Microcrystal tin-based halide solid electrolyte, preparation method thereof and all-solid-state battery

Abstract

The invention provides a microcrystalline tin-based halide solid electrolyte and a preparation method thereof and an all-solid-state battery, the chemical general formula of the microcrystalline tin-based halide solid electrolyte is Lib-2d-2yMySndXb, b is greater than or equal to 2 and less than or equal to 6, d is greater than or equal to 1 and less than or equal to 2, y is greater than or equal to 0 and less than or equal to 0.01, Sn is + 2 valence, and M comprises + 2 valence alkaline earth metal elements and X halogen elements. The microcrystalline tin-based halide solid electrolyte has the advantages of high room-temperature ionic conductivity, good thermal stability, stable microcrystalline structure, simple preparation process and cheap and easily available raw materials, and halogen elements in the microcrystalline tin-based halide solid electrolyte can react with a lithium negative electrode to generate lithium halide. And a layer of relatively stable SEI film is formed on the surface of the lithium negative electrode, so that the interface stability of the SEI film and lithium metal can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries and relates to a microcrystalline tin-based halide solid electrolyte and a preparation method thereof and an all-solid-state battery. Background Art

[0002] All-solid-state lithium batteries, with their high energy density, long cycle life, and high safety, have become a highly competitive candidate for next-generation battery systems. The key to developing high-performance all-solid-state lithium batteries lies in preparing solid electrolyte materials with excellent room-temperature lithium-ion conductivity, a wide electrochemical stability window, and good compatibility with the electrode / electrolyte interface.

[0003] At present, the types of inorganic solid electrolyte materials mainly include oxide-type, sulfide-type and halide-type solid electrolytes. Oxide-type solid electrolytes have good electrochemical stability, but their rigid lattice makes the electrode / electrolyte interface contact poor, and is also accompanied by low lithium ion conductivity and high grain boundary impedance, which is not suitable for high-power density all-solid-state lithium batteries. Sulfide-type solid electrolytes have room-temperature lithium ion conductivity comparable to or even exceeding that of liquid electrolytes, but their limited electrochemical stability and structural and interfacial instability are shortcomings that restrict their further development. Halide-type solid electrolytes can take into account the oxidation resistance of oxides and the high ionic conductivity and mechanical ductility of sulfides. In addition, the preparation process is simple and does not require harsh environments and extremely high sintering temperatures. They have great potential in high-performance all-solid-state lithium battery applications.

[0004] At present, halide electrolytes (general formula LiaMX b , where M is any one of Sc, Y, La, Lu, Al, Ga or In or a combination of at least two thereof, and X is a halogen atom) is a wide variety of electrolytes, but there are few electrolytes that simultaneously meet the advantages of high room temperature ionic conductivity, stable structural performance, simple preparation process, and cheap and readily available raw materials. For example, the prior art discloses LiAlCl4 (monoclinic crystal structure), which has stable structural performance, simple preparation process, and cheap and readily available raw materials, but its room temperature ionic conductivity is only 1×10 -3 mS / cm. Therefore, it is necessary to provide a halide solid electrolyte that can simultaneously meet the advantages of high room temperature ionic conductivity, stable structural performance, simple preparation process, and cheap and readily available raw materials. Summary of the Invention

[0005] The object of the present invention is to provide a microcrystalline tin-based halide solid electrolyte, a preparation method thereof, and an all-solid-state battery. The microcrystalline tin-based halide solid electrolyte has the advantages of high room temperature ionic conductivity, good thermal stability, stable microcrystalline structure, simple preparation process, cheap and readily available raw materials, and good compatibility with metallic lithium negative electrodes.

[0006] To achieve the object of this invention, the following technical solutions are adopted in this invention:

[0007] In a first aspect, this invention provides a microcrystalline tin-based halide solid electrolyte, and the chemical general formula of the microcrystalline tin-based halide solid electrolyte is: Li b-2d-2y M y Sn d X b , where 2 ≤ b ≤ 6, 1 ≤ d ≤ 2, 0 ≤ y ≤ 0.01, Sn is +2 valence, M includes alkaline earth metal elements with +2 valence, and X includes halogen elements.

[0008] Preferably, the room temperature ionic conductivity of the microcrystalline tin-based halide solid electrolyte is 0.1 mS / cm to 5 mS / cm.

[0009] Preferably, 3 ≤ b ≤ 5.

[0010] Preferably, d = 2.

[0011] Preferably, 0.005 ≤ y ≤ 0.01.

[0012] Preferably, M includes any one or a combination of at least two of Mg, Ca, Sr or Ba.

[0013] Preferably, X includes any one or a combination of at least two of F, Br, Cl or I.

[0014] In a second aspect, this invention provides a preparation method of the microcrystalline tin-based halide solid electrolyte as described in the first aspect, and the preparation method includes the following steps:

[0015] Mix a lithium-containing halide, a tin-containing halide and an M-containing halide, or mix a lithium-containing halide and a tin-containing halide;

[0016] Then carry out a melting reaction on the mixture obtained by mixing in a sealed environment to obtain the microcrystalline tin-based halide solid electrolyte.

[0017] Preferably, the melting reaction in the sealed environment includes the following steps: Place the mixture in a sealed glass tube for melting reaction.

[0018] Preferably, the temperature of the melting reaction is 300 °C to 500 °C, the time of the melting reaction is 0.5 h to 3 h, and the pressure of the melting reaction is P, where P0 < P ≤ 3P0 and P0 is the standard atmospheric pressure. [[ID=​​​​​​​Preferably, a grinding step is performed after the melting reaction.

[0022] Preferably, the melting reaction is followed by a ball milling step.

[0023] Preferably, the melting reaction is followed by grinding and ball milling steps.

[0024] Preferably, the rotation speed of the ball mill is 200 rpm to 500 rpm, the time of the ball mill is 1 h to 5 h, and the ball-to-material ratio of the ball mill is (10 to 15):1.

[0025] In a third aspect, the present invention provides an all-solid-state battery, comprising the microcrystalline tin-based halide solid electrolyte as described in the first aspect, or the microcrystalline tin-based halide solid electrolyte prepared by the preparation method described in the second aspect.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention provides a microcrystalline tin-based halide solid electrolyte and introduces a certain amount of Sn into the site of the Li element. 2+ Ions (or Sn 2+ ions and M 2+ ions), thereby causing the microcrystalline structure to have a large number of defects and distortions, significantly improving the room temperature ionic conductivity of the solid electrolyte; at the same time, the tin-based halide solid electrolyte provided by the present invention introduces Sn on the basis of the halide solid electrolyte 2+ Tin is modified with tin ions, and tin acts as a glass network former, which increases the degree of vitrification of the halide solid electrolyte, which is beneficial to improving ionic conductivity and reducing the elastic modulus of the halide solid electrolyte, providing a significant effect for improving the interface contact of the solid-state battery. Therefore, the tin-based halide solid electrolyte provided by the present invention has a stable structure and high ionic conductivity. The preparation of an all-solid-state battery with it, a positive electrode, and a lithium negative electrode is beneficial to improving the rate performance, fast charging performance, and safety performance of the all-solid-state battery.

[0028] In the preparation method described in the present invention, microcrystallization and raw material reaction can be completed in just one step, and the preparation process is simple. In addition, the present invention performs a melting reaction in a sealed environment, and the reaction is thorough and efficient. It is easy to prepare a microcrystalline tin-based halide solid electrolyte with a stable structure and high ionic conductivity, and the application prospects are broad. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 These are the XRD patterns of the microcrystalline tin-based halide solid electrolyte and the polyimide tape described in Example 1, Example 2, and Example 3 of the present invention.

[0030] Figure 2These are electrochemical impedance spectroscopy graphs of the microcrystalline tin-based halide solid electrolytes described in Example 1, Example 2, and Example 3 of the present invention.

[0031] Figure 3 This is a high-resolution transmission electron microscopy image of the microcrystalline tin-based halide solid electrolyte described in Example 1 of the present invention.

[0032] Figure 4 This is a high-resolution transmission electron microscopy image of the halide solid electrolyte described in Comparative Example 3 of the present invention.

[0033] Figure 5 This is a high-resolution transmission electron microscopy image of the halide solid electrolyte described in Comparative Example 4 of the present invention.

[0034] Figure 6 This is the calendar aging impedance spectrum of the lithium-lithium symmetrical battery prepared with the microcrystalline tin-based halide solid electrolyte described in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0036] In a first aspect, the present invention provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of the microcrystalline tin-based halide solid electrolyte is: Li b-2d-2y M y Sn d X b , wherein 2≤b≤6, 1≤d≤2, 0≤y≤0.01, Sn is +2 valence, M includes an alkaline earth metal element with +2 valence, and X includes a halogen element.

[0037] The chemical formula of the microcrystalline tin-based halide solid electrolyte is: Li b-2d-2y M y Sn d X b , wherein 2≤b≤6, for example, it can be 2, 3, 4, 5 or 6, 1≤d≤2, for example, it can be 1, 1.5 or 2, 0≤y≤0.01, for example, it can be 0, 0.0025, 0.005, 0.0075 or 0.01, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] The halide solid electrolyte provided by the present invention has a microcrystalline structure, which can introduce a large number of defects and distortions, significantly improving the room temperature ionic conductivity of the solid electrolyte; at the same time, the halide solid electrolyte provided by the present invention is a tin-based halide solid electrolyte. Tin, as a glass network former, improves the degree of vitrification of the halide solid electrolyte, which is beneficial to improving the ionic conductivity and reducing the elastic modulus of the halide solid electrolyte, providing a significant effect on improving the interface contact of the solid-state battery, and the Sn 2+ There is a synergistic effect with the microcrystalline structure for the following reasons: 2+ The intrinsic properties of the solid electrolyte can effectively accelerate the migration of lithium ions. At the same time, divalent tin can replace lithium ions to form lithium vacancies, which is more conducive to the migration of lithium ions. The microcrystalline structure of the solid electrolyte can further introduce lattice distortion and defects while maintaining the original crystal structure, further reducing the activation energy of lithium ion migration. The synergistic effect of the two makes the solid electrolyte of the present invention have high ionic conductivity. In addition, the outer electron orbital arrangement of the tin ground state atom is 5S 2 5p 2 When the outer two electrons are lost, the electron configuration becomes 5S 2 , the 5S orbital in the fully filled structure complies with Hund rule, has low energy and stable structure, so Sn 2+ Tin-based halide solid electrolytes also have a more stable chemical structure. However, the applicants of this application have found that if tetravalent tin ions are introduced into halide solid electrolytes, since tetravalent tin compounds are usually liquid, the resulting substance after the introduction of tetravalent tin ions is also liquid and cannot be effectively used as a solid electrolyte. Therefore, the halide solid electrolyte provided by the present invention has a microcrystalline structure, Sn is +2 valent, and has a stable structure and high ionic conductivity.

[0039] At the same time, when the microcrystalline tin-based halide solid electrolyte described in the present invention is assembled with the positive electrode and the lithium negative electrode into an all-solid-state battery, the halogen elements in the microcrystalline tin-based halide solid electrolyte described in the present invention will react with the lithium negative electrode to generate lithium halide, which can form a relatively stable SEI film on the surface of the lithium negative electrode, thereby improving its interface stability with lithium metal.

[0040] In a specific embodiment, the room temperature ionic conductivity of the microcrystalline tin-based halide solid electrolyte (room temperature refers to 25° C.) is 0.1 mS / cm to 5 mS / cm, for example, 0.1 mS / cm, 0.25 mS / cm, 0.5 mS / cm, 0.75 mS / cm, 1 mS / cm, 1.25 mS / cm, 1.5 mS / cm, 1.75 mS / cm, 2.0 mS / cm, 2.25 mS / cm, 2.5 mS / cm, 2.75 mS / cm, 3.0 mS / cm, 3.25 mS / cm, 3.5 mS / cm, 3.75 mS / cm, 4.0 mS / cm, 4.25 mS / cm, 4.5 mS / cm, 4.75 mS / cm or 5.0 mS / cm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] The room temperature ionic conductivity of the microcrystalline tin-based halide solid electrolyte of the present invention is high and can reach 0.1 mS / cm to 5 mS / cm.

[0042] In a specific embodiment, in the chemical formula of the microcrystalline tin-based halide solid electrolyte, 3≤b≤5, for example, it can be 3, 4 or 5, d=2, 0.005≤y≤0.01, for example, it can be 0.005, 0.008, or 0.01.

[0043] In a specific embodiment, M includes any one of Be (beryllium), Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium) or Ra (radium), or a combination of at least two of them; preferably, it is any one of Mg (magnesium), Ca (calcium), Sr (strontium) or Ba (barium), or a combination of at least two of them.

[0044] In one embodiment, X comprises any one of F, Br, Cl or I, or a combination of at least two thereof.

[0045] The microcrystalline tin-based halide solid electrolyte of the present invention may further include M. Appropriate doping of M can further create defects and vacancies, provide more channels for lithium ion transmission, and further improve the ionic conductivity of the microcrystalline tin-based halide solid electrolyte; however, excessive M content causes the original crystal form of the phase to be damaged to a certain extent, and the lithium ion transmission efficiency is reduced.

[0046] In a second aspect, the present invention provides a method for preparing the microcrystalline tin-based halide solid electrolyte as described in the first aspect, the preparation method comprising the following steps:

[0047] Mixing a lithium-containing halide, a tin-containing halide and a M-containing halide, or mixing a lithium-containing halide and a tin-containing halide;

[0048] Then, the obtained mixture is subjected to a melting reaction in a sealed environment to obtain the microcrystalline tin-based halide solid electrolyte.

[0049] The preparation method of the microcrystalline tin-based halide solid electrolyte of the present invention can be achieved by directly sealing and melting the raw material mixture. The microcrystallization and the reaction of the raw materials can be completed in only one step, and the preparation process is simple. Moreover, the melting reaction of the present invention is carried out in a sealed manner, that is, the melting reaction is carried out under a certain temperature and pressure. That is, the synthesis process of the present invention prepares the microcrystalline tin-based solid electrolyte through a high-temperature melting reaction, and the reaction is thorough and efficient.

[0050] In a specific embodiment, the melting reaction in a sealed environment includes the following steps: placing the mixture in a sealed glass tube for melting reaction.

[0051] In a specific embodiment, the temperature of the melting reaction is 300°C to 500°C, for example, it can be 300°C, 350°C, 400°C, 450°C or 500°C. The time of the melting reaction is 0.5 h to 3 h, for example, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h or 3 h. The pressure of the melting reaction is P, where P0 < P ≤ 3P0, and P0 is the standard atmospheric pressure (101.3 KPa). P can be, for example, 1.5P0, 2P0 or 3P0, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0052] In a specific embodiment, the melting reaction is carried out in an inert atmosphere, which is any one or a combination of at least two of argon, helium or neon.

[0053] In a specific embodiment, the mixing method includes grinding. Grinding can make the raw materials mix more uniformly.

[0054] In a specific embodiment, a grinding step is also carried out after the melting reaction. Grinding after the melting reaction can promote the uniformization of the particle size of the melting reaction product.

[0055] In a specific embodiment, a ball milling step is also carried out after the melting reaction. Ball milling after the melting reaction instead of ball milling the raw materials before the reaction is beneficial to further promoting the microcrystalline uniformity of the melting reaction product, thereby ensuring the uniform and stable performance of the solid electrolyte; if ball milling is carried out first, the raw materials will react through the energy of ball milling, and there are obvious problems of incomplete reaction and extremely uneven local areas, and the target product cannot obtain a uniform microcrystalline product, which is not conducive to the uniform and stable performance of the electrolyte.

[0056] In a specific embodiment, a grinding step and a ball milling step are sequentially carried out after the melting reaction.

[0057] In a specific embodiment, the ball milling speed is 200 rpm to 500 rpm, for example, it can be 200 rpm, 300 rpm, 400 rpm or 500 rpm, the ball milling time is 1 h to 5 h, for example, it can be 1 h, 2 h, 3 h, 4 h or 5 h, and the ball-to-material ratio of the ball milling is (10 to 15):1, for example, it can be 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] In a third aspect, the present invention provides an all-solid-state battery, comprising the microcrystalline tin-based halide solid electrolyte as described in the first aspect, or the microcrystalline tin-based halide solid electrolyte prepared by the preparation method described in the second aspect.

[0059] Example 1

[0060] This embodiment provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of which is Li 0.99 Ba 0.005 Sn2Cl5, where Sn is +2;

[0061] The preparation method of the microcrystalline tin-based halide solid electrolyte comprises the following steps:

[0062] According to the formula, LiCl, SnCl2 and BaCl2 were weighed and placed in an agate mortar for manual grinding and mixing. The mixture was then placed in a glass sealed tube and heated at 450°C for a melting reaction for 2 hours under an argon atmosphere. The pressure of the melting reaction was 2P0 (P0 was 101.3 kPa). After the melted sample was cooled, it was ground into a uniform granular powder in a mortar. Finally, ball milling was performed at a rotation speed of 400 rpm for 4 hours, wherein the ball-to-material ratio was 15:1, to obtain the microcrystalline tin-based halide solid electrolyte.

[0063] Example 2

[0064] This embodiment provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of the microcrystalline tin-based halide solid electrolyte is LiSn2Cl5, wherein Sn is +2;

[0065] The preparation method of the microcrystalline tin-based halide solid electrolyte is the same as that of Example 1, except that the raw materials are changed according to the formula amount and the raw materials do not include BaCl2.

[0066] Example 3

[0067] This embodiment provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of the microcrystalline tin-based halide solid electrolyte is LiSnCl3, wherein Sn is +2;

[0068] The preparation method of the microcrystalline tin-based halide solid electrolyte is the same as that of Example 1, except that the raw materials are changed according to the formula amount and the raw materials do not include BaCl2.

[0069] Example 4

[0070] This embodiment provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of which is Li 0.98 Ba 0.01 Sn2Cl5, where Sn is +2;

[0071] The preparation method of the microcrystalline tin-based halide solid electrolyte comprises the following steps:

[0072] According to the formula, LiCl, SnCl2 and BaCl2 were weighed and placed in an agate mortar for manual grinding and mixing. The mixture was then placed in a glass sealed tube and heated at 500°C for a melting reaction for 0.5h under an argon atmosphere, wherein the pressure of the melting reaction was 1.5P0 (P0 was 101.3KPa). After the melted sample was cooled, it was ground into a uniform granular powder in a mortar. Finally, ball milling was performed at a rotation speed of 500rpm for 1h, wherein the ball-to-material ratio was 12:1, to obtain the microcrystalline tin-based halide solid electrolyte.

[0073] Example 5

[0074] This embodiment provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of which is Li 0.98 Ba 0.01 SnCl3, wherein Sn is +2; the preparation method of the microcrystalline tin-based halide solid electrolyte comprises the following steps:

[0075] According to the formula, LiCl, SnCl2 and BaCl2 were weighed and placed in an agate mortar for manual grinding and mixing. The mixture was then placed in a glass sealed tube and heated at 300°C for a melting reaction for 3 hours under an argon atmosphere. The pressure of the melting reaction was 3P0 (P0 was 101.3 kPa). After the melted sample was cooled, it was ground into a uniform granular powder in a mortar. Finally, ball milling was performed at a rotation speed of 200 rpm for 5 hours, wherein the ball-to-material ratio was 10:1, to obtain the microcrystalline tin-based halide solid electrolyte.

[0076] Example 6

[0077] This embodiment provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of which is Li 0.99 Mg 0.005 Sn2Cl5, where Sn is +2;

[0078] The preparation method of the microcrystalline tin-based halide solid electrolyte is the same as that of Example 1, except that the raw materials are changed according to the formula amount and BaCl2 is replaced by MgCl2.

[0079] Example 7

[0080] This embodiment provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of which is Li 0.99 Ca 0.005 Sn2Cl5, where Sn is +2;

[0081] The preparation method of the microcrystalline tin-based halide solid electrolyte is the same as that of Example 1, except that the raw materials are changed according to the formula amount and BaCl2 is replaced by CaCl2.

[0082] Example 8

[0083] This embodiment provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of which is Li 0.99 Sr 0.005 Sn2Cl5, where Sn is +2;

[0084] The preparation method of the microcrystalline tin-based halide solid electrolyte is the same as that of Example 1, except that the raw materials are changed according to the formula amount and BaCl2 is replaced by SrCl2.

[0085] Embodiment 9

[0086] This embodiment provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of which is Li 0.99 Ba 0.005 Sn2Cl5, where Sn is +2;

[0087] The preparation method of the microcrystalline tin-based halide solid electrolyte is basically the same as that of Example 1, except that after the melting reaction, the melted sample is cooled and then ground into a uniform granular powder in a mortar, namely the microcrystalline tin-based halide solid electrolyte, without subsequent ball milling treatment.

[0088] Comparative Example 1

[0089] This comparative example provides a halide material, wherein the halide material is LiBa2Cl5 and has a microcrystalline structure;

[0090] The preparation method of the halide material is the same as that of Example 1 except that the raw materials are changed according to the formula amount and the raw materials do not include SnCl2.

[0091] Comparative Example 2

[0092] This comparative example attempts to prepare a microcrystalline tin-based halide solid electrolyte with a theoretical chemical formula of Li 1.99 Ba 0.005 SnCl6 and Sn is +4 valence, but since the tetravalent tin compound is liquid, after the reaction is completed, it is found that the reactant obtained after the reaction is liquid and cannot be used as a solid electrolyte.

[0093] The preparation method of this comparative example is the same as that of Example 1 except that the raw materials are changed according to the formula amount and SnCl2 is replaced by SnCl4.

[0094] Comparative Example 3

[0095] This comparative example provides a halide solid electrolyte, the chemical formula of which is Li 0.99 Ba 0.005 Sn2Cl5, and has an amorphous structure, wherein Sn is +2 valence;

[0096] The preparation method of the halide solid electrolyte comprises the following steps:

[0097] According to the formula, LiCl, SnCl2 and BaCl2 were ball-milled at a rotation speed of 400 rpm for 4 hours, wherein the ball-to-material ratio was 15:1, to obtain the halide solid electrolyte.

[0098] Comparative Example 4

[0099] This comparative example provides a halide solid electrolyte, the chemical formula of which is Li 0.99 Ba 0.005 Sn2Cl5, and has an amorphous-microcrystalline structure, wherein Sn is +2 valence;

[0100] The preparation method of the halide solid electrolyte comprises the following steps:

[0101] According to the formula, LiCl, SnCl2 and BaCl2 were ball-milled at a rotation speed of 400 rpm for 4 hours, wherein the ball-to-material ratio was 15:1, and then annealed at a temperature of 450°C for 2 hours under an argon atmosphere to obtain the halide solid electrolyte.

[0102] Comparative Example 5

[0103] This comparative example provides a microcrystalline tin-based halide solid electrolyte, the chemical formula of which is Li 0.96 Ba 0.02 Sn2Cl5, where Sn is +2;

[0104] The preparation method of the microcrystalline tin-based halide solid electrolyte is the same as that of Example 1 except that the raw materials are changed according to the formula amount.

[0105] Performance testing:

[0106] XRD spectrum test: Take an appropriate amount of the microcrystalline tin-based halide solid electrolyte powder in a quartz glass test tank, then compact and smooth it with a glass plate, and then seal it with polyimide tape for testing; the XRD test spectra of the microcrystalline tin-based halide solid electrolyte and polyimide tape in Example 1, Example 2, and Example 3 are as follows: Figure 1 As shown, according to Figure 1 The diffraction peak intensity and peak width can assist in analyzing the crystalline state of the sample.

[0107] Crystal form test: High-resolution transmission electron microscopy test of crystal form type, the high-resolution transmission electron microscopy image of the microcrystalline tin-based halide solid electrolyte described in Example 1 is as follows Figure 3 As shown by Figure 3 The lattice fringes of the material can be seen; the high-resolution transmission electron microscopy image of the halide solid electrolyte described in Comparative Example 3 is as follows Figure 4 As shown, Figure 4 There are no lattice fringes in the solid electrolyte of Comparative Example 3, and the solid electrolyte of Comparative Example 4 is an amorphous material; the high-resolution transmission electron microscopy image of the halide solid electrolyte of Comparative Example 4 is as follows Figure 5 As shown, Figure 5 There are some lattice fringes in the tin-based halide solid electrolyte, which is a microcrystalline-amorphous material. Figure 3 Basically the same / similar, also a microcrystalline material.

[0108] Room temperature ionic conductivity test: 120 mg of the products of the examples and comparative examples (tin-based halide solid electrolytes, halide solid electrolytes or halogenated materials, etc.) were weighed respectively, placed in a PEEK (stainless steel) mold, and a stainless steel counter electrode rod was installed. The pressure was maintained at 350 MPa for 1 minute, and then the stainless steel mold was locked to obtain a mold battery; the mold battery was tested using an electrochemical workstation Gamry under the following test conditions: AC voltage 10 mV, test frequency range 1 Hz to 1 MHz; and the ionic impedance spectrum of the solid electrolyte was obtained by testing (the electrochemical impedance spectra of Examples 1, 2 and 3 are shown in Figure 2). Figure 2 As shown), the ionic conductivity of the solid electrolyte is calculated (the specific method is to use the ionic conductivity calculation formula: σ=d / (R*S), σ is the ionic conductivity, unit S / cm; d is the thickness of the ceramic sheet, unit is cm; R is the tested ionic impedance, unit is Ω; S is the area of ​​the effective electrode, unit is cm 2), the room temperature ionic conductivity obtained is shown in Table 1. In addition, Table 1 also includes the chemical formula and crystal form of the tin-based halide solid electrolyte or halide solid electrolyte described in the above embodiments and comparative examples, wherein the sample of Comparative Example 2 is liquid and the ionic conductivity cannot be measured.

[0109] Aging test: Taking the tin-based halide solid electrolyte of Example 1 as an example, an aging test was performed to further clarify its interfacial stability with lithium metal. The specific steps are as follows: the tin-based halide solid electrolyte of Example 1 was prepared into a lithium-lithium symmetrical battery. The process is as follows: 120 mg of the tin-based halide solid electrolyte was weighed and placed in a PEEK mold. The stainless steel counter electrode rod was installed and the pressure was maintained at 350 MPa for 1 minute. Then, lithium sheets were placed on both sides of the tin-based halide solid electrolyte and the pressure was maintained at 65 MPa for 1 minute. The stainless steel mold was then tightened with a torque wrench at 2 N.m to obtain a lithium-lithium symmetrical battery. The lithium-lithium symmetrical battery was placed in a constant temperature box with a humidity of 80% RH and 25°C for calendar aging for 239 hours. The calendar aging impedance was tested at 0h (i.e. 0H), 16h, 24h, 44h, 48h, 69h, and 239h of calendar aging. The test method is as follows: The test was performed using a Gamry electrochemical workstation. The test conditions were: AC voltage 10mV, test frequency range 1Hz~1MHz. The test results of calendar aging impedance are shown as follows: Figure 6 As shown, from Figure 6 It can be seen that after 239 hours of calendar aging, the impedance of the lithium-lithium symmetric cell only slightly increased, indicating that the interface between the tin-based halide solid electrolyte and the lithium metal is relatively stable, that is, it has a significant affinity for lithium metal. The tin-based halide solid electrolytes provided in the remaining examples also have consistent test results, and the tin-based halide solid electrolytes are relatively stable at the interface with the lithium metal, that is, they have a significant affinity for lithium metal.

[0110] Table 1 Test results

[0111]

[0112]

[0113] From Table 1 we can see that:

[0114] (1) The microcrystalline tin-based halide solid electrolytes provided in each embodiment of the present application are all in microcrystalline form, have stable structure, and have high room temperature ionic conductivity; it can be seen from Example 1 and Example 9 that a microcrystalline tin-based halide solid electrolyte with stable structure and high room temperature ionic conductivity can be obtained after a one-step melting reaction; and ball milling treatment after the melting reaction can further promote the homogenization of the microcrystals, thereby obtaining a higher room temperature ionic conductivity. It can be seen from Example 1, Example 2 and Example 4 and from Example 3 and Example 5 that the microcrystalline tin-based halide solid electrolyte of the present invention preferably also includes a +2 valence alkaline earth metal element, and the cooperation between Sn ions and +2 valence alkaline earth metal elements can further improve the room temperature ionic conductivity of the solid electrolyte; it can be seen from Example 1, Example 6, Example 7 and Example 8 that the microcrystalline tin-based halide solid electrolytes obtained by the introduction of different M elements all have good structural stability and high room temperature ionic conductivity.

[0115] (2) It can be seen from Example 1 and Comparative Example 1 that in the halide solid electrolyte of the present invention, Sn 2+ The addition of Ba can effectively accelerate the migration of lithium ions, and at the same time can replace lithium ions to form lithium vacancies, which is more conducive to the migration of lithium ions and improves the room temperature ionic conductivity; while the comparative example 1 is a microcrystalline halide solid electrolyte, although Ba is introduced at the site of the Li element 2+ , but does not contain Sn 2+ , the migration rate of lithium ions decreases, and the room temperature ionic conductivity decreases compared with Example 1; From Example 1 and Comparative Example 2, it can be seen that when the present invention introduces tin into the microcrystalline halide solid electrolyte, Sn is introduced. 2+ , and tetravalent tin compounds were used as raw materials to try to prepare Sn 4+ When the microcrystalline halide solid electrolyte is prepared, since the tetravalent tin compound is usually in liquid form, the obtained product is also in liquid form and cannot be effectively used as a solid electrolyte. 2+ The microcrystalline tin-based halide solid electrolyte obtained by introducing is provided with higher room temperature ionic conductivity;It is known from Example 1, Comparative Example 3 and Comparative Example 4 that the tin-based halide solid electrolyte of the present invention is microcrystalline, compared to amorphous, or amorphous-microcrystalline, a large amount of defects and distortions can be introduced in microcrystalline structure, significantly improving the room temperature ionic conductivity of solid electrolyte.It is known from Example 1, Example 4 and Comparative Example 5 that the appropriate introduction of the alkaline earth metal M element of +2 valence can further introduce defects and distortions in microcrystalline structure, promote the room temperature ionic conductivity of tin-based halide solid electrolyte, but when the alkaline earth metal M element content of +2 valence is too much (such as Comparative Example 5), on the one hand, the original crystalline structure collapses, on the other hand, excessive doping elements can form a second inert heterophase, thereby causing the lithium ion transport barrier to increase instead, and the room temperature ionic conductivity is significantly reduced instead.

[0116] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A microcrystalline tin-based halide solid electrolyte, characterized in that: The chemical formula of the microcrystalline tin-based halide solid electrolyte is: Li b-2d-2y M y Sn d X b , Among them, 2 ≤ b ≤ 6, 1 ≤ d ≤ 2, 0 ≤ y ≤ 0.01, Sn is +2 valence, M includes alkaline earth metal elements with +2 valence, and X includes halogen elements.

2. The microcrystalline tin-based halide solid electrolyte according to claim 1, characterized in that The room-temperature ionic conductivity of the microcrystalline tin-based halide solid electrolyte is 0.1 mS / cm to 5 mS / cm.

3. The microcrystalline tin-based halide solid electrolyte according to claim 1 or 2, characterized in that: 3≤b≤5； And / or, d = 2; And / or, 0.005 ≤ y ≤ 0.01; And / or, M includes any one or a combination of at least two of Mg, Ca, Sr, or Ba; And / or, X includes any one or a combination of at least two of F, Br, Cl, or I.

4. A method for preparing the microcrystalline tin-based halide solid electrolyte according to any one of claims 1 to 3, characterized in that: The preparation method includes the following steps: Mix the lithium halide, tin halide, and M halide, or mix the lithium halide and tin halide; Then carry out a melting reaction on the mixture obtained by mixing in a sealed environment to obtain the microcrystalline tin-based halide solid electrolyte.

5. The preparation method according to claim 4, characterized in that The melting reaction in the sealed environment includes the following steps: Place the mixture in a sealed glass tube for melting reaction.

6. The preparation method according to claim 4 or 5, characterized in that The temperature of the melting reaction is 300°C to 500°C, the time of the melting reaction is 0.5 h to 3 h, and the pressure of the melting reaction is P, where P0 < P ≤ 3P0 and P0 is the standard atmospheric pressure; And / or, the melting reaction is carried out in an inert atmosphere.

7. The preparation method according to claim 4 or 5, characterized in that The mixing method includes grinding.

8. The preparation method according to claim 4 or 5, characterized in that A grinding step is also carried out after the melting reaction; And / or, a ball milling step is also carried out after the melting reaction; And / or, a grinding step and a ball milling step are sequentially carried out after the melting reaction.

9. The preparation method according to claim 8, characterized in that The rotation speed of the ball milling is 200 rpm to 500 rpm, the time of the ball milling is 1 h to 5 h, and the ball-to-material ratio of the ball milling is (10 to 15):

1.

10. An all-solid-state battery, characterized in that: The all-solid-state battery includes the microcrystalline tin-based halide solid electrolyte according to any one of claims 1-3, or the microcrystalline tin-based halide solid electrolyte prepared by the preparation method according to any one of claims 4-9.

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