CN116207244A - High-density high-purity silicon-carbon negative electrode material and preparation method thereof - Google Patents
High-density high-purity silicon-carbon negative electrode material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a preparation method of a high-density high-purity silicon-carbon negative electrode material, which relates to the technical field of composite material preparation, wherein the negative electrode material comprises silicon and carbon which are uniformly and densely distributed, and the density of the material is more than or equal to 95 percent, wherein ρ1 is the actual test density, and ρ2 is the theoretical density. The preparation method comprises the steps of carrying out physical vapor deposition on the carbon raw material and the silicon raw material, cooling to obtain the high-density high-purity silicon-carbon negative electrode material, wherein the physical deposition can be carried out in a synchronous or alternate deposition mode, amorphous carbon and a gas-phase silicon source are utilized to form a uniform and compact composite material structure, the material is uniformly distributed in amorphous carbon by sub-nano silicon, and the compact structure can improve the compaction of the material and effectively relieve the volume effect in the charging and discharging processes. Meanwhile, the silicon particles are of sub-nanometer level, and the self-expansion of the silicon particles is smaller than that of nanometer silicon, so that the cycle performance of the silicon particles can be further improved.
Description
Technical Field
The invention relates to the technical field of composite material preparation, in particular to a high-density high-purity silicon-carbon negative electrode material and a preparation method thereof.
Background
The lithium battery is the new energy field with the widest application and the best prospect in the world, wherein the performance of the anode material plays a very important role in the development prospect of the lithium battery.
Currently, lithium battery anode materials mainly include the following: one is a carbon negative electrode material, and the negative electrode materials practically used in lithium ion batteries at present are basically carbon materials, such as artificial graphite, natural graphite, mesophase carbon microspheres, petroleum coke, carbon fibers, pyrolytic resin carbon, graphite-based composite materials and the like. Secondly, tin-based anode materials can be divided into tin oxides and tin-based composite oxides, wherein the oxides refer to oxides of tin in various valence states, and at present, commercial products are hardly available. Thirdly, the lithium-containing transition metal nitride anode material has almost no commercial products at present. Fourth, alloy-type negative electrode materials including tin-based alloys, silicon-based alloys, germanium-based alloys, aluminum-based alloys, antimony-based alloys, magnesium-based alloys, and other alloys are hardly commercialized at present. Fifth, nano-scale cathode materials, nano carbon tubes, nano alloy materials, nano oxide materials and the like.
In order to improve the existing negative electrode material and further improve the battery performance, scientists have conducted a great deal of research to obtain graphene-nano silicon composite materials and other silicon-carbon composite materials, but the prepared product has serious problems, and the application of the product in batteries is affected.
The chinese patent No. cn201810830729.X discloses a method for preparing a silicon-carbon composite material, wherein nano silicon is prepared by a grinding method, and then the silicon-carbon composite material is prepared, so that holes exist between nano silicon, the holes lead to lower tap density of the material, the defects cannot be overcome by any subsequent steps, and the defects can cause hole collapse in the cyclic process when the material is applied to a battery (negative electrode), so that the material is pulverized, and the cyclic performance of the battery is directly reduced greatly.
Disclosure of Invention
In order to solve the problems, the high-density high-purity silicon-carbon anode material is prepared by vapor deposition, and the specific scheme is as follows:
a high-density high-purity silicon-carbon negative electrode material comprises silicon and carbon which are uniformly and densely distributed, wherein the density of the material meets the requirement that ρ1/ρ2 is more than or equal to 95%, ρ1 is the actual test density, and ρ2 is the theoretical density (namely the sum of the theoretical true densities of the contents of all components of the material).
The preparation method of the high-density high-purity silicon-carbon negative electrode material comprises the following steps: and performing physical vapor deposition on the carbon raw material and the silicon raw material, and cooling to obtain the high-density high-purity silicon-carbon anode material.
Preferably, the method specifically comprises the following steps:
1) Fixing carbon raw materials on an evaporation source at room temperature, and fixing a substrate on a substrate supporting sheet;
2) Introducing silicon raw material gas into the direction of the substrate;
3) And (3) switching on a power supply of the vapor deposition instrument, adjusting parameters, performing synchronous vapor deposition, stopping vapor deposition, and cooling to obtain the high-density high-purity silicon-carbon anode material.
Preferably, the carbon raw material comprises a carbon rope or a carbon rod, the carbon rope is made of graphite fibers with purity of 99% and diameter of 2 mm, and the length of the carbon rope is 1 cm; the purity of the carbon rod is 99%, the diameter is 2 mm, and the length is 1 cm.
Preferably, the silicon raw material gas comprises one or more of silane, disilane and dichlorosilane.
Preferably, the flow rate of the introduced silicon raw material gas is 130-200sccm.
Preferably, the evaporation in the step 3) is heated to the temperature of 420-580 ℃, and the current of an evaporator is 47-55A; maintaining an ambient pressure of 3x10 -2 pa。
Preferably, the above steps are carried out under an atmosphere of helium or argon.
Preferably, the atmosphere is achieved by a flow rate of 1000-5000 sccm.
The evaporation takes the breakage of the carbon rope or the carbon rod as an ending time point.
Preferably, the above method may further comprise the steps of:
(1) Fixing the substrate on the substrate support sheet at room temperature;
(2) Fixing carbon raw materials on an evaporation source;
(3) Turning on a power supply of the evaporation instrument, adjusting parameters, and evaporating carbon raw materials;
(4) Stopping evaporation of the carbon raw material, and introducing silicon raw material gas to the direction of the substrate;
(5) Turning on a power supply of the evaporation instrument, adjusting parameters, evaporating silicon raw material gas, and stopping evaporating the silicon raw material gas;
(6) Repeating the steps 3-6, wherein the repetition times are n, and n is a positive integer;
(7) And cooling to obtain the high-density high-purity silicon-carbon anode material.
Preferably, the carbon raw material in the step (3) is evaporated, and the current of an evaporator is 40-50A.
Preferably, the gas flow rate of the silicon raw material gas in the step (4) is 10-300sccm.
Preferably, the silicon raw material gas in the step (5) is evaporated at the temperature of 420-580 ℃ and the pressure of 3x10 -2 pa。
Preferably, the above steps are carried out under an atmosphere of helium or argon.
Preferably, the atmosphere is realized by a flow rate of 15000-20000 sccm.
Preferably, the carbon raw material comprises a carbon rope or a carbon rod, wherein the carbon rope is made of graphite fibers with purity of 99% and diameter of 4 mm, and the length of the carbon rope is 1-3 cm; the purity of the carbon rod is 99%, the diameter is 3 mm, and the length is 1-3 cm.
Preferably, the carbon raw material is evaporated for 1-2min each time, and the silicon raw material gas is evaporated for 1-4min each time.
Preferably, the substrate is a substrate for vapor deposition of a common electrode film material, and comprises any one of an amorphous silicon substrate, a Pt conductive substrate or an FTO conductive substrate, and the like, and the substrate is cleaned conventionally before use, including cleaning with acetone, ethanol, deionized water, and the like.
Advantageous effects
The invention has the beneficial effects that:
the invention adopts a physical vapor deposition mode, utilizes amorphous carbon and a vapor silicon source to form a uniform and compact composite material structure, the material is uniformly distributed in amorphous carbon by sub-nanometer silicon, and the compact structure can improve the compaction of the material and effectively relieve the volume effect in the charge and discharge process. Meanwhile, the silicon particles are of sub-nanometer level, and the self-expansion of the silicon particles is smaller than that of nanometer silicon, so that the cycle performance of the silicon particles can be further improved.
Drawings
FIG. 1 is a scanning electron microscope (3000) of the surface of the negative electrode material obtained in example 2;
FIG. 2 is an EDS layered image of the negative electrode material obtained in example 2;
FIG. 3 is an electron diffraction pattern of the negative electrode material C obtained in example 2;
FIG. 4 is a Si electron diffraction chart of the negative electrode material obtained in example 2;
FIG. 5 is a sectional electron micrograph (magnification:. Times.5000) of the negative electrode material obtained in example 2 after 50 weeks of small cycles in an expansion test.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
Unless otherwise indicated, the following examples and comparative examples were parallel runs, using the same processing steps and parameters. The substrate used in the examples and comparative examples of the present invention is a substrate for vapor deposition of a common electrode film material: FTO conductive substrates are conventionally cleaned prior to use, including cleaning with acetone, ethanol, deionized water, and the like.
Example 1 preparation (simultaneous deposition) of a high-density high-purity silicon-carbon negative electrode material:
1) Fixing carbon raw materials on an evaporation source at room temperature, and fixing a substrate on a substrate supporting sheet;
2) Introducing silicon raw material gas into the direction of the substrate;
3) And (3) switching on a power supply of the vapor deposition instrument, adjusting parameters, performing synchronous vapor deposition, stopping vapor deposition, and cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 2 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
The gas flow rate of the silicon source gas was 130sccm.
And 3) evaporating, heating to 420 ℃, wherein the current of an evaporator is 47A.
The vapor deposition in the step 3) is carried out, and the ambient pressure is kept to be 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere was achieved by a helium flow of 1000 sccm.
The evaporation takes the breakage of the carbon rope or the carbon rod as an ending time point.
Example 2 preparation (simultaneous deposition) of a high-density high-purity silicon-carbon negative electrode material:
1) Fixing carbon raw materials on an evaporation source at room temperature, and fixing a substrate on a substrate supporting sheet;
2) Introducing silicon raw material gas into the direction of the substrate;
3) And (3) switching on a power supply of the vapor deposition instrument, adjusting parameters, performing synchronous vapor deposition, stopping vapor deposition, and cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 2 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
The gas flow rate of the silicon source gas was 200sccm.
And 3) evaporating, heating to the temperature of 580 ℃, wherein the current of an evaporator is 55A.
The vapor deposition in the step 3) is carried out, and the ambient pressure is kept to be 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere was achieved by a helium flow of 5000 sccm.
The evaporation takes the breakage of the carbon rope or the carbon rod as an ending time point.
Characterization such as scanning electron microscope, electron diffraction and the like is carried out on the anode material obtained in the embodiment, and the result is shown in the accompanying figures 1-5: fig. 1 is a scanning electron microscope (x 3000) of the surface of the obtained anode material, fig. 2 is an EDS layered image of the obtained anode material, and it can be seen from fig. 2 that there are no obvious holes inside the sample, and Si and C are uniformly distributed (no Si or C aggregation region occurs); FIG. 3 is an electron diffraction diagram of the obtained anode material C, and it can be seen from FIG. 3 that the whole particles are uniformly dispersed and distributed inside C; FIG. 4 is a Si electron diffraction diagram of the obtained anode material, and it can be seen from FIG. 4 that Si is uniformly dispersed and distributed in the whole particles; fig. 5 is a section electron microscope image (x 5000) of the obtained anode material after a small cycle of 50 weeks in an expansion test, and it can be seen from fig. 5 that the structure of the silicon-carbon anode material after the cycle remains intact, no pulverization or structural collapse occurs, and the expansion is very small.
Comparative example 1 preparation (simultaneous deposition) of a high-density high-purity silicon-carbon negative electrode material:
1) Fixing carbon raw materials on an evaporation source at room temperature, and fixing a substrate on a substrate supporting sheet;
2) Introducing silicon raw material gas into the direction of the substrate;
3) And (3) switching on a power supply of the vapor deposition instrument, adjusting parameters, performing synchronous vapor deposition, stopping vapor deposition, and cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 2 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
The gas flow rate of the silicon source gas was 130sccm.
And 3) evaporating, heating to the temperature of 410 ℃ and setting the current of an evaporator to be 45A.
The vapor deposition in the step 3) is carried out, and the ambient pressure is kept to be 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere was achieved by a helium flow of 1000 sccm.
The evaporation takes the breakage of the carbon rope or the carbon rod as an ending time point.
Comparative example 2 preparation (simultaneous deposition) of a high-density high-purity silicon-carbon negative electrode material:
1) Fixing carbon raw materials on an evaporation source at room temperature, and fixing a substrate on a substrate supporting sheet;
2) Introducing silicon raw material gas into the direction of the substrate;
3) And (3) switching on a power supply of the vapor deposition instrument, adjusting parameters, performing synchronous vapor deposition, stopping vapor deposition, and cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 2 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
The gas flow rate of the silicon source gas was 130sccm.
And 3) evaporating, namely heating to the temperature of 460 ℃, wherein the current of an evaporator is 45A.
The vapor deposition in the step 3) is carried out, and the ambient pressure is kept to be 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere was achieved by a helium flow of 1000 sccm.
The evaporation takes the breakage of the carbon rope or the carbon rod as an ending time point.
Comparative example 3 preparation (simultaneous deposition) of a high-density high-purity silicon-carbon negative electrode material:
1) Fixing carbon raw materials on an evaporation source at room temperature, and fixing a substrate on a substrate supporting sheet;
2) Introducing silicon raw material gas into the direction of the substrate;
3) And (3) switching on a power supply of the vapor deposition instrument, adjusting parameters, performing synchronous vapor deposition, stopping vapor deposition, and cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 2 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
The gas flow rate of the silicon source gas was 200sccm.
And 3) evaporating, namely heating to the temperature of 590 ℃, wherein the current of an evaporator is 60A.
The vapor deposition in the step 3) is carried out, and the ambient pressure is kept to be 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere was achieved by a helium flow of 5000 sccm.
The evaporation takes the breakage of the carbon rope or the carbon rod as an ending time point.
Comparative example 3 preparation (simultaneous deposition) of a high-density high-purity silicon-carbon negative electrode material:
1) Fixing carbon raw materials on an evaporation source at room temperature, and fixing a substrate on a substrate supporting sheet;
2) Introducing silicon raw material gas into the direction of the substrate;
3) And (3) switching on a power supply of the vapor deposition instrument, adjusting parameters, performing synchronous vapor deposition, stopping vapor deposition, and cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 3 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
The gas flow rate of the silicon source gas was 200sccm.
And 3) evaporating, heating to 590 ℃, and setting the current of an evaporator to 55A.
The vapor deposition in the step 3) is carried out, and the ambient pressure is kept to be 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere was achieved by a helium flow of 5000 sccm.
The evaporation takes the breakage of the carbon rope or the carbon rod as an ending time point.
Example 4 preparation (alternate deposition) of a high density high purity silicon carbon negative electrode material:
(1) Fixing the substrate on the substrate support sheet at room temperature;
(2) Fixing carbon raw materials on an evaporation source;
(3) Turning on a power supply of the evaporation instrument, adjusting parameters, and evaporating carbon raw materials;
(4) Stopping evaporation of the carbon raw material, and introducing silicon raw material gas to the direction of the substrate;
(5) Turning on a power supply of the evaporation instrument, adjusting parameters, evaporating silicon raw material gas, and stopping evaporating the silicon raw material gas;
(6) Repeating the steps 3-6, wherein the repetition times are n, and n is 3;
(7) And cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 4 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
And (3) evaporating the carbon raw material, wherein the current of an evaporator is 40A.
And (3) the flow rate of the introduced silicon raw material gas in the step (4) is 50sccm.
The silicon raw material gas in the step (5) is evaporated, the temperature is 420 ℃, and the pressure is 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere was achieved by a helium flow of 15000 sccm.
And the carbon raw material is evaporated for 2min each time, and the silicon raw material gas is evaporated for 1min each time.
Example 5 preparation (alternate deposition) of a high density high purity silicon carbon negative electrode material:
(1) Fixing the substrate on the substrate support sheet at room temperature;
(2) Fixing carbon raw materials on an evaporation source;
(3) Turning on a power supply of the evaporation instrument, adjusting parameters, and evaporating carbon raw materials;
(4) Stopping evaporation of the carbon raw material, and introducing silicon raw material gas to the direction of the substrate;
(5) Turning on a power supply of the evaporation instrument, adjusting parameters, evaporating silicon raw material gas, and stopping evaporating the silicon raw material gas;
(6) Repeating the steps 3-6, wherein the repetition times are n, and n is 3;
(7) And cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 4 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
And (3) evaporating the carbon raw material, wherein the current of an evaporator is 40A.
And (3) the flow rate of the introduced silicon raw material gas in the step (4) is 50sccm.
The silicon raw material gas in the step (5) is evaporated, the temperature is 460 ℃, and the pressure is 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere was achieved by a helium flow of 15000 sccm.
And the carbon raw material is evaporated for 2min each time, and the silicon raw material gas is evaporated for 1min each time.
Example 6 preparation (alternate deposition) of a high density high purity silicon carbon negative electrode material:
(1) Fixing the substrate on the substrate support sheet at room temperature;
(2) Fixing carbon raw materials on an evaporation source;
(3) Turning on a power supply of the evaporation instrument, adjusting parameters, and evaporating carbon raw materials;
(4) Stopping evaporation of the carbon raw material, and introducing silicon raw material gas to the direction of the substrate;
(5) Turning on a power supply of the evaporation instrument, adjusting parameters, evaporating silicon raw material gas, and stopping evaporating the silicon raw material gas;
(6) Repeating the steps 3-6, wherein the repetition times are n, and n is 3;
(7) And cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 4 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
And (3) evaporating the carbon raw material, wherein the current of an evaporator is 50A.
And (3) the flow rate of the introduced silicon raw material gas in the step (4) is 300sccm.
The silicon raw material gas in the step (5) is evaporated, the temperature is 580 ℃, and the pressure is 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere is realized by a helium flow of 20000 sccm.
And the carbon raw material is evaporated for 4min each time, and the silicon raw material gas is evaporated for 2min each time.
Comparative example 4 preparation (alternate deposition) of a high density high purity silicon carbon negative electrode material:
(1) Fixing the substrate on the substrate support sheet at room temperature;
(2) Fixing carbon raw materials on an evaporation source;
(3) Turning on a power supply of the evaporation instrument, adjusting parameters, and evaporating carbon raw materials;
(4) Stopping evaporation of the carbon raw material, and introducing silicon raw material gas to the direction of the substrate;
(5) Turning on a power supply of the evaporation instrument, adjusting parameters, evaporating silicon raw material gas, and stopping evaporating the silicon raw material gas;
(6) Repeating the steps 3-6, wherein the repetition times are n, and n is 3;
(7) And cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 4 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
And (3) evaporating the carbon raw material, wherein the current of an evaporator is 35A.
And (3) the flow rate of the introduced silicon raw material gas in the step (4) is 50sccm.
The silicon raw material gas in the step (5) is evaporated, the temperature is 420 ℃, and the pressure is 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere was achieved by a helium flow of 15000 sccm.
And the carbon raw material is evaporated for 2min each time, and the silicon raw material gas is evaporated for 1min each time.
Comparative example 5 preparation (alternate deposition) of a high density high purity silicon carbon negative electrode material:
(1) Fixing the substrate on the substrate support sheet at room temperature;
(2) Fixing carbon raw materials on an evaporation source;
(3) Turning on a power supply of the evaporation instrument, adjusting parameters, and evaporating carbon raw materials;
(4) Stopping evaporation of the carbon raw material, and introducing silicon raw material gas to the direction of the substrate;
(5) Turning on a power supply of the evaporation instrument, adjusting parameters, evaporating silicon raw material gas, and stopping evaporating the silicon raw material gas;
(6) Repeating the steps 3-6, wherein the repetition times are n, and n is 3;
(7) And cooling to obtain the high-density high-purity silicon-carbon anode material.
The carbon raw material comprises a carbon rope, the carbon rope is made of graphite fibers with purity of 99% and diameter of 4 mm, and the length of the carbon rope is 1 cm.
The silicon feedstock gas includes silane.
And (3) evaporating the carbon raw material, wherein the current of an evaporator is 55A.
And (3) the flow rate of the introduced silicon raw material gas in the step (4) is 300sccm.
The silicon raw material gas in the step (5) is evaporated, the temperature is 590 ℃, and the pressure is 3x10 -2 pa。
The above steps were performed under helium atmosphere.
The helium atmosphere is realized by a helium flow of 20000 sccm.
And the carbon raw material is evaporated for 4min each time, and the silicon raw material gas is evaporated for 2min each time.
And (3) performance detection:
1. and (3) testing the electrical properties of the anode material:
test conditions: taking the materials prepared in the comparative examples and the examples as a negative electrode material, mixing the negative electrode material with a binder polyvinylidene fluoride (PVDF) and a conductive agent (Super-P) according to the mass ratio of 70:15:15, adding a proper amount of N-methyl pyrrolidone (NMP) as a solvent to prepare slurry, coating the slurry on a copper foil, and carrying out vacuum drying and rolling to prepare a negative electrode plate; a metal lithium sheet is used as a counter electrode, a three-component LiPF6 mixed solvent with the concentration of 1mol/L is used for preparing a CR2032 button cell in a glove box filled with inert gas according to electrolyte mixed by the concentration of EC, DMC, EMC=1:1:1 (v/v), and a polypropylene microporous membrane is used as a diaphragm.
The charge and discharge test of button cell is carried out on LANHE cell test system of blue electric power electronic Co Ltd in Wuhan city, and under normal temperature condition, 0.1C constant current charge and discharge is carried out, and the charge and discharge voltage is limited to 0.005-1.5V.
The volume expansion rate of the material was tested and calculated using the following method: the prepared silicon-carbon composite material and graphite are compounded to prepare the composite material with the capacity of 500mAh/g, and the cycle performance is tested, and the expansion rate= (the thickness of the pole piece after 50 weeks of cycle-the thickness of the pole piece before cycle)/(the thickness of the pole piece before cycle-the thickness of the copper foil) ×100%. The results obtained are shown in the following table:
from the results of the table, the method adopted by the application can achieve the conditions that the first reversible capacity is not lower than 1800mAh/g, the expansion rate is lower than 35% after 50 times of circulation, the capacity retention rate is higher than 90%, and the density parameter is achieved. As can be seen from the comparative examples, electrochemical performance is greatly reduced when the deposition temperature is below or above the range defined herein; when the temperature of simultaneous deposition is below the range defined herein, the silicon source gas deposition efficiency is extremely low or even absent; when the simultaneous deposition temperature is above the range defined herein, the deposited nanosilicon reacts with the carbon material to produce silicon carbide.
While the preferred embodiments and examples of the present invention have been described in detail, the present invention is not limited to the above-described embodiments and examples, and various changes may be made within the knowledge of those skilled in the art without departing from the spirit of the present invention.
Claims (10)
1. A high-density high-purity silicon-carbon negative electrode material is characterized in that: the material comprises silicon and carbon which are uniformly and densely distributed, wherein the density of the material meets the requirement that ρ1/ρ2 is more than or equal to 95%, wherein ρ1 is the actual test density, and ρ2 is the theoretical density.
2. The high-density high-purity silicon-carbon negative electrode material according to claim 1, wherein: and performing physical vapor deposition on the carbon raw material and the silicon raw material, and cooling to obtain the high-density high-purity silicon-carbon anode material.
3. The high-density high-purity silicon-carbon negative electrode material according to claim 1, wherein: the high-density high-purity silicon-carbon negative electrode material is prepared by the following steps:
1) Fixing carbon raw materials on an evaporation source at room temperature, and fixing a substrate on a substrate supporting sheet;
2) Introducing silicon raw material gas into the direction of the substrate;
3) And (3) switching on a power supply of the vapor deposition instrument, adjusting parameters, performing synchronous vapor deposition, stopping vapor deposition, and cooling to obtain the high-density high-purity silicon-carbon anode material.
4. A high density high purity silicon carbon negative electrode material according to claim 3 wherein: the carbon raw material comprises a carbon rope or a carbon rod, the purity is 99 percent, the diameter is 2 millimeters, and the length is 1 centimeter; optionally, the silicon raw material gas comprises one or more of silane, disilane and dichlorosilane.
5. A high density high purity silicon carbon negative electrode material according to claim 3 wherein: the flow rate of the introduced silicon raw material gas is 130-200sccm.
6. A high density high purity silicon carbon negative electrode material according to claim 3 wherein: step 3) evaporation is carried out, the temperature is heated to 420-580 ℃, and the current of an evaporator is 47-55A; maintaining an ambient pressure of 3x10 -2 pa。
7. A high density high purity silicon carbon negative electrode material according to claim 3 wherein: the above steps are carried out under one atmosphere of nitrogen, hydrogen, helium or argon; optionally, the atmosphere is achieved at a flow rate of 1000-5000 sccm.
8. The high-density high-purity silicon-carbon negative electrode material according to claim 2, characterized in that: the high-density high-purity silicon-carbon negative electrode material is prepared by the following steps:
(1) Fixing the substrate on the substrate support at room temperature
(2) Fixing carbon raw materials on an evaporation source;
(3) Turning on a power supply of the evaporation instrument, adjusting parameters, and evaporating carbon raw materials;
(4) Stopping evaporation of the carbon raw material, and introducing silicon raw material gas to the direction of the substrate;
(5) Turning on a power supply of the evaporation instrument, adjusting parameters, evaporating silicon raw material gas, and stopping evaporating the silicon raw material gas and the material gas;
(6) Repeating the steps 3-6, wherein the repetition times are n, and n is a positive integer;
(7) And cooling to obtain the high-density high-purity silicon-carbon anode material.
9. The high-density high-purity silicon-carbon negative electrode material according to claim 8, wherein: the carbon raw material comprises a carbon rope or a carbon rod, the purity is 99 percent, the diameter is 2 millimeters, and the length is 1 centimeter; optionally, the silicon raw material gas comprises one or more than two of silane, disilane and dichlorosilane; optionally, evaporating the carbon raw material in the step (3), wherein the current of an evaporator is 40-50A.
10. The high-density high-purity silicon-carbon negative electrode material according to claim 8, wherein: the gas flow rate of the silicon raw material gas in the step (4) is 10-300sccm; optionally, the silicon raw material gas in the step (5) is evaporated at the temperature of 420-580 ℃ and the pressure of 3x10 -2 pa。
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