A type of solid electrolyte material and its preparation method and application

Abstract

The present invention relates to a solid electrolyte material and its preparation method and application. x M y O z X (x+4y‑2z) Or Na x M y O z X (x+5y‑2z)。 The solid-state electrolyte material in this invention not only has high ionic conductivity and excellent physical properties, but is also compatible with layered oxides and polyanionic cathode materials. This solves the problems of poor interfacial contact between the solid-state electrolyte material and the cathode material, as well as chemical and electrochemical instability, in all-solid-state secondary batteries, facilitating the commercial application of all-solid-state sodium-ion batteries.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a solid electrolyte material and a preparation method and application thereof. Background Art

[0002] As a typical energy storage device, secondary batteries have been widely used in fields such as portable electronic devices and electric vehicles, and have broad development prospects in various large-scale energy storage in the future. Lithium-ion batteries occupy a vast market due to their advantages such as high energy density and long cycle life. However, with the large-scale development of lithium-ion batteries, they are inevitably faced with soaring costs due to the shortage of lithium resources. Compared with the shortage of lithium reserves, sodium resources are abundant and inexpensive. The development of sodium-ion batteries is of great strategic significance to the development of energy storage technology in my country. Although sodium-ion batteries have outstanding advantages, the organic liquid electrolytes they currently use have hidden dangers such as flammability, explosiveness, and volatility, which can easily cause safety problems. All-solid-state batteries have higher safety performance and energy density than currently commercial liquid batteries, and are an important development direction for the next generation of sodium-ion batteries, especially power batteries.

[0003] Solid electrolytes are the core of all-solid-state sodium-ion batteries. At present, the superionic conductor NASICON-type solid electrolyte, which has been widely studied, has the advantages of high ionic conductivity, wide electrochemical stability window, and stability to metallic sodium negative electrode. However, its sintering temperature is relatively high, usually above 1000°C, and there are problems such as poor interface contact with electrode materials, which are the main technical bottlenecks restricting its application. The good mechanical properties of sulfide solid electrolytes can promote the solid-solid interface contact between solid electrolytes and electrodes, but they have the problems of poor air stability and narrow electrochemical stability window. Recently, halides have attracted great interest as a new type of solid electrolyte. However, the sodium-based halide solid electrolytes reported so far, such as Na2ZrCl , NaAlCl4 and Na3ErCl6 have low room temperature ionic conductivity (10 -5 -10 -8 S cm -1 ) problem, is far from satisfying practical application. In view of this, the present invention is proposed. Summary of the Invention

[0004] Purpose: This invention provides a sodium-based solid-state electrolyte material containing elements such as Na, M, O, and Cl. This solid-state electrolyte not only exhibits high ionic conductivity, a wide electrochemical stability window, and excellent mechanical properties, but is also compatible with a variety of cathode materials. All-solid-state sodium-ion batteries constructed using this solid-state electrolyte exhibit high stability, high charge-discharge capacity, and excellent cycling performance, contributing to the commercial application of all-solid-state sodium-ion batteries.

[0005] To achieve the above object, the present invention discloses the following technical content:

[0006] A class of solid electrolyte materials, the composition of which is expressed as:

[0007] Na x M y O z X (x+4y-2z) or Na x M y O z X (x+5y-2z)

[0008] which includes elements Na, M, O, X; wherein M is selected from one or a combination of more of Ta, Nb, Hf, Zr; X is a combination of one or more of F, Cl, Br, I; x, y, z satisfy 0 < x < 10, 0 < y < 10, 0 < z < 10; the source of O element is selected from one or more substances of oxygen-containing sodium salts, metal oxides and oxygen-containing metal compounds; the source of X halogen is selected from one or more substances of sodium salts containing X halogen, metal halides and metal compounds containing halogen. The solid electrolyte material is a crystalline phase, a crystalline-amorphous phase or an amorphous phase;

[0009] M is preferably a combination of one or two of Ta and Hf. X is preferably Cl. x, y, z preferably satisfy 0 < x ≤ 2; z = 1.

[0010] For the solid electrolyte material of the present invention, the metal oxides or oxygen-containing sodium salts used to prepare the solid electrolyte are selected from one or several substances of Na2O, Na2O2, NaOH, Na2CO3, NaHCO3, preferably Na2O and Na2O2; the metal halides and metal compounds containing halogen are selected from one or several substances of NaCl, MCl4, MCl5, MOCl4, MOCl3. Preferably TaCl5, HfCl4. M is selected from one or a combination of more of Ta, Nb, Hf, Zr; preferably Ta and Hf.

[0011] The solid electrolyte material described in the present invention is cation-doped, anion-doped, or both anion- and cation-doped to obtain a doped solid electrolyte. The cations are selected from one or more of Hf, Ta, Zr, Nb, V, Ti, Sn, Sc, W, Y, Lu, Fe, As, Cr, Al, Ga, In, P, Sb, Mg, Ca, Sr, Ba, Si, Ge, La, Sm, Tb, Ho, Dy, Gd, or Er, with Ta and Hf being preferred. The anions are selected from one or more of F, Cl, Br, I, N, S, or Se, with Cl and Br being preferred. The purpose of doping the solid electrolyte is to enhance the ionic conductivity of the solid electrolyte, broaden the electrolyte's electrochemical stability window, or improve its air stability.

[0012] The doped solid electrolyte of the present invention is prepared by at least one or more methods selected from the group consisting of eutectic, ball milling, and calcination after ball milling.

[0013] The present invention further discloses the application of solid electrolyte materials in improving the conductivity, electrochemical stability, and compatibility with electrode materials of sodium ion electrolytes. In particular, the problems of poor interface contact between solid electrolyte materials and cathode materials in all-solid-state secondary batteries, as well as chemical and electrochemical instability are solved. Experimental results show that the above-mentioned solid electrolyte of the present invention has excellent ionic conductivity, a wide electrochemical stability window, and good chemical and electrochemical compatibility with layered oxides, Prussian blue and polyanion cathode materials. The sodium ion secondary battery of the present invention containing the above-mentioned solid electrolyte can achieve long-term stable circulation at room temperature.

[0014] The present invention also discloses a sodium secondary battery, comprising a positive electrode (layer), a negative electrode (layer), and an electrolyte layer between the positive electrode (layer) and the negative electrode (layer); at least one of the positive electrode (layer), the negative electrode (layer) and the electrolyte layer contains one of the solid electrolyte materials.

[0015] The present invention is described in more detail as follows:

[0016] First embodiment:

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

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

[0019] Na x M y O z X (x+4y-2z) Or Na x My O z X (x+5y-2z)（1） Composed of formula (1)

[0020] It includes elements Na, M, O, X; where M is selected from one or more combinations of Ta, Nb, Hf, Zr; X is one or more combinations of F, Cl, Br, I; x, y, z satisfy 0 < x < 10, 0 < y < 10, 0 < z < 10. The solid electrolyte material shown by (1) has a high sodium ion conductivity.

[0021] Furthermore, in order to achieve a wide electrochemical stability window, in formula (1), X is preferably Cl, and at this time the solid electrolyte (1) can be written as Na x M y O z Cl (x+4y-2z) or Na x M y O z Cl (x+5y-2z)

[0022] Furthermore, in order to improve the electrochemical stability window of the solid electrolyte, in formula (1), M is preferably Zr or Hf.

[0023] Furthermore, in order to improve the ionic conductivity of the solid electrolyte, in formula (1), M is preferably Ta or Nb.

[0024] Furthermore, in formula (1), when x = 2, y = 1, z = 1 are satisfied, the obtained electrolyte material has a relatively high ionic conductivity.

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

[0026] In the first embodiment, the size and shape of the obtained electrolyte material are not limited. Preferably, the particle size is above 0.1 µm and below 20 µm.

[0027] The solid electrolyte obtained in the above embodiment can be carried out according to the following steps:

[0028] (1) Place the precursors MCl4 (or MCl5) and Na2O2 in a ball milling jar made of ZrO2 according to the target formula. Taking Na2HfOCl4 as an example, HfCl4 and Na2O2 can be mixed and added to the ball milling jar according to the stoichiometric ratio of 1:1. The assembly of the precursors is carried out in a glove box filled with inert gas, and the water content in the glove box is less than 1 ppm and the oxygen content is less than 1 ppm.

[0029] (2) The ball mill jar assembled in step (1) is evacuated or filled with inert gas for protection, and then placed on a planetary ball mill for ball milling to prepare the solid electrolyte. The rotation speed of the solid phase ball mill is 300-800 rpm, and the ball milling time is 10 hours.

[0030] The electrolyte described in the first embodiment can be obtained using the above method.

[0031] Second embodiment

[0032] A sodium battery comprises a positive electrode, a negative electrode, and an electrolyte (liquid) layer between the positive electrode and the negative electrode. At least one of the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte material described in the first embodiment.

[0033] The electrolyte layer is between the positive and negative electrodes.

[0034] The positive electrode contains positive electrode active material particles and electrolyte particles.

[0035] The negative electrode contains negative electrode active material particles and electrolyte particles.

[0036] Positive electrode active materials refer to materials that can absorb and release metal ions, such as layered metal oxides, Prussian blue, and polyanion materials.

[0037] The negative electrode active material refers to a material that can absorb and release metal ions, such as metal materials, carbon materials, nitrogen materials, etc. The metal material can be a single metal or an alloy. For example, sodium metal or Na 15 Sn4 alloy.

[0038] To ensure electrochemical / electrochemical cycling stability and ionic conductivity, at least one of the positive electrode, negative electrode, and electrolyte layer of the sodium battery may contain one or more additional electrolyte (liquid) materials. The additional electrolyte material is not critical and may include oxide solid electrolytes, sulfide solid electrolytes, halide solid electrolytes, polymer electrolytes, and electrolyte solutions.

[0039] To ensure electrochemical stability during battery cycling, the positive or negative active materials can be modified. For example, inorganic or organic protective layers can be prepared using solution deposition or molecular layer / atomic layer deposition techniques to modify the surface and interface of the active materials.

[0040] The present invention mainly solves the current problem of lack of excellent sodium-based solid electrolytes. Through a series of studies, a class of sodium ion superionic conductors that combine the advantages of oxide-, sulfide- and halide-based solid electrolytes is invented; the focus is on the ionic conductivity, electrochemical stability window and electrochemical compatibility of the solid electrolyte with various positive electrodes. The main difficulty lies in the optimization of the solid electrolyte performance and the assembly of all-solid-state batteries.

[0041] The beneficial effects of a class of solid electrolyte materials and applications disclosed in the present invention are:

[0042] (1) The solid electrolyte material of the present invention has high ionic conductivity and a wide operating temperature range.

[0043] (2) The solid electrolyte material of the present invention has a wide electrochemical stability window.

[0044] (3) The solid electrolyte material of the present invention is compatible with a variety of positive electrode materials.

[0045] (4) The solid electrolyte material provided by the present invention has a low Young's modulus and can form a good interface contact with the positive electrode material under a certain pressure, thereby promoting the rapid conduction of sodium ions between the interfaces;

[0046] (5) The all-solid electrolyte material of the present invention can be used as a separator material for sodium secondary batteries and has high safety and strong stability at room temperature / high temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Impedance diagram of the solid electrolyte prepared in Example 1 of the present invention at 25°C;

[0048] Figure 2 X-ray diffraction patterns of the solid electrolytes prepared in Examples 1-3 of the present invention;

[0049] Figure 3 X-ray diffraction patterns of the solid electrolytes prepared in Examples 4-6 of the present invention;

[0050] Figure 4 Initial charge and discharge curves of an all-solid-state battery assembled with a solid electrolyte and a layered cathode material prepared in Example 1 of the present invention in the voltage range of 2-4 V vs Na + / Na;

[0051] Figure 5 Initial charge and discharge curves of an all-solid-state battery assembled with the solid electrolyte prepared in Example 5 of the present invention and the sodium vanadium phosphate positive electrode material in the voltage range of 2.7-3.7VvsNa+ / Na. DETAILED DESCRIPTION

[0052] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0053] Example 1

[0054] Solid electrolyte preparation: Na₂O₂:HfCl₄ was mixed in a 1:1 molar ratio in a glove box with water and oxygen concentrations below 0.1 ppm. Approximately 1 g of the mixed precursor was transferred to a ZrO₂ ball mill. The ball mill was then evacuated, sealed, and milled at 450 rpm in a high-energy ball mill. This yielded Sample 1, an amorphous solid electrolyte powder composed of Na, Hf, O, and Cl.

[0055] Battery assembly for ionic conductivity testing: In a glove box with water and oxygen contents below 0.1 ppm, the powder of the solid electrolyte material of Example 1 was loaded into a conventional mold battery 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. The ionic conductivity at 25°C was 0.52 mS cm -1 .

[0056] X-ray diffraction test: The solid electrolyte is sealed in an inert atmosphere and the X-ray diffraction pattern of the solid electrolyte is tested at 10°-60° under an X-ray source of Cu-Kα ray ( Figure 2 ).

[0057] Example 2

[0058] Sample 2 was prepared using the same method as Sample 1 with a Na2O2:HfCl4 molar ratio of 1:0.8. The ion conductance and X-ray diffraction pattern of Sample 2 were measured using the same method as Sample 1. The ion conductance of Sample 2 at room temperature was 0.34 mS cm -1 .

[0059] Example 3

[0060] Sample 3 was prepared using the same method as Sample 1 with a Na2O2:HfCl4 molar ratio of 1:1.2. The ion conductance and X-ray diffraction pattern of Sample 3 were measured using the same method as Sample 1. The ion conductance of Sample 3 at room temperature was 0.14 mS cm -1 .

[0061] Example 4

[0062] Sample 4 was prepared in the same manner as Sample 1 with a molar ratio of Na2O:HfCl4 of 1:1. The ion conductance and X-ray diffraction pattern of Sample 4 were measured in the same manner as Sample 1. The ion conductance of Sample 4 at room temperature was 0.5 mS cm -1 .

[0063] Example 5

[0064] Sample 5 was prepared in the same manner as Sample 1 with a molar ratio of Na2O2:TaCl5 of 1:1. The ion conductance and X-ray diffraction pattern of Sample 5 were measured in the same manner as Sample 1. The ion conductance of Sample 5 at room temperature was 2 mS cm -1 .

[0065] Example 6

[0066] Sample 6 was prepared using the same method as Sample 1 with a molar ratio of Na2O2:TaCl5:HfCl4 of 1:0.5:0.5. The ion conductivity, X-ray diffraction, and morphology of Sample 6 were measured using the same methods as Sample 1. The ion conductivity of Sample 5 at room temperature was 1.2 mS cm -1 .

[0067] Example 7

[0068] Sample 7 was prepared in the same manner as Sample 1 with a molar ratio of Na2O2:TaCl5:AlCl3 of 1:0.5:0.5. The ion conductivity of Sample 7 was tested in the same manner as Sample 1. The ion conductivity of Sample 7 at room temperature was 1.12 mS cm -1 .

[0069] Example 8

[0070] Sample 8 was prepared in the same manner as Sample 1 with a molar ratio of Na2O2:TaF5 of 1:1. The ion conductivity of Sample 8 was tested in the same manner as Sample 1. The ion conductivity of Sample 8 at room temperature was 1.68 mS cm -1 .

[0071] Application Example 1

[0072] 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 positive electrode materials are used in room temperature all-solid-state sodium ion batteries.

[0073] In a glove box with water and oxygen contents below 0.1 ppm, the solid electrolyte material of sample 1 and Na as the positive electrode active material were mixed. 0.85 Mn 0.5 Ni 0.4 Fe 0.1O2 was mixed in a volume ratio of 40:60, and the mixing method was manual grinding for 5 minutes. The ground sample was the positive electrode powder of the secondary battery. 100 mg of sample 1 solid electrolyte and 10 mg of positive electrode mixture were stacked in sequence to obtain a stacked body. A pressure of 300 MPa was applied to form a solid electrolyte and a positive electrode layer. Then, 200 microns of Na-Sn alloy was stacked on the other side of the solid electrolyte to obtain a stacked body, which was then assembled into a mold battery for electrochemical performance testing. The solid-state battery was subjected to electrochemical charge and discharge tests at room temperature, and the charge and discharge cut-off voltage was 2.0-4.0 V (vs. Na / Na + ), the charge and discharge current density is 0.1C (1C = 140 mA g-1).

[0074] Application Example 2

[0075] The amorphous glassy solid electrolyte prepared in Example 5 is combined with Na3V2(PO4)3 positive electrode material for application in room temperature all-solid-state sodium ion batteries.

[0076] Similar to Application Example 1, the solid electrolyte obtained in Example 5 was used as the positive electrode electrolyte and the electrolyte layer near the positive electrode, respectively. Unmodified Na3V2(PO4)3 was used as the positive electrode material. The solid-state battery was subjected to electrochemical charge and discharge tests at room temperature. The charge and discharge cut-off voltage was 2.7-3.7V (vs. Na / Na + ), with a charge and discharge current density of 0.1C (1C = 117.6 mA g-1). The high Coulombic efficiency and reversibility of the sodium all-solid-state battery demonstrate the compatibility of the solid-state electrolyte and sodium vanadium phosphate. Its excellent electrochemical performance is conducive to promoting and realizing the commercial application of all-solid-state sodium-ion batteries.

Claims

1. A class of solid electrolyte materials, the composition of which is represented as: Na x M y The z X (x+4y-2z) Or Na x M y The z X (x+5y-2z) It includes elements Na, M, O, and X; where M is selected from one or more combinations of Ta, Nb, Hf, and Zr; X is one or more combinations of F, Cl, Br, and I; x, y, z satisfy 0 < x < 10, 0 < y < 10, 0 < z < 10; the source of O element is selected from one or more substances of oxygen-containing sodium salts, metal oxides, and oxygen-containing metal compounds; the source of X halogen is selected from one or more substances of sodium salts containing X halogen, metal halides, and metal compounds containing halogen.

2. The solid electrolyte material according to claim 1, wherein M is selected from one or two combinations of Ta and Hf.

3. The solid electrolyte material according to any one of claims 1-2, X can be Cl.

4. The solid electrolyte material according to any one of claims 1-2, wherein 0 < x ≤ 2 is satisfied.

5. The solid electrolyte material according to any one of claims 1-2, wherein z = 1 is satisfied.

6. The solid electrolyte material according to any one of claims 1 to 2, characterized in that The solid electrolyte material is a crystalline phase, a crystalline-amorphous phase, or an amorphous phase.

7. The solid electrolyte material according to any one of claims 1-2, the oxygen used to prepare the solid electrolyte is selected from one or several substances of metal oxides or oxygen-containing sodium salts Na2O, Na2O2, NaOH, Na2CO3, NaHCO3; the metal halides and metal compounds containing halogen are selected from one or several substances of NaCl, MCl4, MCl5, MOCl4, MOCl3; M is selected from one or more combinations of Ta, Nb, Hf, and Zr.

8. The solid electrolyte material according to any one of claims 1-2 is subjected to cation doping, anion doping, or dual ion doping of cations and anions to obtain a doped solid electrolyte, and its ionic conductivity and electrochemical window are further optimized; the cations are selected from one or several elements of V, Ti, Sn, Sc, W, Y, Lu, Fe, As, Cr, Al, Ga, In, P, Sb, Mg, Ca, Sr, Ba, Si, Ge, La, Sm, Tb, Ho, Dy, Gd, or Er; the anions are selected from one or several elements of F, Cl, Br, I, N, S, or Se.

9. Application of the solid electrolyte material according to any one of claims 1-八 in improving sodium ion electrolyte conductivity, electrochemical stability, and compatibility with electrode materials.

10. A sodium secondary battery, including a positive electrode layer, a negative electrode layer, and an electrolyte layer between the positive electrode layer and the negative electrode layer; at least one of the positive electrode layer, the negative electrode layer, and the electrolyte layer contains the solid electrolyte material according to any one of claims 1-八.

Images