WO2024016827A1 - 铁水孕育人造石墨负极材料的制造装置及方法 - Google Patents

铁水孕育人造石墨负极材料的制造装置及方法 Download PDF

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WO2024016827A1
WO2024016827A1 PCT/CN2023/095580 CN2023095580W WO2024016827A1 WO 2024016827 A1 WO2024016827 A1 WO 2024016827A1 CN 2023095580 W CN2023095580 W CN 2023095580W WO 2024016827 A1 WO2024016827 A1 WO 2024016827A1
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graphite
molten iron
powder
temperature
artificial graphite
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PCT/CN2023/095580
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English (en)
French (fr)
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李鑫
吉学文
王健
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深圳市钢昱碳晶科技有限公司
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/205—Preparation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/21—After-treatment
    • 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
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention belongs to the field of lithium-ion secondary batteries, and in particular relates to the artificial graphite negative electrode material used therein and its novel molten iron incubation and manufacturing device and manufacturing method.
  • Lithium-ion secondary batteries are widely used in mobile phones, laptops, electric vehicles, energy storage and other fields due to their high energy density and no memory effect. Currently, they are used extensively as power batteries and energy storage batteries for mobile energy sources in electric vehicles or electric trucks. The market requires lithium-ion batteries with long service life, high energy density, good charge and discharge rate characteristics, and low manufacturing cost. Graphite anode material has become the mainstream anode material for lithium-ion secondary batteries due to its high specific capacity, low reduction potential, good electrochemical reversibility, low volume expansion rate, high electronic conductivity, and wide source of raw materials. Material.
  • anode materials mainly include artificial graphite and natural graphite.
  • the advantages of natural graphite are low cost and high compaction density.
  • the main disadvantages are that the surface of natural graphite powder is rough, there are many active sites, and the specific surface area is large. It is consumed by the process of forming an SEI film on the surface of the negative active material during the first charge and discharge. There are many wasted lithium sources, resulting in low initial charge and discharge efficiency; in addition, the polycrystalline anisotropy of natural graphite is obvious, and the volume expansion of the negative electrode material during charge/discharge cannot easily offset each other.
  • the battery is easy to bulge, resulting in large fluctuations in the distance between the electrode groups, and the battery cycle
  • the characteristics are poor, lithium is easily precipitated during fast charging, and the battery safety is poor.
  • artificial graphite is obtained by high-temperature graphitization treatment at 2800-3100°C, which is made entirely of mesophase carbon microspheres or calcined needle coke.
  • Artificial graphite polycrystals are basically in various shapes. Isotropic, the powder surface is smooth, there are relatively few active sites on the powder surface, and the specific surface area is small.
  • the first battery efficiency is relatively higher than that of natural graphite, with long cycle life and good rate characteristics.
  • the disadvantage is that artificial graphite must be graphitized at high temperature. , long processing cycle and high energy consumption; the high-temperature graphitization temperature of current artificial graphite is as high as 2800-3100°C.
  • the graphite precursor raw material powder is loosely packed in the graphite crucible, and the tap density is less than 1.10g/cm3; the graphite crucibles are filled with carbon resistance particles, and 70-80% of the heating heat is used for
  • the heating and insulation time takes nearly 15 days, the cooling time is nearly 10 days, and the processing cycle of one furnace is nearly one month.
  • the overall energy consumption is high and the effective energy utilization rate is low.
  • the processing cycle is long and the capital occupation cycle is long, which has become the bottleneck link in reducing the cost of artificial graphite.
  • the mainstream improvement in raw materials is to use core-shell structure coated products, such as using graphite precursors such as asphalt or furfural resin to coat and modify natural graphite powder or needle coke powder. , and then carry out medium/high temperature carbonization and high temperature graphitization to prepare artificial graphite.
  • the coating process is complex, the product manufacturing cycle is long, and the overall energy consumption is still high; in addition, the gap between the shell and core of traditional coated artificial graphite powder materials The interface strength is limited, and the coating uniformity is difficult to control.
  • the coating shell is easily crushed during strong rolling, resulting in fluctuations in battery first efficiency and cycle life quality.
  • the present invention proposes an economical, environmentally friendly, high energy utilization efficiency, fast production speed, high product graphitization degree, and high first-time efficiency manufacturing device and method for artificial graphite anode material incubated in molten iron.
  • the main technical feature of the manufacturing device is that It mainly includes: vacuum system and water-cooled furnace body, electromagnetic induction heating and temperature measurement system, graphite crucible inside the furnace body used to breed artificial graphite anode material in molten iron and its attached insulation layer, graphite main piston with enhanced dispersion function ( The combination of CP1)/graphite auxiliary piston (CP2) and its two independent upper and lower displacement control systems, negative pressure suction and cache system for artificial graphite powder; graphite main piston (CP1)/graphite auxiliary with enhanced dispersion function
  • the assembly of the piston (CP2) has the following main features: (T1), the graphite main piston (CP1) has a clearance fit with the inner circle of the graphite crucible and can controllably adjust its up and down displacement independently;
  • the angle between the busbar of the conical slope surface and the center line of the graphite main piston (CP1) is less than 45 degrees. , more preferably less than or equal to 30 degrees;
  • T3 more than 10 graphite rods are fixedly installed at the bottom of the graphite main piston (CP1), the diameter of the graphite rods is between 20-60 mm, and the graphite main piston (CP1) is used for dispersion When moving up and down for the purpose, these bottom-fixed graphite rods play an enhanced dispersion function of forced flow and local shearing on the liquid/solid two-phase mixed material (L/S) of molten iron and graphite precursor fine powder;
  • T4 there is a through hole (H1) on the graphite main piston (CP1), the graphite auxiliary piston (CP2) has a clearance fit with the inner circle of the through hole (H1), and the center of the graphite auxiliary piston (CP2) and the graphite main piston (CP1) Lines are parallel or coincident, the graph
  • (H3) and/or (H4) are used to inject inert gas from the outside, so that The artificial graphite powder that floats from the molten iron becomes fluidized.
  • (H5) is used to transfer the fluidized artificial graphite powder to an external buffer silo using negative pressure suction for buffering and continued cooling;
  • the following technical solution can also be adopted for the negative pressure suction of artificial graphite powder and its buffer system: when collecting the artificial graphite powder that floats to the surface of molten iron, the through hole (H2) and its extension from the center of the secondary piston (CP2)
  • the graphite tube that comes out is sprayed with inert gases such as nitrogen or argon, and at the same time or separately from (H3) and/or (H4) and/or (H5) to the outside, the artificial graphite powder is sucked into the cache container using negative pressure suction. .
  • the manufacturing method of artificial graphite anode material incubated by molten iron of the present invention uses high-temperature molten iron to have good wetting ability for graphite precursor fine powder in the high temperature range of 1850-2150°C (TH).
  • the wetting angle is less than 90 degrees and is at (TH).
  • the high-temperature molten iron in the high-temperature range has the characteristic of preferential and selective dissolution of the carbon in the amorphous region of the graphite precursor fine powder and the highly active carbon on the surface relative to the crystallized carbon.
  • the carbon element in the body essence powder has a relatively high saturated solubility.
  • the graphite piston assembly of the present invention enhances the dispersion of the graphite precursor essence powder in high-temperature molten iron. After being evenly dispersed in the high-temperature molten iron, the graphite piston assembly is used to continuously suppress the graphite precursor fine powder and immerse it in the high-temperature molten iron.
  • the total time for high-temperature incubation of the graphite precursor fine powder immersed in the (TH) high temperature range is preferably between 60 and 120 minutes to achieve the dissolution of the carbon in the amorphous region of the graphite precursor fine powder and the dissolution of the powder by the high-temperature molten iron.
  • the highly active carbon on the surface of the body is eroded.
  • the carbon element in the graphite precursor fine powder will also undergo a certain thermal diffusion and recrystallization process in the (TH) high temperature range, and the enhanced dispersion and suppression state in the (TH) high temperature range will occur.
  • the high-temperature inoculation process under high temperature can also be divided into multiple time periods for alternating; then, the liquid/solid mixture of molten iron and high-temperature incubated graphite precursor fine powder is kept pressed by the (TH)
  • the high-temperature range is cooled together to the low-temperature range of 1350-1650°C (TL).
  • the relatively low-temperature molten iron has a relatively low saturated solubility for carbon elements. The supersaturated carbon dissolved in the molten iron will dynamically precipitate from the molten iron.
  • Part of the precipitated carbon can achieve epitaxial crystallization on the surface of the graphite precursor fine powder, and a small part of the carbon directly precipitates in the molten iron and grows into artificial graphite powder. It is incubated when the temperature is cooled to the (TL) temperature range and maintained at low temperature. After the total time is between 30 and 360 minutes, the enhanced dispersion in the (TL) temperature range and the low-temperature incubation process in the pressed state can also be divided into multiple time periods for alternation. It is preferred to maintain the total time of low-temperature incubation between 60 and 120 minutes.
  • an artificial graphite powder with a mainly natural coating core-shell structure forming an artificial graphite powder with a mainly natural coating core-shell structure; then the graphite piston assembly is moved upward, and the relatively low-temperature molten iron in the (TL) low-temperature range is used to deteriorate the wettability of the artificial graphite powder and wet it.
  • the angle is greater than 90 degrees, and the huge density difference between the artificial graphite powder and the low-temperature molten iron is used to float the naturally coated artificial graphite powder or part of the naturally precipitated artificial graphite powder above the liquid surface of the low-temperature molten iron. Then use negative pressure to suck out the floating artificial graphite powder and store it in a material buffer container.
  • the manufacturing method of artificial graphite anode material incubated by molten iron mainly includes the following main steps:
  • Step 1 Prepare graphite precursor fine powder (PG).
  • the graphite precursor raw materials include one or a combination of metallurgical coke, anthracite, needle coke, pellet coke, natural graphite, asphalt powder, hard carbon and other carbon materials.
  • the graphite precursor raw material is acid washed and/or alkali washed and purified, neutralized and dried, with or without high-temperature calcination or carbonization treatment, to achieve a volatile weight loss of less than 0.5% after treatment at 900°C/30 minutes under inert gas protection. , the ash content is less than 0.5%.
  • the powder particle size is controlled to an average particle size D50 between 5-22 microns, and D95 less than 35 microns, to obtain graphite precursor fine powder (PG);
  • Step 2 Prepare high-temperature molten iron by vacuum induction melting. Enhance the dispersion and high-temperature incubation of the graphite precursor powder (PG) in the high-temperature molten iron. After evacuation, fill the vacuum chamber with inert gases such as nitrogen or argon for protection. Use induction heating to above 1350°C, more preferably to above 1550°C and below 2150°C, and then use a graphite auxiliary piston (CP2) with a central through hole (H2) to absorb the graphite precursor packed in steel drums by negative pressure adsorption.
  • inert gases such as nitrogen or argon
  • the entire package of fine powder material is transported into the molten iron, or the graphite precursor fine powder raw material is directly sprayed into the molten iron through the central through hole (H2) and its extended graphite tube immersed in the molten iron using positive pressure air flow transportation. in water; then the liquid/solid two-phase mixture (L/S) of molten iron and graphite precursor fine powder is heated together to a high temperature range (TH) of 1850-2150°C, and the liquid/solid mixture is heated in this (TH) high temperature range.
  • TH high temperature range
  • the mixed material undergoes enhanced dispersion processing.
  • the combination of the graphite main piston (CP1) and the graphite auxiliary piston (CP2) makes a controllable upward/downward displacement movement.
  • Step 3 Low-temperature incubation and negative pressure suction transfer of artificial graphite powder.
  • the mixture of graphite precursor fine powder and molten iron after high-temperature incubation is cooled to the 1350-1650°C (TL) range while maintaining the suppressed state, and then In this (TL) low-temperature range, the total time of low-temperature incubation using molten iron is between 30 and 360 minutes, and the preferred total time of low-temperature incubation is between 60 and 120 minutes; then the graphite main piston (CP1) and the graphite auxiliary piston (CP2) are combined
  • the naturally coated artificial graphite powder and a small amount of the analyzed artificial graphite powder will naturally float above the liquid surface of the molten iron, and then use inert gases such as nitrogen or argon to flow out from (H2) or its extension Inert gas is blown into the graphite tube to fluidize the artificial graphite powder that floats from the molten iron.
  • inert gases such as nitrogen or
  • negative pressure suction is used to fluidize the artificial graphite powder from (H3) and/or (H4).
  • ) and/or (H5) are sucked out and transferred to a material buffer container for continued cooling; or inert gases such as nitrogen or argon are used to inlet gas from (H3) and/or (H4) to float the molten iron.
  • the artificial graphite powder is fluidized.
  • negative pressure is used to suck the fluidized artificial graphite powder out of (H5) and transfer it to the material buffer container for continued cooling; the artificial graphite powder continues to be protected by inert gas. After being cooled to below 200°C or under vacuum conditions, the particles are sorted and demagnetized to obtain the artificial graphite anode material incubated in molten iron;
  • Step 4 Continue to put the next batch of graphite precursor fine powder materials into the molten iron, and repeat the above-mentioned high/low-temperature molten iron to incubate artificial graphite anode materials.
  • the present invention is preferably prepared by vacuum induction melting
  • the initial carbon content in the raw material molten iron at high temperature is greater than 4.5%.
  • the maximum temperature range (TH) of the molten iron incubation of the present invention is preferably controlled between 1850-2150°C;
  • the wetting angle between high-temperature molten iron and graphite precursor fine powder in the temperature range of 1850-2150°C is less than 90 degrees, it is convenient to use the graphite piston assembly with enhanced dispersion function of the present invention to first uniformly disperse the graphite precursor fine powder in the high-temperature iron In water, the liquid/solid two-phase material is then subjected to high-temperature incubation treatment using a graphite piston assembly while maintaining a suppressed state to prevent the graphite precursor fine powder from floating prematurely; in addition, the saturated solubility of high-temperature molten iron for carbon in the (TH) temperature range is greater than 5wt.%, the carbon in the amorphous region of
  • the new coated artificial graphite negative electrode material grown naturally by the method of the present invention has high coating uniformity between the core and the shell, and close proximity between the shell layer and the core. There is no obvious physical interface.
  • the coating shell layer of the artificial graphite negative electrode material incubated with high and low temperature molten iron of the present invention is not easily crushed.
  • the prepared battery has a high gram capacity and a high first charge and discharge efficiency. , good rate characteristics and long cycle life.
  • the present invention uses high-temperature molten iron to perform surface erosion on the graphite precursor fine powder, thereby reducing the number of active end groups of the graphite precursor fine powder and reducing the specific surface area of the powder.
  • the artificial graphite material coated with epitaxial crystals reduces the The amount of lithium consumed in SEI film production is reduced, resulting in the first irreversible capacity reduction.
  • the present invention uses the highest temperature range of 1850-2150°C for high-temperature incubation, which is far lower than the high-temperature graphitization temperature of 2800-3100°C used in conventional artificial graphite, and can greatly reduce the waste of radiant heat and energy; the energy utilization efficiency of the present invention
  • the thermal efficiency is much higher than that of traditional high-temperature graphitization furnaces; the method of the present invention greatly reduces the heating time of graphitization and does not require secondary coating and secondary carbonization heating, reduces overall energy consumption, and can obtain high graphitization degree and various An artificial graphite anode material based on a new core-shell structure with good isotropy.
  • the present invention utilizes the poor wettability between artificial graphite powder and low-temperature molten iron and the huge density difference between the two to simply and easily realize the effective use of artificial graphite powder and low-temperature molten iron after incubation with high/low-temperature molten iron.
  • Natural floating separation eliminates the need to use subsequent processes such as chemical corrosion to treat the iron.
  • the molten iron used in the present invention is only used as a process medium, with basically no material loss. The process is environmentally friendly, energy-saving, has low production costs and has strong market competitiveness.
  • FIG. 1 of the accompanying drawings is a schematic diagram of the graphite main piston (CP1) of the present invention, in which the upper surface of the graphite main piston (CP1) is a conical slope surface to prevent leakage from the gap between the graphite main piston and the graphite crucible.
  • the molten iron and graphite precursor fine powder are retained on the upper surface of the main piston.
  • the angle between the conical slope surface busbar and the center line of the graphite main piston (CP1) is 30 degrees; the bottom of the graphite main piston (CP1) is fixedly installed with a uniform
  • FIG. 2 of the accompanying drawings is a schematic diagram of the graphite piston assembly of the present invention before enhanced dispersion and suppression of graphite precursor fine powder and high-temperature molten iron.
  • the design gap between the graphite main piston (CP1) and the inner circle of the graphite crucible is 0.25 mm
  • the design gap between the inner circle of the graphite auxiliary piston (CP2) and the graphite main piston (CP1) is 0.25 mm.
  • FIG. 3 of the accompanying drawings of the description is a schematic diagram of the artificial graphite powder obtained after high/low temperature incubation treatment of the present invention being suctioned under negative pressure to an external buffer device.
  • the H3 and H4 graphite tubes installed on the upper part of the graphite crucible are used for injection. Inert gas is used to fluidize the artificial graphite powder.
  • the H5 graphite tube installed on the upper part of the graphite crucible is used to suck the artificial graphite powder into the buffer container using negative pressure suction. Continue cooling.
  • Example 1 Artificial graphite anode material incubated with molten iron, the average particle size D50 is between 10-16 microns, D95 is less than 25 microns, the XRD test d002 is 0.3349 nanometers, the true density is between 2.21-2.25g/cm3, and the gram capacity is 360mAh/ g, the first charge and discharge efficiency is greater than 94.5%;
  • the manufacturing equipment for artificial graphite anode materials incubated by molten iron mainly includes: vacuum system and water-cooled furnace body, electromagnetic induction heating and temperature measurement system, aeration system, fluidization and negative pressure suction Powder system, a graphite crucible inside the furnace used to incubate artificial graphite anode materials in high and low temperature molten iron and its attached insulation layer, see Figures 1-3 attached to the instruction manual.
  • the graphite main piston (CP1) has a large hole (H1) on the graphite main piston (CP1), the graphite auxiliary piston (CP2) fits with the inner circle of the large hole (H1), and the graphite auxiliary piston (CP2) matches the graphite main piston (CP1).
  • the central axes of the piston (CP1) are parallel and coincident.
  • the graphite auxiliary piston (CP2) can independently control the up and down displacement relative to the graphite main piston (CP1). When combined with the up and down coordinated movement of the graphite main piston (CP1), it can move molten iron and graphite.
  • the liquid/solid two-phase mixture of precursor fine powder has a quasi-stirring function.
  • the bottom of the graphite auxiliary piston (CP2) has a negative pressure adsorption hole (H2) for adsorbing and transporting the graphite precursor fine powder packed in steel drums and placing it. into the molten iron; the graphite main piston (CP1) also has holes and is installed with (H3) and/or (H4) and/or (H5) graphite tubes, (H3) and/or (H4) are used to The external air intake fluidizes the artificial graphite powder that floats from the molten iron, and (H5) is used to transfer the fluidized artificial graphite powder that floats to an external buffer container using negative pressure suction.
  • the manufacturing method of artificial graphite anode material incubated by molten iron mainly includes the following main steps:
  • Step 1 Prepare graphite precursor fine powder.
  • the graphite precursor raw material is needle coke.
  • the volatilization weight loss after treatment at 900°C/30 minutes under inert gas protection is less than 0.20%.
  • the particle size is controlled to an average particle size of D50 between 10-18 microns, D95 is less than 25 microns, ash content is less than 0.20%;
  • Step 2 Prepare high-temperature molten iron by vacuum induction smelting and perform enhanced dispersion and high-temperature molten iron incubation. After vacuuming, fill the vacuum chamber with argon for protection. The molten iron is heated to 1700°C by induction, using a vacuum chamber with negative pressure adsorption holes (H2).
  • the auxiliary piston (CP2) transports the graphite precursor fine powder material packed in steel drums into the molten iron, and heats the molten iron and the liquid/solid mixture of graphite precursor fine powder together to a high temperature range of 1950-2000°C (TH).
  • the up/down reverse controllable displacement of the piston assembly is carried out to enhance the dispersion of high-temperature molten iron and graphite precursor fine powder, and then the dispersion is stopped to keep the graphite piston assembly suppressing the liquid/solid mixture material. Incubate at high temperature for 90 minutes;
  • Step 3 Low-temperature incubation and negative pressure adsorption of artificial graphite powder.
  • TL 1350-1450°C
  • float the naturally coated artificial graphite powder above the liquid surface of the molten iron and then use the method shown in Figure 3 of the instruction manual to use argon gas to inject air from (H3)/(H4) respectively, so that the artificial graphite powder after floating is The graphite powder is fluidized.
  • Step 4 Continue to use the graphite auxiliary piston (CP2) to put the next batch of steel barrel-packed graphite precursor fine powder into the molten iron, and repeat the above-mentioned high/low-temperature molten iron to incubate the artificial graphite anode material.
  • CP2 graphite auxiliary piston

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Abstract

提供一种铁水孕育人造石墨负极材料的制造装置及方法，装置主要包括：真空系统及炉体，加热及测温系统，石墨坩埚，具有增强分散功能的活塞组合体及位移控制系统，人造石墨粉体负压抽吸及缓存系统；活塞组合体中主活塞CP1的上表面为圆锥形，其母线与中心线的夹角小于45度，CP1底部安装多个石墨棒，对液/固两相混合物料L/S起到强制流动和局部剪切的增强分散功能；高温铁水对石墨前驱体精粉具有低于90度的润湿角，对碳元素具有较高的饱和溶解度，具备对非晶碳及表面高活性碳进行选择性溶解的能力；L/S冷却到低温区间，低温铁水中析出的碳在石墨粉体的表面实现附生结晶，形成包覆型核壳结构为主的人造石墨负极材料。

Description

铁水孕育人造石墨负极材料的制造装置及方法 技术领域
本发明属于锂离子二次电池领域，尤其是关于其中使用的人造石墨负极材料及其新型铁水孕育制造装置及其制造方法。
 背景技术
锂离子二次电池以其能量密度高，无记忆效应，广泛应用于手机、笔记本电脑、电动汽车、储能等领域，目前作为电动汽车或电动货车移动能源的动力电池和储能电池使用量很大，市场要求锂离子电池使用寿命长，能量密度高，充放电倍率特性佳，制造成本低。石墨负极材料由于具有较高的比容量，较低的还原电位，良好的电化学可逆性，低的体积膨胀率，高的电子导电率，原料来源广泛，为目前锂离子二次电池主流的负极材料。
商业化的负极材料主要包括人造石墨和天然石墨。天然石墨的优点是成本低，压实密度高，主要缺点是天然石墨粉体的表面粗糙，活性位点多，比表面积大，首次充放电时在负极活性材料的表面形成SEI膜的过程反应消耗浪费的锂源多，导致首次充放电效率低； 另外天然石墨的多晶体各向异性明显，充/放电时负极材料的体积膨胀不容易互相抵消，电池容易鼓胀导致极组间距波动大，电池循环寿命下降较快；另外多晶体的各向异性还导致锂离子的插入/脱出只能从石墨粉体多晶体的某些端面进行，导致有效插入/脱出的面积较小，电池的充/放电倍率特性较差，快充时容易析锂，电池安全性不佳。
目前行业主流的是使用人造石墨作为负极活性材料，如全部由中间相碳微球或者煅烧后的针状焦进行2800—3100℃高温石墨化处理后得到的人造石墨，人造石墨多晶体基本呈各向同性，粉体表面光滑，粉体表面的活性位点相对较少，比表面积小，电池首效相对比天然石墨的高，循环寿命长，倍率特性佳，缺点是人造石墨必须进行高温石墨化，加工周期长，能耗高；目前的人造石墨的高温石墨化温度高达2800—3100℃，主要利用高温下碳原子热扩散重新参与结晶来提高石墨前驱体的石墨化度，传统的艾奇逊石墨化炉，石墨前驱体原材料粉体松装于石墨坩埚内，振实密度小于1.10g/cm3；对石墨坩埚之间充填上碳素电阻颗粒料，加热热量的70—80％都是用于这些工艺辅料及外部的保温料，为了生产产品的均匀性，加热及保温时间需要近15天，冷却时间近10天，一炉的加工周期接近一个月，整体能耗高，能源有效利用率低下，加工周期长，资金占用周期长，成为人造石墨降低成本的瓶颈环节。
为了降低人造石墨的成本，在原材料方面主流的改进是采用核壳结构的包覆型产品，如采用沥青或糠醛树脂等石墨前驱体将天然石墨粉体或者针状焦粉体进行包覆改性， 然后进行中/高温碳化及高温石墨化处理制备人造石墨，包覆工艺复杂，产品制造周期长，整体能耗仍然偏高；另外传统包覆型人造石墨粉体材料的壳和核之间的界面强度有限，包覆均匀性很难控制，制造负极极片时在强力辊压时，包覆壳层容易被压溃，导致电池首效和循环寿命质量波动。
为克服现有人造石墨负极材料制造方法和装置的缺点，特提出本发明。
 技术解决方案
本发明提出一种经济，环保，能源利用效率高，生产速度快，产品石墨化度高，首次效率高，铁水孕育人造石墨负极材料的制造装置及方法，制造装置的主要技术特征在于，制造装置主要包括：真空系统及水冷炉体，电磁感应加热及测温系统，炉体内部用于铁水孕育人造石墨负极材料的石墨坩埚及其石墨坩埚的附属保温层，具有增强分散功能的石墨主活塞(CP1)/石墨副活塞(CP2)的组合体及其两套独立的上下位移控制系统，人造石墨粉体负压抽吸及其缓存系统；具有增强分散功能的石墨主活塞(CP1)/石墨副活塞 (CP2)的组合体具有以下主要特征：(T1)，石墨主活塞(CP1)与石墨坩埚的内圆呈间隙配合并能可控地独立上下位移调节；(T2)，石墨主活塞(CP1)的上表面为圆锥形斜坡面，用于防止铁水和石墨前驱体精粉滞留而影响产品的均一性，圆锥形斜坡面的母线与石墨主活塞(CP1)的中心线的夹角小于45度，更优选小于等于30度；(T3)，石墨主活塞的(CP1)底部固定安装有10个以上的石墨棒，石墨棒的直径介于20—60毫米，石墨主活塞(CP1)作以分散为目的的上下运动 时，这些底部固定的石墨棒对铁水和石墨前驱体精粉的液/固两相混合物料(L/S)起到强制 流动和局部剪切的增强分散功能；(T4)，石墨主活塞(CP1)上开有通孔(H1)，石墨副活塞(CP2)与通孔(H1)的内圆呈间隙配合，石墨副活塞(CP2)与石墨主活塞(CP1)的中心线平行或重合，石墨副活塞(CP2)能够相对石墨主活塞(CP1)作独立地可控上下位移，与石墨主活塞(CP1)二者上下协调运动组合，能够对铁水和石墨前驱体精粉的液/固两相混合物(L/S) 起到增强分散功能；(T5)，石墨副活塞(CP2)的中心开有通孔(H2)用于负压吸附住钢桶包装的石墨前驱体精粉或者通过 (H2)及其延伸浸没在铁水中的石墨管采用正压气流输送方式直接将石墨前驱体精粉喷吹进熔化后的高温铁水中；本发明的制造装置在石墨坩埚的上 部的侧壁上开有中小孔(H3)和/或(H4)和/或(H5)并安装相应的石墨管道，(H3)和/或(H4)用于从外部喷吹惰性气体，使得从铁水中上浮后的人造石墨粉体呈流态化，(H5)用于采用负压抽吸方式将呈流态化的人造石墨粉体转移到外部的缓存料仓，进行缓存并继续冷却；人造石墨粉体负压抽吸及其缓存系还可以采用如下的技术方案：在收集上浮到铁水表面的人造石墨粉体时，从副活塞(CP2)的中心的通孔(H2)及其延伸出来的石墨管喷吹氮气或氩气等惰性气体，同时或分别从(H3)和/或(H4)和/或(H5)向外部采用负压吸尘方式抽吸人造石墨粉体进入缓存容器。
本发明的铁水孕育人造石墨负极材料的制造方法，利用高温铁水在1850—2150℃(TH)高温区间对石墨前驱体精粉具有较好的润湿能力，润湿角小于90度，处于(TH)高温区间的高温铁水对石墨前驱体精粉其中的非晶区部分的碳以及表面的高活性的碳，相对于其中的结晶碳而言，具有优先选择性溶解的特性，高温铁水对石墨前驱体精粉中的碳元素具有相对较高的饱和溶解度，在此(TH)高温区间利用以上三点技术特性，本发明的石墨活塞组合体将石墨前驱体精粉在高温铁水中进行增强分散，均匀分散在高温铁水中以后，采用石墨活塞组合体对石墨前驱体精粉进行持续压制并浸没在高温铁水中，在(TH)高温区间对浸没其中的石墨前驱体精粉进行高温孕育的总时间介于30—360分钟，考虑到生产效率和质量的平衡，优选进行高温孕育的总时间介于60—120分钟，实现高温铁水对石墨前驱体精粉非晶区部分的碳的溶解以及对粉体表面的高活性碳的熔蚀，同时石墨前驱体精粉其中的碳元素在 (TH)高温区间也会进行一定的热扩散及重结晶过程，在(TH)高温区间的增强分散和压制状态下的高温孕育处理也可以分成多个时间段交替进行；然后将铁水和经过高温孕育的石墨前驱体精粉的液/固混合物在保持石墨活塞组合体对其持续压制的同时，由(TH)高温区间一起冷却到1350—1650℃(TL) 低温区间，在降温过程中，相对低温的铁水对碳元素具有相对较低的饱和溶解度，铁水中溶解的过饱和的碳从铁水中会动态析出，部分析出的碳在石墨前驱体精粉的表面能够实现附生结晶，还有少部分的碳直接在铁水中析出长大为人造石墨粉体，在降温到(TL)温度区间并保持低温孕育总时间介于 30—360分钟后，在(TL)温度区间的增强分散和压制状态下的低温孕育处理也可以分成多个时间段交替进行，优选保持低温孕育的总时间介于60—120分钟，形成自然包覆型核壳结构为主的人造石墨粉体；随后将石墨活塞组合体上移，利用(TL)低温区间相对低温的铁水对人造石墨粉体的润湿性变差，润湿角大于90度，并利用人造石墨粉体和低温铁水之间巨大的密度差，将实现自然包覆后的人造石墨粉体或者部分自然析出的人造石墨粉体上浮到低温铁水的液面以上，然后利用负压将上浮后的人造石墨粉体抽吸出去存放在物料缓存容器中，继续在惰性气体 保护下或真空条件下将人造石墨粉体冷却到200℃以后出炉，颗粒分选并除磁后得到铁水孕育人造石墨负极材料，XRD测试d002小于0.3390纳米，真密度介于2.17—2.27g/cm3，克容量大于350mAh/g，首次充放电效率大于93％。
铁水孕育人造石墨负极材料的制造方法主要包括以下主要步骤：
Step1，制备石墨前驱体精粉(PG)，石墨前驱体原料包括冶金焦炭，无烟煤，针状焦，弹丸焦，天然石墨，沥青粉，硬碳等碳素材料中的一种或多种的组合物，将石墨前驱体原料进行酸洗和/或碱洗提纯，中和干燥，进行或不进行高温煅烧或碳化处理，达成惰性气体 保护下900℃/30分钟处理后的挥发减重小于0.5％，灰分小于0.5％，破碎分级后粉体颗粒度控制在平均粒径D50介于5—22微米，D95小于35微米，得到石墨前驱体精粉(PG)；
Step2，真空感应熔炼制备高温铁水，对石墨前驱体精粉(PG)在高温铁水中进行增强分散及高温孕育，在抽真空后向真空室内充入氮气或氩气等惰性气体进行保护，将铁水采用感应加热到1350℃以上，更优选加热到1550℃以上，2150℃以下，然后采用带有中心通孔(H2)的石墨副活塞(CP2)以负压吸附方式将钢桶包装的石墨前驱体精粉物料整包原料输送进铁水中，或者通过中心通孔(H2)及其延伸浸没在铁水中的石墨管采用正压气流输送方式直接将石墨前驱体精粉原料喷吹进熔化后的铁水中；然后将铁水和石墨前驱体精粉的液/固两相混合物料(L/S)一起加热到1850—2150℃的高温区间(TH)，并在此(TH)高温区间对液/固混合物料进行增强分散加工，在进行增强分散加工时，石墨主活塞(CP1)与石墨副活塞(CP2)的组合体作可控的上/下位移运动，二者你上/我下或你下/我上做协调配合运 动，组合利用主活塞底面所固定的多个石墨棒对液/固两相混合物料(L/S)的强制流动和局 部剪切功能，石墨主活塞(CP1)与石墨副活塞(CP2)的组合体能够对液/固两相混合物料(L/ S)起到增强分散功能；然后在(TH)的高温区间，采用石墨主活塞(CP1)和石墨副活塞(CP2)一起将石墨前驱体精粉压制并浸没在高温铁水中进行高温孕育的总时间介于30—360分钟；
Step3，低温孕育及负压抽吸转移人造石墨粉体，将经过高温孕育后的石墨前驱体精粉和铁水的混合物在保持压制状态下，一起降温到1350—1650℃ (TL)区间，并在此(TL) 低温区间利用铁水进行低温孕育总时间介于30—360分钟，优选进行低温孕育总时间介于60—120分钟；随后将石墨主活塞(CP1)和石墨副活赛(CP2)一起上移，将实现自然包覆后的人造石墨粉体及少部分析出的人造石墨粉体自然上浮到铁水的液面以上，然后采用氮气或氩气等惰性气体从(H2)或其延伸出的石墨管喷吹进惰性气体，使从铁水中上浮后的人造石墨粉体实现流态化，同时利用负压抽吸方式将流态化的人造石墨粉体从(H3)和/或(H4)和/或(H5)抽吸出去，转移到物料缓存容器中进行继续冷却；或者采用氮气或氩气等惰性气体 从(H3)和/或(H4)进气，使从铁水中上浮后的人造石墨粉体呈流态化，同时利用负压将流态化的人造石墨粉体从(H5)抽吸出去，转移到物料缓存容器中进行继续冷却；将人造石墨粉体继续进行惰性气体保护下或真空条件下的冷却至200℃以下出炉，颗粒分选并除磁后得到铁水孕育人造石墨负极材料；
Step4，继续向铁水中投放下一批的石墨前驱体精粉物料，重复进行上述的高/低温铁水孕育人造石墨负极材料的制造。
 有益效果
以下对本发明的优势进行进一步阐释。
为了提高石墨坩埚和/或石墨/陶瓷复合材料坩埚和/或石墨活塞组合体的使用寿命，防止高温下铁水对上述的零部件中的石墨材料熔蚀过多，本发明优选在真空感应熔炼制备高温铁水时的原材料铁水中的初始碳含量大于4.5％。
为了平衡石墨化的速度和石墨化的程度以及降低高温下的辐射损耗，以及保证石墨坩埚和石墨活塞的寿命，本发明的铁水孕育的最高温度区间(TH) 优选控制介于1850—2150℃；鉴于1850—2150℃温度区间高温铁水与石墨前驱体精粉的润湿角低于90度，便于采用本发明的具有增强分散功能的石墨活塞组合体首先将石墨前驱体精粉均匀分散在高温铁水中，随后对液/固两相物料采用石墨活塞组合体保持压制状态下进行高温孕育处理，防止石墨前驱体精粉过早浮起；另外(TH)温度区间高温铁水对于碳元素的饱和溶解度大于5wt.％，对石墨前驱体精粉其中非晶区的碳及粉体表面高活性的碳具有润湿及选择性高温 溶解的特点；在后面的降温过程中铁水中溶解的过饱和的碳会逐步析出，在石墨前驱体精粉的表面会附生结晶生长出新的石墨壳层，构成新型核壳结构的人造石墨负极材料，能够提升石墨前驱体的各向同性特征，与传统的沥青包覆/中温碳化/高温石墨化的人造石墨制造方法相对比，本发明的方法自然生长的新型包覆型人造石墨负极材料，其核壳之间的包覆均匀度高，壳层和核之间近无明显的物理界面，在制备负极极片的压实过程中，本发明的高低温铁水孕育人造石墨负极材料的包覆壳层不易被压溃，制备的电池克容量高，首次充放电效率高，倍率特性好，循环寿命长。
本发明利用高温铁水对石墨前驱体精粉进行表面熔蚀，从而降低了石墨前驱体精 粉的活性端基的数量和降低了粉体的比表面积，附生结晶包覆后的人造石墨材料降低了SEI膜生产长消耗的锂量，从而首次不可逆容量降低。
本发明利用1850—2150℃的最高温度区间进行高温孕育，远低于常规人造石墨所采用的2800—3100℃的高温石墨化温度，可以大大降低辐射热及能量的浪费；本发明的能源利用效率远高于传统的高温石墨化炉的热效率；本发明的方法大大降低了石墨化的加热时间以及不用二次包覆及二次碳化加热，降低了总体能耗，能够得到高石墨化度和各向同性 度佳的新型核壳结构为主的人造石墨负极材料。
本发明利用人造石墨粉体和低温铁水之间的润湿性变差以及二者之间巨大的密度差，简单易行地实现了高/低温铁水孕育后的人造石墨粉体和低温铁水的有效自然上浮分离，不必采用化学腐蚀等后续工序处理铁，本发明采用的铁水仅作为工艺介质，基本没有材料损耗，工艺环保，节能，生产成本低，市场竞争力强。
 附图说明
说明书附图的图1为本发明的石墨主活塞(CP1)的示意图，其中石墨主活塞(CP1) 的上表面为圆锥形斜坡面，用于防止从石墨主活塞和石墨坩埚之间的间隙泄露到主活塞上表面的铁水和石墨前驱体精粉的滞留，圆锥形斜坡面母线与石墨主活塞(CP1)的中心线的夹角为30度；石墨主活塞的(CP1) 底部固定安装有均匀分布的20个石墨棒，石墨棒的直径为30毫米，采用螺纹连接方式均匀固定在石墨主活塞(CP1)的下部。
说明书附图的图2为本发明的石墨活塞组合体对石墨前驱体精粉及高温铁水进行增强分散及压制前的示意图，其中石墨主活塞(CP1)与石墨坩埚内圆之间的设计间隙为0.25毫米，石墨副活塞(CP2)与石墨主活塞(CP1)内圆之间的设计间隙为0.25毫米。
说明书附图的图3为本发明的经过高/低温孕育处理后得到的人造石墨粉体向外部缓存装置进行负压抽吸的示意图，安装在石墨坩埚上部的H3，H4 石墨管用于喷吹进惰性气体，将人造石墨粉体流态化，安装在石墨坩埚上部的H5石墨管用于采用负压吸尘方式将人造石墨粉体抽吸到缓存容器中。继续进行冷却。
 本发明的最佳实施方式
以下所述实施例以本发明的技术方案和精神要义为前提进行实施，给出了详细的实施方式和具体的工艺，但并不限制本发明专利的保护范围，凡采用替换或等效变换的形式所获得技术方案，如铁原料中的碳含量适当调整等，或者铁原料中含有一定量的Si，Ce等合金元素，或者采用其他真空加热方式，适当提高铁水的高温孕育温度，或者适当调低铁水的低温孕育温度，或者采用陶瓷材料的活塞组合体替代石墨活塞组合体，或者适当调整负压吸附人造石墨粉料的方式，均应理解为落在本发明的保护范围内。
实施例1 .铁水孕育人造石墨负极材料，平均粒径D50介于10—16微米，D95小于25 微米，XRD测试d002为0.3349纳米，真密度介于2.21—2.25g/cm3，克容量大360mAh/g，首次充放电效率大于94 .5％；铁水孕育人造石墨负极材料的制造装置主要包括：真空系统及水冷炉体，电磁感应加热及测温系统，充气系统，流态化及负压抽吸粉料系统，炉体内部用于高低温铁水孕育人造石墨负极材料的石墨坩埚及其石墨坩埚的附属保温层，见说明书附图1—3，与石墨坩埚的内圆间隙配合并能上下位移调节的石墨主活塞(CP1)，石墨主活塞(CP1) 上开有大孔(H1)，石墨副活塞(CP2)与大孔(H1)的内圆间隙配合，石墨副活塞(CP2)与石墨主活塞(CP1)的中心轴线平行并重合，石墨副活塞(CP2)能够相对石墨主活塞(CP1)作上下 独立位移控制，与石墨主活塞(CP1)二者上下协调运动组合后能够对铁水和石墨前驱体精粉的液/固两相混合物料起到准搅拌功能，石墨副活塞(CP2)的底部开有负压吸附孔 (H2) 用于吸附传送钢桶包装的石墨前驱体精粉并放置进熔化后的铁水中；石墨主活塞(CP1)上还开有孔并安装(H3)和/或(H4)和/或(H5)石墨管，(H3)和/或(H4)用于从外部进气使从铁水中上浮后的人造石墨粉体流态化，(H5)用于采用负压吸尘方式将上浮后的呈流态化的人造石墨粉体转移到外部的缓存容器。
铁水孕育人造石墨负极材料的制造方法主要包括以下主要步骤：
Step1，制备石墨前驱体精粉，石墨前驱体原料采用针状焦，惰性气体保护下900℃/30分钟处理后的挥发减重小于0.20％，破碎分级后颗粒度控制在平均粒径D50介于10—18微米，D95小于25微米，灰分小于0.20％；
Step2，真空感应熔炼制备高温铁水并进行增强分散及高温铁水孕育，在抽真空后向真空室内充入氩气进行保护，将铁水采用感应加热到1700℃，采用带有负压吸附孔(H2)的副活塞(CP2)将钢桶包装的石墨前驱体精粉物料输送进铁水中，将铁水和石墨前驱体精粉的液/固混合物料一起加热到 1950—2000℃(TH)的高温区间，并在此高温区间进行活塞 组合体的上/下逆向可控位移，对高温铁水和石墨前驱体精粉进行增强型分散，然后停止分散，保持石墨活塞组合体对液/固混合物料保持压制的状态下进行高温孕育90分钟；
Step3，低温孕育及负压吸附人造石墨粉体，将液/固混合物采用石墨活塞组合体持续进行压制状态下一起降温到1350—1450℃(TL)区间，并在此低温区间进行低温孕育90分钟，将实现自然包覆后的人造石墨粉体上浮到铁水的液面以上，然后采用说明书附图3所示方式，采用氩气从(H3)/(H4)分别进气，使上浮后的人造石墨粉体呈流态化，同时利用负压将人造石墨粉体从(H5)抽吸出去，转移到物料缓存容器中，继续进行氩气保护下冷却，到 200℃以下出炉，颗粒分选并除磁后得到高低温铁水孕育人造石墨负极材料；
Step4，继续采用石墨副活塞(CP2)向铁水中投放下一批的钢桶包装石墨前驱体精粉，重复进行上述的高/低温铁水孕育人造石墨负极材料的制造。

Claims (3)

  1. 铁水孕育人造石墨负极材料的制造装置及方法，其特征在于，制造装置主要包括：真空系统及水冷炉体，电磁感应加热及测温系统，炉体内部用于铁水孕育人造石墨负极材料的石墨坩埚及其石墨坩埚的附属保温层，具有增强分散功能的石墨主活塞(CP1)/石墨副活 塞(CP2)的组合体及其两套独立的上下位移控制系统，人造石墨粉体负压抽吸及其缓存系统；具有增强分散功能的石墨主活塞(CP1)/石墨副活塞(CP2)的组合体具有以下主要特征： (T1)，石墨主活塞(CP1)与石墨坩埚的内圆呈间隙配合并能可控地独立上下位移调节；(T2)，石墨主活塞(CP1)的上表面为圆锥形斜坡面，用于防止铁水和石墨前驱体精粉滞留，圆锥形斜坡面的母线与石墨主活塞(CP1)的中心线的夹角小于45度；(T3)，石墨主活塞的(CP1)底部固定安装有10个以上的石墨棒，石墨主活塞(CP1)作以分散为目的的上下运动时，这些底部固定的石墨棒对铁水和石墨前驱体精粉的液/固两相混合物料(L/S)起到强制流动和局部剪切的增强分散功能；(T4)，石墨主活塞(CP1)上开有通孔(H1)，石墨副活塞 (CP2)与通孔(H1)的内圆呈间隙配合，石墨副活塞(CP2)与石墨主活塞(CP1)的中心线平行或重合，石墨副活塞(CP2)能够相对石墨主活塞(CP1)作独立地可控上下位移，与石墨主活 塞(CP1)二者上下协调运动组合，能够对铁水和石墨前驱体精粉的液/固两相混合物(L/S)起到增强分散功能；(T5)，石墨副活塞(CP2)的中心开有通孔(H2)用于负压吸附住钢桶包装的石墨前驱体精粉或者通过(H2)及其延伸浸没在铁水中的石墨管采用正压气流输送方式直接将石墨前驱体精粉喷吹进熔化后的高温铁水中；本发明的制造装置在石墨坩埚的上部的侧壁上开有中小孔(H3)和/或(H4)和/或(H5)并安装相应的石墨管道，(H3)和/或(H4)用于从外部喷吹惰性气体，使得从铁水中上浮后的人造石墨粉体呈流态化，(H5)用于采用负压抽吸方式将呈流态化的人造石墨粉体转移到外部的料仓，进行缓存并继续冷却。
  2. 根据权利要求1所述的铁水孕育人造石墨负极材料的制造装置及方法，其特征在于， 制造装置的石墨坩埚的上部的侧壁上开有中小孔(H3)和/或(H4)和/或(H5)并安装相应的石墨管道，在收集上浮在铁水表面的人造石墨粉体时，从副活塞(CP2)的中心的通孔(H2)喷吹惰性气体，从(H3)和/或(H4)和/或(H5)向外部采用负压抽吸方式抽吸人造石墨粉体。
  3. 根据权利要求1所述的铁水孕育人造石墨负极材料的制造装置及方法，其特征在于，铁水孕育人造石墨负极材料的制造方法，利用高温铁水在1850—2150℃(TH)高温区间对石墨前驱体精粉具有较好的润湿能力，润湿角小于90度，以及对石墨前驱体精粉中的碳元素具有相对较高的饱和溶解度，处于(TH)高温区间的高温铁水对石墨前驱体精粉其中的非晶区部分的碳以及表面的高活性的碳，相对于其中的结晶碳而言，具有优先选择性溶解的特性，在此(TH)高温区间利用以上三点技术特性，本发明的石墨活塞组合体将石墨前驱体精粉在高温铁水中先进行增强分散，均匀分散在高温铁水中以后，采用石墨活塞组合体对石墨前驱体精粉进行持续压制并浸没在高温铁水中，在(TH)高温区间对浸没其中的石墨前驱体精粉进行高温孕育总时间介于30—360分钟，实现高温铁水对石墨前驱体精粉非晶区部分的碳的选择性溶解以及对粉体表面的高活性碳的选择性熔蚀，同时石墨前驱体精粉其中的碳元素在(TH)高温区间也会进行一定的热扩散及重结晶过程；然后将铁水和经过高温孕育的石墨前驱体精粉的液/固混合物在保持石墨活塞组合体对其持续压制的同时，由(TH)高温区间一起冷却到1350—1650℃(TL)低温区间，在降温过程中，相对低温的铁水对碳元素具有相对较低的饱和溶解度，铁水中溶解的过饱和的碳从铁水中会动态析出，部分析出的碳在石墨前驱体精粉的表面能够实现附生结晶，还有少部分的碳直接在铁水中析出长大为人造石墨粉体，在降温到(TL)温度区间并保持低温孕育总时间介于30—360分钟后，形成自然包覆型核壳结构为主的人造石墨粉体；随后将石墨活塞组合体上移，利用(TL)低温区间相对低温的铁水对人造石墨粉体的润湿性变差，润湿角大于90度，并利用人造石墨粉体和低温铁水之间巨大的密度差，将实现自然包覆后的人造石墨粉体或者部分自然析出的人造石墨粉体上浮到低温铁水的液面以上，然后利用负压将上浮后的人造石墨粉体抽吸出去存放在物料缓存容器中，继续在惰性气体保护下或真空条件下将人造石墨粉体冷却到200℃以 后出炉，颗粒分选并除磁后得到铁水孕育人造石墨负极材料，XRD测试d002小于0 .3390纳 米，真密度介于2.17—2.27g/cm3，克容量大于350mAh/g，首次充放电效率大于93％。
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