CN113023734A - Porous nitrogen-doped silicon-based negative electrode material and preparation method thereof, negative electrode plate and lithium ion battery - Google Patents
Porous nitrogen-doped silicon-based negative electrode material and preparation method thereof, negative electrode plate and lithium ion battery Download PDFInfo
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Abstract
A porous nitrogen-doped silicon-based negative electrode material, a preparation method thereof, a negative electrode plate and a lithium ion battery belong to the field of batteries. The preparation method comprises the following steps: mixing and dispersing a nitrogen-containing organic carbon source and an organic dispersing solvent, coating the mixture on the surface of a silicon-based negative electrode substrate, and drying to remove the organic dispersing solvent to obtain a negative electrode material precursor; placing the anode material precursor in an inert atmosphere for heat treatment to carbonize the nitrogen-containing organic carbon source; wherein the mass ratio of the nitrogen-containing organic carbon source to the silicon-based negative electrode substrate is 2-20: 100. The porous nitrogen-doped silicon-based negative electrode material is prepared through one-step reaction, so that the equipment requirement is low, the manufacturing difficulty is effectively reduced, and the porous nitrogen-doped silicon-based negative electrode material is easy to popularize. Meanwhile, the obtained porous nitrogen-doped silicon-based negative electrode material has the advantages of high initial efficiency and high rate, and can be applied to negative electrode plates and lithium ion batteries to effectively improve rate performance.
Description
Technical Field
The application relates to the field of batteries, in particular to a porous nitrogen-doped silicon-based negative electrode material, a preparation method thereof, a negative electrode plate and a lithium ion battery.
Background
In recent years, the field of energy, particularly lithium ion batteries and supercapacitors, has attracted much attention. At present, the commercialization degree of lithium batteries is mature, and as one of four main materials (positive electrode material, negative electrode material, diaphragm and electrolyte) of the lithium batteries, the performance of the negative electrode material has a key influence on the battery performance. The main types and characteristics of the current negative electrode materials are shown in table one, lithium battery manufacturers in the current market mainly select graphite as a negative electrode material of a lithium battery, the graphite belongs to one of carbon negative electrode materials, and comprises artificial graphite and natural graphite, and the graphite is still most widely used in the lithium battery as the graphite has good cycle stability, excellent conductivity and a layered structure with good lithium intercalation space. However, with the increasing performance requirements of lithium batteries, the main disadvantages of graphite as a negative electrode material are revealed, namely, the theoretical gram capacitance is low (372mAh/g), the layered structure is easy to peel off and fall off when the cycle times are long, and the like, so that the specific energy and the performance of the lithium battery are limited to be further improved.
In recent years, researchers and research and development workers in enterprises have focused on the use of silicon materials instead of carbon negative electrode materials, and the silicon can form binary alloy with lithium and has more than 10 times of theoretical capacity (4200mAh/g) of graphite, so that the silicon material is attracting attention. In addition, silicon also has the advantages of low lithium intercalation/deintercalation voltage platform (lower than 0.5V vs Li/Li +), low reaction activity with electrolyte, rich storage in earth crust, low price and the like, and is a lithium battery cathode material with prospect naturally. However, silicon has a fatal disadvantage as a negative electrode of a lithium battery, and lithium ions are extracted from a positive electrode material and inserted into crystal spaces inside silicon crystals during charging, so that a silicon-lithium alloy is formed to cause a large volume expansion (about 300%). During discharging, lithium ions are removed from crystal lattices, gaps among the volumes are formed, and the material structure is pulverized under repeated circulation, so that the capacity and the service life of the battery are rapidly reduced.
Therefore, at present, researchers mainly improve the capacity of the lithium battery and reduce the defect of silicon particle expansion and crushing through the preparation process of the silicon-carbon composite material, but relatively few researches on improving the rate capability of the silicon-based anode material are carried out. It is worth mentioning that the current preparation method of the silicon-based negative electrode is generally complex and difficult to produce in large scale.
In view of this, the present application is hereby presented.
Disclosure of Invention
The application provides a porous nitrogen-doped silicon-based negative electrode material, a preparation method thereof, a negative electrode plate and a lithium ion battery, which can solve at least one technical problem.
The embodiment of the application is realized as follows:
in a first aspect, the present application provides a method for preparing a porous nitrogen-doped silicon-based anode material, which comprises the following steps:
and mixing and dispersing a nitrogen-containing organic carbon source and an organic dispersing solvent, coating the mixture on the surface of the silicon-based negative electrode substrate, and drying to remove the organic dispersing solvent to obtain a negative electrode material precursor.
And (3) placing the anode material precursor in an inert atmosphere for heat treatment so as to carbonize the nitrogen-containing organic carbon source.
Wherein the mass ratio of the nitrogen-containing organic carbon source to the silicon-based negative electrode substrate is 2-20: 100.
The preparation method adopts a liquid-phase coating doping method, ensures that the coating and pore-forming effects are more uniform, obtains the porous nitrogen-doped silicon-based negative electrode material with high rate performance through one-step reaction, has low equipment requirement, effectively simplifies the operation process, reduces the manufacturing difficulty and is easy to popularize.
The preparation method utilizes a nitrogen-containing organic carbon source, a pore-forming agent and a silicon-based negative electrode substrate in a specific proportion, mainly takes the nitrogen-containing organic carbon source as the carbon source and the nitrogen source, and carries out heat treatment at high temperature so as to decompose the nitrogen-containing organic carbon source to form a carbon coating layer, the carbon coating layer can reduce the surface defects of the silicon-based negative electrode substrate, and a carbon-nitrogen bond is formed in the coating layer in an in-situ doping mode in the decomposition process, so that the nitrogen-doped modified silicon-based negative electrode material coated by the carbon layer is obtained, the interlayer spacing of the amorphous carbon coating layer can be increased by doping nitrogen atoms, more channels are provided for the insertion and extraction of lithium ions, and meanwhile, gas generated by the decomposition of the nitrogen-containing organic carbon source enables the carbon coating layer to generate certain pores, an additional lithium.
In a second aspect, the application example provides the porous nitrogen-doped silicon-based anode material prepared by the preparation method provided by the first aspect.
Wherein, the porous nitrogen-doped silicon-based negative electrode material is a multi-particle composite system.
The obtained porous nitrogen-doped silicon-based negative electrode material is a multi-particle composite system, wherein each particle is of a core-shell structure, each particle comprises a silicon-based negative electrode substrate serving as an inner core and a porous nitrogen-doped amorphous carbon layer coated on the inner core, wherein the original defect state of the surface of the silicon-based negative electrode substrate forms a carbon-nitrogen bond, a carbon-oxygen bond and other composite structures after modification, through surface modification, on one hand, the surface defect of the inner core can be reduced, the primary efficiency of the inner core is improved, on the other hand, the interlayer spacing of the amorphous carbon coating layer can be increased through the doped nitrogen atoms, more channels are provided for the embedding and the extraction of lithium ions, and the rate performance of the silicon-based negative electrode material is.
In a third aspect, the present application provides a negative electrode tab, the negative electrode tab includes a current collector and a negative electrode material disposed on the current collector, and the negative electrode material includes the porous nitrogen-doped silicon-based negative electrode material provided in the second aspect.
By introducing the porous nitrogen-doped silicon-based negative electrode material, the rate capability of the negative electrode piece is effectively improved.
In a fourth aspect, the present application provides a lithium ion battery, which includes the negative electrode tab provided in the third aspect of the present application.
By introducing the porous nitrogen-doped silicon-based negative electrode material, the rate capability of the lithium ion battery is effectively improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 is an SEM image of a porous N-doped Si-based anode material of example 3;
FIG. 2 is a graph showing the first charge-discharge specific capacity curves of examples 1 to 3 and comparative example 1.
Detailed Description
Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The porous nitrogen-doped silicon-based negative electrode material, the preparation method thereof, the negative electrode sheet and the lithium ion battery in the embodiment of the present application are specifically described as follows:
a preparation method of a porous nitrogen-doped silicon-based negative electrode material comprises the following steps:
and S1, mixing and dispersing the nitrogen-containing organic carbon source and the organic dispersing solvent to obtain slurry.
The nitrogen-containing organic carbon source is an organic compound containing carbon-nitrogen bonds, so that the nitrogen is favorably doped into carbon to form nitrogen-doped carbon, and the conductivity of carbon electrons is improved.
The decomposition temperature of the nitrogen-containing organic carbon source is not less than 600 ℃.
The nitrogen-containing organic carbon source includes, but is not limited to, dopamine, amino acid, melamine and other substances, and can also be high molecular polymers such as polyimide, polyaniline and the like. The amino acid includes but is not limited to methionine, and other amino acids such as histidine, glutamic acid and the like can be used.
Optionally, the nitrogen-containing organic carbon source includes at least one of melamine, amino acid, polyaniline and polyimide, for example, the nitrogen-containing organic carbon source may be melamine, amino acid, polyaniline or polyimide, and the nitrogen-containing organic carbon source may also be a mixture of melamine and amino acid, or a mixture of amino acid and polyaniline.
The nitrogen-containing organic carbon source is nano-micron.
Alternatively, the nitrogen-containing organic carbon source has a median particle size of 0.05 μm to 20 μm, for example, the nitrogen-containing organic carbon source has a median particle size of any value or between any two values of 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 17 μm, or 20 μm, and optionally 2 μm to 10 μm.
Through the selection of the appropriate median particle size of the nitrogen-containing organic carbon source, on one hand, the nitrogen-containing organic carbon source is conveniently and fully dispersed in an organic dispersing solvent, so that the uniformity of subsequent coating is ensured, and on the other hand, the reasonable selection of the median particle size does not significantly increase the cost on the premise of effectively improving the performance of the porous nitrogen-doped silicon-based anode material.
Optionally, the pore-forming agent is mixed and dispersed with the nitrogen-containing organic carbon source and the organic dispersing solvent before the slurry of step S2 is coated on the surface of the silicon-based negative electrode substrate.
Namely, the slurry contains the pore-forming agent, and the addition of the pore-forming agent can further form a porous structure, provide an additional lithium storage site, further improve the rate capability and capacity of the porous nitrogen-doped silicon-based negative electrode material, and obtain the high-rate porous nitrogen-doped silicon-based negative electrode material.
The step of mixing and dispersing the nitrogen-containing organic carbon source, the pore-forming agent and the organic dispersing solvent includes, but is not limited to, adding the nitrogen-containing organic carbon source and the pore-forming agent into the organic dispersing solvent, stirring and mixing, and may also adopt adding the nitrogen-containing organic carbon source and the pore-forming agent into the organic dispersing solvent, stirring and mixing.
In the stirring and mixing process, the stirring speed is, for example, 10r/min to 200r/min, and the stirring time is 1h to 10h, optionally 1h to 5 h. And by utilizing the selection of proper stirring speed and stirring time, the nitrogen-containing organic carbon source and the pore-forming agent are fully dispersed in the organic dispersing solvent, and the uniformity of the pore distribution on the surface of the finally obtained porous nitrogen-doped silicon-based negative electrode material is ensured.
The pore-forming agent is disposed to facilitate sublimation or decomposition of the pore-forming agent during subsequent thermal processing to remove the pore-forming agent to further form the porous structure.
The pore-forming agent is a pore-forming agent that can be sublimated or decomposed during the heat treatment in step S3.
Specifically, the pore-forming agent includes ammonium salts that can be decomposed or sublimated during the carbonization of the nitrogen-containing organic carbon source, including but not limited to ammonium bicarbonate, ammonium nitrate, urea, etc., and may also be a high molecular polymer such as polyvinylpyrrolidone, etc., that can be decomposed substantially completely during the heat treatment of the nitrogen-containing organic carbon source to generate a large amount of gas, form micropores, and have a small residual amount without introducing impurities.
Optionally, the pore former comprises at least one of ammonium bicarbonate, polyvinylpyrrolidone, and urea. The pore-forming agent is convenient to obtain, can be decomposed or sublimated in the carbonization process of the nitrogen-containing organic carbon source, and does not introduce impurities on the basis of forming pores.
The dispersing solvent is used for dispersing the nitrogen-containing organic carbon source and the pore-forming agent to form slurry.
Optionally, the dispersion solvent comprises at least one of ethanol, n-propanol, isopropanol, and butanol. The dispersing solvent is convenient to obtain and remove, the production efficiency is improved, and the processing difficulty is reduced.
And S2, coating the slurry on the surface of the silicon-based negative electrode substrate, and drying to remove the dispersion solvent to obtain the negative electrode material precursor.
It is to be noted that the purpose of the drying herein is to remove the dispersion solvent, that is, the drying is performed at a temperature lower than the temperature at which the pore-forming agent is decomposed or sublimated.
The silicon-based negative electrode substrate includes, but is not limited to, a silicon-oxygen negative electrode substrate and/or nano silicon, and may further include other materials based on the above.
Optionally, the silicon-based anode substrate is at least one of a silicon-oxygen anode substrate or nano-silicon.
Wherein, the silicon-based negative electrode substrate is a micron-order raw material, so that the rate capability of the finally obtained product is ensured to be good.
The mode of coating the slurry on the surface of the silicon-based negative electrode substrate comprises the following steps: and stirring and mixing the silicon-based negative electrode base material and the slurry, wherein the stirring speed is 10 r/min-200 r/min, and the stirring time is 1h-24h, optionally 3h-10 h. By utilizing the selection of proper stirring speed and stirring time, the slurry is ensured to be uniformly coated on the surface of the silicon-based negative electrode substrate, the pore-forming agent is ensured to be uniformly dispersed on the surface of the silicon-based negative electrode substrate, the shell thickness of the surface of the obtained negative electrode material precursor is ensured to be uniform, the components are uniformly distributed, and the uniform distribution of pores is finally improved.
Optionally, the mass ratio of the nitrogen-containing organic carbon source, the pore-forming agent and the silicon-based negative electrode substrate is 2-20:0.1-3:100 in sequence, for example, the mass ratio of the nitrogen-containing organic carbon source, the pore-forming agent and the silicon-based negative electrode substrate is any one of or between any two of 2:0.1:100, 2:1:100, 5:1:100, 10:0.1:100, 20:3:100 or 30:2.5:100 in sequence.
By utilizing the nitrogen-containing organic carbon source, the pore-forming agent and the silicon-based negative electrode substrate in the specific proportion, the rate capability and the capacity of the porous nitrogen-doped silicon-based negative electrode material are effectively improved.
And S2, placing the anode material precursor in an inert atmosphere, and carrying out heat treatment at the temperature of not less than 600 ℃ so as to carbonize the nitrogen-containing organic carbon source and remove the pore-forming agent.
Specifically, the anode material precursor is placed in a carbonization device and heat-treated in an inert atmosphere.
The carbonization equipment includes, but is not limited to, a CVD furnace, and may be any one of a tubular carbonization furnace, a box-type carbonization furnace, a roller kiln, a pusher kiln, and the like, and those skilled in the art can select the carbonization equipment according to actual needs.
And carrying out heat treatment in an inert atmosphere to obtain an amorphous carbon coating layer, and reducing the surface defects of the silicon-based negative electrode substrate.
Optionally, the inert atmosphere is any one of argon, nitrogen, helium and argon-hydrogen mixture.
And carbonizing the nitrogen-containing organic carbon source through heat treatment to form a nitrogen-doped carbon coating layer, removing the pore-forming agent, and forming pores on the carbon coating layer to further form the porous nitrogen-doped silicon-based negative electrode material.
Alternatively, the heat treatment temperature is 600 ℃ to 1200 ℃, specifically, for example, the heat treatment temperature is any one of 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃, 1100 ℃, 1200 ℃, or the like or between any two temperature values, the heat treatment time is 1h to 24h, specifically, for example, the heat treatment time is any one of 1h, 3h, 5h, 8h, 10h, 15h, 20h, or 24h, or between any two time values, and the decomposition temperature of the nitrogen-containing organic carbon source is less than or equal to the heat treatment temperature.
Optionally, the heat treatment temperature is 800 ℃ to 1000 ℃.
Optionally, the heat treatment time is 3h to 10 h.
Optionally, the preparation method of the porous nitrogen-doped silicon-based anode material further includes, after the heat treatment in the inert atmosphere, cooling the product obtained by the heat treatment, and then sieving, specifically, for example, sieving with a 200-mesh sieve, wherein the undersize is the porous nitrogen-doped silicon-based anode material.
Namely, screening is utilized to remove the product which does not meet the requirement, and finally the obtained porous nitrogen-doped silicon-based negative electrode material which meets the requirement is obtained.
A porous nitrogen-doped silicon-based negative electrode material is prepared by the preparation method. Wherein, the porous nitrogen-doped silicon-based negative electrode material is a multi-particle composite system.
The median particle size of the porous nitrogen-doped silicon-based negative electrode material is 1-30 μm, and specifically, the median particle size of the porous nitrogen-doped silicon-based negative electrode material is any value or between any two values of 1 μm, 5 μm, 10 μm, 15 μm, 18 μm, 20 μm, 25 μm or 30 μm.
Optionally, the porous nitrogen-doped silicon-based anode material has a median particle size of 5-10 μm.
The porous nitrogen-doped silicon-based negative electrode material is of a core-shell structure and comprises a silicon-based negative electrode base material serving as an inner core and a porous nitrogen-doped carbon coating layer coated on the surface of the inner core, wherein pores formed by the carbon coating layer are nanoscale, and the pore diameter of the pores formed by the carbon coating layer is nanoscale and is basically within 10 nm.
A negative pole piece comprises a current collector and a negative pole material arranged on the current collector, wherein the negative pole material comprises the porous nitrogen-doped silicon-based negative pole material.
The current collector is a metal current collector, such as a copper foil, a copper mesh, and the like, which is not limited herein.
A lithium ion battery comprises a diaphragm, electrolyte, a positive pole piece and the negative pole piece.
The electrolyte may be one or more of a gel electrolyte, a solid electrolyte and an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent.
The porous nitrogen-doped silicon-based negative electrode material, the preparation method thereof, the negative electrode plate and the lithium ion battery are further described in detail with reference to the following embodiments.
Example 1
Taking 3g of melamine powder (the median particle size is 3 mu m) and 0.1g of ammonium bicarbonate, adding 300mL of ethanol, and uniformly stirring and dispersing to obtain slurry; and then adding 100g of silicon-oxygen negative electrode material (the median particle size is 5.15 microns) into the slurry, quickly stirring for 1 hour, uniformly mixing, heating and drying to remove ethanol, transferring into an alumina crucible, heating to 1000 ℃ in a nitrogen atmosphere, preserving the temperature for 6 hours, cooling to room temperature, and screening by using a 200-mesh sieve to obtain a screen underflow, namely the porous nitrogen-doped silicon-based negative electrode material.
The obtained porous nitrogen-doped silicon-based negative electrode material is a multi-particle composite system.
Example 2
Taking 5g of melamine powder (the median particle size is 3 mu m) and 1g of ammonium bicarbonate, adding 300mL of ethanol, and uniformly stirring and dispersing to obtain slurry; and then adding 100g of silicon-oxygen negative electrode material (the median particle size is 5.15 microns) into the slurry, quickly stirring for 1 hour, uniformly mixing, heating and drying, transferring into an alumina crucible, heating to 1000 ℃ in a nitrogen atmosphere, preserving the heat for 6 hours, cooling to room temperature, and screening by using a 200-mesh sieve to obtain a screen underflow which is a porous nitrogen-doped silicon-based negative electrode material.
The obtained porous nitrogen-doped silicon-based negative electrode material is a multi-particle composite system.
Example 3
Taking 10g of polyaniline powder (with the median particle size of 3 microns) and 3g of PVP, adding 300mL of ethanol, stirring and dispersing uniformly, then adding 100g of silicon-oxygen negative electrode material (with the median particle size of 5.15 microns), quickly stirring for 1 hour, mixing uniformly, heating and drying, transferring into an alumina crucible, heating to 1000 ℃ in a nitrogen atmosphere, preserving heat for 6 hours, cooling to room temperature, and screening with a 200-mesh sieve to obtain a screen underflow, namely the porous nitrogen-doped silicon-based negative electrode material.
The obtained product is shown in figure 1 and is a multi-particle composite system.
Example 4
Taking 10g of tryptophan powder (with the median particle size of 7 microns) and 3g of PVP, adding 300mL of ethanol, stirring and dispersing uniformly, then adding 100g of silicon-oxygen negative electrode material (with the median particle size of 5.15 microns), quickly stirring for 1 hour, mixing uniformly, heating and drying, transferring into an alumina crucible, heating to 1000 ℃ in a nitrogen atmosphere, preserving heat for 6 hours, cooling to room temperature, and screening with a 200-mesh sieve to obtain a screen underflow, namely the porous nitrogen-doped silicon-based negative electrode material.
Example 5
Taking 13g of melamine powder (the median particle size is 5 microns), adding 300mL of ethanol, stirring and dispersing uniformly, then adding 100g of nano silicon, stirring rapidly for 1 hour, mixing uniformly, heating and drying, transferring into an alumina crucible, heating to 1100 ℃ under the atmosphere of nitrogen, preserving heat for 6 hours, then cooling to room temperature, and screening with a 200-mesh sieve to obtain a screen underflow, namely the porous nitrogen-doped silicon-based negative electrode material.
Example 6
Example 6 was compared with example 3, except that it was not added with PVP, and the rest was the same, to obtain a modified silicone negative electrode material.
Comparative example 1
An untreated silicon oxide negative electrode material (median particle diameter of 5.15 μm) was used as comparative example 1.
Comparative example 2
Comparative example 2 is compared with example 3 with the only difference that 10g of PVP was used in place of the polyaniline powder, and the rest was the same, to obtain a modified silicon-oxygen negative electrode material.
Comparative example 3
Comparative example 3 differs from example 1 only in that the amount of melamine powder added was 1 g.
Comparative example 4
Comparative example 4 differs from example 1 only in that the amount of melamine powder added was 30 g.
Test example 1
The porous nitrogen-doped silicon-based anode materials prepared in examples 1 to 6, the silicon-oxygen anode material provided in comparative example 1 and the modified silicon-oxygen anode materials provided in comparative examples 2 to 4 were selected as samples, and the specific surface area (BET) and the median particle size of each sample were obtained.
And (3) uniformly mixing each sample with SP, CMC and SBR according to a ratio of 90:5:2:3, pulping, coating, rolling, forming a negative electrode plate on a copper foil, assembling and manufacturing a button cell under the protection of inert atmosphere by taking a lithium plate as a counter electrode, and carrying out charge and discharge tests.
The results are shown in table 1 and fig. 2.
TABLE 1 test results
From table 1, it can be seen that the first efficiency of examples 1 to 6 of the present application is significantly improved as compared to comparative example 1, and the first efficiency thereof is improved to 73.25% or more.
As can be seen from table 1, comparative example 1 has a 267.3mAh/g of charge capacity at 0.3C and a 37.74% of charge capacity at 0.3C, and has poor rate performance, while examples 1 to 6 of the present application have significantly improved charge capacity at 0.3C and the 0.3C compared to comparative example 1, and the charge capacity at 0.3C can reach 72.53% or more, which also proves that the high-rate porous nitrogen-doped silicon-based negative electrode material obtained by the present application is high.
Compared with example 6, example 3 has a significantly increased specific surface area and a rate capability superior to example 6, which illustrates that example 3 has a large number of pore structures due to the addition of pore formers, so that the specific surface area is increased, and an additional lithium channel is provided to improve the rate capability.
Comparative example 2 compared to example 3, all PVP was used as the starting material, and it can be seen that the first efficiency and the charge capacity fraction at 0.3C are both significantly reduced, i.e. the selection of the nitrogen-containing organic carbon source has a significant effect on the first efficiency and rate performance.
Although the first efficiency and rate capability of comparative examples 3 and 4 are improved compared with comparative example 1, the first efficiency is less than that of examples 1-6, that is, the mass ratio of the specific nitrogen-containing organic carbon source and the silicon-based negative electrode substrate selected by the application has a prominent influence on the first efficiency and rate capability.
FIG. 2 is a graph showing the first charge-discharge specific capacity curves of examples 1 to 3 and comparative example 1. As is apparent from fig. 2, the first charge specific capacities of examples 1 to 3 were all significantly improved as compared with comparative example 1.
In conclusion, the preparation method of the porous nitrogen-doped silicon-based negative electrode material provided by the application obtains the porous nitrogen-doped silicon-based negative electrode material with high rate performance through one-step reaction, has low equipment requirement, effectively simplifies the operation process, reduces the manufacturing difficulty, and is easy to popularize. The porous nitrogen-doped silicon-based negative electrode material obtained by the preparation method is a multi-particle composite system, wherein each particle is of a core-shell structure, each particle comprises a silicon-based negative electrode substrate serving as an inner core and a porous nitrogen-doped amorphous carbon layer coated on the inner core, the original defect state of the surface of the silicon-based negative electrode substrate forms a carbon-nitrogen bond, carbon-oxygen bond and other composite structures after modification, through surface modification, on one hand, the surface defect of the inner core can be reduced, the primary efficiency of the inner core is improved, on the other hand, a porous structure can be formed in the coating layer through a pore-forming agent, meanwhile, the interlayer spacing of the amorphous carbon coating layer is increased through doped nitrogen atoms, more channels are provided for the insertion and the extraction of lithium ions, and the rate performance of the silicon-based negative electrode material is improved, so that the porous nitrogen-doped.
Therefore, the negative pole piece comprising the porous nitrogen-doped silicon-based negative pole material and the lithium ion battery comprising the negative pole piece can improve the primary efficiency and the rate capability of the lithium ion battery.
The foregoing is merely exemplary of the present application and is not intended to limit the present application, which may be modified or varied by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (10)
1. A preparation method of a porous nitrogen-doped silicon-based negative electrode material is characterized by comprising the following steps:
mixing and dispersing a nitrogen-containing organic carbon source and an organic dispersing solvent, coating the mixture on the surface of a silicon-based negative electrode substrate, and drying to remove the organic dispersing solvent to obtain a negative electrode material precursor;
placing the anode material precursor in an inert atmosphere for heat treatment so as to carbonize the nitrogen-containing organic carbon source;
wherein the mass ratio of the nitrogen-containing organic carbon source to the silicon-based negative electrode substrate is 2-20: 100.
2. The method according to claim 1, wherein the decomposition temperature of the nitrogen-containing organic carbon source is not less than 600 ℃;
optionally, the nitrogen-containing organic carbon source comprises at least one of melamine, amino acid, polyaniline and polyimide;
optionally, the nitrogen-containing organic carbon source has a median particle size of 0.05 to 20 μm, optionally 2 to 10 μm.
3. The method according to claim 2, wherein the heat treatment temperature is 600 ℃ to 1200 ℃, the heat treatment time is 1h to 24h, and the decomposition temperature of the nitrogen-containing organic carbon source is less than or equal to the heat treatment temperature;
optionally, the temperature of the heat treatment is 800 ℃ to 1000 ℃;
optionally, the time of the heat treatment is 3h to 10 h.
4. The method of manufacturing according to claim 1, further comprising: mixing and dispersing a pore-forming agent, a nitrogen-containing organic carbon source and an organic dispersing solvent before the step of coating the surface of the silicon-based negative electrode substrate; and removing the pore former by the heat treatment.
5. The preparation method of claim 4, wherein the mass ratio of the pore-forming agent to the silicon-based negative electrode substrate is 0.1-3: 100;
optionally, the pore former comprises at least one of ammonium bicarbonate, polyvinylpyrrolidone, and urea.
6. The production method according to any one of claims 1 to 4, wherein the organic dispersion solvent includes at least one of ethanol, n-propanol, isopropanol and butanol.
7. The production method according to any one of claims 1 to 4, wherein the inert gas atmosphere is any one of argon, nitrogen, helium and a mixed gas of argon and hydrogen.
8. A porous nitrogen-doped silicon-based anode material, characterized in that it is produced by the production method according to any one of claims 1 to 7;
the porous nitrogen-doped silicon-based negative electrode material is a multi-particle composite system;
optionally, the median particle size of the porous nitrogen-doped silicon-based anode material is 1-30 μm, optionally 5-10 μm.
9. A negative electrode tab, comprising a current collector and a negative electrode material disposed on the current collector, wherein the negative electrode material comprises the porous nitrogen-doped silicon-based negative electrode material of claim 8.
10. A lithium ion battery comprising the negative electrode sheet of claim 9.
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