Ge-c composite mesocarbon microbeads, and preparation method and application thereof

Abstract

The present application relates to a kind of Ge-C composite mesophase carbon microspheres and its preparation method and application, biomass tar pitch and nanoscale germanium dioxide are added to raw oil, and Ge-C preliminary composite mesophase carbon microspheres are obtained by direct thermal polycondensation reaction;Linoleic acid is sprayed as sacrificial layer to its surface, and after pre-oxidation, nanometer Ge is attached to the surface of mesophase carbon microspheres, and a layer of amorphous carbon is attached to the outermost layer of surface, forming the mesophase carbon microspheres of the structure of core Ge / C composite-irregular carbon skeleton / Ge composite-inner surface-amorphous carbon layer structure on the surface.The present application uses cheap and easily available heavy oil as raw material, uses direct thermal polycondensation method and series modification, forms complete Ge / C composite mesophase carbon microspheres, has good conductivity, higher reversible specific capacity and rate performance, and can be stable after 200 cycles after being prepared into battery, the reversible capacity is as high as 1275 mAh / g after 200 cycles at 0.1C current density, and the reversible capacity is as high as 1162 mAh / g after 200 cycles at 1C current density.

Description

Technical Field

[0001] The present invention relates to Ge-C composite mesophase carbon microspheres and a preparation method and application thereof, and is used to prepare Ge / C composite mesophase carbon microspheres with high electrochemical performance, belonging to the field of advanced novel carbon material preparation. Background Art

[0002] Mesocarbon microspheres are a new type of carbon material with excellent chemical and thermal stability, as well as excellent electrical and thermal conductivity, and are a promising carbon material for a wide range of applications. Mesocarbon microspheres have a structure composed of parallel stacked lamellar molecules, yet are spherical, with small and uniform sphere diameters. They serve as the foundation for a variety of new carbon materials, such as isostatically pressed graphite, ultra-high power electrodes, lithium-ion battery anode materials, high-density isotropic carbon, and high-surface-area activated carbon, filling materials for high-performance liquid chromatography columns, and catalyst supports. They are widely used in the machinery, nuclear energy, chemical, semiconductor, new energy, and environmental protection industries.

[0003] Existing methods, through thermal polycondensation or direct catalytic polycondensation, produce mesophase carbon microspheres with low yield, poor sphericity, uneven particle size, unstable electrochemical cycling performance, and low reversible capacity. CN116514103A discloses a method for preparing multi-element co-doped mesophase carbon microspheres, comprising the following steps: using residual oil as feedstock, subjecting the feedstock to a shallow hydrogenation reaction via hydrogenation catalysis, then subjecting the feedstock to induced polymerization of nitrogen-containing linear polymers to obtain a preliminary polymerized nitrogen-containing oil product, adding lead sulfide to the preliminary polymerized nitrogen-containing oil product for plasma-induced high-temperature and high-pressure polymerization to obtain crude asphalt, subjecting the crude asphalt to oxidative polymerization to obtain refined asphalt, and subjecting the refined asphalt to thermal polycondensation extraction to obtain sulfur-nitrogen-lead co-doped mesophase carbon microspheres. CN108441244A discloses a method for preparing mesophase carbon microspheres and mesophase asphalt, comprising mixing coal-based asphalt with a first solvent as a co-carbonization raw material, performing a first thermal polycondensation reaction, and obtaining polycondensation asphalt containing mesophase carbon microspheres; mixing the polycondensation asphalt with a second solvent and separating the mixture to obtain mesophase carbon microspheres; and distilling the liquid component to obtain by-product asphalt; and performing a second thermal polycondensation reaction on the by-product asphalt to obtain mesophase asphalt. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art, improve the preparation process of mesocarbon microspheres, and achieve Ge / C composites in the mesocarbon microspheres during the preparation process, as well as further Ge / C composites in subsequent modifications. Using heavy oil as a raw material, biomass tar pitch, and nano-scale germanium dioxide additives, high-quality Ge / C preliminary composite mesocarbon microspheres are prepared through a direct thermal polycondensation process. These composites are then used as raw materials to prepare Ge / C composite mesocarbon microspheres with excellent electrochemical properties, thereby optimizing the production process.

[0005] The purpose of the present invention is achieved by adopting the following technical solutions:

[0006] A method for preparing Ge-C composite mesophase carbon microspheres, using one or more of medium- and low-temperature coal tar, high-temperature coal tar and its fractions, vacuum residue, ethylene tar, and FCC slurry as raw oil, comprises the following steps:

[0007] (1) adding biomass tar pitch and nano-scale germanium dioxide to raw oil, and obtaining Ge-C preliminarily composited mesophase carbon microspheres through direct thermal polycondensation reaction;

[0008] (2) The Ge-C preliminarily composited mesophase carbon microspheres obtained in step (1) are washed and placed in a culture dish, sprayed with a linoleic acid ethanol solution having a mass concentration of 5 to 15%, dried, and pre-oxidized in a tube furnace to form an irregular carbon skeleton on the surface of the mesophase carbon microspheres, thereby obtaining mesophase carbon microspheres with an internal Ge / C composite and a surface irregular carbon skeleton structure;

[0009] (3) taking the mesophase carbon microspheres obtained in step (2) and anhydrous ethanol and placing them in a beaker, adding 10-20 nm nano-scale germanium powder, ultrasonically treating and drying, and preparing mesophase carbon microspheres with an internal Ge / C composite-surface irregular carbon skeleton / Ge composite structure;

[0010] (4) Saturated glucose solution is slowly added dropwise to the surface of the mesophase carbon microspheres obtained in step (3), and after drying, carbonization is carried out in a tubular furnace under an argon atmosphere to prepare mesophase carbon microspheres with a structure of Ge / C composite in the inner core-irregular carbon skeleton / Ge composite on the inner surface-amorphous carbon layer on the outer surface, that is, Ge-C composite mesophase carbon microspheres.

[0011] In the present invention, in step (1), the particle size of the nano-scale germanium dioxide is 50-200 nm, and it is doped inside the mesophase carbon microspheres as a nucleation factor of the mesophase carbon microspheres; the mass ratio of the raw material oil, biomass tar pitch and nano-scale germanium dioxide is 150-200:20-30:1-15; the direct thermal polycondensation is carried out under the protection of inert gas, with a reaction temperature of 420-440°C, a reaction pressure of 0.1-3 MPa, and a reaction time of 3-5 hours; in the mesophase carbon microspheres preliminarily composited with Ge-C, germanium dioxide is uniformly distributed in the nucleation center and layered structure of the mesophase carbon microspheres.

[0012] In the present invention, in step (2), the cleaning refers to cleaning the surface of the mesophase carbon microspheres with anhydrous ethanol solution, the amount of the linoleic acid ethanol solution is 20-30wt% of the Ge-C preliminarily composited mesophase carbon microspheres, the drying refers to placing them in an oven and drying them at 50-60°C for 1-3h, the pre-oxidation temperature is 250-300°C, and the pre-oxidation time is 1-4h.

[0013] In the present invention, in step (3), the mass ratio of the mesophase carbon microspheres, anhydrous ethanol and nano-grade germanium powder obtained in step (2) is 5:15:1; the ultrasonication refers to ultrasonication at 30-40°C for 1-2 hours; and the drying refers to placing in an oven and drying at 50-60°C for 1-3 hours.

[0014] In the present invention, in step (4), the mass ratio of the mesophase carbon microspheres obtained in step (3) to the saturated glucose solution is 1:2, the drying refers to placing the microspheres in an oven at 80-90°C for 2 hours, the carbonization temperature is 800-900°C, and the carbonization time is 2-3 hours.

[0015] The yield of the Ge-C preliminarily composited mesophase carbon microspheres prepared in step (1) of the present invention is 50-60%. Biomass tar pitch is added to the raw oil to modify the oil, and nano-scale germanium dioxide is used as an additive. Biomass tar pitch can increase the yield of the prepared mesophase carbon microspheres, provide additional nucleation areas for the formation of mesophase carbon microspheres, and delay the formation of large mesophases during the thermal polycondensation process. Nano-scale germanium dioxide can serve as a nucleation factor for the mesophase carbon microspheres, and enter the interior of the particles during the formation of the mesophase carbon microspheres and remain stable therein. Nano-scale germanium dioxide can also adhere to the surface of the formed mesophase carbon microspheres, preventing the fusion of the mesophase beads and allowing the mesophase carbon microspheres to maintain good sphericity, while ensuring that the generated carbon microspheres maintain a uniform particle size. The element distribution characterization of the mesophase carbon microspheres obtained by direct thermal polycondensation in a high-temperature reactor confirmed that germanium was present not only in the nucleation center of the microspheres, but also in the layered structure of the microspheres. Ge and C were initially compounded during the direct thermal polycondensation in a high-temperature reactor.

[0016] In step (2) of the present invention, after drying the mesocarbon microspheres sprayed with the linoleic acid ethanol solution, uneven linoleic acid is attached to the surface of the carbon microspheres. During the pre-oxidation process, the linoleic acid attached to the surface of the mesocarbon microspheres is oxidized into an irregular carbon skeleton attached to the surface of the mesocarbon microspheres. The irregular long-chain carbon skeleton has many pores in the carbon skeleton, which can be used for subsequent attachment of nano-germanium. The irregular carbon skeleton is formed on the surface of the mesocarbon microspheres preliminarily composited with Ge-C.

[0017] In step (3) of the present invention, germanium nanoparticles with a size of 10 to 20 nm are made to enter the pores of the carbon skeleton formed in step (2) through ultrasonic action. After simple drying, a saturated glucose solution is slowly added dropwise in step (4). Sufficient glucose is attached to the surface of the mesophase carbon microspheres with an internal Ge / C composite-surface irregular carbon skeleton / Ge composite structure obtained in step (3). After carbonization, an amorphous carbon layer is formed. Finally, complete Ge-C composite mesophase carbon microspheres are prepared. The mesophase carbon microspheres have a three-layer structure, wherein the interior is a Ge / C preliminary composite structure, i.e., germanium dioxide is uniformly distributed in the nucleation center and layered structure of the mesophase carbon microspheres, the second layer, i.e., the inner surface, is an irregular carbon skeleton / Ge composite layer, and the third layer, i.e., the outer surface, is an amorphous carbon layer.

[0018] The Ge-C composite mesocarbon microspheres prepared by the present invention have a particle size of 20-30 microns, a core size of 13-17 microns, an inner surface size of 4-7 microns, and an outer surface size of 3-6 microns. Preferably, the Ge-C composite mesocarbon microspheres have a particle size of 20 microns, a core size of 13 microns, an inner surface size of 4 microns, and an outer surface size of 3 microns.

[0019] The Ge-C composite mesophase carbon microspheres prepared by the present invention have good electrical conductivity, high reversible specific capacity and rate performance. After being prepared into a battery, it can remain stable after 200 cycles. The reversible capacity after 200 cycles at a current density of 0.1C is as high as 1275mAh / g, and the reversible capacity after 200 cycles at a current density of 1C is as high as 1162mAh / g.

[0020] The present invention also provides a Ge-C composite mesophase carbon microsphere product prepared by the above method.

[0021] The present invention also provides the use of the Ge-C composite mesophase carbon microspheres in batteries.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention has abundant raw material sources, low additive costs, and high degree of freedom; it has reasonable design, precise production process, high raw material processing depth, low equipment requirements, and is easy to industrialize.

[0024] (2) In the Ge-C composite mesophase carbon microsphere material, the carbon substrate is a mesophase carbon microsphere prepared by heavy oil, and the internal carbon layer arrangement presents a disordered layer structure, which has excellent rate performance. By uniformly inserting Ge into the nucleation center and layered structure inside the mesophase carbon microsphere, the electrochemical capacity of the microsphere is improved and the cycling performance is good.

[0025] (3) Linoleic acid is used as a sacrificial layer to form an irregular carbon skeleton, which greatly increases the number of active sites on the surface of the mesophase carbon microspheres and adds a large number of pore structures, which is conducive to the attachment of germanium atoms on the surface and improves the electrochemical performance.

[0026] (4) A layer of amorphous carbon is wrapped around the outermost layer of the material, which effectively constrains the volume expansion of germanium during the charging and discharging process and improves the cycle stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figures in the specification

[0028] Figure 1 Schematic diagram of Ge / C preliminary composite mesophase carbon microspheres obtained in step (1) of the present invention.

[0029] Figure 2 Schematic diagram of the mesophase carbon microspheres with internal Ge / C composite and surface irregular carbon skeleton obtained in step (2) of the present invention.

[0030] Figure 3 Schematic diagram of the mesophase carbon microspheres with internal Ge / C composite-surface irregular carbon skeleton / Ge composite structure obtained in step (3) of the present invention.

[0031] Figure 4 Schematic diagram of the complete Ge-C composite mesophase carbon microspheres obtained in step (4) of the present invention.

[0032] In the figure, 1 is an irregular carbon skeleton, 2 is the pores in the irregular carbon skeleton, 3 is a composite layer of irregular carbon skeleton and Ge, 4 is a Ge / C preliminary composite mesophase carbon microsphere obtained by direct thermal shrinkage method, and 5 is an amorphous carbon layer. DETAILED DESCRIPTION

[0033] The following further describes a method for preparing Ge-C composite mesophase carbon microspheres and products provided by the present invention in conjunction with examples.

[0034] Example 1

[0035] 180g of ethylene tar, 36g of biomass tar pitch and 11.7g of 150nm nano-scale germanium dioxide were added to a high-temperature reactor, and a thermal polycondensation reaction was carried out at a reaction temperature of 425°C and a reaction time of 3.5h under N2 atmosphere protection to obtain Ge-C preliminary composite mesophase carbon microspheres; after washing, 20g was placed in a culture dish, sprayed with a spray bottle filled with 12% linoleic acid ethanol solution, placed in an oven at 50°C for drying for 2h, and then pre-oxidized in a tubular furnace at 230°C. Treat for 2h; take 5g of pre-oxidized mesophase carbon microspheres and 15g of anhydrous ethanol and place them in a beaker, add 1g of 15nm nano-grade germanium powder, ultrasonicate at 33℃ for 2h, and place the sonicated solution in an oven at 50℃ for drying for 3h; slowly add 20g of saturated glucose solution to the dried beaker containing the mesophase carbon microspheres, place the beaker in an oven at 90℃ for drying for 2h, and carbonize at 900℃ in an argon atmosphere in a tubular furnace for 3h; prepare Ge-C composite mesophase carbon microspheres.

[0036] The Ge-C composite mesophase carbon microspheres prepared in this embodiment have a particle size of 23 microns, a core size of 15 microns, an inner surface size of 5 microns, and an outer surface size of 3 microns.

[0037] The Ge-C composite mesocarbon microspheres prepared in Example 1 were fabricated into a battery. The preparation steps included uniformly mixing the mesocarbon microspheres, acetylene black, and polyvinylidene fluoride (PVDF) in a ratio of 8:1:1, slurrying them with N-methylpyrrolidone, and evenly coating the slurry on copper foil. The button cell was assembled in a glove box. After 200 cycles at a current density of 0.1C, the reversible capacity reached 1194 mAh / g, and after 200 cycles at a current density of 1C, the reversible capacity reached 1027 mAh / g.

[0038] Example 2

[0039] Take 200g of FCC oil slurry, 40g of biomass tar pitch and 7g of 200nm nano-scale germanium dioxide powder and add them into a high-temperature reactor. Perform thermal polycondensation at a reaction temperature of 420℃ and a reaction time of 4h under N2 atmosphere protection to obtain Ge-C preliminary composite mesophase carbon microspheres; after washing, take 20g and place it in a culture dish, spray it with a spray bottle filled with 9% linoleic acid ethanol solution, and then put it into an oven at 60℃ for drying for 1.5h, and then pre-oxidize it in a tube furnace at 290℃. The method comprises the following steps: taking 5 g of the pre-oxidized mesophase carbon microspheres and 15 g of anhydrous ethanol and placing them in a beaker, adding 1 g of 10 nm nano-scale germanium powder, ultrasonicating them at 40 ° C for 2 h, and drying the ultrasonicated solution in an oven at 60 ° C for 3 h; slowly adding 20 g of saturated glucose solution to the dried beaker containing the mesophase carbon microspheres, placing the beaker in an oven at 90 ° C for drying for 2 h, and carbonizing them at 800 ° C for 3 h in an argon atmosphere in a tubular furnace to prepare Ge-C composite mesophase carbon microspheres.

[0040] The Ge-C composite mesophase carbon microspheres prepared in this embodiment have a particle size of 25 microns, a core size of 17 microns, an inner surface size of 4 microns, and an outer surface size of 4 microns.

[0041] The Ge-C composite mesophase carbon microspheres prepared in Example 2 were prepared into a battery, and the reversible capacity was as high as 1275 mAh / g after 200 cycles at a current density of 0.1 C, and the reversible capacity was as high as 1162 mAh / g after 200 cycles at a current density of 1 C.

Claims

1. A method for preparing Ge-C composite mesophase carbon microspheres, characterized in that: The steps include: (1) Biomass tar pitch and nano-scale germanium dioxide are added to the raw oil, and Ge-C preliminary composite mesophase carbon microspheres are obtained through direct thermal polycondensation reaction; (2) The Ge-C preliminarily composited mesophase carbon microspheres obtained in step (1) are washed, placed in a culture dish, sprayed with a 5-15% linoleic acid ethanol solution, dried, and then pre-oxidized in a tube furnace to form an irregular carbon skeleton on the surface of the mesophase carbon microspheres, thereby obtaining mesophase carbon microspheres with an internal Ge / C composite and a surface irregular carbon skeleton structure; (3) The mesophase carbon microspheres obtained in step (2) and anhydrous ethanol are placed in a beaker, and 10-20 nm nano-scale germanium powder is added. After ultrasonic treatment, the mixture is dried to prepare mesophase carbon microspheres with an internal Ge / C composite-surface irregular carbon skeleton / Ge composite structure; (4) Saturated glucose solution is slowly added dropwise to the surface of the mesophase carbon microspheres obtained in step (3), and after drying, carbonization is carried out in a tube furnace under an argon atmosphere to prepare a structure of Ge / C composite inner core-irregular carbon skeleton / Ge composite-amorphous carbon layer outer surface, namely Ge-C composite mesophase carbon microspheres.

2. The method for preparing Ge-C composite mesocarbon microspheres according to claim 1, characterized in that: In step (1), the raw oil is selected from one or more of medium- and low-temperature coal tar, high-temperature coal tar and its fractions, vacuum residue, ethylene tar, and FCC oil slurry; the particle size of the nano-scale germanium dioxide is 50-200 nm; and the mass ratio of the raw oil, biomass tar pitch, and nano-scale germanium dioxide is 150-200:20-30:1-15.

3. The method for preparing Ge-C composite mesocarbon microspheres according to claim 1, characterized in that: The direct thermal polycondensation is carried out under inert gas protection at a reaction temperature of 420 to 440° C., a reaction pressure of 0.1 to 3 MPa, and a reaction time of 3 to 5 hours. In the Ge-C preliminarily composited mesophase carbon microspheres, germanium dioxide is uniformly distributed in the nucleation center and layered structure of the mesophase carbon microspheres.

4. The method for preparing Ge-C composite mesocarbon microspheres according to claim 1, characterized in that: In step (2), the cleaning refers to cleaning the surface of the mesophase carbon microspheres with anhydrous ethanol solution, the amount of the linoleic acid ethanol solution is 20-30wt% of the Ge-C preliminarily composited mesophase carbon microspheres, the drying refers to placing them in an oven and drying them at 50-60°C for 1-3h, the pre-oxidation temperature is 250-300°C, and the pre-oxidation time is 1-4h.

5. The method for preparing Ge-C composite mesocarbon microspheres according to claim 1, characterized in that: In step (3), the mass ratio of the mesophase carbon microspheres, anhydrous ethanol and nano-scale germanium powder obtained in step (2) is 5:15:1; the ultrasonication refers to ultrasonication at 30-40° C. for 1-2 hours; and the drying refers to drying in an oven at 50-60° C. for 1-3 hours.

6. The method for preparing Ge-C composite mesocarbon microspheres according to claim 1, characterized in that: In step (4), the mass ratio of the mesophase carbon microspheres obtained in step (3) to the saturated glucose solution is 1:2, the drying refers to placing the microspheres in an oven at 80-90° C. for 2 h, the carbonization temperature is 800-900° C., and the carbonization time is 2-3 h.

7. The Ge-C composite mesocarbon microsphere product prepared by the method according to any one of claims 1 to 6, characterized in that: The particle size of the Ge-C composite mesophase carbon microspheres is 20-30 microns, the core size is 13-17 microns, the inner surface size is 4-7 microns, and the outer surface size is 3-6 microns.

8. The product according to claim 7, characterized in that: The particle size of the Ge-C composite mesophase carbon microspheres is 20 microns, the core size is 13 microns, the inner surface size is 4 microns, and the outer surface size is 3 microns.

9. Use of the Ge-C composite mesophase carbon microspheres according to claim 7 or 8 in batteries.

Images