CN111232981B

CN111232981B - High lithium storage capacity Ti3C2TxMechanochemical preparation method of

Info

Publication number: CN111232981B
Application number: CN202010056029.7A
Authority: CN
Inventors: 秦锦雯; 曹敏花; 王洁; 王鑫
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2020-01-17
Filing date: 2020-01-17
Publication date: 2020-12-29
Anticipated expiration: 2040-01-17
Also published as: CN111232981A

Abstract

The invention provides a mechanochemical method (mechanochemistry) for preparing Ti with high lithium storage capacity₃C₂T_xBelonging to the technical field of MXene preparation. In the present invention, MAX phase Ti is used₃AlC₂Preparing stable small-size Ti by applying mechanical force to induce chemical reaction in strong alkaline environment₃C₂T_x. The material has a two-dimensional nano-flake structure, larger interlayer spacing and stable surface characteristics. The abundant exposed edge and the large specific surface area increase the number of lithium storage active sites, and are more beneficial to full contact with electrolyte and transmission and diffusion of lithium ions, thereby obtaining high lithium storage capacity. The Ti prepared by strong base assisted mechanochemical method adopted by the invention₃C₂T_xThe method has the characteristics of simple and controllable process, small pollution, low cost and the like, and has the potential of realizing large-scale production.

Description

High lithium storage capacity Ti3C2TxMechanochemical preparation method of

Technical Field

The invention belongs to the technical field of MXene preparation, and relates to Ti with high lithium storage capacity₃C₂T_xMechanochemical preparation method and Ti₃C₂T_xThe material is applied as a negative electrode material of a lithium ion battery.

Background

The lithium ion battery has the advantages of high energy density, excellent cycle performance, high voltage, high safety, environmental friendliness and the like, and is widely applied to the fields of various portable electronic devices, electric automobiles and the like. In lithium ion batteries, the negative electrode material plays a critical role in battery performance. At present, although graphite carbon serving as a commercial negative electrode material has better cycle stability, the theoretical capacity of the graphite carbon is lower, and the graphite carbon cannot meet the increasing energy requirement. Therefore, it is very important to develop a new lithium ion battery anode material having excellent performance.

MXene is a novel graphene-like two-dimensional transition metal carbon/nitride with a chemical formula of M_n+1X_nT_xWherein M is an early transition metal element, X is carbon or nitrogen, T is a functional group carried on the surface, and n is 1, 2 or 3. Since the first preparation by a Drexel university researcher in 2011, MXene has shown great potential in the aspect of lithium ion battery anode materials. Most MXene materials are made by selectively etching an "A" layer (A is a group IIIA or IVA element) in the MAX phase, the most common etchant being hydrofluoric acid. Relevant researches show that MXene has high intrinsic electronic conductivity, good hydrophilicity, mechanical stability, abundant surface functional groups and chemical compositions, and is widely applied to the fields of super capacitors, lithium/sodium ion batteries, electromagnetic shielding, sensing, photoelectrocatalysis and the like.

Ti₃C₂T_xIs the earliest and most deeply researched MXene material due to high conductivity and higher lithium storage capacity (320-410mAh g)^-1) The low lithium ion diffusion energy barrier (0.07eV) and the unique metal ion adsorption characteristic show good application prospects in the lithium ion battery. However, Ti₃C₂T_xThe interlayer stacking aggregation, which is subject to van der waals forces, causes a large reduction in contact area with the electrolyte and a reduction in lithium ion transport channels, resulting in slow kinetics of the electrochemical reaction. Researchers usually adopt means such as intercalation agent layer expansion, functional group modification, heteroatom doping, in-sheet pore formation and the like to prevent interlayer stacking, reduce ion diffusion resistance and increase ion adsorption sites. However, Ti constructed by the above method₃C₂T_xThe capacity of the material is still far lower than the theoretical capacity, so a simple and feasible strategy is urgently needed to be found to further improve the lithium storage capacity of the material.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a mechanochemical method (mechanochemistry) for preparing Ti₃C₂T_xThe method is also applied to the lithium ion battery cathode material. In the aluminium industryInspired by Bayer method, OH in NaOH strong alkaline environment^-Capable of etching Ti₃AlC₂Al layer in (1) to form soluble Al (OH)₄ ^-. In addition, NaOH can also shear Ti₃AlC₂(iii) ACS Sustainable chem. Eng.2018,6,8976), thereby facilitating OH utilisation^-The etching effect of (1). Based on the principle, the invention uses MAX phase Ti₃AlC₂Preparing stable small-size Ti by applying mechanical force to induce chemical reaction in strong alkaline environment₃C₂T_x. The mechanical force includes compression, shear, friction, extension, impact, etc., thereby inducing Ti₃AlC₂Changes the physicochemical properties of Ti₃AlC₂The Al layer in the alloy undergoes chemical change with alkali metal hydroxide in the surrounding environment to form soluble Al (OH)₄ ^-. Ti prepared by mechanochemical method₃C₂T_xHas two-dimensional nano-flake structure, larger interlayer spacing and stable surface characteristics. The abundant exposed edge and the large specific surface area greatly increase the number of lithium storage active sites, and are more beneficial to full contact with electrolyte and transmission and diffusion of lithium ions, thereby obtaining high lithium storage capacity. Adding the Ti₃C₂T_xAs the negative electrode material of the lithium ion battery, the amount of the negative electrode material is 100mA g^-1Under the current density of the electrode, the electrode material can reach 380mAh g after circulating for 100 circles^-1And exhibits excellent cycle stability and rate capability. Preparation of Ti in the invention₃C₂T_xThe method has the characteristics of simplicity, convenience, easy operation, little pollution, low cost and the like, and can be used for treating Ti₃C₂T_xThe research on the lithium ion battery cathode material has important significance and value.

The technical scheme adopted by the invention is as follows:

high lithium storage capacity Ti₃C₂T_xThe mechanochemical preparation method of (1), which comprises the steps of:

1) mixing Ti₃AlC₂Loading into stainless steel reactor, charging nitrogen gas, sealing, and mechanically reacting for 2-24 hr;

2) dissolving 5.0-15.0g of alkali metal hydroxide in deionized water to prepare supersaturated strong base solution, adding the supersaturated strong base solution into the reactor in the step 1), filling nitrogen and sealing, and carrying out mechanochemical reaction for 2-24 h;

3) after the reaction is finished, adding deionized water into the product of the mechanochemical reaction in the step (2) under the protection of nitrogen and ice bath for dissolving and cooling, washing the cooled product to be neutral, adding deionized water, taking the supernatant of 3500rpm, and freeze-drying to obtain Ti₃C₂T_x。

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

the Ti prepared by the mechanochemical method of the invention₃C₂T_xHas nanometer small size, thickness of 2-5nm, and size of 10-30 nm;

supersaturated alkali solution to Ti during mechanochemical reaction₃AlC₂The raw material plays the roles of shearing, etching and serving as an alkaline medium, thereby forming small-sized Ti₃C₂T_xThe abundant exposed edge and the large specific surface area can provide more lithium storage active sites;

alkali metal ions can be inserted into Ti during etching₃C₂T_xInterlamination (Nano Energy,2017,40,1) facilitates the reaction kinetics of electrochemical processes by enlarging the interlayer spacing.

The invention relates to Ti prepared by a mechanochemical method₃C₂T_xThe method has the characteristics of simple and controllable process, small pollution, low cost and the like, and has the potential of realizing large-scale production.

Drawings

FIG. 1 shows the preparation of Ti by the mechanochemical method of example 1₃C₂T_xAnd Ti prepared by the conventional method of comparative example 1₃C₂T_xAn XRD pattern of (a);

FIG. 2 shows the preparation of Ti by mechanochemical method in example 1₃C₂T_xAnd Ti prepared by the conventional method of comparative example 1₃C₂T_xA TEM pattern of (A);

FIG. 3 shows a machine according to embodiment 1Chemically prepared Ti₃C₂T_xAnd Ti prepared by the conventional method of comparative example 1₃C₂T_xA constant current discharge curve diagram of;

FIG. 4 shows the preparation of Ti by mechanochemical method in example 1₃C₂T_xAnd Ti prepared by the conventional method of comparative example 1₃C₂T_xThe rate performance graph of (1).

Detailed Description

The technical solution of the present invention is illustrated below, and the claimed scope of the present invention includes, but is not limited to, the following examples.

Example 1

Mixing Ti₃AlC₂Charging into a stainless steel reactor, Ti₃AlC₂The total weight is 1.0g, the mixture is sealed by filling nitrogen and mechanically reacted for 12 hours at the rotating speed of 300 rpm. Dissolving 15.0g of sodium hydroxide into 10mL of deionized water, cooling to room temperature, introducing nitrogen for 5min, adding the strong base solution into the reactor, filling nitrogen again, sealing, rotating at 300rpm, and carrying out mechanochemical reaction for 12 h. After the reactor was cooled to room temperature, deionized water was added under nitrogen protection in an ice bath. After cooling to room temperature, the mixed solution was washed to neutrality by centrifugation at 9000 rpm. Adding deionized water into the precipitate, centrifuging at 3500rpm for 5min, collecting supernatant, and freeze drying to obtain mechanochemical Ti₃C₂T_x。

Adopting the following steps: 1: 1, weighing the Ti prepared by mechanochemical reaction in example 1₃C₂T_xMixing, grinding and adding a proper amount of deionized water as a solvent. Uniformly coating the ground slurry on a copper foil, and drying the copper foil in vacuum at 120 ℃ for 12 hours to obtain a working electrode with the active material loading of about 0.72-0.94mg cm^-2. And assembling the electrode plates into a CR2025 button cell to perform electrochemical performance test. Assembling in Ar-filled glove box, water and oxygen partial pressure is less than 1.0ppm, metal lithium sheet for counter electrode, and electrolyte containing 1MLiPF₆In Ethylene Carbonate (EC)/dimethyl carbonate (DMC)/diethyl carbonate (DEC) solution (volume ratio 1:1: 1) the separator was a polypropylene membrane (Celgard 2400). Half-cell electrochemical tests were carried out on a LAND CT2001A model cell tester with a voltage window of 0.01-3.0V (vs Li)⁺/Li)。

Example 2

Mixing Ti₃AlC₂Charging into a stainless steel reactor, Ti₃AlC₂The total weight is 1.0g, the mixture is sealed by filling nitrogen and mechanically reacted for 12 hours at the rotating speed of 300 rpm. Dissolving 7.5g of sodium hydroxide into 10mL of deionized water, cooling to room temperature, introducing nitrogen for 5min, adding the strong base solution into the reactor, filling nitrogen again, sealing, rotating at 300rpm, and carrying out mechanochemical reaction for 12 h. After the reactor was cooled to room temperature, deionized water was added under nitrogen protection in an ice bath. After cooling to room temperature, the mixed solution was washed to neutrality by centrifugation at 9000 rpm. Adding deionized water into the precipitate, centrifuging at 3500rpm for 5min, collecting supernatant, and freeze drying to obtain mechanochemical Ti₃C₂T_x。

Adopting the following steps: 1: 1, weighing the Ti prepared by mechanochemical reaction in example 2₃C₂T_xMixing, grinding and adding a proper amount of deionized water as a solvent. Uniformly coating the ground slurry on a copper foil, and drying the copper foil in vacuum at 120 ℃ for 12 hours to obtain a working electrode with the active material loading of about 0.72-0.94mg cm^-2. And assembling the electrode plates into a CR2025 button cell to perform electrochemical performance test. Assembling in Ar-filled glove box, water and oxygen partial pressure is less than 1.0ppm, metal lithium sheet for counter electrode, and electrolyte containing 1MLiPF₆In a 1: 1: 1 volume ratio, and the diaphragm is a polypropylene film (Celgard 2400). Half-cell electrochemical tests were carried out on a LAND CT2001A model cell tester with a voltage window of 0.01-3.0V (vs Li)⁺/Li)。

Example 3

Mixing Ti₃AlC₂Charging into a stainless steel reactor, Ti₃AlC₂The total weight is 1.0g, the mixture is sealed by filling nitrogen and mechanically reacted for 6 hours at the rotating speed of 300 rpm. Will be provided withDissolving 15.0g of sodium hydroxide into 10mL of deionized water, cooling to room temperature, introducing nitrogen for 5min, adding the strong base solution into the reactor, filling nitrogen again, sealing, rotating at 300rpm, and carrying out mechanochemical reaction for 12 h. After the reactor was cooled to room temperature, deionized water was added under nitrogen protection in an ice bath. After cooling to room temperature, the mixed solution was washed to neutrality by centrifugation at 9000 rpm. Adding deionized water into the precipitate, centrifuging at 3500rpm for 5min, collecting supernatant, and freeze drying to obtain mechanochemical Ti₃C₂T_x。

Adopting the following steps: 1: 1, weighing the Ti prepared by mechanochemical reaction in example 3₃C₂T_xMixing, grinding and adding a proper amount of deionized water as a solvent. Uniformly coating the ground slurry on a copper foil, and drying the copper foil in vacuum at 120 ℃ for 12 hours to obtain a working electrode with the active material loading of about 0.72-0.94mg cm^-2. And assembling the electrode plates into a CR2025 button cell to perform electrochemical performance test. Assembling in Ar-filled glove box, water and oxygen partial pressure is less than 1.0ppm, metal lithium sheet for counter electrode, and electrolyte containing 1MLiPF₆In a 1: 1: 1 volume ratio, and the diaphragm is a polypropylene film (Celgard 2400). Half-cell electrochemical tests were carried out on a LAND CT2001A model cell tester with a voltage window of 0.01-3.0V (vs Li)⁺/Li)。

Example 4

Mixing Ti₃AlC₂Charging into a stainless steel reactor, Ti₃AlC₂The total weight is 1.0g, the mixture is sealed by filling nitrogen and mechanically reacted for 12 hours at the rotating speed of 300 rpm. Dissolving 15.0g of sodium hydroxide into 10mL of deionized water, cooling to room temperature, introducing nitrogen for 5min, adding the strong base solution into the reactor, filling nitrogen again, sealing, rotating at 300rpm, and carrying out mechanochemical reaction for 6 h. After the reactor was cooled to room temperature, deionized water was added under nitrogen protection in an ice bath. After cooling to room temperature, the mixed solution was washed to neutrality by centrifugation at 9000 rpm. Deionized water was added to the precipitate and the precipitate was separated at 3500rpmTaking the core for 5min, collecting the supernatant, and freeze drying to obtain mechanochemical Ti₃C₂T_x。

Adopting the following steps: 1: 1, Ti prepared in mechanochemical preparation of example 4 was weighed₃C₂T_xMixing, grinding and adding a proper amount of deionized water as a solvent. Uniformly coating the ground slurry on a copper foil, and drying the copper foil in vacuum at 120 ℃ for 12 hours to obtain a working electrode with the active material loading of about 0.72-0.94mg cm^-2. And assembling the electrode plates into a CR2025 button cell to perform electrochemical performance test. Assembling in Ar-filled glove box, water and oxygen partial pressure is less than 1.0ppm, metal lithium sheet for counter electrode, and electrolyte containing 1MLiPF₆In a 1: 1: 1 volume ratio, and the diaphragm is a polypropylene film (Celgard 2400). Half-cell electrochemical tests were carried out on a LAND CT2001A model cell tester with a voltage window of 0.01-3.0V (vs Li)⁺/Li)。

Example 5

Mixing Ti₃AlC₂Charging into a stainless steel reactor, Ti₃AlC₂The total weight is 1.0g, the mixture is sealed by filling nitrogen and mechanically reacted for 12 hours at the rotating speed of 300 rpm. Dissolving 7.5g of sodium hydroxide and 7.5g of potassium hydroxide in 10mL of deionized water, cooling to room temperature, introducing nitrogen for 5min, adding the strong base solution into the reactor, filling nitrogen again, sealing, and carrying out mechanochemical reaction for 12h at the rotating speed of 300 rpm. After the reactor was cooled to room temperature, deionized water was added under nitrogen protection in an ice bath. After cooling to room temperature, the mixed solution was washed to neutrality by centrifugation at 9000 rpm. Adding deionized water into the precipitate, centrifuging at 3500rpm for 5min, collecting supernatant, and freeze drying to obtain mechanochemical Ti₃C₂T_x。

Adopting the following steps: 1: 1, weighing the Ti prepared by mechanochemical reaction in example 5₃C₂T_xMixing, grinding and adding a proper amount of deionized water as a solvent. The grinded slurry isUniformly coating the material on a copper foil, and vacuum drying at 120 deg.C for 12 hr to obtain a working electrode with active material loading of about 0.72-0.94mg cm^-2. And assembling the electrode plates into a CR2025 button cell to perform electrochemical performance test. Assembling in Ar-filled glove box, water and oxygen partial pressure is less than 1.0ppm, metal lithium sheet for counter electrode, and electrolyte containing 1MLiPF₆In a 1: 1: 1 volume ratio, and the diaphragm is a polypropylene film (Celgard 2400). Half-cell electrochemical tests were carried out on a LAND CT2001A model cell tester with a voltage window of 0.01-3.0V (vs Li)⁺/Li)。

Comparative example 1

0.998g of lithium fluoride (LiF) was added to 10mL of concentrated hydrochloric acid solution (HCl, 9.0M) and stirred for 10 minutes to dissolve the solid. Under ice-bath condition, 1.0g of Ti₃AlC₂The powder was slowly added to the above solution, followed by reaction at a constant temperature of 35 ℃ for 24 hours. After etching for 24h, the resulting multilayer Ti₃C₂T_xWashed with deionized water and centrifuged (3500rpm) until the pH was about 6. A plurality of layers of Ti₃C₂T_xAdding into 20mL deionized water, and carrying out ultrasonic treatment for 1h in an ice bath under the Ar atmosphere. Centrifuging the solution obtained by ultrasonic treatment at 3500rpm for 1h, collecting dark green supernatant, and freeze drying to obtain Ti prepared by conventional method₃C₂T_x。

Adopting the following steps: 1: 1, weighing Ti prepared by the conventional method of comparative example 1₃C₂T_xMixing, grinding and adding a proper amount of deionized water as a solvent. Uniformly coating the ground slurry on a copper foil, and drying the copper foil in vacuum at 120 ℃ for 12 hours to obtain a working electrode with the active material loading of about 0.72-0.94mg cm^-2. And assembling the electrode plates into a CR2025 button cell to perform electrochemical performance test. Assembling in a glove box filled with Ar, wherein the water and oxygen partial pressure is less than 1.0ppm, the metal lithium sheet for counter electrode contains 1M LiPF as electrolyte₆The volume ratio of Ethylene Carbonate (EC)/dimethyl carbonate (DMC)/diethyl carbonate (DEC) solution is 1: 1: 1, and the diaphragm isPolypropylene film (Celgard 2400). Half-cell electrochemical tests were carried out on a LAND CT2001A model cell tester with a voltage window of 0.01-3.0V (vs Li)⁺/Li)。

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. Mechanochemical method for preparing Ti with high lithium storage capacity₃C₂T_xThe method is characterized by comprising the following steps:

(1) mixing Ti₃AlC₂Loading into stainless steel reactor, charging nitrogen gas, sealing, and mechanically reacting for 2-24 hr;

(2) dissolving 5.0-15.0g of alkali metal hydroxide in deionized water to prepare supersaturated strong base solution, adding the supersaturated strong base solution into the reactor in the step (1), filling nitrogen and sealing, and carrying out mechanochemical reaction for 2-24 h; the alkali metal hydroxide comprises one or a mixture of more of LiOH, NaOH and KOH;

(3) after the reaction is finished, adding deionized water into the product of the mechanochemical reaction in the step (2) under the conditions of nitrogen protection and ice bath for dissolving and cooling, washing the cooled product to be neutral, adding deionized water, taking supernate obtained after centrifugation at 3500rpm, and freeze-drying to obtain Ti₃C₂T_x。

2. The mechanochemical method for preparing Ti with high lithium storage capacity according to claim 1₃C₂T_xCharacterized in that, in step (1), the Ti is₃AlC₂The total weight is 1.0-3.0 g.

3. The mechanochemical method for preparing Ti with high lithium storage capacity according to claim 1₃C₂T_xThe method of (3), wherein the time for centrifugation in step (3) is 5 min.