Sodium ion halide solid electrolyte, preparation method thereof and uses thereof

Abstract

The present invention discloses a sodium ion halide solid electrolyte, a preparation method and a use thereof. The chemical composition of the sodium ion halide solid electrolyte is Na z La 4 / 3‑x‑y A x B y X4, wherein A is a low-valence metal element with a valence < 3 or a vacancy, and the low-valence metal element is selected from one of Na, K, and Ca; B is a high-valence transition metal element with a valence ≥ 3, and the high-valence transition metal element is selected from one of Y, In, Sc, Zr, Er, Ti, and Hf; X is selected from at least one of Cl and Br; 0 < z ≤ 1, 0 < x, y < 4 / 3, x + y < 4 / 3 and charge balance is satisfied. It is a one-dimensional ion conductor, and the space group structure is P63 / m, and sodium ions can migrate along the c-axis direction. This sodium ion halide solid electrolyte has extremely high ionic conductivity (up to 10 ‑4 S·cm ‑1 ), thereby effectively improving the application of the halide solid electrolyte in all-solid-state sodium metal batteries and improving the performance of all-solid-state sodium metal batteries. In addition, its preparation method is simple and has a low preparation cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state sodium metal batteries, and specifically relates to a sodium ion halide solid electrolyte and a preparation method thereof, and also relates to the use of the sodium ion halide solid electrolyte in a solid-state sodium metal battery. Background Art

[0002] A all-solid-state battery is a secondary battery that uses a solid-state electrolyte (SSE) instead of a liquid electrolyte. Due to its high safety, compatibility with cathode materials with higher voltages and anode materials with lower voltages, and higher energy density, it gradually replaces secondary batteries using traditional organic electrolytes. Among all-solid-state batteries, due to the abundant and widespread distribution of sodium resources, all-solid-state sodium metal batteries have lower costs than all-solid-state lithium metal batteries and are more cost-effective in large-scale energy storage applications.

[0003] Existing research has shown that some sodium ion oxide, sulfide, and borohydride materials exhibit high ionic conductivities and are considered promising sodium ion solid electrolyte materials. Among them, sulfides have the highest ionic conductivities (such as Na3PS4, Na3SbS4, etc., with ionic conductivities in the range of 0.1 - 10 mS·cm -1 ), approaching or even exceeding those of organic liquid electrolytes. However, their chemical and electrochemical stabilities are poor, and the capacity of the battery decays rapidly when paired with high-voltage cathodes or sodium metal anodes; while oxide solid electrolytes such as Na3Zr2Si2PO 12 etc. are relatively hard and not easily deformed, resulting in poor physical contact with electrode materials, severely hindering the transport of sodium ions at the interface, and thus deteriorating the battery performance.

[0004] Halide solid electrolytes have made breakthrough progress in lithium-ion batteries due to their high-voltage stability and advantages in interfacial compatibility with electrode materials. For example, the Asano research team reported two halide SSEs prepared by mechanochemical methods, namely Li3YCl6 with a hexagonal close-packed (hcp) structure and Li3YBr6 with a cubic close-packed (ccp) structure, which can reach high ionic conductivities of 0.51 and 1 mS·cm -1 at room temperature. In addition, there are also reports on isovalent substitution using Zr 4+ to synthesize the halide Li 3-x M 1-x Zr x Cl6 (M = Er, Y), whose room-temperature ionic conductivity is increased to 10 -3 S·cm -1 by introducing vacancies. The high-voltage stability of sodium ion halide solid electrolytes is relatively good (>3.7 V vs. Na / Na +) and is relatively soft in texture, and can make good contact with the electrode material under a certain pressure, with a low interfacial impedance; however, in sodium-ion batteries, due to the relatively large ionic size of sodium ions, the room-temperature ionic conductivity in halides is not high, which limits its application in all-solid-state sodium-ion batteries. Currently, the highest ionic conductivity reported in the literature is 6.6×10 -5 S·cm -1 (Na 2.25 Y 0.25 Zr 0.75 Cl6), which still has a large gap compared with the solid electrolytes of lithium-ion batteries and limits its application in all-solid-state sodium-ion batteries.

[0005] The present invention is committed to elucidating a sodium-ion halide solid electrolyte with high ionic conductivity and low preparation cost. Summary of the Invention

[0006] In view of this, it is necessary for the present invention to provide a sodium-ion halide solid electrolyte, which has a one-dimensional conductor structure, sodium ions are continuously arranged along the c-axis, and the distance between different sodium-ion sites is short, which is conducive to the migration of sodium ions, has high ionic conductivity, and can improve the performance of all-solid-state sodium metal batteries.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a sodium-ion halide solid electrolyte, the chemical composition of which is Na z La 4 / 3-x-y A x B y X4, wherein A is a low-valence metal element with a valence < 3 or a vacancy, and the low-valence metal element is selected from one of Na, K, and Ca; B is a high-valence transition metal element with a valence ≥ 3, and the high-valence transition metal element is selected from one of Y, In, Sc, Zr, Er, Ti, and Hf; X is selected from at least one of Cl and Br; 0 < z ≤ 1, 0 < x, y < 4 / 3, x + y < 4 / 3 and satisfies charge balance;

[0009] The sodium-ion halide solid electrolyte is a one-dimensional ion conductor, and the space group structure is P63 / m, and sodium ions can migrate along the c-axis direction.

[0010] In a further aspect, its chemical composition is Na 0.7 La 0.7 Zr 0.3 Cl4.

[0011] The present invention further provides a preparation method of the sodium-ion halide solid electrolyte as described above, including the following steps:

[0012] Take the halides of metals Na, La, A, and B according to the stoichiometric ratio and synthesize a sodium-ion halide solid electrolyte by a mechanochemical method.

[0013] In a further embodiment, the mechanochemical method includes a high-energy ball milling step, where the rotation speed of the high-energy ball milling is not less than 500 rpm and the time is not less than 8 h;

[0014] Preferably, the rotation speed of the high-energy ball milling is 500 - 600 rpm and the time is 8 - 12 h;

[0015] Preferably, the rotation speed of the high-energy ball milling is 550 rpm and the time is 10 h.

[0016] In a further embodiment, in a typical embodiment of the present invention, the preparation method includes the following steps:

[0017] In an inert atmosphere, mix the halides of metals Na, La, A, and B according to the stoichiometric ratio and then perform high-energy ball milling to obtain a sodium-ion halide solid electrolyte.

[0018] In a further embodiment, in another typical embodiment of the present invention, the preparation method includes the following steps:

[0019] In an inert atmosphere, mix the halides of metals Na, La, A, and B according to the stoichiometric ratio and then perform high-energy ball milling to obtain a precursor;

[0020] In an inert atmosphere, sinter the precursor to obtain a sodium-ion halide solid electrolyte.

[0021] In a further embodiment, the heating rate of the sintering is 1 - 10 °C / min, the temperature is 350 °C - 550 °C, and the holding time is 2 h - 12 h.

[0022] In a further embodiment, in another typical embodiment of the present invention, the preparation method includes the following steps:

[0023] In an inert atmosphere, mix the halides of metals Na, La, A, and B according to the stoichiometric ratio and then perform high-energy ball milling to obtain a precursor;

[0024] In an inert atmosphere, after sintering the precursor, perform secondary high-energy ball milling to obtain a sodium-ion halide solid electrolyte;

[0025] Preferably, the heating rate of the sintering is 1 - 5 °C / min, the sintering temperature is 200 °C - 550 °C, and the holding time is 2 h - 10 h;

[0026] Preferably, the rotation speed of the secondary high-energy ball milling is 500 - 600 rpm and the time is 1 - 12 h.

[0027] The present invention further provides an application of the sodium ion halide solid electrolyte as described above in the preparation of sodium ion batteries.

[0028] The present invention further provides a all-solid-state sodium ion battery, which includes a solid electrolyte, and the solid electrolyte is the aforementioned sodium ion halide solid electrolyte or the sodium ion halide solid electrolyte prepared by the aforementioned preparation method.

[0029] The beneficial effects of the present invention are as follows:

[0030] The sodium ion halide solid electrolyte in the present invention has a one-dimensional conductor structure, with a space group of P63 / m, and it has extremely high ionic conductivity (up to 10 -4 S·cm -1 ), thereby being able to effectively improve the application of the halide solid electrolyte in all-solid-state sodium metal batteries and enhancing the performance of all-solid-state sodium metal batteries.

[0031] The preparation method of the sodium ion halide solid electrolyte is simple, and it can be prepared by a conventional mechanochemical method, with a relatively low preparation cost. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the sodium ion halide solid electrolyte NaLaCl4 in a typical embodiment of the present invention;

[0033] Figure 2 It is the XRD pattern of the sodium ion halide solid electrolytes NaLaCl4 and Na 0.7 La 0.7 Zr 0.3 Cl4 in a typical embodiment of the present invention;

[0034] Figure 3 It is the AC impedance spectra of the sodium ion halide solid electrolytes Na 0.7 La 0.7 Zr 0.3 Cl4 and Na 0.6 La 0.6 Zr 0.4 Cl4 in Examples 5 and 6 of the present invention;

[0035] Figure 4 It is a schematic diagram of the NLZC+NVP / NLZC+NPS / Na-Sn all-solid-state battery assembled with the sodium ion halide solid electrolyte in Example 5;

[0036] Figure 5 It is the cyclic performance test result of the NLZC+NVP / NLZC+NPS / Na-Sn all-solid-state battery assembled with the sodium ion halide solid electrolyte in Example 5. Detailed implementation manners

[0037] The embodiments of the present invention will be described in detail below. The following described embodiments are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific implementation manners and are not intended to limit the present invention.

[0039] The first aspect of the present invention discloses a sodium halide solid electrolyte, and its chemical composition is Na z La 4 / 3-x- y A x B y X4, wherein A is a low-valence metal element with a valence < 3 or a vacancy, and the low-valence metal element is selected from one of Na, K, and Ca; B is a high-valence transition metal element with a valence ≥ 3, and the high-valence transition metal element is selected from one of Y, In, Sc, Zr, Er, Ti, and Hf; X is selected from at least one of Cl and Br; 0 < z ≤ 1, 0 < x, y < 4 / 3, x + y < 4 / 3 and charge balance is satisfied. This sodium halide solid electrolyte has a high ionic conductivity at room temperature (up to 10 - 4 S·cm -1 ), so that when it is applied to a solid sodium-ion battery, it can effectively improve the performance of the solid sodium-ion battery.

[0040] Specifically, the sodium halide solid electrolyte described herein is a one-dimensional ion conductor, and the space group structure is P63 / m, and sodium ions can migrate along the c-axis direction.

[0041] In a typical embodiment of the present invention, A is a vacancy, X is Cl, y = 0, x = 1 / 3, z = 1. At this time, the composition of the sodium halide solid electrolyte is NaLaCl4, and its structure is as shown in Figure 1 . It can be seen that the structure of NaLaCl4 is a one-dimensional conductor, sodium ions are arranged continuously along the c-axis, and the distance between different sodium ion sites is short, which is beneficial to the migration of sodium ions. Among them, Na ions do not completely occupy the sites, and there are a large number of vacancies, which is more conducive to the migration and transmission of sodium ions and improves the ionic conductivity.

[0042] In another typical embodiment of the present invention, A is a vacancy, B is Zr, X is Cl, x = 1 / 3, 0.3 ≤ y ≤ 1, z = 1 - y. At this time, the composition of the sodium ion halide solid electrolyte is Na z La 1-y Zr y Cl4, Figure 2 The X-ray diffraction pattern (XRD) of one specific sodium ion halide solid electrolyte is shown in Figure 2 Among them, NLZC0.3 is Na 0.7 La 0.7 Zr 0.3 Cl4, NLC is NaLaCl4. It can be seen from Figure 2 that the crystal structures of NLZC0.3 and NLC are basically the same. The introduction of Zr ions does not change the structure of this solid electrolyte, which is still a one-dimensional conductor and also has high ionic conductivity.

[0043] Preferably, the chemical composition of the sodium ion halide solid electrolyte described herein is Na 0.7 La 0.7 Zr 0.3 Cl4.

[0044] The second aspect of the present invention discloses a preparation method of a sodium ion halide solid electrolyte as described in the first aspect of the present invention, including the following steps:

[0045] Take the halides of metals Na, La, A, and B according to the stoichiometric ratio and synthesize the sodium ion halide solid electrolyte by mechanochemical method.

[0046] Specifically, according to the chemical composition of the sodium ion halide solid electrolyte to be prepared, take the halides of metals Na, La, A, and B according to the stoichiometric ratio of its chemical composition, and then synthesize the sodium ion halide solid electrolyte by mechanochemical method.

[0047] The mechanochemical method at least includes the step of high-energy ball milling, wherein the rotation speed of the high-energy ball milling is not less than 500 rpm and the time is not less than 8 h; preferably, the rotation speed of the high-energy ball milling is 500 - 600 rpm and the time is 8 - 12 h; more preferably, the rotation speed of the high-energy ball milling is 550 rpm and the time is 10 h.

[0048] There are three synthesis methods of the sodium ion halide solid electrolyte herein. Each synthesis method will be described below one by one.

[0049] In a typical embodiment of the present invention, a preparation method of a sodium ion halide solid electrolyte (denoted as Method 1 herein) is disclosed, and the specific steps are as follows:

[0050] In an inert atmosphere, the metal Na, La, A, and B halides are mixed according to the stoichiometric ratio and then subjected to high-energy ball milling to obtain a sodium-ion halide solid electrolyte.

[0051] Another typical embodiment of the present invention discloses a method for preparing a sodium-ion halide solid electrolyte (denoted as Method 2 herein), and the specific steps are as follows:

[0052] In an inert atmosphere, the metal Na, La, A, and B halides are mixed according to the stoichiometric ratio and then subjected to high-energy ball milling. After obtaining a precursor, the precursor is sintered in an inert atmosphere to obtain a sodium-ion halide solid electrolyte.

[0053] Among them, the sintering parameters can be adjusted according to the actual situation. Preferably, the heating rate is 1 - 10 °C / min, the sintering temperature is 350 °C - 550 °C, and the holding time is 2 h - 12 h; more preferably, it is heated to 400 °C at a rate of 5 °C / min and annealed for 2 h.

[0054] Another typical embodiment of the present invention discloses a method for preparing a sodium-ion halide solid electrolyte (denoted as Method 3 in the text), and the specific steps are as follows:

[0055] In an inert atmosphere, the metal Na, La, A, and B halides are mixed according to the stoichiometric ratio and then subjected to high-energy ball milling to obtain a precursor;

[0056] In an inert atmosphere, after sintering the precursor, it is subjected to secondary high-energy ball milling to adjust the structure to obtain a sodium-ion halide solid electrolyte.

[0057] Among them, the sintering parameters can be adjusted according to the actual situation. Preferably, the heating rate is 1 - 5 °C / min, the sintering temperature is 200 °C - 550 °C, and the holding time is 2 - 10 h; more preferably, it is heated to 400 °C at a rate of 5 °C / min and annealed for 5 h. Preferably, the rotation speed of the secondary high-energy ball milling is 500 rpm - 600 rpm, and the time is 1 h - 12 h. More preferably, it is ball milled at a rotation speed of 550 rpm for 10 h.

[0058] It can be understood that in the above preparation methods, the "inert atmosphere" has the same meaning, which refers to at least one of noble gases (i.e., Group 0 element gases such as helium, argon, etc.) or nitrogen, and can be selected according to the needs of those skilled in the art, so it will not be specifically elaborated here.

[0059] The third aspect of the present invention discloses the application of the sodium-ion halide solid electrolyte as described in the first aspect of the present invention in the preparation of sodium-ion batteries.

[0060] The fourth aspect of the present invention discloses an all-solid-state sodium-ion battery, which includes a solid electrolyte. It is characterized in that the solid electrolyte is the sodium halide solid electrolyte described in the first aspect of the present invention or the sodium halide solid electrolyte prepared by using the preparation method described in the second aspect of the present invention. It can be understood that the all-solid-state sodium-ion battery further includes a positive electrode, a negative electrode, etc., all of which can adopt conventional sodium-ion battery materials in the art, so they will not be specifically elaborated here. Since the sodium halide solid electrolyte in this article has excellent ionic conductivity, the all-solid-state sodium-ion battery assembled therefrom has excellent cycle performance and rate performance.

[0061] The present invention will be described below through specific examples. It should be noted that the following specific examples are only for illustrative purposes and do not limit the scope of the present invention in any way. In addition, unless otherwise specified, the methods without specific recorded conditions or steps are all conventional methods, and the reagents and materials used can be obtained from commercial channels.

[0062] Example 1 Preparation of NaLaCl4 (Method 1)

[0063] In an argon atmosphere, sodium chloride (NaCl) and lanthanum chloride (LaCl3) were mixed at a molar ratio of 1:1 respectively, and then sealed in a zirconia (ZrO2) ball mill jar. Ball milling was carried out in a planetary ball mill at a speed of 550 rpm for 8 h to obtain a NaLaCl4 sample.

[0064] Example 2 0.4 La 0.6 In 0.6 Preparation of Cl4 (Method 2)

[0065] In an argon atmosphere, sodium chloride (NaCl), lanthanum chloride (LaCl3) and indium chloride (InCl3) were mixed at a molar ratio of 2:3:3 respectively, and then sealed in a zirconia (ZrO2) ball mill jar. Ball milling was carried out in a planetary ball mill at a speed of 550 rpm for 10 h to obtain a 0.4 La 0.6 In 0.6 Cl4 precursor;

[0066] In an argon atmosphere, the 0.4 La 0.6 In 0.6 Cl4 precursor was loaded into a tube furnace and heated to 400 °C at a rate of 5 °C / min, and annealed for 2 h to obtain a 0.4 La 0.6 In 0.6 Cl4 sample.

[0067] Example 3 0.7 La0.7 Zr 0.3 Preparation of ZrCl4 (Method 1)

[0068] In an argon atmosphere, sodium chloride (NaCl), lanthanum chloride (LaCl3), and zirconium chloride (ZrCl4) were mixed in a molar ratio of 7:7:3 respectively, and then sealed in a zirconia (ZrO2) ball milling jar. Ball milling was carried out in a planetary ball mill at a speed of 500 rpm for 8 h to obtain a sample of Na 0.7 La 0.7 Zr 0.3 Cl4

[0069] Example 4 Na 0.7 La 0.7 Zr 0.3 Preparation of ZrCl4 (Method 2)

[0070] In an argon atmosphere, sodium chloride (NaCl), lanthanum chloride (LaCl3), and zirconium chloride (ZrCl4) were mixed in a molar ratio of 7:7:3 respectively, and then sealed in a zirconia (ZrO2) ball milling jar. Ball milling was carried out in a planetary ball mill at a speed of 550 rpm for 9 h to obtain a Na 0.7 La 0.7 Zr 0.3 Cl4 precursor;

[0071] In an argon atmosphere, the Na 0.7 La 0.7 Zr 0.3 Cl4 precursor was loaded into a tube furnace and heated to 400 °C at a rate of 5 °C / min. After annealing for 2 h, a sample of Na 0.7 La 0.7 Zr 0.3 Cl4 was obtained.

[0072] Example 5 Na 0.7 La 0.7 Zr 0.3 Preparation of ZrCl4 (Method 3)

[0073] In an argon atmosphere, sodium chloride (NaCl), lanthanum chloride (LaCl3), and zirconium chloride (ZrCl4) were mixed in a molar ratio of 7:7:3 respectively. After grinding in a planetary ball mill at a speed of 550 rpm for 10 h, a Na 0.7 La 0.7 Zr 0.3 Cl4 precursor was obtained;

[0074] In an argon atmosphere, the Na 0.7 La 0.7 Zr 0.3The Cl4 precursor was loaded into a tubular furnace and heated to 500 °C at a rate of 5 °C / min. After annealing for 2 h, the sintered sample was sealed in a zirconia (ZrO2) ball milling jar and ball milled in a planetary ball mill at a speed of 550 rpm for 10 h to obtain the Na 0.7 La 0.7 Zr 0.3 Cl4 sample.

[0075] Example 6 Na 0.6 La 0.6 Zr 0.4 Preparation of Cl4 (Method 3)

[0076] In an argon atmosphere, sodium chloride (NaCl), lanthanum chloride (LaCl3), and zirconium chloride (ZrCl4) were mixed in a molar ratio of 6:6:4, respectively, and then sealed in a zirconia (ZrO2) ball milling jar and ball milled in a planetary ball mill at a speed of 550 rpm for 12 h to obtain the Na 0.6 La 0.6 Zr 0.4 Cl4 precursor;

[0077] In an argon atmosphere, the Na 0.6 La 0.6 Zr 0.4 Cl4 precursor was loaded into a tubular furnace and heated to 400 °C at a rate of 5 °C / min. After annealing for 2 hours, the sintered sample was sealed in a zirconia ball milling jar and ball milled at 550 rpm for 5 h to obtain the Na 0.6 La 0.6 Zr 0.4 Cl4 sample.

[0078] Preparation of the comparative example Na3PS4

[0079] Sodium sulfide (Na2S) and phosphorus pentasulfide (P2S5) were sealed in a zirconia (ZrO2) ball milling jar in a molar ratio of 3:1 and ball milled in a planetary ball mill at a speed of 500 rpm for 10 h, and then annealed at 270 °C for 1 h to obtain the sulfide electrolyte Na3PS4.

[0080] Test example

[0081] 1. AC impedance spectroscopy (EIS) and activation energy test

[0082] The sodium-ion halide solid electrolytes in Examples 1-6 were respectively subjected to EIS and activation energy tests. The methods are as follows:

[0083] 200 mg of sodium halide solid electrolyte was pressed into tablets in a polytetrafluoroethylene mold with a diameter of 12 mm. After installing stainless steel current collectors at both ends, AC impedance spectroscopy (EIS) tests were carried out at different temperatures using the Donghua DH70001 electrochemical workstation. The test results are shown in Table 1 and Figure 3 as shown in

[0084] Table 1 Test results of EIS and activation energy

[0085] Sample Preparation method Ionic conductivity Activation energy Example 1 <![CDATA[NaLaCl4]]> Method 1 <![CDATA[3.47×10 -5 S·cm -1 > 0.42eV Example 2 <![CDATA[Sodium 0.4 Lanthanum 0.6 Indium 0.6 Chloride]]> Method 2 <![CDATA[1.37×10 -5 S·cm -1 > 0.43eV Example 3 <![CDATA[Sodium 0.7 Lanthanum 0.7 Zirconium 0.3 Chloride]]> Method 1 <![CDATA[4.48×10 -5 S·cm -1 > 0.34eV Example 4 <![CDATA[Sodium 0.7 Lanthanum 0.7 Zirconium 0.3 Chloride]]> Method 2 <![CDATA[4.13×10 -5 S·cm -1 > 0.38eV Example 5 <![CDATA[Sodium 0.7 Lanthanum 0.7 Zirconium 0.3 Cl4]]> Method 3 <![CDATA[2.90×10 -4 S·cm -1 > 0.33eV Example 6 <![CDATA[Sodium 0.6 Lanthanum 0.6 Zirconium 0.4 Cl4]]> Method 3 <![CDATA[1.00×10 -4 S·cm -1 > 0.35eV

[0086] From Table 1 and Figure 3 the test results in the AC impedance diagram, it can be seen that the Na 0.7 La 0.7 Zr 0.3 Cl4 sample prepared by Method 3 (secondary high-energy ball milling after sintering) in Example 5 can achieve a high ionic conductivity of about 2.90×10 -4 S cm -1 and has a minimum activation energy of 0.33 eV; the Na 0.6 La 0.6 Zr 0.4 Cl4 prepared by Method 3 in Example 6 has an ionic conductivity of up to 1.00×10 -4 S·cm -1 , and the activation energy is 0.35 eV.

[0087] 2. Assembly and testing of the full cell

[0088] After the sodium halide solid electrolyte Na 0.7 La 0.7 Zr 0.3 Cl4 prepared in Example 5 was made into the positive electrode material, the full cell was assembled, and the specific steps are as follows:

[0089] Preparation of the positive electrode: The positive electrode active material sodium vanadium phosphate (Na3V2(PO4)3), Na 0.7 La 0.7 Zr 0.3 Cl4 (NLZC) and the conductive agent SP were mixed in a mass ratio of 11:16:1, and then ball milled in a planetary ball mill at a speed of 200 rpm for 30 min using a stainless steel ball milling tank to obtain the positive electrode powder.

[0090] Preparation of the negative electrode: Metallic sodium and metallic tin were mixed in a molar ratio of 2:1 in a stainless steel ball milling tank and ball milled in a planetary ball mill at a speed of 300 rpm for 20 h to obtain a sodium-tin alloy.

[0091] Assembly of the full cell: Using sodium vanadium phosphate (NVP), Na 0.7 La0.7 Zr 0.3 A mixture of ZrCl4(NLZC) (Example 5) and conductive agent SP was used as the positive electrode, sodium-tin alloy as the negative electrode, and NLZC and Na3PS4 as the electrolyte. They were respectively pressed into tablets in a polytetrafluoroethylene mold with a diameter of 12 mm to form a full cell. The schematic diagram of the full cell is as shown in Figure 4 that shown in. The full cell was cycled at a rate of 0.1C, and the test results are shown in Figure 5 .

[0092] From Figure 5 the test results in, it can be seen that the novel halide electrolyte Na 1-x La 1-x Zr x Cl4 can be assembled with common positive electrode materials to form a full cell, and the cell also has excellent cycling performance and rate performance.

[0093] Other parallel embodiments

[0094] Preparation of Example 7 NaLaBr4

[0095] In an argon atmosphere, sodium bromide (NaBr) and lanthanum bromide (LaBr3) were mixed in a molar ratio of 1:1, and then sealed in a zirconia (ZrO2) ball milling jar. The mixture was ball milled in a planetary ball mill at a speed of 550 rpm for 8 h to obtain a NaLaBr4 precursor;

[0096] In an argon atmosphere, the NaLaBr4 precursor was loaded into a tube furnace and heated to 450 °C at a rate of 5 °C / min. After annealing for 2 h, the sintered sample was sealed in a zirconia ball milling jar and ball milled at 550 rpm for 5 h to obtain a NaLaBr4 sample.

[0097] Example 8 Preparation of Na 0.3 La 0.3 Hf 0.7 Cl4

[0098] In an argon atmosphere, NaCl, LaCl3, and HfCl4 were mixed in a molar ratio of 3:3:7, and then sealed in a zirconia (ZrO2) ball milling jar. The mixture was ball milled in a planetary ball mill at a speed of 500 rpm for 12 h to obtain a Na 0.3 La 0.3 Hf 0.7 Cl4 precursor;

[0099] In an argon atmosphere, the Na 0.3 La 0.3 Hf 0.7 Cl4 precursor was loaded into a tube furnace and heated to 350 °C at a rate of 1 °C / min. After annealing for 12 h, Na0.3 La 0.3 Hf 0.7 Cl4 sample.

[0100] Example 9 Na 0.5 La 1.1 Na 0.2 Preparation of Cl4

[0101] In an argon atmosphere, NaCl and LaCl3 were mixed at a molar ratio of 7:11 respectively, and then sealed in a zirconia (ZrO2) ball milling jar. Ball milling was carried out in a planetary ball mill at a speed of 600 rpm for 8 h to obtain Na 0.5 La 1.1 Na 0.2 Cl4 precursor;

[0102] In an argon atmosphere, Na 0.5 La 1.1 Na 0.2 Cl precursor was loaded into a tube furnace and heated to 550 °C at a rate of 5 °C / min. After annealing for 2 h, the sintered sample was sealed in a zirconia ball milling jar and ball milled at 600 rpm for 1 h to obtain Na 0.5 La 1.1 Na 0.2 Cl sample.

[0103] Example 10 NaLa 0.7 Sc 0.3 Preparation of Cl4

[0104] In an argon atmosphere, NaCl, LaCl3 and ScCl3 were mixed at a molar ratio of 10:7:3 respectively, and then sealed in a zirconia (ZrO2) ball milling jar. Ball milling was carried out in a planetary ball mill at a speed of 550 rpm for 10 h to obtain NaLa 0.7 Sc 0.3 Cl4 precursor;

[0105] In an argon atmosphere, NaLa 0.7 Sc 0.3 Cl4 precursor was loaded into a tube furnace and heated to 550 °C at a rate of 10 °C / min. After annealing for 2 h, NaLa 0.7 Sc 0.3 Cl4 sample was obtained.

[0106] Example 11 NaLa 0.7 Er 0.3 Preparation of Cl4

[0107] In an argon atmosphere, NaCl, LaCl3, and ErCl3 were mixed in a molar ratio of 10:7:3, and then sealed in a zirconia (ZrO2) ball milling jar. After ball milling for 10 h at a speed of 550 rpm in a planetary ball mill, a NaLa 0.7 Er 0.3 Cl4 precursor was obtained;

[0108] In an argon atmosphere, the NaLa 0.7 Er 0.3 Cl4 precursor was loaded into a tube furnace and heated to 200 °C at a rate of 1 °C / min. After annealing for 5 min, the sintered sample was sealed in a zirconia ball milling jar and ball milled for 10 h at 550 rpm to obtain NaLa 0.7 Er 0.3 Cl4 sample.

[0109] Example 12 Preparation of Na 0.5 La 0.7 Zr 0.3 K 0.2 Cl4

[0110] In an argon atmosphere, NaCl, LaCl3, ZrCl4, and KCl were mixed in a molar ratio of 5:7:3:2, and then sealed in a zirconia (ZrO2) ball milling jar. After ball milling for 10 h at a speed of 550 rpm in a planetary ball mill, a Na 0.5 La 0.7 Zr 0.3 K 0.2 Cl4 precursor was obtained;

[0111] In an argon atmosphere, the Na 0.5 La 0.7 Zr 0.3 K 0.2 Cl4 precursor was loaded into a tube furnace and heated to 300 °C at a rate of 5 °C / min. After annealing for 30 min, the sintered sample was sealed in a zirconia ball milling jar and ball milled for 10 h at 550 rpm to obtain Na 0.5 La 0.7 Zr 0.3 K 0.2 Cl4 sample.

[0112] The prepared sodium ion halide solid electrolyte was tested for its relevant ionic conductivity by the same method as in Examples 1-6. After testing, its ionic conductivity was between 10 -6 -10 -4 S·cm -1 . At the same time, a all-solid-state sodium ion battery was assembled by the same method as in Examples 1-6. After testing, it also had excellent cycling performance and rate performance.

[0113] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0114] The above-described embodiments only express several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be understood as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A sodium-ion halide solid electrolyte, characterized in that, Its chemical composition is Na z La 4 / 3-x-y A x B y X4, where A is a low-valence metal element with a valence < 3 or a vacancy, and the low-valence metal element is selected from one of Na, K, and Ca; B is a high-valence transition metal element with a valence ≥ 3, and the high-valence transition metal element is selected from one of Y, In, Sc, Zr, Er, Ti, and Hf; X is selected from at least one of Cl and Br; 0 < z ≤ 1, 0 < x, y < 4 / 3, x + y < 4 / 3 and satisfies charge balance; when A is a vacancy, x = 1 / 3; The sodium ion halide solid electrolyte is a one-dimensional ionic conductor with a space group structure of P63 / m, and sodium ions can migrate along the c-axis direction.

2. The sodium-ion halide solid electrolyte according to claim 1, characterized in that, Its chemical composition is Na 0.7 La 0.7 Zr 0.3 Cl4.

3. A preparation method of the sodium-ion halide solid electrolyte according to claim 1 or 2, characterized in that, It includes the following steps: Take the halides of metals Na, La, A, and B respectively according to the stoichiometric ratio and synthesize the sodium ion halide solid electrolyte by mechanochemical method; The mechanochemical method is as follows: In an inert atmosphere, mix the halides of metals Na, La, A, and B according to the stoichiometric ratio, and then perform high-energy ball milling to obtain a precursor; in an inert atmosphere, sinter the precursor and then perform secondary high-energy ball milling to prepare the sodium ion halide solid electrolyte.

4. The preparation method according to claim 3, characterized in that, The rotation speed of the high-energy ball milling is not less than 500 rpm, and the time is not less than 8 h.

5. The preparation method according to claim 4, characterized in that, The rotation speed of the high-energy ball milling is 500 - 600 rpm, and the time is 8 - 12 h.

6. The preparation method according to claim 5, characterized in that, The rotation speed of the high-energy ball milling is 550 rpm, and the time is 10 h.

7. The preparation method according to claim 3, characterized in that, The heating rate of the sintering is 1 - 5 °C / minute, the sintering temperature is 200 °C - 550 °C, and the holding time is 2 h - 10 h.

8. The preparation method according to claim 3, characterized in that, The rotation speed of the secondary high-energy ball milling is 500 - 600 rpm, and the time is 1 - 12 h.

9. Application of the sodium-ion halide solid electrolyte according to any one of claims 1 or 2 in the preparation of a sodium-ion battery.

10. A all-solid-state sodium-ion battery, which includes a solid electrolyte, characterized in that, The solid electrolyte is the sodium ion halide solid electrolyte described in Claim 1 or 2, or the sodium ion halide solid electrolyte prepared by using the preparation method described in any one of Claims 3 - 8.

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