CN115799475A - High-rate high-capacity hard carbon negative electrode material and preparation method thereof - Google Patents
High-rate high-capacity hard carbon negative electrode material and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of lithium ion battery cathode materials, and discloses a high-rate high-capacity hard carbon cathode material and a preparation method thereof. Mixing a carbonaceous precursor with an alkaline solution, and then carbonizing to obtain a hard carbon matrix; mixing nano silicon with citric acid to obtain a modified nano silicon material precursor; mixing a hard carbon matrix, a modified nano silicon material precursor and a liquid phase binder, and then sequentially carrying out isostatic compaction, carbonization, crushing and spheroidization to obtain a mixed material; and mixing the mixed material with asphalt, and then carbonizing to obtain the high-rate high-capacity hard carbon negative electrode material. The nano silicon is embedded into the hard carbon containing the porous structure by applying pressure, and the rate capability and the capacity of the hard carbon material are improved by utilizing the higher energy density and the excellent rate capability of the nano silicon; meanwhile, the compression molding process also realizes partial densification of the hard carbon material, and improves the tap density of the hard carbon.
Description
Technical Field
The invention relates to the technical field of lithium ion battery cathode materials, in particular to a high-rate high-capacity hard carbon cathode material and a preparation method thereof.
Background
With the increasing demand of the automobile market for endurance mileage and charging duration, the technology of high-energy density and high-power negative electrode materials is rapidly developed. Among them, the silicon-based negative electrode has been widely studied due to its high energy density and has been initially produced in large quantities; hard carbon is also favored by the market and researchers due to its higher rate capability.
At present, hard carbon has some pain points in practical application, such as low capacity (200-400 mAh/g), low first efficiency (40-80%), low tap density, poor processability and the like, so that the hard carbon is not used on a large scale.
Therefore, how to improve the capacity and the rate of the hard carbon negative electrode material has important significance for the development and the large-scale use of the hard carbon negative electrode material.
Disclosure of Invention
The invention aims to provide a high-rate high-capacity hard carbon negative electrode material and a preparation method thereof, and solves the technical problem of low capacity of the conventional hard carbon negative electrode material.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a high-rate high-capacity hard carbon negative electrode material, which comprises the following components in percentage by weight: the carbon coating comprises a hard carbon matrix, a nano silicon negative electrode, a carbon layer coating the nano silicon negative electrode and a carbon layer coating the hard carbon matrix; the hard carbon matrix is of a porous structure, and the nano silicon negative electrode is distributed in the pore diameter of the hard carbon matrix;
the particle size of the nano silicon negative electrode is 2-50 nm.
Preferably, in the above-described one high-rate high-capacity hard carbon negative electrode material, the mass of the carbon layer coating the nano-silicon negative electrode is 0.2 to 1% of the mass of the nano-silicon negative electrode, the carbon layer coating the hard carbon substrate is soft carbon, and the mass of the carbon layer coating the hard carbon substrate is 2 to 8% of the mass of the hard carbon substrate; the mass ratio of the hard carbon matrix to the nano silicon cathode is 100:5 to 15.
Preferably, in the above-mentioned one high-rate high-capacity hard carbon negative electrode material, D50 of the hard carbon negative electrode material is 5 to 15 μm, and a specific surface area of the hard carbon negative electrode material is 5 to 20m 2 /g。
The invention also provides a preparation method of the high-rate high-capacity hard carbon negative electrode material, which comprises the following steps:
(1) Mixing the carbonaceous precursor with an alkaline solution, and then carbonizing to obtain a hard carbon matrix;
(2) Mixing nano silicon with citric acid to obtain a modified nano silicon material precursor;
(3) Mixing a hard carbon matrix, a modified nano silicon material precursor and a liquid phase binder, and then sequentially carrying out isostatic compaction, carbonization, crushing and spheroidization to obtain a mixed material;
(4) Mixing the mixed material with asphalt, and then carbonizing to obtain a high-rate high-capacity hard carbon negative electrode material;
the step (1) and the step (2) are not limited in sequence.
Preferably, in the preparation method of the high-rate high-capacity hard carbon negative electrode material, the carbonaceous precursor in the step (1) is one or more of epoxy resin, phenolic resin, polyformaldehyde resin, polyvinyl chloride, polyformaldehyde, furfuryl ketone resin, petroleum asphalt, coal asphalt and a biomass carbon source;
the alkaline solution in the step (1) is one or more of a sodium hydroxide solution, a potassium hydroxide solution and ammonia water; the concentration of the alkaline solution in the step (1) is 20-40 wt%.
Preferably, in the above method for preparing a high-rate high-capacity hard carbon negative electrode material, the mass ratio of the carbonaceous precursor to the alkaline solution in step (1) is 0.5 to 2:2 to 4; the carbonization conditions in the step (1) are as follows: the temperature is 1000-2000 ℃, the heating rate is 0.5-4 ℃/min, the time is 2-8 h, and the atmosphere is nitrogen or argon.
Preferably, in the above method for preparing a high-rate high-capacity hard carbon negative electrode material, the mass of citric acid in step (2) is 0.58-2.9% of the mass of nano silicon; the temperature of mixing in the step (2) is 80-120 ℃, and the rotating speed of mixing in the step (2) is 10-200 r/min.
Preferably, in the above preparation method of the high-rate high-capacity hard carbon negative electrode material, in the step (3), the mass ratio of the hard carbon matrix to the modified nano silicon material precursor to the liquid-phase binder is 100:5 to 15:5 to 10; the liquid phase binder is heavy oil solution of high softening point asphalt or molten medium-low temperature asphalt formed by heating, the D50 of the asphalt is 2-5 mu m, and the mass ratio of the high softening point asphalt to the heavy oil is 5-20: 100, and the heating temperature is 60-180 ℃.
Preferably, in the above method for preparing a high-rate high-capacity hard carbon negative electrode material, the pressure for isostatic pressing in step (3) is 50 to 300MPa, and the dwell time for isostatic pressing in step (3) is 10 to 30min; the carbonization conditions in the step (3) are as follows: the temperature is 400-600 ℃, the time is 2-6 h, and the atmosphere is nitrogen or argon.
Preferably, in the above method for preparing a high-rate high-capacity hard carbon negative electrode material, the pitch in step (4) is a high-softening-point pitch; the mass of the asphalt in the step (4) is 2.8-11.4% of the mass of the hard carbon matrix, and the carbonization condition in the step (4) is as follows: the temperature is 1000-1400 ℃, the time is 2-6 h, and the atmosphere is nitrogen or argon.
Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:
(1) The addition of the nano silicon can obviously improve the specific capacity of the hard carbon cathode; meanwhile, the carbon-coated nano silicon is embedded into the macropores of the hard carbon, so that the problem of large volume expansion of the nano silicon is effectively solved; moreover, the nano silicon has better rate performance due to smaller size, and well coordinates with the excellent rate performance of the hard carbon.
(2) Preparing a porous hard carbon matrix with mesopores and macropores by the etching action of an alkaline solution and carbonization, wherein the nano-silicon cathodes are uniformly distributed in the pore diameter of the hard carbon matrix, and the mesopores in the hard carbon matrix are used for storing lithium; the nano silicon is embedded into the hard carbon containing the porous structure by applying pressure (isostatic compaction), and the rate capability and the capacity of the hard carbon material are improved by utilizing the higher energy density and the excellent rate capability of the nano silicon; meanwhile, partial densification of the hard carbon material is realized in the compression process (the nano silicon is pressed into the macropores of the hard carbon), and the tap density of the hard carbon is improved.
Detailed Description
The invention provides a high-rate high-capacity hard carbon negative electrode material, which comprises the following components in percentage by weight: the carbon coating comprises a hard carbon substrate, a nano silicon cathode, a carbon layer coating the nano silicon cathode and a carbon layer coating the hard carbon substrate; the hard carbon matrix is of a porous structure, and the nano silicon negative electrode is distributed in the pore diameter of the hard carbon matrix.
In the present invention, the particle size of the nano-silicon negative electrode is preferably 2 to 50nm, more preferably 2, 6, 9, 12, 16, 18, 20, 25, 28, 30, 32, 36, 40, 43, 48 or 50nm, and still more preferably 20 or 25nm.
In the present invention, the mass of the carbon layer covering the nano-silicon negative electrode is preferably 0.2 to 1%, more preferably 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1%, and still more preferably 0.5 or 0.6% of the mass of the nano-silicon negative electrode.
In the present invention, the carbon layer coating the hard carbon substrate is preferably soft carbon.
In the present invention, the mass of the carbon layer coating the hard carbon substrate is preferably 2 to 8%, more preferably 2, 2.4, 2.8, 3, 3.5, 4, 4.2, 4.5, 4.8, 5, 5.5, 6, 6.5, 7, 7.5 or 8%, and still more preferably 5, 5.5 or 6% of the mass of the hard carbon substrate.
In the present invention, the mass ratio of the hard carbon matrix to the nano silicon negative electrode is preferably 100:5 to 15, more preferably 100:5.5 to 14, more preferably 100:8.
in the present invention, the D50 of the hard carbon negative electrode material is preferably 5 to 15 μm, more preferably 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 μm, and still more preferably 9 or 10 μm.
In the present invention, the hard carbon negative electrode material preferably has a specific surface area of 5 to 20m 2 Per g, more preferably 5, 6.5, 7, 9, 10.5, 12, 13, 14.5, 15, 16, 17, 18.5, 19 or 20m 2 G, more preferably 14.5 or 15m 2 /g。
The invention also provides a preparation method of the high-rate high-capacity hard carbon negative electrode material, which comprises the following steps:
(1) Mixing the carbonaceous precursor with an alkaline solution, and then carbonizing to obtain a hard carbon matrix;
(2) Mixing nano silicon with citric acid to obtain a modified nano silicon material precursor;
(3) Mixing a hard carbon matrix, a modified nano silicon material precursor and a liquid phase binder, and then sequentially carrying out isostatic compaction, carbonization, crushing and spheroidization to obtain a mixed material;
(4) Mixing the mixed material with asphalt, and then carbonizing to obtain a high-rate high-capacity hard carbon negative electrode material;
the step (1) and the step (2) are not limited in sequence.
In the invention, the carbonaceous precursor in the step (1) further comprises a pretreatment process, specifically: and (5) coarse crushing.
In the invention, the carbonaceous precursor in the step (1) is preferably one or more of epoxy resin, phenolic resin, polyformaldehyde resin, polyvinyl chloride, polyformaldehyde, furfuryl ketone resin, petroleum pitch, coal pitch and biomass carbon source, more preferably one or more of epoxy resin, polyvinyl chloride, polyformaldehyde, furfuryl ketone resin and petroleum pitch, and even more preferably epoxy resin.
In the invention, the alkaline solution in the step (1) is preferably one or more of a sodium hydroxide solution, a potassium hydroxide solution and ammonia water, more preferably one or more of a sodium hydroxide solution and ammonia water, and even more preferably a sodium hydroxide solution.
In the present invention, the concentration of the alkaline solution in the step (1) is preferably 20 to 40wt%, more preferably 20, 22, 25, 27, 29, 30, 32, 34, 36, 38 or 40wt%, and still more preferably 30 or 32wt%.
In the present invention, the mass ratio of the carbonaceous precursor to the alkaline solution in step (1) is preferably 0.5 to 2:2 to 4, more preferably 0.65 to 1.85:2.2 to 3.7, more preferably 1.05:3.
in the present invention, the conditions for the carbonization in the step (1) are: the temperature is preferably 1000 to 2000 ℃, more preferably 1000, 1120, 1250, 1360, 1450, 1500, 1620, 1740, 1860, 1930, or 2000 ℃, and more preferably 1360 or 1450 ℃; the temperature rise rate is preferably 0.5 to 4 ℃/min, more preferably 0.5, 0.7, 1, 1.3, 1.5, 1.8, 2, 2.3, 2.5, 2.8, 3, 3.3, 3.6, 3.8 or 4 ℃/min, and still more preferably 1.8 or 2 ℃/min; the time is preferably 2 to 8 hours, more preferably 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5 or 8 hours, and still more preferably 4 or 4.5 hours; the atmosphere is preferably nitrogen or argon, more preferably nitrogen.
In the invention, the specific process of mixing the nano silicon and the citric acid in the step (2) is as follows: sanding the micron silicon, adding citric acid for ball milling, and evaporating the solvent to dryness under stirring; the stirring temperature is preferably 80 to 120 ℃, more preferably 80, 85, 90, 95, 100, 105, 110, 115 or 120 ℃, and more preferably 95 or 100 ℃; the rotation speed of the stirring is preferably 10 to 200r/min, more preferably 10, 30, 50, 80, 100, 105, 130, 155, 170, 190 or 200r/min, and even more preferably 130 or 155r/min.
In the present invention, the mass of the citric acid in the step (2) is preferably 0.58 to 2.9% of the mass of the nano silicon, more preferably 0.58, 0.86, 1.16, 1.45, 1.74, 2.03, 2.32, 2.61 or 2.89%, and even more preferably 1.45 or 1.74%; the carbon content in the citric acid was 34.5wt%.
In the present invention, the mixing time in the step (3) is preferably 20 to 40min, more preferably 20, 22, 23, 25, 28, 30, 33, 35, 37 or 40min, and still more preferably 28 or 30min.
In the invention, in the step (3), the mass ratio of the hard carbon matrix to the modified nano silicon material precursor to the liquid-phase binder is preferably 100:5 to 15:5 to 10, more preferably 100: 6.5-13: 7 to 9.5, more preferably 100:9:8.
in the invention, the liquid-phase binder is preferably heavy oil solution of high-softening-point asphalt or medium-low temperature asphalt which is heated to form a molten state, and is more preferably medium-low temperature asphalt which is heated to form a molten state; the D50 of the asphalt is preferably 2 to 5 μm, more preferably 2, 2.3, 2.5, 2.8, 3, 3.5, 3.7, 4, 4.2, 4.5, 4.8 or 5 μm, and even more preferably 3 or 3.5 μm; the mass ratio of the high softening point asphalt to the heavy oil is preferably 5-20: 100, more preferably 5.5 to 18.5:100, more preferably 12.5:100; the heating temperature is preferably 60 to 180 ℃, more preferably 60, 70, 80, 90, 100, 110, 130, 150 or 180 ℃, and even more preferably 100 or 110 ℃.
In the present invention, the pressure for isostatic pressing in the step (3) is preferably 50 to 300MPa, more preferably 50, 100, 130, 150, 200, 220, 250, 280 or 300MPa, and even more preferably 150 or 200MPa; the dwell time of the isostatic pressing in the step (3) is preferably 10 to 30min, more preferably 10, 12, 15, 17, 20, 22, 24, 25, 28 or 30min, and even more preferably 20 or 22min; the carbonization conditions in the step (3) are as follows: the temperature is preferably 400 to 600 ℃, more preferably 400, 420, 440, 450, 470, 500, 520, 550, 580 or 600 ℃, and more preferably 500 or 520 ℃; the time is preferably 2 to 6 hours, more preferably 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5 or 6 hours, and even more preferably 4 hours; the atmosphere is preferably nitrogen or argon, more preferably nitrogen.
In the present invention, the pitch of the step (4) is preferably a high softening point pitch, and the carbon content in the pitch is 70wt%.
In the present invention, the mass of the pitch in the step (4) is preferably 2.8 to 11.4%, more preferably 2.8, 3.4, 4, 4.3, 5, 5.7, 6, 6.4, 6.8, 7.1, 7.8, 8.6, 9.3, 10, 10.7, 11.4%, more preferably 7.1, 7.8 or 8.6% of the mass of the hard carbon matrix; the carbonization conditions in the step (4) are as follows: the temperature is preferably 1000 to 1400 ℃, more preferably 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350 or 1400 ℃, and even more preferably 1200 ℃; the time is preferably 2 to 6 hours, more preferably 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5 or 6 hours, and even more preferably 4 hours; the atmosphere is preferably nitrogen or argon, more preferably nitrogen.
In the present invention, after the carbonization in the step (4), the method further comprises: and (4) sieving and scattering.
The method of bonding in the present invention is not limited, and may be a method known to those skilled in the art.
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
(1) Mixing the coarsely broken thermoplastic phenolic resin with a 30wt% sodium hydroxide solution according to a mass ratio of 1:3, mixing, then placing the mixture in a carbonization furnace, heating to 1600 ℃ at the speed of 2 ℃/min under the nitrogen atmosphere, and preserving heat for 4 hours to obtain a hard carbon matrix;
(2) Sanding the micron silicon, adding citric acid for ball milling, and then evaporating the solvent to dryness under stirring to obtain a precursor of the modified nano silicon material with the D50 of 15 nm; wherein the mass of the citric acid is 1 percent of that of the micron silicon, the carbon content in the citric acid is 34.5wt percent, the stirring temperature is 100 ℃, and the stirring rotating speed is 150r/min;
(3) Mixing a hard carbon matrix, a modified nano silicon precursor and a liquid phase binder according to the mass ratio of 100:8:10, mixing, mechanically stirring for 30min to obtain a mixture, and keeping the mixture under the pressure of 100MPa for 10min to obtain a block body after isostatic pressing; carbonizing the block subjected to isostatic pressing at 400 ℃ for 2h in a nitrogen atmosphere to obtain a carbonized block; crushing and spheroidizing the carbonized block to obtain a hard carbon material with D50 of 9 mu m; wherein the liquid phase binder is 180# heavy oil solution of petroleum asphalt with high softening point, and the mass ratio of asphalt to heavy oil is 10:100, wherein the D50 of the asphalt is 3 mu m, and the softening point of the high-softening-point petroleum asphalt is 250 ℃;
(4) Mixing a hard carbon material and high-softening-point petroleum asphalt (the carbon content in the asphalt is 70 wt%) according to a mass ratio of 100:5, carrying out physical mixing, wherein the softening point of the high-softening-point petroleum asphalt is 250 ℃; and then placing the mixture in a carbonization furnace to react for 4 hours at 1200 ℃ in the nitrogen atmosphere, and then screening and scattering the mixture to obtain the high-rate high-capacity hard carbon negative electrode material.
Example 2
(1) Mixing the coarsely broken polyvinyl chloride resin with 28wt% ammonia water according to a mass ratio of 1.5:3.5, mixing, then placing the mixture in a carbonization furnace, heating to 1550 ℃ at the speed of 2.5 ℃/min under the nitrogen atmosphere, and preserving heat for 5 hours to obtain a hard carbon matrix;
(2) Sanding the micron silicon, adding citric acid for ball milling, and evaporating the solvent to dryness under stirring to obtain a modified nano silicon material precursor with the D50 of 20 nm; wherein the mass of the citric acid is 0.8 percent of the mass of the micron silicon, the carbon content in the citric acid is 34.5 weight percent, the stirring temperature is 100 ℃, and the stirring rotating speed is 150r/min;
(3) Mixing a hard carbon matrix, a modified nano silicon precursor and a liquid phase binder according to the mass ratio of 100:12:8, mixing, mechanically stirring for 25min to obtain a mixture, and keeping the mixture under the pressure of 180MPa for 8min to obtain a block after isostatic pressing; treating the block subjected to isostatic pressing at 480 ℃ for 2.5h in a nitrogen atmosphere to obtain a carbonized block; crushing and spheroidizing the carbonized block to obtain a hard carbon material with the D50 of 12 mu m; wherein the liquid phase binder is 180# heavy oil solution of petroleum asphalt with high softening point, and the mass ratio of asphalt to heavy oil is 8:100, wherein the D50 of the asphalt is 3 mu m, and the softening point of the high-softening-point petroleum asphalt is 250 ℃;
(4) Mixing a hard carbon material and high-softening-point petroleum asphalt (the carbon content in the asphalt is 70 wt%) according to a mass ratio of 100:5, carrying out physical mixing, wherein the softening point of the high-softening-point petroleum asphalt is 250 ℃; and then placing the mixture in a carbonization furnace to react for 4 hours at 1200 ℃ in the nitrogen atmosphere, and then screening and scattering the mixture to obtain the high-rate high-capacity hard carbon negative electrode material.
Example 3
(1) Mixing coarsely crushed polyformaldehyde with 25wt% sodium hydroxide solution according to the mass ratio of 1:2, mixing, then placing the mixture in a carbonization furnace, heating to 1860 ℃ at a speed of 4 ℃/min under the nitrogen atmosphere, and preserving heat for 4 hours to obtain a hard carbon matrix;
(2) Sanding the micron silicon, adding citric acid for ball milling, and then evaporating the solvent to dryness under stirring to obtain a precursor of the modified nano silicon material with the D50 of 20 nm; wherein the mass of the citric acid is 2.5 percent of that of the micron silicon, the carbon content in the citric acid is 34.5 weight percent, the stirring temperature is 120 ℃, and the stirring rotating speed is 100r/min;
(3) Mixing a hard carbon matrix, a modified nano silicon precursor and a liquid phase binder according to the mass ratio of 100:5:7, mixing, mechanically stirring for 32min to obtain a mixture, and keeping the mixture under the pressure of 245MPa for 10min to obtain a block body after isostatic pressing; treating the block subjected to isostatic pressing at 450 ℃ for 2h in a nitrogen atmosphere to obtain a carbonized block; crushing and spheroidizing the carbonized block to obtain a hard carbon material with D50 of 9 mu m; wherein the liquid phase binder is medium and low temperature asphalt which is heated to form a molten state, the heating temperature is 60 ℃, the D50 of the asphalt is 3 mu m, and the softening point of the medium and low temperature asphalt is 80 ℃;
(4) Mixing a hard carbon material and high-softening-point petroleum asphalt (the carbon content in the asphalt is 70 wt%) according to a mass ratio of 100:10, performing physical mixing, wherein the softening point of the high-softening-point petroleum asphalt is 250 ℃; and then placing the mixture in a carbonization furnace to react for 4 hours at 1200 ℃ in the nitrogen atmosphere, and then screening and scattering the mixture to obtain the high-rate high-capacity hard carbon negative electrode material.
Example 4
(1) Mixing the coarsely broken thermoplastic phenolic resin with a 30wt% sodium hydroxide solution according to the mass ratio of 2:3.5, mixing, then placing the mixture in a carbonization furnace, heating to 1200 ℃ at the speed of 0.8 ℃/min under the nitrogen atmosphere, and preserving heat for 7 hours to obtain a hard carbon matrix;
(2) Sanding the micron silicon, adding citric acid for ball milling, and then evaporating the solvent to dryness under stirring to obtain a precursor of the modified nano silicon material with the D50 of 15 nm; wherein the mass of the citric acid is 2.3 percent of that of the micron silicon, the carbon content in the citric acid is 34.5 weight percent, the stirring temperature is 100 ℃, and the stirring rotating speed is 150r/min;
(3) Mixing a hard carbon matrix, a modified nano silicon precursor and a liquid phase binder according to the mass ratio of 100:15:9, mixing, mechanically stirring for 30min to obtain a mixture, and keeping the mixture under the pressure of 300MPa for 14min to obtain a block body after isostatic pressing; treating the block at 400 ℃ for 2h in a nitrogen atmosphere to obtain a carbonized block; crushing and spheroidizing the carbonized block to obtain a hard carbon material with the D50 of 7 mu m; wherein the liquid phase binder is medium and low temperature asphalt which is heated to form a molten state, the heating temperature is 160 ℃, the D50 of the asphalt is 3 mu m, and the softening point of the medium and low temperature asphalt is 60 ℃;
(4) Mixing a hard carbon material and high-softening-point petroleum asphalt (the carbon content in the asphalt is 70 wt%) according to a mass ratio of 100:5, carrying out physical mixing, wherein the softening point of the high-temperature softening point petroleum asphalt is 200 ℃; and then placing the mixture in a carbonization furnace to react for 4 hours at 1200 ℃ in the nitrogen atmosphere, and then screening and scattering the mixture to obtain the high-rate high-capacity hard carbon negative electrode material.
The thermoplastic phenolic resin in the example 1 and the example 4 is 2123F thermoplastic phenolic resin in a Zhite industrial product special shop.
The performances of the high rate and high capacity hard carbon negative electrode materials prepared in examples 1 to 4 are shown in tables 1 and 2.
TABLE 1
TABLE 2
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A high rate, high capacity hard carbon anode material, comprising: the carbon coating comprises a hard carbon substrate, a nano silicon cathode, a carbon layer coating the nano silicon cathode and a carbon layer coating the hard carbon substrate; the hard carbon substrate is of a porous structure, and the nano silicon negative electrode is distributed in the pore diameter of the hard carbon substrate;
the particle size of the nano silicon negative electrode is 2-50 nm.
2. The high-rate high-capacity hard carbon anode material according to claim 1, wherein the mass of the carbon layer coating the nano silicon anode is 0.2 to 1% of the mass of the nano silicon anode, the carbon layer coating the hard carbon matrix is soft carbon, and the mass of the carbon layer coating the hard carbon matrix is 2 to 8% of the mass of the hard carbon matrix; the mass ratio of the hard carbon matrix to the nano silicon cathode is 100:5 to 15.
3. The high-rate high-capacity hard carbon negative electrode material according to claim 1 or 2, wherein the hard carbon negative electrode material has a D50 of 5 to 15 μm and a specific surface area of 5 to 20m 2 /g。
4. The method for preparing the high-rate high-capacity hard carbon negative electrode material according to any one of claims 1 to 3, comprising the steps of:
(1) Mixing a carbonaceous precursor with an alkaline solution, and then carbonizing to obtain a hard carbon matrix;
(2) Mixing nano silicon with citric acid to obtain a modified nano silicon material precursor;
(3) Mixing a hard carbon matrix, a modified nano silicon material precursor and a liquid phase binder, and then sequentially carrying out isostatic compaction, carbonization, crushing and spheroidization to obtain a mixed material;
(4) Mixing the mixed material with asphalt, and then carbonizing to obtain a high-rate high-capacity hard carbon negative electrode material;
the step (1) and the step (2) are not limited in sequence.
5. The preparation method of the high-rate high-capacity hard carbon negative electrode material according to claim 4, wherein the carbonaceous precursor in the step (1) is one or more of epoxy resin, phenolic resin, polyformaldehyde resin, polyvinyl chloride, polyformaldehyde, furfuryl ketone resin, petroleum pitch, coal pitch and a biomass carbon source;
the alkaline solution in the step (1) is one or more of sodium hydroxide solution, potassium hydroxide solution and ammonia water; the concentration of the alkaline solution in the step (1) is 20-40 wt%.
6. The preparation method of the high-rate high-capacity hard carbon negative electrode material according to claim 5, wherein the mass ratio of the carbonaceous precursor to the alkaline solution in the step (1) is 0.5-2: 2 to 4; the carbonization conditions in the step (1) are as follows: the temperature is 1000-2000 ℃, the heating rate is 0.5-4 ℃/min, the time is 2-8 h, and the atmosphere is nitrogen or argon.
7. The preparation method of the high-rate high-capacity hard carbon negative electrode material according to claim 5 or 6, wherein the mass of the citric acid in the step (2) is 0.58-2.9% of the mass of the nano silicon; the temperature of mixing in the step (2) is 80-120 ℃, and the rotating speed of mixing in the step (2) is 10-200 r/min.
8. The preparation method of the high-rate high-capacity hard carbon negative electrode material according to claim 5 or 6, wherein in the step (3), the mass ratio of the hard carbon matrix to the modified nano silicon material precursor to the liquid-phase binder is 100:5 to 15:5 to 10; the liquid phase binder is a heavy oil solution of high softening point asphalt or molten medium-low temperature asphalt formed by heating, the D50 of the asphalt is 2-5 mu m, and the mass ratio of the high softening point asphalt to the heavy oil is 5-20: 100, and the heating temperature is 60-180 ℃.
9. The method for preparing the high-rate high-capacity hard carbon anode material according to claim 8, wherein the isostatic pressing pressure in the step (3) is 50-300 MPa, and the dwell time in the step (3) is 10-30 min; the carbonization conditions in the step (3) are as follows: the temperature is 400-600 ℃, the time is 2-6 h, and the atmosphere is nitrogen or argon.
10. The method for preparing the high-rate high-capacity hard carbon anode material according to claim 9, wherein the asphalt obtained in the step (4) is high-softening-point asphalt; the mass of the asphalt in the step (4) is 2.8-11.4% of the mass of the hard carbon matrix, and the carbonization condition in the step (4) is as follows: the temperature is 1000-1400 ℃, the time is 2-6 h, and the atmosphere is nitrogen or argon.
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| CN110178251A (en) * | 2017-02-07 | 2019-08-27 | 瓦克化学股份公司 | The nucleocapsid composite particles of anode material for lithium ion battery |
| CN114275760A (en) * | 2021-12-22 | 2022-04-05 | 江西紫宸科技有限公司 | Silicon-carbon composite material and preparation method and application thereof |
| CN115020689A (en) * | 2022-08-08 | 2022-09-06 | 溧阳天目先导电池材料科技有限公司 | Nano silicon-carbon composite material for secondary lithium battery and preparation method and application thereof |
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| CN110178251A (en) * | 2017-02-07 | 2019-08-27 | 瓦克化学股份公司 | The nucleocapsid composite particles of anode material for lithium ion battery |
| CN114275760A (en) * | 2021-12-22 | 2022-04-05 | 江西紫宸科技有限公司 | Silicon-carbon composite material and preparation method and application thereof |
| CN115020689A (en) * | 2022-08-08 | 2022-09-06 | 溧阳天目先导电池材料科技有限公司 | Nano silicon-carbon composite material for secondary lithium battery and preparation method and application thereof |
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