NaCl type sodium ion solid electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a NaCl type sodium ion solid electrolyte and a preparation method and application thereof, the space group of the NaCl type sodium ion solid electrolyte is Fm3m, and the general chemical formula of the NaCl type sodium ion solid electrolyte is represented as NazAyCl1-xBx, wherein A is a divalent or more than divalent metal cation, and B is selected from at least one of O, S, F, Cl, Br and I; 0 < x < 1, 0 < z + y < = 1, and x, y, and z satisfy charge balance. The NaCl type sodium ion solid electrolyte has a wide electrochemical window, high ionic conductivity, high air stability and good compatibility with an electrode material, can be matched with a high-voltage positive electrode material and a sodium metal or alloy negative electrode, and is particularly suitable for realizing an all-solid-state battery with high energy density.

Description

Technical Field

[0001] This application belongs to the technical field of solid electrolytes, and specifically relates to an NaCl-type sodium ion solid electrolyte, its preparation method and application. Background Art

[0002] In secondary battery systems, traditional organic electrolytes have serious safety hazards due to their flammability. Therefore, solid state electrolytes (SSEs) have become a research hotspot due to their inherent safety. All-solid-state batteries can not only significantly improve safety, but also be compatible with high-voltage cathodes (such as layered oxides) and low-voltage metal anodes (such as sodium metal), thus breaking through the current energy density bottleneck of secondary batteries. In all-solid-state batteries, sodium resources, due to their rich reserves (2.83% in the earth's crust) and cost advantages (about 1 / 3 of lithium), make sodium ion all-solid-state batteries more promising for industrialization in large-scale energy storage.

[0003] Among current sodium ion solid electrolyte materials, sulfide solid electrolytes (such as Na3PS4, Na3SbS4, etc.) have high ionic conductivities (0.1 - 10 mS·cm-1), but their chemical / electrochemical stabilities are insufficient, and they are prone to side reactions with high-voltage cathodes, resulting in rapid capacity decay. Oxide solid electrolytes (such as Na3Zr2Si2PO 12 ) have excellent mechanical strength, but the rigid interface leads to a sharp increase in the electrode / electrolyte contact impedance, seriously hindering sodium ion transport.

[0004] In recent years, halide SSEs have attracted much attention due to their high-voltage stability and interface compatibility. For example: The team of Xueliang Sun developed a Na 0.75 Sm 1.75 Cl6 composite material through the synergistic effect of high / low coordination halide frameworks, with an ionic conductivity of 2.7 mS·cm -1 ; The team of Yongsheng Hu achieved an ionic conduction of 1.3×10 -3 S·cm -1 by doping O element into NaAlCl4; The team of Wei Luo designed a cubic structure Na 3-x Cr 1-x Zr x Cl6, with a room temperature conductivity of 10 -4 S·cm -1 .

[0005] However, there are many problems with existing halide SSEs: their stability with Na metal anodes is poor. A sulfide SSE interlayer (such as Na3PS4) usually needs to be added between the metal anode and the halide SSE in the assembled all-solid-state battery, which reduces the energy density of the all-solid-state battery and hinders the advantages of all-solid-state batteries from being fully realized. Moreover, there are potential interface stability issues between the sulfide SSE interlayer and the halide, increasing the additional interface impedance and reducing the performance of the all-solid-state battery. In addition, the oxidation potential of common halide SSEs is around 4.1 V, which cannot fully match high-voltage cathode materials, and the oxidation stability needs to be improved to increase the energy density of the battery. Furthermore, common halide solid electrolytes are unstable and prone to decomposition in air, and inert gas protection is required during use, which affects industrial applications. Summary of the Invention

[0006] In view of this, the primary object of this application is to provide a NaCl-type sodium-ion solid electrolyte, which is a halide SSE modified based on the NaCl structure. This halide SSE inherits the wide electrochemical window, high air stability, and good compatibility with electrode materials of NaCl to a certain extent, and on this basis, high ionic conductivity is achieved, which can match high-voltage cathode materials and use sodium metal or alloy anodes to realize all-solid-state sodium-metal batteries with high energy density.

[0007] To achieve the above object, this application adopts the following technical solutions:

[0008] One aspect of this application discloses a NaCl-type sodium-ion solid electrolyte. The space group of the NaCl-type sodium-ion solid electrolyte is Fm3m, and its chemical general formula is expressed as Na z A y Cl 1-x B x ;

[0009] wherein, A is a divalent or higher-valent metal cation, B is selected from at least one of O, S, F, Cl, Br, and I; 0 < x < 1, 0 < z + y ≤ 1, and x, y, and z satisfy charge balance.

[0010] Another aspect of this application discloses a preparation method of the NaCl-type sodium-ion solid electrolyte as described above, including the following steps:

[0011] Mix two or more precursors in an inert atmosphere according to the stoichiometric ratio to obtain a mixture;

[0012] Use mechanochemical synthesis to make the mixture undergo solid-phase chemical reactions to prepare the NaCl-type sodium-ion solid electrolyte.

[0013] Another aspect of the present application discloses the use of the NaCl-type sodium ion solid electrolyte as described above or the NaCl-type sodium ion solid electrolyte prepared by the preparation method as described above in the preparation of sodium ion batteries.

[0014] Another aspect of the present application discloses a all-solid-state sodium ion battery containing the NaCl-type sodium ion solid electrolyte as described above or the NaCl-type sodium ion solid electrolyte prepared by the preparation method as described above.

[0015] Advantages of the present application:

[0016] The sodium ion solid electrolyte in the present application is a halide SSE modified based on NaCl, and its space group structure is Fm3m. Sodium ions can be transported along the Na + vacancies at the 2b site, with a three-dimensional ion transport network; in this NaCl structure, by doping a heterovalent metal ion A at the 2b site, the concentration of Na + vacancies is increased, providing a path for ion transport; in addition, by doping an anion B, the average anion radius is regulated to make the structure more stable, while further improving its ionic conductivity and oxidation stability. The sodium ion halide solid electrolyte in the present application has extremely high ionic conductivity (up to 10 -3 S·cm -1 order of magnitude), a wider electrochemical window (0.05V - 4.6V vs. Na / Na + ), thus effectively improving the application of the halide solid electrolyte in all-solid-state sodium ion batteries, especially sodium metal batteries, and enhancing the performance of all-solid-state sodium metal batteries.

[0017] In addition, the NaCl-type sodium ion solid electrolyte in the present application can be prepared by a mechanochemical synthesis method, with the advantages of simple preparation method and low preparation cost. Description of the drawings

[0018] Figure 1 It is a schematic diagram of the spatial structure of the NaCl-type sodium ion solid electrolyte described in the present application.

[0019] Figure 2 It is the XRD pattern of the sample Na 0.25+x Al 0.25 Cl 1-x O x -HM in Example 7 of the present application.

[0020] Figure 3 It is the electrochemical window test result of the sample Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM in Example 7 of the present application.

[0021] Figure 4 For the sample Na in Example 2 of this application 0.6 Y 0.2 Cl 0.8 O 0.2 -BM, test results of the electrochemical window.

[0022] Figure 5 For the sample Na in Example 7 of this application 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM, XRD pattern after being placed in air ( Figure 5 a) and test results of the AC impedance spectrum ( Figure 5 b).

[0023] Figure 6 For the sample Na in Example 7 of this application 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM, test results of the full cell cycling performance.

[0024] Figure 7 For the sample Na in Example 9 of this application 0.6 Zr 0.2 Cl 0.6 O 0.4 -HM, test results of the full cell cycling performance. Detailed implementation manners

[0025] The embodiments of this application will be clearly and completely described below. The technical solutions in the following described embodiments are exemplary and are only possible technical implementations of this application, not all possible implementations. Those skilled in the art can fully combine the embodiments of this application and obtain other embodiments without creative work, and these embodiments are also within the protection scope of this application.

[0026] The first aspect of this application discloses an NaCl-type sodium-ion solid electrolyte, which has a specific space group and chemical general formula. Specifically, the space group of the NaCl-type sodium-ion solid electrolyte is Fm3m, and its chemical general formula is expressed as Na z A y Cl 1-x B x, wherein A is selected from high-valence (divalent or higher) metal cations, and specific examples include, but are not limited to, one of Ca, Mg, Ga, Y, Al, Fe, In, La, Ho, Yb, Ce, Sc, Zr, Er, Ti, Hf, Cr, Ta, Nd, Sm, Nb; B is selected from at least one of O, S, F, Cl, Br, I; 0 < x < 1, 0 < z + y ≤ 1 and x, y, z satisfy charge balance.

[0027] As is well known to those skilled in the art, the space group structure of NaCl is Fm3m, which is a typical cubic crystal structure. In this structure, sodium ions (Na + ) are located at specific positions in the lattice, forming an ordered ionic arrangement. Specifically, sodium ions can transport along the Na + vacancies at the 2b site, with a three-dimensional ionic transport network. This three-dimensional ionic transport network provides an effective path for the rapid transport of sodium ions. In this application, the specific spatial structure is schematically shown as Figure 1 shown in, by hetero-valent doping of metal ions A at the 2b site, thereby increasing the Na + vacancy concentration and providing a path for ionic transport; in addition, by doping with anion B, the average anion radius is regulated to make the structure more stable, while further improving its ionic conductivity and oxidation stability. This structural design and doping strategy can achieve efficient transport of Na ions in the solid-state electrolyte, achieving extremely high ionic conductivity (up to 10 -3 S·cm -1 order of magnitude). In addition, this structure also has a wider electrochemical window (0.05V - 4.6V vs. Na / Na + ), which makes it have better application prospects in all-solid-state sodium-ion batteries, especially all-solid-state sodium metal batteries, and can effectively improve the performance of all-solid-state sodium metal batteries.

[0028] In some examples, the NaCl-type sodium-ion solid electrolyte has excellent ionic conductivity and a wide electrochemical window. Specifically, the ionic conductivity of the NaCl-type sodium-ion solid electrolyte is 4.1×10 -5 ~5×10 -3 S·cm -1 , and the electrochemical window is 0.05V - 4.6V vs. Na / Na + . This characteristic of high ionic conductivity and wide electrochemical window enables this solid electrolyte to provide good ionic transport performance and stable electrochemical performance in all-solid-state sodium-ion batteries, which helps to improve the energy density and cycle life of all-solid-state sodium-ion batteries.

[0029] The second aspect of the present application discloses a method for preparing the above-mentioned NaCl-type sodium-ion solid electrolyte. The preparation method includes the following steps:

[0030] Mix two or more precursors in an inert atmosphere according to the stoichiometric ratio to obtain a mixture;

[0031] Use mechanochemical synthesis to cause the mixture to undergo a solid-phase reaction to prepare an NaCl-type sodium-ion solid electrolyte.

[0032] In the present application, the precursor refers to at least one of halides, hydroxides, oxides, and sulfides of Na and / or A. However, it should be noted that the precursor includes at least chlorides of Na and / or A. The specific selection of the precursor can be selected or adjusted based on actual needs, as long as the space group structure and composition of the finally prepared product meet the requirements of the present application.

[0033] In the present application, the mechanochemical synthesis method refers to a solvent-free and low-temperature solid-phase chemical reaction realized by mechanical energy. A more conventional approach is to place the reaction raw materials in a ball milling tank and mix and rub them with the ball milling medium, so that the reaction powder forms a new crystal structure or chemical reaction product under the action of mechanical force. This method has advantages such as fast reaction rate, clear chemical reaction pathway, sufficient crystallization, and less reaction waste. Therefore, the mechanochemical synthesis method adopted in the present application can effectively synthesize an NaCl-type sodium-ion solid electrolyte with high purity and good crystallinity, thereby ensuring its performance in sodium-ion batteries. In addition, this preparation method is simple and has a low preparation cost, which is beneficial to large-scale production and application.

[0034] In some examples of the present application, the mechanochemical synthesis method is high-energy ball milling (abbreviated as BM in this article). Specifically, the mixture is ball milled at a rotation speed of 300-800 rpm for 10-30 h.

[0035] In some other examples of the present application, the mechanochemical synthesis method is manual grinding combined with low-temperature heat treatment (abbreviated as HT in this article). Specifically, after the mixture is manually ground for 12-18 min, the ground powder is heat-treated in an inert atmosphere at 200-600 °C for 2-10 h and then naturally cooled or quenched to room temperature. Here, the quenching refers to quenching to room temperature at the heat treatment temperature, that is, 200-600 °C. The same applies to the following preparation methods.

[0036] In some other examples of the present application, the mechanochemical synthesis method is high-energy ball milling combined with low-temperature heat treatment (abbreviated as HM in this article). Specifically, the mixture is ball milled at a speed of 300 - 800 rpm for 10 - 12 h, and then the ball-milled powder is heat treated in an inert atmosphere at 200 - 600 °C for 2 - 10 h and then naturally cooled or quenched to room temperature.

[0037] In some other examples of the present application, the mechanochemical synthesis method is high-energy ball milling combined with low-temperature heat treatment followed by secondary high-energy ball milling (abbreviated as BHB in this article). Specifically, the mixture is ball milled at a speed of 300 - 800 rpm for 10 - 12 h, and then the ball-milled powder is heat treated in an inert atmosphere at 200 - 600 °C for 2 - 10 h, naturally cooled or quenched to room temperature, and finally the heat-treated powder is ball milled again at a speed of 300 - 800 rpm for 10 - 12 h.

[0038] Through the above four methods, the expected NaCl-type sodium-ion solid electrolyte can be prepared.

[0039] It can be understood that the inert atmosphere described in this article is the conventional definition in the art, which refers to an inert gas that does not react with reaction raw materials, reaction products, etc. Common nitrogen, noble gases (such as helium, argon, etc.) can all be used.

[0040] The third aspect of the present application discloses the application of the above-mentioned NaCl-type sodium-ion solid electrolyte or the NaCl-type sodium-ion solid electrolyte prepared by the preparation method as described above in the preparation of sodium-ion batteries.

[0041] The fourth aspect of the present application discloses a all-solid-state sodium-ion battery, which contains the above-mentioned NaCl-type sodium-ion solid electrolyte or the NaCl-type sodium-ion solid electrolyte prepared by the preparation method as described above.

[0042] In some examples, the sodium-ion battery is an all-solid-state sodium-ion battery. Preferably, the sodium-ion battery is an all-solid-state sodium metal battery. By using the NaCl-type sodium-ion solid electrolyte in the present application, the all-solid-state of the sodium-ion battery can be realized, thereby improving the safety and reliability of the battery, while maintaining good electrochemical performance and meeting the requirements for high-performance sodium-ion batteries. Specifically, due to the high ionic conductivity, wide electrochemical window and excellent oxidation stability of the NaCl-type sodium-ion solid electrolyte in the present application, when it is applied to all-solid-state sodium-ion batteries, the performance of all-solid-state sodium-ion batteries can be improved, including aspects such as energy density, cycle life and safety.

[0043] It is understandable that the sodium-ion battery further includes materials such as a positive electrode and a negative electrode, all of which can adopt conventional and well-known materials in the art. In a sodium-ion battery, the positive electrode material is usually an active material capable of reversibly inserting and extracting sodium ions. Specific examples include, but are not limited to, sodium transition metal oxides (such as NaCoO2, NaMnO2, NaFeO2, etc.), sodium iron phosphates (such as NaFePO4, etc.), sodium nickel manganese oxides (such as Na(Ni,Mn)O2, etc.). These positive electrode materials can achieve the insertion and extraction of sodium ions during charge and discharge, thereby realizing the mutual conversion of electrical energy and chemical energy. In addition, in the positive electrode material, functional additives such as conductive agents can be added as needed. These conductive agents can improve the conductivity of the positive electrode material, thereby enhancing the overall performance of the battery. In a sodium-ion battery, specific examples of the conductive agent include, but are not limited to, carbon nanotubes (CNTs), graphene, Ketjen black (KB), acetylene black, carbon black (CB), Super-P (SP), etc. These conductive agents have excellent electrical conductivity and good chemical stability, and can effectively improve the conductivity and cycle stability of the positive electrode material.

[0044] The negative electrode material is usually a material capable of reversibly storing and releasing sodium ions. Specific examples include, but are not limited to, sodium metal negative electrodes, sodium-containing alloys, hard carbon, soft carbon, sodium titanates (such as NaTiO2, etc.). Sodium metal negative electrodes have a high theoretical specific capacity and a low electrochemical potential, which can significantly improve the energy density of the battery. Hard carbon and soft carbon have good cycle stability and safety, and are commonly used negative electrode materials for sodium-ion batteries. Sodium titanates have excellent rate performance and cycle stability, and are also a potential negative electrode material for sodium-ion batteries. In some examples, the negative electrode material is preferably a sodium metal negative electrode or a sodium-containing alloy.

[0045] The following are specific embodiments of the present application. It should be noted that the following specific embodiments are only for illustrative purposes and do not limit the scope of the present application in any way.

[0046] 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 this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0047] In addition, unless otherwise specified, the methods without specific conditions or steps recorded are conventional methods, and the reagents and materials used can be obtained from commercial sources.

[0048] Example 1

[0049] In this embodiment, Na 0.6 Ca 0.2 Cl0.9 F 0.1 The preparation method is as follows:

[0050] In an inert atmosphere, sodium chloride (NaCl), calcium chloride (CaCl2), and sodium fluoride (NaF) are mixed according to a molar ratio of 0.5:0.2:0.1 respectively, sealed in a zirconia (ZrO2) ball milling jar, and ball milled in a planetary ball mill at a speed of 500 rpm for 30 hours to obtain an NaCl-type sodium-ion solid electrolyte, denoted as Na 0.6 Ca 0.2 Cl 0.9 F 0.1 -BM.

[0051] Example 2

[0052] In this example, a preparation method of Na 0.6 Y 0.2 Cl 0.8 O 0.2 is provided, and the specific steps are as follows:

[0053] In an inert atmosphere, sodium chloride (NaCl), yttrium chloride (YCl3), and sodium hydroxide (NaOH) are mixed according to a molar ratio of 0.4:0.2:0.2 respectively, sealed in a zirconia (ZrO2) ball milling jar, and ball milled in a planetary ball mill at a speed of 500 rpm for 20 hours to obtain an NaCl-type sodium-ion solid electrolyte, denoted as Na 0.6 Y 0.2 Cl 0.8 O 0.2 -BM.

[0054] Example 3

[0055] In this example, a preparation method of Na 0.4 In 0.2 Cl 0.6 S 0.2 is provided, and the specific steps are as follows:

[0056] In an inert atmosphere, sodium sulfide (Na2S) and indium chloride (InCl3) are mixed according to a molar ratio of 0.2:0.2 respectively, sealed in a zirconia (ZrO2) ball milling jar, and ball milled in a planetary ball mill at a speed of 500 rpm for 20 hours to obtain an NaCl-type sodium-ion solid electrolyte, denoted as Na 0.4 In 0.2 Cl 0.6 S 0.2 -BM.

[0057] Example 4

[0058] In this example, a preparation method of Na 0.8 Fe0.1 Cl 0.9 O 0.1 Preparation method of

[0059] In an inert atmosphere, sodium chloride (NaCl), iron(III) chloride (FeCl3), and sodium hydroxide (NaOH) are mixed at a molar ratio of 0.7:0.1:0.1 respectively. After manually grinding with an agate mortar for 15 minutes, the ground powder is loaded into a glass tube filled with argon, heat-treated at 400 °C for 3 hours, and then cooled naturally to obtain an NaCl-type sodium-ion solid electrolyte, denoted as Na 0.8 Fe 0.1 Cl 0.9 O 0.1 -HT.

[0060] Example 5

[0061] In this example, a preparation method of Na 0.3 Al 0.3 Cl 0.8 O 0.2 is provided, and the specific steps are as follows:

[0062] In an inert atmosphere, sodium chloride (NaCl), aluminum chloride (AlCl3), and sodium hydroxide (NaOH) are mixed at a molar ratio of 0.1:0.3:0.2 respectively. After manually grinding with an agate mortar for 15 minutes, the ground powder is loaded into a glass tube filled with argon, heat-treated at 300 °C for 2 hours, and then cooled naturally to obtain an NaCl-type sodium-ion solid electrolyte, denoted as Na 0.3 Al 0.3 Cl 0.8 O 0.2 -HT.

[0063] Example 6

[0064] In this example, a preparation method of Na 0.4 Cr 0.2 Cl 0.7 Br 0.3 is provided, and the specific steps are as follows:

[0065] In an inert atmosphere, sodium chloride (NaCl), chromium(III) chloride (CrCl3), and sodium bromide (NaBr) are mixed at a molar ratio of 0.1:0.2:0.3 respectively. After manually grinding with an agate mortar for 15 minutes, the ground powder is loaded into a glass tube filled with argon, heat-treated at 200 °C for 4 hours, and then cooled naturally to obtain an NaCl-type sodium-ion solid electrolyte, denoted as Na 0.4 Cr 0.2 Cl 0.7 Br 0.3 -HT.

[0066] Example 7

[0067] In this example, a preparation method of Na 0.25+x Al 0.25 Cl 1-x O x is provided, and the specific steps are as follows:

[0068] In an inert atmosphere, sodium chloride (NaCl), aluminum chloride (AlCl3), and sodium hydroxide (NaOH) are mixed in a molar ratio of 0.25:0.25:x, where x is 0, 0.15, 0.175, 0.2, 0.2125, 0.225 respectively. After sealing in a zirconia (ZrO2) ball milling jar, ball milling is carried out in a planetary ball mill at a speed of 550 rpm for 2 hours. The ball-milled powder is loaded into a glass tube filled with argon, heat-treated at 300 °C for 3 hours, and then quenched to room temperature to obtain an NaCl-type sodium-ion solid electrolyte, denoted as Na 0.25+x Al 0.25 Cl 1-x O x -HM.

[0069] Example 8

[0070] In this example, a preparation method of Na 0.6 Zr 0.1 Cl 0.8 I 0.2 is provided, and the specific steps are as follows:

[0071] In an inert atmosphere, sodium chloride (NaCl), zirconium chloride (ZrCl4), and sodium iodide (NaI) are mixed in a molar ratio of 0.4:0.1:0.2. After sealing in a zirconia (ZrO2) ball milling jar, ball milling is carried out in a planetary ball mill at a speed of 600 rpm for 2 hours. The ball-milled powder is loaded into a glass tube filled with argon, heat-treated at 300 °C for 2 hours, and then quenched to room temperature to obtain an NaCl-type sodium-ion solid electrolyte, denoted as Na 0.6 Zr 0.1 Cl 0.8 I 0.2 -HM.

[0072] Example 9

[0073] In this example, a preparation method of Na 0.6 Zr 0.2 Cl 0.6 O 0.4 is provided, and the specific steps are as follows:

[0074] In an inert atmosphere, sodium chloride (NaCl), zirconium chloride (ZrCl4), and sodium hydroxide (NaOH) are mixed at a molar ratio of 0.2:0.2:0.4 respectively, sealed in a zirconia (ZrO2) ball milling jar, and ball milled in a planetary ball mill at a speed of 600 rpm for 10 hours. The ball milled powder is loaded into a glass tube filled with argon, heat treated at 400 °C for 4 hours, and then cooled naturally to obtain an NaCl-type sodium ion solid electrolyte, denoted as Na 0.6 Zr 0.2 Cl 0.6 O 0.4 -HM。

[0075] Example 10

[0076] In this example, a preparation method of Na 0.4 Nb 0.2 Cl 0.6 O 0.4 is provided, and the specific steps are as follows:

[0077] In an inert atmosphere, niobium chloride (NbCl5) and sodium hydroxide (NaOH) are mixed at a molar ratio of 0.2:0.4 respectively, sealed in a zirconia (ZrO2) ball milling jar, and ball milled in a planetary ball mill at a speed of 600 rpm for 10 hours. The ball milled powder is loaded into a glass tube filled with argon, heat treated at 400 °C for 4 hours, and then cooled naturally to obtain an NaCl-type sodium ion solid electrolyte, denoted as Na 0.4 Nb 0.2 Cl 0.6 O 0.4 -HM。

[0078] Example 11

[0079] In this example, a preparation method of Na 0.6 Zr 0.2 Cl 0.6 O 0.4 is provided, and the specific steps are as follows:

[0080] In an inert atmosphere, sodium chloride (NaCl), zirconium chloride (ZrCl4), and sodium hydroxide (NaOH) are mixed at a molar ratio of 0.2:0.2:0.4 respectively, sealed in a zirconia (ZrO2) ball milling jar, and ball milled in a planetary ball mill at a speed of 600 rpm for 10 hours. The ball milled powder is loaded into a glass tube filled with argon, heat treated at 600 °C for 4 hours, and then cooled naturally; finally, the heat treated powder is sealed again in a zirconia (ZrO2) ball milling jar and ball milled in a planetary ball mill at a speed of 600 rpm for 10 hours to obtain an NaCl-type sodium ion solid electrolyte, denoted as Na 0.6 Zr 0.2 Cl 0.6O 0.4 -BHB。

[0081] Performance test

[0082] 1. The sodium halide solid electrolytes in Examples 1-11 were subjected to alternating current impedance spectroscopy (EIS) and activation energy tests. The specific methods are as follows:

[0083] 200 mg of the sodium halide solid electrolyte was pressed into a tablet in a polytetrafluoroethylene mold with a diameter of 12 mm, about 0.7 cm thick. After installing 8 cm thick stainless steel current collectors at both ends, the alternating current impedance spectroscopy (EIS) test was carried out at different temperatures using the Donghua DH70001 electrochemical workstation. The test results are shown in Table 1.

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

[0085]

[0086] It can be seen from the test results in Table 1 that the NaCl-type sodium ion solid electrolyte provided in this application has high ionic conductivity and low migration activation energy, which can meet the industrial production requirements.

[0087] 2. The samples in Example 7 were characterized by XRD. The characterization results are shown in Figure 2 .

[0088] The results show that when the O content increases to 0.2125, the sample is a pure phase, which is consistent with the standard card of NaCl at this time, indicating that the space group structure of the sample is the Fm3m phase. When 0≤x≤2, there are impurities of NaAlCl4 in the sample, but the overall structure of the sample is still the NaCl structure of Fm3m. In addition, it was found through experiments that as the impurity content decreases, the ionic conductivity of the sample gradually increases, and among them, the ionic conductivity of Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM is the highest. Therefore, Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM was used as the experimental sample for testing in subsequent experiments.

[0089] 3. Electrochemical window test

[0090] The sample Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM in Example 7 and the conductive agent SP were mixed in a mass ratio of 7:3, ground for 15 minutes, and used as the positive electrode powder (10 mg in total), and pressed into a positive electrode with a thickness of 35 μm.

[0091] Take 20 mg of Na2Sn sodium-tin alloy and press it into a negative electrode with a thickness of 45 μm.

[0092] Take 70 mg of the sample Na in Example 7 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM and press it into a solid electrolyte with a thickness of 150 μm.

[0093] The above pressing is carried out in a polytetrafluoroethylene mold with a diameter of 12 mm under a pressure of 375 MPa.

[0094] After assembling the positive electrode, solid electrolyte and negative electrode in sequence, a full cell is assembled.

[0095] Use the Donghua DH70001 electrochemical workstation to conduct linear sweep voltammetry (LSV) tests at 30 °C.

[0096] At the same time, test the sample Na in Example 2 according to the above battery assembly and test methods 0.6 Y 0.2 Cl 0.8 O 0.2 -BM's electrochemical window.

[0097] Among them, the test results of Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM are as Figure 3 shown. It can be seen that Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM has a wide electrochemical window of 1.83 - 4.52 V.

[0098] Na 0.6 Y 0.2 Cl 0.8 O 0.2 -BM's test results are as Figure 4 shown. It can be seen that Na 0.6 Y 0.2 Cl 0.6 O 0.2 -BM has a wide electrochemical window of 1.05 - 4.24 V.

[0099] 4. Air stability test

[0100] At 25 °C, the sample Na in Example 7 0.4625 Al 0.25 Cl 0.7875 O0.2125 -HM was left in air for 24 h, and its performance was tested by XRD patterns and AC impedance spectra. The results are as Figure 5 shown.

[0101] It can be seen that Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM has excellent air stability and can be stored and used in air.

[0102] 5. Cycling performance test

[0103] The sample Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM in Example 7 was prepared into a full cell according to the following method. The specific steps are as follows:

[0104] Positive electrode: The positive electrode active material sodium vanadium phosphate (Na3V2(PO4)3), Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM and the conductive agent SP were mixed at a mass ratio of 50:50:3, and then ball-milled in a planetary ball mill at a speed of 200 rpm for 30 min using a stainless steel ball milling jar to obtain positive electrode powder (10 mg in total), and then pressed into a composite positive electrode with a thickness of 30 μm.

[0105] Negative electrode: Sodium and tin were mixed in a stainless steel ball milling jar at a molar ratio of 2:1, and then ball-milled in a planetary ball mill at a speed of 300 rpm for 20 h to obtain a sodium-tin alloy (20 mg in total), and then pressed into a negative electrode with a thickness of 45 μm.

[0106] Solid-state electrolyte: 80 mg of Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM was pressed into a solid-state electrolyte with a thickness of 300 μm.

[0107] All the above pressings were carried out in a polytetrafluoroethylene mold with a diameter of 12 mm under a pressure of 375 MPa.

[0108] The full cell was assembled in the order of positive electrode, solid-state electrolyte, transition layer, and negative electrode.

[0109] The above full cell was subjected to a cycling test at a rate of 0.3C.

[0110] Meanwhile, according to the above full cell assembly and test methods, the sample Na 0.6 Zr 0.2Cl 0.6 O 0.4 Perform the same test on -HM.

[0111] Among them, the sample Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 The test results of -HM can be seen in Figure 6 For the sample Na 0.6 Zr 0.2 Cl 0.6 O 0.4 -HM can be seen in Figure 7 .

[0112] Through Figure 6 it can be seen that the all-solid-state battery assembled with Na 0.4625 Al 0.25 Cl 0.7875 O 0.2125 -HM still has a discharge specific capacity of 78 mAh·g after cycling 60 times at a rate of 0.3C, and the Coulomb efficiency is 99.7%; furthermore, through -1 it can be seen that the all-solid-state battery using Na Figure 7 0.6 Zr 0.2 Cl 0.6 O 0.4 -HM can also maintain 79 mAh·g after cycling 100 times at a rate of 0.3C -1 , and the capacity retention rate is 85%.

[0113] Through the above experimental results, it can be proved that the NaCl-type sodium-ion solid electrolyte disclosed in this application has excellent performance and can simultaneously match a high-voltage positive electrode and a sodium metal or alloy negative electrode in an all-solid-state battery.

[0114] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same structure and the same function and effect as the technical idea within the scope of the technical solution of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be thought of by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of this application.

Claims

1. A NaCl-type sodium ion solid electrolyte, characterized in that: The space group of the NaCl-type sodium ion solid electrolyte is Fm3m, and its chemical formula is Na z A y Cl 1-x B x ; Wherein, A is a divalent or higher valent metal cation, B is selected from at least one of O, S, F, Cl, Br, and I; 0<x<1, 0<z+y≤1, and x, y, and z satisfy charge balance; Preferably, A is selected from one of Ca, Mg, Ga, Y, Al, Fe, In, La, Ho, Yb, Ce, Sc, Zr, Er, Ti, Hf, Cr, Ta, Nd, Sm, and Nb.

2. The NaCl type sodium ion solid electrolyte according to claim 1, characterized in that The ionic conductivity of the NaCl-based sodium ion solid electrolyte is 4.1×10 -5 ~5×10 -3 S cm -1 , electrochemical window 0.05V~4.6V vs.Na / Na + .

3. A method for preparing a NaCl-type sodium ion solid electrolyte as claimed in claim 1 or 2, characterized in that: The following steps are involved: Mixing two or more precursors in an inert atmosphere according to a stoichiometric ratio to obtain a mixture; The mechanochemical synthesis method is used to make the mixture undergo a solid-phase chemical reaction to obtain a NaCl-type sodium ion solid electrolyte.

4. The preparation method according to claim 3, characterized in that: The precursor is at least one of halides, hydroxides, oxides and sulfides of Na and / or A.

5. The preparation method according to claim 3, characterized in that: The mechanochemical synthesis method is a high-energy ball milling method, and the specific process is: the mixture is ball milled at a rotation speed of 300 to 800 rpm for 10 to 30 hours.

6. The preparation method according to claim 3, characterized in that: The mechanochemical synthesis method includes manual grinding combined with low-temperature heat treatment. The specific process is: after the mixture is manually ground for 12 to 18 minutes, the ground powder is heat treated at 200 to 600° C. for 2 to 10 hours in an inert atmosphere and then naturally cooled or quenched to room temperature.

7. The preparation method according to claim 3, characterized in that: The mechanochemical synthesis method is a combination of high-energy ball milling and low-temperature heat treatment. The specific process is: after the mixture is ball milled at a speed of 300-800 rpm for 10-12 hours, the ball-milled powder is heat treated at 200-600° C. for 2-10 hours in an inert atmosphere and then naturally cooled or quenched to room temperature.

8. The preparation method according to claim 3, characterized in that: The mechanochemical synthesis method is high-energy ball milling combined with low-temperature heat treatment and then secondary high-energy ball milling. The specific process is: after the mixture is ball milled at a speed of 300-800rpm for 10-12h, the ball-milled powder is placed in an inert atmosphere and heat treated at 200-600℃ for 2-10h, and then naturally cooled or quenched to room temperature. Finally, the heat-treated powder is ball milled at a speed of 300-800rpm for 10-12h.

9. Use of the NaCl-type sodium ion solid electrolyte according to claim 1 or 2 or the NaCl-type sodium ion solid electrolyte prepared by the preparation method according to any one of claims 3 to 8 in the preparation of a sodium ion battery.

10. An all-solid-state sodium ion battery, characterized in that: Contains the NaCl type sodium ion solid electrolyte according to claim 1 or 2 or a NaCl type sodium ion solid electrolyte prepared by the preparation method according to any one of claims 3 to 8.

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