CN113184898A

CN113184898A - Tin dioxide-carbon core-shell nanosphere composite material, and preparation method and application thereof

Info

Publication number: CN113184898A
Application number: CN202110496425.6A
Authority: CN
Inventors: 李奇; 刘肖; 张翠; 白锋
Original assignee: Henan University
Current assignee: Henan University
Priority date: 2021-05-07
Filing date: 2021-05-07
Publication date: 2021-07-30
Anticipated expiration: 2041-05-07
Also published as: CN113184898B

Abstract

The invention discloses a tin dioxide-carbon core-shell nanosphere composite material, a preparation method and application thereof, and belongs to the technical field of lithium ion battery electrode materials. The tin dioxide-carbon core-shell nanosphere composite material is composed of nitrogenThe shell layer formed by doping carbon and the core of the tin dioxide uniformly embedded in the carbon form the composite material, wherein the conductive nitrogen-doped carbon shell layer completely covers the tin dioxide-carbon central nanospheres, and meanwhile, the particle size of tin dioxide particles is about 2 nm-5 nm and does not contain large tin dioxide particles with the particle size of more than 50 nm. The composite material not only effectively relieves SnO₂The volume of the conductive material is expanded, the conductivity is remarkably improved, and a rapid electron transfer path is provided. At the same time, the nitrogen-doped carbon shell also serves as armor to ensure SnO in the cyclic process₂The structure stability of the/carbon composite nanosphere.

Description

Tin dioxide-carbon core-shell nanosphere composite material, and preparation method and application thereof

Technical Field

The invention belongs to the technical field of lithium ion battery electrode materials, and particularly relates to a tin dioxide-carbon core-shell nanosphere composite material, and a preparation method and application thereof.

Background

With the rapid development of electric vehicles, people put higher demands on lithium ion batteries. The specific capacity of the common graphite cathode is low (372 mAh g)^-1) And the high energy consumption requirement cannot be met. Metal oxides of high theoretical capacity have received much attention as alternative negative electrode materials for high efficiency lithium ion batteries. Tin dioxide (SnO)₂) Because of its higher theoretical capacity (1494 mAh g)^-1) Low toxicity and high natural abundance, and has been widely researched. Alloying process of Sn and Li (Sn +4.4 Li +4.4 e)^-⇋ li4.4sn) has a significant contribution to LIBs capacity, but this process leads to milling, aggregation, fast capacity fade, poor rate performance due to large volume expansion (ca 300% when fully lithiated). In the past decades, the exploration for SnO₂A great deal of effort is made as a next-generation anode, but the problems of rapid capacity fade and poor rate performance are still not solved.

To solve these problems, further development of advanced-architecture SnO is required₂And (3) a base anode material. Reasonably designed nano SnO₂The structure is capable of effectively controlling the internal strain caused by lithiation/delithiation, and is a strategy capable of providing better reversibility. Furthermore, nano SnO₂And the diffusion path of Li ions can be effectively shortened, and the contact area with the electrolyte is increased, so that the rate capability is improved. However, since nano SnO₂Self-aggregation and low conductivity of (b), resulting in nanosized SnO₂The cycling performance of the anode material is still limited. The second strategy is to design a tin dioxide-soft material nanocomposite (e.g., SnO)₂Carbon) to solve self-aggregation and the like. Carbon matrix made ofIs a barrier layer against Li_xSn aggregates to serve as a conductive layer, promoting electron conduction. Meanwhile, the porous structure of the carbon matrix may partially accommodate Li_xThe volume of Sn changes, facilitating rapid migration of Li +. A third effective method is in nano SnO₂The particles are coated with a highly conductive material (e.g., N-doped carbon) to significantly increase conductivity, stabilize Solid Electrolyte Interface (SEI), and maintain mechanical integrity during charging and discharging. Although the above three approaches to solve the problem can improve SnO to some extent₂Based on the electrochemical properties of LIBs, but synthesizing SnO with high rate performance and stable cycle performance₂The base anode material remains a formidable challenge.

Disclosure of Invention

Based on the defects of the prior art, the invention aims to provide a tin dioxide-carbon core-shell nanosphere composite material, a preparation method and application thereof.

In order to achieve the purpose, the invention adopts the technical scheme that:

a preparation method of a stannic oxide-carbon core-shell nanosphere composite material comprises the following steps:

(1) preparation of polymeric microspheres (pMS): dissolving ethylene glycol dimethacrylate (1.5-2.5 g), alpha-methacrylic acid (6.0-10.0 g) and azobisisobutyronitrile (0.1-0.4 g) in 300-500 mL of acetonitrile in a drying flask, distilling, precipitating and copolymerizing, and standing and passivating the product by absolute ethyl alcohol to obtain polymer microspheres (pMS) with the particle size range of 200-500 nm;

(2) preparation of tin polymer microspheres (Sn-pMS) by cation exchange: dissolving anhydrous sodium acetate (0.7-1.2 g) in absolute ethyl alcohol, then adding the synthesized polymer microsphere pMS (0.1-0.4 g) under stirring, stirring for 10-15 hours, centrifuging, washing the precipitate with absolute ethyl alcohol for several times, and then pouring into a reactor dissolved with SnCl₂•2H₂Stirring the mixture in an absolute ethanol solution of O (0.5 g to 0.8 g) for 20 to 30 hours. Centrifugally separating the precipitate, washing with absolute ethyl alcohol, and finally freeze-drying to obtain the tin polymer microsphere Sn-pMS;

(3) preparation of monodisperse pre-oxidized nanospheres: Sn-pMS powder is put in air at the temperature of less than 5 ℃ for min^-1The temperature is raised to 280-320 ℃ at the temperature raising speed, and the mixture is heated and oxidized for 2-5 hours. Dispersing the nanospheres (0.1-0.3 g) in water by using ultrasonic waves, transferring the nanospheres into a reaction kettle, preserving the heat for 4-6 hours at the temperature of 120-180 ℃, and performing centrifugal separation to obtain monodisperse pre-oxidized nanospheres after the nanospheres are cooled to room temperature;

(4) tin dioxide-carbon core-shell composite nanospheres: dispersing 0.1-0.3 g of the pre-oxidized nanospheres in a trihydroxymethyl aminomethane hydrochloric acid buffer solution, adding dopamine with the same mass as the pre-oxidized nanospheres, continuously stirring for 20-30 h, centrifuging, freeze-drying to obtain dopamine-coated nanospheres, and finally calcining the dopamine-coated nanospheres for 1-5 h at 400-600 ℃ under a protective atmosphere to obtain the tin dioxide-carbon core-shell nanosphere composite material.

Further, in the step (2), 0.7 g to 1.2g of anhydrous sodium acetate is dissolved in 100mL of anhydrous ethanol, and 0.5 g to 0.8 g of SnCl is added₂•2H₂O is dissolved in 100mL of absolute ethanol, and freeze-drying means freeze-drying at 5 ℃ or below to obtain a solid.

Further, in the step (3), the tin polymer microspheres are placed in the air for less than 5 ℃ for min^-1The temperature is raised to 300 ℃ at the temperature raising speed, the oxidation is carried out for 4h, and the temperature is kept in the reaction kettle for 5h at the temperature of 150 ℃.

Further, in the step (4), 0.1 g to 0.3 g of the pre-oxidized nanospheres are dispersed in 150mL of tris (hydroxymethyl) aminomethane hydrochloride buffer solution, wherein the tris (hydroxymethyl) aminomethane hydrochloride buffer solution is prepared by dissolving 186 mg of tris (hydroxymethyl) aminomethane hydrochloride in 150mL of water, and freeze drying refers to dissolving a product obtained after centrifugal separation in a proper amount of tert-butyl alcohol and freeze drying the product at a temperature of below 5 ℃ to obtain a solid.

Further, in the step (4), the dopamine-coated nanospheres are coated in N₂Calcining for 3h at 500 ℃ under the atmosphere.

The stannic oxide-carbon core-shell nanosphere composite material prepared by the preparation method.

The tin dioxide-carbon core-shell nanosphere composite material is applied as a lithium ion battery cathode material, and is prepared by mixing the tin dioxide-carbon core-shell nanosphere composite material withMixing acetylene black and polyvinylidene fluoride according to the mass ratio of 8:1:1, mixing with methyl-2-pyrrolidone to form slurry, coating the slurry on a copper foil, drying in vacuum, placing the copper foil in a glove box filled with Ar inert gas, taking Li foil as a counter electrode and a reference electrode, and taking 1M LiPF₆The ethylene carbonate/diethyl carbonate is used as electrolyte to assemble the battery.

Preferably, the vacuum drying refers to vacuum drying at 110 ℃ for 10 hours, and the loading capacity of the stannic oxide-carbon core-shell nanosphere composite material is 1.0 mg cm^-2The Li foil diameter is 16 mm.

The invention synthesizes the stannic oxide-carbon core-shell nanosphere composite lithium ion battery cathode material by a simple cation exchange method and subsequent calcination, and the composite material is uniformly distributed in nano SnO of the porous carbon nanosphere₂The core is coated with a shell layer formed by nitrogen-doped carbon. The composite material not only effectively relieves SnO₂The volume of the conductive material is expanded, the conductivity is remarkably improved, and a rapid electron transfer path is provided. At the same time, the nitrogen-doped carbon shell also serves as armor to ensure SnO in the cyclic process₂The structure stability of the/carbon composite nanosphere.

Drawings

FIG. 1 is an SEM image of polymer microspheres (pMS) prepared by distillation precipitation and a corresponding statistical size distribution;

FIG. 2 shows Sn²⁺Exchange for Na⁺SEM picture of the polymer microsphere prepared later;

FIG. 3 is SEM, TEM and corresponding XRD patterns of monodisperse microspheres prepared after hydrothermal treatment of pre-oxidized microspheres;

FIG. 4 is SEM, TEM and high resolution TEM images of the prepared pitaya-shaped stannic oxide-carbon core-shell nanosphere composite material;

FIG. 5 is an electrochemical impedance spectrum (a), a cyclic voltammogram (b), 0.1A g of a lithium ion battery assembled by the prepared tin dioxide/carbon @ nitrogen carbon core-shell nano-microspheres^-1Under current density, testing the cycling stability of the battery and corresponding coulombic efficiency (c), and multiplying power performance (d) of the battery under different current densities;

fig. 6 is a schematic structural diagram of the tin dioxide-carbon core-shell nanosphere composite lithium ion battery negative electrode material prepared by the present application.

Detailed Description

In order to make the technical purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention are further described with reference to specific examples, which are intended to explain the present invention and are not to be construed as limiting the present invention, and those who do not specify a specific technique or condition in the examples follow the techniques or conditions described in the literature in the art or follow the product specification.

Example 1

(1) ethylene glycol dimethacrylate (2.0 g, 10.1 mmol), α -methacrylic acid (8.0 g, 93.1 mmol), azobisisobutyronitrile (0.2067 g, 1.26mmol) were dissolved in 400 mL acetonitrile in a 500 mL dry two-necked flask and subjected to a typical distillation precipitation copolymerization process (Polymer 2006, 47, 5775-5784), yielding polymeric microspheres (designated pMS) with a particle size of about 400 nm. After polymerization, centrifuging, adding absolute ethyl alcohol again, centrifuging, and finally dispersing the polymer microspheres in absolute ethyl alcohol to ensure that the concentration of the polymer microspheres in absolute ethyl alcohol is 100 mg/ml, wherein a scanning electron microscope image and particle size statistics are shown in figure 1, and as can be seen from figure 1, the particle size of the prepared polymer microspheres is about 400 nm.

(2) Dissolving anhydrous sodium acetate (0.984 g) in 100mL anhydrous ethanol, adding 3mL ethanol dispersion of polymer microsphere under stirring (i.e. pMS addition amount is 0.3 g), stirring for 12 hr, centrifuging, washing precipitate with anhydrous ethanol for 2-3 times, pouring SnCl dissolved therein₂•2H₂And O (0.68 g) in 100mL of absolute ethyl alcohol solution, stirring for 24 hours, centrifugally separating precipitates, washing for 2-3 times by using absolute ethyl alcohol, and freeze-drying for 48 hours at the temperature of 5 ℃ to obtain the Sn-pMS, wherein the basic morphology of the pMS is basically maintained as shown in figure 2.

(3) 0.2 g of Sn-pMS powder is put in air at 1 ℃ for min^-1Speed ofHeating to 300 ℃, oxidizing for 4h at 300 ℃, and naturally cooling to room temperature to obtain the pre-oxidized nanospheres. The pre-oxidized nanospheres (0.2 g) were then dispersed into 70 mL of water using 400W ultrasound for 2 min. Then, transferring the product into a 100mL stainless steel autoclave lined with polytetrafluoroethylene, preserving the heat for 5h at 150 ℃, opening the autoclave, cooling to room temperature, performing centrifugal separation to obtain monodisperse pre-oxidized nanospheres, wherein a scanning and transmission electron microscope is shown as figure 3, the monodisperse pre-oxidized nanospheres inherit the appearance of the precursor after pretreatment, and the polymer microspheres can be seen to be in a monodisperse state from the large-range SEM scanning result₂Nanoparticles are small (<5 nm), which also corresponds to a broader diffraction peak in XRD. The X-ray diffraction (XRD) result shows that the crystallization degree is also improved to some extent.

(4) Dispersing monodisperse pre-oxidized nanosphere (0.2 g) in 150mL buffer of Tris hydrochloride (prepared by dissolving 186 mg Tris hydrochloride in 150mL water), adding dopamine (200 mg), stirring for 24 hr, polymerizing dopamine on nanosphere surface, centrifuging, dispersing the obtained product in 5 mL tert-butanol, freeze drying (drying at 5 deg.C for 24 hr), and freeze drying at 500 deg.C (at 1 deg.C for min)^-1Heating to 500 ℃ N₂Calcining for 3h under the atmosphere to obtain the tin dioxide-carbon core-shell nanosphere composite material shown in figure 4. From the TEM results, SnO was observed₂The particle diameter increases after heat treatment and the polymer microspheres have a uniform carbon layer on the outside. From the results of high resolution TEM, SnO can be seen₂The particle is about 5nm, and the thickness of the coating carbon layer is about 2-5 nm.

Mixing the prepared stannic oxide-carbon core-shell nanosphere composite material with acetylene black and polyvinylidene fluoride (PVDF) according to the mass ratio of 8:1:1, mixing the mixture with methyl-2-pyrrolidone (NMP) to form slurry, coating the slurry on a copper foil, and drying the slurry in vacuum at 110 ℃ for 10 hours, wherein the loading capacity of the stannic oxide-carbon core-shell nanosphere composite material is controlled to be 1.0 mg cm^-2Left and right. And in a glove box filled with Ar inert gas, with Li foil (diameter 16 mm) as counter and reference electrode, with 1M ethylene carbonate/diethyl carbonate of LiPF6 (EC/DEC 1:1 by volume)) The battery was assembled as an electrolyte. Cyclic Voltammograms (CVs), discharge-charge measurements (voltage range 0.005-3.0V) and Electrochemical Impedance Spectroscopy (EIS) measurements were performed and the electrochemical performance is shown in figure 5.

As shown in fig. 5, the electrochemical impedance spectrum shows that the charge transfer resistance of the assembled lithium ion battery is about 80 Ω; the significant reduction peak at the first cycle of 0.72V in the Cyclic Voltammetry (CV) curve is attributed to SnO₂Reduction to Sn and formation of solid electrolyte interphase layer (SEI), another reduction peak at 0.05V due to the alloying process of Li and Sn, a strong peak at 0.59V and a broad peak at 1.22V during anode scan corresponding to Li, respectively_xSn is detinned into Sn and the metallic Sn is reversibly oxidized. In subsequent cycles, the CV curves almost overlapped, indicating that the polymer electrode had excellent electrochemical reversibility; galvanostatic charge/discharge test evaluation the above samples were tested at 0.1A g at a potential window of 3.0-0.005V^-1The prepared electrode can still provide about 936.8 mAh g after 100 cycles^-1The coulombic efficiency of (1) is close to 99.0%. (ii) a FIG. 5d shows current densities of 0.1, 0.2, 0.4, 0.8, 1.6 and 3.2A g^-1Rate capability of the prepared electrode, even at 3.2A g^-1The average specific capacity is still maintained at 460.0 mA h g under the high current density^-1To (3). In addition, when the current density returned to 0.1A g^-1Then, the discharge capacity can be recovered to 805.2 mA h g^-1。

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims

1. A preparation method of a stannic oxide-carbon core-shell nanosphere composite material is characterized by comprising the following steps:

(1) preparing polymer microspheres with the particle size range of 200 nm-500 nm, and dispersing the prepared polymer microspheres in ethanol;

(2) cation exchange processPreparing tin polymer microspheres: dissolving 0.7-1.2 g of anhydrous sodium acetate in ethanol, adding the ethanol dispersion of the synthesized polymer microspheres under stirring, wherein the addition amount of the polymer microspheres is 0.1-0.4 g, stirring for 10-15 hours, centrifuging, washing precipitates, and pouring washed solids into a reactor with 0.5-0.8 g of SnCl dissolved therein₂•2H₂Stirring in ethanol of O for 20-30 hours, centrifuging, precipitating, washing, and freeze-drying to obtain tin polymer microspheres;

(3) preparing monodisperse pre-oxidized nanospheres: the tin polymer microspheres are put in the air for less than 5 ℃ min^-1The heating speed is increased to 280-320 ℃ for oxidation for 2-5 hours, then 0.1-0.3 g of the oxidized nanospheres are dispersed in water, then the nanospheres are transferred into a reaction kettle, the temperature is kept at 120-180 ℃ for 4-6 hours, and after the nanospheres are cooled to room temperature, the monodisperse pre-oxidized nanospheres are obtained through centrifugal separation;

2. The method for preparing the tin dioxide-carbon core-shell nanosphere composite material according to claim 1, wherein in the step (2), 0.7-1.2 g of anhydrous sodium acetate is dissolved in 100mL of anhydrous ethanol, and 0.5-0.8 g of SnCl is dissolved in the anhydrous ethanol₂•2H₂O is dissolved in 100mL of absolute ethanol, and freeze-drying means freeze-drying at 5 ℃ or below to obtain a solid.

3. The method for preparing the tin dioxide-carbon core-shell nanosphere composite material of claim 1, wherein in step (3), the tin polymer microspheres are exposed to air at a temperature of less than 5 ℃ for a period of time^-1The temperature is raised to 300 ℃ at the temperature raising speed, the oxidation is carried out for 4h, and the temperature is kept in the reaction kettle for 5h at the temperature of 150 ℃.

4. The method for preparing a tin dioxide-carbon core-shell nanosphere composite material according to claim 1, wherein in step (4), 0.1-0.3 g of pre-oxidized nanospheres are dispersed in 150mL of tris (hydroxymethyl) aminomethane hydrochloride buffer solution, wherein tris (hydroxymethyl) aminomethane hydrochloride buffer solution is prepared by dissolving 186 mg of tris (hydroxymethyl) aminomethane hydrochloride in 150mL of water, and the step of freeze-drying is to dissolve the product obtained after centrifugal separation in a proper amount of tert-butyl alcohol and freeze-dry the product to a solid at a temperature below 5 ℃.

5. The method for preparing the tin dioxide-carbon core-shell nanosphere composite material according to claim 1, wherein in the step (4), the dopamine-coated nanospheres are coated on N₂Calcining for 3h at 500 ℃ under the atmosphere.

6. The tin dioxide-carbon core-shell nanosphere composite prepared by the preparation method of any one of claims 1 to 5.

7. The use of the tin dioxide-carbon core-shell nanosphere composite of claim 6 as a lithium ion battery negative electrode material.

8. The use according to claim 7, wherein the tin dioxide-carbon core shell nanosphere composite is mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1, mixed with methyl-2-pyrrolidone to form a slurry, coated on copper foil, vacuum dried, and placed in a glove box filled with Ar inert gas, with Li foil as counter and reference electrodes, and 1M LiPF₆The ethylene carbonate/diethyl carbonate is used as electrolyte to assemble the battery.

9. The use as claimed in claim 8, wherein the vacuum drying is performed at 110 ℃ for 10h, and the loading capacity of the stannic oxide-carbon core-shell nanosphere composite material is 1.0 mg cm^-2The Li foil diameter is 16 mm.