Sodium ion halide solid electrolyte, preparation method therefor, and use thereof

Abstract

Provided are a sodium ion halide solid electrolyte, a preparation method therefor, and a use thereof. The sodium ion halide solid-state electrolyte achieves optimization of a sodium ion transmission path and a microstructure by means of doping BH4 and O anions into the structure thereof, and adjusting the doping amount, thereby reducing sodium ion migration activation energy, effectively improving the ionic conductivity of a product. In addition the electrolyte has oxidation resistance and high electrochemical stability, and is compatible with a high-voltage positive electrode material in applications.

Description

A sodium-ion halide solid electrolyte, its preparation method and application Technical Field

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

[0002] Sodium-ion solid electrolytes are generally classified into sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, and polymer solid electrolytes. Among them, sulfide solid electrolytes have high ionic conductivity, but their electrochemical window is narrow, their compatibility with cathode materials is poor, and their sensitivity to water and oxygen is high. Oxide solid electrolytes have good electrochemical stability, but their air stability is poor and their interfacial compatibility is insufficient, while their processing requires high energy consumption. Polymer solid electrolytes have the advantage of good interfacial compatibility, but their ionic conductivity at room temperature is insufficient, their electrochemical window is narrow, and their thermal stability is poor.

[0003] In contrast, halide solid electrolytes have the characteristics of high ionic conductivity, high interfacial compatibility, high electrochemical stability and excellent mechanical properties. However, in the field of sodium solid-state batteries, the ionic conductivity and high voltage resistance of existing sodium-ion halide solid electrolytes still cannot meet the needs of the rapid development of the technology. Summary of the Invention

[0004] Based on the shortcomings of existing technologies, the purpose of this invention is to provide a sodium-ion halide solid electrolyte. By incorporating BH4 anions and O anions into the structure and controlling the doping amount, the sodium ion transport path and microstructure are optimized, reducing the sodium ion migration activation energy and effectively improving the ionic conductivity of the product. At the same time, the product has oxidation resistance, high electrochemical stability, and is compatible with high-voltage cathode materials in application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A sodium-ion halide solid electrolyte has the following chemical formula:

[0007] Na 2+2x MO 1+x (BH4) y X 4-y M is at least one of Zr, Hf, Ti, and Mo, X is a halogen, 0≤x≤1, 0≤y≤1.

[0008] The sodium-ion halide solid electrolyte of this invention incorporates specific BH4 and O anions into its molecular structure. These two anions can adjust the overall amorphization degree of the solid electrolyte, thereby optimizing the sodium ion transport path when applied to solid-state batteries, reducing the sodium ion migration activation energy, and improving the ionic conductivity of the product. Simultaneously, they can increase the strength of the MO bonds in the solid electrolyte, improving its oxidation resistance and making it compatible with cathode materials such as layered oxides or polyanionic cathodes, thus enabling adjustable and improved energy density of solid-state batteries. Furthermore, this product has a certain degree of deformability, thus achieving close contact with cathode materials and maintaining good interfacial stability.

[0009] However, since the simultaneous doping of the two anions can also affect the microstructure and composition of the product, if an excessive amount is introduced, it may lead to the generation of a large amount of NaCl and Na2O impurities outside the amorphous phase, which will reduce the amorphization degree of the entire sodium ion halide solid electrolyte and fail to achieve the expected high ionic conductivity. Therefore, it is necessary to optimize and limit the amount of doping.

[0010] Preferably, M is at least one of Zr and Hf.

[0011] When the above-mentioned metals are used to construct the sodium ion halide solid electrolyte of the present invention, the metal oxygen bond strength formed is higher, and the product can achieve better ionic conductivity and oxidation resistance.

[0012] Preferably, the sodium halide solid electrolyte has an ionic conductivity ≥0.1 mS·cm at 25–30 °C. -1 .

[0013] Preferably, the sodium-ion halide solid electrolyte is Na 2+2x ZrO 1+x (BH4) y Cl 4-y Where 0.25≤x≤2, 0.3≤y≤0.5;

[0014] More preferably, the sodium-ion halide solid electrolyte is Na 2+2x ZrO 1+x (BH4) y Cl 4-y , where 0.375≤x≤0.5, 0.3≤y≤0.4.

[0015] Through optimization, when the doping ratio of BH4 anions and O anions is selected as described above, the resulting sodium halide solid electrolyte exhibits higher ionic conductivity and superior performance. Furthermore, using Zr as the central metal ion, which has higher abundance and lower cost, offers better cost-effectiveness in actual production.

[0016] Another object of the present invention is to provide a method for preparing the sodium ion halide solid electrolyte, comprising the following steps:

[0017] The sodium ion halide solid electrolyte is obtained by mixing and ball milling the raw materials.

[0018] Preferably, the raw materials for preparation include a sodium source, an oxygen source, NaBH4, an M source, and a halogen source;

[0019] More preferably, the sodium source and the oxygen source can be the same type; even more preferably, the sodium source and the oxygen source are at least one of NaOH and Na2O.

[0020] More preferably, the M source and the halogen source can be the same type; more preferably, the M source and the halogen source are halides of metal M.

[0021] Preferably, the ball milling speed is ≥300 rpm, the ball milling time is ≥1 h, and the ball-to-material ratio during ball milling is (40~85):1.

[0022] More preferably, the ball milling speed is 300-650 rpm, the ball milling time is 1-10 h, and the ball-to-material ratio during ball milling is (75-85):1.

[0023] Another object of the present invention is to provide another method for preparing the sodium ion halide solid electrolyte, comprising the following steps:

[0024] The raw materials are mixed and heated to melt under a protective atmosphere, then cooled to obtain the sodium ion halide solid electrolyte.

[0025] Preferably, the raw materials for preparation include NaBH4, an oxygen source, an M source, and a halogen source;

[0026] More preferably, the M source, oxygen source, and halogen source can be the same type;

[0027] More preferably, the oxygen source is an oxide of metal M, and the halogen source is a halide of metal M.

[0028] Preferably, the temperature during the heating and melting process is 120–500°C, and the time is 0.5–20 h.

[0029] Another object of the present invention is to provide another method for preparing the sodium ion halide solid electrolyte, comprising the following steps:

[0030] The raw materials are mixed and ball-milled, and the resulting powder is pressed into tablets and then sintered to obtain the sodium ion halide solid electrolyte.

[0031] Preferably, the raw materials for preparation include a sodium source, an oxygen source, NaBH4, an M source, and a halogen source;

[0032] More preferably, the sodium source and the oxygen source can be the same type; even more preferably, the sodium source and the oxygen source are at least one of NaOH and Na2O.

[0033] More preferably, the M source and the halogen source can be the same type; more preferably, the M source and the halogen source are halides of metal M.

[0034] Preferably, the ball milling speed is ≥300 rpm, the ball milling time is ≥1 h, and the ball-to-material ratio during ball milling is (40~85):1.

[0035] More preferably, the ball milling speed is 300-650 rpm, the ball milling time is 1-10 h, and the ball-to-material ratio during ball milling is (75-85):1.

[0036] Preferably, the sintering temperature is 150–600°C and the time is 1–100 h.

[0037] It should be noted that the preparation method of sodium ion halide solid electrolyte of the present invention includes, but is not limited to, the above-mentioned method. Those skilled in the art know that the existing preparation process of sodium ion halide solid electrolyte is mature. In addition to the above-mentioned process, conventional synthesis methods such as chemical vapor spraying and hydrothermal synthesis can also be used to synthesize the product. It can also be prepared by doping commercially available solid electrolytes. As long as its chemical composition and chemical structure meet the limitations of the scheme described in the present invention and similar technical effects can be obtained, it is acceptable.

[0038] Another object of the present invention is to provide the application of the sodium-ion halide solid electrolyte in the preparation of secondary batteries.

[0039] Another object of the present invention is to provide a secondary battery comprising the sodium-ion halide solid electrolyte described herein.

[0040] Preferably, the secondary battery is an all-solid-state sodium-ion secondary battery.

[0041] The sodium-ion halide solid electrolyte of this invention effectively improves ionic conductivity by doping with specific anions to regulate the site and transport path of sodium ions in the structure, achieving a maximum conductivity of 0.35 mS·cm at room temperature. -1 Meanwhile, this product has ideal high oxidation potential and interfacial compatibility, low interfacial resistance, and low degree of interfacial side reactions. When applied in secondary batteries, especially all-solid-state sodium-ion secondary batteries, it can exhibit excellent electrochemical performance with high safety and high cycle stability. This secondary battery can be used as a power supply device in large-scale energy storage equipment such as solar power generation, wind power generation, smart grid peak shaving, distributed power stations, backup power supplies, or communication base stations.

[0042] Preferably, the secondary battery includes a positive electrode and a negative electrode.

[0043] Preferably, the oxidation resistance potential of the secondary battery is ≥4V.

[0044] The beneficial effects of this invention are that it provides a sodium-ion halide solid electrolyte, which optimizes the sodium ion transport path and microstructure by incorporating BH4 anions and O anions into the structure and controlling the doping amount, thereby reducing the sodium ion migration activation energy and effectively improving the ionic conductivity of the product. At the same time, the product has oxidation resistance, high electrochemical stability, and is compatible with high-voltage cathode materials in application. Attached Figure Description

[0045] Figure 1 is the AC impedance diagram of the sodium ion halide solid electrolyte obtained in Example 1;

[0046] Figure 2 is the AC impedance diagram of the sodium ion halide solid electrolyte obtained in Example 2;

[0047] Figure 3 is the AC impedance diagram of the sodium ion halide solid electrolyte obtained in Example 3;

[0048] Figure 4 is the AC impedance diagram of the sodium ion halide solid electrolyte obtained in Example 4;

[0049] Figure 5 is the AC impedance diagram of the sodium ion halide solid electrolyte obtained in Example 5;

[0050] Figure 6 is the AC impedance diagram of the sodium ion halide solid electrolyte obtained in Example 6;

[0051] Figure 7 shows the AC impedance diagram of the sodium ion halide solid electrolyte obtained in Comparative Example 2.

[0052] Figure 8 shows the AC impedance diagram of the sodium ion halide solid electrolyte obtained in Comparative Example 5.

[0053] Figure 9 shows the XRD pattern of the sodium ion halide solid electrolyte obtained in Example 1;

[0054] Figure 10 shows the XRD pattern of the sodium ion halide solid electrolyte obtained in Example 2;

[0055] Figure 11 shows the XRD pattern of the sodium ion halide solid electrolyte obtained in Example 3;

[0056] Figure 12 shows the XRD pattern of the sodium ion halide solid electrolyte obtained in Example 4;

[0057] Figure 13 shows the XRD pattern of the sodium ion halide solid electrolyte obtained in Example 5;

[0058] Figure 14 shows the XRD pattern of the sodium ion halide solid electrolyte obtained in Example 6;

[0059] Figure 15 shows the XRD pattern of the sodium ion halide solid electrolyte obtained in Comparative Example 2.

[0060] Figure 16 shows the XRD pattern of the sodium ion halide solid electrolyte obtained in Comparative Example 2. Detailed Implementation

[0061] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0062] Example 1

[0063] An embodiment of the sodium ion halide solid electrolyte, its preparation method, and its application according to the present invention, wherein the preparation method of the sodium ion halide solid electrolyte includes the following steps:

[0064] (1) In an inert gas environment with water and oxygen content ≤0.01ppm, the raw materials are mixed, then ground and mixed evenly in a mortar to obtain a mixed powder; the raw materials are Na2O, ZrCl4 and NaBH4 in a molar ratio of 1.25:1:0.3.

[0065] (2) The mixed powder was ball-milled in a sealed ball mill jar with an inert atmosphere protection at a ball mill speed of 500 rpm for 2 hours at a ball ratio of 75:1. Then, the ball was separated by molecular sieve to obtain the sodium ion halide solid electrolyte. The chemical formula of the product is shown in Table 1.

[0066] Example 2

[0067] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrCl₄, and NaBH₄ in a molar ratio of 1.375:1:0.3.

[0068] Example 3

[0069] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrCl₄, and NaBH₄ in a molar ratio of 1.5:1:0.3.

[0070] Example 4

[0071] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrCl₄, and NaBH₄ in a molar ratio of 1.75:1:0.3.

[0072] Example 5

[0073] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrCl₄, and NaBH₄ in a molar ratio of 2:1:0.3.

[0074] Example 6

[0075] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrCl₄, and NaBH₄ in a molar ratio of 1.375:1:0.4.

[0076] Example 7

[0077] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrCl₄, and NaBH₄ in a molar ratio of 1.5:1:0.4.

[0078] Example 8

[0079] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrCl₄, and NaBH₄ in a molar ratio of 1.75:1:0.4.

[0080] Example 9

[0081] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrCl₄, and NaBH₄ in a molar ratio of 1.375:1:0.5.

[0082] Example 10

[0083] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrCl₄, and NaBH₄ in a molar ratio of 1.5:1:0.5.

[0084] Example 11

[0085] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrCl₄, and NaBH₄ in a molar ratio of 1.75:1:0.5.

[0086] Example 12

[0087] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, HfCl₄, and NaBH₄ in a molar ratio of 1.375:1:0.3.

[0088] Example 13

[0089] This invention relates to an embodiment of a sodium-ion halide solid electrolyte, its preparation method, and its application. The only difference from the previous embodiment is that the raw materials used in the preparation are Na₂O, ZrBr₄, and NaBH₄ in a molar ratio of 1.375:1:0.3.

[0090] Comparative Example 1

[0091] A sodium-ion halide solid electrolyte, its preparation method and application, differs from the examples only in that the raw materials for preparation are Na2O and ZrCl4 in a molar ratio of 1.25:1.

[0092] Comparative Example 2

[0093] A sodium-ion halide solid electrolyte, its preparation method and application, differs from the examples only in that the raw materials for preparation are Na2O and ZrCl4 in a molar ratio of 1.375:1.

[0094] Comparative Example 3

[0095] A sodium-ion halide solid electrolyte, its preparation method and application, differs from the examples only in that the raw materials for preparation are Na2O and ZrCl4 in a molar ratio of 1.5:1.

[0096] Comparative Example 4

[0097] A sodium-ion halide solid electrolyte, its preparation method and application, differs from the examples only in that the raw materials for preparation are Na2O and ZrCl4 in a molar ratio of 1:1, and the ball milling time is 6 hours.

[0098] Comparative Example 5

[0099] A sodium-ion halide solid electrolyte, its preparation method and application, differs from the examples only in that the raw materials for preparation are Na2O and ZrCl4 in a molar ratio of 2:1, and the ball milling time is 8 hours.

[0100] Comparative Example 6

[0101] A sodium-ion halide solid electrolyte, its preparation method and application, differs from the embodiments only in that the raw materials for preparation are Na2O, ZrCl4 and NaBH4 in a molar ratio of 2:1:0.3, the ball milling speed is 400 rpm and the ball milling time is 4 h.

[0102] Comparative Example 7

[0103] A sodium-ion halide solid electrolyte, its preparation method and application, differs from the examples only in that the raw materials for preparation are Na2O, ZrCl4 and NaBH4 in a molar ratio of 2:1:0.4, the ball milling speed is 400 rpm and the ball milling time is 4 h.

[0104] Comparative Example 8

[0105] A sodium-ion halide solid electrolyte, its preparation method and application, differs from the examples only in that the raw materials for preparation are Na2O, ZrCl4 and NaBH4 in a molar ratio of 2:1:0.5, the ball milling speed is 400 rpm and the ball milling time is 4 h.

[0106] Example 1

[0107] To verify the ionic conductivity of the sodium halide solid electrolyte described in this invention, films of the same size were cut from each embodiment and comparative example, and then subjected to AC impedance spectroscopy. The AC impedance spectroscopy was performed on a Biologic electrochemical workstation, and the ionic conductivity was calculated based on the obtained AC impedance spectra and the formula: σ = L / R; where σ is the ionic conductivity (S / cm), L is the thickness of the electrolyte film (cm), R is the measured impedance (Ω), and S is the area of ​​the electrolyte film (cm²). 2 ).

[0108] The test results are shown in Table 1 and Figures 1-8.

[0109] Table 1

[0110] The test results show that the sodium halide solid electrolyte of this invention, due to the incorporation of BH4 and O anions, optimizes the ion transport channel and significantly improves the transport efficiency. Compared with the products of Comparative Examples 1-8, which did not incorporate anions or only incorporated O anions or only incorporated BH4 anions, the ionic conductivity is significantly improved, ranging from 0.16 to 0.35 mS·cm. -1 Within the range. Simultaneously, it can be seen that the doping amounts of the two anions also affect the ionic conductivity of the product. When the sodium ion halide solid electrolyte Na... 2+2x ZrO 1+x(BH4) y Cl 4-y The product exhibits higher ionic conductivity when the values ​​are within the range of 0.375≤x≤0.5 and 0.3≤y≤0.4.

[0111] XRD tests were performed on the sodium-ion halide solid electrolytes prepared in Examples 1-6 and Comparative Examples 2 and 5. The results are shown in Figures 9-16. Comparing the products of Comparative Examples 2 and 5 (one without doping and the other with only oxygen anion doping), it can be seen that at lower O anion doping levels, the product obtained in Example 1, besides the amorphous main phase, mainly exhibits diffraction peaks of Na₂O, NaCl, and Na₂ZrCl₆, with the Na₂ZrCl₆ impurity peak showing strong crystallinity. As the doping level increases, the intensity of each characteristic peak in the spectrum of the product of Example 2 decreases, indicating that O anions at this doping level regulate the degree of amorphization of the product. The spectrum of the product of Example 3 also shows corresponding characteristic peaks, and the crystallinity is relatively stable. With increasing O anion doping level... With further increases in the amount of anion incorporated, the amorphization degree of the products in Examples 4 and 5 decreased, and the ion conduction efficiency decreased. The main reason is that Cl ions close to Zr ions are gradually replaced by a large number of O anions, while more impurities such as NaCl are generated. Therefore, the intensity of the corresponding characteristic peaks also increases, ultimately affecting the ionic conductivity of the products, as shown in Table 1. After fixing the amount of Na2O added, thereby fixing the amount of O anion incorporated, the product in Example 6 has increased the amount of BH4 anion incorporated compared to the product in Example 2. It can be seen that the intensity of the characteristic peaks corresponding to the impurities in the product decreases, while the intensity of the amorphous main phase increases. This indicates that the product can achieve better structural control at this amount of incorporation, thus improving the ionic conductivity, which corresponds to the results in Table 1.

[0112] Furthermore, the sodium-ion halide solid electrolyte obtained in Example 2 was used to prepare an all-solid-state battery: the sodium-ion halide solid electrolyte obtained in Example 2 and conductive carbon black were mixed at a mass ratio of 7:3 and pressed into a positive electrode sheet, a commercial sodium-tin alloy was cut into a negative electrode sheet, and the sodium-ion halide solid electrolyte obtained in Example 2 was cut and pressed into a solid electrolyte membrane sheet and assembled into an all-solid-state battery.

[0113] The oxidation potential of the all-solid-state battery was then tested using cyclic voltammetry. The scanning voltage range was from open circuit voltage to 5V, and the scan rate was 0.1mV / s. The tested oxidation potential was 4.1V, indicating that the sodium-ion halide solid electrolyte of this invention has high oxidation resistance.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the present invention.

Claims

1. A sodium-ion halide solid-state electrolyte, characterized by, Its chemical formula is as follows: Na 2+2x MO 1+x (BH4) y X 4-y wherein M is at least one of Zr, Hf, Ti, Mo, X is halogen, 0 < x < 1, 0 < y < 1.

2. The sodium-ion halide solid-state electrolyte of claim 1, wherein, M is at least one of Zr and Hf.

3. The sodium-ion halide solid-state electrolyte of claim 1, wherein, The sodium ion halide solid-state electrolyte has an ionic conductivity ≥ 0.1 mS·cm at 25-30℃ -1 .

4. The sodium-ion halide solid-state electrolyte of claim 2, wherein, The sodium ion halide solid-state electrolyte is Na 2+2x ZrO 1+x (BH4) y Cl 4-y wherein 0.25≤x≤2, 0.3≤y≤0.

5.

5. The sodium-ion halide solid-state electrolyte of claim 4, wherein, The sodium-ion halide solid-state electrolyte is Na 2+2x ZrO 1+x (BH4) y Cl 4-y wherein 0.375≤x≤0.5, 0.3≤y≤0.

4.

6. The method of producing a sodium-ion halide solid-state electrolyte according to any one of claims 1 to 5, wherein Includes the following steps: The sodium ion halide solid electrolyte is obtained by mixing and ball milling the raw materials.

7. The method of producing a sodium-ion halide solid-state electrolyte according to any one of claims 1 to 5, wherein Includes the following steps: The raw materials are mixed and heated to melt under a protective atmosphere, then cooled to obtain the sodium ion halide solid electrolyte.

8. The method of producing a sodium-ion halide solid-state electrolyte according to any one of claims 1 to 5, wherein Includes the following steps: The raw materials are mixed and ball-milled, and the resulting powder is pressed into tablets and then sintered to obtain the sodium ion halide solid electrolyte.

9. The application of the sodium-ion halide solid electrolyte as described in any one of claims 1 to 5 in the preparation of secondary batteries.

10. A secondary battery characterized by comprising: Includes the sodium-ion halide solid electrolyte as described in any one of claims 1 to 5; preferably, the secondary battery is an all-solid-state sodium-ion secondary battery.

Images