WO2019227703A1 - 表面具有锂层的隔膜及其制备方法和锂离子电池 - Google Patents

表面具有锂层的隔膜及其制备方法和锂离子电池 Download PDF

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WO2019227703A1
WO2019227703A1 PCT/CN2018/101934 CN2018101934W WO2019227703A1 WO 2019227703 A1 WO2019227703 A1 WO 2019227703A1 CN 2018101934 W CN2018101934 W CN 2018101934W WO 2019227703 A1 WO2019227703 A1 WO 2019227703A1
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lithium
separator
layer
coating
lithium layer
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PCT/CN2018/101934
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English (en)
French (fr)
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王亚龙
陈强
牟瀚波
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中能中科（天津）新能源科技有限公司
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Publication of WO2019227703A1 publication Critical patent/WO2019227703A1/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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • 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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/443—Particulate material
    • 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 invention relates to the technical field of electrochemical energy storage, in particular to a separator for a lithium ion battery, a preparation method thereof, and a corresponding lithium ion battery.
  • Lithium-ion batteries have become one of the most widely used secondary batteries due to their advantages of high voltage, high energy density, and long cycle life.
  • the energy density of lithium-ion batteries has been increasingly proposed.
  • High requirements For a lithium-ion battery, the active lithium of the positive electrode is consumed during the first charge and discharge process due to the formation of a solid electrolyte (SEI) film, which causes the first decrease in efficiency, and the loss of active lithium in the battery causes the battery capacity to decrease. This phenomenon is particularly apparent in a negative electrode using silicon as an active material.
  • SEI solid electrolyte
  • a lithium-containing composite separator can be used as one of the technical means to solve the above problems.
  • lithium-containing composite separators are mainly obtained by: directly spraying lithium powder on the separator and then cold-pressing to form a composite separator (dry method); coating the lithium powder with a slurry on the surface of the separator; and applying lithium tape and the separator Compounding together by cold pressing (lithium ribbon compounding); and compounding molten lithium and the separator together.
  • the slurry prepared from lithium powder can control the amount of metal lithium added, it needs to be mixed with an organic solvent during the operation, followed by coating, drying, and complicated procedures. Large amounts of organic solvents are used, which is not environmentally friendly. The thickness of the coating cannot be controlled very thin, and the liquid slurry can easily block the micropore structure of the separator, resulting in a large impedance of the assembled battery. The uniformity of the lithium powder distribution on the separator needs further evaluation.
  • an ultra-thin lithium band formed by melting a lithium ingot and covering the surface of a previously cooled separator, and then cooling the separator to allow the lithium metal to solidify has the disadvantage that the closed cell temperature of the separator itself is 130 ° C to 150 ° C, and The melting point of metallic lithium is 180 ° C.
  • the separator is pre-cooled, the instantaneous temperature at which the surface of the separator contacts the molten metallic lithium will reach 180 ° C, which will cause the separator to close its pores and the assembled battery cannot be used.
  • the main object of the present invention is to provide a separator having a lithium layer on the surface and a method for preparing the same, and a lithium ion battery using the separator, which can effectively provide a lithium supplement effect and has almost no disadvantages in the above methods.
  • a uniform ultra-thin lithium plating layer is formed on the surface of the separator by introducing a lithium-friendly compound or functional group on the surface of the separator and combining lithium deposition technology. At the same time, it will not block the micropores of the separator, and enhance the tensile strength of the separator, thereby significantly improving the performance of the lithium battery.
  • An aspect of the present invention provides a separator having a lithium layer on a surface, including: a separator; a lithium-friendly pretreatment layer on one surface of the separator; and a lithium layer deposited on the pretreatment layer.
  • Another aspect of the present invention provides a method for preparing a separator having a lithium layer on the surface, comprising: performing a modification treatment or a coating treatment on one surface of the separator to form a lithium-friendly pretreatment layer; and a physical deposition method Forming a lithium layer on the pre-treatment layer.
  • Another aspect of the present invention provides a lithium-ion battery including the above-mentioned separator having a lithium layer on the surface.
  • the ultra-thin lithium layer can be used for negative lithium replenishment to improve the first charge and discharge efficiency.
  • the ultra-thin lithium layer has a uniform distribution and a small thickness, and does not block the micropores of the separator.
  • the ultra-thin lithium layer enhances the transverse and longitudinal tensile strength of the separator.
  • the thickness of the ultra-thin lithium layer is adjustable, which can adapt to different application environments.
  • FIG. 1 is a schematic structural diagram of a separator having a lithium layer on a surface of the present invention
  • FIG. 2 is a schematic diagram of another structure of a separator having a lithium layer on the surface of the present invention.
  • FIG. 3 is a SEM comparison diagram of the membrane surface before and after pretreatment in Example 1 (A is an untreated SEM of the membrane surface; B is an SEM of the membrane surface pretreatment);
  • FIG. 4 is a SEM comparison diagram of the untreated separator and the surface-treated separator after lithium plating in Example 3 (A is a lithium-plated SEM without a pre-treatment on the surface of the separator layer; B is a plated coating after the surface treatment of the separator is performed) SEM of lithium).
  • One aspect of the present invention provides a separator having a lithium layer on the surface, wherein a lithium-friendly pretreatment layer is provided on one surface of the separator, and a lithium metal layer is deposited on the lithium-pretreatment layer.
  • the lithium-philic pre-treatment layer includes a lithium-philic compound or functional group.
  • the lithium-philic compound may include one or more of alumina, boehmite, tin oxide, polymelamine, polyacrylonitrile, and polyaniline.
  • the lithium-philic functional group may include a lithium-philic nitrogen-containing functional group and the like.
  • the lithium-friendly pretreatment layer may be formed by modifying the surface of the separator.
  • the modification treatment may include, for example, a plasma treatment and a corona treatment.
  • the lithium-friendly pretreatment layer may be a surface coating formed by coating inorganic particles and / or organic polymers.
  • the diaphragm includes a non-ceramic diaphragm and a ceramic diaphragm.
  • the non-ceramic diaphragm is composed of a diaphragm substrate alone, while the ceramic diaphragm is composed of a diaphragm substrate and a surface ceramic coating.
  • the material of the separator substrate includes one or more of polypropylene, polyethylene, polyvinylidene fluoride, polyester, polyimide, polyamide, cellulose, aramid, and spandex. Composite material. Its thickness can be 5-50 ⁇ m.
  • the thickness of the surface ceramic coating of the separator substrate may be 0.1-20 ⁇ m.
  • FIG. 1 is a schematic structural diagram of a separator having a lithium layer on the surface of the present invention.
  • a lithium-friendly pretreatment layer 2 is provided on one surface of the separator substrate 1, and a lithium metal layer 3 is formed on the pretreatment layer 2.
  • the pretreatment layer 2 can be formed by directly modifying the surface of the diaphragm.
  • FIG. 2 is a schematic diagram of another structure having a lithium layer on the surface of the present invention, wherein one surface of the separator substrate 1 has a coating layer 4 of a lithium-philic substance, and a metallic lithium layer 3 is formed on the surface of the coating layer 4, wherein The coating layer 4 can be formed by coating on the surface of the diaphragm.
  • the metal lithium layer is formed by a deposition method.
  • a deposition method due to the presence of a lithium-friendly layer in the pretreatment layer on the surface of the separator, metallic lithium is more easily combined and uniformly distributed on the surface of the separator to form a stable ultra-thin lithium layer.
  • the thickness of the lithium deposition layer may be 0.1-200 ⁇ m, such as 1-20 ⁇ m or 1-10 ⁇ m. It should be noted that the thickness of the lithium deposition layer is determined by the deposition time. Therefore, the thickness of the lithium deposition layer can be controlled by appropriately adjusting the deposition time.
  • Another aspect of the present invention provides a method for preparing a separator having a lithium layer on the surface, which includes: modifying or coating a surface of the separator to form a lithium-philic pretreatment layer, and by a physical deposition method, A lithium layer is formed on the pre-treatment layer.
  • lithium-friendly pretreatment layer refers to the related descriptions in the previous part, which will not be repeated here, and only the methods and process steps for forming the pretreatment layer and forming the lithium metal layer are performed. description.
  • the lithium-friendly pretreatment layer may be formed by subjecting a separator substrate or a ceramic coating of the separator to a surface modification treatment.
  • the surface modification treatment may include a corona method or a plasma method. This treatment may be performed in an atmosphere of a reactive gas to form lithium-philic functional groups on the treated surface.
  • plasma surface treatment is performed using compressed nitrogen as the working gas.
  • the conditions of the plasma treatment may be as follows: using compressed nitrogen as the working gas (pressure range is 0-1 MPa), voltage is 1-10 kV, and speed is 1-50 m / min.
  • the lithium-friendly pretreatment layer may be formed by performing a coating treatment on the surface of the separator.
  • a zinc oxide inorganic nanoparticle layer is coated on one surface of the separator, and the thickness may be 5 ⁇ m.
  • the metal lithium layer on the pre-treatment layer is formed by a physical deposition method, and the physical deposition method may include evaporation or magnetron sputtering.
  • a metal lithium layer is formed by an evaporation method, and the conditions for evaporation can be as follows: the arc current of the evaporated lithium is 10-150A, the temperature is 100-500 ° C, and the vacuum pressure is 10-1-10-4Pa The plating time is 1min-500min.
  • the present invention can achieve a uniformly distributed ultra-thin lithium layer.
  • the ultra-thin lithium layer can be supplemented with lithium at the negative electrode to improve the first charge and discharge efficiency; moreover, the ultra-thin lithium layer is distributed Uniform and small thickness, although it enhances the transverse and longitudinal tensile strength of the diaphragm, but does not block the micropores of the diaphragm.
  • Another aspect of the present invention provides a lithium-ion battery including the above-mentioned separator having a lithium layer on a surface thereof.
  • the lithium ion battery includes a positive electrode, an electrolytic solution, a negative electrode, and a separator having a lithium layer on a surface between the positive electrode and the negative electrode, wherein the surface lithium layer faces the negative electrode.
  • the active material of the negative electrode is a material obtained by mixing one or two or more of graphite-based, silicon-based materials, and other negative-electrode materials.
  • the electrolyte includes EC (ethylene carbonate), DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), PC (propylene carbonate), DOL (dimethoxyethane), DME (Dioxolane), LiPF 6 (lithium hexafluorophosphate), LiTFSI (lithium bistrifluorosulfonate).
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • PC propylene carbonate
  • DOL diimethoxyethane
  • DME Dioxolane
  • LiPF 6 lithium hexafluorophosphate
  • LiTFSI lithium bistrifluorosulfonate
  • the lithium ion battery of the present invention uses a separator having a lithium layer on its surface, the first charge and discharge efficiency is significantly improved.
  • Polypropylene microporous film (Celgard 2500) was selected as the lithium-plated substrate.
  • the pre-lithium-plated surface was subjected to plasma surface pretreatment in a nitrogen environment.
  • the voltage was 5 kV
  • the current was 2 mA
  • the speed was 20 m / min.
  • Nitrogen-containing functional groups were introduced.
  • the XPS test was performed on the treated diaphragm.
  • the treated diaphragm was fixed on a sample holder of a vacuum coating machine (Shenyang Scientific Instrument Co., Ltd., Chinese Academy of Sciences, RH400 thermal evaporation vacuum coating equipment), and a high-purity lithium foil was selected as an evaporation source.
  • the arc current of the evaporated lithium was 120A.
  • the temperature was 600 ° C.
  • the vacuum pressure was 10 -2
  • the evaporation time was 60 min
  • the lithium plating thickness was 2 ⁇ m.
  • a single-sided lithium-plated separator was prepared. The separator was tested for tensile strength in the horizontal and vertical directions. Combine this separator with LiFePO 4 (lithium iron phosphate positive electrode sheet, Suzhou Nano New Energy Technology Co., Ltd., areal density 6.7 mg / cm2, lithium nickel cobalt manganate content is 90%), graphite negative electrode (Suzhou Na New Energy Technology Co., Ltd.
  • the separator was selected from polyethylene (Shanghai Liangneng New Material Technology Development Co., Ltd. 2000), alumina (Aladdin Reagent Co., Ltd. A102091) was used to coat the surface of the separator, and the treated separator was subjected to XPS test.
  • the treated diaphragm was fixed on the sample holder of a vacuum coating machine (Shenyang Scientific Instrument Co., Ltd., Chinese Academy of Sciences, RH400 thermal evaporation vacuum coating equipment), and a high-purity lithium foil was selected as the evaporation source.
  • the arc current of the evaporated lithium was 100A.
  • the temperature is 750 ° C
  • the vacuum pressure is 10 -3 Pa
  • the evaporation time is 120 minutes
  • the lithium plating thickness is 3 ⁇ m
  • a 3 ⁇ m lithium layer is plated on one side of the treated diaphragm; the diaphragm is subjected to lateral and longitudinal tensile strength. Strength test.
  • LiNi 5 Mn 3 Co 2 O 2 lithium nickel cobalt manganate cathode sheet, Suzhou Naxin Energy Technology Co., Ltd., areal density 14 mg / cm2, lithium nickel cobalt manganate content 90%
  • silicon carbon Composite negative electrode Sizhou Nano New Energy Technology Co., Ltd., areal density 5 mg / cm2, silicon carbon active material content is 90%
  • LiPF6, EC / DMC Handong Hairong Electrolyte Co., Ltd.
  • the lithium-plated layer is opposite to the negative electrode, and the first charging efficiency test is performed after the electrolyte is left for 24 hours after the injection.
  • the separator substrate was polypropylene (Cangzhou Mingzhu Plastics Co., Ltd. ND1637), and the solution was coated with N, N-dimethylformamide (Aladdin Reagent Co., Ltd. D112004) of polyacrylonitrile (Sigma-Aldrich GF18031711-1EA). Apply on the diaphragm surface.
  • the treated diaphragm was fixed on the sample holder of a vacuum coating machine (Shenyang Scientific Instrument Co., Ltd., Chinese Academy of Sciences, RH400 thermal evaporation vacuum coating equipment), and a high-purity lithium foil was selected as the evaporation source.
  • the arc current of the evaporated lithium was 100A.
  • the temperature is 750 ° C
  • the vacuum pressure is 10 -3 Pa
  • the evaporation time is 60 minutes
  • the lithium plating thickness is 1.5 ⁇ m
  • a 1.5 ⁇ m lithium layer is plated on one side of the treated separator.
  • LiMnFePO 4 lithium manganese iron phosphate positive electrode sheet, Suzhou Nano New Energy Technology Co., Ltd., areal density 10 mg / cm2, lithium manganese iron phosphate content 90%), silicon-carbon composite negative electrode (Suzhou Nano New Energy Technology Co., Ltd., with an areal density of 4 mg / cm2 and a silicon carbon active material content of 90%).
  • LiPF6, EC / DMC (Shandong Hairong Electrolyte Co., Ltd.) is used as the electrolyte to form a lithium ion battery.
  • the first charging efficiency test was performed after the electrolyte was left standing for 12 hours. Its first efficiency is significantly higher than the first charge and discharge efficiency of the battery in Comparative Example 3.
  • Example 1 Like the electrode material used in Example 1, a polypropylene microporous separator, a lithium iron phosphate positive electrode, a graphite negative electrode, LiPF6, and an EC / DMC commercial lithium-ion battery electrolyte were used to form a lithium-ion battery; the electrolyte was left to stand for 24 hours after the injection. After that, the first charging efficiency test was performed, and the diaphragm was subjected to the XPS test, and the transverse and longitudinal tensile strength of the diaphragm were also tested at the same time.
  • a polyethylene-based separator was selected, a nickel-cobalt lithium manganate positive electrode, a silicon carbon negative electrode, LiPF6, and an EC / DMC commercial lithium-ion battery electrolyte were used to form a lithium-ion battery; electrolysis was finished After the liquid was left to stand for 24 hours, the first charging efficiency test was performed. The separator was subjected to an XPS test, and the lateral and longitudinal tensile strength of the separator was also tested.
  • Example 3 Consistent with the electrode material used in Example 3, a polypropylene-based separator was selected, a lithium manganese iron phosphate positive electrode, a silicon carbon negative electrode, LiPF6, and an EC / DMC commercial lithium-ion battery electrolyte constituted a lithium-ion battery; after the injection was completed, , Let stand for 20 hours to test the first charge and discharge efficiency.
  • the XPS test is as follows:
  • Example 1 the surface of the separator was flat after being pretreated, and the surface without the pretreatment was rough.
  • FIG. 4 in Example 3, it can be seen from the SEM of the single side of the separator that is untreated and lithium plated after the single side treatment. After the pretreatment of the single side of the separator, the lithium-plated surface is flat and the particles are complete without being treated. The lithium-plated surface of the separator is uneven, and there are also large gaps between the particles. This indicates that the pre-treated separator has lithium affinity, which is conducive to the deposition of lithium and makes the surface smooth after deposition.

Abstract

公开了一种表面具有锂层的隔膜及其制备方法和锂离子电池。本发明的表面具有锂层的隔膜包括：隔膜；位于隔膜的一个表面上的亲锂的预处理层；以及沉积在所述预处理层上的锂层。通过在隔膜表面引入亲锂的化合物或官能团，并且结合锂沉积技术，在隔膜表面形成了均匀的超薄镀锂层，该超薄镀锂层能够有效地起到补锂效果，同时不会堵塞隔膜的微孔，且增强了隔膜的拉伸强度，从而显著提高锂电池性能。

Description

表面具有锂层的隔膜及其制备方法和锂离子电池 技术领域
本发明涉及电化学储能技术领域，特别涉及用于锂离子电池的隔膜及其制备方法和相应的锂离子电池。
背景技术
锂离子电池由于具有高电压、高能量密度和长循环寿命的优势，成为应用范围最广的二次电池之一。但随着便携式电子设备微型化、长待机的不断发展，以及电动自行车、电动汽车等大功率、高能量设备的启用，都对作为储能电源的锂离子电池的能量密度的提出了越来越高的要求。对于锂离子电池而言，在首次充放电过程中都会因固态电解质(SEI)膜的生成而消耗正极的活性锂，造成首次效率的降低，而电池中活性锂损失导致电池容量下降。这种现象在以硅为活性物质的负极中尤为明显。
含锂的复合隔膜可以作为解决上述问题的技术手段之一。目前，主要通过以下方法获得含锂的复合隔膜：将锂粉直接撒在隔膜上然后冷压形成复合隔膜(干法)；将锂粉制成浆料涂覆在隔膜表面；将锂带和隔膜通过冷压的方法复合在一起(锂带复合)；以及将熔融状态的锂和隔膜复合在一起。
但是，申请人发现这些方法存在以下不足：第一，锂带复合技术很难精确控制复合在隔膜上的金属锂的含量，其锂金属处在一个过量的状态，一部分锂作为补锂使用，而多余的锂会作为锂离子成核位点，导致析锂，产生锂枝晶。第二，将金属锂粉撒在隔膜表面，然后进行冷压复合，虽然也可制得复合隔膜，但锂粉比表面积大，活性高，整个操作过程需要在干燥环境下进行，对环境要求苛刻。第三，采用锂粉制备成浆料虽然可以控制金属锂的添加量，但是操作过程中需要采用有机溶剂进行混浆，之后涂膜，烘干，工序繁琐，大量使用有机溶剂，不环保，同时，涂布的厚度也无法控制的很薄，液态的浆料也很容易堵塞隔膜的微孔结构，造成所组装的电池阻抗大，锂粉在隔膜上分布的均匀性需要进一步评估。第四，采用锂锭熔融后覆在预先冷却的隔膜表面，然后再对隔膜降温后使得锂金属凝固形成的超薄锂带，其缺点在于隔膜本身的闭孔温度为130℃-150℃，而金属锂的熔点为180℃，尽管对隔膜有预先冷却，但隔膜表层接触到熔融金属锂的的瞬间温度也会达到180℃，从而造成隔膜闭孔，其所组装的电池无法使用。
发明内容
本发明的主要目的在于提供一种表面具有锂层的隔膜及其制备方法，以及使用该隔膜的锂离子电池，其能够有效地提供补锂效果且几乎不存在上述方法中的不足之处。
具体而言，本发明通过在隔膜表面引入亲锂的化合物或官能团，并且结合锂沉积技术，在隔膜表面形成均匀的超薄镀锂层，该超薄镀锂层能够有效地起到补锂效果，同时不会堵塞隔膜的微孔，且增强隔膜的拉伸强度，从而显著提高锂电池的性能。
本发明采用如下技术方案：
本发明的一个方面提供一种表面具有锂层的隔膜，包括：隔膜；位于隔膜的一个表面上的亲锂的预处理层；以及沉积在所述预处理层上的锂层。
本发明的另一个方面提供一种制备上述表面具有锂层的隔膜的方法，包括：对隔膜的一个表面进行改性处理或涂覆处理以形成的亲锂的预处理层；和通过物理沉积方法，在所述预处理层上形成锂层。
本发明的再一个方面提供一种锂离子电池，其包含上述的表面具有锂层的隔膜。
本发明可以具有以下有益效果中的至少一种：
(1)通过在隔膜表面形成亲锂的预处理层与锂沉积技术的结合，实现了均匀分布的超薄锂层，该超薄锂层可以负极进行补锂，提高首次充放电效率。
(2)超薄锂层分布均匀且厚度小，不堵塞隔膜的微孔。
(3)超薄锂层增强了隔膜的横向以及纵向的拉伸强度。
(4)超薄锂层的厚度可调，可适应不同的应用环境。
(5)对隔膜基材的材料和厚度没有限制，适用范围广
附图说明
图1为本发明的表面具有锂层的隔膜的一种结构示意图；
图2为本发明的表面具有锂层的隔膜的另一种结构示意图；
图3为实施例1中隔膜表面预处理前后的SEM对比图(A为隔膜表面未预处理的SEM；B为隔膜表层预处理后的SEM)；
图4为实施例3中未进行预处理的隔膜和经表面预处理的隔膜在镀锂后的SEM对比图(A为隔膜层表面未预处理的镀锂SEM；B为隔膜表层预处理后镀锂的SEM)。
具体实施方式
本发明的一个方面提供一种表面具有锂层的隔膜，其中在隔膜的一个表面具有亲锂的预处理层，并且在该亲锂的预处理层上具有沉积的金属锂层。
在一些实施例中，亲锂的预处理层包含亲锂的化合物或官能团。例如，亲锂的化合物可以包括氧化铝、勃姆石、氧化锡、聚三聚氰胺、聚丙烯腈，聚苯胺中的一种或几种。亲锂的官能团可以包括亲锂的含氮官能团等。
在一些实施例中，亲锂的预处理层可以通过对所述隔膜表面进行改性处理而形成。所述改性处理可以包括，例如，等离子体处理和电晕处理。
在一些实施例中，亲锂的预处理层可以为通过涂覆无机颗粒和/或有机聚合物而形成的表面涂层。
在一些实施例中，隔膜包括非陶瓷隔膜和陶瓷隔膜。非陶瓷隔膜由隔膜基材单独构成，而陶瓷隔膜由隔膜基材和表面陶瓷涂层构成。
在一些实施例中，隔膜基材的材料包括聚丙烯、聚乙烯、聚偏氟乙烯、聚酯、聚酰亚胺、聚酰胺、纤维素、芳纶、氨纶中的一种或两种以上的复合材料。其厚度可以为5-50μm。
在一些实施例中，隔膜基材的表面陶瓷涂层的厚度可以为0.1-20μm。
图1为本发明的表面具有锂层的隔膜的一种结构示意图，其中在隔膜基材1的一个表面上具有亲锂的预处理层2，在预处理层2上形成金属锂层3。其中，预处理层2可以通过对隔膜表面直接进行改性处理而形成.
图2为本发明的表面具有锂层的另一种结构示意图，其中隔膜基材1的一个表面上具有亲锂的物质的涂层4，在涂层4的表面上形成金属锂层3，其中，涂层4可以通过在隔膜表面涂敷形成。
在一些实施例中，金属锂层是通过沉积方法形成的。在沉积过程中，由于隔膜表面的预处理层中存在亲锂层，金属锂更容易结合和均匀分布在隔膜表面上，形成稳定的超薄锂层。例如锂沉积层的厚度可以为0.1-200μm，例如1-20μm或1-10μm。需要说明的是，锂沉积层的厚度是由沉积时间决定的，因此，可以通过适当调节沉积时间来控制锂沉积层的厚度。
本发明的另一个方面提供制备上述表面具有锂层的隔膜的方法，包括：对隔膜的一个表面进行改性处理或涂覆处理以形成的亲锂的预处理层，和通过物理沉积方法，在所述预处理层上形成锂层。
关于“隔膜”、“亲锂的预处理层”和“金属锂层”，参见前述部分的相关描述，此处不再赘述，仅对形成预处理层和形成金属锂层的方法和工艺步骤进行描述。
在一些实施例中，亲锂的预处理层可以通过对隔膜基材或隔膜的陶瓷涂层进行表面改性处理而形成。在一些实施例中，表面改性处理可以包括电晕法或等离子法。该处理可以在反应性气体的气氛中进行，以在处理的表面上形成亲锂的官能团。例如，采用压缩氮气作为工作气体进行等离子表面处理。
在一些实施例中，等离子处理的条件可以如下：采用压缩氮气作为工作气体(压力范围为0-1MPa)，电压为1-10kV，速度为1-50m/min。
在一些实施例中，亲锂的预处理层可以通过隔膜表面进行涂覆处理而形成。
在一些实施例中，在隔膜的一个表面涂敷氧化锌无机纳米颗粒层，其厚度可以为5μm。
在预处理层上的金属锂层通过物理沉积方法形成，物理沉积方法可以包括蒸镀或磁控溅射等。
在一些实施例中，采用蒸镀法形成金属锂层，蒸镀的条件可以如下：蒸发锂的弧电流为10-150A，温度为100-500℃，真空压力为10-1-10-4Pa蒸镀时间为1min-500min。
通过物理沉积锂层与隔膜表面预处理相结合，本发明可以实现了均匀分布的超薄锂层，该超薄锂层可以负极进行补锂，提高首次充放电效率；而且，超薄锂层分布均匀且厚度小，虽增强了隔膜的横向以及纵向的拉伸强度但不堵塞隔膜的微孔。
本发明的再一个方面提供一种锂离子电池，所述锂离子电池包括上述的表面具有锂层的隔膜。
在一些实施例中，锂离子电池包括正极、电解液、负极，以及位于正负极之间的表面具有锂层的隔膜，其中表面锂层面对负极。
在一些实施例中，正极的的活性物质材料是LiFePO 4(磷酸铁锂)、LiMn 2O 2(锰酸锂)、LiNi xCo yMn zO 2(镍钴锰酸锂)，LiNi xCo yAl zO 2(镍钴铝酸锂)(0＜x、y、z＜1，x+y+z＝1＝中的一种，或由两种以上混合形成。
在一些实施例中，负极的活性物质为石墨类、硅类材料以及其他负极材料中的一种或两种以上混合而成的材料。
在一些实施例中，电解液包括EC(碳酸乙烯酯)，DMC(碳酸二甲酯)，EMC(碳酸甲乙酯)，PC(碳酸丙烯酯)，DOL(二甲氧基乙烷)，DME(二氧戊环)，LiPF 6(六氟磷酸锂)，LiTFSI(双三氟磺酸亚氨基锂)。
本发明的锂离子电池，由于采用了表面具有锂层的隔膜，首次充放电效率显著提高。
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合实施例和对比例对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。此外，下面所描述的本发明各个实施方式中所涉及到的技术特征只要彼此之间未构成冲突就可以相互组合。
又及，在如下实施例之中所采用的各种产品结构参数、各种反应参与物及工艺条件均是较为典型的范例，但经过本案发明人大量试验验证，于上文所列出的其它不同结构参数、其它类型的反应参与物及其它工艺条件也均是适用的，并也均可达成本发明所声称的技术效果。
实施例1
选择聚丙烯微孔薄膜(Celgard 2500)作为镀锂的基材，预镀锂面在氮气环境下进行等离子表面预处理，电压为5kV，电流为2mA，速度为20m/min，引入含氮的官能团，将处理过的隔膜进行XPS测试。将处理后的隔膜固定在真空镀膜机(中国科学院沈阳科学仪器股份有限公司，RH400热蒸发真空镀膜设备)的样品架上，选择高纯度的锂箔作为蒸发源，蒸发锂的弧电流为120A，温度为600℃，真空压力为10 -2，蒸镀时间为60min，镀锂厚度为2μm，制得一种表面单面镀锂的隔膜，对此隔膜进行横向以及纵向的抗拉强度的测试。将此隔膜与LiFePO 4(磷酸铁锂正极片，苏州纳新能源科技有限公司，面密度6.7毫克/平方厘米，镍钴锰酸锂含量为90％)、石墨负极(苏州纳新能源科技 有限公司，面密度2.5毫克/平方厘米，硅碳活性物质含量为90％)，采用LiPF6,EC/DMC(山东海容电解液有限公司)为电解液组成锂离子电池，其中，镀锂层面对负极，注完电解液静置24小时后进行首次充电效率的测试。
实施例2
选择隔膜基材为聚乙烯(上海量能新材料科技发展有限公司2000)、采用氧化铝(阿拉丁试剂有限公司A102091)涂敷在隔膜表面，将处理过的隔膜进行XPS测试。将处理后的隔膜固定在真空镀膜机(中国科学院沈阳科学仪器股份有限公司，RH400热蒸发真空镀膜设备)的样品架上，选择高纯度的锂箔作为蒸发源，蒸发锂的弧电流为100A，温度为750℃，真空压力为10 -3Pa，蒸镀时间为120min，镀锂厚度为3μm，在处理好的隔膜单面镀一层3μm的锂层；对此隔膜进行横向以及纵向的抗拉强度的测试。将此隔膜与LiNi 5Mn 3Co 2O 2(镍钴锰酸锂正极片，苏州纳新能源科技有限公司，面密度14毫克/平方厘米，镍钴锰酸锂含量为90％)、硅碳复合负极(苏州纳新能源科技有限公司，面密度5毫克/平方厘米，硅碳活性物质含量为90％)，采用LiPF6,EC/DMC(山东海容电解液有限公司)为电解液组成锂离子电池，其中，镀锂层面对负极，注完电解液静置24小时后进行首次充电效率的测试。
实施例3
选择隔膜基材为聚丙烯(沧州明珠塑料股份有限公司ND1637)，采用聚丙烯腈(Sigma-Aldrich GF18031711-1EA)的N,N-二甲基甲酰胺(阿拉丁试剂有限公司D112004)的溶液涂敷在隔膜表面。将处理后的隔膜固定在真空镀膜机(中国科学院沈阳科学仪器股份有限公司，RH400热蒸发真空镀膜设备)的样品架上，选择高纯度的锂箔作为蒸发源，蒸发锂的弧电流为100A，温度为750℃，真空压力为10 -3Pa，蒸镀时间为60min，镀锂厚度为1.5μm，在处理好的隔膜单面镀一层1.5μm的锂层。将此隔膜与LiMnFePO 4(磷酸锰铁锂正极片，苏州纳新能源科技有限公司，面密度10毫克/平方厘米，磷酸锰铁锂含量为90％)、硅碳复合负极(苏州纳新能源科技有限公司，面密度4毫克/平方厘米，硅碳活性物质含量为90％)，采用LiPF6,EC/DMC(山东海容电解液有限公司)为电解液组成锂离子电池，其中，镀锂层面对负极，注完电解液静置12小时后进行首次充电效率的测试。其首次效率要明显高于对比例3中的电池首次充放电效率。
对比例1
与实施例1中采用的电极材料一样，将聚丙烯微孔隔膜、磷酸铁锂正极、石墨负极、LiPF6,EC/DMC商用锂离子电池电解液组成锂离子电池；注完电解液静置24小时后进行首次充电效率的测试，对隔膜进行XPS测试，同时测试隔膜的横向以及纵向抗拉强度。
对比例2
与实施例2中采用的电极材料一致，选择基材为聚乙烯的隔膜，镍钴锰酸锂正极、硅碳负极、LiPF6,EC/DMC商用锂离子电池电解液组成锂离子电池；注完电解液静置24小时后进行首次充电效率的测试，对隔膜进行XPS测试，同时测试隔膜的横向以及纵向抗拉强度。
对比例3
与实施例3中采用的电极材料一致，选择基材为聚丙烯的隔膜，磷酸锰铁锂正极、硅碳负极、LiPF6，EC/DMC商用锂离子电池电解液组成锂离子电池；注液完成之后，搁置20小时，进行首次充放电效率的测试。
XPS测试如下：
Figure PCTCN2018101934-appb-000001
其他测试数据如下表所示：
Figure PCTCN2018101934-appb-000002
Figure PCTCN2018101934-appb-000003
如图3所示，实施例1中隔膜经过预处理后表面平整，而未经预处理的表面粗糙不平。如图4所示，实施例3中通过隔膜单面未处理和单面处理后镀锂的SEM中可以看出，隔膜单面经过预处理后，镀锂表面平整，颗粒完整，而未经处理的隔膜镀锂表面不平，颗粒与颗粒之间也存在较大缝隙，这说明经过预处理后的隔膜具有了亲锂性，有利于锂的沉积，使得沉积后的表面平整。通过XPS测试数据可以看出，比较实施例1和对比例1，经过表面改性处理后的隔膜中N元素的含量显著增加；对比实施例2和对比例2，隔膜表面经过氧化铝的涂敷，Al元素的含量明显变多。通过其他测试数据也可看出，隔膜表面镀锂以后，在抗拉强度以及首次充放电效率上均有显著改善。
应当理解，以上实施例所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种表面具有锂层的隔膜，包括：
    隔膜；
    位于隔膜的一个表面上的亲锂的预处理层；以及
    沉积在所述预处理层上的锂层。
  2. 如权利要求1所述的表面具有锂层的隔膜，其特征在于，所述预处理层包含亲锂的化合物或官能团。
  3. 如权利要求1和2所述的表面具有锂层的隔膜，其特征在于，所述隔膜的材料包括聚丙烯、聚乙烯、聚偏氟乙烯、聚酯、聚酰亚胺、聚酰胺、纤维素、芳纶、氨纶中的一种或两种以上的复合材料，任选地，隔膜材料表面具有陶瓷涂层。
  4. 如权利要求3所述的表面具有锂层的隔膜，其特征在于，隔膜基材的厚度为5-50μm；表面陶瓷涂层的厚度为0.1-20μm。
  5. 如权利要求1所述的表面具有锂层的隔膜，其特征在于，所述预处理层通过对所述隔膜表面进行改性处理而形成，或者为通过涂覆无机颗粒和/或有机聚合物而形成的表面涂层。
  6. 如权利要求5所述的表面具有锂层的隔膜，其特征在于，所述表面涂层包含氧化铝、勃姆石、氧化锡、聚三聚氰胺、聚丙烯腈，聚苯胺中的一种或几种的混合物。
  7. 如权利要求1所述的表面具有锂层的隔膜，其特征在于，所述锂层的厚度为0.1-200μm。
  8. 一种制备如权利要求1-7中任一项所述的表面具有锂层的隔膜的方法，包括：
    对隔膜的一个表面进行改性处理或涂覆处理以形成的亲锂的预处理层；
    通过物理沉积方法，在所述预处理层上形成锂层。
  9. 如权利要求7所述的方法，其特征在于，所述改性处理包括电晕法或等离子法；所述涂覆处理包括涂覆无机颗粒和/或有机聚合物的涂层；所述物理沉积方法包括蒸镀或磁控溅射。
  10. 一种锂离子电池，其包含如权利要求1-7中任一项所述的表面具有锂层的隔膜。
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