CN115395003B - Negative electrode material and preparation method and application thereof - Google Patents

Negative electrode material and preparation method and application thereof Download PDF

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CN115395003B
CN115395003B CN202211330616.6A CN202211330616A CN115395003B CN 115395003 B CN115395003 B CN 115395003B CN 202211330616 A CN202211330616 A CN 202211330616A CN 115395003 B CN115395003 B CN 115395003B
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negative electrode
mixture
electrode material
graphite
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CN115395003A (en
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赵春雷
庞文文
刘东任
李辉
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Liyang Zichen New Material Technology Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention provides a negative electrode material and a preparation method and application thereof, wherein the negative electrode material comprises a core body and a shell layer, the core body comprises graphite, and the shell layer comprises a graphitizable carbon material; in the Raman spectrum of the cathode material, the ID/IG value is normally distributed, the distribution range is between 0.18 and 0.55, and the median value is between 0.3 and 0.5; the distribution range of the ID/IG value of the negative electrode material is narrow and is in normal distribution, which shows that the defects of the shell layer on the surface of the negative electrode material are uniformly distributed, namely, the negative electrode material is coated with uniform shell layers, so that the active sites and shuttle channels of lithium ions are increased, the lithium embedding space of the negative electrode material is increased, and the rate capability of the negative electrode material is improved.

Description

Negative electrode material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of batteries, and relates to a negative electrode material, and a preparation method and application thereof.
Background
With the rapid development of new energy industries, the lithium ion battery and cathode material field is adapted to the overall market trend, the demand of the corresponding product is continuously increased, the technical process is continuously updated, especially for the performance of the lithium ion battery in the aspect of rapid charging, the charging efficiency and the scarce resources become the great challenges which still exist at present, and the problem of low charging efficiency can be improved by the cathode material with higher multiplying power.
In order to improve the charge-discharge rate characteristic of the lithium ion battery, except for the raw material graphite of the negative electrode material which is the most important influencing factor, the contact interface of the graphite and the electrolyte in the lithium ion battery is improved, the material is coated on the surface of the graphite, so that the rate performance of the whole negative electrode material can be improved, on the other hand, in terms of the processing technology, the coating effect of the traditional solid-phase coating technology is relatively poor, the distribution uniformity of the coating material on the surface of the coating material is always influenced by the contact area among solid particles, and a relatively ideal coating layer is difficult to obtain on the surface of the graphite.
Therefore, the rate capability of the composite graphite material in the prior art still needs to be improved, and an ideal coating layer cannot be obtained by the coating method, so that the rate capability of the composite graphite material is limited; for example, the invention patent with the publication number of CN 103647055A discloses an epoxy resin modified graphite cathode material and a preparation method thereof, the organic silicon modified epoxy resin and natural graphite are ground, cured, carbonized and crushed to obtain the epoxy resin modified graphite cathode material, an epoxy resin carbon film coated on the surface of the graphite really plays a role in preventing large-volume solvent molecules from being co-embedded, a graphite layer can reversibly expand and contract only in a small range without rapidly collapsing and collapsing, the cycle life of a graphite cathode is prolonged, but the rate capability of the obtained graphite cathode material is to be improved, the coating effect is poor, and a uniform coating layer cannot be obtained.
Based on the above research, it is necessary to provide an anode material, the surface of which is coated with a uniform, complete and compact coating layer, so that the anode material has excellent rate performance.
Disclosure of Invention
The invention aims to provide a negative electrode material and a preparation method and application thereof, and particularly relates to a high-rate negative electrode material and a preparation method and application thereof, wherein the surface of the negative electrode material is coated with a graphitizable carbon material, and the existence of the coating layer can improve the lithium desorption speed, so that the integral rate performance of the negative electrode material is improved; meanwhile, the preparation method of the negative electrode material can enable the surface of the graphite material to generate an ideal coating layer, effectively reduce the specific surface area of the graphite and improve the charging rate.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a negative electrode material comprising a core and a shell, the core comprising graphite and the shell comprising a graphitizable carbon material;
in the Raman spectrum of the cathode material, the ID/IG value is normally distributed, the distribution range is between 0.18 and 0.55, and the median value is between 0.3 and 0.5.
The ID/IG value of the cathode material in the Raman spectrum is substitutedThe defect value content and the ID/IG value distribution range on the surface of the surface graphite are narrow and normally distributed, which shows that the shell layer defects on the surface of the negative electrode material are uniformly distributed and the coated shell layer is uniform, and simultaneously, the median value is larger, the defect content on the surface of the shell graphite accounts for more, so that the active sites and the whole shuttle channels of lithium ions in the transmission process are increased, the lithium embedding space of the negative electrode material is increased, and the Li is distributed in a normal manner + The resistance embedded in the negative electrode material is reduced, the dynamic performance is improved, and the occurrence of the lithium separation phenomenon is favorably reduced, so the rate capability of the negative electrode material is improved, and the quick charge performance is improved.
The ID value represents the D peak intensity of the Raman spectrum, and the IG value represents the G peak intensity of the Raman spectrum.
A distribution range of 0.18 to 0.55 means that the minimum ID/IG value is above 0.18, for example 0.18, 0.19, 0.2, 0.21, 0.22 or 0.23 and the maximum ID/IG value is below 0.55, for example 0.55, 0.54, 0.53, 0.52, 0.51 or 0.50, but is not limited to the values listed and other values not listed in the range are equally applicable.
The median value is from 0.3 to 0.5, and may be, for example, 0.3, 0.35, 0.4, 0.45 or 0.5, but is not limited to the values recited, and other values not recited in the range of values are equally applicable.
Preferably, the specific surface area of the negative electrode material is 0.9-1.5m 2 Per g, may be, for example, 0.9m 2 /g、0.95m 2 /g、1.0m 2 /g、1.05m 2 /g、1.1m 2 /g、1.15m 2 /g、1.2m 2 /g、1.25m 2 /g、1.3m 2 /g、1.35m 2 /g、1.4m 2 /g、1.45m 2 G or 1.5m 2 In terms of/g, but not limited to the values recited, other values not recited in the range of values are equally applicable.
Preferably, the particle diameter D50 of the negative electrode material is 8 to 14 μm, and may be, for example, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or 14 μm, but is not limited to the enumerated values, and other unrecited values within the numerical range are also applicable.
The specific surface area of the negative electrode material is smaller, so that the coating of the shell layer is uniform, the specific surface area of the graphite material can be reduced through coating, and the charging rate is improved; meanwhile, the particle size of the cathode material is reasonable, and the reversible capacity and the dynamic performance of the material cannot be influenced.
Preferably, the graphitizable carbon material includes soft carbon.
The shell layer is made of soft carbon, and the soft carbon has the characteristic of easy graphitization, and the inter-lamellar spacing of the microcrystal structure is slightly larger than the inter-lamellar spacing of the graphite microcrystal, so that the shuttle of lithium ions is facilitated, the lithium desorption speed is improved, and the integral multiplying power performance of the cathode material can be improved.
When the anode material is treated at 3000 ℃ for 48 hours and then XRD is tested, the intensity of a diffraction peak between 25 and 28 degrees in a spectrogram can be increased by more than 1 time and less than 2 times, and the half-peak width is reduced, so that the shell layer is a graphitizable soft carbon material.
Preferably, the shell layer has a thickness of 10 to 20nm, which may be, for example, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm or 20nm, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
In a second aspect, the present invention provides a method for preparing the anode material according to the first aspect, the method comprising the steps of:
(1) Mixing a first solvent and a shell precursor, and mixing the obtained mixed solution with a graphite material to obtain a first mixture;
(2) Adding the first mixture obtained in the step (1) into a second solvent for mixing to obtain a second mixture;
(3) Carrying out solid-liquid separation and carbonization on the second mixture obtained in the step (2) to obtain the anode material;
and (2) the solubility of the shell layer precursor in the first solvent is greater than that in the second solvent in the step (1).
According to the invention, a suspension coating method is adopted, firstly, a shell precursor is mixed with a first solvent, then, a graphite material is dispersed, after the obtained first mixture is added into a second solvent, as the solubility of the shell precursor in the first solvent is greater than that in the second solvent, the shell precursor can be separated out in a suspension manner in the second solvent, and can be coated on the surface of the graphite material through mixing, compared with the conventional coating, the coating effect is better, meanwhile, the suspension separation coating is equivalent to a secondary granulation process, the particle size of the negative electrode material can be proper, the specific surface area is smaller, and defects formed on the surface after coating are uniformly distributed, so that the ID/IG value distribution range of the negative electrode material is narrow, and the distribution is uniform.
Preferably, the mass ratio of the first solvent to the shell layer precursor in step (1) is 100 (1-4), and may be, for example, 100.
In order to realize suspension coating, the shell precursor can be dissolved in the first solvent and can be smoothly separated out after the second solvent is added, and the mass ratio of the first solvent to the shell precursor is in a reasonable range.
Preferably, the mass ratio of the mixed solution to the graphite material in the step (1) is (0.7-1.3): 1, and for example, the ratio may be 0.7.
The mass ratio of the mixed solution to the graphite material affects the particle size, the specific surface area, the thickness of a coating layer and an ID/IG value of the negative electrode material, when the mass ratio of the first mixture to the graphite material is too small, the particle size is smaller, when the particle size of the material is smaller, uneven small particles or a large exposed surface exists on the particle surface, so that the coating is not uniform, the distribution of the ID/IG value is affected, and the multiplying power performance of the final material cannot be guaranteed; when the mass ratio of the first mixture to the graphite material is too large, the larger particle size may result in a decrease in reversible capacity and kinetics of the material, and may also affect the size of the specific surface area, roughen the surface, cause an increase in side reactions, and deteriorate high-temperature properties and cycle performance of the material.
Preferably, the shell precursor of step (1) comprises any one of pitch, petroleum coke or needle coke or a combination of at least two of them, and typical but non-limiting combinations include a combination of pitch and petroleum coke, or a combination of needle coke and pitch.
Preferably, the first solvent of step (1) comprises an organic polar solvent.
Preferably, the organic polar solvent comprises any one of quinoline, toluene or tetrahydrofuran or a combination of at least two thereof, typical but non-limiting combinations include a combination of quinoline and toluene, a combination of toluene and tetrahydrofuran, preferably quinoline.
Preferably, the particle size D50 of the graphite material in step (1) is 7 to 35 μm, and may be, for example, 7 μm, 10 μm, 12.5 μm, 15 μm, 17.5 μm, 20 μm, 22.5 μm, 25 μm, 27.5 μm, 30 μm, 32.5 μm or 35 μm, but is not limited to the values listed, and other values not listed in the numerical range are equally applicable, preferably 7 to 12 μm.
The particle size of the graphite material can also influence the particle size and the specific surface area of the prepared negative electrode material, so that the coating effect of the negative electrode material can be ensured within a reasonable range, the particle size and the specific surface area can be within a reasonable range, and the influence of overlarge or overlow particle size and specific surface area on the material performance is avoided.
Preferably, the graphite material in step (1) comprises artificial graphite and/or natural graphite.
Preferably, the adding manner in the step (2) is dropping.
The present invention is not particularly limited with respect to the amount of dropping, and preferably, the amount per dropping is smaller than the amount of the second solvent in the step (2).
When the first mixture is added into the second solvent for mixing, in order to ensure that the shell layer precursor can be smoothly separated out, the first mixture needs to be added into the second solvent in a dropwise manner, and the dropwise adding amount of each time is smaller than that of the second solvent, so that the shell layer precursor can be further ensured to be separated out in a suspended manner, the coating and granulation can be smoothly carried out, and the coating uniformity is improved.
Preferably, in the second mixture in step (2), the mass ratio of the first mixture to the second solvent is 10 (1-3), and may be, for example, 10.
Preferably, the second solvent of step (2) comprises an alcoholic solvent and/or water.
Preferably, the alcoholic solvent comprises any one of methanol, ethanol or propanol or a combination of at least two thereof, typical but non-limiting combinations include a combination of methanol and ethanol, or a combination of propanol and methanol.
Preferably, the solid-liquid separation in step (3) comprises drying and filtration, preferably filtration.
The preferable solid-liquid separation mode is filtration, and as the drying is to evaporate the solvent to dryness, compared with filtration, the precursor of the shell layer cannot be uniformly coated, so that the coating effect is reduced.
Preferably, the carbonizing of step (3) includes pre-sintering and sintering, and the sintering temperature is higher than that of the pre-sintering.
Preferably, the pre-firing temperature is 200-350 ℃, for example, 200 ℃, 220 ℃, 240 ℃, 260 ℃, 280 ℃, 300 ℃, 320 ℃, 340 ℃ or 350 ℃, but not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the temperature increase rate of the pre-firing is 0.2 to 1.5 ℃/min, for example, 0.2 ℃/min, 0.4 ℃/min, 0.6 ℃/min, 0.8 ℃/min, 1.0 ℃/min, 1.2 ℃/min, 1.4 ℃/min, or 1.5 ℃/min, but not limited to the values recited, and other values not recited within the range of values are equally applicable, preferably 0.5 to 1.5 ℃/min.
The temperature rising rate in the pre-sintering process is not suitable to be too high, if the temperature rising rate is too high, the dissolving speed and the curing speed of the shell precursor are too high, the contact reaction with oxygen in the pre-sintering atmosphere is not effective, small particles with rough and uneven surfaces appear on the appearance of a negative electrode material, the surface defect content of graphite is too high, the capacity loss of the coated graphite and side reactions in electrolyte are obviously increased, and the performance is deteriorated.
Preferably, the burn-in time is 8-15h, such as 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h, but not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the pre-firing is performed in an air atmosphere.
Preferably, the sintering is carried out at a temperature of 1100 to 1300 ℃, for example 1100 ℃, 1150 ℃, 1200 ℃, 1250 ℃ or 1300 ℃, for a time of 4 to 6 hours, for example 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, at a rate of 1 to 5 ℃/min, for example 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min or 5 ℃/min, without being limited to the values cited, other values not listed within the range of values being equally applicable.
Preferably, the sintering is performed in nitrogen and/or inert gas.
Preferably, the inert gas comprises any one of argon, helium or krypton or a combination of at least two thereof, with typical but non-limiting combinations including a combination of argon and helium or a combination of argon and krypton.
Preferably, a drying step is further performed after the solid-liquid separation and before the carbonization in the step (3).
Preferably, the carbonization in step (3) is followed by a dispersion and sieving step.
Preferably, the screening mesh number is 200-600 mesh, such as 200 mesh, 300 mesh, 400 mesh, 500 mesh or 600 mesh, but not limited to the recited values, and other values not recited in the numerical range are also applicable.
As a preferable technical scheme of the preparation method, the preparation method comprises the following steps:
(1) Mixing a first solvent and a shell layer precursor according to the mass ratio of 100 (1-4), and mixing the obtained mixed solution and a graphite material according to the mass ratio of (0.7-1.3) to 1 to obtain a first mixture;
the first solvent comprises any one or the combination of at least two of quinoline, toluene or tetrahydrofuran, and the particle size D50 of the graphite material is 7-35 μm;
(2) Dripping the first mixture obtained in the step (1) into a second solvent for mixing to obtain a second mixture, wherein the mass ratio of the first mixture to the second solvent in the second mixture is 10 (1-3);
the amount of the first mixture dropped in each time is smaller than that of the second solvent, and the second solvent comprises an alcohol solvent and/or water;
(3) Filtering the second mixture obtained in the step (2), heating the obtained solid substance to 200-350 ℃ at a heating rate of 0.2-1.5 ℃/min in an air atmosphere, presintering for 8-15h, heating to 1100-1300 ℃ at a heating rate of 1-5 ℃/min in nitrogen and/or inert gas, sintering for 4-6h, dispersing, and sieving by a 200-600 mesh sieve to obtain the cathode material;
and (2) the solubility of the shell layer precursor in the first solvent is greater than that in the second solvent in the step (1).
In a third aspect, the present invention provides a lithium ion battery comprising the negative electrode material of the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) The defect value content distribution range of the surface of the nucleus body of the negative electrode material is narrow, the distribution is uniform, the median value is larger, the uniformity and the integrity of the shell layer of the negative electrode material are shown, the shuttle channel of the active sites and the whole lithium ions of the lithium ions is improved, the lithium embedding space of the negative electrode material is increased, the lithium embedding resistance of the lithium ions is reduced, and the multiplying power and other performances of the negative electrode material are improved;
(2) According to the invention, a suspension coating method is adopted, the shell precursor can be separated out in a suspension manner by utilizing the dissolution difference of the shell precursor in different solvents, and then the separated shell precursor can be uniformly coated on the surface of the graphite material through mixing, and secondary granulation can be carried out.
Drawings
FIG. 1 is an SEM image of a negative electrode material according to example 1 of the present invention;
FIG. 2 is an SEM image of the anode material according to example 2 of the present invention;
FIG. 3 is an SEM photograph of the negative electrode material of example 4 of the present invention;
FIG. 4 is a graph showing the distribution of ID/IG values of a graphite raw material and an anode material according to example 1 of the present invention and an anode material according to comparative example 1;
FIG. 5 is an XRD (X-ray diffraction) pattern of the anode material before and after graphitization treatment according to example 1 of the present invention;
FIG. 6 is a TEM image of the graphite starting material according to example 1 of the present invention on a 10nm scale;
FIG. 7 is a TEM image of the anode material of example 1 of the present invention on a 10nm scale;
FIG. 8 is a TEM image of the anode material according to example 1 of the present invention on a 20nm scale.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a negative electrode material, which comprises a core and a shell, wherein the core comprises graphite, the shell comprises soft carbon, and the thickness of the shell is 15nm;
in the Raman spectrum of the cathode material, the ID/IG value is normally distributed, and the distribution range is between 0.2 and 0.54;
the preparation method of the anode material comprises the following steps:
(1) Mixing quinoline and asphalt according to a mass ratio of 100;
the graphite raw material is artificial graphite with the particle size D50 of 8 mu m;
(2) Dripping the first mixture obtained in the step (1) into ethanol, and mixing to obtain a second mixture, wherein the mass ratio of the first mixture to the ethanol in the second mixture is 10;
the amount of the first mixture per dropping is less than the amount of the ethanol;
(3) Filtering the second mixture obtained in the step (2), drying the obtained solid matter, heating the solid matter to 270 ℃ at a heating rate of 0.5 ℃/min in the air, pre-burning for 8 hours, replacing nitrogen atmosphere, heating to 1200 ℃ at a heating rate of 1 ℃/min, sintering for 5 hours, dispersing, and screening by a 500-mesh sieve to obtain the negative electrode material;
XRD detection was performed on the negative electrode material obtained in this example and the graphitized material obtained after the negative electrode material is graphitized again for 48 hours at 3000 ℃, and the obtained XRD pattern is shown in fig. 5, in which the peak a is the peak of the negative electrode material, and the peak b is the peak of the graphitized material. As can be seen from FIG. 5, the intensity of the b peak between 23 and 30 ℃ in the spectrum is increased by 1.18 times from that of the a peak by 8.7X 10 5 Increased to 1.9X 10 6 The half-peak width of the diffraction peak is reduced from 0.2054 to 0.1956, and is reduced by 0.048 times, which proves that the hard and soft shell layer is successfully coated;
the SEM image of the negative electrode material of this example is shown in fig. 1; the distribution diagram of the ID/IG value is shown in FIG. 4; the XRD pattern at 23-30 ° 2 theta is shown in figure 5; a TEM image on a 10nm scale is shown in fig. 7; a TEM image under a 20nm scale is shown in FIG. 8, the disorder degree of the lamellar structure at the edge of the graphite particle is larger, the graphite particle is different from a regular graphite lamellar, and the thickness interval of the disordered layer is 10-20nm; the distribution of the ID/IG value of the graphite raw material in this example is shown in FIG. 4; a TEM image on a 10nm scale is shown in FIG. 6.
Example 2
The embodiment provides a negative electrode material, which comprises a core body and a shell layer, wherein the core body comprises graphite, the shell layer comprises soft carbon and has the thickness of 10nm;
in the Raman spectrum of the cathode material, the ID/IG value is normally distributed, and the distribution range is between 0.18 and 0.55;
the preparation method of the anode material comprises the following steps:
(1) Mixing toluene and asphalt in a mass ratio of 100;
the graphite raw material is artificial graphite with the particle size D50 of 10 mu m;
(2) Dripping the first mixture obtained in the step (1) into ethanol, and mixing to obtain a second mixture, wherein the mass ratio of the first mixture to the ethanol in the second mixture is 10;
the amount of the first mixture per dropping is less than the amount of the ethanol;
(3) Filtering the second mixture obtained in the step (2), drying the obtained solid matter, heating the dried solid matter to 300 ℃ at the heating rate of 1 ℃/min in the air, pre-sintering for 12h, replacing nitrogen atmosphere, heating to 1100 ℃ at the heating rate of 2 ℃/min, sintering for 6h, dispersing, and sieving with a 600-mesh sieve to obtain the cathode material;
the SEM image of the negative electrode material of this example is shown in fig. 2.
Example 3
The embodiment provides a negative electrode material, which comprises a core body and a shell layer, wherein the core body comprises graphite, the shell layer comprises soft carbon and has a thickness of 20nm;
in the Raman spectrum of the cathode material, the ID/IG value is normally distributed, and the distribution range is between 0.18 and 0.55;
the preparation method of the anode material comprises the following steps:
(1) Mixing tetrahydrofuran and asphalt in a mass ratio of 100:1.5, and mixing the obtained mixed solution and a graphite raw material in a mass ratio of 1.3;
the graphite raw material is artificial graphite with the particle size D50 of 12 mu m;
(2) Dripping the first mixture obtained in the step (1) into ethanol, and mixing to obtain a second mixture, wherein the mass ratio of the first mixture to the ethanol in the second mixture is 10;
the amount of the first mixture per dropping is less than the amount of the ethanol;
(3) And (3) filtering the second mixture obtained in the step (2), drying the obtained solid matter, heating the dried solid matter to 350 ℃ at the heating rate of 1.5 ℃/min in the air, presintering for 10 hours, replacing nitrogen atmosphere, heating to 1300 ℃ at the heating rate of 1 ℃/min, sintering for 4 hours, dispersing, and sieving with a 200-mesh sieve to obtain the cathode material.
Example 4
The embodiment provides a negative electrode material, which comprises a core and a shell, wherein the core comprises graphite, the shell comprises soft carbon, and the thickness of the shell is 15nm;
in the Raman spectrum of the cathode material, the ID/IG value is normally distributed, and the distribution range is between 0.18 and 0.55;
the preparation method of the anode material comprises the following steps:
(1) Mixing quinoline and asphalt in a mass ratio of 100;
the graphite raw material is artificial graphite with the particle size D50 of 8 mu m;
(2) Dripping the first mixture obtained in the step (1) into water, and mixing to obtain a second mixture, wherein the mass ratio of the first mixture to the water in the second mixture is 10;
the amount of the first mixture per dropping is smaller than the amount of the water;
(3) Filtering the second mixture obtained in the step (2), drying the obtained solid matter, heating the solid matter to 350 ℃ at the heating rate of 1.5 ℃/min in the air, presintering for 15h, replacing nitrogen atmosphere, heating to 1200 ℃ at the heating rate of 5 ℃/min, sintering for 5h, dispersing, and screening by a 500-mesh sieve to obtain the negative electrode material;
the SEM image of the negative electrode material of this example is shown in fig. 3.
Example 5
This example provides an anode material, which is the same as that in example 1 except that the mass ratio of the mixed solution in step (1) to the graphite raw material in the preparation method was changed to 0.6.
Example 6
This example provides an anode material, which is the same as that in example 1 except that the mass ratio of the mixed solution in step (1) to the graphite raw material in the preparation method was changed to 1.4.
Example 7
This example provides an anode material which was the same as in example 1 except that the particle diameter D50 of the graphite raw material in step (1) was changed to 6 μm in the preparation method, and the anode material was changed accordingly.
Example 8
This example provides an anode material which was the same as in example 1 except that the particle diameter D50 of the graphite raw material in step (1) was 15 μm in the preparation method, and the anode material was changed accordingly.
Example 9
This example provides an anode material, which is the same as that of example 1 except that the first mixture of step (1) was added to ethanol all at once and mixed in the preparation method, and the anode material was changed accordingly.
Example 10
This example provides a negative electrode material which was the same as in example 1 except that the preparation method was such that the first mixture in step (1) was divided into two equal parts, and the two parts were mixed with ethanol to change the negative electrode material accordingly.
Example 11
This example provides an anode material, which is the same as in example 1 except that in the preparation method, the temperature increase rate of the pre-firing in the step (3) is 0.2 ℃/min, and the anode material is changed accordingly.
Example 12
This example provides an anode material, which is the same as in example 1 except that in the preparation method, the temperature increase rate of the pre-firing in the step (3) is 2 ℃/min, and the anode material is changed accordingly.
Example 13
This example provides an anode material, which is the same as that in example 1 except that in the preparation method, the second mixture in step (3) is dried instead of being filtered, and the anode material is changed accordingly.
Example 14
This example provides a negative electrode material, which is the same as that in example 1 except that the preparation method does not include step (2), and the first mixture obtained in step (1) is directly dried and then subjected to the pre-firing and sintering described in step (3), so that the negative electrode material is changed accordingly.
Example 15
This example provides an anode material, which is the same as that in example 1, except that in the preparation method, step (2) is not performed, and the mass of quinoline and the like in step (1) is replaced by ethanol, so that the anode material is changed accordingly.
Comparative example 1
The comparative example provides a negative electrode material, in the Raman spectrum of the negative electrode material, the ID/IG value is in abnormal distribution, and the distribution range is between 0.02 and 0.32;
the preparation method of the negative electrode material was the same as that of example 1, except that the artificial graphite and the pitch were mechanically dry-mixed at a mass ratio of 100;
the distribution of the ID/IG values of the negative electrode material of this comparative example is shown in FIG. 4.
Comparative example 2
The comparative example provides a negative electrode material, in the Raman spectrum of the negative electrode material, the ID/IG value is in abnormal distribution, and the distribution range is between 0.02 and 0.32;
the preparation method of the negative electrode material was the same as in example 2, except that the artificial graphite and the pitch were mechanically dry-mixed at a mass ratio of 100.
Comparative example 3
The comparative example provides a negative electrode material, in the Raman spectrum of the negative electrode material, the ID/IG value is in abnormal distribution, and the distribution range is between 0.02 and 0.32;
the preparation method of the negative electrode material was the same as in example 3, except that the solid material was obtained by mechanically dry-mixing artificial graphite and pitch at a mass ratio of 100.5, and the obtained negative electrode material was changed accordingly.
Comparative example 4
The comparative example provides a cathode material, wherein in a Raman spectrum of the cathode material, the ID/IG value is in abnormal distribution, and the distribution range is between 0.02 and 0.32;
the preparation method of the negative electrode material was the same as that of example 4 except that the artificial graphite and the pitch were mechanically dry-mixed at a mass ratio of 100.
The particle diameter D50, specific surface area and median value of ID/IG of the negative electrode materials described in the above examples and comparative examples are shown in table 1; the negative electrode materials described in the above embodiments and comparative examples are compounded into a negative electrode sheet, and the negative electrode sheet, an LFP positive electrode sheet, a PP diaphragm and a lithium hexafluorophosphate electrolyte are prepared into a lithium ion battery, and the capacity retention rate of the lithium ion battery at 2C/0.2C is tested, the lithium ion battery is discharged to 5mV at 0.1C constant voltage, is kept stand for 10min, and then is charged to 2V at 0.1C to test the capacity and the first effect.
The test results are shown in table 1:
TABLE 1
Figure 140693DEST_PATH_IMAGE001
From table 1, the following points can be seen:
(1) Compared with the negative electrode material obtained by adopting dry mixing in comparative examples 1-4, the negative electrode material obtained by the invention has the advantages that the ID/IG value distribution range is narrow, the median value is larger, the multiplying power performance is obviously improved, and as can be seen from the figure, the ID/IG of the negative electrode material is uniformly distributed, the shell layer is uniformly coated, the graphitization degree is reduced compared with that of the raw material, the particle size of the graphite raw material with the same size is smaller after being coated by the invention, the specific surface area is also smaller, and the coating uniformity is further proved to be high; as is clear from examples 1 and 5 to 6, the mass ratio of the first mixture to the graphite raw material is not within a reasonable range, and the amount of the precursor of the shell layer is too large or too small, which affects the particle size, specific surface area, and coating uniformity of the obtained negative electrode material, and deteriorates the rate capability and the like of the material; it is understood from examples 1 and 7 to 8 that the particle size of the graphite raw material used similarly affects the particle size and specific surface area of the finally obtained negative electrode material, and the coating effect is lowered, and the performance of the material is lowered.
(2) As can be seen from examples 1 and 9 to 10, in example 9, the first mixture dissolved with the asphalt is directly added to ethanol at one time, the effect of suspension precipitation coating cannot be achieved, and the asphalt and the graphite raw material cannot be fully mixed, so that the coating effect is reduced, and the performance of the material is reduced, in example 10, although the first mixture dissolved with the asphalt is added to ethanol twice, the amount of the first mixture added each time is larger than that of the ethanol, and the coating effect cannot be guaranteed, therefore, the shell precursor can be slowly precipitated by adopting a dropwise adding mode, so that the shell layer of the precursor can be fully mixed with the graphite raw material, and the coating effect is greatly improved; it is understood from examples 1 and 11 to 12 that too fast and too slow temperature rise in the pre-firing step affects the coating effect and deteriorates the properties of the material.
(3) From the examples 1 and 13, it can be known that the coating effect is better by adopting a filtering mode after the shell layer precursor and the graphite material are fully mixed compared with the mode of directly drying and removing the solvent; as is clear from examples 1 and 13 to 14, although the liquid phase coating method was similarly employed, in example 14, the coating effect was greatly reduced compared to the suspension coating method in which the shell layer precursor was directly dissolved in the first solvent, the graphite raw material was mixed, and the shell layer precursor was coated by drying, and in example 15, the shell layer precursor and the graphite material were dispersed in the second solvent, and the second solvent was removed by filtration, and the coating effect was similarly reduced.
In conclusion, the invention provides the negative electrode material and the preparation method and application thereof, the shell precursor of the negative electrode material is uniformly and effectively coated on the graphite surface by the solvent suspension method, and the graphite negative electrode material with high multiplying power is obtained after heat treatment, the particle size of the negative electrode material is small, the coating uniformity of the graphite surface is good, side reactions are reduced, the dynamic performance is improved, and particularly the multiplying power performance is greatly improved.
The above description is only for the specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the protection scope and the disclosure of the present invention.

Claims (10)

1. An anode material, comprising a core body comprising graphite and a shell layer comprising a graphitizable carbon material;
in the Raman spectrum of the cathode material, the ID/IG value is normally distributed, the distribution range is between 0.18 and 0.55, and the median value is between 0.3 and 0.5;
the negative electrode material is prepared by the following method: (1) Mixing a first solvent and a shell precursor, and mixing the obtained mixed solution with a graphite material to obtain a first mixture;
(2) Adding the first mixture obtained in the step (1) into a second solvent for mixing to obtain a second mixture;
(3) Carrying out solid-liquid separation and carbonization on the second mixture obtained in the step (2) to obtain the anode material;
the solubility of the shell layer precursor in a first solvent is larger than that in a second solvent in the step (1);
the mass ratio of the first solvent to the shell precursor in the step (1) is 100 (1-4), and the mass ratio of the mixed solution to the graphite material is (0.7-1.3) to 1;
the adding mode of the step (2) is dripping, and the amount of the dripping is less than that of the second solvent in the step (2).
2. The negative electrode material according to claim 1, wherein the specific surface area of the negative electrode material is 0.9 to 1.5m 2 (g), the particle diameter D50 is 8-14 μm.
3. The anode material according to claim 1 or 2, characterized in that the graphitizable carbon material includes soft carbon;
the thickness of the shell layer is 10-20nm.
4. A method for preparing the negative electrode material according to any one of claims 1 to 3, characterized by comprising the steps of:
(1) Mixing a first solvent and a shell precursor, and mixing the obtained mixed solution with a graphite material to obtain a first mixture;
(2) Adding the first mixture obtained in the step (1) into a second solvent for mixing to obtain a second mixture;
(3) Carrying out solid-liquid separation and carbonization on the second mixture obtained in the step (2) to obtain the anode material;
the solubility of the shell layer precursor in a first solvent is higher than that in a second solvent in the step (1);
the mass ratio of the first solvent to the shell layer precursor in the step (1) is 100 (1-4), and the mass ratio of the mixed solution to the graphite material is (0.7-1.3) to 1;
the adding mode of the step (2) is dripping, and the dripping amount is less than the amount of the second solvent in the step (2).
5. The method of claim 4, wherein the shell precursor of step (1) comprises any one of pitch, petroleum coke, or needle coke, or a combination of at least two thereof.
6. The method according to claim 4 or 5, wherein the first solvent in step (1) comprises an organic polar solvent comprising any one or a combination of at least two of quinoline, toluene or tetrahydrofuran;
the graphite material in the step (1) has a particle size D50 of 7-35 μm and comprises artificial graphite and/or natural graphite.
7. The preparation method according to claim 4 or 5, wherein in the second mixture in the step (2), the mass ratio of the first mixture to the second solvent is 10 (1-3), and the second solvent comprises an alcohol solvent and/or water.
8. The production method according to claim 4 or 5, wherein the solid-liquid separation in step (3) comprises drying and filtration;
the carbonization in the step (3) comprises pre-sintering and sintering, wherein the sintering temperature is higher than that of the pre-sintering;
the presintering is carried out in the air atmosphere at the temperature of 200-350 ℃, at the heating rate of 0.2-1.5 ℃/min for 8-15h, and at the sintering temperature of 1100-1300 ℃ for 4-6h at the heating rate of 1-5 ℃/min in nitrogen and/or inert gas;
and (3) after carbonization, performing dispersion and screening, wherein the screened mesh number is 200-600 meshes.
9. The method according to claim 4 or 5, characterized in that it comprises the steps of:
(1) Mixing a first solvent and a shell layer precursor according to the mass ratio of 100 (1-4), and mixing the obtained mixed solution and a graphite material according to the mass ratio of (0.7-1.3) to 1 to obtain a first mixture;
the first solvent comprises any one or the combination of at least two of quinoline, toluene or tetrahydrofuran, and the particle size D50 of the graphite material is 7-12 μm;
(2) Dripping the first mixture obtained in the step (1) into a second solvent for mixing to obtain a second mixture, wherein the mass ratio of the first mixture to the second solvent in the second mixture is 10 (1-3);
the amount of the first mixture per dropping is less than that of the second solvent, and the second solvent comprises an alcohol solvent and/or water;
(3) Filtering the second mixture obtained in the step (2), heating the obtained solid substance to 200-350 ℃ at a heating rate of 0.2-1.5 ℃/min in the air atmosphere, presintering for 8-15h, heating to 1100-1300 ℃ at a heating rate of 1-5 ℃/min in nitrogen and/or inert gas, sintering for 4-6h, dispersing, and sieving by a 200-600 mesh sieve to obtain the negative electrode material;
and (2) the solubility of the shell layer precursor in the first solvent is greater than that in the second solvent in the step (1).
10. A lithium ion battery comprising the negative electrode material according to any one of claims 1 to 3.
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