CN110797517A - Preparation method of nickel-silver alloy particle doped silicon-carbon negative electrode material - Google Patents
Preparation method of nickel-silver alloy particle doped silicon-carbon negative electrode material Download PDFInfo
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Abstract
The invention relates to the field of lithium batteries, and discloses a method for preparing a silicon-carbon negative electrode material by doping nickel-silver alloy particles, which comprises the following steps of ① ball-milling micron-sized silicon powder as a raw material to prepare nano-sized silicon powder, ② mutual mixing of the nano-sized silicon powder and the nickel-silver alloy particles by adopting a solid-phase mixing method, ③ coating by adopting a liquid phase to form an amorphous carbon coating layer on the surfaces of the nano-sized silicon powder and the nickel-silver alloy particles, ④ coating material is sintered at high temperature in an inert gas protection furnace, ⑤ adopts a mechanical ball-milling method to prepare a silicon-carbon material with proper particle size, ⑥ mixing the silicon-carbon material and commercial graphite to prepare the silicon-carbon negative electrode material.
Description
Technical Field
The invention relates to the field of lithium batteries, in particular to a preparation method of a nickel-silver alloy particle doped silicon-carbon cathode and application of the material in a lithium ion battery cathode.
Background
The energy crisis and the environmental problem of contemporary society are becoming more serious, and the search for a new clean energy is urgent. The lithium ion battery is a green and environment-friendly power battery with long cycle life, high power density and low self-discharge rate, and meets new opportunities, and simultaneously faces huge challenges. At present, the energy density and the endurance mileage of the power lithium ion battery are difficult to meet the use requirements of the electric vehicle.
At present, the most widely used lithium ion batteries are still graphite, the theoretical specific capacity of the lithium ion batteries is only 372mAh/g, and the requirements of high energy density of the power batteries for vehicles are difficult to meet. Silicon has attracted considerable attention because of its higher theoretical specific capacity and lower intercalation potential. Li and Si can form alloy Li4.4Si with theoretical specific capacity as high as 4200mAh/g, but silicon can generate great volume effect (as high as 300%) in the process of alloying with lithium, which results in the collapse of electrode structure and the peeling of active material, so that the electrode material loses electric contact, and the capacity is rapidly attenuated, and the poor conductivity of silicon seriously hinders the practicability of pure-phase silicon as the negative electrode material of the lithium ion battery. Silicon in the silicon-carbon composite negative electrode material is used as an active substance to provide lithium storage capacity; the carbon serves as a dispersion matrix, buffers volume change of silicon particles during lithium intercalation and deintercalation, maintains the structural integrity of the electrode, and maintains internal electrical contact of the electrode. Therefore, the silicon-carbon composite material integrates the advantages of the silicon-carbon composite material and the carbon-carbon composite material, shows high specific capacity and longer cycle life, and is expected to replace graphite to become a new-generation lithium ion battery cathode material.
However, the problems of low first coulombic efficiency of ①, short cycle life of ②, poor ③ rate performance, low production efficiency of ④ materials, high cost of ⑤ raw materials and inconvenience for industrial production still exist in the aspect of preparation of silicon-carbon cathode materials at present.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the preparation method of the nickel-silver alloy doped silicon-carbon cathode material, which can obviously improve the first coulombic efficiency and the cycle performance, has simple, efficient and environment-friendly preparation process, and is beneficial to the large-scale production of the silicon-carbon cathode material.
The invention is realized by the following technical scheme:
a preparation method of a nickel-silver alloy particle doped silicon-carbon cathode comprises the following steps:
step (1): preparing nano silicon: ball-milling the silicon powder with micron-sized particle size to prepare nano-scale silicon powder;
step (2): preparing a nickel-silver alloy: mixing nickel powder and silver powder according to a certain mass ratio and carrying out ball milling to prepare nickel-silver alloy powder;
and (3): mixing the nickel-silver alloy powder obtained in the step (2) with the nano-scale silicon powder obtained in the step (1) according to a certain proportion, ball-milling, taking out the nickel-silver alloy silicon compound, carrying out suction filtration and drying, carrying out high-temperature heat treatment under the protection of inert gas, heating to 900-1000 ℃ at a certain heating rate, keeping the temperature for 2-6 hours, cooling and taking out to obtain the composite material of nano-silicon and nickel-silver alloy;
and (4): amorphous carbon coating: adding a solvent into a stirring tank, simultaneously adding a soluble carbon source precursor, starting a high-speed stirrer, adding the composite material of the nano silicon and the nickel-silver alloy obtained in the step (3) into the stirring tank after the carbon source precursor is completely dissolved, adjusting the viscosity of a coating material by changing the using amount of the solvent, and putting the coating material into an oven for drying after the coating material is completely stirred;
and (5): and (3) sintering: putting the product obtained in the step (4) into a rotary furnace, introducing inert gas, and sintering at the high temperature of 800-1200 ℃ for 6-10 hours to obtain a sintered product;
and (6): milling: putting the sintered product obtained in the step (5) into a zirconia ball milling tank for milling, wherein the mass ratio of the sintered product to zirconia balls is 1: 2-1: 4, and operating at the rotating speed of 200-300 r/min for 20-40 min to obtain a silicon-carbon material with the D50 being 15-20 mu m;
and (7): preparing a silicon-carbon negative electrode material: and mixing the silicon-carbon material and commercial graphite according to a certain mass ratio to prepare the silicon-carbon negative electrode material.
Further, the ball milling is to put the materials into a ball milling tank, add zirconia balls, use normal hexane as a solvent, and put the materials into a high-energy ball mill for ball milling.
Furthermore, the micron-sized silicon powder in the step (1) is one or a mixture of more than two of polycrystalline and monocrystalline silicon powder with the diameter D50 being 8-10 μm, and the prepared nanoscale silicon powder D50 is 50-80 nm.
Further, the specific processing method of the step (1) comprises the following steps: adding micron-sized silicon powder and zirconia spheres into a zirconia tank according to a certain mass ratio, positively rotating at 200-400 r/min for 30min, then standing for 5min, reversely rotating at 200-400 r/min for 30min after standing is completed, continuously standing for 5min, then continuously positively rotating, and repeating in the same way to meet the total ball milling time of 12-24 h.
Further, the mass ratio of the nickel powder to the silver powder in the step (2) is 1: 1-1: 5, preferably 1: 3; ball milling is carried out for 8-10 hours.
Further, the nickel-silver alloy can be replaced by one or a mixture of more than two of graphene, carbon nanotubes, metallic silver, metallic copper and nickel-silver alloy.
Further, the mass ratio of the nano-scale silicon powder to the nickel-silver alloy powder in the step (3) is 20: 1-20: 5, preferably 20: 3.
Further, the mass ratio of the carbon source precursor to the nano silicon-nickel-silver alloy composite material in the step (4) is 1: 15-1: 20.
Further, the carbon source precursor in the step (4) is one or a mixture of more than two of sucrose, glucose, starch, polystyrene, polyvinyl chloride, sodium carboxymethylcellulose and asphalt, preferably asphalt; the solvent is one or more of water, ethanol, acetone, N-butanol, N-methylpyrrolidone and toluene, preferably N-methylpyrrolidone. The dispersion method of the high-speed stirrer is that the high-speed stirrer operates for 3-8 hours at 500-1000 r/min, and preferably operates for 5 hours at 800 r/min.
Further, the sintering mode in the step (5) is to perform carbonization reaction on the precursor of the carbon source at a high temperature, the temperature is programmed to rise to be 5-10 ℃/min, the temperature is raised to be 800-1200 ℃, and the temperature is kept for 6-10 h; the inert gas is one or a mixture of more than two of the following gases: argon, helium, hydrogen, carbon dioxide, preferably argon.
Further, the commercial graphite in the step (7) is one or a mixture of more than two of natural crystalline flake graphite, spherical natural graphite, artificial graphite and mesocarbon microbeads, preferably artificial graphite; the mass ratio of the silicon-carbon material to the commercial graphite is 1: 5-1: 8.
The invention has the beneficial effects that:
the silicon-carbon cathode material is prepared by mixing a silicon-carbon material and artificial graphite according to a certain proportion, wherein the silicon-carbon material is the combination of nano silicon with the surface coated with amorphous carbon and nickel-silver alloy. The silicon-carbon anode material prepared by the method obviously improves the first efficiency, the cycle performance, the rate capability and the specific capacity of the anode material.
In the technical scheme of the invention, due to the introduction of the nickel-silver alloy and the good ductility of the metal nickel, the de-intercalation expansion rate of the electrode material in lithium can be greatly reduced, the volume expansion of nano silicon can be effectively relieved, the metal nickel serves as a buffering agent in the silicon expansion process, and due to the high conductivity of the metal silver, the conductivity of the material can be improved, the polarization of the electrode can be reduced, so that the material has good cycle performance and rate capability, and the continuous exertion of the silicon capacity can be ensured.
The preparation method has the advantages that the raw materials are rich and wide, and the micron-sized silicon powder is sufficiently supplied; the equipment only needs a high-energy ball mill, a high-speed stirrer, an oven, an inert gas protection furnace and an oven, and is low in cost and easy for large-scale production.
Drawings
Fig. 1 is a graph of different rate performance for the experimental group (example 1) and the comparative group (comparative example 1).
Fig. 2 is a graph showing normal temperature cycle data of the experimental group (example 1) and the comparative group (comparative example 1).
Detailed Description
For a better understanding of the present invention, the present invention will be further described with reference to the following examples and the accompanying drawings, which are illustrative of the present invention and are not to be construed as limiting thereof.
Example 1
The embodiment 1 of the invention provides a preparation method of a nickel-silver alloy particle doped silicon-carbon cathode, which comprises the following steps:
(1) adding polycrystalline silicon with the diameter of 8-10 mu m and zirconia balls into a zirconia ball-milling tank according to the mass ratio of 1:4, taking n-hexane as a solvent, positively rotating at 300r/min for 30min, standing for 5min, reversely rotating at 300r/min for 30min after standing, continuously standing for 5min, continuously positively rotating, and repeating in such a way, so that the total ball-milling time is 12 h. And after the ball milling is finished, sieving the sieve to separate the zirconia balls from the silicon powder to obtain the nanoscale silicon powder.
(2) Preparing a nickel-silver alloy: adding nickel powder and silver powder into a ball milling tank according to the mass ratio of 1:3, adding zirconia balls, taking n-hexane as a solvent, placing into a high-energy mechanical ball mill, and carrying out ball milling for 9 hours to obtain nickel-silver alloy powder.
(3) And (3) mixing the nickel-silver alloy powder obtained in the step (2) with the nano-scale silicon powder obtained in the step (1) according to a ratio of 1:20, carrying out ball milling, taking out the nickel-silver alloy silicon composite, carrying out suction filtration and drying, carrying out high-temperature heat treatment under the protection of nitrogen, heating to 900 ℃ at a certain heating rate, keeping the temperature for 3 hours, cooling and taking out, thus obtaining the composite material of nano-silicon and nickel-silver alloy.
(4) And (4) adding the uniform powder obtained in the step (3) into an N-methyl pyrrolidone solution of asphalt for liquid phase coating, wherein the mass ratio of the asphalt to the silicon-nickel-silver composite material is 1: 15. The mass ratio of the asphalt to the N-methyl pyrrolidone is 1: 10. The materials are stirred for 5 hours at the rotating speed of 1000r/min and then dried for 5 hours in an oven at the temperature of 130 ℃ to obtain the coating material.
(5) And (4) sintering the cladding material in the step (4) in an inert gas protection furnace, wherein the inert gas is argon, the temperature is increased to 900 ℃ at the heating rate of 5 ℃/min, and the temperature is kept for 6 hours, so that a sintered product is obtained.
(6) And (3) sintering the sintered product in the step (5) according to the following materials: and adding normal hexane serving as a solvent into a ball milling tank, and running at a rotating speed of 250r/min for 30min to obtain the silicon-carbon material with D50 being 15-20 mu m.
(7) And (4) mixing the silicon-carbon material in the step (6) with artificial graphite according to the mass ratio of 1:8 to obtain the silicon-carbon composite negative electrode material.
Example 2
The embodiment 2 of the invention provides a preparation method of a nickel-silver alloy doped silicon-carbon cathode material, which comprises the following steps.
(1) Adding polycrystalline silicon with the diameter of D50-10 mu m and zirconia balls into a zirconia ball milling tank according to the mass ratio of 1:3, using normal hexane as a solvent, rotating forwards for 30min at 200r/min, standing for 5min, rotating backwards for 30min at 200r/min after standing is finished, continuing to stand for 5min, then continuing to rotate forwards, and repeating the steps in the same way to meet the requirement that the total ball milling time is 14 h. And after the ball milling is finished, sieving the sieve to separate the zirconia balls from the silicon powder to obtain the nanoscale silicon powder.
(2) Preparing a nickel-silver alloy: adding nickel powder and silver powder into a ball milling tank according to the mass ratio of 1:1, adding zirconia balls, taking n-hexane as a solvent, placing into a high-energy mechanical ball mill, and carrying out ball milling for 9 hours to obtain nickel-silver alloy powder.
(3) Adding the nano-scale silicon powder obtained in the step (1) and the nickel-silver alloy into a zirconia ball-milling tank according to the mass ratio of 10:1, taking n-hexane as a solvent, and continuing to take the following materials: adding zirconia balls according to the mass ratio of 1:3 into the zirconia balls, performing ball milling for 14h, taking out the nickel-silver alloy silicon composite, performing suction filtration and drying, performing high-temperature heat treatment under the protection of nitrogen, heating to 950 ℃ at a certain heating rate, keeping the temperature constant for 4h, cooling and taking out to obtain the composite material of nano silicon and nickel-silver alloy.
(4) And (4) adding the uniform powder obtained in the step (3) into an N-methyl pyrrolidone solution of asphalt for liquid phase coating, wherein the mass ratio of the asphalt to the nano silicon-nickel-silver alloy is 1: 20. The mass ratio of the asphalt to the N-methyl pyrrolidone is 1: 15. The materials are stirred for 60min at the rotating speed of 1000r/min and then dried for 5h in an oven at the temperature of 130 ℃ to obtain the coating material.
(5) And (4) sintering the cladding material in the step (4) in an inert gas protection furnace, wherein the inert gas is argon, the temperature is raised to 1000 ℃ at the heating rate of 10 ℃/min, and the temperature is kept for 8 hours, so that a sintered product is obtained.
(6) And (3) sintering the sintered product in the step (5) according to the following materials: adding zirconia balls into a ball milling tank according to the mass ratio of 1:3, and operating at the rotating speed of 250r/min for 30min to obtain the silicon-carbon material with the D50 being 15-20 mu m.
(7) And (4) mixing the silicon-carbon material in the step (6) with artificial graphite according to the mass ratio of 1:8 to obtain the silicon-carbon negative electrode material.
Example 3
Embodiment 3 of the invention provides a preparation method of a nickel-silver alloy doped silicon-carbon negative electrode material, which comprises the following steps.
(1) Adding polycrystalline silicon with the diameter of D50-10 mu m and zirconia balls into a zirconia ball milling tank according to the mass ratio of 1:3, taking n-hexane as a solvent, rotating forwards at 400r/min for 30min, standing for 5min, rotating backwards at 400r/min for 30min after standing, continuing to stand for 5min, then rotating forwards continuously, and repeating the steps in the same way to meet the requirement that the total ball milling time is 16 h. And after the ball milling is finished, sieving the sieve to separate the zirconia balls from the silicon powder to obtain the nanoscale silicon powder.
(2) Preparing a nickel-silver alloy: adding nickel powder and silver powder into a ball milling tank according to the mass ratio of 1:5, adding zirconia balls, taking n-hexane as a solvent, placing into a high-energy mechanical ball mill, and carrying out ball milling for 9 hours to obtain nickel-silver alloy powder.
(3) Adding the nanoscale silicon powder obtained in the step (1) and the nickel-silver alloy into a zirconia ball-milling tank according to the mass ratio of 20:3, taking n-hexane as a solvent, and continuing to take the following materials: adding zirconia balls according to the mass ratio of 1:3 into the zirconia balls, performing ball milling for 16h, taking out the nickel-silver alloy silicon composite, performing suction filtration and drying, performing high-temperature heat treatment under the protection of nitrogen, heating to 900 ℃ at a certain heating rate, keeping the temperature constant for 6h, cooling and taking out to obtain the composite material of nano silicon and nickel-silver alloy.
(4) And (4) adding the uniform powder obtained in the step (3) into an N-methyl pyrrolidone solution of polystyrene for liquid phase coating, wherein the mass ratio of the polystyrene to the nano silicon-nickel-silver composite is 1: 15. The mass ratio of the polystyrene to the N-methylpyrrolidone is 1: 20. The materials are stirred for 5 hours at the rotating speed of 1000r/min and then dried for 5 hours in an oven at the temperature of 130 ℃ to obtain the coating material.
(5) And (4) sintering the cladding material in the step (4) in an inert gas protection furnace, wherein the inert gas is argon, the temperature is raised to 1200 ℃ at the heating rate of 10 ℃/min, and the temperature is kept for 10 hours, so that a sintered product is obtained.
(6) And (3) sintering the sintered product in the step (5) according to the following materials: adding zirconia balls into a ball milling tank according to the mass ratio of 1:3, and operating at the rotating speed of 250r/min for 30min to obtain the silicon-carbon material with the D50 being 15-20 mu m.
(7) And (4) mixing the silicon-carbon material in the step (6) with artificial graphite according to the mass ratio of 1:8 to obtain the silicon-carbon negative electrode material.
Example 4
The embodiment 4 of the invention provides a preparation method of a nickel-silver alloy particle doped silicon-carbon cathode, which comprises the following steps:
(1) adding polycrystalline silicon with the diameter of 8-10 mu m and zirconia balls into a zirconia ball-milling tank according to the mass ratio of 1:4, taking n-hexane as a solvent, positively rotating at 300r/min for 30min, standing for 5min, reversely rotating at 300r/min for 30min after standing, continuously standing for 5min, continuously positively rotating, and repeating in such a way, so that the total ball-milling time is 12 h. And after the ball milling is finished, sieving the sieve to separate the zirconia balls from the silicon powder to obtain the nanoscale silicon powder.
(2) Preparing a nickel-silver alloy: adding nickel powder and silver powder into a ball milling tank according to the mass ratio of 1:5, adding zirconia balls, taking n-hexane as a solvent, placing into a high-energy mechanical ball mill, and carrying out ball milling for 9 hours to obtain nickel-silver alloy powder.
(3) Mixing the nickel-silver alloy powder obtained in the step (2) and the nano-scale silicon powder obtained in the step (1) according to a ratio of 1:5, ball-milling, taking out the nickel-silver alloy silicon composite, performing suction filtration and drying, performing high-temperature heat treatment under the protection of helium, heating to 900 ℃ at a certain heating rate, keeping the temperature for 3 hours, cooling and taking out, and thus obtaining the composite material of nano-silicon and nickel-silver alloy.
(4) And (4) adding the uniform powder obtained in the step (3) into an N-methyl pyrrolidone solution of asphalt for liquid phase coating, wherein the mass ratio of the asphalt to the silicon-nickel-silver composite material is 1: 15. The mass ratio of the asphalt to the N-methyl pyrrolidone is 1: 10. The materials are stirred for 5 hours at the rotating speed of 1000r/min and then dried for 5 hours in an oven at the temperature of 130 ℃ to obtain the coating material.
(5) And (4) sintering the cladding material in the step (4) in an inert gas protection furnace, wherein the inert gas is argon, the temperature is increased to 900 ℃ at the heating rate of 5 ℃/min, and the temperature is kept for 6 hours, so that a sintered product is obtained.
(6) And (3) sintering the sintered product in the step (5) according to the following materials: and adding normal hexane serving as a solvent into a ball milling tank, and running at a rotating speed of 250r/min for 30min to obtain the silicon-carbon material with D50 being 15-20 mu m.
(7) And (4) mixing the silicon-carbon material in the step (6) with natural graphite according to the mass ratio of 1:8 to obtain the silicon-carbon composite negative electrode material.
Example 5
The embodiment 5 of the invention provides a preparation method of a nickel-silver alloy particle doped silicon-carbon cathode, which comprises the following steps:
(1) adding 8-10 mu m single crystal silicon D50 and zirconia balls into a zirconia ball milling tank according to the mass ratio of 1:4, taking n-hexane as a solvent, positively rotating at 300r/min for 30min, standing for 5min, reversely rotating at 300r/min for 30min after standing, continuously standing for 5min, continuously positively rotating, and repeating in such a way to meet the total ball milling time of 24 h. And after the ball milling is finished, sieving the sieve to separate the zirconia balls from the silicon powder to obtain the nanoscale silicon powder.
(2) Preparing a nickel-silver alloy: adding nickel powder and silver powder into a ball milling tank according to the mass ratio of 1:5, adding zirconia balls, taking n-hexane as a solvent, placing into a high-energy mechanical ball mill, and carrying out ball milling for 10 hours to obtain nickel-silver alloy powder.
(3) Mixing the nickel-silver alloy powder obtained in the step (2) and the nano-scale silicon powder obtained in the step (1) according to a ratio of 1:4, ball-milling, taking out the nickel-silver alloy silicon composite, performing suction filtration and drying, performing high-temperature heat treatment under the protection of helium, heating to 1000 ℃ at a certain heating rate, keeping the temperature for 2 hours, cooling and taking out, and thus obtaining the composite material of nano-silicon and nickel-silver alloy.
(4) And (4) adding the uniform powder obtained in the step (3) into an aqueous solution of sodium carboxymethyl cellulose for liquid phase coating, wherein the mass ratio of the sodium carboxymethyl cellulose to the silicon-nickel-silver composite material is 1: 17. The mass ratio of the sodium carboxymethylcellulose to the water is 1: 10. The materials are stirred for 5 hours at the rotating speed of 800r/min and then dried for 5 hours in an oven at the temperature of 130 ℃ to obtain the coating material.
(5) And (4) sintering the cladding material in the step (4) in an inert gas protection furnace, wherein the inert gas is argon, the temperature is raised to 800 ℃ at the heating rate of 5 ℃/min, and the temperature is kept for 6 hours, so that a sintered product is obtained.
(6) And (3) sintering the sintered product in the step (5) according to the following materials: and adding normal hexane serving as a solvent into a ball milling tank, and operating at the rotating speed of 300r/min for 20min to obtain the silicon-carbon material with the D50 of 15-20 mu m.
(7) And (4) mixing the silicon-carbon material in the step (6) with the mesocarbon microbeads according to the mass ratio of 1:5 to obtain the silicon-carbon composite negative electrode material.
Comparative example 1
(1) Preparing a nickel-silver alloy: adding nickel powder and silver powder into a ball milling tank according to the mass ratio of 1:5, adding zirconia balls, taking n-hexane as a solvent, placing into a high-energy mechanical ball mill, and carrying out ball milling for 9 hours to obtain nickel-silver alloy powder.
(2) Adding polycrystalline silicon with the diameter of D50-8-10 mu m and nickel-silver alloy into a zirconia ball milling tank according to the mass ratio of 20:3, taking n-hexane as a solvent, and continuing to take the following materials: adding zirconia balls according to the mass ratio of 1:3 into the zirconia balls, performing ball milling for 6 hours, taking out the nickel-silver alloy silicon composite, performing suction filtration and drying, performing high-temperature heat treatment under the protection of hydrogen, heating to 1000 ℃ at a certain heating rate, keeping the temperature for 2 hours, cooling and taking out to obtain the micron silicon and nickel-silver alloy composite material.
(3) And (3) adding the uniform powder obtained in the step (2) into an N-methyl pyrrolidone solution of asphalt for liquid phase coating, wherein the mass ratio of the asphalt to the silicon-nickel-silver compound is 1: 17. The mass ratio of the asphalt to the N-methyl pyrrolidone is 1: 15. The materials are stirred for 5 hours at the rotating speed of 1000r/min and then dried for 5 hours in an oven at the temperature of 130 ℃ to obtain the coating material.
(4) And (4) sintering the cladding material in the step (3) in an inert gas protection furnace, wherein the inert gas is argon, the temperature is raised to 1000 ℃ at the heating rate of 10 ℃/min, and the temperature is kept for 6 hours, so that a sintered product is obtained.
(5) And (4) sintering the product obtained in the step (4) according to the following materials: adding zirconia balls into a ball milling tank according to the mass ratio of 1:3, and operating at the rotating speed of 250r/min for 30min to obtain the silicon-carbon material with the D50 being 15-20 mu m.
(6) And (4) mixing the silicon-carbon material in the step (5) with artificial graphite according to the mass ratio of 1:8 to obtain the silicon-carbon negative electrode material.
Comparative example 2
(1) Adding polycrystalline silicon with the diameter of D50-10 mu m and zirconia balls into a zirconia ball milling tank according to the mass ratio of 1:3, rotating forwards for 30min at 300r/min, standing for 5min, rotating backwards for 30min at 300r/min after standing is finished, continuing to stand for 5min, then continuing to rotate forwards, and repeating in the same way to meet the requirement that the total ball milling time is 12 h. And after the ball milling is finished, sieving the sieve to separate the zirconia balls from the silicon powder to obtain the nanoscale silicon powder.
(2) And (2) adding the nano silicon powder obtained in the step (1) into an N-methyl pyrrolidone solution of asphalt for liquid phase coating, wherein the mass ratio of the asphalt to the nano silicon is 2: 10. The mass ratio of the asphalt to the N-methyl pyrrolidone is 1: 15. The materials are stirred for 5 hours at the rotating speed of 1000r/min and then dried for 5 hours in an oven at the temperature of 130 ℃ to obtain the coating material.
(3) And (3) sintering the cladding material in the step (2) in an inert gas protection furnace, wherein the inert gas is argon, the temperature is raised to 1000 ℃ at the heating rate of 10 ℃/min, and the temperature is kept for 6 hours, so that a sintered product is obtained.
(4) Sintering products in the step (3) are prepared according to the following materials: adding zirconia balls into a ball milling tank according to the mass ratio of 1:3, and operating at the rotating speed of 250r/min for 30min to obtain the silicon-carbon material with the D50 being 15-20 mu m.
(5) And (5) mixing the silicon-carbon material in the step (4) with artificial graphite according to the mass ratio of 1:8 to obtain the silicon-carbon negative electrode material.
In order to test the performance of the lithium ion battery cathode material, a half-cell test method is used for testing, and the silicon-carbon cathode materials prepared in examples 1-5 and comparative examples 1-2 are used as cathode active materials to prepare slurry, wherein the slurry comprises the following active materials: super p: and (3) coating the slurry on a copper foil, and performing vacuum drying for 12h to prepare a negative plate, wherein the electrolyte is commercially available, the PE is a diaphragm, the lithium plate is a counter electrode, and the positive plate is assembled into a half cell in a glove box. And (3) carrying out a constant-current charge and discharge experiment in the LAND battery test system, limiting the charge and discharge voltage to be 0.005-1.5V, and carrying out data acquisition and control by using a charge and discharge cabinet controlled by a computer.
Table 1 shows the comparison of the performances of the negative electrode materials in examples 1 to 5 and comparative examples 1 to 2.
TABLE 1
As can be seen from Table 1 and FIGS. 1-2, the silicon-carbon negative electrode materials prepared in examples 1-5 have high reversible specific capacity, first charge-discharge efficiency and cycle performance. The silicon-carbon negative electrode material in the embodiment 1 is the silicon-carbon negative electrode material with the best performance, and compared with the silicon powder which is not subjected to ball milling treatment and micron-sized silicon powder which is directly mixed with the nickel-silver alloy in the comparative example 1, the silicon-carbon negative electrode material in the embodiment 1 has higher first coulombic efficiency and better cycle performance. The result shows that the volume effect of the nanoscale silicon powder prepared by ball milling can be effectively inhibited when the silicon expands, and the cycle performance is improved. The nano-scale silicon powder prepared in the comparative example 2 is not subjected to ball milling and intermixing with the conductive agent, but is subjected to liquid phase coating alone, and the first efficiency and the cycle performance of the nano-scale silicon powder are lower than those of the nano-scale silicon powder prepared in the example 1, which shows that the conductive agent and the nano-scale silicon are introduced to be uniformly intermixed, and then the liquid phase coating is carried out to lead the nano-scale silicon powder and the conductive agent to be bound in an amorphous carbon frame, so that the conductive performance of the nano-scale silicon powder can be.
The present invention is illustrated in detail by the above-described examples, but the present invention is not limited thereto. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention and the addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A preparation method of a nickel-silver alloy particle doped silicon-carbon cathode is characterized by comprising the following steps:
step (1): preparing nano silicon: ball-milling the silicon powder with micron-sized particle size to prepare nano-scale silicon powder;
step (2): preparing a nickel-silver alloy: mixing nickel powder and silver powder according to a certain mass ratio and carrying out ball milling to prepare nickel-silver alloy powder;
and (3): mixing the nickel-silver alloy powder obtained in the step (2) with the nano-scale silicon powder obtained in the step (1) according to a certain proportion, ball-milling, taking out the nickel-silver alloy silicon compound, carrying out suction filtration and drying, carrying out high-temperature heat treatment under the protection of inert gas, heating to 900-1000 ℃ at a certain heating rate, keeping the temperature for 2-6 hours, cooling and taking out to obtain the composite material of nano-silicon and nickel-silver alloy;
and (4): amorphous carbon coating: adding a certain amount of solvent into a stirring tank, simultaneously adding a soluble carbon source precursor, starting a high-speed stirrer, adding the composite material of nano silicon and nickel-silver alloy obtained in the step (3) into the stirring tank after the carbon source precursor is completely dissolved, adjusting the viscosity of the coating material by changing the using amount of the solvent, and putting the coating material into an oven for drying after the coating material is completely stirred;
and (5): and (3) sintering: putting the product obtained in the step (4) into a rotary furnace, introducing inert gas, and sintering at the high temperature of 800-1200 ℃ for 6-10 hours to obtain a sintered product;
and (6): milling: putting the sintered product obtained in the step (5) into a zirconia ball milling tank for milling, wherein the mass ratio of the sintered product to zirconia balls is 1: 2-1: 4, and the sintered product is operated at a rotating speed of 200-300 r/min for 20-40 min to obtain a silicon-carbon material with D50= 15-20 microns;
and (7): preparing a silicon-carbon negative electrode material: and mixing the silicon-carbon material and commercial graphite according to a certain mass ratio to prepare the silicon-carbon negative electrode material.
2. The method for preparing the silicon-carbon cathode doped with the nickel-silver alloy particles as claimed in claim 1, wherein the method comprises the following steps: the ball milling is to put the material into a ball milling tank, add zirconia balls, use normal hexane as a solvent, and put the mixture into a high-energy ball mill for ball milling.
3. The method for preparing the silicon-carbon cathode doped with the nickel-silver alloy particles as claimed in claim 1, wherein the method comprises the following steps: the micron-sized silicon powder in the step (1) is one or a mixture of more than two of polycrystalline silicon powder and monocrystalline silicon powder with the diameter of D50= 8-10 μm, and the prepared nano-sized silicon powder D50= 50-80 nm.
4. The preparation method of the silicon-carbon cathode doped with the nickel-silver alloy particles as claimed in claim 1, wherein the specific treatment method in the step (1) is as follows: adding micron-sized silicon powder and zirconia spheres into a zirconia tank according to a certain mass ratio, positively rotating at 200-400 r/min for 30min, then standing for 5min, reversely rotating at 200-400 r/min for 30min after standing is completed, continuously standing for 5min, then continuously positively rotating, and repeating in the same way to meet the total ball milling time of 12-24 h.
5. The method for preparing the silicon-carbon cathode doped with the nickel-silver alloy particles as claimed in claim 1, wherein the method comprises the following steps: and (3) ball-milling the nickel powder and the silver powder in the step (2) for 8-10 hours, wherein the mass ratio of the nickel powder to the silver powder is 1: 1-1: 5.
6. The method for preparing the silicon-carbon cathode doped with the nickel-silver alloy particles as claimed in claim 1, wherein the method comprises the following steps: the nickel-silver alloy can be replaced by one or a mixture of more than two of graphene, carbon nano tubes, metal silver, metal copper and nickel-silver alloy.
7. The method for preparing the silicon-carbon cathode doped with the nickel-silver alloy particles as claimed in claim 1, wherein the method comprises the following steps: the mass ratio of the nano-scale silicon powder to the nickel-silver alloy powder in the step (3) is 20: 1-20: 5.
8. The method for preparing the silicon-carbon cathode doped with the nickel-silver alloy particles as claimed in claim 1, wherein the method comprises the following steps: and (4) the mass ratio of the carbon source precursor to the nano silicon to the nickel-silver alloy composite material is 1: 15-1: 20.
9. The method for preparing the silicon-carbon cathode doped with the nickel-silver alloy particles as claimed in claim 1, wherein the method comprises the following steps: and (4) the precursor of the carbon source is one or a mixture of more than two of cane sugar, glucose, starch, polystyrene, polyvinyl chloride, sodium carboxymethylcellulose and asphalt, and the solvent is one or a mixture of more than two of water, ethanol, acetone, N-butanol, N-methylpyrrolidone and toluene.
10. The method for preparing the silicon-carbon cathode doped with the nickel-silver alloy particles as claimed in claim 1, wherein the method comprises the following steps: the commercial graphite in the step (7) is one or a mixture of more than two of natural crystalline flake graphite, spherical natural graphite, artificial graphite and mesocarbon microbeads, and the mass ratio of the silicon-carbon material to the commercial graphite is 1: 5-1: 8.
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