CN111540887A - Carbon-coated cobaltosic oxide and tin dioxide composite lithium battery material and preparation method thereof - Google Patents

Abstract

The invention discloses a carbon-coated cobaltosic oxide and tin dioxide compound lithium battery material and a preparation method thereof.

Description

A kind of carbon-coated tricobalt tetroxide and tin dioxide composite lithium battery material and preparation method thereof

technical field

The invention belongs to the field of material chemistry, and particularly relates to a carbon-coated tricobalt tetroxide and tin dioxide composite lithium battery material and a preparation method thereof.

Background technique

With the continuous development of human economy and society and the continuous advancement of the process of economic globalization, the consumption of fossil fuels has made the problems of environmental pollution and energy shortage increasingly prominent. Humans have begun to realize the importance of green environmental protection and sustainable development. It is of great strategic significance to develop clean and sustainable renewable energy and efficient energy storage systems, and to realize the rational allocation of renewable energy. Lithium-ion batteries (LIBs) have the advantages of high specific energy, low self-discharge, good cycle performance, no memory effect, and environmental protection. They are the most promising high-efficiency secondary batteries and the most mature chemical energy storage power source. In today's world, lithium-ion batteries have a wide range of applications, ranging from mobile phones, computers, electric vehicles, to Mars landers, UAVs, Earth orbiters, civil aviation aircraft and other aerospace vehicles, lithium-ion batteries play an important role. , With the development of strategic emerging industries such as energy saving and environmental protection, information technology, new energy vehicles and aerospace, human beings have put forward higher requirements for the performance of lithium secondary batteries, and researchers urgently need to research and develop on the basis of material innovation High-efficiency lithium secondary battery with higher energy density and higher safety. At present, the main factors restricting the improvement of the performance of high-performance lithium-ion batteries are the lack of systematic electrochemical theory of lithium-ion batteries, new lithium-ion battery systems, and high-performance lithium storage materials. The core and key of lithium-ion batteries is the development and application of new lithium storage materials and electrolyte materials. Nanomaterials have attracted widespread attention due to their special effects such as small size effects, quantum effects, surface effects, and macroscopic quantum orbital effects. Lithium storage materials for high-performance lithium secondary batteries.

Nanomaterials refer to materials that have at least one dimension in the three-dimensional space in the nanoscale range or are composed of nanostructures as basic units. Due to these characteristics, nanomaterials have characteristics that ordinary materials do not have. Nanomaterials can be used as optical materials, electronic materials, etc. Materials, magnetic materials and high-strength, high-density materials have been widely used in catalysis, biomedicine, environmental protection, engineering materials and other fields. The synthesis methods of one-dimensional nanomaterials mainly include phase transfer method, hydrothermal method, electrospinning method, chemical vapor deposition method, vapor evaporation method, etc. Among them, electrospinning technology is the most simple and effective method to prepare continuous nanofibers, S. Agarwal et al. (Progress in Polymer Science, 2013, 38:963-991) reviewed the working principle of electrospinning and its application in optoelectronic devices. The electrospinning device is mainly composed of a spinning needle, a high-voltage device, a spinning collector, a temperature and humidity control device and other device parts. In the process of electrospinning, the solution ejected from the needle is subjected to both electrostatic field force and solution surface tension. When the electrostatic field force and surface tension of the small droplets are balanced, a Taylor cone will be formed at the needle ( Taylor), when the voltage continues to increase so that the electrostatic field force received by the droplet is greater than the surface tension, the droplet will be stretched into fibers and continue to be sprayed on the spinning collector under the action of the electrostatic field force to be collected. The morphology of spinning fibers is mainly affected by the following factors: system parameters (such as the molecular weight of the polymer, conductivity, viscosity, dielectric constant of the precursor solution, etc.), operating parameters (such as the size of the needle, voltage, flow rate, distance between the spinneret and the spinning collection device, etc.), environmental parameters (such as humidity, temperature, etc.), in addition, parameters during the annealing process of spinning fibers (such as calcination temperature, atmosphere, heating rate, etc.) The structure, morphology, and performance have a great impact.

Transition metal oxide Co ₃ O ₄ is an important magnetic p-type semiconductor, which is widely used in lithium-ion batteries, supercapacitors, gas sensors and catalysts. Its preparation methods include thermal decomposition, chemical spray thermal decomposition , chemical vapor deposition method, electrospinning method, sol-gel method and other methods, due to the different preparation methods of Co ₃ O ₄ , the morphology is also very different, including nanospheres, nanocubes, nanorods, nanosheets, nanofibers Different morphologies lead to different properties of materials. Q. Yang et al. (Applied Surface Science, 2018, 443:401-406) reported that Co ₃ O ₄ encapsulated in carbon nanofibers as a negative electrode material for Li-ion batteries maintained 1024.1 mA h after 100 charge-discharge cycles ^{- 1} , the metal oxide _SnO is an n-type wide-bandgap semiconductor material, which has broad applications in catalysis, gas sensing devices, lithium-ion batteries, etc., J. Liu et al. (Chemical Cummunications, 2010, 46: 1437-1439) reported SnO ₂ @C core-shell structure as a negative electrode material for Li-ion batteries, and the capacity remained 630 mA h ^{-1 after 50 charge-discharge cycles at a current density of 100 mA g -1 .} Liu Yuzhou et al. reported a composite nanowire of cobalt tetroxide and tin oxide, but its capacity is too low as a lithium battery material (application number 201910990193.2), and it shows good catalytic performance in organic synthesis catalytic oxidation. Carbon coating is beneficial to improve the electrical conductivity and electrochemical performance of materials, so this technology is widely used.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a carbon-coated tricobalt tetroxide and tin dioxide composite lithium battery material and a preparation method thereof by using the combination of electrospinning technology and high temperature sintering technology.

The technical solution adopted by the present invention in order to solve the above technical problems is: a preparation method of carbon-coated tricobalt tetroxide and tin dioxide composite lithium battery material, the preparation method utilizes electrospinning technology to obtain cobalt acetate tetrahydrate, cobalt acetate tetrahydrate, Dibutyltin diacetate is the main raw material, an appropriate amount of macromolecule is added as a binder, stirred for a period of time, and a clear and transparent spinning precursor is obtained. Electrospinning technology is used to prepare electrospinning products under high voltage conditions. Sintering is carried out under the atmosphere of air and nitrogen in the furnace to obtain a carbon-coated tricobalt tetroxide and tin dioxide composite lithium battery material, which specifically includes the following steps:

(1) Add N,N-dimethylformamide (DMF) and anhydrous ethanol to a beaker, add an appropriate amount of dibutyltin diacetate ((C ₄ H ₉ ) ₂ Sn(OOCCH ₃ ) ₂ ) and cobalt acetate tetra Hydrate (C ₄ H ₆ CoO ₄ ·4H ₂ O), adjust the pH of the solution to 4-6 with glacial acetic acid, and stir for 2 hours to obtain a clear and transparent solution A;

(2) adding an appropriate amount of PVP (K-130, polyvinylpyrrolidone) into the beaker containing solution A, and stirring for 3h to obtain clear and transparent spinning precursor solution B;

(3) Put the clear and transparent precursor solution B into the syringe, the voltage is 15-18kV, the vertical distance between the spinning needle and the receiver is 13-16cm, the flow rate is 0.7-1.0mL h ^-1 , the spinning box is Electrospinning is carried out under the conditions of temperature of 30～40℃ and humidity of 20%～30% to obtain electrospinning products, and drying at 80℃ for 5h;

(4) Transfer the dried electrospinning product to the air atmosphere of a tube furnace, sinter at 400-500°C for 3 hours, and then sinter at 700-800°C for 1-2 hours in a nitrogen atmosphere to obtain a carbon coating Cobalt tetroxide and tin dioxide composite lithium battery material;

The carbon content in the composite lithium battery material is 5-10% by mass;

The chemical formula of the composite lithium battery material is abbreviated as Co ₃ O ₄ ·SnO ₂ @C;

The solvents and synthetic raw materials are all chemically pure.

In some embodiments of the present invention, the molar ratio of dibutyltin diacetate to cobalt acetate tetrahydrate is 1:1, and the mass ratio of PVP to dibutyltin diacetate is 2:0.7.

Further, the present invention also provides the carbon-coated tricobalt tetroxide and tin dioxide composite lithium battery material obtained by the above preparation method, and the composite nanorod is used as the negative electrode material of the lithium battery, under the current density of 800mA g ^-1 , the cycle is 400 times. , the discharge specific capacity can be maintained above 91mAh·g ^-1 , and the Coulomb efficiency can be maintained at 93%.

Compared with the prior art, the characteristics of the carbon-coated tricobalt tetroxide and tin dioxide composite lithium battery material synthesized by the electrospinning technology of the present invention are as follows:

(1) The carbon-coated Co ₃ O ₄ ·SnO ₂ composite was prepared by electrospinning and high temperature sintering technology;

(2) The composite lithium battery material increases the contact area between the electrode material and the electrolyte due to its nanometer size, shortens the transport path of Li ⁺ , and improves the transport rate of lithium ions;

(3) Carbon coating can effectively alleviate the volume expansion effect of metal oxides during the charging and discharging process, and also increase the electrical conductivity of the composite material and improve the theoretical specific capacity of the composite material.

Description of drawings

Fig. 1 is the XRD pattern of the composite lithium battery material obtained by the present invention;

Fig. 2 is the SEM image of the composite lithium battery material prepared by the present invention;

FIG. 3 is a graph of the charge-discharge cycle performance and Coulomb efficiency graph of the composite prepared by the present invention as a negative electrode material for a lithium ion battery at a current density of 800 mA g ^-1 .

Detailed ways

The present invention will be further described in detail below with reference to the examples. The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of specific embodiments.

Example 1:

5.0 mL of N,N-dimethylformamide and 5.0 mL of absolute ethanol were added to the beaker, 0.498 g (2 mmol) of cobalt acetate tetrahydrate (C ₄ H ₆ CoO ₄ ·4H ₂ O) and 0.70 g (2 mmol) of cobalt acetate tetrahydrate were added to the beaker. ) Dibutyltin diacetate ((C ₄ H ₉ ) ₂ Sn(OOCCH ₃ ) ₂ ), adjust the pH of the solution with glacial acetic acid to be 4, stir for 2h to obtain a transparent and clear solution A, add 2.0g of PVP (K-130, poly Vinylpyrrolidone) was added to solution A, stirred for 3h to form a clear and transparent spinning precursor solution B, and the clear and transparent spinning precursor solution B was loaded into the syringe, at a voltage of 15kV, the vertical distance between the spinning needle and the receiver Electrospinning was carried out under the conditions of 13 cm, flow rate 0.7 mL h ^-1 , the temperature of the spinning box body was 30 °C, and the air humidity in the box was 20%. Dry at ℃ for 5h; transfer the dried electrospinning product to the crucible of the tube furnace, sinter at 400℃ for 3h in an air atmosphere, and then sinter at 700℃ for 1h in a nitrogen atmosphere to obtain a black powder product, which is a A carbon-coated tricobalt tetroxide and tin dioxide composite; elemental analysis of the obtained product shows that the mass percentage of carbon is 10%; X-ray powder diffraction is used for testing and analysis, and the results show that the prepared product is carbon-coated Co ₃ O The composite of ₄ and _SnO2 (Fig. 1); observation and analysis by scanning electron microscope showed that the morphology of the as-prepared product was nanorods (Fig. 2), and the obtained product was used as a negative electrode material for lithium-ion batteries, at 800 mA g ^-1 Under the current density, the cycle performance was tested by charging and discharging. The results showed that the discharge specific capacity could be maintained above 91mAh·g ^-1 and the Coulomb efficiency could be maintained at 93% after 400 cycles (Fig. 3).

Example 2:

5.0 mL of N,N-dimethylformamide and 5.0 mL of absolute ethanol were added to the beaker, 0.498 g (2 mmol) of cobalt acetate tetrahydrate (C ₄ H ₆ CoO ₄ ·4H ₂ O) and 0.70 g (2 mmol) of cobalt acetate tetrahydrate were added to the beaker. ) dibutyltin diacetate ((C ₄ H ₉ ) ₂ Sn(OOCCH ₃ ) ₂ ), adjust the pH of the solution with glacial acetic acid to be 6, stir for 2 h to obtain a transparent and clear solution A, mix 2.0 g of PVP (K-130, poly Vinylpyrrolidone) was added to solution A, stirred for 3h to form a clear and transparent spinning precursor solution B, put the clear and transparent spinning precursor solution B into a syringe, at a voltage of 18kV, the vertical distance between the spinning needle and the receiver Electrospinning was carried out under the conditions of 16 cm, flow rate 1.0 mL h ^-1 , the temperature of the spinning box body was 40 °C, and the air humidity in the box was 30%. Dry at ℃ for 5h; transfer the dried electrospinning product to the crucible of the tube furnace, sinter at 500℃ for 3h in an air atmosphere, and then sinter at 800℃ for 2h in a nitrogen atmosphere to obtain a black powder product, which will be obtained Elemental analysis was carried out, and the results showed that the mass percentage of carbon was 5%; the composition and structure of the product were analyzed by X-ray powder diffraction; the morphology of the test product was analyzed by scanning electron microscopy, and the obtained product was used as a negative electrode material for lithium ion batteries. The charge-discharge cycle performance and Coulomb efficiency were tested at a certain current density.

Example 3:

5.0 mL of N,N-dimethylformamide and 5.0 mL of absolute ethanol were added to the beaker, 0.498 g (2 mmol) of cobalt acetate tetrahydrate (C ₄ H ₆ CoO ₄ ·4H ₂ O) and 0.70 g (2 mmol) of cobalt acetate tetrahydrate were added to the beaker. ) dibutyltin diacetate ((C ₄ H ₉ ) ₂ Sn(OOCCH ₃ ) ₂ ), adjust the pH of the solution to 5 with glacial acetic acid, stir for 2 h to obtain a transparent and clear solution A, add 2.0 g of PVP (K-130, poly Vinylpyrrolidone) was added to solution A, stirred for 3h to form a clear and transparent spinning precursor solution B, and the clear and transparent spinning precursor solution B was loaded into the syringe, at a voltage of 16.5kV, the spinning needle and the receiver were vertical The distance was 15 cm, the flow rate was 0.8 mL h ^-1 , the temperature of the spinning box was 35 °C, and the air humidity in the box was 25%. Dry at 80°C for 5h; transfer the dried electrospinning product to the crucible of the tube furnace, sinter at 450°C for 3h in an air atmosphere, and then sinter at 750°C for 1.5h in a nitrogen atmosphere to obtain a black powder product. The obtained product was subjected to elemental analysis, and the result showed that the mass percentage of carbon was 7%; the composition structure of the product was analyzed by X-ray powder diffraction; the morphology of the test product was analyzed by scanning electron microscope, and the obtained product was used as a lithium ion battery negative electrode material , and test its charge-discharge cycle performance and Coulomb efficiency at a certain current density.

Claims (3)

1. A preparation method of a carbon-coated cobaltosic oxide and tin dioxide compound lithium battery material is characterized by comprising the following steps:

(1) adding N, N-dimethylformamide and absolute ethyl alcohol into a beaker, adding a proper amount of dibutyltin diacetate and cobalt acetate tetrahydrate, regulating the pH of the solution to be 4-6 by using glacial acetic acid, and stirring for 2 hours to obtain a clear and transparent solution A;

(2) adding a proper amount of PVP into a beaker containing the solution A, and stirring for 3 hours to obtain a clear and transparent spinning precursor solution B;

(3) filling the clear transparent precursor solution B into an injector, wherein the voltage is 15-18 kV, the vertical distance between a spinning needle and a receiver is 13-16 cm, and the flow rate is 0.7-1.0 mL h^-1Carrying out electrostatic spinning under the conditions that the temperature of a spinning box body is 30-40 ℃ and the humidity is 20-30% to obtain an electrostatic spinning product, and drying for 5 hours at 80 ℃;

(4) transferring the dried electrostatic spinning product to a tubular furnace in an air atmosphere, sintering at the temperature of 400-500 ℃ for 3h, and then sintering at the temperature of 700-800 ℃ for 1-2 h in a nitrogen atmosphere to obtain a carbon-coated cobaltosic oxide and tin dioxide composite lithium battery material;

the composite lithium battery material contains 5-10% of carbon by mass;

the chemical formula of the composite lithium battery material is abbreviated as Co₃O₄·SnO₂@C；

The solvent and the synthetic raw materials are all chemically pure.

2. The production process according to claim 1, wherein the molar ratio of dibutyltin diacetate to cobalt acetate tetrahydrate is 1: 1, the mass ratio of PVP to dibutyltin diacetate is 2: 0.7.

3. the carbon-coated cobaltosic oxide and tin dioxide composite lithium battery material prepared by the preparation method of claim 1, wherein the composite nanorod is used as a lithium battery negative electrode material and has a current density of 800mAg^-1Under the condition, after the charge and discharge are cycled for 400 times, the specific discharge capacity can be kept at 91mAh g^-1Above, the coulombic efficiency can be maintained at 93%.

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