CN113437292A - Modified soft carbon negative electrode material and preparation method thereof - Google Patents

Modified soft carbon negative electrode material and preparation method thereof Download PDF

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CN113437292A
CN113437292A CN202010205981.9A CN202010205981A CN113437292A CN 113437292 A CN113437292 A CN 113437292A CN 202010205981 A CN202010205981 A CN 202010205981A CN 113437292 A CN113437292 A CN 113437292A
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soft carbon
carbonization
carbon material
carbonized
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CN113437292B (en
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涂志强
林伟国
荣峻峰
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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China Petroleum and Chemical Corp
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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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • C—CHEMISTRY; METALLURGY
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    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • 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
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/10—Energy storage using batteries

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Abstract

The application relates to a modified soft carbon material and a preparation method thereof. The preparation method comprises the following steps: pre-carbonizing a soft carbon raw material to obtain a carbonized soft carbon material; uniformly mixing the carbonized soft carbon material and the mesophase pitch in an organic solvent, and drying to obtain a loaded pitch soft carbon material; and crushing the loaded asphalt soft carbon material, and co-carbonizing the crushed loaded asphalt soft carbon material to obtain the modified soft carbon material. The method utilizes the conventional mesophase pitch to further co-carbonize the modified soft carbon material, thereby improving the rate capability and simultaneously ensuring the capacity and the efficiency; the method directly uses the mesophase pitch for modification, does not introduce redundant impurities, and has small influence on the performance of the material; the modification process is a heat treatment process, and the operation is simpler.

Description

Modified soft carbon negative electrode material and preparation method thereof
Technical Field
The invention relates to a lithium ion battery negative electrode material and a preparation method thereof, in particular to a high-rate modified soft carbon negative electrode material and a preparation method thereof.
Background
The lithium ion battery is a recyclable energy storage device, also called a lithium ion secondary battery, and mainly comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte system. At present, the mainstream negative electrode materials are natural graphite and artificial graphite, if the materials are not modified, the compatibility of the materials and electrolyte is poor, the co-embedding condition is easy to occur, and a negative electrode graphite layer is peeled off during the cyclic charge and discharge, so that the cyclic stability of the battery is reduced. The modification method comprises surface light oxidation, particle shaping, surface amorphous carbon coating and the like. However, the low temperature and rate performance of the two materials is not good, and the risk of lithium metal precipitation exists when the working voltage is low.
The soft carbon is a non-graphite negative electrode material, contains a certain amount of graphite microcrystals and amorphous carbon, has large interlayer spacing and is easy to graphitize at high temperature. The soft carbon has the advantages of higher working voltage ratio, overcharge and overdischarge resistance, capability of preventing the problems of influence on safe use caused by short circuit and the like caused by lithium metal precipitation and low cost. And the electrolyte has good compatibility with the electrolyte, good cycle performance and great advantages in normal-temperature high-rate charging performance and low-temperature charging performance. The disadvantage is poor first charge and discharge capacity and coulombic efficiency. The abundant soft carbon materials on the market include petroleum coke and coal tar coke.
The soft carbon material has certain advantages in high-rate charging and low-temperature charging, but has defects in capacity and first efficiency, and most researches aim to improve the defects. However, in order to meet the requirement of the power battery on large-current charge and discharge of the electrode material, the rate capability of the soft carbon negative electrode material is further improved, and the soft carbon negative electrode material is also worthy of attention. In the prior art, soft carbon is generally used as an additive material to modify main materials such as graphite or silicon carbon, for example, in patent CN105449162B, soft carbon is used to modify natural graphite powder and then mixed with artificial graphite according to a certain ratio to obtain a negative electrode material with high specific capacity and excellent cycle performance. Certainly, the soft carbon is a cathode material with great potential for preparing a high-safety lithium ion power battery, so related researches are also reported. The patent CN106876710A discloses that ammonium molybdate and cobalt nitrate are added into raw materials such as coal tar, coal pitch, petroleum residual oil, petroleum pitch and the like, and are carbonized at the temperature of 900-1300 ℃ to obtain modified soft carbon, and the first efficiency of the soft carbon is as high as 86%. CN104852049A discloses that graphene powder is used for carrying out mixing modification on soft carbon powder, and the soft carbon negative electrode material with reversible specific capacity of more than 360mAh/g and efficiency of more than 85% is obtained through mixing, grinding, adding a binder and roasting. CN102428594A discloses a preparation method of a phosphorus and boron co-doped modified soft carbon material, which improves the capacity of soft carbon, but has the problems of higher average voltage, low compaction density and low energy density when used singly. Patent CN105261734B discloses that soft carbon is modified by doping phosphorus, and is compounded with natural graphite, and then coated to obtain various forms of core-shell structure negative electrode materials, and the result shows that the capacity of coke soft carbon is improved by doping heteroatom. The composite material can be compounded with graphite to better utilize the advantages of the composite material and increase the multiplying power and the cycle performance of the composite cathode material.
The above-mentioned soft carbon material modification process has some problems, for example, 1, the first effect and reversible capacity are improved with more attention, and the rate performance is less attention. 2. The catalyst is added for modification in the raw material carbonization process or the soft carbon secondary carbonization process, so that ash impurities are easily introduced, and the performance of the material is influenced to a greater or lesser extent. 3. The modification process is complex, and although the effect is good, the modification process brings more problems to operation and cost control.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: on the premise of ensuring the capacity and the efficiency, the soft carbon material is modified, and the multiplying power performance of the soft carbon material is improved.
The application provides a preparation method of a modified soft carbon material, which comprises the following steps:
pre-carbonizing a soft carbon raw material to obtain a carbonized soft carbon material;
uniformly mixing the carbonized soft carbon material and the mesophase pitch in an organic solvent, and drying to obtain a loaded pitch soft carbon material;
and crushing the loaded asphalt soft carbon material, and co-carbonizing the crushed loaded asphalt soft carbon material to obtain the modified soft carbon material.
In one embodiment, the temperature of the co-carbonization is 800 ℃ to 1800 ℃, preferably 950 ℃ to 1400 ℃; the co-carbonization time is 2-8h, preferably 4-6 h.
In one embodiment, the mesophase pitch has a softening point <260 ℃, a C content > 93% by mass, an S content < 0.2% by mass, a H/C molar ratio of 0.4 to 0.8, a mesophase content > 50% by volume, and a toluene insoluble-quinoline soluble content > 50%.
In one embodiment, the loaded pitch content in the loaded asphaltic nanocarbon material is from 10 to 50 wt% based on the weight of the loaded asphaltic nanocarbon material.
In one embodiment, the particle size D of the crushed pitch loaded pyrocarbon material90<50μm。
In one embodiment, the organic solvent is one or more of xylene, petroleum ether, carbon disulfide, solvent rosin water, n-hexane, tetrahydrofuran, and quinoline.
In one embodiment, the method further comprises crushing the modified soft carbon material again to obtain D90<30 μm and D50Particles of a modified soft carbon material of 7 to 15 μm; and carrying out gas phase coating treatment on the modified soft carbon material particles.
In one embodiment, the pre-carbonization comprises:
carrying out first carbonization on the soft carbon raw material at a first carbonization temperature to obtain a first carbonized material;
second carbonizing the first carbonized material at a second carbonization temperature to obtain the carbonized soft carbon material.
In one embodiment, the first carbonization temperature is 700 ℃ to 1700 ℃, preferably 700 ℃ to 900 ℃; the first carbonization time is 1 to 7h, preferably 4 to 6 h.
In one embodiment, the second carbonization temperature is 1000 ℃ to 2000 ℃, preferably 1150-; the second carbonization time is 1 to 10 hours, preferably 6 to 8 hours.
In one embodiment, the pre-carbonization further comprises crushing the soft carbon feedstock to obtain D before the first carbonization is performed90<Crushed soft carbon feedstock particles of 70 μm.
In one embodiment, the pre-carbonization further comprises crushing the first carbonized material to obtain D before the second carbonization is performed90<30 μm of crushed particles of the first carbonized material.
The invention also relates to the modified soft carbon material obtained by the method.
The method utilizes the conventional mesophase pitch to further co-carbonize the modified soft carbon material, thereby improving the rate capability and simultaneously ensuring the capacity and the efficiency; the method directly uses the mesophase pitch for modification, does not introduce redundant impurities, and has small influence on the performance of the material; the modification process is a heat treatment process, and the operation is simpler.
Drawings
FIG. 1 shows a schematic modification flow diagram of one embodiment of the present invention.
Fig. 2 shows a graph of rate performance for different modified soft carbon materials.
Detailed Description
The technical solution of the present invention is further explained below according to specific embodiments. The scope of protection of the invention is not limited to the following examples, which are set forth for illustrative purposes only and are not intended to limit the invention in any way.
The invention provides a preparation method of a modified soft carbon material, which comprises the following steps:
pre-carbonizing a soft carbon raw material to obtain a carbonized soft carbon material;
uniformly mixing the carbonized soft carbon material and the mesophase pitch in an organic solvent, and drying to obtain a loaded pitch soft carbon material;
and crushing the loaded asphalt soft carbon material, and co-carbonizing the crushed loaded asphalt soft carbon material to obtain the modified soft carbon material.
The method comprises the step of pre-carbonizing the soft carbon raw material to obtain a carbonized soft carbon material. The soft carbon feedstock that may be used in the present invention may include various soft carbon feedstocks that may be used in the art to form soft carbon materials, such as petroleum coke, coal tar coke, needle coke, carbon fibers, carbon microspheres, and other graphitizable carbon materials, particularly low sulfur petroleum coke or low sulfur coal tar coke produced in refineries. In order to increase the efficiency and extent of carbonization, the soft carbon feedstock is usually subjected to a crushing treatment, for example to D, before being subjected to preliminary carbonization90<Particles of a soft carbon raw material of 70 μm.
The pre-carbonization can adopt a one-time carbonization process or a multi-time carbonization process. For the primary carbonization process, the soft carbon raw material particles are carbonized at the temperature of 700-1700 ℃ for 1-10 hours to obtain the carbonized soft carbon material.
In one embodiment, the pre-carbonization comprises:
carrying out first carbonization on the soft carbon raw material at a first carbonization temperature to obtain a first carbonized material;
second carbonizing the first carbonized material at a second carbonization temperature to obtain the carbonized soft carbon material.
Compared with a primary carbonization process, the secondary carbonization process is adopted for pre-carbonization, and has the following advantages: 1. the step carbonization helps to form a temperature gradient and process different structures and compositions at different stages. 2. Compared with single carbonization, the obtained material has better use effect. Thus, the present application prefers the secondary precarbonization process described above.
In one embodiment, the pre-carbonization further comprises crushing the soft carbon feedstock to obtain D before the first carbonization is performed90<Crushed soft carbon feedstock particles of 70 μm. In one embodiment, the first carbonization temperature is 700 ℃ to 1700 ℃, preferably 700 ℃ to 900 ℃; the first carbonization time is 1 to 7h, preferably 4 to 6 h.
In one embodiment, the pre-carbonization further comprises crushing the first carbonized material to obtain D before the second carbonization is performed90<30 μm of crushed particles of the first carbonized material. In one embodiment, the second carbonization temperature is 1000 ℃ to 2000 ℃, preferably 1150-; the second carbonization time is 1 to 10 hours, preferably 6 to 8 hours.
The process of the present invention also co-carbonizes the resulting carbonized soft carbon material with mesophase pitch after pre-carbonization. In one embodiment, mesophase pitch having a softening point <260 ℃, a C content > 93% by mass, an S content < 0.2% by mass, a H/C molar ratio of 0.4 to 0.8, a mesophase content > 50% by volume, a toluene insoluble-quinoline solubles content > 50% is used.
The mesophase pitch needs to be supported on the carbonized soft carbon material before the co-carbonization treatment is performed. In the method of the present invention, organic solvent assisted loading may be employed. The mesophase pitch is dissolved by an organic solvent, and the carbonized soft carbon material is added for dispersion and stirring. Then drying to obtain the solid, and recovering the used solvent. The ratio of carbonized soft carbon material to mesophase pitch may be controlled such that the content of pitch supported in the supported pitch soft carbon material is 10 to 50 wt% based on the weight of the supported pitch soft carbon material. In one embodiment, the weight ratio of the carbonized soft carbon material to the mesophase pitch is 9-1: 1.
In the present invention, the organic solvent which can be used includes one or more of xylene, petroleum ether, carbon disulfide, solvent rosin water, n-hexane, tetrahydrofuran, quinoline.
In order to facilitate the next step of co-carbonization, the asphalt-loaded soft carbon material is generally crushed, and the particle size D of the crushed asphalt-loaded soft carbon material can be controlled90<50μm。
In one embodiment, the temperature at which co-carbonization is carried out is 800 ℃ to 1800 ℃, preferably 950 ℃ to 1400 ℃; the co-carbonization time is 2-8h, preferably 4-6 h.
After the co-carbonization, the co-carbonized adhesive particles can be crushed again to obtain the productSoft carbon material particles. The particle diameter D can be controlled as required90<30μm，D50Is 7-15 μm. And then, according to the requirement, carrying out gas phase coating treatment on the modified soft carbon material particles to obtain the soft carbon negative electrode material suitable for the lithium ion battery. The vapor phase coating treatment can be performed by chemical vapor deposition method commonly used in the art, and the details are not repeated herein.
In the present invention, the crushing method which can be used includes ball mill crushing, gear crushing, vibration crushing, etc., and the particle size range thereof may be controlled to a desired level.
In the present application, the particle diameter D50And D90The measurement was carried out according to the specification of appendix A of GB/T2433and 2019.
Figure 1 shows a schematic of a preferred modification scheme. As shown in the schematic flow chart of FIG. 1, the pre-carbonization comprises two carbonization processes, a first stage crushing carbonization and a second stage crushing carbonization. Crushing and carbonizing the raw materials in a first stage to obtain soft carbon powder 1; and then, crushing and carbonizing at the second stage to obtain the soft carbon powder 2. Loading the mesophase pitch on the soft carbon powder 2, and crushing and carbonizing (namely co-carbonizing) through a third stage to obtain soft carbon powder 3; and (3) carrying out gas phase coating to obtain the soft carbon cathode material. Specifically, the following steps can be performed:
1. using low-sulfur petroleum coke or low-sulfur coal tar pitch coke produced in oil refineries, D90<70 μm, and carrying out first-stage carbonization at a first temperature range of 700-1700 ℃ under normal pressure and in an inert gas atmosphere for 1-7h to obtain soft carbon powder 1.
2. Mechanically crushing the obtained soft carbon powder 1 to obtain D90<30 μm soft carbon powder. Then carrying out second-stage carbonization at a second temperature range (1000-2000 ℃) for 1-10h under normal pressure to obtain soft carbon powder 2.
3. Dissolving the mesophase pitch in an organic solvent at a ratio of 2-5g/50ml, and then adding 10-20g of pulverized soft carbon powder 2. And drying after uniform mixing, and controlling the content of the asphalt loaded on the soft carbon powder 2 to be 10-50%.
4. The asphalt-loaded soft carbon powder 2 is further crushed for the second time to have a particle diameter D due to the cohesive property of the asphalt90<50μm。
5. And co-carbonizing the secondarily crushed particles at a third temperature range (800-1800 ℃), wherein the carbonization time is 2-8h and the pressure is normal pressure to obtain soft carbon powder 3.
6. The soft carbon powder 3 after the third carbonization is crushed again, D90<30μm，D50Is 7-15 μm. And carrying out subsequent gas-phase surface carbon coating treatment on the obtained soft carbon material to obtain the soft carbon cathode material suitable for the lithium ion battery.
The method of the invention adds mesophase pitch in the modification process, and performs co-carbonization after the mesophase pitch is uniformly mixed with soft carbon to obtain the modified soft carbon material with high rate capability.
The following examples will be further illustrative of the methods provided by the present invention, including examples and experimental results data. The apparatus and process capable of achieving carbonization-like effects, and the carbon precursor capable of achieving carbonization-like modification effects should not be excluded from the present invention. The raw material is low-sulfur petroleum coke with S content<0.25%, 96% of C, 3.5% of H, 5.63% of volatile components and 0.15% of ash, the powder is subjected to primary crushing and is sieved by a 200-mesh sieve, and the particle size D is90<70 μm. The carbonization mode is carbonization in a calcining tube furnace, and the temperature range is normal temperature-2000 ℃. The asphalt used was mesophase asphalt, the softening point was 220 ℃, the mass content of C was 93.5%, the content of S was 0.17%, the content H/C molar ratio was 0.46, the volume content of mesophase was 70%, and the content of toluene-insoluble-quinoline soluble matter was 51%.
[ example 1 ]
Low sulfur petroleum coke after primary crushing, D90<70 μm, carbonizing at 850 deg.C under normal pressure and inert gas atmosphere for 4.5h to obtain soft carbon material.
Mechanically crushing the obtained soft carbon material to obtain D90<30 μm soft carbon powder. Then carrying out secondary carbonization at 1250 ℃, wherein the carbonization time is 6h, and the pressure is normal pressure.
Dissolving the mesophase pitch in a mixed solvent of xylene and petroleum ether (volume ratio of 2:1) to obtain a mixed solution with the pitch mass content of 10%. The mixed solution is added with the crushed soft carbon powder. The ratio of the two is 1g powder/20 ml solution, and the two are dried after being mixed evenly.
The soft carbon powder loaded with the asphalt is continuously crushed for the second time, and the particle diameter D90<50μm。
And carrying out third carbonization on the granules after the secondary crushing at 1200 ℃, wherein the carbonization time is 4h, and the pressure is normal pressure.
The soft carbon material after the third carbonization is crushed again, D90<30μm，D 5010 μm. And carrying out subsequent gas-phase surface carbon coating treatment on the obtained soft carbon material to obtain the soft carbon cathode material suitable for the lithium ion battery. And assembling the obtained soft carbon negative electrode material into a button cell, and testing the charge and discharge performance of the button cell.
[ example 2 ]
Low sulfur petroleum coke after primary crushing, D90<70 μm, carbonizing at 850 deg.C under normal pressure and inert gas atmosphere for 4.5h to obtain soft carbon material.
Mechanically crushing the obtained soft carbon material to obtain D90<30 μm soft carbon powder. Then carrying out secondary carbonization at 1250 ℃, wherein the carbonization time is 6h, and the pressure is normal pressure.
Dissolving the mesophase pitch in a mixed solvent of xylene and petroleum ether (volume ratio of 2:1) to obtain a mixed solution with the pitch mass content of 10%. The mixed solution is added with the crushed soft carbon powder. The ratio of the two is 1g powder/20 ml solution, and the two are dried after being mixed evenly.
The soft carbon powder loaded with the asphalt is continuously crushed for the second time, and the particle diameter D90<50μm。
And carrying out third carbonization on the granules after the secondary crushing at 900 ℃, wherein the carbonization time is 4h, and the pressure is normal pressure.
The soft carbon material after the third carbonization is crushed again, D90<30μm，D 5010 μm. The obtained soft carbon material is subjected to subsequent gas phase tableAnd (4) performing surface carbon coating treatment to obtain the soft carbon negative electrode material suitable for the lithium ion battery. And assembling the obtained soft carbon negative electrode material into a button cell, and testing the charge and discharge performance of the button cell.
[ example 3 ]
Low sulfur petroleum coke after primary crushing, D90<70 μm, carbonizing at 850 deg.C under normal pressure and inert gas atmosphere for 4.5h to obtain soft carbon material.
Mechanically crushing the obtained soft carbon material to obtain D90<30 μm soft carbon powder. Then carrying out secondary carbonization at 850 ℃ for 6h under normal pressure.
Dissolving the mesophase pitch in a mixed solvent of xylene and petroleum ether (volume ratio of 2:1) to obtain a mixed solution with the pitch mass content of 10%. The mixed solution is added with the crushed soft carbon powder. The ratio of the two is 1g powder/20 ml solution, and the two are dried after being mixed evenly.
The soft carbon powder loaded with the asphalt is continuously crushed for the second time, and the particle diameter D90<50μm。
And carrying out third carbonization on the granules after the secondary crushing at 900 ℃, wherein the carbonization time is 4h, and the pressure is normal pressure.
The soft carbon material after the third carbonization is crushed again, D90<30μm，D 5010 μm. And carrying out subsequent gas-phase surface carbon coating treatment on the obtained soft carbon material to obtain the soft carbon cathode material suitable for the lithium ion battery. And assembling the obtained soft carbon negative electrode material into a button cell, and testing the charge and discharge performance of the button cell.
Comparative example 1
Low sulfur petroleum coke after primary crushing, D90<70 μm, carbonizing at 850 deg.C under normal pressure and inert gas atmosphere for 4.5h to obtain soft carbon material.
Mechanically crushing the obtained soft carbon material to obtain D90<30 μm soft carbon powder. Then carrying out secondary carbonization at 1250 ℃, wherein the carbonization time is 6h, and the pressure is normal pressure.
The particles are carbonized for the third time at 1200 ℃, the carbonization time is 4h, and the pressure is normal pressure.
The soft carbon material after the third carbonization is crushed again, D90<30μm，D 5010 μm. And carrying out subsequent gas-phase surface carbon coating treatment on the obtained soft carbon material to obtain the soft carbon cathode material suitable for the lithium ion battery. And assembling the obtained soft carbon negative electrode material into a button cell, and testing the charge and discharge performance of the button cell.
Comparative example 2
Low sulfur petroleum coke after primary crushing, D90<70 μm, carbonizing at 850 deg.C under normal pressure and inert gas atmosphere for 4.5h to obtain soft carbon material.
Mixing the soft carbon material with resin hard carbon material, and mechanically crushing to obtain D90<30 μm soft carbon mixed powder. Then carrying out secondary carbonization at 1250 ℃, wherein the carbonization time is 6h, and the pressure is normal pressure.
The particles are carbonized for the third time at 1200 ℃, the carbonization time is 4h, and the pressure is normal pressure.
The soft carbon mixed material after the third carbonization is crushed again, D90<30μm，D 5010 μm. And carrying out subsequent gas-phase surface carbon coating treatment on the obtained soft carbon mixed material to obtain the cathode material suitable for the lithium ion battery. And assembling the obtained negative electrode material into a button cell, and testing the charge and discharge performance of the button cell.
[ test examples ]
Button cells were assembled using the negative electrode materials obtained in examples 1-3 and comparative examples 1-2 as follows:
weighing 92 parts of negative electrode material, 4 parts of conductive carbon black and 4 parts of binder (CMC + SBR), mixing and pulping, uniformly coating the slurry on a current collector by using a wet film coater with a gap of 150 mu m, and drying in vacuum at 70 ℃ for 6-10h to obtain the negative electrode plate. Then rolling and punching are carried out, a metal lithium sheet is taken as a negative electrode in a glove box, a Celgard 2500 polypropylene film is taken as a diaphragm, and an electrolyte contains 1mol/l LiPF6The EC/EMC/DMC (the mass ratio is 1: 1) is assembled into the button cell.
The button cell was tested as follows:
under the condition of 23 +/-2 ℃, the performance of the battery is evaluated by using CT2001A type battery testing equipment, and the current precision requirement is as follows: 0.05% RD + 0.05% FS, voltage accuracy requirement: 0.05% RD + 0.05% FS, voltage measurement range of 0.005V-2.0V, charge and discharge rate of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, 20C, etc.
Table 1 shows the charge and discharge results of the button cells assembled using the negative electrode materials obtained in examples 1 to 3 and comparative examples 1 to 2. The results in table 1 show that: under the condition of 0.2C charge and discharge, comparative examples 1, 2 and 3 show that different carbonization temperatures have influence on the performance of the material, wherein the carbonization condition in example 1 is better, the first coulombic efficiency of the material is higher, and the capacity also reaches 252 mAh/g. However, even under the same temperature carbonization condition, the material performance is poor if the mesophase co-carbonization is not carried out (comparative example 1), and particularly, the rate performance at 5C is worse and is only about half of that of the embodiment; if the resin is co-carbonized (comparative example 2), although the capacity of the material at low rate can be improved, the coulombic efficiency and the high rate performance cannot be improved, and the capacity is only 60 mAh/g.
TABLE 1 statistical table of charging and discharging results
Figure BDA0002421101250000101
Fig. 2 shows a rate performance graph of button cells assembled using the negative electrode materials obtained in examples 1-3 and comparative examples 1-2. Fig. 2 further illustrates that materials obtained under different conditions show different battery capacities under different charging and discharging current levels, and the influence of different materials is different as the current is larger. The material of example 1 has the best rate capability because the capacity remains the highest at 5C current. The results of fig. 2 show that: 1. the intermediate phase co-carbonization modification of the soft carbon material can improve the rate capability and the first coulombic efficiency of the material; 2. when the intermediate phase co-carbonization is carried out, the pre-carbonization process is better divided into two steps, the temperature control in the carbonization process needs to be paid attention, the carbonization is about 850 ℃ for the first time, and the temperature of the two subsequent carbonizations needs to reach about 1200 ℃.
It should be noted by those skilled in the art that the described embodiments of the present invention are merely exemplary and that various other substitutions, alterations, and modifications may be made within the scope of the present invention. Accordingly, the present invention is not limited to the above-described embodiments, but is only limited by the claims.

Claims (13)

1. A preparation method of a modified soft carbon material comprises the following steps:
pre-carbonizing a soft carbon raw material to obtain a carbonized soft carbon material;
uniformly mixing the carbonized soft carbon material and the mesophase pitch in an organic solvent, and drying to obtain a loaded pitch soft carbon material;
and crushing the loaded asphalt soft carbon material, and co-carbonizing the crushed loaded asphalt soft carbon material to obtain the modified soft carbon material.
2. The method of claim 1, wherein the temperature of the co-carbonization is 800-1800 ℃, preferably 950-1400 ℃; the co-carbonization time is 2-8h, preferably 4-6 h.
3. The process according to claim 1, wherein the mesophase pitch has a softening point <260 ℃, a C content > 93% by mass, an S content < 0.2% by mass, an H/C molar ratio of 0.4 to 0.8, a mesophase volume content > 50% and a toluene insoluble-quinoline solubles content > 50%.
4. The production method according to claim 1, wherein the content of the asphalt supported in the soft asphalt carbon-supported material is 10 to 50% by weight based on the weight of the soft asphalt carbon-supported material.
5. The production method according to claim 1, wherein the particle diameter D of the crushed pitch-loaded soft carbon material90<50μm。
6. The preparation method according to claim 1, wherein the organic solvent is one or more of xylene, petroleum ether, carbon disulfide, solvent rosin water, n-hexane, tetrahydrofuran, and quinoline.
7. The method of claim 1, further comprising crushing the modified soft carbon material again to obtain D90<30 μm and D50Particles of a modified soft carbon material of 7 to 15 μm; and carrying out gas phase coating treatment on the modified soft carbon material particles.
8. The production method according to claim 1, wherein the pre-carbonization includes:
carrying out first carbonization on the soft carbon raw material at a first carbonization temperature to obtain a first carbonized material;
second carbonizing the first carbonized material at a second carbonization temperature to obtain the carbonized soft carbon material.
9. The preparation method according to claim 8, wherein the first carbonization temperature is 700-1700 ℃, preferably 700-900 ℃; the first carbonization time is 1 to 7h, preferably 4 to 6 h.
10. The preparation method according to claim 8, wherein the second carbonization temperature is 1000-2000 ℃, preferably 1150-1450 ℃; the second carbonization time is 1 to 10 hours, preferably 6 to 8 hours.
11. The method of claim 5, wherein the pre-carbonization further comprises crushing the soft carbon feedstock to obtain D prior to the first carbonization90<Crushed soft carbon feedstock particles of 70 μm.
12. The production method according to claim 5, wherein the preliminary carbonization further comprises crushing the first carbonized material to obtain D before the second carbonization is performed90<30 μm of the crushed firstParticles of a carbonized material.
13. A modified soft carbon material obtainable by a process according to any one of claims 1 to 12.
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