Ge-C composite mesocarbon microbeads as well as preparation method and application thereof

Abstract

The invention relates to a Ge-C composite mesocarbon microbead and a preparation method and application thereof.The preparation method includes the steps that biomass tar pitch and nanoscale germanium dioxide are added into raw oil, and Ge-C preliminary composite mesocarbon microbeads are obtained through direct thermal polycondensation; the preparation method comprises the following steps: pre-oxidizing mesocarbon microbeads, spraying linoleic acid on the surfaces of the mesocarbon microbeads as sacrificial layers, attaching nano Ge to the surfaces of the mesocarbon microbeads after pre-oxidation, and attaching a layer of amorphous carbon to the surface of the outermost layer to form the mesocarbon microbeads with inner core Ge / C composite-inner surface irregular carbon skeleton / Ge composite-outer surface amorphous carbon layer structure. The intact Ge / C composite mesocarbon microbeads are formed by adopting cheap and easily available heavy oil as a raw material and adopting a direct thermal polycondensation method and series modification, have good electrical conductivity and relatively high reversible specific capacity and rate capability, can be kept stable after 200 cycles after being prepared into a battery, have the reversible capacity of up to 1275mAh / g after 200 cycles at 0.1 C current density, and can be applied to the field of lithium ion batteries, such as lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries, lithium ion batteries and lithium ion batteries. The reversible capacity reaches up to 1162mAh / g after 200 cycles at 1C current density.

Description

Technical Field

[0001] The invention relates to a Ge-C composite mesophase carbon microsphere and a preparation method and application thereof, and Ge / C composite mesophase carbon microspheres with high electrochemical performance are prepared, belonging to the field of advanced new carbon material preparation. Background Art

[0002] Mesophase carbon microspheres are a new type of carbon material with good chemical stability, thermal stability, excellent electrical and thermal conductivity, and are a carbon material with broad application prospects. Mesophase carbon microspheres have a structure of parallel stacking of lamellar molecules and are spherical in shape, with small diameters and uniform distribution. They are the basic materials for a variety of new carbon materials, such as isostatic graphite materials, ultra-high power electrodes, negative electrode materials for lithium-ion batteries, high-density isotropic carbon, high-specific surface area activated carbon, high-performance liquid chromatography column filling materials and catalyst carriers, etc. They can be widely used in the fields of machinery industry, nuclear energy industry, chemical industry, semiconductor industry, new energy and environmental protection.

[0003] The existing method undergoes a thermal polycondensation reaction or a direct catalytic polycondensation process, and the obtained mesophase carbon microspheres have a low yield, poor sphericity, uneven particle size, unstable electrochemical cycle performance, and low reversible capacity. CN116514103A discloses a method for preparing multi-element co-doped mesophase carbon microspheres, which is carried out in the following steps: using residual oil as raw oil, shallowly hydrogenating the raw oil through hydrogenation catalysis, and then inducing polymerization through nitrogen-containing linear polymers to obtain a preliminary polymerized nitrogen-containing oil product, adding lead sulfide to the preliminary polymerized nitrogen-containing oil product to carry out plasma-induced high-temperature and high-pressure polymerization to obtain crude asphalt, oxidatively polymerizing the crude asphalt to obtain refined asphalt, and extracting the refined asphalt through a thermal polycondensation reaction 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 purpose of the present invention is to overcome the shortcomings of the prior art, improve the preparation process of mesophase carbon microspheres, and realize Ge / C composite of mesophase carbon microspheres in the process of preparing mesophase carbon microspheres and further realize Ge / C composite in subsequent modification. Using heavy oil as raw material, biomass tar pitch and nano-grade germanium dioxide additives, high-quality Ge / C preliminary composite mesophase carbon microspheres are prepared by direct thermal polycondensation, and Ge / C composite mesophase carbon microspheres with excellent electrochemical performance are prepared using the heavy oil as raw material, biomass tar pitch and nano-grade germanium dioxide additives, 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-low temperature coal tar, high temperature coal tar and its fractions, vacuum residue, ethylene tar, and FCC slurry as raw oil, comprising the following steps:

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

[0008] (2) washing the Ge-C preliminarily composited mesophase carbon microspheres obtained in step (1) and placing them in a culture dish, spraying them with a linoleic acid ethanol solution having a mass concentration of 5 to 15%, drying them, and pre-oxidizing them 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-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) Slowly dripping a saturated glucose solution onto the surface of the mesophase carbon microspheres obtained in step (3), drying and carbonizing the microspheres in an argon atmosphere in a tubular furnace to prepare mesophase carbon microspheres with a structure of a Ge / C composite inner core-an irregular carbon skeleton / Ge composite inner surface-an amorphous carbon layer outer surface, i.e., 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 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 0.1-3MPa, and a reaction time of 3-5h; 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 mesophase carbon microspheres preliminarily composited with Ge-C, the drying refers to placing in an oven and drying 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 in an oven and drying 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 mesophase carbon microspheres prepared by the preliminary composite of Ge-C 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 an additive. Biomass tar pitch can improve 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 mesophase carbon microspheres, and enter the interior of the particles during the formation of mesophase carbon microspheres and remain stable therein; nano-scale germanium dioxide can also adhere to the surface of the formed mesophase carbon microspheres, prevent the fusion of the mesophase beads, and enable the mesophase carbon microspheres to maintain a good spherical shape, while ensuring that the generated carbon microspheres maintain a uniform particle size. The element distribution of the mesophase carbon microspheres obtained by direct thermal polycondensation in a high-temperature reactor was characterized, which 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 composited during the direct thermal polycondensation in a high-temperature reactor.

[0016] In step (2) of the present invention, after the mesophase carbon microspheres sprayed with the linoleic acid ethanol solution are dried, uneven linoleic acid is attached to the surface of the carbon microspheres; in the pre-oxidation process, the linoleic acid attached to the surface of the mesophase carbon microspheres is oxidized into an irregular carbon skeleton attached to the surface of the mesophase carbon microspheres, and the irregular long-chain carbon skeleton has many holes and pores, which can be used for subsequent nano-scale germanium to attach to these holes. An irregular carbon skeleton is formed on the surface of the mesophase carbon microspheres preliminarily compounded with Ge-C.

[0017] In step (3) of the present invention, the germanium nanoparticles with a size of 10 to 20 nm are made to enter the pores of the carbon skeleton formed in step (2) by 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, a complete Ge-C composite mesophase carbon microsphere is prepared. The mesophase carbon microsphere has 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 the layered structure of the mesophase carbon microsphere, 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 mesophase carbon 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 mesophase carbon 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 is as high as 1275mAh / g after 200 cycles at a current density of 0.1C, and the reversible capacity is as high as 1162mAh / g after 200 cycles at a current density of 1C.

[0020] The present invention also provides a Ge-C composite mesophase carbon microsphere product prepared by the 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 raw materials involved in the present invention are rich in sources, the additive cost is low, and the degree of freedom is high; the design is reasonable, the production process is precise, the raw material processing depth is high, the equipment requirements are low, and it is easy to realize industrialization.

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

[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 beneficial 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 restricts the volume expansion of germanium during the charging and discharging process and improves the cyclic stability of the material.

[0027] Instruction Manual

[0028] Figure 1 Schematic diagram of the 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 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 intermediate phase 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 embodiments.

[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 put them in a beaker, add 1g of 15nm nano-grade germanium powder, ultrasonicate at 33℃ for 2h, and put the sonicated solution into an oven at 50℃ for drying for 3h; slowly add 20g of saturated glucose solution to the dried beaker containing the mesophase carbon microspheres, put the beaker into an oven at 90℃ for drying for 2h, and carbonize at 900℃ in a tubular furnace under argon atmosphere 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 mesophase carbon microspheres prepared in Example 1 were prepared into batteries. The preparation steps were as follows: the mesophase carbon microspheres, acetylene black and polyvinylidene fluoride (PVDF) were uniformly mixed at a ratio of 8:1:1, and slurried with N-methylpyrrolidone, the slurry was uniformly coated on copper foil, and the button battery was assembled in a glove box. The reversible capacity was as high as 1194 mAh / g after 200 cycles at a current density of 0.1C, and the reversible capacity was as high as 1027 mAh / g after 200 cycles at a current density of 1C.

[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, and carry out thermal polycondensation reaction 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 tubular 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-grade 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 dropping 20 g of saturated glucose solution into the dried beaker containing the mesophase carbon microspheres, drying the beaker in an oven at 90°C for 2 h, and carbonizing them at 800°C for 3 h in an argon atmosphere in a tubular furnace to obtain 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, It is characterized in that The steps include: (1) adding biomass tar pitch and nano-scale germanium dioxide to raw oil to obtain Ge-C preliminary composite mesophase carbon microspheres through direct thermal polycondensation reaction; (2) washing the Ge-C preliminarily composited mesophase carbon microspheres obtained in step (1), placing them in a culture dish, spraying them with a 5-15% linoleic acid ethanol solution, drying them, and then pre-oxidizing them 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 an irregular carbon skeleton structure on the surface; (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; (4) Slowly adding a saturated glucose solution to the surface of the mesophase carbon microspheres obtained in step (3), drying and carbonizing in a tubular furnace under an argon atmosphere to prepare a structure of Ge / C composite inner core-irregular carbon skeleton / Ge composite inner surface-amorphous carbon layer outer surface, i.e., Ge-C composite mesophase carbon microspheres.

2. The method for preparing Ge-C composite mesophase carbon microspheres according to claim 1, Features: In step (1), the raw oil is selected from one or more of medium-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-grade germanium dioxide is 50-200 nm; and the mass ratio of the raw oil, biomass tar pitch and nano-grade germanium dioxide is 150-200:20-30:1-15.

3. The method for preparing Ge-C composite mesophase carbon microspheres according to claim 1, Features: 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 Ge-C preliminary composite mesophase carbon microspheres, germanium dioxide is evenly distributed in the nucleation center and layered structure of the mesophase carbon microspheres.

4. The method for preparing Ge-C composite mesophase carbon microspheres according to claim 1, Features: 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 preliminary composited mesophase carbon microspheres, the drying refers to placing in an oven and drying 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 mesophase carbon microspheres according to claim 1, Features: 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 drying in an oven at 50-60° C. for 1-3 hours.

6. The method for preparing Ge-C composite mesophase carbon microspheres according to claim 1, Features: 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 in an oven and drying at 80-90° C. for 2 hours, the carbonization temperature is 800-900° C., and the carbonization time is 2-3 hours.

7. The Ge-C composite mesophase carbon microsphere product prepared by the method according to any one of claims 1 to 6, Features: The particle size of the Ge-C composite mesophase carbon microspheres is 20-30 microns, the inner 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, Features: 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.

10. The use according to claim 9, It is characterized in that The Ge-C composite mesophase carbon microspheres have good electrical conductivity, high reversible specific capacity and rate performance. After being prepared into a battery, they can remain stable after 200 cycles. The reversible capacity is as high as 1275 mAh / g after 200 cycles at a current density of 0.1C, and the reversible capacity is as high as 1162 mAh / g after 200 cycles at a current density of 1C.

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