WO2020134765A1 - 一种降低锂离子电池阻抗的负极片及其制备方法 - Google Patents

一种降低锂离子电池阻抗的负极片及其制备方法 Download PDF

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WO2020134765A1
WO2020134765A1 PCT/CN2019/120268 CN2019120268W WO2020134765A1 WO 2020134765 A1 WO2020134765 A1 WO 2020134765A1 CN 2019120268 W CN2019120268 W CN 2019120268W WO 2020134765 A1 WO2020134765 A1 WO 2020134765A1
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negative electrode
lithium
conductive
electrode sheet
lithium ion
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PCT/CN2019/120268
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English (en)
French (fr)
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颜世银
徐延铭
李素丽
李俊义
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珠海冠宇电池有限公司
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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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • 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 application belongs to the technical field of lithium ion batteries, and particularly relates to a negative electrode sheet for reducing the impedance of lithium ion batteries and a preparation method thereof.
  • lithium-ion battery As a new type of high-energy battery, lithium-ion battery has made important progress in its research and development in recent years. As people pay more attention to environmentally friendly industries, electric vehicles are more and more popular, and the state has issued various forms of policies to subsidize and support the electric vehicle industry. Therefore, higher requirements are put forward for power batteries, and one of the indicators is the battery impedance requirements.
  • the prior art generally reduces the impedance by increasing the thickness of the current collector or modifying the current collector.
  • the invention patent application with publication number CN108598361A uses a plating method to form a copper-tin alloy plating layer on the surface of the current collector, which can be effectively improved
  • the dynamic performance of the pole piece relieves the expansion of the pole piece, and the improvement range of the battery impedance is limited.
  • the impedance of the lithium-ion battery can be reduced, but a large part of the energy density is sacrificed, and its practicality is limited.
  • the purpose of this application is to solve the problems of the existing battery with high impedance, large temperature rise, and poor kinetics, and to provide a negative electrode sheet for reducing the impedance of a lithium ion battery and a preparation method thereof.
  • This method can reduce the internal resistance of the negative electrode sheet.
  • the overall internal resistance of the battery is reduced, the temperature rise of the battery charge and discharge is reduced, the cycle performance of the lithium ion battery is improved, and the efficiency of the first charge and discharge of the battery is improved, thereby increasing the volumetric energy density of the battery.
  • a negative electrode sheet for reducing the impedance of a lithium ion battery includes a current collector, a conductive layer and a negative electrode layer, a surface of the current collector is provided with a conductive layer, and a surface of the conductive layer is provided with a negative electrode layer;
  • the conductive layer includes lithium carboxymethyl cellulose.
  • the current collector is copper foil.
  • the copper foil is selected from one of porous copper foil and etched copper foil.
  • the thickness of the current collector is less than 25 ⁇ m.
  • the thickness of the conductive layer is 0.2-3 ⁇ m.
  • the preparation method of the conductive layer is as follows: mixing and stirring lithium carboxymethyl cellulose, a conductive agent, a binder, and a solvent to obtain a conductive slurry, and uniformly coating the conductive slurry on the surface of the current collector side, Vacuum baking to obtain a conductive layer.
  • the thickness of the negative electrode layer is 10-200 ⁇ m.
  • lithium carboxymethyl cellulose is added to the negative electrode layer, and the content of the lithium carboxymethyl cellulose in the negative electrode layer is 0.05 wt.% to 5 wt.%.
  • a method for preparing the above negative electrode sheet the method steps are as follows: mixing and stirring lithium carboxymethyl cellulose, a conductive agent, a binder and a solvent to obtain a solid content of 10% to 50% and a viscosity of less than 2000 mPa.s Conductive paste, uniformly apply the conductive paste to the surface of the current collector side, and vacuum-bake to obtain a conductive layer; stir the negative electrode slurry to make it fully mixed, and then coat the surface of the conductive layer to obtain the negative electrode layer. Vacuum baking, the negative electrode is prepared.
  • a lithium ion battery includes a positive electrode sheet of a lithium ion battery and any negative electrode sheet described above.
  • the conductive layer of the present application can increase the conductivity of the negative electrode sheet and reduce the impedance; on the other hand, it can increase the adhesion of the negative electrode and reduce the expansion of the pole piece.
  • the cellulose-based lithium provides a certain source of lithium for the negative electrode and improves the first formation efficiency of the battery.
  • the negative electrode layer on the surface of the conductive layer uses lithium carboxymethyl cellulose instead of the traditional sodium carboxymethyl cellulose as a thickener, which greatly reduces the impedance of the pole piece and greatly improves the battery cycle.
  • the preparation method of the negative plate of the lithium ion battery of the present application is simple, the effect is remarkable, and the performance of the battery is effectively improved.
  • FIG. 1 is a schematic diagram of the structure of a negative plate for reducing the impedance of a lithium ion battery in this application;
  • FIG. 3 is a graph of the cycle performance of the batteries of Comparative Example 2 and Examples 6 to 7 of the present application at 25°C.
  • the reagents, materials, and instruments used in the following descriptions are all conventional reagents, conventional materials, and conventional instruments, which are all commercially available.
  • the reagents involved can also be synthesized by conventional synthesis methods.
  • FIG. 1 is a schematic diagram of the structure of a negative plate for reducing the impedance of a lithium-ion battery according to the present application. As shown in FIG. 1, this embodiment describes a negative plate for reducing the impedance of a lithium-ion battery. Fluid 1, conductive layer 2 and negative electrode layer 3, a conductive layer 2 is provided on one surface of the current collector 1, and a negative electrode layer 3 is provided on the surface of the conductive layer 2; the conductive layer includes lithium carboxymethyl cellulose .
  • the conductive layer 2 is a coating containing a conductive material, which includes lithium carboxymethyl cellulose, which is used as a thickener and has a certain adhesiveness.
  • the negative electrode sheet for reducing the impedance of a lithium ion battery as described in specific embodiment one the current collector 1 is a copper foil.
  • Embodiment 3 The negative electrode sheet for reducing the impedance of a lithium ion battery as described in Embodiment 2, wherein the copper foil is selected from one of porous copper foil and etched copper foil.
  • Embodiment 4 The negative electrode sheet for reducing the impedance of a lithium ion battery according to any one of Embodiments 1 to 3, the thickness of the current collector 1 is set from the viewpoint of energy density, and is less than 25 ⁇ m.
  • Embodiment 5 The negative electrode sheet for reducing the impedance of a lithium ion battery as described in Embodiment 1, the thickness of the conductive layer 2 is 0.2 to 3 ⁇ m.
  • Embodiment 6 A negative electrode sheet for reducing the impedance of a lithium ion battery as described in Embodiment 1 or 5, the preparation method of the conductive layer 2 is as follows: the lithium carboxymethyl cellulose, a conductive agent, a binder and The solvent is mixed and stirred in the planetary stirring tank for 5 to 8 hours to make it fully mixed to obtain the conductive slurry. The conductive slurry is evenly coated on the surface of the current collector 1 side, and vacuum baked in a vacuum drying box at 85 °C for 4h-8h to obtain Conductive layer 2.
  • the role of the conductive agent is to increase the conductivity of the pole piece.
  • Lithium carboxymethyl cellulose can improve the lithium ion transmission efficiency, reduce the impedance, and can provide a small amount of lithium source, reducing the loss of irreversible lithium during the battery charge and discharge process, thereby improving the battery for the first time.
  • the conductive agent includes but is not limited to superP, carbon nanotubes, carbon black and other conductive substances.
  • the lithium carboxymethyl cellulose replaces the traditional sodium carboxymethyl cellulose and is used as a thickener for conductive paste and negative electrode paste, which can reduce the overall impedance of the pole piece and improve the lithium ion transmission efficiency.
  • the content of lithium carboxymethyl cellulose is 0.1 wt.% to 10 wt.%
  • the content of the conductive agent is 50 wt.% to 75 wt.%
  • the content of the binder is 20 wt.% to 40 wt.%.
  • the viscosity of the conductive paste is less than 2000 mPa.s, and the solid content of the paste is 10% to 50%. Specifically, it is adjusted by a solvent.
  • Embodiment 7 The negative electrode sheet for reducing the impedance of a lithium ion battery as described in Embodiment 1, wherein the thickness of the negative electrode layer 3 is 10 to 200 ⁇ m.
  • Embodiment 8 A negative electrode sheet for reducing the impedance of a lithium ion battery as described in Embodiment 1 or 7, wherein lithium carboxymethyl cellulose is added to the negative electrode layer 3, and lithium carboxymethyl cellulose is added to the negative electrode layer 3
  • the content is 0.05wt.% ⁇ 5wt.%.
  • lithium carboxymethyl cellulose and negative electrode powder are directly added and mixed together in a planetary stirring tank.
  • Embodiment 9 A method for preparing a negative electrode sheet according to any one of Embodiments 1 to 8,
  • the steps of the method are as follows: the lithium carboxymethyl cellulose, the conductive agent, the binder and the solvent are mixed and stirred in a planetary stirring tank for 5 to 8 hours to make them fully mixed to obtain a solid content of 10% to 50% and a viscosity of less than 2000mPa.s conductive paste, evenly apply the conductive paste to the surface of the current collector 1, and vacuum-bake in a vacuum drying box at 85°C for 4h-8h to obtain the conductive layer 2; place the negative electrode slurry in the planetary stirring tank Stir for 5 to 8 hours to make it fully mixed, then coat the surface of the conductive layer 2 to obtain the negative electrode layer 3, and vacuum-bake in a vacuum drying oven at 85°C for 12 to 24 hours to prepare a negative electrode sheet.
  • Embodiment 10 A lithium-ion battery, including a positive electrode sheet of a lithium-ion battery and a negative electrode sheet according to any one of the specific embodiments 1 to 8.
  • the positive electrode active material used in the positive electrode sheet is a conventional material that can be used as a positive electrode of a lithium ion battery and contains a lithium source.
  • the negative electrode slurry When preparing the negative electrode slurry, add 2% sodium carboxymethylcellulose and stir for 6h using planetary stirring to prepare the negative electrode slurry, which is coated on the surface of the current collector to obtain a negative electrode layer with a thickness of 120 ⁇ m, and then vacuum Bake for 12h in the drying oven, and finally prepare the negative electrode.
  • the positive electrode sheet is prepared by a conventional method, and the positive electrode active material on the positive electrode sheet is lithium cobalt oxide.
  • the negative electrode sheet, the lithium cobalt oxide lithium positive electrode sheet, and the separator obtained above are used in a winding process, and the liquid electrolyte is used to form a lithium ion battery.
  • the negative electrode slurry When preparing the negative electrode slurry, add 2% sodium carboxymethylcellulose and stir for 6h using planetary stirring to prepare the negative electrode slurry, coat it on the surface of the conductive layer to obtain a negative electrode layer with a thickness of 120 ⁇ m, and then vacuum Bake for 12h in the drying oven, and finally prepare the negative electrode.
  • the positive electrode sheet is prepared by a conventional method, and the positive electrode active material on the positive electrode sheet is lithium cobalt oxide.
  • the negative electrode sheet, the lithium cobalt oxide lithium positive electrode sheet, and the separator obtained above are used in a winding process, and the liquid electrolyte is used to form a lithium ion battery.
  • the negative electrode slurry When preparing the negative electrode slurry, add 2% lithium carboxymethylcellulose and stir it for 6h using planetary stirring. The negative electrode slurry is prepared and coated on the surface of the conductive layer to obtain a negative electrode layer with a thickness of 120 ⁇ m. Bake for 12h in the drying oven, and finally prepare the negative electrode.
  • the positive electrode sheet is prepared by a conventional method.
  • the positive electrode active material on the positive electrode sheet is lithium cobalt oxide.
  • the negative electrode sheet, lithium cobalt oxide lithium positive electrode sheet, and separator obtained above are wound using a winding process, and a liquid electrolyte is used to form a lithium ion battery.
  • negative electrode slurry When preparing negative electrode slurry, add 1.5% lithium carboxymethylcellulose and 0.5% sodium carboxymethylcellulose and stir for 6h using planetary stirring to prepare negative electrode slurry, which is coated on the surface of the conductive layer to obtain the thickness A negative electrode layer of 120 ⁇ m was then baked in a vacuum oven for 12 hours, and finally a negative electrode sheet was prepared.
  • the positive electrode sheet is prepared by a conventional method, and the positive electrode active material on the positive electrode sheet is lithium cobalt oxide.
  • the negative electrode sheet, the lithium cobalt oxide lithium positive electrode sheet, and the separator obtained above are used in a winding process, and the liquid electrolyte is used to form a lithium ion battery.
  • the negative electrode slurry When preparing the negative electrode slurry, add 1% lithium carboxymethylcellulose and 1% sodium carboxymethylcellulose, and stir for 6h using planetary stirring to prepare the negative electrode slurry, which is coated on the surface of the conductive layer to obtain the thickness A negative electrode layer of 120 ⁇ m was then baked in a vacuum oven for 12 hours, and finally a negative electrode sheet was prepared.
  • the positive electrode sheet is prepared by a conventional method, and the positive electrode active material on the positive electrode sheet is lithium cobalt oxide.
  • the negative electrode sheet, the lithium cobalt oxide lithium positive electrode sheet, and the separator obtained above are used in a winding process, and the liquid electrolyte is used to form a lithium ion battery.
  • the negative electrode slurry When preparing the negative electrode slurry, add 0.5% lithium carboxymethyl cellulose and 1.5% sodium carboxymethyl cellulose, and stir for 6h using planetary stirring to prepare the negative electrode slurry, which is coated on the surface of the conductive layer to obtain the thickness A negative electrode layer of 120 ⁇ m was then baked in a vacuum oven for 12 hours, and finally a negative electrode sheet was prepared.
  • the positive electrode sheet is prepared by a conventional method, and the positive electrode active material on the positive electrode sheet is lithium cobalt oxide.
  • the negative electrode sheet, the lithium cobalt oxide lithium positive electrode sheet, and the separator obtained above are used in a winding process, and the liquid electrolyte is used to form a lithium ion battery.
  • the negative electrode slurry When preparing the negative electrode slurry, add 2% lithium carboxymethylcellulose and 1.5% sodium carboxymethylcellulose, and stir for 6h using planetary stirring to prepare the negative electrode slurry, which is coated on the surface of the conductive layer to obtain the thickness A negative electrode layer of 120 ⁇ m was then baked in a vacuum oven for 12 hours, and finally a negative electrode sheet was prepared.
  • the positive electrode sheet is prepared by a conventional method, and the positive electrode active material on the positive electrode sheet is lithium cobalt oxide.
  • the negative electrode sheet, the lithium cobalt oxide lithium positive electrode sheet, and the separator obtained above are used in a winding process, and the liquid electrolyte is used to form a lithium ion battery.
  • the positive electrode sheet is prepared by a conventional method.
  • the positive electrode active material on the positive electrode sheet is lithium cobaltate.
  • the negative electrode sheet, the lithium cobaltate lithium positive electrode sheet and the separator obtained above are wound by a winding process, and the liquid electrolyte is used to form a lithium ion battery.
  • the negative electrode slurry When preparing the negative electrode slurry, add 2% lithium carboxymethylcellulose and stir it for 6h using planetary stirring. The negative electrode slurry is prepared and coated on the surface of the conductive layer to obtain a negative electrode layer with a thickness of 120 ⁇ m. Bake for 12h in the drying oven, and finally prepare the negative electrode.
  • the positive electrode sheet is prepared by a conventional method, and the positive electrode active material on the positive electrode sheet is lithium cobalt oxide.
  • the negative electrode sheet, the lithium cobalt oxide lithium positive electrode sheet, and the separator obtained above are used in a winding process, and the liquid electrolyte is used to form a lithium ion battery.
  • FIG. 2 is a graph of the cycle performance of the batteries of Comparative Example 1 and Examples 1 to 5 of the present application at 25° C.
  • FIG. 3 is a graph of the cycle performance of the batteries of Comparative Example 2 and Examples 6 to 7 of the present application at 25°C.

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Abstract

一种降低锂离子电池阻抗的负极片及其制备方法，属于锂离子电池领域。所述负极片包括集流体，导电层，负极层，导电层和负极层中均含有羧甲基纤维素锂。制备方法包括如下步骤：将羧甲基纤维素锂，导电剂，粘结剂，溶剂充分搅拌配制成均匀浆料，将导电浆料均匀涂覆到集流体表面，烘干得到导电层。将含有羧甲基纤维素锂的负极浆料涂覆在导电层表面，烘干后得到负极层，即制得负极片。本申请通过在负极层与集流体之间加入一层导电层，在增加极片粘结力的同时，导电性更好，同时在导电层及负极层中加入羧甲基纤维素锂，有效提高锂的传输效率，从而极大降低了电池阻抗，并对循环和首次化成效率有一定的改善作用。

Description

一种降低锂离子电池阻抗的负极片及其制备方法
本申请要求于2018年12月24日提交中国专利局、申请号为201811582875.1、申请名称为“一种降低锂离子电池阻抗的负极片及其制备方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请属于锂离子电池技术领域，尤其涉及一种降低锂离子电池阻抗的负极片及其制备方法。
背景技术
锂离子电池作为新型高能量电池，近年来人们对它的研究和开发取得了重要进展。随着人们对环境友好型产业的重视，电动汽车越来越受到人们的青睐，国家也出台各种形式的政策，补助扶持电动汽车行业。因而对于动力电池提出了较高的要求，其中的一个指标就是电池阻抗要求。
此外，对于通信设备、笔记本电脑、数码相机等电子产品，一方面对电池能量密度要求越来越高，相应的极片压实就要很高，如何解决极片高压实高阻抗带来的电池动力学差问题，成为人们首要面临的难题；另一方面对电池快充性能也提出了很高的要求，很多厂商包括手机、笔电等数码产品，以及动力产品纷纷提出快充需求，快充电池最重要的一项要求就是温升问题，归根结底就是电池阻抗问题。
现有技术一般是通过增加集流体的厚度或对集流体进行修饰改进，来降低阻抗，如公开号为CN108598361A的发明专利申请在集流体表面采用电镀方法形成一层铜锡合金镀层，可以有效改善极片动力学性能，缓解极片膨胀，对电池阻抗改善幅度有限。通过增加集流体厚度或减小面密度能够减小锂离子电池阻抗，但是会牺牲很大一部分能量密度，实用性受限。
发明内容
本申请的目的是为了解决现有的电池阻抗高、温升大、动力学差的问题， 提供一种降低锂离子电池阻抗的负极片及其制备方法，该种方法可以降低负极片内阻，进而降低电池整体内阻，降低电池充放电温升，提高锂离子电池循环性能，提升了电池首次充放电效率，从而提升电池体积能量密度。
为实现上述目的，本申请采取的技术方案如下：
一种降低锂离子电池阻抗的负极片，所述负极片包括集流体、导电层和负极层，所述集流体的一侧表面设有导电层，所述导电层的表面设有负极层；所述导电层包括羧甲基纤维素锂。
进一步地，所述集流体为铜箔。
进一步地，所述铜箔选自多孔铜箔、刻蚀铜箔中的一种。
进一步地，所述集流体的厚度小于25μm。
进一步地，所述导电层的厚度为0.2～3μm。
进一步地，所述导电层的制备方法如下：将羧甲基纤维素锂、导电剂、粘结剂和溶剂混合搅拌，得到导电浆料，将导电浆料均匀涂覆到集流体一侧表面，真空烘烤得到导电层。
进一步地，所述负极层的厚度为10～200μm。
进一步地，所述负极层中加入羧甲基纤维素锂，所述羧甲基纤维素锂在所述负极层中的含量为0.05wt.％～5wt.％。
一种上述的负极片的制备方法，所述方法步骤如下：将羧甲基纤维素锂、导电剂、粘结剂和溶剂混合搅拌，得到固含量为10％～50％，粘度小于2000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体一侧表面，真空烘烤得到导电层；将负极浆料搅拌，使其充分混合，然后涂覆在导电层表面，得到负极层，进行真空烘烤，即制得负极片。
一种锂离子电池，包括锂离子电池正极片以及上述任一所述的负极片。
本申请相对于现有技术的有益效果是：本申请的导电层一方面可以增加负极片导电性，降低阻抗，另一方面，可以增加负极粘结性，减小极片膨胀，其中的羧甲基纤维素锂在提高锂离子传输效率基础上，为负极提供一定的锂源，提升电池首次化成效率。导电层表面的负极层采用羧甲基纤维素锂代替传统的羧甲基纤维素钠作增稠剂，大大降低了极片阻抗，对电池循环有很大改善作用。本申请的锂离子电池负极片制备方法简单，效果显著，有效改善电池性能。
附图说明
图1为本申请降低锂离子电池阻抗的负极片结构示意图；
图2为本申请对比例1与实施例1～5的电池在25℃条件下的循环性能曲线图；
图3为本申请对比例2与实施例6～7的电池在25℃条件下的循环性能曲线图。
具体实施方式
以下结合附图对本申请的具体实施方式作进一步详细地说明，为了让本申请的上述和其它目的、特征及优点能更明显，下面通过具体实施例和对比例对本申请作进一步的说明。显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
下述说明中所使用到的试剂、材料以及仪器如没有特殊的说明，均为常规试剂、常规材料以及常规仪器，均可商购获得，所涉及的试剂也可通过常规合成方法合成获得。
具体实施方式一：图1为本申请降低锂离子电池阻抗的负极片结构示意图，如图1所示，本实施方式记载的是一种降低锂离子电池阻抗的负极片，所述负极片包括集流体1、导电层2和负极层3，所述集流体1的一侧表面设有导电层2，所述导电层2的表面设有负极层3；所述导电层包括羧甲基纤维素锂。
导电层2是含有导电材料的涂层，其中包括羧甲基纤维素锂，该羧甲基纤维素锂用作增稠剂并具有一定粘结性。
具体实施方式二：具体实施方式一所述的一种降低锂离子电池阻抗的负极片，所述集流体1为铜箔。
具体实施方式三：具体实施方式二所述的一种降低锂离子电池阻抗的负极片，所述铜箔选自多孔铜箔、刻蚀铜箔中的一种。
具体实施方式四：具体实施方式一至三任一所述的一种降低锂离子电 池阻抗的负极片，所述集流体1的厚度是从能量密度的角度考虑进行设置的，小于25μm。
具体实施方式五：具体实施方式一所述的一种降低锂离子电池阻抗的负极片，所述导电层2的厚度为0.2～3μm。
具体实施方式六：具体实施方式一或五所述的一种降低锂离子电池阻抗的负极片，所述导电层2的制备方法如下：将羧甲基纤维素锂、导电剂、粘结剂和溶剂在行星搅拌罐中混合搅拌5～8h，使其充分混合得到导电浆料，将导电浆料均匀涂覆到集流体1一侧表面，在真空干燥箱中85℃真空烘烤4h-8h得到导电层2。
导电剂的作用是增加极片导电性，羧甲基纤维素锂可提高锂离子传输效率，降低阻抗，又可以提供少量的锂源，减少电池充放电过程中不可逆锂的损失，从而提高电池首次化成效率。所述导电剂包括但不限于superP，碳纳米管，炭黑等导电性物质。所述羧甲基纤维素锂代替传统的羧甲基纤维素钠，用于导电浆料及负极浆料的增稠剂，可减小极片整体阻抗，提高锂离子传输效率。
所述导电层2中，羧甲基纤维素锂的含量为0.1wt.％～10wt.％，导电剂含量为50wt.％～75wt.％，粘结剂含量为20wt.％～40wt.％。所述导电浆料的粘度小于2000mPa.s，浆料固含量为10％～50％，具体地，由溶剂来调整。
具体实施方式七：具体实施方式一所述的一种降低锂离子电池阻抗的负极片，所述负极层3的厚度为10～200μm。
具体实施方式八：具体实施方式一或七所述的一种降低锂离子电池阻抗的负极片，所述负极层3中加入羧甲基纤维素锂，羧甲基纤维素锂在负极层3中的含量为0.05wt.％～5wt.％。具体地，在配料阶段，在行星式搅拌罐中羧甲基纤维素锂和负极粉料一起直接加入混合均匀。
具体实施方式九：一种具体实施方式一至八任一具体实施方式所述的负极片的制备方法，
所述方法步骤如下：将羧甲基纤维素锂、导电剂、粘结剂和溶剂在行星搅拌罐中混合搅拌5～8h，使其充分混合，得到固含量为10％～50％，粘度小于2000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体1一侧表面，在真空干燥箱中85℃真空烘烤4h～8h得到导电层2；将负极浆料在行星搅 拌罐中搅拌5～8h，使其充分混合，然后涂覆在导电层2表面，得到负极层3，在85℃的真空干燥箱中进行真空烘烤12h～24h，即制得负极片。
具体实施方式十：一种锂离子电池，包括锂离子电池正极片以及含有具体实施方式一至八任一具体实施方式所述的负极片。所述正极片采用的正极活性物质为含锂源的可用作锂离子电池正极的常规材料。
对比例1
配制负极浆料时，加入2％羧甲基纤维素钠，采用行星搅拌的方式搅拌6h，制得负极浆料，将其涂覆在集流体表面，得到厚度为120μm的负极层，然后在真空干燥箱中烘烤12h，最终制得负极片。采用常规方法制备正极片，正极片上的正极活性物质为钴酸锂，将上述所得负极片、钴酸锂锂正极片、隔膜采用卷绕工艺，搭配液态电解液制成锂离子电池。
对比例2
将4％羧甲基纤维素钠，68％导电剂，28％粘结剂，溶剂在行星搅拌罐中搅拌6h，使其充分混合配制固含30％，粘度在500～1000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体上，涂布厚度1.5μm，然后在真空干燥箱中烘烤4h，得到导电层。
配制负极浆料时，加入2％羧甲基纤维素钠，采用行星搅拌的方式搅拌6h，制得负极浆料，将其涂覆在导电层表面，得到厚度为120μm的负极层，然后在真空干燥箱中烘烤12h，最终制得负极片。采用常规方法制备正极片，正极片上的正极活性物质为钴酸锂，将上述所得负极片、钴酸锂锂正极片、隔膜采用卷绕工艺，搭配液态电解液制成锂离子电池。
实施例1
将4％羧甲基纤维素锂，68％导电剂，28％粘结剂，溶剂在行星搅拌罐中搅拌6h，使其充分混合配制固含30％，粘度在500～1000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体上，涂布厚度1.5μm，然后在真空干燥箱中烘烤4h，得到导电层。
配制负极浆料时，加入2％羧甲基纤维素锂，采用行星搅拌的方式搅拌6h，制得负极浆料，将其涂覆在导电层表面，得到厚度为120μm的负极层，然后在真空干燥箱中烘烤12h，最终制得负极片。采用常规方法制备正极片，正极片上的正极活性物质为钴酸锂，将上述所得负极片、钴酸 锂锂正极片、隔膜采用卷绕工艺，搭配液态电解液制成锂离子电池。
实施例2
将4％羧甲基纤维素锂，68％导电剂，28％粘结剂，溶剂在行星搅拌罐中搅拌6h，使其充分混合配制固含30％，粘度在500～1000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体上，涂布厚度1.5μm，然后在真空干燥箱中烘烤4h，得到导电层。
配制负极浆料时，加入1.5％羧甲基纤维素锂和0.5％羧甲基纤维素钠，采用行星搅拌的方式搅拌6h，制得负极浆料，将其涂覆在导电层表面，得到厚度为120μm的负极层，然后在真空干燥箱中烘烤12h，最终制得负极片。采用常规方法制备正极片，正极片上的正极活性物质为钴酸锂，将上述所得负极片、钴酸锂锂正极片、隔膜采用卷绕工艺，搭配液态电解液制成锂离子电池。
实施例3
将4％羧甲基纤维素锂，68％导电剂，28％粘结剂，溶剂在行星搅拌罐中搅拌6h，使其充分混合配制固含30％，粘度在500～1000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体上，涂布厚度1.5μm，然后在真空干燥箱中烘烤4h，得到导电层。
配制负极浆料时，加入1％羧甲基纤维素锂和1％羧甲基纤维素钠，采用行星搅拌的方式搅拌6h，制得负极浆料，将其涂覆在导电层表面，得到厚度为120μm的负极层，然后在真空干燥箱中烘烤12h，最终制得负极片。采用常规方法制备正极片，正极片上的正极活性物质为钴酸锂，将上述所得负极片、钴酸锂锂正极片、隔膜采用卷绕工艺，搭配液态电解液制成锂离子电池。
实施例4
将4％羧甲基纤维素锂，68％导电剂，28％粘结剂，溶剂在行星搅拌罐中搅拌6h，使其充分混合配制固含30％，粘度在500～1000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体上，涂布厚度1.5μm，然后在真空干燥箱中烘烤4h，得到导电层。
配制负极浆料时，加入0.5％羧甲基纤维素锂和1.5％羧甲基纤维素钠，采用行星搅拌的方式搅拌6h，制得负极浆料，将其涂覆在导电层表面，得 到厚度为120μm的负极层，然后在真空干燥箱中烘烤12h，最终制得负极片。采用常规方法制备正极片，正极片上的正极活性物质为钴酸锂，将上述所得负极片、钴酸锂锂正极片、隔膜采用卷绕工艺，搭配液态电解液制成锂离子电池。
实施例5
将4％羧甲基纤维素锂，68％导电剂，28％粘结剂，溶剂在行星搅拌罐中搅拌6h，使其充分混合配制固含30％，粘度在500～1000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体上，涂布厚度1.5μm，然后在真空干燥箱中烘烤4h，得到导电层。
配制负极浆料时，加入2％羧甲基纤维素锂和1.5％羧甲基纤维素钠，采用行星搅拌的方式搅拌6h，制得负极浆料，将其涂覆在导电层表面，得到厚度为120μm的负极层，然后在真空干燥箱中烘烤12h，最终制得负极片。采用常规方法制备正极片，正极片上的正极活性物质为钴酸锂，将上述所得负极片、钴酸锂锂正极片、隔膜采用卷绕工艺，搭配液态电解液制成锂离子电池。
实施例6
将4％羧甲基纤维素锂，68％导电剂，28％粘结剂，溶剂在行星搅拌罐中搅拌6h，使其充分混合配制固含30％，粘度在500～1000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体上，涂布厚度1.5μm，然后在真空干燥箱中烘烤4h，得到导电层。
配制负极浆料时，加入2％羧甲基纤维素钠，采用行星搅拌的方式搅拌6h，制得负极浆料，将其涂覆在导电层表面，得到厚度为120μm的负极层，然后在真空干燥箱中烘烤12h，最终制得负极片。采用常规方法制备正极片，正极片上的正极活性物质为钴酸锂，将上述所得负极片、钴酸锂锂正极片、隔膜采用卷绕工艺，搭配液态电解液制成锂离子电池。
实施例7
将4％羧甲基纤维素钠，68％导电剂，28％粘结剂，溶剂在行星搅拌罐中搅拌6h，使其充分混合配制固含30％，粘度在500～1000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体上，涂布厚度1.5μm，然后在真空干燥箱中烘烤4h，得到导电层。
配制负极浆料时，加入2％羧甲基纤维素锂，采用行星搅拌的方式搅拌6h，制得负极浆料，将其涂覆在导电层表面，得到厚度为120μm的负极层，然后在真空干燥箱中烘烤12h，最终制得负极片。采用常规方法制备正极片，正极片上的正极活性物质为钴酸锂，将上述所得负极片、钴酸锂锂正极片、隔膜采用卷绕工艺，搭配液态电解液制成锂离子电池。
将对比例1和实施例1～5制得的锂离子电池进行测试，进行阻抗测试，首次化成效率测试，25℃1C/1C下的循环性能测试以及循环后电池厚度膨胀测试；测试结果如表1和图2所示，图2为本申请对比例1与实施例1～5的电池在25℃条件下的循环性能曲线图。
将对比例2和实施例6、7制得的锂离子电池进行测试，进行阻抗测试，首次化成效率测试，25℃1C/1C下的循环性能测试以及循环后电池厚度膨胀测试；测试结果如表2和图3所示，图3为本申请对比例2与实施例6～7的电池在25℃条件下的循环性能曲线图。
表1
Figure PCTCN2019120268-appb-000001
表2
Figure PCTCN2019120268-appb-000002
从表1和表2的测试结果可知，采用本申请方法制备的负极片制得的锂离子电池，相比对比例常规极片制得的锂离子电池内阻及首次化成效率均有明显改善，电池循环性能及电池循环厚度膨胀也有明显改善；表2表明，羧甲基纤维素锂加入到负极层比加入到导电层效果更明显；图2和图3为电池循环曲线图，可以看出，本申请所得含有羧甲基纤维素锂的负极片，循环稳定性更好，700周循环容量保持率更高。

Claims (10)

  1. 一种降低锂离子电池阻抗的负极片，其中，所述负极片包括集流体(1)、导电层(2)和负极层(3)，所述集流体(1)的一侧表面设有导电层(2)，所述导电层(2)的表面设有负极层(3)；所述导电层(2)包括羧甲基纤维素锂。
  2. 根据权利要求1所述的降低锂离子电池阻抗的负极片，其中，所述集流体(1)为铜箔。
  3. 根据权利要求2所述的降低锂离子电池阻抗的负极片，其中，所述铜箔选自多孔铜箔、刻蚀铜箔中的一种。
  4. 根据权利要求1～3任一所述的降低锂离子电池阻抗的负极片，其中，所述集流体(1)的厚度小于25μm。
  5. 根据权利要求1所述的降低锂离子电池阻抗的负极片，其中，所述导电层(2)的厚度为0.2～3μm。
  6. 根据权利要求1或5所述的降低锂离子电池阻抗的负极片，其中，所述导电层(2)的制备方法如下：将羧甲基纤维素锂、导电剂、粘结剂和溶剂混合搅拌，得到导电浆料，将导电浆料均匀涂覆到集流体(1)一侧表面，真空烘烤得到导电层(2)。
  7. 根据权利要求1所述的降低锂离子电池阻抗的负极片，其中，所述负极层(3)的厚度为10～200μm。
  8. 根据权利要求1或7所述的降低锂离子电池阻抗的负极片，其中，所述负极层(3)中加入羧甲基纤维素锂，所述羧甲基纤维素锂在所述负极层(3)中的含量为0.05wt.％～5wt.％。
  9. 一种权利要求1～8任一项所述的负极片的制备方法，其中，
    所述方法步骤如下：将羧甲基纤维素锂、导电剂、粘结剂和溶剂混合搅拌，得到固含量为10％～50％，粘度小于2000mPa.s的导电浆料，将导电浆料均匀涂覆到集流体(1)一侧表面，真空烘烤得到导电层(2)；将负极浆料搅拌，使其充分混合，然后涂覆在导电层(2)表面，得到负极层(3)，进行真空烘烤，即制得负极片。
  10. 一种锂离子电池，其中，包括锂离子电池正极片以及权利要求1～8任一项所述的负极片。
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