WO2023279379A1 - 负极极片及包含其的电化学装置、电子装置 - Google Patents

负极极片及包含其的电化学装置、电子装置 Download PDF

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WO2023279379A1
WO2023279379A1 PCT/CN2021/105515 CN2021105515W WO2023279379A1 WO 2023279379 A1 WO2023279379 A1 WO 2023279379A1 CN 2021105515 W CN2021105515 W CN 2021105515W WO 2023279379 A1 WO2023279379 A1 WO 2023279379A1
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negative electrode
porous layer
lithium
lithium metal
electrode sheet
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PCT/CN2021/105515
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English (en)
French (fr)
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林小萍
陈茂华
谢远森
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宁德新能源科技有限公司
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Priority to PCT/CN2021/105515 priority Critical patent/WO2023279379A1/zh
Priority to EP21948873.1A priority patent/EP4369441A1/en
Priority to CN202180017969.8A priority patent/CN115280550A/zh
Publication of WO2023279379A1 publication Critical patent/WO2023279379A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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 relates to the field of energy storage, and specifically relates to a negative electrode sheet containing a three-dimensional skeleton structure and an electrochemical device and an electronic device containing the same, especially a lithium ion battery.
  • Lithium metal is one of the metals with the largest mass-to-energy ratio discovered so far. Lithium-ion batteries using lithium metal as the negative electrode material can greatly improve the energy density and working voltage of electrochemical devices.
  • lithium dendrites can pierce the separator and cause a short circuit of the battery, which brings safety risks; 3) With the continuous charging and discharging process of the battery, lithium metal precipitation will Continuous volume expansion and contraction lead to damage to the electrode structure, and in severe cases, the interface between the negative electrode sheet and the less flexible inorganic protective coating will be peeled off, thereby losing the protective effect.
  • the embodiments of the present application solve at least one problem existing in the related field at least to some extent by providing a pole piece that improves the safety of the electrode assembly and an electrochemical device including the pole piece.
  • the application provides a negative electrode sheet, which includes: a negative electrode current collector and a porous layer.
  • the porous layer is located on the negative current collector, and the porous layer includes a three-dimensional framework containing electrically insulating fibers.
  • the three-dimensional framework can be configured to accommodate lithium metal deposition.
  • the present application provides an electrochemical device, which includes the positive electrode in the above embodiment.
  • the negative electrode of the present application is provided with a porous layer comprising a three-dimensional framework, and the three-dimensional framework is made of electrically insulating fibers, which can effectively improve the deposition of lithium metal on the surface of the negative electrode during the charge-discharge cycle of the electrochemical device; and inhibit lithium metal volume expansion; at the same time slow down the growth of lithium dendrites, thereby improving the cycle performance, capacity performance and safety performance of electrochemical devices.
  • the three-dimensional skeleton with electrically insulating fibers can block the transmission of electrons from the side of the negative electrode current collector to the surface of the porous layer, realize the control of the deposition direction and position of lithium metal, and further improve the volume of the pole piece Expansion and cycle stability.
  • the present application provides an electronic device, which includes the above-mentioned electrochemical device.
  • FIG. 1 is a schematic structural diagram of an anode according to some embodiments of the present application.
  • Fig. 2 is a schematic cross-sectional structure diagram of an anode according to some embodiments of the present application.
  • SEM scanning electron microscope
  • FIG. 4 is a scanning electron microscope image of lithium metal deposition in a porous layer according to some embodiments of the present application.
  • Fig. 5 is a schematic structural view of fibers with a hollow structure according to some embodiments of the present application.
  • Fig. 6 is a molecular structure diagram of the ⁇ phase of polyvinylidene fluoride.
  • FIG. 7 is a schematic structural diagram of negative electrodes according to other embodiments of the present application.
  • the terms “approximately,” “substantially,” “substantially,” and “about” are used to describe and account for minor variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurred exactly as well as instances in which the event or circumstance occurred with close approximation.
  • the term when used in conjunction with a numerical value, the term may refer to a range of variation of less than or equal to ⁇ 10% of the stated value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, less than or equal to ⁇ 10%, Less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • the difference between two numerical values is less than or equal to ⁇ 10% of the mean of the stated values (e.g., less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%), then the two values can be considered to be "substantially" the same.
  • a list of items linked by the terms “at least one of”, “at least one of”, “at least one of” or other similar terms may mean that the listed items any combination of .
  • the phrase “at least one of A and B” means only A; only B; or A and B.
  • the phrase “at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single element or multiple elements.
  • Item B may contain a single element or multiple elements.
  • Item C may contain a single element or multiple elements.
  • first”, “second”, “third”, etc. may be used herein to distinguish different components of a figure or series of figures. Unless otherwise specified or limited, “first”, “second”, “third” and the like are not intended to describe the corresponding component.
  • Lithium metal is the metal with the smallest relative atomic mass (6.94) and the lowest standard electrode potential (-3.045V) among all metal elements, and its theoretical specific capacity is as high as 3860mAh/g.
  • the use of lithium metal as the negative electrode active material can increase the working voltage and capacity of the electrochemical device.
  • the current lithium-ion batteries mainly face the following problems: First, the commonly used lithium-ion battery negative electrode materials such as graphite, etc., when charging Lithium ions exist in the graphite layer structure in the form of intercalation, and the graphite layer has a porous structure that provides storage space for lithium metal.
  • FIG 1 and 2 are schematic diagrams and cross-sectional diagrams of negative electrodes according to some embodiments of the present application.
  • the embodiment of the present application provides a negative electrode 10, which is provided with a porous layer 101 including a three-dimensional framework on the surface of the negative electrode current collector 100 to provide a host for lithium metal, Ensure that lithium metal can be stored in the three-dimensional framework in the porous layer on the surface of the current collector during the charging and discharging process of the battery, thereby inhibiting volume expansion.
  • the three-dimensional framework can improve the deposition morphology of lithium metal and inhibit the formation of lithium dendrites.
  • the porous layer 101 is entirely composed of a three-dimensional skeleton.
  • the material of the three-dimensional framework in the porous layer 101 includes electrically insulating fibers. Due to the electrically insulating fibers, electrons can be prevented from migrating from the surface of the negative electrode current collector to the outer surface of the porous layer, thereby inducing lithium metal to gradually deposit from the surface side of the negative electrode current collector to the interior of the porous layer, further improving the volume expansion of the negative electrode. Inhibit the growth of lithium dendrites, thereby improving the cycle performance of electrochemical devices.
  • the three-dimensional framework is entirely composed of electrically insulating fibers.
  • the three-dimensional framework comprises electrically insulating fibers having an electrical conductivity of less than 10 ⁇ 10 S/cm.
  • FIG. 3 and 4 respectively show the top view surface of the three-dimensional framework and the scanning electron microscope images of lithium metal deposition in the porous layer according to some embodiments of the present application.
  • Figures 3 and 4 by controlling the electronic non-conduction of the three-dimensional framework in the porous layer, the control of the deposition direction of lithium metal can be realized, and lithium metal can be completely deposited inside the porous layer, improving the expansion and circulation of the negative electrode sheet. stability.
  • the structure of electrically insulating fibers can include strip fibers, spherical fibers, and bulk fibers.
  • the structure of the fiber is a strip fiber, wherein the three-dimensional skeleton is built by a plurality of single strip fibers and strip fibers, and the material of the strip fiber can better build a three-dimensional skeleton and form a self-supporting structure .
  • the fibers are 50 nm to 10 ⁇ m in diameter.
  • the individual fibers have a diameter of approximately, for example, about 50 nm, about 100 nm, about 200 nm, about 300 nm, about 400 nm, about 500 nm, about 700 nm, about 1 ⁇ m, about 2 ⁇ m, about 5 ⁇ m, about 10 ⁇ m, or A range consisting of any two of these values.
  • individual fibers have a diameter of 200 nm to 2 ⁇ m.
  • the porous layer has a porosity greater than or equal to 70% or 80%. In some other embodiments, the porosity of the porous layer is 70% to 90%, so as to ensure that there is enough space in the porous layer for accommodating lithium metal deposition, and maintaining a certain structural strength and stability.
  • the porous layer includes holes formed by fibers built up with each other in the three-dimensional framework, and the holes are formed between fibers.
  • the fibers in the three-dimensional framework are interwoven to form pores, and the size of the pores is approximately in the range of 100 nm to 10 ⁇ m.
  • the size of the pores formed by the interweaving of fibers in the three-dimensional framework is approximately, for example, about 100 nm, about 200 nm, about 500 nm, about 1 ⁇ m, about 2 ⁇ m, about 5 ⁇ m, about 10 ⁇ m, or any two of these values. range of components.
  • the holes formed by the strip-shaped fibers and the strip-shaped fibers have a more consistent pore distribution range, and the pore structure is more stable, which can improve the deposition law of lithium metal and inhibit the formation of irregular lithium dendrites. form.
  • the size of pores formed by the interweaving of fibers in the three-dimensional framework ranges from 500 nm to 5 ⁇ m.
  • the fiber can also be defined by the hole structure of the fiber itself, which can include a solid structure, a hollow structure or both.
  • the solid structure means that the fiber itself does not have any holes, while the hollow structure means that the fiber itself has a hole structure.
  • the fibers in the three-dimensional framework have a hollow structure, and the porous layer contains holes in the fibers themselves, and the holes are formed inside the fibers.
  • the hole size of the hollow structure is 10 nm to 500 nm. In some other embodiments, the hole size of the hollow structure is approximately, for example, about 10 nm, about 50 nm, about 200 nm, about 500 nm, or a range consisting of any two of these values.
  • Fig. 5 is a schematic structural view of fibers with a hollow structure according to some embodiments of the present application.
  • the pore structure of the hollow structural fiber can be in three forms, including a hollow structure, a pore-forming structure on the wall, or a hollow and pore-forming structure on the wall.
  • the fiber wall thickness of the fiber is 50 nm to 4.5 ⁇ m.
  • the size of the pores of the pore-forming structure on the wall is 50 nm to 500 nm.
  • the transmission rate of the electrolyte in the three-dimensional skeleton can be accelerated; at the same time, the design of the hollow structure can further reduce the structural weight of the three-dimensional skeleton and improve the lithium metal in the three-dimensional framework.
  • the surface utilization in the three-dimensional framework is also beneficial to improve the overall energy density of electrochemical devices.
  • the fibers include ion-conducting fibers, in which lithium ions can combine with some active groups on the surface of the ion-conducting fibers to form associations, and as the fiber surface moves, the active sites associated with lithium ions can Continuously moving and converting, so as to realize the transmission of lithium ions, and further improve the transmission efficiency of lithium ions in the porous layer.
  • the fiber material includes one or more of polymer materials and inorganic materials, wherein the polymer materials include one or more of the following components and derivatives of each component: Vinyl fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyphenylene ether, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyepoxide Ethane, polyvinylidene fluoride-hexafluoropropylene or polyvinylidene fluoride-chlorotrifluoroethylene; and the inorganic material includes, but is not limited to, one or more of the following components and derivatives of each component : Sodium silicate, aluminum oxide or silicon oxide.
  • the fibers include piezoelectric materials.
  • material having piezoelectricity refers to a material that is an electrical insulator under normal pressure, but when a certain range of pressure is applied thereto, allows an electric current to pass due to a change in its internal structure.
  • Materials that are piezoelectric can exhibit high dielectric constants above 100, and when a range of pressures are applied to stretch or compress them, they charge positively on one surface and negatively on the other. Therefore, when the negative electrode is charged, due to the deposition of lithium metal in the porous layer, the three-dimensional framework will further expand and stretch.
  • the fibers of piezoelectric materials can be used in the two regions of the lithium ion metal deposition area in the porous layer A potential difference is generated between the surfaces, thereby improving the conductivity of the three-dimensional skeleton between the lithium ion metal deposition regions, thereby improving the electric cycle effect of the negative electrode, and optimizing the density and direction of lithium metal deposition.
  • piezoelectric materials include, but are not limited to, BaTiO 3 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT) , PB(Mg 3 Nb 2/3 )O 3 -PbTiO 3 (PMN-PT), and one or more of hafnium dioxide (HfO2).
  • the fibers comprise a fluoropolymer having a beta phase.
  • ⁇ -phase refers to a thermodynamically stable phase in a crystal phase stack structure of a polymer material.
  • polyvinylidene fluoride when polyvinylidene fluoride is used as a three-dimensional skeleton fiber, there are five crystal phases in polyvinylidene fluoride, ⁇ , the common one is ⁇ phase, ⁇ phase is the kinetic control phase, and ⁇ phase is thermodynamically stable Mutually.
  • the H-F-C atoms in the ⁇ -phase of fluoropolymer fibers (such as, but not limited to, polyvinylidene fluoride) present an ordered folding arrangement, resulting in dipole moments pointing in the same direction, and its monomer units are relatively It has the highest dipole moment among other phases, so the ⁇ phase has better piezoelectricity, pyroelectricity and ferroelectricity.
  • the ⁇ -phase in the fluoropolymer fiber can be effectively increased, and by adding the ⁇ -phase fluoropolymer fiber to the three-dimensional skeleton fiber, the stacking structure of the polymer material in the fiber can be optimized to make it It has good piezoelectric properties, thereby improving the deposition of lithium metal.
  • the stacked structure of fibers employed in the 3D framework can be tested by Fourier transform infrared spectroscopy (FTIR) to determine the crystal phase of the stacked structure of polymer materials in its fibers.
  • FTIR Fourier transform infrared spectroscopy
  • the deposition density of lithium metal in the three-dimensional framework can reach 0.534 g/cm 3 .
  • the porous layer has a thickness of 30 ⁇ m to 500 ⁇ m. In other embodiments, the thickness of the porous layer is approximately, for example, about 30 ⁇ m, about 40 ⁇ m, about 50 ⁇ m, about 60 ⁇ m, about 70 ⁇ m, about 80 ⁇ m, about 90 ⁇ m, about 100 ⁇ m, about 200 ⁇ m, about 250 ⁇ m, about 300 ⁇ m, about 400 ⁇ m, about 500 ⁇ m, or a range consisting of any two of these values. In some embodiments, the porous layer has a thickness of 300 ⁇ m to 500 ⁇ m. The thickness of the porous layer can provide a stable pore utilization rate, increase the deposition amount of lithium metal in the electrochemical device, and provide a high-capacity electrochemical device.
  • the porous layer in the negative electrode can be pre-supplemented with lithium to improve the lithium capacity and cycle performance of the electrochemical device.
  • One or more of the following processes can be used for pre-replenishing lithium treatment: cold pressing, hot pressing, electrochemical lithium replenishing or physical vapor deposition (PVD).
  • the lithium metal pre-supplemented in the negative electrode can be disposed inside the porous layer or between the porous layer and the negative electrode current collector.
  • FIG. 7 is a schematic structural diagram of negative electrodes according to other embodiments of the present application.
  • the anode 10 can further include lithium metal 102 , wherein the lithium metal is disposed between the porous layer and the anode current collector, as a supplementary lithium metal to increase the energy density of the electrochemical device.
  • the thickness of lithium metal is equal to or less than 50 ⁇ m. In some embodiments, the thickness of the lithium metal is equal to or less than 30 ⁇ m in order to obtain an optimal energy density for the electrochemical device.
  • the negative electrode current collector may be copper foil or nickel foil, however, other materials commonly used in the art may be used as the negative electrode current collector without limitation.
  • an embodiment of the present application provides a method for preparing a negative electrode, which includes the following steps: preparing an electrically insulating three-dimensional framework by electrospinning technology, and then applying a cold pressing process on the negative electrode current collector A porous layer composed of a three-dimensional skeleton is provided. Finally, the anode is obtained through a cutting process.
  • the present application further adds acetone to the solvent N,N-dimethylformamide by changing the precursor solution, wherein acetone is calculated based on the total amount of the precursor solution
  • the content is 10wt% to 20wt%, so as to increase the ⁇ -phase content of the fluorine-containing polymer in the three-dimensional skeleton fiber.
  • the present application increases the pulling force of the electric field by controlling and increasing the rotating speed of the drum to 1500rpm to 2500rpm, and can also provide the fluoropolymer in the fiber of the three-dimensional skeleton ⁇ -phase content.
  • the present application in the preparation process of electrospinning technology, can increase the solvent evaporation rate and further increase the content of ⁇ phase by increasing the distance between the collecting plate and the needle to 15 cm to 20 cm.
  • the embodiments of the present application provide an electrochemical device, and the electrochemical device includes a positive electrode, a separator, and the negative electrode provided in the above embodiments.
  • the electrochemical device is a lithium ion battery.
  • the thickness t of the lithium metal deposited portion is at least greater than or equal to 30% of the thickness T of the porous layer when the electrochemical device is fully charged. It should be understood that the porous layer of the negative electrode in the present application will expand or decrease in volume with the deposition of lithium metal in the charge-discharge cycle process. Therefore, the "thickness T" of the porous layer herein is the thickness of the electrochemical device when it is fully charged. The thickness of the porous layer.
  • the present application can alleviate the volume expansion of the negative electrode or the porous layer in the electrochemical device by limiting the thickness t of the lithium metal deposited part to be at least greater than or equal to 30% of the thickness T of the porous layer, thereby improving the cycle performance of the full battery; at the same time, improving The utilization rate of lithium metal deposition in the porous layer can further ensure the overall energy density of the electrochemical device.
  • the thickness T of the porous layer in the negative electrode and the thickness t of the lithium metal deposition part can be tested by common thickness measurement methods in the art, without being limited thereto.
  • the test method for the thickness of the porous layer of the negative electrode and its lithium metal deposition part is as follows: using a positive electrode made of lithium iron phosphate positive electrode material, and the negative electrode with a porous layer in the above-mentioned embodiments, through a single-layer lamination method form an electrochemical device.
  • the electrochemical device was cycled several times, and the discharge capacity of each cycle was recorded; when the discharge capacity of the electrochemical device was reduced to 80%, the cycle was stopped and the electrochemical device was charged to a fully charged state; then the battery was disassembled and taken out
  • the negative pole piece is soaked in dimethyl carbonate solution
  • the sample of the negative pole piece is prepared by argon ion polishing CP method, the cross-section of the negative pole piece is observed with a scanning electron microscope, and the thickness T of the porous layer in the negative pole and the thickness T of the lithium metal are recorded. Thickness t of the deposited part.
  • the electrochemical device performs one or more cycles as follows: in a constant temperature environment of 20°C, charge at a constant current rate of 0.2C to 3.7V, then charge at a constant voltage to 0.025C, and stand for 5 Minutes; then, discharge to 2.55V with a constant current of 0.5C, and let it stand for 5 minutes, which is a cycle.
  • the positive electrode includes a positive current collector.
  • the positive current collector may be aluminum foil or nickel foil, however, other positive current collectors commonly used in the art may be used without limitation.
  • the positive electrode includes a positive active material layer.
  • the cathode active material layer includes a cathode active material capable of absorbing and releasing lithium (Li) (hereinafter, sometimes referred to as “a cathode active material capable of absorbing/releasing lithium Li”).
  • positive electrode active materials capable of absorbing/releasing lithium (Li) may include lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, One or more of lithium iron phosphate, lithium titanate and lithium-rich manganese-based materials.
  • the chemical formula of lithium cobaltate can be Li y Co a M1 b O 2-c , wherein, M1 means that it is selected from nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al) , boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca) , strontium (Sr), tungsten (W), yttrium (Y), lanthanum (La), zirconium (Zr) and silicon (Si), the values of y, a, b and c are respectively in the following ranges: 0.8 ⁇ y ⁇ 1.2, 0.8 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 0.2, -0.1 ⁇ c ⁇ 0.2;
  • the chemical formula of nickel-cobalt lithium manganese oxide or nickel-cobalt lithium aluminate can be Li z Ni d M2 e O 2-f , wherein, M2 is selected from cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin At least one of (Sn), calcium (Ca), strontium (Sr), tungsten (W), zirconium (Zr) and silicon (Si), the values of z, d, e and f are respectively in the following ranges: 0.8 ⁇ z ⁇ 1.2, 0.3 ⁇ d ⁇ 0.98, 0.02 ⁇ e ⁇ 0.7, -0.1 ⁇ f ⁇ 0.2;
  • the chemical formula of lithium manganate is Li u Mn 2-g M 3g O 4-h , wherein M3 represents a group selected from cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al) , boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca) , strontium (Sr) and tungsten (W), the values of u, g and h are respectively in the following ranges: 0.8 ⁇ u ⁇ 1.2, 0 ⁇ g ⁇ 1.0 and -0.2 ⁇ h ⁇ 0.2.
  • the chemical formula of lithium iron phosphate is LiFePO 4 .
  • the positive electrode active material layer can further include at least one of a binder and a conductive agent. It should be understood that those skilled in the art may select conventional binders and conductive agents in the art according to actual needs, without being limited thereto.
  • the isolation film includes, but is not limited to, at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyimide, and aramid.
  • polyethylene includes at least one component selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene.
  • polyethylene and polypropylene which have a good effect on preventing short circuits and can improve the stability of the battery through the shutdown effect. It should be understood that those skilled in the art may select conventional separators in the art according to actual needs, without being limited thereto.
  • the lithium ion battery of the present application also includes an electrolytic solution including a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , One or more of LiC(SO 2 CF 3 ) 3 , LiSiF 6 , LiBOB and lithium difluoroborate.
  • LiPF 6 is selected as the lithium salt because it can give high ion conductivity and improve cycle characteristics.
  • the non-aqueous solvent can be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents or any combination thereof.
  • the above-mentioned carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound or any combination thereof.
  • Examples of the aforementioned other organic solvents are dimethylsulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, Formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters, and any combination thereof.
  • the non-aqueous solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, fluorinated The group consisting of ethylene carbonate and any combination thereof.
  • the non-aqueous solvent is a mixture of dioxolane (DOL) and dimethyl ether (DME) at a volume ratio of 0.5-2.
  • DOL dioxolane
  • DME dimethyl ether
  • the preparation method of a lithium-ion battery includes: winding, folding or stacking the negative electrode, the separator and the positive electrode in the above-mentioned examples in order to form an electrode assembly, and packing the electrode assembly into, for example, Aluminum-plastic film, and injected electrolyte, followed by vacuum packaging, static, chemical formation, shaping and other processes to obtain lithium-ion batteries.
  • the adhesive layer of the present application can be used in other suitable electrochemical devices after reading this application.
  • Such an electrochemical device includes any device in which an electrochemical reaction occurs, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.
  • Some embodiments of the present application further provide an electronic device, and the electronic device includes the electrochemical device in the embodiments of the present application.
  • the electronic device in the embodiment of the present application is not particularly limited, and it may be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen-based computers, mobile computers, e-book players, cellular phones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, Lighting appliances, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • lithium metal deposition test cycle performance test and cycle thickness expansion rate test are respectively carried out on its electrochemical device (lithium ion battery) to better illustrate the technical solution of the present application.
  • the lithium-ion batteries of the following examples and comparative examples were placed in a thermostat at 25°C ⁇ 2°C for 2 hours, and then discharged to 3.00V at a constant current of 0.5C. After standing for 5 minutes, it was charged to 4.45V with a constant current of 0.7C, and then charged to 0.02C with a constant voltage of 4.45V. This is a lithium metal deposition test cycle. After repeating the above lithium metal deposition test cycle 10 times, the fully charged lithium ion battery is disassembled and the lithium metal deposition position is recorded.
  • the cycle capacity retention rate of the lithium ion battery the discharge capacity (mAh) of the 200th cycle/the discharge capacity (mAh) after the first cycle ⁇ 100%.
  • a 600g flat plate thickness gauge (ELASTOCON, EV 01) was used to test the thickness of lithium-ion batteries.
  • Cycle thickness expansion ratio of the lithium ion battery (thickness of the lithium ion battery at the 200th cycle/thickness of the lithium ion battery at the first cycle ⁇ 1) ⁇ 100%.
  • the positive active material lithium iron phosphate (LiFePO4), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed according to a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) was added as a solvent.
  • NMP N-methylpyrrolidone
  • the slurry was evenly coated on the positive electrode current collector aluminum foil, and dried at 90°C. Afterwards, a positive electrode cut into (14 mm) specifications was obtained after cold pressing and cutting procedures.
  • the loading capacity of the positive electrode was 1 mAh/cm 2 .
  • polyvinylidene fluoride was dissolved in 8 mL of N,N-dimethylformamide and 2 mL of acetone, and the polyvinylidene fluoride in the mixed solution
  • the weight ratio of ethylene is 8%, fully stirred for 8 hours, and the solution is transferred to the syringe for electrospinning.
  • the parameters of the electrospinning process are: negative pressure is -4kV, positive pressure is 18kV, liquid feed rate is 0.3mL/h, The distance between the collection plate and the needle is 15cm-20cm and the rotation speed of the collection drum is 2000rpm.
  • the polyvinylidene fluoride fiber prepared by electrospinning was placed in a vacuum drying oven at 80° C. for 12 hours.
  • a three-dimensional framework composed of polyvinylidene fluoride fibers the lithium metal film and the three-dimensional framework are sequentially pressed onto the copper foil current collector, and the three-dimensional framework forms a porous layer after cold pressing.
  • direct punching was performed to obtain a negative electrode cut into (18 mm) specifications.
  • Negative electrode structure measurement the thickness of the porous layer is 50 ⁇ m, the porosity is 80%, the diameter of a single fiber ranges from 0.4 ⁇ m to 1 ⁇ m, the thickness of the lithium metal film is 20 ⁇ m, and the crystal phase structure in the polyvinylidene fluoride fiber is ⁇ phase dominant.
  • the preparation method is substantially the same as in Example 1, except that a pressure of 1T is used in the cold pressing process, so that the thickness of the porous layer is 30 ⁇ m and the porosity is 40%.
  • the preparation method is roughly the same as in Example 1, except that the parameters used in the electrospinning process are: negative pressure is -1kV, positive pressure is 8kV, liquid feeding rate is 0.8mL/h, the distance between the collecting plate and the needle is 12cm, and the collecting roller The rotational speed is 100rpm.
  • Negative electrode structure measurement The thickness of the porous layer is 50 ⁇ m, the porosity is 80%, the diameter of a single fiber ranges from 0.4 ⁇ m to 1 ⁇ m, the thickness of the lithium metal film is 20 ⁇ m, the ⁇ phase in the crystal phase structure of the polyvinylidene fluoride fiber The proportion is lower than that of Example 1.
  • the preparation method is roughly the same as in Example 1, except that polymethyl methacrylate is used as the precursor, and the parameters used in the electrospinning process are: negative pressure is -4kV, positive pressure is 12kV, and the liquid feeding rate is 0.6mL/h , the distance between the collection plate and the needle is 15cm-20cm; the rotation speed of the collection drum is 2000rpm. Three-dimensional skeleton made of polymethyl methacrylate fibers. Negative electrode structure measurement: the thickness of the porous layer is 50 ⁇ m, the porosity is 80%, the diameter of a single fiber ranges from 0.4 ⁇ m to 1 ⁇ m, and the thickness of the lithium metal film is 20 ⁇ m.
  • the preparation method is roughly the same as in Example 1, except that polyacrylonitrile is used as a precursor, and polyacrylonitrile is dissolved in 10 mL of N,N-dimethylformamide, wherein the weight ratio of polyacrylonitrile in the mixed solution is
  • the parameters used in the electrospinning process are: voltage 12kV, liquid feed rate 0.6mL/h, distance between collecting plate and needle head 15cm and collecting drum rotating speed 2000rpm. Three-dimensional skeleton made of polyacrylonitrile fibers.
  • Negative electrode structure measurement the thickness of the porous layer is 50 ⁇ m, the porosity is 80%, the diameter of a single fiber ranges from 0.4 ⁇ m to 1 ⁇ m, and the thickness of the lithium metal film is 20 ⁇ m.
  • the preparation method was substantially the same as in Example 1, except that the thickness of the porous layer was 300 ⁇ m.
  • the preparation method was substantially the same as in Example 1, except that the thickness of the porous layer was 500 ⁇ m.
  • the preparation method was substantially the same as in Example 1, except that the thickness of the porous layer was 200 ⁇ m.
  • PP/PE/PP composite diaphragm is used as the porous layer.
  • the lithium metal film and the PP/PE/PP composite separator were sequentially pressed on the copper foil current collector, wherein the negative electrode was directly punched to obtain a cut-to-size (18mm) negative electrode.
  • the thickness of the porous layer composed of the PP/PE/PP composite separator is 20 ⁇ m
  • the porosity is 30% to 50%
  • the thickness of the lithium metal film is 20 ⁇ m.
  • the preparation method is roughly the same as in Example 1, except that after keeping the polyvinylidene fluoride fiber in a vacuum oven at 80°C for 12 hours, the polyvinylidene fluoride fiber is further placed in a 230-degree muffle furnace for 2 hours, And placed in a high-purity argon tube furnace at 800°C for 6 hours to obtain carbonized polyvinylidene fluoride fibers, and adopt a three-dimensional framework composed of carbonized polyvinylidene fluoride fibers.
  • the thickness of the porous layer is 50 ⁇ m
  • the porosity is 80%
  • the diameter of a single fiber ranges from 0.4 ⁇ m to 1 ⁇ m
  • the thickness of the lithium metal film is 20 ⁇ m.
  • a polyethylene film is used as the separator, wherein the thickness of the polyethylene film is 15 ⁇ m, and the above-mentioned positive electrode, separator and negative electrode in the above embodiment are stacked in sequence, so that the separator is placed between the positive electrode and the negative electrode to play the role of isolation.
  • the stacked electrode assembly was packed into an aluminum-plastic film package, and after dehydration at 80°C, a dry electrode assembly was obtained. Subsequently, the above-mentioned electrolyte solution was injected into the dry electrode assembly, and then assembled into a button battery through processes such as vacuum packaging, standing, forming, and shaping, and the preparation of the lithium-ion batteries of the following examples and comparative examples was completed.
  • Example 1 shows that the present application can effectively improve the cycle performance of the lithium-ion battery and effectively suppress the cycle expansion rate of the lithium-ion battery by arranging the negative electrode containing the porous layer of the three-dimensional skeleton.
  • the negative electrode with a three-dimensional skeleton proposed in the embodiment of the present application can greatly improve the volume expansion and cycle stability of the current lithium-copper composite tape, making the cycle of lithium-ion batteries Overrun is reduced to 15%.
  • the porous layer of the embodiment of the present application has a good size and distribution of pores between the fibers due to its three-dimensional skeleton fiber structure, which is used to provide accommodating space for lithium metal precipitation.
  • the membranes in Comparative Examples 2 and 3 have a certain porosity, they cannot provide holes with sufficient pore size, so lithium metal cannot be deposited in the pores of the membrane.
  • Example 1 and Comparative Example 4 From Example 1 and Comparative Example 4, it can be seen that the deposition position and direction of lithium metal can be controlled by using the three-dimensional framework of the electrically insulating fiber.
  • the deposition of lithium metal in the electronically conductive three-dimensional framework is random, and it tends to deposit on the surface of the porous layer; the electrically insulating three-dimensional framework can better control the deposition position, thereby inhibiting the volume expansion of the pole piece and improving the battery. cycle performance.
  • the porosity of the porous layer has an effect on the precipitation of lithium metal.
  • the porosity is greater than 70%, most of the circulating lithium metal can enter the porous layer, so that the porous layer can better inhibit the volume expansion of lithium metal and improve the electrochemical performance.
  • Example 1 and Example 3 it can be seen that by improving the crystal phase structure of the fiber material in the three-dimensional skeleton to make it present a ⁇ phase, the piezoelectric properties of the fiber structure can be optimized, and the effect on the cyclic expansion rate of the lithium-ion battery can be effectively improved. control.
  • Example 1 and Examples 4 and 5 it can be known that different three-dimensional skeletons of fiber materials will lead to different stability of the porous layer.
  • the polyvinylidene fluoride fiber three-dimensional framework is not easy to dissolve and expand in the electrolyte, so it can maintain a good three-dimensional structure and morphology, so that the porous layer containing it has better cycle retention and volume expansion performance.
  • the telephony device of the present application can effectively improve the lithium concentration on the surface of the negative electrode during the charge-discharge cycle of the electrochemical device by setting a porous layer comprising a three-dimensional framework and using an electrically insulating three-dimensional framework material. Metal deposition; and inhibit the volume expansion of lithium metal; at the same time slow down the growth of lithium dendrites, thereby improving the cycle performance, capacity performance and safety performance of electrochemical devices.
  • references to “embodiment”, “partial embodiment”, “an embodiment”, “another example”, “example”, “specific example” or “partial example” in the entire specification mean that At least one embodiment or example in the present application includes a specific feature, structure, material or characteristic described in the embodiment or example.
  • descriptions that appear throughout the specification such as: “in some embodiments”, “in an embodiment”, “in one embodiment”, “in another example”, “in an example In”, “in a particular example” or “example”, they are not necessarily referring to the same embodiment or example in this application.
  • the particular features, structures, materials, or characteristics herein may be combined in any suitable manner in one or more embodiments or examples.

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Abstract

本申请涉及一种负极极片及包含其的电化学装置、电子装置。本申请提供了一种负极极片，其包括：负极集流体以及多孔层。该多孔层位于负极集流体上，且所述多孔层包括含有电性绝缘纤维的三维骨架。三维骨架经配置能够用于容纳锂金属沉积。本申请的负极通过设置包含三维骨架的多孔层及采用电性绝缘的三维骨架材料，能够在电化学装置的充放电循环中有效改善负极表面上的锂金属沉积情形；并抑制锂金属的体积膨胀；同时减缓锂枝晶的生长，进而提高电化学装置的循环性能，容量性能以及安全性能。

Description

负极极片及包含其的电化学装置、电子装置 技术领域
本申请涉及储能领域，具体涉及一种包含三维骨架结构的负极极片及包含其的电化学装置及电子装置，特别是锂离子电池。
背景技术
随着技术的发展和对移动装置的需求的增加，人们对电化学装置(例如，锂离子电池)的需求显著增加。锂金属是目前发现的质能比最大的金属之一，利用锂金属作为负极材料的锂离子电池，可以大大提高电化学装置的能量密度以及工作电压。
在电化学装置实际使用过程中，直接利用锂金属作为负极材料至少存在以下问题：1)锂金属容易与电解液中的物质发生副反应，造成电解液与新鲜锂金属的消耗，从而导致库伦效率降低；2)锂金属在充放电过程中，由于锂金属表面电位分布以及电解液中锂离子浓度分布不均匀，会使得锂金属的沉积和溶解不均匀，进而形成“锂枝晶”和“死锂”，锂枝晶和死锂的形成会进一步降电池容量，严重时，锂枝晶能够刺穿隔膜导致电池短路，带来安全风险；3)随着电池不断充放电过程，锂金属沉淀会不断的发生体积膨胀收缩，导致电极结构遭受破坏，严重时会导致负极极片与柔韧性较差的无机保护涂层之间界面发生剥离，进而失去保护效果。
有鉴于此，确有必要对电极极片进行研究与改进，以提升其电化学装置和电子装置使用上的安全性。
发明内容
本申请实施例通过提供一种改善电极组件安全性的极片及包含其的电化学装置以在至少某种程度上解决至少一种存在于相关领域中的问题。
在本申请的一方面，本申请提供了一种负极极片，其包括：负极集流体 以及多孔层。该多孔层位于负极集流体上，且所述多孔层包括含有电性绝缘纤维的三维骨架。三维骨架经配置能够用于容纳锂金属沉积。
在本申请的另一方面，本申请提供一种电化学装置，其包括上述实施例中的正极。
本申请的负极通过设置包含三维骨架的多孔层，并且三维骨架采用电性绝缘的纤维构成，其能够在电化学装置的充放电循环中有效改善负极表面上的锂金属沉积情形；并抑制锂金属的体积膨胀；同时减缓锂枝晶的生长，进而提高电化学装置的循环性能，容量性能以及安全性能。当本申请的电化学装置充电时，具有电性绝缘纤维的三维骨架能够阻挡电子从负极集流体侧向多孔层表面的传输，实现对锂金属沉积方向与位置的控制，进一步改善极片的体积膨胀与循环稳定性。
在本申请的另一方面，本申请提供一种电子装置，其包括上述电化学装置。
本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1为根据本申请一些实施例的负极的结构示意图。
图2为根据本申请一些实施例的负极的剖面结构示意图。
图3为根据本申请一些实施例的三维骨架的俯视表面的扫描式电子显微镜(SEM)图。
图4为根据本申请一些实施例的多孔层中的锂金属沉积的扫描式电子显微镜图。
图5为根据本申请的部分实施例的空心结构的纤维的结构示意图。
图6为聚偏二氟乙烯的β相的分子结构图。
图7为根据本申请另一些实施例的负极的结构示意图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。本申请的实施例不应该被解释为对本申请的限制。
除非另外明确指明，本文使用的下述术语具有下文指出的含义。
如本文中所使用，术语“大致”、“大体上”、“实质”及“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数值使用时，术语可指代小于或等于所述数值的±10％的变化范围，例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％。举例来说，如果两个数值之间的差值小于或等于所述值的平均值的±10％(例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％)，那么可认为所述两个数值“大体上”相同。
在具体实施方式及权利要求书中，由术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
再者，为便于描述，“第一”、“第二”、“第三”等等可在本文中用于区分一个图或一系列图的不同组件。除非经特别指定或限定之外，“第一”、 “第二”、“第三”等等不意欲描述对应组件。
锂金属是所有金属元素中相对原子质量最小(6.94)、标准电极电位(-3.045V)最低的金属，其理论比容量高达3860mAh/g。理论上，利用锂金属作为负极活性材料能够提高电化学装置的工作电压以及容量，然而目前的锂离子电池主要面临以下几个难题：首先，常用的锂离子电池负极材料如石墨等，在充电时锂离子以嵌入的形式存在于石墨层结构中，石墨层具有多孔结构为锂金属提供了存储空间。而对于纯锂金属电极，并不存在这样的多孔结构，因此在充放电过程中会出现及其剧烈的体积变化，由此导致一系列问题影响电池的循环等性能；再者，由于电流密度以及电解液中锂离子浓度的不均匀性，沉积过程中会出现某些位点沉积速度过快的现象，进而形成尖锐的枝晶结构。锂枝晶的存在会导致沉积密度的大大降低，使得能量密度降低。目前，在部分的锂金属电池中，锂金属的实际沉积密度为0.2g/cc左右，远小于锂金属的真密度0.534g/cc。能量密度由于锂金属的疏松沉积，会降低超过100Wh/L。此外，锂枝晶还可能会刺穿隔膜形成短路，引发安全问题。
图1及图2是根据本申请部分实施例的负极的示意图及剖面示意图。
根据本申请的一个方面，如图1及图2所示，本申请实施例提供了一种负极10，其在负极集流体100表面上设置包含三维骨架的多孔层101，为锂金属提供宿主，保证电池在充放电过程中，锂金属能够存储于集流体表面多孔层中的三维骨架中，从而抑制体积膨胀，同时，三维骨架能够改善锂金属的沉积形貌，抑制锂枝晶的形成。在一些实施例中，多孔层101全部由三维骨架所构成。
在一些实施例中，多孔层101中三维骨架的材料包含电性绝缘的纤维。由于电性绝缘的纤维，能够阻止电子自负极集流体的表面向多孔层的外表面迁移，从而诱导锂金属自负极集流体的表面一侧逐渐向多孔层内部沉积，进一步改善负极的体积膨胀，抑制锂枝晶的生长，进而改善电化学装置的循环性能。在一些实施例中，三维骨架全部由电性绝缘的纤维所构成。
本领域技术人员应理解，本文中的术语“电性绝缘”并非代表完全无法传导电子，而是表示其具有极低的电子传导率(电导率)。在一些实施例中， 三维骨架包含的电性绝缘纤维的电导率小于10 -10S/cm。
图3及图4分别展示了根据本申请部分实施例的三维骨架的俯视表面以及在多孔层中的锂金属沉积的扫描式电子显微镜图。如图3及4中所示，通过对多孔层中三维骨架的电子不导通控制，能够实现锂金属沉积方向的控制，锂金属能够完全沉积在多孔层的内部，改善负极极片膨胀与循环稳定性。
在一些实施例中，电性绝缘的纤维的结构能够包含条状纤维、球状纤维及块状纤维。在一些实施例中，纤维的结构为条状纤维，其中三维骨架由多个单根条状纤维与条状纤维搭建而成，条状纤维的材料能够更好的构建三维骨架，形成自支撑结构。
在一些实施例中，纤维的直径为50nm至10μm。在另一些实施例中，单根纤维的直径大致为，例如，约50nm、约100nm、约200nm、约300nm、约400nm、约500nm、约700nm、约1μm、约2μm、约5μm、约10μm或这些数值中任意两者组成的范围。在一些实施例中，单根纤维的直径为200nm至2μm。
在一些实施例中，多孔层的孔隙率大于或等于70％或80％。在另一些实施例中，多孔层的孔隙率为70％至90％，以确保多孔层中具备足够的空间用于容纳锂金属沉积，并维持一定的结构强度及稳定度。
在一些实施例中，多孔层中包含由三维骨架中纤维与纤维所彼此搭建形成的孔洞，该孔洞形成于纤维与纤维之间。在一些实施例中，三维骨架中纤维之间交织构成孔洞，该孔洞尺寸范围大致为100nm至10μm。在另一些实施例中，三维骨架中纤维之间交织所构成的孔洞尺寸大致为，例如，约100nm、约200nm、约500nm、约1μm、约2μm、约5μm、约10μm或这些数值中任意两者组成的范围。在一些实施例中，条状纤维与条状纤维彼此搭建形成的孔洞，具有更一致的孔洞分布范围，其孔洞结构更为稳定，能够提高锂金属的沉积规律，抑制不规则的锂枝晶的形成。在一些实施例中，三维骨架中纤维之间交织所构成的孔洞尺寸范围为500nm至5μm。
纤维除了通过形状结构限定外，还能够通过纤维本身所具有的孔洞结构加以限定，其能够包含实心结构、空心结构或两者。实心结构表示纤维本身 不具有任何孔洞，而空心结构则代表纤维本身存在孔洞结构。在一些实施例中，三维骨架中的纤维具有空心结构，且多孔层中包含纤维本身存在孔洞，该孔洞形成于纤维内部。在一些实施例中，空心结构的孔洞尺寸为10nm至500nm。在另一些实施例中，空心结构的孔洞大小大致为，例如，约10nm、约50nm、约200nm、约500nm或这些数值中任意两者组成的范围。
图5为根据本申请的部分实施例的空心结构的纤维的结构示意图。
在一些实施例中，如图5所示，空心结构纤维的孔洞结构可以为三种形态，包含中空结构、壁上造孔结构或者中空且壁上造孔结构。在一些实施例中，纤维为中空结构时，纤维的纤维壁厚度为50nm至4.5μm。在一些实施例中，纤维为壁上造孔结构时，壁上造孔结构的孔洞的大小为50nm至500nm。当纤维具有空心结构时，包含中空结构或是壁上造孔结构，能够加快电解液在三维骨架中的传输速率；同时，空心结构的设计，能够进一步降低三维骨架的结构重量，提高锂金属在三维骨架中的表面利用率，也有利于提高电化学装置的总体能量密度。
在一些实施例中，纤维包括离子导体型纤维，其中锂离子能够与离子导体型纤维表面上的一些活性基团结合形成缔合体，随着纤维表面的运动，锂离子缔合的活性位点能够不断移动和转换，从而实现锂离子的传输，并进一步提高多孔层中的锂离子传输效率。
在一些实施例中，纤维的材料包含高分子材料及无机材料中的一种或多种，其中高分子材料包含以下组分及各个组分的衍生物中的一种或多种：聚偏二氟乙烯、聚酰亚胺、聚酰胺、聚丙烯腈、聚乙二醇、聚苯醚、聚碳酸亚丙酯、聚甲基丙烯酸甲酯、聚对苯二甲酸乙二醇酯、聚环氧乙烷、聚偏二氟乙烯-六氟丙烯或聚偏二氟乙烯-三氟氯乙烯；且无机材料包含，但不限于，以下组分及各个组分的衍生物中的一种或多种：硅酸钠、氧化铝或氧化硅。
在一些实施例中，纤维包括具有压电性的材料。本文中的术语“具有压电性的材料”是指在常压下为电性绝缘体，但是当向其施加一定范围的压力时，因其内部结构的变化而允许电流通过的材料。具有压电性的材料能够表现出100以上的高介电常数，当施加一定范围的压力拉伸或压缩它们时，在它们一个表面上充正电，而在另一表面上充负电。因此，当负极充电时，由 于多孔层中的锂金属沉积，会导致三维骨架进一步膨胀并拉伸，其中采用具有压电性的材料的纤维，能够在多孔层中锂离子金属沉积区域的两个表面之间产生电位差，进而提高锂离子金属沉积区域间的三维骨架的电导性，从而提高负极的电循环效果，并优化锂金属沉积的密度及方向。在一些实施例中，具有压电性的材料包含，但不限于，BaTiO 3、Pb(Zr，Ti)O 3(PZT)、Pb 1-xLa xZr 1-yTi yO 3(PLZT)、PB(Mg 3Nb 2/3)O 3-PbTiO 3(PMN-PT)、二氧化铪(HfO2)中的一种或多种。
在一些实施例中，纤维包括具有β相的含氟聚合物。本文中的术语“β相”是指高分子材料的晶相堆叠结构中的热力学稳定相。举例而言，当采用聚偏二氟乙烯作为三维骨架的纤维时，聚偏二氟乙烯共有五种晶相，αβγδε，常见的为αβγ相，α相为动力学控制相，β相为热力学稳定相。如图6所示，含氟聚合物纤维(例如，但不限于，聚偏二氟乙烯)的β相中H-F-C原子呈现有序的折叠排列，导致偶极矩指向同一方向，其单体单元相对于其他相具有最高的偶极矩，因此β相具有更好的压电性、热电性及铁电性。本申请中通过制备工艺的改进，能够有效提高含氟聚合物纤维中的β相，并通过在三维骨架的纤维中添加β相含氟聚合物纤维，优化纤维中高分子材料的堆叠结构以使其具有良好的压电性质，进而改善锂金属的沉积情况。
在本文中，三维骨架中采用的纤维的堆叠结构能够通过傅里叶转换红外光谱(FTIR)进行测试，以确定其纤维中高分子材料的堆叠结构的晶相。
在一些实施例中，本申请三维骨架的单位体积中锂金属的最大沉积量M符合以下公式：M＝T/4.85(mAh/cm 3)，其中，T为三维骨架的厚度。在一些实施例中，三维骨架中锂金属的沉积密度能够达到0.534g/cm 3。
在一些实施例中，多孔层的厚度为30μm至500μm。在另一些实施例中，多孔层的厚度大致为，例如，约30μm、约40μm、约50μm、约60μm、约70μm、约80μm、约90μm、约100μm、约200μm、约250μm、约300μm、约400μm、约500μm或这些数值中任意两者组成的范围。在一些实施例中，多孔层的厚度为300μm至500μm。多孔层的厚度可以提供稳定的孔隙使用率，在电化学装置中提高锂金属的沉积量，进而提供高容量的电化学装置。
在一些实施例中，负极中的多孔层可以通过预补锂处理，来提高电化学装置中的锂容量以及循环性能。预补锂处理可以采用以下工艺中的一种或多种：冷压、热压、电化学补锂或者物理气相沉积(PVD)。在一些实施例中，负极中预补锂处理的锂金属能够设置于多孔层的内部或多孔层与负极集流体之间。
图7为根据本申请另一些实施例的负极的结构示意图。
如图7所示，在一些实施例中，负极10能够进一步包含锂金属102，其中锂金属设置于多孔层与负极集流体之间，作为补充锂金属提升电化学装置的能量密度。在一些实施例中，锂金属的厚度等于或小于50μm。在一些实施例中，锂金属的厚度等于或小于30μm，以使电化学装置获得最佳的能量密度。
在一些实施例中，负极集流体可为铜箔或镍箔，然而，可以采用本领域常用的其他材料作为负极集流体，而不受其限制。
根据本申请的另一个方面，本申请的实施例提供一种负极的制备方法，其中包含以下步骤：通过静电纺丝技术制备电性绝缘的三维骨架，并随后通过冷压工艺在负极集流体上设置由三维骨架所构成的多孔层。最后，通过裁切工艺获得负极。
在一些实施例中，在静电纺丝技术的制备工艺中，本申请进一步通过改变前驱体溶液，在溶剂N,N-二甲基甲酰胺中加入丙酮，其中以前驱体溶液的总量计丙酮的含量为10wt％至20wt％，以提高三维骨架的纤维中的含氟聚合物的β相含量。在一些实施例中，在静电纺丝技术的制备工艺中，本申请通过控制增大滚筒的转速至1500rpm至2500rpm，提高电场拉伸作用力，也可以提供三维骨架的纤维中的含氟聚合物的β相含量。在一些实施例中，在静电纺丝技术的制备工艺中，本申请通过增大收集板与针头距离的范围至15cm至20cm，可以提高溶剂蒸发速率，也可以进一步提高β相的含量。
根据本申请的另一个方面，本申请的实施例提供一种电化学装置，电化学装置包含正极、隔离膜以及上述实施例中所提供的负极。在一些实施例中，电化学装置为锂离子电池。
在一些实施例中，在电化学装置满充的情况下，锂金属沉积的部分的厚度t至少大于或等于多孔层的厚度T的30％。应理解，本申请中的负极的多孔层会随着充放电循环过程中的锂金属沉积发生体积膨胀或减少，因此，本文中多孔层的“厚度T”为电化学装置为满充状态下的多孔层的厚度。本申请通过限定锂金属沉积的部分的厚度t至少大于或等于多孔层的厚度T的30％，能够缓解电化学装置中的负极或多孔层的体积膨胀，进而改善全电池循环性能；同时，提高多孔层中的锂金属沉积的使用率能够进一步保证电化学装置整体的能量密度。
应理解，在电化学装置中，负极中多孔层的厚度T，以及锂金属沉积部分的厚度t可以通过本领域中常见的厚度测试方式进行测试，而不受其限制。在一些实施例中，对于负极的多孔层与其锂金属沉积部分的厚度测试方法如下：采用以磷酸铁锂正极材料的正极，以及上述实施例中的具有多孔层的负极，通过单层叠片的方式形成电化学装置。将电化学装置进行多次循环，并记录每次循环放电容量；待电化学装置的放电容量降低至80％时，停止循环并将电化学装置充电至满充状态；随后将电池拆解，取出负极极片后，浸泡在碳酸二甲酯溶液中，采用氩离子抛光CP法制备负极极片的样品，使用扫描电子显微镜观察负极极片的截面，并记录负极中多孔层的厚度T以及锂金属沉积部分的厚度t。在一些实施例中，电化学装置进行一次或多次循环的方式如下：在20℃的恒温环境中，以0.2C的倍率恒流充电至3.7V，然后恒压充电至0.025C，静置5分钟；随后，以0.5C恒流放电至2.55V，静置5分钟，此为一个循环。
在一些实施例中，正极包含正极集流体。正极集流体可以为铝箔或镍箔，然而，可以采用本领域常用的其他正极集流体，而不受其限制。
在一些实施例中，正极包含正极活性材料层。正极活性材料层包括能够吸收和释放锂(Li)的正极活性材料(下文中，有时称为“能够吸收/释放锂Li的正极活性材料”)。能够吸收/释放锂(Li)的正极活性材料的实例可以包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、锰酸锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、磷酸铁锂、钛酸锂和富锂锰基材料中的一种或多种。
在上述正极活性材料中，钴酸锂的化学式可以为Li yCo aM1 bO 2-c，其中， M1表示选自镍(Ni)、锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)、钇(Y)、镧(La)、锆(Zr)和硅(Si)中的至少一种，y、a、b和c值分别在以下范围内：0.8≤y≤1.2、0.8≤a≤1、0≤b≤0.2、-0.1≤c≤0.2；
在上述正极活性材料中，镍钴锰酸锂或镍钴铝酸锂的化学式可以为Li zNi dM2 eO 2-f，其中，M2表示选自钴(Co)、锰(Mn)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)、钨(W)、锆(Zr)和硅(Si)中的至少一种，z、d、e和f值分别在以下范围内：0.8≤z≤1.2、0.3≤d≤0.98、0.02≤e≤0.7、-0.1≤f≤0.2；
在上述正极活性材料中，锰酸锂的化学式为Li uMn 2-gM 3gO 4-h，其中M3表示选自钴(Co)、镍(Ni)、镁(Mg)、铝(Al)、硼(B)、钛(Ti)、钒(V)、铬(Cr)、铁(Fe)、铜(Cu)、锌(Zn)、钼(Mo)、锡(Sn)、钙(Ca)、锶(Sr)和钨(W)中的至少一种，u、g和h值分别在以下范围内：0.8≤u≤1.2、0≤g<1.0和-0.2≤h≤0.2。
在上述正极活性材料中，磷酸铁锂的化学式为LiFePO 4。
在一些实施例中，正极活性材料层能够进一步包含粘结剂及导电剂中的至少一种。应理解，本领域技术人员可以根据实际需要选择本领域常规的粘结剂及导电剂，而不受其限制。
在一些实施例中，隔离膜包括，但不限于，选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺和芳纶中的至少一种。举例来说，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯和超高分子量聚乙烯中的至少一种组分。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。应理解，本领域技术人员可以根据实际需要选择本领域常规的隔离膜，而不受其限制。
本申请的锂离子电池还包括电解液，该电解液包括锂盐和非水溶剂。
在一些实施例中，锂盐选自LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、 LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB和二氟硼酸锂中的一种或多种。举例来说，锂盐选用LiPF 6，因为它可以给出高的离子导电率并改善循环特性。
非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的任意组合。
上述碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其任意组合。
上述其它有机溶剂的实例为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯及其任意组合。
在一些实施例中，非水溶剂选自由碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸二甲酯、碳酸甲乙酯、碳酸亚丙酯、醋酸甲酯、丙酸乙酯、氟代碳酸乙烯酯及其任意组合所组成的群组。
在一些实施例中，非水溶剂是二氧环戊烷(DOL)和二甲醚(DME)以体积比0.5-2混合而成。
应理解，本申请实施例中的正极、隔离膜以及电解质的制备方法，在不违背本申请的精神下，可以根据具体需要选择本领域任何合适的常规方法，而不受其限制。在制造电化学装置的方法的一个实施方案中，锂离子电池的制备方法包括：将上述实施例中的负极、隔膜及正极按顺序卷绕、折叠或堆叠成电极组件，将电极组件装入例如铝塑膜中，并注入电解液，随后进行真空封装、静置、化成、整形等工序，以获得锂离子电池。
虽然上面以锂离子电池进行了举例说明，但是本领域技术人员在阅读本申请之后，能够想到由本申请的粘结层可以用于其他合适的电化学装置。这样的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容。特别地，该电化学装置是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
本申请的一些实施例进一步提供了一种电子装置，电子装置包含本申请 实施例中的电化学装置。
本申请实施例的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
具体实施例
下面列举了一些具体实施例及对比例并分别对其电化学装置(锂离子电池)进行锂金属沉积测试、循环性能测试及循环厚度膨胀率测试以更好地对本申请的技术方案进行说明。
一、测试方法
1.1锂金属沉积测试：
将以下实施例及对比例的锂离子电池置于25℃±2℃的恒温箱中静置2小时，以0.5C恒流放电至3.00V。静置5分钟后，以0.7C恒流充电至4.45V，然后以4.45V恒压充电至0.02C。此为一次锂金属沉积测试循环，重复10次上述锂金属沉积测试循环后，将满充的锂离子电池拆解锂离子电池并记录锂金属沉积位置。
1.2循环性能测试：
将以下实施例及对比例中化成后的锂离子电池置于25℃±2℃的恒温箱中静置2小时，以0.7C恒流充电至4.45V，然后以4.45V恒压充电至0.05C并静置15分钟；再以0.5C恒流放电至3.0V，此为一次充放电循环过程，记录锂离子电池首次循环的放电容量；而后按上述方法重复进行200次的充放电循环过程，并记录200次循环后的放电容量。
每组取10块锂离子电池，计算锂离子电池的容量保持率的平均值。锂 离子电池的循环容量保持率＝第200次循环的放电容量(mAh)/首次循环后的放电容量(mAh)×100％。
1.3循环厚度膨胀率测试：
采用600g平板测厚仪(ELASTOCON,EV 01)测试锂离子电池的厚度。
将以下实施例及对比例的化成后锂离子电池置于25℃±2℃的恒温箱中静置2小时，以0.7C恒流充电至4.45V，然后以4.45V恒压充电至0.05C并静置15分钟，纪录满充状态下的锂离子电池厚度；再以0.5C恒流放电至3.0V，此为一次充放电循环过程，记录锂离子电池首次循环的锂离子电池厚度；而后按上述方法重复进行200次的充放电循环过程，并记录200次循环后的锂离子电池厚度。
每组取10块锂离子电池，计算锂离子电池的循环厚度膨胀率的平均值。锂离子电池的循环厚度膨胀率＝(第200次循环的锂离子电池厚度/首次循环的锂离子电池厚度-1)×100％。
二、制备方法
2.1正极的制备
将正极活性材料磷酸铁锂(LiFePO4)、导电炭黑(Super P)、聚偏二氟乙烯(PVDF)按照重量比97.5:1.0:1.5进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成为固含量为0.75的浆料，并搅拌均匀。将浆料均匀涂覆在正极集流体铝箔上，90℃条件下烘干。随后经过冷压、裁切程序后得到裁切成(14mm)的规格的正极。正极的负载量为1mAh/cm 2。
2.2电解液的制备
在含水量小于10ppm的环境(干燥氩气气氛中)下，将二氧环戊烷(DOL)、二甲醚(DME)以1:1的体积比混，然后在无水溶剂中加入锂盐LiN(SO 2CF 3) 2溶解并混合均匀，进而得到锂盐的浓度为1M的电解液。
2.3负极的制备
实施例1
采用静电纺丝技术，以聚偏二氟乙烯为前驱体，将聚偏二氟乙烯溶解于 8mL的N,N-二甲基甲酰胺与2mL的丙酮中，其中混合溶液中的聚偏二氟乙烯的重量比为8％，充分搅拌8小时，将溶液转移至针筒中进行静电纺丝，静电纺丝过程参数：负压为-4kV、正压为18kV、进液速率为0.3mL/h、收集板与针头距离为15cm-20cm且收集滚筒转速为2000rpm。静电纺丝制备所得的聚偏二氟乙烯纤维置于真空干燥箱中80℃保持12小时。采用聚偏二氟乙烯纤维构成的三维骨架，将锂金属膜与三维骨架依序压至于铜箔集流体上，其中三维骨架经冷压工艺后形成多孔层。最后，直接冲切得到裁切成(18mm)的规格的负极。负极结构测量：多孔层厚度为50μm、孔隙率为80％、单根纤维的直径范围为0.4μm至1μm、锂金属膜的厚度为20μm、聚偏二氟乙烯纤维中的晶相结构为β相占主导。
实施例2
与实施例1的制备方式大致上相同，除了冷压工艺时采用了1T的压力，使得多孔层厚度为30μm，孔隙率为40％。
实施例3
与实施例1的制备方式大致上相同，除了静电纺织工艺采用的参数为：负压为-1kV、正压为8kV,进液速率为0.8mL/h、收集板与针头距离为12cm及收集滚筒转速为100rpm。负极结构测量：多孔层厚度为50μm、孔隙率为80％、单根纤维的直径范围为0.4μm至1μm、锂金属膜的厚度为20μm、聚偏二氟乙烯纤维中的晶相结构中β相的占比低于实施例1。
实施例4
与实施例1的制备方式大致上相同，除了采用聚甲基丙烯酸甲酯为前驱体，静电纺织工艺采用的参数为：负压为-4kV,正压为12kV,进液速率为0.6mL/h，收集板与针头距离为15cm-20cm；收集滚筒转速为2000rpm。采用聚甲基丙烯酸甲酯纤维构成的三维骨架。负极结构测量：多孔层厚度为50μm、孔隙率为80％、单根纤维的直径范围为0.4μm至1μm、锂金属膜的厚度为20μm。
实施例5
与实施例1的制备方式大致上相同，除了采用聚丙烯腈为前驱体，将聚 丙烯腈溶解于10mL的N,N-二甲基甲酰胺中，其中混合溶液中的聚丙烯腈的重量比为8％，静电纺织工艺采用的参数为：电压12kV、进液速率为0.6mL/h、收集板与针头距离为15cm且收集滚筒转速为2000rpm。采用聚丙烯腈纤维构成的三维骨架。负极结构测量：多孔层厚度为50μm、孔隙率为80％、单根纤维的直径范围为0.4μm至1μm、锂金属膜的厚度为20μm。
实施例6
与实施例1的制备方式大致上相同，除了多孔层厚度为300μm。
实施例7
与实施例1的制备方式大致上相同，除了多孔层厚度为500μm。
实施例8
与实施例1的制备方式大致上相同，除了多孔层厚度为200μm。
对比例1
利用20μm的锂铜复合带，直接冲切成(18mm)规格，用作负极极片。
对比例2
采用PP/PE/PP复合隔膜作为多孔层。通过冷压，将锂金属膜与PP/PE/PP复合隔膜依序压置于铜箔集流体上，其中，直接冲切得到裁切成(18mm)的规格的负极。通过结构测量，PP/PE/PP复合隔膜构成的多孔层厚度为20μm、孔隙率为30％至50％，且锂金属膜的厚度为20μm。
对比例3
将聚偏二氟乙烯溶解于10mL的N-甲基吡咯烷酮中，混合溶液中的聚偏二氟乙烯的重量比为8％，充分搅拌4小时之后，将浆料涂布至铜箔集流体上；涂布后极片放置于80度真空干燥箱放置24小时。最后，通过冷压，将锂金属膜压置于负极极片表面上，直接冲切得到裁切成(18mm)的规格的负极。
对比例4
与实施例1的制备方式大致上相同，除了将聚偏二氟乙烯纤维至于真空干燥箱中80℃保持12小时后，进一步聚偏二氟乙烯纤维置于230度马弗炉 中保持2小时，并置于高纯氩气的管式炉中800度保持6小时，以获得碳化的聚偏二氟乙烯纤维，并采用碳化的聚偏二氟乙烯纤维构成的三维骨架。负极结构测量，多孔层厚度为50μm、孔隙率为80％、单根纤维的直径范围为0.4μm至1μm且锂金属膜的厚度为20μm。
2.4锂离子电池的制备
采用聚乙烯膜作为隔离膜，其中聚乙烯膜的厚度为15μm，将上述正极、隔离膜与上述实施例中的负极依顺序堆叠，使隔离膜处于正极与负极中间起到隔离的作用。将堆叠的电极组件装入铝塑膜包装中，并在80℃下脱去水分后，获得干电极组件。随后将上述电解液注入干电极组件中，经过真空封装、静置、化成、整形等工序，组装成扣式电池，即完成以下各实施例和对比例的锂离子电池的制备。
实施例1-9及对比例1-3的负极参数与通过锂金属沉积测试、循环性能测试及循环厚度膨胀率测试的结构记载于下表1中。
表1
Figure PCTCN2021105515-appb-000001
Figure PCTCN2021105515-appb-000002
结果表明，本申请通过设置包含三维骨架的多孔层的负极，能够有效的提升锂离子电池的循环性能，并有效抑制锂离子电池的循环膨胀率。具体的，通过实施例1与对比例1可知，本申请实施例提出的具有三维骨架的负极能够在极大程度上改善目前锂铜复合带的体积膨胀与循环稳定性，使锂离子电池的循环膨胀率降至15％。
通过实施例1与对比例2及3可知，本申请实施例的多孔层由于其三维骨架的纤维结构，故具有良好大小与分布的纤维与纤维间的孔洞，用于提供锂金属沉淀的容纳空间，相较之下，对比例2及3中的膜片虽然具有一定的孔隙率，然而却无法提供足够孔洞大小的孔洞，因此，锂金属无法沉淀于膜片的孔洞中。
通过实施例1与对比例4可知，采用电性绝缘纤维的三维骨架，能够控制锂金属的沉积位置与沉积方向。锂金属在电子导通的三维骨架中沉积具有随机性，更趋向于沉积在多孔层的表面；电性绝缘的三维骨架能够更好的控制沉积位置，从而抑制极片的体积膨胀，提高电池的循环性能。
通过实施例1与实施例2可知，多孔层的孔隙率对于锂金属沉淀的影响。在孔隙率大于70％时，大部分循环的锂金属都能够进入多孔层中，使得多孔层能够较好的抑制锂金属的体积膨胀，改善电化学性能。
通过实施例1与实施例3可知，通过改善三维骨架中的纤维材料的晶相结构，使其呈现β相，能够优化纤维结构的压电性质，并有效提高对锂离子电池的循环膨胀率的控制。
通过实施例1与实施例4及5可知，不同的纤维材料的三维骨架会导致多孔层的稳定性不同。聚偏二氟乙烯纤维三维骨架在电解液中不容易溶解膨胀，因此可以保持良好的三维结构形貌，使包含其的多孔层在循环保持率与体积膨胀性能均较佳。
通过上述实施例及对比例可知，本申请的电话学装置通过设置包含三维骨架的多孔层及采用电性绝缘的三维骨架材料，能够在电化学装置的充放电循环中有效改善负极表面上的锂金属沉积情形；并抑制锂金属的体积膨胀；同时减缓锂枝晶的生长，进而提高电化学装置的循环性能，容量性能以及安全性能。
整个说明书中对“实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例”，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (14)

  1. 一种负极极片，其包括：
    负极集流体；及
    多孔层，所述多孔层位于所述负极集流体上，且所述多孔层包括含有电性绝缘纤维的三维骨架。
  2. 根据权利要求1所述的负极极片，其中所述多孔层的孔隙率大于或等于70％。
  3. 根据权利要求1所述的负极极片，其中所述纤维的直径为50nm至10μm。
  4. 根据权利要求1所述的负极极片，其中所述三维骨架中所述纤维之间交织构成孔洞，所述孔洞尺寸为100nm至10μm。
  5. 根据权利要求1所述的负极极片，其中所述纤维包括离子导体型纤维。
  6. 根据权利要求1所述的负极极片，其中所述纤维具有空心结构，其中所述空心结构的孔洞尺寸为10nm至500nm。
  7. 根据权利要求1所述的负极极片，其中所述纤维的材料包含高分子材料及无机材料中的一种或多种，其中所述高分子材料包含以下组分及各个组分的衍生物中的一种或多种：聚偏二氟乙烯、聚酰亚胺、聚酰胺、聚丙烯腈、聚乙二醇、聚苯醚、聚碳酸亚丙酯、聚甲基丙烯酸甲酯、聚对苯二甲酸乙二醇酯、聚环氧乙烷、聚偏二氟乙烯-六氟丙烯或聚偏二氟乙烯-三氟氯乙烯；且所述无机材料包含硅酸钠、氧化铝及氧化硅中的一种或多种。
  8. 根据权利要求1所述的负极极片，其中所述纤维包括具有压电性的材料。
  9. 根据权利要求1所述的负极极片，其中所述纤维包括具有β相的含氟聚合物。
  10. 根据权利要求1所述的负极极片，其中所述多孔层的厚度为30μm至500μm。
  11. 根据权利要求1所述的负极极片，其进一步包含锂金属，其中所述锂金属位于所述多孔层的内部或所述多孔层与所述集流体之间。
  12. 一种电化学装置，其包含：
    正极极片；
    隔离膜；及
    根据权利要求1至11中任一项所述的负极极片。
  13. 根据权利要求12所述的电化学装置，其中，在所述电化学装置满充的情况下，所述锂金属沉积部分的厚度t至少大于或等于所述多孔层的厚度T的30％。
  14. 一种电子装置，其包含权利要求12或13中任一项所述的电化学装置。
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024152140A1 (zh) * 2023-01-16 2024-07-25 宁德时代新能源科技股份有限公司 负极极片及其制备方法、二次电池和用电装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5895731A (en) * 1997-05-15 1999-04-20 Nelson E. Smith Thin-film lithium battery and process
US20200127294A1 (en) * 2017-04-17 2020-04-23 Institute Of Chemistry, Chinese Academy Of Sciences Three-dimensional current collector for metal secondary battery anode, its preparation and application

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103779581A (zh) * 2012-10-25 2014-05-07 华为技术有限公司 一种多孔负极极片及其制备方法和锂离子电池
CN103855360B (zh) * 2014-02-27 2016-08-17 宁德新能源科技有限公司 锂离子电池及其负极极片及制备方法
CN109994739B (zh) * 2019-03-25 2021-07-23 宁德新能源科技有限公司 负极极片与包含其的电化学装置及电子装置
KR102340319B1 (ko) * 2019-10-25 2021-12-21 주식회사 그리너지 리튬 메탈 음극 구조체, 이를 포함하는 전기화학소자, 및 상기 리튬 메탈 음극 구조체의 제조방법
CN112599723A (zh) * 2020-12-03 2021-04-02 天津市捷威动力工业有限公司 补锂负极极片及其制备方法和锂离子电池

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5895731A (en) * 1997-05-15 1999-04-20 Nelson E. Smith Thin-film lithium battery and process
US20200127294A1 (en) * 2017-04-17 2020-04-23 Institute Of Chemistry, Chinese Academy Of Sciences Three-dimensional current collector for metal secondary battery anode, its preparation and application

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
ABRHA LJALEM HADUSH, NIKODIMOS YOSEF, WELDEYOHANNES HAILE HISHO, HAGOS TESFAYE TEKA, WANG DAO-YI, HUANG CHEN-JUI, JIANG SHI-KAI, W: "Effects of a Thermally Electrochemically Activated β-PVDF Fiber on Suppression of Li Dendrite Growth for Anode-Free Batteries", ACS APPLIED ENERGY MATERIALS, vol. 4, no. 4, 26 April 2021 (2021-04-26), pages 3240 - 3248, XP093020443, ISSN: 2574-0962, DOI: 10.1021/acsaem.0c03015 *
LAI YIMEI, YUN ZHAO, WEIPING CAI, JUN SONG, YONGTANG JIA, BIN DING, JIANHUA YAN: "Constructing Ionic Gradient and Lithiophilic Interphase for High-Rate Li-Metal Anode", SMALL, WILEY, vol. 15, no. 47, 16 October 2019 (2019-10-16), pages 1905171, XP093020444, ISSN: 1613-6810, DOI: 10.1002/smll.201905171 *
LANG, J.; SONG, J.; QI L; LUO, Y.; LUO, X.; WU, H: "Uniform Lithium Deposition Induced by Polyacrylonitrile Submicron Fiber Array for Stable Lithium Metal Anode. ", APPLIED MATERIALS & INTERFACES, AMERICAN CHEMICAL SOCIETY, US, vol. 9, no. 12, 1 January 2017 (2017-01-01), US , pages 10360 - 10365, XP009539977, ISSN: 1944-8244, DOI: 10.1021/acsami.7b00181 *
TIAN RAN, FENG XIAOQIAN, DUAN HUANAN, ZHANG PENG, LI HUA, LIU HEZHOU, GAO LIAN: "Low-Weight 3D Al 2 O 3 Network as an Artificial Layer to Stabilize Lithium Deposition", CHEMSUSCHEM, WILEY-VCH, DE, vol. 11, no. 18, 21 September 2018 (2018-09-21), DE , pages 3243 - 3252, XP093020441, ISSN: 1864-5631, DOI: 10.1002/cssc.201801234 *
XIA SHUHUI, ZHAO YUN, YAN JIANHUA, YU JIANYONG, DING BIN: "Dynamic Regulation of Lithium Dendrite Growth with Electromechanical Coupling Effect of Soft BaTiO 3 Ceramic Nanofiber Films", ACS NANO, AMERICAN CHEMICAL SOCIETY, US, vol. 15, no. 2, 23 February 2021 (2021-02-23), US , pages 3161 - 3170, XP093020442, ISSN: 1936-0851, DOI: 10.1021/acsnano.0c09745 *

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