WO2023138018A1 - Composite negative electrode plate and preparation method therefor, and lithium metal secondary battery - Google Patents

Composite negative electrode plate and preparation method therefor, and lithium metal secondary battery Download PDF

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WO2023138018A1
WO2023138018A1 PCT/CN2022/108258 CN2022108258W WO2023138018A1 WO 2023138018 A1 WO2023138018 A1 WO 2023138018A1 CN 2022108258 W CN2022108258 W CN 2022108258W WO 2023138018 A1 WO2023138018 A1 WO 2023138018A1
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negative electrode
lithium
current collector
electrode current
electrode sheet
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PCT/CN2022/108258
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French (fr)
Chinese (zh)
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李玉冰
徐雄文
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湖南立方新能源科技有限责任公司
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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
    • H01M4/13—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of 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
    • 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 invention belongs to the technical field of lithium metal secondary batteries, and in particular relates to a composite negative electrode sheet, a preparation method thereof, and a lithium metal secondary battery.
  • metal lithium is considered to be the ideal negative electrode material for the next generation of high energy density lithium batteries due to its ultra-high theoretical specific capacity (3860mAh/g) and extremely low potential (-3.04V, compared to standard hydrogen electrodes), known as the "holy grail" in electrodes.
  • the high-nickel ternary system material matching the metal lithium negative electrode is considered to be the battery system that can break through the energy density of 500Wh/Kg the fastest.
  • Lithium-sulfur batteries, lithium-oxygen batteries and other secondary batteries with metal lithium as the negative electrode are considered to be a new generation of high specific energy batteries with great potential.
  • lithium dendrites can also greatly accelerate the consumption rate of the electrolyte and reversible lithium sources, and can also be converted into "dead lithium” that loses electrochemical activity and covers the surface of the negative electrode, hindering the transfer of lithium ions and shortening the battery cycle life.
  • the SEI film also known as the solid-liquid phase interface film, is a film on the surface of lithium metal that isolates the continuous reaction between the electrolyte and lithium, and has the properties of a good ion conductor and an electronic insulator. Since the lithium metal anode is not constrained by the main structure, its volume expansion is almost infinite during the cycle. This large volume expansion often leads to the rupture of the SEI film during the battery cycle. Therefore, although the artificial SEI film can prolong the battery life to a certain extent, it still has the problem of repeated rupture and repair of the SEI film as the cycle progresses, and the growth of lithium dendrites in the later stage of the cycle is uncontrollable.
  • One of the objectives of the present invention is to provide a composite negative electrode sheet for the deficiencies of the prior art, which can reduce the consumption of electrolyte and reversible active lithium, and improve the battery cycle life and battery safety performance.
  • a composite negative electrode sheet comprising a negative electrode current collector and a coating layer coated on at least one surface of the negative electrode current collector, a plurality of graphite sheets are arranged in the coating layer, at least a part of the graphite sheets are arranged vertically to the negative electrode current collector, and the graphite sheets are separated from each other.
  • SEI films grown in situ during battery cycling usually have poor mechanical properties and flexibility, and are prone to rupture due to factors such as volume expansion during long cycles, resulting in uncontrolled dendrite growth, short cycle life, and poor safety performance.
  • a coating layer is provided on the surface of the negative electrode current collector, and there are graphite sheets arranged vertically and separated from each other in the coating layer.
  • the graphite sheets arranged vertically to the current collector and parallel to each other can partially accommodate the 'dead lithium' and lithium dendrites generated by them during the subsequent cycle of the battery, and to a certain extent avoid safety accidents caused by internal short circuits caused by dendrites piercing through the separator.
  • the negative electrode current collector is any one of copper foil (including perforated copper foil and non-perforated copper foil), nickel foil, stainless steel sheet, metallic lithium foil, and metallic lithium-based alloy foil.
  • the negative electrode current collector can be a lithium metal current collector, or a non-lithium metal alloy based current collector.
  • the negative electrode When a non-lithium-based current collector or a non-lithium metal alloy-based current collector is selected, the negative electrode initially does not contain lithium. At this time, the ratio of the acceptable theoretical capacity of the magnetic vertical graphite sheet coated on it to the theoretical capacity that can be exerted by the positive electrode material in the voltage range must be much smaller than 1, that is, the N/P ratio should be much smaller than 1. At this time, when the battery is charged, part of the lithium ions released from the positive electrode are embedded in the graphite negative electrode and exist in the form of LiC 6 and so on.
  • the theoretical amount of lithium ions that the negative electrode can accept is far less than the theoretical amount that can be released by the positive electrode
  • another part of the excess lithium ions that are not inlaid by the graphite material on the negative electrode side is partially deposited between the graphite sheets of the parallel vertical current collectors at the negative electrode until it is filled and overflows. After the overflow, the excess lithium continues to deposit on the top surface of the graphite sheet to form a lithium metal layer of a certain thickness. Due to the partial irreversibility of lithium ions after extraction, some of the lithium extracted from the positive electrode side cannot return to the positive electrode during discharge, and remain on the top of the graphite layer or in the gap between the graphite sheets.
  • the lithium deposited on the top of the graphite is preferentially stripped, and then the lithium deposited in the gap between the graphite sheets is stripped.
  • the 'dead lithium' and lithium dendrites will fall into the graphite gap and be buried by subsequent reversible active lithium, thereby reducing the effect of hindering lithium ion transmission, reducing electrolyte consumption, and improving battery cycle life and safety performance.
  • the current collector used is a lithium-based current collector
  • the negative electrode itself can provide a lithium source
  • the theoretical capacity ratio between the negative electrode and the positive electrode should be greater than 1, that is, the N/P ratio mentioned in the patent should be greater than 1.
  • the coated graphite sheet described in the patent can be understood as a cage structure, whose function is to trap the lithium coming out of the anode side to form lithium dendrites and 'dead lithium' in the subsequent cycle process, so as to reduce electrolyte consumption, improve cycle life and safety performance.
  • the coating layer further includes a thickener and a binder, and the weight-to-number ratio of the graphite sheet, the thickener, and the binder is 94-98:1-3:1-3.
  • a certain amount of graphite flakes, thickeners and binders are arranged so that the prepared coating slurry has a certain viscosity, which is convenient for coating and fixing of the coating slurry.
  • the binder includes one or more of polytetrafluoroethylene, styrene-butadiene rubber, polyacrylate, polyimide, sodium polyacrylate, chitosan, polyvinylidene fluoride, and polyvinylidene fluoride.
  • all graphite sheets are arranged vertically to the negative electrode current collector. All the graphite sheets are vertically arranged with the negative electrode current collector, which can increase the electrochemical performance of the composite negative electrode sheet.
  • the thickener is sodium carboxymethylcellulose.
  • the second object of the present invention is to provide a method for preparing a composite negative plate, which is easy to operate and can be mass-produced in view of the deficiencies in the prior art.
  • a method for preparing a composite negative plate comprising the following steps:
  • Step S1 mixing the graphite sheet modified by the magnetic substance with a binder and a thickener, adding a solvent, and stirring to prepare a coating slurry;
  • Step S2 selecting the negative electrode current collector, installing a magnetic field emission device, coating the coating slurry on at least one surface of the negative electrode current collector, drying the coating slurry under the magnetic field emission device to form a coating layer, and obtaining a composite negative electrode sheet, wherein the magnetic field emission device is used to vertically arrange the graphite sheet modified by the magnetic substance in the coating slurry and the negative electrode current collector.
  • micron-sized flakes suspended in a fluid and decorated with magnetic nanoparticles have two different orientation states. It is highly dependent on the magnetic field rotation frequency and the rheological properties of the fluid.
  • the magnetic field rotation frequency is low enough, the magnetic substance-modified particles are controlled by the magnetic torque, and they rotate synchronously on the surface of the current collector along the direction of the rotating field.
  • the rotation frequency is high enough, the determining step of the motion state of the magnetic substance is changed to the fluid viscosity, and at this time, the magnetic substance will be arranged parallel to the plane of the rotating magnetic field.
  • the coating layer further includes a solvent
  • the solvent is a water-based solvent or an oil-based solvent.
  • the negative electrode slurry can be a water-based solvent.
  • the water-based solvent includes and is not limited to water, methanol, and ethanol.
  • the solvent used in the above-mentioned negative electrode slurry is an oil-based solvent.
  • the oil-based solvent includes but is not limited to N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) etc.
  • NMP N-methylpyrrolidone
  • DMF N,N-dimethylformamide
  • DMSO dimethyl sulfoxide
  • the third object of the present invention is to provide a lithium metal secondary battery with good electrochemical performance and safety performance in view of the deficiencies of the prior art.
  • a lithium metal secondary battery comprising a positive electrode sheet, a separator, a negative electrode sheet, an electrolyte and a casing, the separator separates the positive electrode sheet and the negative electrode sheet, the casing is used to install the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte, and the negative electrode sheet is the above-mentioned composite negative electrode sheet.
  • the battery structure of the above-mentioned lithium metal secondary battery may be a laminated type, a wound type, or a hybrid type of both.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector.
  • the positive electrode active material layer includes one or more mixtures of lithium cobalt oxide, lithium nickel manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganate, lithium-rich manganese base, or lithium manganese iron phosphate.
  • the isolation film is any one of polyethylene film, polypropylene film, polyethylene-polypropylene composite film, polyimide film and ceramic film.
  • the beneficial effect of the present invention is: the negative electrode sheet of the present invention is provided with a coating layer on the surface of the negative electrode current collector, and there are graphite sheets arranged vertically and separated from each other in the coating layer.
  • the graphite sheets arranged in parallel with each other in this vertical current collector can partially accommodate the 'dead lithium' and lithium dendrites produced by them during the subsequent cycle of the battery, and to a certain extent avoid safety accidents caused by internal short circuits caused by dendrites piercing through the diaphragm.
  • FIG. 1 is a schematic structural view of a negative electrode sheet in the prior art.
  • Fig. 2 is a schematic structural view of the negative electrode sheet of the present invention.
  • FIG. 3 is a graph comparing the capacity retention curves of Example 1 and Comparative Example 1 of the present invention.
  • Negative electrode current collector 1.
  • Graphite sheet 3.
  • Lithium ion 1.
  • a method for preparing a composite negative plate comprising the following steps:
  • Step S1 mixing the graphite sheet 2 modified by the magnetic substance with a binder and a thickener, adding a solvent, and stirring to prepare a coating slurry;
  • Step S2 select the negative electrode current collector 1, install a magnetic field emission device, coat the coating slurry on at least one surface of the negative electrode current collector 1, dry the coating slurry under the magnetic field emission device to form a coating layer, and obtain a composite negative electrode sheet, wherein the magnetic field emission device is used to vertically arrange the graphite sheet 2 modified by the magnetic substance in the coating slurry with the negative electrode current collector 1.
  • the prepared composite negative electrode sheet is shown in Figure 2.
  • the negative electrode collector 1 placed horizontally is the negative electrode collector 1, and the graphite sheet 2 is arranged vertically and spaced apart from the negative electrode collector 1.
  • the multiple graphite sheets 2 are separated from each other and form an upward-opening accommodation space with the negative electrode current collector 1, which can accommodate lithium ions 3.
  • the formed accommodation space can be installed.
  • the contact between the electrolyte and lithium dendrites can be reduced to a certain extent, and the consumption of the electrolyte can be reduced, thereby improving the safety performance and prolonging the cycle life of the battery.
  • the ratio of graphite sheet 2, thickener, and binder in the coating layer is 95:2.5:2.5.
  • the binder is polytetrafluoroethylene
  • the thickener is sodium carboxymethyl cellulose
  • the negative electrode current collector 1 is metal lithium foil
  • the solvent is an oil-based solvent
  • the oil-based solvent is N-methylpyrrolidone
  • the isolation film is a polyethylene film.
  • Example 2 The difference from Example 1 is that the ratio of graphite sheet 2, thickener, and binder in the coating layer is 98:2:2.
  • Example 2 The difference from Example 1 is that the ratio of graphite sheet 2, thickener, and binder in the coating layer is 94:2:2.
  • Example 1 The difference from Example 1 is that the ratio of graphite sheet 2, thickener, and binder in the coating layer is 95:1:1 by weight.
  • Example 1 The difference from Example 1 is that the ratio of graphite sheet 2, thickener, and binder in the coating layer is 95:1:3 by weight.
  • Example 1 The difference from Example 1 is that: the negative electrode current collector 1 is copper foil, the solvent is an aqueous solvent, and the solvent is water.
  • the preparation square step of negative electrode sheet comprises the following steps:
  • Step S1 mixing the graphite sheet 2 modified by the magnetic substance with a binder and a thickener, adding a solvent, and stirring to prepare a coating slurry;
  • Step S2 selecting the negative electrode collector 1, coating the coating slurry on at least one surface of the negative electrode collector 1, drying to form a coating layer, and preparing the negative electrode sheet, as shown in FIG. 1 .
  • Example 2 86
  • Example 3 85
  • Example 4 85
  • Example 5 85
  • Example 6 Comparative example 1 80 / /

Abstract

The present invention relates to the technical field of lithium metal secondary batteries, in particular to a composite negative electrode plate and a preparation method therefor, and a lithium metal secondary battery. The composite negative electrode plate comprises a negative electrode current collector and a coating layer coated on at least one surface of the negative electrode current collector; a plurality of graphite sheets are provided in the coating layer, at least some of the graphite sheets are perpendicular to the negative electrode current collector, and said some of the graphite sheets are separated from one another. According to the composite negative electrode plate in the present invention, the coating layer is provided on the surface of the negative electrode current collector, and graphite sheet layers which are perpendicular to the current collector and are arranged in parallel to each other are provided in the coating layer, so that 'dead lithium' and lithium dendrites generated thereby can be partially accommodated, and safety accidents caused by internal short circuit due to the fact that the dendrites pierce a separator can be avoided. Moreover, some of the lithium dendrites can be deposited at the bottom of the graphite coating layer and are buried by 'dead lithium' or active lithium and the like generated subsequently, so that contact between the dendrites and an electrolyte is reduced, the consumption of the electrolyte is reduced, and the cycle life of the battery is prolonged.

Description

一种复合负极片及其制备方法、锂金属二次电池A composite negative electrode sheet and its preparation method, lithium metal secondary battery 技术领域technical field
本发明属于锂金属二次电池技术领域，尤其涉及一种复合负极片及其制备方法、锂金属二次电池。The invention belongs to the technical field of lithium metal secondary batteries, and in particular relates to a composite negative electrode sheet, a preparation method thereof, and a lithium metal secondary battery.
背景技术Background technique
在锂二次电池所有材料中，金属锂其因超高的理论比容量(3860mAh/g)，极低的电势(-3.04V，相对于标准氢电极)，被认为是下一代高能量密度锂电池的理想负极材料，被称为电极中的“圣杯”。其中，匹配金属锂负极的高镍三元体系材料，被认为是能最快突破能量密度500Wh/Kg的电池体系。锂硫电池、锂氧电池等以金属锂为负极的二次电池，被认为是极具潜力的新一代高比能量电池。然而在电池循环过程中，由于负极表面不平整，电流分布、热分布不均匀等内在或外在因素，锂离子在负极表面的沉积剥离往往并不均匀，这种不均匀的沉积剥离容易生成锂枝晶，大量锂枝晶的存在容易刺穿隔膜，导致正负极直接接触造成内短路，可能引发安全事故。同时，锂枝晶的存在还可导致电解液和可逆锂源消耗速率大大加快，还可转化为失去电化学活性的‘死锂’覆盖在负极表面，阻碍锂离子的传递，缩短电池循环寿命。Among all lithium secondary battery materials, metal lithium is considered to be the ideal negative electrode material for the next generation of high energy density lithium batteries due to its ultra-high theoretical specific capacity (3860mAh/g) and extremely low potential (-3.04V, compared to standard hydrogen electrodes), known as the "holy grail" in electrodes. Among them, the high-nickel ternary system material matching the metal lithium negative electrode is considered to be the battery system that can break through the energy density of 500Wh/Kg the fastest. Lithium-sulfur batteries, lithium-oxygen batteries and other secondary batteries with metal lithium as the negative electrode are considered to be a new generation of high specific energy batteries with great potential. However, during the battery cycle, due to internal or external factors such as uneven negative electrode surface, uneven current distribution, and uneven heat distribution, the deposition and peeling of lithium ions on the negative electrode surface is often uneven. This uneven deposition and peeling is easy to generate lithium dendrites. The existence of a large number of lithium dendrites is easy to pierce the separator, resulting in direct contact between the positive and negative electrodes, resulting in an internal short circuit, which may cause safety accidents. At the same time, the existence of lithium dendrites can also greatly accelerate the consumption rate of the electrolyte and reversible lithium sources, and can also be converted into "dead lithium" that loses electrochemical activity and covers the surface of the negative electrode, hindering the transfer of lithium ions and shortening the battery cycle life.
为了应对上述锂枝晶及‘死锂’问题，研究者们通过调整电解液配方，开发新型电解液添加剂，构建3D宿主结构或在锂金属表面覆盖一层人造SEI保护层。这其中，调整电解液配方及研发新型电解液添加剂往往成本较高，使得应用其的产品售价随之上涨。具有3D结构复合负极往往比表面积较大，电池循环的首次库伦效率较低，且副反应程度较大。SEI膜又称固液相界面膜，为锂金属表面一层为隔绝电解液与锂持续反应的膜，具有离子良导体与电子绝缘体的性质。锂金属负极由于没有主体结构的束缚，在循环过程中其体积膨胀近乎无限，这种大的体积膨胀往往导致电池循环过程中SEI膜的破裂，因此，人造SEI膜虽然能在一定程度上延长电池寿命，但随着循环进行，其仍存在SEI 膜反复破裂修复的问题，循环后期锂枝晶生长不可控。In order to deal with the above-mentioned problems of lithium dendrites and ‘dead lithium’, researchers have adjusted the electrolyte formula, developed new electrolyte additives, constructed a 3D host structure or covered an artificial SEI protective layer on the surface of lithium metal. Among them, the cost of adjusting the electrolyte formula and developing new electrolyte additives is often high, which makes the price of products using them rise accordingly. Composite anodes with 3D structures tend to have larger specific surface areas, lower first-time Coulombic efficiency of battery cycles, and greater degree of side reactions. The SEI film, also known as the solid-liquid phase interface film, is a film on the surface of lithium metal that isolates the continuous reaction between the electrolyte and lithium, and has the properties of a good ion conductor and an electronic insulator. Since the lithium metal anode is not constrained by the main structure, its volume expansion is almost infinite during the cycle. This large volume expansion often leads to the rupture of the SEI film during the battery cycle. Therefore, although the artificial SEI film can prolong the battery life to a certain extent, it still has the problem of repeated rupture and repair of the SEI film as the cycle progresses, and the growth of lithium dendrites in the later stage of the cycle is uncontrollable.
综上所述，寻找一种合适的方法以减小电解液及可逆活性锂消耗以提升锂金属电池循环寿命及电池安全性能，是业界极为迫切的问题。To sum up, it is an extremely urgent problem in the industry to find a suitable method to reduce the consumption of electrolyte and reversible active lithium so as to improve the cycle life and battery safety performance of lithium metal batteries.
发明内容Contents of the invention
本发明的目的之一在于：针对现有技术的不足，而提供一种复合负极片，能够减少电解液及可逆活性锂消耗，提高电池循环寿命和电池安全性能。One of the objectives of the present invention is to provide a composite negative electrode sheet for the deficiencies of the prior art, which can reduce the consumption of electrolyte and reversible active lithium, and improve the battery cycle life and battery safety performance.
为了实现上述目的，本发明采用以下技术方案：In order to achieve the above object, the present invention adopts the following technical solutions:
一种复合负极片，包括负极集流体以及涂覆于负极集流体至少一表面的涂覆层，所述涂覆层中设置有若干石墨片，至少一部分石墨片与负极集流体垂直设置，且该部分石墨片之间彼此分隔设置。A composite negative electrode sheet, comprising a negative electrode current collector and a coating layer coated on at least one surface of the negative electrode current collector, a plurality of graphite sheets are arranged in the coating layer, at least a part of the graphite sheets are arranged vertically to the negative electrode current collector, and the graphite sheets are separated from each other.
电池循环过程中原位生长的SEI膜通常机械性能及柔韧性较差，容易在长循环过程中由于体积膨胀等因素破裂，从而导致枝晶生长不受控，循环寿命短，安全性能差。本发明的负极片，在负极集流体表面设置涂覆层，涂覆层中有垂直设置且彼此分隔的石墨片，这种垂直集流体且相互之间平行排列的石墨片层，可以在电池随后的循环过程中部分容纳其产生的‘死锂’和锂枝晶，在一定程度上避免由于枝晶刺穿隔膜而导致的内短路所引发的安全事故。同时，由于在循环过程中产生的部分锂枝晶会沉积在这种石墨涂层的底部，其被随后所产生的‘死锂’或活性锂等掩埋，这在一定程度上减少了枝晶和电解液的接触，减低电解液消耗，起到了增加电池循环寿命的作用。SEI films grown in situ during battery cycling usually have poor mechanical properties and flexibility, and are prone to rupture due to factors such as volume expansion during long cycles, resulting in uncontrolled dendrite growth, short cycle life, and poor safety performance. In the negative electrode sheet of the present invention, a coating layer is provided on the surface of the negative electrode current collector, and there are graphite sheets arranged vertically and separated from each other in the coating layer. The graphite sheets arranged vertically to the current collector and parallel to each other can partially accommodate the 'dead lithium' and lithium dendrites generated by them during the subsequent cycle of the battery, and to a certain extent avoid safety accidents caused by internal short circuits caused by dendrites piercing through the separator. At the same time, since part of the lithium dendrites generated during the cycle will be deposited on the bottom of the graphite coating, they will be buried by the subsequent generation of 'dead lithium' or active lithium, which reduces the contact between the dendrites and the electrolyte to a certain extent, reduces the consumption of the electrolyte, and increases the cycle life of the battery.
优选地，所述负极集流体为铜箔(包括打孔铜箔和非打孔铜箔)、镍箔、不锈钢片、金属锂箔、金属锂基合金箔材中的任意一种。负极集流体可以为锂金属集流体，也可以是非锂金属合金基集流体。Preferably, the negative electrode current collector is any one of copper foil (including perforated copper foil and non-perforated copper foil), nickel foil, stainless steel sheet, metallic lithium foil, and metallic lithium-based alloy foil. The negative electrode current collector can be a lithium metal current collector, or a non-lithium metal alloy based current collector.
当选择非锂基集流体或非锂金属合金基集流体时，负极初始不含锂，此时涂覆在其上的磁性垂直石墨片可接受的的理论容量与正极材料在电压区间可发挥出来的理论容量比需远小于1，即N/P比值要远小于1。这个时候，当电池充电时，从正极测释放出来的锂离子一部分嵌入石墨负极，以LiC 6等形式 存在。因为负极可接受锂离子的理论数量远小于正极可释放出来的理论数量，这样，另一部分未被负极侧石墨材料所镶嵌的多余出来的锂离子，一部分沉积在负极处那些相互平行的垂直集流体的石墨片层的间隙之间，直至将其填满溢出，溢出之后还多余的的锂在石墨片层顶部表面继续沉积，形成一定厚度的锂金属层。由于锂离子脱出后部分不可逆性，这些从正极侧脱出来的锂在放电时有一部分不能重新重新回到正极，继续留在石墨层顶部或石墨片层间隙中。放电阶段，优先剥离沉积在石墨顶部的锂，之后再剥离沉积在石墨片层间隙中的锂。在此过程中，即使因为剥离不均匀而产生枝晶或‘死锂’，但因为石墨片层开口向上且有一定深度，因此‘死锂’和锂枝晶会掉入石墨间隙中而被后续的可逆活性锂所掩埋，从而减轻阻碍锂离子传输效果，减少与电解液消耗，提升电池循环寿命及安全性能。 When a non-lithium-based current collector or a non-lithium metal alloy-based current collector is selected, the negative electrode initially does not contain lithium. At this time, the ratio of the acceptable theoretical capacity of the magnetic vertical graphite sheet coated on it to the theoretical capacity that can be exerted by the positive electrode material in the voltage range must be much smaller than 1, that is, the N/P ratio should be much smaller than 1. At this time, when the battery is charged, part of the lithium ions released from the positive electrode are embedded in the graphite negative electrode and exist in the form of LiC 6 and so on. Because the theoretical amount of lithium ions that the negative electrode can accept is far less than the theoretical amount that can be released by the positive electrode, another part of the excess lithium ions that are not inlaid by the graphite material on the negative electrode side is partially deposited between the graphite sheets of the parallel vertical current collectors at the negative electrode until it is filled and overflows. After the overflow, the excess lithium continues to deposit on the top surface of the graphite sheet to form a lithium metal layer of a certain thickness. Due to the partial irreversibility of lithium ions after extraction, some of the lithium extracted from the positive electrode side cannot return to the positive electrode during discharge, and remain on the top of the graphite layer or in the gap between the graphite sheets. In the discharge stage, the lithium deposited on the top of the graphite is preferentially stripped, and then the lithium deposited in the gap between the graphite sheets is stripped. In this process, even if dendrites or 'dead lithium' are generated due to uneven peeling, because the graphite sheet opens upward and has a certain depth, the 'dead lithium' and lithium dendrites will fall into the graphite gap and be buried by subsequent reversible active lithium, thereby reducing the effect of hindering lithium ion transmission, reducing electrolyte consumption, and improving battery cycle life and safety performance.
当所用集流体为锂基集流体，由于负极侧本身能提供锂源，因此，此时负极侧与正极侧理论容量比要大于1，即专利所说的N/P比值要大于1。这个时候，相比与未涂覆的锂箔负极，专利中所述的涂覆的石墨片层，可以将其理解成一个牢笼结构，其作用完全是为了困住从负极侧出来的锂在后续的循环过程中形成锂枝晶及‘死锂’，达到减少电解液消耗，提升循环寿命和安全性能的目的。另一方面，亦可以理解为专利中所述的涂覆的石墨片层和箔材之间有一层锂或者锂合金，起到补锂作用。同时，需要注意的是，当负极所用集流体为锂基材料时，虽然此时若只计算涂覆的石墨片层的理论容量与正极理论容量比，其值仍小于1。但由于负极此时实际上是石墨和锂的一个复合负极，本身能提供锂源，因此此时负极侧总的理论容量与正极理论容量比是要远大于1的。When the current collector used is a lithium-based current collector, since the negative electrode itself can provide a lithium source, the theoretical capacity ratio between the negative electrode and the positive electrode should be greater than 1, that is, the N/P ratio mentioned in the patent should be greater than 1. At this time, compared with the uncoated lithium foil anode, the coated graphite sheet described in the patent can be understood as a cage structure, whose function is to trap the lithium coming out of the anode side to form lithium dendrites and 'dead lithium' in the subsequent cycle process, so as to reduce electrolyte consumption, improve cycle life and safety performance. On the other hand, it can also be understood that there is a layer of lithium or lithium alloy between the coated graphite sheet and the foil described in the patent, which acts as a lithium supplement. At the same time, it should be noted that when the current collector used in the negative electrode is a lithium-based material, even if only the ratio of the theoretical capacity of the coated graphite sheet to the theoretical capacity of the positive electrode is calculated at this time, the value is still less than 1. However, since the negative electrode is actually a composite negative electrode of graphite and lithium at this time, which can provide a lithium source, the ratio of the total theoretical capacity of the negative electrode side to the theoretical capacity of the positive electrode is much greater than 1 at this time.
优选地，所述涂覆层还包括增稠剂、粘结剂，所述石墨片、增稠剂、粘结剂的重量份数比为94～98：1～3:1～3。设置一定量的石墨片、增稠剂和粘结剂，使制备出的涂覆浆料具有一定的粘度，便于涂覆浆料的涂覆固定。Preferably, the coating layer further includes a thickener and a binder, and the weight-to-number ratio of the graphite sheet, the thickener, and the binder is 94-98:1-3:1-3. A certain amount of graphite flakes, thickeners and binders are arranged so that the prepared coating slurry has a certain viscosity, which is convenient for coating and fixing of the coating slurry.
优选地，所述粘结剂包括聚四氟乙烯、丁苯橡胶、聚丙烯酸酯、聚酰亚胺、 聚丙烯酸钠、壳聚糖、聚偏氟乙烯、聚偏二氟乙烯中的一种或几种。Preferably, the binder includes one or more of polytetrafluoroethylene, styrene-butadiene rubber, polyacrylate, polyimide, sodium polyacrylate, chitosan, polyvinylidene fluoride, and polyvinylidene fluoride.
优选地，所有石墨片与负极集流体垂直设置。所有的石墨片与负极集流体垂直设置，能够增加复合负极片的电化学性能。Preferably, all graphite sheets are arranged vertically to the negative electrode current collector. All the graphite sheets are vertically arranged with the negative electrode current collector, which can increase the electrochemical performance of the composite negative electrode sheet.
其中，所述增稠剂为羧甲基纤维素钠。Wherein, the thickener is sodium carboxymethylcellulose.
本发明的目的之二在于：针对现有技术的不足，而提供一种复合负极片的制备方法，操作简单，可批量生产。The second object of the present invention is to provide a method for preparing a composite negative plate, which is easy to operate and can be mass-produced in view of the deficiencies in the prior art.
为了实现上述目的，本发明采用以下技术方案：In order to achieve the above object, the present invention adopts the following technical solutions:
一种复合负极片的制备方法，包括以下步骤：A method for preparing a composite negative plate, comprising the following steps:
步骤S1、将磁性物质修饰后的石墨片与粘结剂、增稠剂混合，加入溶剂，搅拌制得涂覆浆料；Step S1, mixing the graphite sheet modified by the magnetic substance with a binder and a thickener, adding a solvent, and stirring to prepare a coating slurry;
步骤S2、选取负极集流体，设置磁场发射装置，将涂覆浆料涂覆在负极集流体的至少一表面，将涂覆浆料在磁场发射装置下干燥形成涂覆层，制得复合负极片，其中，磁场发射装置用于将涂覆浆料中的磁性物质修饰后的石墨片与负极集流体垂直设置。Step S2, selecting the negative electrode current collector, installing a magnetic field emission device, coating the coating slurry on at least one surface of the negative electrode current collector, drying the coating slurry under the magnetic field emission device to form a coating layer, and obtaining a composite negative electrode sheet, wherein the magnetic field emission device is used to vertically arrange the graphite sheet modified by the magnetic substance in the coating slurry and the negative electrode current collector.
在旋转磁场下，悬浮在流体中并用磁性纳米粒子装饰的微米级小片，具有两种不同的取向状态。其高度依赖于磁场旋转频率和流体的流变特性。当磁场旋转频率足够低时，磁性物质修饰粒子受磁扭矩控制，其在集流体表面沿旋转场方向同步转动。而当旋转频率足够高时，磁性物质运动状态的决定步骤变更为流体粘度，此时，磁性物质将与旋转磁场平面平行排列。Under a rotating magnetic field, micron-sized flakes suspended in a fluid and decorated with magnetic nanoparticles have two different orientation states. It is highly dependent on the magnetic field rotation frequency and the rheological properties of the fluid. When the magnetic field rotation frequency is low enough, the magnetic substance-modified particles are controlled by the magnetic torque, and they rotate synchronously on the surface of the current collector along the direction of the rotating field. When the rotation frequency is high enough, the determining step of the motion state of the magnetic substance is changed to the fluid viscosity, and at this time, the magnetic substance will be arranged parallel to the plane of the rotating magnetic field.
优选地，所述涂覆层还包括溶剂，所述溶剂为水系溶剂或油系溶剂。当负极集流体使用铜箔、镍箔时，上述负极浆料可以用水系溶剂，所述水系溶剂包括且不限于水、甲醇、乙醇，当所用负极集流体为金属锂及金属锂基合金箔材等在常规环境下容易发生燃烧***等危险事故的集流体时，则上述负极浆料所用溶剂为油系溶剂，所述油系溶剂包括且不限于N-甲基吡咯烷酮(NMP)、N,N-二甲基甲酰胺(DMF)、二甲基亚砜(DMSO)等。使用油系溶剂时，涂覆奖学金料涂布及后续电池组装工序必须全部在露点温度小于-36℃的干燥房 中进行。用油系溶剂进行浆料配置时，配置前，应确保溶剂水含量<20ppm。Preferably, the coating layer further includes a solvent, and the solvent is a water-based solvent or an oil-based solvent. When copper foil or nickel foil is used as the negative electrode current collector, the negative electrode slurry can be a water-based solvent. The water-based solvent includes and is not limited to water, methanol, and ethanol. When the negative electrode current collector used is a current collector that is prone to dangerous accidents such as combustion and explosion under normal circumstances, such as metal lithium and metal lithium-based alloy foil, the solvent used in the above-mentioned negative electrode slurry is an oil-based solvent. The oil-based solvent includes but is not limited to N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) etc. When oil-based solvents are used, the coating of the scholarship material and the subsequent battery assembly process must all be carried out in a drying room with a dew point temperature lower than -36°C. When using oil-based solvents for slurry preparation, ensure that the water content of the solvent is <20ppm before preparation.
本发明的目的之三在于：针对现有技术的不足，而提供一种锂金属二次电池，具有良好的电化学性能和安全性能。The third object of the present invention is to provide a lithium metal secondary battery with good electrochemical performance and safety performance in view of the deficiencies of the prior art.
为了实现上述目的，本发明采用以下技术方案：In order to achieve the above object, the present invention adopts the following technical solutions:
一种锂金属二次电池，包括正极片、隔离膜、负极片、电解液以及壳体，所述隔离膜分隔所述正极片和所述负极片，所述壳体用于装设正极片、隔离膜、负极片和电解液，所述负极片为上述的复合负极片。A lithium metal secondary battery, comprising a positive electrode sheet, a separator, a negative electrode sheet, an electrolyte and a casing, the separator separates the positive electrode sheet and the negative electrode sheet, the casing is used to install the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte, and the negative electrode sheet is the above-mentioned composite negative electrode sheet.
上述的锂金属二次电池的电池结构可以是叠片式、卷绕式或两者混合式等。The battery structure of the above-mentioned lithium metal secondary battery may be a laminated type, a wound type, or a hybrid type of both.
优选地，所述正极片包括正极集流体和涂覆于正极集流体至少一表面的正极活性物质层，所述正极活性物质层包括钴酸锂、镍锰酸锂、镍锰钴酸锂、镍钴铝酸锂、磷酸铁锂、锰酸锂、富锂锰基或磷酸锰铁锂中的一种或几种混合物。Preferably, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector. The positive electrode active material layer includes one or more mixtures of lithium cobalt oxide, lithium nickel manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganate, lithium-rich manganese base, or lithium manganese iron phosphate.
优选地，所述隔离膜为聚乙烯膜、聚丙烯膜、聚乙烯-聚丙烯复合膜、聚酰亚胺膜、陶瓷膜中的任意一种。Preferably, the isolation film is any one of polyethylene film, polypropylene film, polyethylene-polypropylene composite film, polyimide film and ceramic film.
相对于现有技术，本发明的有益效果在于：本发明的负极片，在负极集流体表面设置涂覆层，涂覆层中有垂直设置且彼此分隔的石墨片，这种垂直集流体且相互之间平行排列的石墨片层，可以在电池随后的循环过程中部分容纳其产生的‘死锂’和锂枝晶，在一定程度上避免由于枝晶刺穿隔膜而导致的内短路所引发的安全事故。同时，由于在循环过程中产生的部分锂枝晶会沉积在这种石墨涂层的底部，其被随后所产生的‘死锂’或活性锂等掩埋，这在一定程度上减少了枝晶和电解液的接触，减低电解液消耗，起到了增加电池循环寿命的作用。Compared with the prior art, the beneficial effect of the present invention is: the negative electrode sheet of the present invention is provided with a coating layer on the surface of the negative electrode current collector, and there are graphite sheets arranged vertically and separated from each other in the coating layer. The graphite sheets arranged in parallel with each other in this vertical current collector can partially accommodate the 'dead lithium' and lithium dendrites produced by them during the subsequent cycle of the battery, and to a certain extent avoid safety accidents caused by internal short circuits caused by dendrites piercing through the diaphragm. At the same time, since part of the lithium dendrites generated during the cycle will be deposited on the bottom of the graphite coating, they will be buried by the subsequent generation of 'dead lithium' or active lithium, which reduces the contact between the dendrites and the electrolyte to a certain extent, reduces the consumption of the electrolyte, and increases the cycle life of the battery.
附图说明Description of drawings
图1是现有技术的负极片的结构示意图。FIG. 1 is a schematic structural view of a negative electrode sheet in the prior art.
图2是本发明的负极片的结构示意图。Fig. 2 is a schematic structural view of the negative electrode sheet of the present invention.
图3是本发明的实施例1与对比例1的容量保持率曲线对比图。FIG. 3 is a graph comparing the capacity retention curves of Example 1 and Comparative Example 1 of the present invention.
其中：1、负极集流体；2、石墨片；3、锂离子。Among them: 1. Negative electrode current collector; 2. Graphite sheet; 3. Lithium ion.
具体实施方式Detailed ways
下面结合具体实施方式和说明书附图，对本发明作进一步详细的描述，但本发明的实施方式并不限于此。The present invention will be described in further detail below in conjunction with the specific embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.
实施例1Example 1
一种复合负极片的制备方法，包括以下步骤：A method for preparing a composite negative plate, comprising the following steps:
步骤S1、将磁性物质修饰后的石墨片2与粘结剂、增稠剂混合，加入溶剂，搅拌制得涂覆浆料；Step S1, mixing the graphite sheet 2 modified by the magnetic substance with a binder and a thickener, adding a solvent, and stirring to prepare a coating slurry;
步骤S2、选取负极集流体1，设置磁场发射装置，将涂覆浆料涂覆在负极集流体1的至少一表面，将涂覆浆料在磁场发射装置下干燥形成涂覆层，制得复合负极片，其中，磁场发射装置用于将涂覆浆料中的磁性物质修饰后的石墨片2与负极集流体1垂直设置。制备出的复合负极片如图2所示，水平放置的为负极集流体1，与负极集流体1垂直且间隔设置的为石墨片2，多个石墨片2相互分隔设置，与负极集流体1形成一个向上开口的容纳空间，能够容纳锂离子3，出现‘死锂’或锂枝晶时，形成的容纳空间能够装设‘死锂’或锂枝晶，避免生成的锂枝晶刺穿隔膜从而导致内短路，引发电池安全事故。同时，可在一定程度上减少电解液与锂枝晶之间的接触，降低电解液消耗，从而起到提升安全性能，延长电池循环寿命的作用。Step S2, select the negative electrode current collector 1, install a magnetic field emission device, coat the coating slurry on at least one surface of the negative electrode current collector 1, dry the coating slurry under the magnetic field emission device to form a coating layer, and obtain a composite negative electrode sheet, wherein the magnetic field emission device is used to vertically arrange the graphite sheet 2 modified by the magnetic substance in the coating slurry with the negative electrode current collector 1. The prepared composite negative electrode sheet is shown in Figure 2. The negative electrode collector 1 placed horizontally is the negative electrode collector 1, and the graphite sheet 2 is arranged vertically and spaced apart from the negative electrode collector 1. The multiple graphite sheets 2 are separated from each other and form an upward-opening accommodation space with the negative electrode current collector 1, which can accommodate lithium ions 3. When 'dead lithium' or lithium dendrites appear, the formed accommodation space can be installed. At the same time, the contact between the electrolyte and lithium dendrites can be reduced to a certain extent, and the consumption of the electrolyte can be reduced, thereby improving the safety performance and prolonging the cycle life of the battery.
其中，涂覆层中所述石墨片2、增稠剂、粘结剂的重量份数比为95:2.5:2.5。Wherein, the ratio of graphite sheet 2, thickener, and binder in the coating layer is 95:2.5:2.5.
其中，粘结剂为聚四氟乙烯，增稠剂为羧甲基纤维素钠。Wherein, the binder is polytetrafluoroethylene, and the thickener is sodium carboxymethyl cellulose.
其中，负极集流体1为金属锂箔，溶剂为油系溶剂，油系溶剂为N-甲基吡咯烷酮。Wherein, the negative electrode current collector 1 is metal lithium foil, the solvent is an oil-based solvent, and the oil-based solvent is N-methylpyrrolidone.
其中，隔离膜为聚乙烯膜。Wherein, the isolation film is a polyethylene film.
实施例2Example 2
与实施例1的不同之处在于：涂覆层中所述石墨片2、增稠剂、粘结剂的重量份数比为98:2:2。The difference from Example 1 is that the ratio of graphite sheet 2, thickener, and binder in the coating layer is 98:2:2.
其余与实施例1相同，这里不再赘述。The rest are the same as in Embodiment 1, and will not be repeated here.
实施例3Example 3
与实施例1的不同之处在于：涂覆层中所述石墨片2、增稠剂、粘结剂的重量份数比为94:2:2。The difference from Example 1 is that the ratio of graphite sheet 2, thickener, and binder in the coating layer is 94:2:2.
其余与实施例1相同，这里不再赘述。The rest are the same as in Embodiment 1, and will not be repeated here.
实施例4Example 4
与实施例1的不同之处在于：涂覆层中所述石墨片2、增稠剂、粘结剂的重量份数比为95:1:1。The difference from Example 1 is that the ratio of graphite sheet 2, thickener, and binder in the coating layer is 95:1:1 by weight.
其余与实施例1相同，这里不再赘述。The rest are the same as in Embodiment 1, and will not be repeated here.
实施例5Example 5
与实施例1的不同之处在于：涂覆层中所述石墨片2、增稠剂、粘结剂的重量份数比为95:1:3。The difference from Example 1 is that the ratio of graphite sheet 2, thickener, and binder in the coating layer is 95:1:3 by weight.
其余与实施例1相同，这里不再赘述。The rest are the same as in Embodiment 1, and will not be repeated here.
实施例6Example 6
与实施例1的不同之处在于：所述负极集流体1为铜箔，所述溶剂为水系溶剂，溶剂为水。The difference from Example 1 is that: the negative electrode current collector 1 is copper foil, the solvent is an aqueous solvent, and the solvent is water.
其余与实施例1相同，这里不再赘述。The rest are the same as in Embodiment 1, and will not be repeated here.
对比例1Comparative example 1
与实施例1的区别在于：负极片的制备方步，包括以下步骤：The difference with embodiment 1 is: the preparation square step of negative electrode sheet comprises the following steps:
步骤S1、将磁性物质修饰后的石墨片2与粘结剂、增稠剂混合，加入溶剂，搅拌制得涂覆浆料；Step S1, mixing the graphite sheet 2 modified by the magnetic substance with a binder and a thickener, adding a solvent, and stirring to prepare a coating slurry;
步骤S2、选取负极集流体1，将涂覆浆料涂覆在负极集流体1的至少一表面，干燥形成涂覆层，制得负极片，如图1所示。Step S2, selecting the negative electrode collector 1, coating the coating slurry on at least one surface of the negative electrode collector 1, drying to form a coating layer, and preparing the negative electrode sheet, as shown in FIG. 1 .
其余与实施例1相同，这里不再赘述。The rest are the same as in Embodiment 1, and will not be repeated here.
性能测试：将上述实施例1-6以及对比例1制备出的二次电池进行120次充放电循环后进行容量保持率性能测试，测试结果记录表1。Performance test: The capacity retention performance test was performed after 120 charge-discharge cycles of the secondary batteries prepared in Examples 1-6 and Comparative Example 1 above, and the test results are recorded in Table 1.
表1Table 1
项目project 容量保持率(％)Capacity retention (%) 项目project 容量保持率(％)Capacity retention (%)
实施例1Example 1 8888 实施例2Example 2 8686
实施例3Example 3 8585 实施例4Example 4 8585
实施例5Example 5 8585 实施例6Example 6 8484
对比例1Comparative example 1 8080 // //
结合图3和上述表1可以得出，本发明的二次电池相对于对比例1的二次电池经过120次充放电后仍然保持有84％～88％的容量保持率，电化学性能好。而且由实施例1-5对比得出，当设置涂覆层中所述石墨片2、增稠剂、粘结剂的重量份数比为95:2.5:2.5时，制备出的二次电池具有更好的容量保持率。由实施例1-5和6对比得出，当负极集流体1为金属锂箔，溶剂为油系溶剂时制备出的二次电池相对于负极集流体1使用铜箔，溶剂使用水系溶剂时制备出的二次电池具有更好的电化学性能。Combining FIG. 3 and the above Table 1, it can be concluded that the secondary battery of the present invention still maintains a capacity retention rate of 84% to 88% after 120 charges and discharges compared with the secondary battery of Comparative Example 1, and the electrochemical performance is good. Moreover, it can be concluded from the comparison of Examples 1-5 that when the ratio of graphite sheet 2, thickener, and binder in the coating layer is set to be 95:2.5:2.5 by weight, the prepared secondary battery has better capacity retention. From the comparison of Examples 1-5 and 6, it can be concluded that the secondary battery prepared when the negative electrode current collector 1 is metal lithium foil and the solvent is an oil-based solvent has better electrochemical performance than the secondary battery prepared when the negative electrode current collector 1 uses copper foil and the solvent uses a water-based solvent.
将实施例1-3与对比例1进行不同倍率的放电容量和放电倍率测试，测试结果记录表2。Examples 1-3 and Comparative Example 1 were tested for discharge capacity and discharge rate at different rates, and the test results are recorded in Table 2.
表2Table 2
Figure PCTCN2022108258-appb-000001
Figure PCTCN2022108258-appb-000001
Figure PCTCN2022108258-appb-000002
Figure PCTCN2022108258-appb-000002
由上述表2可以得出，对比例1在3C倍率下容量约为40mAh，容量保持率仅为初始的16.89％；本发明的实施例1-3的3C倍率下放电容量平均达到75.7mAh/g，约为初始值的36.63％，同时，本发明电池的容量保持率、放电倍率以及放电电压均比对比例1高，而且结合图3可以看出，本发明所述电池具有更好的电化学性能。It can be concluded from the above Table 2 that the capacity of Comparative Example 1 is about 40mAh at 3C rate, and the capacity retention rate is only 16.89% of the initial value; the average discharge capacity of Examples 1-3 of the present invention at 3C rate reaches 75.7mAh/g, which is about 36.63% of the initial value.
根据上述说明书的揭示和教导，本发明所属领域的技术人员还能够对上述实施方式进行变更和修改。因此，本发明并不局限于上述的具体实施方式，凡是本领域技术人员在本发明的基础上所作出的任何显而易见的改进、替换或变型均属于本发明的保护范围。此外，尽管本说明书中使用了一些特定的术语，但这些术语只是为了方便说明，并不对本发明构成任何限制。According to the disclosure and teaching of the above specification, those skilled in the art to which the present invention pertains can also change and modify the above embodiment. Therefore, the present invention is not limited to the above-mentioned specific implementation manners, and any obvious improvement, substitution or modification made by those skilled in the art on the basis of the present invention shall fall within the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (10)

  1. 一种复合负极片，其特征在于，包括负极集流体以及涂覆于负极集流体至少一表面的涂覆层，所述涂覆层中设置有若干石墨片，至少一部分石墨片与负极集流体垂直设置，且该部分石墨片之间彼此分隔设置。A composite negative electrode sheet, characterized in that it includes a negative electrode current collector and a coating layer coated on at least one surface of the negative electrode current collector, a plurality of graphite sheets are arranged in the coating layer, at least a part of the graphite sheets are arranged vertically to the negative electrode current collector, and the graphite sheets are separated from each other.
  2. 根据权利要求1所述的复合负极片，其特征在于，所述负极集流体为铜箔、镍箔、不锈钢片、金属锂箔、金属锂基合金箔材中的任意一种。The composite negative electrode sheet according to claim 1, wherein the negative electrode current collector is any one of copper foil, nickel foil, stainless steel sheet, metallic lithium foil, and metallic lithium-based alloy foil.
  3. 根据权利要求1或2所述的复合负极片，其特征在于，所述涂覆层还包括增稠剂、粘结剂，所述石墨片、增稠剂、粘结剂的重量份数比为94～98：1～3:1～3。The composite negative electrode sheet according to claim 1 or 2, characterized in that the coating layer further comprises a thickener and a binder, and the ratio of parts by weight of the graphite sheet, thickener and binder is 94-98:1-3:1-3.
  4. 根据权利要求3所述的复合负极片，其特征在于，所述粘结剂包括聚四氟乙烯、丁苯橡胶、聚丙烯酸酯、聚酰亚胺、聚丙烯酸钠、壳聚糖、聚偏氟乙烯、聚偏二氟乙烯中的一种或几种。The composite negative electrode sheet according to claim 3, wherein the binder includes one or more of polytetrafluoroethylene, styrene-butadiene rubber, polyacrylate, polyimide, sodium polyacrylate, chitosan, polyvinylidene fluoride, and polyvinylidene fluoride.
  5. 根据权利要求1所述的复合负极片，其特征在于，所有石墨片与负极集流体垂直设置。The composite negative electrode sheet according to claim 1, wherein all the graphite sheets are vertically arranged with the negative electrode current collector.
  6. 根据权利要求1-5中任一项所述的复合负极片的制备方法，其特征在于，包括以下步骤：The preparation method of the composite negative plate according to any one of claims 1-5, is characterized in that, comprises the following steps:
    步骤S1、将磁性物质修饰后的石墨片与粘结剂、增稠剂混合，加入溶剂，搅拌制得涂覆浆料；Step S1, mixing the graphite sheet modified by the magnetic substance with a binder and a thickener, adding a solvent, and stirring to prepare a coating slurry;
    步骤S2、选取负极集流体，设置磁场发射装置，将涂覆浆料涂覆在负极集流体的至少一表面，将涂覆浆料在磁场发射装置下干燥形成涂覆层，制得复合负极片，其中，磁场发射装置用于将涂覆浆料中的磁性物质修饰后的石墨片与负极集流体垂直设置。Step S2, selecting the negative electrode current collector, installing a magnetic field emission device, coating the coating slurry on at least one surface of the negative electrode current collector, drying the coating slurry under the magnetic field emission device to form a coating layer, and obtaining a composite negative electrode sheet, wherein the magnetic field emission device is used to vertically arrange the graphite sheet modified by the magnetic substance in the coating slurry and the negative electrode current collector.
  7. 根据权利要求6中所述的复合负极片的制备方法，其特征在于，所述涂覆层还包括溶剂，所述溶剂为水系溶剂或油系溶剂。The method for preparing a composite negative electrode according to claim 6, wherein the coating layer further includes a solvent, and the solvent is a water-based solvent or an oil-based solvent.
  8. 一种锂金属二次电池，其特征在于，包括正极片、隔离膜、负极片、电解液以及壳体，所述隔离膜分隔所述正极片和所述负极片，所述壳体用于装设正极片、隔离膜、负极片和电解液，所述负极片为权利要求1-5中任一项所 述的复合负极片。A lithium metal secondary battery, characterized in that it comprises a positive electrode sheet, a separator, a negative electrode sheet, an electrolyte and a housing, the separator separates the positive electrode sheet and the negative electrode sheet, the housing is used to house the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte, and the negative electrode sheet is the composite negative electrode sheet according to any one of claims 1-5.
  9. 根据权利要求8所述的一种锂金属二次电池，其特征在于，所述正极片包括正极集流体和涂覆于正极集流体至少一表面的正极活性物质层，所述正极活性物质层包括钴酸锂、镍锰酸锂、镍锰钴酸锂、镍钴铝酸锂、磷酸铁锂、锰酸锂、富锂锰基或磷酸锰铁锂中的一种或几种混合物。The lithium metal secondary battery according to claim 8, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, and the positive electrode active material layer comprises one or more mixtures of lithium cobalt oxide, lithium nickel manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium manganate, lithium-rich manganese base, or lithium manganese iron phosphate.
  10. 根据权利要求8所述的一种锂金属二次电池，其特征在于，所述隔离膜为聚乙烯膜、聚丙烯膜、聚乙烯-聚丙烯复合膜、聚酰亚胺膜、陶瓷膜中的任意一种。The lithium metal secondary battery according to claim 8, wherein the separator is any one of polyethylene film, polypropylene film, polyethylene-polypropylene composite film, polyimide film, and ceramic film.
PCT/CN2022/108258 2022-01-21 2022-07-27 Composite negative electrode plate and preparation method therefor, and lithium metal secondary battery WO2023138018A1 (en)

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