A lignin-based carbon-coated stannous sulfide composite material, its preparation method and application

Abstract

The present invention discloses a lignin-based carbon-coated tin sulfide composite material, its preparation method and application, which include the following steps: (1) First, mix a tetravalent tin salt with acetic acid, and then mix it with thioacetamide; water and ethanol are also added as solvents to obtain a mixed solution; (2) Add lignin to the mixed solution, stir and dissolve it, carry out a hydrothermal reaction, wash and dry to obtain a SnS2 / C composite material; (3) Calcinate the obtained SnS2 / C composite material at 500-700 °C for 2-5 h under a protective atmosphere, wash and dry to obtain a lignin-based carbon-coated tin sulfide composite material. The present invention uses industrial lignin as a carbon precursor and in-situ generates a reducing gas to reduce SnS2 to SnS. The process is simple, the cost is low, and the consumption of fossil energy is reduced; the prepared battery negative electrode has a high capacity, good cycle stability and a good specific surface area.

Description

Technical Field

[0001] The present invention belongs to the fields of high-value utilization of lignin and anode materials for batteries. Background Art

[0002] Two-dimensional (2D) layered metal sulfides show great potential in sodium-ion anode materials due to fast interlayer diffusion. As one of the 2D layered metal sulfides, SnS has been widely studied because of its high theoretical specific capacity (1022 mAh / g, while that of hard carbon is 372 mAh / g) and relatively large interlayer spacing ( about that of hard carbon ). However, SnS still faces problems such as low electronic conductivity, large volume change (forming Na 15 Sn 4 with sodium ions, and the volume expands by about 420%), dissolution of intermediate products, and poor structural stability.

[0003] In view of the above problems, researchers have proposed many methods to improve the sodium storage performance of SnS, mainly including the following three solutions: (1) Conduct structural design on SnS to construct a nano-layered heterojunction, thereby exposing more active sites and providing a fast channel for ion transport and electron transfer. However, changing the structure still cannot obtain a SnS material with good cycle stability. (2) Composite with sulfides. Ru et al. proposed a covalent self-assembly strategy to construct a heterostructure (MoS 2 flakes chemically bonded to SnS nanoparticles) hollow sphere (MoS 2 / SnS). After 150 cycles at 0.5 A / g, the capacity retention rate of this material reaches 90.6%. However, the capacity of this material shows an obvious downward trend after 200 cycles in lithium-ion batteries. It can be inferred that the stability of the material has been improved to a certain extent but is still not stable enough during long cycles. (3) Composite with carbon materials. Carbon-based materials are relatively stable and have a small volume change during the sodiation / desodiation process of sodium ions. Composite with them is an effective method to improve the sodium storage performance. Gao et al. synthesized multi-layer hollow carbon spheres C@SnS@C of S, N co-doped carbon-coated SnS nanosheets using polydopamine (PDA) as the carbon source through a multi-step method. The initial capacity is 330 mAh / g, and after 100 cycles, the capacity retention rate reaches 90%. However, it can be clearly found that during the 100-cycle process, the capacity starts to decay at the 60th cycle, and the hollow carbon spheres are easily broken, and it is also impossible to stably maintain a long cycle.

[0004] Currently, the reported processes for preparing SnS / C composites at low temperature require the use of H 2 / Ar mixed gas for calcination or the addition of an extra reducing agent during the reaction process. For example, Xia et al. obtained SnS / C composites by calcining with H 2 / Ar mixed gas at 650 °C for 8 h. Xue et al. used2 3D SnS / C was obtained by calcining the mixture of / Ar at 350℃ for 12 h. It can be seen that the preparation of materials using these methods not only takes a long time, but also requires H 2 As a reducing agent, it increases the demand for fossil fuels and aggravates environmental pollution.

[0005] Lignin, the second most abundant biomass, is a biopolymer with a three-dimensional network structure formed by three phenylpropane units connected by ether bonds and carbon-carbon bonds. It contains abundant aromatic ring structures, aliphatic and aromatic hydroxyl groups, quinone groups and other active groups, and is a by-product of the papermaking industry. At present, the annual output of industrial lignin in my country has exceeded 20 million tons, but due to the shortcomings of industrial lignin such as severe molecular aggregation and low reactivity, its high-value utilization is a world-class problem, resulting in a current high-value utilization rate of less than 10%. Therefore, it is of great significance to research and develop new technologies for the high-value utilization of lignin.

[0006] At present, there is still no report on the application of lignin in SnS negative electrode materials. The present invention is the first to use low-temperature pyrolysis and synchronous reduction of lignin to prepare SnS / C composite negative electrode materials that can be used in sodium ion batteries and lithium ion batteries, which is of great significance to promoting the development of high-capacity and long-life sodium ion batteries and lithium ion batteries. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing a battery negative electrode SnS / C composite material by using lignin as a carbon precursor and pyrolyzing and reducing lignin.

[0008] The invention uses lignin, thioacetamide and tin chloride as raw materials, adopts a one-pot method, and performs low-temperature heat treatment in two steps to obtain a stannous sulfide-based carbon composite material with high specific capacity and good cycle stability. The chemical composition of the stannous sulfide-based carbon composite material is SnS / C.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A method for preparing a lignin-based carbon-coated stannous sulfide composite material comprises the following steps:

[0011] (1) firstly mixing a tetravalent tin salt with acetic acid, and then mixing with thioacetamide; water and ethanol are also added as solvents to obtain a mixed solution;

[0012] (2) Add lignin to the mixed solution, stir and dissolve, perform hydrothermal reaction, wash, and dry to obtain SnS 2 / C composite material; the hydrothermal reaction conditions are 140-200°C for 8-16h;

[0013] (3) The obtained SnS 2The lignin-based carbon-coated tin sulfide composite material is obtained by calcining the / C composite material at 500 - 700 °C for 2 - 5 h under a protective atmosphere, washing, and drying.

[0014] Preferably, the volume ratio of water, ethanol, and acetic acid is (40 - 50):(5 - 10):(1 - 5), the mass concentration of the tin salt is 0.5 - 5%, and the mass ratio of thioacetamide to the tin salt is (0.3 - 1.0):1.

[0015] Preferably, the volume ratio of water, ethanol, and acetic acid is (40 - 50):(5 - 10):3, the mass concentration of the tin salt is 1 - 3%, and the mass ratio of thioacetamide to the tin salt is 0.5 ± 0.1.

[0016] Preferably, the mass ratio of lignin to the tin salt is 0.2 - 1.0.

[0017] Preferably, the mass ratio of lignin to the tin salt is 0.5 ± 0.1; the lignin is one or more of sodium lignosulfonate, alkali lignin, ammonia-oxidized lignin, enzymatically hydrolyzed lignin, and pre-hydrolyzed lignin; the tin salt is tin(IV) chloride pentahydrate.

[0018] Preferably, the conditions for the hydrothermal reaction are to react at 160 ± 5 °C for 12 ± 2 h.

[0019] Preferably, in step (3), the calcination temperature is 500 ± 100 °C and the calcination time is 3 ± 1 h.

[0020] Preferably, the protective atmosphere in step (3) is at least one of nitrogen, argon, and helium;

[0021] The lignin-based carbon-coated tin sulfide composite material is used in the preparation of a negative electrode material for a sodium-ion battery or a negative electrode material for a lithium-ion battery.

[0022] In step (1), acetic acid plays a role in inhibiting the hydrolysis of thioacetamide. If acetic acid is not added and ultrapure water is added after adding thioacetamide, thioacetamide will rapidly hydrolyze and release harmful hydrogen sulfide gas. At the same time, experiments have shown that when all water is used as the solvent, the cycle stability of the material is poor, and adding an appropriate amount of ethanol can not only maintain the solubility of lignin in the solvent but also increase the long-cycle stability of the material.

[0023] In step (2), adding different amounts of lignin can play the role of carbon layer coating material after calcination, and the content of lignin added needs to be further determined through experiments. If too much lignin is added, more gases will be released and foaming will occur during pyrolysis, resulting in less contact between the carbon layer and the material and greatly reducing the coating effect. At the same time, different hydrothermal temperatures will result in different material morphologies. Generally speaking, higher hydrothermal temperatures and longer times will result in materials with smaller thickness and smaller morphologies, but will also cause the materials to aggregate. In this step, multiple washings are mainly to wash away the unreacted lignin and excess sulfur source.

[0024] In step (3), low-temperature calcination at 300 - 700 °C is mainly adopted. Due to the self-characteristics of the material, there will be a process of sulfur sublimation when the temperature is above 600 °C. Low-temperature calcination can ensure the proportion of sulfur source and reduce the loss of Sn material.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) Compared with the current domestic and foreign research, at the same temperature, without adding an additional reducing agent and without using H 2 / Ar mixed gas as the reducing gas, tin sulfide can be in-situ reduced to SnS to prepare the layered SnS / C material, realizing the purpose of in-situ self-reduction preparation of SnS / C at low temperature (500 °C). Experiments have proved that if lignin is not added, SnS material cannot be obtained, and only SnS 2 can be obtained. The reducing gases H 2 and CO decomposed from lignin during pyrolysis play the role of reducing agents, in-situ reducing tin sulfide to SnS during pyrolysis, and at the same time transforming themselves into carbon materials to wrap SnS and inhibit the volume expansion of SnS during charge and discharge. The present invention first proposes a method for preparing SnS / C anode material by in-situ reduction of tin sulfide by lignin pyrolysis, which also provides a way for the high-value utilization of lignin and avoids the use of gases such as H 2 and Ar.

[0027] (2) The present invention uses industrial lignin as the carbon precursor and in-situ generates reducing gas to reduce SnS 2 to SnS. The process is simple, the cost is low, the consumption of fossil energy is reduced, the safety of the operation process is increased, which is beneficial to industrial application and the high-value utilization of lignin.

[0028] (3) The present invention only prepares the SnS / C sodium-ion battery anode material and lithium-ion battery anode material through two steps of one-pot hydrothermal method and low-temperature heat treatment in a tube furnace, greatly reducing the energy consumption and cost. The preparation process is simple, easy to operate, highly controllable, low in energy consumption, high in production efficiency and high in output, and has the potential for large-scale production.

[0029] (4) In the SnS / C composite material of the present invention, the carbon coating on the surface of stannous sulfide can alleviate the volume change during the charge and discharge process of stannous sulfide. The obtained material has a high capacity, good cycle stability, a relatively large specific surface area, and meets the excellent anode of sodium-ion batteries lacking in the current market.

[0030] (5) The stannous sulfide in the composite material prepared by the present invention has an obviously uniform layered structure, and a carbon layer is coated on the surface, increasing the specific surface area and facilitating ion and electron transport. Description of the Drawings

[0031] Figure 1 It is the XRD pattern of the composite material after calcination at different temperatures prepared in Example 1.

[0032] Figure 2 It is the XRD pattern of the composite material after calcination at 500 °C with and without lignin prepared in Example 1.

[0033] Figure 3 It is the SEM image of the SnS / C composite material prepared in Example 1 at different magnification factors.

[0034] Figure 4 It is the first charge-discharge curve of the SnS / C composite material prepared in Example 1 assembled into a coin cell (sodium-ion battery) at a current density of 0.1 A g -1 at this time.

[0035] Figure 5 It is the rate performance graph of the SnS / C composite material prepared in Example 1 assembled into a coin cell (sodium-ion battery) at different current densities.

[0036] Figure 6 It is the cycle performance graph of the SnS / C composite material prepared in Example 1 assembled into a coin cell (sodium-ion battery) at a current density of 1 A g -1 at this time.

[0037] Figure 7 It is the XRD pattern of the SnS / C composite material prepared in Comparative Example 2.

[0038] Figure 8 It is the SEM image of the SnS / C composite material prepared in Comparative Example 2 at different magnification factors.

[0039] Figure 9 It is the rate performance graph of the SnS / C composite material prepared in Comparative Example 2 assembled into a coin cell (sodium-ion battery) at different current densities.

[0040] Figure 10The SnS / C composite material prepared in Example 1 was assembled into a button battery (lithium-ion battery) at a high current density of 1 A g -1 The long cycle performance graph at this time. Detailed implementation mode

[0041] The present invention will be further specifically and detailedly described below in conjunction with specific embodiments, but the implementation mode of the present invention is not limited thereto. For process parameters not specifically noted, reference can be made to conventional technologies.

[0042] Example 1: Influence of different calcination temperatures on the synthesis of product SnS / C

[0043] (1) Add 3 mL of acetic acid to 1 g of tin (V) chloride pentahydrate (SnCl 4 ·5H 2 O). Add 0.5 g of thioacetamide to the obtained solution, stir until evenly dispersed, and continue to add 10 mL of ethanol and 40 mL of water to the obtained solution to obtain a mixed solution A;

[0044] (2) Add 0.5 g of sodium lignosulfonate to the solution obtained in step (1), stir and dissolve it, then add it to a reaction kettle and react at 160 °C for 12 h. Centrifuge the obtained substance, wash it with water and ethanol three times to obtain SnS 2 / C;

[0045] (3) Calcinate the powder obtained in step (2) at 500 °C for 3 h under a protective atmosphere, wash it, and dry it to obtain the SnS / C composite material. And use 400 °C and 700 °C calcination as a control.

[0046] Example 2: Influence of different lignin types on the synthesis and performance of product SnS / C

[0047] (1) Add 3 mL of acetic acid to 1 g of tin (V) chloride pentahydrate. Add 0.5 g of thioacetamide to the obtained solution, stir until evenly dispersed, and continue to add 10 mL of ethanol and 40 mL of water to the obtained solution to obtain a mixed solution A;

[0048] (2) Add 0.5 g of ammonia lignin to the solution obtained in step (1), stir and dissolve it, then add it to a reaction kettle and react at 160 °C for 12 h. Centrifuge the obtained substance, wash it with water and ethanol three times to obtain SnS 2 / C.

[0049] (3) Calcinate the powder obtained in step (2) at 500 °C for 3 h under a protective atmosphere, wash it, and dry it to obtain the SnS / C composite material.

[0050] Example 3: Influence of different lignin contents on the synthesis and performance of product SnS / C

[0051] (1) Add 3 mL of acetic acid to 1 g of tin(II) chloride pentahydrate. Add 0.5 g of thioacetamide to the resulting solution and stir until evenly dispersed. Then continue to add 10 mL of ethanol and 40 mL of water to the resulting solution to obtain a mixed solution A;

[0052] (2) Add 0.2 g of sodium lignosulfonate to the solution obtained in step (1). After stirring and dissolving, add it to a reaction kettle and react at 160 °C for 12 h. Centrifuge the resulting substance, wash it with water and ethanol three times to obtain SnS 2 / C. And use 1 g of sodium lignosulfonate as a control.

[0053] (3) Calcinate the powder obtained in step (2) at 500 °C for 3 h under a protective atmosphere, wash it, and dry it to obtain the SnS / C composite material.

[0054] Example 4: Effect of different ethanol contents on the synthesis and properties of the product SnS / C

[0055] (1) Add 3 mL of acetic acid to 1 g of tin(II) chloride pentahydrate. Add 0.5 g of thioacetamide to the resulting solution and stir until evenly dispersed. Then continue to add 5 mL of ethanol and 45 mL of water as solvents to the resulting solution to obtain a mixed solution A. And use 50 mL of water as a solvent for comparison.

[0056] (2) Add 0.5 g of sodium lignosulfonate to the solution obtained in step (1). After stirring and dissolving, add it to a reaction kettle and react at 160 °C for 12 h. Centrifuge the resulting substance, wash it with water and ethanol three times to obtain SnS 2 / C;

[0057] (3) Calcinate the powder obtained in step (2) at 500 °C for 3 h under a protective atmosphere, wash it, and dry it to obtain the SnS / C composite material.

[0058] Example 5: Effect of different hydrothermal temperatures on the synthesis and properties of the product SnS / C

[0059] (1) Add 3 mL of acetic acid to 1 g of tin(II) chloride pentahydrate. Add 0.5 g of thioacetamide to the resulting solution and stir until evenly dispersed. Then continue to add 10 mL of ethanol and 40 mL of water to the resulting solution to obtain a mixed solution A;

[0060] (2) Add 0.5 g of sodium lignosulfonate to the solution obtained in step (1). After stirring and dissolving, add it to a reaction kettle and react at 200 °C for 12 h. Centrifuge the resulting substance, wash it with water and ethanol three times to obtain SnS 2 / C;

[0061] (3) Calcinate the powder obtained in step (2) at 500 °C for 3 h under a protective atmosphere, wash it, and dry it to obtain the SnS / C composite material.

[0062] Comparative Example 1: Preparation of SnS by calcination without adding lignin under inert gas 2 Material

[0063] (1) Add 3 mL of acetic acid to 1 g of tin (IV) chloride pentahydrate. Add 0.5 g of thioacetamide to the resulting solution and stir until evenly dispersed. Then add 10 mL of ethanol and 40 mL of water to the resulting solution to obtain a mixed solution A;

[0064] (2) Add the solution obtained in step (1) to a reaction kettle and react at 160 °C for 12 h. Centrifuge the resulting substance, wash it with water and alcohol three times to obtain SnS 2 Material;

[0065] (3) Calcinate the powder obtained in step (2) at 500 °C for 3 h under a protective atmosphere of nitrogen, wash it, and dry it to obtain SnS 2 Material.

[0066] Comparative Example 2: Preparation of SnS material by calcination with H 2 / Ar mixed gas at 500 °C without adding lignin

[0067] (1) Add 3 mL of acetic acid to 1 g of tin (IV) chloride pentahydrate. Add 0.5 g of thioacetamide to the resulting solution and stir until evenly dispersed. Then add 10 mL of ethanol and 40 mL of water to the resulting solution to obtain a mixed solution A;

[0068] (2) Add the solution obtained in step (1) to a reaction kettle and react at 160 °C for 12 h. Centrifuge the resulting substance, wash it with water and alcohol three times to obtain SnS 2

[0069] (3) Calcinate the powder obtained in step (2) at 500 °C for 3 h under H 2 / Ar mixed gas, wash it, and dry it to obtain SnS material.

[0070] Comparative Example 3: Preparation of SnS / C composite material using thiourea as sulfur source

[0071] (1) Add 3 mL of acetic acid to 1 g of tin (IV) chloride pentahydrate. Add 0.5 g of thiourea to the resulting solution and stir until evenly dispersed. Then add 10 mL of ethanol and 40 mL of water to the resulting solution to obtain a mixed solution A;

[0072] (2) Add 0.5 g of sodium lignosulfonate to the solution obtained in step (1), stir to dissolve it, then add it to a reaction kettle and react at 160 °C for 12 h. Centrifuge the resulting substance, wash it with water and alcohol three times to obtain SnS 2 / C;

[0073] (3) Calcinate the powder obtained in step (2) under H 2The SnS / C composite material was obtained by calcining the Ar mixed gas at 500 °C for 3 h, washing, and drying.

[0074] Comparative Example 4: Directly use SnS 2 To prepare the SnS / C material

[0075] (1) Add 10 mL of ethanol and 40 mL of water to 1 g of SnS to obtain a mixed solution A; add 0.5 g of sodium lignosulfonate and stir to dissolve, then add it to the reaction kettle and react at 160 °C for 12 h. Centrifuge the obtained substance, wash it with water and alcohol 3 times to obtain SnS 2 / C; 2

[0076] (2) Calcinate the powder obtained in step (1) in an inert gas at 500 °C for 3 h, wash, and dry to obtain the SnS / C composite material.

[0077] Comparative Example 5: SnS / C nanofiber composite material

[0078] (1) Dissolve 4 mmol of SnCl 2 ·2H 2 O in 5 mL of DMF and stir to dissolve until a transparent solution is obtained. Then add 0.5 g of PVP to the above solution and continuously stir for 3 h to obtain a precursor solution. Load the precursor solution into a 5 mL plastic syringe equipped with a flat needle, and this syringe is connected to a single-channel syringe pump. Set the flow rate of the solution to be constant at 0.3 mL / h. Collect the nanofibers using aluminum foil, keep the distance between the aluminum foil and the needle at about 15 cm, and apply a voltage of 18 kV to initiate electrospinning to obtain SnCl 2 / PVP.

[0079] (2) Treat the powder obtained in step (1) in a muffle furnace at 280 °C for 2 h. Subsequently, place thiourea upstream of the sample and perform sulfidation treatment by calcining in a H 2 / Ar mixed gas at 250 °C for 2 h. Finally, place the sample in a tube furnace and calcine in a H 2 / Ar mixed gas at 650 °C for 8 h to obtain the SnS / C composite material.

[0080] Comparative Example 6: SnS / CBC nanocomposite material

[0081] (1) Freeze-dry the purified hydrogel to form a BC aerogel, and then cut it into rectangles. Immerse a piece of BC aerogel in a solution containing 0.35 g of SnCl 4 , 0.26 g of thioacetamide and 50 mL of ethanol, and after treating at 80 °C for 40 minutes, take the obtained sample out of the solution, wash it repeatedly with distilled water and ethanol, and then freeze-dry it in a bulk tray dryer to obtain SnS 2 / BC.

[0082] (2) The powder obtained in step (1) was placed in a tube furnace and calcined at 700 °C for 1 h in an H 2 / Ar mixed gas to obtain the SnS / CBC composite material.

[0083] Comparative Example 7: High-N-content carbon-confined amorphous SnS composite material

[0084] (1) In a glove box, 1.5 g of SnCl 4 , 0.54 g of Na 2 S and 0.35 g of polyacrylonitrile were added to 10 mL of N,N-dimethylformamide organic solution and stirred until dissolved. Subsequently, the solution was added dropwise to 100 mL of deionized water under stirring; the resulting white precipitate was collected by centrifugation and washed several times with water, and then dried at 60 °C.

[0085] (2) The powder obtained in step (1) was placed in a tube furnace and calcined at 450 °C for 4 h using argon as the protective gas to obtain the SnS / C composite material.

[0086] Comparative Example 8: Honeycomb-like SnS / C nanocomposite material

[0087] (1) Uniform-sized silica sphere templates were synthesized by the Steber method. 1.0 g of silica, 0.5 g of SnCl 2 ·2H 2 O and 1.0 g of allyl thiourea were dissolved in 15 ml of deionized water. After ultrasonic treatment for 30 minutes, the mixture was stirred at 80 °C for 6 h, and the resulting mixture was dried at 80 °C for 12 h.

[0088] (2) The powder obtained in step (1) was placed in a tube furnace and calcined at 600 °C for 4 h using nitrogen as the protective gas to obtain the SnS / C composite material.

[0089] (3) The composite material in step (2) was placed in 5% HF solution overnight to remove the silica template and dried for standby.

[0090] Example 1: Application of SnS / C composite material in sodium-ion batteries

[0091] The morphology and size of the samples of the present invention were tested by a field emission scanning electron microscope (SEM, Hitachi SU8220). The battery was assembled as a half-cell, with the model number CR2032. The composition of the negative electrode material was 70 wt% active material, 15 wt% carbon black, and 15 wt% carboxymethyl cellulose (CMC), where the active material was the composite material prepared in Examples 1-5 and Comparative Examples 1-4 above. A sodium sheet was used as the counter electrode, and the electrolyte was prepared with 1 mol / L NaPF6 as the solute and dimethyl ether (DME) as the solvent. The entire installation process of the sodium ion half-cell was completed in a glove box under argon protection. The constant current charge / discharge performance of the battery was tested using a Neware battery performance test system at a voltage range of 0.01 V to 3.0 V and current densities of 100 mA / g and 2 A / g. The rate performance test was completed at current densities of 100 mA / g, 200 mA / g, 500 mA / g, 1000 mA / g, and 2000 mA / g, and the long cycle stability test was carried out at a large current density of 1 A / g.

[0092] The SnS / C composite materials prepared in Examples 1-5 and Comparative Examples 1-4 were applied to the negative electrode material of sodium ion batteries and subjected to electrochemical tests and material characterization. The results are shown in Table 1 and Figure 1-9 .

[0093] Table 1 Comparison of battery performance of samples prepared in Examples 1-5 and Comparative Examples 1-4 in sodium ion batteries

[0094]

[0095] Table 1 shows that when the SnS negative electrode material prepared in Example 1 was used in a sodium ion battery, at a current density of 100 mA·g -1 , the initial capacity was 513.92 mAh·g -1 , which had a relatively high initial capacity and good cycle stability, significantly superior to similar materials. Moreover, the cycle performance of all the samples in the examples was better than that of the other comparative example samples. This was mainly due to the effective coating of lignin carbon and the in-situ reduction of SnS 2 materials during the pyrolysis process of lignin, which reduced the volume expansion of the materials by 82%. Comparing Figure 2 , 6 , 8, and 9, it can be seen that although SnS 2 had a relatively high specific capacity, there was great instability. Using sodium lignosulfonate and lignin ammonia also had the effect of low-temperature pyrolysis reduction. The SnS was coated by low-temperature carbonization of lignin, and the stability of the materials was improved, resulting in better electrochemical performance of the sodium ion battery.

[0096] In Table 1, Comparative Example 1 and Comparative Example 2 are materials obtained without adding lignin. In Comparative Example 1, since no lignin was added, the final product was SnS 2 , as described in the literature, SnS 2 has a higher capacity than SnS, but its initial Coulomb efficiency is much lower than that of the SnS / C composite material. At the same time, its volume expansion is also larger, resulting in instability in subsequent electrochemical tests. In Comparative Example 2, no lignin was added, and H 2 / Ar was used for reduction to obtain a SnS material without carbon coating. From the results, it can be seen that the SnS material without carbon coating not only has no capacity advantage but also is accompanied by a low first Coulomb efficiency and a decrease in cycle stability.

[0097] Figure 1 is the XRD pattern of the composite material in Example 1 of the present invention after calcination at different temperatures. It can be seen that above 500 °C, with the pyrolysis of lignin, the material is successfully reduced by the pyrolysis products of lignin, and 500 °C is a watershed for the pyrolysis reduction of this material by lignin.

[0098] Figure 2 is the XRD pattern of adding lignin in Example 1 of the present invention and not adding lignin in Comparative Example 1 after calcination at 500 °C, which proves the reduction effect of lignin pyrolysis.

[0099] Figure 3 is the SEM image of the composite material SnS / C in Example 1 of the present invention. It can be seen that the material presents an irregular block shape, and the inside of the material is stacked in layers. This morphology has a larger specific surface area relative to the entire block-shaped material, so the area in contact with the electrolyte will also increase, and the sodium storage active sites will increase accordingly, resulting in excellent electrochemical performance.

[0100] Figure 4 is the first-cycle specific capacity-voltage diagram of the composite material SnS / C in Example 1 of the present invention at a current density of 0.1 A / g, and it can be seen that the initial capacity is relatively high.

[0101] Figure 5 is the rate diagram of the composite material SnS / C in Example 1 of the present invention at different current densities. It can be seen that at a large current density of 2 A / g, it still retains a capacity of about 300 mAh / g and has excellent stability. When finally returning to 0.1 A / g, the capacity does not decrease compared with the initial capacity and even shows an upward trend, indicating that the composite material has good reversibility and is gradually activated during the charge-discharge process.

[0102] Figure 6 is the SnS / C composite material prepared in Example 1 assembled into a button battery at a large current density of 1 A g -1From the long cycle performance diagram, it can be seen that the material has excellent stability under the coating of the carbon layer, and the Coulomb efficiency has no obvious attenuation.

[0103] Figure 7 The XRD pattern of the SnS composite material prepared in Comparative Example 2 shows that 2 A pure SnS material can be obtained by reduction with a mixture of Ar and N2O3.

[0104] Figure 8 In comparative example 2, no lignin was added and H 2 From the SnS material prepared by / Ar reduction, it can be clearly seen that although the material also presents a block structure, there is no obvious layer-by-layer stacking structure and the specific surface area is smaller.

[0105] Figure 9 The figure is the rate performance diagram of the button-type battery assembled with the SnS composite material prepared in Example 2 at different current densities. Compared with the rate performance diagram of Example 1, it can be seen that the capacity of the SnS material without lignin is significantly attenuated at high current density, and is much lower than Figure 5 The capacity at this current when lignin was added can be judged as the capacity attenuation at high current density due to the volume expansion of the material when there is no lignin carbon wrapping.

[0106] Example 7: Application of SnS / C composite materials in lithium-ion batteries

[0107] The lithium-ion battery is assembled using a half-cell assembly, model CR2032. The composition of the negative electrode material is 70wt% active material, 15wt% carbon black, and 15wt% carboxymethyl cellulose (CMC), wherein the active material is the SnS / C composite material prepared in the above embodiments and comparative examples. The lithium sheet is used as the counter electrode, and the electrolyte uses a lithium-ion secondary electrolyte (LB-002). The entire assembly process of the lithium-ion half-cell is completed in an argon-protected glove box. The Neware battery performance test system is used in the voltage range of 0.01V to 3.0V, and the long cycle stability test is carried out at a high current density of 1A / g.

[0108] Table 2 Battery performance of samples prepared in Example 1 and Comparative Examples 5-8 in lithium ion battery applications

[0109]

[0110] Table 2 shows that when the SnS negative electrode material prepared in Example 1 is used in a lithium-ion battery, the -1 The initial capacity is 1180 mAh g -1, has a high initial capacity and excellent cycling stability, significantly superior to similar materials, and the cycling performance of all example samples is better than that of other comparative example samples. This is mainly due to the effective coating of lignin carbon and the in-situ reduction of SnS 2 materials during the pyrolysis process of lignin, which reduces the volume expansion of the materials, thereby improving the material stability and enabling excellent electrochemical performance of the lithium-ion battery.

[0111] Figure 10 The long cycling performance graph of the button cell assembled with the SnS / C composite material prepared in Example 1 at a high current density of 1 A g -1 is shown. It can be seen that the material can also maintain stable cycling in the lithium-ion battery.

[0112] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A preparation method of a lignin-based carbon-coated tin sulfide composite material, characterized in that, it includes the following steps: (1) First, mix a tetravalent tin salt with acetic acid, and then mix it with thioacetamide; water and ethanol are also added as solvents to obtain a mixed solution; (2) Add lignin to the mixed solution, stir to dissolve it, then carry out a hydrothermal reaction, wash, and dry to obtain the SnS 2 / C composite material; the conditions of the hydrothermal reaction are 140 - 200 °C for 8 - 16 h; the mass ratio of lignin to tin salt is 0.2 - 1.0; the lignin is one or both of sodium lignosulfonate and ammonia-oxidized lignin; (3) The obtained SnS 2 / C composite material is calcined at 500 - 700 °C for 2 - 5 h under a protective atmosphere, washed, and dried to obtain a lignin-based carbon-coated tin sulfide composite material.

2. The preparation method according to claim 1, characterized in that, the volume ratio of the water, ethanol, and acetic acid is (40 - 50):(5 - 10):(1 - 5), the mass concentration of the tin salt is 0.5 - 5%, and the mass ratio of thioacetamide to the tin salt is (0.3 - 1.0):

1.

3. The preparation method according to claim 2, characterized in that, the volume ratio of the water, ethanol, and acetic acid is (40 - 50):(5 - 10):3, the mass concentration of the tin salt is 1 - 3%, and the mass ratio of thioacetamide to the tin salt is 0.5 ± 0.

1.

4. The preparation method according to claim 3, characterized in that, the mass ratio of the lignin to the tin salt is 0.5 ± 0.1; the tin salt is tin tetrachloride pentahydrate.

5. The preparation method according to claim 1 or 2 or 3 or 4, characterized in that, the conditions of the hydrothermal reaction are to react at 160 ± 5 °C for 12 ± 2 h.

6. The preparation method according to claim 1 or 2 or 3 or 4, characterized in that, the calcination temperature in step (3) is 500 ± 100 °C, and the calcination time is 3 ± 1 h.

7. The preparation method according to claim 1 or 2 or 3 or 4, characterized in that, the protective atmosphere in step (3) is at least one of nitrogen, argon, and helium.

8. A lignin-based carbon-coated tin sulfide composite material prepared by the method according to any one of claims 1 to 7.

9. Application of the lignin-based carbon-coated tin sulfide composite material according to claim 8 in the preparation of a negative electrode material for a sodium-ion battery or a negative electrode material for a lithium-ion battery.

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