Sulfide solid electrolyte and preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion batteries, and relates to a sulfide solid electrolyte as well as a preparation method and application thereof. The sulfide solid-state electrolyte comprises a lithium tin sulfur and phosphorus-free sulfide solid-state electrolyte matrix material, and a Sr element, a B element and an O element doped in the lithium tin sulfur and phosphorus-free sulfide solid-state electrolyte matrix material. The Sr element, the B element and the O element are co-doped on the lithium tin sulfur and phosphorus-free sulfide solid electrolyte matrix material, so that the structural stability and the ionic conductivity of the material are improved, and the air stability is further improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and relates to a sulfide solid electrolyte, its preparation method and application. Background Technology

[0002] In the development of next-generation high-safety, high-energy-density lithium batteries, breakthroughs in solid-state electrolytes are undoubtedly a core component. Among them, sulfide solid-state electrolytes, with their significant advantages such as ultra-high ionic conductivity (in some systems, room-temperature ionic conductivity surpasses that of traditional liquid electrolytes), good interfacial compatibility, and a wide electrochemical stability window, are widely recognized as one of the most commercially promising solid-state electrolyte materials. However, their fatal flaw—extremely poor air stability—has become a major bottleneck restricting their large-scale production and practical application. Most sulfide electrolytes, when exposed to air, rapidly react chemically with moisture and oxygen, leading not only to a sharp drop in their ionic conductivity but also potentially generating corrosive H2S gas, endangering equipment and operator safety. To avoid this problem, current production processes must be conducted entirely in glove boxes or closed environments protected by inert gases such as argon. This significantly increases equipment investment and process control difficulty, resulting in high production costs and severely hindering the industrialization of sulfide solid-state electrolytes.

[0003] A thorough investigation into the degradation mechanism of the air stability of sulfide electrolytes is a prerequisite for developing effective improvement strategies. Currently, most sulfide electrolyte systems with high ionic conductivity contain phosphorus (P). According to the hard-soft acid-base theory, sulfide electrolytes containing P have poor air stability and readily react with moisture and oxygen in the air, producing toxic hydrogen sulfide gas. This damages the electrolyte's structure, alters its chemical composition, and consequently leads to a sharp deterioration in its ionic conductivity and other properties.

[0004] In stark contrast to thiophosphate-based solid electrolytes, lithium-tin-sulfur, phosphorus-free sulfide solid electrolytes produce negligible hydrogen sulfide, and their structure and ionic conductivity can be restored through heat treatment after immersion in water. However, the low ionic conductivity of these sulfide solid electrolytes makes them unsuitable for use in all-solid-state batteries or as a modifier in liquid lithium-ion batteries.

[0005] Therefore, improving the ionic conductivity of sulfide solid electrolytes while ensuring good air stability is an urgent technical problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a sulfide solid electrolyte, its preparation method, and its applications. The present invention co-dops Sr, B, and O elements into a lithium-tin-sulfur, phosphorus-free sulfide solid electrolyte matrix material, thereby improving the material's structural stability and ionic conductivity, and further enhancing its air stability.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a sulfide solid electrolyte, the sulfide solid electrolyte comprising a lithium tin sulfide and phosphorus-free sulfide solid electrolyte matrix material and Sr, B and O elements doped in the lithium tin sulfide and phosphorus-free sulfide solid electrolyte matrix material.

[0009] In the sulfide solid electrolyte of the present invention, the matrix material comprises a lithium tin sulfide compound material, wherein Sr, B, and O are co-doped; wherein strontium is in the +2 valence and Sr 2+ Replacement of Li + (Radius difference: Li) + Around 76 pm, Sr 2+ (Approximately 118 pm), due to charge mismatch issues, additional Li will be generated in the lattice. + Vacancy, which serves as Li + The "temporary site" for migration lowers the ion migration energy barrier and simultaneously broadens the Li migration path. + Conduction channel, and Sr 2+ Its electronegativity (1.0) is lower than that of Li. + (0.98), Na + (0.93), with S 2− The higher binding energy (forming more stable Sr-S bonds) can reduce S 2− The reaction with H2O in the air enhances air stability; element B can slightly replace the position of Sn to form BS bonds, inhibiting the production of H2S and further improving air stability. Simultaneously, element B forms BO3 / BO4 units through BO bonds, indirectly replacing some of the S. 2- This reduces non-bridging sulfur and inhibits H2S release; that is, the synergistic effect of the three element dopings together improves the ionic conductivity of the sulfide solid electrolyte material and also enhances its air stability.

[0010] Preferably, the chemical formula of the sulfide solid electrolyte is Li. x Sr y B z Sn a O b S c, where 0 < x < 4, 0 < y ≤ 1, 0 < z ≤ 0.2, 0 < a < 1, 0 < b ≤ 1, 0 < c < 4.

[0011] For example, x can be 0.1, 0.3, 0.5, 0.8, 1, 1.3, 1.5, 1.8, 2, 2.3, 2.5, 2.8, 3, 3.3, 3.5, 3.8, or 4, etc.; y can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc.; and z can be 0.01, 0.03, 0.05, 0.08, or 0. 1, 0.13, 0.15, 0.18, or 0.2, etc.; a can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc.; b can be 0.1, 0.3, 0.5, 0.8, 1, 1.3, 1.5, 1.8, 2, 2.3, 2.5, 2.8, or 3, etc.; c can be 0.1, 0.3, 0.5, 0.8, or 14.

[0012] Preferably, the Li x Sr y B z Sn a O b S c In this case, 0 < y ≤ 0.3.

[0013] For example, y can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, or 0.3, etc.

[0014] This invention regulates Li x Sr y B z Sn a O b S c The stoichiometric ratios of each element were specifically limited to 0 < x < 4, 0 < y ≤ 0.3, 0 < z ≤ 0.2, 0 < a < 1, 0 < b ≤ 1, and 0 < c < 4, thereby further regulating the doping amounts of Sr, B, and O elements and better improving its air stability and ionic conductivity.

[0015] Preferably, in addition to being co-doped with Sr, B and O elements, the sulfide solid electrolyte matrix material also has a coating layer on its surface, and the coating layer material includes boric acid.

[0016] This invention, based on the co-doping of Sr, B and O elements, simultaneously coats the material with boric acid, which can further prevent water vapor from corroding the electrolyte material and improve the material's air stability.

[0017] Preferably, in addition to being co-doped with Sr, B and O elements, the sulfide solid electrolyte matrix material also has a coating layer on its surface, and the raw material of the coating layer includes boric acid.

[0018] Preferably, when the raw material of the coating layer includes boric acid, the material of the coating layer includes lithium boron oxide, and the boron element in the sulfide solid electrolyte matrix material includes lithium boron oxide.

[0019] Preferably, the lithium boron oxide includes lithium metaborate (LiBO2) and / or lithium tetraborate (Li2B4O7).

[0020] When boric acid is used as the coating material in this invention, the coating layer can react to obtain lithium boron oxide. The boron-doped boron (BO) in the matrix material undergoes a "self-stitching" reaction, forming a through-hole Li-BO glass bridge, improving interfacial compatibility. This allows the BO inside the matrix material and the BO units in the outer coating to be lithiated simultaneously, thereby generating high-Li content ions. + The concentration of lithium metaborate (LiBO2) and / or lithium tetraborate (Li2B4O7) phases increases the Li⁺ migration number at the interface, further improves the ionic conductivity, and enhances the interfacial bonding between the matrix material core and the coating layer.

[0021] In a second aspect, the present invention provides a method for preparing a sulfide solid electrolyte as described in the first aspect, the method comprising the following steps:

[0022] The raw materials are mixed and sintered to obtain the sulfide solid electrolyte;

[0023] The raw materials used in the preparation process include lithium, strontium, tin, sulfur, and boron sources, with the boron source including an oxygen-containing boron source.

[0024] The preparation method of the present invention can achieve bulk doping of Sr, B and O elements in lithium-tin-sulfur and phosphorus-free sulfide solid electrolyte matrix materials through simple raw material mixing, and achieve a good synergistic effect.

[0025] Preferably, the strontium source, lithium source, and tin source in the raw materials are each independently selected from their respective sulfides.

[0026] It is understood that when the strontium source, lithium source and tin source in this invention are each independently selected from the corresponding sulfides, such as strontium sulfide, lithium sulfide and tin disulfide as raw materials, the corresponding strontium, lithium and tin elements can be provided, or the corresponding sulfur source can be provided at the same time. Those skilled in the art can make adaptive selections and adjustments according to the target ratio.

[0027] Preferably, the oxygen-containing boron source includes lithium metaborate and / or lithium tetraborate.

[0028] Using lithium metaborate and / or lithium tetraborate as boron sources not only provides B and O but also introduces BO groups, which can lower the glass transition temperature, act as a flux, and improve processability.

[0029] Preferably, the mixing method includes mechanical grinding, which includes sequential coarse grinding and fine grinding.

[0030] Preferably, the rotation speed of the coarse grinding is 100rpm~200rpm, such as 100rpm, 130rpm, 150rpm, 180rpm or 200rpm.

[0031] Preferably, the coarse grinding time is 1h to 10h, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0032] The grinding speed is 400rpm~600rpm, such as 400rpm, 430rpm, 450rpm, 480rpm, 500rpm, 530rpm, 550rpm, 580rpm or 600rpm.

[0033] Preferably, the fine grinding time is 15h to 30h, for example, 15h, 18h, 20h, 24h, 25h, 28h or 30h.

[0034] In this invention, the mixing process of coarse grinding followed by fine grinding can reduce the temperature rise during the mixing process, keeping the instantaneous temperature rise ≤80°C, thus avoiding volatilization or lattice decomposition when using low-melting-point sulfides (such as tin disulfide) as raw materials.

[0035] Preferably, the sintering is carried out under a protective atmosphere.

[0036] Preferably, the sintering temperature is ≥400℃, such as 400℃, 425℃, 450℃, 475℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃.

[0037] Preferably, the sintering time is 1h to 10h, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0038] Preferably, the sintered product is coated, and the coating material includes boric acid.

[0039] It is understood that the sintered product in this invention is a lithium tin sulfide and phosphorus-free sulfide solid electrolyte matrix material, and Sr, B and O elements doped in the lithium tin sulfide and phosphorus-free sulfide solid electrolyte matrix material.

[0040] Preferably, the mass ratio of boric acid to the sintered product is 1:(50~200), for example, 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, 1:110, 1:120, 1:130, 1:140, 1:150, 1:160, 1:170, 1:180, 1:190 or 1:200, etc.

[0041] Preferably, the coating method includes ball milling or deposition.

[0042] Preferably, the coating process includes: mixing the product after liquid-phase sintering with boric acid, ball milling the mixture for coating, and drying the coated mixture to obtain a sulfide solid electrolyte with a boric acid coating layer.

[0043] Preferably, the ball-milled coated material is spray-dried and heat-treated to obtain a sulfide solid electrolyte with a lithium boron oxide coating.

[0044] In this invention, after boric acid coating, a further heat treatment is performed. During the heat treatment process, the BO units inside the matrix material and the BO units in the outer coating are simultaneously lithiated, thereby generating high-Li content materials. + The concentration of lithium metaborate (LiBO2) and / or lithium tetraborate (Li2B4O7) phases increases the Li⁺ migration number at the interface, further improves the ionic conductivity, and enhances the interfacial bonding between the matrix material core and the coating layer.

[0045] Preferably, the heat treatment is performed under a protective atmosphere.

[0046] Preferably, the heat treatment temperature is 200℃~600℃, such as 300℃, 325℃, 350℃, 375℃, 400℃, 425℃, 450℃, 475℃, 500℃, 525℃, 575℃ or 600℃.

[0047] In this invention, the heat treatment temperature is controlled between 200℃ and 600℃. Too high a temperature may cause sulfide decomposition, borate phase transformation or interface reaction, reducing the coating effect and electrical conductivity; too low a temperature may not be able to fully crystallize or stabilize the interface.

[0048] Preferably, the heat treatment time is 8h to 16h, such as 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or 16h.

[0049] Optionally, the protective gas in the protective atmosphere includes nitrogen and / or an inert gas, wherein the inert gas includes argon and / or helium.

[0050] Thirdly, the present invention provides an electrochemical device comprising a sulfide solid electrolyte as described in the first aspect or a sulfide solid electrolyte prepared by the preparation method described in the second aspect.

[0051] Preferably, the electrochemical device comprises a solid-state lithium-ion battery and / or a liquid lithium-ion battery.

[0052] The sulfide solid electrolyte provided by this invention can be used as a raw material for preparing the positive electrode and / or negative electrode and / or solid electrolyte layer in solid-state batteries; it can also be used in the modification of the positive electrode and / or negative electrode and / or separator in liquid lithium-ion batteries. Those skilled in the art can make adaptive selections and adjustments according to actual needs.

[0053] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] In the sulfide solid electrolyte of the present invention, the matrix material comprises a lithium tin sulfide compound material, wherein Sr, B, and O are co-doped; wherein strontium is in the +2 valence and Sr 2+ Replacement of Li + (Radius difference: Li+ approximately 76 pm, Sr) 2+ (Approximately 118 pm), due to charge mismatch issues, additional Li will be generated in the lattice. + Vacancy, which serves as Li + The "temporary site" for migration lowers the ion migration energy barrier and simultaneously broadens the Li migration path. + Conduction channel, and Sr 2+ Its electronegativity (1.0) is lower than that of Li. + (0.98), Na + (0.93), with S 2− The higher binding energy (forming more stable Sr-S bonds) can reduce S 2− The reaction with H2O in the air enhances air stability; element B can slightly replace the position of Sn to form BS bonds, inhibiting the production of H2S and further improving air stability. Simultaneously, element B forms BO3 / BO4 units through BO bonds, indirectly replacing some of the S. 2-This reduces non-bridging sulfur and inhibits H2S release; that is, the synergistic effect of the three element dopings together improves the ionic conductivity of the sulfide solid electrolyte material and also enhances its air stability. Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0057] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0058] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0059] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0060] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0061] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0062] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0063] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0064] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0065] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0066] In this invention, "room temperature" generally refers to 4℃~35℃, and can refer to 20℃±5℃. In some embodiments of this invention, room temperature refers to 20℃~30℃.

[0067] Example 1

[0068] This embodiment provides a sulfide solid electrolyte material, which includes a three-element doped matrix material and a coating layer covering the surface of the matrix material; the chemical formula of the three-element doped matrix material is Li. 3.8 Sr 0.1 B 0.02 Sn 0.985 O 0.2 S 3.8 The coating material includes LiBO2 and / or Li2B4O7.

[0069] The preparation method of the sulfide solid electrolyte material is as follows:

[0070] (1) Strontium sulfide (SrS), lithium sulfide (Li2S), tin disulfide (such as SnS2), lithium metaborate (LiBO2), and lithium tetraborate (Li2B4O7) are mixed according to the target stoichiometric ratio, with a molar ratio of lithium metaborate to lithium tetraborate of 1:1; the mixture is mechanically ground, and the obtained raw material composition is put into a ball mill jar containing a mixture of zirconia balls with a diameter of 3 mm and zirconia balls with a diameter of 5 mm. Anhydrous ethanol is added to it, and the mixture is first mechanically ground at a rotation speed of 100 rpm for 3 h, and then mechanically ground at a rotation speed of 500 rpm for 20 h to obtain the precursor material; the precursor material is sintered at a sintering temperature of 500 °C for 5 h under a nitrogen atmosphere to obtain the tri-element doped sulfide matrix material;

[0071] (2) The sulfide matrix material doped with three elements and boric acid are mixed at a mass ratio of 100:1, and then anhydrous ethanol is added. After sand milling, a solid-liquid mixture is obtained. The solid-liquid mixture is placed in a nitrogen-protected spray dryer for spray drying at a temperature of 150°C. The spray-dried material is then heat-treated in a nitrogen atmosphere at a temperature of 400°C for 12 hours. After that, it is subjected to airflow crushing to obtain a sulfide solid electrolyte that is simultaneously doped and coated.

[0072] Example 2

[0073] This embodiment provides a sulfide solid electrolyte material, which includes a three-element doped matrix material and a coating layer covering the surface of the matrix material; the chemical formula of the three-element doped matrix material is Li. 3.8 Sr 0.1 B 0.02 Sn 0.985 O 0.2 S 3.8 The coating material includes LiBO2 and / or Li2B4O7.

[0074] The preparation method of the sulfide solid electrolyte material is as follows:

[0075] (1) Strontium sulfide (SrS), lithium sulfide (Li2S), tin disulfide (such as SnS2), lithium metaborate (LiBO2), and lithium tetraborate (Li2B4O7) are mixed according to the target stoichiometric ratio, with a molar ratio of lithium metaborate to lithium tetraborate of 1:1; the mixture is mechanically ground, and the resulting raw material composition is put into a ball mill jar containing a mixture of zirconia balls with a diameter of 3 mm and zirconia balls with a diameter of 5 mm. Anhydrous ethanol is added to the mixture, and it is first mechanically ground at a rotation speed of 100 rpm for 3 h, and then mechanically ground at a rotation speed of 500 rpm for 20 h to obtain the precursor material; the precursor material is sintered at a sintering temperature of 500 °C for 5 h under a nitrogen atmosphere to obtain the tri-element doped sulfide matrix material (the sintered material).

[0076] (2) The sulfide matrix material doped with three elements and boric acid are mixed at a mass ratio of 50:1, and then anhydrous ethanol is added. After sand milling, a solid-liquid mixture is obtained. The solid-liquid mixture is placed in a nitrogen-protected spray dryer for spray drying at a temperature of 150°C. The spray-dried material is then heat-treated in a nitrogen atmosphere at a temperature of 600°C for 12 hours. After that, it is air-jet crushed to obtain a sulfide solid electrolyte that is both doped and coated.

[0077] Example 3

[0078] This embodiment provides a sulfide solid electrolyte material, which includes a three-element doped matrix material and a coating layer covering the surface of the matrix material; the chemical formula of the three-element doped matrix material is Li. 3.8 Sr 0.1 B 0.02 Sn 0.985 O 0.2 S 3.8 The coating material includes LiBO2 and / or Li2B4O7.

[0079] The preparation method of the sulfide solid electrolyte material is as follows:

[0080] (1) Strontium sulfide (SrS), lithium sulfide (Li2S), tin disulfide (such as SnS2), lithium metaborate (LiBO2), and lithium tetraborate (Li2B4O7) are mixed according to the target stoichiometric ratio, with a molar ratio of lithium metaborate to lithium tetraborate of 1:1; the mixture is mechanically ground, and the obtained raw material composition is put into a ball mill jar containing a mixture of zirconia balls with a diameter of 3 mm and zirconia balls with a diameter of 5 mm. Anhydrous ethanol is added to it, and the mixture is first mechanically ground at a rotation speed of 100 rpm for 3 h, and then mechanically ground at a rotation speed of 500 rpm for 20 h to obtain the precursor material; the precursor material is sintered at a sintering temperature of 500 °C for 5 h under a nitrogen atmosphere to obtain the tri-element doped sulfide matrix material;

[0081] (2) The sulfide matrix material doped with three elements and boric acid are mixed at a mass ratio of 200:1. Then anhydrous ethanol is added and the mixture is milled in a sand mill to obtain a solid-liquid mixture. The solid-liquid mixture is placed in a nitrogen-protected spray dryer for spray drying at a temperature of 150°C. The spray-dried material is then heat-treated in a nitrogen atmosphere at a temperature of 200°C for 12 hours. After that, it is subjected to airflow crushing to obtain a sulfide solid electrolyte that is both doped and coated.

[0082] Example 4

[0083] The difference between this embodiment and Embodiment 1 is that the chemical formula of the three-element doped matrix material in this embodiment is Li. 3.8 Sr 0.1 B 0.1 Sn 0.925 O 0.5 S 3.5 .

[0084] In the preparation method, the stoichiometric ratio of the raw materials in the adaptive adjustment step (1) is adjusted.

[0085] All other conditions remain the same as in Example 1.

[0086] Example 5

[0087] The difference between this embodiment and Embodiment 1 is that the chemical formula of the three-element doped matrix material in this embodiment is Li. 3.4 Sr 0.3 B 0.2 Sn 0.85 O1S3.

[0088] In the preparation method, the stoichiometric ratio of the raw materials in the adaptive adjustment step (1) is adjusted.

[0089] All other conditions remain the same as in Example 1.

[0090] Example 6

[0091] The difference between this embodiment and Embodiment 1 is that the chemical formula of the three-element doped matrix material in this embodiment is Li2Sr1B. 0.02 Sn 0.94 O 0.2 S 3.8 .

[0092] In the preparation method, the stoichiometric ratio of the raw materials in the adaptive adjustment step (1) is adjusted.

[0093] All other conditions remain the same as in Example 1.

[0094] Example 7

[0095] The difference between this embodiment and Embodiment 1 is that in step (2) of this embodiment, the mass ratio of the three-element doped sulfide matrix material to boric acid is Li. 3.8 Sr 0.1 B 0.4 Sn 0.7 O 0.2 S 3.8 .

[0096] All other conditions remain the same as in Example 1.

[0097] Example 8

[0098] The difference between this embodiment and Embodiment 1 is that in step (2) of this embodiment, the mass ratio of the three-element doped sulfide matrix material to boric acid is Li. 3.8 Sr 0.1 B 0.02 Sn 0.985 O 1.5 S 2.5 .

[0099] All other conditions remain the same as in Example 1.

[0100] Example 9

[0101] The difference between this embodiment and embodiment 1 is that the heat treatment temperature in step (2) of this embodiment is 150°C.

[0102] All other conditions remain the same as in Example 1.

[0103] Example 10

[0104] The difference between this embodiment and embodiment 1 is that the heat treatment temperature in step (2) of this embodiment is 650℃.

[0105] All other conditions remain the same as in Example 1.

[0106] Example 11

[0107] The difference between this embodiment and Embodiment 1 is that the coating material of the sulfide solid electrolyte in this embodiment is boric acid.

[0108] In step (2) of the preparation method, no heat treatment is performed after spray drying, that is, the product of spray drying is the final product.

[0109] All other conditions remain the same as in Example 1.

[0110] Comparative Example 1

[0111] The difference between this comparative example and Example 1 is that the matrix material of the sulfide solid electrolyte material in this comparative example is not doped with Sr, B and O elements, and the corresponding chemical formula is Li4SnS4.

[0112] In step (1) of the preparation method, strontium sulfide, lithium metaborate (LiBO) and lithium tetraborate (Li2B4O7) are not added, and the remaining raw materials are mixed according to the target stoichiometric ratio.

[0113] All other conditions remain the same as in Example 1.

[0114] Comparative Example 2

[0115] The difference between this comparative example and Example 1 is that the matrix material of the sulfide solid electrolyte material in this comparative example is not doped with Sr, but is doped with B and O, with the corresponding chemical formula being Li4B. 0.02 Sn 0.985 O 0.2 S 3.8 .

[0116] In step (1) of the preparation method, strontium sulfide is not added, and the remaining raw materials are mixed according to the target stoichiometric ratio.

[0117] All other conditions remain the same as in Example 1.

[0118] Comparative Example 3

[0119] The difference between this comparative example and Example 1 is that the matrix material of the sulfide solid electrolyte material in this comparative example is not doped with B and O elements, but only with Sr element, and the corresponding chemical formula is Li. 3.8 Sr 0.1 Sn1S4.

[0120] In step (1) of the preparation method, lithium metaborate (LiBO) and lithium tetraborate (Li2B4O7) are not added, and the remaining raw materials are mixed according to the target stoichiometric ratio.

[0121] All other conditions remain the same as in Example 1.

[0122] Performance testing

[0123] The ionic conductivity and hydrogen sulfide gas concentration of the sulfide solid electrolyte finished materials provided in the examples and comparative examples were tested respectively. 1g of sample was exposed to air (temperature 25°C, relative humidity 20%) for 30 minutes, and the amount of H2S gas released was collected and measured. The ionic conductivity was tested using electrochemical impedance spectroscopy with a test frequency range of 0.1 Hz to 10 MHz, an applied voltage of 10 mV, and a test temperature of 25°C. The ionic conductivity was obtained, and the test results are shown in Table 1.

[0124] Table 1

[0125]

[0126] From Table 1, we can obtain:

[0127] This invention involves co-doping Sr, B, and O elements into a lithium-tin-sulfur, phosphorus-free sulfide solid electrolyte matrix material, which improves the structural stability and ionic conductivity of the material and further enhances its air stability.

[0128] Data analysis of Examples 1, 4, 5, 6, 7, and 8 shows that the sulfide solid electrolyte provided by this invention can effectively improve the overall performance of the material by controlling the stoichiometric ratio of Sr, B, and O elements, especially limiting 0 < x < 4, 0 < y ≤ 0.3, 0 < z ≤ 0.2, 0 < a < 1, 0 < b ≤ 1, and 0 < c < 4. However, if the y value is too large, i.e., excessive Sr doping, a large number of lithium sites will be occupied, the lithium ion migration channel will be blocked, resulting in a decrease in ionic conductivity and an increase in H2S release. If B doping is excessive, it may cause phase separation or the formation of a low-conductivity phase. If O doping is excessive, excessive oxygen substitution of sulfur will weaken the high conductivity of the sulfide matrix, resulting in a decrease in ionic conductivity and an increase in H2S release.

[0129] Data analysis of Examples 1, 9, and 10 shows that the heat treatment temperature during the coating process of the present invention is 200℃~600℃, which can yield a more stable high-ion-conductivity lithium interface phase.

[0130] Data analysis of Examples 1 and 2 shows that converting boric acid into a lithium boron oxide coating (LiBO2 / Li2B4O7) through appropriate heat treatment is a key step in achieving better interfacial ion transport and air stability.

[0131] Data analysis of Example 1 and Comparative Examples 1, 2, and 3 demonstrates a significant synergistic effect of co-doping with Sr, B, and O, which is indispensable for achieving both high ionic conductivity and excellent air stability.

[0132] In summary, this invention successfully prepared a sulfide solid-state electrolyte with both high ionic conductivity (>2.4 mS / cm) and excellent air stability (H2S release <5 ppm in 30 minutes) by precisely controlling the doping amounts of Sr, B, and O within specific ranges (e.g., 0 < y ≤ 0.3, 0 < z ≤ 0.2, 0 < b ≤ 1) and employing optimized boric acid derivatization coating and heat treatment processes. This synergistic doping strategy and process optimization effectively overcome the challenges of low ionic conductivity in traditional lithium-tin-sulfur electrolytes and poor air stability in conventional sulfide electrolytes, providing a key material foundation for the development of high-performance all-solid-state batteries.

[0133] 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A sulfide solid electrolyte, characterized in that, The sulfide solid electrolyte comprises a lithium tin sulfide and phosphorus-free sulfide solid electrolyte matrix material and Sr, B and O elements doped in the lithium tin sulfide and phosphorus-free sulfide solid electrolyte matrix material.

2. The sulfide solid electrolyte according to claim 1, characterized in that, The chemical formula of the sulfide solid electrolyte is Li x Sr y B z Sn a O b S c , where 0 < x < 4, 0 < y ≤ 1, 0 < z ≤ 0.2, 0 < a < 1, 0 < b ≤ 1, 0 < c < 4; Preferably, the Li x Sr y B z Sn a O b S c In this case, 0 < y ≤ 0.

3.

3. The sulfide solid electrolyte according to claim 1 or 2, characterized in that, In addition to being co-doped with Sr, B and O elements, the sulfide solid electrolyte matrix material also has a coating layer on its surface, and the coating layer material includes boric acid.

4. The sulfide solid electrolyte according to claim 1 or 2, characterized in that, In addition to being co-doped with Sr, B and O, the sulfide solid electrolyte matrix material also has a coating layer on its surface, and the raw material of the coating layer includes boric acid. Preferably, when the raw material of the coating layer includes boric acid, the material of the coating layer includes lithium boron oxide, and the boron element in the sulfide solid electrolyte matrix material includes lithium boron oxide; Preferably, the lithium boron oxide comprises LiBO2 and / or Li2B4O7.

5. A method for preparing a sulfide solid electrolyte as described in any one of claims 1-4, characterized in that, The preparation method includes the following steps: The raw materials are mixed and sintered to obtain the sulfide solid electrolyte; The raw materials used in the preparation process include lithium, strontium, tin, sulfur, and boron sources, with the boron source including an oxygen-containing boron source.

6. The preparation method according to claim 5, characterized in that, The strontium source, lithium source, and tin source in the raw materials are each independently selected from their respective sulfides; Preferably, the oxygen-containing boron source includes lithium metaborate and / or lithium tetraborate.

7. The preparation method according to claim 5 or 6, characterized in that, The mixing method includes mechanical grinding, which includes sequential coarse grinding and fine grinding. Preferably, the coarse grinding speed is 100 rpm to 200 rpm, and the coarse grinding time is 1 h to 10 h; The grinding speed is 400 rpm to 600 rpm, and the grinding time is 15 h to 30 h. Preferably, the sintering is carried out under a protective atmosphere, the sintering temperature is ≥400℃, and the sintering time is 1h~10h.

8. The preparation method according to claim 5, characterized in that, The sintered product is coated, and the coating material includes boric acid; Preferably, the mass ratio of boric acid to the sintered product is 1:(50~200). Preferably, the coating method includes ball milling or deposition. Preferably, the coating process includes: mixing the product after liquid-phase sintering with boric acid, ball milling the mixture, and drying the ball-milled product to obtain a sulfide solid electrolyte with a boric acid coating layer. Preferably, the ball-milled coated material is spray-dried and heat-treated to obtain a sulfide solid electrolyte with a lithium boron oxide coating layer. Preferably, the heat treatment is carried out under a protective atmosphere, the temperature of the heat treatment is 200℃~600℃, and the time of the heat treatment is 8h~16h.

9. An electrochemical device, characterized in that, The electrochemical device includes a sulfide solid electrolyte as described in any one of claims 1-4 or a sulfide solid electrolyte prepared by the preparation method described in any one of claims 5-8.

10. The electrochemical device as claimed in claim 9, characterized in that, The electrochemical device includes a solid-state lithium-ion battery and / or a liquid lithium-ion battery.

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