CN103715404B - A kind of preparation method of graphene oxide cladding lithium salts - Google Patents

Abstract

The present invention relates to the preparation method of a kind of graphene oxide cladding lithium salts.The method comprises following operating procedure: A, is added in N methylpyrrolidone solution by the Polyethylene Glycol of 3 20% mass percents, is stirred to dissolve, obtains solution A；B, adding in solution A by lithium salts, stirring makes dispersion, obtains solution B；C, take the graphene oxide being dispersed in dehydrated alcohol, wherein soluble solids mass ratio is 0.5% 5%), mix (suspension is 1:1 2.5 with the amount ratio of solution B) with solution B and stir, being heated to temperature is 70 ~ 100 DEG C, this temperature is kept to volatilize solution, obtaining moist solids, moist solids is dried through room temperature, to obtain final product.The method of the present invention for other cladding means, more energy-conserving and environment-protective, it is not required that special process, and without loss of material, it is easier to commercial production.

Description

A kind of preparation method of graphene oxide coated lithium salt

technical field

The invention relates to a preparation method of a composite material, in particular to a preparation method of graphene oxide-coated lithium salt.

Background technique

Graphene has a two-dimensional lattice structure, and the carbon atoms in the plane are connected by sp ² hybrid orbitals to form a hexagonal lattice structure, that is, carbon atoms are connected to three adjacent carbon atoms through strong σ bonds, and CC bonds Make graphene have good structural rigidity; the remaining one p electron orbit is perpendicular to the graphene plane, forming π bonds with surrounding atoms, and the delocalization of π electrons in the lattice makes graphene have good conductivity, room temperature The electron mobility on the lower plane is 1.5×104cm ² /V·s, far exceeding the conduction rate of electrons in general conductors, so it has great potential in microelectronics, aerospace military industry, energy storage devices, nanoelectronic devices, and nanocomposites. Broad potential application space. The lithium salt/graphene composite material can not only alleviate the volume effect of lithium salt particles during use through graphene, but also use the electron-hole pairs of graphene as a medium for high-speed electron migration. At present, the lithium salt/graphene mixture is mainly obtained by physical doping, that is, the prepared lithium salt and graphene are directly mixed.

Graphene oxide flakes are the product of graphite powder after chemical oxidation and exfoliation. Graphene oxide is a single atomic layer that can expand to tens of microns in lateral dimension at any time. Therefore, its structure spans the typical of general chemistry and materials science. scale. Graphene oxide can be regarded as an unconventional type of soft material with properties of polymers, colloids, films, and amphiphiles. Graphene oxide has long been regarded as a hydrophilic substance because of its superior dispersibility in water. However, related experimental results show that graphene oxide is actually amphiphilic, showing hydrophilicity from the edge to the center of the graphene sheet. to the hydrophobic property distribution. Therefore, graphene oxide can exist at the interface like a surfactant and reduce the energy between the interfaces.

Under the air condition of 0.01Pa ~ 10kPa, heat graphite oxide at a heating rate of 5 ~ 50℃/min to 150 ~ 600℃ for high vacuum heat treatment, maintain a constant temperature for 0.5 ~ 20h, the volume of graphite oxide expands rapidly, and a specific surface area of 200 ~ 800m ² /g, a graphene oxide material with an electrochemical specific capacity of 50-200F/g. Generally speaking, graphene oxide exhibits strong polarity due to the presence of groups such as -C-OH, -COC, and even -COOH. Dry graphene oxide is less stable in the air, and it is easy to absorb moisture to form hydrated graphene oxide. As an electrode material, graphene oxide has good discharge capacity and good wettability with electrolyte, but graphene oxide also has some shortcomings, such as relatively low conductivity of fluorinated graphite oxide, and its stability needs to be further improved, which leads to high current performance of the battery. Not enough.

The graphene used in the above methods is simply ultrasonically dispersed without adding other substances, and accompanied by high temperature heating process, the material will undergo a sharp change in temperature and finally form a composite material. The coating method has the problem of poor uniformity of dispersion and coating, and does not consider the effective effect of using more functional groups of graphene oxide on coating, and cannot effectively separate graphene oxide sheets, and the temperature drops sharply after high temperature heating. The change makes the graphene coating too tight, which affects the lithium ion intercalation and extraction efficiency.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned defects in the prior art, and provide a graphene oxide coating that is more energy-saving and environmentally friendly, does not require special processes, has no material loss, is easier for industrial production, and can improve the charging and discharging performance of lithium batteries. Preparation method of lithium salt.

In order to realize the above-mentioned purpose of the invention, the technical scheme of the present invention is as follows:

The preparation method of graphene oxide coated lithium salt of the present invention comprises the following steps:

A. Add polyethylene glycol with a weight percentage of 3-20% into the N-methylpyrrolidone solution, stir to dissolve, and obtain solution A;

B. Add lithium salt into solution A, stir to disperse, and obtain solution B;

C. Take the absolute ethanol suspension of graphene oxide with a weight percentage of 0.5%-5%, mix it with solution B, the volume ratio of the suspension to solution B is 1:1-2.5, stir evenly, and heat to a temperature of 70~100°C, keep the temperature and evaporate the solution to obtain a wet solid, which can be obtained after drying at normal temperature.

In the step A, during the process of dissolving the polyethylene glycol in the N-methylpyrrolidone solution, the solution system is heated, and the temperature is controlled at 30-95°C to promote the dissolution of the polyethylene glycol. Remove from heat and cool to room temperature.

The graphene oxide suspension in step C is prepared in the following way: adding graphene oxide into absolute ethanol and stirring evenly, and then performing ultrasonic treatment to obtain the suspension.

The present invention also provides a graphene oxide-coated lithium salt composite material, which is prepared by the preparation method described in any one of claims 1-3.

The graphene oxide-coated lithium salt composite material can be used as a lithium ion battery positive electrode material in the manufacture of lithium batteries.

The coating method adopted in the present invention introduces a solvent system innovatively, so that the lithium salt coated with graphene oxide can not be reacted at high temperature, and only through the compounding of the components in the solvent, the solvent can be volatilized to realize the composite material. Production preparation.

In the method of the present invention, polyethylene glycol is cleverly used as one of the raw materials, and polyethylene glycol helps the dispersion of graphene oxide sheets. Polyethylene glycol is combined with functional groups on the surface of graphene oxide and coated on lithium Large particles are formed on the surface of the salt, which increases the surface area of the particles and reduces the contact area with the electrolyte. The growth of the coated lithium salt particles does not exceed the limit, and is still micron-sized, with excellent properties of micron-sized materials. .

The coating method of the present invention does not require high-temperature heating, is more energy-saving and environment-friendly, has simple process, no material loss, better dispersion performance, and is easier for industrial production.

After the lithium salt/polyethylene glycol/graphene oxide composite material prepared by the invention is applied to a lithium battery, its charging and discharging performance can be improved.

Description of drawings

Figure 1 Uncoated LiMn2O4 cycle diagram;

Fig. 2 embodiment 1-3 three groups of experimental scheme cycle diagrams.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments.

Example 1

1. Preparation of graphene oxide suspension: adding 0.5% graphene oxide by weight into absolute ethanol and stirring evenly, and then performing ultrasonic treatment;

2. Add 3% polyethylene glycol by weight into the N-methylpyrrolidone solution, stir to dissolve, and obtain solution A;

3. Add lithium salt into solution A, stir to disperse, and obtain solution B;

4. Take the graphene oxide suspension and add it to solution B. The volume ratio of the suspension to solution B is 1:1.5. Stir evenly and heat to a temperature of 70°C. Keep the temperature and evaporate the solution to obtain a wet solid. The wet solid is in Dry at room temperature.

Example 2

1. Preparation of graphene oxide suspension: adding 5% graphene oxide by weight into absolute ethanol and stirring evenly, and then performing ultrasonic treatment;

2. Add polyethylene glycol with a weight percentage of 20% into the N-methylpyrrolidone solution, stir, and heat the solution system during the stirring process. The temperature is controlled at 30°C, the polyethylene glycol is dissolved, and cooled to room temperature to obtain a solution A;

3. Add lithium salt into solution A, stir to disperse, and obtain solution B;

4. Take the graphene oxide suspension and add it to solution B. The volume ratio of the suspension to solution B is 1:2.5. Stir evenly and heat to a temperature of 100°C. Keep the temperature and evaporate the solution to obtain a wet solid. The wet solid is in Dry at room temperature.

Example 3

1. Preparation of graphene oxide suspension: adding 3% graphene oxide by weight into absolute ethanol and stirring evenly, and then performing ultrasonic treatment;

2. Add polyethylene glycol with a weight percentage of 10% into the N-methylpyrrolidone solution, stir, heat the solution system during the stirring process, control the temperature at 70°C, dissolve the polyethylene glycol, and cool to room temperature to obtain a solution A;

3. Add lithium salt into solution A, stir to disperse, and obtain solution B;

4. Take the graphene oxide suspension and add it to solution B. The volume ratio of the suspension to solution B is 1:1.8. Stir evenly and heat to a temperature of 90°C. Keep the temperature and evaporate the solution to obtain a wet solid. The wet solid is in Dry at room temperature.

Example 4

1. Preparation of graphene oxide suspension: adding 2% graphene oxide by weight into absolute ethanol and stirring evenly, and then performing ultrasonic treatment;

2. Add polyethylene glycol with a weight percentage of 15% into the N-methylpyrrolidone solution, stir, heat the solution system during the stirring process, and control the temperature at 50°C, dissolve the polyethylene glycol, and cool to room temperature to obtain a solution A;

3. Add lithium salt into solution A, stir to disperse, and obtain solution B;

4. Take the graphene oxide suspension and add it to solution B. The volume ratio of the suspension to solution B is 1:2.2. Stir evenly and heat to a temperature of 80°C. Keep the temperature and evaporate the solution to obtain a wet solid. The wet solid is in Dry at room temperature.

Example 5

1. Preparation of graphene oxide suspension: add 1% graphene oxide by weight into absolute ethanol and stir evenly, then perform ultrasonic treatment;

2. Add polyethylene glycol with a weight percentage of 8% into the N-methylpyrrolidone solution, stir, heat the solution system during the stirring process, and control the temperature at 80°C, dissolve the polyethylene glycol, and cool to room temperature to obtain a solution A;

3. Add lithium salt into solution A, stir to disperse, and obtain solution B;

4. Take the graphene oxide suspension and add it to solution B. The volume ratio of the suspension to solution B is 1:2.1. Stir evenly and heat to a temperature of 75°C. Keep the temperature and evaporate the solution to obtain a wet solid. The wet solid is in Dry at room temperature.

Example 6

Take the uncoated LiMn2O4 and the LiMn2O4 coated with the embodiment of the present invention 1, 2, 3 to carry out the lithium-ion battery capacity test comparison, the test instrument is Xinwei BTS-3008W high-precision battery tester, the test condition is: voltage range 3 —4.3V, the current range is 0.1C, 0.5C, 1C, and the number of cycles is 60 times. The results are shown in Table 1:

Table 1 The first discharge specific capacity and capacity retention rate

Claims (4)

1. the preparation method of a graphene oxide cladding lithium salt composite, it is characterised in that comprise following Operating procedure:

A, Polyethylene Glycol that percentage by weight is 3-20% being added in N-Methyl pyrrolidone solution, stirring makes Dissolve, obtain solution A

B, adding in solution A by lithium salts, stirring makes dispersion, obtains solution B；

C, take the dehydrated alcohol suspension of the graphene oxide that percentage by weight is 0.5%-5%, mix with solution B Closing, suspension is 1:1-2.5 with the volume ratio of solution B, stirs, and being heated to temperature is 70～100 DEG C, Keeping this temperature to volatilize solution, obtain moist solids, moist solids is dried through room temperature, to obtain final product；

In described step A, during Polyethylene Glycol is dissolved in N-Methyl pyrrolidone solution, to solution System heats, and temperature controls, at 30～95 DEG C, to promote the dissolving of Polyethylene Glycol, to stop until completely dissolved Only heating, is cooled to room temperature.

2. wanting the preparation method of graphene oxide cladding lithium salt composite described in 1 according to right, its feature exists In:

Described step C graphene oxide suspension is prepared: add graphene oxide into dehydrated alcohol In stir, then carry out supersound process, to obtain final product.

3. a graphene oxide cladding lithium salt composite, it is characterised in that: it is by such as claim 1 Or preparation method that 2 described in any one is prepared from.

4. graphene oxide cladding lithium salt composite as claimed in claim 3 is as lithium ion cell positive Application in material.