WO2020224382A1 - 锂金属电池 - Google Patents

锂金属电池 Download PDF

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Publication number
WO2020224382A1
WO2020224382A1 PCT/CN2020/084345 CN2020084345W WO2020224382A1 WO 2020224382 A1 WO2020224382 A1 WO 2020224382A1 CN 2020084345 W CN2020084345 W CN 2020084345W WO 2020224382 A1 WO2020224382 A1 WO 2020224382A1
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Prior art keywords
lithium
lithium metal
metal battery
negative electrode
electrolyte
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PCT/CN2020/084345
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English (en)
French (fr)
Inventor
程萌
刘成勇
胡波兵
郭永胜
付佳玮
李谦
梁成都
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宁德时代新能源科技股份有限公司
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Priority to EP20801533.9A priority Critical patent/EP3890089B1/en
Publication of WO2020224382A1 publication Critical patent/WO2020224382A1/zh
Priority to US17/521,766 priority patent/US20220069355A1/en

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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M4/134—Electrodes based on metals, Si 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
    • H01M4/36—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
    • H01M4/40—Alloys based on alkali metals
    • H01M4/405—Alloys based on lithium
    • 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
    • H01M4/46—Alloys based on magnesium or aluminium
    • H01M4/463—Aluminium based
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H01M2300/004—Three solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
    • H01M50/209—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for prismatic or rectangular cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of batteries, in particular to a lithium metal battery.
  • Lithium-ion batteries (referred to as LIBs) are widely used in the field of electronic products due to their advantages of high voltage, high specific energy, and long cycle life. With the increasing demand for energy storage such as new energy vehicles, wind energy and solar energy, the requirements for lithium-ion batteries are also getting higher and higher, and the current commercial lithium-ion batteries have gradually been unable to meet the demand for energy storage.
  • lithium metal batteries with lithium metal as the anode referred to as LMBs
  • LMBs lithium metal batteries with lithium metal as the anode
  • lithium ions in LMBs are completely different from that of lithium ions in LIBs.
  • lithium ions obtain electrons from an external circuit, and are then deposited directly on or under the negative electrode in the form of metal-lithium particles.
  • a series of problems will be caused, such as the volume expansion of the lithium metal negative electrode during the charging and discharging process, resulting in increased electrolyte consumption, thereby reducing the cycle performance of the battery; at the same time, lithium
  • the incompactness of metal deposition will lead to the growth of dendrites of deposited lithium during the cycle, and in severe cases, it will cause safety problems such as fire. This seriously hinders the commercialization of lithium metal batteries.
  • the purpose of this application is to provide a lithium metal battery to solve at least one of the technical problems mentioned above.
  • a lithium metal battery including:
  • the negative electrode includes a negative electrode current collector and a lithium aluminum alloy layer compounded on at least one surface of the negative electrode current collector;
  • the electrolyte includes an electrolyte and a solvent, and the solvent contains a film-forming agent, and the film-forming agent includes FEC and/or DFEC.
  • the mass percentage of aluminum in the lithium aluminum alloy layer is 0.1-3%, preferably 0.3-2%, especially 0.3-0.8%.
  • the binding force between the lithium aluminum alloy layer and the negative electrode current collector is greater than or equal to 0.01 N/mm.
  • the thickness of the lithium aluminum alloy layer is 10-40 ⁇ m, preferably 15-30 ⁇ m, especially 15-25 ⁇ m.
  • the film-forming agent accounts for 15-80% by mass of the solvent, preferably 15-55%, especially 20-40%.
  • the electrolyte includes LiFSI and/or LiTFSI.
  • the molar concentration of the electrolyte in the electrolyte is 0.5-6 mol/L, preferably 0.8-4 mol/L, especially 1-2 mol/L.
  • the surface of the negative electrode contains Li 3 N and/or LiF.
  • the surface of the negative electrode contains Li 3 N and LiF.
  • the surface of the negative electrode after the formation of the lithium metal battery, the surface of the negative electrode further contains lithium oxynitride.
  • the second aspect of the application provides a device, which includes the lithium metal battery according to the first aspect of the application
  • the uniformity and compactness of the lithium ion deposition during the charging process can be significantly improved, thereby reducing the volume expansion of the lithium metal negative electrode during the charging process; Reduce the contact area between the lithium metal negative electrode and the electrolyte, reduce the consumption of the electrolyte, and improve the cycle performance of the lithium metal battery.
  • the use of lithium aluminum alloy as the negative electrode material improves the uniformity and compactness of lithium ion deposition, so that the lithium metal negative electrode has a better structural stability during the charge and discharge cycle, thereby improving the safety of the lithium metal battery Sex.
  • FEC and/or DFEC are more likely to generate LiF products insoluble in the electrolyte at the interface between the lithium aluminum alloy layer and the electrolyte.
  • the LiF products can inhibit the electrolyte and Further side reactions of the lithium aluminum alloy layer improve the safety and stability of the lithium metal battery.
  • the lithium metal battery provided by the embodiments of the present application can improve the uniformity of lithium deposition and dissolution. At the same time, it can form a stable interface film on the surface of the alloy with the film-forming agent FEC/DFEC.
  • the lithium aluminum alloy and the film-forming agent The combined effect of sulphur can effectively inhibit side reactions, thereby effectively improving the safety and stability of lithium metal batteries.
  • the device of the present application includes the lithium metal battery, and therefore has at least the same advantages as the lithium metal battery.
  • FIG. 1 is a schematic diagram of an embodiment of a lithium metal battery.
  • Figure 2 is an exploded view of Figure 1.
  • Fig. 3 is a schematic diagram of an embodiment of a battery module.
  • Fig. 4 is a schematic diagram of an embodiment of a battery pack.
  • Fig. 5 is an exploded view of Fig. 4.
  • Fig. 6 is a schematic diagram of an embodiment of a device in which a lithium metal battery is used as a power source.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where both a and b are real numbers.
  • the numerical range "6-22” means that all real numbers between “6-22” have been listed in this article, and “6-22" is only an abbreviation of these numerical combinations.
  • the lower limit and upper limit of the "range” applied for in this application can be one or more lower limits and one or more upper limits, respectively.
  • each reaction or operation step can be carried out in sequence or in sequence. Preferably, the reaction method herein is carried out sequentially.
  • the first aspect of the present application provides a lithium metal battery, including:
  • the negative electrode includes a negative electrode current collector and a lithium aluminum alloy layer compounded on at least one surface of the negative electrode current collector;
  • the electrolyte includes an electrolyte and a solvent, and the solvent contains a film-forming agent, and the film-forming agent is FEC and/or DFEC.
  • the thickness of the SEI film has a certain relationship with the volume expansion.
  • the greater the volume expansion the easier the SEI film is to be destroyed.
  • the continuous progress of the destruction and repair of the SEI film will result in a continuous increase in the thickness of the SEI film. If the SEI film is too thick, it will increase the interface resistance and cause voltage attenuation.
  • the lithium metal battery provided by the present application by selecting lithium aluminum alloy as the negative electrode material, can significantly improve the uniformity and compactness of lithium ion deposition during the charging process, thereby reducing the volume expansion of the lithium metal negative electrode during the charging process.
  • the lithium deposition is uneven and compact, it will cause the deposited lithium metal to have a larger specific surface area, which will result in a larger contact area with the electrolyte, resulting in excessive electrolyte consumption during charge and discharge.
  • the embodiments of the present application use lithium aluminum alloy as the negative electrode, and after improving the uniformity of the deposited lithium, the contact area between the lithium metal negative electrode and the electrolyte can be effectively reduced, the consumption of the electrolyte is reduced, and the cycle performance of the lithium metal battery is improved.
  • the use of lithium aluminum alloy as the negative electrode material improves the uniformity and compactness of lithium ion deposition, the lithium metal negative electrode has a better structural stability during the charge and discharge cycle, thereby improving the safety of the lithium metal battery.
  • the film forming agent may be fluoroethylene carbonate (FEC for short), bisfluoroethylene carbonate (DFEC for short), or a combination of FEC and DFEC.
  • FEC and/or DFEC are more likely to generate LiF products insoluble in the electrolyte at the interface between the lithium aluminum alloy layer and the electrolyte.
  • the LiF products can inhibit the electrolyte and Further side reactions of the lithium aluminum alloy layer improve the safety and stability of the lithium metal battery.
  • film-forming agents FEC and DFEC in the examples of the present application are also solvents in nature.
  • FEC and DFEC have film-forming effects, so they are called film-forming agents. Different from other solvents, it is essentially a kind of solvent, which forms a complete solvent system together with other solvents in the electrolyte.
  • the lithium metal battery provided by the embodiments of the present application can improve the uniformity of lithium deposition and dissolution. At the same time, it can form a stable interface film on the surface of the alloy with the film-forming agent FEC and/or DFEC. The combined action of the film-forming agent can effectively inhibit side reactions, thereby effectively improving the safety and stability of lithium metal batteries.
  • the positive electrode is not specifically limited, and it can be prepared by using conventional positive electrode materials.
  • the structure of the positive electrode includes a positive electrode current collector and a positive electrode material layer on the surface of the positive electrode current collector.
  • the positive electrode material layer may be provided on one surface of the positive electrode current collector or on both surfaces of the positive electrode current collector.
  • the positive electrode material layer may include positive electrode active materials, binders, and conductive agents.
  • the specific type of the positive electrode active material is not particularly limited, as long as it can accept and extract lithium ions.
  • the positive electrode active material can be either a layered structure material to diffuse lithium ions in a two-dimensional space, or a spinel structure to diffuse lithium ions in a three-dimensional space.
  • the positive electrode active material may be preferably selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and olivine structure containing One or a combination of lithium phosphates.
  • the binder and conductive agent in the positive electrode and the types and contents of the two are not specifically limited, and can be selected according to actual needs.
  • Binders usually include fluorine-containing polyolefin-based binders.
  • Fluorine-containing polyolefin-based binders include but are not limited to polyvinylidene fluoride (PVDF), vinylidene fluoride copolymers or their modifications (for example, carboxylic acid, Modified acrylic acid, acrylonitrile, etc.) derivatives.
  • PVDF polyvinylidene fluoride
  • vinylidene fluoride copolymers or their modifications (for example, carboxylic acid, Modified acrylic acid, acrylonitrile, etc.) derivatives.
  • the mass percentage of the binder in the positive electrode active material layer is less than or equal to 2 wt%, so as to obtain a lower pole piece impedance.
  • the conductive agent may be various conductive agents suitable for lithium ion (secondary) batteries in the field, for example, may include but not limited to acetylene black, conductive carbon black, carbon fiber (VGCF), carbon nanotube (CNT), Ketjen One or a combination of black grades.
  • the weight of the conductive agent may account for 1 wt% to 10 wt% of the total weight of the positive electrode material layer.
  • the type of the positive current collector is not specifically limited, and can be selected according to actual needs.
  • the positive electrode current collector can usually be a layered body, the positive electrode current collector is usually a structure or part that can collect current, and the positive electrode current collector can be various materials in the field suitable for use as the positive electrode current collector of an electrochemical energy storage device, for example
  • the positive current collector may include but is not limited to metal foil, and more specifically may include but not limited to nickel foil and aluminum foil.
  • the negative electrode in the lithium metal battery is made of lithium aluminum alloy as the negative electrode material layer.
  • the lithium aluminum alloy layer can be arranged on one side of the negative electrode current collector or on both sides of the negative electrode current collector. surface.
  • the negative electrode current collector in the embodiments of the present application may include but is not limited to metal foil, and more specifically may include but not limited to nickel foil and aluminum foil.
  • the isolation membrane can be various materials in the field suitable for the isolation membrane of electrochemical energy storage devices, for example, it can include but not limited to polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate A combination of one or more of ester, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.
  • the electrolyte usually includes an electrolyte and a solvent.
  • LiFSI and/or LiTFSI are selected as the electrolyte.
  • the solvent may be various solvents suitable for the electrolyte of electrochemical energy storage devices in the field, usually a non-aqueous solvent, preferably an organic solvent, and may specifically include but not limited to ethylene carbonate, propylene carbonate, and butylene carbonate One or a combination of one or more of esters, pentene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, or their halogenated derivatives.
  • the mass percentage of aluminum in the lithium aluminum alloy layer is 0.1-3%, preferably 0.3-2%, especially 0.3-0.8%.
  • the mass percentage of aluminum can be, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%. , 1.6%, 1.8%, 2%, 2.5% or 3%.
  • the aluminum content in this range can not only ensure that the charge and discharge potential of the lithium aluminum alloy negative electrode is closer to the potential of pure lithium, but has no effect on the overall energy density of the cell, and can also ensure the processability of the lithium aluminum alloy strip.
  • the mass percentage of aluminum when the mass percentage of aluminum is 0.1 to 3%, it can also ensure that the binding force between the lithium aluminum alloy layer and the negative electrode current collector is greater than or equal to 0.01 N/mm. Therefore, in the lithium aluminum alloy layer, by optimizing the aluminum content, it can not only ensure that the lithium aluminum alloy has good ductility, but also ensure that the lithium aluminum alloy has a good affinity with the negative electrode current collector, so that it can be integrated with the negative electrode.
  • the fluid has a better connection to ensure good electron transmission between the lithium aluminum alloy layer and the negative electrode current collector.
  • the thickness of the lithium aluminum alloy layer is 10-40 ⁇ m, preferably 15-30 ⁇ m, especially 15-25 ⁇ m.
  • the thickness of the lithium aluminum alloy layer may be, for example, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, or 40 ⁇ m.
  • the lithium aluminum alloy layer can not only ensure that the lithium aluminum alloy layer has a strong anti-pulverization ability, but also can maintain a higher energy density of the battery as a whole.
  • the mass percentage of the film-forming agent in the solvent is 15-80%, preferably 15-55%, especially 20-40%.
  • the mass percentage of the film-forming agent in the solvent can be, for example, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, or 80%.
  • the added amount of the film-forming agent can be appropriately reduced.
  • maintaining a low content of film-forming agent can also improve the wettability of the electrolyte to the diaphragm and the pole piece, reduce the polarization, and thus increase the discharge voltage and energy density.
  • the electrolyte is LiFSI and/or LiTFSI.
  • the electrolyte may be lithium bisfluorosulfonimide (LiFSI for short), lithium bistrifluoromethanesulfonimide (LiTFSI for short), or a combination of LiFSI and LiTFSI.
  • LiFSI and/or LiTFSI are easier to decompose to form part of the LiF interface film on the surface of the lithium aluminum alloy, and at the same time to form a stable Li 3 N-LiN x O y interface film, LiF interface
  • the combined action of the film and the Li 3 N-LiN x O y interface film can effectively inhibit the occurrence of side reactions between the lithium metal negative electrode and the electrolyte, thereby further improving the safety and stability of the lithium metal battery.
  • the molar concentration of the electrolyte in the electrolyte is 0.5-6 mol/L, preferably 0.8-4 mol/L, especially 1-2 mol/L.
  • the molar concentration of the electrolyte can be, for example, 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L, 2.5mol/L, 3mol/L, 4mol/L, 5mol/L or 6mol/L.
  • LiFSI and/or LiTFSI which are lithium salts as electrolytes, are also materials that provide SEI film components.
  • the volume expansion of the negative electrode material layer is reduced, the side reaction is reduced, and the lithium salt concentration can be appropriately reduced. This can ensure the electrical performance of the lithium metal battery while also being effective.
  • Reduce costs; at the same time, the use of low-concentration electrolyte concentration can also improve the wettability of the electrolyte to the diaphragm and pole pieces, reduce polarization, and thereby increase the discharge voltage and energy density.
  • the preparation method of the lithium metal battery of the present application is as follows. After the positive electrode, the negative electrode, the separator and the electrolyte are packaged, the lithium metal battery is obtained.
  • the preparation method provided in the embodiments of the present application is the same as the preparation method of a conventional lithium metal battery.
  • the positive electrode, negative electrode, separator and electrolyte provided in the embodiments of the present application can be used to make a wound lithium metal battery. Or stacked lithium metal batteries.
  • Fig. 1 shows a lithium metal battery 5 with a square structure as an example.
  • the outer packaging of the lithium metal battery of the present application can be a hard shell (such as aluminum shell, steel shell, etc.), or a soft package (such as a bag type, and the material can be plastic, such as polypropylene PP, polybutylene terephthalate) One or more of glycol ester PBT, polybutylene succinate PBS, etc.).
  • the outer package may include a housing 51 and a cover 53.
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the housing 51 has an opening communicating with the containing cavity, and a cover plate 53 can cover the opening to close the containing cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly through a winding process or a lamination process.
  • the electrode assembly is packaged in the containing cavity.
  • the electrolyte is soaked in the electrode assembly.
  • 52 in FIG. 2 shows an embodiment of an electrode assembly.
  • the number of electrode assemblies 52 contained in the lithium metal battery 5 can be one or several, which can be adjusted according to requirements.
  • the lithium metal battery can be assembled into a battery module, and the number of lithium metal batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • a plurality of lithium metal batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, the plurality of lithium metal batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing with a containing space, and a plurality of lithium metal batteries 5 are contained in the containing space.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4.
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the second aspect of the present application provides a device.
  • the device includes the lithium metal battery of the first aspect of the present application.
  • the lithium metal battery can be used as a power source for the device.
  • the device in this application uses the lithium metal battery provided in this application, and therefore has at least the same advantages as the lithium metal battery.
  • the device can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf Vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • mobile devices such as mobile phones, laptop computers, etc.
  • electric vehicles such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf Vehicles, electric trucks, etc.
  • electric trains ships and satellites, energy storage systems, etc.
  • the device can select a lithium metal battery, battery module or battery pack according to its usage requirements.
  • Figure 6 is a device as an example.
  • the device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle.
  • battery packs or battery modules can be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the device usually requires light and thin, and can use lithium metal batteries as a power source.
  • lithium metal battery of the present application will be further described in detail with reference to the examples and comparative examples.
  • This embodiment is a lithium metal battery, and its structure is as follows:
  • Positive electrode It includes aluminum foil and a positive electrode material layer coated on the surface of the aluminum foil.
  • the positive electrode material layer is composed of the positive electrode active material LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NCM811) with a weight ratio of 97:2:1, conductive agent carbon black SP, adhesive Mixed with binder polyvinylidene fluoride;
  • Negative electrode including aluminum foil and a lithium aluminum alloy layer compounded on the surface of the aluminum foil, the weight percentage of aluminum in the lithium aluminum alloy layer is 0.1%, and the thickness of the lithium aluminum alloy layer is 20 ⁇ m;
  • Isolation film polyimide isolation film
  • Electrolyte includes electrolyte and solvent, where the solvent is a combination of ethylene carbonate EC and dimethyl carbonate DMC with a mass ratio of 3:7, the electrolyte is LiFSI, and the molar concentration of the electrolyte is 1 mol/L; in the electrolyte It also includes the medium film-forming agent DFEC, calculated on the basis of the solvent, the mass percentage of the film-forming agent DFEC in the solvent is 30%.
  • a lithium metal battery is obtained by sequentially stacking, assembling, injecting, sealing and forming the positive electrode/separating film/negative electrode.
  • Examples 2-6 are respectively a lithium metal battery, which is different from Example 1 in that the aluminum content in the lithium aluminum alloy layer is different, and the rest are the same as Example 1.
  • the specific composition is shown in Table 1.
  • Examples 7-10 are respectively a lithium metal battery.
  • the difference from Example 4 is that the thickness of the lithium aluminum alloy layer is different, and the rest are the same as Example 4.
  • the specific composition is shown in Table 1.
  • Examples 11-16 are respectively a lithium metal battery. The difference from Example 3 is that the concentration of electrolyte in the electrolyte is different. The rest are the same as Example 3. The specific composition is shown in Table 1.
  • Example 17 is a lithium metal battery, which is different from Example 3 in that the composition of the electrolyte in the electrolyte is different, and the rest are the same as Example 3.
  • the specific composition is shown in Table 1.
  • Examples 18-21 are respectively a lithium metal battery.
  • the difference from Example 17 is that the composition of the film-forming agent in the electrolyte is different, and the rest are the same as Example 3.
  • the specific composition is shown in Table 1.
  • This comparative example is a lithium metal battery.
  • the difference from Examples 1-6 is that the negative electrode material layer in this comparative example is a pure lithium layer, that is, a pure lithium belt layer without aluminum addition.
  • Examples 1-6 are the same, and the specific composition is shown in Table 1.
  • This comparative example is a lithium metal battery.
  • the difference from Example 17 is that the negative electrode material layer in this comparative example is a pure lithium layer, that is, a pure lithium belt layer without aluminum addition.
  • the rest are the same as those of Example 17. Same, see Table 1 for specific composition.
  • This comparative example is a lithium metal battery.
  • the difference from Example 18 is that the negative electrode material layer in this comparative example is a pure lithium layer, that is, a pure lithium belt layer without aluminum addition.
  • the rest are the same as those of Example 18. Same, see Table 1 for specific composition.
  • This comparative example is a lithium metal battery.
  • the difference from Example 3 is that no film-forming agent is added to the electrolyte of this comparative example, and the rest are the same as Example 3.
  • the specific composition is shown in Table 1.
  • the thickness measurement method of the lithium aluminum alloy in Table 1 is: use a micrometer for thickness measurement, the unit is ⁇ m.
  • Volume expansion refers to the change in the volume of the cell during charging and discharging.
  • the measurement in this application is the change in the thickness of the cell relative to the thickness of the initial cell after the 20th week is fully discharged.
  • the unit is %.
  • Cycles Use the Xinwei battery tester to carry out the charge and discharge test, the test temperature is 25°C normal temperature test, 0.5C constant current charge to 4.3V, 4.3V constant voltage charge to 0.05C, 0.5C constant current discharge to 2.8V, then Charge and discharge for cycle test.
  • Median voltage the median voltage of the discharge. In this application, the ratio of the discharge energy of the third circle to the discharge capacity is measured.
  • Adhesion test Test with a peel strength tester, the peel angle is 180°, and the test speed is 300mm/min. The adhesion between the alloy and lithium metal foil and the current collector is judged by the peel strength.
  • Example 1 and Examples 11-16 From the data in Example 1 and Examples 11-16, it can be seen that as the electrolyte lithium salt concentration increases, the number of cycles first increases and then decreases, which shows that when the electrolyte concentration is low, the number of ions is low and the conductivity is low; When the electrolyte concentration is high, the viscosity of the electrolyte will increase, and the conductivity and wettability of the electrolyte will become worse, thereby reducing the electrical performance of the lithium metal battery.
  • This application provides a lithium metal battery with good cycle performance and good safety performance, which can solve the problems of poor cycle performance and poor safety performance of existing lithium metal batteries.

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Abstract

本申请提供了一种锂金属电池，涉及电池领域。该锂金属电池，包括：正极、负极、和介于所述正极与所述负极之间的隔离膜以及浸润所述隔离膜的电解液；所述负极包括负极集流体和复合于所述负极集流体至少一侧表面的锂铝合金层；所述电解液包括电解质和溶剂，所述溶剂中含有成膜剂，所述成膜剂为FEC和/或DFEC。

Description

锂金属电池
本申请要求享有2019年05月08日提交的名称为“锂金属电池”的中国专利申请CN201910383572.5的优先权，其全部内容通过引用并入本文中。
技术领域
本申请涉及电池领域，尤其涉及一种锂金属电池。
背景技术
锂离子电池(简称LIBs)因其高电压、高比能量、循环寿命长等优点而广泛应用于电子产品领域。随着新能源汽车，风能太阳能等的储能的需求量越来越大，对锂离子电池的要求也越来越高，目前商业化的锂离子电池已渐渐不能满足储能需求。
由于锂金属具有极高的理论比容量(3860mAh/g)和极低的电化学电位，以锂金属为阳极的锂金属电池(简称LMBs)具有极高的理论能量密度，因此，锂金属电池是最有希望的下一代高能量密度存储设备之一，以满足新兴行业的严格要求。
LMBs中锂离子的行为与LIBs中锂离子的插入/脱嵌行为完全不同。通常，在充电期间，锂离子从外部电路获得电子，然后以金属-锂颗粒的形式直接沉积在负极表面或下方。锂离子在沉积的过程中，由于沉积的不均匀性会带来一系列的问题，如锂金属负极在充放电过程中的体积膨胀，导致电解液消耗加剧，从而降低电池的循环性能；同时锂金属沉积的不致密性在循环过程中会导致沉积锂的枝晶生长，严重时会引起失火等安全问题。这严重阻碍了锂金属电池的商业化。
发明内容
本申请的目的在于提供一种锂金属电池，以解决上述所提及技术问题中的至少一个。
为实现上述发明目的，本申请采用的技术方案为：
一种锂金属电池，包括：
正极、负极、和介于所述正极与所述负极之间的隔离膜以及浸润所述隔离膜的电解液；
所述负极包括负极集流体和复合于所述负极集流体至少一侧表面的锂铝合金层；
所述电解液包括电解质和溶剂，所述溶剂中含有成膜剂，所述成膜剂包括FEC和/或DFEC。
在一些实施例中，所述锂铝合金层中，铝的质量百分含量为0.1～3％，优选为0.3～2％，尤其为0.3～0.8％。
在一些优选的实施例中，所述锂铝合金层与所述负极集流体的粘结力≥0.01N/mm。
在一些实施例中，所述锂铝合金层的厚度10～40μm，优选为15～30μm，尤其为15～25μm。
在一些实施例中，所述成膜剂占所述溶剂的质量百分含量为15～80％，优选为15～55％，尤其为20～40％。
在一些实施例中，所述电解质包括LiFSI和/或LiTFSI。
在一些实施例中，所述电解液中，所述电解质的摩尔浓度为0.5～6mol/L，优选为0.8～4mol/L，尤其为1～2mol/L。
在一些实施例中，所述锂金属电池化成后，所述负极表面含有Li 3N和/或LiF。
在一些实施例中，所述锂金属电池化成后，所述负极表面含有Li 3N和LiF。
在一些实施例中，所述锂金属电池化成后，所述负极表面还含有氮氧化锂。
本申请的第二方面提供一种装置，其包括本申请第一方面所述的锂金属电池
本申请提供的技术方案可以达到以下有益效果：
本申请的实施例提供的锂金属电池，通过选用锂铝合金作为负极材料，可以显著提高充电过程中锂离子沉积的均匀性和致密性，从而减少锂金属负极在充电过程中的体积膨胀；同时减少锂金属负极与电解液的接触面积，降低电解液的消耗，提高锂金属电池的循环性能。另外，由于利用锂铝合金作为负极材料后提高了锂离子沉积的均匀性和致密性，从而使锂金属负极在充放电循环过程中具有更好的结构稳定形，进而提高了锂金属电池的安全性。
此外，通过选用FEC和/或DFEC作为主要的成膜剂，FEC和/或DFEC更易于在锂铝合金层与电解液的界面处生成不溶于电解液的LiF产物，LiF产物可抑制电解液和锂铝合金层的进一步副反应，从而改善锂金属电池的安全性及稳定性。
综上，本申请的实施例提供的锂金属电池，能提高锂沉积和溶出的均匀性，同时搭配成膜剂FEC/DFEC，能够在合金表面生成稳定的界面膜，锂铝合金和成膜剂的共同作用能有效抑制副反应，从而有效改善锂金属电池的安全性及稳定性。本申请的装置包括所述的 锂金属电池，因而至少具有与所述锂金属电池相同的优势。
应当理解的是，以上的一般描述和后文的细节描述仅是示例性的，并不能限制本申请。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是锂金属电池的一实施方式的示意图。
图2是图1的分解图。
图3是电池模块的一实施方式的示意图。
图4是电池包的一实施方式的示意图。
图5是图4的分解图。
图6是锂金属电池用作电源的装置的一实施方式的示意图。
其中，附图标记说明如下：
1电池包
2上箱体
3下箱体
4电池模块
5锂金属电池
具体实施方式
下面将结合实施例对本申请的实施方案进行详细描述，但是本领域技术人员将会理解，下列实施例仅用于说明本申请，而不应视为限制本申请的范围。实施例中未注明具体条件者，按照常规条件或制造商建议的条件进行。所用试剂或仪器未注明生产厂商者，均为可以通过市售购买获得的常规产品。
需要说明的是：本申请中，如果没有特别的说明，本文所提到的所有实施方式以及优选实施方法可以相互组合形成新的技术方案。本申请中，如果没有特别的说明，本文所提 到的所有技术特征以及优选特征可以相互组合形成新的技术方案。本申请中，如果没有特别的说明，百分数(％)或者份指的是相对于组合物的重量百分数或重量份,或者质量百分数或质量份。本申请中，如果没有特别的说明，所涉及的各组分或其优选组分可以相互组合形成新的技术方案。本申请中，除非有其他说明，数值范围“a～b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“6～22”表示本文中已经全部列出了“6～22”之间的全部实数，“6～22”只是这些数值组合的缩略表示。本申请所申请的“范围”以下限和上限的形式，可以分别为一个或多个下限，和一个或多个上限。本申请中，除非另有说明，各个反应或操作步骤可以顺序进行，也可以按照顺序进行。优选地，本文中的反应方法是顺序进行的。
除非另有说明，本文中所用的专业与科学术语与本领域熟练人员所熟悉的意义相同。此外，任何与所记载内容相似或均等的方法或材料也可应用于本申请中。
锂金属电池
本申请的第一方面提供一种锂金属电池，包括：
正极、负极、和介于所述正极与所述负极之间的隔离膜以及浸润所述隔离膜的电解液；
所述负极包括负极集流体和复合于所述负极集流体至少一侧表面的锂铝合金层；
所述电解液包括电解质和溶剂，所述溶剂中含有成膜剂，所述成膜剂为FEC和/或DFEC。
在锂金属电池中，SEI膜的厚度与体积膨胀存在一定关系，体积膨胀越大，SEI膜越容易被破坏，SEI膜的破坏和修复的不断进行会导致SEI膜厚度的持续增加。SEI膜过厚又会增加界面电阻，造成电压的衰减。
通过研究发现，以锂铝合金为负极，形成于锂铝合金表面的SEI膜不容易破裂，该SEI膜的结构更稳定且更均匀，可以改善充电过程中锂离子沉积的不均匀性和松散性。因此，本申请提供的锂金属电池，通过选用锂铝合金作为负极材料，可以显著提高充电过程中锂离子沉积的均匀性和致密性，从而减少锂金属负极在充电过程中的体积膨胀。
另外，若锂沉积不均匀不致密，则会导致沉积锂金属有较大的比表面积，因此会造成其与电解液有较大的接触面积，造成充放电过程中电解液的消耗量过大。而本申请的实施例通过利用锂铝合金作为负极，在提高沉积锂的均匀性后，可以有效减少锂金属负极与电解液的接触面积，降低电解液的消耗，提高锂金属电池的循环性能。同时，由于利用锂铝合金作为负极材料后提高了锂离子沉积的均匀性和致密性，锂金属负极在充放电循环过程中具有更好的结构稳定形，进而提高了锂金属电池的安全性。
在本申请的实施例中，成膜剂可以为氟代碳酸乙烯酯(简称FEC)，也可以为双氟 代碳酸乙烯酯(简称DFEC)，还可以为FEC和DFEC的组合。此外，通过选用FEC和/或DFEC作为主要的成膜剂，FEC和/或DFEC更易于在锂铝合金层与电解液的界面处生成不溶于电解液的LiF产物，LiF产物可抑制电解液和锂铝合金层的进一步副反应，从而改善锂金属电池的安全性及稳定性。
需要说明的是，本申请的实施例中的成膜剂FEC和DFEC在本质上也属于溶剂，在本申请的实施例中，FEC和DFEC具有成膜的功效，因此称为成膜剂，以与其他溶剂相区别，其实质上也是一种溶剂，在电解液中与其他溶剂一起构成完整的溶剂体系。
由此可见，本申请的实施例提供的锂金属电池，能提高锂沉积和溶出的均匀性，同时搭配成膜剂FEC和/或DFEC，能够在合金表面生成稳定的界面膜，锂铝合金和成膜剂的共同作用能有效抑制副反应，从而有效改善锂金属电池的安全性及稳定性。
[正极]
在本申请的实施例中并未对正极做出具体的限定，可以利用常规正极材料制备而成。例如，正极的结构包括正极集流体和位于正极集流体表面的正极材料层。正极材料层可以设置在正极集流体的其中一个表面上也可以设置在正极集流体的两个表面上。其中，正极材料层又可以包括正极活性物质、粘结剂和导电剂等。正极活性物质的具体种类没有特别的限制，只要能满足接受、脱出锂离子即可。正极活性物质既可为层状结构材料，使锂离子在二维空间扩散，也可为尖晶石结构，使锂离子在三维空间扩散。具体地，正极活性物质可优选选自锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物、橄榄石结构的含锂磷酸盐中的一种或几种的组合。
正极中的粘结剂和导电剂以及两者的种类和含量不受具体的限制，可根据实际需求进行选择。
粘结剂通常包括含氟聚烯烃类粘结剂，含氟聚烯烃类粘结剂包括但不限于聚偏氟乙烯(PVDF)、偏氟乙烯共聚物或它们的改性(例如，羧酸、丙烯酸、丙烯腈等改性)衍生物等。在所述正极材料层中，由于粘结剂本身的导电性较差，因此粘结剂的用量不能过高。优选地，正极活性物质层中粘结剂的质量百分含量小于等于2wt％，以获得较低的极片阻抗。
导电剂可以是本领域各种适用于锂离子(二次)电池的导电剂，例如，可以是包括但不限于乙炔黑、导电炭黑、碳纤维(VGCF)、碳纳米管(CNT)、科琴黑等中的一种或多种的组合。所述导电剂的重量可以占正极材料层总重量的1wt％～10wt％。
正极极片中，正极集流体的种类也不受具体的限制，可根据实际需求进行选择。正极集流体通常可以为层体，所述正极集流体通常是可以汇集电流的结构或零件，所述正极集 流体可以是本领域各种适用于作为电化学储能装置正极集流体的材料，例如，所述正极集流体可以是包括但不限于金属箔，更具体可以是包括但不限于镍箔、铝箔。
[负极]
在本申请的实施例中，锂金属电池中的负极，是以锂铝合金制作负极材料层，其中，锂铝合金层可以设置在负极集流体一侧表面也可以设置在负极集流体的两侧表面。
本申请的实施例中的负极集流体可以是包括但不限于金属箔，更具体可以是包括但不限于镍箔、铝箔。
[隔离膜]
隔离膜可以是本领域各种适用于电化学储能装置隔离膜的材料，例如，可以是包括但不限于聚乙烯、聚丙烯、聚偏氟乙烯、芳纶、聚对苯二甲酸乙二醇酯、聚四氟乙烯、聚丙烯腈、聚酰亚胺，聚酰胺、聚酯和天然纤维中的一种或多种的组合。
[电解液]
电解液通常包括电解质和溶剂，本申请的实施例中选择LiFSI和/或LiTFSI作为电解质。
溶剂可以是本领域各种适用于电化学储能装置的电解液的溶剂，通常为非水溶剂，优选可以为有机溶剂，具体可以是包括但不限于碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸戊烯酯、碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯或它们的卤代衍生物中的一种或多种的组合。
在本申请的一些实施方式中，所述锂铝合金层中，铝的质量百分含量为0.1～3％，优选为0.3～2％，尤其为0.3～0.8％。在该实施方式中，铝的质量百分含量典型但非限制性的例如可以为0.1％、0.2％、0.3％、0.4％、0.5％、0.6％、0.8％、1％、1.2％、1.4％、1.6％、1.8％、2％、2.5％或3％。
铝含量在此范围中既可以保证锂铝合金负极充放电电位与纯锂的电位更接近，且对电芯整体能量密度没有影响，同时还可以保证锂铝合金带的加工性。
另外，当铝的质量百分含量为0.1～3％时，还可以保证锂铝合金层与负极集流体之间的粘结力≥0.01N/mm。因此，锂铝合金层中，通过优化铝的含量，既可以保证锂铝合金具有较好的延展性，还可以保证锂铝合金与负极集流体有较好的亲和性，使其与负极集流体有较好的连接，从而保证锂铝合金层与负极集流体之间有良好的电子传输。
在本申请的一些实施方式中，所述锂铝合金层的厚度10～40μm，优选为15～30μm，尤其为15～25μm。其中，锂铝合金层的厚度典型但非限制性的例如可以为10μm、15μm、20μm、25μm、30μm、35μm或40μm。
通过将锂铝合金层的厚度设置为10～40μm，既可以保证锂铝合金层有较强的抗粉化能力，又可以使电芯从整体上保持较高的能量密度。
在本申请的一些实施方式中，所述成膜剂占所述溶剂的质量百分含量为15～80％，优选为15～55％，尤其为20～40％。该实施方式中，成膜剂占所述溶剂的质量百分含量例如可以为15％、20％、25％、30％、40％、50％、60％、70％或80％。
由于采用锂铝合金作为负极，其与电解液的副反应会降低，因此，本申请的实施例中可适当减少成膜剂的加入量。在溶剂中，保持低含量的成膜剂，还可以提高电解液对隔膜和极片的浸润性，降低极化，从而提高放电电压和能量密度。
在本申请的一些实施方式中，所述电解质为LiFSI和/或LiTFSI。其中，电解质可以为双氟磺酰亚胺锂(简称LiFSI)，也可以为双三氟甲基磺酸亚酰胺锂(简称LiTFSI)，也可以为LiFSI和LiTFSI的组合。
通过选用LiFSI和/或LiTFSI作为电解质，相对于纯锂负极，LiFSI和LiTFSI更易于在锂铝合金表面分解生成部分LiF界面膜，同时生成稳定的Li 3N-LiN xO y界面膜，LiF界面膜和Li 3N-LiN xO y界面膜共同作用能有效抑制锂金属负极与电解液之间副反应的发生，从而进一步改善锂金属电池的安全性及稳定性。
在本申请的一些实施方式中，所述电解液中，所述电解质的摩尔浓度为0.5～6mol/L，优选为0.8～4mol/L，尤其为1～2mol/L。其中，电解质的摩尔浓度典型但非限制性的例如可以为0.5mol/L、1mol/L、1.5mol/L、2mol/L、2.5mol/L、3mol/L、4mol/L、5mol/L或6mol/L。
作为电解质的锂盐LiFSI和/或LiTFSI，也是提供SEI膜成分的物质。在本申请的实施例中，通过选用锂铝合金作为负极，负极材料层的体积膨胀减小，副反应减小，锂盐浓度可适当降低，这样既能保证锂金属电池电性能同时还能有效降低成本；同时，采用低浓度的电解质浓度，还可以提高电解液对隔膜和极片的浸润性，降低极化，从而提高放电电压和能量密度。
本申请的锂金属电池的制备方法如下，将所述正极、所述负极、所述隔离膜和所述电解液封装后，得到所述锂金属电池。
具体的，本申请的实施例提供的制备方法与常规锂金属电池的制备方法相同，例如，可以利用本申请的实施例提供的正极、负极、隔离膜和电解液做成卷绕式锂金属电池或层叠式锂金属电池。
本申请对锂金属电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图1是作为一个示例的方形结构的锂金属电池5。
本申请的锂金属电池的外包装可以是硬壳(例如铝壳、钢壳等)，也可以是软包(例如袋式，其材质可以是塑料，如聚丙烯PP、聚对苯二甲酸丁二醇酯PBT、聚丁二酸丁二醇酯PBS等中的一种或几种)。
在一些实施例中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。
正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件。电极组件封装于所述容纳腔。电解液浸润于电极组件中。图2中的52示出了一种电极组件的实施方式。
锂金属电池5所含电极组件52的数量可以为一个或几个，可根据需求来调节。
在一些实施例中，锂金属电池可以组装成电池模块，电池模块所含锂金属电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个锂金属电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个锂金属电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个锂金属电池5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
装置
本申请的第二方面提供一种装置。该装置包括本申请第一方面的锂金属电池。所述锂金属电池可以用作装置的电源。本申请的装置采用了本申请所提供的锂金属电池，因此至少具有与所述锂金属电池相同的优势。
所述装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
所述装置可以根据其使用需求来选择锂金属电池、电池模块或电池包。
图6是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动 力电动车等。为了满足该装置对锂金属电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用锂金属电池作为电源。
以下结合实施例进一步说明本申请的有益效果。
下面将结合实施例和对比例对本申请的锂金属电池做进一步详细说明。
实施例1
本实施例是一种锂金属电池，其结构如下：
正极：包括铝箔和涂敷于铝箔表面的正极材料层，正极材料层由重量比为97：2：1的正极活性材料LiNi 0.8Mn 0.1Co 0.1O 2(NCM811)、导电剂炭黑SP、粘结剂聚偏氟乙烯混合而成；
负极：包括铝箔和复合于铝箔表面的锂铝合金层，该锂铝合金层中铝的重量百分比为0.1％，该锂铝合金层的厚度为20μm；
隔离膜：聚酰亚胺隔离膜；
电解液：包括电解质和溶剂，其中，溶剂为质量比为3：7的碳酸乙烯酯EC和碳酸二甲酯DMC的组合，电解质为LiFSI，且电解质的摩尔浓度为1mol/L；该电解液中还包括中成膜剂DFEC，以溶剂为基准计算，该溶剂中成膜剂DFEC的质量百分含量为30％。
将上述正极/隔离膜/负极依次层叠、组装、注液、密封和化成后得到锂金属电池。
实施例2-6
实施例2-6分别是一种锂金属电池，其与实施例1的不同之处在于锂铝合金层中铝含量不同，其余均与实施例1相同，具体组成见表1。
实施例7-10
实施例7-10分别是一种锂金属电池，其与实施例4的不同之处在于锂铝合金层的厚度不同，其余均与实施例4相同，具体组成见表1。
实施例11-16
实施例11-16分别是一种锂金属电池，其与实施例3的不同之处在于电解液中电解质的浓度不同，其余均与实施例3相同，具体组成见表1。
实施例17
实施例17是一种锂金属电池，其与实施例3的不同之处在于电解液中电解质的组成不同，其余均与实施例3相同，具体组成见表1。
实施例18-21
实施例18-21分别是一种锂金属电池，其与实施例17的不同之处在于电解液中成膜剂的组成不同，其余均与实施例3相同，具体组成见表1。
对比例1
本对比例是一种锂金属电池，其与实施例1-6的不同之处在于，该对比例中的负极材料层为纯锂层，即不添加铝的纯锂带层，其余均与实施例1-6相同，具体组成见表1。
对比例2
本对比例是一种锂金属电池，其与实施例17的不同之处在于，该对比例中的负极材料层为纯锂层，即不添加铝的纯锂带层，其余均与实施例17相同，具体组成见表1。
对比例3
本对比例是一种锂金属电池，其与实施例18的不同之处在于，该对比例中的负极材料层为纯锂层，即不添加铝的纯锂带层，其余均与实施例18相同，具体组成见表1。
对比例4
本对比例是一种锂金属电池，其与实施例3的不同之处在于，该对比例的电解液中未添加成膜剂，其余均与实施例3相同，具体组成见表1。
实施例1-20的锂金属电池的具体组成列于表1，除表1所示内容外，实施例1-20其他组成成分均相同。
表1
Figure PCTCN2020084345-appb-000001
Figure PCTCN2020084345-appb-000002
Figure PCTCN2020084345-appb-000003
注：表1中的锂铝合金的厚度测量方法为：使用千分尺进行厚度测试，单位为μm。
分别测试实施例1-21和对比例1-4中的锂金属电池的各项性能参数，具体的测试项目和测试方法如下所示，测试结果列于表2。
测试项目及测试方法：
体积膨胀：指在充放电过程中电芯体积的变化，在本申请中测量的是在第20周满放后电芯厚度相对于初始电芯厚度的变化值，单位为％。
循环次数：利用新威电池测试机进行充放电测试，测试温度为25℃常温测试，0.5C恒流充电至4.3V，4.3V恒压充电至0.05C，0.5C恒流放电至2.8V，然后充放进行循环测试。
中值电压：为放电中值电压，在本申请中测量的是第三圈的放电能量与放电容量的比值。
粘结力测试：通过剥离强度测试仪进行测试，剥离角度为180°，测试速度300mm/min。通过剥离强度判断合金及锂金属箔与集流体间的粘结力。
表2
Figure PCTCN2020084345-appb-000004
Figure PCTCN2020084345-appb-000005
参照表2，从实施例1-6中的数据可以看出，随着锂铝合金层中铝含量的增加，锂铝合金层与负极集流体的粘结力会有所下降，体积膨胀减小，铝含量在一定范围内对中值电压无影响，超过一定含量中值电压明显下降。
从实施例1和实施例7-10中的数据可以看出，随着锂铝合金层厚度的增加，锂金属电池的循环次数明显提升，但是厚度的增加会增加质量，能量密度会降低。
从实施例1和实施例11-16中的数据可以看出，随着电解质锂盐浓度的增加，循环次数先增后减，这说明当电解质浓度低时，离子数低，电导率低；而当电解质浓度高时，又会增加电解液的粘度，使电解液的电导率和浸润性均变差，从而降低锂金属电池的电性能。
从实施例3和实施例17的对比数据可以看出，单组分锂盐(LiFSI)和双组分锂盐(0.5M LiFSI+0.5MLiTFSI)对体系循环性能影响不大。
从实施例17和实施例18-21的对比数据可以看出，单组分成膜剂(DFEC)和双组分成膜剂(DFEC+FEC)对体系循环性能影响不大。
从实施例17和实施例22的对比数据可以看出，DFEC过量，会在一定程度上降低电解液的电导率，极化增加，降低锂金属电池的循环性能。
从实施例1-22和对比例1-4的对比数据可以看出，实施例1-22的锂金属电池的电性能均优于对比例1-4。
具体的，从实施例1-6和对比例1的对比数据，以及从实施例17-18和对比例2-3的对比数据可知，当用纯锂作为负极材料层时，其体积膨胀率均在45％以上，而循环次数在187次以下，远低于实施例1-22中的数据。
另外，从实施例3和对比例4中的对比数据可知，当使用锂铝合金层作为负极材料层，且不添加成膜剂或改变溶剂的类型时，得到的锂金属电池的电性能和对比例1-2的数据相差不大。
通过上述分析可知，当选用锂铝合金作为负极，同时配合DFEC和FEC作为成膜剂时，得到的锂金属电池的电性能均远远高于单独使用锂铝合金或单独使用DFEC和FEC作为成膜剂时的电性能，证明锂铝合金和DFEC和FEC作为成膜剂的协同增效作用，会显著提高锂金属电池的电性能。
本申请提供了一种循环性能好和安全性能佳的锂金属电池，能够解决现有锂金属电池循环性能差和安全性能差的问题。
以上所述仅为本申请的优选实施例而已，并不用于限制本申请，对于本领域的技术人 员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (10)

  1. 一种锂金属电池，包括：正极、负极、和介于所述正极与所述负极之间的隔离膜以及浸润所述隔离膜的电解液；
    其中，所述负极包括负极集流体和复合于所述负极集流体至少一侧表面的锂铝合金层；所述电解液包括电解质和溶剂，所述溶剂中含有成膜剂，所述成膜剂包括FEC和/或DFEC。
  2. 根据权利要求1所述的锂金属电池，其中，所述锂铝合金层中，铝的质量百分含量为0.1～3％，优选为0.3～2％。
  3. 根据权利要求1-2任一项所述的锂金属电池，其中，所述锂铝合金层与所述负极集流体的粘结力≥0.01N/mm。
  4. 根据权利要求1-3任一项所述的锂金属电池，其中，所述锂铝合金层的厚度10～40μm，优选为15～30μm。
  5. 根据权利要求1-4任一项所述的锂金属电池，其中，所述成膜剂占所述溶剂的质量百分含量为15～80％，优选为15～55％。
  6. 根据权利要求1-5任一项所述的锂金属电池，其中，所述电解质包括LiFSI和/或LiTFSI。
  7. 根据权利要求1-6任一项所述的锂金属电池，其中，所述电解液中，所述电解质的摩尔浓度为0.5～6mol/L，优选为0.8～4mol/L。
  8. 根据权利要求1-7任一项所述的锂金属电池，其中，所述锂金属电池化成后，所述负极表面含有Li 3N和/或LiF。
  9. 根据权利要求1-8任一项所述的锂金属电池，其中，所述锂金属电池化成后，所述负极表面还含有氮氧化锂。
  10. 一种装置，包括权利要求1-9任一项所述的锂金属电池。
PCT/CN2020/084345 2019-05-08 2020-04-11 锂金属电池 WO2020224382A1 (zh)

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