Sodium ion solid-state electrolyte material, preparation method and application thereof

Abstract

The application relates to a kind of sodium ion solid electrolyte materials and preparation method and application thereof.The composition formula is MX5-nNa2O y (T) The solid electrolyte not only has high ion conductivity and wide electrochemical stability window, but also is compatible with commonly used positive electrode materials such as Prussian blue, polyanion and layered oxide, etc.The assembled battery has excellent electrochemical performance, which is beneficial to realize the commercial application value of full-solid-state secondary battery.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, specifically to a class of sodium-ion solid electrolyte materials, their preparation methods, and applications. Background Technology

[0002] In recent years, sodium-ion batteries have received widespread attention due to the advantages of abundant and inexpensive sodium resources and their application value in large-scale energy storage systems. However, traditional sodium-ion batteries mostly use flammable and volatile organic solvents as electrolytes. When the battery is overcharged, over-discharged, or exposed to high temperatures, it can expand and leak electrolytes, easily leading to safety accidents. All-solid-state sodium-ion batteries use flame-retardant, non-volatile, and leak-proof solid electrolytes instead of organic electrolytes. This ensures battery safety while significantly improving energy density, aligning better with the current development direction of power batteries.

[0003] As a core component of all-solid-state sodium batteries, solid-state electrolyte materials are a key technology for the success of solid-state sodium battery technology. To date, reported solid-state electrolytes can be divided into inorganic and organic electrolytes. Inorganic solid-state electrolytes, such as β-alumina, sodium superionic conductors, and sulfides, typically exhibit considerable ionic conductivity (>10⁻⁶). -4 S cm -1 While oxide electrolytes offer good thermal stability, the inherent rigidity of oxide electrolytes leads to poor interfacial contact between the electrolyte and electrode materials. Sulfides also exhibit air instability and a narrow electrochemical stability window, significantly impacting the electrochemical performance of all-solid-state batteries. Compared to inorganic electrolytes, the flexibility of organic polymer solid electrolytes ensures good interfacial contact between the electrode and electrolyte. However, organic polymer solid electrolytes typically exhibit low room-temperature ionic conductivity and low ion transfer numbers (mostly below 0.5), limiting their application in sodium-ion batteries. Therefore, developing a solid electrolyte material with high ionic conductivity and good interfacial contact with the cathode is of great significance.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] This invention provides a sodium-ion solid electrolyte material for secondary batteries and its preparation method. The material possesses high ionic conductivity and excellent mechanical properties, is compatible with various cathode materials and forms good interfacial contact, combining the advantages of both organic and inorganic solid electrolytes. This solid electrolyte is used to construct all-solid-state sodium-ion batteries, exhibiting high stability, high charge-discharge specific capacity, and excellent cycle performance. This contributes to realizing the commercial application value of all-solid-state sodium-ion batteries.

[0006] To achieve the above objectives, the present invention discloses the following technical contents:

[0007] A class of solid electrolyte materials is represented by the following composition formula (1),

[0008] MX5-nNa2Oy(T) Equation (1)

[0009] This includes elements Na, M, O, and X, where 0.3 ≤ n ≤ 2.0; M is selected from one or both of Ta and Nb; X is one or a combination of F, Cl, Br, and I; y is one or both of 1 or 2; the synthesis temperature is 200℃ ≤ T ≤ 800℃; the solid electrolyte material is a crystalline phase, a crystalline-amorphous phase, or an amorphous phase; preferably, it satisfies 0.3 ≤ n ≤ 0.8. The synthesis temperature preferably satisfies 350℃ ≤ T ≤ 550℃.

[0010] The electrolyte of this invention is subjected to cation doping, anion doping, or dual cation-anion doping to obtain a doped solid electrolyte. The cations are selected from one or more elements chosen from V, Ti, Sn, Sc, W, Y, Lu, Fe, As, Hf, Zr, Cr, Al, Ga, In, P, Sb, Mg, Ca, Sr, Ba, Si, Ge, La, Sm, Tb, Ho, Dy, Gd, and Er. The purpose of doping the solid electrolyte is to improve its ionic conductivity, broaden its electrochemical stability window, or improve its air stability; typically, Hf and Zr are used for doping. The anions are selected from one or more elements chosen from F, Cl, Br, I, N, S, and Se; typically, F and Cl are used for doping.

[0011] The preparation method of the doped solid electrolyte described in this invention is selected from at least one or more of the following methods: eutectic melting, ball milling, and calcination after ball milling.

[0012] The present invention further discloses a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte layer between the positive electrode and the negative electrode, the electrolyte being selected from at least one of the positive electrode, the negative electrode, and the electrolyte layer, and various solid electrolyte materials described herein.

[0013] This invention also discloses the application of a class of sodium-ion solid electrolyte materials in the preparation of room-temperature and low-temperature all-solid-state sodium secondary batteries, particularly in improving the electrochemical stability of the electrolyte and its compatibility with electrode active materials. Experimental results show that a sodium-ion secondary battery containing the above-mentioned solid electrolyte according to this invention can achieve stable cycling at low and room temperatures.

[0014] The present invention is described in more detail below:

[0015] First implementation method:

[0016] The electrolyte material contains the following elements: Na, M, O, and X. X is selected from one or more combinations of F, Cl, Br, and I.

[0017] The solid electrolyte material can be used in sodium secondary batteries, and the preferred secondary batteries include liquid-phase sodium secondary batteries, semi-solid-state sodium secondary batteries, and all-solid-state sodium secondary batteries.

[0018] Furthermore, the electrolyte material can be represented by the following formula:

[0019] MX5-nNa2O y (T) (1)

[0020] This includes elements Na, M, O, and X, with 0.3 ≤ n ≤ 2.0; M is selected from one or both of Ta or Nb; X is one or a combination of F, Cl, Br, and I; y is one or both of 1 or 2; and the synthesis temperature is 200℃ ≤ T ≤ 800℃.

[0021] Furthermore, in order to improve the ionic conductivity of the solid electrolyte, M is preferably Ta in the composition formula (1).

[0022] Furthermore, in order to improve the compatibility between the solid electrolyte and the positive electrode active material, in the composition formula (1), X is preferably Cl, and the solid electrolyte (1) can be written as MCl5-nNa2O y (T).

[0023] Furthermore, in the composition formula (1), when 450 ≤ T ≤ 550℃ is satisfied, the obtained solid electrolyte has high ionic conductivity.

[0024] Furthermore, in order to improve the ionic conductivity of the solid electrolyte, n is preferably 0.5 in formula (1).

[0025] The electrolyte material obtained in the first embodiment can be a crystalline phase, an amorphous phase, or a mixture of crystalline and amorphous phases.

[0026] The color, size, and shape of the electrolyte material obtained in the first embodiment are not limited.

[0027] Generally, the solid electrolyte materials described above in this invention can be prepared using conventional techniques in the field.

[0028] The method for preparing a type of sodium-ion solid electrolyte material according to the present invention includes the following steps:

[0029] (1) The halides and oxides are mixed according to the target composition. For example, when the target composition is TaCl5-nNa2O2, TaCl5 and Na2O2 can be mixed in a molar ratio of 1:0.5 and placed in a quartz glass tube. The quartz tube is then evacuated and sealed. The precursor is assembled in an argon-filled glove box. The moisture content and oxygen content of the atmosphere in the glove box are less than 1 ppm.

[0030] (2) The quartz glass tube sealed in step (1) is placed in a high-temperature muffle furnace for heating and calcination. The heating rate during calcination is 10℃ / min, and the temperature is raised to 350-550℃ and held for 12 hours. After cooling to room temperature, the inorganic solid electrolyte material is obtained.

[0031] The electrolyte described in the first embodiment can be obtained using the above method.

[0032] Second Implementation Method

[0033] A sodium battery includes a positive electrode, a negative electrode, and an electrolyte (liquid) layer between the positive and negative electrodes. At least one of the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte material described in the first embodiment. The electrolyte layer is located between the positive and negative electrodes. The positive electrode comprises positive electrode active material particles and electrolyte particles. The negative electrode comprises negative electrode active material particles and electrolyte particles. The positive electrode active material refers to a material capable of absorbing and releasing metal ions, such as layered metal oxides, Prussian blue, and polyanionic materials. The negative electrode active material refers to a material capable of absorbing and releasing metal ions, such as metallic materials, carbon materials, and nitrogen materials. The metallic material can be elemental sodium or an alloy, such as elemental sodium or Na. 15 Sn4 alloy.

[0034] To ensure electrochemical / electrochemical cycle stability and ionic conductivity, at least one of the positive electrode, negative electrode, and electrolyte layer of the aforementioned sodium battery may contain one or more additional electrolyte (liquid) materials. These additional electrolyte materials are not specified and can be oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, polymer electrolytes, and electrolyte solutions, etc.

[0035] To ensure the electrochemical stability of the battery during cycling, the positive or negative electrode active materials can be modified. For example, inorganic or organic protective layers can be prepared using solution methods or molecular / atomic layer deposition techniques to modify the surface and interface of the active materials.

[0036] This invention primarily addresses the lack of excellent sodium-based solid electrolytes. Through a series of studies, a sodium-ion superconductor combining the advantages of oxide, sulfide, and halide-based solid electrolytes has been invented. The ionic conductivity, electrochemical stability window, and electrochemical compatibility with various cathodes of the solid electrolyte were investigated. The main challenges lie in optimizing the performance of the solid electrolyte and assembling all-solid-state batteries.

[0037] The beneficial effects of the sodium-ion solid electrolyte material and its application disclosed in this invention are as follows:

[0038] (1) The solid electrolyte material described in this invention has high ionic conductivity and a wide operating temperature range.

[0039] (2) The solid electrolyte material described in this invention has a wide electrochemical stability window.

[0040] (3) The solid electrolyte material described in this invention is compatible with a variety of cathode materials.

[0041] (4) The solid electrolyte material provided by the present invention has excellent mechanical properties and can form a good interfacial contact with the positive electrode material under certain pressure, thereby promoting the rapid conduction of sodium ions between the interfaces.

[0042] (5) The all-solid electrolyte material of the present invention can be used as a membrane material for sodium secondary batteries. It has high safety and strong stability at room temperature / high temperature.

[0043] (6) The present invention can be prepared by high temperature eutectic method, which directly places tantalum chloride and sodium peroxide in a vacuum quartz tube for calcination. The preparation method is simple to operate and has good repeatability. Attached Figure Description

[0044] Figure 1 This is the X-ray diffraction (XRD) pattern of the solid electrolyte material TaCl5-xNa2O2 (0.3 ≤ x ≤ 0.8; T=450℃) prepared in Example 1 of this invention;

[0045] Figure 2 This is the X-ray diffraction (XRD) pattern of the solid electrolyte material TaCl5-0.5Na2O2 (350℃≤ T ≤550℃) prepared in Example 2 of the present invention;

[0046] Figure 3 This is a charge-discharge curve of the all-solid-state sodium-ion battery obtained in Application Example 1 of the present invention at room temperature;

[0047] Figure 4 This is a charge-discharge curve of the all-solid-state sodium-ion battery obtained in Application Example 1 of the present invention at low temperature. Detailed Implementation

[0048] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0049] Example 1

[0050] Preparation of TaCl5-nNa2O2 (0.3 ≤ n ≤ 0.8; T=450℃) solid electrolyte material by high-temperature eutectic method

[0051] TaCl5 and Na2O2 were weighed in a glove box at a ratio of 1:n (n=0.3, 0.5, 0.8) and transferred to a 10 mm diameter quartz glass tube. The quartz tube was then evacuated and sealed. The quartz glass tube was placed in a muffle furnace and calcined at 450 °C for 12 hours. The sample obtained after cooling was the TaCl5-nNa2O2 (n=0.3, 0.5, 0.8) solid electrolyte material.

[0052] X-ray diffraction test: The solid electrolyte was sealed in an inert atmosphere, and the X-ray diffraction pattern of the solid electrolyte was tested at 10º-60º under a Cu-Kα X-ray source. Figure 1 ).

[0053] Battery assembly for testing ionic conductivity: The powder of the solid electrolyte material of Example 1 was loaded into a conventional molded battery in a glove box with water and oxygen contents both below 0.1 ppm, and a pressure of 300 MPa was applied to obtain a solid electrolyte sheet. The battery was then assembled, and the electrochemical impedance spectroscopy of the battery was tested. Its ionic conductivity at 25°C is shown in the table below.

[0054]

[0055] Example 2

[0056] Preparation of TaCl5-0.5Na2O2 solid electrolyte material (350℃ ≤ T ≤ 550℃) by high-temperature eutectic method

[0057] The synthesis steps were the same as in Example 1, except that TaCl5 and Na2O2 were weighed in a glove box at a ratio of 1:0.5 and calcined at 350, 450, and 550 °C, respectively. XRD phase analysis was performed on the resulting series of products, and the results are as follows: Figure 2 As shown in the table below, its ionic conductivity at 25℃ is as follows;

[0058]

[0059] Example 3

[0060] The synthesis steps were the same as in Example 1, except that NbCl5:Na2O2 was weighed in a glove box at a molar ratio of 1:0.5 and calcined at 450 °C. The ionic conductance of Sample 3 was tested using the same method as for Sample 1, and the ionic conductance of Sample 3 at room temperature was 3.2 mS / cm. -1 .

[0061] Example 4

[0062] The synthesis steps were the same as in Example 1, except that HfCl4: TaCl5: Na2O2 were weighed in a glove box at a molar ratio of 0.5:0.5:0.5 and calcined at 450 °C. The ionic conductance of Sample 4 was tested using the same method as Sample 1, and the ionic conductance of Sample 4 at room temperature was 1.32 mS / cm. -1 .

[0063] Application Example 1:

[0064] The amorphous glassy solid electrolyte prepared in Example 1 is combined with Na 0.85 Mn 0.5 Ni 0.4 Fe 0.1 O2 cathode material is used in room temperature all-solid-state sodium-ion batteries.

[0065] Using unmodified Na 0.85 Mn 0.5 Ni 0.4 Fe 0.1 O2 was used as the positive electrode material. The positive electrode material and the TaCl5-0.5Na2O2 solid electrolyte material obtained in Example 1 were mixed in a ratio of 60:40 (mass ratio) by manual grinding for 5 minutes. The ground sample became the positive electrode powder for the secondary battery. The entire mixing process was carried out in an argon-filled glove box. A Na-Sn alloy was used as the negative electrode, and the solid electrolyte consisted of TaCl5-0.5Na2O2 solid electrolyte and synthesized Na3PS4 electrolyte material. A solid-state battery was assembled using a mold battery. Electrochemical charge-discharge tests were conducted on the solid-state battery at room temperature. The charge-discharge cutoff voltage was 2.5-3.8V (vs. Na / Na-Sn), and the charge-discharge current density was 0.1C (1C = 140 mAg). -1 ).

[0066] Figure 3 The charge-discharge curves are shown for a room-temperature all-solid-state sodium battery assembled using TaCl5-0.5Na2O2 prepared in Example 1 and layered oxide cathode material.

[0067] Application Example 2

[0068] This implementation is basically the same as the steps in "Example 1", except that the positive electrode material is changed to Na3V2(PO4)3. Electrochemical charge-discharge tests were performed on the solid-state battery at -10°C, with a charge-discharge cutoff voltage of 2.7-3.7V (vs. Na / Na-Sn) and a charge-discharge current density of 0.1C (1C = 117.6 mA g). -1 ).

[0069] Figure 4 The charge-discharge curves are shown for a low-temperature all-solid-state sodium battery assembled using the TaCl5-0.5Na2O2 solid electrolyte prepared in Example 1 and the Na3V2(PO4)3 cathode material.

[0070] The solid electrolyte in this invention possesses high sodium ion conductivity and a wide electrochemical stability window, enabling it to form stable interfaces with various cathode materials and achieve stable cycling. Furthermore, the high ion conductivity of this solid electrolyte allows all-solid-state sodium secondary batteries to operate at low temperatures, potentially expanding the application areas of all-solid-state sodium-ion batteries.

[0071] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A type of sodium-ion solid electrolyte material, represented by the following composition formula (1), MX5-nNa2Oy(T) Equation (1) This includes elements Na, M, O, and X, with 0.3 ≤ n ≤ 2.0; M is selected from one or two of Ta or Nb; X is one or more of F, Cl, Br, and I; y is one or two of 1 or 2; the synthesis temperature is 200℃ ≤ T ≤ 800℃; the solid electrolyte material is a crystalline phase, a crystalline-amorphous phase, or an amorphous phase.

2. The electrolyte material according to claim 1, wherein M is Ta.

3. The electrolyte material according to any one of claims 1-2, characterized in that... It satisfies 0.3 ≤ n ≤ 0.

8.

4. The electrolyte material according to any one of claims 1-2, characterized in that... y = 2。 5. The electrolyte material according to any one of claims 1-2, characterized in that... 350 ℃≤ T ≤ 550 ℃。 6. The electrolyte material according to any one of claims 1-2, characterized in that: Doped electrolytes are obtained by cation doping, anion doping, or dual doping of cations and anions; the cations are selected from one or more elements selected from V, Ti, Sn, Sc, W, Y, Lu, Fe, As, Hf, Zr, Cr, Al, Ga, In, P, Sb, Mg, Ca, Sr, Ba, Si, Ge, La, Sm, Tb, Ho, Dy, Gd, Er; the anions are selected from one or more elements selected from F, Cl, Br, I, N, S, Se.

7. A method for preparing a type of sodium-ion solid electrolyte material according to any one of claims 1-2, characterized in that: Prepared by fusion, ball milling, or calcination after ball milling.

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