CN113809312A - Nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material and preparation method and application thereof - Google Patents

Nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material and preparation method and application thereof Download PDF

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CN113809312A
CN113809312A CN202010543313.7A CN202010543313A CN113809312A CN 113809312 A CN113809312 A CN 113809312A CN 202010543313 A CN202010543313 A CN 202010543313A CN 113809312 A CN113809312 A CN 113809312A
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silicon
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CN113809312B (en
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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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    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

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

Description

Nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material and preparation method and application thereof
Technical Field
The invention relates to the technical field of material preparation, in particular to a nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material and a preparation method and application thereof.
Background
With the rapid development of new energy automobiles, higher requirements on the performance of power batteries are put forward in the industry. The anode and cathode materials determine the key components of the energy density, power density, cycle life, high and low temperature performance and safety performance of the power battery, and the main function of the lithium ion battery is to enable lithium ions to be freely deintercalated and realize the charging and discharging functions of the battery. The requirements of the lithium ion battery cathode material at least meet the following points: 1. a lower chemical potential; 2. good conductivity; 3. good cycle stability and safety; 4. inexpensive raw materials, and the like.
The cathode material is one of the most critical materials of the lithium ion battery technology. The graphite negative electrodes currently on the market have reached their technical bottleneck due to their low gram capacity. And silicon is one of the most promising lithium ion negative electrode materials to replace it. The silicon-based anode material with specific capacity as high as 4200mAh/g gradually shows the advantage of high energy density. Although silicon-based anode materials can achieve satisfactory energy density, there is also a technical bottleneck of the materials. The silicon-based negative electrode material has a series of defects of volume expansion effect, poor conductivity and the like, and practical application of the silicon-based negative electrode material is limited.
Nitrogen doping is a relatively common modification. Patent CN110911665A provides a method for preparing a boron and nitrogen doped lithium ion battery negative electrode material, which comprises mixing melamine, ammonium borate, ethyl orthosilicate, hydrochloric acid, deionized water and ethanol to obtain a colloidal precursor solution, drying the solution, carbonizing, ball-milling, and performing a series of treatments to obtain the boron and nitrogen doped lithium ion battery negative electrode material. The battery prepared from the obtained cathode material has good rate performance and electrochemical performance. But the solution also has disadvantages. Since solid particles are mixed in a liquid phase and still subjected to mass transfer contact in a solid phase manner after drying, the conditions of non-uniform reaction and poor particle dispersion still exist, which affect the consistency of the material obtained by the preparation method and may consequently affect the cycle performance of the material.
Disclosure of Invention
The embodiment of the invention provides a nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material, and a preparation method and application thereof.
In a first aspect, an embodiment of the present invention provides a method for preparing a nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material, including:
taking a nitrogen-containing gas source or a high-boiling point nitrogen-containing compound as a doping material, and carrying out gas-phase mixing reaction on vapor of the doping material and preheated silicon source vapor at 1200-1700 ℃ for 1-24 hours to obtain a nitrogen-doped silicon protoxide material; wherein the silicon source vapor is a mixed vapor of silicon vapor and silicon dioxide vapor; the nitrogen-containing gas source is a nitrogen-containing compound which is gaseous at normal temperature, and the high-boiling point nitrogen-containing compound is a liquid or solid nitrogen-containing compound at normal temperature;
cooling the nitrogen-doped silicon oxide material to room temperature, discharging, crushing and screening;
performing a flight time secondary ion mass spectrometry test on the crushed and screened material to determine whether the doping uniformity of nitrogen doped in the silicon monoxide meets a preset condition;
and (3) carrying out carbon coating on the material with the doping uniformity meeting the preset condition to obtain the nitrogen-doped silicon-based lithium ion cathode material.
Preferably, the nitrogen-containing gas source specifically comprises: one or more of nitrogen, ammonia, nitrous oxide, or dimethylamine;
the high-boiling nitrogen-containing compound specifically includes: carbonamides or melamines.
Preferably, the vapour of the doping material is obtained by heating the doping material to a temperature of 25 ℃ to 800 ℃.
Preferably, the silicon source vapor and the silicon dioxide vapor in the silicon source vapor are in a molar ratio of silicon: silica 1: 1 and mixing.
Preferably, the mass of nitrogen atoms in the doping material is 100ppm to 100000ppm of the total mass of silicon and silicon dioxide in the silicon source vapor.
Preferably, the preset conditions are specifically as follows: in the process of the flight time secondary ion mass spectrometry analysis and test, the fluctuation range of the nitrogen atom concentration is within +/-50% in all the particle sputtering time periods.
Preferably, the carbon coating specifically comprises: placing the material with the doping uniformity meeting the preset condition in a rotary furnace, heating to 800-1000 ℃ under the 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 gas source specifically comprises: 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, including the nitrogen-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 of the third aspect.
According to the preparation method of the nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material, the nitrogen-containing substance is subjected to gas phase mixing reaction with the silicon vapor and the silicon oxide vapor, so that the reaction substances are fully contacted to obtain the lithium ion battery negative electrode material with uniform phase doping, the obtained material has higher cycle stability, and the consistency of the material is more excellent.
Drawings
The technical solutions of the embodiments of the present invention are further described in detail with reference to the accompanying drawings and embodiments.
Fig. 1 is a flowchart of a method for preparing a nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material according to an embodiment of the present invention;
fig. 2 is a time-of-flight secondary ion mass spectrum diagram of the negative electrode material of the nitrogen-doped silicon-based lithium ion battery provided in example 1 of the present invention;
FIG. 3 is a time-of-flight secondary ion mass spectrum of the uniform nitrogen-doped silicon-based lithium ion battery anode material provided in comparative example 1 of the present invention;
FIG. 4 is a time-of-flight secondary ion mass spectrum of the uniform nitrogen-doped silicon-based lithium ion battery anode material provided in comparative example 2 of the present invention;
fig. 5 is a comparison of the time-of-flight secondary ion mass spectrograms of the uniform nitrogen-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 following figures and specific examples, but it should be understood that these examples are for the purpose of illustration only and are not to be construed as in any way limiting the present invention, i.e., as in no way limiting its scope.
The preparation method of the nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material disclosed by the invention comprises the following steps as shown in figure 1:
step 110, taking a nitrogen-containing gas source or a high-boiling-point nitrogen-containing compound as a doping material, and carrying out gas-phase mixing reaction on vapor of the doping material and preheated silicon source vapor at 1200-1700 ℃ for 1-24 hours to obtain a nitrogen-doped silicon protoxide material;
wherein the vapor of the doping material is obtained by heating the doping material to 25 ℃ -800 ℃.
In the doping material, the nitrogen-containing gas source is a nitrogen-containing compound which is gaseous at normal temperature, and specifically can comprise one or more of nitrogen, ammonia, nitrous oxide or dimethylamine; the high-boiling point nitrogen-containing compound is a nitrogen-containing compound which is liquid or solid at normal temperature, and specifically may include one or more of carbamide or melamine.
The silicon source vapor is a mixed vapor of silicon vapor and silicon dioxide vapor, preferably in a molar ratio of silicon: silica 1: 1 and mixing.
The mass of nitrogen atoms in the doping material accounts for 100ppm-100000ppm of the total mass of silicon and silicon dioxide in the silicon source steam.
Step 120, cooling the nitrogen-doped silicon monoxide material to room temperature, discharging, crushing and screening;
130, performing a flight time secondary ion mass spectrometry test on the crushed and sieved material to determine whether the doping uniformity of nitrogen doped in the silicon monoxide meets a preset condition;
the preset conditions in this step are specifically: in the process of the flight time secondary ion mass spectrometry analysis and test, the fluctuation range of the nitrogen atom concentration is within +/-50% in all the particle sputtering time periods. If this condition is satisfied, it is considered to be acceptable, and the next carbon coating is performed.
And 140, performing carbon coating on the material with the doping uniformity meeting the preset condition to obtain the nitrogen-doped silicon-based lithium ion cathode material.
The carbon coating specifically comprises the following steps: placing the material with the doping uniformity meeting the preset condition in a rotary furnace, heating to 800-1000 ℃ under the 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 gas source specifically includes: one or more of methane, acetylene, propylene or propane.
According to the preparation method, the nitrogen-containing substance, the silicon vapor and the silicon oxide vapor are subjected to gas phase mixing reaction, so that the reaction substances are fully contacted to obtain the lithium ion battery cathode material with uniform phase doping, the obtained material has higher cycle stability, and the consistency of the material is more excellent.
The nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material prepared by the preparation method of the embodiment can be used as a lithium ion battery negative electrode material and applied to a lithium battery pole piece and a lithium battery.
In order to better understand the technical solutions provided by the present invention, the following description respectively describes specific processes for preparing a negative electrode material of a lithium battery by using the methods provided by the above embodiments of the present invention, and a method for applying the negative electrode material to a lithium battery and battery characteristics by using the negative electrode material.
Example 1
1.4kg of silicon powder and 3kg of silica were placed in a high-temperature reaction furnace and heated to steam, while 1.6L (2 g in terms of mass) of nitrogen gas was slowly introduced under an argon-protected atmosphere, reacted at 1400 ℃ for 3 hours, and cooled to room temperature. And detecting the crushed material by a time-of-flight secondary ion mass spectrometer (TOF-SIMS). Fig. 2 is a time-of-flight secondary ion mass spectrum of the nitrogen-doped silicon-based lithium ion battery anode material provided in example 1 of the present invention, which is subsequently used for comparison and explanation with a comparative example.
Placing 2kg of qualified materials in a rotary furnace, heating to 1000 ℃ under the protective argon atmosphere, and mixing the materials according to the volume ratio of 1: 1 introducing argon and carrying out chemical vapor deposition with organic mixed gas equal to the argon, wherein the organic mixed gas is a mixture of the following components in a volume ratio of 1: 1, keeping the temperature for 2 hours, closing an organic gas source, and cooling to obtain the uniform nitrogen-doped soft carbon-coated silicon-based lithium ion battery cathode material, wherein the nitrogen content in the obtained cathode material is 0.045%.
Mixing the obtained negative electrode material, conductive additive carbon black and adhesive 1: 1, and the sodium cellulose and styrene butadiene rubber in a mass ratio of 95%: 2%: 3% are weighed out. And (5) placing the mixture into a beater to prepare the pulp at room temperature. And uniformly coating the prepared slurry on a copper foil. Drying in a forced air drying oven at 50 deg.C for 2 hr, cutting into 8 × 8mm pole pieces, and vacuum drying in a vacuum drying oven at 100 deg.C 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 lithium metal as the counter electrode and 1 mole of LiPF6The solution in Ethylene Carbonate (EC)/dimethyl carbonate (DMC) was used as an electrolyte to assemble a battery. And (3) carrying out a constant-current charge-discharge mode test by using a charge-discharge instrument, wherein the discharge cutoff voltage is 0.005V, the charge cutoff voltage is 1.5V, the first-week charge-discharge test is carried out at a current density of C/10, and the second-week discharge test is carried out at a current density of C/10.
Example 2
4.2kg of silicon powder and 9kg of silicon dioxide are placed in a high-temperature reaction furnace and heated to steam, 23.4L (18 g in terms of mass) of ammonia gas is slowly introduced under the argon protection environment, the reaction is carried out for 8 hours at 1200 ℃, and the reaction is cooled to room temperature. And after the discharged material is crushed, the material is qualified by TOF-SIMS detection. Placing 2kg of qualified materials in a rotary furnace, heating to 850 ℃ under the protective argon atmosphere, and mixing the materials according to the volume ratio of 1: 1 introducing argon and carrying out chemical vapor deposition with organic mixed gas equal to the argon, wherein the organic mixed gas is in a volume ratio of 2: 3, preserving the heat for 3 hours, closing an organic gas source, and cooling to obtain the uniform nitrogen-doped soft carbon-coated silicon-based lithium ion battery cathode material, wherein the nitrogen content in the obtained cathode material is 0.14%.
The preparation process of the negative electrode plate, the battery assembly and the battery test method are the same as those in example 1.
Example 3
2.8kg of silicon powder and 6kg of silicon dioxide are placed in a high-temperature reaction furnace and heated to steam, 1L (2 g in terms of mass) of nitrous oxide is slowly introduced under the argon protection environment, the reaction is carried out for 5 hours at 1500 ℃, and the reaction is cooled to room temperature. And after the discharged material is crushed, the material is qualified by TOF-SIMS detection. Placing 2kg of qualified materials in a rotary furnace, heating to 850 ℃ under the protective argon atmosphere, and mixing the materials according to the volume ratio of 1: 1, introducing argon and propane with the same quantity as the argon for chemical vapor deposition, preserving the heat for 2.5 hours, closing an organic gas source, and cooling to obtain the uniform nitrogen-doped soft carbon-coated silicon-based lithium ion battery cathode material, wherein the nitrogen content in the obtained cathode material is 0.014%.
The preparation process of the negative electrode plate, the battery assembly and the battery test method are the same as those in example 1.
Example 4
2.8kg of silicon powder and 6kg of silicon dioxide were placed in a high temperature reaction furnace and heated to steam, and at the same time 450g of carbamide was heated to 400 ℃ to steam, and after mixing the steam with each other, the mixture was reacted at 1600 ℃ for 7 hours, and cooled to room temperature. And after the discharged material is crushed, the material is qualified by TOF-SIMS detection. Placing 2kg of qualified materials in a rotary furnace, heating to 900 ℃ under the protective argon atmosphere, and mixing the materials according to the volume ratio of 1: 2 introducing argon and acetylene to carry out chemical vapor deposition, keeping the temperature for 3 hours, closing an organic gas source, and cooling to obtain the uniform nitrogen-doped soft carbon-coated silicon-based lithium ion battery cathode material, wherein the nitrogen content in the obtained cathode material is 2.4%.
The preparation process of the negative electrode plate, the battery assembly and the battery test method are the same as those in example 1.
Example 5
1.4kg of silicon powder and 3kg of silicon dioxide are placed in a high-temperature reaction furnace and heated to steam, 60g of melamine is heated to 320 ℃ to steam, the steam is mixed with each other and reacted at 1600 ℃ for 3.5 hours, and the mixture is cooled to room temperature. And after the discharged material is crushed, the material is qualified by TOF-SIMS detection. Placing 2kg of qualified materials in a rotary furnace, heating to 1000 ℃ under the protective argon atmosphere, and mixing the materials according to the volume ratio of 1: 1 introducing argon and carrying out chemical vapor deposition with organic mixed gas equal to the argon, wherein the organic mixed gas is a mixture of 3: 1, keeping the temperature for 3 hours, closing an organic gas source, and cooling to obtain the uniform nitrogen-doped soft carbon-coated silicon-based lithium ion battery cathode material, wherein the nitrogen content in the obtained cathode material is 0.9%.
The preparation process of the negative electrode plate, the battery assembly and the battery test method are the same as those in example 1.
Example 6
1.4kg of silicon powder and 3kg of silicon dioxide are placed in a high-temperature reaction furnace and heated to steam, 30L (30 g in terms of mass) of nitrous oxide is slowly introduced under the argon protection environment, the reaction is carried out for 4 hours at 1400 ℃, and the reaction is cooled to room temperature. And after the discharged material is crushed, the material is qualified by TOF-SIMS detection. Placing 2kg of qualified materials in a rotary furnace, heating to 1000 ℃ under the protective argon atmosphere, and mixing the materials according to the volume ratio of 1: 1, introducing argon and propylene to carry out chemical vapor deposition, preserving the heat for 2 hours, closing an organic gas source, and cooling to obtain the uniform nitrogen-doped soft carbon-coated silicon-based lithium ion battery cathode material, wherein the nitrogen content in the obtained cathode material is 0.43%.
The preparation process of the negative electrode plate, the battery assembly and the battery test method are the same as those in example 1.
Example 7
4.2kg of silicon powder and 9kg of silicon dioxide are placed in a high-temperature reaction furnace and heated to steam, 5L (5 g in terms of mass) of nitrous oxide is slowly introduced under the protection of argon gas, the reaction is carried out for 10 hours at 1200 ℃, and the reaction is cooled to room temperature. And after the discharged material is crushed, the material is qualified by TOF-SIMS detection. Placing 2kg of qualified materials in a rotary furnace, heating to 800 ℃ under the protective argon atmosphere, and mixing the materials according to the volume ratio of 1: 1 introducing argon and carrying out chemical vapor deposition with organic mixed gas equal to the argon, wherein the organic mixed gas is in a volume ratio of 3: 1, keeping the temperature for 4 hours, closing an organic gas source, and cooling to obtain the uniform nitrogen-doped soft carbon-coated silicon-based lithium ion battery cathode material, wherein the nitrogen content in the obtained cathode material is 0.024%.
The preparation process of the negative electrode plate, the battery assembly and the battery test method are the same as those in example 1.
Example 8
2.8kg of silicon powder and 6kg of silicon dioxide are placed in a high-temperature reaction furnace and heated to steam, and at the same time 350g of melamine is heated to 320 ℃ to steam, the steam is mixed with each other and reacted at 1500 ℃ for 6.5 hours, and then the mixture is cooled to room temperature. And after the discharged material is crushed, the material is qualified by TOF-SIMS detection. Placing 2kg of qualified materials in a rotary furnace, heating to 1000 ℃ under the protective argon atmosphere, and mixing the materials according to the volume ratio of 1: 1 introducing argon and carrying out chemical vapor deposition with organic mixed gas equal to the argon, wherein the organic mixed gas is in a volume ratio of 2: 1, keeping the temperature for 2 hours, closing an organic gas source, and cooling to obtain the uniform nitrogen-doped soft carbon-coated silicon-based lithium ion battery cathode material, wherein the nitrogen content in the obtained cathode material is 2.7%.
The preparation process of the negative electrode plate, the battery assembly and the battery test method are the same as those in example 1.
Comparative example 1
This comparative example provides a lithium ion battery negative electrode material that is comparable to example 1. After mechanically mixing 2kg of silica and 1.9g of carbamide, the mixture was subjected to a time of flight secondary ion mass spectrometer (TOF-SIMS) test, and then placed in a rotary kiln, heated to 1000 ℃ under an argon gas-protected environment, and mixed in a volume ratio of 1: 1 introducing argon and performing chemical vapor deposition on propylene and methane mixed gas which is equal to the argon, wherein the volume ratio of the propylene to the methane is 1: 1, 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 nitrogen content in the obtained negative electrode material is 0.045%.
The preparation process of the negative electrode plate, the battery assembly and the battery test method are the same as those in example 1.
Comparative example 2
Comparative example 2 provides a negative electrode material for a lithium ion battery, compared to example 1. 2kg of silica and 1.9g of carbamide are uniformly mixed by ethanol, and the compound silica material is obtained after spray drying. Detecting the composite silicon oxide material by a time-of-flight secondary ion mass spectrometer (TOF-SIMS), placing the composite silicon oxide material in a rotary furnace, heating to 1000 ℃ under the argon protection environment, and mixing the materials according to the volume ratio of 1: 1 introducing argon and carrying out chemical vapor deposition with organic mixed gas equal to the argon, wherein the organic mixed gas is a mixture of the following components in a volume ratio of 1: 1, 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 nitrogen content in the obtained negative electrode material is 0.045%.
The preparation process of the negative electrode plate, the battery assembly and the battery test method are the same as those in example 1.
The above negative electrode materials of examples 1 to 8 and comparative examples 1 to 2 were subjected to index tests of initial efficiency, reversible capacity at 0.1C, cycle performance at 0.1C magnification, and the like, and the results are shown in table 1.
Figure BDA0002539794110000101
TABLE 1
As can be seen from the data in table 1, under the same conditions, the silicon-based negative electrode materials in examples 1 to 8 are modified by gas phase mixing using a bulk phase doping technique, and the lithium battery has good performance consistency, high specific charge capacity and high cycle performance due to uniform gas phase mass transfer. Comparative examples 1-2 adopt solid phase coating and liquid phase coating respectively to carry out silicon-based negative electrode material modification, and it can be seen from comparative example 1 that although initial first effect and specific charge capacity are high, the cycle stability is poor after 100 and 500 cycles of cycle, which is mainly because the solid phase reaction contact is insufficient, so that nitrogen doping is not uniform, and the cycle stability is influenced. Comparative example 2, which employs liquid phase coating, is relatively more uniform in doping than comparative example 1, but the improvement of the cycle performance is not significant since it is only a surface doping technique, but only nitrogen-containing particles are attached to the surface of the silica.
In addition, fig. 5 is a comparison of the flight time secondary ion mass spectrograms of the uniform nitrogen-doped silicon-based lithium ion battery anode materials provided in example 1 and comparative examples 1-2 of the present invention. As can be seen by comparison, when sputtering is started, since example 1 employs gas phase mixture doping and nitrogen atoms are doped during the preparation of the raw material, the nitrogen atom concentration distribution is uniform in different periods of sputtering. In contrast, comparative examples 1 and 2, which employ solid phase and liquid phase doping, respectively, have a very uneven distribution of nitrogen atoms. When the sputtering time is more than 250s, no nitrogen atom concentration exists because the etching is performed to the inner part, and no nitrogen atom is distributed, and the fact that the gas-phase vapor doping can be doped into the material is also proved, and the solid-phase doping and the liquid-phase doping are only doped on the surface.
According to the preparation method of the nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material, the nitrogen-containing substance is subjected to gas phase mixing reaction with the silicon vapor and the silicon oxide vapor, so that the reaction substances are fully contacted to obtain the lithium ion battery negative electrode material with uniform phase doping, the obtained material has higher cycle stability, and the consistency of the material is more excellent.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A preparation method of a nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material is characterized by comprising the following steps:
taking a nitrogen-containing gas source or a high-boiling point nitrogen-containing compound as a doping material, and carrying out gas-phase mixing reaction on vapor of the doping material and preheated silicon source vapor at 1200-1700 ℃ for 1-24 hours to obtain a nitrogen-doped silicon protoxide material; wherein the silicon source vapor is a mixed vapor of silicon vapor and silicon dioxide vapor; the nitrogen-containing gas source is a nitrogen-containing compound which is gaseous at normal temperature, and the high-boiling point nitrogen-containing compound is a liquid or solid nitrogen-containing compound at normal temperature;
cooling the nitrogen-doped silicon oxide material to room temperature, discharging, crushing and screening;
performing a flight time secondary ion mass spectrometry test on the crushed and screened material to determine whether the doping uniformity of nitrogen doped in the silicon monoxide meets a preset condition;
and (3) carrying out carbon coating on the material with the doping uniformity meeting the preset condition to obtain the nitrogen-doped silicon-based lithium ion cathode material.
2. The method according to claim 1, wherein the nitrogen-containing gas source specifically comprises: one or more of nitrogen, ammonia, nitrous oxide, or dimethylamine;
the high-boiling nitrogen-containing compound specifically includes: carbonamides or melamines.
3. The method for preparing according to claim 1, wherein the vapor of the doping material is obtained by heating the doping material to 25 ℃ -800 ℃.
4. The method of claim 1, wherein the silicon source vapor comprises silicon vapor and silicon dioxide vapor in a molar ratio of silicon: silica 1: 1 and mixing.
5. The method according to claim 1, wherein the mass of nitrogen atoms in the dopant material is 100ppm to 100000ppm based on the total mass of silicon and silicon dioxide in the silicon source vapor.
6. The preparation method according to claim 1, wherein the preset conditions are specifically: in the process of the flight time secondary ion mass spectrometry analysis and test, the fluctuation range of the nitrogen atom concentration is within +/-50% in all the particle sputtering time periods.
7. The preparation method according to claim 1, wherein the carbon coating is specifically: placing the material with the doping uniformity meeting the preset condition in a rotary furnace, heating to 800-1000 ℃ under the 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 gas source specifically comprises: one or more of methane, acetylene, propylene or propane.
8. The negative electrode material of the lithium ion battery is characterized in that the negative electrode material is the nitrogen-doped soft carbon-coated silicon-based lithium ion negative electrode material prepared by the preparation method of any one of claims 1 to 7.
9. A lithium battery pole piece, characterized in that the lithium battery pole piece comprises the lithium ion battery negative electrode material of the claim 8.
10. A lithium battery comprising a lithium battery electrode sheet according to claim 9.
CN202010543313.7A 2020-06-15 2020-06-15 Nitrogen-doped soft carbon coated silicon-based lithium ion anode material and preparation method and application thereof Active CN113809312B (en)

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