CN114242946B - Composite metal lithium negative electrode and preparation method and application thereof - Google Patents
Composite metal lithium negative electrode and preparation method and application thereof Download PDFInfo
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- H01M4/00—Electrodes
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H01M4/00—Electrodes
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/381—Alkaline or alkaline earth metals elements
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- 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
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Abstract
The invention discloses a composite metal lithium negative electrode, a preparation method and application thereof, and belongs 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 anode, 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 alloy phase, lithium fluoride and metal lithium; raising the temperature to melt the lithium fluoride; adding a metal-rare earth intermediate alloy, reacting to obtain a composite anode containing rare earth, and performing post-treatment to obtain the composite anode. According to the invention, lithium fluoride is melted at high temperature, metal fluoride is added to obtain lithium fluoride and alloy phases which are uniformly distributed in the whole phase, uniform and rapid deposition of lithium is realized, volume change is accommodated, then metal-rare earth intermediate alloy is added, and segregation of alloy is reduced by utilizing grain refinement of rare earth, so that the composite metal lithium anode with excellent cycle performance and rate capability is prepared.
Description
Technical Field
The invention belongs to the technical field of lithium batteries, and particularly relates to a composite metal lithium negative electrode, 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 the batteries is increasing. At present, the graphite cathode adopted by the lithium ion battery has lower theoretical specific capacity, and the metal lithium cathode has ultrahigh theoretical specific capacity and lowest electrode potential, which is regarded as 'holy cup' of the cathode material of the secondary battery, but the metal lithium cathode has a plurality of problems in practical application. 1) When lithium is deposited, the uneven surface of the metal lithium causes uneven electric field distribution, so that the metal lithium is more prone to be deposited at the convex part and the electric field concentration part, the growth of lithium dendrites is caused, and the continuously grown lithium dendrites can puncture the diaphragm to cause short circuit of the battery. 2) The high-activity lithium metal reacts with the electrolyte, is continuously consumed in the circulating process, and reduces the coulombic efficiency and the circulating life of the battery. 3) The host-free nature of metallic lithium causes it to undergo large volume changes during cycling, which can lead to structural failure of the electrode and electrode pulverization. These problems easily cause a series of safety problems, which affect the practical application of the lithium metal anode.
The problems of the metallic lithium anode are solved by the methods of surface coating, electrolyte additives, three-dimensional structure anode and the like, but no final solution exists at present. The alloy cathode has three skeleton structures, so that the actual current density can be reduced, the growth of dendrites can be inhibited, and meanwhile, the alloy cathode can accommodate the volume change in the circulation process and is widely studied.
CN201811182577.3 discloses a metal lithium alloy electrode material, a preparation method and application thereof, and uses the alloy formed by Li and Al, zn and Ag to reduce side reactions between a metal lithium negative electrode and an electrolyte, improve coulombic efficiency, and realize the advantages of high safety and long cycle at the same time; however, the alloy cathode of the method has the problem of alloy component segregation, so that the alloy is unevenly distributed in the material, and the uniform deposition of lithium is affected.
CN201910315106.3 discloses that the generated lithium fluoride has good ionic conductivity by using the action of metal fluoride and metal lithium, can effectively improve the mobility of lithium ions on the surface of the metal lithium, and meanwhile, the metal or alloy layer formed on the surface of the metal lithium can greatly improve the surface conductivity of the metal lithium, is favorable for uniform distribution of an electric field, and can inhibit the growth of dendrites. The protective layer formed by the lithium fluoride and the metal or alloy is uniform and compact, the structure is more stable, the lithium fluoride and the metal or alloy are not easy to break, and the service life is prolonged; however, the method can only exist lithium fluoride particles and alloy phases on the surface of the lithium negative electrode, can only play a role on the surface part, and cannot accommodate volume change in the cycle of the lithium negative electrode.
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, then the metal-rare earth intermediate alloy is added, the segregation of the alloy is reduced by utilizing the grain refinement effect of rare earth, and the composite metal lithium anode with excellent performance is prepared.
The invention provides a preparation method of a composite metal lithium anode, which comprises the following steps:
A. under the protection of inert gas, melting metal lithium to obtain molten lithium liquid;
B. adding metal fluoride into the molten lithium liquid, and obtaining a mixed system of 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 liquid, obtaining a composite negative electrode containing rare earth after the reaction is finished, and obtaining the composite metal lithium negative electrode through post-treatment.
In the preparation method of the composite metal lithium anode, in the step A, the melting temperature of the metal lithium is 250-400 ℃.
In the preparation method of the composite metal lithium anode, in the step B, the metal fluoride is MgF 2 、AlF 3 、ZnF 2 、CaF 2 、CuF 2 、SnF 2 、InF 3 、GaF 3 、BaF 2 One of them.
In the preparation method of the composite metal lithium anode, in the step B, the addition amount of the metal fluoride is 1-50wt% of the mass of the metal lithium in the step A.
Preferably, in the preparation method of the composite metal lithium anode, 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 anode, in the step B, the reaction temperature is 250-400 ℃.
In the preparation method of the composite metal lithium anode, in the step B, the reaction time is 1-5 h.
In the method for preparing the composite metal lithium anode, in the step C, the melting temperature of the lithium fluoride is 850-1000 ℃.
In the above preparation method of the composite metal lithium anode, in the step D, the metal-rare earth intermediate alloy is: 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, at least one of the obtained alloys is combined, and the metal of the metal fluoride in the step B is the same as the metal of the metal-rare earth intermediate alloy in the step D.
In the preparation method of the composite metal lithium anode, 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 anode, in the step D, 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.
In the preparation method of the composite metal lithium anode, in the step D, the reaction temperature is 850-1000 ℃.
In the preparation method of the composite metal lithium anode, in the step D, the reaction time is 1-5 h.
The invention also provides the composite metal lithium anode prepared by the preparation method of the composite metal lithium anode.
The invention also provides an application of the composite metal lithium anode prepared by the preparation method of the composite metal lithium anode in preparation of a lithium battery.
The invention has the beneficial effects that:
according to the invention, the metal fluoride reacts with the metal lithium to generate the corresponding lithium alloy and lithium fluoride, the metal fluoride reacts with the lithium to generate the lithium fluoride and an alloy framework, the alloy framework provides a stable three-dimensional structure, is suitable for volume change in circulation, solves the problem of huge volume change in the circulation process of the lithium negative electrode, and meanwhile, the molten lithium fluoride can be more uniformly distributed in the composite negative electrode, so that the potential barrier of lithium ion diffusion is reduced, the lithium ion is helped to be more quickly extracted/deposited from the alloy, the growth of dendrite is inhibited, and the rate capability of the composite negative electrode is improved; and further through adding the metal-rare earth intermediate alloy with low melting point, the three-dimensional structure of the alloy can accommodate the volume change in the circulation process, meanwhile, the rare earth metal can refine crystal grains of the alloy, and segregation of alloy materials is reduced, so that the alloy is distributed more uniformly in the whole material, uniform deposition of lithium is facilitated, the mechanical strength of an alloy negative electrode is enhanced by adding the rare earth, and the rolling production of the composite negative electrode is facilitated, so that the circulation performance and the multiplying power performance of the prepared composite negative electrode are obviously improved.
Detailed Description
Specifically, the preparation process of the composite metal lithium anode comprises the following steps:
A. under the protection of inert gas, melting metal lithium to obtain molten lithium liquid;
B. adding metal fluoride into the molten lithium liquid, and obtaining a mixed system of 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 liquid, obtaining a composite negative electrode containing rare earth after the reaction is finished, and obtaining the composite metal lithium negative electrode through 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, the metal fluoride reacts with the molten lithium liquid to generate the corresponding lithium alloy and lithium fluoride, the metal fluoride reacts with the lithium to generate the lithium fluoride and an 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 the lithium cathode is solved, meanwhile, the molten lithium fluoride can be more uniformly distributed in the composite cathode, the diffusion barrier of lithium ions is reduced, and the lithium ions are helped to be more rapidly extracted/precipitated from the alloyThe product is formed, so that the growth of dendrites is inhibited, and the rate capability of the composite anode is improved; the metal fluoride is MgF 2 、AlF 3 、ZnF 2 、CaF 2 、CuF 2 、SnF 2 、InF 3 、GaF 3 、BaF 2 One of them.
The purpose of adding the metal fluoride is to react with lithium to produce lithium fluoride and lithium alloy, and experiments prove that too little metal fluoride can lead to too little generated alloy phase to form a continuous three-dimensional structure and can not play a role of a frame of a three-dimensional negative electrode; if too much is added, most of the lithium metal is consumed in the reaction with the metal fluoride, and the resulting composite anode contains too little lithium metal. Therefore, in the step B, the addition amount of the metal fluoride is controlled to be 1-50wt% of the mass of the metal lithium in the step A; preferably 20 to 45wt%.
In the step B, in order to ensure the reaction to be complete, the temperature of the reaction is controlled to be 250-400 ℃ and the reaction time is controlled to be 1-5 h.
The melting point of the lithium alloy phase is generally lower than that of the metal lithium, namely lower than 180 ℃, so that the alloy phase and the metal lithium in the mixed system of the alloy phase, the lithium fluoride and the metal lithium obtained in the step B are in a liquid state, and the temperature is increased to ensure that the lithium fluoride can be melted.
In step C of the present invention, the temperature is raised to 850-1000 deg.C (typically held for 1-3 h) to maintain the entire system in a fully molten state.
In the step D, the low-melting-point metal-rare earth intermediate alloy is added, so that the three-dimensional structure of the obtained composite alloy can accommodate volume change in the cyclic process, meanwhile, the rare earth metal can refine crystal grains of the alloy, segregation of alloy materials is reduced, the alloy is distributed more uniformly in the whole material, and uniform deposition of lithium is facilitated; the metal-rare earth intermediate alloy comprises the following components: 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 obtained alloys is combined. In order to ensure consistency of the produced lithium alloy phases, the metal of the metal fluoride in the step B is the same as the metal of the metal-rare earth intermediate alloy in the step D, and the intermediate alloy of a single metal and at least one rare earth is adopted in the step D.
In the step D, the addition amount of the rare earth intermediate alloy is controlled because of the grain refinement effect of the rare earth; tests prove that the rare earth can achieve the corresponding effect when the addition amount of the rare earth is smaller, so that the addition amount of the rare earth is lower, but the effect of grain refinement cannot be achieved when the addition amount of the rare earth is too small. Therefore, the addition 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 3wt%.
In the step D, the reaction temperature is controlled to be 850-1000 ℃ and the reaction time is controlled to be 1-5 h.
The invention also provides the composite metal lithium anode prepared by the preparation method of the composite metal lithium anode.
The invention also provides an application of the composite metal lithium anode prepared by the preparation method of the composite metal lithium anode in preparation of a lithium battery.
In the invention, a composite anode containing rare earth is obtained, molten composite lithium liquid is poured into a mould to be cooled and molded through conventional post-treatment means, then a composite anode belt is obtained through rolling, and finally a slicing machine is used for slicing, so that the composite metal lithium anode suitable for assembling a battery is obtained.
The present invention will be described in further detail by way of examples, which are not intended to limit the scope of the invention.
Example 1
In an argon environment, heating metallic lithium to 300 ℃ in a smelting furnace to melt the metallic lithium; adding aluminum fluoride accounting for 40wt% of the mass of the metal lithium into the molten lithium liquid, stirring for 1h at 300 ℃ to enable the aluminum fluoride to react completely so as to generate lithium aluminum alloy and lithium fluoride, and obtaining a mixed system of alloy phase, lithium fluoride and metal lithium; further raising the temperature to 900 ℃ to melt the lithium fluoride, and preserving the heat for 1-3 hours; after the lithium fluoride is melted, adding aluminum-lanthanum intermediate alloy accounting for 2wt% 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 mould for cooling and forming, obtaining a composite negative electrode belt with the thickness of 100 micrometers through rolling, and slicing by using a slicer to obtain the composite metal lithium negative electrode suitable for assembling a battery.
In an inert atmosphere glove box, use LiNi 0.8 Co 0.1 Mn 0.1 O 2 (i.e., NCM 811) was used as the positive electrode sheet, the above-described composite lithium metal negative electrode was used as the negative electrode, EC: DEC: dmc=1:1:1 was used as the electrolyte, and a 2032 coin cell was assembled, followed by electrochemical performance testing.
Li-Li pair cell, DME with 1M LiTFSI: dol=1:1 (volume ratio) solution was used as electrolyte containing 2wt% lithium nitrate as additive, assembled into 2032 button cell for electrochemical testing.
Example 2
In an argon environment, heating metallic lithium to 300 ℃ in a smelting furnace to melt the metallic lithium; adding zinc fluoride accounting for 40wt% of the mass of the metal lithium into the molten lithium liquid, stirring for 1h at 300 ℃ to enable the zinc fluoride to react completely so as to generate lithium aluminum alloy and lithium fluoride, and obtaining a mixed system of alloy phase, lithium fluoride and metal lithium; further raising the temperature to 900 ℃ to melt the lithium fluoride, and preserving the heat for 1-3 hours; after the lithium fluoride is melted, adding zinc-cerium with the total mass of 1.5wt% and zinc-lanthanum intermediate alloy with the total mass of 1.5wt% into the composite lithium solution, heating and stirring for 1h at 900 ℃ to obtain a composite negative electrode containing rare earth, pouring the melted composite lithium solution into a mould for cooling and molding, obtaining a composite negative electrode belt with the thickness of 100 micrometers through rolling, and slicing by using a slicer to obtain the composite metal lithium negative electrode suitable for assembling a battery.
In an inert atmosphere glove box, use LiNi 0.8 Co 0.1 Mn 0.1 O 2 (i.e., NCM 811) was used as the positive electrode sheet, the above-described composite lithium metal negative electrode was used as the negative electrode, EC: DEC: dmc=1:1:1 was used as the electrolyte, and a 2032 coin cell was assembled, followed by electrochemical performance testing.
Li-Li pair cell, DME with 1M LiTFSI: dol=1:1 (volume ratio) solution was used as electrolyte containing 2wt% lithium nitrate as additive, assembled into 2032 button cell for electrochemical testing.
Example 3
In an argon environment, heating metallic lithium to 300 ℃ in a smelting furnace to melt the metallic lithium; adding 35wt% of copper fluoride of the mass of the metal lithium into the molten lithium liquid, stirring for 1h at 300 ℃ to enable the copper fluoride to react completely, so as to generate a lithium copper alloy and lithium fluoride, and obtaining 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 preserving the heat for 1-3 hours; after the lithium fluoride is melted, adding copper-lanthanum intermediate alloy with the total mass of 2.5 percent of the metal lithium and the copper fluoride into the composite lithium liquid, heating and stirring for 1h at 850 ℃ to obtain a composite negative electrode containing rare earth, pouring the melted composite lithium liquid into a mould for cooling and forming, obtaining a composite negative electrode belt with the thickness of 100 microns through rolling, and slicing by using a slicer to obtain the composite metal lithium negative electrode suitable for assembling a battery.
In an inert atmosphere glove box, use LiNi 0.8 Co 0.1 Mn 0.1 O 2 (i.e., NCM 811) was used as the positive electrode sheet, the above-described composite lithium metal negative electrode was used as the negative electrode, EC: DEC: dmc=1:1:1 was used as the electrolyte, and a 2032 coin cell was assembled, followed by electrochemical performance testing.
Li-Li pair cell, DME with 1M LiTFSI: dol=1:1 (volume ratio) solution was used as electrolyte containing 2wt% lithium nitrate as additive, assembled into 2032 button cell for electrochemical testing.
Example 4
In an argon environment, heating metallic lithium to 300 ℃ in a smelting furnace to melt the metallic lithium; adding zinc fluoride accounting for 30wt% of the mass of the metal lithium into the molten lithium liquid, stirring for 1h at 300 ℃ to enable the zinc fluoride to react completely so as to generate lithium zinc alloy and lithium fluoride, and obtaining a mixed system of alloy phase, lithium fluoride and metal lithium; further raising the temperature to 850 ℃ to melt the lithium fluoride, and preserving the heat for 1-3 hours; after the lithium fluoride is melted, adding zinc-neodymium intermediate alloy with the total mass of 1.5 percent of the metal lithium and the zinc fluoride into the composite lithium liquid, heating and stirring for 1h at 850 ℃ to obtain a composite negative electrode containing rare earth, pouring the melted composite lithium liquid into a mould for cooling and forming, obtaining a composite negative electrode belt with the thickness of 100 microns through rolling, and slicing by using a slicer to obtain the composite metal lithium negative electrode suitable for assembling a battery.
In an inert atmosphere glove box, use LiNi 0.8 Co 0.1 Mn 0.1 O 2 (i.e., NCM 811) was used as the positive electrode sheet, the above-described composite lithium metal negative electrode was used as the negative electrode, EC: DEC: dmc=1:1:1 was used as the electrolyte, and a 2032 coin cell was assembled, followed by electrochemical performance testing.
Li-Li pair cell, DME with 1M LiTFSI: dol=1:1 (volume ratio) solution was used as electrolyte containing 2wt% lithium nitrate as additive, assembled into 2032 button cell for electrochemical testing.
Example 5
In an argon environment, heating metallic lithium to 300 ℃ in a smelting furnace to melt the metallic lithium; adding 35wt% magnesium fluoride of metal lithium into the molten lithium liquid, stirring for 1h at 300 ℃ to enable the magnesium fluoride to react completely so as to generate lithium magnesium alloy and lithium fluoride, and obtaining a mixed system of alloy phase, lithium fluoride and metal lithium; further raising the temperature to 900 ℃ to melt the lithium fluoride, and preserving the heat for 1-3 hours; after the lithium fluoride is melted, adding magnesium-neodymium intermediate alloy with the total mass of 2wt% of metal lithium and magnesium fluoride into the composite lithium liquid, heating and stirring for 1h at 900 ℃ to obtain a rare earth-containing composite negative electrode, pouring the melted composite lithium liquid into a mould for cooling and forming, rolling to obtain a composite negative electrode belt with the thickness of 100 micrometers, and slicing by using a slicer. And obtaining the composite metal lithium anode suitable for assembling the battery.
In an inert atmosphere glove box, use LiNi 0.8 Co 0.1 Mn 0.1 O 2 (i.e., NCM 811) was used as the positive electrode sheet, the above-described composite lithium metal negative electrode was used as the negative electrode, EC: DEC: dmc=1:1:1 was used as the electrolyte, and a 2032 coin cell was assembled, followed by electrochemical performance testing.
Li-Li pair cell, DME with 1M LiTFSI: dol=1:1 (volume ratio) solution was used as electrolyte containing 2wt% lithium nitrate as additive, assembled into 2032 button cell for electrochemical testing.
Example 6
In an argon environment, heating metallic lithium to 300 ℃ in a smelting furnace to melt the metallic lithium; adding 35wt% magnesium fluoride of metal lithium into the molten lithium liquid, stirring for 1h at 300 ℃ to enable the magnesium fluoride to react completely so as to generate lithium magnesium alloy and lithium fluoride, and obtaining a mixed system of alloy phase, lithium fluoride and metal lithium; further raising the temperature to 900 ℃ to melt the lithium fluoride, and preserving the heat for 1-3 hours; after the lithium fluoride is melted, adding magnesium-neodymium intermediate alloy accounting for 2wt% of the total mass of the metal lithium and the magnesium fluoride and magnesium-ytterbium intermediate alloy accounting for 1wt% 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 mould for cooling and molding, rolling to obtain a composite negative electrode belt with the thickness of 100 microns, and slicing by using a slicer. And obtaining the composite metal lithium anode suitable for assembling the battery.
In an inert atmosphere glove box, use LiNi 0.8 Co 0.1 Mn 0.1 O 2 (i.e., NCM 811) was used as the positive electrode sheet, the above-described composite lithium metal negative electrode was used as the negative electrode, EC: DEC: dmc=1:1:1 was used as the electrolyte, and a 2032 coin cell was assembled, followed by electrochemical performance testing.
Li-Li pair cell, DME with 1M LiTFSI: dol=1:1 (volume ratio) solution was used as electrolyte containing 2wt% lithium nitrate as additive, assembled into 2032 button cell for electrochemical testing.
Example 7
In an argon environment, heating metallic lithium to 300 ℃ in a smelting furnace to melt the metallic lithium; adding 30wt% calcium fluoride of the mass of the metal lithium into the molten lithium liquid, stirring for 1h at 300 ℃ to enable the calcium fluoride to react completely, so as to generate a lithium-calcium alloy and lithium fluoride, and obtaining 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 preserving the heat for 1-3 hours; after the lithium fluoride is melted, adding a calcium-lanthanum intermediate alloy accounting for 2wt% of the total mass of the metal lithium and the calcium fluoride into the composite lithium liquid, heating and stirring for 1h at 850 ℃ to obtain a composite negative electrode containing rare earth, pouring the melted composite lithium liquid into a mould for cooling and forming, rolling to obtain a composite negative electrode belt with the thickness of 100 micrometers, and slicing by using a slicer. And obtaining the composite metal lithium anode suitable for assembling the battery.
In an inert atmosphere glove box, use LiNi 0.8 Co 0.1 Mn 0.1 O 2 (i.e., NCM 811) was used as the positive electrode sheet, the above-described composite lithium metal negative electrode was used as the negative electrode, EC: DEC: dmc=1:1:1 was used as the electrolyte, and a 2032 coin cell was assembled, followed by electrochemical performance testing.
Li-Li pair cell, DME with 1M LiTFSI: dol=1:1 (volume ratio) solution was used as electrolyte containing 2wt% lithium nitrate as additive, assembled into 2032 button cell for electrochemical testing.
Example 8
In an argon environment, heating metallic lithium to 300 ℃ in a smelting furnace to melt the metallic lithium; adding tin fluoride accounting for 40wt% of the mass of the metal lithium into the molten lithium liquid, stirring for 1h at 300 ℃ to enable the tin fluoride to react completely, so as to generate a lithium tin alloy and lithium fluoride, and obtaining 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 preserving the heat for 1-3 hours; after the lithium fluoride is melted, adding tin-ytterbium intermediate alloy accounting for 3 weight percent of the total mass of the metal lithium and the tin fluoride and the composite lithium solution, heating and stirring for 1h at 850 ℃ to obtain a composite negative electrode containing rare earth, pouring the melted composite lithium solution into a mould for cooling and forming, rolling to obtain a composite negative electrode belt with the thickness of 100 micrometers, and slicing by using a slicer. And obtaining the composite metal lithium anode suitable for assembling the battery.
In an inert atmosphere glove box, use LiNi 0.8 Co 0.1 Mn 0.1 O 2 (i.e., NCM 811) was used as the positive electrode sheet, the above-described composite lithium metal negative electrode was used as the negative electrode, EC: DEC: dmc=1:1:1 was used as the electrolyte, and a 2032 coin cell was assembled, followed by electrochemical performance testing.
Assembled Li-Li pair cell, DME with 1M LiTFSI: dol=1:1 (volume ratio) solution was used as electrolyte containing 2wt% lithium nitrate as additive, assembled into 2032 button cell for electrochemical testing.
Example 9
In an argon environment, heating metallic lithium to 300 ℃ in a smelting furnace to melt the metallic lithium; adding 30wt% calcium fluoride of the mass of the metal lithium into the molten lithium liquid, stirring for 1h at 300 ℃ to enable the calcium fluoride to react completely, so as to generate a lithium-calcium alloy and lithium fluoride, and obtaining 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 preserving the heat for 1-3 hours; after the lithium fluoride is melted, adding a calcium-lanthanum intermediate alloy accounting for 2 weight percent of the total mass of the metal lithium and the calcium fluoride and a calcium-cerium intermediate alloy accounting for 1 weight percent into the composite lithium liquid, heating and stirring for 1h at 950 ℃ to obtain a composite negative electrode containing rare earth, pouring the melted composite lithium liquid into a mould for cooling and molding, rolling to obtain a composite negative electrode belt with the thickness of 100 micrometers, and slicing by using a slicer. And obtaining the composite metal lithium anode suitable for assembling the battery.
In an inert atmosphere glove box, use LiNi 0.8 Co 0.1 Mn 0.1 O 2 (i.e., NCM 811) was used as the positive electrode sheet, the above-described composite lithium metal negative electrode was used as the negative electrode, EC: DEC: dmc=1:1:1 was used as the electrolyte, and a 2032 coin cell was assembled, followed by electrochemical performance testing.
Assembled Li-Li pair cell, DME with 1M LiTFSI: dol=1:1 (volume ratio) solution was used as electrolyte containing 2wt% lithium nitrate as additive, assembled into 2032 button cell for electrochemical testing.
Example 10: electrochemical performance test of cells
For the batteries of examples 1 to 9 in which NCM811 was used as the positive electrode and the composite metal lithium negative electrode was used as the negative electrode, and for the comparative battery in which NCM811 was used as the positive electrode and the metal lithium was used as the negative electrode, the positive electrode material load was 15mg cm -2 The performance was tested at a rate of 0.5C using EC: DEC: dmc=1:1:1 as electrolyte and the results are shown in table 1.
TABLE 1
As can be seen from table 1, the cycle life and capacity retention rate of the full battery assembled by using the composite lithium anode of the present invention are significantly improved compared with those of pure metal lithium, which indicates that the composite lithium anode can reduce the occurrence of side reactions, and helps the uniform deposition of lithium, thereby exhibiting more excellent performance.
For the lithium-negative symmetric batteries of the composite metals of examples 1 to 9, and the Li symmetric comparative batteries, the current density was 2mAcm -2 Capacity of 4mAh cm -2 DME of 1M LiTFSI was used: the dol=1:1 (volume ratio) solution was used as an electrolyte containing 2wt% of lithium nitrate as an additive, and performance test was performed, and the results are shown in table 2.
TABLE 2
As can be seen from table 2, the composite lithium negative electrode of the present invention exhibits lower polarization voltage in the symmetrical 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 lithium dendrite growth, and help lithium to be deposited uniformly.
Claims (7)
1. The preparation method of the composite metal lithium anode is characterized by comprising the following steps of: the method comprises the following steps:
A. under the protection of inert gas, melting metal lithium to obtain molten lithium liquid;
B. adding metal fluoride into the molten lithium liquid, and obtaining a mixed system of 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. adding a metal-rare earth intermediate alloy into the composite lithium liquid, obtaining a composite negative electrode containing rare earth after the reaction is finished, and obtaining the composite metal lithium negative electrode through post-treatment;
in the step B, the metal fluoride is MgF 2 、AlF 3 、ZnF 2 、CaF 2 、CuF 2 、SnF 2 、InF 3 、GaF 3 、BaF 2 One of the following;
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 step D, the metal-rare earth intermediate alloy is formed by combining any one of aluminum, magnesium, copper, zinc, calcium, tin, indium, gallium or barium and any one of lanthanum, ytterbium, cerium, neodymium or erbium serving as the rare earth, and at least one of the obtained alloys, wherein the metal of the metal fluoride in the step B is the same as the metal of the metal-rare earth intermediate alloy in the step D;
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;
in the step D, the reaction temperature is 850-1000 ℃.
2. The method for preparing a composite metal lithium anode according to claim 1, characterized in that: 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 ℃.
3. The method for preparing a composite metal lithium anode according to claim 1, characterized in that: in step B, at least one of the following is satisfied:
the reaction temperature is 250-400 ℃;
the reaction time is 1-5 h.
4. The method for preparing a composite metal lithium anode according to claim 1, characterized in that: in the step D, 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.
5. The method for producing a composite metal lithium anode according to any one of claims 1 to 4, characterized in that: in the step D, the reaction time is 1-5 h.
6. The composite metal lithium anode produced by the production method of the composite metal lithium anode of any one of claims 1 to 5.
7. A composite metal lithium anode prepared by the method for preparing a composite metal lithium anode according to any one of claims 1 to 5, and the use of the composite metal lithium anode according to claim 6 in the preparation of lithium batteries.
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