CN114242946A - Composite metal lithium cathode and preparation method and application thereof - Google Patents

Composite metal lithium cathode and preparation method and application thereof Download PDF

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CN114242946A
CN114242946A CN202111520412.4A CN202111520412A CN114242946A CN 114242946 A CN114242946 A CN 114242946A CN 202111520412 A CN202111520412 A CN 202111520412A CN 114242946 A CN114242946 A CN 114242946A
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lithium
metal
composite
fluoride
rare earth
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CN114242946B (en
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高剑
邓金祥
邓云龙
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Sichuan Qiruike Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/362—Composites
    • 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
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • 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

Abstract

The invention discloses a composite metal lithium cathode and a preparation method and application thereof, belonging to the technical field of lithium batteries. Aiming at the problems in the prior art, the invention provides a preparation method of a composite metal lithium negative electrode, which comprises the following steps: under the protection of inert gas, melting the metal lithium; adding metal fluoride, and reacting to obtain a mixed system of an alloy phase, lithium fluoride and metal lithium; raising the temperature to melt the lithium fluoride; adding metal-rare earth intermediate alloy, reacting to obtain the composite cathode containing rare earth, and post-treating to obtain the final product. According to the invention, lithium fluoride is melted at high temperature, and metal fluoride is added to obtain lithium fluoride and an alloy phase which are uniformly distributed in the whole phase, so that uniform and rapid deposition of lithium is realized, and volume change is accommodated, and then a metal-rare earth intermediate alloy is added, so that segregation of the alloy is reduced by utilizing the grain refinement effect of rare earth, and the composite metal lithium cathode with excellent cycle performance and rate performance is prepared.

Description

Composite metal lithium cathode and preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a composite metal lithium cathode and a preparation method and application thereof.
Background
With the application of lithium ion batteries in the field of power automobiles, the demand for energy density of batteries is increasing. The graphite negative electrode adopted by the lithium ion battery at present has lower theoretical specific capacity, and the metal lithium negative electrode is considered to be a 'holy cup' of the negative electrode material of the secondary battery due to the ultrahigh theoretical specific capacity and the lowest electrode potential, but the metal lithium negative electrode has a plurality of problems in practical application. 1) When lithium is deposited, the electric field distribution is uneven due to the uneven surface of the metal lithium, so that the metal lithium is more prone to be deposited at the convex part and the electric field concentration part to cause the growth of lithium dendrites, and the continuously grown lithium dendrites can pierce through the diaphragm to cause the short circuit of the battery. 2) The high-activity metal lithium reacts with the electrolyte and is continuously consumed in the circulating process, so that the coulomb efficiency and the cycle life of the battery are reduced. 3) The host-free nature of lithium metal causes a large volume change during cycling, which can lead to structural failure of the electrode and electrode chalking. These problems are liable to cause a series of safety problems, which affect the practical application of the metallic lithium negative electrode.
The problems of the lithium metal negative electrode are solved by methods such as surface coating, electrolyte additives, three-dimensional structure negative electrodes and the like, but no final solution exists at present. The alloy negative electrode has a skeleton structure which can reduce the actual current density, inhibit the growth of dendrites and accommodate the volume change in the circulation process, so that the alloy negative electrode is widely researched.
CN201811182577.3 discloses a metallic lithium alloy electrode material, a preparation method and application thereof, wherein Li, Al, Zn and Ag are used for forming an alloy to reduce side reactions between a metallic lithium cathode and an electrolyte, thereby improving the coulombic efficiency and simultaneously realizing the advantages of high safety and long circulation; however, the alloy negative electrode of the method has the problem of alloy component segregation, so that the distribution of the alloy in the material is not uniform, and the uniform deposition of lithium is influenced.
CN201910315106.3 discloses a method for producing lithium fluoride by using metal fluoride to react with lithium metal, wherein the produced lithium fluoride has good ionic conductivity, and can effectively improve the mobility of lithium ions on the surface of lithium metal, and at the same time, the metal or alloy layer formed on the surface of lithium metal can greatly improve the surface conductivity of lithium metal, which is beneficial to the uniform distribution of electric field, and can also inhibit the growth of dendrite. The protective layer formed by the lithium fluoride and the metal or the alloy is uniform and compact, the structure is more stable, the lithium fluoride is not easy to break, and the service life is prolonged; however, this method can only have lithium fluoride particles and an alloy phase on the surface of the lithium negative electrode, and can only function on the surface portion, and cannot accommodate volume changes in the lithium negative electrode cycle.
Disclosure of Invention
Aiming at the problems in the prior art, the lithium fluoride is melted at high temperature, the metal fluoride is added to obtain the lithium fluoride and alloy phase which are uniformly distributed in the whole phase, the uniform and rapid deposition of lithium is realized, the volume change is accommodated, the metal-rare earth intermediate alloy is added, the segregation of the alloy is reduced by utilizing the grain refinement effect of the rare earth, and the composite metal lithium cathode with excellent performance is prepared.
The invention provides a preparation method of a composite metal lithium cathode, which comprises the following steps:
A. under the protection of inert gas, melting the metal lithium to obtain molten lithium liquid;
B. adding metal fluoride into the molten lithium liquid, and obtaining a mixed system of an alloy phase, lithium fluoride and metal lithium after the reaction is finished;
C. raising the temperature to melt the lithium fluoride to obtain a composite lithium liquid;
D. and adding a metal-rare earth intermediate alloy into the composite lithium solution, obtaining a composite cathode containing rare earth after the reaction is finished, and obtaining the composite lithium metal cathode after post-treatment.
In the preparation method of the composite lithium metal cathode, in the step A, the melting temperature of the lithium metal is 250-400 ℃.
In the preparation method of the composite metal lithium negative electrode, in the step B, the metal fluoride is MgF2、AlF3、ZnF2、CaF2、CuF2、SnF2、InF3、GaF3、BaF2One kind of (1).
In the preparation method of the composite lithium metal cathode, in the step B, the addition amount of the metal fluoride is 1-50 wt% of the mass of the metal lithium in the step A.
Preferably, in the preparation method of the composite lithium metal negative electrode, in the step B, the addition amount of the metal fluoride is 20-45 wt% of the mass of the metal lithium in the step a.
In the preparation method of the composite metal lithium cathode, in the step B, the reaction temperature is 250-400 ℃.
In the preparation method of the composite metal lithium cathode, in the step B, the reaction time is 1-5 hours.
In the preparation method of the composite metal lithium negative electrode, in the step C, the temperature for melting the lithium fluoride is 850-1000 ℃.
In the preparation method of the composite metal lithium negative electrode, in the step D, the metal-rare earth intermediate alloy is: the metal is at least one of the alloys obtained by combining any one of aluminum, magnesium, copper, zinc, calcium, tin, indium, gallium or barium and the rare earth is any one of lanthanum, ytterbium, cerium, neodymium or erbium, and the metal of the metal fluoride in the step B is the same as that of the metal-rare earth intermediate alloy in the step D.
In the preparation method of the composite metal lithium cathode, in the step D, the addition amount of the metal-rare earth intermediate alloy is 1-5 wt% of the total mass of the metal lithium in the step A and the metal fluoride in the step B.
Preferably, in the preparation method of the composite metal lithium cathode, in the step D, the addition amount of the metal-rare earth intermediate alloy is 1 to 3 wt% of the total mass of the metal lithium in the step a and the metal fluoride in the step B.
In the preparation method of the composite metal lithium cathode, in the step D, the reaction temperature is 850-1000 ℃.
In the preparation method of the composite metal lithium cathode, in the step D, the reaction time is 1-5 hours.
The invention also provides the composite lithium metal cathode prepared according to the preparation method of the composite lithium metal cathode.
The invention also provides application of the composite lithium metal cathode prepared according to the preparation method of the composite lithium metal cathode in preparation of a lithium battery.
The invention has the beneficial effects that:
according to the lithium fluoride composite cathode, the metal fluoride and the lithium metal are added to react to generate the corresponding lithium alloy and the lithium fluoride, the lithium fluoride and the alloy framework are generated by utilizing the reaction of the metal fluoride and the lithium, the alloy framework provides a stable three-dimensional structure, the lithium fluoride composite cathode adapts to volume change in circulation, the problem of huge volume change in the circulation process of the lithium cathode is solved, meanwhile, the molten lithium fluoride can be more uniformly distributed in the composite cathode, the potential barrier of lithium ion diffusion is reduced, the lithium ions are helped to be more rapidly separated/deposited from the alloy, the growth of dendritic crystals is inhibited, and the rate capability of the composite cathode is improved; and further, by adding the low-melting-point metal-rare earth intermediate alloy, the volume change of the alloy in the circulating process can be accommodated by the three-dimensional structure of the alloy, meanwhile, the rare earth metal can refine the crystal grains of the alloy, the segregation of the alloy material is reduced, the alloy is more uniformly distributed in the whole material, the uniform deposition of lithium is facilitated, the mechanical strength of the alloy cathode is enhanced by adding the rare earth, the rolling production of the composite cathode is more facilitated, and the circulating performance and the multiplying power performance of the prepared composite cathode are obviously improved.
Detailed Description
Specifically, the preparation process of the composite metal lithium negative electrode comprises the following steps:
A. under the protection of inert gas, melting the metal lithium to obtain molten lithium liquid;
B. adding metal fluoride into the molten lithium liquid, and obtaining a mixed system of an alloy phase, lithium fluoride and metal lithium after the reaction is finished;
C. raising the temperature to melt the lithium fluoride to obtain a composite lithium liquid;
D. and adding a metal-rare earth intermediate alloy into the composite lithium solution, obtaining a composite cathode containing rare earth after the reaction is finished, and obtaining the composite lithium metal cathode after post-treatment.
In the step A, the temperature is controlled to be 250-400 ℃ so as to ensure that the metal lithium is completely melted to obtain molten lithium liquid.
In the step B, a metal fluoride is added to react with molten lithium liquid to generate corresponding lithium alloy and lithium fluoride, the metal fluoride reacts with lithium to generate a lithium fluoride and alloy framework, the alloy framework provides a stable three-dimensional structure and adapts to volume change in circulation, the problem of huge volume change in the circulation process of a lithium cathode is solved, and meanwhile, the molten lithium fluoride can be more uniformly distributed in the composite cathode, so that the potential barrier of lithium ion diffusion is reduced, lithium ions are more rapidly separated/deposited from the interior of the alloy, the growth of dendrites is inhibited, and the rate capability of the composite cathode is improved; the metal fluoride is MgF2、AlF3、ZnF2、CaF2、CuF2、SnF2、InF3、GaF3、BaF2One kind of (1).
The purpose of adding the metal fluoride is to react with lithium to produce lithium fluoride and lithium alloy, and through tests, the metal fluoride is too little, so that the generated alloy phase is too little to form a continuous three-dimensional structure, and the metal fluoride cannot play a role of a frame of a three-dimensional cathode; if the amount of the metal fluoride is too large, most of the metal lithium is consumed in the reaction with the metal fluoride, and the resultant composite negative electrode contains too little metal lithium. Therefore, in the step B of the invention, the adding amount of the metal fluoride is controlled to be 1-50 wt% of the mass of the metal lithium in the step A; preferably 20 to 45 wt%.
In the step B, in order to ensure the reaction to be complete, the reaction temperature is controlled to be 250-400 ℃, and the reaction time is 1-5 h.
The melting point of the lithium alloy phase is generally lower than that of metallic lithium, namely lower than 180 ℃, so that the alloy phase and the metallic lithium in the mixed system of the alloy phase obtained in the step B, the lithium fluoride and the metallic lithium are in liquid states, and the temperature is increased to ensure that the lithium fluoride can be molten.
The melting point of the lithium alloy phase is generally lower than that of metal lithium, but in order to ensure that the lithium fluoride can be melted, in the step C, the temperature is increased to 850-1000 ℃ (the temperature is generally kept for 1-3 h), so that the whole system is in a completely melted state.
In the step D, by adding the low-melting-point metal-rare earth intermediate alloy, the three-dimensional structure of the obtained composite alloy can accommodate the volume change in the circulating process, and meanwhile, the rare earth metal can refine the crystal grains of the alloy and reduce the segregation of the alloy material, so that the alloy is more uniformly distributed in the whole material, and the uniform deposition of lithium is facilitated; the metal-rare earth intermediate alloy is as follows: the metal is any one of aluminum, magnesium, copper, zinc, calcium, tin, indium, gallium or barium, and the rare earth is any one of lanthanum, ytterbium, cerium, neodymium or erbium, and at least one of the alloys is obtained by combination. In order to ensure the consistency of the produced lithium alloy phase, the metal of the metal fluoride in the step B is the same as that of the metal-rare earth master alloy in the step D, and the master alloy of a single metal and at least one rare earth is adopted in the step D.
In the step D, the addition of the rare earth intermediate alloy is controlled because of the grain refinement effect of the rare earth; tests show that the corresponding effect can be achieved when the addition amount of the rare earth is small, so that the addition amount is low, but if the addition amount is too small, the effect of grain refinement can not be achieved. Therefore, the adding amount of the metal-rare earth intermediate alloy is controlled to be 1-5 wt% of the total mass of the metal lithium in the step A and the metal fluoride in the step B; preferably 1 to 3 wt%.
In the step D of the invention, the reaction temperature is controlled to be 850-1000 ℃, and the reaction time is 1-5 h.
The invention also provides the composite lithium metal cathode prepared according to the preparation method of the composite lithium metal cathode.
The invention also provides application of the composite lithium metal cathode prepared according to the preparation method of the composite lithium metal cathode in preparation of a lithium battery.
According to the invention, the composite cathode containing rare earth is obtained, and the composite metal lithium cathode suitable for assembling a battery is obtained by a conventional post-treatment means, such as pouring molten composite lithium liquid into a mold for cooling and forming, then rolling to obtain a composite cathode strip, and finally slicing by using a slicing machine.
The present invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.
Example 1
Heating metallic lithium to 300 ℃ in an argon environment in a smelting furnace to melt the metallic lithium; adding aluminum fluoride accounting for 40 wt% of the mass of the metal lithium into the molten lithium liquid, and stirring for 1h at 300 ℃ to enable the aluminum fluoride to react completely to generate a lithium-aluminum alloy and lithium fluoride so as to obtain a mixed system of an alloy phase, the lithium fluoride and the metal lithium; further raising the temperature to 900 ℃ to melt the lithium fluoride, and keeping the temperature for 1-3 h; after lithium fluoride is melted, adding an aluminum-lanthanum intermediate alloy accounting for 2 wt% of the total mass of the metal lithium and the aluminum fluoride into the composite lithium liquid, heating and stirring for 1h at 900 ℃ to obtain a composite negative electrode containing rare earth, pouring the melted composite lithium liquid into a mold for cooling and forming, rolling to obtain a composite negative electrode strip with the thickness of 100 microns, and slicing by using a slicing machine to obtain the composite metal lithium negative electrode suitable for assembling a battery.
In an inert atmosphere glove box, LiNi was used0.8Co0.1Mn0.1O2(i.e., NCM811) was used as the positive electrode sheet, the lithium composite metal negative electrode was used as the negative electrode, a 2032 coin cell was assembled using EC: DEC: DMC ═ 1:1:1 as the electrolyte, and then the electrochemical performance test was performed.
With Li-Li couple cells, DME with 1M LiTFSI: a solution of DOL 1:1 (volume ratio) as electrolyte containing 2 wt% lithium nitrate as additive was assembled into 2032 coin cells for electrochemical testing.
Example 2
Heating metallic lithium to 300 ℃ in an argon environment in a smelting furnace to melt the metallic lithium; adding zinc fluoride accounting for 40 wt% of the mass of the metal lithium into the molten lithium liquid, and stirring for 1h at 300 ℃ to enable the zinc fluoride to react completely to generate a lithium-aluminum alloy and lithium fluoride so as to obtain a mixed system of an alloy phase, the lithium fluoride and the metal lithium; further raising the temperature to 900 ℃ to melt the lithium fluoride, and keeping the temperature for 1-3 h; after lithium fluoride is melted, adding zinc-cerium accounting for 1.5 wt% of the total mass of metal lithium and zinc fluoride and zinc-lanthanum intermediate alloy accounting for 1 wt% of the total mass of the metal lithium and the zinc fluoride into the composite lithium liquid, heating and stirring the mixture at 900 ℃ for 1 hour to obtain a composite cathode containing rare earth, pouring the melted composite lithium liquid into a mold for cooling and forming, obtaining a composite cathode strip with the thickness of 100 microns through rolling, and slicing the composite cathode strip by using a slicer to obtain the composite metal lithium cathode suitable for assembling a battery.
In an inert atmosphere glove box, LiNi was used0.8Co0.1Mn0.1O2(i.e., NCM811) was used as the positive electrode sheet, the lithium composite metal negative electrode was used as the negative electrode, a 2032 coin cell was assembled using EC: DEC: DMC ═ 1:1:1 as the electrolyte, and then the electrochemical performance test was performed.
With Li-Li couple cells, DME with 1M LiTFSI: a solution of DOL 1:1 (volume ratio) as electrolyte containing 2 wt% lithium nitrate as additive was assembled into 2032 coin cells for electrochemical testing.
Example 3
Heating metallic lithium to 300 ℃ in an argon environment in a smelting furnace to melt the metallic lithium; adding copper fluoride accounting for 35 wt% of the mass of the metal lithium into the molten lithium liquid, and stirring for 1h at 300 ℃ to enable the mixture to react completely to generate a lithium-copper alloy and lithium fluoride so as to obtain a mixed system of an alloy phase, the lithium fluoride and the metal lithium; further raising the temperature to 850 ℃ to melt the lithium fluoride, and keeping the temperature for 1-3 h; after lithium fluoride is melted, adding copper-lanthanum intermediate alloy with the total mass of metal lithium and copper fluoride being 2.5 wt% into the composite lithium liquid, heating and stirring for 1h at 850 ℃ to obtain the composite cathode containing rare earth, pouring the melted composite lithium liquid into a mould for cooling and forming, obtaining a composite cathode strip with the thickness of 100 microns through rolling, and then slicing by using a slicing machine to obtain the composite metal lithium cathode suitable for assembling a battery.
In an inert atmosphere glove box, LiNi was used0.8Co0.1Mn0.1O2(i.e., NCM811) was used as the positive electrode sheet, the lithium composite metal negative electrode was used as the negative electrode, a 2032 coin cell was assembled using EC: DEC: DMC ═ 1:1:1 as the electrolyte, and then the electrochemical performance test was performed.
With Li-Li couple cells, DME with 1M LiTFSI: a solution of DOL 1:1 (volume ratio) as electrolyte containing 2 wt% lithium nitrate as additive was assembled into 2032 coin cells for electrochemical testing.
Example 4
Heating metallic lithium to 300 ℃ in an argon environment in a smelting furnace to melt the metallic lithium; adding zinc fluoride accounting for 30 wt% of the mass of the metal lithium into the molten lithium liquid, and stirring for 1h at 300 ℃ to enable the mixture to react completely to generate a lithium-zinc alloy and lithium fluoride so as to obtain a mixed system of an alloy phase, the lithium fluoride and the metal lithium; further raising the temperature to 850 ℃ to melt the lithium fluoride, and keeping the temperature for 1-3 h; after lithium fluoride is melted, adding zinc-neodymium intermediate alloy accounting for 1.5 wt% of the total mass of the metal lithium and the zinc fluoride into the composite lithium liquid, heating and stirring for 1h at 850 ℃ to obtain the composite cathode containing rare earth, pouring the melted composite lithium liquid into a mould for cooling and forming, rolling to obtain a composite cathode strip with the thickness of 100 microns, and slicing by using a slicing machine to obtain the composite metal lithium cathode suitable for assembling a battery.
In an inert atmosphere glove box, LiNi was used0.8Co0.1Mn0.1O2(i.e., NCM811) was used as the positive electrode sheet, the lithium composite metal negative electrode was used as the negative electrode, a 2032 coin cell was assembled using EC: DEC: DMC ═ 1:1:1 as the electrolyte, and then the electrochemical performance test was performed.
With Li-Li couple cells, DME with 1M LiTFSI: a solution of DOL 1:1 (volume ratio) as electrolyte containing 2 wt% lithium nitrate as additive was assembled into 2032 coin cells for electrochemical testing.
Example 5
Heating metallic lithium to 300 ℃ in an argon environment in a smelting furnace to melt the metallic lithium; adding magnesium fluoride accounting for 35 wt% of the mass of the metal lithium into the molten lithium liquid, and stirring for 1h at 300 ℃ to enable the magnesium fluoride to react completely to generate a lithium magnesium alloy and lithium fluoride so as to obtain a mixed system of an alloy phase, the lithium fluoride and the metal lithium; further raising the temperature to 900 ℃ to melt the lithium fluoride, and keeping the temperature for 1-3 h; after lithium fluoride is molten, adding magnesium-neodymium intermediate alloy accounting for 2 wt% of the total mass of metal lithium and magnesium fluoride into the composite lithium liquid, heating and stirring for 1h at 900 ℃ to obtain a composite cathode containing rare earth, pouring the molten composite lithium liquid into a mould for cooling and forming, rolling to obtain a composite cathode strip with the thickness of 100 microns, and then slicing by using a slicing machine. And obtaining the composite metal lithium cathode suitable for assembling a battery.
Gloves under inert atmosphereIn a tank, LiNi was used0.8Co0.1Mn0.1O2(i.e., NCM811) was used as the positive electrode sheet, the lithium composite metal negative electrode was used as the negative electrode, a 2032 coin cell was assembled using EC: DEC: DMC ═ 1:1:1 as the electrolyte, and then the electrochemical performance test was performed.
With Li-Li couple cells, DME with 1M LiTFSI: a solution of DOL 1:1 (volume ratio) as electrolyte containing 2 wt% lithium nitrate as additive was assembled into 2032 coin cells for electrochemical testing.
Example 6
Heating metallic lithium to 300 ℃ in an argon environment in a smelting furnace to melt the metallic lithium; adding magnesium fluoride accounting for 35 wt% of the mass of the metal lithium into the molten lithium liquid, and stirring for 1h at 300 ℃ to enable the magnesium fluoride to react completely to generate a lithium magnesium alloy and lithium fluoride so as to obtain a mixed system of an alloy phase, the lithium fluoride and the metal lithium; further raising the temperature to 900 ℃ to melt the lithium fluoride, and keeping the temperature for 1-3 h; after lithium fluoride is melted, adding a magnesium-neodymium intermediate alloy accounting for 2 wt% of the total mass of metal lithium and magnesium fluoride and a magnesium-ytterbium intermediate alloy accounting for 1 wt% of the total mass of the metal lithium and the magnesium fluoride into the composite lithium liquid, heating and stirring the mixture at 900 ℃ for 1 hour to obtain a composite cathode containing rare earth, pouring the melted composite lithium liquid into a mold for cooling and forming, rolling the mixture to obtain a composite cathode strip with the thickness of 100 microns, and then slicing the composite cathode strip by using a slicer. And obtaining the composite metal lithium cathode suitable for assembling a battery.
In an inert atmosphere glove box, LiNi was used0.8Co0.1Mn0.1O2(i.e., NCM811) was used as the positive electrode sheet, the lithium composite metal negative electrode was used as the negative electrode, a 2032 coin cell was assembled using EC: DEC: DMC ═ 1:1:1 as the electrolyte, and then the electrochemical performance test was performed.
With Li-Li couple cells, DME with 1M LiTFSI: a solution of DOL 1:1 (volume ratio) as electrolyte containing 2 wt% lithium nitrate as additive was assembled into 2032 coin cells for electrochemical testing.
Example 7
Heating metallic lithium to 300 ℃ in an argon environment in a smelting furnace to melt the metallic lithium; adding calcium fluoride accounting for 30 wt% of the mass of the metal lithium into the molten lithium liquid, and stirring for 1h at 300 ℃ to enable the calcium fluoride to react completely to generate a lithium-calcium alloy and lithium fluoride so as to obtain a mixed system of an alloy phase, the lithium fluoride and the metal lithium; further raising the temperature to 850 ℃ to melt the lithium fluoride, and keeping the temperature for 1-3 h; after lithium fluoride is melted, adding a calcium-lanthanum intermediate alloy accounting for 2 wt% of the total mass of metal lithium and calcium fluoride into the composite lithium liquid, heating and stirring for 1h at 850 ℃ to obtain a composite cathode containing rare earth, pouring the melted composite lithium liquid into a mould for cooling and forming, rolling to obtain a composite cathode strip with the thickness of 100 microns, and then slicing by using a slicing machine. And obtaining the composite metal lithium cathode suitable for assembling a battery.
In an inert atmosphere glove box, LiNi was used0.8Co0.1Mn0.1O2(i.e., NCM811) was used as the positive electrode sheet, the lithium composite metal negative electrode was used as the negative electrode, a 2032 coin cell was assembled using EC: DEC: DMC ═ 1:1:1 as the electrolyte, and then the electrochemical performance test was performed.
With Li-Li couple cells, DME with 1M LiTFSI: a solution of DOL 1:1 (volume ratio) as electrolyte containing 2 wt% lithium nitrate as additive was assembled into 2032 coin cells for electrochemical testing.
Example 8
Heating metallic lithium to 300 ℃ in an argon environment in a smelting furnace to melt the metallic lithium; adding tin fluoride accounting for 40 wt% of the mass of the metal lithium into the molten lithium liquid, and stirring for 1h at 300 ℃ to enable the mixture to react completely to generate a lithium-tin alloy and lithium fluoride so as to obtain a mixed system of an alloy phase, the lithium fluoride and the metal lithium; further raising the temperature to 850 ℃ to melt the lithium fluoride, and keeping the temperature for 1-3 h; after lithium fluoride is melted, adding tin-ytterbium intermediate alloy accounting for 3 wt% of the total mass of metal lithium and tin fluoride into the composite lithium liquid, heating and stirring for 1h at 850 ℃ to obtain the composite cathode containing rare earth, pouring the melted composite lithium liquid into a mold for cooling and forming, rolling to obtain a composite cathode strip with the thickness of 100 microns, and then slicing by using a slicing machine. And obtaining the composite metal lithium cathode suitable for assembling a battery.
In an inert atmosphere glove box, LiNi was used0.8Co0.1Mn0.1O2(i.e., NCM811) was used as the positive electrode sheet, the lithium composite metal negative electrode was used as the negative electrode, a 2032 coin cell was assembled using EC: DEC: DMC ═ 1:1:1 as the electrolyte, and then the electrochemical performance test was performed.
Assembly of Li-Li pair cells, DME using 1M LiTFSI: a solution of DOL 1:1 (volume ratio) as electrolyte containing 2 wt% lithium nitrate as additive was assembled into 2032 coin cells for electrochemical testing.
Example 9
Heating metallic lithium to 300 ℃ in an argon environment in a smelting furnace to melt the metallic lithium; adding calcium fluoride accounting for 30 wt% of the mass of the metal lithium into the molten lithium liquid, and stirring for 1h at 300 ℃ to enable the calcium fluoride to react completely to generate a lithium-calcium alloy and lithium fluoride so as to obtain a mixed system of an alloy phase, the lithium fluoride and the metal lithium; further raising the temperature to 950 ℃ to melt the lithium fluoride, and keeping the temperature for 1-3 h; after lithium fluoride is melted, adding a calcium-lanthanum intermediate alloy accounting for 2 wt% of the total mass of metal lithium and calcium fluoride and a calcium-cerium intermediate alloy accounting for 1 wt% of the total mass of the metal lithium and the calcium fluoride into the composite lithium liquid, heating and stirring the mixture at 950 ℃ for 1 hour to obtain a composite cathode containing rare earth, pouring the melted composite lithium liquid into a mold for cooling and forming, rolling the mixture to obtain a composite cathode strip with the thickness of 100 microns, and then slicing the composite cathode strip by using a slicer. And obtaining the composite metal lithium cathode suitable for assembling a battery.
In an inert atmosphere glove box, LiNi was used0.8Co0.1Mn0.1O2(i.e., NCM811) was used as the positive electrode sheet, the lithium composite metal negative electrode was used as the negative electrode, a 2032 coin cell was assembled using EC: DEC: DMC ═ 1:1:1 as the electrolyte, and then the electrochemical performance test was performed.
Assembly of Li-Li pair cells, DME using 1M LiTFSI: a solution of DOL 1:1 (volume ratio) as electrolyte containing 2 wt% lithium nitrate as additive was assembled into 2032 coin cells for electrochemical testing.
Example 10: cell electrochemical performance testing
In examples 1 to 9, the positive electrode of the battery using NCM811 as the positive electrode and the negative electrode of the composite metal lithium as the negative electrode and the comparative battery using NCM811 as the positive electrode and the negative electrode of the metal lithium as the negative electrode were set to be differentThe material loading was 15mg cm-2The results of performance tests using EC: DEC: DMC ═ 1:1:1 as the electrolyte are shown in table 1, with a magnification of 0.5C.
TABLE 1
Figure BDA0003407097420000081
Figure BDA0003407097420000091
As can be seen from table 1, the cycle life and the capacity retention rate of the full battery assembled by using the composite lithium negative electrode of the present invention are significantly improved compared to pure metal lithium, which indicates that the composite lithium negative electrode can reduce the occurrence of side reactions and help lithium to be uniformly deposited, thereby exhibiting more excellent performance.
For the composite metal lithium negative electrode symmetric batteries of examples 1-9, and the Li symmetric comparative battery, the current density is 2mAcm-2Capacity of 4mAh cm-2DME with 1M LiTFSI: the electrolyte was a 1:1 (vol/vol) solution containing 2 wt% of lithium nitrate as an additive, and the results of the performance test were shown in table 2.
TABLE 2
Figure BDA0003407097420000092
Figure BDA0003407097420000101
As can be seen from table 2, the composite lithium negative electrode of the present invention exhibits a lower polarization voltage in a symmetric battery test, which indicates that the composite lithium negative electrode can help lithium to be transported faster at the electrode interface, and the longer cycle life also indicates that the composite lithium negative electrode can reduce side reactions, inhibit the growth of lithium dendrites, and help lithium to be deposited uniformly.

Claims (10)

1. The preparation method of the composite metal lithium cathode is characterized by comprising the following steps: the method comprises the following steps:
A. under the protection of inert gas, melting the metal lithium to obtain molten lithium liquid;
B. adding metal fluoride into the molten lithium liquid, and obtaining a mixed system of an alloy phase, lithium fluoride and metal lithium after the reaction is finished;
C. raising the temperature to melt the lithium fluoride to obtain a composite lithium liquid;
D. and adding a metal-rare earth intermediate alloy into the composite lithium solution, obtaining a composite cathode containing rare earth after the reaction is finished, and obtaining the composite lithium metal cathode after post-treatment.
2. The method of preparing a composite lithium metal anode of claim 1, wherein: in step B, the metal fluoride is MgF2、AlF3、ZnF2、CaF2、CuF2、SnF2、InF3、GaF3、BaF2One kind of (1).
3. The method of producing a lithium composite metal anode according to claim 1 or 2, characterized in that: in the step B, the addition amount of the metal fluoride is 1-50 wt% of the mass of the metal lithium in the step A; preferably, the addition amount of the metal fluoride is 20-45 wt% of the mass of the metal lithium in the step A.
4. The method of preparing a composite lithium metal anode of claim 1, wherein: at least one of the following is satisfied:
in the step A, the melting temperature of the metal lithium is 250-400 ℃;
in the step C, the temperature for melting the lithium fluoride is 850-1000 ℃.
5. The method of preparing a composite lithium metal anode of claim 1, wherein: in the step B, at least one of the following items is satisfied:
the reaction temperature is 250-400 ℃;
the reaction time is 1-5 h.
6. The method of preparing a composite lithium metal anode of claim 1, wherein: in the step D, the metal-rare earth intermediate alloy is at least one alloy obtained by combining any one of aluminum, magnesium, copper, zinc, calcium, tin, indium, gallium or barium with the rare earth of lanthanum, ytterbium, cerium, neodymium or erbium, and the metal of the metal fluoride in the step B is the same as that of the metal-rare earth intermediate alloy in the step D.
7. The method for producing a lithium composite metal anode according to any one of claims 1 to 6, characterized in that: in the step D, the addition amount of the metal-rare earth intermediate alloy is 1-5 wt% of the total mass of the metal lithium in the step A and the metal fluoride in the step B; preferably, the addition amount of the metal-rare earth intermediate alloy is 1-3 wt% of the total mass of the metal lithium in the step A and the metal fluoride in the step B.
8. The method for producing a lithium composite metal anode according to any one of claims 1 to 7, characterized in that: in step D, at least one of the following is satisfied:
the reaction temperature is 850-1000 ℃;
the reaction time is 1-5 h.
9. The method for preparing a lithium composite metal negative electrode according to any one of claims 1 to 8.
10. The lithium composite metal negative electrode prepared by the method for preparing the lithium composite metal negative electrode according to any one of claims 1 to 8, and the use of the lithium composite metal negative electrode according to claim 9 in the preparation of a lithium battery.
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