Self-supporting sulfide solid electrolyte membrane and preparation method and application thereof

Abstract

The invention relates to the field of batteries, in particular to a self-supporting sulfide solid electrolyte membrane as well as a preparation method and application thereof. The self-supporting sulfide solid electrolyte membrane comprises a sulfonated bacterial cellulose aerogel skeleton and a sulfide solid electrolyte compounded on the sulfonated bacterial cellulose aerogel skeleton. According to the solid electrolyte membrane, the affinity of a cellulose skeleton and sulfide electrolyte powder is improved mainly by introducing the cellulose skeleton into a sulfonic acid group, so that the cellulose skeleton is fully filled, and the ionic conductivity of the electrolyte membrane is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a self-supporting sulfide solid electrolyte film and a preparation method and application thereof. BACKGROUND

[0002] All-solid-state batteries have intrinsic safety and high energy density advantages, and are known as one of the most promising electrochemical energy storage devices in the next generation. Due to its ultra-high ionic conductivity, sulfide solid electrolyte has the most practical prospect, but the inherent brittleness and difficulty in batch processing into a film of the electrolyte hinder its further application in solid-state batteries.

[0003] Solid electrolyte thinning and flexibility are the core technical directions for the breakthrough of solid-state battery technology, and are of great significance for promoting the industrial application of solid-state batteries. At present, the main method for forming a self-supporting sulfide electrolyte film is to use a mechanical support skeleton, such as a cellulose film, a polyphenylene terephthalamide non-woven fabric, a PET non-woven fabric, etc. The sulfide electrolyte is then filled into the skeleton, or the dried electrolyte film is directly mechanically compressed with the fiber skeleton to realize a self-supporting electrolyte film. Although this method improves the mechanical strength of the electrolyte film, the ion-inert mechanical skeleton intermediate layer often hinders ion transmission, and the sulfide electrolyte is not fully filled, resulting in low ion conductivity of the electrolyte film, which is not conducive to the rate characteristics of the battery. Therefore, it is necessary to design a high-performance sulfide electrolyte film with ultra-thin, high mechanical strength and good ion transmission capacity.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] For solid-state batteries using cellulose as a support, cellulose material is generally directly compounded with solid-state electrolyte, and the ion transmission capacity of cellulose material itself is limited, so the support skeleton will inevitably affect the ionic conductivity of the solid-state electrolyte material. The present application aims to provide a high-ionic-conductivity self-supporting sulfide solid electrolyte film and a preparation method thereof. The solid electrolyte film mainly introduces sulfonic acid groups into the cellulose skeleton to improve the affinity of the cellulose skeleton and the sulfide electrolyte powder, so that the electrolyte film is fully filled and the ionic conductivity is improved.

[0006] In order to achieve the above-mentioned purpose of the present application, the following technical solutions are adopted: In one aspect of the present application, a self-supporting sulfide solid electrolyte film is provided, comprising: a sulfonated bacterial cellulose aerogel skeleton, and a sulfide solid electrolyte compounded on the sulfonated bacterial cellulose aerogel skeleton.

[0007] The solid electrolyte membrane mainly improves the affinity of the cellulose skeleton and sulfide electrolyte powder by introducing sulfonic acid groups into the cellulose skeleton, makes the sulfide electrolyte powder filled sufficiently, and improves the ionic conductivity of the electrolyte membrane.

[0008] Another aspect of the present application also relates to a preparation method of the self-supporting sulfide solid electrolyte membrane, comprising the following steps: The sulfide solid electrolyte is compounded with the sulfonated bacterial cellulose aerogel skeleton.

[0009] The preparation method of the self-supporting sulfide solid electrolyte membrane is simple, efficient and has strong universality. Through the classic sulfonation reaction and the aerogel freeze-drying technology, a three-dimensional supporting skeleton with enhanced ionic conductivity is constructed, and the inherent brittleness and difficulty of forming a film of the sulfide electrolyte are ingeniously solved.

[0010] Another aspect of the present application also relates to a solid-state battery comprising the self-supporting sulfide solid electrolyte membrane or the self-supporting sulfide solid electrolyte membrane prepared by the preparation method of the self-supporting sulfide solid electrolyte membrane.

[0011] Compared with the prior art, the present application has the following beneficial effects: (1) The self-supporting sulfide solid electrolyte membrane provided by the present application successfully prepares an integrated membrane product with ultra-thin, high mechanical strength and excellent ionic conductivity by introducing a sulfonic acid group bacterial cellulose aerogel as a three-dimensional skeleton. The sulfonic acid group significantly improves the interfacial affinity between the cellulose skeleton and the sulfide electrolyte particles, so that the electrolyte is more fully and densely filled, effectively reducing the interfacial ion transfer resistance; at the same time, the sulfonic acid group itself can act as an additional lithium ion transfer site, and has a synergistic ion conduction effect with the sulfide electrolyte, which greatly improves the bulk ion conductivity of the electrolyte membrane. In addition, the membrane also exhibits improved negative electrode interface dynamics, laying a foundation for key materials for building high-performance and high-safety all-solid-state batteries.

[0012] (2) The preparation method of the self-supporting sulfide solid electrolyte membrane provided by the present application is simple, efficient and has strong universality. The method uses widely available and green bacterial cellulose as raw material, constructs a three-dimensional supporting skeleton with enhanced ionic conductivity through classic sulfonation reaction and aerogel freeze-drying technology, and ingeniously solves the inherent brittleness and difficulty of forming a film of the sulfide electrolyte. The method provides two compounding paths of "slurry direct coating" and "dry film cold pressing", which has high flexibility and can be compatible with different types of sulfide electrolytes and process equipment requirements, and is easy to realize large-scale preparation. The whole process has mild and controllable conditions, which provides a feasible technical route for batch production of high-performance self-supporting sulfide electrolyte membranes. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0014] Figure 1 schematic diagram for sulfonation reaction; Figure 2 structural formula of bacterial cellulose; Figure 3 comparative cycle capacity curve. DETAILED DESCRIPTION

[0015] The technical solutions of the present application will be described clearly and completely in combination with the drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be purchased in the market.

[0016] In one aspect of the present application, a self-supporting sulfide solid electrolyte film comprises: a sulfonated bacterial cellulose aerogel skeleton, and a sulfide solid electrolyte compounded on the sulfonated bacterial cellulose aerogel skeleton.

[0017] The technical concept of the present application is: 1) using sulfonation reaction, by sulfonating the surface hydroxyl groups of bacterial cellulose, a grafted sulfonate bacterial cellulose aerogel is prepared; 2) a sulfide solid electrolyte is directly coated on the sulfonated bacterial cellulose aerogel or cold-pressed on the sulfonated bacterial cellulose aerogel film to prepare an ultrathin self-supporting sulfide solid electrolyte film.

[0018] The self-supporting sulfide electrolyte film introduces sulfonate groups into bacterial cellulose in advance, and prepares cellulose aerogel by freeze-drying, which provides support for solid electrolyte, overcomes the difficulty of poor flexibility and difficulty of self-supporting film of inorganic solid electrolyte, and thus an ultrathin, lightweight and high mechanical strength electrolyte film is prepared.

[0019] The introduction of sulfonates into the cellulose skeleton of this self-supporting sulfide electrolyte membrane improves the affinity between the cellulose skeleton and the sulfide electrolyte powder, enhances the filling capacity of the sulfide electrolyte in the skeleton, and improves the ionic conductivity of the self-supporting electrolyte membrane.

[0020] The introduction of sulfonates improves the lithium-ion transport capacity of the framework in the self-supporting electrolyte film and has a synergistic effect with the ion transport between sulfide electrolyte particles, jointly improving the overall ionic conductivity of the electrolyte film. In addition, sulfonates can also improve the interfacial dynamics between the electrolyte film and the negative electrode.

[0021] Furthermore, the sulfonated bacterial cellulose aerogel skeleton is mainly composed of sulfonated bacterial cellulose aerogel, which is obtained by reacting bacterial cellulose with a sulfonating agent to graft sulfonic acid groups and / or sulfonate groups onto its surface hydroxyl groups.

[0022] Furthermore, the sulfonating agent includes sodium sulfite.

[0023] Furthermore, the bacterial cellulose has a fiber diameter of 50~200nm, including but not limited to a point value of any one of 50nm, 100nm, 150nm or 200nm or a range between any two.

[0024] Furthermore, the particle size D of the sulfide solid electrolyte 50 Its wavelength ranges from 600 nm to 15 μm.

[0025] Another aspect of the present invention relates to a method for preparing the aforementioned self-supporting sulfide solid electrolyte membrane, comprising the following steps: The sulfide solid electrolyte was combined with the sulfonated bacterial cellulose aerogel framework.

[0026] The method for preparing the self-supporting sulfide solid electrolyte membrane is simple, efficient, and highly versatile. Using widely available and environmentally friendly bacterial cellulose as raw material, this method constructs a three-dimensional support framework with enhanced ionic conductivity through classic sulfonation and aerogel freeze-drying techniques, cleverly solving the inherent brittleness and difficulty in film formation of sulfide electrolytes. The method offers two composite pathways: "direct coating of slurry" and "cold pressing of dry film," providing high flexibility and compatibility with different types of sulfide electrolytes and process equipment requirements, facilitating large-scale production. The entire process is characterized by mild and controllable conditions, providing a practical technical route for the mass production of high-performance self-supporting sulfide electrolyte membranes.

[0027] Furthermore, the preparation method of the sulfonated bacterial cellulose aerogel skeleton includes the following steps: The mixture containing the bacterial cellulose, the catalyst and the sulfonating agent is subjected to a sulfonation reaction (the reaction process of the sulfonation reaction is as shown in Figure 1 and Figure 2 cooling, adjusting the pH to neutral and washing to obtain a sulfonic acid bacterial fiber suspension; the sulfonic acid bacterial fiber suspension is subjected to freeze-drying.

[0028] Further, the addition ratio of the bacterial cellulose, the catalyst and the sulfonating agent is 100 g: 0.2~0.4 mol: 0.01~0.5 mol, including but not limited to 100 g: 0.2 mol: 0.5 mol, 100 g: 0.3 mol: 0.3 mol or 100 g: 0.4 mol: 0.01 mol.

[0029] Further, the catalyst includes NaOH.

[0030] Further, the sulfonating agent includes Na2SO3.

[0031] Further, the mass ratio of the sulfonic acid bacterial fiber suspension and the sulfide solid-state electrolyte is 10: 15~25.

[0032] Further, the temperature of the sulfonation reaction is 60~90℃ (for example, it can be but is not limited to any one of 60℃, 65℃, 70℃, 75℃, 80℃, 85℃ or 90℃ or a range value between any two of them), and the time is 4~12h (for example, it can be but is not limited to any one of 4h, 6h, 8h, 10h or 12h or a range value between any two of them).

[0033] Further, the temperature of the freeze-drying is -55~-50℃ (for example, it can be but is not limited to any one of -55℃, -53℃ or -50℃ or a range value between any two of them), and the time is 10~15h (for example, it can be but is not limited to any one of 10h, 12h, 14h or 15h or a range value between any two of them).

[0034] Further, the pH adjusted to neutral is 6.8~7 (for example, it can be but is not limited to any one of 6.8, 6.9 or 7.0 or a range value between any two of them).

[0035] Further, the sulfide solid-state electrolyte is compounded with the sulfonated bacterial cellulose aerogel framework in one of the following ways: (1) a slurry containing the sulfide solid-state electrolyte, a binder and a solvent is coated on the sulfonated bacterial cellulose aerogel, followed by drying and hot pressing; (2) dry film of the pre-prepared sulfide solid electrolyte is cold-pressed with the sulfonated bacterial cellulose aerogel.

[0036] Further, when the method (1) is adopted, the mass ratio of the sulfide solid electrolyte to the high-molecular binder is (90-99.5):(0.5-10) (for example, but not limited to, 90:10, 93:7, 95:5, 98:2, or 99.5:0.5), and the solid content of the slurry is 25%-65% (for example, but not limited to, 25%, 35%, 45%, 55%, or 65%, any one of which is a point value or a range value between any two of them).

[0037] Further, the sulfide solid electrolyte comprises at least one of Li6PS5Cl, Li6PS5Br, Li6PS5I, Li 10 SnPS 12 or Li 10 GeP2S 12 .

[0038] Further, the solvent comprises at least one of dichloromethane, tetrahydrofuran, ethyl acetate, butyl butyrate, toluene, xylene, diethylbenzene, or anisole.

[0039] Further, the binder comprises at least one of SBR, NBR, PIB, HNBR, SEBS, or SEPS.

[0040] Further, the mixing method of the sulfide solid electrolyte slurry is defoaming stirring.

[0041] Further, the coating thickness is 30-100 μm, including but not limited to 30, 40, 50, 60, 70, 80, 90, or 100, any one of which is a point value or a range value between any two of them.

[0042] Another aspect of the present application also relates to a solid-state battery comprising the self-supporting sulfide solid electrolyte film or the self-supporting sulfide solid electrolyte film prepared by the preparation method of the self-supporting sulfide solid electrolyte film.

[0043] Embodiments of the present application will be described in detail below with reference to Examples, but those skilled in the art will understand that the following Examples are only for illustration of the present application and should not be considered as limiting the scope of the present application. The specific conditions not specified in the Examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained by purchase.

[0044] The unpurified bacterial cellulose is usually directly taken from the culture solution, and its form is usually a moist, jelly-like gel film. It contains not only the bacterial cellulose itself, but also the production bacteria, culture medium ingredients, metabolic byproducts, water, and the like. The purified bacterial cellulose is a relatively pure cellulose material after a series of physical and chemical treatments to remove all the above impurities.

[0045] Example 1 The preparation method of the self-supporting sulfide solid electrolyte film provided in this embodiment includes the following steps: 1. The purified bacterial cellulose is washed with deionized water until it is neutral, and the surface moisture is gently absorbed with filter paper. 100 g of the bacterial cellulose is weighed and placed in a 500 mL flask, 200 mL of 1.0 M NaOH solution is added, and stirring is performed at room temperature for 30 min. 0.05 mol of anhydrous Na2SO3 is added, nitrogen is introduced for protection, sodium hydroxide is used as a catalyst, and reaction is performed at 80°C. After cooling, 1 M HCl solution is slowly added dropwise under ice water bath stirring to adjust the pH value to 7.0. The obtained product is washed with deionized water to obtain a sulfonic acid bacterial cellulose suspension.

[0046] 2. Preparation of bacterial cellulose aerogel: 10 g of the sulfonate bacterial cellulose suspension is added to 40 g of deionized water. The obtained suspension is stirred and ultrasonically treated at room temperature, and then transferred to a mold. After freeze-drying at -52°C for 12 h, a sulfonic acid bacterial cellulose aerogel is obtained.

[0047] 3. Preparation of self-supporting sulfide solid electrolyte: 20 g of the sulfide solid electrolyte and NBR binder are dissolved in 50 ml of butyl butyrate solution to form a slurry with an active material content of 99%, and the slurry is coated on the dried sulfonic acid bacterial cellulose aerogel. The cellulose membrane aerogel coated with the sulfide solid electrolyte is hot-pressed into a film, thereby preparing a self-supporting sulfide solid electrolyte film.

[0048] 4. Assembly of solid-state battery: The tri-element positive electrode sheet after isostatic pressing, the sulfide solid electrolyte film, and the indium foil / lithium foil are assembled into a single-piece battery in a glove box, packaged in an aluminum plastic film, subjected to 500 MPa isostatic pressing, and tested at 20 MPa.

[0049] Example 2 The amount of anhydrous Na2SO3 added in step 1 of Example 1 is 0.02 mol, and other conditions remain unchanged.

[0050] Example 3 The amount of anhydrous Na2SO3 added in step 1 of Example 1 is 0.1 mol, and other conditions remain unchanged.

[0051] Example 4 Other conditions being the same, the slurry is coated on an Al substrate to dry into a film, the sulfide solid electrolyte-coated cold-pressed to the support, and the solid electrolyte layer transferred to the cellulose film composite support by pressing to prepare a self-supporting sulfide solid electrolyte film.

[0052] Example 5 The difference between this example and Example 1 is that the conditions of the sulfonation reaction and freeze-drying are different, the temperature of the sulfonation reaction is 60°C, the time is 4h, and the temperature of the freeze-drying is -50°C, the time is 15h.

[0053] Example 6 The difference between this example and Example 1 is that the conditions of the sulfonation reaction and freeze-drying are different, the temperature of the sulfonation reaction is 90°C, the time is 12h, and the temperature of the freeze-drying is -55°C, the time is 10h.

[0054] Comparative Example 1 1. Preparation of an ultrathin self-supporting sulfide solid electrolyte film: 20g of sulfide solid electrolyte and NBR binder are dissolved in 50ml of butyl butyrate solution to form a slurry with an active material content of 99%, which is coated on an Al substrate to dry into a film, the sulfide solid electrolyte-coated cold-pressed to the cellulose film support, and the solid electrolyte layer transferred to the cellulose film composite support by pressing to prepare a self-supporting sulfide solid electrolyte film.

[0055] 2. Assembly of a solid-state battery: same as Example 1.

[0056] Comparative Example 2 1. Preparation of an ultrathin self-supporting sulfide solid electrolyte film: 20g of sulfide solid electrolyte and NBR binder are dissolved in 50ml of butyl butyrate solution to form a slurry with an active material content of 99%, which is coated on an Al substrate to dry into a film, the sulfide solid electrolyte-coated cold-pressed to the cellulose film support, and the solid electrolyte layer transferred to the cellulose film composite support by pressing to prepare a self-supporting sulfide solid electrolyte film.

[0057] 2. Assembly of a solid-state battery: same as Example 1.

[0058] Table 1 Battery performance of electrolyte films in Examples and Comparative Examples (ion conductivity of electrolyte films was tested after 300MPa isostatic pressing)

[0059] Comparative Example 1 involved compounding a sulfide electrolyte with an unmodified cellulose backbone via simple mechanical cold pressing. Comparison with the embodiments of this invention shows that whether or not the cellulose backbone undergoes "sulfonation" chemical modification is crucial in determining the significant performance differences. Comparative Example 1 significantly lagged behind in ionic conductivity, discharge capacity, and cycle life, especially in cycle retention (65.9%), which was far lower than the highest example (91.2%). This demonstrates that simple physical-mechanical compounding leads to poor interfacial bonding between the electrolyte and the backbone, obstructed ion transport channels, and interfacial instability. Conversely, the sulfonation treatment of this invention fundamentally solves these problems by enhancing interfacial affinity and synergistic ion conduction mechanisms, achieving a leap in performance.

[0060] Comparative Example 2 employed a process of directly coating the electrolyte slurry onto an unsulfonated cellulose membrane. This process is similar in steps to some embodiments of the present invention, with the key difference being whether the cellulose backbone underwent "sulfonation" modification. The comparative data clearly show that even with similar processes, the ionic conductivity of Comparative Example 2 (0.55 mS / cm) was less than half that of the optimal example (1.32 mS / cm). This strongly demonstrates that the performance improvement does not simply stem from the physical step of "coating," but rather from the fundamental change brought about by the sulfonic acid groups—which significantly improve the wetting and filling effect of the electrolyte slurry within the backbone and provide additional ion jumping sites. Therefore, sulfonation is an indispensable technical feature for achieving the beneficial effect of high ionic conductivity.

[0061] Depend on Figure 3 As can be seen, Examples 1-3 using the technical solution of this invention exhibit significantly better cycle stability than the comparative examples, with their discharge capacity decreasing very slowly with increasing cycle number, resulting in a flat curve. Comparative Example 1, on the other hand, shows the most rapid capacity decay, with the steepest curve slope, highlighting the interface instability problem caused by simple physical recombination. Although the cycle performance of Comparative Example 2 is better than that of Comparative Example 1, it is still significantly inferior to all examples. This figure strongly demonstrates with visual data that sulfonation modification, by improving interface affinity and stability, is key to significantly improving the long cycle life of all-solid-state batteries.

[0062] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A self-supporting sulfide solid electrolyte membrane, characterized in that, include: Sulfonated bacterial cellulose aerogel framework, and a sulfide solid electrolyte compounded on the sulfonated bacterial cellulose aerogel framework.

2. The self-supporting sulfide solid electrolyte membrane according to claim 1, characterized in that, The sulfonated bacterial cellulose aerogel skeleton is mainly composed of sulfonated bacterial cellulose aerogel, which is obtained by reacting bacterial cellulose with a sulfonating agent to graft sulfonic acid groups and / or sulfonate groups onto its surface hydroxyl groups.

3. The self-supporting sulfide solid electrolyte membrane according to claim 2, characterized in that, The sulfonating agent includes sodium sulfite.

4. The self-supporting sulfide solid electrolyte membrane according to claim 1, characterized in that, The bacterial cellulose fibers have a diameter of 50~200nm.

5. The self-supporting sulfide solid electrolyte membrane according to claim 1, characterized in that, The particle size D of the sulfide solid electrolyte 50 Its wavelength ranges from 600 nm to 15 μm.

6. The method for preparing a self-supporting sulfide solid electrolyte membrane according to any one of claims 1 to 5, characterized in that, Includes the following steps: The sulfide solid electrolyte was combined with the sulfonated bacterial cellulose aerogel framework.

7. The method for preparing a self-supporting sulfide solid electrolyte membrane according to claim 6, characterized in that, The preparation method of the sulfonated bacterial cellulose aerogel skeleton includes the following steps: The mixture containing the bacterial cellulose, catalyst, and sulfonating agent is subjected to sulfonation under nitrogen protection, followed by cooling, pH adjustment to neutralization, and washing to obtain a sulfonic acid bacterial cellulose suspension; the sulfonic acid bacterial cellulose suspension is then freeze-dried.

8. The method for preparing a self-supporting sulfide solid electrolyte membrane according to claim 7, characterized in that, Includes at least one of the following technical features: (1) The addition ratio of the bacterial cellulose, the catalyst and the sulfonating agent is 100g: 0.2~0.4mol: 0.01~0.5mol; (2) The catalyst includes: NaOH; (3) The sulfonating agent includes: Na2SO3; (4) The mass ratio of the sulfonic acid bacterial fiber suspension to the sulfide solid electrolyte is 10:15~25.

9. The method for preparing a self-supporting sulfide solid electrolyte membrane according to claim 7, characterized in that, The sulfonation reaction is carried out at a temperature of 60~90℃ for 4~12 hours. And / or, the freeze-drying temperature is -55~-50℃, and the time is 10~15h.

10. A solid-state battery, characterized in that, The self-supporting sulfide solid electrolyte membrane includes the self-supporting sulfide solid electrolyte membrane prepared by the preparation method of the self-supporting sulfide solid electrolyte membrane according to any one of claims 1 to 5 or any one of claims 6 to 9.

Images