WO2023226934A1 - 铁水孕育人造石墨负极材料及制造方法 - Google Patents

铁水孕育人造石墨负极材料及制造方法 Download PDF

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WO2023226934A1
WO2023226934A1 PCT/CN2023/095543 CN2023095543W WO2023226934A1 WO 2023226934 A1 WO2023226934 A1 WO 2023226934A1 CN 2023095543 W CN2023095543 W CN 2023095543W WO 2023226934 A1 WO2023226934 A1 WO 2023226934A1
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molten iron
graphite
powder
carbon
artificial graphite
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PCT/CN2023/095543
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English (en)
French (fr)
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李鑫
吉学文
李硕
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深圳市钢昱碳晶科技有限公司
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Publication of WO2023226934A1 publication Critical patent/WO2023226934A1/zh

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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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • 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 particularly relates to artificial graphite negative electrode materials used therein.
  • 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 is currently 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. .
  • anode materials mainly include artificial graphite and natural graphite.
  • the advantages of natural graphite are low cost and high compaction density.
  • the main disadvantage is that the surface of natural graphite powder is rough and the specific surface area is large.
  • the process reaction of forming an SEI film on the surface of the negative active material during the first charge and discharge consumes a lot of wasted lithium sources. , resulting in low initial charge and discharge efficiency; 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 electrode group spacing, and the battery cycle life decreases rapidly.
  • the anisotropy of the polycrystal also causes the insertion/extraction of lithium ions only from certain end faces of the graphite powder polycrystal, resulting in a small effective insertion/extraction area and poor charge/discharge rate characteristics of the battery.
  • artificial graphite is made entirely of mesophase carbon microspheres or calcined needle coke and subjected to high-temperature graphitization treatment at 2800-3100°C.
  • Artificial graphite polycrystals are basically isotropic. , the powder surface is smooth, the specific surface area is small, the battery first efficiency is high, the irreversible capacity is low, the cycle life is long, and the rate characteristics are good.
  • the disadvantage is that the high-temperature graphitization process that artificial graphite must undergo is long and energy-consuming; current artificial graphite
  • the high-temperature graphitization temperature is as high as 2800-3100°C.
  • the graphite precursor raw material powder is basically loosely packed.
  • the tap density is less than 1.10g/cm3; the graphite crucible is filled with carbon resistance granules, and 70-80% of the heating heat is used for these process auxiliary materials and external insulation materials, in order to produce
  • the uniformity of the product requires nearly 15 days of heating and holding time, nearly 10 days of cooling time, and the processing cycle of one furnace is close to one month.
  • the overall energy consumption is high, the effective energy utilization rate is low, the processing cycle is long, and the capital occupation cycle is long.
  • Artificial graphite is the bottleneck link in cost reduction.
  • 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 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 interface strength between the shell and the core of this coating type is limited, and it is difficult to manufacture the negative electrode.
  • the pole pieces are easily crushed, causing fluctuations in battery cycle life quality.
  • the invention proposes an economical, environmentally friendly, high energy utilization efficiency, fast production speed, and good product consistency.
  • the molten iron incubates artificial graphite anode material and its manufacturing method. It is characterized in that the molten iron inoculates the artificial graphite anode material using molten iron at 1750-2000°C.
  • the (TH) high-temperature range has a high saturated solubility for carbon, achieving surface erosion and spheroidization of the graphite precursor fine powder by the molten iron, and using the stirring function of electromagnetic induction to cause surface friction between the molten iron and the graphite precursor fine powder, correspondingly Shear stress is formed inside the graphite precursor fine powder, thereby accelerating the stress-induced recrystallization inside the graphite precursor fine powder and promoting graphitization; using molten iron to cool it to 1250-1600°C in the high temperature range of (TH) TL) relatively low temperature range, but the molten iron is still in the liquid cooling process.
  • the relatively low-temperature molten iron has a relatively low saturated solubility for carbon.
  • Supersaturated carbon dynamically precipitates from the molten iron.
  • Some carbon elements are in the fine powder of graphite precursor.
  • Epitaxial crystallization is realized on the surface to form a coating shell; in the (TL) temperature range, the naturally coated graphite powder is floated above the surface of the molten iron.
  • negative pressure is used to remove the graphite powder.
  • the body is sucked out, and continues to be cooled to 300°C under inert gas protection or vacuum conditions before being released. After demagnetization, the molten iron incubated artificial graphite anode material is obtained.
  • XRD test d002 is less than 0.3390 nanometers, and the true density is between 2.17-2.27g/cm3 , the gram capacity is greater than 350mAh/g, the first charge and discharge efficiency is greater than 92%, and the particle sphericity is greater than 0.70.
  • 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 metallurgical coke, anthracite, needle coke, pellet coke, natural graphite, and asphalt powder.
  • One or more combinations of carbon materials such as hard carbon.
  • the graphite precursor raw materials are acid washed and/or alkali washed to purify, neutralized and dried, with or without high-temperature calcination or carbonization, to achieve inert gas protection.
  • Step 2 vacuum induction melting
  • inert protective gases such as nitrogen or argon under vacuum conditions or after evacuating
  • heat the molten iron to above 1350°C using induction and use protective gases such as nitrogen or argon to finely powder
  • the graphite precursor ( PG) is blown and transported into the molten iron, and the molten iron is continued to be induction heated to a high temperature range of 1750-2000°C, and intermittent electromagnetic stirring is carried out in this high temperature range for high temperature incubation for 15-120 minutes, and then the molten iron and graphite powder are The temperature of the mixture is cooled to the range of 1250-1600°C, allowing the graphite powder to float above the
  • the present invention preferably uses vacuum induction melting in the raw material iron when preparing high-temperature molten iron.
  • the initial carbon content is greater than 3%, more preferably greater than 4%.
  • the molten iron is heated to above 1550°C by induction melting under vacuum conditions, and then nitrogen or argon is used to refine the graphite precursor powder (PG) Blow and transport the molten iron into the molten iron, continue to inductively heat the molten iron together to a high temperature range of 1800-1950°C, and perform intermittent electromagnetic stirring and high-temperature incubation in this high-temperature range for 60-90 minutes, and then cool down the mixture of molten iron and graphite powder.
  • nitrogen or argon is used to refine the graphite precursor powder (PG) Blow and transport the molten iron into the molten iron, continue to inductively heat the molten iron together to a high temperature range of 1800-1950°C, and perform intermittent electromagnetic stirring and high-temperature incubation in this high-temperature range for 60-90 minutes, and then cool down the mixture of molten iron and graphite powder.
  • the graphite powder is allowed to float above the liquid level of the molten iron, and then negative pressure adsorption is used to transfer the high-temperature graphite powder to the material buffer container, and continues to be slowly cooled to below 300°C under vacuum conditions. After being released from the furnace Demagnetize, obtain the artificial graphite anode material incubated with molten iron, continue to spray the next batch of graphite precursor fine powder (PG) into the high-temperature molten iron, and repeat the above-mentioned manufacturing of the artificial graphite anode material incubated with molten iron.
  • PG graphite precursor fine powder
  • the maximum temperature of the molten iron incubation of the present invention is preferably controlled between 1800-1950°C; in view of the fact that the iron content at high temperatures of 1800-1950°C
  • the saturated solubility of carbon in water is greater than 6wt.%.
  • the method of the present invention naturally grows
  • the new type of coated artificial graphite negative electrode material has high coating uniformity between the core and shell and high interface strength.
  • the artificial graphite negative electrode material incubated with molten iron of the present invention is not easily crushed.
  • the prepared battery has high gram capacity, high first charge and discharge efficiency, good rate characteristics, and long cycle life.
  • the present invention uses molten iron at high temperature to perform surface erosion on the fine graphite precursor powder, thereby reducing the active end groups and specific surface area of the fine graphite precursor powder, and reducing the amount of lithium consumed by the artificial graphite negative electrode material to form the SEI film, thereby increasing the irreversible capacity. reduce.
  • This invention uses the highest temperature range of 1750-2000°C for processing, which can greatly reduce radiant heat. It uses electromagnetic stirring of molten iron in combination to form internal friction on the carbon material precursor, and microscopic shear stress is formed inside the carbon material, thus having the ability to induce stress.
  • the recrystallization characteristics under high temperature can be independent of the traditional thermal diffusion graphitization at high temperature of 2800-3150°C.
  • the present invention can realize graphite in the medium high temperature range of 1750-2000°C with the help of mechanisms such as internal friction and stress-induced recrystallization.
  • the economical artificial graphite negative electrode material is prepared by incubating high-temperature molten iron to effectively increase the degree of chemical transformation.
  • the invention adopts electromagnetic induction heating under vacuum conditions, and the thermal energy utilization efficiency is much higher than that of traditional high-temperature graphitization furnaces.
  • the invented method greatly reduces the heating time of graphitization, reduces the overall energy consumption, and can obtain a new core-shell structure artificial graphite anode material with high graphitization degree and good isotropy.
  • the present invention utilizes the difference in density to realize the effective separation of artificial graphite powder and molten iron simply and easily. There is no need to use subsequent processes such as chemical corrosion to treat the iron.
  • the high-temperature molten iron in the present invention is only used as a process medium, with basically no material loss, and the process is environmentally friendly and energy-saving. , low production cost and strong market competitiveness.
  • Example 1 Artificial graphite negative electrode material was incubated in molten iron.
  • XRD test d002 was 0.3360 nanometers, the true density was between 2.21-2.25g/cm3, the gram capacity was greater than 360mAh/g, the first charge and discharge efficiency was greater than 94%, and the particle sphericity was greater than 0.85.
  • the manufacturing method of artificial graphite anode material incubated by molten iron includes the following main steps: Step 1, prepare graphite precursor fine powder (PG).
  • the graphite precursor raw material is calcined needle coke, crushed, classified, and the particle size is controlled at the average particle size D50 Between 9-16 microns, D90 is less than 25 microns, and the ash content is less than 0.1%;
  • Step 2 vacuum induction melting prepares high-temperature molten iron. Under vacuum conditions, the molten iron with an initial carbon content greater than 4.5% is heated to 1550-1650°C by induction, using argon.
  • the graphite precursor fine powder (PG) is blown and transported into the molten iron by gas, and the molten iron is continuously inductively heated to a high temperature range of 1800-1950°C, and intermittent electromagnetic stirring and high-temperature incubation are performed in this high temperature range for 90 minutes, and then the The temperature of the mixture of molten iron and graphite powder is cooled to the range of 1350-1450°C, so that the graphite powder floats above the liquid surface of the molten iron, and then negative pressure adsorption is used to transfer the high-temperature graphite powder to the material buffer container, and the vacuum condition is continued.
  • PG graphite precursor fine powder
  • Step 3 Slowly cool to below 300°C, fill with balancing gas, and demagnetize after coming out of the furnace to obtain artificial graphite anode material incubated with molten iron. Step 3, continue to spray the next batch of graphite precursor fine powder (PG) into the high-temperature molten iron, and repeat The above-described molten iron inoculated artificial graphite negative electrode material is produced.
  • PG graphite precursor fine powder

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Abstract

一种铁水孕育人造石墨负极材料及其制造方法，所述方法包括以下步骤：1、利用铁水在1750—2000℃高温区间对碳具有较高的饱和溶解度，实现铁水对石墨前驱体精粉的表面熔蚀和球形化，并利用电磁感应的搅拌功能，利用高温铁水对石墨前驱体精粉形成表面摩擦，加速精粉内部的应力诱导再结晶，促进石墨化；2、利用铁水在降温过程中碳具有相对较低的饱和溶解度，使过饱和的碳从铁水中析出，在精粉表面附生结晶形成碳包覆壳层；3、将实现自然包覆后的石墨粉体上浮到铁水的液面以上，负压将石墨粉体抽吸出去，冷却到300℃以后出炉，继续冷却，除磁后得到所述负极材料。所述方法经济环保，能源利用效率高，生产速度快；所述方法获得的负极材料球形度好，首次充放电效率高，克容量大。

Description

铁水孕育人造石墨负极材料及制造方法 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。
 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，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；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/脱出面积小，电池的充/放电倍率特性差。
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，比表面积小，电池首效高，不可逆容量低，循环寿命长，倍率特性佳，缺点是人造石墨必须进行的高温石墨化工序加工周期长，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基本松装于石墨坩埚内，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；另外这种包覆型的壳和核之间的界面强度有限，制造负极极片时容易压溃，导致电池循环寿命质量波动。
为克服现有人造石墨负极材料制造方法的以上种种缺点和不足，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，产品一致性好的铁水孕育人造石墨负极材料及制造方法，其特征在于，铁水孕育人造石墨负极材料利用铁水在1750—2000℃(TH)高温区间对碳具有较高的饱和溶解度，实现铁水对石墨前驱体精粉的表面熔蚀和球形化，并利用电磁感应的搅拌功能使铁水对石墨前驱体精粉形成表面摩擦，相应地在石墨前驱体精粉粉体的内部形成剪切应力，从而加速石墨前驱体精粉内部的应力诱导再结晶，促进石墨化；利用铁水在由 (TH)高温区间冷却到1250—1600℃(TL)相对低温区间，但铁水仍处于液态的降温过程中，相对低温的铁水对碳具有相对较低的饱和溶解度，过饱和的碳从铁水中动态析出，部分碳元素在石墨前驱体精粉的表面实现附生结晶形成包覆 壳层；在(TL)温度区间，将实现自然包覆后的石墨粉体上浮到铁水的液面以上，在石墨粉体处于高温下，利用负压将石墨粉体抽吸出去，继续在惰性气体保护下或真空条件下冷却到 300℃以后出炉，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92％，颗粒球形度大于0.70。
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850℃/2小时处理后的挥发减重小于0.5％，破碎，分级，颗粒度控制在平均粒径D50介于5—20微米，D90小于30微米，灰分小于0.5％；Step2，真空感应熔炼制备高温铁水，在真空条件下或抽真空后向真空室内充氮气或氩气等惰性保护气体，将铁水采用感应加热到1350℃以上，采用氮气或氩气等保护气体将石墨前驱体精粉(PG)喷吹输送进铁水中，在铁水中继续一起感应加热到 1750—2000℃的高温区间，并在此高温区间进行间歇式电磁搅拌高温孕育15—120分钟，然后 将铁水和石墨粉体的混合物的温度降温到1250—1600℃区间，实现石墨粉体上浮到铁水的液面以上，再采用负压吸附将石墨粉体转移到物料缓存容器中，继续进行惰性气体保护下或真空条件下冷却到300℃以下出炉，继续冷却，除磁后得到铁水孕育人造石墨负极材料，Step3，继续向高温铁水中喷吹下一批的石墨前驱体精粉(PG)，重复进行上述的铁水孕育人造石墨负极材料的制造。
为了提高石墨坩埚和/或石墨/陶瓷复合材料坩埚和/或石墨活塞压头的使用寿命，防止高温下铁水对其熔蚀过多，本发明优选在真空感应熔炼制备高温铁水时的原材料铁中的初始碳含量大于3％，更优选大于4％，为了提高生产效率，在真空条件下，将铁水采用感应熔炼加热到1550℃以上，然后采用氮气或氩气将石墨前驱体精粉(PG)喷吹输送进铁水中，在铁水中继续一起感应加热到1800—1950℃的高温区间，并在此高温区间进行间歇式电磁搅拌高温孕育60—90分钟，然后将铁水和石墨粉体的混合物降温到1350—1450℃区间，实现石墨粉体上浮到铁水的液面以上，再采用负压吸附将高温石墨粉体转移到物料缓存容器中，继续进行真空条件下缓慢冷却到300℃以下，出炉后除磁，得到铁水孕育人造石墨负极材料，继续向高温铁水中喷吹下一批的石墨前驱体精粉(PG)，重复进行上述的铁水孕育人造石墨负极材料的制造。
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，以及保证坩埚的寿命，本发明的铁水孕育的最高温度优选控制介于1800—1950℃；鉴于1800—1950℃高 温下铁水中的碳饱和溶解度大于6wt.％，在后面的铁水降温过程中铁水中溶解的过饱和的碳会逐步析出，在碳素材料前驱体粉体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，界面强度高，在制备负极极片的压实过程中，本发明的铁水孕育人造石墨负极材料不易被压溃，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。
本发明利用高温下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和比表面积，降低了人造石墨负极材料形成SEI膜消耗的锂量，从而不可逆容量降低。
 有益效果
本发明利用1750—2000℃的最高温度区间进行加工，可以大大降低辐射热，组合利用铁水的电磁搅拌对碳素材料前驱体形成内摩擦，碳素材料内部形成微观剪切应力，从而具备应力诱导下的再结晶特性，可以不依赖传统的2800—3150℃高温下的热扩散型石墨化，本发明能够在1750—2000℃的中等高温区间下借助于内摩擦和应力诱导再结晶等机制实现 石墨化度的有效提升，借助于高温铁水的孕育制备出经济型的人造石墨负极材料；本发明采用真空条件下的电磁感应加热方式，热能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，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的人造石墨负极材料。
本发明利用密度差，简单易行地实现了人造石墨粉体和铁水有效分离，不必采用化学腐蚀等后续工序处理铁，本发明中高温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。
 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，Mg，Mn等合金元素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，XRD测试d002为0.3360纳米，真密度介于2.21—2.25g/cm3，克容量大于360mAh/g，首次充放电效率大于94％，颗粒球形度大于0.85。
铁水孕育人造石墨负极材料的制造方法包括以下主要步骤：Step1，制备石墨前驱体精粉(PG)，石墨前驱体原料采用煅烧后的针状焦，破碎，分级，颗粒度控制在平均粒径D50 介于9—16微米，D90小于25微米，灰分小于0.1％；Step2，真空感应熔炼制备高温铁水，在真空条件下将初始碳含量大于4.5％的铁水采用感应加热到1550—1650℃，采用氩气将石墨前驱体精粉(PG)喷吹输送进铁水中，在铁水中继续一起感应加热到1800—1950℃的高温区间，并在此高温区间进行间歇式电磁搅拌高温孕育90分钟，然后将铁水和石墨粉体的混合物的温度降温到1350—1450℃区间，实现石墨粉体上浮到铁水的液面以上，再采用负压吸附将高 温石墨粉体转移到物料缓存容器中，继续进行真空条件下的缓慢冷却到300℃以下，充平衡气体后，出炉后除磁，得到铁水孕育人造石墨负极材料，Step3，继续向高温铁水中喷吹下一批的石墨前驱体精粉(PG)，重复进行上述的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及制造方法，其特征在于，铁水孕育人造石墨负极材料利用铁水在1750—2000℃(TH)高温区间对碳具有较高的饱和溶解度，实现铁水对石墨前驱体精粉的表面熔蚀和球形化，并利用电磁感应的搅拌功能使铁水对石墨前驱体精粉形成表面摩擦，相应地在石墨前驱体精粉粉体的内部形成剪切应力，从而加速石墨前驱体精粉内部的应力诱导再结晶，促进石墨化；利用铁水在由(TH)高温区间冷却到1250—1600℃(TL)相对低温区间的降温过程中，相对低温的铁水对碳具有相对较低的饱和溶解度，过饱和的碳从铁水中动态析出，部分碳元素在石墨前驱体精粉的表面实现附生结晶形成包覆壳层；在(TL)温度区间，将实现自然包覆后的石墨粉体上浮到铁水的液面以上，利用负压将石墨粉体抽吸出去，继续在惰性气体保护下或真空条件下将石墨粉体冷却到300℃以后出炉，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92％，颗粒球形度大于0.70。
  2. 根据权利要求1所述的铁水孕育人造石墨负极材料及制造方法，其特征在于，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850℃/2小时处理后的挥发减重小于0.5％，破碎，分级，颗粒度控制在平均粒径D50介于5—20微米，D90小于30微米，灰分小于0.5％；Step2，真空感应熔炼制备高温铁水，在真空条件下或抽真空后向真空室内充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，采用氮气或氩气等惰性保护气体将石墨前驱体精粉(PG)喷吹输送进铁水中，在铁水中继续一起感应加热到1750—2000℃(TH)的高温区间，并在此高温区间进行间歇式电磁搅拌高温孕育15—120分钟，然后 将铁水和石墨粉体的混合物降温到1250—1600℃(TL)区间后，实现石墨粉体上浮到铁水的液面以上，再采用负压吸附将高温石墨粉体转移到物料缓存容器中，继续进行惰性气体保护下或真空条件下的冷却到300℃以下出炉，继续冷却，除磁后得到铁水孕育人造石墨负极材料，Step3，继续向高温铁水中喷吹下一批的石墨前驱体精粉(PG)，重复进行上述的铁水孕育人造石墨负极材料的制造。
  3. 根据权利要求1所述的铁水孕育人造石墨负极材料及制造方法，其特征在于，真空感应熔炼制备高温铁水时的初始碳含量大于4％，将铁水采用感应熔炼加热到1550℃以上，然后采用氮气将石墨前驱体精粉(PG)喷吹输送进铁水中，在铁水中继续一起感应加热到1800—1950℃的高温区间，并在此高温区间进行间歇式电磁搅拌高温孕育60—90分钟，然后 将铁水和石墨粉体的混合物降温到1350—1450℃区间，实现石墨粉体上浮到铁水的液面以上，再采用负压吸附将石墨粉体转移到物料缓存容器中，冷却到300℃以下，出炉后继续冷却，除磁，得到铁水孕育人造石墨负极材料，继续向高温铁水中喷吹下一批的石墨前驱体精粉(PG)，重复进行上述的铁水孕育人造石墨负极材料的制造。
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