CN110970599B - Graphene-based composite negative electrode material, preparation method thereof and lithium ion battery - Google Patents

Graphene-based composite negative electrode material, preparation method thereof and lithium ion battery Download PDF

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CN110970599B
CN110970599B CN201811138457.3A CN201811138457A CN110970599B CN 110970599 B CN110970599 B CN 110970599B CN 201811138457 A CN201811138457 A CN 201811138457A CN 110970599 B CN110970599 B CN 110970599B
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graphene
based composite
graphite
negative electrode
electrode material
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CN110970599A (en
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李子坤
杨书展
岳敏
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Shenzhen Beiteri New Energy Technology Research Institute Co ltd
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BTR New Material Group Co Ltd
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/362Composites
    • H01M4/366Composites as layered products
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/58Selection 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
    • H01M4/583Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/62Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624Electric conductive fillers
    • H01M4/625Carbon or graphite
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M2004/021Physical characteristics, e.g. porosity, surface area
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M2004/026Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027Negative electrodes
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract

The invention provides a graphene-based composite negative electrode material, a preparation method thereof and a lithium ion battery. The graphene-based composite negative electrode material provided by the invention comprises a large-particle core, small particles adhered to the surface of the large-particle core, and graphene sheets inserted between the large-particle core and the small particles, wherein the large-particle core and the small particles are both made of graphite materials, and the small particles are derived from graphite tailings. The preparation method comprises the following steps: mixing raw materials, (2) carrying out polymerization reaction, and (3) carrying out graphitization treatment. The graphene-based composite negative electrode material provided by the invention has the advantages of stable structure, good orientation, good conductivity, high rate performance, excellent liquid absorption performance and excellent cycle performance, and can meet various requirements in application. The preparation method provided by the invention has the advantages of simple production flow, accurate process control, no harsh conditions, easy industrialization, low cost and resource waste avoidance.

Description

Graphene-based composite negative electrode material, preparation method thereof and lithium ion battery
Technical Field
The invention belongs to the technical field of energy storage materials, relates to a negative electrode material, and particularly relates to a graphene-based composite negative electrode material, a preparation method thereof and a lithium ion battery.
Background
As a mature electrochemical power system, lithium ion batteries have been applied to various aspects of people's daily life, but their performance still cannot fully meet various requirements in application. The most widely applied lithium ion battery cathode material at present is a graphite material, which has a good layered structure, a stable discharge platform, small volume change in the lithium intercalation and deintercalation process and no voltage hysteresis phenomenon, but the graphite cathode material has a capacity upper limit value and is difficult to break through; the compatibility and the liquid absorption capacity with the electrolyte are poor, so that the cycling stability of the battery is poor; and the high-current charge and discharge performance and the multiplying power performance need to be improved. At present, the successful modification methods such as oxidation or halogenation on the surface of a graphite matrix, coating of amorphous carbon, metal and oxides thereof, polymers and the like on the surface, or doping of metal or nonmetal elements can achieve the purpose of improving the comprehensive performance of the graphite cathode by simultaneously modifying the composition and the surface state of the graphite matrix.
The difference of the rate charge and discharge of the lithium ion battery depends on the diffusion rate of lithium ions in the material and the conduction speed of electrons. For the graphite cathode material, the conduction rate of electrons is good, and the electron conduction is difficult to further improve unless graphene with better conductivity is adopted to enhance the electron conduction. Graphene is a single-layer structure of graphite, can be obtained by liquid-phase oxidation, thermal expansion, mechanical peeling and reduction of graphite, and has the characteristics of high electrical conductivity, high thermal conductivity, high mechanical strength, high flexibility, high stability and the like, so that the composite of graphene and graphite shows various excellent performances. The composite material is used as a lithium ion battery cathode material, shows enhanced conductivity and improves the battery power characteristic; the lithium storage capacity is increased, and the energy density of the battery is improved; enhanced cycle stability, extended battery life, etc. However, the pure-phase graphene material has high production cost, and the graphene sheet has a large specific surface area, is difficult to exist independently, is easy to agglomerate, and is difficult to disperse uniformly in the graphite phase. Therefore, the selection of a proper graphene-based composite process in the graphite negative electrode material is the first technical problem to be solved in the field.
For graphite negative electrode materials, the conduction rate of lithium ions is mainly influenced by factors such as particle size, particle size distribution, orientation, morphology and surface state. The smaller particles lead to the great shortening of the lithium ion diffusion path, can reduce the concentration polarization of lithium ions, and is more favorable for the rapid charge and discharge and the cycling stability of the battery; the polymer particles are formed by aggregating a plurality of smaller particles, have better orientation and imbibition capability, and are beneficial to the diffusion of lithium ions, especially the charging performance and the cycling performance at low temperature. Therefore, how to select a proper process to control the composition of the material, construct the structural morphology of the particles, and improve the comprehensive performance of the graphite anode material is a second technical problem to be solved in the field.
In the production process of graphite as a negative electrode material, raw materials need to be subjected to multiple processes of crushing, shaping, grading and the like, and the processes can cause the problems of reduction of the utilization rate of the raw materials, pollution of dust environment, increase of process cost and the like, and the raw material utilization rate in the whole production process is usually 40-50% and the rest 50-60% of the raw materials form 'tailings', and the 'tailings' consist of micro powder and have the characteristics of small particle size, high specific surface area, irregular shape, low tap density and the like, can not be directly used as the negative electrode material of the lithium ion battery, and are usually used as a carburant in the aspects of ferrous metallurgy and the like, so the utilization value is extremely low, the production cost is increased, and a large amount of material waste is caused. Therefore, finding a suitable method to treat the 'tailings' in the production process and improve the utilization value of the materials is a third technical problem to be solved urgently in the field.
CN108206268A discloses a negative electrode material, a preparation method thereof, a negative electrode plate and a lithium ion battery, wherein the negative electrode material includes a plurality of first particles and a cross-linked polymer, and the plurality of first particles are close-packed by the cross-linked polymer to form second particles, wherein the first particles include a silicon core and a shell material coating layer, and a cavity is formed between the silicon core and the shell material coating layer. The negative electrode material further comprises a conductive additive, wherein the conductive additive comprises at least one of graphene, carbon nanotubes, carbon fibers and conductive carbon black. The homodisperse of graphite alkene can't effectively be realized to this scheme, can't solve the processing problem of graphite tails simultaneously.
CN107200322A discloses a method for preparing a negative electrode material for a lithium battery by using special graphite tailings. The method comprises the following steps: s1, performing spheroidization treatment on special graphite tailing particles, adding a binder, and uniformly mixing to obtain a premix; s2, ultrasonically dispersing graphene oxide in a solvent to obtain a suspension dispersion liquid, standing, and uniformly spraying and mixing the upper layer stable dispersion liquid into the premix in the S1 to obtain a mixture; and S3, pressing the mixture in the S2 to obtain a pressed block, roasting the pressed block in the mixed atmosphere of nitrogen and hydrogen, cooling to room temperature, and then sequentially performing crushing, demagnetizing and screening on the pressed block to obtain the magnetic material. Although the scheme can solve the problem of processing graphite tailings, the problem of dispersion of graphene in the negative electrode material cannot be solved, and the appearance of the negative electrode is further optimized to improve the material performance.
CN107863511A discloses a method for preparing negative electrode powder for a lithium battery by recycling high-purity graphite scraps. Which comprises the following steps: sl, performing spheroidization treatment on special graphite tailing particles, then adding a binder and uniformly mixing to obtain a premix; s2, mixing graphene oxide and nano silicon in proportion in a solvent, performing ultrasonic dispersion to obtain a suspension dispersion liquid, standing, and uniformly spraying and mixing an upper layer of stable dispersion liquid into a premix in Sl to obtain a mixture, wherein the upper layer of stable dispersion liquid can be regarded as a dispersion system of the graphene oxide and the nano silicon powder; and (3) pressing the mixture in the step (S2) to obtain a pressed block, roasting the pressed block in the mixed atmosphere of nitrogen and hydrogen, cooling to room temperature, and crushing, demagnetizing and screening the pressed block in sequence to obtain the negative electrode material for the lithium battery. Although the scheme can solve the problem of processing the graphite tailings, the problem of dispersion of graphene in the negative electrode material cannot be solved, and the appearance of the negative electrode is further optimized to improve the material performance.
Therefore, the development of the cathode material which has a proper structural morphology and high graphene dispersion degree and can solve the problem of graphite tailing treatment is of great significance to the field.
Disclosure of Invention
In view of the above disadvantages in the prior art, the present invention aims to provide a graphene-based composite negative electrode material, a preparation method thereof, and a lithium ion battery. The graphene in the graphene-based composite negative electrode material provided by the invention has the advantages of high dispersion degree of graphene, stable structure, good orientation, good conductivity, high rate performance, excellent liquid absorption performance and cycle performance, can meet various requirements in application, and solves the problem of treatment of graphite tailings.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a graphene-based composite negative electrode material, including a large-particle core, small particles adhered to the surface of the large-particle core, and graphene sheets interposed between the large-particle core and the small particles, where the large-particle core and the small particles are both graphite materials, and the small particles are derived from graphite tailings.
The graphene-based composite material provided by the invention can also comprise a graphite material formed by a part of polymerization additives. The graphite tailings comprise micro powder particles left in the production, crushing, shaping or grading process of the graphite cathode.
In the present invention, the morphology of the small particles is not completely the same. The graphene-based composite negative electrode material provided by the invention has an embedded structure, small particles with different shapes are adhered to the surface of a large-particle core to form composite particles with larger particle size, and graphene sheets are inserted among the large particles to form a conductive network. The unique structure ensures that the graphene-based composite negative electrode material provided by the invention has the advantages of stable structure, good orientation, good conductivity, high rate performance, excellent liquid absorption performance and cycle performance, and can meet various requirements in application. The raw material of the small particles in the graphene-based composite negative electrode material provided by the invention is graphite tailings, so that high-value utilization of the graphite tailings is realized.
In the graphene-based composite material provided by the invention, small particle tailing adheres to the surface of a large particle core to form a larger particle composite particle, and the small particle tailing is different in appearance and orientation, shows isotropy macroscopically, and eliminates direction selectivity in the lithium ion transfer process; the diffusion path of lithium ions is greatly shortened due to smaller particles; the small particle tailing is firmly adhered and agglomerated together by using the polymeric additive, the structural stability is good, the expansion of a pole piece is low in the charging and discharging processes of the battery, and the cycling stability is shown. On the other hand, graphene with better conductivity is adopted for compounding, and point contact among particles is communicated, so that the conductivity of the negative electrode material is enhanced, the polarization of the battery is reduced, and the power characteristic is improved; the lithium storage capacity of graphene is high, so that the energy density of the battery is improved; enhanced cycle stability, extended battery life, etc.
In the graphene-based composite material provided by the invention, graphene is uniformly dispersed among large and small particles.
The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
In a preferred embodiment of the present invention, the average particle size D50 of the large particle cores is 5 to 20 μm, for example, 5 μm, 7.5 μm, 10 μm, 12.5 μm, 15 μm or 20 μm, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.
Preferably, the small particles have an average particle size D50 of 1 to 10 μm, for example 1 μm, 2 μm, 4 μm, 6 μm, 8 μm or 10 μm, but are not limited to the values listed, and other values not listed in this range are equally suitable.
Preferably, the graphene sheets are few-layer graphene sheets.
Preferably, the graphene-based composite negative electrode material has an average particle size D50 of 10.0 to 40.0 μm, for example, 10.0 μm, 15.0 μm, 20.0 μm, 25.0 μm, 30.0 μm, 35.0 μm, 40.0 μm, etc., but is not limited to the recited values, and other values not recited within this range of values are also applicable.
Preferably, the graphene-based composite anode material has a particle size distribution dispersion of 0.5 to 2.0, such as 0.5, 1.0, 1.5, or 2.0, but not limited to the recited values, and other values not recited within the range of values are also applicable.
Preferably, the graphene-based composite anode material has a sphericity S50 of 0.8 to 0.9, for example, 0.8, 0.82, 0.84, 0.86, 0.88, or 0.9, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the specific surface area of the graphene-based composite negative electrode material is 2.0-20.0m 2 In g, e.g. 2.0m 2 /g、5.0m 2 /g、10.0m 2 /g、15.0m 2 G or 20.0m 2 And/g, but are not limited to the recited values, and other unrecited values within the numerical range are equally applicable.
The first lithium removal specific capacity of the graphene-based composite negative electrode material provided by the invention is more than or equal to 355mAh/g, and the first coulombic efficiency is more than or equal to 90 percentAt 1.65g/cm 3 The liquid absorption time of the pole piece under the compacted density is less than or equal to 180s, the multiplying power charging performance 10C/0.2C is more than or equal to 80%, and the circulating capacity retention rate at 1000 weeks is more than or equal to 85%.
In a second aspect, the present invention provides a method for preparing the graphene-based composite anode material according to the first aspect, the method comprising the following steps:
(1) Mixing a graphite precursor main material, graphite oxide, a graphite tailing material and a polymerization additive to obtain a mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) under a protective atmosphere to obtain polymer particles;
(3) And (3) carrying out graphitization treatment on the polymer particles in the step (2) in a protective atmosphere to obtain the graphene-based composite negative electrode material.
According to the preparation method provided by the invention, through polymerization reaction and graphitization treatment, the graphite precursor main material finally forms a large-particle kernel, the graphite tailing forms small particles adhered to the surface of the large-particle kernel, and the graphite oxide forms a graphene sheet.
The method disclosed by the invention gets rid of the design idea of the traditional cathode material, adopts a brand-new material design concept, integrates the advantages of the graphene material, fully utilizes the structures of small-particle tailing and polymeric particles, is simple in production flow, accurate in process control, free from harsh conditions, easy to industrialize, low in cost and capable of avoiding resource waste. The graphene-based composite negative electrode material prepared by the method is stable in structure and has excellent comprehensive performance.
As a preferable technical scheme of the invention, the graphite precursor main material in the step (1) comprises any one or combination of at least two of green coke, cooked coke and carbon microspheres.
Preferably, the green coke comprises any one of petroleum coke, pitch coke or coal coke or a combination of at least two of them.
Preferably, the cooked coke comprises any one of petroleum coke, pitch coke, or coal coke, or a combination of at least two thereof.
Preferably, the carbon microspheres include petroleum pitch-based carbon microspheres and/or coal pitch-based carbon microspheres.
Preferably, the graphite precursor of step (1) has a volatility of 2 to 20%, for example, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, etc., but is not limited to the recited values, and other values not recited in the range of values are also applicable.
Preferably, the ash content of the graphite precursor in step (1) is below 0.5%, such as 0.5%, 0.4%, 0.3%, 0.2%, etc.
Preferably, the graphite precursor of step (1) has an average particle size D50 of 5 to 20 μm, such as 5 μm, 7.5 μm, 10 μm, 12.5 μm, 15 μm or 20 μm, but is not limited to the recited values, and other values not recited in this range are also applicable.
Preferably, the graphite oxide in the step (1) comprises a material obtained by oxidizing graphite in a liquid phase with an acid.
Preferably, the graphite oxide of step (1) has an average particle size D50 of 1-10 μm, for example 1 μm, 2 μm, 4 μm, 6 μm, 8 μm or 10 μm, but is not limited to the recited values, and other values not recited in this range are equally applicable.
Preferably, the graphite oxide of step (1) is added in an amount of 1.0% to 10.0% by weight, e.g., 1.0%, 2.0%, 4.0%, 6.0%, 8.0%, or 10.0% by weight, based on the total weight of the mixture, but is not limited to the recited values, and other unrecited values within the range of values are equally applicable. If the addition of the graphite oxide is excessive, a large number of graphene lamellar results are generated, the specific surface area is increased, the agglomeration is serious, the dispersion effect is poor, and the electrochemical performance of the composite material is not facilitated; if the amount of graphite oxide added is too small, the content of the generated graphene is low, the improvement range of the electric conductivity of the composite material is limited, and the performance advantage cannot be fully shown.
Preferably, the graphite tailings in the step (1) comprise micro powder particles left in the production crushing, shaping or grading process of the graphite cathode.
Preferably, the graphite tailings of step (1) have an average particle size D50 of 1-10 μm, such as 1 μm, 2 μm, 4 μm, 6 μm, 8 μm or 10 μm, but not limited to the recited values, and other values not recited in this range are equally applicable.
Preferably, the specific surface area of the graphite tailings in the step (1) is 5-15m 2 In terms of/g, e.g. 5m 2 /g、10m 2 G or 15m 2 And/g, but are not limited to the recited values, and other unrecited values within the numerical range are equally applicable.
Preferably, the graphite tailings of step (1) are added in an amount of 1.0% to 20.0% by weight of the total weight of the mixture, such as 1.0%, 2.0%, 4.0%, 6.0%, 8.0%, 10.0%, 12.0%, 14.0%, 16.0%, 18.0%, or 20.0%, but not limited to the recited values, and other values not recited in this range are equally applicable. If the graphite tailing is added too much, the bonding polymerization of all tailing small particles cannot be ensured, and finally, the micro powder in the material is too much, the specific surface area is increased, and the electrochemical performance of the material is reduced; if the graphite tailing is added too little, the small particle dosage of the bonding polymerization is insufficient, so that the large particles are directly bonded and polymerized, and finally, the integral particle size of the material is larger, which is not beneficial to the multiplying power and the quick charging performance of the material.
Preferably, the polymeric additive in step (1) comprises any one of asphalt, resin, high molecular material or polymer or a combination of at least two of the above.
Preferably, the bitumen comprises any one of coal tar pitch, petroleum pitch, natural pitch or mesophase pitch, or a combination of at least two thereof.
Preferably, the polymeric additive is added in an amount of 10.0% to 30.0%, such as 10.0%, 15.0%, 20.0%, 25.0% or 30.0% by weight of the total weight of the mixture, but not limited to the recited values, and other values not recited within this range are equally applicable. If the addition amount of the polymerization additive is too much, the particle size of the particles generated by polymerization is too large, and too much additive components are not beneficial to exerting the comprehensive performance of the particles; if the addition amount of the polymerization additive is too small, the amount of the binder required for the polymerization of the small-particle tailing is insufficient, and the polymerization bonding cannot be well carried out.
In a preferred embodiment of the present invention, the mixing in step (1) is performed by a mixer.
Preferably, the mixer comprises any one of a V-blender, a trough blender, a drum blender, a conical twin-screw mixer or a double-cone mixer or a combination of at least two of them.
Preferably, the mixing time in step (1) is 10-180min, such as 10min, 20min, 50min, 80min, 100min, 120min, 140min, 160min or 180min, but not limited to the recited values, and other values not recited in the range of values are also applicable.
As a preferable technical scheme of the invention, the polymerization reaction in the step (2) is carried out in a reaction kettle. The reaction kettle can be any one of a VC-1500J type reaction kettle for stannless fresh optical powder, a VC-1000L reaction kettle for stannless Qingxin powder, a VC-2000L reaction kettle for Hengaojia in Foshan, a VC-2000L reaction kettle for Shuoshongxing in Foshan and a VC-2000L reaction kettle for Shianoxing machinery in Foshan.
Preferably, the polymerization temperature in step (2) is 300 to 800 ℃, such as 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃ or 800 ℃ and the like, but is not limited to the recited values, and other unrecited values within the range of values are equally applicable.
Preferably, the polymerization reaction time in step (2) is 3 to 9 hours, such as 3 hours, 4 hours, 6 hours, 8 hours, or 9 hours, but not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the polymerization reaction of step (2) is accompanied by stirring.
Preferably, the stirring speed is 10-40r/min, such as 10r/min, 20r/min, 30r/min, or 40r/min, but not limited to the recited values, and other values not recited within the range of values are equally applicable. Here, if the stirring speed is too high, cohesive polymerization of the particles is not facilitated, and even the particles in which cohesive polymerization has occurred are broken; if the stirring speed is too slow, the dispersion of the polymerization additive and the large and small particles is not facilitated, and the polymerization reaction cannot be uniformly carried out, which finally results in poor particle size distribution, uniformity and the like of the material.
Preferably, the protective atmosphere in step (2) comprises any one of helium, neon, argon or nitrogen or a combination of at least two of them.
Preferably, the gas flow rate of the protective atmosphere in step (2) is 20-50L/min, such as 20L/min, 30L/min, 40L/min or 50L/min, but not limited to the recited values, and other values not recited in the range of the recited values are also applicable.
As a preferred technical solution of the present invention, the protective atmosphere in step (3) includes any one of helium, neon, argon or nitrogen, or a combination of at least two of them.
Preferably, the graphitization treatment in step (3) is performed by using a graphitization furnace. The graphitization furnace comprises an inner-string type graphitization furnace or an Acheson graphitization furnace.
Preferably, the graphitization treatment in step (3) is performed at a temperature of 2500-3300 deg.C, such as 2500 deg.C, 2600 deg.C, 2700 deg.C, 2800 deg.C, 2900 deg.C, 3000 deg.C, 3100 deg.C, 3200 deg.C, 3300 deg.C, etc., but it is not limited to the recited values, and other values not recited in the range of the recited values are also applicable.
Preferably, the temperature rise time of the graphitization treatment in the step (3) is 12-72h, such as 12h, 24h, 36h, 48h, 60h or 72h, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the graphitization treatment in step (3) is performed at an incubation time of 15-30 days, such as 15 days, 20 days, 25 days, or 30 days, but not limited to the recited values, and other values not recited in the range of values are also applicable.
In the graphitization treatment in the step (3), the temperature is firstly increased to the temperature required by the graphitization treatment, and then the temperature is kept for heat preservation treatment.
As a preferred technical scheme of the invention, the method further comprises the following step (4): and (4) carrying out crushing, particle shaping and screening treatment on the graphene-based composite negative electrode material in the step (3).
And (5) obtaining the graphene-based composite negative electrode material with the average particle size of 10.0-40.0 microns through the treatment of the step (4).
Preferably, the crushing and particle shaping device comprises any one or a combination of at least two of a turbine type crusher, an airflow vortex pulverizer, a super cyclone vortex mill, an air separation crusher or a double-rod crusher.
As a further preferable technical scheme of the preparation method, the method comprises the following steps:
(1) Mixing the graphite precursor main material, graphite oxide, graphite tailings and the polymerization additive in a mixer for 10-180min to obtain a mixed material;
wherein, the adding amount of the graphite oxide is 1.0-10.0 percent of the total weight of the mixed material, the adding amount of the graphite tailing is 1.0-20.0 percent of the total weight of the mixed material, and the adding amount of the polymeric additive is 10.0-30.0 percent of the total weight of the mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) at the temperature of 300-800 ℃ and the stirring speed of 10-40r/min under the protective atmosphere with the gas flow of 20-50L/min for 3-9h to obtain polymer particles;
(3) Graphitizing the polymer particles in the step (2) by using a graphitizing furnace at the temperature of 2500-3300 ℃ in a protective atmosphere, wherein the temperature rise time of the graphitizing treatment is 12-72h, and the heat preservation time is 15-30 days, so as to obtain the graphene-based composite negative electrode material;
(4) And (4) carrying out crushing, particle shaping and screening treatment on the graphene-based composite negative electrode material in the step (3).
In a third aspect, the present invention provides a lithium ion battery comprising the graphene-based composite anode material according to the first aspect.
In the lithium ion battery provided by the invention, the graphene-based composite negative electrode material of the first aspect is used as a negative electrode active material and is combined with a binding additive to form a negative electrode material. The graphene-based composite negative electrode material used as the negative electrode active substance has higher electronic conductivity and better lithium ion diffusion performance, and is more favorable for eliminating the generation of internal polarization of the battery, so that an additional conductive agent is omitted in the manufacturing process of the lithium ion battery, more active substances are placed in a limited battery space, and the energy density of the battery is increased.
Compared with the prior art, the invention has the following beneficial effects:
(1) The graphene-based composite negative electrode material provided by the invention has the advantages of stable structure, good orientation, good conductivity, high rate performance, excellent liquid absorption performance and excellent cycle performance, and can meet various requirements in application. The graphene-based composite negative electrode material provided by the invention can realize that the first lithium removal specific capacity is more than or equal to 355mAh/g, the first coulombic efficiency is more than or equal to 90%, and the first lithium removal specific capacity is 1.65g/cm 3 The liquid absorption time of the pole piece under the compacted density is less than or equal to 180s, the rate charging performance of 10C/0.2C is more than or equal to 80%, and the cycle capacity retention rate of 1000 weeks is more than or equal to 85%.
(2) The preparation method provided by the invention integrates the advantages of the graphene material, fully utilizes the structures of the small-particle graphite tailings and the polymeric particles, has the advantages of simple production flow, accurate process control, no harsh conditions, easy industrialization and low cost, and avoids resource waste.
Drawings
Fig. 1 is a schematic structural view of a graphene-based composite anode material prepared in example 1 of the present invention, wherein 1 is a large-particle core, 2 is a graphene sheet, and 3 is a small particle;
fig. 2 is an SEM image of the graphene-based composite anode material prepared in example 1 of the present invention;
fig. 3 is a graph showing different-rate charging curves of the graphene-based composite anode material prepared in example 1 of the present invention;
fig. 4 is a cycle curve diagram of the graphene-based composite anode material prepared in example 1 of the present invention.
Detailed Description
In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
The following are typical, but non-limiting, examples of the present invention:
example 1
In this example, a graphene-based composite negative electrode material was prepared as follows:
(1) Mixing a graphite precursor main material, graphite oxide, a graphite tailing material and a polymerization additive in a V-shaped mixer for 10min to obtain a mixed material;
wherein, the parameters of each raw material are shown in table 1. The adding amount of the graphite oxide is 1.2 percent of the total weight of the mixed material, the adding amount of the graphite tailing is 18.9 percent of the total weight of the mixed material, and the adding amount of the polymerization additive is 10.2 percent of the total weight of the mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) at the temperature of 300 ℃ and the stirring speed of 10r/min under the argon atmosphere with the gas flow of 20L/min, wherein the reaction kettle is a tin-free new optical powder VC-1500J type reaction kettle, and the reaction time is 3h to obtain polymer particles;
(3) Carrying out graphitization treatment on the polymer particles in the step (2) by using an Acheson graphitization furnace at the temperature of 2500 ℃ in an argon atmosphere, wherein the temperature rise time of the graphitization treatment is 24h, and the heat preservation time is 20 days, so as to obtain the graphene-based composite negative electrode material;
(4) And (4) crushing, particle shaping and screening the graphene-based composite negative electrode material obtained in the step (3) by using a turbine type crusher to obtain the graphene-based composite negative electrode material with the average particle size D50 of 11.5 microns.
The graphene-based composite negative electrode material finally obtained in the embodiment comprises a large-particle core, small particles adhered to the surface of the large-particle core, and a few-layer graphene sheet inserted between the large-particle core and the small particles, wherein the large-particle core and the small particles are both made of graphite materials, and the small particles are derived from graphite tailings.
The performance test results of the finally obtained graphene-based composite negative electrode material in this example are shown in table 2.
Fig. 1 is a schematic structural diagram of the graphene-based composite anode material prepared in this embodiment. As can be seen from the figure, in the graphene-based composite anode material prepared in this embodiment, small particles 3 with different morphologies are adhered to the surface of the large particle core 1 to form a composite particle with a larger particle size, and the few graphene sheets 2 are inserted between the large particle core 1 and the small particles 3 to form a conductive network.
Fig. 2 is an SEM image of the graphene-based composite anode material prepared in this embodiment, and it can be seen from the SEM image that the particle morphology of the graphene-based composite anode material prepared in this embodiment is represented by small particle aggregates with different shapes, and the surface has a microporous structure.
Fig. 3 is a graph of different-rate charge curves of the graphene-based composite negative electrode material prepared in this example, and it can be seen from the graph that the high-rate charge capacity and the low-rate charge capacity are close to each other, for example, the 10C-rate charge can reach more than 80% relative to 0.2C.
Fig. 4 is a cycle curve diagram of the graphene-based composite anode material prepared in this embodiment, and it can be seen from the cycle capacity retention rate of the anode material for 1000 weeks is more than 85%. In this figure, the cycle retention rate fluctuates due to the unstable structure of the battery in the early stage, and the cycle retention rate is more than 100% in the early stage.
Example 2
In this example, a graphene-based composite negative electrode material was prepared as follows:
(1) Mixing a graphite precursor main material, graphite oxide, a graphite tailing material and a polymerization additive in a trough type mixer for 180min to obtain a mixed material;
wherein, the parameters of each raw material are shown in table 1. The adding amount of the graphite oxide is 9.7 percent of the total weight of the mixed material, the adding amount of the graphite tailing is 1.2 percent of the total weight of the mixed material, and the adding amount of the polymerization additive is 28.9 percent of the total weight of the mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) at the temperature of 800 ℃ and the stirring speed of 40r/min under the nitrogen atmosphere with the gas flow of 50L/min, wherein the reaction kettle is a Wuxi Xin powder VC-1000L reaction kettle, and the reaction time is 9h to obtain polymer particles;
(3) Carrying out graphitization treatment on the polymer particles in the step (2) by using an internal-series graphitization furnace at the temperature of 2800 ℃ in a nitrogen atmosphere, wherein the temperature rise time of the graphitization treatment is 12h, and the heat preservation time is 30 days to obtain the graphene-based composite negative electrode material;
(4) And (4) crushing, particle shaping and screening the graphene-based composite negative electrode material obtained in the step (3) by using an airflow vortex micro-pulverizer to obtain the graphene-based composite negative electrode material with the average particle size D50 of 38.3 microns.
The graphene-based composite negative electrode material finally obtained in the embodiment comprises a large-particle core, small particles adhered to the surface of the large-particle core, and an oligolayer graphene sheet inserted between the large-particle core and the small particles, wherein the large-particle core and the small particles are both made of graphite materials, and the small particles are made of graphite tailings.
The performance test results of the graphene-based composite negative electrode material finally obtained in this embodiment are shown in table 2.
Example 3
In this example, a graphene-based composite negative electrode material was prepared as follows:
(1) Mixing a graphite precursor main material, graphite oxide, a graphite tailing material and a polymerization additive in a roller mixer for 60min to obtain a mixed material;
wherein, the parameters of each raw material are shown in Table 1. The adding amount of the graphite oxide is 2.5 percent of the total weight of the mixed material, the adding amount of the graphite tailing is 2.5 percent of the total weight of the mixed material, and the adding amount of the polymerization additive is 15.8 percent of the total weight of the mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) at the temperature of 450 ℃ and the stirring speed of 25r/min under the helium atmosphere with the gas flow of 20L/min, wherein the reaction kettle is a Fushan Hengaojia VC-2000L reaction kettle, and the reaction time is 5h to obtain polymer particles;
(3) Carrying out graphitization treatment on the polymer particles in the step (2) by using an Acheson graphitization furnace at the temperature of 3000 ℃ in the neon atmosphere, wherein the temperature rise time of the graphitization treatment is 36h, and the heat preservation time is 15 days, so as to obtain the graphene-based composite negative electrode material;
(4) And (3) crushing, particle shaping and screening the graphene-based composite negative electrode material obtained in the step (3) by using a super cyclone vortex mill to obtain the graphene-based composite negative electrode material with the average particle size D50 of 15.6 microns.
The graphene-based composite negative electrode material finally obtained in the embodiment comprises a large-particle core, small particles adhered to the surface of the large-particle core, and a few-layer graphene sheet inserted between the large-particle core and the small particles, wherein the large-particle core and the small particles are both made of graphite materials, and the small particles are derived from graphite tailings.
The performance test results of the finally obtained graphene-based composite negative electrode material in this example are shown in table 2.
Example 4
In this example, a graphene-based composite negative electrode material was prepared as follows:
(1) Mixing a graphite precursor main material, graphite oxide, a graphite tailing material and a polymerization additive in a conical double-helix mixer for 120min to obtain a mixed material;
wherein, the parameters of each raw material are shown in table 1. The adding amount of the graphite oxide is 6.8 percent of the total weight of the mixed material, the adding amount of the graphite tailing is 6.8 percent of the total weight of the mixed material, and the adding amount of the polymerization additive is 24.7 percent of the total weight of the mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) at the temperature of 550 ℃ and the stirring speed of 30r/min under the neon gas atmosphere with the gas flow of 30L/min, wherein the reaction kettle is a Foshan Shuoxing VC-2000L reaction kettle, and the reaction time is 7h to obtain polymer particles;
(3) Graphitizing the polymer particles in the step (2) by using an inner-string type graphitizing furnace under neon atmosphere at the temperature of 3100 ℃, wherein the temperature rise time of the graphitizing treatment is 48 hours, and the heat preservation time is 20 days, so as to obtain the graphene-based composite negative electrode material;
(4) And (4) crushing, particle shaping and screening the graphene-based composite negative electrode material obtained in the step (3) by using a winnowing grinder to obtain the graphene-based composite negative electrode material with the average particle size D50 of 22.4 microns.
The graphene-based composite negative electrode material finally obtained in the embodiment comprises a large-particle core, small particles adhered to the surface of the large-particle core, and a few-layer graphene sheet inserted between the large-particle core and the small particles, wherein the large-particle core and the small particles are both made of graphite materials, and the small particles are derived from graphite tailings.
The performance test results of the graphene-based composite negative electrode material finally obtained in this embodiment are shown in table 2.
Example 5
In this example, a graphene-based composite negative electrode material was prepared as follows:
(1) Mixing a graphite precursor main material, graphite oxide, a graphite tailing material and a polymerization additive in a double-cone mixer for 70min to obtain a mixed material;
wherein, the parameters of each raw material are shown in table 1. The adding amount of the graphite oxide is 7.4 percent of the total weight of the mixed material, the adding amount of the graphite tailing is 12.4 percent of the total weight of the mixed material, and the adding amount of the polymerization additive is 21.5 percent of the total weight of the mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) at the temperature of 750 ℃ and the stirring speed of 35r/min under the helium atmosphere with the gas flow of 35L/min, wherein the reaction kettle is a Fushannuoxing mechanical VC-2000L reaction kettle, and the reaction time is 8h to obtain polymer particles;
(3) Carrying out graphitization treatment on the polymer particles in the step (2) by using an Acheson graphitization furnace at the temperature of 3300 ℃ in a helium atmosphere, wherein the temperature rise time of the graphitization treatment is 60h, and the heat preservation time is 25 days, so as to obtain the graphene-based composite negative electrode material;
(4) And (4) crushing, particle shaping and screening the graphene-based composite negative electrode material obtained in the step (3) by using a double-rod crusher to obtain the graphene-based composite negative electrode material with the average particle size D50 of 35.0 microns.
The graphene-based composite negative electrode material finally obtained in the embodiment comprises a large-particle core, small particles adhered to the surface of the large-particle core, and an oligolayer graphene sheet inserted between the large-particle core and the small particles, wherein the large-particle core and the small particles are both made of graphite materials, and the small particles are made of graphite tailings.
The performance test results of the finally obtained graphene-based composite negative electrode material in this example are shown in table 2.
Example 6
In this example, a graphene-based composite negative electrode material was prepared as follows:
(1) Mixing a graphite precursor main material, graphite oxide, a graphite tailing material and a polymerization additive in a trough type mixer for 60min to obtain a mixed material;
wherein, the parameters of each raw material are shown in table 1. The adding amount of the graphite oxide is 2.5 percent of the total weight of the mixed material, the adding amount of the graphite tailing is 5.4 percent of the total weight of the mixed material, and the adding amount of the polymerization additive is 20.9 percent of the total weight of the mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) at the temperature of 500 ℃ and the stirring speed of 45r/min under the argon atmosphere with the gas flow of 45L/min, wherein the reaction kettle is a Fushan Hengaojia VC-2000L reaction kettle, and the reaction time is 6h to obtain polymer particles;
(3) Carrying out graphitization treatment on the polymer particles in the step (2) by using an internal-series graphitization furnace at the temperature of 3100 ℃ in an argon atmosphere, wherein the temperature rise time of the graphitization treatment is 72h, and the heat preservation time is 30 days, so as to obtain the graphene-based composite negative electrode material;
(4) And (4) crushing, particle shaping and screening the graphene-based composite negative electrode material obtained in the step (3) by using a turbine type crusher to obtain the graphene-based composite negative electrode material with the average particle size D50 of 7.6 microns.
The graphene-based composite negative electrode material finally obtained in the embodiment comprises a large-particle core, small particles adhered to the surface of the large-particle core, and a few-layer graphene sheet inserted between the large-particle core and the small particles, wherein the large-particle core and the small particles are both made of graphite materials, and the small particles are derived from graphite tailings.
The performance test results of the finally obtained graphene-based composite negative electrode material in this example are shown in table 2.
Example 7
In this example, a graphene-based composite negative electrode material was prepared as follows:
(1) Mixing a graphite precursor main material, graphite oxide, a graphite tailing material and a polymerization additive in a conical double-helix mixer for 120min to obtain a mixed material;
wherein, the parameters of each raw material are shown in Table 1. The adding amount of the graphite oxide is 8.6 percent of the total weight of the mixed material, the adding amount of the graphite tailing is 8.7 percent of the total weight of the mixed material, and the adding amount of the polymerization additive is 8.8 percent of the total weight of the mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) at the temperature of 700 ℃ and the stirring speed of 25r/min under the nitrogen atmosphere with the gas flow of 30L/min, wherein the reaction kettle is a Foshan Shuoxing VC-2000L reaction kettle, and the reaction time is 8h to obtain polymer particles;
(3) Graphitizing the polymer particles in the step (2) by using an Acheson graphitizing furnace in a nitrogen atmosphere at the temperature of 3000 ℃, wherein the temperature rise time of the graphitizing treatment is 34h, and the heat preservation time is 25 days, so as to obtain the graphene-based composite negative electrode material;
(4) And (4) crushing, particle shaping and screening the graphene-based composite negative electrode material obtained in the step (3) by using a super cyclone vortex mill to obtain the graphene-based composite negative electrode material with the average particle size D50 of 12.3 microns.
The graphene-based composite negative electrode material finally obtained in the embodiment comprises a large-particle core, small particles adhered to the surface of the large-particle core, and a few-layer graphene sheet inserted between the large-particle core and the small particles, wherein the large-particle core and the small particles are both made of graphite materials, and the small particles are derived from graphite tailings.
The performance test results of the graphene-based composite negative electrode material finally obtained in this embodiment are shown in table 2.
Comparative example 1
The graphene-based composite negative electrode material was prepared according to the following method:
(1) Mixing the main material of the graphite precursor, the graphite tailing and the polymerization additive in a double cone mixer for 30min to obtain a mixed material;
wherein, the parameters of each raw material are shown in table 1. The adding amount of the graphite tailing is 16.8 percent of the total weight of the mixed material, and the adding amount of the polymeric additive is 15.4 percent of the total weight of the mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) at the temperature of 380 ℃ and the stirring speed of 20r/min under the neon atmosphere with the gas flow of 40L/min, wherein the reaction kettle is a Xiqingxin powder VC-1000L reaction kettle, and the reaction time is 4h to obtain polymer particles;
(3) Carrying out graphitization treatment on the polymer particles in the step (2) by using an internal-series graphitization furnace at the temperature of 3100 ℃ in a helium atmosphere, wherein the temperature rise time of the graphitization treatment is 36h, and the heat preservation time is 25 days, so as to obtain the graphene-based composite negative electrode material;
(4) And (3) crushing, particle shaping and screening the graphene-based composite negative electrode material obtained in the step (3) by using a super cyclone vortex mill to obtain the graphene-based composite negative electrode material with the average particle size D50 of 25.3 mu m.
The performance test results of the graphene-based composite negative electrode material finally obtained in the comparative example are shown in table 2.
TABLE 1
Figure GDA0003764416480000201
Figure GDA0003764416480000211
Performance test method
The physical property and electrochemical property test method of the graphene-based composite negative electrode material finally obtained in each embodiment and comparative example of the invention is as follows:
(1) Microscopic state:
the surface morphology of the graphene-based composite negative electrode material prepared in each embodiment and comparative example of the invention is tested by adopting a KYKY-2800B type scanning electron microscope of a Chinese traditional science apparatus.
(2) Particle size and particle size distribution dispersion:
the graphene-based composite negative electrode material of each example except example 6 of the invention is tested by a laser particle size analyzer of British Malvern-Mastersizer 2000 type, and the average particle size D50 of the graphene-based composite negative electrode material is 10.0-40.0 μm. The formula for calculating the dispersion of the particle size distribution is as follows: particle size distribution dispersion = (D90-D10)/D50, resulting in a dispersion between 0.5-2.0.
(3) Sphericity:
the sphericity S50 of the graphene-based composite anode material according to each example of the present invention was measured to be between 0.8 and 0.9 using a german QICPIC particle size particle shape analyzer.
(4) Specific surface area:
the specific surface area of the graphene-based composite negative electrode material of each example of the present invention was measured to be 2.0 to 20.0m2/g by a BET method of nitrogen adsorption and a U.S. conta Nova 1000e specific surface area/pore size analyzer.
(5) And (3) electrochemical performance testing:
A. the preparation method of the lithium ion simulation battery by using the graphene-based composite negative electrode material comprises the following steps:
(1) the graphene-based composite negative electrode material prepared by the method is used as a negative electrode active substance of a lithium ion battery, carboxymethyl cellulose (CMC) is used as a thickening agent, styrene Butadiene Rubber (SBR) is used as a binder, and a conductive agent is not needed, so that the electrode material is prepared, and the three materials are used as the active substances according to the mass ratio: CMC: SBR =96.5, 1.5. Adding a proper amount of deionized water, uniformly mixing into paste by using a paste mixer, coating the paste on a copper foil by using a coating machine, coating the paste to the thickness of 200 mu m, and punching into a pole piece with the diameter of 8.4mm after drying.
(2) A pure lithium sheet is taken as a counter electrode, the pole sheet is taken as a working electrode, a Celgard 2400 type PE/PP/PE composite diaphragm is adopted to be assembled into a die type (the diameter of a positive stainless steel gasket is 8.4mm, the diameter of a negative copper gasket is 11.4 mm) simulation battery in a Germany Braun glove box, and H is 2 O and O 2 The bias voltage was below 1ppm. The electrolyte adopts 1M LiPF 6 Solution of/EC + DMC + EMC.
B. A charging and discharging test cabinet of Wuhanjinnuo Land CT 2001A is used for carrying out a simulation battery charging and discharging performance test by sectional current density within the voltage range of 0.001-1.5V. Test methods and data were calculated as follows:
the first lithium intercalation specific capacity: a capacitance/mass of the negative electrode active material charged to 0.005V at a current density of 0.1C and then charged to 0.001V at a current density of 0.02C;
first lithium removal specific capacity: discharge to a capacity of 2.0V/mass of the negative electrode active material at a current density of 0.1C;
Figure GDA0003764416480000221
(6) Evaluation of the performance of the full cell:
A. the method for preparing the lithium ion full cell by using the graphene-based composite negative electrode material comprises the following steps:
(1) the composite material prepared by the method is used as a lithium ion battery cathode active substance, a conductive agent is not needed, styrene Butadiene Rubber (SBR) is used as a binder, and carboxymethyl cellulose (CMC) is used as a thickening agent to prepare an electrode material; the three are active substances according to mass ratio: CMC: SBR =96.5, 1.5. Adding a proper amount of deionized water, uniformly mixing the mixture into paste by using a paste mixer, then coating the paste on a copper foil by using a coating machine, and drying the paste in vacuum to obtain the lithium ion full battery cathode.
(2) With a ternary material LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM 523 for short) is a positive electrode material; with 1M LiPF 6 the/EC + DMC + EMC is electrolyte; the Celgard 2400 type PE/PP/PE composite membrane is taken as a diaphragm; the whole battery is assembled by adopting the conventional 18650 type single battery production process.
B. Charging and discharging tests are carried out by using a charging and discharging test cabinet of Wuhanjinuo Land CT 2001A at different current densities within a voltage range of 3.0-4.2V. The performance evaluation and test method is as follows:
evaluating the liquid absorption performance of the pole piece: the graphene-based composite negative electrode material prepared by the method is coated according to the requirements, and is dried to form a pole piece, and the pole piece is rolled to a compaction density of 1.65g/cm 3 The glove box is moved into a German Braun glove box,and (3) dripping 10 mu L of electrolyte on the plane of the pole piece by using a liquid gun, starting timing until the electrolyte is completely soaked on the surface of the pole piece, and ending timing. Test three times, and take the average value.
Evaluation of battery rate charging performance: constant current charging is carried out on the full battery at the current density of 0.2C, then constant current charging is carried out at the current densities of 5C and 10C respectively, and the capacity proportion under different charging multiplying factors is calculated:
5C/0.2C represents the ratio of 5C multiplying power constant current charging capacity to 0.2C multiplying power constant current charging capacity;
10C/0.2C represents the ratio of 10C-rate constant current charge capacity to 0.2C-rate constant current charge capacity.
The larger the two ratios are, the higher the capacities at different charging rates are, the better the rate performance of the 18650 type full-cell is, and the better the electrochemical performance of the graphene-based composite negative electrode material is.
Evaluation of cycle Performance of the Battery: the full cell was subjected to constant-current charging at a current density of 1C, and then discharged at a current density of 1C with constant current, and the capacity retention rate at 1000 cycles was calculated: represents the ratio of the 1000 th week discharge capacity of the cell to the 1 st week discharge capacity. The larger the ratio is, the higher the cycle capacity retention rate of the battery is, the better the cycle performance is, and the better the electrochemical performance of the graphene-based composite negative electrode material is.
TABLE 2
Figure GDA0003764416480000241
It can be known from the above examples and comparative examples that the graphene-based composite negative electrode materials obtained in examples 1 to 5 have better electrochemical properties: the first lithium removing specific capacity is more than or equal to 355mAh/g, the first coulombic efficiency is more than or equal to 90 percent and is 1.65g/cm 3 The liquid absorption time of the pole piece under the compacted density is less than or equal to 180s, the multiplying power charging performance 10C/0.2C is more than or equal to 80%, and the circulating capacity retention rate at 1000 weeks is more than or equal to 85%. Therefore, the graphene composite negative electrode material for the lithium ion battery has the remarkable advantages in various performances, such as stable structure, good orientation, good conductivity and high powerThe composite material has high rate performance, excellent liquid absorption performance and excellent cycle performance, and can be used as a preferred negative electrode material of future energy storage batteries and power batteries.
The composite negative electrode material obtained in example 6 has poor granulation effect due to excessively high stirring speed of the reaction kettle in the polymerization reaction process, small particle "tails" cannot be well adhered to the surface of the inner core, and aggregates cannot be formed, so that the particle size is small, the capacity exertion is low, the liquid absorption is slow, and the rate and the cycle performance are poor.
The composite negative electrode material obtained in example 7 has a small amount of the polymeric additive, and a part of small particle "tails" cannot be firmly adhered and polymerized on the surface of a large particle core in the polymerization reaction process, so that the structure of the polymeric particles is poor, the battery capacity performance is affected, the liquid absorption speed is affected by the reduction of voids, and the cycle performance is poor.
The composite negative electrode material obtained in the comparative example 1 does not contain graphite oxide, so that the final composite material does not contain graphene, the conductivity of the material is not improved completely, the internal resistance of the battery is larger, the polarization in the charging and discharging process is larger, the capacity exertion is lower, and the rate capability is poorer.
The applicant states that the present invention is described by the above embodiments to explain the detailed features and detailed methods of the present invention, but the present invention is not limited to the above detailed features and detailed methods, that is, the present invention is not meant to be implemented by relying on the above detailed features and detailed methods. It will be apparent to those skilled in the art that any modification, equivalent substitution of selected components for the invention, addition of auxiliary components, selection of specific modes and the like, of the present invention may be made within the scope and disclosure of the present invention.

Claims (45)

1. The graphene-based composite anode material is characterized by comprising a large-particle inner core, small particles adhered to the surface of the large-particle inner core, and graphene sheets interposed between the large-particle inner core and the small particles, wherein the large-particle inner core and the small particles are both graphite materials, and the small particles are derived from graphite tailings;
the morphology of the small particles is not exactly the same.
2. The graphene-based composite anode material according to claim 1, wherein the large particle inner core has an average particle size D50 of 5-20 μ ι η.
3. The graphene-based composite anode material according to claim 1, wherein the average particle size D50 of the small particles is 1 to 10 μm.
4. The graphene-based composite anode material according to claim 1, wherein the graphene sheet is an few-layer graphene sheet.
5. The graphene-based composite anode material according to claim 1, wherein the graphene-based composite anode material has an average particle size D50 of 10.0 to 40.0 μ ι η.
6. The graphene-based composite anode material according to claim 1, wherein the dispersion of the particle size distribution of the graphene-based composite anode material is 0.5-2.0.
7. The graphene-based composite anode material according to claim 1, wherein the graphene-based composite anode material has a sphericity S50 of 0.8 to 0.9.
8. The graphene-based composite anode material according to claim 1, wherein the graphene-based composite anode material has a specific surface area of 2.0-20.0m 2 /g。
9. A method for preparing the graphene-based composite anode material according to any one of claims 1 to 8, wherein the method comprises the following steps:
(1) Mixing a graphite precursor main material, graphite oxide, a graphite tailing material and a polymerization additive to obtain a mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) under a protective atmosphere to obtain polymer particles;
(3) And (3) carrying out graphitization treatment on the polymer particles in the step (2) in a protective atmosphere to obtain the graphene-based composite negative electrode material.
10. The preparation method according to claim 9, wherein the graphite precursor main material in step (1) comprises any one of green coke, cooked coke or carbon microspheres or a combination of at least two of the green coke, the cooked coke and the carbon microspheres.
11. The method of claim 10, wherein the green coke comprises any one of petroleum coke, pitch coke, or coal coke, or a combination of at least two thereof.
12. The method of claim 10, wherein the cooked coke comprises any one of petroleum coke, pitch coke, or coal coke, or a combination of at least two thereof.
13. The production method according to claim 10, wherein the carbon microsphere includes a petroleum pitch-based carbon microsphere and/or a coal pitch-based carbon microsphere.
14. The method according to claim 9, wherein the graphite precursor in the step (1) has a volatile matter content of 2 to 20%.
15. The method according to claim 9, wherein the ash content of the graphite precursor in the step (1) is 0.5% or less.
16. The method according to claim 9, wherein the graphite precursor of step (1) has an average particle size D50 of 5 to 20 μm.
17. The method according to claim 9, wherein the graphite oxide in the step (1) comprises a material obtained by oxidizing graphite with an acid in a liquid phase.
18. The method according to claim 9, wherein the graphite oxide of step (1) has an average particle size D50 of 1 to 10 μm.
19. The preparation method according to claim 9, wherein the graphite oxide in the step (1) is added in an amount of 1.0-10.0% by weight based on the total weight of the mixture.
20. The preparation method according to claim 9, wherein the graphite tailings in the step (1) comprise micropowder particles left in the production crushing, shaping or classifying process of the graphite cathode.
21. The preparation method according to claim 9, characterized in that the graphite tailings in the step (1) have an average particle size D50 of 1-10 μm.
22. The preparation method according to claim 9, wherein the specific surface area of the graphite tailings in the step (1) is 5-15m 2 /g。
23. The preparation method according to claim 9, wherein the graphite tailings in the step (1) are added in an amount of 1.0-20.0% of the total weight of the mixed materials.
24. The method of claim 9, wherein the polymeric additive of step (1) comprises any one of asphalt, resin, polymer material or polymer or a combination of at least two of the above.
25. The method of claim 24, wherein the pitch comprises any one of coal pitch, petroleum pitch, natural pitch, or mesophase pitch, or a combination of at least two thereof.
26. The method of claim 9, wherein the polymeric additive is added in an amount of 10.0% to 30.0% by weight based on the total weight of the mixture.
27. The method according to claim 9, wherein the mixing in step (1) is mixing using a mixer.
28. The method of claim 27, wherein the mixer comprises any one of a V-blender, a trough-blender, a drum mixer, a conical twin-screw mixer, or a double-cone mixer, or a combination of at least two thereof.
29. The method of claim 9, wherein the mixing in step (1) is carried out for a period of time ranging from 10 to 180min.
30. The method according to claim 9, wherein the polymerization reaction in step (2) is carried out in a reaction tank.
31. The method according to claim 9, wherein the polymerization reaction in the step (2) is carried out at a temperature of 300 to 800 ℃.
32. The method according to claim 9, wherein the polymerization reaction time in the step (2) is 3 to 9 hours.
33. The method according to claim 9, wherein the polymerization reaction in the step (2) is accompanied by stirring.
34. The method of claim 33, wherein the stirring speed is 10 to 40r/min.
35. The method of claim 9, wherein the protective atmosphere of step (2) comprises any one of helium, neon, argon or nitrogen or a combination of at least two thereof.
36. The method of claim 9, wherein the gas flow rate of the protective atmosphere in step (2) is 20 to 50L/min.
37. The method of claim 9, wherein the protective atmosphere of step (3) comprises any one of helium, neon, argon, or nitrogen, or a combination of at least two thereof.
38. The production method according to claim 9, wherein the graphitization treatment in the step (3) is performed by using a graphitization furnace.
39. The method according to claim 9, wherein the temperature of the graphitization treatment in the step (3) is 2500 to 3300 ℃.
40. The production method according to claim 9, characterized in that the temperature rise time of the graphitization treatment in step (3) is 12 to 72 hours.
41. The method according to claim 9, wherein the holding time for the graphitization treatment in step (3) is 15 to 30 days.
42. The method for producing according to claim 9, characterized in that the method further comprises step (4): and (4) carrying out crushing, particle shaping and screening treatment on the graphene-based composite negative electrode material in the step (3).
43. The method for preparing the compound of claim 42, wherein the crushing and particle shaping device comprises any one or a combination of at least two of a turbine type pulverizer, a gas flow vortex pulverizer, a super cyclone vortex mill, a winnowing pulverizer or a double-rod pulverizer.
44. The method for preparing according to claim 9, characterized in that it comprises the following steps:
(1) Mixing the graphite precursor main material, graphite oxide, graphite tailings and the polymerization additive in a mixer for 10-180min to obtain a mixed material;
wherein, the adding amount of the graphite oxide is 1.0-10.0 percent of the total weight of the mixed material, the adding amount of the graphite tailing is 1.0-20.0 percent of the total weight of the mixed material, and the adding amount of the polymeric additive is 10.0-30.0 percent of the total weight of the mixed material;
(2) Carrying out polymerization reaction on the mixed material in the step (1) at the temperature of 300-800 ℃ and the stirring speed of 10-40r/min under the protective atmosphere with the gas flow of 20-50L/min for 3-9h to obtain polymer particles;
(3) Graphitizing the polymer particles in the step (2) at 2500-3300 ℃ in a graphitizing furnace under a protective atmosphere, wherein the temperature rise time of the graphitizing treatment is 12-72h, and the heat preservation time is 15-30 days, so as to obtain the graphene-based composite negative electrode material;
(4) And (4) carrying out crushing, particle shaping and screening treatment on the graphene-based composite negative electrode material in the step (3).
45. A lithium ion battery comprising the graphene-based composite anode material according to any one of claims 1 to 8.
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