SnS2@Sn-SA electrode material, preparation method and application thereof

Abstract

This invention belongs to the technical field of lithium-ion battery electrode materials, and discloses a SnS2@Sn-SA electrode material, its preparation method, and its application. This invention employs a one-step solvothermal method, mixing tetravalent tin salt, a sulfur source, sodium alginate, and a solvent, so that the H2S generated by the decomposition of the sulfur source during the solvothermal reaction reacts with the Sn in the tetravalent tin salt. 4+ The reaction generates SnS2 nanosheet particles; and makes the Sn in the tetravalent tin salt... 4+ Chemical cross-linking with the carboxyl groups in sodium alginate forms Sn-SA hydrogel, resulting in a SnS2@Sn-SA electrode material with SnS2 nanosheets as the core and Sn-SA hydrogel as the shell. The Sn-SA hydrogel shell in the SnS2@Sn-SA electrode material prepared by this invention effectively alleviates the problems of large volume changes, aggregation, and dissolution of SnS2 during charge-discharge cycles, achieving a balance between high-density energy storage and superior performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode material technology, specifically relating to a SnS2@Sn-SA electrode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries, as energy storage devices that combine high energy density and high voltage, have been widely used in portable electronic devices, power tools, hybrid power and electric vehicles.

[0003] Graphite, as the most widely used carbon-based anode material in lithium-ion batteries, possesses high conductivity, excellent interlayer structure, and stable electrochemical performance. However, the limitations of the lithium storage mechanism on the surface of graphite anode materials result in a relatively low theoretical specific capacity, making it difficult to meet the ever-increasing demands for high-density energy storage. Therefore, exploring alternatives to carbon-based anode materials is both indispensable and challenging.

[0004] Various lithium-ion battery anode materials have been prepared in existing technologies, such as metal alloys, metal oxides, metal sulfides, and metal phosphides. Among them, layered metal dichalcogenides possess numerous advantageous properties, making them promising alternative materials. The large specific surface area of ​​layered metal dichalcogenides ensures optimal contact between active sites and lithium ions, while their tunable interlayer spacing enhances lithium ion transport, thereby reducing impedance during electrochemical reactions. Among layered metal dichalcogenides, tin disulfide stands out due to its suitable redox potential, high reactivity, and high theoretical specific capacity. However, tin disulfide has inherently low conductivity, significant volume change during charging and discharging (approximately 340%), and a tendency to aggregate and dissolve in the electrolyte, leading to significant capacity decay and failure to meet capacity requirements, exhibiting unsatisfactory rate and cycle performance.

[0005] To address the aforementioned issues, existing technologies propose the following solutions: First, by constructing tin disulfide materials with nanostructures, such as nanosheets, nanoparticles, and nanoflowers, the impact of tin disulfide volume changes on the structural stability of lithium-ion batteries can be effectively mitigated, enhancing lithium-ion diffusion kinetics. Second, by combining tin-based materials with carbonaceous materials, electronic / ionic conductivity can be improved, and structural collapse caused by tin disulfide volume changes can be buffered.

[0006] Although the tin disulfide materials prepared by the above methods alleviate the impact of tin disulfide volume change on the electrode structure of lithium-ion batteries to some extent, the synthesis process of the above methods is complicated, and the prepared tin disulfide still has problems such as poor intrinsic conductivity and unstable electrochemical performance of lithium-ion batteries due to volume change. Therefore, they cannot effectively solve the problem of lithium-ion battery electrochemical performance caused by tin disulfide volume change. Summary of the Invention

[0007] To address the technical problems of complex preparation methods for tin disulfide materials and the impact of tin disulfide volume changes on the electrode structure of lithium-ion batteries, leading to unstable electrochemical performance, this invention provides a SnS2@Sn-SA electrode material, its preparation method, and its applications. This invention uses safe and readily available raw materials, and the preparation method is simple. This invention employs a one-step solvothermal method, mixing tetravalent tin salt, a sulfur source, sodium alginate, and a solvent, so that the H2S generated during the solvothermal reaction of the sulfur source reacts with the Sn in the tetravalent tin salt. 4+ The reaction generates SnS2 nanosheet particles; and makes the Sn in the tetravalent tin salt... 4+ Chemical cross-linking with the carboxyl groups in sodium alginate forms Sn-SA hydrogel, yielding a core-shell structured SnS2@Sn-SA electrode material with SnS2 nanosheets as the core and Sn-SA hydrogel as the outer shell. The Sn-SA hydrogel outer shell of the SnS2@Sn-SA electrode material prepared in this invention effectively mitigates the large volume change of the internal SnS2 nanosheets, hindering the growth of Sn... 4+ The shuttle motion inhibits further dissolution and aggregation of SnS2 in organic solvents. This effectively solves the problems of large volume changes, aggregation, and dissolution of SnS2 during charge-discharge cycles, achieving a balance between high-density energy storage and superior stability.

[0008] The first objective of this invention is to provide a method for preparing SnS2@Sn-SA electrode material, comprising the following steps:

[0009] A tetravalent tin salt, a sulfur source, sodium alginate, and a solvent are mixed and subjected to a solvothermal reaction, so that the H2S generated by the decomposition of the sulfur source during the solvothermal reaction reacts with the Sn in the tetravalent tin salt. 4+ The reaction generates SnS2 nanosheets; and makes the Sn in the tetravalent tin salt... 4+ By chemically crosslinking with the carboxyl and hydroxyl groups in sodium alginate, a Sn-SA hydrogel is formed, resulting in a SnS2@Sn-SA electrode material with SnS2 nanosheet particles as the core and Sn-SA hydrogel as the shell.

[0010] It should be noted that in the solvothermal reaction process of the SnS2@Sn-SA electrode material prepared by this invention, the reaction temperature is the main condition and is the key to ensuring the effective synthesis of the active material SnS2. Therefore, this invention explores the effect of solvothermal reaction temperature on the formation and growth of SnS2 nanosheets, and finds that the reaction temperature plays a crucial role in the formation and growth of SnS2 nanosheets. When the temperature is below 160℃, the H2S generated by the decomposition of the sulfur source reacts with the Sn in the tetravalent tin salt. 4+The reaction is slow, the growth rate of SnS2 nanosheets is inhibited, and very few SnS2 nanoparticles are obtained. When the temperature is higher than 200℃, the temperature rise will accelerate the dissolution of some of the generated SnS2, and the growth rate of SnS2 nanosheets is difficult to control. The resulting material contains very little active SnS2. The preferred solvothermal reaction temperature of this invention is 160℃~200℃, and the preferred solvothermal reaction time is 10h~14h.

[0011] Furthermore, in this invention, the external Sn-SA hydrogel plays a crucial role in the structure of the internal SnS2 nanoparticles and the lithium-ion transport performance. If the sodium alginate thickness is too thin, i.e., the proportion of sodium alginate is too low, it will affect the interaction between the Sn in the tetravalent tin salt and the... 4+ If the Sn-SA hydrogel formed by the cross-linking reaction is too thin, it will affect the Sn-SA hydrogel's resistance to volume deformation and be detrimental to the structural stability; if the Sn-SA hydrogel is too thick, it will cause difficulties in lithium-ion transport, resulting in a decrease in lithium-ion transport efficiency. The preferred Sn in this invention is the tetravalent tin salt. 4+ The molar ratio of sulfur source to sodium alginate is 1:2-3:0.4-0.8.

[0012] Preferably, the tetravalent tin salt is one of tin tetrachloride pentahydrate and tin diethyldithiocarbamate.

[0013] Preferably, the sulfur source is one of thioacetamide and thiourea.

[0014] Preferably, the solvent is one of isopropanol, water, and ethylene glycol.

[0015] The second objective of this invention is to provide a SnS2@Sn-SA electrode material prepared by the above-described preparation method.

[0016] A third objective of this invention is to provide the application of the SnS2@Sn-SA electrode material in the preparation of lithium-ion batteries, wherein the SnS2@Sn-SA electrode material serves as the negative electrode material of the lithium-ion battery.

[0017] Preferably, the method for preparing a lithium-ion battery includes the following steps:

[0018] Preparation of working electrode sheet: Mix SnS2@Sn-SA electrode material, conductive agent and binder, and coat it on copper foil.

[0019] Counter electrode preparation: lithium metal is compressed and cut into sheets.

[0020] Preparation of electrolyte: Lithium bis(trifluoromethanesulfonyl)imide was dissolved in an organic solvent and lithium nitrate was added to prepare an electrolyte.

[0021] Preparation of lithium-ion batteries: The counter electrode, separator material, electrolyte and working electrode are assembled in sequence to obtain lithium-ion batteries.

[0022] Preferably, the concentration of lithium bis(trifluoromethanesulfonyl)imide in the electrolyte is 1 mol / L, and the content of lithium nitrate is 2.0%.

[0023] Preferably, the organic solvent is ethylene glycol dimethyl ether and 1,3-dioxane in a volume ratio of 1:1.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention involves mixing tetravalent tin salt, a sulfur source, sodium alginate, and a solvent to conduct a solvothermal reaction. During the solvothermal reaction, the H₂S generated from the decomposition of the sulfur source reacts with the Sn in the tetravalent tin salt. 4+ The reaction generates SnS2 nanosheet particles; and makes the Sn in the tetravalent tin salt... 4+ Chemical cross-linking with the carboxyl and hydroxyl groups in sodium alginate forms a Sn-SA hydrogel, resulting in a SnS2@Sn-SA electrode material with SnS2 nanosheets as the core and Sn-SA hydrogel as the shell. This invention employs a one-step solvothermal method to prepare the SnS2@Sn-SA electrode material. The preparation method is simple, and the raw materials used are safe and readily available.

[0026] The SnS2@Sn-SA electrode material prepared by this invention utilizes the Sn in tetravalent tin salt during a solvothermal reaction. 4+ Chemical cross-linking with the carboxyl and hydroxyl groups in sodium alginate forms Sn-SA hydrogel, which serves as the shell for the SnS2@Sn-SA electrode material. Due to the viscous and elastic gel-like structure of the formed Sn-SA hydrogel, it effectively mitigates the volume change of SnS2 during cycling, inhibits further dissolution of SnS2 in organic solvents, and prevents SnS2 aggregation. This effectively solves the problems of large volume change, aggregation, and dissolution of SnS2 during charge-discharge cycling.

[0027] The SnS2@Sn-SA electrode material prepared in this invention reacts with H2S generated from the decomposition of the sulfur source during a solvothermal reaction, along with Sn from the tetravalent tin salt. 4+ The reaction generates SnS2 nanosheets, which serve as the core of the SnS2@Sn-SA electrode material. This invention synthesizes relatively thin SnS2 nanosheets, while the Sn-SA hydrogel contains a higher concentration of Sn. 4+ Ions, large amounts of Sn 4+ Ion coating on the SnS2 surface acts as a protective layer for SnS2, improving the conductivity of the SnS2 composite material and enhancing the Li content. +The transmission rate is improved, overcoming the problem of poor conductivity of SnS2, which significantly reduces the resistance between the composite material and the electrolyte, thus achieving a balance between high-density energy storage and excellent stability of SnS2. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the fabrication principle of the SnS2@Sn-SA electrode material of this invention.

[0029] Figure 2 The images show the XRD characterization of the SnS2@Sn-SA electrode material in Example 1, the SnS2@SA electrode material in Comparative Example 1, and the SnS2 electrode material in Comparative Example 2.

[0030] Figure 3 The images show the Raman spectra of the SnS2@Sn-SA electrode material in Example 1, the SnS2@SA electrode material in Comparative Example 1, and the SnS2 electrode material in Comparative Example 2 of this invention. Figure 3 The illustration in the middle is Figure 3 1000cm -1 ~2000cm -1 A magnified view within the specified range.

[0031] Figure 4 Thermogravimetric analysis characterization diagrams of the SnS2@Sn-SA electrode material in Example 1 and the SnS2@SA electrode material in Comparative Example 1 are shown.

[0032] Figure 5 These are transmission electron microscope (TEM) images of the SnS2@Sn-SA electrode material in Example 1 of the present invention at different magnifications; wherein, Figure a is a TEM image at 200 nm, Figure b is a TEM image at 50 nm, Figure c is a TEM image at 20 nm, Figure d is a TEM scan of the SnS2@Sn-SA electrode material in Example 1 at 500 nm, Figure e is the Sn element distribution map in Figure d, Figure f is the S element distribution map in Figure d, and Figure g is the C element distribution map in Figure d.

[0033] Figure 6 This is a cyclic voltammetry curve of the SnS2@Sn-SA electrode material in Example 1 of the present invention.

[0034] Figure 7 This is a constant current charge-discharge curve of the SnS2@Sn-SA electrode material in Embodiment 1 of the present invention.

[0035] Figure 8 This is a charge / discharge capacity diagram of the SnS2@Sn-SA electrode material in Embodiment 1 of the present invention at different current densities.

[0036] Figure 9Figure 1 shows the impedance data of the SnS2@Sn-SA electrode material in Embodiment 1 of the present invention; wherein, Figure a is the AC impedance spectrum of the SnS2@Sn-SA electrode material in Embodiment 1, the inset in Figure a is an enlarged view of Figure a in the high-frequency region, and Figure b is the equivalent circuit diagram of fitting the AC impedance of Figure a.

[0037] Figure 10 This is a test graph showing the cyclic stability of the SnS2@Sn-SA electrode material in Example 1 of the present invention at 1C.

[0038] Figure 11 Figure 1 shows the capacitance contribution calculation diagram of the SnS2@Sn-SA electrode material in Example 1 of the present invention; wherein, Figure 1a is the cyclic voltammetry curve of the SnS2@Sn-SA electrode material in Example 1, Figure 1b is the capacitance storage contribution diagram of the SnS2@Sn-SA electrode material in Example 1, and Figure 1c is the capacitance contribution diagram of the SnS2@Sn-SA electrode material in Example 1 at different scan rates.

[0039] Figure 12 This is a comparison chart of the capacity of the SnS2@Sn-SA electrode material in Example 1 of the present invention with that reported in existing literature. Detailed Implementation

[0040] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0041] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0042] The following specific examples will provide further explanation.

[0043] Example 1

[0044] This embodiment provides a method for preparing SnS2@Sn-SA electrode material.

[0045] 0.36 g of tin tetrachloride pentahydrate, 0.21 g of thioacetamide, and 0.1 g of sodium alginate were dissolved in 20 mL of water and stirred at room temperature for 30 min. After stirring until homogeneous, the mixture was subjected to a solvothermal reaction at 180 °C for 12 h in a high-pressure reactor. After the solvothermal reaction was completed, the solid powder was removed and rinsed with deionized water and anhydrous ethanol in sequence. Then, it was placed in a vacuum drying oven and dried at 60 °C for 8 h to obtain the SnS2@Sn-SA electrode material.

[0046] Example 2

[0047] This embodiment provides a method for preparing SnS2@Sn-SA electrode material.

[0048] 0.36 g of tin tetrachloride pentahydrate, 0.21 g of thioacetamide, and 0.15 g of sodium alginate were dissolved in 20 mL of isopropanol and stirred at room temperature for 30 min. After stirring until homogeneous, the mixture was subjected to a solvothermal reaction at 160 °C for 10 h in a high-pressure reactor. After the solvothermal reaction was completed, the solid powder was removed and rinsed with deionized water and anhydrous ethanol in sequence. Then, it was placed in a vacuum drying oven and dried at 60 °C for 8 h to obtain the SnS2@Sn-SA electrode material.

[0049] The difference between this embodiment and Example 1 is that the temperature of the solvothermal reaction is 160°C and the time is 10 hours.

[0050] Example 3

[0051] This embodiment provides a method for preparing SnS2@Sn-SA electrode material.

[0052] 0.36 g of tin tetrachloride pentahydrate, 0.21 g of thioacetamide, and 0.09 g of sodium alginate were dissolved in 20 mL of isopropanol and stirred at room temperature for 30 min. After stirring until homogeneous, the mixture was subjected to a solvothermal reaction at 200 °C for 14 h in a high-pressure reactor. After the solvothermal reaction was completed, the solid powder was removed and rinsed with deionized water and anhydrous ethanol in sequence. Then, it was placed in a vacuum drying oven and dried at 60 °C for 8 h to obtain the SnS2@Sn-SA electrode material.

[0053] The difference between this embodiment and Example 1 is that the temperature of the solvothermal reaction is 200°C and the time is 14 hours.

[0054] Example 4

[0055] This embodiment provides a method for preparing SnS2@Sn-SA electrode material.

[0056] 0.36 g of tin diethyldithiocarbamate, 0.21 g of thioacetamide, and 0.1 g of sodium alginate were dissolved in 20 mL of isopropanol and stirred at room temperature for 30 min. After stirring until homogeneous, the mixture was subjected to a solvothermal reaction at 160 °C for 10 h in a high-pressure reactor. After the solvothermal reaction was completed, the solid powder was removed and rinsed with deionized water and anhydrous ethanol in sequence. Then, it was placed in a vacuum drying oven and dried at 60 °C for 8 h to obtain the SnS2@Sn-SA electrode material.

[0057] The difference between this embodiment and Example 1 is that the sulfur source is thioacetamide.

[0058] Example 5

[0059] This embodiment provides a method for preparing SnS2@Sn-SA electrode material.

[0060] 0.36 g of tin tetrachloride pentahydrate, 0.21 g of thiourea, and 0.1 g of sodium alginate were dissolved in 20 mL of water and stirred at room temperature for 30 min. After stirring until homogeneous, the mixture was subjected to a solvothermal reaction at 180 °C for 12 h in a high-pressure reactor. After the solvothermal reaction was completed, the solid powder was removed and rinsed with deionized water and anhydrous ethanol in sequence. Then, it was placed in a vacuum drying oven and dried at 60 °C for 8 h to obtain the SnS2@Sn-SA electrode material.

[0061] The difference between this embodiment and Embodiment 1 is that the tin source is tin diethyldithiocarbamate.

[0062] Example 6

[0063] This embodiment provides a method for preparing a lithium-ion battery.

[0064] Preparation of working electrode sheet: The SnS2@Sn-SA electrode material of Example 1, polyvinylidene fluoride and acetylene black were uniformly mixed at a mass ratio of 80:10:10, dissolved in N-methylpyrrolidone, and the slurry was uniformly coated on a 15μm thick copper foil and dried.

[0065] Preparation of the electrode sheet: The lithium metal is pressed into sheets and cut into 0.6 cm discs.

[0066] Preparation of electrolyte: 28.71 g of lithium bis(trifluoromethanesulfonyl)imide was dissolved in 100 mL of organic solvent, and 2.0 g of lithium nitrate was added. The organic solvent was ethylene glycol dimethyl ether and 1,3-dioxane, and the volume ratio of ethylene glycol dimethyl ether to 1,3-dioxane was 1:1.

[0067] Preparation of lithium-ion batteries: Copper foil was cut into circular pieces with a radius of 0.6 cm as working electrode plates, lithium foil was used as counter electrode plates, and Cellgard 2400 separator and electrolyte were used. CR2025 button cell assembly was carried out in a glove box filled with argon gas (O2 and H2O < 1 ppm).

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing SnS2@SA electrode material.

[0070] S1. Dissolve 0.36g of tin tetrachloride pentahydrate and 0.21g of thioacetamide in 20mL of isopropanol. Stir at room temperature for 30min. After stirring evenly, solvothermal reaction is carried out in a high-pressure reactor at 180℃ for 12h. After solvothermal reaction is completed, the solid powder is taken out and washed with deionized water and anhydrous ethanol in sequence. Then, it is placed in a vacuum drying oven to dry at 60℃ for 8h to obtain SnS2 electrode material.

[0071] S2. Soak 0.3g of SnS2 obtained in S1 above in 25mL of aqueous solution containing 0.125g sodium alginate for 4h. Then, centrifuge the solid and wash it with deionized water and anhydrous ethanol in sequence. Then, place it in a vacuum drying oven to dry at 60℃ for 8h to obtain SnS2@SA electrode material.

[0072] The difference between Comparative Example 1 and Example 1 is that SnS2 electrode material was first synthesized by a solvothermal method, and then SnS2 electrode material was mixed with sodium alginate aqueous solution to obtain SnS2@SA electrode material.

[0073] Comparative Example 2

[0074] This comparative example provides a method for preparing SnS2 electrode material.

[0075] 0.36 g of tin tetrachloride pentahydrate and 0.21 g of thioacetamide were dissolved in 20 mL of isopropanol and stirred at room temperature for 30 min. After stirring until homogeneous, the mixture was subjected to a solvothermal reaction at 180 °C for 12 h in a high-pressure reactor. After the solvothermal reaction was completed, the solid powder was removed and rinsed with deionized water and anhydrous ethanol in sequence. Then, it was placed in a vacuum drying oven and dried at 60 °C for 8 h to obtain SnS2 electrode material.

[0076] The difference between Comparative Example 2 and Example 1 is that SnS2 electrode material was synthesized using only a solvothermal method and was not mixed with sodium alginate aqueous solution.

[0077] Experimental Section

[0078] Examples 1-3 of this invention all yielded SnS2@Sn-SA electrode materials that solve the problems of large volume change, agglomeration, and dissolution of SnS2 during charge-discharge cycles. The SnS2@Sn-SA electrode materials obtained in Example 1 and Comparative Examples 1-2 are used as examples for further research. The specific research methods and results are shown below:

[0079] I. Material Characterization

[0080] Figure 1 This is a schematic diagram illustrating the fabrication principle of the SnS2@Sn-SA electrode material of this invention.

[0081] Figure 2 The images show the XRD characterization patterns of the SnS2@Sn-SA electrode material in Example 1, the SnS2@SA electrode material in Comparative Example 1, and the SnS2 electrode material in Comparative Example 2. Figure 2 As shown, the sharp characteristic peaks at 2θ = 14.86°, 28.22°, 32.08° and 49.99° correspond to the (001), (100), (101) and (110) crystal planes of SnS2, indicating that the present invention has prepared SnS2 crystals by a one-step hot solvent method.

[0082] Figure 3 The images show the Raman spectra of the SnS2@Sn-SA electrode material in Example 1, the SnS2@SA electrode material in Comparative Example 1, and the SnS2 electrode material in Comparative Example 2. Figure 3 As shown, at 311cm -1 It has a strong Raman characteristic peak at point A. 1g The pattern is at 1350cm. -1 ~1580cm -1 The observation of broad characteristic peaks of the SA organic structure fully confirms the successful synthesis of SnS2@Sn-SA electrode material.

[0083] Figure 4 The thermogravimetric analysis (TGA) diagrams are shown for the SnS2@Sn-SA electrode material in Example 1 and the SnS2@SA electrode material in Comparative Example 1. From... Figure 4 As can be seen, the slow decrease in mass before 400°C corresponds to the loss of water molecules in sodium alginate, while the rapid decrease in weight between 400°C and 430°C is attributed to the decomposition of sodium alginate molecules. It can be calculated that the mass proportions of SnS2 in Example 1 and Comparative Example 1 are 78.67% and 79.27%, respectively.

[0084] Figure 5 The images show transmission electron microscopy (TEM) characterizations of the SnS2@Sn-SA electrode material in Example 1 at different magnifications; Figure a shows the morphology at 200 nm, Figure b at 50 nm, Figure c at 20 nm, Figure d shows the elemental analysis, Figure e shows the elemental analysis of Sn, Figure f shows the elemental analysis of S, and Figure g shows the elemental analysis of C. Figure 5 Figure a in Figure 5 Figure b and Figure 5 As shown in Figure c, SnS2 exhibits a two-dimensional nanosheet morphology. A hydrogel protective layer, Sn-SA, is observed on the SnS2 surface with an interlayer spacing of ~0.59 nm, which corresponds to the (001) lattice plane of SnS2. Such a large interlayer spacing can ensure the Li +Efficient access and rapid transport of ions. The absence of any obvious lattice planes in the Sn-SA layer confirms its amorphous nature, which is consistent with... Figure 1 The XRD results were very consistent. For example... Figure 5 As shown in Figures d to g, it can be clearly observed that Sn, S, and C elements are concentrated on the central nanoparticle, confirming the presence of SnS2 in the electrode material and demonstrating that the Sn-SA layer is uniformly distributed on the surface of the SnS2 nanosheet.

[0085] II. Electrochemical performance testing:

[0086] Electrochemical testing of the battery was performed. During cyclic voltammetry scanning, the range of the cyclic voltammetric characteristic curves was 0.01V–3V, and the scan rate was 0.2mV / s. -1 ~1mV s -1 During constant current charge-discharge testing, the voltage range was set to 0.01V–3V, and the current intensity to 10μA–640μA. During impedance testing, the frequency range was set to 100kHz–10mHz, and the voltage amplitude to 10mV. During cycle stability testing using constant current charge-discharge, the voltage range was set to 0.01V–3V, the current density to 1C, and the number of cycles to 1000.

[0087] The electrochemical performance of the SnS2@Sn-SA electrode material was investigated by assembling coin-shaped lithium-ion batteries using the electrode material of Example 1 as the working electrode, lithium foil as the counter electrode, and lithium foil as the reference electrode. The electrode material of Example 1 exhibited electrochemical performance at 0.2 mV s⁻¹. -1 The first four cycles of cyclic voltammetry curves are as follows: Figure 6 As shown, during the first discharge cycle, two relatively obvious reduction peaks appeared at ~1.87V and ~1.17V, corresponding to the lithiation reaction peaks of SnS2. 4+ Reduced to Sn 0 The reaction formula is SnS2 + xLi + +xe - →Li x SnS2 and Li x SnS2+(4-x)Li + +4e - →Sn + 2Li₂S, the reduction peak at ~0.53V corresponds to the formation of Li-Sn alloys, and the reaction formula is as follows: During the first charging cycle, a significant oxidation peak appeared at ~0.53V, corresponding to the delithiation of the Li-Sn alloy to form Sn. Compared with the SA-coated electrode materials of Example 1 and Comparative Example 1, the SnS2 prepared in Comparative Example 2 showed a small oxidation peak at ~1.47V, indicating that the introduction of SA promoted the reaction kinetics of SnS2. With increasing scan cycles, during discharge cycles 2-4, the cyclic voltammetry curves of the SnS2@Sn-SA electrode material with the cross-linked protective Sn-SA layer rapidly overlapped in subsequent cycles, while the cyclic voltammetry curves of SnS2 prepared in Comparative Example 1 and SnS2@SA prepared in Comparative Example 2 showed continuous decay. This comparison demonstrates that SnS2@Sn-SA possesses superior reversibility and structural stability imparted by the cross-linked protective Sn-SA layer combination.

[0088] Figure 7 This is a constant current charge-discharge curve of the SnS2@Sn-SA electrode material in Example 1. Figure 7 As shown, the charge / discharge capacity of the SnS2@Sn-SA electrode material in Example 1 is stable at 875 mAh g. -1 and 939mAh g -1 Thanks to the protection of the Sn-SA layer in the SnS2@Sn-SA electrode material structure, the structural breakage caused by volume changes during SnS2 nanosheet cycling can be effectively mitigated, and the SnS2@Sn-SA electrode material exhibits excellent redox reversibility.

[0089] Figure 8 This is a charge / discharge capacity diagram of the SnS2@Sn-SA electrode material in Example 1 at different current densities. From... Figure 8 As can be seen, the SnS2@Sn-SA electrode material has excellent rate performance and can achieve deep charge and discharge at high current densities.

[0090] Figure 9 The impedance data for the SnS2@Sn-SA electrode material in Example 1 are shown; Figure a is an AC impedance spectrum, the inset is an enlarged view of the high-frequency region, and Figure b is an equivalent circuit diagram used to fit the AC impedance. Figure 9 As shown in Figure a, the impedance spectrum indicates that the intrinsic resistance of the SnS2@Sn-SA electrode material is ~1.25Ω before cycling and ~2.26Ω after cycling. The lower resistance facilitates the transport of electrons and ions, improves the utilization rate of SnS2, and the small change in resistance before and after cycling indicates that the SnS2@Sn-SA electrode material has a stable structure.

[0091] Figure 10The graph shows the cycle stability test results of the SnS2@Sn-SA electrode material in Example 1 at 1C. The cycle stability of the SnS2@Sn-SA electrode material was further verified by long-term charge-discharge cycles, as shown below. Figure 10 As shown, after 1000 cycles, the capacity remained at 223 mAh g. -1 It exhibits excellent lithium storage capacity and outstanding cycle stability. Throughout the cycle, the coulombic efficiency of the SnS2@Sn-SA electrode material remains close to 100%.

[0092] Figure 11 Figure 1 shows the capacitance contribution calculation of the SnS2@Sn-SA electrode material in Example 1; Figure 2a is the cyclic voltammogram of the SnS2@Sn-SA electrode material in Example 1, Figure 2b is the capacitance storage contribution of the SnS2@Sn-SA electrode material in Example 1, and Figure 2c is the capacitance contribution of the SnS2@Sn-SA electrode material in Example 1 at different scan rates. Figure 11 As shown, by studying the capacitance contribution of the SnS2@Sn-SA electrode material, the utilization rate of SnS2 in the SnS2@Sn-SA electrode material was further calculated to be ~57.5%.

[0093] Figure 12 This is a comparison graph showing the capacity of the SnS2@Sn-SA electrode material in Example 1 with that reported in existing literature. Figure 12 As shown, compared with other SnS2-based electrode materials in the prior art, the SnS2@Sn-SA electrode material of the present invention has excellent capacity. The references corresponding to the samples in the figure are shown in Table 1:

[0094] Table 1 References

[0095] Electrode materials References capacity SnS2@SWCNTs doi:0.1021 / acs.nanolett.4c01641 520 (0.2 A g -1 )]]> SnS2 / HGF doi:0.1007 / s40820-022-00914-5 510 (0.1 A g -1 )]]> SnS2@C / CNF doi:10.1002 / smtd.202101484 788 (0.5 A g -1 ) SnS2-MoS2 doi:10.34133 / 2022 / 9846797 482 (0.1 A g -1 ) [HPC-SnS2-PAN-500] doi:10.1016 / j.jmst.2020.12.068 663.7 (0.5 A g -1 ) <!-- 7 -->]]> S-TC-2 doi:10.1016 / j.cej.2019.122590 540.4 (0.2 A g -1 )]]> H-TiO2@SnS2@PPy doi:10.1002 / anie.201811784 702.5 (0.2 A g -1 ) Sb2S3-SnS2 doi:10.1016 / j.ensm.2018.10.002 661 (0.5 A g -1 ) SnO2@SnS2@NG doi:10.1016 / j.ensm.2018.11.024 715 (0.5 A g -1 ) SnS2@CNT doi:10.1021 / acsnano.8b02861 740 (0.1 A g -1 ) <![CDATA[Sn 0.91 What 0.19 S2]]> doi:10.1002 / smll.201702184 <![CDATA[766.8(0.2A g -1 )]]>

[0096] Obviously, the above embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing SnS2@Sn-SA electrode material, characterized in that, Includes the following steps: A tetravalent tin salt, a sulfur source, sodium alginate, and a solvent are mixed and subjected to a solvothermal reaction, so that the H2S generated by the decomposition of the sulfur source during the solvothermal reaction reacts with the Sn in the tetravalent tin salt. 4+ The reaction generates SnS2 nanosheet particles; and makes the Sn in the tetravalent tin salt... 4+ Chemical cross-linking with the carboxyl and hydroxyl groups in sodium alginate forms Sn-SA hydrogel, resulting in SnS2@Sn-SA electrode material with SnS2 nanosheet particles as the core and Sn-SA hydrogel as the shell.

2. The method for preparing the SnS2@Sn-SA electrode material according to claim 1, characterized in that, The temperature of the solvothermal reaction is 160℃~200℃.

3. The method for preparing the SnS2@Sn-SA electrode material according to claim 1, characterized in that, The solvothermal reaction takes 10 to 14 hours.

4. The method for preparing the SnS2@Sn-SA electrode material according to claim 1, characterized in that, Sn in the tetravalent tin salt 4+ The molar ratio of sulfur source to sodium alginate is 1:2-3:0.4-0.

8.

5. The method for preparing the SnS2@Sn-SA electrode material according to claim 1, characterized in that, The tetravalent tin salt is one of tin tetrachloride pentahydrate and tin diethyldithiocarbamate.

6. The method for preparing the SnS2@Sn-SA electrode material according to claim 1, characterized in that, The sulfur source is either thioacetamide or thiourea.

7. The method for preparing the SnS2@Sn-SA electrode material according to claim 1, characterized in that, The solvent is one of isopropanol, water, and ethylene glycol.

8. A SnS2@Sn-SA electrode material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the SnS2@Sn-SA electrode material according to claim 8 in the negative electrode material of lithium-ion batteries.

10. The application according to claim 9, characterized in that, The preparation of the lithium-ion battery includes the following steps: Preparation of working electrode sheet: Mix SnS2@Sn-SA electrode material, conductive agent and binder, and coat it on copper foil; Electrode preparation: Lithium metal is compressed and cut into sheets; Preparation of electrolyte: Lithium bis(trifluoromethanesulfonyl)imide was dissolved in an organic solvent and lithium nitrate was added to prepare an electrolyte; Preparation of lithium-ion batteries: The counter electrode, separator material, electrolyte and working electrode are assembled in sequence to obtain lithium-ion batteries.

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