CN113629236B - 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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CN113629236B
CN113629236B CN202110798500.4A CN202110798500A CN113629236B CN 113629236 B CN113629236 B CN 113629236B CN 202110798500 A CN202110798500 A CN 202110798500A CN 113629236 B CN113629236 B CN 113629236B
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lithium
metal
composite
current collector
philic
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CN113629236A (en
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谢佳
张涵
金留
曾子琪
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Huazhong University of Science and Technology
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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
    • H01M4/36—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
    • 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
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/80—Porous plates, e.g. sintered carriers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention belongs to the technical field of lithium batteries, and particularly discloses a composite metal lithium negative electrode and a preparation method and application thereof, wherein the negative electrode comprises a three-dimensional carbon-based current collector with a porous structure, metal lithium attached to the surface and in internal pores of the three-dimensional carbon-based current collector, and a protective film covering the metal lithium; the protective film comprises lithium-philic metal and lithium salt, wherein the lithium-philic metal is metal capable of being reductively replaced by lithium metal; the composite metal lithium cathode reacts with electrolyte in the first charge-discharge process to form a stable solid electrolyte phase interface, and the solid electrolyte phase interface is not decomposed in the subsequent charge-discharge process. The three-dimensional carbon-based current collector, the lithium-philic metal and the lithium salt in the composite metal lithium cathode respectively play roles in relieving the volume strain of the cathode, inducing the uniform deposition of lithium and forming a stable SEI film on the surface of the cathode.

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 negative electrode and a preparation method and application thereof.
Background
The use of fossil fuels in large quantities brings energy crisis and environmental problems, and the development of new energy technologies is imminent. The new energy technology has higher and higher requirements on high-efficiency energy storage systems with high specific energy, and the traditional lithium ion battery has the upper limit of theoretical energy density and is difficult to meet the requirements. Therefore, the development of lithium batteries with higher specific capacity has far-reaching significance. Among them, the lithium metal battery using lithium metal as the battery negative electrode has obvious advantages: the metallic lithium has extremely high theoretical specific capacity (3860mAh g) -1 ) With the lowest chemical potential (-3.04V vs. standard hydrogen electrode). In addition, lithium-sulfur and lithium-air batteries assembled by high-specific-capacity positive electrode materials such as a sulfur positive electrode and an air positive electrode, which are made of lithium metal, have high energy density, and are hot spots for the research of high-specific-energy secondary batteries in recent years.
The uneven deposition of lithium ions in the circulation process can cause the growth of lithium dendrite on the negative electrode side, and along with the circulation of the battery, the growth of the lithium dendrite can be accelerated, and finally the lithium dendrite can puncture a diaphragm to be contacted with a positive electrode material, so that the short circuit failure of the battery is caused, and even the safety problem is caused. In addition, unlike an intercalation-type negative electrode such as graphite, lithium metal is a conversion-type electrode based on a single electron reaction, and undergoes a large volume change when electron substitution is performed. Although metallic lithium reacts with components in the electrolyte to form a Solid Electrolyte Interface (SEI) film having a certain protective effect, such SEI film is easily broken and reconstructed continuously during the cycle process. Under the dual influence of dendrite growth and volume expansion, the SEI layer continuously consumes electrolyte and metallic lithium, which causes irreversible attenuation of battery capacity, and finally leads to battery failure. These problems have severely restricted the development of lithium metal batteries.
The current solutions to the lithium metal negative electrode problem mainly include: (1) electrolyte modification: regulating and controlling the components of the electrolyte to control the deposition morphology and SEI composition of the metal lithium; (2) constructing an artificial SEI film: the physical layer inhibits dendritic crystal growth; (3) designing a three-dimensional current collector: inhibiting volume expansion and retarding dendrite growth. These methods can inhibit lithium dendrite growth to some extent, but all have certain limitations: the modification of the electrolyte is difficult to avoid the influence of volume expansion; artificial SEI films are costly and have poor consistency; the three-dimensional current collector lacks stable SEI interface protection.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a composite lithium metal cathode and a preparation method and application thereof, the composite lithium metal cathode takes a porous three-dimensional carbon-based current collector as a framework, metal lithium is embedded in the inner cavity and the surface of the composite lithium metal cathode, and meanwhile, a protective film containing lithium-philic metal and lithium salt is arranged on the surface of the composite lithium metal cathode, so that a stable SEI film can be formed in the first charge-discharge process, and the problem that the conventional lithium metal cathode utilizing the three-dimensional current collector is lack of stable SEI interface protection is solved.
In order to achieve the above object, the present invention provides a composite lithium metal anode comprising a three-dimensional carbon-based current collector having a porous structure, metal lithium attached to the surface and in the internal pores of the three-dimensional carbon-based current collector, and a protective film covering the metal lithium; the protective film comprises lithium-philic metal and lithium salt, wherein the lithium-philic metal is metal capable of being reductively replaced by lithium metal;
the composite metal lithium cathode reacts with electrolyte in the first charge-discharge process to form a stable solid electrolyte phase interface, and the solid electrolyte phase interface is not decomposed in the subsequent charge-discharge process.
Preferably, the lithium-philic metal is one or more of silver, aluminum, zinc, magnesium, tin and gold.
Preferably, the three-dimensional carbon-based current collector is made of one or more of graphene, carbon nanotubes, carbon fibers, carbon spheres and porous carbon, the thickness of the three-dimensional carbon-based current collector is 50-300 μm, and the porosity of the three-dimensional carbon-based current collector is 60-90%.
According to another aspect of the present invention, there is also provided a method of preparing a composite lithium metal anode, comprising the steps of:
firstly, carrying out lithium-philic metal salt pretreatment on a three-dimensional carbon-based current collector with a porous structure;
and compounding the molten metal lithium with the pretreated three-dimensional carbon-based current collector, and generating lithium-philic metal and lithium salt through a displacement reaction to obtain the composite metal lithium cathode.
Preferably, the lithium-philic metal salt pretreatment comprises the following specific steps: cleaning and drying the three-dimensional carbon-based current collector with the porous structure, then performing infiltration treatment in a lithium-philic metal salt solution, and drying the three-dimensional carbon-based current collector after the infiltration treatment in vacuum or inert atmosphere.
Preferably, the solute in the lithium-philic metal salt solution is one or more of aluminum fluoride, aluminum chloride, aluminum sulfide, zinc sulfate, aluminum nitride, aluminum nitrate, magnesium chloride, magnesium sulfide, magnesium sulfate, magnesium nitrate, zinc fluoride, zinc chloride, zinc sulfide, zinc sulfate, zinc nitrate, tin dichloride, tin tetrachloride, tin difluoride, tin tetrafluoride, tin sulfate, tin nitrate, silver fluoride, silver chloride, silver sulfate, silver nitrate, and aurofluoric acid; the solvent in the lithium-philic metal salt solution is one or more of ethanol, water and acetone.
Preferably, the concentration of the lithium-philic metal salt solution is 0.1mol/L to 5 mol/L.
Further preferably, the concentration of the lithium-philic metal salt solution is 0.5mol/L to 3 mol/L.
Preferably, the inert atmosphere is argon, which has a purity greater than 95%.
Preferably, the drying temperature is 70-200 ℃, and the drying time is 8-24 h.
Further preferably, the drying temperature is 80-120 ℃, and the drying time is 10-16 h.
Preferably, the temperature of the molten lithium metal is from 180 ℃ to 450 ℃.
Further preferably, the temperature of the molten lithium metal is in the range of 220 ℃ to 300 ℃.
According to another aspect of the invention, the invention also provides application of the composite metal lithium negative electrode in preparing a metal secondary electrode.
According to another aspect of the present invention, there is also provided a metal secondary battery including the composite lithium metal anode of the present invention.
According to another aspect of the present invention, there is also provided an energy storage element including the metal secondary battery according to the present invention.
Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
(1) the composite metal lithium negative electrode main body is a three-dimensional carbon-based current collector framework with a porous structure, so that the volume expansion of metal lithium in the circulation process can be relieved; lithium-philic metal particles in the composite negative electrode provide lithium-philic sites, so that the nucleation energy barrier of lithium ions can be effectively reduced and the lithium ions are induced to be uniformly deposited; the lithium salt is beneficial to forming a stable SEI film on the surface of the lithium metal, and the SEI film cannot be continuously broken and reconstructed in multiple circulating processes to consume electrolyte and the lithium metal, so that irreversible attenuation of the battery capacity is avoided.
(2) According to the preparation method of the composite metal lithium negative electrode, in the process of compounding the molten metal lithium and the carbon-based current collector pretreated by the lithium-philic metal salt, a displacement reaction is carried out between the molten metal lithium and the lithium-philic metal salt to obtain the lithium-philic metal particles and the lithium salt. The composite cathode has the advantages of easily obtained required materials, simple preparation method and low cost, and is suitable for large-scale production.
(3) The invention regulates and controls the type of lithium-philic metal and the component of a surface SEI film by regulating and controlling the component of the lithium-philic metal salt solution so as to achieve the effects of inhibiting the growth of lithium dendrite in the circulation process and forming stable SEI interface protection; the concentration of the lithium-philic metal salt solution is controlled within a certain range, so that the carbon-based current collector is prevented from being melted due to a large amount of heat released in the replacement reaction, and the performance of the battery cathode is further influenced.
(4) The composite lithium metal cathode is used as a cathode material of a lithium metal secondary battery, and a solution is provided for the problems of dendritic crystal growth, volume expansion, SEI (solid electrolyte interphase) continuous reconstruction and the like of the lithium metal cathode, so that the cycling stability and the cycling life of the lithium metal cathode in the cycling process are effectively improved, and the capacity retention rate of the lithium metal cathode can be greatly improved when the lithium metal cathode is used for the lithium metal secondary battery.
Drawings
Fig. 1 is a scanning electron microscope image of a composite lithium metal anode provided in example 1 of the present invention;
fig. 2 is X-ray photoelectron spectra of two lithium metal anodes provided in example 1 and a comparative example of the present invention, wherein (a) is an X-ray photoelectron spectrum of a common lithium carbon-based metal anode of the comparative example, and (b) is an X-ray photoelectron spectrum of a composite lithium metal anode of example 1;
FIG. 3 shows two lithium copper half-cells at 1mA cm for example 2 of the present invention and a comparative example -2 、1mAh cm -2 Cycling test patterns under conditions;
fig. 4 is a cycle test chart of two lithium iron phosphate full cells provided in example 4 and comparative example of the present invention under the conditions of an activation rate of 0.5C and a cycle rate of 1C;
fig. 5 is a cycle test chart of two ternary lithium batteries provided in example 5 of the present invention and the comparative example under the conditions of an activation rate of 0.1C and a cycle rate of 0.5C.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a composite metal lithium cathode, which comprises a three-dimensional carbon-based current collector with a porous structure, metal lithium attached to the surface and the inner pores of the three-dimensional carbon-based current collector, and a protective film covering the metal lithium; the protective film comprises lithium-philic metal and lithium salt, wherein the lithium-philic metal is metal capable of being reductively replaced by lithium metal, and preferably one or more of silver, aluminum, zinc, magnesium, tin and gold;
the composite metal lithium cathode reacts with electrolyte in the first charge-discharge process to form a stable solid electrolyte phase interface, and the solid electrolyte phase interface is not decomposed in the subsequent charge-discharge process.
The composite metal lithium negative electrode provided by the invention takes a porous three-dimensional carbon-based current collector as a framework, metal lithium is embedded in the porous three-dimensional carbon-based current collector, and meanwhile, a protective film containing lithium-philic metal and lithium salt is arranged on the surface of the porous three-dimensional carbon-based current collector. In the composite lithium metal cathode, the three-dimensional current collector can effectively relieve the huge volume change of the lithium metal cathode in the circulation process; the lithium-philic metal can obviously reduce the nucleation energy barrier of lithium and induce the uniform deposition of lithium ions, thereby inhibiting the growth of lithium dendrites; the lithium salt helps to form a stable SEI film on the lithium metal negative electrode, and the SEI film is not decomposed after being formed during first charge and discharge, so that the loss of active materials in a circulating process is reduced, and the lithium composite metal negative electrode has excellent circulating stability.
The invention also provides a preparation method of the composite metal lithium cathode, which comprises the following steps:
firstly, carrying out lithium-philic metal salt pretreatment on a three-dimensional carbon-based current collector with a porous structure;
and compounding the molten metal lithium with the pretreated three-dimensional carbon-based current collector, and generating lithium-philic metal and lithium salt through a displacement reaction to obtain the composite metal lithium cathode.
Specifically, after cleaning and drying a three-dimensional carbon-based current collector with a porous structure, carrying out infiltration treatment in a lithium-philic metal salt solution, drying the three-dimensional carbon-based current collector subjected to the infiltration treatment in vacuum or inert atmosphere, and then compounding molten metal lithium and the three-dimensional carbon-based current collector infiltrated with the lithium-philic metal salt solution, so that the molten metal lithium contacts with the lithium-philic metal salt to carry out a displacement reaction, a lithium-philic metal and a lithium salt are generated, and simultaneously, metal lithium is induced to be attached to a framework of the three-dimensional carbon-based current collector. The lithium-philic metal plays roles of reducing nucleation energy barrier and inducing lithium ions to be uniformly deposited, and the lithium salt plays a role of helping the surface of the lithium metal to generate a stable SEI film. The three-dimensional carbon-based current collector can be graphene, carbon nanotubes, carbon fibers, carbon spheres, porous carbon and the like, the thickness of the three-dimensional carbon-based current collector is 50-300 mu m, and the porosity of the three-dimensional carbon-based current collector is 60-90%. The lithium-philic metal salt solution comprises a solute and a solvent, wherein cations in the solute are lithium-philic metal cations and can be replaced by lithium simple substances to form lithium-philic metal simple substances; the solvent is used to dissolve the solute and does not react with the solute and the three-dimensional carbon-based current collector.
In some embodiments of the invention, the solute is one or more of aluminum fluoride, aluminum chloride, aluminum sulfide, zinc sulfate, aluminum nitride, aluminum nitrate, magnesium chloride, magnesium sulfide, magnesium sulfate, magnesium nitrate, zinc fluoride, zinc chloride, zinc sulfide, zinc sulfate, zinc nitrate, tin dichloride, tin tetrachloride, tin difluoride, tin tetrafluoride, tin sulfate, tin nitrate, silver fluoride, silver chloride, silver sulfate, silver nitrate, and auric acid. The solvent is any one or more of ethanol, water and acetone.
In some embodiments, the lithium-philic metal salt solution has a concentration in the range of 0.1mol/L to 5mol/L, preferably in the range of 0.5mol/L to 3 mol/L. The lithium-philic metal salt solution with a certain concentration can perform a displacement reaction with excessive lithium metal to generate lithium salt and a lithium-philic metal simple substance, so that lithium-philic sites are formed on the surface of the three-dimensional carbon-based current collector, and lithium ions are induced to be uniformly deposited; the concentration of the lithium-philic metal salt is not high enough, otherwise, a large amount of displacement reaction can occur in the preparation process of the negative electrode, a large amount of heat is generated, and the framework of the current collector can be ablated, so that the performance of the negative electrode is influenced.
In some embodiments, the drying temperature of the three-dimensional carbon-based current collector after the soaking treatment is 70-200 ℃, preferably 80-120 ℃; the drying time is 8-24 h, preferably 10-16 h. The inert gas atmosphere used is preferably Ar gas (> 95% purity).
In some embodiments, the temperature of the molten lithium metal during the preparation of the lithium composite metal anode is from 180 ℃ to 450 ℃, preferably from 220 ℃ to 300 ℃.
The composite lithium metal cathode with lithium affinity and capable of forming a stable SEI film is prepared according to the preparation method.
The invention also provides application of the composite metal lithium negative electrode, and the composite metal lithium negative electrode is used as a negative electrode material of a metal lithium secondary battery, preferably used as a negative electrode material of a lithium iron phosphate secondary battery or a lithium ternary secondary battery. During the operation of the battery, the three-dimensional current collector can effectively relieve the volume strain, the lithium-philic metal plays a role in inducing the uniform deposition of lithium ions, and the lithium salt plays a role in helping the surface of the lithium metal to form a stable SEI.
The invention provides a metal secondary battery, which comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the negative electrode of the battery is the composite metal lithium negative electrode; the battery positive electrode can be an intercalation compound material (LiCoO) 2 、LiFePO 4 、LiTiO 2 Ternary lithium ion materials or lithium-rich materials), oxide materials (manganese oxide or vanadium oxide), sulfur-containing positive electrodes, air positive electrode materials, and the like; the diaphragm is standard PP, PE, PP/PE composite or PP/PE/PP composite film; the electrolyte is selected from esters, ethers and ionic liquid electrolytes, and specifically can be a mixed solution of ethylene carbonate and diethyl carbonate (volume ratio is 1:1) containing 1mol/L lithium hexafluorophosphate, 1, 3-dioxolane and ethylene glycol dimethyl ether (volume ratio is 1:1) containing 1mol/L lithium bistrifluoromethanesulfonimide and 1% mass percent lithium nitrate1:1) mixed solution, etc.
In another aspect, the present invention provides an energy storage element comprising the above-described metal secondary battery.
The invention prepares a composite metal lithium cathode which takes a three-dimensional carbon-based current collector as a framework, is embedded with metal lithium on the surface and in the surface of the current collector and has a protective film of lithium-philic metal and lithium salt through a displacement reaction, and the metal lithium cathode can be used for a metal lithium secondary battery with high specific energy. The lithium metal cathode provided by the invention is a composite lithium cathode based on a displacement reaction, and the preparation method has the advantages of simplicity, practicability, economy and the like. The secondary lithium metal battery assembled by the composite lithium metal cathode can greatly prolong the cycle life of the lithium metal battery, improve the performance of the lithium metal battery and has wide application prospect.
The above technical solution is described in detail below with reference to specific examples.
Example 1
And repeatedly washing the film-shaped three-dimensional carbon fiber paper with the porosity of 60% and the thickness of 150 microns by deionized water, alcohol and acetone for three times respectively, and drying in a vacuum drying oven to obtain the clean three-dimensional carbon-based current collector. Preparing 0.5mol/L silver nitrate aqueous solution by using deionized water, soaking the three-dimensional carbon-based current collector in the aqueous solution for 3 hours, taking out the three-dimensional carbon-based current collector fully soaked in the solution, drying the three-dimensional carbon-based current collector for 10 hours at room temperature, and then drying the three-dimensional carbon-based current collector for 8 hours at 70 ℃ in a vacuum drying oven.
Transferring the dried three-dimensional carbon-based current collector into a glove box under a high-purity argon atmosphere, contacting with molten metal lithium at the temperature of 200 ℃, performing a displacement reaction on lithium-philic metal salt and the metal lithium to obtain a composite metal lithium cathode, and cooling and placing the composite metal lithium cathode after the reaction is finished.
And assembling the composite metal lithium cathode and the diaphragm into a lithium-copper symmetrical button cell in a glove box protected by argon, and adding electrolyte of ethylene carbonate and diethyl carbonate (the volume ratio is 1:1) containing 1mol/L lithium hexafluorophosphate. The button cell assembled above is tested, and the batteries of the same batch are respectively tested at 1mA cm -2 、2mA cm -2 Current density, insertion and extraction capacityIs 1mAh cm -2 Lithium copper half cell testing was performed under the conditions.
And (2) assembling the composite metal lithium cathode and the diaphragm with the lithium iron phosphate cathode material in a glove box under the protection of argon to form a full battery, adding ethylene carbonate and diethyl carbonate (volume ratio is 1:1) electrolyte containing 1mol/L lithium hexafluorophosphate, and performing a charging and discharging test on the full battery after the assembly is finished.
The composite lithium metal cathode interface is observed through a scanning electron microscope, the appearance of lithium-philic metal deposited on lithium metal is an integrated structure as shown in figure 1, the three-dimensional carbon fiber paper is in good contact with the lithium metal, the lithium metal is uniformly deposited in the inner cavity and on the surface of the three-dimensional carbon fiber paper, the growth of lithium dendrites is effectively inhibited, and meanwhile, the volume expansion effect of the lithium metal in the reaction process can be effectively relieved due to the porous structure of the three-dimensional carbon fiber paper.
The composite metal lithium cathode interface is detected by an X-ray photoelectron spectroscopy technology, and as can be seen from fig. 2, a large amount of chemical components of lithium nitrate, lithium nitrite and lithium nitride are detected on the composite metal lithium cathode interface treated by the silver nitrate aqueous solution, and the nitrogen-rich components are beneficial to forming stable SEI, so that the cycle life of the battery is prolonged.
Example 2
In accordance with the preparation methods of the composite metal lithium negative electrode, the half cell and the full cell in example 1, the concentration of the silver nitrate aqueous solution was adjusted to 1mol/L, and the other conditions were not changed.
The lithium copper half cell prepared in this example was tested for cycling performance and the lithium composite metal negative electrode treated in this way was used to deliver high current (1mA cm) during half cell cycling as shown in FIG. 3 -2 ) The cycle can be stabilized at an average coulombic efficiency of 99% for 200 cycles under the conditions.
Example 3
In accordance with the preparation methods of the composite metal lithium negative electrode, the half cell and the full cell in example 1, the lithium-philic metal salt was adjusted to 0.5mol/L zinc nitrate aqueous solution, and other conditions were not changed.
The composite metal lithium cathode treated by the method has high current (1mA cm) in half-cell circulation -2 ) The cycle can be stabilized at an average coulombic efficiency of 99% for 150 cycles under the conditions.
Example 4
In accordance with the preparation methods of the composite metal lithium negative electrode, the half cell and the full cell in example 1, the lithium-philic metal salt was adjusted to a magnesium chloride aqueous solution of 0.5mol/L, and other conditions were not changed.
The composite lithium metal anode prepared in this example was operated at high current (1mA cm) during half-cell cycling -2 ) The cycle can be stabilized for 100 cycles with an average coulombic efficiency of 99% under the conditions.
As shown in fig. 4, the lithium iron phosphate full cell prepared in this embodiment can be stably cycled for 300 cycles with a coulombic efficiency of 99.9% under the conditions of an activation rate of 0.5C and a cycle rate of 1C, and the capacity retention rate is 99%.
Example 5
The preparation method of the composite metal lithium negative electrode, half cell and full cell in example 1 was the same, the temperature of the molten metal lithium was adjusted to 300 ℃, and the composite metal lithium negative electrode, separator and ternary positive electrode material were assembled into a full cell in a glove box protected by argon, and other conditions were unchanged.
The full cell prepared in this example was subjected to cycle performance test, as shown in FIG. 5, at high capacity (3.1mAh cm) -2 ) The reversible capacity retention rate of the ternary full battery after 115 cycles is 80% under the conditions of 0.1C of activation rate and 0.5C of cycle rate.
Example 6
In accordance with the preparation methods of the composite metal lithium negative electrode, the half cell and the full cell in the embodiment 1, the material adopted by the three-dimensional carbon-based current collector is adjusted to be the carbon nanotube, and other conditions are not changed.
The half cell and the full cell prepared in the example were tested for performance, and the lithium composite metal cathode was operated at a high current (1mA cm) during the half cell cycle -2 ) The cycle can be stabilized at an average coulombic efficiency of 99% for 150 cycles under the conditions.
Example 7
In accordance with the preparation methods of the composite metal lithium negative electrode, the half cell and the full cell in example 1, the solvent for dissolving silver nitrate is a mixed solution of ethanol and water (1:1), and other conditions are not changed.
The half cell and the full cell prepared in the example were tested for performance, and the lithium composite metal cathode was operated at a high current (1mA cm) during the half cell cycle -2 ) The cycle can be stabilized at an average coulombic efficiency of 99% for 150 cycles under the conditions.
Example 8
In accordance with the preparation methods of the composite metal lithium negative electrode, the half cell and the full cell in example 1, the lithium-philic metal salt was adjusted to 0.5mol/L zinc fluoride aqueous solution, and other conditions were not changed.
The half-cell and full-cell prepared in this example were tested for performance, and the lithium composite anode was cycled through the half-cell at high current (1mA cm) -2 ) The cycle can be stabilized at an average coulombic efficiency of 99% for 160 cycles under the conditions.
Example 9
In accordance with the preparation methods of the composite metal lithium negative electrode, the half cell and the full cell in example 1, the lithium-philic metal salt was adjusted to 0.5mol/L zinc sulfide aqueous solution, and other conditions were not changed.
The half cell and the full cell prepared in the example were tested for performance, and the lithium composite metal cathode was operated at a high current (1mA cm) during the half cell cycle -2 ) The cycle can be stabilized at an average coulombic efficiency of 99% for 140 cycles under the conditions.
Example 10
In accordance with the preparation methods of the composite metal lithium negative electrode, the half cell and the full cell in the embodiment 1, the material adopted by the three-dimensional carbon-based current collector is adjusted to graphene, and other conditions are unchanged.
The half cell and the full cell prepared in the example were tested for performance, and the lithium composite metal cathode was operated at a high current (1mA cm) during the half cell cycle -2 ) The cycle can be stabilized at an average coulombic efficiency of 99% for 140 cycles under the conditions.
Comparative example
And repeatedly washing the film-shaped three-dimensional carbon fiber paper with the porosity of 60% and the thickness of 150 microns by deionized water, alcohol and acetone for three times respectively, and drying in a vacuum drying oven to obtain the clean three-dimensional carbon-based current collector.
And assembling the three-dimensional carbon-based current collector and the diaphragm into a lithium-copper symmetrical button cell in a glove box under the protection of argon, and adding electrolyte of ethylene carbonate and diethyl carbonate (the volume ratio is 1:1) containing 1mol/L lithium hexafluorophosphate. The button cell assembled above is tested, and the batteries of the same batch are respectively tested at 1mA cm -2 、2mA cm -2 Current density, insertion and extraction capacity of 1mAh cm -2 Lithium copper half cell testing was performed under the conditions.
And (3) respectively assembling the metal lithium deposited with 20mAh on the three-dimensional carbon-based current collector as a negative electrode and a diaphragm with a lithium iron phosphate positive electrode material and a ternary positive electrode material in an argon-protected glove box to form a full battery, and respectively adding ethylene carbonate and diethyl carbonate (volume ratio is 1:1) electrolyte containing 1mol/L lithium hexafluorophosphate. And carrying out the charging and discharging test of the full battery after the assembly is finished.
As shown in fig. 2, it can be seen from the X-ray photoelectron spectroscopy that no nitrogen-containing substance is detected at the interface of the common lithium-carbon-based metal anode prepared in the comparative example, which is not good for stabilizing the generation of the SEI film.
The common lithium-carbon-based metal negative electrode prepared in this comparative example was cycled at 1mA cm in half cell cycle as shown in FIG. 3 -2 The circulation can be performed for about 100 circles under the condition, and the average coulombic efficiency is about 98%.
When the cycle performance of the full battery assembled by the common carbon-based metal lithium cathode and the lithium iron phosphate anode in the comparative example is tested, as shown in fig. 4, the full battery can only cycle for about 180 cycles under the conditions of the activation rate of 0.5C and the cycle rate of 1C, and an obvious decline phenomenon occurs.
When the cycle performance of the full battery assembled by the common carbon-based metal lithium cathode and the ternary cathode in the comparative example is tested, as shown in fig. 5, the full battery can only cycle for about 50 cycles under the conditions of the activation rate of 0.1C and the cycle rate of 0.5C, and an obvious decline phenomenon occurs.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. A composite lithium metal anode characterized by: the lithium ion battery comprises a three-dimensional carbon-based current collector with a porous structure, metal lithium attached to the surface and in internal pores of the three-dimensional carbon-based current collector, and a protective film covering the metal lithium; the protective film comprises lithium-philic metal and lithium salt, wherein the lithium-philic metal is metal capable of being reductively replaced by lithium metal;
the composite metal lithium cathode reacts with electrolyte in the first charge-discharge process to form a stable solid electrolyte phase interface, and the solid electrolyte phase interface is not decomposed in the subsequent charge-discharge process;
the preparation method of the composite metal lithium negative electrode comprises the following steps:
firstly, carrying out lithium-philic metal salt pretreatment on a three-dimensional carbon-based current collector with a porous structure;
and compounding the molten metal lithium with the pretreated three-dimensional carbon-based current collector, and generating lithium-philic metal and lithium salt through a displacement reaction to obtain the composite metal lithium cathode.
2. The composite lithium metal anode of claim 1, wherein: the lithium-philic metal is one or more of silver, aluminum, zinc, magnesium, tin and gold.
3. The composite lithium metal anode of claim 1, wherein: the three-dimensional carbon-based current collector is made of one or more of graphene, carbon nano tubes, carbon fibers, carbon spheres and porous carbon, the thickness of the three-dimensional carbon-based current collector is 50-300 mu m, and the porosity of the three-dimensional carbon-based current collector is 60-90%.
4. The composite lithium metal anode of claim 1, wherein the lithium-philic metal salt pretreatment comprises the following specific steps: cleaning and drying the three-dimensional carbon-based current collector with the porous structure, then performing infiltration treatment in a lithium-philic metal salt solution, and drying the three-dimensional carbon-based current collector after the infiltration treatment in vacuum or inert atmosphere.
5. The composite lithium metal anode of claim 4, wherein: the solute in the lithium-philic metal salt solution is one or more of aluminum fluoride, aluminum chloride, aluminum sulfide, aluminum nitride, aluminum nitrate, magnesium chloride, magnesium sulfide, magnesium sulfate, magnesium nitrate, zinc fluoride, zinc chloride, zinc sulfide, zinc sulfate, zinc nitrate, tin dichloride, tin tetrachloride, tin difluoride, tin tetrafluoride, tin sulfate, tin nitrate, silver fluoride, silver chloride, silver sulfate, silver nitrate and aurofluoric acid; the solvent in the lithium-philic metal salt solution is one or more of ethanol, water and acetone.
6. The composite lithium metal anode of claim 5, wherein: the concentration of the lithium-philic metal salt solution is 0.1mol/L-5 mol/L.
7. The composite lithium metal anode of claim 1, wherein: the temperature of the molten metal lithium is 180 ℃ to 450 ℃.
8. Use of a lithium composite metal negative electrode according to any one of claims 1 to 3 for the preparation of a metal secondary electrode.
9. A metal secondary battery characterized in that: comprising the lithium composite metal anode of any one of claims 1 to 3.
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