A sodium-ion battery composite negative electrode material, its preparation method, negative electrode sheet, and secondary battery.

Abstract

This invention provides a MoS2 / MXene@HC@rGO / CNT / C composite anode material, comprising: a composite material of carbon nanotubes, graphene, and hard carbon; a hard carbon layer coating the composite material; and a MoS2 / MXene heterojunction layer coating the hard carbon layer. The MoS2 / MXene@HC@rGO / CNT / C sodium-ion battery anode composite material prepared by this invention combines the advantages of high theoretical specific capacity of molybdenum disulfide and high conductivity of the MoS2 / MXene heterojunction, resulting in a sodium-ion battery with high charge-discharge specific capacity, good rate performance, and long cycle life, offering significant economic and social benefits.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion secondary battery anode material preparation technology, specifically to a MoS2 / MXene@HC@rGO / CNT / C composite anode material, its preparation method, applications, an anode sheet, and a secondary battery. Background Technology

[0002] As demand continues to grow, the applications of lithium-ion batteries are expanding from portable electronic devices to wearable electronic devices, emerging electrical equipment, new energy electric vehicles, and smart grids. However, given the uneven geographical distribution of lithium resources, the low overall abundance of lithium reserves on Earth, and the high cost of applications in certain fields, developing new energy storage systems to replace lithium-ion batteries is of great significance. Since sodium resources are abundant globally, the refining technology is simple and convenient, and the energy storage mechanism is similar, sodium-ion batteries are a promising alternative to lithium-ion batteries.

[0003] Currently, carbon-based materials are attracting attention among available anode materials for sodium-ion batteries due to their advantages such as abundant resources, structural stability, and low preparation cost. Graphite anode materials, which have achieved great success in lithium-ion batteries, possess advantages such as high conductivity and structural stability; however, their application in sodium-ion batteries is limited because sodium ions are difficult to intercalate within them. Hard carbon, due to its large carbon interlayer spacing and unique microstructure, is considered a sodium-ion battery anode material with great development potential. Phenolic resin is one source of hard carbon, possessing advantages such as high carbon yield, stable structure after carbonization, and stable preparation technology. However, hard carbon anodes alone cannot meet the required energy density. Therefore, to obtain higher energy densities, researchers need to construct composite materials to meet high energy density requirements. Two-dimensional transition metal sulfides, with their low cost and high theoretical specific capacity, have become a research hotspot for sodium battery anode materials. However, when used alone as electrode materials, they are prone to stacking, leading to a reduction in the number of surface active sites and limiting the rapid transport of ions. During sodium storage, the electrode material undergoes significant volume changes, affecting the overall structural stability of the material and causing a rapid decline in electrochemical performance.

[0004] Therefore, finding a more suitable way to further improve the performance of sodium-ion battery anode materials and solve the above-mentioned problems of current sodium-ion battery anode materials has become one of the focuses of attention for many leading researchers in the industry. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a MoS2 / MXene@HC@rGO / CNT / C composite anode material, its preparation method, applications, an anode sheet, and a secondary battery. The present invention combines the advantages of high theoretical specific capacity of molybdenum disulfide and high conductivity of the MoS2 / MXene heterojunction, and designs a specific structure and composition for the anode material, thereby obtaining a sodium-ion battery with high charge-discharge specific capacity, good rate performance, and long cycle life, resulting in good economic and social benefits.

[0006] This invention provides a MoS2 / MXene@HC@rGO / CNT / C composite anode material, comprising:

[0007] Composite materials of carbon nanotubes, graphene, and hard carbon;

[0008] A hard carbon layer coating the composite material of carbon nanotubes, graphene, and hard carbon;

[0009] And the MoS2 / MXene heterojunction layer coated on the hard carbon layer.

[0010] Preferably, the composite material of carbon nanotubes, graphene, and hard carbon has a three-dimensional network interconnected structure;

[0011] The hard carbon layer includes a resin-based hard carbon layer.

[0012] Preferably, the structure of the three-dimensional network interconnection is as follows:

[0013] Carbon nanotubes are composited between graphene sheets, and the carbon nanotubes and graphene sheets intertwine to form a three-dimensional structure. Hard carbon is cross-linked in the carbon nanotubes and graphene sheets to form a three-dimensional network of carbon material framework structure.

[0014] Preferably, the thickness of the hard carbon layer is 20–100 nm;

[0015] The particle size of the composite negative electrode material is 10–30 μm;

[0016] In the composite anode material, the composite material of carbon nanotubes, graphene, and hard carbon accounts for 10% to 15% of the mass content of the composite anode material, or the hard carbon layer accounts for 5% to 10% of the mass content of the composite anode material, or the MoS2 / MXene heterojunction layer accounts for 75% to 85% of the mass content of the composite anode material.

[0017] This invention provides a method for preparing a MoS2 / MXene@HC@rGO / CNT / C composite anode material, comprising:

[0018] 1) Mix graphene oxide, carbon nanotubes and water, then add acidic organic polymer and organic base and mix again to obtain a mixed solution. After freeze-drying, a composite is obtained. Finally, the composite is carbonized under a protective atmosphere to obtain a graphene oxide-carbon nanotube-carbon composite material.

[0019] 2) After mixing the graphene oxide-carbon nanotube-carbon composite material obtained in the above steps with sodium dodecyl sulfate, add acid catalyst, phenolic compound and aldehyde compound solution, mix again and react to obtain wet gel. After drying, carbonize under a protective atmosphere to obtain composite material coated with resin-based hard carbon layer.

[0020] 3) The composite material coated with resin-based hard carbon layer obtained in the above steps, molybdenum source, sulfur source, MXene and water are mixed, and then subjected to hydrothermal reaction. After calcination under a protective atmosphere, MoS2 / MXene@HC@rGO / CNT / C composite anode material is obtained.

[0021] Preferably, the graphene oxide is a graphene oxide solution;

[0022] The concentration of the graphene oxide solution is 0.5–2.0 mg / mL;

[0023] The ratio of the carbon nanotubes to the graphene oxide solution is 1 mg: (2-5) mL;

[0024] The acidic organic polymers include polyamic acid and / or polyacrylic acid;

[0025] The organic base includes triethylamine and / or triethanolamine;

[0026] The mass ratio of the carbon nanotubes to the acidic organic polymer is 1:(3-5);

[0027] The ratio of the acidic organic polymer to the organic base is 1 g: (4-6) mL.

[0028] Preferably, the freeze-drying temperature is -50 to -60°C;

[0029] The carbonization temperature in step 1) is 1000–1500°C;

[0030] The carbonization process in step 1) takes 3 to 6 hours.

[0031] The protective atmosphere includes nitrogen and / or an inert gas.

[0032] Preferably, the mass ratio of the graphene oxide-carbon nanotube-carbon composite material to sodium dodecyl sulfate is 1:(3-10);

[0033] The acid catalyst includes acetic acid;

[0034] The phenolic compounds include resorcinol;

[0035] The aldehyde compounds include formaldehyde;

[0036] The molar ratio of the phenolic compound to the aldehyde compound is 1:(2-4).

[0037] Preferably, in step 2), the reaction temperature is 100–120°C;

[0038] In step 2), the reaction time is 8 to 16 hours;

[0039] In step 2), the carbonization temperature is 800–1000°C;

[0040] In step 2), the carbonization process takes 2 to 5 hours.

[0041] Preferably, in step 2), the carbonization process specifically includes a two-stage heat treatment process;

[0042] In the two-stage heat treatment process, the heating rate of the first stage is 1-2℃ / min;

[0043] In the two-stage heat treatment process, the cutoff temperature of the first stage is 450-550℃;

[0044] In the two-stage heat treatment process, the heating rate of the second stage is 3-5℃ / min.

[0045] Preferably, the molybdenum source includes sodium molybdate;

[0046] Preferably, the sulfur source includes thiourea;

[0047] Preferably, the amounts of the molybdenum source and the sulfur source, in terms of the atomic ratio of molybdenum to sulfur, are (1:2) to (1:10);

[0048] The mass ratio of the composite material coated with a resin-based hard carbon layer to the molybdenum source is 1:(2-10);

[0049] The mass ratio of the composite material coated with a resin-based hard carbon layer to MXene is 1:(2-10);

[0050] The general formula for MXene is M n+1 X n T x ;

[0051] Where n is 1 to 3, M is a transition metal, X is C and / or N, and T is T. x It is one or more of O, F and OH;

[0052] The M includes one or more of Ti, V, Nb, Ta, Cr, Zn, Hf, Zr, Cr, Mo, Sc, Y, and Lu.

[0053] Preferably, the temperature of the hydrothermal reaction is 180–220°C;

[0054] The hydrothermal reaction takes 12 to 24 hours;

[0055] The heating rate during calcination is 0.5–5 °C / min;

[0056] The calcination temperature is 400–500°C;

[0057] The calcination time is 2 to 5 hours.

[0058] This invention provides the application of the MoS2 / MXene@HC@rGO / CNT / C composite anode material described in any one of the above technical solutions or the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared by any one of the above technical solutions in sodium-ion batteries.

[0059] The present invention provides a negative electrode sheet, wherein the negative electrode sheet comprises the MoS2 / MXene@HC@rGO / CNT / C composite negative electrode material as described in any one of the above technical solutions or the MoS2 / MXene@HC@rGO / CNT / C composite negative electrode material prepared by the preparation method described in any one of the above technical solutions.

[0060] This invention provides a secondary battery comprising the MoS2 / MXene@HC@rGO / CNT / C composite anode material as described in any one of the above technical solutions, or the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared by the preparation method described in any one of the above technical solutions, or the anode sheet as described in the above technical solutions.

[0061] This invention provides a MoS2 / MXene@HC@rGO / CNT / C composite anode material, comprising: a composite material of carbon nanotubes, graphene, and hard carbon; a hard carbon layer coating the composite material; and a MoS2 / MXene heterojunction layer coating the hard carbon layer. Compared with existing technologies, this invention suggests that although hard carbon anode materials and two-dimensional transition metal sulfides have the aforementioned technical problems, constructing heterostructures using different two-dimensional materials can improve electrochemical performance. Molybdenum disulfide and MXene nanosheets both possess unique sheet-like structures, and this unique two-dimensional heterostructure has an internal heterojunction interface, which is beneficial for sodium ion diffusion. Furthermore, this invention combines a three-dimensional interconnected network structure, the excellent conductivity of the MoS2 / MXene heterojunction, and the high capacity of molybdenum disulfide to construct a three-dimensional composite material, which can effectively improve the overall electrochemical performance of the electrode.

[0062] Based on this, the present invention creatively designs a MoS2 / MXene@HC@rGO / CNT / C sodium-ion battery anode (negative electrode) composite material, combining the advantages of high theoretical specific capacity of molybdenum disulfide and high conductivity of MoS2 / MXene heterojunction, and prepares a sodium-ion battery with high charge-discharge specific capacity, good rate performance and long cycle life, which has good economic and social benefits.

[0063] The MoS2 / MXene@HC@rGO / CNT / C composite anode material provided by this invention possesses a three-dimensional highly conductive structure of carbon nanotubes interconnected with reduced graphene oxide. Simultaneously, the hard carbon coating at the junctions provides excellent fixation and connection, ensuring structural stability. Furthermore, hard carbon is an ideal sodium storage material; its short-range ordered and long-range disordered structure effectively provides sodium storage capacity. To further improve the battery's energy density, composite materials are constructed to meet high energy density requirements. This invention further enhances electrochemical performance by constructing heterostructures using different two-dimensional materials. Molybdenum disulfide and MXene nanosheets possess unique sheet-like structures. This unique two-dimensional heterostructure has built-in heterointerfaces, facilitating sodium ion diffusion, abundant intercalation sites, high charge storage capacity, and a high ion diffusion coefficient.

[0064] The negative electrode material provided by this invention has a stable three-dimensional interconnected network structure. Combined with the excellent conductivity of the MoS2 / MXene heterojunction and the high capacity of molybdenum disulfide, its unique structure has the following advantages: (1) During cycling, the electrolyte can achieve rapid penetration, rapid ion transport and rapid electron channels in the three-dimensional interconnected structure, effectively shortening the ion transport path and improving the overall electrochemical performance of the electrode; (2) During charging and discharging, the stable structure can alleviate volume changes and ensure long cycle life; (3) The active sites of molybdenum disulfide and MXene nanosheets are fully exposed, thereby providing higher energy density.

[0065] This invention also provides a corresponding preparation method, which is simple, mild, and well controllable, and yields a stable anode material with a three-dimensional interconnected structure, which is of great significance for improving the electrochemical performance of sodium-ion battery anode materials.

[0066] Experimental results show that the MoS2 / MXene@HC@rGO / CNT / C composite material prepared in this invention exhibits excellent electrochemical performance as a sodium-ion battery anode material. The sodium-ion battery prepared has high reversible capacity and good cycle performance, making it a very promising sodium-ion battery anode material. Attached Figure Description

[0067] Figure 1 Electron micrographs of the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared in this invention at different magnifications;

[0068] Figure 2 Transmission electron microscopy image of the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared in this invention;

[0069] Figure 3 High-resolution electron microscope image of the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared in this invention. Detailed Implementation

[0070] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the claims of the present invention.

[0071] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0072] The raw materials used in this invention, which involve specific brands, are not particularly limited in terms of their source. They can be products sold by conventional manufacturers of that brand that are well known to those skilled in the art.

[0073] There are no particular restrictions on the purity of any raw materials used in this invention. Preferably, analytical grade or conventional purity in the field of sodium-ion secondary battery anode materials is sufficient.

[0074] This invention provides a MoS2 / MXene@HC@rGO / CNT / C composite anode material, comprising:

[0075] Composite materials of carbon nanotubes, graphene, and hard carbon;

[0076] A hard carbon layer coating the composite material of carbon nanotubes, graphene, and hard carbon;

[0077] And the MoS2 / MXene heterojunction layer coated on the hard carbon layer.

[0078] In this invention, the composite negative electrode material preferably has a core-shell structure.

[0079] In this invention, the composite material of carbon nanotubes, graphene, and graphite is preferably the core of a composite negative electrode material.

[0080] In this invention, the composite material of carbon nanotubes, graphene and hard carbon preferably has a three-dimensional network interconnection structure.

[0081] In this invention, the hard carbon layer preferably comprises a resin-based hard carbon layer.

[0082] In this invention, the structure of the three-dimensional network interconnection is preferably a three-dimensional skeleton network interconnection structure.

[0083] In this invention, the structure of the three-dimensional network interconnection is preferably as follows:

[0084] Carbon nanotubes are composited between graphene sheets, and the carbon nanotubes and graphene sheets intertwine to form a three-dimensional structure. Hard carbon is cross-linked in the carbon nanotubes and graphene sheets to form a three-dimensional network of carbon material framework structure.

[0085] In this invention, the thickness of the hard carbon layer is preferably 20-100 nm, more preferably 30-90 nm, more preferably 40-80 nm, and even more preferably 50-70 nm.

[0086] In this invention, the particle size of the composite negative electrode material is preferably 10-30 μm, more preferably 14-26 μm, and even more preferably 18-22 μm.

[0087] In this invention, the composite material of carbon nanotubes, graphene and graphite accounts for 10% to 15% of the mass of the composite negative electrode material, more preferably 11% to 14%, and even more preferably 12% to 13%.

[0088] In this invention, the hard carbon layer preferably accounts for 5% to 10% of the mass content of the composite negative electrode material, more preferably 6% to 9%, and even more preferably 7% to 8%.

[0089] In this invention, the MoS2 / MXene heterojunction layer preferably accounts for 75% to 85% of the mass content of the composite anode material, more preferably 77% to 83%, and even more preferably 79% to 81%.

[0090] This invention provides a method for preparing a MoS2 / MXene@HC@rGO / CNT / C composite anode material, comprising:

[0091] 1) Mix graphene oxide, carbon nanotubes and water, then add acidic organic polymer and organic base and mix again to obtain a mixed solution. After freeze-drying, a composite is obtained. Finally, the composite is carbonized under a protective atmosphere to obtain a graphene oxide-carbon nanotube-carbon composite material.

[0092] 2) After mixing the graphene oxide-carbon nanotube-carbon composite material obtained in the above steps with sodium dodecyl sulfate, add acid catalyst, phenolic compound and aldehyde compound solution, mix again and react to obtain wet gel. After drying, carbonize under a protective atmosphere to obtain composite material coated with resin-based hard carbon layer.

[0093] 3) The composite material coated with resin-based hard carbon layer obtained in the above steps, molybdenum source, sulfur source, MXene and water are mixed, and then subjected to hydrothermal reaction. After calcination under a protective atmosphere, MoS2 / MXene@HC@rGO / CNT / C composite anode material is obtained.

[0094] This invention first mixes graphene oxide, carbon nanotubes and water, then adds an acidic organic polymer and an organic base and mixes again to obtain a mixed solution. After freeze-drying, a composite is obtained. Finally, the composite is carbonized under a protective atmosphere to obtain a graphene oxide-carbon nanotube-carbon composite material.

[0095] In this invention, the graphene oxide is preferably a graphene oxide solution.

[0096] In this invention, the concentration of the graphene oxide solution is preferably 0.5–2.0 mg / mL, more preferably 0.8–1.7 mg / mL, and even more preferably 1.1–1.4 mg / mL.

[0097] In this invention, the ratio of carbon nanotubes to graphene oxide solution is preferably 1 mg:(2-5) mL, more preferably 1 mg:(2.5-4.5) mL, and even more preferably 1 mg:(3-4) mL.

[0098] In this invention, the acidic organic polymer is preferably a soluble acidic organic polymer, specifically an acidic organic polymer that can complex or react with an organic base to form ester compounds.

[0099] In this invention, the acidic organic polymer preferably includes polyamic acid and / or polyacrylic acid, more preferably polyamic acid or polyacrylic acid.

[0100] In this invention, the organic base preferably includes triethylamine and / or triethanolamine, more preferably triethylamine or triethanolamine.

[0101] In this invention, the mass ratio of the carbon nanotubes to the acidic organic polymer is preferably 1:(3-5), more preferably 1:(3.4-4.6), and even more preferably 1:(3.8-4.2).

[0102] In this invention, the ratio of the acidic organic polymer to the organic base is preferably 1g:(4-6)mL, more preferably 1g:(4.4-5.6)mL, and even more preferably 1g:(4.8-5.2)mL.

[0103] In this invention, prior to the freeze-drying process, it is preferable to further include the step of immersing the mixed solution in liquid nitrogen.

[0104] In this invention, the freeze-drying process is preferably vacuum freeze-drying.

[0105] In this invention, the temperature of the vacuum freeze-drying process is preferably -50 to -60°C, more preferably -52 to -58°C, and even more preferably -54 to -56°C.

[0106] In this invention, the carbonization temperature in step 1) is preferably 1000-1500℃, more preferably 1100-1400℃, and even more preferably 1200-1300℃.

[0107] In this invention, the carbonization treatment time in step 1) is preferably 3 to 6 hours, more preferably 3.5 to 5.5 hours, and even more preferably 4 to 5 hours.

[0108] In this invention, the protective atmosphere preferably includes nitrogen and / or an inert gas, more preferably nitrogen or an inert gas.

[0109] In this invention, the graphene oxide-carbon nanotube-carbon composite material obtained in the above steps is mixed with sodium dodecyl sulfate, and then an acid catalyst, phenolic compound and aldehyde compound solution are added. After mixing again, the mixture is reacted to obtain a wet gel. After drying, it is carbonized under a protective atmosphere to obtain a composite material coated with a resin-based hard carbon layer.

[0110] In this invention, the mass ratio of the graphene oxide-carbon nanotube-carbon composite material to sodium dodecyl sulfate is preferably 1:(3-10), more preferably 1:(4-9), more preferably 1:(5-8), and even more preferably 1:(6-7).

[0111] In this invention, the acid catalyst preferably comprises acetic acid.

[0112] In this invention, the phenolic compound preferably includes resorcinol.

[0113] In this invention, the aldehyde compound preferably includes formaldehyde.

[0114] In this invention, the molar ratio of the phenolic compound to the aldehyde compound is preferably 1:(2-4), more preferably 1:(2.4-3.6), and even more preferably 1:(2.8-3.2).

[0115] In this invention, the reaction temperature in step 2) is preferably 100-120°C, more preferably 104-116°C, and even more preferably 108-112°C.

[0116] In this invention, the reaction time in step 2) is preferably 8 to 16 hours, more preferably 9 to 15 hours, more preferably 10 to 14 hours, and even more preferably 11 to 13 hours.

[0117] In this invention, the step of soaking in alcohol to remove water is preferably included before drying.

[0118] In this invention, the drying method preferably includes supercritical CO2 drying.

[0119] In this invention, the carbonization temperature in step 2) is preferably 800-1000°C, more preferably 840-960°C, and even more preferably 880-920°C.

[0120] In this invention, in step 2), the carbonization treatment time is preferably 2 to 5 hours, more preferably 2.5 to 4.5 hours, and even more preferably 3 to 4 hours.

[0121] In this invention, step 2) of the carbonization process preferably includes a two-stage heat treatment process.

[0122] In this invention, during the two-stage heat treatment process, the heating rate of the first stage is preferably 1-2℃ / min, more preferably 1.2-1.8℃ / min, and even more preferably 1.4-1.6℃ / min.

[0123] In this invention, during the two-stage heat treatment process, the cutoff temperature of the first stage is preferably 450–550°C, more preferably 470–530°C, and even more preferably 490–510°C.

[0124] In this invention, during the two-stage heat treatment process, the heating rate of the second stage is preferably 3-5℃ / min, more preferably 3.4-4.6℃ / min, and even more preferably 3.8-4.2℃ / min.

[0125] Finally, the present invention mixes the composite material coated with resin-based hard carbon layer obtained in the above steps, molybdenum source, sulfur source, MXene and water, then performs a hydrothermal reaction, and then calcines it under a protective atmosphere to obtain MoS2 / MXene@HC@rGO / CNT / C composite anode material.

[0126] In this invention, the molybdenum source preferably includes sodium molybdate.

[0127] In this invention, the sulfur source preferably includes thiourea.

[0128] In this invention, the amounts of the molybdenum source and the sulfur source, in terms of the atomic ratio of molybdenum to sulfur, are preferably (1:2) to (1:10), more preferably (1.2:1.8) to (3:8), and even more preferably (1.4:1.6) to (5:6).

[0129] In this invention, the mass ratio of the composite material coated with the resin-based hard carbon layer to the molybdenum source is preferably 1:(2-10), more preferably 1:(3-9), more preferably 1:(4-8), and even more preferably 1:(5-7).

[0130] In this invention, the mass ratio of the composite material coated with the resin-based hard carbon layer to MXene is preferably 1:(2-10), more preferably 1:(3-9), more preferably 1:(4-8), and even more preferably 1:(5-7).

[0131] In this invention, the general formula of MXene is specifically M n+1 X n T x .

[0132] In this invention, n is preferably 1 to 3, and can be 1, 2 or 3.

[0133] In this invention, M is preferably a transition metal, X is preferably C and / or N, and X is more preferably C or N.

[0134] In this invention, M preferably includes one or more of Ti, V, Nb, Ta, Cr, Zn, Hf, Zr, Cr, Mo, Sc, Y and Lu, and more preferably Ti, V, Nb, Ta, Cr, Zn, Hf, Zr, Cr, Mo, Sc, Y or Lu.

[0135] In this invention, T xPreferably, it is one or more of O, F and OH, more preferably O, F or OH.

[0136] In this invention, the temperature of the hydrothermal reaction is preferably 180-220°C, more preferably 188-212°C, and even more preferably 196-204°C.

[0137] In this invention, the hydrothermal reaction time is preferably 12 to 24 hours, more preferably 14 to 22 hours, and even more preferably 16 to 20 hours.

[0138] In this invention, the heating rate of the calcination is preferably 0.5 to 5 °C / min, more preferably 1 to 4 °C / min, and even more preferably 2 to 3 °C / min.

[0139] In this invention, the calcination temperature is preferably 400-500°C, more preferably 420-480°C, and even more preferably 440-460°C.

[0140] In this invention, the calcination time is preferably 2 to 5 hours, more preferably 2.5 to 4.5 hours, and even more preferably 3 to 4 hours.

[0141] The composite anode material provided by this invention features a three-dimensional interconnected network structure that offers a continuous conductive framework. Simultaneously, its robust mechanical properties alleviate stress caused by volume changes during charging and discharging. The interconnected three-dimensional structure increases the available active sites for MoS2, resulting in superior electrochemical performance. By combining the characteristics of various materials and mitigating their weaknesses, the designed MoS2 / MXene@HC@rGO / CNT / C interconnected three-dimensional composite material not only leverages the high capacity of layered MoS2 materials but also possesses a three-dimensional structural feature, enhancing conductivity, improving cycle stability, and ultimately improving the overall electrochemical performance of the electrode.

[0142] This invention aims to complete and refine the overall technical solution, better ensure the composition and specific structure of the MoS2 / MXene@HC@rGO / CNT / C composite anode material, and improve the electrochemical performance of the composite anode material. Specifically, the aforementioned MoS2 / MXene@HC@rGO / CNT / C composite anode material and its preparation method may include the following:

[0143] A method for preparing a high-performance MoS2 / MXene@HC@rGO / CNT / C sodium-ion battery anode composite material:

[0144] Graphene oxide and carbon nanotubes are immersed in deionized water and the mixture is ultrasonically stirred. Then, polyacrylic acid and triethylamine are dispersed in ultrapure water to form polyacrylic acid chains. The carbon nanotubes and graphene oxide sheets can be tightly linked with the help of the polyacrylic acid molecular chains. The resulting mixed solution is immersed in liquid nitrogen and then freeze-dried using a freeze dryer to obtain a three-dimensional network interconnected structure of graphene sheets supported by carbon nanotubes.

[0145] At this point, the freeze-dried material is placed in a tube furnace and carbonized under an argon atmosphere. The ramp rate is controlled, and the resulting sample is labeled as material number 1.

[0146] Next, material No. 1 and sodium dodecyl sulfate were mixed and slowly stirred. Then, acetic acid, resorcinol, and formaldehyde solution were added to the solution, with the preferred molar ratio of resorcinol to formaldehyde being 1:2. The mixture was stirred. The solution was then placed in a Teflon-lined high-pressure reactor and heated to produce a wet gel. The resulting wet gel was then soaked in ethanol and dried using supercritical CO2. The resulting material was placed in a tube furnace under a nitrogen atmosphere for a two-stage heat treatment carbonization process. After carbonization, this invention yielded a highly graphitized three-dimensional network structure with an inner layer of reduced graphene oxide and carbon nanotubes, and a resin-derived hard carbon coating with a thickness of 20 nm to 100 nm was applied to the outer layer of the three-dimensional network structure, designated as material No. 2.

[0147] Next, add material No. 2, sodium molybdate, thiourea and MXene into deionized water and stir. Then transfer it to a high-pressure reactor with a Teflon liner and heat it to react. After the hydrothermal reaction is completed, wash the black sample repeatedly with deionized water and anhydrous ethanol, and then put it into a vacuum drying oven to dry. The resulting sample is recorded as material No. 3.

[0148] Finally, the sample was placed in a tube furnace under an argon atmosphere, heated and calcined, and the resulting material was denoted as MoS2 / MXene@HC@rGO / CNT / C.

[0149] Furthermore, the specific steps for producing the aforementioned high-performance MoS2 / MXene@HC@rGO / CNT / C composite material can also be as follows:

[0150] (1) Carbon nanotubes were added to a dispersed graphene oxide solution and stirred and sonicated. Then, polyacrylic acid powder was dispersed into the mixture, and triethylamine was added. The mixture was then vertically immersed in liquid nitrogen. After freezing, it was placed in a freeze dryer. The resulting GO / CNT / polyacrylic acid was further carbonized in an inert atmosphere to obtain a highly graphitized three-dimensional interconnected network structure, designated as material 1.

[0151] (2) Sodium dodecyl sulfate was added to the aqueous dispersion of material 1 and stirred. Acetic acid, resorcinol, and formaldehyde solution were then added and stirred continuously. The mixture was then placed into a Teflon-lined high-pressure reactor and heated to 100–120 degrees Celsius for 8–16 hours. A wet gel was obtained after the reaction. The wet gel was soaked in ethanol multiple times, each time for 12–24 hours, and then dried using supercritical CO2 drying. After drying, the material was placed in a tube furnace and calcined under an inert gas atmosphere. After calcination, a highly graphitized three-dimensional network interconnected structure with an inner layer of reduced graphene oxide and carbon nanotubes was obtained, and resin-derived hard carbon was coated on the outer layer of the three-dimensional network interconnected structure. This material was designated as material 2.

[0152] (3) MXene was dispersed in 50 mL of deionized water and sonicated. Then, sodium molybdate, thiourea, and material No. 2 were added and stirred. The mixed solution was then poured into a high-pressure reactor for hydrothermal reaction. The material obtained by hydrothermal reaction was washed with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven. After drying, the material was placed in a tube furnace and calcined under an inert gas atmosphere. The calcined material was named MoS2 / MXene@HC@rGO / CNT / C.

[0153] Specifically, in step (1), the solid-liquid ratio of carbon nanotubes, graphene oxide solution and polyacrylic acid powder is 1:2:4 (mg:ml:mg), and the concentration of graphene oxide solution is 0.5-2.0 mg / ml.

[0154] Specifically, in step (1), the inert gas can be one or more of nitrogen, argon, and helium. The inert gas flow rate can be 40–80 mL / min. The heating rate can be 0.5–5 degrees Celsius per minute. The calcination temperature is 1000–1500 degrees Celsius, and the time is 3–6 hours.

[0155] Specifically, the molar ratio of resorcinol to formaldehyde in step (2) is 1:2.

[0156] Specifically, the inert gas in step (2) can be one or more of nitrogen, argon, and helium. The inert gas flow rate can be 40-80 mL / min. The calcination process is divided into two heating stages: the first stage heats the gas to 450-550 degrees Celsius at a rate of 1-2 degrees Celsius per minute, and the second stage heats the gas to 800-1000 degrees Celsius at a rate of 3-5 degrees Celsius per minute, carbonizing for 2-5 hours.

[0157] Specifically, in step (3), the atomic ratio of molybdenum to sulfur in the precursor material is 1:2 to 1:10.

[0158] Specifically, in step (3), the hydrothermal temperature is 180 to 220 degrees Celsius, and the heat preservation time is 12 to 24 hours.

[0159] Specifically, the inert atmosphere of the tubular furnace in step (3) can be one or more of nitrogen, argon, and helium. The inert gas flow rate can be 40-80 mL / min. The heating rate can be 0.5-5 degrees Celsius per minute to 400-500 degrees Celsius, and the temperature can be maintained for 2-5 hours.

[0160] The present invention also provides the application of the MoS2 / MXene@HC@rGO / CNT / C composite anode material described in any one of the above technical solutions or the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared by the preparation method described in any one of the above technical solutions in sodium-ion batteries.

[0161] The present invention also provides a negative electrode sheet, wherein the negative electrode sheet comprises the MoS2 / MXene@HC@rGO / CNT / C composite negative electrode material as described in any one of the above technical solutions or the MoS2 / MXene@HC@rGO / CNT / C composite negative electrode material prepared by the preparation method described in any one of the above technical solutions.

[0162] The present invention also provides a secondary battery comprising the MoS2 / MXene@HC@rGO / CNT / C composite anode material as described in any one of the above technical solutions, or the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared by the preparation method described in any one of the above technical solutions, or the anode sheet as described in the above technical solutions.

[0163] The present invention provides a high-performance MoS2 / MXene@HC@rGO / CNT / C sodium-ion battery anode composite material, its preparation method, anode sheet, and secondary battery. The present invention specifically designs a MoS2 / MXene@HC@rGO / CNT / C sodium-ion battery anode (anode) composite material with a specific structure and composition, combining the advantages of high theoretical specific capacity of molybdenum disulfide and high conductivity of the MoS2 / MXene heterojunction. This results in a sodium-ion battery with high charge-discharge specific capacity, good rate performance, and long cycle life, offering significant economic and social benefits.

[0164] The MoS2 / MXene@HC@rGO / CNT / C composite anode material provided by this invention possesses a three-dimensional highly conductive structure of carbon nanotubes interconnected with reduced graphene oxide. Simultaneously, the hard carbon coating at the junctions provides excellent fixation and connection, ensuring structural stability. Furthermore, hard carbon is an ideal sodium storage material; its short-range ordered and long-range disordered structure effectively provides sodium storage capacity. To further improve the battery's energy density, composite materials are constructed to meet high energy density requirements. This invention further enhances electrochemical performance by constructing heterostructures using different two-dimensional materials. Molybdenum disulfide and MXene nanosheets possess unique sheet-like structures. This unique two-dimensional heterostructure has built-in heterointerfaces, facilitating sodium ion diffusion, abundant intercalation sites, high charge storage capacity, and a high ion diffusion coefficient.

[0165] The negative electrode material provided by this invention has a stable three-dimensional interconnected network structure. Combined with the excellent conductivity of the MoS2 / MXene heterojunction and the high capacity of molybdenum disulfide, its unique structure has the following advantages: (1) During cycling, the electrolyte can achieve rapid penetration, rapid ion transport and rapid electron channels in the three-dimensional interconnected structure, effectively shortening the ion transport path and improving the overall electrochemical performance of the electrode; (2) During charging and discharging, the stable structure can alleviate volume changes and ensure long cycle life; (3) The active sites of molybdenum disulfide and MXene nanosheets are fully exposed, thereby providing higher energy density.

[0166] This invention also provides a corresponding preparation method, which is simple, mild, and well controllable, and yields a stable anode material with a three-dimensional interconnected structure, which is of great significance for improving the electrochemical performance of sodium-ion battery anode materials.

[0167] Experimental results show that the MoS2 / MXene@HC@rGO / CNT / C composite material prepared in this invention exhibits excellent electrochemical performance as a sodium-ion battery anode material. The sodium-ion battery prepared has high reversible capacity and good cycle performance, making it a very promising sodium-ion battery anode material.

[0168] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, describes a MoS2 / MXene@HC@rGO / CNT / C composite anode material, its preparation method, applications, an anode sheet, and a secondary battery provided by the present invention. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operating procedures, only to further illustrate the features and advantages of the present invention, and not to limit the scope of protection of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0169] Example 1

[0170] (1) 50 mg of carbon nanotubes were added to a dispersed graphene oxide solution (100 ml, 1.0 mg / ml) and stirred and sonicated for 1 hour. Then, 0.2 g of polyacrylic acid powder was dispersed into the mixture, and 1 ml of triethylamine was added. The mixture was then vertically immersed in liquid nitrogen. After freezing, it was placed in a freeze dryer with conditions set to -50 degrees Celsius and a pressure less than 10 Pa. The obtained GO / CNT / polyacrylic acid was further carbonized in an argon atmosphere at a heating rate of 5 degrees Celsius per minute to a temperature of 1400 degrees Celsius for 2 hours to obtain a highly graphitized three-dimensional interconnected network structure, designated as material No. 1.

[0171] (2) 0.2 g of sodium dodecyl sulfate was added to the aqueous dispersion of material 1 (20 ml, 2 mg / ml), and stirred for 1 hour. Then, 0.2 g of acetic acid, 0.22 g of resorcinol, and 0.3 ml of formaldehyde solution were added, and the mixture was stirred for 10 minutes. The mixture was then placed into a 50 mL Teflon-lined high-pressure reactor and heated to 100 degrees Celsius for 12 hours. After the reaction, a wet gel was obtained. The wet gel was soaked in ethanol three times, each time for 24 hours, and then dried using a supercritical CO2 drying method. After drying, the material was placed in a tube furnace under an argon atmosphere. The calcination process was divided into two stages of heating. The first stage heated the material to 500 degrees Celsius at a rate of 2 degrees Celsius per minute, and the second stage heated the material to 800 degrees Celsius at a rate of 5 degrees Celsius per minute. The carbonization lasted for 2 hours. After calcination, we obtained a highly graphitized three-dimensional network interconnected structure with an inner layer of reduced graphene oxide and carbon nanotubes. Resin-derived hard carbon was then coated on the outer layer of the three-dimensional network interconnected structure, which was designated as material No. 2.

[0172] (3) Add 0.1g MXene(Ti3C2T) x The material was dispersed in 50 mL of deionized water and sonicated for 1 hour. Then, 30 mg of sodium molybdate, 38 mg of thiourea, and 0.2 g of material No. 2 were added, and the mixture was stirred for 1 hour. The solution was then poured into a 100 mL high-pressure reactor, heated to 200°C, and held at that temperature for 24 hours. The hydrothermal material was washed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60°C for 24 hours. After drying, the material was placed in a tube furnace and calcined under an argon atmosphere at a heating rate of 5°C per minute to a temperature of 500°C for 2 hours. After calcination, the MoS2 / MXene@HC@rGO / CNT / C composite anode material was obtained.

[0173] The composite anode material prepared in Example 1 of the present invention was characterized.

[0174] See Figure 1 , Figure 1 This is an electron microscope image of the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared in this invention.

[0175] See Figure 2 , Figure 2 Transmission electron microscopy (TEM) image of the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared in this invention.

[0176] Depend on Figure 2 The transmission electron microscopy image shows that the material is uniformly loaded on the surface of the structure.

[0177] See Figure 3 , Figure 3 High-resolution electron microscope image of the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared in this invention.

[0178] Depend on Figure 3 The high-resolution transmission electron microscopy images show the interlayer spacing of MXene and MoS2, respectively. In the left image, 2DMXene has a layered structure with an interlayer spacing of 0.72 nm, while in the right image, MoS2 has a smaller interlayer spacing of 0.63 nm, and the presence of heterojunctions can be clearly observed within the dashed box in the left image.

[0179] Example 2

[0180] (1) 50 mg of carbon nanotubes were added to a dispersed graphene oxide solution (100 ml, 1.0 mg / ml) and stirred and sonicated for 1 hour. Then, 0.2 g of polyacrylic acid powder was dispersed into the mixture, and 1 ml of triethylamine was added. The mixture was then vertically immersed in liquid nitrogen. After freezing, it was placed in a freeze dryer with conditions set to -50 degrees Celsius and a pressure less than 10 Pa. The obtained GO / CNT / polyacrylic acid was further carbonized in an argon atmosphere at a heating rate of 5 degrees Celsius per minute to a temperature of 1500 degrees Celsius for 3 hours to obtain a highly graphitized three-dimensional interconnected network structure, designated as material No. 1.

[0181] (2) 0.2 g of sodium dodecyl sulfate was added to the aqueous dispersion of material 1 (20 ml, 2 mg / ml), and stirred for 1 hour. Then, 0.2 g of acetic acid, 0.22 g of resorcinol, and 0.3 ml of formaldehyde solution were added, and the mixture was stirred for 10 minutes. The mixture was then placed into a 50 mL Teflon-lined high-pressure reactor and heated to 110 degrees Celsius for 24 hours. After the reaction, a wet gel was obtained. The wet gel was soaked in ethanol three times, each time for 24 hours, and then dried using a supercritical CO2 drying method. After drying, the material was placed in a tube furnace under an argon atmosphere. The calcination process was divided into two heating stages. The first stage heated the material to 550 degrees Celsius at a rate of 2 degrees Celsius per minute, and the second stage heated the material to 900 degrees Celsius at a rate of 5 degrees Celsius per minute. The carbonization lasted for 5 hours. After calcination, we obtained a highly graphitized three-dimensional network interconnected structure with an inner layer of reduced graphene oxide and carbon nanotubes. Resin-derived hard carbon was then coated on the outer layer of the three-dimensional network interconnected structure, which was designated as material No. 2.

[0182] (3) Add 0.1g MXene(Ti3C2T) x The material was dispersed in 50 mL of deionized water and sonicated for 1 hour. Then, 30 mg of sodium molybdate, 40 mg of thiourea, and 0.2 g of material No. 2 were added, and the mixture was stirred for 1 hour. The solution was then poured into a 100 mL high-pressure reactor, heated to 220°C, and held at that temperature for 24 hours. The hydrothermal material was washed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60°C for 24 hours. After drying, the material was placed in a tube furnace and calcined under an argon atmosphere at a heating rate of 5°C per minute to a temperature of 450°C for 5 hours. After calcination, the MoS2 / MXene@HC@rGO / CNT / C composite anode material was obtained.

[0183] Example 3

[0184] (1) 25 mg of carbon nanotubes were added to a dispersed graphene oxide solution (50 ml, 1.0 mg / ml) and stirred and sonicated for 1 hour. Then, 0.1 g of polyacrylic acid powder was dispersed into the mixture, and 1 ml of triethylamine was added. The mixture was then vertically immersed in liquid nitrogen. After freezing, it was placed in a freeze dryer with conditions set to -50 degrees Celsius and a pressure less than 10 Pa. The obtained GO / CNT / polyacrylic acid was further carbonized in an argon atmosphere at a heating rate of 5 degrees Celsius per minute to a temperature of 1200 degrees Celsius for 2 hours to obtain a highly graphitized three-dimensional interconnected network structure, designated as material No. 1.

[0185] (2) 0.3 g of sodium dodecyl sulfate was added to the aqueous dispersion of material 1 (20 ml, 2 mg / ml), and stirred for 1 hour. Then, 0.2 g of acetic acid, 0.33 g of resorcinol, and 0.4 ml of formaldehyde solution were added, and stirred for 10 minutes. The mixture was then placed into a 50 mL Teflon-lined high-pressure reactor and heated to 100 degrees Celsius for 18 hours. After the reaction, a wet gel was obtained. The wet gel was soaked in ethanol three times, each time for 24 hours, and then dried using a supercritical CO2 drying method. After drying, the material was placed in a tube furnace under an argon atmosphere. The calcination process was divided into two stages of heating. The first stage heated the material to 500 degrees Celsius at a rate of 2 degrees Celsius per minute, and the second stage heated the material to 800 degrees Celsius at a rate of 5 degrees Celsius per minute. The carbonization lasted for 2 hours. After calcination, we obtained a highly graphitized three-dimensional network interconnected structure with an inner layer of reduced graphene oxide and carbon nanotubes. Resin-derived hard carbon was then coated on the outer layer of the three-dimensional network interconnected structure, which was designated as material No. 2.

[0186] (3) Add 0.15g MXene(Ti3C2T) x The material was dispersed in 75 mL of deionized water and sonicated for 1 hour. Then, 40 mg of sodium molybdate, 40 mg of thiourea, and 0.3 g of material No. 2 were added, and the mixture was stirred for 1 hour. The solution was then poured into a 100 mL high-pressure reactor, heated to 200°C, and held at that temperature for 24 hours. The hydrothermal material was washed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60°C for 24 hours. After drying, the material was placed in a tube furnace and calcined under an argon atmosphere at a heating rate of 5°C per minute to a temperature of 500°C for 3 hours. After calcination, the MoS2 / MXene@HC@rGO / CNT / C composite anode material was obtained.

[0187] Example 4

[0188] (1) 25 mg of carbon nanotubes were added to a dispersed graphene oxide solution (50 ml, 1.0 mg / ml) and stirred and sonicated for 1 hour. Then, 0.1 g of polyacrylic acid powder was dispersed into the mixture, and 1 ml of triethylamine was added. The mixture was then vertically immersed in liquid nitrogen. After freezing, it was placed in a freeze dryer with conditions set to -50 degrees Celsius and a pressure less than 10 Pa. The obtained GO / CNT / polyacrylic acid was further carbonized in an argon atmosphere at a heating rate of 5 degrees Celsius per minute to a temperature of 1200 degrees Celsius for 2 hours to obtain a highly graphitized three-dimensional interconnected network structure, designated as material No. 1.

[0189] (2) 0.3 g of sodium dodecyl sulfate was added to the aqueous dispersion of material 1 (20 ml, 2 mg / ml), and stirred for 1 hour. Then, 0.2 g of acetic acid, 0.33 g of resorcinol, and 0.4 ml of formaldehyde solution were added, and stirred for 10 minutes. The mixture was then placed into a 50 mL Teflon-lined high-pressure reactor and heated to 100 degrees Celsius for 18 hours. After the reaction, a wet gel was obtained. The wet gel was soaked in ethanol three times, each time for 24 hours, and then dried using a supercritical CO2 drying method. After drying, the material was placed in a tube furnace under an argon atmosphere. The calcination process was divided into two heating stages. The first stage heated the material to 500 degrees Celsius at a rate of 2 degrees Celsius per minute, and the second stage heated the material to 800 degrees Celsius at a rate of 5 degrees Celsius per minute. The carbonization lasted for 3 hours. After calcination, we obtained a highly graphitized three-dimensional network interconnected structure with an inner layer of reduced graphene oxide and carbon nanotubes. Resin-derived hard carbon was then coated on the outer layer of the three-dimensional network interconnected structure, which was designated as material No. 2.

[0190] (3) Add 0.15g MXene(Ti3C2T) x The material was dispersed in 75 mL of deionized water and sonicated for 1 hour. Then, 50 mg of sodium molybdate, 50 mg of thiourea, and 0.3 g of material No. 2 were added, and the mixture was stirred for 1 hour. The solution was then poured into a 100 mL high-pressure reactor, heated to 200°C, and held at that temperature for 16 hours. The hydrothermal material was washed three times with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60°C for 24 hours. After drying, the material was placed in a tube furnace and calcined under an argon atmosphere at a heating rate of 5°C per minute to a temperature of 500°C for 3 hours. After calcination, the MoS2 / MXene@HC@rGO / CNT / C composite anode material was obtained.

[0191] Comparative Example 1 (MoS2)

[0192] (1) Place 3.1 mg sodium molybdate and 2.5 mg thiourea in 50 ml of deionized water to prepare a solvothermal reaction solution.

[0193] (2) Place the mixed solution in an oven and set the solvothermal reaction conditions to 160°C for 10 hours.

[0194] (3) After natural cooling, molybdenum disulfide nanosheet sodium-ion battery anode material is obtained by washing, filtering and drying.

[0195] Comparative Example 2 (Glucose-derived carbon)

[0196] (1) Place 10g of glucose granules into a crucible and then place it in a tube furnace.

[0197] (2) The atmosphere of the tube furnace is nitrogen atmosphere. The heating rate is set to 5℃ / min. The temperature is raised to 500℃. The nitrogen flow rate is 60mL / min. The constant temperature calcination time is 2 hours. After natural cooling, glucose-derived sodium carbonate battery anode material is obtained.

[0198] Comparative Example 3 (Resin-derived carbon)

[0199] (1) 2g acetic acid, 3.3g resorcinol, formaldehyde solution (molar ratio of resorcinol to formaldehyde is 1:2) were stirred for 10 minutes and then the mixture was put into a 50mL high-pressure reactor with Teflon lining. The temperature was 100 degrees Celsius and the time was 24 hours. After the reaction, a phenolic resin-based precursor was obtained.

[0200] (2) The phenolic resin-based precursor was dried. After drying, the material was placed in a tube furnace under an argon atmosphere. The calcination process was divided into two stages of heating. The first stage was heated to 500 degrees Celsius at a rate of 2 degrees Celsius per minute, and the second stage was heated to 800 degrees Celsius at a rate of 5 degrees Celsius per minute. The carbonization was carried out for 2 hours. After calcination, the resin-derived sodium carbon-ion battery anode material was obtained.

[0201] Comparative Example 4 (Coconut Shell Derivative Hard Carbon)

[0202] (1) Dry the coconut shell in an oven at 200°C for 24 hours. Take 10g of the dried coconut shell and put it into a crucible. Then place it in a tube furnace.

[0203] (2) The atmosphere of the tube furnace is nitrogen atmosphere. The heating rate is set to 2℃ / min. The temperature is raised to 500℃. The nitrogen flow rate is 60mL / min. The constant temperature calcination time is 2 hours. After natural cooling, the biomass-derived sodium-carbon battery anode material is obtained.

[0204] Electrodes were prepared using the composite materials prepared in Examples 1-4 and Comparative Examples 1-4. A sodium metal sheet was used as the counter electrode. CR2032 button cells were assembled in an argon glove box using a 1.0 mol / L LiPF6 / EC (ethylene carbonate) + DMC (dimethyl carbonate) + FEC (fluoroethylene carbonate) solution (EC, DMC, and FEC volume ratio 4.5:4.5:1). The gas density coefficient (GCD) was tested using a Land battery testing system within a voltage window of 0.01-2V. The test conditions and results are as follows:

[0205] Button batteries were subjected to constant current charge-discharge tests at a current density of 50 mA / g, with a voltage range of 0–2 V. The high-performance MoS2 / MXene@HC@rGO / CNT / C sodium-ion battery anode composite materials prepared in Examples 1–4 all exhibited high initial discharge capacity (over 450 mAh / g) and initial storage efficiency exceeding 84%. In contrast, Comparative Example 1 had a higher initial discharge capacity (582.9 mAh / g) but an initial coulombic efficiency of only 82.4%, while the capacities of glucose-derived carbon, phenolic resin-derived carbon, and coconut shell-derived carbon materials were all below 300 mAh / g. Due to the high specific capacity of MoS2, the sodium storage capacity of the three-dimensional network interconnected structure of the MoS2 / MXene@HC@rGO / CNT / C composite material formed by the sheet-like MoS2 and the carbon substrate is more than 1.5 times that of porous carbon materials. Specific values ​​are shown in Table 1, which presents the initial discharge capacity and initial coulombic efficiency of the button half-cells of the electrode materials obtained in Examples 1–4 and Comparative Examples 1–4 of this invention.

[0206] Table 1

[0207]

[0208] Button batteries were subjected to constant current charge-discharge tests at a current density of 500 mA / g, with a voltage range of 0–2 V. After 200 cycles, the coin half-cells of the MoS2 / MXene@HC@rGO / CNT / C sodium-ion battery anode composite materials prepared in Examples 1–4 all exhibited high cycle retention rates (greater than 90%) and excellent cycle stability. In contrast, the capacity retention rate of Comparative Example 1 was only 50.4%. Specific values ​​are shown in Table 2, which presents the capacity retention rates of the coin half-cells of the electrode materials obtained in Examples 1–4 and Comparative Examples 1–4 after 200 cycles.

[0209] Table 2

[0210]

[0211]

[0212] The experiments above demonstrate that the three-dimensional interconnected network structure in the composite anode material provided by this invention offers a continuous conductive framework. Simultaneously, its robust mechanical properties alleviate stress caused by volume changes during charging and discharging. The interconnected three-dimensional structure increases the available active sites of MoS2, resulting in superior electrochemical performance. By combining the characteristics of various materials and mitigating their weaknesses, the designed MoS2 / MXene@HC@rGO / CNT / C interconnected three-dimensional composite material not only leverages the high capacity of layered MoS2 materials but also possesses a three-dimensional structural feature, enhancing conductivity, improving cycle stability, and ultimately improving the overall electrochemical performance of the electrode.

[0213] The present invention provides a detailed description of a sodium-ion battery composite negative electrode material, its preparation method, the negative electrode sheet, and the secondary battery. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the wording of the claims, or if they include equivalent structural elements that are not substantially different from the wording of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A MoS2 / MXene@HC@rGO / CNT / C composite anode material for use in sodium-ion batteries, characterized in that, include: Composite materials of carbon nanotubes, graphene oxide, and hard carbon; A hard carbon layer coating the composite material of carbon nanotubes, graphene oxide, and hard carbon; And the MoS2 / MXene heterojunction layer coated on the hard carbon layer; The general formula for MXene is M n+1 X n T x Where n is 1~3, M is a transition metal, X is C and / or N, and T is T. x The carbon is one or more of O, F, and OH; M includes one or more of Ti, V, Nb, Ta, Cr, Zn, Hf, Zr, Mo, Sc, Y, and Lu; the hard carbon layer HC includes a resin-based hard carbon layer; and CNT is a carbon nanotube.

2. The composite negative electrode material according to claim 1, characterized in that, The composite material of carbon nanotubes, graphene oxide, and hard carbon has a three-dimensional network interconnected structure.

3. The composite negative electrode material according to claim 2, characterized in that, The specific structure of the three-dimensional network interconnection is as follows: Carbon nanotubes are composited between graphene oxide sheets, and the carbon nanotubes and graphene oxide sheets intertwine to form a three-dimensional structure. Hard carbon is cross-linked in the carbon nanotubes and graphene oxide sheets to form a three-dimensional network of carbon material framework structure.

4. The composite negative electrode material according to claim 1, characterized in that, The thickness of the hard carbon layer is 20~100nm; The particle size of the composite negative electrode material is 10~30 μm; In the composite anode material, the composite material of carbon nanotubes, graphene oxide and hard carbon accounts for 10% to 15% of the mass content of the composite anode material, or the hard carbon layer accounts for 5% to 10% of the mass content of the composite anode material, or the MoS2 / MXene heterojunction layer accounts for 75% to 85% of the mass content of the composite anode material.

5. A method for preparing a MoS2 / MXene@HC@rGO / CNT / C composite anode material for use in sodium-ion batteries, characterized in that, include: 1) Mix graphene oxide, carbon nanotubes and water, add acidic organic polymer and organic base and mix again to obtain a mixed solution, then freeze dry to obtain a composite, and finally carbonize the composite under a protective atmosphere to obtain a graphene oxide-carbon nanotube-carbon composite material. 2) After mixing the graphene oxide-carbon nanotube-carbon composite material obtained in the above steps with sodium dodecyl sulfate, an acid catalyst, phenolic compound and aldehyde compound solution are added, and the mixture is mixed again and reacted to obtain a wet gel. After drying, it is carbonized under a protective atmosphere to obtain a composite material coated with a resin-based hard carbon layer. 3) The composite material coated with resin-based hard carbon layer obtained in the above steps, molybdenum source, sulfur source, MXene and water are mixed, and then subjected to hydrothermal reaction. After calcination under a protective atmosphere, MoS2 / MXene@HC@rGO / CNT / C composite anode material is obtained. The general formula for MXene is M n+1 X n T x Where n is 1~3, M is a transition metal, X is C and / or N, and T is T. x The carbon is one or more of O, F, and OH; M includes one or more of Ti, V, Nb, Ta, Cr, Zn, Hf, Zr, Mo, Sc, Y, and Lu; the hard carbon layer HC includes a resin-based hard carbon layer; and CNT is a carbon nanotube.

6. The preparation method according to claim 5, characterized in that, The graphene oxide is a graphene oxide solution; The concentration of the graphene oxide solution is 0.5~2.0 mg / mL; The ratio of the carbon nanotubes to the graphene oxide solution is 1 mg: (2~5) mL; The acidic organic polymers include polyamic acid and / or polyacrylic acid; The organic base includes triethylamine and / or triethanolamine; The mass ratio of the carbon nanotubes to the acidic organic polymer is 1:(3~5). The ratio of the acidic organic polymer to the organic base is 1 g: (4~6) mL.

7. The preparation method according to claim 5, characterized in that, In step 1), the freeze-drying temperature is -50~-60℃; The carbonization treatment temperature is 1000~1500℃; The carbonization process takes 3 to 6 hours.

8. The preparation method according to claim 5, characterized in that, The mass ratio of the graphene oxide-carbon nanotube-carbon composite material to sodium dodecyl sulfate is 1:(3~10). The acid catalyst includes acetic acid; The phenolic compounds include resorcinol; The aldehyde compounds include formaldehyde; The molar ratio of the phenolic compound to the aldehyde compound is 1:(2~4).

9. The preparation method according to claim 5, characterized in that, In step 2), the reaction temperature is 100~120℃; The reaction time is 8-16 hours; The carbonization treatment temperature is 800~1000℃; The carbonization process takes 2 to 5 hours.

10. The preparation method according to claim 5, characterized in that, In step 2), the carbonization process specifically includes a two-stage heat treatment process; In the two-stage heat treatment process, the heating rate of the first stage is 1~2℃ / min; In the two-stage heat treatment process, the cutoff temperature of the first stage is 450~550℃; In the two-stage heat treatment process, the heating rate of the second stage is 3~5℃ / min.

11. The preparation method according to claim 5, characterized in that, The molybdenum source includes sodium molybdate; The sulfur source includes thiourea; The amounts of the molybdenum source and the sulfur source, in terms of the atomic ratio of molybdenum to sulfur, are (1:2) to (1:10). The mass ratio of the composite material coated with the resin-based hard carbon layer to the molybdenum source is 1:(2~10). The mass ratio of the composite material coated with the resin-based hard carbon layer to MXene is 1:(2~10).

12. The preparation method according to claim 5, characterized in that, The temperature of the hydrothermal reaction is 180~220℃; The hydrothermal reaction takes 12 to 24 hours; The heating rate during calcination is 0.5~5℃ / min; The calcination temperature is 400~500℃; The calcination time is 2 to 5 hours.

13. The application of the MoS2 / MXene@HC@rGO / CNT / C composite anode material according to any one of claims 1 to 4 or the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared by the preparation method according to any one of claims 5 to 12 in sodium-ion batteries.

14. A negative electrode sheet, characterized in that, The negative electrode sheet comprises the MoS2 / MXene@HC@rGO / CNT / C composite negative electrode material according to any one of claims 1 to 4 or the MoS2 / MXene@HC@rGO / CNT / C composite negative electrode material prepared by the preparation method according to any one of claims 5 to 12.

15. A secondary battery, characterized in that, The secondary battery comprises the MoS2 / MXene@HC@rGO / CNT / C composite anode material according to any one of claims 1 to 4, or the MoS2 / MXene@HC@rGO / CNT / C composite anode material prepared by the preparation method according to any one of claims 5 to 12, or the anode sheet according to claim 14.

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