Composite polysulfide electrolyte membrane, method for preparing the same, and solid-state battery

Abstract

The application provides a composite polysulfide electrolyte film, a preparation method thereof and a solid-state battery, and the preparation method comprises the following steps: mixing a sulfide electrolyte material and a polymer precursor material to perform dry grinding, so as to obtain a sulfide-polymer composite precursor powder; mixing and stirring the sulfide-polymer composite precursor powder and an aprotic organic solvent to obtain a composite polysulfide electrolyte solution; and after film formation of the composite polysulfide electrolyte solution, drying is performed to obtain the composite polysulfide electrolyte film. In the application, the sulfide electrolyte material is introduced into the polymer electrolyte, the two are combined to realize complementary advantages, high conductivity, good interface stability and excellent processing performance are considered, and the long cycle stability of the full solid-state battery can be obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, and relates to a composite polysulfide electrolyte membrane, its preparation method, and a solid-state battery. Background Technology

[0002] Solid-state batteries (SSBs), with their core advantages of high energy density, high safety, and long cycle life, have become an important research and development direction for next-generation energy storage technology. Solid electrolytes, as a key component of SSBs, directly determine many of the battery's core performance indicators. Among the three main types of solid electrolyte systems, sulfide electrolytes have high room-temperature ionic conductivity, low interfacial impedance, good compatibility with lithium metal, and are easy to process, but their stability is generally low; polymer electrolytes are flexible, easy to form films, and have mature processing technology, but their room-temperature conductivity is relatively low, making them suitable for high-temperature applications; oxide electrolytes have excellent chemical stability and safety, and high mechanical strength, but poor interfacial contact, low ionic conductivity, and are difficult to prepare and process. The unique characteristics of these three types of electrolyte materials offer multiple possibilities for overcoming the current limitations of battery technology. In SSBs, the solid electrolyte maintains solid-solid contact with both the positive and negative electrodes, lacking the wetting effect of current electrolytes. In practical applications, the key challenge of insufficient solid-solid contact still needs to be addressed.

[0003] Sulfide solid electrolytes are a key research area in all-solid-state batteries, exhibiting extremely high room-temperature ionic conductivity, approaching or even reaching the level of liquid electrolytes. They also possess low interfacial impedance, good compatibility with lithium metal anodes, and a degree of mechanical flexibility, facilitating densification and large-scale fabrication. However, their chemical stability is poor, readily reacting with air and moisture to produce harmful gases, and their interfacial stability and cycle consistency still require optimization. Polymer solid electrolytes possess good flexibility, adhesion, and film-forming properties, with mature processes suitable for traditional battery manufacturing processes such as winding. They are easy to machine and offer high safety. However, their room-temperature ionic conductivity is relatively low, typically requiring operation at high temperatures. They also exhibit weaker mechanical strength, generally lower interfacial stability with lithium metal, and limitations in energy density and rate performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a composite polysulfide electrolyte membrane, its preparation method, and a solid-state battery. This invention introduces sulfide electrolyte materials into a polymer electrolyte, significantly improving the room-temperature ionic conductivity of the system and compensating for the insufficient conductivity of pure polymers. Simultaneously, the flexibility and bonding properties of the polymer effectively improve the problems of poor solid-solid contact and high interfacial impedance between sulfide particles, enhancing the mechanical properties and film-forming processability of the electrolyte. The combination of these two materials achieves complementary advantages, balancing high conductivity, good interfacial stability, and excellent processing performance, thus significantly improving the long-cycle stability of all-solid-state batteries.

[0005] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a composite polysulfide electrolyte membrane, the method comprising the following steps: The sulfide electrolyte material and the polymer precursor material are mixed and dry-milled to obtain sulfide-polymer composite precursor powder. The sulfide-polymer composite precursor powder is mixed and stirred with an aprotic organic solvent to obtain a composite polysulfide electrolyte solution. The composite polysulfide electrolyte solution is then formed into a film and dried to obtain the composite polysulfide electrolyte membrane.

[0006] This invention employs a pre-process dry grinding method to eliminate side reactions between sulfides and protic solvents, thus preserving their high ionic conductivity. The mechanical grinding force repeatedly breaks, cold-welds, and redisperses the brittle sulfide particles and the tough polymer precursor, forming an ultrafine, homogeneous composite powder. Subsequently, an aprotic solvent is used as the film-forming medium. The aprotic solvent does not dissolve, swell, or damage the sulfide crystal structure, maximizing the preservation of the intrinsic high ionic conductivity of the sulfide. This ensures system homogeneity while maximizing the retention of the sulfide's high ionic conductivity. Furthermore, the aprotic solvent has moderate solubility for the polymer precursor, forming a homogeneous and stable solution, avoiding severe phase separation and numerous internal pores in the membrane. This results in a composite polysulfide electrolyte membrane with complete polymer and sulfide phases. The polymer phase effectively improves the defects of sulfide, such as high brittleness, poor particle contact, and high interfacial impedance, enhancing mechanical properties and film-forming ability. The sulfide phase significantly improves the room-temperature ionic conductivity of the polymer electrolyte. The two complement each other, achieving a balance between high ionic conductivity, low interfacial impedance, and good processing performance, effectively improving the electrochemical performance and cycle stability of all-solid-state batteries.

[0007] Preferably, the sulfide electrolyte material includes Li3PS4 sulfide solid electrolyte and Li7P3S... 11 Any one or a combination of at least two of the following: sulfide solid electrolyte or Li4P2S6 sulfide solid electrolyte.

[0008] Preferably, the polymer precursor material includes any one or a combination of at least two of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, or polyvinylidene fluoride. Typical but non-limiting combinations include combinations of polyethylene oxide and polyacrylonitrile, combinations of polyacrylonitrile and polymethyl methacrylate, or combinations of polymethyl methacrylate and polyvinylidene fluoride, etc., and preferably polyethylene oxide and / or polyacrylonitrile.

[0009] Preferably, the mass ratio of the sulfide electrolyte material to the polymer precursor material is 1:(10~30), for example: 1:10, 1:15, 1:20, 1:25 or 1:30, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1:(10~15).

[0010] Preferably, the grinding speed of the dry grinding is 300rpm~500rpm, for example: 300rpm, 350rpm, 400rpm, 450rpm or 500rpm, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0011] Preferably, the dry grinding time is 10h to 30h, for example: 10h, 15h, 20h, 25h or 30h, etc., not limited to the listed values, other unlisted values ​​within this range are also applicable, preferably 15h to 20h.

[0012] Preferably, the aprotic organic solvent includes any one or a combination of at least two of acetonitrile, 1,2-dimethoxyethane, N-methylformamide, or ethylenedithiol. Typical but non-limiting combinations include combinations of acetonitrile and 1,2-dimethoxyethane, combinations of 1,2-dimethoxyethane and N,N-dimethylformamide, or combinations of acetonitrile and ethylenedithiol, etc., preferably acetonitrile and / or ethylenedithiol.

[0013] Preferably, the mass ratio of the sulfide-polymer composite precursor powder to the aprotic organic solvent is 1:(5~50), for example: 1:5, 1:10, 1:20, 1:30 or 1:50, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 1:(5~10).

[0014] Preferably, the mixing speed is 100 rpm to 500 rpm, for example: 100 rpm, 200 rpm, 300 rpm, 400 rpm or 500 rpm, etc., not limited to the listed values, other unlisted values ​​within this range are also applicable, preferably 100 rpm to 300 rpm.

[0015] Preferably, the mixing time is 24h to 120h, for example: 24h, 48h, 60h, 90h or 120h, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, the drying temperature is 60℃~120℃, for example: 60℃, 80℃, 90℃, 100℃ or 120℃, etc., not limited to the listed values, other unlisted values ​​within this range are also applicable, preferably 70℃~90℃.

[0017] Preferably, the drying time is 24h to 120h, for example: 24h, 48h, 60h, 90h or 120h, etc., not limited to the listed values, other unlisted values ​​within this range are also applicable, preferably 24h to 48h.

[0018] In a second aspect, the present invention provides a composite polysulfide electrolyte membrane, which is prepared by the preparation method described in the first aspect.

[0019] Thirdly, the present invention provides a solid-state battery comprising a composite polysulfide electrolyte membrane as described in the second aspect.

[0020] 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.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention introduces sulfide electrolyte materials into polymer electrolytes, where sulfides and polymer solid electrolytes exhibit significant complementarity in performance. Sulfides have high room temperature ionic conductivity and low interfacial impedance, which can compensate for the insufficient conductivity of polymers; polymers have good flexibility, are easy to process, and have strong adhesion, which can improve the defects of poor solid-solid contact and weak interfacial stability of sulfides. At the same time, the flexible structure of polymers can buffer the interfacial stress of sulfides and improve interfacial contact, while sulfides improve the rate capability and cycle performance of polymer systems. The combination of the two can take into account high ionic conductivity, good interfacial compatibility and processability, and can significantly improve the room temperature ionic conductivity of the system, making up for the insufficient conductivity of pure polymers.

[0022] (2) The composite polysulfide electrolyte membrane of the present invention can be used to make an all-solid-state battery with an initial discharge capacity of more than 101 mAh / g, a discharge capacity of more than 93.8% after 30 cycles, and a capacity retention rate of more than 81.4% after 30 cycles. Detailed Implementation

[0023] 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.

[0024] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0025] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The 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" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0026] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. 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 locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0027] The Li3PS4 sulfide electrolyte material used in the embodiments and comparative examples of this invention was prepared by the following method: Lithium sulfide and phosphorus pentasulfide, totaling 5g, were mixed in a 3:1 molar ratio and ball-milled at 1000rpm for 48h to obtain an LPS-type precursor material. The powdered precursor material was then directly placed into a tableting mold and held at 10MPa for 10min before being placed in an argon atmosphere sintering furnace and reacted at 330℃ for 60h to obtain the Li3PS4 sulfide electrolyte material.

[0028] Example 1 This embodiment provides a composite polysulfide electrolyte membrane, which is prepared by the following method: Li3PS4 sulfide electrolyte material was mixed with polyethylene oxide at a mass ratio of 1:10 and dry ball-milled at 400 rpm for 20 h to obtain sulfide-polymer composite precursor powder. The sulfide-polymer composite precursor powder was mixed with acetonitrile at a mass ratio of 1:5, stirred at 100 rpm for 48 h, transferred to a mold to form a film, and then vacuum dried at 80 °C for 24 h to obtain the composite polysulfide electrolyte membrane.

[0029] Example 2 This embodiment provides a composite polysulfide electrolyte membrane, which is prepared by the following method: Li3PS4 sulfide electrolyte material was mixed with polyacrylonitrile at a mass ratio of 1:12 and dry ball-milled at 300 rpm for 18 h to obtain sulfide-polymer composite precursor powder. The sulfide-polymer composite precursor powder was mixed with ethylenedithiol at a mass ratio of 1:8, stirred at 200 rpm for 60 h, transferred to a mold to form a film, and then vacuum dried at 70 °C for 36 h to obtain the composite polysulfide electrolyte membrane.

[0030] Example 3 This embodiment provides a composite polysulfide electrolyte membrane, which is prepared by the following method: Li3PS4 sulfide electrolyte material was mixed with polyethylene oxide at a mass ratio of 1:15 and dry ball-milled at 500 rpm for 15 h to obtain sulfide-polymer composite precursor powder. The sulfide-polymer composite precursor powder was mixed with acetonitrile at a mass ratio of 1:10, stirred at 300 rpm for 120 h, transferred to a mold to form a film, and then vacuum dried at 90 °C for 24 h to obtain the composite polysulfide electrolyte membrane.

[0031] Example 4 The only difference between this embodiment and Embodiment 1 is that the Li3PS4 sulfide electrolyte material and polyethylene oxide are in a mass ratio of 1:5, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0032] Example 5 The only difference between this embodiment and Embodiment 1 is that the Li3PS4 sulfide electrolyte material and polyethylene oxide are in a mass ratio of 1:20, while the other conditions and parameters are exactly the same as in Embodiment 1.

[0033] Example 6 The only difference between this embodiment and Example 1 is that the mass ratio of sulfide-polymer composite precursor powder to acetonitrile is 1:3, while the other conditions and parameters are exactly the same as in Example 1.

[0034] Example 7 The only difference between this embodiment and Example 1 is that the mass ratio of sulfide-polymer composite precursor powder to acetonitrile is 1:15. All other conditions and parameters are exactly the same as in Example 1.

[0035] Comparative Example 1 The only difference between this comparative example and Example 1 is that the Li3PS4 sulfide electrolyte material is wet-mixed and ground with polyethylene oxide (the solvent is acetonitrile). All other conditions and parameters are exactly the same as in Example 1.

[0036] Comparative Example 2 The only difference between this comparative example and Example 1 is that acetonitrile is replaced with acetic acid (a protic organic solvent), while the other conditions and parameters are exactly the same as in Example 1.

[0037] Performance testing: The composite polysulfide electrolyte membranes obtained in the examples and comparative examples were assembled into all-solid-state batteries. Lithium cobalt oxide was used as the positive electrode material, and fresh-cut lithium foil was used as the negative electrode. Performance tests were performed on the obtained all-solid-state batteries, and the test results are shown in Table 1. Table 1 As can be seen from Table 1, as obtained from Examples 1 to 7, the initial discharge capacity of the all-solid-state battery made of the composite polysulfide electrolyte membrane of the present invention can reach more than 101 mAh / g, the discharge capacity after 30 cycles can reach more than 93.8 mAh / g, and the capacity retention rate after 30 cycles can reach more than 81.4%.

[0038] A comparison of Examples 1 and 4-5 shows that the mass ratio of sulfide electrolyte material to polymer precursor material affects the performance of the composite polysulfide electrolyte membrane described in this invention. A mass ratio of sulfide electrolyte material to polymer precursor material of 1:(10-15) yields a composite polysulfide electrolyte membrane with better performance. If the proportion of sulfide electrolyte material is too large, the polysulfide electrolyte membrane material will have a poor film-forming state, affecting its use. If the proportion of sulfide electrolyte material is too small, the polysulfide electrolyte membrane material will have poor performance due to the lack of active material.

[0039] A comparison of Examples 1 and 6-7 shows that the mass ratio of sulfide-polymer composite precursor powder to aprotic organic solvent affects the performance of the composite polysulfide electrolyte membrane described in this invention. A mass ratio of sulfide-polymer composite precursor powder to aprotic organic solvent of 1:(5-10) yields a composite polysulfide electrolyte membrane with better performance. If the proportion of aprotic organic solvent is too high, the energy consumption for membrane formation will increase. Furthermore, residual organic solution may remain in the membrane material, leading to a deterioration in performance. If the proportion of aprotic organic solvent is too low, the reaction between the sulfide and polymer electrolyte in the solvent will be incomplete, resulting in phase separation and affecting the material's performance.

[0040] As can be seen from the comparison between Example 1 and Comparative Example 1, the present invention eliminates the side reaction between sulfide and protic solvent by dry grinding of sulfide electrolyte material and polymer precursor material in advance, and fully preserves its high ionic conductivity. The mechanical grinding force can repeatedly break, cold weld and redisperse the brittle sulfide particles and tough polymer precursor to form ultrafine and homogeneous composite powder.

[0041] Comparing Example 1 and Comparative Example 2, it can be seen that using an aprotic solvent as the film-forming medium does not dissolve, swell, or destroy the sulfide crystal structure, thus preserving the intrinsic high ionic conductivity of the sulfide to the greatest extent. While ensuring the homogeneity of the system, it also preserves the high ionic conductivity of the sulfide to the greatest extent. Moreover, the aprotic solvent has moderate solubility for the polymer precursor, forming a homogeneous and stable solution, avoiding severe phase separation and numerous internal pores in the membrane. This results in a composite polysulfide electrolyte membrane with a complete polymer phase and a sulfide phase. The polymer phase effectively improves the defects of sulfide, such as high brittleness, poor particle contact, and high interfacial impedance, thereby enhancing mechanical properties and film-forming properties. The sulfide phase significantly improves the room temperature ionic conductivity of the polymer electrolyte.

[0042] The applicant declares that 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 method for preparing a composite polysulfide electrolyte membrane, characterized in that, The preparation method includes the following steps: The sulfide electrolyte material and the polymer precursor material are mixed and dry-milled to obtain sulfide-polymer composite precursor powder. The sulfide-polymer composite precursor powder is mixed and stirred with an aprotic organic solvent to obtain a composite polysulfide electrolyte solution. The composite polysulfide electrolyte solution is then formed into a film and dried to obtain the composite polysulfide electrolyte membrane.

2. The preparation method according to claim 1, characterized in that, The sulfide electrolyte material includes Li3PS4 sulfide solid electrolyte and Li7P3S... 11 Any one or a combination of at least two of the following: sulfide solid electrolyte or Li4P2S6 sulfide solid electrolyte.

3. The preparation method according to claim 1 or 2, characterized in that, The polymer precursor material includes any one or a combination of at least two of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, or polyvinylidene fluoride, preferably polyethylene oxide and / or polyacrylonitrile.

4. The preparation method according to any one of claims 1-3, characterized in that, The mass ratio of the sulfide electrolyte material to the polymer precursor material is 1:(10~30), preferably 1:(10~15).

5. The preparation method according to any one of claims 1-4, characterized in that, The grinding speed of the dry grinding method is 300 rpm to 500 rpm; Preferably, the dry grinding time is 10h~30h, more preferably 15h~20h.

6. The preparation method according to any one of claims 1-5, characterized in that, The aprotic organic solvent includes any one or a combination of at least two of acetonitrile, 1,2-dimethoxyethane, N,N-dimethylformamide or ethylenedithiol, preferably acetonitrile and / or ethylenedithiol.

7. The preparation method according to any one of claims 1-6, characterized in that, The mass ratio of the sulfide-polymer composite precursor powder to the aprotic organic solvent is 1:(5~50), preferably 1:(5~10).

8. The preparation method according to any one of claims 1-7, characterized in that, The mixing speed is 100 rpm to 500 rpm, preferably 100 rpm to 300 rpm; Preferably, the mixing and stirring time is 24h~120h; Preferably, the drying temperature is 60℃~120℃, more preferably 70℃~90℃; Preferably, the drying time is 24h to 120h, and more preferably 24h to 48h.

9. A composite polysulfide electrolyte membrane, characterized in that, The composite polysulfide electrolyte membrane is prepared by the preparation method according to any one of claims 1-8.

10. A solid-state battery, characterized in that, The solid-state battery comprises the composite polysulfide electrolyte membrane as described in claim 9.

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