Mxene material, preparation method thereof and application thereof in negative electrode material of lithium ion battery

Abstract

The present application relates to the technical field of lithium ion battery negative electrode material preparation, and particularly relates to a Mxene material, a preparation method thereof and application of the Mxene material in a lithium ion battery negative electrode material, wherein the present application takes nano titanium powder, nano carbon powder and nano aluminum powder as precursors, reacts in a molten salt bath to generate a MAX phase material, and etches aluminum components in the MAX phase material in the molten salt bath by using CuCl2 to obtain a Mxene two-dimensional material; and the present application prepares a nano-scale layered Mxene material with an accordion-like and porous structure morphology.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery anode material preparation technology, specifically to an Mxene material, its preparation method, and its application in lithium-ion battery anode materials. Background Technology

[0002] Commercial lithium-ion battery anode materials generally use graphite, which remains the dominant material in the anode material field. There are many types of graphite materials, including natural flake graphite, artificial graphite, and fibrous carbon materials (with a graphite structure). However, commercial graphite materials are made primarily from non-renewable natural flake graphite, thus inevitably facing the problem of graphite resource depletion. Other novel lithium-ion battery anode materials, such as silicon-based materials, are mostly prepared using demanding and complex nanotechnology, resulting in low production volumes; no company has yet achieved an annual production scale of hundreds of tons. The preparation process of commercial artificial graphite anode materials is complex and requires stringent technology. Faced with the rapid upgrading of consumer electronics devices and the demand for extended driving range in electric vehicles, there is an urgent need to significantly increase battery energy density, thus necessitating the development of new high-performance batteries. Developing lithium-ion batteries with high energy density, high power density, and long lifespan is of significant application importance for the development of portable electronic devices and electric vehicles.

[0003] In the exploration of lithium-ion battery anode materials, since the successful exfoliation of graphene nanosheets from graphite in 2004, various two-dimensional materials have attracted extensive research, such as layered hydrogen hydroxides (LDHs), black phosphorus (BP), and transition metal dichalcogenides (TMDs). Due to their structural and chemical diversity, two-dimensional materials have exhibited excellent performance in multiple fields, especially in electrochemical energy storage. MXene, a novel type of two-dimensional material, possesses flexible and tunable elemental composition, hydrophilicity, metallic conductivity, unique in-plane anisotropy, high carrier mobility, and good optical and mechanical properties. Since the first report of the synthesis of Ti3C2Tx in 2011, it has become the most studied type of MXene due to its abundant raw materials, simple structure, and relative ease of preparation compared to other types. Furthermore, Ti3C2Tx exhibits excellent electronic conductivity, low open-circuit voltage and lithium-ion transport barrier, and good mechanical properties, making it highly suitable as an electrochemical active material for high-rate lithium-ion battery anodes and a support matrix for other electrochemical active materials.

[0004] The layered structure of Ti3C2Tx materials prepared in the prior art is basically at the micrometer level, and it is difficult to achieve the nanometer level. The advantage of nanoscale Ti3C2Tx materials is that their layers are relatively thinner, their specific surface area is larger, and their contact with the electrolyte is more sufficient, which is conducive to lithium ion shuttle. The reason why the prior art cannot produce nanoscale Ti3C2Tx materials is: (1) The unique micro-ceramic structure of MXene; the parent body of MXene is the MAX phase, which is a kind of extremely tough layered conductive ceramic. After the A layer is etched away, MXene exhibits a three-dimensional accordion-like morphology with strictly stacked two-dimensional layers. (2) Mxene obtained by general hydrofluoric acid etching is at the micrometer level. (3) Common methods cannot directly etch and peel it into high-quality nanoscale MXene. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides an Mxene material, its preparation method, and its application in lithium-ion battery anode materials. This invention uses nano-titanium powder, nano-carbon powder, and nano-aluminum powder as precursors, reacting them in a molten salt bath to generate a MAX phase material. The aluminum components in the MAX phase material are then etched with CuCl2 in the molten salt bath to obtain a two-dimensional Mxene material. This invention prepares a nanoscale, accordion-shaped, porous layered Mxene material.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing MXene material includes the following steps:

[0008] (1) Preparation of MAX phase material: Nano titanium powder, nano aluminum powder, nano carbon powder, sodium chloride and potassium chloride are mixed to obtain precursor material. The precursor material is pressed into tablets, then placed in a crucible and covered with molten salt. Then it is kept at 1000-1500℃ for 1-3h to obtain MAX phase material.

[0009] (2) Preparation of Mxene material: The MAX phase material from step (1) was cooled to 650-800℃, then CuCl2 etchant was added to it, and the mixture was kept at 700℃ for 5 min-2 h before being cooled to room temperature to obtain Ti3C2T x Materials, including Ti3C2T x After the material is treated to remove inorganic salts and copper, Ti3C2T is obtained. x Two-dimensional materials.

[0010] Preferably, the particle size of the nano-titanium powder, nano-aluminum powder, and nano-carbon powder in step (1) is ≤100nm.

[0011] Preferably, the nano-carbon powder in step (1) is selected from one of graphite powder, graphene, high thermal conductivity graphite, and high density graphite.

[0012] Preferably, the molar ratio of nano-titanium powder, nano-aluminum powder, nano-carbon powder, sodium chloride and potassium chloride in step (1) is (3-4.5):(1.2-1.8):(1.5-2.85):1-4:1-4.

[0013] Preferably, the method for removing inorganic salts in step (2) is as follows: washing Ti3C2T with deionized water. x The material undergoes removal of inorganic salts; the method for removing copper is as follows: after the inorganic salts are removed, Ti3C2T is cleaned with (NH4)2S2O8 solution. x The material is used to remove copper elements.

[0014] Preferably, the mass ratio of CuCl2 etchant to nano-aluminum powder in the MAX phase material in step (2) is 104:3-7.

[0015] This invention also protects the MXene material prepared by the above preparation method.

[0016] This invention also protects the application of the above-mentioned MXene material in the preparation of lithium-ion battery anode sheets.

[0017] This invention also protects a lithium-ion battery negative electrode sheet prepared from MXene material, wherein the lithium-ion battery negative electrode sheet is prepared according to the following steps:

[0018] MXene material, conductive agent and binder are mixed and then mixed with solvent to obtain slurry. Copper foil is used as a base and the slurry is uniformly coated on the surface. After drying, lithium-ion battery negative electrode sheet is obtained.

[0019] The mass ratio of MXene material, conductive agent and binder is 7-8:1-2:1;

[0020] The conductive agent is selected from conductive carbon black, carbon nanotubes, or graphene; the binder is selected from polyvinylidene fluoride or carboxymethyl cellulose; and the solvent is selected from N-methylpyrrolidone or deionized water.

[0021] This invention also protects the application of lithium-ion battery negative electrode sheets in the preparation of lithium-ion batteries, wherein the lithium-ion batteries are prepared according to the following steps:

[0022] Positive electrode preparation: pressing and cutting metallic lithium into sheets;

[0023] Preparation of electrolyte: LiPF6 was dissolved in an organic solvent to prepare a LiPF6 electrolyte with a concentration of 1 mol / L;

[0024] The organic solvent is composed of ethylene carbonate, dimethyl carbonate and vinylene carbonate in a volume ratio of 47.5:47.5:5.

[0025] Preparation of lithium-ion batteries: The positive electrode, Cellgard2400 separator, electrolyte and lithium-ion battery negative electrode are assembled sequentially to obtain a lithium-ion battery.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. This invention uses nano-titanium powder, nano-aluminum powder, and nano-carbon powder as precursors to prepare titanium aluminum carbide material, reacts in a molten salt bath to generate MAX phase material, and then uses CuCl2 to etch the aluminum components in the MAX phase material in the molten salt bath to obtain Mxene two-dimensional material.

[0028] 2. This invention is the first to propose a nanoscale layered Mxene material exhibiting an accordion-like, porous structure. Mxene two-dimensional materials, as lithium-ion anode materials, possess excellent conductivity, facilitating rapid lithium-ion transport. They also feature a porous and accordion-like structure, making them suitable for preparing high-performance lithium-ion batteries. Existing micron-level Mxene two-dimensional materials can achieve a specific capacity of up to 150-280 mAh / g, while the nanoscale Mxene material of this application can reach a specific capacity of 347 mAh / g. Therefore, the nanoscale Mxene two-dimensional material of this application can be used to prepare lithium-ion battery anode materials, whereas existing micron-level Mxene two-dimensional materials can only be used in supercapacitors.

[0029] 3. The preparation method provided in this application has no stringent technical requirements, is suitable for mass production, and generates no toxic gases during the preparation process, meeting the requirements of green, environmentally friendly, and sustainable development. It meets the inherent requirements for a lithium-ion battery anode material and is expected to become a new generation of novel graphite anode material for lithium-ion batteries. Furthermore, compared to the preparation of traditional graphite materials, the method of this invention does not require a graphitization process, thus saving costs.

[0030] 4. The high lithium storage capacity of the Mxene two-dimensional material in this application is attributed to the accordion-like structure and porous structure of the material, which is different from the typical graphite sheet structure. Therefore, this application proposes a new synergistic structure lithium storage mechanism, namely (1) lithium ions are stored between Mxene layers. Mxene sheets contain titanium atoms and carbon atoms, and their spatial field is richer than that between graphite sheets; (2) during the etching process, defects such as microporous structures and sheet bending will appear in Mxene sheets, which can all store lithium ions. Attached Figure Description

[0031] Figure 1This is a schematic diagram of a scanning electron microscope of Mxene material according to Embodiment 1 of the present invention;

[0032] Figure 2 The graph shows the electrochemical performance of a lithium-ion battery prepared using Mxene material from Example 1 as the negative electrode material.

[0033] Figure 3 This is a schematic diagram of a scanning electron microscope of the Mxene material used in Comparative Example 1 of this invention. Detailed Implementation

[0034] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0035] Example 1

[0036] A method for preparing Mxene material includes the following steps:

[0037] (1) Preparation of MAX phase material: The raw materials were weighed according to the molar ratio Ti:Al:C:NaCl:KCl = 3:1.2:1.9:3:3, including 1.45g of nano Ti powder, 0.33g of nano aluminum powder, 0.23g of nano graphite powder, 1.77g of sodium chloride and 2.25g of potassium chloride. The powder was ground in a mortar for 20min to make it evenly mixed to obtain the precursor material. The precursor material was pressed into a cylinder with a diameter of 20mm and a thickness of 9mm by applying an axial force of 2KN using a benchtop powder press. Then it was placed in a corundum crucible and covered with a mixed salt of NaCl and KCl (8g of NaCl and 10g of KCl). The crucible was then placed in a muffle furnace and heated to 1300℃ and kept at that temperature for 1h to obtain the MAX phase material.

[0038] (2) Preparation of Mxene material: The temperature of the MAX phase material in step (1) was cooled to 700℃, and then 9g of CuCl2 etchant was added to it. After maintaining the temperature at 700℃ for 20min, the furnace was allowed to cool to room temperature to obtain Ti3C2T. x Materials; the obtained Ti3C2T x The material was washed with deionized water to remove inorganic salts, then washed with 0.3 mol of (NH4)2S2O8 to remove copper, and finally dried under vacuum at 80 °C for 12 h to obtain Ti3C2T. x Two-dimensional materials.

[0039] Example 2

[0040] A method for preparing Mxene material includes the following steps:

[0041] (1) Preparation of MAX phase material: The raw materials were weighed according to the molar ratio Ti:Al:C:NaCl:KCl = 3:1.2:1.5:3:3, including 1.45g of nano Ti powder, 0.33g of nano aluminum powder, 0.181g of nano graphite powder, 1.77g of sodium chloride and 2.25g of potassium chloride. The powder was ground in a mortar for 20min to make it uniformly mixed and obtain the precursor material. The precursor material was pressed into a cylinder with a diameter of 20mm by applying an axial force of 2KN using a benchtop powder press. Then it was placed in a corundum crucible and covered with a mixed salt of NaCl and KCl (8g of NaCl and 10g of KCl). The crucible was then placed in a muffle furnace and heated to 1300℃ and kept at that temperature for 2h to obtain the MAX phase material.

[0042] (2) Preparation of Mxene material: The temperature of the MAX phase material in step (1) was cooled to 700℃, and then 9g of CuCl2 etchant was added to it. After maintaining the temperature at 700℃ for 30min, the furnace was allowed to cool to room temperature to obtain Ti3C2T. x Materials; the obtained Ti3C2T x The material was washed with deionized water to remove inorganic salts, then washed with 0.25 mol of (NH4)2S2O8 to remove copper, and finally dried under vacuum at 80 °C for 12 h to obtain Ti3C2T. x Two-dimensional materials.

[0043] Example 3

[0044] A method for preparing Mxene material includes the following steps:

[0045] (1) Preparation of MAX phase material: The raw materials were weighed according to the molar ratio Ti:Al:C:NaCl:KCl = 4.5:1.8:2.85:3:3, including 2.22g of nano Ti powder, 0.45g of nano aluminum powder, 0.345g of nano graphite powder, 1.77g of sodium chloride and 2.25g of potassium chloride. The powder was ground in a mortar for 20min to make it evenly mixed to obtain the precursor material. The precursor material was pressed into a cylinder with a diameter of 20mm by applying an axial force of 2KN using a benchtop powder press. Then it was placed in a corundum crucible and covered with a mixed salt of NaCl and KCl (14g of NaCl and 15g of KCl). The crucible was then placed in a muffle furnace and heated to 1300℃ and kept at that temperature for 3h to obtain the MAX phase material.

[0046] (2) Preparation of Mxene material: The temperature of the MAX phase material in step (1) was cooled to 700℃, and then 15g of CuCl2 etchant was added to it. After maintaining the temperature at 700℃ for 40min, the furnace was allowed to cool to room temperature to obtain Ti3C2T. x Materials; the obtained Ti3C2T x The material was washed with deionized water to remove inorganic salts, then washed with 0.4 mol of (NH4)2S2O8 to remove copper, and finally dried under vacuum at 80 °C for 12 h to obtain Ti3C2T. x Two-dimensional materials.

[0047] Example 4

[0048] A method for preparing Mxene material includes the following steps:

[0049] (1) Preparation of MAX phase material: The raw materials were weighed according to the molar ratio Ti:Al:C:NaCl:KCl=4:1.5:2:1:1, including 1.97g of nano Ti powder, 0.375g of nano aluminum powder, 0.24g of nano graphite powder, 0.59g of sodium chloride and 0.75g of potassium chloride. The powder was ground in a mortar for 20min to make it uniformly mixed to obtain the precursor material. The precursor material was pressed into a cylinder with a diameter of 20mm by applying an axial force of 2KN using a benchtop powder press. Then it was placed in a corundum crucible and covered with a mixed salt of NaCl and KCl (14g of NaCl and 15g of KCl). The crucible was then placed in a muffle furnace and heated to 1000℃ and kept at that temperature for 3h to obtain the MAX phase material.

[0050] (2) Preparation of Mxene material: The temperature of the MAX phase material in step (1) was cooled to 650℃, and then 13g of CuCl2 etchant was added to it. After maintaining it at 700℃ for 5min, the furnace was allowed to cool to room temperature to obtain Ti3C2T x Materials; the obtained Ti3C2T x The material was washed with deionized water to remove inorganic salts, then washed with 0.4 mol of (NH4)2S2O8 to remove copper, and finally dried under vacuum at 80 °C for 12 h to obtain Ti3C2T. x Two-dimensional materials.

[0051] Example 5

[0052] A method for preparing Mxene material includes the following steps:

[0053] (1) Preparation of MAX phase material: The raw materials were weighed according to the molar ratio Ti:Al:C:NaCl:KCl = 3.5:1.6:2.5:4:4, including 1.73g of nano Ti powder, 0.4g of nano aluminum powder, 0.3g of nano graphite powder, 2.36g of sodium chloride and 3g of potassium chloride. The powder was ground in a mortar for 20min to make it uniformly mixed to obtain the precursor material. The precursor material was pressed into a cylinder with a diameter of 20mm by applying an axial force of 2KN using a benchtop powder press. Then it was placed in a corundum crucible and covered with a mixed salt of NaCl and KCl (14g of NaCl and 15g of KCl). The crucible was then placed in a muffle furnace and heated to 1500℃ and kept at that temperature for 1h to obtain the MAX phase material.

[0054] (2) Preparation of Mxene material: The temperature of the MAX phase material in step (1) was cooled to 800℃, and then 6g of CuCl2 etchant was added to it. After maintaining it at 700℃ for 2h, the furnace was allowed to cool to room temperature to obtain Ti3C2T. x Materials; the obtained Ti3C2T x The material was washed with deionized water to remove inorganic salts, then washed with 0.4 mol of (NH4)2S2O8 to remove copper, and finally dried under vacuum at 80 °C for 12 h to obtain Ti3C2T. x Two-dimensional materials.

[0055] Comparative Example 1

[0056] This comparative example provides a conventional method for preparing existing Mxene materials, namely, synthesizing Ti3AlC2 by selectively etching the MAX phase of Ti3AlC2 in a mixed solution of HCl and LiF. The specific steps are as follows:

[0057] 2g of LiF was added to a polytetrafluoroethylene test tube containing 20mL of 9mol / L HCl solution and sonicated for 30min. Then, the polytetrafluoroethylene test tube was placed in a 35℃ water bath, and 2g of Ti3AlC2 MAX phase material was slowly added to the test tube. The temperature was maintained at 35℃ and the reaction was stirred for 24h at a stirring rate of 350rpm. After the reaction was completed, the solution was centrifuged and washed multiple times at a speed of 3500rpm until the pH reached 7.

[0058] Next, the solution was shaken for 30 minutes and then centrifuged at 3500 rpm for 30 minutes. The dark green supernatant was collected, frozen with liquid nitrogen, and then placed in a freeze dryer. After freeze-drying, monolayer MXene nanosheets were obtained.

[0059] Examples 1-5 of this invention all yielded Ti3C2T with good electrical conductivity. xTwo-dimensional materials with parallel effects are used as an example. The Mxene material prepared in Example 1 is compared with that in Comparative Example 1. The specific research methods and results are as follows:

[0060] The Ti3C2T prepared in Example 1 x Material morphology such as Figure 1 As shown, the layered structure of this material is at the nanoscale, with the microscopic carbon layers exhibiting an accordion-like, porous morphology. This differs from the layered stacking pattern of typical graphite, the quasi-two-dimensional atomic crystal structure of graphene, the structure of micron-scale carbon fibers, and the existing micron-scale Ti3C2Tx material structure. Furthermore, the existing micron-scale Ti3C2Tx material structure is approximately 100 times larger in scale than that presented in this application. The Ti3C2Tx material prepared in this application... x Material microstructure is a novel type of structure.

[0061] Electrochemical performance analysis

[0062] (1) Battery assembly:

[0063] Negative electrode material / electrolyte / lithium metal positive electrode, battery assembly is carried out in a glove box and under argon protection;

[0064] (2) Battery performance testing: The electrochemical performance was examined by cycling at a current density of 100 mA / g, and the results are as follows: Figure 2 As shown, the initial intercalation specific capacity reaches 287 mAh / g when cycled at a current density of 0.1 A / g; after 150 cycles, the reversible specific capacity remains at 347 mAh / g, and the coulombic efficiency is very stable during cycling, demonstrating excellent electrochemical performance.

[0065] This material has a fundamentally different structure from Mxene prepared by the traditional method (Comparative Example 1); the Mxene material prepared by the traditional method does not have a porous structure, such as... Figure 3 As shown, it only presents an accordion shape.

[0066] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing nanoscale MXene materials, characterized in that, Includes the following steps: (1) Preparation of MAX phase material: Nano titanium powder, nano aluminum powder, nano carbon powder, sodium chloride and potassium chloride are mixed to obtain precursor material. The precursor material is pressed into tablets, then placed in a crucible and covered with molten salt. Then it is kept at 1000-1500℃ for 1-3h to obtain MAX phase material. (2) Preparation of nanoscale MXene material: The MAX phase material from step (1) was cooled to 650-800℃, and then CuCl2 etchant was added to it. After being kept at 700℃ for 5 min-2 h, it was cooled to room temperature to obtain Ti3C2T x Materials, including Ti3C2T x After the material is treated to remove inorganic salts and copper, Ti3C2T is obtained. x Two-dimensional materials; In step (1), the particle size of nano-titanium powder, nano-aluminum powder, and nano-carbon powder is ≤100nm.

2. The method for preparing nanoscale MXene materials according to claim 1, characterized in that, The nano-carbon powder in step (1) is selected from one of graphite powder, graphene, high thermal conductivity graphite, and high density graphite.

3. The method for preparing nanoscale MXene materials according to claim 1, characterized in that, In step (1), the molar ratio of nano-titanium powder, nano-aluminum powder, nano-carbon powder, sodium chloride and potassium chloride is (3-4.5):(1.2-1.8):(1.5-2.85):1-4:1-4.

4. The method for preparing nanoscale MXene material according to claim 1, characterized in that, The method for removing inorganic salts in step (2) is as follows: Ti3C2T is cleaned with deionized water. x The material undergoes removal of inorganic salts; the method for removing copper is as follows: after the inorganic salts are removed, Ti3C2T is cleaned with (NH4)2S2O8 solution. x The material is used to remove copper elements.

5. The method for preparing nanoscale MXene material according to claim 1, characterized in that, The mass ratio of CuCl2 etchant to nano-aluminum powder in the MAX phase material in step (2) is 104:3-7.

6. A nanoscale MXene material prepared by the preparation method according to any one of claims 1-5.

7. The application of the nanoscale MXene material as described in claim 6 in the preparation of a negative electrode sheet for lithium-ion batteries.

8. A lithium-ion battery negative electrode sheet prepared using the nanoscale MXene material as described in claim 6, characterized in that, The lithium-ion battery negative electrode sheet is prepared according to the following steps: Nanoscale MXene material, conductive agent and binder are mixed and then mixed with solvent to obtain slurry. Copper foil is used as a substrate, and the slurry is uniformly coated on the surface. After drying, lithium-ion battery negative electrode sheet is obtained. The mass ratio of nano-sized MXene material, conductive agent and binder is 7-8:1-2:1; The conductive agent is selected from conductive carbon black, carbon nanotubes, or graphene; the binder is selected from polyvinylidene fluoride or carboxymethyl cellulose; and the solvent is selected from N-methylpyrrolidone or deionized water.

9. The application of the lithium-ion battery negative electrode sheet according to claim 8 in the preparation of lithium-ion batteries, characterized in that, The lithium-ion battery is prepared according to the following steps: Positive electrode preparation: pressing and cutting metallic lithium into sheets; Preparation of electrolyte: LiPF6 was dissolved in an organic solvent to prepare a LiPF6 electrolyte with a concentration of 1 mol / L; The organic solvent is composed of ethylene carbonate, dimethyl carbonate and vinylene carbonate in a volume ratio of 47.5:47.5:

5. Preparation of lithium-ion batteries: The positive electrode, Cellgard2400 separator, electrolyte and lithium-ion battery negative electrode are assembled sequentially to obtain a lithium-ion battery.

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