WO2020253285A1 - 多孔石墨烯钴酸锂复合材料及其制备方法和用途 - Google Patents

多孔石墨烯钴酸锂复合材料及其制备方法和用途 Download PDF

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WO2020253285A1
WO2020253285A1 PCT/CN2020/079716 CN2020079716W WO2020253285A1 WO 2020253285 A1 WO2020253285 A1 WO 2020253285A1 CN 2020079716 W CN2020079716 W CN 2020079716W WO 2020253285 A1 WO2020253285 A1 WO 2020253285A1
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porous graphene
composite material
lithium
cobalt oxide
lithium cobalt
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PCT/CN2020/079716
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English (en)
French (fr)
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沈文卓
晁丹丹
吴宏超
丘海东
孙卫山
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中兴通讯股份有限公司
上海交通大学
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Publication of WO2020253285A1 publication Critical patent/WO2020253285A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • 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
    • 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

  • This application relates to but not limited to the field of electrochemistry, specifically, but not limited to a porous graphene lithium cobaltate composite material and its preparation method and application.
  • Lithium-ion batteries have the advantages of high energy density, convenient use, and long cycle life. They are widely used in portable electronic equipment, power tools, hybrid/all-electric vehicles and other fields.
  • Lithium-ion battery cathode materials include lithium iron phosphate, ternary materials, lithium cobaltate, lithium manganate, lithium titanate, and the like. The cathode material occupies a large proportion in the composition of lithium batteries, and its performance directly affects the performance of lithium batteries.
  • Layered lithium cobalt oxide is a commonly used cathode material for lithium-ion batteries. It has the advantages of large tap density, high working voltage, and simple preparation method. However, there are also problems such as low electronic conductivity and slow ion diffusion rate, which further affect Its high-rate charge-discharge performance, cycle stability and other comprehensive electrochemical performance. Therefore, it is an important content of current research work to improve the electrical conductivity of the positive electrode material and improve the high-current charge and discharge performance by introducing surface functional material modification.
  • graphene has been widely concerned and used in electrode material modification due to its excellent physical and chemical properties.
  • graphene mostly participates in electrochemical reactions in the form of conductive additives. Simple physical mixing results in the weak bonding of graphene and electrode materials, which makes it difficult to fully utilize the excellent physical and chemical properties of graphene.
  • the present application provides a method for preparing lithium cobalt oxide composite material by using porous graphene.
  • the method has simple process, high bonding degree and good uniformity between porous graphene and lithium cobalt oxide.
  • This application provides a method for preparing a porous graphene lithium cobalt oxide composite material, which includes: preparing an aqueous solution of porous graphene; adding lithium cobalt oxide to the aqueous solution of porous graphene; and spray drying after uniform mixing to obtain the composite material .
  • the present application also provides a porous graphene lithium cobalt oxide composite material, which is prepared by the above method.
  • the application also provides the use of a porous graphene lithium cobalt oxide composite material as a positive electrode active material of a lithium ion battery.
  • the present application also provides a lithium ion battery.
  • the positive electrode of the lithium ion battery includes a binder, a conductive agent, and the foregoing porous graphene lithium cobalt oxide composite material.
  • Figure 1 is a field emission scanning electron micrograph of a conventional lithium cobalt oxide cathode active material
  • Figure 3 is a cycle performance curve of a lithium-ion battery in a comparative example of the application
  • FIG. 4 is a cycle performance curve of a lithium ion battery according to an embodiment of the application.
  • FIG. 6 is a rate charge and discharge curve of a lithium ion battery according to an embodiment of the application.
  • the embodiment of the present application provides a method for preparing a porous graphene lithium cobalt oxide composite material, which includes: preparing an aqueous solution of porous graphene; adding lithium cobalt oxide to the aqueous solution of porous graphene; The composite material.
  • the examples of this application utilize the good conductive anisotropy of porous graphene and the structural characteristics of controllable curvature to coat lithium cobalt oxide, thereby constructing porous graphene cobalt acid with a three-dimensional conductive network structure and good conductivity Lithium composite material.
  • the examples of this application are coated with porous graphene.
  • the holes on the graphene sheets can not only increase the ion transmission efficiency between the sheets, but also serve as the "skeleton" of graphene, giving it a three-dimensional framework network structure, further improving Graphene's performance as a surface functionalized material.
  • the preparation method of the embodiments of the present application can form the porous graphene coating layer in one operation, the process is simple, and there is no need to add organic solvents, surfactants, reducing agents, oxidizing agents, etc. during the formation of the porous graphene coating layer Additive, low production cost.
  • the preparation method of the embodiment of the present application combines the mixing process of porous graphene and lithium cobalt oxide with spray drying technology, and has a simple process and is suitable for mass production of porous graphene lithium cobalt oxide composite materials.
  • the mass ratio of porous graphene to water may be 1 ⁇ 10-5:1 to 100 ⁇ 10-5:1, for example, it may be 10 ⁇ 10-5:1, 20 ⁇ 10-5: 1. 50 ⁇ 10-5:1, 80 ⁇ 10-5:1, 90 ⁇ 10-5:1, etc.
  • the mass ratio of porous graphene to water is in the range of 1 ⁇ 10-5:1 to 100 ⁇ 10-5:1, the conductivity of lithium cobalt oxide can be greatly improved, and the porous graphene can be uniformly dispersed In water, it is conducive to the full progress of the modification reaction.
  • the mass ratio of lithium cobaltate to the porous graphene aqueous solution may be 0.01:1 to 0.5:1, for example, may be 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1 Wait.
  • the coating layer can be formed well, and the coating layer is not prone to be too thick, which is more conducive to the formation of porous graphite Olefin coating.
  • mixing can be performed by means such as stirring.
  • the stirring speed may be 120 revolutions/min to 360 revolutions/min, for example, it may be 150 revolutions/min, 180 revolutions/min, 200 revolutions/min, 250 revolutions/min, 300 revolutions/min, etc.;
  • the stirring time may be 5 min to 120 min, for example, 10 min, 30 min, 60 min, 90 min, etc.
  • spray drying can be performed under the condition that the outlet temperature is 150°C to 200°C, for example, it can be 160°C, 170°C, 180°C, 190°C, etc.; the feed flow rate can be 300mL/min ⁇ 800mL /min, for example, 400 mL/min, 500 mL/min, 600 mL/min, 700 mL/min, etc.
  • the porous graphene can be a commercially available porous graphene, for example, it can be a porous graphene purchased from Shanghai Carbon Source Huigu New Energy Technology Co., Ltd.
  • the porous graphene lithium cobalt oxide composite material prepared in the examples of this application has a continuous three-dimensional conductive structure, wherein the porous graphene is coated on the surface of the lithium cobalt oxide, thereby forming a complete, continuous and good conductivity on the surface of the lithium cobalt oxide
  • the porous graphene coating layer and the bridging connection between lithium cobalt oxide has a continuous three-dimensional conductive structure, wherein the porous graphene is coated on the surface of the lithium cobalt oxide, thereby forming a complete, continuous and good conductivity on the surface of the lithium cobalt oxide.
  • the coated porous graphene may be a single layer, and the thickness of the coating layer may be 0.34 nm, for example.
  • the embodiment of the present application provides the use of a porous graphene lithium cobalt oxide composite material as a positive electrode active material of a lithium ion battery.
  • the embodiment of the application provides a lithium ion battery, including: a positive electrode, a negative electrode, a separator, and an electrolyte.
  • the positive electrode includes a binder, a conductive agent, and the porous graphene lithium cobaltate composite material;
  • the negative electrode can be a carbon material, a metal oxide
  • the material, metal or alloy, for example, may be a metal lithium sheet.
  • the lithium ion battery has excellent rate discharge performance and cycle stability.
  • the binder can be selected from any one or more of various lithium ion battery binders such as polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber and the like.
  • the conductive agent can be selected from any one or more of various lithium ion battery conductive agents such as acetylene black, carbon black, graphite, carbon nanotubes, and Ketjen black.
  • the mass ratio of the porous graphene lithium cobalt oxide composite material, the binder, and the conductive agent can be 80:10:10.
  • the positive electrode of the lithium ion battery can be prepared by the following method: the porous graphene lithium ion positive electrode composite material, the binder, and the conductive agent are stirred in a solvent according to the proportion to form a slurry, coated on the surface of the current collector, and dried in vacuum. Press the pellets to make the positive electrode.
  • the solvent can be selected from any one or more of various lithium ion battery solvents such as N-methylpyrrolidone, ethylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.
  • the current collector can be selected from various lithium ion battery current collectors such as aluminum foil.
  • the vacuum drying time can be 8 hours, 10 hours, 12 hours, 15 hours and so on.
  • the separator can be selected from various lithium ion battery separators such as a microporous polypropylene (Celgard 2300) membrane.
  • the electrolyte can be selected from any one or more of various lithium-ion battery electrolytes such as liquid electrode solutions, solid electrolytes, and gel electrolytes. In some embodiments, it is composed of lithium hexafluorophosphate (LiPF6)/ethylene carbonate (EC). ), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) are mixed, and the content is 1mol/L LiPF6/EC, DEC, EMC in some embodiments in a volume ratio of 1:1: 1 Mix.
  • LiPF6 lithium hexafluorophosphate
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • EMC methyl ethyl carbonate
  • Lithium-ion batteries can be assembled in a glove box filled with high-purity argon.
  • porous graphene used in the following examples was purchased from Shanghai Carbon Source Huigu New Energy Technology Co., Ltd.
  • porous graphene lithium cobalt oxide composite material prepared above is used as the positive electrode active material of the lithium ion battery to prepare a lithium ion battery:
  • N-methylpyrrolidone as solvent and mass ratio 80:10:10, mix porous graphene lithium cobalt oxide composite material, conductive agent carbon black and binder polyvinylidene fluoride, stir evenly into a slurry coating On the surface of the aluminum foil, vacuum-dried for 12 hours, and pressed into a positive electrode sheet with a diameter of 10 mm.
  • Metal lithium is used as the negative electrode
  • the microporous polypropylene (Celgard2300) membrane is used as the separator
  • the 1mol/l LiPF6/EC+DEC+EMC volume ratio is 1:1:1 is used as the electrolyte.
  • the CR2032 button cell is assembled. After standing for 12 hours, the electrochemical performance test was performed.
  • porous graphene lithium cobalt oxide composite material prepared above is used as the positive electrode active material of the lithium ion battery to prepare a lithium ion battery:
  • N-methylpyrrolidone as solvent and mass ratio 80:10:10, mix porous graphene lithium cobalt oxide composite material, conductive agent carbon black and binder polyvinylidene fluoride, stir evenly into a slurry coating On the surface of the aluminum foil, then vacuum-dried for 12 hours, and pressed into a positive electrode sheet with a diameter of 10 mm.
  • Metal lithium is used as the negative electrode
  • the microporous polypropylene (Celgard2300) membrane is used as the separator
  • the 1mol/L LiPF6/EC+DEC+EMC volume ratio is 1:1:1 is used as the electrolyte.
  • the CR2032 button cell is assembled. After standing for 12 hours, the electrochemical performance test was performed.
  • porous graphene lithium cobalt oxide composite material prepared above is used as the positive electrode active material of the lithium ion battery to prepare a lithium ion battery:
  • N-methylpyrrolidone as solvent and mass ratio 80:10:10, mix porous graphene lithium cobalt oxide composite material, conductive agent carbon black and binder polyvinylidene fluoride, stir evenly into a slurry coating On the surface of the aluminum foil, then vacuum-dried for 12 hours, and pressed into a positive electrode sheet with a diameter of 10 mm.
  • Metal lithium is used as the negative electrode
  • the microporous polypropylene (Celgard2300) membrane is used as the separator
  • the 1mol/L LiPF6/EC+DEC+EMC volume ratio is 1:1:1 is used as the electrolyte.
  • the CR2032 button cell is assembled. After standing for 12 hours, the electrochemical performance test was performed.
  • N-methylpyrrolidone as solvent, mix the lithium cobalt oxide cathode active material, conductive agent carbon black and binder polyvinylidene fluoride with a mass ratio of 80:10:10, stir and evenly form a slurry and coat it on the aluminum foil The surface is then vacuum dried for 12 hours and pressed into a positive electrode sheet with a diameter of 10 mm.
  • Metal lithium is used as the negative electrode
  • the microporous polypropylene (Celgard2300) membrane is used as the separator
  • the 1mol/L LiPF6/EC+DEC+EMC volume ratio is 1:1:1 is used as the electrolyte.
  • the CR2032 button cell is assembled. After standing for 12 hours, the electrochemical performance test was performed.
  • a field emission scanning electron microscope (Zeiss Ultra 55, Germany) was used to test the existing lithium cobalt oxide cathode active material and the porous graphene lithium cobalt oxide composite material of Example 1. The test results are shown in Figure 1 and As shown in Figure 2.
  • the lithium cobalt oxide powder in Figure 1 is compared with the porous graphene lithium cobalt oxide composite material in Figure 2.
  • the surface of the lithium cobalt oxide can be clearly observed
  • the single-layer graphene has a porous structure and forms a bridge connection between the lithium cobalt oxide powders to form a continuous and complete three-dimensional conductive structure, which can effectively improve the conductive performance of the lithium ion cathode material.
  • the lithium ion battery of Example 2 can be cycled stably for more than 500 times, and the specific capacity at 0.2C and 5C discharge is about 195.4mAh/g and 87.3mAh/g, respectively.
  • the lithium ion battery of Example 3 can be cycled stably for more than 500 times, and the specific capacity at 0.2C and 5C discharge is about 200.5mAh/g and 77.1mAh/g, respectively.
  • the cycle performance of the embodiment of the application is greatly improved, and both can reach more than 500 times, and both the low-rate discharge performance and the high-rate discharge performance are improved.
  • the preparation method of the present application can form a complete, continuous and good conductive porous graphene coating layer on the surface of lithium cobalt oxide with a simple process;
  • the lithium ion battery prepared in this application has excellent rate discharge performance and cycle stability.

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Abstract

一种多孔石墨烯钴酸锂复合材料及其制备方法和用途。制备方法包括：配制多孔石墨烯的水溶液；向多孔石墨烯的水溶液中加入钴酸锂；混合均匀后进行喷雾干燥，得到该复合材料。该复合材料具有连续的三维导电结构，其中的多孔石墨烯包覆于钴酸锂表面，并在钴酸锂之间形成架桥连接。

Description

多孔石墨烯钴酸锂复合材料及其制备方法和用途
相关申请的交叉引用
本申请基于申请号为201910522462.2、申请日为2019年06月17日的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本申请涉及但不限于电化学领域，具体地，涉及但不限于一种多孔石墨烯钴酸锂复合材料及其制备方法和用途。
背景技术
锂离子电池具有能量密度高、使用方便、循环寿命长等优点，广泛用于便携式电子设备、电动工具、混合/全电动汽车等领域。锂离子电池正极材料包括磷酸铁锂、三元材料、钴酸锂、锰酸锂、钛酸锂等。正极材料在锂电池构成中占有很大比例，其性能直接影响锂电池的性能。
层状结构的钴酸锂是常用的锂离子电池正极材料，其具有振实密度大、工作电压高、制备方法简单等优点，但是也存在电子电导率低、离子扩散速率慢等问题，进而影响其高倍率充放电性能、循环稳定性等综合电化学性能。因此，通过引入表面功能化材料改性，提高正极材料的导电性能，改善大电流充放电性能是目前研究工作的重要内容。
近年来，石墨烯因具有优异的物理化学性能，被广泛关注并应用于电极材料改性中。目前石墨烯多以导电添加剂的形式参与到电化学反应中，简单的物理混合导致石墨烯与电极材料的结合力不强，难以充分发挥石墨烯优异的物理化学性质。
发明内容
本申请提供了一种采用多孔石墨烯制备钴酸锂复合材料的方法，该方法工艺简单，多孔石墨烯与钴酸锂之间的结合度高、均匀性好。
本申请提供了一种制备多孔石墨烯钴酸锂复合材料的方法，包括：配制多孔石墨烯的水溶液；向多孔石墨烯的水溶液中加入钴酸锂；混合均匀后进行喷雾干燥，得到该复合材料。
本申请还提供了一种多孔石墨烯钴酸锂复合材料，该复合材料通过上述方法制备得到。
本申请还提供了一种多孔石墨烯钴酸锂复合材料作为锂离子电池正极活性材料的用途。
本申请还提供了一种锂离子电池，该锂离子电池的正极包括粘结剂、导电剂以及上述多孔石墨烯钴酸锂复合材料。本申请的其它特征和优点将在随后的说明书中阐述，并且，部分地从说明书中变得显而易见，或者通过实施本申请而了解。本申请的目的和其他优点可通过在说明书、权利要求书以及附图中所特别指出的结构来实现和获得。
附图说明
附图用来提供对本申请技术方案的进一步理解，并且构成说明书的一部分，与本申请的实施例一起用于解释本申请的技术方案，并不构成对本申请技术方案的限制。
图1为现有的钴酸锂正极活性材料的场发射扫描电镜图；
图2为本申请实施例的多孔石墨烯钴酸锂复合材料的场发射扫描电镜图；
图3为本申请对比例的锂离子电池的循环性能曲线；
图4为本申请实施例的锂离子电池的循环性能曲线；
图5本申请对比例的锂离子电池的倍率充放电曲线；
图6为本申请实施例的锂离子电池的倍率充放电曲线。
具体实施方式
为使本申请的目的、技术方案和优点更加清楚明白，下文中将结合附图对本申请的实施例进行详细说明。需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互任意组合。
本申请实施例提供了一种制备多孔石墨烯钴酸锂复合材料的方法，包括：配制多孔石墨烯的水溶液；向多孔石墨烯的水溶液中加入钴酸锂；混合均匀后进行喷雾干燥，得到所述复合材料。
本申请实施例利用多孔石墨烯良好的导电各向异性以及曲度可控的结构特性，对钴酸锂进行表面包覆，从而构造出具有三维导电网络结构、导电性良好的多孔石墨烯钴酸锂复合材料。
本申请实施例采用多孔的石墨烯进行包覆，石墨烯片层上的孔洞既可以增加片层间的离子传输效率，也可以作为石墨烯“骨架”，使其具有三维骨架网络结构，进一步提升石墨烯作为表面功能化材料的性能。
本申请实施例的制备方法经一次操作即可形成多孔石墨烯包覆层，工艺简单，而且在多孔石墨烯包覆层生成过程中无需添加有机溶剂、表面活性剂、还原剂、氧化剂等各类添加剂，生产成本低。
本申请实施例的制备方法将多孔石墨烯与钴酸锂的混合过程与喷雾干燥技术相结合，工艺简单，适于多孔石墨烯锂钴酸锂复合材料的大批量生产制造。
在本申请实施例中，多孔石墨烯与水的质量比可以为1×10-5:1～100×10-5:1，例如可以为10×10-5:1、20×10-5:1、50×10-5:1、80×10-5:1、90×10-5:1等。当多孔石墨烯与水的质量比在1×10-5:1～100×10-5:1范围内时，能够使钴酸锂的导电性得到较大提高，而且多孔石墨烯能够均匀地分散在水中，有利于改性反应充分进行。
在本申请实施例中，钴酸锂与多孔石墨烯水溶液的质量比可为0.01:1～0.5:1，例如可以为0.05:1、0.1:1、0.2:1、0.3:1、0.4:1等。当钴酸锂与多孔石墨烯水溶液的质量比在0.01:1～0.5:1范围内时，能够很好的形成包覆层，且不易出现包覆层过厚的情况，更有利于形成多孔石墨烯的包覆层。
在本申请实施例中，可采用搅拌等方式进行混合。
在本申请实施例中，搅拌速度可为120转/min～360转/min，例如可以为150转/min、180转/min、200转/min、250转/min、300转/min等；搅拌时间可为5min～120min，例如可以为10min、30min、60min、90min等。
在本申请实施例中，可以在出口温度为150℃～200℃的条件下进行喷雾干燥，例如可以为160℃、170℃、180℃、190℃等；入料流量可以为300mL/min～800mL/min，例如可以为400mL/min、500mL/min、600mL/min、700mL/min等。
在本申请实施例中，多孔石墨烯可以选择市售的多孔石墨烯，例如，可以是购于上海碳源汇谷新能源科技有限公司的多孔石墨烯。
本申请实施例制备得到的多孔石墨烯钴酸锂复合材料，具有连续的三维导电结构，其中的多孔石墨烯包覆于钴酸锂表面，从而在钴酸锂表面形成完整、连续且导电性良好的多孔石墨烯包覆层，并在钴酸锂之间形成架桥连接。
本申请实施例制备得到的多孔石墨烯钴酸锂复合材料中，包覆的多孔石墨烯可以为单层，包覆层的厚度例如可以为0.34nm。
本申请实施例提供了一种多孔石墨烯钴酸锂复合材料作为锂离子电池正极活性材料的用途。
本申请实施例提供了一种锂离子电池，包括：正极、负极、隔膜以及电解液，正极包括粘结剂、导电剂以及上述多孔石墨烯钴酸锂复合材料；负极可以为碳材料、金属氧化物、金属或合金，例如可以为金属锂片。该锂离子电池具有优异的倍率放电性能和循环稳定性。
粘结剂可以选自聚偏氟乙烯、羧甲基纤维素钠、丁苯橡胶等各种锂离子电池粘结剂中的任意一种或更多种。
导电剂可以选自乙炔黑、炭黑、石墨、碳纳米管、科琴黑等各种锂离子电池导电剂中的任意一种或更多种。
多孔石墨烯钴酸锂复合材料、粘结剂、导电剂的质量比可以为80:10:10。
锂离子电池的正极可以通过下述方法制备得到：将多孔石墨烯锂离子正极复合材料、粘结剂、导电剂按比例在溶剂中搅拌均匀成泥浆状，涂覆于集流体表面，真空干燥，压片制成正极。
其中，溶剂可选自N-甲基吡咯烷酮、碳酸乙烯酯、碳酸二乙酯、碳酸二甲酯、碳酸甲乙酯等各种锂离子电池溶剂中的任意一种或更多种。
集流体可选自铝箔等各种锂离子电池集流体。
真空干燥时间可以为8小时、10小时、12小时、15小时等。
隔膜可选自微孔聚丙烯(Celgard2300)膜等各种锂离子电池隔膜。
电解液可选自液体电极液、固体电解质、凝胶电解质等各种锂离子电池电解液中的任意一种或更多种，在某些实施例中由六氟磷酸锂(LiPF6)/碳酸乙烯酯(EC)、碳酸二乙酯(DEC)、碳酸甲基乙基酯(EMC)混合制成，含量在某些实施例中为1mol/L的LiPF6/EC、DEC、EMC以体积比为1:1:1混合。
锂离子电池可在充满高纯氩气的手套箱内组装得到。
以下实施例中所采用的多孔石墨烯购买自上海碳源汇谷新能源科技有限公司。
实施例1
制备多孔石墨烯钴酸锂复合材料：
配制200ml含0.01g多孔石墨烯的水溶液；在多孔石墨烯的水溶液中加入2g钴酸锂粉末，在搅拌速度为240转/min的条件下搅拌20min；将反应后的混合溶液在出口温度为180℃、入料流量为400mL/min的条件下进行喷雾干燥。得到多孔石墨烯钴酸锂复合材料。
采用上述制备的多孔石墨烯钴酸锂复合材料作为锂离子电池正极活性材料制备锂离子电池：
以N-甲基吡咯烷酮为溶剂，按质量比80:10:10，将多孔石墨烯钴酸锂复合材料、导电剂炭黑和粘结剂聚偏氟乙稀混合，搅拌均匀成泥浆状涂覆于铝箔表面，真空干燥12小时，压片制成直径为10mm的正极片。
以金属锂作为负极，以微孔聚丙烯(Celgard2300)膜为隔膜，以1mol/l的LiPF6/EC+DEC+EMC(体积比为1:1:1)为电解液。
在充满高纯氩气的手套箱内，组装成CR2032扣式电池。静置12小时后进行电化学性能测试。
实施例2
制备多孔石墨烯钴酸锂复合材料：
配制200ml含0.1g多孔石墨烯的水溶液；在多孔石墨烯的水溶液中加入100g钴酸锂 粉末，在搅拌速度为360转/min的条件下搅拌120min；将反应后的混合溶液在出口温度为200℃、入料流量为800mL/min的条件下进行喷雾干燥。得到多孔石墨烯钴酸锂复合材料。
采用上述制备的多孔石墨烯钴酸锂复合材料作为锂离子电池正极活性材料制备锂离子电池：
以N-甲基吡咯烷酮为溶剂，按质量比80:10:10，将多孔石墨烯钴酸锂复合材料、导电剂炭黑和粘结剂聚偏氟乙稀混合，搅拌均匀成泥浆状涂覆于铝箔表面，然后真空干燥12小时，压片制成直径为10mm的正极片。
以金属锂作为负极，以微孔聚丙烯(Celgard2300)膜为隔膜，以1mol/L的LiPF6/EC+DEC+EMC(体积比为1:1:1)为电解液。
在充满高纯氩气的手套箱内，组装成CR2032扣式电池。静置12小时后进行电化学性能测试。
实施例3
制备多孔石墨烯钴酸锂复合材料：
配制200ml含0.002g多孔石墨烯的水溶液；在多孔石墨烯的水溶液中加入10g钴酸锂粉末，在搅拌速度为120转/min的条件下搅拌5min；将反应后的混合溶液在出口温度为150℃、入料流量为300mL/min的条件下进行喷雾干燥。得到多孔石墨烯钴酸锂复合材料。
采用上述制备的多孔石墨烯钴酸锂复合材料作为锂离子电池正极活性材料制备锂离子电池：
以N-甲基吡咯烷酮为溶剂，按质量比80:10:10，将多孔石墨烯钴酸锂复合材料、导电剂炭黑和粘结剂聚偏氟乙稀混合，搅拌均匀成泥浆状涂覆于铝箔表面，然后真空干燥12小时，压片制成直径为10mm的正极片。
以金属锂作为负极，以微孔聚丙烯(Celgard2300)膜为隔膜，以1mol/L的LiPF6/EC+DEC+EMC(体积比为1:1:1)为电解液。
在充满高纯氩气的手套箱内，组装成CR2032扣式电池。静置12小时后进行电化学性能测试。
对比例1：
以N-甲基吡咯烷酮为溶剂，按质量比80:10:10，将钴酸锂正极活性材料、导电剂炭黑和粘结剂聚偏氟乙稀混合，搅拌均匀成泥浆状涂覆于铝箔表面，然后真空干燥12小时，压片制成直径为10mm的正极片。
以金属锂作为负极，以微孔聚丙烯(Celgard2300)膜为隔膜，以1mol/L的LiPF6/EC+DEC+EMC(体积比为1:1:1)为电解液。
在充满高纯氩气的手套箱内，组装成CR2032扣式电池。静置12小时后进行电化学性能测试。
性能测试与结果：
(1)采用场发射扫描电镜(德国，Zeiss Ultra 55)，测试现有的钴酸锂正极活性材料与实施例1的多孔石墨烯钴酸锂复合材料的微观形貌，测试结果如图1和图2所示。
图1中的钴酸锂粉末与图2中的多孔石墨烯钴酸锂复合材料相比，在图2的多孔石墨烯钴酸锂复合材料表面，可明显观察到包覆于钴酸锂表面的单层石墨烯具有孔洞结构，且在钴酸锂粉末之间形成架桥连接，构成连续完整的三维导电结构，该结构能够有效的提高锂离子正极材料的导电性能。
(2)采用蓝电电池测试系统(中国，LAND CT-2001A)对实施例和对比例的锂离子 电池以不同充放电倍率(0.2C、0.5C、1C、2C、5C)，在2.5～4.6V电压范围内进行充放电性能测试。
对比例1的锂离子电池循环性能和倍率充放电性能测试结果如图3、图5所示，可以看出对比例1的锂离子电池在循环370次左右容量衰减严重，在0.2C和5C放电时的比容量分别约为140mAh/g和0mAh/g。
实施例1的锂离子电池循环性能和倍率充放电性能测试结果如图4、图6所示，可以看出实施例1的锂离子电池可稳定循环500次以上，在0.2C和5C放电时的比容量分别约为225.1mAh/g和85.6mAh/g。
实施例2的锂离子电池可稳定循环500次以上，在0.2C和5C放电时的比容量分别约为195.4mAh/g和87.3mAh/g。
实施例3的锂离子电池可稳定循环500次以上，在0.2C和5C放电时的比容量分别约为200.5mAh/g和77.1mAh/g。
本申请实施例与对比例1相比较，循环性能大幅提升，均能达到500次以上，小倍率放电性能和大倍率放电性能均得以改善。
本申请具有的有益效果在于：
(1)本申请的制备方法经一次操作即可在钴酸锂表面形成完整、连续且导电性良好的多孔石墨烯包覆层，工艺简单；
(2)在多孔石墨烯包覆层生成过程中无需添加有机溶剂、表面活性剂、还原剂、氧化剂等各类添加剂，生产成本低；
(3)本申请的制备方法将多孔石墨烯与钴酸锂的混合过程与高效的喷雾干燥技术巧妙结合，适于多孔石墨烯钴酸锂复合材料的大批量生产制造；
(4)本申请制备得到的锂离子电池具有优异的倍率放电性能和循环稳定性。
虽然本申请所揭露的实施方式如上，但所述的内容仅为便于理解本申请而采用的实施方式，并非用以限定本申请。任何本申请所属领域内的技术人员，在不脱离本申请所揭露的精神和范围的前提下，可以在实施的形式及细节上进行任何的修改与变化，但本申请的专利保护范围，仍须以所附的权利要求书所界定的范围为准。

Claims (10)

  1. 一种制备多孔石墨烯钴酸锂复合材料的方法，包括：配制多孔石墨烯的水溶液；向所述多孔石墨烯的水溶液中加入钴酸锂；混合均匀后进行喷雾干燥，得到所述复合材料。
  2. 根据权利要求1所述的方法，其中，所述多孔石墨烯与水的质量比为1×10 - 5:1～100×10 -5:1。
  3. 根据权利要求1或2所述的方法，其中，所述钴酸锂与所述多孔石墨烯的水溶液的质量比为0.01:1～0.5:1。
  4. 根据权利要求1或2所述的方法，其中，所述混合采用搅拌的方式，搅拌速度为120转/min～360转/min，搅拌时间为5min～120min。
  5. 根据权利要求1或2所述的方法，其中，在出口温度为150℃～200℃、入料流量为300mL/min～800mL/min的条件下进行所述喷雾干燥。
  6. 一种多孔石墨烯钴酸锂复合材料，所述复合材料通过权利要求1-5中任一项所述的方法制备得到。
  7. 根据权利要求6所述的复合材料，其具有连续的三维导电结构，其中，多孔石墨烯包覆于钴酸锂表面，并在所述钴酸锂之间形成架桥连接。
  8. 根据权利要求7所述的复合材料，其中，包覆在钴酸锂表面的多孔石墨烯为单层。
  9. 权利要求6-8中任一项所述的多孔石墨烯钴酸锂复合材料，作为锂离子电池正极活性材料的用途。
  10. 一种锂离子电池，所述锂离子电池的正极包括粘结剂、导电剂以及权利要求6-8中任一项所述的多孔石墨烯钴酸锂复合材料。
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