A sodium superionic conductor solid electrolyte with both internal and external advantages, its preparation method and application

Abstract

This invention belongs to the field of solid electrolytes, and discloses a sodium superionic conductor solid electrolyte with both internal and external advantages, its preparation method, and its applications. The sodium superionic conductor solid electrolyte has the following general chemical formula: Na 1+x+2y+z‑i+j [Zr 2‑y‑z‑h‑i‑j A Ⅱ y A Ⅲ z A Ⅳ h A Ⅴ i B j Si x P 3‑x O 12 This invention provides a doping strategy that simultaneously performs bulk doping and grain boundary modification. By doping and modifying a sodium superionic conductor-type solid electrolyte, its high ionic conductivity is achieved while its density is improved.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolytes, and more specifically, relates to a sodium superionic conductor solid electrolyte with both internal and external properties, its preparation method, and its application. Background Technology

[0002] Developing efficient rechargeable battery energy storage devices is of significant strategic importance for improving power balance, developing sustainable wind and solar energy, and promoting the development of new energy vehicles. Lithium-ion batteries possess advantages such as high specific energy, high specific power, low self-discharge, and no memory effect, and have gradually entered fields such as electric vehicles, rail transportation, and large-scale energy storage. However, lithium-ion batteries are not the most ideal energy storage devices. Due to the scarcity, uneven geographical distribution, and high cost of lithium resources, there are irreconcilable contradictions in the application of lithium-ion batteries in large-scale energy storage.

[0003] Sodium ions and lithium ions both belong to Group 1, possessing similar chemical properties and intercalation mechanisms. Furthermore, sodium resources are abundant, making sodium-ion batteries a complementary technology to lithium-ion batteries. However, the organic electrolytes used in sodium-ion batteries are flammable and volatile, posing safety hazards and limiting energy density. Replacing organic liquid electrolytes with solid electrolytes holds promise for solving these safety issues. Currently, the most researched sodium-ion inorganic solid electrolytes mainly include three types: Na-β”-Al2O3, sodium superionic conductors, and sulfides. Among these, sodium superionic conductor solid electrolytes hold great potential for solid-state sodium-ion battery applications due to their wide electrochemical window, high mechanical strength, air stability, and high ionic conductivity. However, their ionic conductivity is lower than that of organic electrolytes, limiting their application in solid-state sodium batteries. Therefore, improving the ionic conductivity of sodium superionic conductor solid electrolytes is beneficial for their application in energy storage.

[0004] Currently, researchers have discovered that solid electrolytes with high ionic conductivity can be obtained by doping them. However, simply doping sodium superionic conductor-type solid electrolytes only affects their ionic conductivity and does not significantly improve their ability to suppress sodium dendrites.

[0005] Therefore, there is an urgent need to propose a sodium superionic conductor-type solid electrolyte with both internal and external advantages, and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a sodium superionic conductor solid electrolyte and its preparation method that simultaneously improves bulk doping and grain boundary modification. This invention provides a doping strategy for sodium superionic conductor solid electrolytes, achieving both high ionic conductivity and improved density through doping modification.

[0007] To achieve the above objectives, the first aspect of the present invention provides a sodium superion conductor type solid electrolyte that is both internally and externally superior, the sodium superion conductor type solid electrolyte having the general chemical formula shown in formula (1):

[0008] Na 1+x+2y+z-i+j [Zr 2-y-z-h-i-j A Ⅱ y A Ⅲ z A Ⅳ h A Ⅴ i B j Si x P 3-x O 12 (1);

[0009] Wherein: x, y, z, h, i, j are the molar percentages of the corresponding elements, where 0≤x≤3, 0≤y≤0.5, 0≤z≤0.5, 0≤h≤0.5, 0≤i≤0.5, 0≤j≤0.5, 0 <y+z+h+i+j≤2;

[0010] A Ⅱ For Zr-doped +2 valent metal elements;

[0011] A Ⅲ For Zr-doped non-lanthanide metals with a +3 valence;

[0012] A Ⅳ For Zr-doped +4 valent metal elements;

[0013] A Ⅴ For Zr-doped +5 valent metal elements;

[0014] B is a +3 lanthanide metal element that is substituted at the Zr site.

[0015] According to the present invention, preferably, the A Ⅱ It is at least one of Mg, Cd, Mn, Co, Ni and Zn.

[0016] According to the present invention, preferably, the A Ⅲ It is at least one of Al, In, Ga, Sc and Y.

[0017] According to the present invention, preferably, the A Ⅳ It is at least one of Hf, Sn, Ge and Ti.

[0018] According to the present invention, preferably, the A Ⅴ It is at least one of Nb, Ta, As and Sb.

[0019] According to the present invention, preferably, B is at least one of La, Ce, Pr, Nd, Eu, Yb and Lu.

[0020] The second aspect of the present invention provides a method for preparing the aforementioned sodium superionic conductor solid electrolyte, wherein the preparation method is a solid-phase method.

[0021] According to the present invention, preferably, the preparation method includes the following steps:

[0022] Dopant element A Ⅱ A Ⅲ A Ⅳ A Ⅴ The mixture is combined with at least one of the precursors in B, Na source, P source, Zr source and Si source, and then subjected to ball milling and calcination in sequence to obtain the powder of the sodium superionic conductor solid electrolyte with both internal and external properties.

[0023] According to the present invention, preferably, dopant element A Ⅱ The precursor is at least one of ZnO, MgO, CdO, MnO, CoO and NiO.

[0024] According to the present invention, preferably, dopant element A Ⅲ The precursor is at least one of Al2O3, In2O3, Ga2O3, Sc2O3 and Y2O3.

[0025] According to the present invention, preferably, dopant element A Ⅳ The precursor is at least one of HfO2, SnO2, GeO2, and TiO2.

[0026] According to the present invention, preferably, dopant element A Ⅴ The precursor is at least one of Nb2O5, Ta2O5, As2O5 and Sb2O5.

[0027] According to the present invention, preferably, the precursor of dopant element B is at least one of Ce2O3, La2O3, Pr2O3, Nd2O3, Eu2O3, Yb2O3 and Lu2O3.

[0028] According to the present invention, preferably, the Na source is at least one selected from Na2CO3, NaHCO3, NaOH, and Na2O.

[0029] According to the present invention, preferably, the P source is at least one of NH4H2PO4, (NH4)2HPO4, and P2O5.

[0030] According to the present invention, preferably, the Zr source is ZrO2 and / or Zr(OH)4, and the Zr source has a size of nanometer scale, preferably, the size of the Zr source is ≤100nm.

[0031] According to the present invention, preferably, the Si source is SiO2 and / or Si(OH)4.

[0032] According to the present invention, preferably, the ball milling process includes: mixing dopant element A with... Ⅱ A Ⅲ A Ⅳ A Ⅴ The mixture is mixed with at least one of the precursors in B, Na source, P source, Zr source, Si source and solvent and ball-milled. The solvent is then heated to evaporate and the mixture is pulverized and sieved to obtain the ball-milled mixed powder.

[0033] According to the present invention, preferably, the calcination treatment is divided into two stages: the calcination temperature of the first stage is 300-500℃ and the calcination time is 1-3 hours; the calcination temperature of the second stage is 900-1150℃ and the calcination time is 4-24 hours; the calcination atmosphere of the calcination treatment is at least one of air, oxygen, nitrogen and argon.

[0034] According to the present invention, preferably, the conditions for the ball milling treatment include:

[0035] The ball-to-material ratio is (3-5):1;

[0036] The ball milling temperature is room temperature, preferably 20-30℃;

[0037] The ball mill speed is 200-500 rpm;

[0038] The ball milling time is 6-24 hours;

[0039] The solvent is ethanol and / or isopropanol.

[0040] According to the present invention, preferably, the preparation method further includes mixing a portion of the powder of the sodium superionic conductor solid electrolyte with a binder, placing it in a mold, and forming a green blank by cold pressing; embedding the green blank in the remaining portion of the powder of the sodium superionic conductor solid electrolyte, and sintering it at high temperature to obtain the sodium superionic conductor solid electrolyte sheet.

[0041] According to the present invention, preferably, the adhesive is a PVA aqueous solution with a concentration of 5%-20% and / or a PVB ethyl acetate solution with a concentration of 3%-10%.

[0042] According to the present invention, preferably, the high-temperature sintering is divided into two stages: the first stage calcination temperature is 200-400℃ and the calcination time is 1-3 hours; the second stage calcination temperature is 1200-1300℃ and the calcination time is 4-24 hours, and the calcination atmosphere of the high-temperature sintering is at least one of air, oxygen, nitrogen and argon.

[0043] The third aspect of this invention provides the application of the aforementioned sodium superionic conductor solid electrolyte in the preparation of at least one device, including sodium batteries, sodium-sulfur batteries, hybrid electrolyte system batteries, novel fuel cells, and electrochemical sensors.

[0044] In this invention, preferably, the sodium battery is a solid-state sodium battery or a sodium symmetric battery.

[0045] The beneficial effects of the technical solution of the present invention are as follows:

[0046] This invention provides a doping strategy for simultaneously performing bulk doping and grain boundary modification ("dual modification") on sodium superionic conductor solid electrolytes. By doping and modifying the sodium superionic conductor solid electrolyte, its high room temperature ionic conductivity is achieved while its density is improved.

[0047] This invention achieves high room-temperature ionic conductivity through bulk doping. The introduction of lanthanides simultaneously realizes bulk doping and grain boundary modification. Grain boundary modification can improve the density of the electrolyte, reduce its electronic conductivity, and thus enhance its ability to suppress sodium dendrites. Batteries and other devices prepared using the sodium superionic conductor solid electrolyte of this invention exhibit good sodium dendrite suppression capabilities and excellent cycle stability.

[0048] The preparation method of the present invention has the advantages of simple preparation process, easy availability of raw materials, and easy mass production, making it suitable for large-scale production.

[0049] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0050] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0051] Figure 1The XRD pattern of a sodium superionic conductor solid electrolyte with both internal and external refinement provided in Embodiment 1 of the present invention is shown (where "Intensity" represents the diffraction peak intensity, "2Theta" is the scanning angle, "Experimental" is the experimental data, "Refined" is the data after XRD refinement, "C2 / c" is the monoclinic crystal structure, "Differences" is the difference between the experimental data and the data on the PDF standard card, and "Rwp" represents the refinement accuracy, which is generally less than 10).

[0052] Figure 2 The image shows a cross-sectional SEM image of a sodium superionic conductor solid electrolyte provided in Embodiment 1 of the present invention.

[0053] Figure 3 An undoped sodium superionic conductor-type solid electrolyte Na3Zr2Si2PO4 is shown. 12 The AC impedance diagram (where "-Z" (Ω) is the impedance, "Z'" (Ω) is the resistance, and "NZSP-contrast" is the undoped sodium superionic conductor solid electrolyte Na3Zr2Si2PO4) 12 ).

[0054] Figure 4 An AC impedance diagram of a sodium superionic conductor type solid electrolyte with both internal and external properties provided in Embodiment 1 of the present invention is shown.

[0055] Figure 5 The DC polarization diagram of a sodium superionic conductor solid electrolyte with both internal and external properties provided in Embodiment 1 of the present invention is shown (where “Current” is current, “Time” is time, and “Au|NZSP|Au” is gold plating on the electrolyte disc of Embodiment 1).

[0056] Figure 6 The diagram shows the Na|NZSP|Na cycle performance of a sodium metal symmetric battery prepared using a sodium superionic conductor solid electrolyte provided in Example 1 of the present invention (where “Voltage” is voltage).

[0057] Figure 7 The charge-discharge cycle diagram of a solid sodium battery prepared using a sodium superionic conductor solid electrolyte provided in Example 1 of the present invention is shown (where “Specific capacity” is the discharge specific capacity, “Cycle number” is the number of cycles, and “Efficiency” is the coulombic efficiency). Detailed Implementation

[0058] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0059] Example 1

[0060] This embodiment provides a sodium superionic conductor-type solid electrolyte that combines internal and external advantages, namely Na 3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12 .

[0061] The preparation method of the above-mentioned superionic conductor type solid electrolyte is as follows:

[0062] (1) Mechanical ball milling: The precursors of sodium (Na), phosphorus (P), zirconium (Zr), silicon (Si), zinc (Zn), and cerium (Ce) were placed in a ball mill jar with a molar ratio of Na, P, Zr, Si, Zn, and Ce of 3.3:1:1.8:2:0.1:0.1 (wherein, Na2CO3, NH4H2PO4, nano-sized ZrO2, SiO2, ZnO, and Ce2O3 were selected as raw materials, and Na2CO3 was in excess by 8wt% and NH4H2PO4 was in excess by 15wt%). Anhydrous ethanol was added to obtain a mixture. The mixture was then ground using grinding balls. After grinding, the solvent in the mixture was evaporated by heating. After pulverizing, the mixture was separated into mixed powders using a sieve separator. The ball-to-material ratio was 5:1, the ball milling temperature was 25℃, the ball milling speed was 200 rpm, and the ball milling time was 12 hours.

[0063] (2) High-temperature calcination: The mixed powder is placed in a muffle furnace for two-stage calcination. The calcined powder is then pulverized and sieved to obtain Na. 3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12 Powder; the first stage calcination temperature is 400℃ and the calcination time is 1 hour; the second stage calcination temperature is 1150℃ and the calcination time is 12 hours; the calcination atmosphere is air.

[0064] (3) Cold pressing sintering: part of Na 3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12After the powder is mixed with a 10% PVA aqueous solution, it is placed in a custom mold and cold-pressed to form a green body. The green body is then buried in the remaining Na. 3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12 The powder undergoes a two-stage high-temperature sintering process in a muffle furnace. The first stage calcination temperature is 400℃, and the calcination time is 1 hour. The second stage calcination temperature is 1250℃, and the calcination time is 12 hours. The calcination atmosphere is air. After annealing, sodium superionic conductor type solid electrolyte sheets are obtained and polished into round sheets with a diameter of 10-12 mm and a thickness of 1-2 mm, thus obtaining a sodium superionic conductor type solid electrolyte with both internal and external finish.

[0065] Depend on Figure 1 It can be seen that the sodium superionic conductor type solid electrolyte Na in this embodiment has both internal and external advantages. 3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12 (NZSP) remains monoclinic with the formation of a second phase, Na3Ce(PO4)2. The formation of the second phase is beneficial to improving the electrolyte density and ionic conductivity at the grain boundaries.

[0066] Depend on Figure 2 It can be seen that the sodium superionic conductor type solid electrolyte Na in this embodiment has both internal and external advantages. 3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12 The close contact between grains and the absence of obvious pores indicate that the prepared solid electrolyte has a high density. Furthermore, the density of the prepared sodium superionic conductor solid electrolyte, which exhibits both internal and external structural integrity, was measured using the Archimedes displacement method. The calculated average density of the prepared solid electrolyte was 99.2%, which is consistent with... Figure 2 The information conveyed is consistent.

[0067] Using magnetron sputtering evaporation technology to deposit Na 3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12 Gold-plated electrodes were applied to both sides of the electrolyte disc, and conductivity was tested. The results are as follows: Figure 4 As shown. Meanwhile, for the undoped sodium superionic conductor solid electrolyte Na3Zr2Si2PO4... 12 The same conductivity test was performed, and the results were as follows: Figure 3 As shown. By Figure 3 , 4 It can be known that Na3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12 The room temperature ionic conductivity of the electrolyte disc is 2.12 mS / cm. -1 The undoped sodium superionic conductor solid electrolyte Na3Zr2Si2PO4 12 Its room temperature ionic conductivity is only 0.58 mS / cm. -1 This indicates that the ionic conductivity of sodium superionic conductor solid electrolytes can be improved through a doping strategy that combines bulk doping and grain boundary modification, i.e., "internal and external treatment".

[0068] Depend on Figure 5 It can be seen that the sodium superionic conductor solid electrolyte of this embodiment, which combines internal and external advantages, has a low electronic conductivity of 6.23 × 10⁻⁶. -8 S cm -1 This helps to suppress the formation of sodium dendrites.

[0069] Preparation of sodium metal symmetric cells: In an inert atmosphere glove box with an oxygen content of less than 0.1 ppm, the sodium superionic conductor solid electrolyte Na, which combines internal and external properties, of this embodiment was prepared. 3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12 Sodium metal sheets are attached to both sides of an (NZSP) disc to form a sodium metal symmetric cell. The structure of the sodium metal symmetric cell is Na|NZSP|Na. A constant current charge-discharge test was performed on this sodium metal symmetric cell. Figure 6 As shown, the Na|NZSP|Na battery operates at a current density of 0.3 mA cm⁻¹. -2 Under the specified conditions, it can cycle stably for 1000 hours without short circuits. This result indicates that the solid electrolyte of this embodiment has excellent sodium dendrite suppression capabilities.

[0070] Preparation of solid-state sodium batteries: Na3V2(PO4)3 (NVP) cathode, conductive agent carbon black, and binder PVDF were mixed at a mass ratio of 8:1:1 to prepare a cathode slurry. After magnetic stirring for 12 hours, the slurry was coated and dried in an oven at 80°C to obtain the NVP@C cathode sheet. In an inert atmosphere glove box with an oxygen content of less than 0.1 ppm, the sodium superionic conductor solid electrolyte Na... (This embodiment is described in detail in the original text). 3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12A sodium sheet is attached to the negative electrode side of a (NZSP) wafer, and an NVP@C positive electrode sheet is attached to the positive electrode side, thus encapsulating a solid-state sodium battery. Electrochemical performance tests were performed on this solid-state sodium battery; the charge / discharge voltage range was 2.8–3.8V. Figure 7 As shown, the solid-state sodium battery exhibits an initial discharge specific capacity of 109.5 mAh g⁻¹ under a rate of 0.2C. -1 The first-cycle coulomb efficiency was 96.2%, and the capacity retention rate was 94.5% after 50 cycles, demonstrating excellent cycle stability.

[0071] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A sodium superionic conductor type solid electrolyte with both internal and external advantages, characterized in that, The chemical formula of the sodium superionic conductor solid electrolyte is: Na 3.3 Zr 1.8 Zn 0.1 Ce 0.1 Si2PO 12 ; The preparation method of the sodium superionic conductor solid electrolyte with both internal and external properties includes the following steps: The precursors of Zn and Ce, Na source, P source, Zr source and Si source are mixed and then ball-milled and calcined in sequence to obtain the powder of the sodium superionic conductor solid electrolyte with both internal and external properties. The ball milling process includes: mixing Zn and Ce precursors, Na source, P source, Zr source, Si source and solvent and ball milling, heating and evaporating the solvent, crushing and sieving to obtain the ball-milled mixed powder; The calcination process is divided into two stages. The calcination temperature in the first stage is 300-500℃ and the calcination time is 1-3 hours. The calcination temperature in the second stage is 900-1150℃ and the calcination time is 4-24 hours. The calcination atmosphere in the calcination process is air. The preparation method further includes mixing a portion of the powder of the sodium superion conductor solid electrolyte with a binder, placing it in a mold, and forming a green blank by cold pressing; embedding the green blank in the remaining portion of the powder of the sodium superion conductor solid electrolyte, and sintering it at high temperature to obtain the sodium superion conductor solid electrolyte sheet. The high-temperature sintering is divided into two stages. The first stage calcination temperature is 200-400℃ and the calcination time is 1-3 hours. The second stage calcination temperature is 1200-1300℃ and the calcination time is 4-24 hours. The calcination atmosphere of the high-temperature sintering is air. The precursor of doped Zn is ZnO; The precursor of the dopant element Ce is Ce₂O₃; The Na source is at least one of Na2CO3, NaHCO3, NaOH, and Na2O; The P source is at least one of NH4H2PO4, (NH4)2HPO4, and P2O5; The Zr source is ZrO2 and / or Zr(OH)4, and the Zr source is nanoscale. The Si source is SiO2 and / or Si(OH)4.

2. The sodium superionic conductor solid electrolyte according to claim 1, wherein, The Zr source has a specification of ≤100nm.

3. The sodium superionic conductor solid electrolyte according to claim 1, wherein, The conditions for the ball milling process include: The ball-to-material ratio is (3-5):1; The ball milling temperature is 20-30℃; The ball mill speed is 200-500 rpm; The ball milling time is 6-24 hours; The solvent is ethanol and / or isopropanol.

4. The sodium superionic conductor solid electrolyte according to claim 1, wherein, The adhesive is a 5%-20% aqueous solution of PVA and / or a 3%-10% ethyl acetate solution of PVB.

5. The method for preparing the sodium superionic conductor type solid electrolyte with both internal and external advantages as described in claim 1, characterized in that, The preparation method includes the following steps: The precursors of Zn and Ce, Na source, P source, Zr source and Si source are mixed and then ball-milled and calcined in sequence to obtain the powder of the sodium superionic conductor solid electrolyte with both internal and external properties. The ball milling process includes: mixing Zn and Ce precursors, Na source, P source, Zr source, Si source and solvent and ball milling, heating and evaporating the solvent, crushing and sieving to obtain the ball-milled mixed powder; The calcination process is divided into two stages. The calcination temperature in the first stage is 300-500℃ and the calcination time is 1-3 hours. The calcination temperature in the second stage is 900-1150℃ and the calcination time is 4-24 hours. The calcination atmosphere in the calcination process is air. The preparation method further includes mixing a portion of the powder of the sodium superion conductor solid electrolyte with a binder, placing it in a mold, and forming a green blank by cold pressing; embedding the green blank in the remaining portion of the powder of the sodium superion conductor solid electrolyte, and sintering it at high temperature to obtain the sodium superion conductor solid electrolyte sheet. The high-temperature sintering is divided into two stages. The first stage calcination temperature is 200-400℃ and the calcination time is 1-3 hours. The second stage calcination temperature is 1200-1300℃ and the calcination time is 4-24 hours. The calcination atmosphere of the high-temperature sintering is air. The precursor of doped Zn is ZnO; The precursor of the dopant element Ce is Ce₂O₃; The Na source is at least one of Na2CO3, NaHCO3, NaOH, and Na2O; The P source is at least one of NH4H2PO4, (NH4)2HPO4, and P2O5; The Zr source is ZrO2 and / or Zr(OH)4, and the Zr source is nanoscale. The Si source is SiO2 and / or Si(OH)4.

6. The method for preparing a sodium superionic conductor-type solid electrolyte according to claim 5, wherein, The Zr source has a specification of ≤100nm.

7. The method for preparing a sodium superionic conductor-type solid electrolyte according to claim 5, wherein, The conditions for the ball milling process include: The ball-to-material ratio is (3-5):1; The ball milling temperature is 20-30℃; The ball mill speed is 200-500 rpm; The ball milling time is 6-24 hours; The solvent is ethanol and / or isopropanol.

8. The method for preparing a sodium superionic conductor-type solid electrolyte according to claim 5, wherein, The adhesive is a 5%-20% aqueous solution of PVA and / or a 3%-10% ethyl acetate solution of PVB.

9. The application of the sodium superionic conductor solid electrolyte according to claim 1 in the preparation of at least one device in sodium batteries, sodium-sulfur batteries, hybrid electrolyte system batteries, and electrochemical sensors.

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