A sodium-ion halide solid electrolyte material and a solid battery

Abstract

This invention provides a sodium ion halide solid electrolyte material, its preparation method, and its application, belonging to the field of solid electrolyte technology; the chemical formula of the solid electrolyte material provided by this invention is: Na 2‑x ZrCl 6‑x‑y M y Where M is a halogen element F, Br, or I; the value range of x is 0 < x < 2, and the value range of y is 0 ≤ y ≤ 2. The sodium-ion halide solid electrolyte of this invention is prepared by the following method: NaCl, ZrCl4, and ZrM4 (M = F, Br, I) are weighed according to the stoichiometric ratio of the general formula and subjected to high-speed ball milling to prepare the target solid electrolyte powder; this powder is used in sodium-ion solid-state batteries. Compared with existing technologies, the sodium-ion halide solid electrolyte of this invention exhibits advantages such as high ionic conductivity, good (electro)chemical stability, humidity stability, and good compressibility in solid-state batteries, and also has advantages such as low raw material prices, simple synthesis process, and easy control of conditions.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte technology, and particularly relates to a sodium ion halide solid electrolyte, its preparation method and application. Background Technology

[0002] Sodium (Na) and lithium (Li) share similar electrochemical storage mechanisms, and sodium is abundant globally and relatively inexpensive, making rechargeable sodium-ion batteries (NIBs) a viable alternative to lithium-ion batteries (LIBs). However, current traditional NIBs, which rely on organic liquid electrolytes, still present several key safety concerns, including the flammability and toxicity of organic solvents and the risk of liquid electrolyte leakage, posing significant safety hazards. Replacing the liquid organic electrolyte in traditional NIBs with solid electrolytes (SEs) may be the best solution to these safety issues. Sodium-ion SEs possess advantages such as non-flammability, high mechanical strength, good thermal stability, and electrochemical stability, making them a relatively ideal electrolyte system for NIBs. As the core of solid-state sodium-ion batteries (SNIBs), the fundamental physicochemical properties of SEs have a crucial impact on the battery's operating voltage, capacity output, rate performance, and cycle life.

[0003] Generally, sodium-ion electrolytes (SEs) can be classified into two types: solid polymer electrolytes (SPEs) and inorganic solid electrolytes (ISEs). Sodium-ion SPEs typically exhibit good mechanical flexibility and are easy to form films, a characteristic that is beneficial for large-scale production. However, the low ionic conductivity and electrochemical window of sodium-ion SPEs severely limit their practical application in high-energy, long-cycle SNIBs. In contrast, sodium-ion ISEs have higher ionic conductivity, better thermal stability, and excellent (electro)chemical stability, making them a more promising choice for coupling sodium metal anodes with high-voltage cathodes. Currently, the sodium-ion ISEs widely reported in the literature mainly include three types: oxide, sulfide, and halide solid electrolytes. Oxide electrolytes have high ionic conductivity and a wide electrochemical window, but their hard and brittle characteristics, as well as the need for high-temperature sintering in their preparation process, severely limit their practical application. Sulfide electrolytes exhibit ultra-high ionic conductivity comparable to liquid electrolytes, and combined with their soft texture and cold-pressing properties, they hold promise for the effective operation of room-temperature all-solid-state batteries. However, sulfide electrolytes still have many problems, such as low oxidation voltage and poor air stability, which limit their compatibility with high-voltage cathodes; in addition, harsh storage conditions increase manufacturing costs. In contrast, sodium-ion halide-based solid electrolytes can combine the softness of sulfides with the high-voltage resistance of oxides, and have certain advantages in terms of raw materials and manufacturing costs. Currently, the development and research of sodium-ion halide solid electrolyte systems are still in their infancy, with relatively few types, mainly including Na... 0.75 Sm1.75 Cl6 / Na 0.75 La 1.75 Cl6-NaTaCl6, ZrO2-Na2ZrCl6, Na2ZrCl6, NaAlCl4, Na 2.25 Y 0.25 Zr 0.75 Cl6, Na 2.25 Yb 0.25 Zr 0.75 Cl6 and Na 2.4 Er 0.4 Zr 0.6 Cl6, etc. The main problems currently facing sodium halide-based solid electrolytes (SNIBs) include their generally low ionic conductivity (0.001–0.1 mS / cm) and poor compatibility with metallic sodium anodes. These issues lead to sluggish ion transport kinetics and severe interfacial side reactions, resulting in deterioration of electrochemical performance and failure of the entire cell. Therefore, developing sodium halide-based solid electrolyte systems with high ionic conductivity, stability to sodium metal anodes, and humidity stability is of great significance for promoting the practical application of SNIBs. Summary of the Invention

[0004] The purpose of this invention is to provide a sodium ion halide solid electrolyte material, its preparation method, and its application.

[0005] A sodium-ion halide solid electrolyte, characterized in that the general structural formula of the sodium-ion halide solid electrolyte is: Na 2-x ZrCl 6-x-y M y Where M is a halogen element F, Br or I, the range of x is 0 < x < 2, and the range of y is 0 ≤ y ≤ 2.

[0006] Furthermore, the electrolyte has a room temperature ionic conductivity greater than 0.02 mS / cm.

[0007] The method for preparing sodium-ion halide-based solid electrolyte materials as described above is characterized by comprising:

[0008] According to the stoichiometric ratio of the general formula for electrolyte structure, the precursors NaCl, ZrCl4 and ZrM4 (M = F, Br, I) were weighed and mixed with ball milling beads at room temperature under an inert atmosphere to obtain sodium ion halide solid electrolyte powder.

[0009] Furthermore, the ball milling speed is 400-600 rpm; the ball milling time is 5-15 h; and the mass ratio of the precursor mixture to the milling beads is 1:(20-40).

[0010] Furthermore, the ball milling speed is preferably 600 rpm, and the ball milling time is preferably 10-15 h; the mass ratio of the precursor mixture to the ball milling beads is preferably 1:30.

[0011] An application of a sodium-ion halide solid electrolyte prepared according to the method described above, characterized in that the solid electrolyte is used to prepare a solid electrolyte or a composite positive and negative electrode additive for sodium-ion batteries; the sodium-ion batteries include all-solid-state, quasi-solid-state, and semi-solid-state batteries.

[0012] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0013] 1. The sodium ion halide solid electrolyte of the present invention can be prepared by conventional mechanical ball milling, and uses inexpensive Zr as the metal ion in the sodium ion halide electrolyte, which has the advantages of simple synthesis process, easy large-scale preparation and low cost.

[0014] 2. Starting from the material structure design, this invention prepares the above-mentioned sodium-ion halide solid electrolyte with high ionic conductivity, good (electro)chemical stability and low price by means of sodium-deficient method combined with anion mixed doping and other strategies, thereby effectively improving the electrochemical performance of solid sodium-ion batteries. Attached Figure Description

[0015] Figure 1 The NaZrCl5 type sodium ion halide solid electrolyte prepared by ball milling in Example 1(a) and the NaZrCl5 type sodium ion halide solid electrolyte prepared by ball milling in Example 2(b) are examples of the present invention. 4.5 F 0.5 X-ray diffraction pattern of sodium-ion halide solid electrolyte;

[0016] Figure 2 The NaZrCl5 and NaZrCl types prepared by ball milling in Example 1(a) and Example 2(b) of this invention are examples of the present invention. 4.5 F 0.5 Scanning electron microscope images of sodium-ion halide solid electrolytes;

[0017] Figure 3 Na prepared by ball milling in Example 1(a) and Example 2(b) of this invention. 2-x ZrCl 6-x-y M y (x=0.5, 1, 1.5; y=0) type and Na 2-x ZrCl 6-x-y M y Electrochemical impedance spectroscopy of sodium halide solid electrolyte of type F (M = 1, x = 1, y = 0.5, 1, 1.5);

[0018] Figure 4The NaZrCl obtained based on Example 2 of the present invention is shown. 4.5 F 0.5 A schematic diagram of the charge-discharge curves of an all-solid-state sodium-ion battery using composite cathode electrolyte material;

[0019] Figure 5 The X-ray diffraction pattern of the Na2ZrCl6 solid electrolyte material in the comparative example;

[0020] Figure 6 The electrochemical impedance spectroscopy (EIS) of the Na₂ZrCl₆ solid electrolyte material in the comparative example is shown. Detailed Implementation

[0021] The following is a more detailed description of a sodium-ion halide solid electrolyte, its preparation method, and its applications, with reference to schematic diagrams. Preferred embodiments of the invention are shown. It should be understood that those skilled in the art can modify the invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as providing broad guidance to those skilled in the art and not as limiting the invention.

[0022] A general formula for a sodium halide solid electrolyte is: Na 2-x ZrCl 6-x-y M y Where M is a halogen element F, Br or I, the range of x is 0 < x < 2, and the range of y is 0 ≤ y ≤ 2.

[0023] A method for preparing a sodium ion halide solid electrolyte includes the following steps: 1) Weighing the precursors NaCl, ZrCl4 and ZrM4 (M = F, Br, I) according to the stoichiometric ratio of the general formula, mixing and ball milling them to obtain solid electrolyte powder.

[0024] 2) The ball milling speed is 400-600 rpm, preferably 600 rpm. The ball milling time is 5-15 h, preferably 10-15 h. The mass ratio of the precursor mixture to the milling beads is 1:(20-40), preferably 1:30.

[0025] In the synthesis of this sodium-ion halide solid electrolyte, precursor materials NaCl, ZrCl4, and ZrM4 (M being F, Br, or I) are weighed according to stoichiometric ratios and mixed during high-speed mechanical ball milling to prepare the solid electrolyte material. The construction of the sodium-depleted phase introduces a large number of sodium ion vacancies, regulating the distribution of sodium ions in the material structure, which can reduce the activation energy of ion migration and broaden ion transport channels. Anionic halogens (F, Br, I) mainly occupy some Cl sites, causing anion mixing and increasing disorder, thus controlling the electrolyte composition and local microstructure. Furthermore, anion doping can form stronger bonds with the central metal element Zr, improving the material's stability to humidity and enhancing the electrolyte's (electro)chemical stability. These characteristics result in a NaCl electrolyte with high ionic conductivity and (electro)chemical stability. 2-x ZrCl 6-x-y M y Solid electrolyte materials.

[0026] The sodium-ion halide solid electrolyte of this invention is mainly used as a solid electrolyte or composite positive and negative electrode additive for preparing solid sodium-ion batteries (including all-solid, quasi-solid and semi-solid batteries).

[0027] Example 1: In this embodiment of the invention, Na 2-x ZrCl 6-x-y M y Preparation and electrochemical performance study of sodium-ion halide solid electrolyte materials of type (x=0.5, 1, 1.5; y=0).

[0028] Weigh out the following amounts in an argon-filled glove box:

[0029] (1) Na 1.5 ZrCl 5.5 0.877g NaCl + 2.33g ZrCl4;

[0030] (2)NaZrCl5:0.584g NaCl+2.33g ZrCl4;

[0031] (3) Na 0.5 ZrCl 4.5 0.292g NaCl + 2.33g ZrCl4;

[0032] The raw materials with different mass ratios were added to a ball mill jar along with zirconium dioxide grinding beads. The diameter of the grinding beads was 2–10 mm, and the ball-to-material ratio was 30:1. Ball milling was performed using an inert atmosphere planetary ball mill at a speed of 600 rpm for 15 hours. After ball milling, the prepared solid electrolyte sample was transferred to an agate mortar and ground for 30 minutes until the powder particle diameter distribution was uniform, finally obtaining a sodium ion halide solid electrolyte powder sample with the corresponding chemical formula.

[0033] Figure 1 a is the X-ray diffraction pattern of the NaZrCl5 solid electrolyte material prepared in this embodiment, which is derived from... Figure 1 The characteristic peak comparison shows that the synthesized NaZrCl5 type sodium ion halide solid electrolyte powder is a crystalline material with low crystallinity and a crystal structure similar to Li3YCl6, belonging to the trigonal crystal system and space group 1.

[0034] Figure 2 a is a scanning electron microscope image of the NaZrCl5 material prepared in this embodiment. Figure 2 As can be seen from a, the particle diameter of the synthesized sodium ion halide solid electrolyte powder is distributed in the range of 1–6 μm.

[0035] Figure 3 a represents the Na prepared in this embodiment. 2-x ZrCl 6-x-y M y Electrochemical impedance spectroscopy of sodium halide solid electrolytes of type (x = 0.5, 1, 1.5; y = 0). Calculations using the formula σ = L / R·S show that Na... 2-x ZrCl 6-x-y M y The ionic conductivity of sodium-based halide solid electrolytes of type (x = 0.5, 1, 1.5; y = 0) first increases and then decreases with increasing sodium deficiency. The room temperature ionic conductivity reaches its maximum value of 0.11 mS / cm when the chemical formula is NaZrCl5. The room temperature ionic conductivity for other ratios is as follows: Na... 1.5 ZrCl 5.5 (0.073 mS / cm) and Na 0.5 ZrCl 4.5 (0.053 mS / cm).

[0036] Example 2: The difference between this example and Example 1 is that the NaZrCl5 electrolyte with the highest ionic conductivity in Example 1 is additionally doped with halogen F anions. Sodium ion halide solid electrolyte material Na is prepared by mechanochemical ball milling. 2-x ZrCl 6-x-y M y(M is F, x = 1, y = 0.5, 1, 1.5).

[0037] Weigh out the following amounts in an argon-filled glove box:

[0038] (1) NaZrCl 4.5 F 0.5 :0.701g NaCl+2.47g ZrCl4+0.251g ZrF4;

[0039] (2) NaZrCl4F: 0.701g NaCl+2.097g ZrCl4+0.502g ZrF4;

[0040] (3) NaZrCl 3.5 F 1.5 :0.701g NaCl+1.748g ZrCl4+0.752g ZrF4;

[0041] (4)NaZrCl3F2:0.701g NaCl+1.398g ZrCl4+1g ZrF4;

[0042] The raw materials with different mass ratios were added to a ball mill jar along with zirconium dioxide grinding beads. The diameter of the grinding beads was 2–10 mm, and the ball-to-material ratio was 30:1. Ball milling was performed using an inert atmosphere planetary ball mill at a speed of 600 rpm for 15 hours. After ball milling, the prepared solid electrolyte sample was transferred to an agate mortar and ground for 30 minutes until the powder particle diameter distribution was uniform, finally obtaining a sodium ion halide solid electrolyte powder sample with the corresponding chemical formula.

[0043] Figure 1 b represents the NaZrCl prepared in this embodiment. 4.5 F 0.5 The X-ray diffraction pattern of the material is composed of Figure 1 The comparison of the characteristic peaks (b) shows that the synthesized NaZrCl 4.5 F 0.5 Sodium-ion halide solid electrolyte powder materials are crystalline materials with low crystallinity and a crystal structure similar to NaZrCl5, belonging to the trigonal crystal system and space group 1.

[0044] Figure 2 b represents the NaZrCl prepared in this embodiment. 4.5 F 0.5 Scanning electron microscope images of materials, from Figure 2 As can be seen from b, the particle diameter of the synthesized sodium ion halide solid electrolyte powder is distributed in the range of 1–6 μm.

[0045] Figure 3 b represents the Na prepared in this embodiment. 2-x ZrCl 6-x-y M y Electrochemical impedance spectroscopy of a sodium halide solid electrolyte of type F (M = 1, x = 1, y = 0.5, 1, 1.5). Calculations using the formula σ = L / R·S show that Na... 2-x ZrCl 6-x-y M y The sodium ionic conductivity of sodium-based halide solid electrolytes (M = F, x = 1, y = 0.5, 1, 1.5, 2) decreases continuously with increasing F doping ratio. The room temperature ionic conductivity reaches a minimum of 0.021 mS / cm when the chemical formula is NaZrCl3F2. The room temperature ionic conductivity for other ratios is as follows: NaZrCl3F2 ... 4.5 F 0.5 (0.081mS / cm), NaZrCl4F (0.065mS / cm) and NaZrCl 3.5 F 1.5 (0.037mS / cm).

[0046] Example 3:

[0047] This invention provides a secondary battery comprising the sodium-ion halide solid electrolyte material;

[0048] The preparation method of the secondary battery is as follows:

[0049] In an argon-filled glove box, Na3V2(PO4)3, VGCF, and the sodium-ion halide solid electrolyte material NaZrCl prepared in Example 2 were... 4.5 F 0.5 A composite positive electrode was prepared by mixing the components in a mass ratio of 70:5:30. Then, 100 mg of Na3PS4 was weighed and pressed into a battery mold at a pressure of 300 MPa. 10 mg of the composite positive electrode was added to one side of the electrolyte, and 40 mg of Na2Sn negative electrode material was added to the other side of the electrolyte. The pressure was maintained at 370 MPa for 2 minutes. Then, the full cell was fixed at 70 MPa for relevant electrochemical performance tests.

[0050] The assembled secondary battery was subjected to constant current charge-discharge testing within a voltage range of 2–4V using the Blue Battery Testing System, with a charge-discharge rate of 0.1C. The charge-discharge curve for the first week of battery testing is shown below. Figure 4 As shown.

[0051] The secondary battery obtained in this embodiment of the invention has a first-cycle coulombic efficiency of 94.4% and a reversible specific capacity of 85 mAh / g.

[0052] Comparative example:

[0053] This invention provides a sodium ion halide solid electrolyte material, Na2ZrCl6, as a comparative example.

[0054] The preparation method of the sodium ion halide solid electrolyte material Na2ZrCl6 includes the following steps: In a glove box, anhydrous NaCl and ZrCl4 are weighed and mixed evenly at a stoichiometric ratio of 2:1, then poured into a ball mill jar. The diameter of the grinding beads is 2–10 mm, and the ball-to-material ratio is 30:1. Ball milling is performed using an inert atmosphere planetary ball mill at a speed of 600 rpm for 15 hours. After ball milling, the prepared solid electrolyte sample is transferred to an agate mortar and ground for 30 minutes until the powder particle diameter distribution is uniform, finally obtaining the Na2ZrCl6 electrolyte powder sample.

[0055] Figure 5 The X-ray diffraction pattern of the Na2ZrCl6 electrolyte material obtained in the comparative example is shown below. Figure 5 The characteristic peak comparison shows that the synthesized Na2ZrCl6 type solid electrolyte powder material is a crystalline material with low crystallinity and a crystal structure similar to Li3YCl6, belonging to the trigonal crystal system and space group [missing information].

[0056] Figure 6 The image shows the AC impedance spectroscopy of the Na₂ZrCl₆ electrolyte material obtained in the comparative example. According to the formula σ = L / R·S, the room temperature ionic conductivity of the Na₂ZrCl₆ electrolyte material obtained in this invention is 0.011 mS / cm.

[0057] As can be seen from Examples 1-2 and the comparative examples, the sodium-ion halide solid electrolyte material obtained by adopting the technical solution of the present invention has a significantly improved ionic conductivity; further, as can be seen from Example 3, when the sodium-ion halide solid electrolyte material prepared by adopting the technical solution of the present invention is applied to the preparation of secondary battery composite electrodes, it exhibits high first-cycle coulombic efficiency and discharge capacity.

[0058] Finally, it should be reiterated that the above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention are considered to have remained within the protection scope of the present invention.

Claims

1. A sodium-ion halide solid electrolyte, characterized in that, The general structural formula of sodium halide solid electrolytes is: Na 2-x ZrCl 6-x-y M y Where M is a halogen element F, Br or I, the range of x is 0 < x < 2, and the range of y is 0 < y ≤ 2. The construction of a sodium-poor phase can introduce a large number of sodium ion vacancies, regulate the distribution of sodium ions in the material structure, and play a role in reducing the activation energy of ion migration and widening the ion transport channels. The solid electrolyte has a room temperature ionic conductivity greater than 0.02 mS / cm.

2. A method for preparing a sodium-ion halide solid electrolyte material as described in claim 1, characterized in that, include: According to the stoichiometric ratio of the general formula for solid electrolyte structure, the precursors NaCl, ZrCl4 and ZrM4, M = F, Br, I, were weighed and mixed with ball milling beads at room temperature under an inert atmosphere to obtain sodium ion halide solid electrolyte powder. The ball milling speed is 400-600 rpm; the ball milling time is 5-15 h; and the mass ratio of the precursor mixture to the ball milling beads is 1:(20-40).

3. The method for preparing sodium-ion halide solid electrolyte material according to claim 2, wherein, The ball milling speed is 600 rpm, and the ball milling time is 10-15 h; the mass ratio of the precursor mixture to the ball milling beads is 1:

30.

4. The application of the sodium-ion halide solid electrolyte prepared by the method according to claim 2, characterized in that, The solid electrolyte is used to prepare solid electrolytes, composite positive electrodes, or composite negative electrode additives for sodium-ion batteries; the sodium-ion batteries include all-solid-state, quasi-solid-state, and semi-solid-state batteries.

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