CN111755676A - Silicon alloy negative electrode material for lithium ion battery and preparation method thereof - Google Patents
Silicon alloy negative electrode material for lithium ion battery and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a silicon alloy cathode material for a lithium ion battery and a preparation method thereof, wherein the silicon alloy cathode material comprises a nano silicon alloy, conductive carbon and amorphous carbon, the nano silicon alloy contains silicon, metal X and oxygen, the metal X refers to one or a combination of more of magnesium, copper, aluminum, zinc, iron, titanium, manganese and lithium, and the proportion of the nano silicon alloy in the cathode material is 30-80 wt%; the proportion of the conductive carbon is 10-30 wt.%; the ratio of the amorphous carbon is 10-40 wt.%, and the silicon alloy contains 1-20 wt.% of oxygen, so that when the silicon alloy negative electrode material for the lithium battery is used as a negative electrode active substance of the lithium ion battery, the battery capacity can be obviously increased, the silicon alloy negative electrode material has excellent cycle performance, and the silicon alloy raw material is low in price and is suitable for large-scale production.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a silicon alloy negative electrode material for a lithium ion battery and a preparation method thereof.
Background
At present, the conventional lithium ion negative electrode material mainly adopts a graphite negative electrode, but the theoretical specific capacity of the graphite negative electrode is only 372mAh/g, and the urgent needs of users cannot be met. The theoretical capacity of silicon is up to 4200mAh/g, which is more than 10 times of the capacity of a graphite cathode material, and simultaneously, the coulomb efficiency of the silicon-carbon composite product is close to that of the graphite cathode, and the silicon-carbon composite product is low in price, environment-friendly, rich in earth reserves, and is the optimal choice of a new generation of high-capacity cathode material. However, since the silicon material has poor conductivity and the volume expansion of silicon reaches up to 300% during charging, the volume expansion during charging and discharging easily causes the collapse of the material structure and the peeling and pulverization of the electrode, resulting in the loss of the active material, further causing the sharp reduction of the battery capacity and the serious deterioration of the cycle performance.
In order to stabilize the structure of silicon in the charging and discharging process, relieve the expansion and achieve the effect of improving the electrochemical performance, a carbon material with high conductivity and high specific surface area is urgently needed, and the carbon material is mixed with silicon to be used as a lithium battery negative electrode material.
Disclosure of Invention
In order to solve the problems of the silicon-carbon negative electrode material, the invention provides a silicon alloy negative electrode material for a lithium ion battery and a preparation method thereof.
Specifically, the invention discloses a silicon alloy cathode material for a lithium ion battery, which is characterized in that: the silicon alloy negative electrode material comprises nano silicon alloy, conductive carbon and amorphous carbon, wherein the nano silicon alloy contains silicon, metal X and oxygen, wherein the metal X refers to one or more of magnesium, copper, aluminum, zinc, iron, titanium, manganese and lithium.
Preferably, the proportion of the nano silicon alloy in the negative electrode material is 30-80 wt.%, preferably 40-60 wt.%; the proportion of the conductive carbon is 10-30 wt.%, preferably 15-25 wt.%; the ratio of amorphous carbon is 10 to 40 wt.%, preferably 20 to 30 wt.%.
Preferably, the median particle diameter of the negative electrode material is 2-20 mu m, and the specific surface area of the negative electrode material is 1-10 m2/g。
Preferably, the silicon alloy contains 1 to 20 wt.% of oxygen. More preferably, the silicon alloy contains 10 to 18 wt.% of oxygen.
Preferably, the preparation method of the nano silicon alloy comprises the following steps: carrying out superfine grinding on a silicon alloy raw material;
the silicon alloy raw material is one or a combination of more of silicon-magnesium alloy, silicon-copper alloy, silicon-aluminum alloy, silicon-zinc alloy, silicon-iron alloy, silicon-titanium alloy, silicon-manganese alloy and silicon-lithium alloy;
the silicon alloy raw material is micron-sized particles, and the median particle size D50 is 10-1000 μm;
the mass content of silicon in the silicon alloy raw material is more than or equal to 60 percent;
the superfine grinding mode is one of dry grinding or wet grinding;
the superfine grinding equipment is one of a sand mill or a planetary ball mill;
the grinding beads are made of one of hard alloy, silicon oxide, zirconium silicate, aluminum oxide, stainless steel, agate, ceramic and zirconium oxide, and the mass ratio of the grinding beads to the silicon alloy is (10-20): 1;
the diameter of the grinding bead is 0.05-2 mm, and the grinding time is 40-60 h;
when wet grinding is adopted, the grinding solvent is one or more of methanol, benzyl alcohol, ethanol, ethylene glycol, propanol, isopropanol, propylene glycol, butanol, n-butanol, isobutanol, pentanol, neopentyl alcohol and octanol; the purity of the alcohol solvent is more than or equal to 99 percent; the solid content of the mixed solution is 10-30 wt.%;
the median particle size D50 of the ground nano-silicon alloy measured by a Malvern laser particle sizer is less than or equal to 100 nm.
Preferably, the silicon alloy is dispersed inside the negative electrode material; the silicon alloy particles and the surface portion of the conductive carbon are covered with amorphous carbon.
Preferably, the conductive carbon is selected from one or more of graphene, multi-layer graphite sheets, carbon nanotubes, carbon nanofibers, conductive carbon black, acetylene black and ketjen black; the conductive carbon is dispersed within the negative electrode material and exists as a conductive network.
Preferably, the surface of the negative electrode material is partially covered with amorphous carbon, and the average thickness of the coating carbon layer is 10 to 2000 nm.
Preferably, the amorphous carbon is carbon formed by decomposing a carbon source material in an inert atmosphere at the temperature of 600-1000 ℃;
the carbon source material is one or more of methane, ethane, ethylene, acetylene, propane, propylene, acetone, butane, butylene, pentane, hexane, benzene, toluene, xylene, styrene, naphthalene, phenol, furan, pyridine, anthracene, liquefied gas, citric acid, triose, tetrose, pentose, hexose, glucose, sucrose, asphalt, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyvinyl chloride resin, polyether polyester resin, polyamide resin, polyimide resin, formaldehyde resin, polyoxymethylene, polyamide, polysulfone, polyethylene glycol, bismaleimide, polyethylene, polyvinyl chloride, polytetrafluoroethylene, polystyrene, polypropylene and polyacrylonitrile;
the high-temperature reaction device is one of a vapor deposition furnace, a fluidized bed, a box furnace, a rotary furnace, a roller kiln and a pushed slab kiln;
the high-temperature reaction is carried out in an inert atmosphere, and the inert gas is one of nitrogen, argon, neon and helium.
The invention also relates to a lithium ion battery cathode material which is characterized by being the silicon alloy cathode material for the lithium ion battery.
Compared with the prior art, the invention has the advantages that:
(1) in the silicon alloy cathode material prepared by the invention, metal components in the silicon alloy can be used as a framework support, so that the volume expansion of silicon in the charging and discharging process is obviously relieved, the nanocrystallization of the silicon alloy is realized, and the absolute volume expansion of the silicon can be reduced; the conductive carbon is dispersed in the negative electrode material to form a conductive network, so that the electronic conductivity of the negative electrode material is improved; the amorphous carbon exists in the negative electrode material and is connected with the silicon alloy and the conductive material, so that the internal impedance of the negative electrode material is reduced, and on the other hand, the amorphous carbon forms a carbon coating layer on the surface of the negative electrode material to isolate the erosion of electrolyte, so that the structural stability and the electrochemical performance of the negative electrode material are improved. Therefore, when the silicon alloy negative electrode material is used as a negative electrode active substance of a lithium ion battery, the silicon alloy negative electrode material can obviously increase the battery capacity and has excellent cycle performance, and the silicon alloy raw material is low in price and suitable for large-scale production;
(2) the silicon alloy cathode material prepared by the invention has excellent electrochemical performance, high specific capacity (900-1500 mAh/g), high primary efficiency (84-89%) and excellent cycle performance (18650 cylindrical battery &450 capacity, and the cycle capacity retention rate is 78.2-83.5% after 1000 cycles under the multiplying power of 1C/1C).
Drawings
The invention is further described below with reference to the accompanying drawings.
FIG. 1 is an SEM image of nano-silicon prepared in example 1 of the present invention.
Fig. 2 is an XRD pattern of nano-silicon prepared in example 1 of the present invention.
Fig. 3 is a first charge-discharge curve of a button cell made of the silicon alloy negative electrode material prepared in example 1 of the present invention.
FIG. 4 is a cycling curve at 1C/1C rate for a 18650 cylindrical cell of silicon alloy negative electrode material made in example 1 of the invention.
Detailed Description
For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
A preparation method of a silicon alloy negative electrode material for a lithium ion battery comprises the following steps:
(1) preparing a nano silicon alloy: adding 1000g of silicon-magnesium alloy raw material with the silicon content of 80% and the median particle size of 10 microns into a ball milling tank of a planetary ball mill, adding hard alloy balls, wherein the size of the hard alloy balls is 1mm, the mass ratio of the silicon-magnesium alloy raw material to the hard alloy balls is 1:10, starting the planetary ball mill, the rotating speed of the ball mill is 1000rpm, the ball milling time is 60 hours, obtaining the nano silicon-magnesium alloy, and detecting that the median particle size of the nano silicon-magnesium alloy is 81nm and the mass content of oxygen element is 17.4%;
(2) preparing a precursor of the negative electrode material: adding the nano silicon-magnesium alloy obtained in the step (1) and graphene into a VC mixer according to the mass ratio of 5:5, adjusting the rotating speed of the VC mixer to 800rpm, and mixing for 1h to obtain a precursor of the negative electrode material;
(3) preparing a silicon alloy negative electrode material: placing the anode material precursor obtained in the step (2) in a vapor deposition furnace, introducing nitrogen for protection, heating to 700 ℃ at a heating rate of 3 ℃/min, introducing methane for vapor deposition, and controlling the content of deposited carbon to be 40 wt.% to obtain a silicon alloy anode material;
in the silicon alloy negative electrode material, the proportion of the nano silicon-magnesium alloy is 30 wt.%, the proportion of the graphene is 30 wt.%, and the proportion of the methane deposited carbon is 40 wt.%.
Example 2
(1) Preparing a nano silicon alloy: adding 1000g of silicon-copper alloy raw material with the silicon content of 75% and the median particle size of 100 microns into a ball milling tank of a planetary ball mill, adding hard alloy balls, wherein the size of the hard alloy balls is 2mm, the mass ratio of the silicon-copper alloy raw material to the hard alloy balls is 1:15, starting the planetary ball mill, the rotating speed of the ball mill is 1000rpm, the ball milling time is 50 hours, obtaining the nano silicon-copper alloy, and detecting that the median particle size of the nano silicon-copper alloy is 97nm and the mass content of oxygen element is 12.1%;
(2) preparing a precursor of the negative electrode material: adding the nano silicon-copper alloy obtained in the step (1) and the carbon nano tube into a VC mixer according to the mass ratio of 6:4, adjusting the rotating speed of the VC mixer to 800rpm, and mixing for 1h to obtain a precursor of the cathode material;
(3) preparing a silicon alloy negative electrode material: placing the cathode material precursor obtained in the step (2) in a vapor deposition furnace, introducing nitrogen for protection, heating to 800 ℃ at a heating rate of 3 ℃/min, introducing acetylene for vapor deposition, and controlling the content of deposited carbon to be 30 wt.% to obtain a silicon alloy cathode material;
in the silicon alloy negative electrode material, the proportion of the nano silicon-copper alloy is 42 wt.%, the proportion of the carbon nano tube is 28 wt.%, and the proportion of the acetylene deposition carbon is 30 wt.%.
Example 3
(1) Preparing a nano silicon alloy: adding 1000g of silicon-aluminum alloy raw material with the silicon content of 70% and the median particle size of 500 mu m into a stirring tank of a sand mill, adding methanol, controlling the solid content of the mixed solution to be 20%, starting stirring for 30 minutes, adding silicon oxide balls into a cavity of the sand mill, wherein the size of the silicon oxide balls is 0.2mm, the mass ratio of the silicon oxide balls to the silicon-aluminum alloy raw material is 20:1, introducing the mixed solution in the stirring tank into the sand mill, and the linear speed of the sand mill is 15m/s, and the grinding time is 40h, so as to obtain the nano silicon-aluminum alloy slurry. Through detection, the median particle size of the nano silicon-magnesium alloy is 86nm, and the mass content of oxygen element is 15.6%;
(2) preparing a precursor of the negative electrode material: adding the nano silicon-aluminum alloy slurry obtained in the step (1) and conductive carbon black into a stirring tank of a spray dryer according to the mass ratio of 7:3, controlling the stirring speed to be 400rpm, stirring for 2 hours, then starting spray drying, controlling the inlet temperature to be 180 ℃ and the outlet temperature to be 100 ℃, and obtaining a cathode material precursor;
(3) preparing a silicon alloy negative electrode material: mixing the anode material precursor obtained in the step (2) with pitch, and then placing the mixture into a box furnace for calcination, introducing nitrogen for protection, wherein the sintering temperature is 600 ℃, the sintering time is 1h, and the content of cracking carbon is controlled to be 20 wt%, so as to obtain a silicon alloy anode material;
in the silicon alloy negative electrode material, the proportion of the nano silicon-aluminum alloy is 56 wt.%, the proportion of the conductive carbon black is 24 wt.%, and the proportion of the asphalt cracking carbon is 20 wt.%.
Example 4
(1) Preparing a nano silicon alloy: adding 1000g of a ferrosilicon raw material with the silicon content of 60% and the median particle size of 1000 microns into a stirring tank of a sand mill, adding ethanol, controlling the solid content of the mixed solution to be 20%, starting stirring for 30 minutes, adding silicon oxide balls into a cavity of the sand mill, wherein the size of the silicon oxide balls is 0.2mm, the mass ratio of the silicon oxide balls to the ferrosilicon raw material is 20:1, and introducing high-purity nitrogen into the stirring tank and the cavity of the sand mill to remove oxygen so that the ferrosilicon is carried out under the protection of nitrogen atmosphere. Introducing the mixed solution in the stirring tank into a sand mill, wherein the linear speed of the sand mill is 16m/s, the grinding time is 40h, and nano silicon-magnesium alloy slurry is obtained, and through detection, the median particle size of the nano silicon-magnesium alloy is 79nm, and the mass content of oxygen is 2.9%;
(2) preparing a precursor of the negative electrode material: adding the nano silicon-iron alloy slurry obtained in the step (1) and acetylene black into a stirring tank of a spray dryer according to the mass ratio of 8:2, controlling the stirring speed to be 400rpm, stirring for 2 hours, then starting spray drying, controlling the inlet temperature to be 180 ℃ and the outlet temperature to be 100 ℃, and obtaining a cathode material precursor;
(3) preparing a silicon alloy negative electrode material: mixing the anode material precursor obtained in the step (2) with formaldehyde resin, and then placing the mixture into a box furnace for calcination, introducing nitrogen for protection, wherein the sintering temperature is 1000 ℃, the sintering time is 1h, and the content of cracking carbon is controlled to be 10 wt%, so as to obtain a silicon alloy anode material;
in the silicon alloy negative electrode material, the proportion of the nano silicon-iron alloy is 72 wt.%, the proportion of the conductive carbon black is 18 wt.%, and the proportion of the asphalt cracking carbon is 10 wt.%.
Comparative example 1
The difference from example 1 is that in step (1), the silicon alloy material is not subjected to nanocrystallization, and the rest is the same as example 1, and will not be described herein again.
The following results are obtained by testing: the elemental oxygen content of the silicon alloy raw material was 1.3 wt.%.
Comparative example 2
The difference from example 1 is that in step (1), the grinding time is shortened to 30h, and the rest is the same as example 1, and is not described again here.
The following results are obtained by testing: the mass content of oxygen element in the nano silicon alloy is 9.2%, and the median particle size is 364 nm.
Comparative example 3
The difference from example 1 is that in step (1), the grinding time is increased to 90h, and the rest is the same as example 1, and will not be described again.
The following results are obtained by testing: the mass content of oxygen element in the nano silicon alloy is 43.5%, and the median particle size is 73 nm.
Comparative example 4
The difference from example 1 is that in step (1), the raw material for grinding is not a silicon-magnesium alloy, but pure silicon powder, and the rest is the same as
Embodiment 1, will not be described herein.
The following results are obtained by testing: the mass content of oxygen element in the nano silicon is 16.3%, and the median particle size is 88 nm.
Comparative example 5
The difference from the embodiment 1 is that in the step (2), the conductive carbon is not added, and the rest is the same as the embodiment 1, and the description is omitted.
Comparative example 6
The difference from example 1 is that in step (3), amorphous carbon is not added, and the rest is the same as example 1, which is not repeated herein.
The silicon alloy negative electrode materials in examples 1 to 4 and comparative examples 1 to 6 were tested by the following methods:
the particle size range of the material was tested using a malvern laser particle sizer Mastersizer 3000.
The morphology and the graphical processing of the material were analyzed using a field emission Scanning Electron Microscope (SEM) (JSM-7160).
The oxygen content in the material is accurately and rapidly determined by adopting an oxygen nitrogen hydrogen analyzer (ONH).
The material is subjected to phase analysis by an XRD diffractometer (X' Pert3Powder), and the grain size of the material is determined.
The specific surface area of the negative electrode material was measured using a U.S. Mach Chart and pore Analyzer (TriStar II 3020).
The detection result shows that the median particle diameter of the negative electrode material of the embodiment 1-4 is 2-20 mu m, and the specific surface area of the negative electrode material is 1-10 m2(ii)/g; the average thickness of the surface amorphous carbon-coated carbon layer of the negative electrode material described in examples 1 to 4 is 10 to 2000 nm.
Mixing the silicon alloy negative electrode materials obtained in the examples 1 to 4 and the comparative examples 1 to 6 in pure water of a solvent according to the mass ratio of 91:2:2:5 of the negative electrode material, carbon black (Super P) as a conductive agent, carbon nano tubes and LA133 glue, homogenizing, controlling the solid content to be 45%, coating the mixture on a copper foil current collector, and drying in vacuum to obtain a negative electrode piece. Button cells were assembled in an argon atmosphere glove box using a separator Celgard2400, an electrolyte of 1mol/L LiPF6/EC + DMC + EMC (v/v 1:1:1), and a metallic lithium plate as the counter electrode. And (3) performing charge and discharge tests on the button cell, wherein the voltage interval is 5 mV-1.5V, and the current density is 80 mA/g. The first reversible capacity and efficiency of the silicon alloy negative electrode materials in the examples and comparative examples were measured.
According to the first reversible capacity measured in the button cell, the silicon alloy negative electrode materials in the examples and the comparative examples are mixed with the same stable artificial graphite, and the first reversible capacity tested by the button cell of the mixed powder is 420 +/-2 mAh/g. And preparing a negative pole piece from the mixed powder by a button cell process, and assembling a 18650 cylindrical single cell by using a ternary pole piece prepared by a mature process as a positive pole, an isolating film and electrode liquid unchanged. The 18650 cylindrical single battery is subjected to charge and discharge tests, the voltage interval is 2.5 mV-4.2V, and the current density is 420mA/g
The test equipment of the button cell and the 18650 cylindrical single cell are both the LAND battery test system of Wuhanjinnuo electronics, Inc.
The performance test results of the nano silicon alloy and silicon alloy negative electrode materials of examples 1 to 4 and comparative examples 1 to 6 are as follows:
table 1 grinding critical parameters and nano-silicon alloy test data in examples 1 to 4 and comparative examples 1 to 6:
table 2 component ratios and performance test data of the silicon alloy negative electrode materials in examples 1 to 4 and comparative examples 1 to 6:
as can be seen from table 1, in the porous silicon anode material prepared by the method of the present application, the particle size D50 and the oxygen content of the nano-porous silicon are determined by the grinding process, and the characteristics of the nano-porous silicon, the conductive carbon and the amorphous carbon together determine the electrochemical performance of the anode material, the fluctuation range of the first reversible capacity is 958.6-1438.7 mAh/g, and the fluctuation range of the first coulombic efficiency is 84.9-88.3%, wherein the first coulombic efficiency of the silicon-carbon anode material in example 1 is the highest and 88.3%, and the cycle performance is optimal, the 18650 cylindrical battery &420 capacity has a capacity retention rate of 83.5% after 1000 cycles at a rate of 1C/1C. (ii) a The first reversible capacity of the silicon-carbon negative electrode material in example 4 is the highest, 1438.7 mAh/g.
In comparative examples 1-2, when the silicon powder raw material of the porous silicon negative electrode material is not subjected to nanocrystallization or the median particle size and the silicon grain size of the nano silicon are far larger than the specifications of example 1, the obtained porous silicon negative electrode material has poor first reversible capacity, first coulombic efficiency and cycle performance; in comparative example 3, when the milling time was increased to 90 hours, the first reversible capacity of the obtained porous silicon negative electrode material was significantly reduced to 738.2mAh/g, and the first coulombic efficiency was also poor by 75.1%. In comparative examples 5 and 6, the first coulombic efficiency and the cycle performance of the obtained porous silicon negative electrode material were remarkably reduced without adding conductive carbon or amorphous carbon.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. 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, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A silicon alloy negative electrode material for a lithium ion battery is characterized in that: the silicon alloy negative electrode material comprises nano silicon alloy, conductive carbon and amorphous carbon, wherein the nano silicon alloy contains silicon, metal X and oxygen, wherein the metal X refers to one or more of magnesium, copper, aluminum, zinc, iron, titanium, manganese and lithium.
2. The silicon alloy negative electrode material for lithium ion batteries according to claim 1, characterized in that: the proportion of the nano silicon alloy in the negative electrode material is 30-80 wt.%, preferably 40-60 wt.%; the proportion of the conductive carbon is 10-30 wt.%, preferably 15-25 wt.%; the ratio of amorphous carbon is 10 to 40 wt.%, preferably 20 to 30 wt.%.
3. The silicon alloy negative electrode material for lithium ion batteries according to claim 1, characterized in that: the median particle diameter of the negative electrode material is 2-20 mu m, and the specific surface area of the negative electrode material is 1-10 m2/g。
4. The silicon alloy negative electrode material for lithium ion batteries according to claim 1, characterized in that: the silicon alloy contains 1-20 wt.% of oxygen; preferably, the silicon alloy contains 10 to 18 wt.% of oxygen.
5. The silicon alloy negative electrode material for lithium ion batteries according to claim 1, characterized in that: the preparation method of the nano silicon alloy comprises the following steps: carrying out superfine grinding on a silicon alloy raw material;
the silicon alloy raw material is one or a combination of more of silicon-magnesium alloy, silicon-copper alloy, silicon-aluminum alloy, silicon-zinc alloy, silicon-iron alloy, silicon-titanium alloy, silicon-manganese alloy and silicon-lithium alloy;
the silicon alloy raw material is micron-sized particles, and the median particle size D50 is 10-1000 μm;
the mass content of silicon in the silicon alloy raw material is more than or equal to 60 percent;
the superfine grinding mode is one of dry grinding or wet grinding;
the superfine grinding equipment is one of a sand mill or a planetary ball mill;
the grinding beads are made of one of hard alloy, silicon oxide, zirconium silicate, aluminum oxide, stainless steel, agate, ceramic and zirconium oxide, and the mass ratio of the grinding beads to the silicon alloy is (10-20): 1;
the diameter of the grinding bead is 0.05-2 mm, and the grinding time is 40-60 h;
when wet grinding is adopted, the grinding solvent is one or more of methanol, benzyl alcohol, ethanol, ethylene glycol, propanol, isopropanol, propylene glycol, butanol, n-butanol, isobutanol, pentanol, neopentyl alcohol and octanol; the purity of the alcohol solvent is more than or equal to 99 percent; the solid content of the mixed solution is 10-30 wt.%;
the median particle size D50 of the ground nano-silicon alloy measured by a Malvern laser particle sizer is less than or equal to 100 nm.
6. The silicon alloy negative electrode material for lithium ion batteries according to claim 1, characterized in that: the silicon alloy is dispersed in the negative electrode material; the silicon alloy particles and the surface portion of the conductive carbon are covered with amorphous carbon.
7. The silicon alloy negative electrode material for lithium ion batteries according to claim 1, characterized in that: the conductive carbon is selected from one or more of graphene, multilayer graphite sheets, carbon nanotubes, carbon nanofibers, conductive carbon black, acetylene black and Ketjen black; the conductive carbon is dispersed inside the negative electrode material.
8. The silicon alloy negative electrode material for lithium ion batteries according to claim 1, characterized in that: the surface of the negative electrode material is covered by amorphous carbon, and the average thickness of the coating carbon layer is 10-2000 nm.
9. The silicon alloy negative electrode material for lithium ion batteries according to claim 1, characterized in that: the amorphous carbon is carbon formed by decomposing a carbon source material in an inert atmosphere at the temperature of 600-1000 ℃;
the carbon source material is one or more of methane, ethane, ethylene, acetylene, propane, propylene, acetone, butane, butylene, pentane, hexane, benzene, toluene, xylene, styrene, naphthalene, phenol, furan, pyridine, anthracene, liquefied gas, citric acid, triose, tetrose, pentose, hexose, glucose, sucrose, asphalt, epoxy resin, phenolic resin, furfural resin, acrylic resin, polyvinyl chloride resin, polyether polyester resin, polyamide resin, polyimide resin, formaldehyde resin, polyoxymethylene, polyamide, polysulfone, polyethylene glycol, bismaleimide, polyethylene, polyvinyl chloride, polytetrafluoroethylene, polystyrene, polypropylene and polyacrylonitrile;
the high-temperature reaction device is one of a vapor deposition furnace, a fluidized bed, a box furnace, a rotary furnace, a roller kiln and a pushed slab kiln;
the high-temperature reaction is carried out in an inert atmosphere, and the inert gas is one of nitrogen, argon, neon and helium.
10. A lithium ion battery negative electrode material, characterized in that the lithium ion battery negative electrode material is the silicon alloy negative electrode material for lithium ion batteries according to any one of claims 1 to 9.
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