Method for preparing MXene material, MXene electrode sheet and lithium-ion battery using MXene electrode sheet

Abstract

The present invention relates to a method for preparing MXene materials, an MXene electrode sheet, and a lithium-ion battery using the MXene electrode sheet. The pressure is provided by a two-sided press hydraulic press or a six-sided press hydraulic press. This application also includes a high-pressure technology method for large-scale preparation of the above-mentioned modified two-dimensional crystal MXene materials. The pressure causes a significant increase in the carrier concentration and a decrease in the grain boundary barrier, thereby resulting in a significant increase in the conductivity of the MXene material, weakening the polarization phenomenon in the lithium-ion battery, increasing the reaction rate in the battery, and improving the reaction kinetics in the lithium-ion battery. By using a two-sided press hydraulic press or a six-sided press hydraulic press, a large number of modified two-dimensional crystal MXene materials can be prepared at one time, overcoming the problem of the small amount of recoverable samples of the diamond anvil press in the high-pressure field. This simple and effective large-scale preparation method is conducive to developing the application value of MXene materials and facilitating further industrial production in the field of lithium-ion batteries.

Description

Technical Field

[0001] The present invention relates to the field of high-pressure modification technology of two-dimensional crystal MXene materials and lithium-ion batteries, and specifically to a preparation method of MXene materials, an MXene electrode sheet, and a lithium-ion battery using the MXene electrode sheet. Background Art

[0002] As a brand-new two-dimensional layered transition metal carbide, nitride or carbonitride, MXene has attracted wide attention in related fields, especially in the energy storage field, due to its accordion-like morphology, high carrier mobility and other characteristics. So far, more than thirty kinds of MXenes have been successfully synthesized, mainly including Ti3C2T x , V2CT x , Nb2CT x and Nb4C3T x etc. (T x represents surface functional groups, such as -OH, -F, -O). Due to the advantages of two-dimensional MXene materials such as high theoretical capacity and fast ion transport, they have potential application value in aspects such as the negative electrode materials of lithium-ion batteries. However, during the charge and discharge process of lithium-ion batteries, problems such as the expansion of the volume of the negative electrode material and the appearance of polarization phenomena will occur, and these problems still long-term limit many commercial applications of it in the field of lithium-ion batteries.

[0003] As an effective synthesis or regulation means, pressure has penetrated into many frontier sciences. Due to the unique layered structure of two-dimensional materials, the changes caused by pressure are more complex and novel. In addition to being able to significantly affect the structural phase transition of two-dimensional materials, the influence on the interlayer spacing, band gap, defects, functional groups and other microstructures is also a particularly prominent aspect, which will affect the properties and performances of materials in all aspects. In view of this, the technology of the present invention is to use pressure to regulate two-dimensional MXene materials, so as to greatly improve the reaction kinetics of MXene materials in lithium-ion batteries and realize batch-scale application. This invention can not only enrich the use value of MXene materials, but also provide technical support for industrial application in liquid and solid lithium-ion batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of MXene materials, an MXene electrode sheet, and a lithium-ion battery using the MXene electrode sheet. The high-pressure treatment means provided by the present invention can effectively improve the compactness of MXene materials, induce the reduction of the interlayer spacing of MXene materials, significantly improve the conductivity of MXene materials, weaken the polarization phenomenon during the charge and discharge process of liquid and solid lithium-ion batteries, and then improve its reaction kinetics in liquid and solid lithium-ion batteries and can be prepared on a large scale.

[0005] To achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0006] A method for preparing MXene material, wherein the pressure of the preparation method is provided by a two-sided top hydraulic press or a six-sided top hydraulic press, and the MXene material described in the present invention is Ti3C2T x .

[0007] Place the original two-dimensional MXene material into the sample cavity of a two-sided top hydraulic press or a six-sided top hydraulic press, apply external pressure and hold the pressure, and a large number of modified MXene two-dimensional crystals are obtained after depressurization; the mass of the original two-dimensional MXene material is between 0-3 g, the range of the applied external pressure is between 2-6.5 GPa, and the pressure holding time is: 3-30 min.

[0008] Steps for preparing MXene electrode sheet:

[0009] Step (1): Grind the MXene two-dimensional crystal in a mortar for a while, then mix it with conductive agent carbon black and polyvinylidene fluoride binder in N-methylpyrrolidone at a weight ratio of 8:1:1, and place it on a magnetic stirrer and stir for 10 h to obtain MXene electrode slurry;

[0010] Step (2): Coat the slurry obtained in step (1) on a circular copper foil with a diameter of 16 mm, and then place the copper foil in an oven and dry it at 70 °C for 12 h to obtain an MXene electrode sheet.

[0011] Method for preparing lithium-ion battery, assemble a button-type half-cell with the MXene electrode sheet in an argon environment in a glove box, and the assembly sequence is negative electrode shell, shrapnel, gasket, lithium sheet, separator, MXene electrode sheet and positive electrode shell. The MXene electrode sheet is the positive electrode, the lithium sheet is the counter electrode, the electrolyte is 1M LiPF6 dissolved in DMC, EC and EMC, and 20 μL is added each time to fully wet the separator. Finally, seal the button battery with a special sealing machine under insulating conditions, and let the sealed button battery stand for 12 h.

[0012] Method for preparing lithium-ion battery, assemble a button-type half-cell with the MXene electrode sheet in an argon environment in a glove box, and the assembly sequence is negative electrode shell, shrapnel, gasket, lithium sheet, separator, MXene electrode sheet and positive electrode shell. The MXene electrode sheet is the positive electrode, the lithium sheet is the counter electrode, and the solid electrolyte membrane is made of Li7La3Zr2O 12 powder pressed to a thickness of 10-50 μm, and the pressure for pressing the sheet is set at 100 MPa-1 GPa. Finally, seal the button battery with a special sealing machine under insulating conditions, and let the sealed button battery stand for 12 h.

[0013] Advantages of the present invention

[0014] 1. The present invention provides a preparation method of a two-dimensional crystal MXene material for regulating the reaction kinetics of a lithium-ion battery under high pressure and a lithium-ion battery using the MXene material. After treatment, the MXene can still maintain its original accordion-like morphology, the compactness of the MXene is improved, the interlayer pores are reduced, and the interlayer spacing d decreases from to Moreover, due to the significant increase in the carrier concentration and the reduction of the grain boundary barrier, the conductivity of the MXene material is increased by an order of magnitude, which can be increased from 0.0019 S·cm-1 to 0.0444 S·cm-1, weakening the polarization phenomenon in the lithium-ion battery. The median polarization potential difference Δ decreases from 0.94 V to 0.85 V, increasing the reaction rate in the battery, and further improving the reaction kinetics in the lithium-ion battery, making the battery have higher stability and reversibility. It provides a simple and practical new method for regulating various nanoscale MXene materials, enriching the application value of MXene materials in the field of lithium-ion batteries.

[0015] 2. The present invention provides a preparation method of a two-dimensional crystal MXene material for regulating the reaction kinetics of a lithium-ion battery under high pressure and a lithium-ion battery using the MXene material. By using a two-sided anvil hydraulic press or a six-sided anvil hydraulic press, the problem of small recoverable sample amount (generally in the microgram level and difficult to recover) of the diamond anvil press commonly used in the high-pressure field is overcome, which is convenient for further industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Planar SEM image of the modified Ti3C2T prepared in the invention example. x

[0017] Figure 2 Graph of the variation of conductivity with pressure during the modification of Ti3C2T. x

[0018] Figure 3 Graph of the variation of lattice parameter, volume, and interlayer spacing with pressure of the modified Ti3C2T prepared in the invention example. x

[0019] Figure 4 Planar SEM image of the modified electrode sheet of Ti3C2T prepared in the invention example. x

[0020] Figure 5 Charge-discharge curve of a lithium-ion battery with the electrode sheet of Ti3C2T prepared in the invention example and a Li sheet as the counter electrode. x DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention relates to the field of high-pressure modification technology of two-dimensional crystal MXene materials and lithium-ion batteries. The high-pressure equipment used is a two-sided hydraulic press or a six-sided hydraulic press, and the MXene material is Ti3C2T x .

[0022] The following further describes the present invention in detail with specific embodiments and accompanying drawings, but the present invention is not limited thereto.

[0023] Example 1:

[0024] (1) Place 0.5 g of the original multi-layer Ti3C2T x MXene powder into the sample chamber of a two-sided hydraulic press and apply an external pressure until 2 GPa, and keep the pressure for 10 min. After depressurization, a large amount of modified Ti3C2T x MXene powder is obtained;

[0025] (2) Grind the Ti3C2T x powder prepared in (1) in a mortar for a while, and then mix it with the conductive agent carbon black and the polyvinylidene fluoride (PVDF) binder in N-methylpyrrolidone (NMP) at a weight ratio of 8:1:1, and place it on a magnetic stirrer and stir for 10 h to obtain Ti3C2T x slurry;

[0026] (3) Coat the slurry obtained in (2) on a round copper foil with a diameter of 16 mm, and then place the copper foil in an oven and dry it at 70 °C for 12 h to obtain a Ti3C2T x MXene electrode sheet;

[0027] (4) Assemble the Ti3C2T x MXene electrode sheet obtained in (3) into a CR2032 type button half-cell in an argon environment in a glove box. The assembly sequence is the negative electrode shell, the shrapnel, the gasket, the lithium sheet, the separator, the Ti3C2T x electrode sheet and the positive electrode shell. The Ti3C2T x electrode sheet is the positive electrode, the lithium sheet is the counter electrode, the electrolyte is 1 M LiPF6 dissolved in DMC, EC and EMC (volume ratio 1:1:1), and 20 μL is added each time to fully wet the separator. Finally, the button cell is sealed with a special sealing machine under insulating conditions, and the sealed button cell is left standing for 12 h;

[0028] Example 2:

[0029] (1) Place 1 g of the original multi-layer Ti3C2T x MXene powder into the sample chamber of a six-sided hydraulic press and apply an external pressure until 4 GPa, and keep the pressure for 30 min. After depressurization, a large amount of modified Ti3C2Tx MXene powder;

[0030] (2) Grind the Ti3C2T powder prepared in (1) in a mortar for a while, then mix it with conductive agent carbon black and polyvinylidene fluoride (PVDF) binder in N-methylpyrrolidone (NMP) at a weight ratio of 8:1:1, and place it on a magnetic stirrer and stir for 10 h to obtain a Ti3C2T x slurry; x slurry;

[0031] (3) Coat the slurry obtained in (2) on a circular copper foil with a diameter of 16 mm, then place the copper foil in an oven and dry it at 70 °C for 12 h to obtain a Ti3C2T x MXene electrode sheet;

[0032] (4) Assemble a button-type half-cell with the Ti3C2T x MXene electrode sheet in an argon environment in a glove box. The assembly order is negative electrode shell, shrapnel, gasket, lithium sheet, separator, Ti3C2T x electrode sheet and positive electrode shell. The Ti3C2T x electrode sheet is the positive electrode, the lithium sheet is the counter electrode, the electrolyte is 1 M LiPF6 dissolved in DMC, EC and EMC (volume ratio 1:1:1), 20 μL is added each time, the separator is fully wetted, and finally the button cell is sealed under insulator conditions with a special sealing machine. The sealed button cell is left standing for 12 h;

[0033] Example 3:

[0034] (1) Place 2 g of the original multi-layer Ti3C2T x MXene powder into the sample cavity of a six-sided top hydraulic press and apply an external pressure up to 6 GPa, and keep the pressure for 20 min. After pressure relief, a large amount of modified Ti3C2T x MXene powder is obtained;

[0035] (2) Grind the Ti3C2T powder prepared in (1) in a mortar for a while, then mix it with conductive agent carbon black and polyvinylidene fluoride (PVDF) binder in N-methylpyrrolidone (NMP) at a weight ratio of 8:1:1, and place it on a magnetic stirrer and stir for 10 h to obtain a Ti3C2T x slurry; x slurry;

[0036] (3) Coat the slurry obtained in (2) on a circular copper foil with a diameter of 16 mm, then place the copper foil in an oven and dry it at 70 °C for 12 h to obtain a Ti3C2T x MXene electrode sheet;

[0037] (4) Assemble the Ti3C2T x MXene electrode sheet into a coin-type half-cell in the argon atmosphere of a glove box. The assembly sequence is the negative electrode case, spring piece, gasket, lithium sheet, separator, Ti3C2T x electrode sheet, and positive electrode case. The Ti3C2T x electrode sheet serves as the positive electrode, the lithium sheet serves as the counter electrode, and the electrolyte is 1 M LiPF6 dissolved in DMC, EC, and EMC (volume ratio 1:1:1). Each time, 20 μL is dropped to fully wet the separator. Finally, the coin-type battery is sealed under insulating conditions using a special sealing machine, and the sealed coin-type battery is left standing for 12 h;

[0038] Example 4

[0039] (1) Place 2 g of the original multi-layer Ti3C2T x MXene powder into the sample chamber of a cubic press and apply an external pressure up to 6.5 GPa and hold the pressure for 25 min. After releasing the pressure, a large amount of modified Ti3C2T x MXene powder is obtained;

[0040] (2) Grind the Ti3C2T x powder obtained in (1) in a mortar for a moment, then mix it with conductive agent carbon black and polyvinylidene fluoride (PVDF) binder in N-methylpyrrolidone (NMP) at a weight ratio of 8:1:1, and place it on a magnetic stirrer and stir for 10 h to obtain Ti3C2T x slurry;

[0041] (3) Coat the slurry obtained in (2) on a circular copper foil with a diameter of 16 mm, and then place the copper foil in an oven and dry it at 70 °C for 12 h to obtain Ti3C2T x MXene electrode sheet;

[0042] (4) Assemble the Ti3C2T x MXene electrode sheet into a CR2032 coin-type half-cell in the argon atmosphere of a glove box. The assembly sequence is the negative electrode case, spring piece, gasket, lithium sheet, separator, Ti3C2T x electrode sheet, and positive electrode case. The Ti3C2T x electrode sheet serves as the positive electrode, the lithium sheet serves as the counter electrode, and the solid electrolyte membrane is made of Li7La3Zr2O 12 powder pressed to a thickness of 10 - 50 μm, and the pressure for pressing the sheet is set at 100 MPa - 1 GPa. Finally, the coin-type battery is sealed under insulating conditions using a special sealing machine, and the sealed coin-type battery is left standing for 12 h;

[0043] The invention of this application uses a two-sided press or a six-sided press to improve the reaction kinetics of two-dimensional crystal MXene materials in lithium-ion batteries and to prepare them on a large scale. Among them, the two-sided press and the six-sided press have the following functions: (1) The two-sided press or the six-sided press can provide a relatively high pressure, weaken the polarization phenomenon during the charge and discharge processes of MXene materials in lithium-ion batteries, increase the reaction rate in the battery, and improve the reaction kinetics in lithium-ion batteries; (2) The two-sided press or the six-sided press can prepare a large amount of modified two-dimensional crystal MXene materials at one time, overcoming the problem of the small amount of recyclable samples in traditional diamond anvil presses. This simple and effective large-scale preparation method is conducive to the development of the application value of MXene materials and facilitates further industrial production.

Claims

1. A method for preparing MXene material, characterized in that: The pressure of the preparation method is provided by a two-sided top hydraulic press or a six-sided top hydraulic press, and the MXene material is Ti3C2T x ; The specific steps are as follows: Place the original two-dimensional MXene material into the sample cavity of a two-sided top hydraulic press or a six-sided top hydraulic press, apply external pressure and keep the pressure constant, and a large number of modified MXene two-dimensional crystals are obtained after pressure relief; the mass of the original two-dimensional MXene material is less than 3 g, the range of the applied external pressure is between 2-6.5 GPa, the pressure holding time is 3-30 min, the layer spacing d drops to 9.8 Å, and the conductivity increases to 0.0444 S·cm-1.

2. The MXene electrode sheet prepared from the MXene material according to claim 1, characterized in that: Step (1): Grind the MXene two-dimensional crystal in a mortar for a while, and then mix it with conductive carbon black and polyvinylidene fluoride binder in N-methylpyrrolidone at a weight ratio of 8:1:1, and place it on a magnetic stirrer and stir for 10 h to obtain the MXene electrode slurry; Step (2): Coat the slurry obtained in step (1) on a round copper foil with a diameter of 16 mm, and then place the copper foil in a drying oven and dry it at 70 °C for 12 h to obtain the MXene electrode sheet.

3. The lithium-ion battery prepared from the MXene electrode sheet according to claim 2, wherein: Assemble a button-type half-cell for the MXene electrode sheet in the argon environment of a glove box. The assembly sequence is the negative electrode shell, shrapnel, gasket, lithium sheet, separator, MXene electrode sheet, and positive electrode shell. The MXene electrode sheet is the positive electrode, the lithium sheet is the counter electrode, and the electrolyte is 1 M LiPF6 dissolved in DMC, EC, and EMC. Each time, 20 µL is added dropwise to fully wet the separator. Finally, seal the button cell with a special sealing machine under insulator conditions, and let the sealed button cell stand for 12 h.

4. The lithium ion battery according to claim 3, wherein: The volume ratio of the described DMC, EC, and EMC is 1:1:

1.

5. The lithium-ion battery prepared from the MXene electrode sheet according to claim 2, characterized in that: The MXene electrode sheet was assembled into a button-type half-cell in an argon atmosphere in a glove box. The assembly order was the negative electrode case, the shrapnel, the gasket, the lithium sheet, the separator, the MXene electrode sheet, and the positive electrode case. The MXene electrode sheet was the positive electrode, and the lithium sheet was the counter electrode. The Li7La3Zr2O 12 powder was pressed into a thickness of 10 - 50 μm, and the pressing pressure was set at 100 MPa - 1 GPa. Finally, the button cell was sealed under insulating conditions with a special sealing machine, and the sealed button cell was left standing for 12 h.

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