A tin sulfide nanofiber film, a preparation method and application thereof

Abstract

The application provides a tin sulfide nanofiber film and a preparation method and application thereof. The tin sulfide nanofiber film has a three-dimensional mesoporous nanofiber network, combines the papermaking film-forming characteristics of cellulose, and has the characteristics of inorganic non-metallic tin sulfide material and lithium metal spontaneous reaction to form lithium-tin alloy lithiumophilic sites and a lithium sulfide interface layer, and can be used for a battery diaphragm modification layer to protect a lithium metal battery, homogenize lithium ion distribution, promote uniform deposition of lithium metal, and inhibit lithium dendrite growth, thereby greatly improving the cycle stability of the lithium metal battery. Compared with a tin sulfide particle material, the tin sulfide nanofiber film has the advantages of flexibility, self-supporting, lightness, thickness controllability, good mechanical strength, high porosity and uniform mesoporous distribution; the application organically links nanocellulose, tin sulfide and a lithium metal battery together, and explores the unique role of the tin sulfide nanofiber film in the battery field, thereby greatly improving the cycle performance of the lithium metal battery and improving the rate performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium battery materials technology, and in particular to a tin sulfide nanofiber thin film, its preparation method, and its application. Background Technology

[0002] Lithium metal anodes possess extremely high theoretical specific capacity (3860 mAh / g) and can be used to construct next-generation high-energy-density lithium metal batteries. However, the electrode interface of lithium metal anodes is unstable, leading to the growth of lithium metal dendrites, which seriously affects the lifespan and safety of lithium metal batteries.

[0003] Against this backdrop, researchers have focused on stabilizing lithium metal anodes by optimizing the lithium metal anode interface. One strategy is to modify the composition and type of electrolyte; for example, high concentrations of lithium salts and electrolyte additives (lithium nitrate, ethylene carbonate, etc.) can promote uniform lithium metal deposition and improve the cycle performance of lithium metal batteries. However, high concentrations of lithium salts impart high viscosity to the electrolyte, which is detrimental to its penetration into the electrode. Constructing artificial interface layers is also an effective way to improve its interface stability. Typically, polymers (such as polydimethylsiloxane) or inorganic substances are coated onto the surface of the lithium metal anode. However, the coating process has strict requirements on the operating environment, which greatly increases the operational difficulty.

[0004] Current research often employs functional coatings to modify separators and improve lithium metal cycle stability. Patent publication CN116470237A discloses that the raw materials for coating preparation typically include inorganic non-metallic ceramic particles, ion sieves, and binders. For example, antimony fluoride is formed on one side of the separator using a binder, and molecular sieves are formed on the other side using a binder. These methods, which achieve the function of the coating by adding binders, have limited application in high-energy-density lithium metal batteries. Recent research has found that tin sulfide, when used as a coating material, can undergo an in-situ electrochemical reaction with lithium metal to form a lithium-tin alloy that induces uniform lithium metal deposition. Simultaneously, the generation of lithium sulfide can improve the stability of the SEI (electrolyte interphase) membrane and suppress lithium dendrite formation. However, due to the powder characteristics of tin sulfide particles, they often rely on binders to coat the separator or lithium metal surface, resulting in the activity of the tin sulfide particles being weakened by the binder covering them. Furthermore, the uneven particle distribution and voids lead to uneven reaction sites and ion distribution, affecting the formation of a highly uniform SEI layer and thus impacting lithium metal cycle stability. Therefore, the method of directly using tin sulfide particles to improve the stability of lithium metal anodes has limitations.

[0005] Previous work by the inventors has shown that cellulose materials, derived from forests and grasslands, possess uniformly distributed hydroxyl groups on their surface, a three-dimensional network structure with uniform pore size distribution, papermaking and film-forming properties, and biodegradability, providing a possibility for designing flexible, self-supporting interface protective layers with uniform porosity. For example, patent authorization number CN115149209B discloses the use of cellulose extracted from common natural plants combined with zirconium ion modification to prepare modified nanocellulose membranes, which significantly improves the rate performance of aqueous zinc-ion batteries or lithium-ion batteries. However, the aforementioned patent only utilizes the ionic cross-linking effect between zirconium ions of soluble zirconium salts and hydroxyl groups on the surface of nanocellulose, essentially still a nanocellulose material. While it utilizes a porous three-dimensional network to improve ion transport, it does not react with the lithium metal anode, making it difficult to control the physicochemical properties of the lithium metal interface electrolyte membrane and unable to effectively protect the lithium metal. Therefore, its application in high-energy-density lithium metal batteries is limited.

[0006] Therefore, we hope to develop a self-supporting tin sulfide nanofiber film with uniform pore size, resistance to lithium dendrites, and ability to strengthen the lithium metal electrolyte interface membrane for use in membrane interlayers to protect lithium metal. Summary of the Invention

[0007] This invention provides a tin sulfide nanofiber thin film, its preparation method, and its application, with the aim of solving the aforementioned problems existing in the background art.

[0008] To achieve the above objectives, embodiments of the present invention provide a tin sulfide nanofiber thin film, its preparation method, and its application. This invention, for the first time, uniformly coats tin sulfide onto nanocellulose, fully utilizing the intrinsic mesoporous network and film-forming properties of nanocellulose to prepare a self-supporting tin sulfide nanofiber thin film, effectively addressing the adverse effects of traditional tin sulfide particle interface control strategies. Simultaneously, this invention utilizes nanocellulose to prepare a high-value tin sulfide nanofiber thin film with uniformly distributed mesopores, enabling homogenization of lithium-ion distribution. The lightweight, self-supporting tin sulfide interface layer can react in situ with lithium metal to form a lithium-philic lithium-tin alloy and a lithium sulfide-rich solid electrolyte interphase (SEI) film, promoting uniform lithium metal deposition, inhibiting dendrite growth, and improving the cycle stability of lithium metal batteries.

[0009] One object of the present invention is to provide a method for preparing tin sulfide nanofiber thin films, comprising the following steps:

[0010] S1: Take nanocellulose powder, add deionized water, and disperse it by ultrasonication to obtain nanocellulose dispersion;

[0011] S2: Add soluble tin salt to the nanocellulose dispersion, and then disperse it by ultrasonication to obtain a nanocellulose dispersion containing tin ions.

[0012] S3: Add soluble sulfide to the tin-ion-containing nanocellulose dispersion and stir to obtain tin sulfide nanofiber suspension, and obtain tin sulfide nanofiber film by filtration, washing and drying.

[0013] The tin sulfide nanofiber film has a uniform and dense tin sulfide coating on the surface of the nanocellulose.

[0014] Preferably, the soluble tin salt is any one of tin methanesulfonate, tin ethanesulfonate, tin dichloride, or tin tetrachloride, with a concentration of 1–12 mmol / L.

[0015] Preferably, the soluble sulfide is any one of potassium sulfide, sodium sulfide, ammonium sulfide, thioacetamide, or thiourea, with a concentration of 1–12 mmol / L.

[0016] Preferably, the stirring reaction time is 1 to 24 hours.

[0017] Preferably, the drying temperature is 40–120°C and the drying time is 6–48 hours.

[0018] Based on a general inventive concept, embodiments of the present invention provide a tin sulfide nanofiber film obtained by the above-described preparation method. This tin sulfide nanofiber film aims to form a uniform and dense tin sulfide coating layer on the surface of nanocellulose, which can undergo an in-situ electrochemical reaction with lithium metal to generate a lithium-philic lithium-tin alloy and lithium sulfide, thereby inducing uniform lithium metal deposition and inhibiting dendrite growth.

[0019] Preferably, the porosity of the tin sulfide nanofiber film is 40% to 80%.

[0020] Preferably, the tin sulfide nanofiber film has a pore size between 20 and 60 nm.

[0021] Preferably, the thickness of the tin sulfide nanofiber film is 1–60 μm.

[0022] The embodiments of the present invention also provide a tin sulfide nanofiber film obtained by the above preparation method or the application of the above tin sulfide nanofiber film in lithium metal batteries.

[0023] Reaction mechanism

[0024] This invention uses nanocellulose as a template and modifies it with tin sulfide to produce a tin sulfide nanofiber film. This film possesses the characteristics of nanocellulose: high mechanical strength, good flexibility, high thermal stability, smooth surface, low density, controllable porosity, and uniform mesopore distribution. Building upon the platform advantages of nanocellulose's solution processability and paper-forming properties, a uniform and dense tin sulfide coating layer is formed on the nanocellulose surface. When applied to lithium metal batteries, this coating forms a lithium sulfide-rich artificial interface protective film and a lithium-tin alloy interface layer, acting as a "skin" for lithium metal. This inhibits lithium dendrite formation during cycling, thereby extending the cycle stability of the lithium metal battery. Simultaneously, it can regulate ion distribution, promote uniform lithium ion transport, and ensure uniform lithium metal deposition. Verification has shown that the tin sulfide nanofiber film protective layer can inhibit lithium dendrite growth and improve the cycle stability of lithium metal batteries.

[0025] The above-described solution of the present invention has the following beneficial effects:

[0026] (1) Compared with pure nanocellulose film, the tin sulfide nanofiber film of the present invention has a unique tin sulfide nanofiber network that can react with lithium metal in situ to form a uniform and continuous lithium-lithium alloy with lithium affinity, promote the uniform nucleation and growth of lithium metal, generate a solid electrolyte interphase (SEI) film rich in Li2S, inhibit the growth of lithium dendrites, and further improve the rate cycle characteristics of lithium metal battery.

[0027] (2) The tin sulfide nanofiber film of the present invention has higher porosity and ionic conductivity, which is beneficial for reducing the internal resistance of the battery and improving the rate performance of lithium metal batteries. The introduction of the inorganic non-metallic tin sulfide coating layer increases the thermal stability of the film and can also shield the hydrogen bonds on the nanocellulose, improving the stability of the film electrolyte and making the battery more stable over a longer period of time. The thickness and porosity of the tin sulfide nanofiber film of the present invention can be adjusted, down to 1 μm, which is significantly thinner than conventional functional coatings based on tin sulfide particles, thus improving the overall energy density of lithium metal batteries.

[0028] (3) Compared with the traditional method of directly coating tin sulfide particles to protect the lithium metal interface, the tin sulfide nanofiber film of the present invention is flexible and self-supporting, has a three-dimensional nanofiber network structure and uniform mesoporous distribution, and is also lightweight and thin, which is in line with the current development trend of lightweight and thin functional lithium metal protective films.

[0029] (4) The preparation process of the tin sulfide nanofiber film of the present invention is simple and fully inherits the intrinsic platform advantages of biomass cellulose materials. The above scheme reveals that inorganic non-metallic tin sulfide nanofibers can be prepared using nanocellulose as a one-dimensional template. The prepared tin sulfide nanofiber film has uniform porosity, which can promote electrolyte wetting, homogenize lithium ion distribution and accelerate lithium ion transport, induce uniform lithium metal deposition, and improve the cycle performance of lithium metal batteries. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 These are scanning electron microscope (SEM) images and optical images of the tin sulfide nanofiber thin film provided in the embodiments of the present invention; (a) SEM image, (b) optical image;

[0032] Figure 2 Scanning electron microscope (SEM) image and optical image of tin sulfide powder provided for Comparative Example 1 of the present invention; (a) SEM image, (b) optical image;

[0033] Figure 3 The XRD patterns of the tin sulfide fiber film provided in the embodiments of the present invention, the tin sulfide provided in Comparative Example 1, and the original nanocellulose film provided in Comparative Example 2 are shown; wherein SnS2-CNF is the tin sulfide nanocellulose film provided in the embodiments of the present invention, SnS2 is the tin sulfide in Comparative Example 1, and CNF is the original nanocellulose film provided in Comparative Example 2.

[0034] Figure 4 The tin sulfide nanofiber film provided in this embodiment of the invention and the original nanocellulose film of Comparative Example 2 are applied to a lithium metal symmetric battery at a capacity of 1 mAh cm⁻¹. -2 Morphology of lithium metal electrode after 200 cycles under the specified conditions; (a) tin sulfide nanofiber film, (b) original nanocellulose film;

[0035] Figure 5 X-ray photoelectron spectroscopy of the tin sulfide nanofiber thin film provided in this embodiment of the invention applied to the lithium metal anode interface in a lithium metal symmetric battery. Detailed Implementation

[0036] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0037] 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.

[0038] 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.

[0039] In this article, "CNF" refers to the original nanocellulose, and "SnS2-CNF" refers to the tin sulfide nanofiber film.

[0040] This invention addresses existing problems by providing a tin sulfide nanofiber thin film, its preparation method, and its applications.

[0041] Example 1

[0042] This embodiment provides a method for preparing tin sulfide nanofiber thin films.

[0043] The method in this embodiment specifically includes the following steps:

[0044] (1) Weigh 40 mg of nanocellulose powder, add a certain amount of deionized water, and sonicate to obtain nanocellulose dispersion;

[0045] (2) Add 0.5g of tin tetrachloride crystals to the nanocellulose dispersion, mix and then ultrasonically disperse to obtain a nanocellulose dispersion containing tin ions.

[0046] (3) Add 0.5 g of thioacetamide to the tin ion-containing nanocellulose dispersion and stir for 6 hours; set up a filtration device and wash the supernatant with deionized water multiple times until the pH is neutral to ensure that excess thioacetamide is washed away and to prevent the synthesis reaction from continuing; disperse the collected precipitate in a certain volume of deionized water by ultrasonication to obtain a uniform tin sulfide nanofiber suspension; take a certain volume of tin sulfide nanofiber suspension for filtration, heat and dry in an oven, and peel off to obtain a tin sulfide nanofiber film with a thickness of 21 micrometers. Its SEM image is shown below. Figure 1 As shown, where Figure 1 (a) It can be seen that the tin sulfide nanofiber film has cross-linked fibers, high porosity and uniform pore size. Figure 1 (b) shows a smooth, flat tin sulfide nanofiber film in a yellowish-brown color.

[0047] Comparative Example 1

[0048] 0.28 g of tin tetrachloride was weighed and dissolved in a certain amount of water to prepare a solution. 0.5 g of thioacetamide was added, and the mixture was stirred for 6 hours. A vacuum filtration apparatus was set up, and the solution was washed repeatedly with deionized water until the pH of the supernatant was neutral. This ensured that excess thioacetamide was removed to prevent further synthesis. The collected precipitate was heated, dried, and then peeled off to obtain tin sulfide powder. Its SEM image is shown below. Figure 2 As shown in (a), without the participation of nanocellulose in the synthesis, the tin sulfide produced consists of particles of varying sizes. Without a binder, a smooth, evenly laid tin sulfide protective layer cannot be obtained; it can only be obtained by... Figure 2 (b) It exists in powder form as shown.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 1 is that: 50mg of nanocellulose powder was weighed, a certain amount of deionized water was added, and the nanocellulose dispersion was obtained after ultrasonic dispersion. The nanocellulose dispersion was then formed by vacuum filtration using a nylon filter membrane. A vacuum filtration device was set up, and the membrane was heated and dried in an oven. The nanocellulose film was then peeled off and the thickness was measured to be 23 micrometers.

[0051] from Figure 3 As can be seen from the XRD pattern, the tin sulfide nanofiber film of the present invention, compared with the nanocellulose film made from the original cellulose, has new peaks at 2θ of 28.19° and 50.06°. Comparison with the XRD pattern of tin sulfide can prove that the new peaks correspond to the characteristic peaks of tin sulfide, indicating that tin sulfide is successfully coated on the surface of nanocellulose.

[0052] The tin sulfide nanofiber film obtained in the examples was applied to a lithium metal symmetric battery, and the lithium metal symmetric battery achieved a 1 mA cm⁻¹ performance. -2 Current density and 1mAh cm -2 After 200 capacity cycles, the lithium metal surface of the matched tin sulfide nanofiber film exhibits a uniform and dense deposition layer (e.g., Figure 4 As shown in the image, the lithium metal surface based on the original nanofiber film is porous and dendritic lithium metal deposition layer appears. This indicates that the tin sulfide nanofiber film can uniformly transport lithium ions, suppress side reactions, and inhibit dendrite growth. Figure 4 XPS phase analysis was performed on the lithium metal surface of the matched tin sulfide nanofiber film in section a, specifically as follows: Figure 5 As shown, Li appears at the lithium metal electrode interface. x Sn y The presence of alloys and Li2S indicates that tin sulfide nanofiber films can undergo in-situ electrochemical reactions with lithium metal to form lithium sulfide and lithium-tin alloys, thereby inducing uniform deposition of lithium metal and inhibiting dendrite growth.

[0053] Comparative Example 3

[0054] The difference between this comparative example and Example 1 is that tin tetrachloride crystals were replaced with bismuth nitrate pentahydrate. All other steps and parameters were the same as in Example 1. In the end, it was impossible to synthesize bismuth sulfide nanofiber films on the basis of nanocellulose, and only powdered bulk samples were obtained.

[0055] In summary, the preparation process of the tin sulfide nanofiber film of this invention is simple. The prepared tin sulfide nanofiber film possesses a three-dimensional mesoporous nanofiber network, combining the papermaking and film-forming properties of cellulose, as well as the characteristics of inorganic non-metallic tin sulfide materials spontaneously reacting with lithium metal to form lithium-tin alloy lithiophilic sites and a lithium sulfide interface layer. Therefore, it can be used as a battery separator modification layer to protect lithium metal batteries, homogenize lithium ion distribution to promote uniform lithium metal deposition, and inhibit lithium dendrite growth, significantly improving the cycle stability of lithium metal batteries. Compared with tin sulfide particulate materials, the tin sulfide nanofiber film of this invention is flexible, self-supporting, lightweight, thin, and has adjustable thickness, with better mechanical strength, high porosity, and uniform mesoporous distribution. This invention organically links nanocellulose, inorganic non-metallic tin sulfide, and lithium metal batteries, and explores the unique role of tin sulfide nanofiber film in the battery field, greatly improving the cycle performance of lithium metal batteries and enhancing their rate performance.

[0056] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a tin sulfide nanofiber thin film, characterized in that, Includes the following steps: S1: Take nanocellulose powder, add deionized water, and disperse it by ultrasonication to obtain nanocellulose dispersion; S2: Add soluble tin salt to the nanocellulose dispersion, and then disperse it by ultrasonication to obtain a nanocellulose dispersion containing tin ions. S3: Add soluble sulfide to the tin-ion-containing nanocellulose dispersion and stir to obtain tin sulfide nanofiber suspension, and obtain tin sulfide nanofiber film by filtration, washing and drying. The tin sulfide nanofiber film has a uniform and dense tin sulfide coating on the surface of the nanocellulose.

2. The method for preparing a tin sulfide nanofiber thin film according to claim 1, characterized in that, The soluble tin salt is any one of tin methanesulfonate, tin ethanesulfonate, tin dichloride, or tin tetrachloride, with a concentration of 1–12 mmol / L.

3. The method for preparing a tin sulfide nanofiber thin film according to claim 1, characterized in that, The soluble sulfide is any one of potassium sulfide, sodium sulfide, ammonium sulfide, thioacetamide, or thiourea, with a concentration of 1–12 mmol / L.

4. The method for preparing a tin sulfide nanofiber thin film according to claim 1, characterized in that, The stirring reaction time is 1 to 24 hours.

5. The method for preparing a tin sulfide nanofiber thin film according to claim 1, characterized in that, The drying temperature is 40–120°C, and the drying time is 6–48 hours.

6. A tin sulfide nanofiber film obtained by the preparation method according to any one of claims 1 to 5.

7. A tin sulfide nanofiber thin film according to claim 6, characterized in that, The porosity of the tin sulfide nanofiber film is 40%–80%.

8. A tin sulfide nanofiber thin film according to claim 6, characterized in that, The pore size of the tin sulfide nanofiber film is between 20 and 60 nm.

9. A tin sulfide nanofiber thin film according to claim 6, characterized in that, The thickness of the tin sulfide nanofiber film is 1–60 μm.

10. The application of a tin sulfide nanofiber film obtained by the preparation method according to any one of claims 1 to 5, or the tin sulfide nanofiber film according to any one of claims 6 to 9, in a lithium metal battery.

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