阅读说明：本技术 MoS2纳米片垂直内嵌生物碳纳米复合材料及其制备方法与应用 (MoS2Nano-sheet vertically embedded biological carbon nano composite material and preparation method and application thereof ) 是由 吴正颖 田浩祥 陈志刚 邢凯 刘谢 钱君超 陈丰 于 2021-07-09 设计创作，主要内容包括：本发明涉及一种MoS-(2)纳米片垂直内嵌生物碳纳米复合材料及其制备方法与应用,属于新材料技术领域。本发明的MoS-(2)/C纳米复合材料是以植物细胞为碳源和结构导向模板,通过浸润、煅烧等过程成功合成的。本发明所合成的材料保留了植物的宏观形貌,同时MoS-(2)纳米片均匀定向地生长在生物碳层上,生物碳的形貌促进了MoS-(2)的分散,所得材料无明显团聚现象。在电池的充放电过程中,MoS-(2)纳米片增加了电极材料和电解液之间的接触面积,产生了更多的Li～(+)嵌入活性位点,形成了具有更高电荷迁移率的混合纳米结构。在500次充放电循环后保留有951mAhg～(-1)的可逆比容量以及98％的库伦效率。(The invention relates to a MoS 2 A nano-sheet vertically embedded biological carbon nano composite material and a preparation method and application thereof belong to the technical field of new materials. MoS of the invention 2 the/C nano composite material is successfully synthesized by taking plant cells as a carbon source and a structure-oriented template through the processes of infiltration, calcination and the like. The material synthesized by the invention keeps the macroscopic morphology of plants, and simultaneously MoS 2 The nano-sheets uniformly and directionally grow on the biological carbon layer, and the morphology of the biological carbon promotes MoS 2 The obtained material has no obvious agglomeration phenomenon. In the charging and discharging process of the battery, MoS 2 The nano-sheet increases the contact area between the electrode material and the electrolyte, and generates more Li + Active sites are embedded, forming a hybrid nanostructure with higher charge mobility. 951mAhg remained after 500 charge-discharge cycles ‑1 Reversible specific capacity and coulombic efficiency of 98%.)

1. MoS₂The preparation method of the nano-sheet vertically embedded biological carbon nano composite material is characterized by comprising the following steps:

s1, soaking, washing and airing the biological template for later use;

s2, immersing the standby biological template obtained in the step S1 into a mixed solution of ammonium molybdate and thiourea for hydrothermal reaction to obtain a reaction solution;

s3, carrying out suction filtration, washing and drying on the reaction liquid obtained in the step S2 to obtain a partially carbonized biological template/MoS₂A material;

s4, the partial carbonization biological template/MoS obtained in the step S3₂Heating and calcining the material under the inert gas atmosphere to obtain the MoS₂The nano-sheet vertically embeds the biological carbon nano-composite material.

2. The MoS of claim 1₂The preparation method of the nano composite material with nano sheets vertically embedded with biological carbon is characterized by comprising the following steps: the biological template is camellia petal, peach flower petal, rhododendron petal or agaricus petal.

3. The MoS of claim 1₂The preparation method of the nano-sheet vertically embedded biochar nano-composite is characterized in that in the step S1, ethanol solution with the concentration of 40% -60% is adopted for soaking, and the pH value of the ethanol solution is 2-4; the soaking time is 2-4 weeks.

4. The MoS of claim 1₂The preparation method of the nano composite material with nano sheets vertically embedded with biological carbon is characterized by comprising the following steps: in thatIn the step S2, the concentration of ammonium molybdate in the mixed solution is 0.007-0.029 mol/L; the concentration of thiourea in the mixed solution is 0.028-0.114 mol/L.

5. The MoS of claim 1₂The preparation method of the nano composite material with nano sheets vertically embedded with biological carbon is characterized by comprising the following steps: in the step S2, the hydrothermal reaction is carried out for 6-24 hours at 180-220 ℃.

6. The MoS of claim 1₂The preparation method of the nano composite material with nano sheets vertically embedded with biological carbon is characterized by comprising the following steps: in the step S3, the drying is carried out for 12-24 hours at the temperature of 40-80 ℃.

7. The MoS of claim 1₂The preparation method of the nano composite material with nano sheets vertically embedded with biological carbon is characterized by comprising the following steps: in the step S4, the temperature rising rate is 5-10 ℃ min^-1。

8. The MoS of claim 1₂The preparation method of the nano composite material with nano sheets vertically embedded with biological carbon is characterized by comprising the following steps: in the step of S4, the calcination is 550 ℃ for 2 h.

9. MoS prepared by the method of any one of claims 1 to 8₂The nano-sheet vertically embeds the biological carbon nano-composite material.

10. A lithium battery characterized in that its negative electrode uses the MoS of claim 9₂The nano-sheet is vertically embedded with the biological carbon nano composite material.

Technical Field

The invention relates to the technical field of new materials, in particular to a MoS₂A nano-sheet vertically embedded biological carbon nano composite material, a preparation method and application thereof.

Background

Molybdenum disulfide (MoS)₂) The transition metal sulfide is a transition metal sulfide with a graphite-like layered structure, has the characteristics of stable property, high temperature resistance, simple preparation, low price and the like, and has wide application prospect in the field of new energy. As a novel energy storage device, the lithium ion battery is considered to be one of high-energy batteries which can best meet the requirements of the sustainable development of the future society, but the graphite cathode of the commercial lithium ion battery has small theoretical specific capacity (372 mAhg)^-1) The demands of people for energy storage equipment with high energy density and high rate performance cannot be met gradually. Researchers expect MoS with special layered structure and high theoretical specific capacity₂(670mAhg^-1) The material can become an effective substitute material of the graphite negative electrode.

MoS₂There are two major problems in practical electrochemical applications: (1) MoS₂The active sites of the plant are reduced due to the easy aggregation of the plant into flower balls in the growth process; simultaneously due to lithium ions and MoS during charging and discharging₂The reaction of (2) causes the volume of the material to expand, and leads to the structural fracture, thereby causing the obvious attenuation of the battery capacity and the deterioration of the cycle performance; (2) MoS₂The conductivity is low, so that the electron transmission rate of the material is low in the charging and discharging processes, and the volume pulverization in the circulating process further influences the electron transmission, so that the low rate performance is caused.

Aiming at the problems, MoS is adopted₂Modification is often required for batteries, and there are two main common methods: (1) MoS reduction₂Layer thickness and constructed few-layer structure MoS₂. Few-layer MoS₂The lithium ion battery can provide a shorter lithium ion migration path and expose more effective lithium storage sites; meanwhile, the contact area of the electrode and the electrolyte can be increased after the layer thickness is reduced, which is beneficial to the rapid charge and discharge of the battery; (2) mixing MoS₂And the material is compounded with carbon materials (such as activated carbon, carbon nano tubes, graphene, mesoporous carbon and the like) to improve the conductivity of the material. Meanwhile, MoS can be effectively relieved by the support of the carbon structure₂The volume of the electrode expands in the charging and discharging process, and the stability of the material is enhanced. Compared with carbon nano-particles and carbon nano-tubes, the lamellar graphite and the amorphous carbon with certain lithium storage specific capacity can better react with MoS₂The nano-sheets are matched to form a two-dimensional sheet-sheet coupling structure. However, currently, two-dimensional MoS is constructed₂The methods of the/C sheet-to-sheet coupling structure are complicated and high in cost. Therefore, how to prepare two-dimensional MoS by a simple and environmentally friendly method₂the/C nano composite material becomes a hot spot of scientific research.

Unlike artificially synthesized materials, animals, plants and microorganisms in nature create various fine structures and tissues in the long-term natural evolution process. By adopting a biological template method, the materials with unique structures and appearances are designed by taking the complex biological tissue structures as matrixes and templates, and a new thought is provided for the synthesis of the materials with complex structures. However, no biological template method is adopted to prepare the special two-dimensional structure MoS at present₂the/C nano composite material is reported.

Disclosure of Invention

In order to solve the technical problem, the invention provides a two-dimensional MoS₂Nanosheet vertically embedded with biochar (MoS)₂/C) nano composite material, preparation method and application thereof. The invention takes plant tissue cells widely existing in nature as a structure directing agent, and directly synthesizes the two-dimensional MoS through hydrothermal reaction, high-temperature calcination and other processes₂the/C nano composite material shows good lithium storage performance as an electrode material of a lithium ion battery.

The first purpose of the invention is to provide a MoS₂The preparation method of the nano-sheet vertically embedded biological carbon nano composite material comprises the following steps:

s1, soaking, washing and airing the biological template for later use;

s2, immersing the standby biological template obtained in the step S1 into a mixed solution of ammonium molybdate and thiourea for hydrothermal reaction to obtain a reaction solution;

s3, carrying out suction filtration, washing and drying on the reaction liquid obtained in the step S2 to obtain a partially carbonized biological template/MoS₂A material;

s4, the partial carbonization biological template/MoS obtained in the step S3₂Heating and calcining the material under the inert gas atmosphere to obtain the MoS₂The nano-sheet vertically embeds the biological carbon nano-composite material.

Further, the biological template is camellia petals, peach flower petals, rhododendron petals or agaricus petals.

Further, in the step S1, an ethanol solution with the concentration of 40% -60% is adopted for soaking, and the pH value of the ethanol solution is 2-4; the soaking time is 2-4 weeks.

Further, in the step S2, the concentration of ammonium molybdate in the mixed solution is 0.0075-0.029 mol/L; the concentration of the thiourea solution in the mixed solution is 0.028-0.114 mol/L;

further, in the step S2, the hydrothermal reaction is carried out for 6-24 hours at 180-220 ℃.

Further, in the step S3, the drying is carried out for 12-24 hours at the temperature of 40-80 ℃.

Further, in the step S4, the temperature rising rate is 5-10 ℃ min^-1。

Further, in the step of S4, the calcination is 550 ℃ for 2 hours.

Further, in the step S4, the inert gas is nitrogen or argon.

The second purpose of the invention is to provide the MoS prepared by the method₂a/C nanocomposite material.

The third purpose of the invention is to provide a lithium battery, and the cathode of the lithium battery adopts the MoS₂the/C nano composite material is prepared.

Compared with the prior art, the technical scheme of the invention has the following advantages:

MoS with two-dimensional structure according to the invention₂the/C nano composite material is successfully synthesized by taking the tissue structure of petals as a biological template through ion permeation, hydrothermal aging and calcining carbonization in a precursor solution. Two-dimensional MoS synthesized by the invention₂the/C nano composite material keeps the macro appearance of the template, and simultaneously MoS₂The nano-sheets are uniformly and directionally grown on the biological carbon layer. In MoS₂Due to the guiding function of the biological tissue structure in the nucleation and growth processes of (1), MoS is enabled₂The growth of the lamellae is spatially limited, the thickness of the lamellae is reduced, and the lamellae grow highly uniform and vertically on the carbon layer after calcination. MoS with reduced layer number, high dispersion and vertical growth in the process of charging and discharging of battery₂The nano-sheet can increase the contact area between the electrode material and the electrolyte, and generate more lithium ion intercalation/deintercalation active sites. Mixing MoS₂The nanoflakes are intimately associated with the carbon matrix to form a hybrid nanostructure having higher charge mobility. Meanwhile, the biochar provides high-stability framework support in the charging and discharging processes, and MoS is relieved₂The volume of (2) is pulverized. The material as a lithium battery cathode material shows good cycle stability and reversibility, and 951mAhg is reserved after 500 cycles^-1Reversible specific capacity and coulombic efficiency of 98%.

Drawings

In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which

FIG. 1 is a two-dimensional MoS synthesized in example 1₂SEM image of/C nanocomposite.

FIG. 2 is the two-dimensional MoS synthesized in example 1₂TEM image of/C nanocomposites.

FIG. 3 is the two-dimensional MoS synthesized in example 1₂XRD pattern of/C nanocomposite.

FIG. 4 is the two-dimensional MoS synthesized in example 1₂/C nanocomposite, biochar, simple MoS₂Cycle performance map of (c).

FIG. 5 is the two-dimensional MoS synthesized in example 2₂SEM image of/C-0.2 nanocomposite.

FIG. 6 is the two-dimensional MoS synthesized in example 3₂SEM image of/C nanocomposite.

FIG. 7 is the two-dimensional MoS synthesized in example 4₂SEM image of/C nanocomposite.

FIG. 8 is a MoS synthesized in comparative example 1₂SEM image of the material.

FIG. 9 shows MoS synthesized in comparative example 2₂SEM image of the material.

Detailed Description

The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.

MoS₂The preparation method of the nano-sheet vertically embedded biological carbon nano composite material comprises the following steps:

(1) collecting camellia petals from campus, and washing with deionized water to remove surface dust. The petals were then soaked in an aqueous ethanol solution (50%) for 2 weeks to remove pigments and other organic matter from the petals.

(2) And washing the pretreated petals with deionized water for 3 times, airing, and then soaking into a mixed solution of ammonium molybdate with the prepared concentration of 0.0075moL/L and thiourea with the prepared concentration of 0.028 moL/L. Then transferring the ammonium molybdate and thiourea soaked biological template into the inner liner of the reaction kettle, and heating for 6 hours at 220 ℃.

(3) And (3) carrying out suction filtration on the mixture after the water heating is finished, respectively washing the mixture with deionized water and ethanol for three times, and then putting the obtained solid product into an oven with the temperature of 80 ℃ for 24 hours. The sample was a partially carbonized petal/MoS₂。

(4) Drying the partially carbonized petals/MoS₂Calcining the mixture for 2 hours in a tubular furnace at 550 ℃ under nitrogen to obtain the material MoS₂a/C nanocomposite material.

The following examples are combined to synthesize nano MoS₂the/C nanocomposites, we further analyzed the nano-MoS of the present invention₂the/C nano composite material has the characteristics of shape structure and performance:

FIG. 1 is a MoS₂Scanning Electron Microscope (SEM) image of/C nanocomposites in MoS₂In SEM images of the/C nanocomposites periodic relief-like arrangements derived from the petal cytoskeleton can be observed, which stem from the original cell surface morphology of the petals. Compared with the original petal template, MoS₂The surface of the/C nano composite material contains a large number of molybdenum sulfide nano sheets, and the nano sheets uniformly and directionally grow on the biological carbon.

FIG. 2 is a MoS₂TEM image of/C nanocomposites. TEM image gives MoS in the composite₂And structures between carbon layers. The TEM image curved lamella is typical of MoS₂The nano-sheets are uniformly distributed and present few-layer shapes. High resolution Transmission Electron microscopy (HR-TEM) display of MoS in composites₂The structure is a few layers (the number of layers is 3-8) structure, and the lattice spacing is 0.65 nm.

FIG. 3 is a MoS₂XRD pattern of/C nano composite material. Characteristic peaks at 8.86 °, 17.96 °, 33.38 °, 33.80 ° and 59.21 ° 2 θ, corresponding to cubic MoS, respectively₂The (002), (004), (100), (101), and (008) crystal planes of (a). MoS with conventional 2H phase₂In contrast, two-dimensional few-layer MoS₂The (002) and (004) crystal planes of the/C nanocomposite are shifted to the left, which illustrates MoS₂MoS in/C nanocomposites₂The crystal structure changes during the growth process, and the crystal structure tends to be converted into a conductive 1T phase. MoS of 1T phase₂MoS of phase 2H₂The conductive performance is better, which is more beneficial to the transmission of electrons when being used as a battery electrode material in the later period, and the lithium storage capacity of the material is improved.

Following two-dimensional MoS synthesized for the present invention₂The electrochemical performance of the/C nano composite material is tested: testingConditions MoS obtained in example₂the/C nano composite material is used as a negative electrode, the lithium sheet is used as a counter electrode and a reference electrode, and the electrochemical performance of the material is tested by adopting a CR2032 button cell system. Specifically, a proper amount of sample is weighed, mixed with conductive carbon black (Super P) and ground for 25-30min, and then PVDF is added as a binder and ground for 5min again (the ratio of the three materials is 7:2: 1). Transferring the uniformly mixed and ground powder into a small beaker, adding a proper amount of NMP as a solvent, and emulsifying for 30min by using an emulsifying machine. And uniformly coating the emulsified solvent on a copper foil by using a blade of 100 mu m, and then drying the copper foil in a vacuum oven at 80 ℃ for 24 hours. And then rolling the dried copper foil by using a roll press, and cutting the copper foil into circular pole pieces with the same size by using a slicing machine. Finally, the button cell is installed in the glove box. The battery performance test was performed by a multi-channel battery tester (LAND CT 2001A).

FIG. 4 is a MoS₂Cycling performance of the/C nanocomposites at high current density of 500 mA/g. Two-dimensional few-layer MoS guided by biological template₂The reversible specific capacity of the/C nano composite material in the first circle is 1041 mAh.g^-1Far higher than biochar and simple MoS₂The sample of (1). Meanwhile, 516mAh & g can be kept after 100 cycles of circulation^-1The reversible specific capacity of the carbon is also higher than that of biological carbon (205 mAh.g)^-1) And simple MoS₂(284mAh·g^-1) The sample of (1). The results show two-dimensional MoS₂the/C nano composite material has the capability of large-current charge and discharge and good stability. The MoS₂The excellent electrochemical performance of the/C nano composite material is mainly due to the conductivity of the biological carbon and the MoS subjected to phase transition₂Has better conductivity. Meanwhile, the lithium ion intercalation/deintercalation basically occurs in MoS during the charging and discharging processes₂In structure, and uniformly dispersed MoS₂Sufficient active sites are provided to make the lithium ion intercalation/deintercalation more simple and rapid. At the same time because of MoS₂The crystal nucleus is embedded in the surface structure of the biological carbon in the crystal growth process, so that the volume expansion caused by the lithium ion embedding/separating is greatly reduced, and the MoS₂Close bonding to carbon enables MoS₂In a stable state, so that the material shows excellent propertiesThe properties are different.

Example 2:

(1) collecting camellia petals from campus, and washing with deionized water to remove surface dust. The petals were then soaked in an aqueous ethanol solution for 2 weeks (50%) to remove pigments and other organic matter from the petals.

(2) And washing the pretreated petals with deionized water for 3 times, then airing, and then soaking into a mixed solution of ammonium molybdate with the concentration of 0.029moL/L and thiourea with the concentration of 0.114 moL/L. Then transferring the ammonium molybdate and thiourea soaked biological template into the inner liner of the reaction kettle, and heating for 6 hours at 220 ℃.

(3) And (3) carrying out suction filtration on the material after the hydrothermal reaction is finished, respectively washing the material with deionized water and ethanol for three times, and then putting the obtained solid product into an oven with the temperature of 80 ℃ for 24 hours. The sample was a partially carbonized petal/MoS₂。

(4) Drying the partially carbonized petals/MoS₂Calcining the mixture for 2 hours in a tubular furnace at 550 ℃ under nitrogen to obtain the material MoS₂the/C-0.2 composite material.

FIG. 5 is the MoS synthesized at an ammonium molybdate concentration of 0.029moL/L₂/C nanocomposites (labelled MoS)₂C-0.2) Scanning Electron Microscope (SEM) image. From MoS₂In the SEM image of the/C-02 composite material, MoS can be obviously observed₂The nano-sheets grow on the biological carbon uniformly and vertically, and MoS is generated due to the high concentration of the molybdenum source during synthesis₂The density of the nanosheets is also relatively high.

Example 3:

(1) peach petals are collected from a campus, and surface dust is removed by washing with deionized water. The petals were then soaked in an aqueous ethanol solution for 2 weeks (50%) to remove pigments and other organic matter from the petals.

(2) And washing the pretreated petals with deionized water for 3 times, then airing, and then soaking into a mixed solution of ammonium molybdate with the concentration of 0.029moL/L and thiourea with the concentration of 0.114 moL/L. Then transferring the ammonium molybdate and thiourea soaked biological template into the inner liner of the reaction kettle, and heating for 6 hours at 220 ℃.

(3) Filtering the hot-water-heated material, and removingThe seed water and the ethanol are respectively washed for three times, and then the obtained solid product is put into an oven with the temperature of 80 ℃ for 24 hours. The sample was a partially carbonized petal/MoS₂。

(4) Drying the partially carbonized petals/MoS₂Calcining the mixture for 2 hours in a tubular furnace at 550 ℃ under nitrogen to obtain the material MoS taking peach blossom as a template₂a/C nanocomposite material.

FIG. 6 shows the MoS synthesized by peach blossom as structure directing agent and biological carbon template, with ammonium molybdate concentration of 0.029moL/L₂/C nanocomposites (labelled MoS)₂C-0.2-p) in a Scanning Electron Microscope (SEM). From MoS₂In SEM images of the/C-02-p composite material, highly oriented growth, vertical to the surface of the biochar and uniformly dispersed MoS can be obviously observed₂Nanosheets. At the same time, very little slightly agglomerated MoS was observed₂The flower balls are on the surface of the composite material, which is caused by the higher concentration of the molybdenum source during synthesis.

Example 4:

(1) collecting petals of agar from campus, and washing with deionized water to remove surface dust. The petals were then soaked in an aqueous ethanol solution for 4 weeks (60%) to remove pigments and other organic matter from the petals.

(2) And cleaning the pretreated petals with deionized water for 3 times, airing, and then soaking into a prepared mixed solution of ammonium molybdate and thiourea with the concentration of 0.029 moL/L. Then transferring the ammonium molybdate and thiourea soaked biological template into the inner liner of the reaction kettle, and heating for 6 hours at 220 ℃.

(3) And (3) carrying out suction filtration on the material after the hydrothermal reaction is finished, respectively washing the material with deionized water and ethanol for three times, and then putting the obtained solid product into an oven with the temperature of 80 ℃ for 24 hours. The sample was a partially carbonized petal/MoS₂。

(4) Drying the partially carbonized petals/MoS₂Calcining the mixture for 2 hours in a tubular furnace at 550 ℃ under nitrogen to obtain the material MoS taking peach blossom as a template₂a/C nanocomposite material.

FIG. 7 is the MoS synthesized by using agar as structure directing agent and biological carbon template, and ammonium molybdate with concentration of 0.029moL/L₂/C nanocomposites (labelled MoS)₂A Scanning Electron Microscope (SEM) image of/C-0.2-v). From MoS₂In SEM images of the/C-02-v composite material, highly oriented MoS which is vertical to the surface of the biochar and uniformly dispersed can be obviously observed₂Nanosheets. Also, the MoS obtained from the agar template due to the subtle differences in the structure of the biological cells₂The nano-sheet is dispersed very uniformly, and the growth orientation is also obvious.

Comparative example 1:

(1) collecting camellia petals from a park, and washing with deionized water to remove surface dust. The petals were then soaked in an aqueous ethanol solution for 4 weeks (50%) to remove pigments and other organic matter from the petals.

(2) And cleaning the pretreated petals with deionized water for 3 times and then drying.

(3) The dried petals are placed in a tube furnace to be calcined for 2 hours at 550 ℃ under nitrogen. Sampling, grinding and collecting to obtain the material, namely the biological carbon material.

Fig. 8 is an SEM image of a simple biochar material obtained in comparative example 1. As can be seen from the figure, the biochar directly obtained by the pretreatment and calcination of the petals has a morphological structure similar to that of the petal template, and has a uniform and smooth surface without any embedding of the nanosheets.

Comparative example 2:

weighing a certain amount of ammonium molybdate, dissolving the ammonium molybdate in water to ensure that the concentration of molybdenum ions is 0.029moL/L, then adding a certain amount of thiourea (the molar ratio of molybdenum to sulfur is 1:4), stirring and dissolving, transferring to an autoclave for summarizing, heating at 220 ℃ for 6 hours, taking out, filtering, washing and drying to obtain pure MoS₂A material.

FIG. 9 shows the MoS alone obtained in comparative example 2₂SEM image of the material, MoS can be seen from the figure₂Without adding biological tissue structure in the synthesis system, the obtained MoS₂Is in the shape of an agglomerated ball with a ball size of 500-600nm and MoS₂The nano sheets are not directionally arranged, and the appearance is completely different from that of the composite material added with the biological template.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.