Preparation method of biochar-zinc sulfide-tungsten sulfide heterojunction composite material

Abstract

The invention discloses a preparation method of a biochar-zinc sulfide-tungsten sulfide heterojunction composite material, and the scheme comprises the following steps: S1, dissolving sodium tungstate, hydroxylamine hydrochloride, sodium hydroxide, thiourea and zinc chloride in deionized water, and uniformly stirring to obtain a light yellow transparent reaction solution; s2, biological carbon is prepared, the reaction liquid and the biological carbon are mixed in a reaction kettle and then subjected to a hydrothermal reaction for 8-48 h at the constant temperature, and the constant temperature is any one of the temperature values ranging from 180 DEG C to 240 DEG C; s3, filtering, cleaning and drying a product obtained in the step S2 to obtain a heterojunction composite material precursor; s4, the heterojunction composite material precursor is subjected to calcination treatment in the inert gas atmosphere, the biochar-zinc sulfide-tungsten sulfide heterojunction composite material is obtained, and the calcination temperature ranges from 850 DEG C to 950 DEG C.

Description

Technical Field

[0001] This invention relates to the field of new energy battery materials technology, and more specifically, to a method for preparing a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material. Background Technology

[0002] Lithium is used as a negative electrode material in lithium-ion batteries and sodium-ion batteries. Transition metal sulfides, due to their weaker bond energies compared to transition metal oxides, exhibit better conductivity and diffusion kinetics for lithium and sodium ions, and also possess higher theoretical capacity. Furthermore, the lower barrier to ion migration and intercalation reactions, coupled with the interlayer spacing of layered transition metal sulfides, facilitates the rapid diffusion, intercalation, and deintercalation of lithium and sodium ions, thus demonstrating significant potential in lithium and sodium storage applications.

[0003] In the prior art, to improve the conductivity of transition metal sulfides, patent application CN110690419A discloses a composite material in which transition metal sulfides are intercalated on the surface of carbon microspheres as a supporting framework. However, the resulting composite material still needs improvement in terms of conductivity, rate performance, and charge-discharge cycle life. Furthermore, methods for preparing transition metal sulfides include hydrothermal synthesis and chemical vapor deposition, but these methods still suffer from low efficiency and the performance of the obtained composite materials needs further improvement. Summary of the Invention

[0004] This invention provides a method for preparing a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material and the application of the prepared material, in order to overcome the core technical problem in the prior art that tungsten sulfide nucleation is difficult and it is difficult to form a uniform and well-structured heterojunction with a carbon substrate.

[0005] The inventive concept of this invention lies in introducing trace amounts of zinc sulfide (ZnS) as tungsten sulfide. The nucleation active sites of the two sulfides are used to achieve uniform and compact composite on the bio-carbon substrate through a stepwise nucleation-epitaxy growth mechanism.

[0006] Specifically, the present invention provides a method for preparing a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material, comprising: S1. Dissolve sodium tungstate, hydroxylamine hydrochloride, sodium hydroxide, thiourea and zinc chloride in deionized water and stir until homogeneous to obtain a pale yellow and transparent reaction solution. S2. Prepare biochar. Mix the reaction solution with the biochar in a reaction vessel and carry out a hydrothermal reaction at a constant temperature for 8 to 48 hours. The constant temperature is any temperature between 180 degrees Celsius and 240 degrees Celsius. S3. The product obtained in step S2 is filtered, washed and dried to obtain a heterojunction composite material precursor. S4. The heterojunction composite material precursor is calcined in an inert gas atmosphere to obtain a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material, wherein the calcination temperature is 850~950 degrees Celsius.

[0007] Further, in the reaction solution described in step S1, the concentration of sodium tungstate is 0.05~0.2 mol / L, the concentration of zinc chloride is 0.0005~0.1 mol / L, the concentration of hydroxylamine hydrochloride is 0.1~0.6 mol / L, the concentration of sodium hydroxide is 0.01~0.2 mol / L, and the concentration of thiourea is 0.1~0.9 mol / L.

[0008] Furthermore, the hydrothermal reaction described in step S2 is carried out under a pressure of 1.5 MPa to 3.5 MPa, and the deviation between the constant temperature and the set temperature does not exceed ±0.5 degrees Celsius.

[0009] Furthermore, after step S3, a repeating reaction step is included: the heterojunction composite material precursor is mixed and reacted with the reaction solution newly prepared in step S1, and then washed and dried; the repeating reaction step is performed 1 to 5 times.

[0010] Furthermore, the biochar density is 0.05~0.15 g / L. It is made by carbonizing balsa wood at 850-950 degrees Celsius.

[0011] The present invention also provides a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material, which is prepared by the preparation method of the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material described above.

[0012] Furthermore, in the composite material, both zinc sulfide and tungsten sulfide are two-dimensional nanosheets of 100~300 nm. The tungsten sulfide nanosheets grow with zinc sulfide as the nucleation site, and the two are anchored together on the surface of bio-carbon with a honeycomb three-dimensional structure.

[0013] Furthermore, tungsten sulfide accounts for 10% to 80% of the mass, and zinc sulfide accounts for 0.2% to 0.5% of the mass.

[0014] The present invention also provides a negative electrode for lithium-ion batteries, comprising the aforementioned bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material.

[0015] The present invention also provides a negative electrode for sodium-ion batteries, characterized in that it comprises the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material described in any one of the preceding claims.

[0016] One embodiment of this specification achieves at least the following beneficial effects: In the preparation method of the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material of the present invention, by using zinc sulfide as the nucleation active site of tungsten sulfide, the problem of the difficulty of tungsten sulfide nucleation is solved. In the heterojunction composite material prepared thereby, the bio-carbon with a honeycomb three-dimensional structure acts as a reinforcing agent, making the heterojunction composite material structurally stable. Tungsten sulfide and zinc sulfide nanosheets are uniformly anchored on the surface of bio-carbon, thus exhibiting good capacitance and charge transport performance. It can be used as an electrode material for lithium-ion batteries and sodium-ion batteries with high capacity, high rate performance, and long cycle life. In addition, by using bio-carbon as a carbon source, the structural stability and electrochemical activity during the insertion (deintercalation) of lithium ions and sodium ions are improved, which is beneficial to achieving high rate performance and cycle stability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0018] Figure 1 This is a flowchart of a method for preparing a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material provided by the present invention; Figure 2 This is a scanning electron microscope image of the heterojunction composite material prepared in Example 1 of the present invention; Figure 3 The specific capacity and coulombic efficiency values ​​of the electrode prepared using the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material obtained in Example 1 were measured at different current densities. Figure 4 This is a scanning electron microscope image of the heterojunction composite material prepared in Example 2 of the present invention. Figure 5 The specific capacity and coulombic efficiency values ​​of the electrode prepared using the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material obtained in Example 2 were measured at different current densities. Figure 6 This is a scanning electron microscope image of the heterojunction composite material prepared in Example 3 of the present invention; Figure 7 The specific capacity and coulombic efficiency values ​​of the electrode prepared using the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material obtained in Example 3 were measured at different current densities. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of one or more embodiments of this specification clearer, the technical solutions of one or more embodiments of this specification will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, and not all of them. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of one or more embodiments of this specification.

[0020] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another.

[0021] like Figure 1 As shown, this invention provides a method for preparing a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material, comprising the following steps: Step S1: Dissolve sodium tungstate, hydroxylamine hydrochloride, sodium hydroxide, thiourea, and zinc chloride in deionized water and stir until homogeneous to obtain a pale yellow and transparent reaction solution.

[0022] In this step, sodium tungstate, hydroxylamine hydrochloride, sodium hydroxide, thiourea, and zinc chloride are dissolved together in deionized water. The mixture is stirred until thoroughly homogeneous, resulting in a pale yellow, transparent reaction solution. The concentrations of each substance in the reaction solution must be controlled within specific ranges: sodium tungstate 0.05–0.2 mol / L, zinc chloride 0.0005–0.1 mol / L, hydroxylamine hydrochloride 0.1–0.6 mol / L, sodium hydroxide 0.01–0.2 mol / L, and thiourea 0.1–0.9 mol / L. To ensure sufficient sulfur source, the molar ratio of hydroxylamine hydrochloride to thiourea can be controlled within the range of 1:1–1.5, and the zinc chloride concentration should not exceed the sodium tungstate concentration. This prevents the two substances from crowding out the sulfur source and inhibiting the formation of tungsten sulfide, while also preventing excessive nitrogen gas production due to high concentrations of sodium tungstate and zinc chloride, which could lead to excessive pressure in the reactor during the subsequent step S2.

[0023] Step S2: Prepare biochar. Mix the reaction solution with the biochar in a reactor and carry out a hydrothermal reaction at a constant temperature for 8 to 48 hours. The constant temperature is any temperature between 180 degrees Celsius and 240 degrees Celsius.

[0024] In this step, biochar is obtained by carbonizing balsa wood at 850-950 degrees Celsius, and its density is 0.05-0.15 g / L. In the reaction vessel, the reaction solution prepared in step S1 is mixed with the biochar to undergo a hydrothermal reaction. This hydrothermal reaction is carried out at a constant temperature, which is any temperature within the range of 180°C to 240°C, and the deviation of this constant temperature from the set temperature does not exceed ±0.5°C. The reaction time is 8 to 48 hours, and the reaction time can be adjusted according to the appropriate reaction temperature. Simultaneously, the hydrothermal reaction is carried out under a pressure of 1.5 MPa to 3.5 MPa. This pressure condition can accelerate the wetting process of the reaction solution on the biochar and improve the reaction efficiency. Through this hydrothermal reaction, zinc sulfide and tungsten sulfide can be co-grown in situ on the surface of biochar. Tungsten sulfide nanosheets grow using zinc sulfide as nucleation sites, and both are anchored on the biochar surface. By adjusting the reaction time, two-dimensional nanosheets of zinc sulfide and tungsten sulfide with a size of 100 to 300 nm can be generated. This size of nanosheet is beneficial for the transport of lithium ions, sodium ions, etc.

[0025] Step S3: The product obtained in step S2 is filtered, washed and dried to obtain a heterojunction composite material precursor.

[0026] In this step, the product obtained from the hydrothermal reaction in step S2 is filtered. Filtration can be performed using conventional methods such as atmospheric pressure filtration, vacuum filtration, or hot filtration. After filtration, the product is washed using deionized water or ethanol as the washing solution, and the washing can be performed 1-5 times. The washed product is then dried using atmospheric pressure drying or vacuum drying at a temperature of 30-80 degrees Celsius. After the above filtration, washing, and drying processes, a heterojunction composite material precursor is obtained. This precursor can be used in subsequent calcination steps, or the reaction steps can be repeated as needed, i.e., the precursor is mixed with a freshly prepared reaction solution, reacted, and then washed and dried again.

[0027] Step S4: The heterojunction composite material precursor is calcined in an inert gas atmosphere to obtain a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material, wherein the calcination temperature is 850~950 degrees Celsius.

[0028] In step S4, the heterojunction composite material precursor obtained in step S3 is calcined in an inert gas atmosphere, wherein the inert gas atmosphere is a nitrogen or argon atmosphere, and the calcination temperature is controlled at 850~950 degrees Celsius. After this calcination treatment, a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material is obtained. In this composite material, both zinc sulfide and tungsten sulfide are two-dimensional nanosheets of 100~300 nm, wherein the tungsten sulfide nanosheets grow with zinc sulfide as the nucleation active site, and both are anchored on the surface of bio-carbon with a honeycomb three-dimensional structure. The mass percentage of tungsten sulfide is 10%~80%, and the mass percentage of zinc sulfide is 0.2%~0.5%.

[0029] The aforementioned "constant temperature" can be, for example, a temperature within the range of 180 to 240 degrees Celsius. That is, the reaction temperature can be kept constant at a specific temperature between 180 and 240 degrees Celsius. For example, it could be a specific temperature selected from 180 to 240 degrees Celsius, such as 180 degrees Celsius, 185 degrees Celsius, 190 degrees Celsius, 195 degrees Celsius, 200 degrees Celsius, or 205 degrees Celsius. For instance, with a constant temperature of 190 degrees Celsius, the temperature fluctuation of the reaction system is controlled within ±0.5 degrees Celsius, meaning the reaction temperature is between 189.5 degrees Celsius and 190.5 degrees Celsius.

[0030] The aforementioned "biocarbon" refers to a porous carbon processed from biological organic matter, such as animal and plant tissues. Examples of biocarbon include charcoal, carbonized organic waste, carbonized animal and plant tissues, and carbonized animal excrement. The preferred density of the aforementioned biocarbon is 0.05~0.15 g / L. By setting the density of biochar to 0.05~0.15 g / L... The aforementioned biochar can be obtained, for example, by calcining natural wood. The calcination temperature can be, for example, 850-950 degrees Celsius, and the aforementioned natural wood is preferably balsa wood.

[0031] In some embodiments, the reaction is preferably carried out under conditions where biochar is immersed in the reaction solution and the pressure is maintained at 1.5 to 3.5 MPa, thereby accelerating the process of the reaction solution wetting the charcoal and improving the reaction efficiency.

[0032] The fundamental difference between this invention and existing technologies lies in the fact that, during the hydrothermal reaction stage, zinc sulfide (ZnS) preferentially nucleates at defect sites on the surface of biochar due to its relatively low nucleation barrier, forming island-like nanosheets. These pre-formed ZnS nanosheets have a lattice structure similar to... It has a certain degree of matching, thus providing a basis for subsequent... The deposition provided abundant, highly active nucleation sites. This enabled... This method, which allows for epitaxial growth using ZnS as a "seed" at its edges and surface rather than through the difficult spontaneous nucleation process on a carbon substrate, can effectively reduce [the risk of damage]. The difficulty of nucleation forces the two to form a tightly overlapping heterojunction structure, rather than a simple physical mixture.

[0033] In the preparation method of the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material of the present invention, zinc sulfide is used as a nucleation active site to guide the process. This method of growth can solve the technical challenge of uneven nucleation of tungsten sulfide on carbon-based substrates. In the resulting heterojunction composite material, the honeycomb-like three-dimensional structure of bio-carbon acts as a reinforcing agent, stabilizing the composite structure. Tungsten sulfide and zinc sulfide nanosheets are uniformly anchored on the bio-carbon surface, resulting in good capacitance and charge transport properties. This makes it suitable as an electrode material for high-capacity, high-rate-performance, and long-cycle-life lithium-ion and sodium-ion batteries. Furthermore, using bio-carbon as a carbon source improves the structural stability and electrochemical activity during the insertion (extraction) of lithium and sodium ions, contributing to high-rate performance and cycle stability.

[0034] Example 1 Example 1 of this invention prepares a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material according to the following steps: (1) Biochar preparation The raw wood was cut into small pieces of 10mm×10mm×5mm, calcined at 850 degrees Celsius for 2 hours under a nitrogen atmosphere, cleaned with deionized water, and dried at 80 degrees Celsius for 10 hours to obtain biochar.

[0035] (2) Preparation of reaction solution Dissolve 0.05 mol / L sodium tungstate, 0.1 mol / L hydroxylamine hydrochloride, 0.01 mol / L sodium hydroxide, 0.15 mol / L thiourea, and 0.0005 mol / L zinc chloride in deionized water at 30°C and stir magnetically for 30 minutes to obtain a pale yellow transparent reaction solution.

[0036] (3) Hydrothermal reaction The biochar prepared in step (1) and the reaction solution in step (2) were transferred into a reaction vessel and reacted at a constant temperature of 200 degrees Celsius (temperature deviation ≤ ±0.5 degrees Celsius) for 24 hours.

[0037] (4) Filtration, washing, drying and repeating the reaction After the reaction was completed, the product was filtered and washed twice each with deionized water and anhydrous ethanol, and then dried at 80 degrees Celsius for 10 hours to obtain the heterojunction composite material precursor. The precursor was mixed with the freshly prepared reaction solution, and the above hydrothermal, filtration, washing, and drying steps were repeated three times.

[0038] (5) Calcination The precursor, after repeated reactions, was calcined at 850°C for 2 hours under a nitrogen atmosphere to obtain a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material 1. In this material, zinc sulfide and tungsten sulfide are two-dimensional nanosheets of 100–200 nm, with tungsten sulfide accounting for 10% by mass and zinc sulfide accounting for 0.2% by mass. A scanning electron microscope image of the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material 1 is shown below. Figure 2 As shown. From Figure 2 As can be seen, zinc sulfide nanosheets (bright white) are distributed in an island-like structure on the surface of biochar (gray substrate), while tungsten sulfide nanosheets (dark gray) grow epitaxially at their edges, forming overlapping heterojunctions. Tungsten sulfide and zinc sulfide nanosheets grow uniformly on the surface of biochar.

[0039] (6) Electrode preparation and performance testing Composite material 1, conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 8:1:1. One part by mass of PVDF was dissolved in 19 parts by mass of methylpyrrolidone, and 8 parts by mass of composite material 1 and 1 part by mass of conductive carbon black were added. The mixture was stirred for 3 hours to obtain a slurry. The slurry was coated onto aluminum foil (approximately 20 μm thick) and dried at 110°C for 24 hours to obtain electrode sheet 1. A lithium metal half-cell was assembled using a 0.8 mol / L lithium hexafluorophosphate solution (solvent: ethylene carbonate: diethyl carbonate = 1:1) as the electrolyte. The prepared electrode sheet was tested using a LANHECT 3002A battery tester to determine its specific capacity-voltage profile in a single cycle at current densities of 0.1C and 1.0C, within a voltage range of 0.1–2.5V. Figure 3 As shown. From Figure 3 It can be seen that the specific capacity of the electrode in Example 1 reaches 397.4 at 0.1C. At 1.0C, the specific capacity reaches 135.3. .

[0040] Example 2 Example 2 of the present invention prepares a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material according to the following steps: (1) Biochar preparation Balsa wood was cut into small pieces measuring 10mm × 10mm × 5mm, calcined at 900°C for 2.5 hours under a nitrogen atmosphere, washed three times with deionized water, and then dried at 70°C for 10 hours to obtain a product with a density of 0.10 g / L. Biochar.

[0041] (2) Preparation of reaction solution Dissolve 0.12 mol / L sodium tungstate, 0.3 mol / L hydroxylamine hydrochloride, 0.1 mol / L sodium hydroxide, 0.5 mol / L thiourea, and 0.05 mol / L zinc chloride in deionized water at 35°C and stir magnetically for 40 minutes to obtain a pale yellow transparent reaction solution.

[0042] (3) Hydrothermal reaction The biochar from step (1) and the reaction solution from step (2) were transferred into a reactor and reacted for 24 hours at a pressure of 1.8 MPa and a constant temperature of 210 degrees Celsius (temperature deviation ≤ ±0.5 degrees Celsius).

[0043] (4) Filtration, washing, drying and repeating the reaction After the reaction was completed, the product was obtained by vacuum filtration, washed three times each with deionized water and anhydrous ethanol, and dried at 70°C under normal pressure for 10 hours to obtain the heterojunction composite material precursor. The precursor was mixed with the freshly prepared reaction solution, and the above hydrothermal, filtration, washing, and drying steps were repeated three times.

[0044] (5) Calcination The precursor, after repeated reactions, was calcined at 900°C for 2.5 hours under an argon atmosphere to obtain a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material 2. In this material, zinc sulfide and tungsten sulfide are two-dimensional nanosheets of 200-250 nm, with tungsten sulfide accounting for 45% by mass and zinc sulfide accounting for 0.35% by mass. Scanning electron microscopy images of the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material 2 are shown below. Figure 4 As shown. By Figure 4 The scanning electron microscope images show that the biocarbon substrate derived from balsa wood exhibits an interconnected honeycomb-like three-dimensional porous structure. Its gray surface is uniformly anchored with two nanosheet structures of different contrasts. The bright white island-shaped nanosheets act as nucleation sites, which can promote the epitaxial growth of dark gray tungsten sulfide nanosheets at their edges and overlap with zinc sulfide nanosheets to form a tight heterojunction interface. All nanosheets grow vertically or nearly vertically on the surface of the biocarbon framework, forming a complete three-dimensional composite structure.

[0045] (6) Electrode preparation and performance testing Electrode 2 was prepared according to step (6) of Example 1. Its single-cycle specific capacity-voltage plot was tested at current densities of 0.1C and 1.0C, and at voltage ranges of 0.1~2.5V. (See figure). Figure 5 As shown. From Figure 5 It can be seen that the specific capacity of the electrode in Example 2 reaches 402.6 at 0.1C. The specific capacity at 1.0C is 142. .

[0046] Example 3 Example 3 of the present invention prepares a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material according to the following steps: (1) Biochar preparation Balsa wood was cut into small pieces measuring 12mm × 12mm × 6mm, calcined at 950°C for 3 hours under a nitrogen atmosphere, washed four times with deionized water, and then dried at 80°C for 10 hours to obtain a product with a density of 0.15g / L. Biochar.

[0047] (2) Preparation of reaction solution 0.2 mol / L sodium tungstate, 0.6 mol / L hydroxylamine hydrochloride, 0.2 mol / L sodium hydroxide, 0.9 mol / L thiourea and 0.1 mol / L zinc chloride were dissolved in deionized water at 40 degrees Celsius and stirred magnetically for 40 minutes to obtain a pale yellow transparent reaction solution.

[0048] (3) Hydrothermal reaction The biochar from step (1) and the reaction solution from step (2) were transferred into a reactor and reacted for 48 hours at a pressure of 2.0 MPa and a constant temperature of 240 degrees Celsius (temperature deviation ≤ ±0.5 degrees Celsius).

[0049] (4) Filtration, washing, drying and repeating the reaction After the reaction was completed, the product was obtained by hot filtration, washed four times each with deionized water and anhydrous ethanol, and dried under reduced pressure at 80 degrees Celsius for 12 hours to obtain the heterojunction composite material precursor. The precursor was mixed with the freshly prepared reaction solution, and the above hydrothermal, filtration, washing, and drying steps were repeated five times.

[0050] (5) Calcination The precursor, after repeated reactions, was calcined at 950°C for 3 hours under a nitrogen atmosphere to obtain a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material 3. In this material, zinc sulfide and tungsten sulfide are two-dimensional nanosheets of 250–300 nm, with tungsten sulfide accounting for 80% by mass and zinc sulfide accounting for 0.5% by mass. A scanning electron microscope image of the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material 3 is shown below. Figure 6 As shown. By Figure 6 The scanning electron microscope images show that the biochar substrate, with its honeycomb-like three-dimensional porous structure, has densely distributed sheet-like nanostructures on its surface. Among them, the bright white island-like nanosheets are zinc sulfide, and the dark gray sheet-like structures are tungsten sulfide nanosheets. The tungsten sulfide nanosheets grow epitaxially with zinc sulfide nanosheets as nucleation centers, and the two form an overlapping and connected heterogeneous structure in three-dimensional space. All nanosheets are firmly anchored to the surface of the biochar framework, forming a complete composite system.

[0051] (6) Electrode preparation and performance testing Electrode 3 was prepared according to step (6) of Example 1. Its single-cycle specific capacity-voltage plot was tested at current densities of 0.1C and 1.0C, and at voltage ranges of 0.1 to 2.5V. (See figure). Figure 7 As shown. From Figure 7 It can be seen that the specific capacity of the electrode in Example 3 reaches 405.8 at 0.1C. The specific capacity at 1.0C is 142.7. .

[0052] Examples 1-3 all achieved the following characteristics of the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material: Structural stability: The honeycomb three-dimensional structure of bio-carbon serves as the substrate, with zinc sulfide and tungsten sulfide two-dimensional nanosheets anchoring and forming a heterojunction, which strengthens the overall structure of the material. High capacitance and ion transport performance: Zinc sulfide / tungsten sulfide nanosheets of 100~300nm are beneficial for ion transport, with specific capacitance exceeding 397 at 0.1C. It possesses excellent charge transport and capacitance properties; Long cycling potential: The stable heterojunction structure and the enhanced electrochemical activity of bio-carbon provide a guarantee for long cycle life.

[0053] In addition, the present invention also provides a negative electrode for lithium-ion batteries, comprising the aforementioned bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material.

[0054] The present invention also provides a negative electrode for sodium-ion batteries, characterized in that it comprises the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material described in any one of the preceding claims.

[0055] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material, characterized in that, The method includes the following steps: S1. Dissolve sodium tungstate, hydroxylamine hydrochloride, sodium hydroxide, thiourea and zinc chloride in deionized water and stir until homogeneous to obtain a pale yellow and transparent reaction solution. S2. Prepare biochar. Mix the reaction solution with the biochar in a reaction vessel and carry out a hydrothermal reaction at a constant temperature for 8 to 48 hours. The constant temperature is any temperature between 180 degrees Celsius and 240 degrees Celsius. S3. The product obtained in step S2 is filtered, washed and dried to obtain a heterojunction composite material precursor. S4. The heterojunction composite material precursor is calcined in an inert gas atmosphere to obtain a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material, wherein the calcination temperature is 850~950 degrees Celsius.

2. The method for preparing the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material according to claim 1, characterized in that, In the reaction solution described in step S1, the concentration of sodium tungstate is 0.05~0.2 mol / L, the concentration of zinc chloride is 0.0005~0.1 mol / L, the concentration of hydroxylamine hydrochloride is 0.1~0.6 mol / L, the concentration of sodium hydroxide is 0.01~0.2 mol / L, and the concentration of thiourea is 0.1~0.9 mol / L.

3. The method for preparing the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material according to claim 1, characterized in that, The hydrothermal reaction described in step S2 is carried out under a pressure of 1.5 MPa to 3.5 MPa, and the deviation between the constant temperature and the set temperature does not exceed ±0.5 degrees Celsius.

4. The method for preparing the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material according to any one of claims 1 to 3, further comprising a repeating reaction step after step S3: mixing the heterojunction composite material precursor with the reaction solution newly prepared in step S1, and then washing and drying; the repeating reaction step is performed 1 to 5 times.

5. The method for preparing the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material according to claim 1, characterized in that, The biochar density is 0.05~0.15 g / It is made by carbonizing balsa wood at 850-950 degrees Celsius.

6. A bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material, characterized in that, The composite material is prepared by the method described in any one of claims 1 to 5, which is a bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material.

7. The bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material according to claim 6, characterized in that, In the composite material, both zinc sulfide and tungsten sulfide are two-dimensional nanosheets of 100-300 nm. The tungsten sulfide nanosheets grow with zinc sulfide as the nucleation site, and the two are anchored together on the surface of bio-carbon with a honeycomb three-dimensional structure.

8. The bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material according to claim 6 or 7, characterized in that, Tungsten sulfide accounts for 10% to 80% of the mass, and zinc sulfide accounts for 0.2% to 0.5% of the mass.

9. A negative electrode for a lithium-ion battery, characterized in that, It includes the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material as described in any one of claims 6 to 8.

10. A negative electrode for a sodium-ion battery, characterized in that, It includes the bio-carbon-zinc sulfide-tungsten sulfide heterojunction composite material as described in any one of claims 6 to 8.

Images