid electrolyte, wherein the solid electrolyte is Na3Zr2Si2PO4. 12 Based on Na3Zr2Si2PO 12 The Zr, Si, and P sites are doped with A, B, and C elements, respectively. Element A includes one or more of Ti, Fe, Y, Ca, or Zn; Element B includes one or more of Al, Mg, or As; The C element includes one or more of B, Se, or S.

[0007] This invention selects the chemical formula Na3Zr2Si2PO4. 12 The elemental doping is based on NASICON-type solid electrolytes, mainly due to their following characteristics: 1. Excellent ionic conductivity; within the NASICON family, Na3Zr2Si2PO4 12 It is recognized as one of the benchmark materials with the highest room-temperature ionic conductivity, which is directly related to its unique crystal structure. Na3Zr2Si2PO 12 The structure is stable, consisting of a three-dimensional framework composed of [ZrO6] octahedra and [(Si / P)O4] tetrahedra sharing a common vertex. The size of its sodium ion transport channels is well matched with the radius of sodium ions (approximately 1.02 Å), providing an optimal geometric basis for the rapid conduction of sodium ions.

[0008] 2. Requirements for structural distortion: To achieve effective amorphization, the base material must possess structural characteristics that can be disrupted by doping with specific elements. (e.g., Na3Zr2Si2PO) 12 The structure combines rigidity and flexibility: its framework is stable enough to form ion channels, but small changes in the bond angles of Zr, Si, P, and O can easily produce cumulative effects, which is the premise for achieving polyhedral distortion and amorphization through doping.

[0009] 3. Complex Structure-Property Relationship Between Chemical Composition and Electrical Conductivity: Relevant literature indicates that the ionic conductivity of NASICON materials exhibits a complex nonlinear relationship with the average radius of metal ions, sodium content, and silicon / phosphorus ratio. (Na3Zr2Si2PO) 12 It is in a window of optimal composition and performance. Substituting its elements may directly change or even destroy this optimal window, leading to drastic changes in the material's sinterability, chemical stability, or basic electrical conductivity.

[0010] The multi-element synergistic doping strategy of this invention, compared to traditional single-element doping, has a fundamental advantage in that it precisely targets the different coordination characteristics of the [ZrO6] octahedron and [(Si / P)O4] tetrahedron in the NASICON structure: by introducing A elements with radius / valence mismatch at the Zr sites to directly distort the rigid octahedral core, and simultaneously introducing B and C elements at the Si / P sites to change the tetrahedron's connection geometry and local charge. This multi-point, multi-type doping generates incompatible strain superposition and complex charge compensation networks at the oxygen atoms with shared corners, forming a strong synergistic lattice distortion effect far exceeding the local perturbation of a single element. This effect can effectively accumulate and solidify, thereby more efficiently destroying the long-range lattice order, and ultimately inducing the generation of a high-content amorphous phase at a lower temperature, simultaneously achieving a significant increase in ionic conductivity and a substantial reduction in sintering temperature.

[0011] Preferably, the chemical formula of the solid electrolyte is Na.3+x Zr 2-a A a Si 2-b B b P 1-c C c O 12 ; Where -0.5≤x≤0.5, 0<a≤0.5, 0<b≤0.5, 0<c≤0.5. x represents the amount of Na added or removed after doping based on charge conservation.

[0012] Preferably, the solid electrolyte comprises an amorphous phase and a NASICON crystalline phase, wherein the content of the amorphous phase is 40-50%.

[0013] Under the same technical concept, the present invention also provides a method for preparing a multi-element doped NASICON-type solid electrolyte, comprising the following steps: S1. Weigh the raw materials of Na source, Zr source, Si source, P source and A, B and C doping elements, mix them and ball mill them once, and sieve them to obtain mixed precursor powder. S2. The mixed precursor powder prepared in S1 is sintered once and naturally cooled to room temperature to obtain the sintered precursor. S3. The sintering precursor prepared in S2 is ball-milled a second time to obtain the initial sintering powder. S4. The initial sintered powder prepared in S3 is sintered a second time and naturally cooled to room temperature to obtain a multi-element doped NASICON-type solid electrolyte.

[0014] Preferably, the Na source in S1 includes one or more of Na2CO3, NaHCO3, NaOH, or Na2O; The P source includes one or more of NH4H2PO4, (NH4)2HPO4, or P2O5; The Si source includes SiO2 and / or Si(OH)4; The Zr source includes ZrO2 and / or Zr(OH)4; The raw materials for element A include one or more of TiO2, Fe2O3, Y2O3, CaO, or ZnO; The raw materials for element B include one or more of Al2O3, MgO, or As2O3; The raw materials for element C include one or more of B2O3, SeO2, or NH4HSO4.

[0015] Preferably, the primary and secondary ball milling in S1 and S3 are carried out using a zirconium dioxide ball milling jar, wherein the mass ratio of the grinding balls to the material being milled in the zirconium dioxide ball milling jar is 10-30:1. The ball milling temperature is 20-30℃; The ball mill speed is 400-500 rpm; The ball milling time is 10-15 hours; The solvent is ethanol and / or isopropanol.

[0016] Preferably, the first sintering in S2 is solid-state sintering, and the atmosphere of solid-state sintering is air or oxygen; the container for solid-state sintering is a corundum / magnesium oxide crucible; the heating rate of solid-state sintering is 2-5℃ / min; the temperature is raised to 800-1000℃ and held for 10-15 hours. Preferably, the secondary sintering in S4 is solid-state sintering, and the atmosphere of solid-state sintering is air or oxygen; the container for solid-state sintering is a corundum / magnesium oxide crucible; the heating rate of solid-state sintering is 2-5℃ / min; first, the temperature is raised to 500-700℃ and held for 2-4 hours, then the temperature is raised to 1000-1200℃ and held for 8-12 hours.

[0017] This application successfully reduced the final sintering temperature of NASICON solid electrolyte to a minimum of 1000°C, a significant reduction of 200 to 300°C compared to the high temperature of 1200°C to 1300°C typically required by conventional processes.

[0018] The two-stage sintering scheme (holding at 600℃ followed by heating to 1000℃) adopted in this application is a precise design closely integrated with the lattice pre-distortion characteristics induced by multi-element doping. Its reaction mechanism is as follows: the first stage, holding at 600℃, aims to allow the PVA binder to slowly and completely decompose and volatilize, while avoiding cracking or elemental segregation of the green body due to excessively rapid heating, thus preserving the metastable distortion structure introduced by doping for the subsequent high-temperature stage. The second stage sintering at 1000℃ then significantly reduces the diffusion barrier of lattice atoms due to the incompatible strain created by the previous doping, enhancing the kinetics of solid-state ion diffusion and grain boundary migration. This allows the material to simultaneously complete the final synthesis of the residual crystalline phase, the relaxation and shaping of the amorphous phase structure, and the densification of the microstructure at lower temperatures than conventional methods, thereby achieving high density and high ionic conductivity in one step while avoiding sodium volatilization.

[0019] Preferably, a binder is added during the secondary sintering in S4, wherein the binder is a 3%-10% PVA aqueous solution and / or a 3%-10% PVB ethyl acetate solution; During secondary sintering, the mass ratio of initial sintering powder to binder is 5-15:1, forming a solid electrolyte green body. The solid electrolyte green blank has a diameter of 12-18 mm and a thickness of 1.0-1.2 mm.

[0020] Under the same technical concept, the present invention also provides an application of a multi-element doped NASICON-type solid electrolyte, which is used in a sodium metal battery system.

[0021] The above-described solution of the present invention has the following beneficial effects: (1) The multi-element doped NASICON-type solid electrolyte provided by the present invention is produced by using Na3Zr2Si2PO4 12 Based on this, specific element doping was introduced. By introducing A elements with radius / valence mismatch at Zr sites to directly distort the rigid octahedral core, and B and C elements at Si / P sites to change the tetrahedral connection geometry and local charge, the long-range lattice order was destroyed, and an amorphous phase was generated in the material. The introduction of this amorphous phase can reduce the energy barrier for sodium ion migration and provide more fast diffusion paths, thereby significantly improving the overall ionic conductivity. (2) The method for preparing the multi-element doped NASICON-type solid electrolyte provided by this invention requires a low sintering temperature; the presence of the amorphous phase enhances the material transport and densification capabilities during the sintering process, enabling the material to achieve high density at a relatively low sintering temperature. The densification effectively reduces defects such as grain boundaries, which not only reduces grain boundary impedance but also strengthens the electrolyte's ability to resist sodium dendrite penetration; (3) In summary, this invention has successfully achieved high-performance preparation of NASICON electrolyte at low temperature by inducing amorphization through element doping; the resulting modified electrolyte has both high ionic conductivity and excellent structural compactness, which can effectively suppress dendrite growth, thus providing a material basis for improving the overall electrochemical performance of solid sodium metal batteries. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope image of the NASICON-type sodium-ion solid electrolyte material with multi-element doping and low-temperature sintering in Example 1; Figure 2 The XRD pattern of the NASICON-type sodium-ion solid electrolyte material with multi-element doping and low-temperature sintering in Example 1 is shown. Figure 3 The AC impedance diagram of the Au|SSE|Au battery assembled at room temperature using the NASICON-type sodium-ion solid electrolyte material with multi-element doping and low-temperature sintering in Example 1. Figure 4The graph shows the constant current charge-discharge cycle performance of the Na|SSE|Na battery assembled from the NASICON-type sodium-ion solid electrolyte material with multi-element doping and low-temperature sintering in Example 1 at a current density of 0.1 mA cm–2. Detailed Implementation

[0023] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a locking connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Example 1 This embodiment provides a multi-element doped, low-temperature sintered NASICON-type sodium-ion solid electrolyte material, Na... 3.36 Zr 1.85 Y 0.05 Fe 0.05 Ti 0.05 Si 1.8 Al 0.2 P 0.97 B 0.03 O 12 .

[0027] The preparation method of the above solid electrolyte is as follows: (1) First mechanical ball milling: 1.68 mol Na2CO3, 1.85 mol ZrO2, 0.025 mol Y2O3, 0.025 mol Fe2O3, 0.05 mol TiO2, 1.8 mol SiO2, 0.1 mol Al2O3, 0.97 mol NH4H2PO4, and 0.015 mol B2O3 were weighed according to the stoichiometric ratio, with Na2CO3 in excess by 10 wt%. The precursor powder was placed in a zirconium dioxide ball mill jar at a ball bead / powder mass ratio of 20:1, and 10 ml of anhydrous ethanol was added. The ball milling temperature was set at 25°C, the ball milling speed at 450 rpm, and the ball milling time at 12 hours. The mixed powder was then uniformly ball milled. After ball milling, the solvent in the mixture was heated to dryness, and the powder was pulverized and separated using a sieve to obtain the mixed precursor.

[0028] (2) First solid-state sintering: The mixed precursor powder is placed in a corundum crucible and sintered in a muffle furnace with an air atmosphere. The heating rate is 3°C / min, and the temperature is raised to 800°C and held for 12 hours. After natural cooling to room temperature, the sintered material is obtained.

[0029] (3) Second mechanical ball milling: The powder material from the first sintering was placed in a zirconia ball mill jar at a ball-milling bead / powder mass ratio of 20:1, and 10 ml of anhydrous ethanol was added. The ball milling temperature was set to 25°C, the ball milling speed to 450 rpm, and the ball milling time to 12 hours. The powder was then uniformly ball-milled. After ball milling, the solvent in the mixture was heated to dryness, and the powder was pulverized and separated using a sieve separator to obtain the initial sintered powder.

[0030] (4) Second solid-state sintering: The initial sintering powder and PVA binder at a mass ratio of 10:1 were uniformly mixed in a mortar, wherein the PVA binder was prepared as a 5% aqueous solution. After grinding until the water was fully evaporated, the mixed powder was pressed into a solid electrolyte green body with a diameter of 16 mm and a thickness of 1.1 mm, and then placed in a corundum crucible. Sintering was carried out in a muffle furnace with an air atmosphere at a heating rate of 3 °C / min. First, the temperature was raised to 600 °C and held for 3 hours, and then raised to 1000 °C and held for 10 hours. After natural cooling to room temperature, a multi-element doped low-temperature sintered NASICON-type sodium ion solid electrolyte material was obtained.

[0031] Depend on Figure 1 It can be seen that the surface of the NASICON-type sodium-ion solid electrolyte in this embodiment contains a certain amount of amorphous phase without a specific morphology, and cubic crystalline phase is distributed around the amorphous phase. The content of the amorphous phase is shown in Table 1. Furthermore, from... Figure 2It can be seen that the NASICON-type sodium ion solid electrolyte of this embodiment has a standard NASICON-type crystal structure with a space group of C2 / c. Furthermore, due to the presence of the amorphous phase, the diffraction peak intensity of its NASICON-type crystal structure is significantly reduced.

[0032] The NASICON-type sodium-ion solid electrolyte of this embodiment was plated with gold on both sides using magnetron sputtering technology, and its conductivity was tested. The conductivity was calculated using the formula for ionic conductivity:

[0033] in l (cm) represents the thickness of the solid electrolyte, S (cm) 2 R is the effective contact area with the blocking electrode, and R (ohms) is the value obtained through electrochemical impedance spectroscopy. Figure 3 The resistance value was measured. The resistance value of the NASICON type sodium-ion solid electrolyte Na in this embodiment was measured. 3.36 Zr 1.85 Y 0.05 Fe 0.05 Ti 0.05 Si 1.8 Al 0.2 P 0.97 B 0.03 O 12 The room temperature ionic conductivity is 0.96 mS / cm. –1 This result fully demonstrates that by inducing the formation of an amorphous phase in the NASICON system, solid electrolytes with high ionic conductivity can be synthesized at low sintering temperatures.

[0034] Preparation of the sodium metal symmetric battery Na|SSE|Na: In an inert atmosphere glove box with an oxygen content of less than 0.01 ppm, sodium metal sheets were attached to both sides of the NASICON-type sodium-ion solid electrolyte disc of this embodiment, and then encapsulated in a CR-2032 coin cell to assemble a sodium metal symmetric battery. The sodium metal symmetric battery was subjected to constant current charge-discharge testing, and the specific test scheme is as follows: First, the Na|SSE|Na symmetric battery was charged at 0.05 mA cm⁻¹. –2 Charge at the current density for one hour, then discharge for one hour, repeating this process three times; then increase the current density to 0.1 mA cm⁻¹. –2 Then, repeat the long cycle of charging for one hour and discharging for one hour. For example... Figure 4 As shown, this sodium metal symmetric cell operates at a current density of 0.1 mA cm⁻¹. –2 Under the specified conditions, it can cycle stably for 500 hours without short circuits. This result indicates that the solid electrolyte of this embodiment has excellent sodium dendrite suppression capabilities.

[0035] Example 2 Compared to Example 1, the only difference is that element A is Ti, Fe, or Ca, and the chemical formula is Na. 3.41 Zr 1.85 Ca 0.05 Fe 0.05 Ti 0.05 Si 1.8 Al 0.2 P 0.97 B 0.03 O 12 The raw materials were 1.705 mol Na2CO, 1.85 mol ZrO2, 0.05 mol CaO3, 0.025 mol Fe2O3, 0.05 mol TiO2, 1.8 mol SiO2, 0.1 mol Al2O3, 0.97 mol NH4H2PO4, and 0.015 mol B2O3. Other operations and parameters were the same as in Example 1.

[0036] Example 3 Compared to Example 1, the only difference is that element A is Ti, Fe, Zn, and the chemical formula is Na. 3.41 Zr 1.85 Zn 0.05 Fe 0.05 Ti 0.05 Si 1.8 Al 0.2 P 0.97 B 0.03 O 12 The raw materials were 1.705 mol Na2CO, 1.85 mol ZrO2, 0.05 mol ZnO3, 0.025 mol Fe2O3, 0.05 mol TiO2, 1.8 mol SiO2, 0.1 mol Al2O3, 0.97 mol NH4H2PO4, and 0.015 mol B2O3. Other operations and parameters were the same as in Example 1.

[0037] Example 4 Compared to Example 1, the only difference is that element A is Ti, Y, and Ca, and the chemical formula is Na. 3.41 Zr 1.85 Ca 0.05 Y 0.05 Ti 0.05 Si 1.8 Al 0.2 P 0.97 B 0.03 O 12The raw materials were 1.705 mol Na2CO3, 1.85 mol ZrO2, 0.05 mol CaO, 0.025 mol Y2O3, 0.05 mol TiO2, 1.8 mol SiO2, 0.1 mol Al2O3, 0.97 mol NH4H2PO4, and 0.015 mol B2O3. Other operations and parameters were the same as in Example 1.

[0038] Example 5 Compared to Example 1, the only difference is that element A is Ti, Y, Zn, and the chemical formula is Na. 3.41 Zr 1.85 Zn 0.05 Y 0.05 Ti 0.05 Si 1.8 Al 0.2 P 0.97 B 0.03 O 12 The raw materials were 1.705 mol Na2CO3, 1.85 mol ZrO2, 0.025 mol Y2O3, 0.05 mol ZnO, 0.05 mol TiO2, 1.8 mol SiO2, 0.1 mol Al2O3, 0.97 mol NH4H2PO4, and 0.015 mol B2O3. Other operations and parameters were the same as in Example 1.

[0039] Example 6 Compared to Example 1, the only difference is that element A is Ti, Ca, Zn, and the chemical formula is Na. 3.46 Zr 1.85 Zn 0.05 Ca 0.05 Ti 0.05 Si 1.8 Al 0.2 P 0.97 B 0.03 O 12 The raw materials were 1.73 mol Na2CO3, 1.85 mol ZrO2, 0.05 mol CaO, 0.05 mol ZnO, 0.05 mol TiO2, 1.8 mol SiO2, 0.1 mol Al2O3, 0.97 mol NH4H2PO4, and 0.015 mol B2O3. Other operations and parameters were the same as in Example 1.

[0040] Example 7 Compared to Example 1, the only difference is that element B is Mg, with the chemical formula Na. 3.56 Zr 1.85 Y0.05 Fe 0.05 Ti 0.05 Si 1. 8Mg 0.2 P 0.97 B 0.03 O 12 The raw materials were 1.78 mol Na2CO3, 1.85 mol ZrO2, 0.025 mol Y2O3, 0.025 mol Fe2O3, 0.05 mol TiO2, 1.8 mol SiO2, 0.2 mol MgO, 0.97 mol NH4H2PO4, and 0.015 mol B2O3. Other operations and parameters were the same as in Example 1.

[0041] Example 8 Compared to Example 1, the only difference is that element B is As, and its chemical formula is Na. 3.36 Zr 1.85 Y 0.05 Fe 0.05 Ti 0.05 Si 1. 8As 0.2 P 0.97 B 0.03 O 12 The raw materials were 1.68 mol Na2CO3, 1.85 mol ZrO2, 0.025 mol Y2O3, 0.025 mol Fe2O3, 0.05 mol TiO2, 1.8 mol SiO2, 0.1 mol As2O3, 0.97 mol NH4H2PO4, and 0.015 mol B2O3. Other operations and parameters were the same as in Example 1.

[0042] Example 9 The only difference from Example 1 is that the C element is Se and the chemical formula is Na. 3.33 Zr 1.85 Y 0.05 Fe 0.05 Ti 0.05 Si 1. 8Al 0.2 P 0.97 Se 0.03 O 12The raw materials were 1.665 mol Na2CO3, 1.85 mol ZrO2, 0.025 mol Y2O3, 0.025 mol Fe2O3, 0.05 mol TiO2, 1.8 mol SiO2, 0.1 mol Al2O3, 0.97 mol NH4H2PO4, and 0.03 mol SeO2. Other operations and parameters were the same as in Example 1.

[0043] Example 10 The only difference from Example 1 is that the C element is S and the chemical formula is Na. 3.27 Zr 1.85 Y 0.05 Fe 0.05 Ti 0.05 Si 1.8 Al 0.2 P 0.97 S 0.03 O 12 The raw materials were 1.635 mol Na2CO3, 1.85 mol ZrO2, 0.025 mol Y2O3, 0.025 mol Fe2O3, 0.05 mol TiO2, 1.8 mol SiO2, 0.1 mol Al2O3, 0.97 mol NH4H2PO4, and 0.03 mol NH4HSO4. Other operations and parameters were the same as in Example 1.

[0044] Comparative Example 1 Compared to Example 1, the only difference is that it is doped with only element A, with the chemical formula Na. 3.1 Zr 1.85 Y 0.05 Fe 0.05 Ti 0.05 Si2PO 12 The raw materials were 1.55 mol Na2CO3, 1.85 mol ZrO2, 0.025 mol Y2O3, 0.025 mol Fe2O3, 0.05 mol TiO2, 2 mol SiO2, and 1 mol NH4H2PO4. Other operations and parameters were the same as in Example 1.

[0045] Comparative Example 2 Compared to Example 1, the only difference is that it is doped with only element B, with the chemical formula Na. 3.2 Zr2Si 1.8 Al 0.2 PO 12The raw materials were 1.6 mol Na2CO3, 2 mol ZrO2, 1.8 mol SiO2, 0.1 mol Al2O3, and 1 mol NH4H2PO. Other operations and parameters were the same as in Example 1.

[0046] Comparative Example 3 Compared to Example 1, the only difference is that it is doped with only element C, with the chemical formula Na. 3.06 Zr2Si2P 0.97 B 0.03 O 12 The raw materials were 1.53 mol Na2CO3, 2 mol ZrO2, 2 mol SiO2, 0.97 mol NH4H2PO4 and 0.015 mol B2O3, and other operations and parameters were the same as in Example 1.

[0047] Comparative Example 4 Compared to Example 1, the only difference is that only elements A and B are doped, and Na... 3.3 Zr 1.85 Y 0.05 Fe 0.05 Ti 0.05 Si 1.8 Al 0. 2PO 12 The raw materials were 1.65 mol Na2CO3, 1.85 mol ZrO2, 0.025 mol Y2O3, 0.025 mol Fe2O3, 0.05 mol TiO2, 1.8 mol SiO2, 0.1 mol Al2O3, and 1 mol NH4H2PO4. Other operations and parameters were the same as in Example 1.

[0048] Comparative Example 5 Compared to Example 1, the only difference is that only A and C elements are doped, and Na... 3.16 Zr 1.85 Y 0.05 Fe 0.05 Ti 0.05 Si2P 0.9 7B 0.03 O 12 The raw materials were 1.58 mol Na2CO3, 1.85 mol ZrO2, 0.025 mol Y2O3, 0.025 mol Fe2O3, 0.05 mol TiO2, 2 mol SiO2, 0.97 mol NH4H2PO4, and 0.015 mol B2O3. Other operations and parameters were the same as in Example 1.

[0049] Comparative Example 6 Compared to Example 1, the only difference is that only elements B and C are doped, and Na... 3.26 Zr2Si 1.8 Al 0.2 P 0.97 B 0.03 O 12 The raw materials were 1.63 mol Na2CO3, 2 mol ZrO2, 1.8 mol SiO2, 0.1 mol Al2O3, 0.97 mol NH4H2PO4 and 0.015 mol B2O3, and other operations and parameters were the same as in Example 1.

[0050] Comparative Example 7 Compared with Example 1, the only difference is that elements A, B, and C are not doped in Na3Zr2Si2PO4. 12 The raw materials are 1.5 mol Na₂CO₃, 2 mol ZrO₂, 2 mol SiO₂, and 1 mol NH₄H₂PO₄. 43 Other operations and parameters are the same as in Example 1.

[0051] Comparative Example 8 Compared with Comparative Example 7, the only difference is that the first sintering temperature was increased to 1000℃ and the second sintering temperature was increased to 1200℃, while all other operations and parameters were the same.

[0052] The experimental data of the above embodiments and comparative examples are shown in Table 1. The following core conclusions can be clearly drawn, highlighting the key role of the amorphous phase in improving the performance of NASICON-type solid electrolytes: 1. Multi-element synergistic doping is a key strategy for inducing the formation of amorphous phases.

[0053] Examples 1-10 successfully introduced significant amorphous phases (40%-48%) into the materials by simultaneously introducing multiple heterovalent elements (such as Y, Fe, Ti, Al, B, etc.). Comparative Examples 1-6 show that doping with only one or two elements resulted in extremely low amorphous phase content (≤8%), with limited performance improvement. This demonstrates that the synergistic effect of multiple elements can effectively disrupt the regular arrangement of [ZrO6] octahedra and [(Si / P)O4] tetrahedra, accumulating structural distortion and thus destroying long-range order, achieving amorphization.

[0054] 2. The content of amorphous phase is strongly positively correlated with ionic conductivity and cycling stability.

[0055] The data clearly show that the higher the amorphous phase content, the better the overall performance of the electrolyte. Example 1 (48% amorphous phase) yielded 0.96 mS cm⁻¹. –1The room-temperature ionic conductivity was achieved, and the cells cycled stably for 500 hours in a sodium-symmetric cell. In contrast, comparative examples 1-6, with lower amorphous phase content (conductivity 0.51-0.60 mS / cm), showed significantly better conductivity. –1 The performance of the control (after 180-320 hours of cycling) is significantly inferior. In particular, Comparative Example 7 (undoped, no amorphous phase) has a conductivity as low as 0.01 mS / cm. –1 The fact that it is almost impossible to recycle confirms the decisive role of the amorphous phase from the opposite perspective.

[0056] 3. Amorphous phases can achieve high performance at lower sintering temperatures, breaking through the limitations of traditional processes.

[0057] The method of this invention achieves a crystallinity close to 1 mS cm⁻¹ at sintering temperatures up to 1000°C, i.e., through amorphization. –1 The high ionic conductivity of the sample. In contrast, Comparative Example 8, using the traditional high-temperature sintering route (1200℃), although no amorphous phase was formed, exhibited a conductivity of 0.41 mS / cm. –1 The ionic conductivity and cycling performance (70 hours) of Example 1, which was sintered at low temperature, were significantly lower than those of Example 1. This demonstrates that induced amorphous phase formation is an effective pathway to simultaneously achieve high ionic conductivity and excellent interfacial stability under relatively mild conditions.

[0058] 4. Amorphous phases enhance battery performance through multiple mechanisms.

[0059] Structural characterization ( Figure 1-2 ) and performance testing ( Figure 3-4 The results show that the introduction of the amorphous phase provides more channels for rapid ion migration, lowers the sodium ion diffusion barrier, and thus significantly improves the bulk ionic conductivity. Simultaneously, it promotes sintering densification, reduces grain boundary defects, not only lowers grain boundary impedance but also effectively blocks the growth path of sodium dendrites along the grain boundaries, enabling the symmetric cell to achieve long-term cycling stability.

[0060] Table 1

[0061] In summary, the core finding of this patent is that inducing the formation of an amorphous phase through multi-element synergistic doping is a fundamental way to break the dependence of NASICON electrolytes on high-temperature sintering while significantly improving their ionic conductivity and dendrite resistance. The content of the amorphous phase directly determines the final performance level of the electrolyte, providing a clear and effective material design direction for developing low-cost, high-performance solid-state sodium battery electrolytes.

[0062] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A multi-element doped NASICON-type solid electrolyte, characterized in that, The solid electrolyte is Na3Zr2Si2PO4 12 Based on Na3Zr2Si2PO 12 The Zr, Si, and P sites are doped with A, B, and C elements, respectively. Element A includes one or more of Ti, Fe, Y, Ca, or Zn; Element B includes one or more of Al, Mg, or As; The C element includes one or more of B, Se, or S.

2. The solid electrolyte as described in claim 1, characterized in that, The chemical formula of the solid electrolyte is Na. 3+x Zr 2- a A a Si 2-b B b P 1-c C c O 12 ; Where -0.5≤x≤0.5, 0<a≤0.5, 0<b≤0.5, 0<c≤0.

5.

3. The solid electrolyte as described in claim 1, characterized in that, The solid electrolyte comprises an amorphous phase and a NASICON crystalline phase, wherein the content of the amorphous phase is 40-50%.

4. A method for preparing a multi-element doped NASICON-type solid electrolyte as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Weigh the raw materials of Na source, Zr source, Si source, P source and A, B and C doping elements, mix them and ball mill them once, and sieve them to obtain mixed precursor powder. S2. The mixed precursor powder prepared in S1 is sintered once and naturally cooled to room temperature to obtain the sintered precursor. S3. The sintering precursor prepared in S2 is ball-milled a second time to obtain the initial sintering powder. S4. The initial sintered powder prepared in S3 is sintered a second time and naturally cooled to room temperature to obtain a multi-element doped NASICON-type solid electrolyte.

5. The preparation method according to claim 4, characterized in that, The Na source mentioned in S1 includes one or more of Na2CO3, NaHCO3, NaOH, or Na2O; The P source includes one or more of NH4H2PO4, (NH4)2HPO4, or P2O5; The Si source includes SiO2 and / or Si(OH)4; The Zr source includes ZrO2 and / or Zr(OH)4; The raw materials for element A include one or more of TiO2, Fe2O3, Y2O3, CaO, or ZnO; The raw materials for element B include one or more of Al2O3, MgO, or As2O3; The raw materials for element C include one or more of B2O3, SeO2, or NH4HSO4.

6. The preparation method according to claim 4, characterized in that, The primary and secondary ball milling described in S1 and S3 are carried out using a zirconia ball milling jar, wherein the mass ratio of the grinding balls to the material being milled in the zirconia ball milling jar is 10-30:

1. The ball milling temperature is 20-30℃; The ball mill speed is 400-500 rpm; The ball milling time is 10-15 hours; The solvent is ethanol and / or isopropanol.

7. The preparation method according to claim 4, characterized in that, The sintering described in S2 is solid-state sintering, and the atmosphere for solid-state sintering is air or oxygen; the container for solid-state sintering is a corundum / magnesium oxide crucible; the heating rate for solid-state sintering is 2-5℃ / minute; the temperature is raised to 800-1000℃ and held for 10-15 hours.

8. The preparation method according to claim 4, characterized in that, The secondary sintering described in S4 is solid-state sintering, and the atmosphere for solid-state sintering is air or oxygen; the container for solid-state sintering is a corundum / magnesium oxide crucible; the heating rate for solid-state sintering is 2-5℃ / min; first, the temperature is raised to 500-700℃ and held for 2-4 hours, then the temperature is raised to 1000-1200℃ and held for 8-12 hours.

9. The preparation method according to claim 8, characterized in that, In the secondary sintering process described in S4, a binder is also added, which is a 3%-10% PVA aqueous solution and / or a 3%-10% PVB ethyl acetate solution. During secondary sintering, the mass ratio of initial sintering powder to binder is 5-15:1, forming a solid electrolyte green body. The solid electrolyte green blank has a diameter of 12-18 mm and a thickness of 1.0-1.2 mm.

10. The application of a multi-element doped NASICON-type solid electrolyte as described in any one of claims 1-3 or a multi-element doped NASICON-type solid electrolyte prepared by the preparation method as described in any one of claims 4-9, characterized in that, The multi-element doped NASICON-type solid electrolyte is used in sodium metal battery systems.

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