阅读说明：本技术 一种石墨化碳泡沫支撑碳材料/碳化钼复合材料及其制备方法和用途 (Graphitized carbon foam support carbon material/molybdenum carbide composite material and preparation method and application thereof ) 是由 程春 牛树章 石润 黄润青 于 2019-11-13 设计创作，主要内容包括：本发明涉及一种石墨化碳泡沫支撑碳材料/碳化钼复合材料及其制备方法和用途。所述复合材料包含石墨化碳泡沫骨架以及依附在其上的碳材料/碳化钼纳米点复合物,所述复合物中碳化钼纳米点原位生长在碳材料上。本发明通过采用浸渍结合热处理的方法,制备得到所述复合材料,碳化钼纳米点在碳材料上分布均匀,提供丰富的活性位点,所述方法条件温和、成本低廉,分散性好；本发明还提供一种石墨化碳泡沫支撑碳材料/碳化钼/硫复合正极材料,实现多硫化物的高效吸附和催化转化,有效消除多硫化物的穿梭效应。本发明提供的石墨化碳泡沫支撑碳材料/碳化钼复合材料在新型高容量锂硫电池方面有广泛的应用前景,可进一步应用到其它相关电子器件领域。(The invention relates to a graphitized carbon foam support carbon material/molybdenum carbide composite material and a preparation method and application thereof. The composite material comprises a graphitized carbon foam skeleton and a carbon material/molybdenum carbide nano-dot composite attached to the graphitized carbon foam skeleton, wherein the molybdenum carbide nano-dots are grown on the carbon material in situ. The composite material is prepared by adopting a method of combining dipping with heat treatment, the molybdenum carbide nanodots are uniformly distributed on the carbon material, rich active sites are provided, and the method has the advantages of mild conditions, low cost and good dispersibility; the invention also provides a graphitized carbon foam support carbon material/molybdenum carbide/sulfur composite anode material, which realizes the high-efficiency adsorption and catalytic conversion of polysulfide and effectively eliminates the shuttle effect of polysulfide. The graphitized carbon foam support carbon material/molybdenum carbide composite material provided by the invention has a wide application prospect in the aspect of novel high-capacity lithium-sulfur batteries, and can be further applied to the field of other related electronic devices.)

1. A graphitized carbon foam supported carbon material/molybdenum carbide composite material, wherein the composite material comprises a graphitized carbon foam skeleton and a carbon material/molybdenum carbide nanodot composite attached thereto, wherein the molybdenum carbide nanodots are grown in situ on the carbon material.

2. The composite material according to claim 1, wherein the specific surface area of the composite material is 50-300m²·g^-1Preferably 80 to 280m²·g^-1；

Preferably, the pore size of the graphitized carbon foam is 0.2 to 20 μm, preferably 0.4 to 18 μm;

preferably, the carbon material comprises any one or a combination of at least two of graphene material, carbon nanotubes, carbon fibers or mesoporous carbon, preferably graphene material;

preferably, the graphene material comprises a two-dimensional graphene material and/or a three-dimensional graphene material;

preferably, the graphene material comprises any one or a combination of at least two of graphene, graphene oxide, reduced graphene oxide or doped graphene, preferably graphene oxide;

preferably, the preparation method of the graphene oxide comprises any one of a redox method, a mechanical stripping method, an electrochemical method or a liquid phase stripping method, preferably a redox method;

preferably, the size of the two-dimensional graphene material is 0.2-100 μm, preferably 0.5-80 μm;

preferably, the specific surface area of the graphene material is 50-1000m²·g^-1Preferably 80-900m²·g^-1；

Preferably, the pore size of the three-dimensional graphene material is between 0.1 and 100nm, preferably between 0.2 and 80 nm;

preferably, the molybdenum carbide nanodots account for 2-50%, preferably 5-45% of the mass of the composite material;

preferably, the size of the molybdenum carbide nanodots is 1 to 1000nm, preferably 1.5 to 700 nm.

3. A method for preparing a composite material according to claim 1 or 2, characterized in that it comprises the following steps:

(1) immersing self-supporting foam into carbon material dispersion liquid containing molybdenum metal ions, taking out and drying to obtain a precursor material;

(2) and (2) carrying out heat treatment on the precursor material obtained in the step (1) to obtain the composite material.

4. The production method according to claim 3, wherein the carbon material dispersion liquid containing molybdenum metal ions in the step (1) is prepared by: adding a molybdenum salt precursor solution into a carbon material solution, and uniformly dispersing to obtain the carbon material dispersion liquid containing molybdenum metal ions;

preferably, the molybdenum salt precursor comprises any one or a combination of at least two of ammonium molybdate, sodium molybdate, potassium molybdate, phosphomolybdic acid, sodium phosphomolybdate, ammonium tetrathiomolybdate, molybdenum acetylacetonate or zinc molybdate, preferably any one or a combination of at least two of sodium molybdate, potassium molybdate, phosphomolybdic acid, sodium phosphomolybdate, ammonium tetrathiomolybdate, molybdenum acetylacetonate or zinc molybdate;

preferably, the mass ratio of the molybdenum salt precursor to the carbon material is 1:10-1:1, preferably 1:9-1: 1.2;

preferably, the means of dispersion is stirring and/or sonication;

preferably, the dispersion time is 1-180min, preferably 5-170 min.

5. The method according to claim 3, wherein the self-supporting foam in step (1) comprises any one or a combination of at least two of melamine foam, polyurethane foam, phenolic foam, or polyurethane foam, preferably any one or a combination of at least two of polyurethane foam, phenolic foam, or polyurethane foam;

preferably, the pore size of the self-supporting foam is between 100nm and 10 μm, preferably between 120nm and 9 μm;

preferably, the mass ratio of the self-supporting foam to the carbon material is 1:0.5 to 1: 2;

preferably, the mass ratio of the self-supporting foam to the molybdenum salt precursor is 1:0.3-1: 2;

preferably, the immersion time is from 0.1 to 48h, preferably from 0.5 to 46 h;

preferably, the drying temperature is 25-150 ℃, preferably 30-140 ℃;

preferably, the drying time is from 0.5 to 48h, preferably from 1 to 46 h.

6. The method according to claim 3, wherein the temperature of the heat treatment in step (2) is 550-1200 ℃, preferably 580-1100 ℃;

preferably, the heating rate of the heat treatment is 1-10 ℃/min, preferably 2-9 ℃/min;

preferably, the time of the heat treatment is 1 to 24 hours, preferably 1.5 to 23 hours;

preferably, the protective atmosphere for the heat treatment comprises any one of argon, nitrogen or hydrogen or a combination of at least two thereof.

7. The method for preparing a composite material according to any one of claims 3 to 6, comprising the steps of:

(1) adding a molybdenum salt precursor solution into a carbon material solution, wherein the mass ratio of the molybdenum salt precursor to the carbon material is 1:10-1: 1; stirring and ultrasonically dispersing for 1-180min to obtain the carbon material dispersion liquid containing molybdenum metal ions, immersing self-supporting foam into the carbon material dispersion liquid, keeping the self-supporting foam and the carbon material at a mass ratio of 1:0.5-1:2 and a mass ratio of 1:0.3-1:2 to a molybdenum salt precursor for 0.1-48h, taking out, and drying at the temperature of 25-150 ℃ for 0.5-48h to obtain a precursor material;

(2) and (3) carrying out heat treatment on the precursor material obtained in the step (1), raising the temperature to 550-1200 ℃ at the heating rate of 1-10 ℃/min, and preserving the heat for 1-24h to obtain the graphitized carbon foam support carbon material/molybdenum carbide composite material.

8. A preparation method of a graphitized carbon foam supported carbon material/molybdenum carbide/sulfur composite cathode material is characterized in that the composite material as claimed in claim 1 or 2 is used as a carrier and is compounded with a sulfur source to prepare the composite cathode material;

preferably, the compounding means comprises immersing the graphitized carbon foam supporting carbon material/molybdenum carbide composite material in a sulfur-containing solution, or dropping the sulfur-containing solution into the graphitized carbon foam supporting carbon material/molybdenum carbide composite material;

preferably, the sulfur source comprises a sulfur-containing solution;

preferably, the sulfur-containing solution is S/CS₂A solution or a solution containing polysulfides;

preferably, the concentration of the sulfur-containing solution is 0.1-6mol/L, preferably 0.15-5.5 mol/L;

preferably, the addition amount of the sulfur-containing solution is 2-100 mu L/cm²Preferably, it is5-90μL/cm²。

9. The graphitized carbon foam supported carbon material/molybdenum carbide/sulfur composite cathode material prepared by the method for preparing a composite cathode material according to claim 8.

10. A lithium-sulfur battery comprising the graphitized carbon foam supported carbon material/molybdenum carbide/sulfur composite positive electrode material according to claim 9.

Technical Field

The invention relates to the field of preparation of carbon-based composite materials and energy storage, in particular to a graphitized carbon foam support carbon material/molybdenum carbide composite material and a preparation method and application thereof.

Background

With the rapid development of economy and society, energy and environmental problems become increasingly serious, and therefore, the development of a novel green and recyclable energy storage system is urgent. The lithium-sulfur battery has 1675mAh g^-1Theoretical specific capacity of (1) 2600 Wh.Kg^-1The theoretical specific energy of (a) is equivalent to 3 to 5 times that of the secondary batteries which have been commercialized at present, and is considered to be one of the most promising next-generation lithium secondary batteries. However, during the charging and discharging processes of the lithium-sulfur battery, the polysulfide in an intermediate valence state generated by sulfur is easily dissolved in the electrolyte, and a side reaction occurs, so that the polysulfide becomes a shuttle effect, loss of active substances is caused, and meanwhile, the collapse and pulverization of the structure of the positive electrode material are caused by the expansion and contraction of the volume of sulfur, so that the performance of the lithium-sulfur battery is rapidly attenuated.

In recent years, researchers have attracted much attention by using carbon materials and metal compounds as sulfur carriers. CN109346678A discloses a preparation method of a high-sulfur-loaded lithium-sulfur battery positive electrode, which comprises the preparation of a carbon-sulfur composite positive electrode material, and the specific steps are as follows: adding a carbon material and sulfur into water, and uniformly mixing to obtain carbon-sulfur mixed slurry; and adding the carbon-sulfur mixed slurry into a sand mill for nano ball milling, drying and crushing, and then heating and melting to obtain the carbon-sulfur composite cathode material. The method adopts the ball milling and heating melting modes, enhances the distribution uniformity of sulfur in the carbon material, ensures that the sulfur can be more uniformly distributed in the pore canal of the carbon material after heating melting, and is beneficial to the exertion of the specific capacity of the sulfur. However, carbon materials have a weak physical adsorption effect on polysulfides and cannot effectively suppress the "shuttle effect", and therefore, researchers have conducted studies on functionalized carbon materials as sulfur carriers.

CN105938900A discloses a study of a surface-modified nitrogen-doped porous carbon-sulfur composite material in a lithium-sulfur battery anode, the invention adopts a hard template method and an ammonia activation method to prepare a nitrogen-doped porous carbon material, the carbon material and sublimed sulfur powder are uniformly mixed, the carbon-sulfur composite material is synthesized by heating under a closed condition, and then dopamine is utilized to polymerize a film on the surface of porous carbon and then is chemically crosslinked with graphene oxide to obtain the surface-modified nitrogen-doped porous carbon-sulfur composite material. The surface of the composite material is uniformly coated with polydopamine and graphene oxide, a nitrogen-containing functional group rich in polydopamine and an oxygen-containing functional group of the graphene oxide can well fix sulfur and inhibit polysulfide shuttling, and in addition, the chemical crosslinking action of the polydopamine and the graphene oxide forms a shell-like structure on the surface of a carbon material to stabilize the structure of the material, so that the lithium-sulfur battery positive electrode composite material with good performance is obtained. However, the carbon-based material has a poor sulfur limiting effect, and the capacity of the lithium-sulfur battery decays relatively quickly.

CN108336308A discloses a lithium-sulfur battery positive electrode protection material, which comprises a nanoporous carbon network and inorganic nanoparticles uniformly distributed in the nanoporous carbon network, wherein the distance between any two adjacent inorganic nanoparticles is 3-50nm, the inorganic nanoparticles are metal compound nanoparticles or metal-metal compound composite nanoparticles, and the nanoporous carbon network and the inorganic nanoparticles form an integrated three-dimensional nanoporous composite network. The positive electrode protection material has a physical and chemical double-effect adsorption effect, can limit lithium polysulfide near a positive electrode, and effectively inhibits the loss of a positive electrode active material of a lithium-sulfur battery; can also accelerate soluble lithium polysulfide to difficultly soluble Li₂S₂Or Li₂And S is converted, so that the energy conversion efficiency and the rate capability of the lithium-sulfur battery are greatly improved. However, the metal compound has poor conductivity, so that the polysulfide is slowly converted into lithium sulfide, and the final electrochemical performance of the battery is influenced.

In view of the above-mentioned literature studies, it is known that how to improve the affinity between polysulfide and the affinity, increase the active sites on the surface of polysulfide, promote the conversion of polysulfide on the surface of the positive electrode, and solve the problems of collapse and pulverization of the positive electrode material structure caused by volume change of sulfur is a problem to be solved at present.

Disclosure of Invention

In view of the problems in the prior art, the invention provides a graphitized carbon foam supported carbon material/molybdenum carbide composite material and a preparation method and application thereof, the invention constructs the carbon material/molybdenum carbide composite material supported by the graphitized carbon foam with a three-dimensional hierarchical structure as a sulfur carrier by adopting a soaking and high-temperature heat treatment method, the graphitized carbon foam framework provides enough space for the volume change of sulfur, and the problems of collapse and pulverization of the structure of a positive electrode material caused by the volume change of sulfur are solved; meanwhile, by utilizing the synergistic effect among the components, the problems of poor adsorption performance of the anode on polysulfide and low catalytic conversion capability in the lithium-sulfur secondary battery are solved, and the high-efficiency adsorption and catalytic conversion on polysulfide are realized.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a graphitized carbon foam supported carbon material/molybdenum carbide composite material, the composite material comprising a graphitized carbon foam skeleton and a carbon material/molybdenum carbide nanodot composite attached thereto, wherein the molybdenum carbide nanodots are grown in situ on the carbon material.

According to the graphitized carbon foam supported carbon material/molybdenum carbide composite material provided by the invention, the porous structure of the graphitized carbon foam can adsorb more carbon material/molybdenum carbide composites, and meanwhile, an enough space is provided for the volume change of the graphitized carbon foam; the carbon material has double functions, firstly, the carbon material has good conductivity and can provide rapid electron transmission, and secondly, the groups on the surface of the carbon material and the molybdenum metal ions form a bonding effect, so that the generated molybdenum nitride nano-dots can be uniformly dispersed on the carbon material and form good electric contact with the carbon material; the molybdenum carbide nano-dots grow on the carbon material in situ, are tightly combined with the carbon material, have stable structure, provide rich active sites, can realize the polar modification of the surface of the graphitized carbon foam framework, and can effectively realize the efficient adsorption and catalytic conversion of polysulfide. The composite material has a wide application prospect in the aspect of novel high-capacity lithium-sulfur batteries, and can be further applied to the field of other related electronic devices.

Preferably, the specific surface area of the composite material is 50-300m²·g^-1For example, it may be 50m²·g^-1、52m²·g^-1、55m²·g^-1、58m²·g^-1、60m²·g^-1、65m²·g^-1、70m²·g^-1、75m²·g^-1、80m²·g^-1、85m²·g^-1、90m²·g^-1、95m²·g^-1、100m²·g^-1、105m²·g^-1、110m²·g^-1、115m²·g^-1、120m²·g^-1、130m²·g^-1、140m²·g^-1、150m²·g^-1、160m²·g^-1、170m²·g^-1、180m²·g^-1、190m²·g^-1、200m²·g^-1、205m²·g^-1、210m²·g^-1、215m²·g^-1、220m²·g^-1、230m²·g^-1、240m²·g^-1、250m²·g^-1、260m²·g^-1、270m²·g^-1、280m²·g^-1、290m²·g^-1、292m²·g^-1、295m²·g^-1、298m²·g^-1Or 300m²·g^-1Etc. the specific surface area of the composite material provides rich active sites, has strong affinity with polysulfide, accelerates the transformation speed thereof, eliminates shuttle effect, and preferably80-280m²·g^-1。

Preferably, the pore size of the graphitized carbon foam is 0.2 to 20 μm, and may be, for example, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.40 μm, 0.45 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 18 μm, 18.5 μm, 19 μm, 19.5 μm, or 20 μm, and the like, preferably 0.4 to 18 μm. The pore diameter is less than 0.2 μm, and a large amount of sulfur is difficult to load; the pore diameter is larger than 20 μm, and it is difficult to limit the dissolution of polysulfide well.

Preferably, the carbon material comprises any one or a combination of at least two of graphene material, carbon nanotubes, carbon fibers or mesoporous carbon, wherein typical but non-limiting combinations are graphene material and carbon nanotubes, carbon nanotubes and carbon fibers, graphene material and mesoporous carbon, the graphene material has a large specific surface area, can provide more attachment sites for molybdenum carbide, and has high electronic conductivity, which is beneficial to electron transport, and is preferably graphene material.

Preferably, the graphene material comprises a two-dimensional graphene material and a three-dimensional graphene material.

Preferably, the graphene material comprises any one or a combination of at least two of graphene, graphene oxide, reduced graphene oxide or doped graphene, wherein typical but non-limiting combinations are graphene oxide and reduced graphene oxide, graphene and doped graphene, graphene oxide and reduced graphene oxide; the oxygen-containing functional group on the surface of the graphene oxide and the molybdenum metal ions form a bonding effect, so that the generated molybdenum carbide nanodots can be uniformly dispersed on the carbon sheet layer, and the graphene oxide is preferred.

Preferably, the preparation method of the graphene oxide includes any one of a redox method, a mechanical exfoliation method, an electrochemical method, and a liquid phase exfoliation method, and preferably, the redox method.

Preferably, the two-dimensional graphene material has a size of 0.2-100 μm, for example, 0.2 μm, 0.3 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 17 μm, 20 μm, 22 μm, 25 μm, 30 μm, 33 μm, 35 μm, 37 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 83 μm, 85 μm, 88 μm, 90 μm, 92 μm, 95 μm, 98 μm, or 100 μm, preferably 0.5-80 μm, and can ensure good ion transport and provide a good electron transport channel for molybdenum carbonization.

Preferably, the specific surface area of the graphene material is 50-1000m²·g^-1May be, for example, 50m²·g^-1、55m²·g^-1、60m²·g^-1、65m²·g^-1、70m²·g^-1、80m²·g^-1、90m²·g^-1、100m²·g^-1、102m²·g^-1、105m²·g^-1、108m²·g^-1、110m²·g^-1、113m²·g^-1、115m²·g^-1、117m²·g^-1、120m²·g^-1、125m²·g^-1、130m²·g^-1、135m²·g^-1、140m²·g^-1、145m²·g^-1、150m²·g^-1、160m²·g^-1、170m²·g^-1、185m²·g^-1、195m²·g^-1、200m²·g^-1、210m²·g^-1、220m²·g^-1、225m²·g^-1、230m²·g^-1、240m²·g^-1、255m²·g^-1、260m²·g^-1、270m²·g^-1、285m²·g^-1、295m²·g^-1、300m²·g^-1、320m²·g^-1、350m²·g^-1、370m²·g^-1、400m²·g^-1、430m²·g^-1、450m²·g^-1、480m²·g^-1、500m²·g^-1、520m²·g^-1、550m²·g^-1、570m²·g^-1、600m²·g^-1、630m²·g^-1、650m²·g^-1、700m²·g^-1、750m²·g^-1、800m²·g^-1、850m²·g^-1、900m²·g^-1、950m²·g^-1、980m²·g^-1、990m²·g^-1Or 1000m²·g^-1Etc., preferably 80 to 900m²·g^-1. The specific surface area of the graphene material can be loaded with a large amount of sulfur, and electrolyte loss caused by overlarge specific surface area can be avoided.

Preferably, the pore size of the three-dimensional graphene material is between 0.1nm and 100nm, for example, 0.1nm, 0.15nm, 0.2nm, 0.25nm, 0.3nm, 0.4nm, 0.5nm, 0.8nm, 1nm, 3nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 50nm, 60nm, 65nm, 70nm, 75nm, 78nm or 80nm, etc., preferably 0.2nm to 80 nm. The aperture size is less than 0.1nm, and the transmission of ions is hindered; the pore diameter is larger than 100nm, so that the shuttle of polysulfide is difficult to be well inhibited.

Preferably, the molybdenum carbide nanodots account for 2-50% of the mass of the composite material, for example, 2%, 4%, 5%, 7%, 10%, 13%, 15%, 18%, 20%, 22%, 25%, 27%, 30%, 33%, 35%, 37%, 40%, 42%, 45%, 48%, or 50%, etc., and the content of the molybdenum carbide nanodots can provide abundant active sites, realize polar modification of the skeleton surface of the graphitized carbon foam, and can realize efficient adsorption and catalytic conversion of polysulfides, preferably 5-45%.

Preferably, the size of the molybdenum carbide nanodots is 1 to 1000nm, and for example, may be 1nm, 1.2nm, 1.5nm, 1.8nm, 2nm, 4nm, 5nm, 8nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 92nm, 95nm, 98nm, 100nm, 120nm, 150nm, 180nm, 200nm, 240nm, 280nm, 300nm, 320nm, 360nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 980nm, or 1000nm, etc., the size of the molybdenum carbide nanodots may be adjusted by experimental parameters, parameters such as the temperature of the heat treatment, the mass ratio of the molybdenum precursor to the carbon material and the like are adjusted and controlled to be adaptive to the surface of the carbon material, and the optimal range is 1.5-700 nm.

In a second aspect, the present invention provides a method for preparing a composite material as described in the first aspect above, comprising the steps of:

(1) immersing self-supporting foam into carbon material dispersion liquid containing molybdenum metal ions, taking out and drying to obtain a precursor material;

(2) and (2) carrying out heat treatment on the precursor material obtained in the step (1) to obtain the composite material.

According to the preparation method of the composite material, the carbon material/molybdenum carbide composite material supported by the graphitized carbon foam with the three-dimensional hierarchical structure is constructed by adopting a method of combining dipping and heat treatment. The composite material is prepared by the steps of adsorbing a carbon material-molybdenum metal ion composite onto the surface and the internal structure of self-supporting foam through an impregnation process, reacting the carbon material with a molybdenum salt precursor through heat treatment, generating molybdenum carbide nanodots through in-situ reaction, uniformly dispersing the molybdenum carbide nanodots, tightly combining the molybdenum carbide nanodots with the carbon material, and having a stable structure, so that the polarity modification of the composite material is realized, and the affinity effect between the carbon material and polysulfide is enhanced. The preparation method has mild conditions, low cost and good dispersibility, provides more active sites, and the proportion of the molybdenum carbide nanodots in the composite material is 2-50%.

Preferably, the method for preparing the carbon material dispersion liquid containing molybdenum metal ions in step (1) is as follows: and adding the molybdenum salt precursor solution into the carbon material solution, and uniformly dispersing to obtain the carbon material dispersion liquid containing molybdenum metal ions.

In the present invention, the kind of the solvent for dissolving the molybdenum salt precursor and the carbon material is not specifically limited, and any solvent commonly used by those skilled in the art is suitable for the present invention.

Preferably, the molybdenum salt precursor comprises any one or a combination of at least two of ammonium molybdate, sodium molybdate, potassium molybdate, phosphomolybdic acid, sodium phosphomolybdate, ammonium tetrathiomolybdate, molybdenum acetylacetonate, or zinc molybdate, preferably any one or a combination of at least two of sodium molybdate, potassium molybdate, phosphomolybdic acid, sodium phosphomolybdate, ammonium tetrathiomolybdate, molybdenum acetylacetonate, or zinc molybdate, wherein a typical but non-limiting combination is sodium molybdate and potassium molybdate, ammonium tetrathiomolybdate and molybdenum acetylacetonate, sodium phosphomolybdate, and ammonium phosphomolybdate.

Preferably, the mass ratio of the molybdenum salt precursor to the carbon material is 1:10 to 1:1, and may be, for example, 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1.8, 1:1.5, 1:1.2, or 1:1, and is preferably 1:9 to 1: 1.2. The mass ratio of the molybdenum salt precursor to the carbon material can ensure that the proportion of the molybdenum carbide nanodots in the composite material is 2-50% after heat treatment.

Preferably, the means of dispersion is stirring and/or sonication.

Preferably, the dispersion time is 1-180min, for example, 1min, 1.5min, 2min, 5min, 10min, 20min, 30min, 50min, 60min, 80min, 90min, 100min, 120min, 150min, 160min, 170min or 180min, etc., preferably 5-170 min.

Preferably, the self-supporting foam comprises any one or a combination of at least two of melamine foam, polyurethane foam, phenolic foam or polyurethane foam, with typical but non-limiting combinations being melamine foam and polyurethane foam, polyurethane foam and polyurethane foam, melamine foam and phenolic foam, polyurethane foam, phenolic foam and polyurethane foam, preferably any one or a combination of at least two of polyurethane foam, phenolic foam or polyurethane foam.

Preferably, the self-supporting foam has a pore size of 100nm to 10 μm, e.g., 100nm, 102nm, 105nm, 108nm, 110nm, 115nm, 120nm, 125nm, 130nm, 140nm, 145nm, 155nm, 160nm, 166nm, 170nm, 177nm, 180nm, 190nm, 200nm, 220nm, 240nm, 260nm, 300nm, 350nm, 400nm, 440nm, 500nm, 550nm, 600nm, 660nm, 700nm, 740nm, 800nm, 860nm, 900nm, 930nm, 1.0 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.5 μm, 3 μm, 3.3 μm, 3.6 μm, 4.0 μm, 4.3 μm, 4.5 μm, 5.0 μm, 5.3 μm, 6.0 μm, 6.3 μm, 8.8 μm, 7.8 μm, 9.0 μm, 7.8 μm, 9.8 μm, 7.8 μm, 9.0 μm, 8 μm, 7.8 μm, 9.0 μm, 7.8 μm, 9.8 μm, 8 μm, 9.0 μm, 9.8 μm, 8 μm, 9.8 μm, 9.0 μm, 8 μm, 3 μm, or more preferably In the above-mentioned channel, it is preferably 120nm to 9 μm.

Preferably, the mass ratio of the self-supporting foam to the carbon material is 1:0.5-1:2, and may be, for example, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:1.9, or 1:2, etc., and the mass ratio of the self-supporting foam to the carbon material is such that the carbon material-molybdenum metal ion complex has sufficient adsorption sites on the self-supporting foam.

Preferably, the mass ratio of the self-supporting foam to the molybdenum salt precursor is 1:0.3 to 1:2, and may be, for example, 1:0.3, 1:0.35, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:1.9, or 1:2, etc., which enables sufficient attachment sites for the formation of the carbon material/molybdenum carbide.

Preferably, the immersion time is 0.1 to 48h, for example, 0.1h, 0.5h, 1h, 2h, 5h, 8h, 10h, 15h, 18h, 20h, 25h, 30h, 35h, 40h, 42h, 46h or 48h, etc., preferably 0.5 to 46 h.

Preferably, the drying temperature is 25-150 ℃, for example, can be 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 145 ℃ or 150 ℃, preferably 30-140 ℃.

Preferably, the drying time is 0.5 to 48h, for example, 0.5h, 1h, 1.5h, 2h, 4h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 25h, 30h, 35h, 40h, 42h, 45h or 48h, etc., preferably 1 to 46 h.

Preferably, the heat treatment temperature is 550-.

Preferably, the heating rate of the heat treatment is 1-10 ℃/min, for example, 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, or 10 ℃/min, etc., and the heating rate can ensure that the reaction system is heated uniformly, preferably 2-9 ℃/min.

Preferably, the heat treatment time is 1 to 24 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 21.5 hours, 22 hours, 22.5 hours, 23 hours, 23.5 hours, or 24 hours, and the like, and the heat treatment time is related to the heat treatment temperature to ensure that the carbon atoms in the carbon material precursor and the molybdenum salt react smoothly, and preferably 1.5 to 23 hours.

Preferably, the protective atmosphere for the heat treatment comprises any one of argon, nitrogen or hydrogen or a combination of at least two of them, with a typical but non-limiting combination being hydrogen and argon.

Preferably, the preparation method comprises the following steps:

(1) adding a molybdenum salt precursor solution into a carbon material solution, wherein the mass ratio of the molybdenum salt precursor to the carbon material is 1:10-1: 1; stirring and ultrasonically dispersing for 1-180min to obtain the carbon material dispersion liquid containing molybdenum metal ions, immersing self-supporting foam into the carbon material dispersion liquid, keeping the self-supporting foam and the carbon material at a mass ratio of 1:0.5-1:2 and a mass ratio of 1:0.3-1:2 to a molybdenum salt precursor for 0.1-48h, taking out, and drying at the temperature of 25-150 ℃ for 0.5-48h to obtain a precursor material;

preferably, the molybdenum salt precursor comprises any one or a combination of at least two of ammonium molybdate, sodium molybdate, potassium molybdate, phosphomolybdic acid, sodium phosphomolybdate, ammonium tetrathiomolybdate, molybdenum acetylacetonate or zinc molybdate, preferably any one or a combination of at least two of sodium molybdate, potassium molybdate, phosphomolybdic acid, sodium phosphomolybdate, ammonium tetrathiomolybdate, molybdenum acetylacetonate or zinc molybdate;

preferably, the carbon material comprises any one or a combination of at least two of graphene material, carbon nanotubes, carbon fibers or mesoporous carbon;

preferably, the self-supporting foam comprises any one of melamine foam, polyurethane foam, phenolic foam or polyurethane foam or a combination of at least two thereof;

(2) and (2) carrying out heat treatment on the precursor material obtained in the step (1), raising the temperature to 550-1200 ℃ at the heating rate of 1-10 ℃/min, and preserving the heat for 1-24h to obtain the graphitized carbon foam support carbon material/molybdenum carbide composite material.

In a third aspect, the invention provides a preparation method of a graphitized carbon foam support carbon material/molybdenum carbide/sulfur composite cathode material, wherein the composite material of the first aspect is used as a carrier to be compounded with a sulfur source to prepare the composite cathode material.

According to the preparation method of the composite anode material, the graphitized carbon foam support carbon material/molybdenum carbide composite material is reacted with the sulfur source, the three-dimensional hierarchical structure of the composite material can accommodate more sulfur sources, so that the sulfur source loading capacity is larger, the capacity of the composite anode material is favorably improved, a space is provided for the volume change of an electrode in the charging and discharging processes, and the cycle stability of the composite anode material is favorably improved. The preparation method is simple to operate and easy to implement.

Preferably, the compounding means comprises immersing the graphitized carbon foam supporting carbon material/molybdenum carbide composite material in a sulfur-containing solution, or dropping the sulfur-containing solution into the graphitized carbon foam supporting carbon material/molybdenum carbide composite material.

Preferably, the sulfur source comprises a sulfur-containing solution.

Preferably, the sulfur-containing solution is S/CS₂Solutions or solutions containing polysulfides.

Preferably, the concentration of the sulfur-containing solution is 0.1 to 6mol/L, for example, 0.1mol/L, 0.3mol/L, 0.5mol/L, 0.8mol/L, 1.0mol/L, 1.3mol/L, 1.6mol/L, 1.8mol/L, 2mol/L, 2.2mol/L, 2.4mol/L, 2.6mol/L, 2.8mol/L, 3mol/L, 3.5mol/L, 3.7mol/L, 4mol/L, 4.5mol/L, 4.8mol/L, 5mol/L, 5.2mol/L, 5.5mol/L, 5.8mol/L, or 6mol/L, etc., and the sulfur-containing solution at the concentration has good fluidity and is easily compounded with a carrier, preferably 0.15 to 5.5 mol/L.

Preferably, the addition amount of the sulfur-containing solution is 2-100 mu L/cm²For example, it may be 2. mu.L/cm²、3μL/cm²、4μL/cm²、5μL/cm²、8μL/cm²、10μL/cm²、12μL/cm²、15μL/cm²、18μL/cm²、20μL/cm²、24μL/cm²、28μL/cm²、30μL/cm²、33μL/cm²、36μL/cm²、40μL/cm²、42μL/cm²、48μL/cm²、50μL/cm²、55μL/cm²、60μL/cm²、63μL/cm²、66μL/cm²、69μL/cm²、72μL/cm²、77μL/cm²、80μL/cm²、84μL/cm²、88μL/cm²、90μL/cm²、92μL/cm²、95μL/cm²、98μL/cm²Or 100. mu.L/cm²Etc., the amount of the sulfur-containing solution added is such that the maximum amount of sulfur loaded on the support is satisfied, and is preferably 5 to 90. mu.L/cm²。

In a fourth aspect, the present invention provides a graphitized carbon foam support carbon material/molybdenum carbide/sulfur composite cathode material prepared by the preparation method of the composite cathode material according to the third aspect.

The composite anode material provided by the invention has more high-activity sites on the surface and excellent electrochemical performance, and mainly provides more high-activity sites by introducing the carbon material/molybdenum carbide nano-dot composite material, so that the electrocatalytic activity of the composite anode material is enhanced, and the high-efficiency adsorption of polysulfide is realized by cooperating with the metal property of molybdenum carbide and the conductivity of the carbon material, the electron transfer to the interface between molybdenum carbide and polysulfide ions is accelerated, the impedance of interface reaction is reduced, the conversion speed of polysulfide to lithium sulfide is promoted, the shuttle effect is effectively eliminated, and the reversible capacity and the cycling stability of the composite anode material are improved.

In a fifth aspect, the present invention also provides a lithium sulfur battery comprising the composite positive electrode material according to the fourth aspect.

According to the lithium-sulfur battery provided by the invention, the composite anode material is compacted by the parallel plates to prepare the anode, the graphitized carbon foam supporting carbon material/molybdenum carbide composite material can be compacted by the parallel plates and is immersed in the sulfur-containing solution or the sulfur-containing solution is directly dripped into the composite material to prepare the anode, the graphitized carbon foam is used as the current collector of the anode, the active substance is tightly combined with the current collector, the use of inactive substances such as a conductive agent, a binder and a metal foil is avoided, the volume and the mass occupied by the inactive substances are reduced, and the specific capacity and the energy density of the lithium-sulfur battery are improved; the composite positive electrode material has high adsorption capacity and catalytic conversion capacity on polysulfide, effectively eliminates shuttle effect, improves reversible capacity and cycle stability of the lithium-sulfur battery, and promotes practicability of the lithium-sulfur battery.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) the molybdenum carbide nanodots introduced into the graphitized carbon foam support carbon material/molybdenum carbide composite material provided by the invention grow on the carbon material in situ and are uniformly distributed, so that abundant active sites are provided, the polar modification of the surface of the graphitized carbon foam framework is realized, and the adsorption and efficient catalytic conversion of polysulfide can be effectively realized;

(2) the preparation method of the graphitized carbon foam support carbon material/molybdenum carbide composite material provided by the invention is mild, low in cost and good in dispersibility, more active sites are provided, and thermogravimetric analysis shows that the proportion of molybdenum carbide nanodots in the composite material is 2% -50%;

(3) the graphitized carbon foam support carbon material/molybdenum carbide/sulfur composite cathode material prepared by the invention has excellent electrochemical properties, and benefits from the catalytic activity and the metal characteristic of the molybdenum carbide nanodots and the excellent conductivity of the carbon material, so that the rapid transfer of electrons between the molybdenum carbide nanodots and a polysulfide interface is realized, and the reaction impedance of the interface is reduced;

(4) the high-activity graphitized carbon foam support carbon material/molybdenum carbide composite material prepared by the method has wide application prospect in the aspect of novel high-capacity lithium-sulfur batteries, and can be further applied to the field of other related electronic devices.

Drawings

Fig. 1 is an SEM image of the graphitized carbon foam-supported graphene oxide/molybdenum carbide composite material obtained in example 1 provided by the present invention.

FIG. 2 shows the graphitized carbon foam-supported graphene oxide/molybdenum carbide composite material and Mo obtained in example 1₂XRD pattern of C standard card control.

Detailed Description

The following further describes the technical means of the present invention to achieve the predetermined technical effects by means of embodiments with reference to the accompanying drawings, and the embodiments of the present invention are described in detail as follows.