CN113809310B - Boron-doped soft carbon-coated silicon-based lithium ion anode material and preparation method and application thereof - Google Patents

Boron-doped soft carbon-coated silicon-based lithium ion anode material and preparation method and application thereof Download PDF

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CN113809310B
CN113809310B CN202010543274.0A CN202010543274A CN113809310B CN 113809310 B CN113809310 B CN 113809310B CN 202010543274 A CN202010543274 A CN 202010543274A CN 113809310 B CN113809310 B CN 113809310B
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潘明军
刘柏男
罗飞
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Tianmulake Excellent Anode Materials Co Ltd
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    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01—ELECTRIC ELEMENTS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract

The invention relates to a boron-doped soft carbon coated silicon-based lithium ion anode material, and a preparation method and application thereof. Taking a boron-containing gas source or a high-boiling point boron-containing compound as a doping material, and carrying out gas-phase mixing reaction on vapor of the doping material and preheated vapor of a silicon source at 1200-1700 ℃ for 1-24 hours to obtain a boron-doped silicon oxide material; wherein the silicon source vapor is a mixed vapor of silicon vapor and silicon dioxide vapor; the boron-containing gas source is a boron-containing compound which is in a gaseous state at normal temperature, and the high-boiling point boron-containing compound is a boron-containing compound which is in a liquid state or a solid state at normal temperature; cooling the boron doped silicon oxide material to room temperature, discharging, crushing and screening; carrying out flight time secondary ion mass spectrometry analysis test on the crushed and sieved material, and confirming whether the doping uniformity of boron doped in the silicon oxide meets the preset condition; and (3) coating the material with the doping uniformity meeting the preset condition with carbon to obtain the boron-doped silicon-based lithium ion battery anode material.

Description

Boron-doped soft carbon-coated silicon-based lithium ion anode material and preparation method and application thereof
Technical Field
The invention relates to the technical field of material preparation, in particular to a boron-doped soft carbon coated silicon-based lithium ion anode material, and a preparation method and application thereof.
Background
With the rapid development of new energy automobiles, higher requirements are put on the performance of power batteries in the industry. The positive and negative electrode materials determine key components of the power battery, such as energy density, power density, cycle life, high and low temperature performance and safety performance, and the positive and negative electrode materials are mainly used for freely deintercalating lithium ions so as to realize the charge and discharge functions of the battery. The requirements of the lithium ion battery anode material at least meet the following points: 1. a lower chemical potential; 2. good electrical conductivity; 3. good cycle stability and safety; 4. inexpensive raw materials, and the like.
The negative electrode material is one of the most critical materials in lithium ion battery technology. Currently commercially available graphite anodes have reached their technical bottlenecks due to their low gram capacity. Silicon is one of the most promising lithium ion negative electrode materials to replace it. The silicon-based anode material has a series of defects such as volume expansion effect, poor conductivity and the like, and limits the practical application thereof.
Patent CN106654194a provides a preparation method of an element doped silicon oxide lithium ion battery anode material. The doped metal and nonmetallic elements are combined, defects of the anode material are constructed through nonmetallic materials, the intrinsic ion transmission capacity of the material is improved, meanwhile, the conductivity of the material is improved through a metal and SiOx mixed conductive network, a certain position is reserved for volume expansion, and the high specific capacity and good cycle performance can be achieved. However, the preparation method adopts liquid-phase and solid-phase mixing, and the uniformity of bulk phase doping cannot be ensured, so that the consistency of the material obtained by the preparation method is affected, and the cycle performance of the material is possibly affected.
Disclosure of Invention
The embodiment of the invention provides a boron-doped soft carbon-coated silicon-based lithium ion anode material, a preparation method and application thereof, and the anode material of a lithium ion battery, which is obtained through gas phase reaction and is uniformly doped in a bulk phase, has higher cycling stability and better consistency.
In a first aspect, an embodiment of the present invention provides a method for preparing a boron doped soft carbon coated silicon-based lithium ion anode material, including:
taking a boron-containing gas source or a high-boiling point boron-containing compound as a doping material, and carrying out gas-phase mixing on vapor of the doping material and preheated vapor of a silicon source to react for 1-24 hours at 1200-1700 ℃ to obtain a boron-doped silicon oxide material; wherein the silicon source vapor is a mixed vapor of silicon vapor and silicon dioxide vapor; the boron-containing gas source is a boron-containing compound which is in a gaseous state at normal temperature, and the high-boiling point boron-containing compound is a boron-containing compound which is in a liquid state or a solid state at normal temperature;
cooling the boron doped silicon oxide material to room temperature, discharging, crushing and screening;
carrying out flight time secondary ion mass spectrometry analysis test on the crushed and sieved material, and confirming whether the doping uniformity of boron doped in the silicon oxide meets the preset condition;
and (3) coating the material with the doping uniformity meeting the preset condition with carbon to obtain the boron-doped silicon-based lithium ion anode material.
Preferably, the boron-containing gas source specifically includes: one or more of diborane, boron trichloride or boron trifluoride;
the high boiling point boron-containing compound specifically comprises: one or more of decaborane, boric acid, or sodium borohydride.
Preferably, the vapour of the doping material is obtained by heating the doping material to a temperature of 25 ℃ to 800 ℃.
Preferably, the silicon vapor and the silicon dioxide vapor in the silicon source vapor are prepared by the following steps of: silica = 1: 1.
Preferably, the atomic mass of boron in the doping material accounts for 100ppm-100000ppm of the total mass of silicon and silicon dioxide in the silicon source vapor.
Preferably, the preset conditions are specifically: in the time-of-flight secondary ion mass spectrometry analysis and test process, the fluctuation range of the boron atom concentration is within +/-50% in the whole particle sputtering time period.
Preferably, the carbon coating is specifically: placing the materials with the doping uniformity meeting the preset conditions in a rotary furnace, heating to 800-1000 ℃ under a protective atmosphere, introducing an organic gas source for chemical vapor deposition, keeping the temperature for 2-4 hours, and then closing the organic gas source for cooling; wherein, the organic air source specifically includes: one or more of methane, acetylene, propylene or propane.
In a second aspect, an embodiment of the present invention provides a lithium ion battery negative electrode material, which includes the boron doped soft carbon coated silicon-based lithium ion negative electrode material prepared by the preparation method in the first aspect.
In a third aspect, an embodiment of the present invention provides a lithium battery pole piece, where the lithium battery pole piece includes the lithium ion battery negative electrode material described in the second aspect.
In a fourth aspect, an embodiment of the present invention provides a lithium battery, where the lithium battery includes the lithium battery pole piece described in the third aspect.
According to the preparation method of the boron-doped soft carbon-coated silicon-based lithium ion anode material, the anode material of the lithium ion battery which is uniformly doped with the bulk phase and is obtained through gas phase reaction has higher cycling stability, and meanwhile, the consistency of the material is better.
Drawings
The technical scheme of the embodiment of the invention is further described in detail through the drawings and the embodiments.
FIG. 1 is a flow chart of a preparation method of a boron doped soft carbon coated silicon-based lithium ion anode material according to an embodiment of the invention;
fig. 2 is a time-of-flight secondary ion mass spectrum of the boron-doped silicon-based lithium ion battery anode material provided in embodiment 1 of the invention;
FIG. 3 is a graph of the time-of-flight secondary ion mass spectrum of the uniform boron-doped silicon-based lithium ion battery anode material provided in comparative example 1 of the present invention;
FIG. 4 is a graph of the time-of-flight secondary ion mass spectrum of the negative electrode material of the uniform boron-doped silicon-based lithium ion battery provided in comparative example 2 of the present invention;
fig. 5 is a comparison of time-of-flight secondary ion mass spectra of the uniform boron-doped silicon-based lithium ion battery anode materials provided in example 1 and comparative examples 1-2 of the present invention.
Detailed Description
The invention is further illustrated by the drawings and the specific examples, which are to be understood as being for the purpose of more detailed description only and are not to be construed as limiting the invention in any way, i.e. not intended to limit the scope of the invention.
The preparation method of the boron-doped soft carbon coated silicon-based lithium ion anode material comprises the following steps as shown in fig. 1:
110, taking a boron-containing gas source or a high-boiling point boron-containing compound as a doping material, and carrying out gas-phase mixing reaction on vapor of the doping material and preheated vapor of a silicon source at 1200-1700 ℃ for 1-24 hours to obtain a boron-doped silicon oxide material;
wherein the vapour of the doping material is obtained by heating the doping material to a temperature of 25 ℃ to 800 ℃.
The boron-containing gas source in the doping material is a boron-containing compound which is in a gaseous state at normal temperature, and can specifically comprise one or more of diborane, boron trichloride or boron trifluoride; the high boiling boron-containing compound is a boron-containing compound which is liquid or solid at normal temperature and can specifically comprise one or more of decaborane, boric acid or sodium borohydride.
The silicon source vapor is a mixed vapor of silicon vapor and silicon dioxide vapor, preferably silicon in a molar ratio: silica = 1: 1.
The atomic mass of boron in the doped material accounts for 100ppm-100000ppm of the total mass of silicon and silicon dioxide in the silicon source vapor.
Step 120, cooling the boron doped silicon oxide material to room temperature, discharging, crushing and screening;
130, performing time-of-flight secondary ion mass spectrometry analysis and test on the crushed and sieved material to confirm whether the doping uniformity of boron doped in the silicon oxide meets the preset condition;
the preset conditions of the step are specifically as follows: in the time-of-flight secondary ion mass spectrometry analysis and test process, the fluctuation range of the boron atom concentration is within +/-50% in the whole particle sputtering time period. If this condition is satisfied, it is considered acceptable to perform the next carbon coating step.
And 140, coating the material with the doping uniformity meeting the preset condition with carbon to obtain the boron-doped silicon-based lithium ion anode material.
The carbon coating is specifically as follows: placing the materials with the doping uniformity meeting the preset conditions in a rotary furnace, heating to 800-1000 ℃ under a protective atmosphere, introducing an organic gas source for chemical vapor deposition, keeping the temperature for 2-4 hours, and then closing the organic gas source for cooling;
wherein, organic air source specifically includes: one or more of methane, acetylene, propylene or propane.
According to the preparation method, the lithium ion battery anode material which is obtained through gas phase reaction and is evenly doped in the bulk phase has higher cycling stability, and meanwhile, the consistency of the material is better.
The boron-doped soft carbon coated silicon-based lithium ion anode material prepared by the preparation method can be used as a lithium ion battery anode material and applied to a lithium battery pole piece and a lithium battery.
In order to better understand the technical scheme provided by the invention, the following specific processes for preparing the lithium battery anode material by applying the method provided by the embodiment of the invention, and the method and the battery characteristics for applying the lithium battery anode material to the lithium battery are respectively described in a plurality of specific examples.
Example 1
1.4kg of silicon powder and 3kg of silicon dioxide are placed in a high-temperature reaction furnace to be heated to steam, 13.4L (12.7 g in terms of mass) of diborane is slowly introduced under the protection of argon, and the mixture is reacted for 4 hours at 1500 ℃ and cooled to room temperature. The output was detected by time-of-flight secondary ion mass spectrometry (TOF-SIMS) after fragmentation. Fig. 2 is a graph of a secondary ion mass spectrum of the time of flight of the boron doped silicon-based lithium ion battery anode material provided in embodiment 1 of the present invention, and it can be seen from the graph that the fluctuation of boron atom concentration is uniformly distributed in etching time within a limited range + -50%.
Placing 2kg of qualified materials into a rotary furnace, heating to 1000 ℃ under the atmosphere of protective argon, and mixing according to the volume ratio of 1:2 introducing argon and acetylene mixed gas to perform chemical vapor deposition, keeping the temperature for 2 hours, closing an organic gas source, and cooling to obtain the uniform boron-doped soft carbon coated silicon-based lithium ion battery anode material, wherein the boron content of the anode material is 0.11%.
The resulting negative electrode material, conductive additive carbon black, binder 1:1, sodium cellulose and styrene-butadiene rubber according to the mass ratio of 95 percent: 2%:3% of the weight was weighed. At room temperature, the mixture is put into a beater for slurry preparation. And uniformly coating the prepared slurry on the copper foil. Drying at 50deg.C in a forced air drying oven for 2 hr, cutting into 8×8mm pole pieces, and vacuum drying at 100deg.C in a vacuum drying oven for 10 hr. And transferring the dried pole piece into a glove box for standby use to assemble a battery.
The simulated cell was assembled in a glove box containing a high purity Ar atmosphere using metallic lithium as the counter electrode, 1 mole LiPF 6 The solution in ethylene carbonate EC/dimethyl carbonate DMC was used as an electrolyte to assemble a battery. The constant current charge and discharge mode test was performed using a charge and discharge meter with a discharge cutoff voltage of 0.005V and a charge cutoff voltage of 1.5V, with the first week of charge and discharge test being performed at C/10 current density and the second week of discharge test being performed at C/10 current density.
Example 2
2.8kg of silicon powder and 6kg of silicon dioxide are placed in a high-temperature reaction furnace to be heated to steam, 3.2L (3 g converted mass) of diborane is slowly introduced under the protection of argon, and the mixture is reacted for 8 hours at 1200 ℃ and cooled to room temperature. And (5) detecting the qualified products by TOF-SIMS after the discharged materials are crushed. Placing 2kg of qualified materials into a rotary furnace, heating to 850 ℃ under the atmosphere of protective argon, and mixing according to the volume ratio of 1:2, introducing argon and mixed gas of propylene and acetylene for chemical vapor deposition, wherein the volume ratio of the propylene to the acetylene is 1:1, preserving heat for 4 hours, closing an organic air source, and cooling to obtain the uniform boron-doped soft carbon coated silicon-based lithium ion battery anode material, wherein the boron content of the anode material is 0.013%.
The preparation process of the negative electrode tab and the battery assembly and battery testing method were the same as in example 1.
Example 3
7kg of silicon powder and 15kg of silicon dioxide are placed in a high-temperature reaction furnace to be heated to steam, 35L (141 g in terms of mass) of boron trichloride is slowly introduced under the protection of argon, and the mixture is reacted for 18 hours at 1300 ℃ and cooled to room temperature. And (5) detecting the qualified products by TOF-SIMS after the discharged materials are crushed. Placing 2kg of qualified materials into a rotary furnace, heating to 900 ℃ under the atmosphere of protective argon, and mixing according to the volume ratio of 1: and 1, introducing argon and propylene equivalent to the argon for chemical vapor deposition, keeping the temperature for 2.5 hours, closing an organic air source, and cooling to obtain the uniform boron-doped soft carbon coated silicon-based lithium ion battery anode material, wherein the boron content of the anode material is 0.059%.
The preparation process of the negative electrode tab and the battery assembly and battery testing method were the same as in example 1.
Example 4
2.8kg of silicon powder and 6kg of silicon dioxide are placed in a high-temperature reaction furnace to be heated to steam, 910g of sodium borohydride is heated to 550 ℃ to be changed into steam, the steam is mixed with each other, and then the mixture is reacted for 7 hours at 1600 ℃ and cooled to room temperature. And (5) detecting the qualified products by TOF-SIMS after the discharged materials are crushed. Placing 2kg of qualified materials into a rotary furnace, heating to 900 ℃ under the atmosphere of protective argon, and mixing according to the volume ratio of 1: and 1, introducing argon and acetylene equivalent to the argon for chemical vapor deposition, keeping the temperature for 3 hours, closing an organic air source, and cooling to obtain the uniform boron-doped soft carbon coated silicon-based lithium ion battery anode material, wherein the boron content of the anode material is 2.9%.
The preparation process of the negative electrode tab and the battery assembly and battery testing method were the same as in example 1.
Example 5
1.4kg of silicon powder and 3kg of silicon dioxide are placed in a high-temperature reaction furnace to be heated to steam, 210g of sodium borohydride is heated to 550 ℃ to be changed into steam, the steam is mixed with each other to react for 3.5 hours at 1500 ℃, and the mixture is cooled to room temperature. And (5) detecting the qualified products by TOF-SIMS after the discharged materials are crushed. Placing 2kg of qualified materials into a rotary furnace, heating to 1000 ℃ under the atmosphere of protective argon, and mixing according to the volume ratio of 1:1, introducing argon and mixed gas of acetylene and propane with the same amount as the argon for chemical vapor deposition, wherein the volume ratio of the acetylene to the propane in the mixed gas is 3:1, preserving heat for 3 hours, closing an organic air source, and cooling to obtain the uniform boron-doped soft carbon coated silicon-based lithium ion battery anode material, wherein the boron content of the anode material is 1.4%.
The preparation process of the negative electrode tab and the battery assembly and battery testing method were the same as in example 1.
Example 6
2.8kg of silicon powder and 6kg of silicon dioxide are placed in a high-temperature reaction furnace to be heated to steam, 8L (the converted mass is 32.2 g) of boron trichloride is slowly introduced under the protection of argon, and the mixture is reacted for 8 hours at 1400 ℃ and cooled to room temperature. And (5) detecting the qualified products by TOF-SIMS after the discharged materials are crushed. Placing 2kg of qualified materials in a rotary furnace, heating to 950 ℃ in a protective argon atmosphere, and mixing according to a volume ratio of 1:2 introducing argon and acetylene for chemical vapor deposition, keeping the temperature for 2.5 hours, closing an organic air source, and cooling to obtain the uniform boron-doped soft carbon coated silicon-based lithium ion battery anode material, wherein the boron content of the anode material is 0.033%.
The preparation process of the negative electrode tab and the battery assembly and battery testing method were the same as in example 1.
Example 7
1.4kg of silicon powder and 3kg of silicon dioxide are placed in a high-temperature reaction furnace to be heated to steam, 10g of decaborane is heated to 230 ℃ to be changed into steam, the steam is mixed with each other, and then the mixture is reacted for 3 hours at 1700 ℃ and cooled to room temperature. And (5) detecting the qualified products by TOF-SIMS after the discharged materials are crushed. Placing 2kg of qualified materials into a rotary furnace, heating to 1000 ℃ under the atmosphere of protective argon, and mixing according to the volume ratio of 1:2 introducing argon and acetylene for chemical vapor deposition, keeping the temperature for 2 hours, closing an organic air source, and cooling to obtain the uniform boron-doped soft carbon coated silicon-based lithium ion battery anode material, wherein the boron content of the anode material is 0.2%.
The preparation process of the negative electrode tab and the battery assembly and battery testing method were the same as in example 1.
Example 8
2.8kg of silicon powder and 6kg of silicon dioxide are placed in a high-temperature reaction furnace to be heated to steam, and simultaneously, 5g of decaborane is heated to 230 ℃ to be changed into steam, and the steam is mixed with each other to react for 9 hours at 1700 ℃, and cooled to room temperature. And (5) detecting the qualified products by TOF-SIMS after the discharged materials are crushed. Placing 2kg of qualified materials into a rotary furnace, heating to 1000 ℃ under the atmosphere of protective argon, and mixing according to the volume ratio of 1: and 1, introducing argon and propylene for chemical vapor deposition, keeping the temperature for 2 hours, closing an organic air source, and cooling to obtain the uniform boron-doped soft carbon coated silicon-based lithium ion battery anode material, wherein the boron content of the anode material is 0.05%.
The preparation process of the negative electrode tab and the battery assembly and battery testing method were the same as in example 1.
Comparative example 1
This comparative example provides a negative electrode material for a lithium ion battery in comparison with example 1. 2kg of silicon oxide and 7.6g of sodium borohydride are mechanically mixed and then subjected to a time-of-flight secondary ion mass spectrometer (TOF-SIMS) test, and then placed in a rotary furnace, heated to 1000 ℃ under the protection of argon, and the volume ratio is 1:1: and 1, introducing argon and propylene and methane gas which are respectively equal to the argon for chemical vapor deposition, keeping the temperature for 2 hours, closing an organic gas source, and cooling to obtain the negative electrode material of the lithium ion battery for comparison, wherein the boron content of the obtained negative electrode material is 0.11%.
The preparation process of the negative electrode tab and the battery assembly and battery testing method were the same as in example 1.
Comparative example 2
Comparative example 2 provides a negative electrode material for a lithium ion battery in comparison with example 1. 2kg of silicon oxide and 7.6g of sodium borohydride are uniformly mixed by water, and spray-dried to obtain the composite silicon oxide raw material. After the composite silica raw material is detected by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), the temperature is raised to 1000 ℃ in a rotary furnace under the protection of argon, and the volume ratio is 1:1: and 1, introducing argon and propylene and methane gas which are respectively equal to the argon for chemical vapor deposition, keeping the temperature for 2 hours, closing an organic gas source, and cooling to obtain the negative electrode material of the lithium ion battery for comparison, wherein the boron content of the obtained negative electrode material is 0.11%.
The preparation process of the negative electrode tab and the battery assembly and battery testing method were the same as in example 1.
The negative electrode materials of examples 1 to 8 and comparative examples 1 to 2 above were respectively subjected to the initial efficiency, 0.1C reversible capacity, cycle performance at 0.1C magnification, and other index tests, and the results are shown in table 1.
Figure BDA0002539788500000101
TABLE 1
As can be seen from the data in table 1, in the same case, examples 1 to 8 all adopt the gas phase mixing technology to modify the silicon-based anode material, and the lithium battery has good performance consistency and high specific charge capacity and cycle performance due to uniform gas phase mass transfer. Comparative examples 1-2 modified silicon-based anode materials with solid-phase coating and liquid-phase coating, respectively, and it can be seen from comparative example 1 that the cycle stability during long cycles is poor, mainly due to insufficient contact of the solid-phase coating and the presence of an activated region of incomplete reaction. Comparative example 2 was liquid phase coated with a relatively more uniform doping than comparative example 1, but since the liquid phase coating was performed with an aqueous phase, the silica contacted a large amount of oxygen dissolved in water, resulting in partial oxidation of the surface, and a reduction in the first efficiency and capacity.
In addition, fig. 5 is a graph comparing the time-of-flight secondary ion mass spectra of the anode materials of the uniform boron-doped silicon-based lithium ion batteries provided in example 1 and comparative examples 1-2 of the present invention. As can be seen from comparison, in comparative examples 1-2, the fluctuation range of boron atoms was uniform at the beginning by the solid phase cladding method and the liquid phase cladding method, respectively, but when etching into the material, the boron atoms were not dispersed inside due to the defect of non-bulk doping with the increase of etching time, so that the boron atom concentration was gradually zero. And because the vapor reaction mode is adopted, when the silicon oxide is generated, corresponding boron atoms enter the silicon oxide material together, so that the boron atoms are uniformly distributed in the whole material from inside to outside.
According to the preparation method of the boron-doped soft carbon-coated silicon-based lithium ion anode material, the anode material of the lithium ion battery which is uniformly doped with the bulk phase and is obtained through gas phase reaction has higher cycling stability, and meanwhile, the consistency of the material is better.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the scope of the invention, but to limit the invention to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (7)

1. The preparation method of the boron-doped soft carbon-coated silicon-based lithium ion anode material is characterized by comprising the following steps of:
taking a boron-containing gas source or a high-boiling point boron-containing compound as a doping material, and carrying out gas-phase mixing reaction on vapor of the doping material and preheated vapor of a silicon source at 1200-1700 ℃ for 1-24 hours to obtain a boron-doped silicon oxide material; wherein the silicon source vapor is a mixed vapor of silicon vapor and silicon dioxide vapor; the boron-containing gas source is a boron-containing compound which is in a gaseous state at normal temperature, and the high-boiling point boron-containing compound is a boron-containing compound which is in a liquid state or a solid state at normal temperature; the boron-containing gas source specifically comprises: one or more of diborane, boron trichloride or boron trifluoride; the high boiling point boron-containing compound specifically comprises: one or more of decaborane, boric acid, or sodium borohydride; the vapor of the doping material is obtained by heating the doping material to 25-800 ℃;
cooling the boron doped silicon oxide material to room temperature, discharging, crushing and screening;
carrying out flight time secondary ion mass spectrometry analysis test on the crushed and sieved material, and confirming whether the doping uniformity of boron doped in the silicon oxide meets the preset condition;
coating the material with the doping uniformity meeting the preset condition with carbon to obtain a boron-doped soft carbon coated silicon-based lithium ion anode material;
wherein, the preset conditions are specifically as follows: in the time-of-flight secondary ion mass spectrometry analysis and test process, the fluctuation range of the boron atom concentration is within +/-50% in the whole particle sputtering time period.
2. The method of claim 1, wherein the silicon vapor and the silicon dioxide vapor in the silicon source vapor are in a molar ratio of silicon: silica = 1: 1.
3. The method of claim 1, wherein the atomic mass of boron in the dopant material is 100ppm to 100000ppm based on the total mass of silicon and silicon dioxide in the silicon source vapor.
4. The method according to claim 1, wherein the carbon coating is specifically: placing the materials with the doping uniformity meeting the preset conditions in a rotary furnace, heating to 800-1000 ℃ under a protective atmosphere, introducing an organic gas source for chemical vapor deposition, preserving the heat for 2-4 hours, and then closing the organic gas source for cooling; wherein, the organic air source specifically includes: one or more of methane, acetylene, propylene or propane.
5. The negative electrode material of the lithium ion battery is characterized in that the negative electrode material is the boron doped soft carbon coated silicon-based lithium ion negative electrode material prepared by the preparation method of any one of claims 1-4.
6. A lithium battery pole piece, characterized in that the lithium battery pole piece comprises the lithium ion battery anode material according to claim 5.
7. A lithium battery comprising the lithium battery pole piece of claim 6.
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