CN115140743B - Two-dimensional metal boride and hydrothermal auxiliary alkali liquor etching preparation method and application - Google Patents

Abstract

The invention discloses a two-dimensional metal boride, which is obtained by the following steps: dispersing MAB phase material in alkali solutionTransferring the suspension into a hydrothermal kettle, heating in an oven or a microwave hydrothermal box, preserving heat for proper reaction time, cooling, filtering, washing and drying to obtain the target product, namely the two-dimensional metal boride. MAB phase material comprises MoAlB, cr ₂ AlB ₂ 、Ni ₂ ZnB、WAlB、Ti ₂ InB ₂ 、Fe ₂ AlB ₂ One or a mixture of two or more of the above; two-dimensional metal boride MoB, crB, ni ₂ B. WB, tiB, feB. The invention also discloses a preparation method of the two-dimensional metal boride and application of the two-dimensional metal boride in preparation of lithium ion batteries. The method adopts the hydrothermal auxiliary alkali liquor etching method to prepare the MBene material, and is environment-friendly and safe. The prepared MBene material is used for a lithium ion battery, has excellent battery capacity and has wide application prospect.

Description

Preparation method and application of two-dimensional metal boride and hydrothermal-assisted alkali etching

Technical field

The present invention relates to a two-dimensional metal boride (MBene) material.

The present invention also relates to a method for efficiently preparing the above-mentioned MBene material by using a hydrothermal-assisted alkali etching method.

The present invention also relates to the application of the above-mentioned MBene material in preparing lithium-ion batteries.

Background technique

In 2011, Yury Gogotsi and others from Drexel University in the United States [Adv.Mater.2011,23:4248-4253] reported a graphene-like material - two-dimensional transition metal carbide, nitrogen and carbonitride (MXene, M is a transition metal element, X is carbon or nitrogen), among which the most types are two-dimensional transition metal carbides. The ternary ceramic MAX phase (such as Ti ₃ AlC _2, etc.) is the precursor for preparing MXene, in which the MA bond strength is relatively weak, so that the metal-bonded A element layer (such as the Al layer) can be removed after etching to obtain Binary layered MXene (such as Ti ₃ C ₂ , etc.).

Recently, Ade and Hillebrecht [Inorg.Chem.2015,54:6122-6135] reported a boron-containing compound similar to the MAX phase, in which boron replaced the X element. This new precursor was named MAB phase, in which B represents the boron element, and it is predicted that a new two-dimensional transition metal boride material (MBene) similar to MXene may be derived, which may have broad application prospects similar to MXene materials (such as lithium-ion battery anode materials). Due to its thermodynamic metastable properties, MXene cannot be directly reacted from M and From the MAX phase etching strategy, MBene can be prepared by etching the MAB phase.

Because of its similar structure, the MXene etching method can be used as a reference. Although there have been many studies on MXene materials, they are limited by the etching methods that mostly use highly toxic fluorine-containing compounds (such as the currently commonly used HCl mixed LiF etching method), and the high cost of wastewater treatment generated by the preparation has seriously restricted the practical application of MXene materials. Green fluorine-free synthesis strategies for MXene have also been reported. For example, Wang Changda et al. [Adv. Mater. 2021, 33, 2101015] reported a hydrothermal method using hydrochloric acid etching for 5 days, which is too long; Li Tengfei et al. [ Angew.Chem.Int.Edit.2018, 57, 6115-6119】Using a high-pressure reactor at 270°C and etching with alkaline solution to prepare MXene. The reaction temperature of this method is too high, the equipment requirements are very high, and it is dangerous. The above methods all have their own shortcomings, and none of them have been used in the synthesis of MBene materials. Since the basic properties of boride (MBene) and carbide (MXene) are quite different, it is not obvious whether they are suitable for direct analogy and there are no reports, so further exploration is needed. The synthesis of MBene has also been reported in the literature. For example, Wang Junjie et al. [Nat. Commun. 2019, 10, 2284] used the metal alloy method and mixed Mo powder with Ti ₂ InB ₂ as the precursor under vacuum conditions and reacted at 1050°C for 6 days to obtain MBene. Dimensional TiB, this method is too time-consuming and the process is complicated. It can be seen from the XRD pattern that the etching degree is low. Alameda et al. [J.Am.Chem.Soc.2018,140:8833-8840] used sodium hydroxide solution to etch boron, aluminum, and molybdenum, but only had a microscopic etching effect, and no product was observed in the XRD spectrum. Molybdenum boride, two-dimensional metal molybdenum boride cannot be obtained macroscopically. At the same time, the boron element is easily oxidized and the etching method cannot introduce oxidants.

Chinese patent (Application No. 202110558638.7) also reports the use of dilute alkali solution etching reaction to remove A-site elements in MAB phase materials to obtain two-dimensional transition metal boride materials. The disadvantages of dilute alkali solution etching are the same as the above-mentioned articles. The effect is not good. Only a weak manganese boride peak can be observed in the XRD pattern, and the etching degree in the precursor phase is very low, indicating that this method is not a good strategy for preparing MBene.

Chinese patent (Application No. 201810140682.4) uses dilute hydrochloric acid to etch boron aluminum chromium to prepare two-dimensional chromium boride. It can also be seen from the XRD pattern that the main etching effect is poor, chromium boride is not the main phase, and chromium boride serves as lithium The specific capacity of the negative electrode of the ion battery is 115mAh g ^-1 in the first cycle, and the specific capacity decays to 70mAh g ^-1 in the second cycle. The electrode material prepared by this method has a specific capacity that is too low and has no battery application prospects.

In order to overcome the above shortcomings, it is of great research significance to study a green, fluorine-free, simple and efficient method for preparing MBene materials by etching MAB phase, which will provide a material basis for the broad application research of two-dimensional metal borides.

Contents of the invention

The object of the present invention is to provide a two-dimensional metal boride (MBene) material.

Another object of the present invention is to provide a method for preparing the above-mentioned MBene material, that is, a method for efficiently preparing the above-mentioned MBene material by using a hydrothermal-assisted alkali etching method.

In order to achieve the above objects, the two-dimensional metal boride provided by the present invention is obtained by the following method:

Disperse the MAB phase material in an alkali solution, transfer the suspension to a hydrothermal kettle, heat it in an oven, and keep it warm for a suitable reaction time. After cooling, filter, wash and dry to obtain the target product two-dimensional metal boride.

Among the two-dimensional metal boride, the two-dimensional metal boride is at least one of MoB, CrB, Ni ₂ B, WB, TiB, and FeB; the MAB phase material includes MoAlB, Cr ₂ AlB ₂ , Ni ₂ ZnB, One or a mixture of two or more of WAAlB, Ti ₂ InB ₂ and Fe ₂ AlB ₂ .

The method for preparing the above two-dimensional metal boride provided by the invention:

Disperse the MAB phase material in an alkali solution, transfer the suspension to a hydrothermal kettle, heat it in an oven or microwave oven, and insulate the reaction. After cooling, filter, wash and dry to obtain the target product two-dimensional metal boride.

In the method, the two-dimensional metal boride is at least one of MoB, CrB, Ni ₂ B, WB, TiB, and FeB; the MAB phase material includes MoAlB, Cr ₂ AlB ₂ , Ni ₂ ZnB, WAIB, and Ti ₂ One or a mixture of two or more of InB ₂ and Fe ₂ AlB ₂ .

In the method, the molar ratio of the MAB phase material to the alkali in the alkali solution is 1:0.01-0.8, and the alkali is sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, tetramethyl hydroxide. One or more of ammonium hydroxide and ammonia water are mixed.

In the method, the solvent of the alkaline solution is at least one of water, ethanol, and methanol.

In the method, the concentration mass ratio of the alkali solution is 15-30 wt.%.

In the method, the temperature of the insulation reaction is 110-150°C; the insulation reaction time is 2-24 hours.

In the method described, the hydrothermal reaction heating method is an oven or a microwave hydrothermal box.

The two-dimensional metal boride provided by the invention can be used in lithium ion batteries.

The hydrothermal-assisted alkali etching method proposed by the present invention etches MAB phase materials, the process is gentle and green, does not use high-risk etchants such as hydrofluoric acid, has high safety, and realizes the green preparation of MBene materials. The new two-dimensional material prepared by this method can be used as anode material for lithium-ion batteries, showing excellent battery specific capacity and having broad application prospects.

Description of drawings

Figure 1 is a scanning electron microscope image of MBene prepared by the preparation method of Example 1 of the present invention.

Figure 2 is an XRD pattern of two-dimensional molybdenum boride MBene prepared by the preparation method of Example 1 of the present invention.

Figure 3 is a charge-discharge curve of two-dimensional molybdenum boride MBene prepared by the preparation method of Example 1 of the present invention as a negative electrode in a lithium-ion battery.

Figure 4 is a cycle number diagram of the two-dimensional molybdenum boride MBene prepared by the preparation method of Example 1 of the present invention as a negative electrode in a lithium-ion battery.

Detailed ways

The technical solution of the present invention is:

Disperse the MAB phase material in an alkaline solution, transfer the suspension to a hydrothermal kettle, heat it in an oven, and keep it warm for a suitable reaction time. After cooling, filter, wash and dry to obtain the target product two-dimensional metal boride (MBene). Two-dimensional metal boride MBene is coated as anode material for lithium-ion batteries. Since the etching effect of alkali solution is not good at normal temperature and pressure, the etching effect of hydroxide ions on the aluminum atomic layer in the MAB phase material can be enhanced under the action of high pressure in the hydrothermal kettle to achieve the ideal etching effect. In this invention, the hydrothermal-assisted alkali etching method is used to prepare two-dimensional metal boride (MBene) materials for the first time. The prepared boride should have excellent specific capacity in lithium-ion batteries.

Optionally, the MAB phase material includes one or a mixture of two or more of MoAlB, Cr ₂ AlB ₂ , Ni ₂ ZnB, WAIB, Ti ₂ InB ₂ , Fe ₂ AlB ₂ .

Optionally, MBene is at least one of MoB, CrB, Ni ₂ B, WB, TiB, and FeB.

Optionally, the molar ratio of the MAB phase material to the alkali in the alkali solution is 1:0.01-0.8. The alkali is sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, or tetramethylammonium hydroxide. , ammonia and water, or a mixture of two or more.

Optionally, the solvent in the alkaline solution is at least one of water, ethanol, and methanol.

Optionally, the concentration mass ratio of the alkali solution is 15-30 wt.%.

Optionally, the temperature of the insulation reaction is 110-150°C; the insulation time is 2-24 hours.

The two-dimensional metal boride MBene of the present invention can be used to prepare negative electrode materials for ion batteries, such as lithium-ion battery negative electrodes.

In view of the shortcomings of the current etching technology, for example, the commonly used etchant hydrofluoric acid is highly dangerous; direct etching with alkali solution is not effective; and the introduction of oxidizing etchants can easily oxidize boron. element. The invention provides a method for preparing MBene materials by green hydrothermal assisted alkaline etching of MBene.

In order to make the purpose, technical solution and effect of the present invention clearer and clearer, the present invention will be described in further detail below. It should be understood that the specific implementation examples described here are only used to explain the present invention and are not used to limit the present invention.

Based on this, embodiments of the present invention provide a method for preparing MBene materials by green hydrothermal-assisted alkali etching, which includes the steps:

S1. Disperse the MAB phase material in an alkaline solution for etching;

S2. Transfer the suspension to the hydrothermal kettle and heat it in an oven or microwave hydrothermal box;

S3. Keep the reaction for an appropriate time. After cooling, filter, wash and dry to obtain the target product, the two-dimensional metal boride MBene;

S4. Coat the two-dimensional metal boride MBene as an anode material for lithium-ion batteries.

In this embodiment, MAB phase material is used as the precursor, and alkali liquid is used as the etchant. MAB is dispersed in the alkali liquid and transferred to a hydrothermal kettle. With the assistance of water heat, the etching effect of the alkali liquid is enhanced. Finally, Two-dimensional metal boride MBene material was obtained. Coating it as an anode material for lithium-ion batteries shows excellent battery capacity.

In addition, the method of preparing MBene materials by green hydrothermal-assisted alkaline etching in this embodiment is a preparation method that is simple to operate and has no safety hazards. It is suitable for large-scale industrial production, and the preparation method is universal.

In step S1, in one embodiment, the MAB phase material includes one or a mixture of two or more of MoAlB, Cr ₂ AlB ₂ , Ni ₂ ZnB, WAIB, Ti ₂ InB ₂ and Fe ₂ AlB ₂ .

In step S2, in one embodiment, the molar ratio of the MAB phase material to the etching alkali is 1:0.01-0.8, and the etching alkali is sodium hydroxide, potassium hydroxide, lithium hydroxide, hydroxide One or a mixture of two or more of calcium, barium hydroxide, tetramethylammonium hydroxide, and ammonia.

In one embodiment, the MBene is at least one of MoB, CrB, Ni ₂ B, WB, TiB, and FeB.

In one embodiment, the reaction solvent is at least one of water, ethanol, and methanol.

In one embodiment, the concentration mass ratio of the alkali aqueous solution is 15-30 wt.%.

In step S3, in one embodiment, the hydrothermal reaction temperature is 110-150°C.

In one embodiment, the etching reaction holding time is 2-24 hours.

In step S4, in one embodiment, the prepared two-dimensional metal boride MBene is used as a negative electrode material for a lithium ion battery.

Examples of the present invention provide a green method for preparing two-dimensional metal boride MBene, in which the MBene described in the embodiments of the present invention is used as anode material for lithium ion batteries.

In order to further illustrate the technical solutions and effects of the present invention, specific examples and comparative examples will be further described below.

Example 1

1. Prepare MBene (MoB) according to the following steps:

Mix 1 g of MoAlB powder and 35 ml of 25 wt% sodium hydroxide solution evenly, then transfer it to a 100 ml reaction kettle. The reaction kettle is placed in an oven and kept at 120°C for 24 hours. After cooling, the suspension was filtered and washed three times with 1 mol/L sodium hydroxide solution and five times with deionized water. The resulting powder was dried at 80°C for 10 hours to obtain a two-dimensional accordion-like structure. The scanning electron microscope of molybdenum boride MBene is shown in Figure 1. Figure 2 is the XRD pattern of the two-dimensional molybdenum boride MBene in this embodiment.

2. Follow the following steps to prepare the MBene lithium-ion battery negative electrode:

Mix the MBene powder prepared in the above steps evenly with acetylene black and sodium alginate. The mass ratio is 80:10:10. Use water as the dispersant. After magnetic stirring for 8 hours, apply the slurry on the copper foil on the coater. above, drying at 70°C for 12h, and then vacuum drying at 80°C for 12h to prepare a battery negative electrode, which can be used in lithium-ion batteries. A lithium-ion CR2032 button battery was assembled in an inert atmosphere glove box. The metal lithium sheet was the counter electrode, lithium hexafluorophosphate was the electrolyte, and the battery separator was Celgard2400. The charge and discharge test was carried out on the blue battery test system. At a current density of 50mAg ^-1 , the first charge specific capacity and discharge specific capacity of the battery were 645.7mAhg ^-1 and 666.0mAhg ^-1 respectively. The capacity attenuation was not significant after three cycles, such as As shown in Figure 3. After 1000 cycles at a current density of 2Ag ^-1 , the capacity is still 144.2mAhg ^-1 , while the unetched boron aluminum molybdenum has almost no capacity, as shown in Figure 4.

Comparative example 1

Mix 1 g of MoAlB powder and 35 ml of 25 wt% sodium hydroxide solution evenly, then transfer it to a 100 ml reaction kettle. The reaction kettle is placed in an oven and kept at 160°C for 24 hours. The prepared MoB particles are not two-dimensional layered structures, so the hydrothermal temperature cannot be too high.

Comparative example 2

Mix 1 g of WAIB powder and 35 ml of 25 wt% sodium hydroxide solution evenly, then transfer it to a 100 ml reaction kettle. The reaction kettle is placed in an oven and kept at 120°C for 24 hours. After cooling, the suspension was filtered and washed three times with 1 mol/L sodium hydroxide solution and five times with deionized water. The resulting powder was dried at 80°C for 10 hours to obtain a two-dimensional accordion-like structure. Tungsten boride MBene. Under the same lithium-ion battery assembly process, at a current density of 50mAg ^-1 , the first charge specific capacity and discharge specific capacity of the battery are 595.6mAhg ^-1 and 603.2mAhg ^-1 respectively. The specific capacity was 134.5mAhg ^-1 after 1000 cycles at a current density of 2Ag ^-1 .

As can be seen from the above examples, the invention provides a green method for preparing two-dimensional metal boride (MBene), which is to disperse the ternary metal boride precursor (MAB) in the boride in an alkali solution, and The suspension is transferred into a hydrothermal kettle, and under the assistance of hydrothermal enhancement, the etching effect of the alkali solution is enhanced. After the reaction is completed, the dispersion containing MBene is filtered and washed to prepare the MBene material. The present invention adopts hydrothermal-assisted alkali etching method to prepare MBene materials for the first time. High-risk substances such as hydrofluoric acid are not used in the preparation process, and the preparation process is green and safe. The prepared MBene material shows excellent battery capacity when used in lithium-ion batteries and has broad application prospects.

It can be seen from the two comparative examples that the method of the present invention is suitable for making MAB phase materials into two-dimensional metal boride (MBene). In Comparative Example 1, due to the higher reaction temperature, the final product was in the form of granules instead of forming a two-dimensional layered structure. Comparative Example 2 does not use MAB phase materials, and the secondary charge specific capacity, discharge specific capacity and cycle effect of the product in the lithium ion battery are far less ideal than Example 1.

It should be understood that the application of the present invention is not limited to the above examples. Those of ordinary skill in the art can make improvements or changes based on the above descriptions. All these improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims (4)

1. Use of a two-dimensional metal boride in a lithium ion battery, wherein the two-dimensional metal boride is obtained by:

dispersing MAB phase material in alkaline solution with concentration mass ratio of 15-30 wt%, transferring the suspension into a hydrothermal kettle, heating in an oven, reacting at 110-150deg.C for 2-24 hr, cooling, filtering, washing, and drying to obtain target product two-dimensional metal boride;

the molar ratio of the MAB phase material to the alkali in the alkali solution is 1:0.01-0.8.

2. The use according to claim 1, wherein the MAB phase material comprises MoAlB, cr ₂ AlB ₂ 、Ni ₂ ZnB、Ti ₂ InB ₂ 、Fe ₂ AlB ₂ One or a mixture of two or more of the above; two-dimensional metal boride MoB, crB, ni ₂ B. WB, tiB, feB.

3. The use according to claim 1, wherein the base is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide, tetramethylammonium hydroxide, aqueous ammonia.

4. The use according to claim 1, wherein the solvent of the alkaline solution is at least one of water, ethanol, methanol.