Sulfide solid electrolyte and method for producing the same

Abstract

The application discloses a sulfide solid electrolyte and a preparation method thereof. A sulfur source, a phosphorus source and a lithium source are uniformly mixed, then a long-chain sulfide is added for ball milling treatment to obtain a sulfide electrolyte precursor, the long-chain sulfide is an alkyl sulfide, the carbon number is 6-16, and the addition amount is less than 10wt% of the mass of the sulfide electrolyte precursor, then the sulfide electrolyte precursor is dried and sintered to obtain the sulfide solid electrolyte. In the formation process of the sulfide electrolyte precursor, the appropriate long-chain alkyl sulfide is added for mixing and ball milling, then the crystal face is regulated through drying and sintering treatment, and the ionic conductivity of the prepared sulfide solid electrolyte is greatly improved.

Description

Technical Field

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

[0002] All-solid-state lithium batteries have attracted much attention due to their combination of high energy density and intrinsic safety. Their core lies in using a non-flammable solid electrolyte to replace the traditional liquid electrolyte, fundamentally solving problems such as battery combustion, leakage, and volatilization. Furthermore, the high hardness and good density of the solid electrolyte can, to some extent, suppress the growth of lithium dendrites, thereby avoiding the risks of short circuits and thermal runaway.

[0003] Among the many solid electrolyte materials, sulfide electrolytes have become the mainstream technology in the field of all-solid-state batteries due to their excellent ionic conductivity and good machinability, and many leading companies have fully deployed related research and development.

[0004] In the prior art, the preparation methods of sulfide electrolytes mainly include dry methods and wet methods. For example, Chinese patent application CN117577929A discloses a method for preparing sulfide electrolytes by dissolving a lithium source, a sulfur source, and additives in an organic solvent under an inert atmosphere; while Chinese patent application CN117477013A discloses a method for preparing sulfide electrolytes by high-temperature roller milling (simultaneous sintering and ball milling) of raw materials under an air atmosphere.

[0005] However, existing methods produce sulfide electrolytes that are mostly particulate materials formed by spherical stacking, with limited internal ion transport channels and unsatisfactory ionic conductivity. Therefore, developing a simple and efficient method to prepare sulfide electrolytes with specific morphologies and advantageous ion transport crystal planes and high ionic conductivity remains a pressing technical challenge in this field. Summary of the Invention

[0006] To overcome the problems in the prior art, the present invention provides a sulfide solid electrolyte and its preparation method. The prepared sulfide solid electrolyte has high ion transport efficiency and excellent ionic conductivity.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0008] This invention provides a method for preparing a sulfide solid electrolyte, comprising the following steps: S1. A sulfide electrolyte is prepared by using a sulfur source, a phosphorus source, and a lithium source. A long-chain sulfide is added to the sulfide electrolyte and ball-milled to obtain a sulfide electrolyte precursor. The long-chain sulfide is an alkyl sulfide with 6 to 16 carbon atoms, and the amount added is less than 10 wt% of the mass of the sulfide electrolyte precursor. S2. The sulfide electrolyte precursor obtained in S1 is dried and then sintered to obtain a sulfide solid electrolyte.

[0009] In this invention, a long-chain sulfide is added before preparing the sulfide electrolyte precursor. The sulfide can be adsorbed onto the S atoms of the electrolyte precursor during the precursor formation process using the interaction of S-S bonds. During the subsequent sintering and crystallization process, the electrolyte material is induced to expose the (111) crystal plane, and the crystal is regulated to grow along a specific dominant crystal plane, thus preparing a layered morphology and a sulfide solid electrolyte with exposed (111) crystal plane. This crystal plane is a lithium ion migration channel in the crystal structure of the sulfide electrolyte. The exposure of this crystal plane provides more channels for lithium ion migration, accelerates the lithium ion migration rate, and thus improves the ionic conductivity of the electrolyte.

[0010] As an optional implementation, in the preparation method provided by the present invention, the amount of the long-chain sulfide added is 1 to 5 wt% of the mass of the sulfide electrolyte precursor.

[0011] In this invention, adding too much long-chain sulfide will lead to the introduction of too much impurity and a decrease in material performance, while adding too little will result in an insignificant modification effect.

[0012] As an optional implementation, in the preparation method provided by the present invention, the long-chain sulfide is an alkyl sulfide with 8 to 16 carbon atoms.

[0013] In this invention, if the number of carbon atoms in the added long-chain sulfide is too short, the sulfide has a low boiling point and will directly vaporize during ball milling, resulting in no modification effect; if the number of carbon atoms is too long, the sulfide molecular chain will be too long, leading to increased steric hindrance, making it difficult to be uniformly adsorbed on the precursor surface, and weakening the crystal facet induction effect.

[0014] As an optional implementation, in the preparation method provided by the present invention, in S1, the ball-to-material ratio during the ball milling process is 10-40:1, the rotation speed is 300-500 r / min, and the ball milling time is 24-48 h.

[0015] As an optional implementation method, in the preparation method provided by the present invention, in step S2, the drying temperature is 60-90°C and the time is 24-48 hours.

[0016] In this invention, long-chain sulfides with a higher carbon number have a higher boiling point and require a longer drying time to remove unreacted sulfides from the system.

[0017] As an optional implementation method, in the preparation method provided by the present invention, in S2, the sintering temperature is 450-550°C and the time is 12-48h.

[0018] As an optional implementation, in the preparation method provided by this invention, the long-chain sulfide is selected from one or more of the following: n-nonyl sulfide (59973-07-8), n-decyl methyl sulfide (22438-39-7), n-dodecyl sulfide (dodecyl sulfide, 3698-89-3), methyl tetradecyl sulfide (7289-45-4), n-hexadecyl sulfide (hexadecyl sulfide, 2690-08-6), and 5-thiodecane (1-(butyro)pentane, 24768-42-1). The names and CAS numbers are in parentheses.

[0019] As an optional implementation, in the preparation method provided by the present invention, in S1, a sulfide electrolyte is prepared using a sulfur source, a phosphorus source, and a lithium source, wherein the sulfur source, phosphorus source, and lithium source are Li2S, P2S5, and LiCl, respectively, and the molar ratio of Li2S, P2S5, and LiCl is 4-5:1:2-3.

[0020] Based on the same technical concept, the present invention also provides a sulfide solid electrolyte prepared by the above method, wherein the sulfide solid electrolyte has a layered structure and exposes the (111) crystal plane.

[0021] As an optional implementation, in the sulfide solid electrolyte provided by the present invention, the chemical formula of the sulfide electrolyte precursor is Li. 6-x PS 5-x Cl 1+x , where 0≦x≦0.7.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Based on the traditional ball milling-sintering process, this invention adds an appropriate amount of long-chain sulfide during the formation of the sulfide electrolyte precursor for mixing and ball milling, followed by drying and sintering to achieve crystal surface control. The ionic conductivity of the prepared sulfide solid electrolyte is significantly improved. The preparation method of this invention does not require complex equipment modification, the process is simple, highly reproducible, and easy to scale up for production.

[0023] (2) By introducing long-chain sulfides as organic additives, this invention successfully induces the sulfide electrolyte to grow along the (111) dominant crystal plane, forming a plate-like sulfide solid electrolyte, using the principle of molecular confinement self-assembly. This structure provides a high-speed transport channel for lithium ions, significantly reducing the migration energy barrier, thereby greatly improving the ionic conductivity of the sulfide solid electrolyte. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The above are the SEM results of the sulfide solid electrolyte prepared in Example 1; Figure 2 The XRD results are for the sulfide solid electrolyte prepared in Example 1; Figure 3 SEM results for the sulfide solid electrolyte prepared in Comparative Example 1; Figure 4 The XRD results are for the sulfide solid electrolyte prepared in Comparative Example 1. Detailed Implementation

[0026] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0027] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0028] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0029] Example 1 The sulfide solid electrolyte of this embodiment was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system is a sulfide electrolyte material. Then, Li... 5.5 PS 4.5 Cl 1.5 3 wt% of hexadecyl sulfide (C16) was added to the sulfide electrolyte material in the system. The mixture was placed in a ball mill jar, and grinding balls were weighed and added to the jar at a ball-to-material ratio of 30:1. After sealing, ball milling was performed at 500 rpm for 24 hours. The milled material was then dried at 90℃ for 30 hours and sintered at 500℃ for 24 hours. After sintering, the material was further ground and crushed.

[0030] Example 2 The sulfide solid electrolyte of this embodiment was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system is a sulfide electrolyte material. 3 wt% of 5-thiodecane (C9) was added to a ball mill jar. Ball beads were weighed and added to the jar at a ball-to-material ratio of 40:1. The jar was sealed and ball milling was performed. The milling speed was 300 r / min, and the time was 48 h. After ball milling, the material was dried at 80℃ for 30 h and then sintered. The sintering temperature was 450℃, and the sintering time was 48 h. After sintering, the material was ground and crushed.

[0031] Example 3 The sulfide solid electrolyte of this embodiment was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system uses sulfide electrolyte materials. 5 wt% of hexadecyl sulfide (C16) is added to a ball mill jar. Ball beads are weighed and added to the jar at a ball-to-material ratio of 30:1. The jar is sealed and ball milling is performed. The milling speed is 500 r / min, and the time is 24 h. After ball milling, the material is dried at 90℃ for 48 h and then sintered. The sintering temperature is 550℃, and the sintering time is 24 h. After sintering, the material is ground and crushed.

[0032] Example 4 The sulfide solid electrolyte of this embodiment was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system uses sulfide electrolyte materials. 1 wt% of n-octyl methyl sulfide (C number 8) is added to a ball mill jar. Ball beads are weighed and added to the jar at a ball-to-material ratio of 30:1. The jar is sealed and ball milling is performed. The ball milling speed is 500 r / min, and the time is 24 h. After ball milling, the material is dried at 60℃ for 24 h and then sintered. The sintering temperature is 500℃, and the sintering time is 24 h. After sintering, the material is ground and crushed.

[0033] Example 5 The sulfide solid electrolyte of this embodiment was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system uses sulfide electrolyte materials. 0.5 wt% of hexadecyl sulfide (C16) is added to a ball mill jar. Ball beads are weighed and added to the jar at a ball-to-material ratio of 30:1. The jar is sealed and ball milling is performed. The milling speed is 500 r / min, and the time is 24 h. After ball milling, the material is dried at 90℃ for 48 h and then sintered. The sintering temperature is 550℃, and the sintering time is 24 h. After sintering, the material is ground and crushed.

[0034] Example 6 The sulfide solid electrolyte of this embodiment was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system is a sulfide electrolyte material. Then, Li... 5.5 PS 4.5 Cl 1.5 7 wt% of hexadecyl sulfide (C16) was added to the sulfide electrolyte material in the system. The mixture was placed in a ball mill jar, and grinding balls were weighed and added to the jar at a ball-to-material ratio of 30:1. After sealing, ball milling was performed at 500 rpm for 24 hours. The milled material was then dried at 90℃ for 30 hours and sintered at 500℃ for 24 hours. The sintered material was then ground and crushed.

[0035] Example 7 The sulfide solid electrolyte of this embodiment was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system is a sulfide electrolyte material. Then, Li... 5.5 PS 4.5 Cl 1.5 9 wt% of hexadecyl sulfide (C16) was added to the sulfide electrolyte material in the system. The mixture was placed in a ball mill jar, and grinding balls were weighed and added to the jar at a ball-to-material ratio of 30:1. After sealing, ball milling was performed at 500 rpm for 24 hours. The milled material was then dried at 90℃ for 30 hours and sintered at 500℃ for 24 hours. The sintered material was then ground and crushed.

[0036] Comparative Example 1 The sulfide solid electrolyte of this comparative example was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system uses sulfide electrolyte materials. Grinding balls were weighed and added to a grinding jar at a ball-to-material ratio of 30:1, sealed, and then ball-milled. The grinding speed was 500 r / min, and the time was 24 h. After ball milling, the material was dried at 60℃ for 24 h and then sintered. The sintering temperature was 500℃, and the sintering time was 24 h. After sintering, the material was ground and crushed.

[0037] Comparative Example 2 The sulfide solid electrolyte of this comparative example was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system is a sulfide electrolyte material. 3 wt% of ethyl n-propyl sulfide (C5) was added to a ball mill jar. Ball beads were weighed and added to the jar at a ball-to-material ratio of 40:1. The jar was sealed and ball milling was performed. The milling speed was 300 r / min, and the time was 48 h. After ball milling, the material was dried at 80℃ for 30 h and then sintered. The sintering temperature was 450℃, and the sintering time was 48 h. After sintering, the material was ground and crushed. The CAS number of ethyl n-propyl sulfide is 4110-50-3.

[0038] Comparative Example 3 The sulfide solid electrolyte of this comparative example was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system uses sulfide electrolyte materials. 10 wt% of hexadecyl sulfide (C16) is added to a ball mill jar. Ball beads are weighed and added to the jar at a ball-to-material ratio of 30:1. The jar is sealed and ball milling is performed. The milling speed is 500 r / min, and the time is 24 h. After ball milling, the material is dried at 90℃ for 48 h and then sintered. The sintering temperature is 500℃, and the sintering time is 24 h. After sintering, the material is ground and crushed.

[0039] Comparative Example 4 The sulfide solid electrolyte of this comparative example was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system is a sulfide electrolyte material. 3 wt% hexadecyl methyl sulfide (C17) was added to a ball mill jar. Ball beads were weighed and added to the jar at a ball-to-material ratio of 30:1. The jar was sealed and ball milling was performed. The milling speed was 500 r / min for 24 h. After ball milling, the material was dried at 90℃ for 48 h and then sintered. The sintering temperature was 550℃ for 24 h. The sintered material was then ground and crushed. The CAS number of hexadecyl methyl sulfide is C17H36S.

[0040] Comparative Example 5 The sulfide solid electrolyte of this comparative example was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system is a sulfide electrolyte material. 3 wt% of 3-(methylthio)propylhexanoate (C number 10) is added to a ball mill jar. Ball beads are weighed and added to the jar at a ball-to-material ratio of 30:1. The jar is sealed and ball milling is performed. The ball milling speed is 500 r / min, and the time is 24 h. After ball milling, the material is dried at 90℃ for 30 h and then sintered. The sintering temperature is 500℃, and the sintering time is 24 h. After sintering, the material is ground and crushed.

[0041] Comparative Example 6 The sulfide solid electrolyte of this comparative example was prepared using the following method: Li₂S, P₂S₅, and LiCl raw materials were weighed in an argon atmosphere at a molar ratio of 4:1:3 to prepare Li₂S. 5.5 PS 4.5 Cl 1.5 The system is a sulfide electrolyte material. 3 wt% of 2-(tert-butylthio)-N,N-diethylethyl-1-amine (C10) was added to a ball mill jar. Ball beads were weighed and added to the jar at a ball-to-material ratio of 30:1. The jar was sealed and ball milling was performed at 500 r / min for 24 h. The milled material was then dried at 90℃ for 30 h and sintered at 500℃ for 24 h. After sintering, the material was further ground and crushed.

[0042] Performance testing The sulfide solid electrolyte prepared in Example 1 was examined by electron microscopy and X-ray diffraction analysis, and the electron microscopy results are as follows: Figure 1As shown, the material exhibits a distinct lamellar structure. The XRD pattern is as follows. Figure 2 As shown, the peak at 15.6° is clearly prominent, corresponding to the (111) crystal plane of the material. Compared with Comparative Example 1... Figure 4 In comparison, the peak corresponding to the (111) crystal plane is more prominent, indicating that the crystal plane of this crystal orientation in the material belongs to the growth-dominant crystal plane and is an exposed crystal plane that can be detected.

[0043] The sulfide electrolyte prepared in Comparative Example 1 was examined by electron microscopy and X-ray diffraction analysis. The electron microscopy results are as follows: Figure 3 As shown, the material exhibits a distinctly irregular granular structure. The XRD pattern is as follows. Figure 4 As shown, the peak at the 15.6° position of the material weakens to the point of no obvious prominence.

[0044] The ionic conductivity of the electrolyte materials prepared in the examples and comparative examples was measured. The measurement method is as follows: 0.1g of electrolyte material was weighed and placed into a mold with a diameter of 10 mm, then pressed into an electrolyte sheet under a pressure of 400 MPa. Stainless steel blocking electrodes were then placed on both sides. Impedance testing was performed on the battery system at a frequency range of 1 MHz to 1 Hz. The conductivity of the material was calculated based on the impedance test results. The calculation formula is as follows: ; Where I represents the electrolyte thickness, R b The value represents the bulk resistance, and A represents the area. The thickness of the electrolyte sheet was tested, and the results for five tests were: 0.635 mm, 0.647 mm, 0.637 mm, 0.640 mm, and 0.641 mm; the average was 0.640 mm.

[0045] The test results are shown in Table 1 below.

[0046] Table 1: Performance Test Results of Examples and Comparative Examples

[0047] Table 1 shows that in Examples 1-4, the addition of sulfide within a specific range during the mixing process significantly improved the conductivity. Comparative Example 1, without the addition of sulfide, followed a conventional material synthesis process, and its conductivity remained at the average level of the system. Example 5, with insufficient sulfide, showed little modification, but its material performance was slightly better than Comparative Example 1. Examples 6 and 7, with larger amounts of sulfide, while able to control the structure of the synthesized electrolyte, still introduced some impurities, resulting in slightly worse performance compared to the preferred examples, but slightly better performance than Comparative Example 1. Comparative Example 2, with its short carbon number and low boiling point of the sulfide, directly vaporized during ball milling, resulting in no modification effect; its material performance was comparable to Comparative Example 1. Comparative Example 3, with its excessive sulfide, introduced too many impurities, significantly reducing material performance. Comparative Example 4, with its excessively long carbon number of the sulfide, increased steric hindrance, making it difficult to uniformly adsorb onto the precursor surface during mixing and harder to remove, leading to excessive impurities and a significant decrease in material performance. Comparative Examples 5 and 6 introduced sulfide-like structures containing O and N functional groups. Due to the excessive polarity of these functional groups, they reacted with the electrolyte material system, resulting in a significant decrease in the material's conductivity.

[0048] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. However, it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a sulfide solid electrolyte, characterized in that, Includes the following steps: S1. A sulfide electrolyte is prepared by using a sulfur source, a phosphorus source, and a lithium source. A long-chain sulfide is added to the sulfide electrolyte and ball-milled to obtain a sulfide electrolyte precursor. The long-chain sulfide is an alkyl sulfide with 6 to 16 carbon atoms, and the amount added is less than 10 wt% of the mass of the sulfide electrolyte precursor. S2. The sulfide electrolyte precursor obtained in S1 is dried and then sintered to obtain a sulfide solid electrolyte.

2. The method for preparing sulfide solid electrolyte according to claim 1, characterized in that, The amount of the long-chain sulfide added is 1 to 5 wt% of the mass of the sulfide electrolyte precursor.

3. The method for preparing sulfide solid electrolyte according to claim 1, characterized in that, The long-chain sulfide is an alkyl sulfide with 8 to 16 carbon atoms.

4. The method for preparing the sulfide solid electrolyte according to claim 1, characterized in that, In S1, the ball-to-material ratio during the ball milling process is 10–40:1, the rotation speed is 300–500 r / min, and the ball milling time is 24–48 h.

5. The method for preparing a sulfide solid electrolyte according to claim 1, characterized in that, In S2, the drying temperature is 60–90℃ and the drying time is 24–48 hours.

6. The method for preparing a sulfide solid electrolyte according to claim 1, characterized in that, In S2, the sintering temperature is 450–550℃ and the sintering time is 12–48h.

7. The method for preparing a sulfide solid electrolyte according to claim 1, characterized in that, The long-chain sulfide is selected from one or more of n-octyl methyl sulfide, n-nonyl sulfide, n-decyl methyl sulfide, n-dodecyl sulfide, methyl tetradecyl sulfide, n-hexadecyl sulfide, and 5-thiodecane.

8. The method for preparing a sulfide solid electrolyte according to claim 1, characterized in that, In S1, a sulfide electrolyte is prepared using a sulfur source, a phosphorus source, and a lithium source, wherein the sulfur source, phosphorus source, and lithium source are Li2S, P2S5, and LiCl, respectively, and the molar ratio of Li2S, P2S5, and LiCl is 4-5:1:2-3.

9. A sulfide solid electrolyte prepared by the method as described in claim 1, characterized in that, The sulfide solid electrolyte has a layered structure with exposed (111) crystal planes.

10. The sulfide solid electrolyte according to claim 9, characterized in that, The chemical formula of the sulfide electrolyte precursor is Li 6-x PS 5-x Cl 1+x , where 0≦x≦0.7.

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