Silicon-carbon double-doped material and preparation method and application thereof

Abstract

The invention belongs to the field of electrode material preparation, and particularly relates to a silicon-carbon double-doped material and a preparation method and application thereof. Porous carbon nitrogen doping is achieved by doping a nitrogen source in situ in the phenolic resin synthesis process, silicon boron doping is achieved by adding a boron source in the silicon vapor deposition process, the conductive performance of a carbon carrier is greatly improved through excessive free electrons of a C-N bond, and the conductive performance of amorphous nano silicon is greatly improved through excessive free electrons of a Si-B bond; and the high-rate fast charging performance of the negative electrode material is realized through silicon-carbon double doping.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of electrode material preparation, and particularly relates to a silicon-carbon double-doped material and a preparation method and application thereof. BACKGROUND

[0002] The theoretical specific capacity of a graphite negative electrode is low, and a silicon-based material is considered as one of the most promising negative electrode materials due to its advantages of abundant reserves, environmental friendliness, and low price. However, the silicon-based material has a huge volume expansion (>300%) in the cycle process, which leads to disadvantages such as structure pulverization, short cycle life, poor conductivity, and the like, which seriously affects the commercialization of the silicon-based material. The fourth-generation silicon-carbon takes porous carbon as a carrier, and silicon is deposited by a gas-phase chemical deposition method, which well inhibits the volume expansion. However, due to the low intrinsic conductivity of silicon, the silicon-carbon interface resistance is large, and a suitable method is needed to improve the conductivity of the material, reduce the interface resistance, and improve the rate performance and cycle performance of the silicon negative electrode material. SUMMARY

[0003] To solve the above problems, the application provides a preparation of a silicon-carbon double-doped material, which comprises the following steps.

[0004] Step S1: mixing formaldehyde and phenol at a molar ratio of 2:1 to obtain a mixture, adding 50 times the weight of the mixture of desalted water, dissolving at 60 DEG C in a water bath to obtain a mixed solution, adding 0.25% of an emulsifier polyethylene glycol, 3% of a curing agent hexamethylenetetramine, 0.1% of a catalyst anhydrous sodium carbonate, and 1-20% of a nitrogen-containing resin in the mixed solution, and then performing reaction for 4 hours, followed by filtration, water washing, and drying to obtain a phenolic spherical resin;

[0005] Step S2: placing the phenolic spherical resin obtained in S1 in a rotary kiln, carbonizing at a reaction temperature 1 under a nitrogen atmosphere, after a first heat preservation process, increasing the temperature of the reactor to a reaction temperature 2, and then introducing a water vapor / carbon dioxide gas mixture to activate, after a second heat preservation process, decreasing to room temperature to discharge, and obtaining a nitrogen-doped resin-based spherical porous carbon;

[0006] Step S3: placing the nitrogen-doped resin-based spherical porous carbon obtained in S2 in a reactor 2, increasing the temperature to a reaction temperature 3 under a nitrogen atmosphere, introducing a boron source gas and silane, after a third heat preservation process, increasing the temperature of the reactor to a reaction temperature 4, and then introducing a carbon source gas, after a fourth heat preservation process, decreasing to room temperature to discharge, and obtaining a silicon-carbon double-doped silicon-carbon negative electrode material.

[0007] Further, the nitrogen-containing resin in step S1 comprises at least one of urea-formaldehyde resin, melamine, or urea.

[0008] Further, the proportion of the nitrogen-containing resin in step S1 is 5-10%.

[0009] Further, the process of heating to reaction temperature 1 is heating to 500-900℃ at 1-10℃ / min; the process of heating to reaction temperature 2 is heating to 700-1000℃ at 1-10℃ / min; the process of heating to reaction temperature 3 is heating to 400-600℃ at 1-10℃ / min; and the process of heating to reaction temperature 4 is heating to 500-700℃ at 1-10℃ / min.

[0010] Further, the first holding process is holding at 500-900℃ for 0.5-2h; the second holding process is holding at 700-1000℃ for 3-6h; and the third holding process is holding at 400-600℃ for 4-6h.

[0011] Further, the boron source gas in step S3 comprises at least one of diborane, ethylborane, boron trichloride, boron trifluoride or boron tribromide.

[0012] Further, the ratio of the boron source gas and silane gas is 0.1-10%.

[0013] Further, the carbon source gas comprises at least one of methane, ethane, acetylene, ethylene, propylene, propane, toluene or xylene.

[0014] The application also provides a silicon-carbon double-doped material prepared by the above preparation method.

[0015] The application also provides application of the above silicon-carbon double-doped material in preparation of a battery electrode.

[0016] The application has the following beneficial effects:

[0017] The application realizes nitrogen doping of porous carbon by in-situ doping of a nitrogen source during the synthesis of phenolic resin, realizes boron doping of silicon by adding a boron source during the gas-phase deposition of silicon, the free electrons of the extra C-N bonds greatly improve the conductivity of the carbon carrier, the free electrons of the extra Si-B bonds greatly improve the conductivity of amorphous nanosilicon, and the silicon-carbon double doping realizes high-rate fast-charging performance of the negative electrode material. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

[0019] Figure 1 Example 1 mapping (Si, C, O);

[0020] Figure 2 Cycling performance. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present application will now be described in detail, with the methods being carried out in accordance with conventional methods unless otherwise specified, and with the reagents being commercially available or prepared according to conventional methods unless otherwise specified. This detailed description is not to be taken in a limiting sense and is merely describing some aspects, features, properties, and embodiments of the present application.

[0022] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of a parameter, unless otherwise stated, each intervening value of the parameter is also specifically included within the scope of the present application. The intervening values of the parameter are combined with a stated value of the parameter in range form. These are only examples of the various values that can be used, and equivalents thereof, are also contemplated. Other combinations of the values of the parameters, both with respect to a single parameter and with respect to multiple parameters, are also contemplated. All scientific and technical terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains unless otherwise specifically defined.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All publications mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The citation of any reference is not an admission that it is prior art with respect to the present application.

[0024] Many modifications and variations of this application of the application can be made without departing from its spirit or scope, which will be apparent to those skilled in the art. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only. It is to be understood that the application is not limited in scope by the specific embodiments described herein. Rather, the intent is to embrace all changes and modifications that can come within the spirit and scope of the application.

[0025] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having", "contain", "containing", and the like are open-ended terms that are intended to mean "including, but not limited to".

[0026] The present application proposes a nitrogen and boron doped porous silicon-carbon negative electrode material, a preparation method and application thereof. The preparation method comprises the following steps.

[0027] Step S1: mixing formaldehyde and phenol in a 2:1 molar ratio, dissolving with 50 times desalted water, 60°C water bath, adding 0.25% emulsifier polyethylene glycol, 3% curing agent hexamethylenetetramine, 0.1% catalyst anhydrous sodium carbonate and a certain proportion of nitrogen-containing resin, after 4 hours of reaction, filtering, washing and drying to obtain in-situ nitrogen-doped phenolic spherical resin.

[0028] Step S2: placing the phenolic resin obtained in S1 in a rotary kiln, carbonizing under a nitrogen atmosphere, heating to reaction temperature 1, after a first holding time, heating the reactor to reaction temperature 2, then introducing water vapor / carbon dioxide gas mixture in proportion to activate, after a second holding time, reducing to room temperature to discharge, obtaining nitrogen-doped resin-based spherical porous carbon.

[0029] Step S3: placing the nitrogen-doped porous carbon obtained in S2 in reactor 2, heating to reaction temperature 3 under a nitrogen atmosphere, introducing boron source gas and silane, after a third holding time, heating the reactor to reaction temperature 4, then introducing carbon source gas, after a fourth holding time, reducing to room temperature to discharge, at this time the internal pores of the nitrogen-doped porous carbon material are deposited with uniform boron-doped amorphous nanosilicon, obtaining silicon-carbon double-doped silicon-carbon negative electrode material.

[0030] The nitrogen-containing resin in step S1 includes one or more of urea-formaldehyde resin, melamine, urea

[0031] The proportion of the nitrogen-containing resin is 1-20%, preferably 5-10%;

[0032] The heating to reaction temperature 1 in step S2 includes heating to 500-900°C at 1-10°C / min

[0033] The first holding time is 0.5-2h at 500-900°C

[0034] The heating to reaction temperature 2 includes heating to 700-1000°C at 1-10°C / min

[0035] The second holding time is 3-6h at 700-1000°C

[0036] The boron source gas in step S3 includes one or more of methylene, ethylene, boron trichloride, boron trifluoride, boron tribromide

[0037] The proportion of the boron source gas and silane gas is 0.1-10%, preferably 0.2-5%;

[0038] The carbon source gas includes one or more of methane, ethane, acetylene, ethylene, propylene, propane, toluene, xylene.

[0039] The temperature rising to the reaction temperature 3 in the step S2 comprises: rising to 400-600℃ at 1-10℃ / min

[0040] The third holding time is 4-6h at 400-600℃

[0041] The temperature rising to the reaction temperature 4 comprises: rising to 500-700℃ at 1-10℃ / min

[0042] The fourth holding time is 1-3h at 500-700℃

[0043] In order to better understand the technical solutions provided by the present application, the following describes the preparation process and characteristics of the nitrogen-doped porous silicon-carbon negative electrode material according to multiple specific examples.

[0044] Example 1

[0045] The present example provides a preparation process of a silicon-carbon double-doped silicon negative electrode material, which is specifically as follows:

[0046] (1) Take 11 kg of formaldehyde and 7.5 kg of phenol and put them into a glass reaction kettle, dissolve them in 30 L of desalted water, 60℃ water bath, add 750 g of polyethylene glycol emulsifier, 9 kg of hexamethylenetetramine curing agent, 10 g of anhydrous sodium carbonate catalyst, and 300 g of urea-formaldehyde resin, filter, wash with water, and dry at 120℃ for 6h after reacting for 4h, to obtain 6 kg of in-situ nitrogen-doped phenolic spherical resin, and the nitrogen doping amount is measured to be 4%.

[0047] (2) Put 5 kg of the phenolic resin into a rotary kiln, carbonize at 700℃ for 1h under a nitrogen atmosphere, raise the temperature of the rotary kiln to 900℃, and pass in 16.5 g / min of a mixed gas of water vapor:carbon dioxide gas = 9:1 to activate for 6h, and then discharge the material after cooling to room temperature, to obtain 1.6 kg of nitrogen-doped resin-based spherical porous carbon.

[0048] (3) Put 1.5 kg of the nitrogen-doped porous carbon into a fluidized bed, raise the temperature to 480℃ under a nitrogen atmosphere, pass in 0.5 L / min of borane and 5 L / min of silane to perform silicon-boron co-deposition for 6h, then raise the reaction temperature to 600℃, pass in 2 L / min of ethyne gas, and react for 2.5h, and then cool to room temperature and discharge the material to obtain 3.15 kg of silicon-carbon double-doped silicon-carbon negative electrode material, and the boron doping amount is tested by ICP to be 2.4%.

[0049] Example 2: The silicon-carbon double-doped silicon negative electrode of the present example is basically the same as that of Example 1, except that the urea-formaldehyde resin is reduced from 300 g to 200 g, and the nitrogen doping concentration is tested by ICP to be 2.1wt%

[0050] Example 3: The silicon-carbon double-doped silicon negative electrode of this example is basically the same as that of Example 1, except that the flow rate of borane gas is reduced from 0.5 L / min to 0.2 L / min. The test results of the boron element doping mass by ICP are 0.9 wt%

[0051] Comparative Example 1: The negative electrode material of this comparative example is prepared basically the same as in Example 1, except that no urea-formaldehyde resin and borane gas are added in this comparative example, and the prepared negative electrode material is not doped with silicon.

[0052] Table 1: Comparison of rate performance

[0053]

[0054] As can be seen from the comparison table, the examples are significantly improved compared with the comparative examples, especially the high rate performance, which shows that nitrogen and boron doping can improve the conductivity and fast charging performance of the material. The capacity retention rate of Example 2 is slightly decreased compared with Example 1 after the nitrogen doping amount is decreased; the capacity retention rate of Example 3 is significantly decreased compared with Example 1 after the boron doping amount is decreased, which shows that boron doping can significantly improve the conductivity and fast charging performance of silicon. The comprehensive performance of Example 1 is the best.

Claims

1. A method for preparing a silicon-carbon dual-doped material, characterized in that, Includes the following steps: Step S1: Mix formaldehyde and phenol at a molar ratio of 2:1 to obtain a mixture. Add 50 times the weight of deionized water to the mixture and dissolve it in a water bath at 60°C to obtain a mixed solution. Add 0.25% of the weight of the mixed solution as emulsifier polyethylene glycol, 3% as curing agent hexamethylenetetramine, 0.1% as catalyst anhydrous sodium carbonate, and 1-20% as nitrogen-containing resin. After reacting for 4 hours, filter, wash with water, and dry to obtain phenolic spherical resin. Step S2: Place the phenolic spherical resin obtained in S1 in a rotary kiln, and heat it to the reaction temperature 1 under a nitrogen atmosphere for carbonization. After the first heat preservation process, heat the reactor to the reaction temperature 2, and then introduce a mixture of water vapor and carbon dioxide gas for activation. After the second heat preservation process, reduce the temperature to room temperature and discharge the material to obtain nitrogen-doped resin-based spherical porous carbon. Step S3: The nitrogen-doped resin-based spherical porous carbon obtained in S2 is placed in reactor 2. Under a nitrogen atmosphere, the temperature is raised to the reaction temperature 3. Boron source gas and silane are introduced. After the third heat preservation process, the reactor is heated to the reaction temperature 4. Then carbon source gas is introduced. After the fourth heat preservation process, the temperature is lowered to room temperature and the material is discharged to obtain silicon-carbon dual-doped silicon-carbon anode material.

2. The method according to claim 1, characterized in that, The nitrogen-containing resin in step S1 includes at least one of urea-formaldehyde resin, melamine, or urea.

3. The method according to claim 1, characterized in that, The proportion of nitrogen-containing resin in step S1 is 5-10%.

4. The method according to claim 1, characterized in that, The process of heating to reaction temperature 1 is to increase the temperature at a rate of 1℃ / min to 10℃ / min to 500℃ to 900℃; the process of heating to reaction temperature 2 is to increase the temperature at a rate of 1℃ / min to 10℃ / min to 700℃ to 1000℃; the process of heating to reaction temperature 3 is to increase the temperature at a rate of 1℃ / min to 10℃ / min to 400℃ to 600℃; and the process of heating to reaction temperature 4 is to increase the temperature at a rate of 1℃ / min to 10℃ / min to 500℃ to 700℃.

5. The method according to claim 1, characterized in that, The first heat preservation process is to keep the temperature at 500℃ to 900℃ for 0.5h to 2h; the second heat preservation process is to keep the temperature at 700℃ to 1000℃ for 3h to 6h; and the third heat preservation process is to keep the temperature at 400℃ to 600℃ for 4h to 6h.

6. The method according to claim 1, characterized in that, The boron source gas in step S3 includes at least one of the following: borane, diborane, boron trichloride, boron trifluoride, or boron tribromide.

7. The method according to claim 1, characterized in that, The ratio of boron source gas to silane gas is 0.1% to 10%.

8. The method according to claim 1, characterized in that, The carbon source gas includes at least one of methane, ethane, acetylene, ethylene, propylene, propane, toluene, or xylene.

9. A silicon-carbon dual-doped material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the silicon-carbon dual-doped material as described in claim 9 in the fabrication of battery electrodes.

Images