CN114447278A - Metal lithium cathode and preparation method thereof, lithium ion battery and vehicle - Google Patents
Metal lithium cathode and preparation method thereof, lithium ion battery and vehicle Download PDFInfo
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- CN114447278A CN114447278A CN202011222329.4A CN202011222329A CN114447278A CN 114447278 A CN114447278 A CN 114447278A CN 202011222329 A CN202011222329 A CN 202011222329A CN 114447278 A CN114447278 A CN 114447278A
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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
- H01M4/134—Electrodes based on metals, Si or alloys
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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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
- H01M4/139—Processes of manufacture
- H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
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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
- H01M2220/00—Batteries for particular applications
- H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
Abstract
The application discloses a metal lithium cathode, a preparation method of the metal lithium cathode, a lithium ion battery and a vehicle. The lithium metal anode includes: a lithium metal matrix; and the protective layer is coated on one side of the lithium metal matrix close to the electrolyte and comprises a metal alloy material, and the metal alloy material comprises any two or three or four elements of palladium, platinum, gold, silver, ruthenium and nickel. The metal alloy in the protective layer has moderate lithium affinity, and the lithium affinity of the metal alloy is lower than that of pure metal, so that the deposition and the separation behavior of lithium are balanced, and the capacity, the coulombic efficiency and the cycle life of the lithium ion battery are improved.
Description
Technical Field
The invention relates to the field of new energy, in particular to a metal lithium cathode and a preparation method thereof, a lithium ion battery and a vehicle.
Background
In the continuous circulation process of the full battery, metal lithium is used as a negative electrode, lithium ions are moved back and forth between the positive electrode and the negative electrode, the lithium ions are moved from the positive electrode to the negative electrode and deposited on the negative electrode when the battery is charged, and the lithium ions are removed from the negative electrode and moved to the positive electrode when the battery is discharged. The metal lithium as the negative electrode material of the lithium ion battery has the advantages of high specific capacity, low reduction potential and the like, and the specific capacity of the metal lithium can reach more than 10 times of that of a graphite negative electrode for industrial application. However, lithium metal as a negative electrode is easy to generate lithium dendrites during cyclic charge and discharge, on one hand, the generation of the lithium dendrites can pierce a diaphragm to cause short circuit inside a lithium ion battery, on the other hand, the lithium dendrites can continuously consume electrolyte during the growth process and cause the formation of dead lithium of the lithium metal to cause irreversible deposition of lithium, and the generation of the lithium dendrites can also damage a generated Solid Electrolyte Interface (SEI) film, thereby affecting the battery capacity and the coulombic efficiency.
The above problems have been solved by using a lithium negative electrode protective layer, for example: nitrogen-doped graphene as a protective layer for metallic lithium, Polyacrylonitrile (PAN) nanofibers as a lithium protective layer, and other non-metallic element-doped carbon materials as a protective layer for metallic lithium. However, the above protective layer has the following problems: on one hand, the lithium affinity of the protective layer is not high, and lithium ions cannot be effectively guided to be transferred in the protective layer; on the other hand, the active sites deposited by lithium in the protective layer are unevenly distributed or have high local lithium affinity, so that local lithium is difficult to be separated in the charging process, and the performance of the lithium ion battery is influenced.
Disclosure of Invention
In view of the above-mentioned drawbacks or deficiencies in the prior art, it is desirable to provide a metallic lithium negative electrode, a method of manufacturing the same, a lithium ion battery, and a vehicle, such that the metallic lithium negative electrode has a moderate lithium affinity, thereby improving the performance of the lithium ion battery.
In a first aspect, the present invention provides a lithium metal anode comprising:
a lithium metal matrix;
and the protective layer is coated on one side of the lithium metal matrix close to the electrolyte and comprises a metal alloy material, and the metal alloy material comprises any two or three or four elements of palladium, platinum, gold, silver, ruthenium and nickel.
Optionally, the metal alloy material is uniformly distributed in the protective layer, and the average diameter of the metal alloy material is 1nm to 10 nm.
As an optional scheme, the thickness of the protective layer is 5 um-10 um.
Optionally, the metal alloy material is palladium-ruthenium alloy, and the atomic ratio of palladium to ruthenium in the palladium-ruthenium alloy is 1 (0.3-3).
Alternatively, the metal alloy material is an alloy of nickel and any one of platinum, gold, and silver.
Optionally, the metal alloy material is an alloy formed by any one or two of platinum, gold, silver and nickel and palladium ruthenium alloy.
In a second aspect, the present invention provides a method for producing the lithium metal anode of the first aspect, comprising the steps of:
preparing a metal alloy material, wherein the metal alloy material is prepared by uniformly stirring and drying any two or three or four mixed solutions of palladium carbon particles, platinum carbon particles, gold carbon particles, silver salt solution, ruthenium salt solution and nickel salt solution, and performing heat treatment;
preparing slurry, wherein the slurry is prepared by grinding a metal alloy material, adding an adhesive and uniformly stirring;
and preparing a lithium metal negative electrode, wherein the lithium metal negative electrode is prepared by uniformly coating the slurry on a lithium metal matrix.
Alternatively, the conditions of the heat treatment are as follows: under inert atmosphere, the temperature is 200-600 ℃, and the time is 3-5 h.
In a third aspect, the present invention provides a lithium ion battery comprising the lithium metal negative electrode of the first aspect.
In a fourth aspect, the present invention provides a vehicle including the lithium ion battery of the third aspect.
The metal alloy material in the protective layer contains noble metal, so that the lithium affinity of the protective layer is high, the deposition and the separation of lithium are balanced, and the capacity, the coulombic efficiency and the cycle life of the lithium ion battery are improved.
Detailed Description
The present application will be described in further detail with reference to examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the invention are shown in the embodiments.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail with reference to examples.
During the battery cycle, lithium ions are reciprocally transmitted between a positive electrode and a negative electrode, the lithium ions are transferred from the positive electrode to the negative electrode and deposited on the negative electrode during charging, and the lithium ions are removed from the negative electrode and transferred to the positive electrode during discharging, so that the deposition and dissolution of the lithium ions on the negative electrode are two reactions in opposite directions. In the continuous circulation process of the battery, if the lithium affinity of the negative electrode is poor, the deposition behavior of lithium ions can be influenced, so that the lithium ions cannot be rapidly and uniformly deposited, and lithium dendrites can be generated; on the contrary, if the lithium affinity of the negative electrode is too high, the deposited lithium is difficult to be uniformly desorbed, which may cause a decrease in available lithium, affecting the coulombic efficiency of the battery. Therefore, the material of the anode protective layer should have a suitable lithium affinity, which is neither too low nor too high, in order to balance the deposition and extraction behavior of lithium.
In a first aspect, embodiments of the present invention provide a lithium metal anode comprising:
a lithium metal matrix;
and the protective layer is coated on one side of the lithium metal matrix close to the electrolyte and comprises a metal alloy material, and the metal alloy material comprises any two or three or four elements of palladium, platinum, gold, silver, ruthenium and nickel.
The lithium metal matrix includes a lithium metal negative active material, which may include one or more of a lithium foil, a lithium thin film, stabilized lithium powder, and a lithium ribbon.
The metal lithium matrix also comprises a current collector, and the current collector can be a lithium foil or a lithium sheet and the like; the lithium foil can be a copper foil loaded with a certain amount of lithium.
The protective layer is coated on one side of the lithium metal matrix, which is close to the electrolyte, so that the phenomenon that lithium is dead due to lithium dendrite formed by the metal lithium cathode in the cyclic charge-discharge process is favorably improved, and the coulomb efficiency of the lithium ion battery is improved.
The protective layer comprises a metal alloy material, and the metal alloy material comprises any two or three or four elements of palladium, platinum, gold, silver, ruthenium and nickel. In the embodiment, the lithium affinity of pure metal is reduced in the form of metal alloy, so that the protective layer has proper affinity, lithium can be uniformly deposited on the negative electrode in the charging process, the generation of lithium dendrite is inhibited, the lithium can be separated from the negative electrode in the discharging process, the deposition and separation behaviors of the lithium on the negative electrode are balanced, and the coulombic efficiency and the service life of the lithium ion battery are improved.
Furthermore, the metal alloy material in the protective layer is granular, the metal alloy material is uniformly distributed in the protective layer, and the average diameter of the metal alloy material is 1 nm-10 nm. For example: the average diameter of the metal alloy material is 1nm, 3nm, 5nm, 10nm, or the like. If the average diameter of the metal alloy material is too small, the number of active sites may be small, lithium affinity is low, and lithium deposition is not easy; if the average diameter of the metal alloy material is too large, the number of active sites may be large, and lithium affinity may be high, resulting in difficulty in lithium extraction. In the embodiment of the invention, the metal alloy material is uniformly distributed, which is beneficial to uniform deposition of lithium and inhibition of generation of lithium dendrite. The average diameter range of the embodiment of the invention is beneficial to improving the specific surface area of the protective layer, providing a proper lithium-philic active site, ensuring the uniform deposition of lithium and the easy extraction of lithium, and improving the battery capacity, the coulombic efficiency and the cycle performance.
Further, the thickness of the protective layer is 5 um-10 um. For example: the thickness of the protective layer may be 5um, 7um, 8um, 10um, etc. If the thickness of the protective layer is too small, the protective effect is suppressed, and if the thickness of the protective layer is too large, the overall energy density of the battery is sacrificed. The thickness of the protective layer of the embodiment of the invention is beneficial to improving the charge and discharge capacity of the lithium ion battery, and is also beneficial to improving the cycle stability and the cycle life of the battery.
In a preferred embodiment, the metal alloy material is palladium-ruthenium alloy, and the atomic ratio of palladium to ruthenium in the palladium-ruthenium alloy is 1 (0.3-3). For example: the atomic ratio of palladium to ruthenium can be 1:0.3, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, and the like. When the atomic ratio of palladium to ruthenium in the palladium-ruthenium alloy meets the range, the problems that the lithium affinity of the protective layer is too high or too low and lithium dendrite is easy to form or lithium is difficult to remove due to too low content of one element and too high content of the other element are avoided, so that the coulombic efficiency and the cycle life of the lithium ion battery are reduced.
Further, the metal alloy material is an alloy of nickel and any one of platinum, gold, and silver. For example: the metal alloy material can be platinum-nickel alloy, gold-nickel alloy and silver-nickel alloy. The alloy material of the embodiment of the invention has easily obtained raw materials, and reduces the cost of the metallic lithium cathode.
Further, the metal alloy material is an alloy formed by any one or two of platinum, gold, silver and nickel and palladium ruthenium alloy. That is, the metal alloy material may be a ternary alloy formed by any one of platinum, gold, silver and nickel and palladium ruthenium alloy, for example: platinum palladium ruthenium alloys, gold palladium ruthenium alloys, silver palladium ruthenium alloys; the metal alloy material can also be a quaternary alloy formed by any two of platinum, gold, silver and nickel and palladium ruthenium alloy, such as: platinum-gold-palladium-ruthenium alloys, platinum-nickel-palladium-ruthenium alloys, gold-silver-palladium-ruthenium alloys, and the like.
In particular embodiments, the metal alloy material may also be a platinum ruthenium alloy, a gold ruthenium alloy, a silver ruthenium alloy, or the like. The protective layer containing the metal alloy material provided by the embodiment of the invention can select different alloys according to requirements in practical application, is convenient to prepare, provides practical guidance for improving the metallic lithium cathode, and is beneficial to improving the coulombic efficiency, the cycle capacity and the cycle life of the lithium ion battery.
In conclusion, the lithium metal negative electrode provided by the invention can effectively relieve the growth of lithium dendrites, the protective layer can effectively balance the deposition and the separation of negative electrode lithium, and the coulombic efficiency, the cycle stability and the cycle life of the battery are improved.
In a second aspect, the present invention provides a method of making a lithium metal anode. According to an embodiment of the present invention, the lithium metal anode may be the lithium metal anode described in the first aspect. The preparation method comprises the following steps:
preparing a metal alloy material, wherein the metal alloy material comprises any two or three or four elements of palladium, platinum, gold, silver, ruthenium and nickel;
the embodiment according to the present invention does not limit the specific manner of preparing the metal alloy material. According to hydrothermal method, one-pot method, high-temperature calcination, solvent evaporation method, etc. The metal alloy material includes any two or three or four elements of palladium, platinum, gold, silver, ruthenium, nickel, as long as it can be a metal alloy material.
Various metal salts such as sulfate, nitrate, hydrochloride, and the like; noble metal-supported carbon materials may also be selected as raw materials, for example: Pd/C, Au/C, Pt/C, etc.
As an example of this, the following is given,
the process for preparing the metal alloy material comprises the following steps:
preparing a precursor, wherein the precursor is prepared by uniformly stirring and drying mixed liquid of any two or three or four of palladium carbon particles, platinum carbon particles, gold carbon particles, silver salt solution, ruthenium salt solution and nickel salt solution;
and carrying out heat treatment on the precursor to obtain the metal alloy material.
Wherein the precursor is prepared by stirring at normal temperature for 3-5 h, and drying at 80-100 ℃; the heat treatment condition is that the temperature is 200-600 ℃ under inert atmosphere, the heating rate is 5 ℃/min, and the time is 3-5 h. The inert atmosphere of the embodiment of the invention is beneficial to preventing the precursor from being oxidized at high temperature, the temperature and time range is beneficial to forming uniform particles of the metal alloy, the particles of the metal alloy are not accumulated to reduce active sites due to too harsh heat treatment, and the metal alloy cannot be formed due to insufficient heat treatment.
Preparing slurry, wherein the slurry is prepared by grinding a metal alloy material, adding an adhesive and uniformly stirring;
in order to ensure that the metal alloy material in the slurry is uniformly distributed, the metal alloy material is ground in any mode to improve the dispersibility of the metal alloy material, and meanwhile, the diameter of the metal alloy material is favorably reduced, and the number of active sites of the metal alloy material is increased.
The grinding method may be a mortar grinding method, a ball grinding method, or the like, and the embodiment of the present invention is not limited thereto.
The binder may be a solution of polyvinylidene fluoride (PVDF) in n-propyl mercaptan (NPM), acrylic resin, polyvinyl alcohol, or the like. Preferably 5 wt.% PVDF in NPM solution.
And preparing a metallic lithium cathode, wherein the metallic lithium cathode is prepared by uniformly coating the slurry on a lithium metal matrix.
The lithium metal matrix includes a lithium metal negative active material, which may include one or more of a lithium foil, a lithium film, stabilized lithium powder, and a lithium ribbon.
The lithium metal matrix also comprises a current collector which can be a lithium foil or a lithium sheet and the like; wherein, the lithium foil is a copper foil loaded with a certain amount of lithium.
Alternatively, a 30um doctor blade slurry is coated on a copper foil, and the copper foil coated with the slurry is hot-pressed on a lithium foil to obtain a lithium metal negative electrode.
Alternatively, the slurry was coated directly on lithium foil using a 30um doctor blade, resulting in a metallic lithium negative electrode.
In a specific embodiment, the process for preparing palladium ruthenium alloy is as follows:
adding RuCl3·3H2Adding O into water, stirring to dissolve, then adding Pd/C particles (Tanaka Kikinzoku Kogyo, TKK,29 wt.%, wherein 29 wt.% refers to 29% of Pd in the Pd/C particles by mass), stirring at normal temperature for 4 hours, and then stirring and evaporating to dryness in a water bath at 90 ℃ to obtain black precursor powder;
and (2) calcining the black precursor powder in a tubular furnace at high temperature in the atmosphere of argon at 200-600 ℃, at the temperature rise speed of 5 ℃/min for 3-5 h, and cooling to room temperature to obtain the palladium-ruthenium alloy nanoparticles.
In a third aspect, embodiments of the present invention provide a lithium ion battery. The lithium ion battery comprises the lithium metal negative electrode of the first aspect. Thus, the lithium ion battery has all the features and advantages of the metal lithium negative electrode described above, and thus, the description thereof is omitted. Generally speaking, the lithium ion battery has the advantages that the lithium metal cathode can prevent the growth of lithium dendrite, the battery stability is good, the coulombic efficiency is high, and the like.
Wherein, the anode active material of the lithium ion battery is selected from LiFexMnyMzPO4(0≤x≤1，0≤y≤Z is more than or equal to 1 and x + y + z is 1, wherein M is at least one of Al, Mg, Ga, Ti, Cr, Cu, Zn and Mo), and Li3V2(PO4)3、Li3V3(PO4)3、LiNi0.5-xMn1.5-yMx+yO4X is more than or equal to 0.1 and less than or equal to 0.5, y is more than or equal to 0 and less than or equal to 1.5, M is at least one of Li, Co, Fe, Al, Mg, Ca, Ti, Mo, Cr, Cu and Zn), and LiVPO4F、Li1+xL1－y－zMyNzO2(L, M, N can be at least one of Li, Co, Mn, Ni, Fe, Al, Mg, Ga, Ti, Cr, Cu, Zn, Mo, F, I, S and B respectively, -0.1-0.2 x, 0-1 y, 0-1 z, 0-1 + z 1.0), Li2CuO2、Li5FeO4One or more of (a).
Preferably, the positive active material is selected from LiAl0.05Co0.15Ni0.80O2、LiNi0.80Co0.10Mn0.10O2、LiNi0.60Co0.20Mn0.20O2、LiCoO2、LiMn2O4、LiFePO4、LiMnPO4、LiNiPO4、LiCoPO4、LiNi0.5Mn1.5O4、Li3V3(PO4)3And the like.
Preferably, the positive active material is selected from sulfur, lithium sulfide, V2O5、MnO2、TiS2、FeS2One or more of (a).
The electrolyte of the lithium ion battery of the embodiment of the present invention includes a solvent and a lithium salt, wherein the solvent has one or more of the following groups: ether groups, nitrile groups, cyanide groups, fluorine ester groups, tetrazolyl groups, fluorosulfonyl groups, chlorosulfonyl groups, nitro groups, carbonate groups, dicarbonate groups, nitrate groups, fluoroamide groups, diketone groups, azole groups, and triazine groups; the lithium salt being LiPF6、LiAsF6、LiClO4、LiBF6、LiN(CF3SO3)2、LiCF3SO3、LiC(CF3SO3)2And LiN (C)4F9SO2)(CF3SO3) One or more of (a).
In a fourth aspect, the present disclosure provides a vehicle including the lithium ion battery of the third aspect. For example, a plurality of battery packs composed of the lithium ion batteries described above may be included. Thus, the vehicle has all of the features and advantages of the lithium ion battery described above, and will not be described in detail herein.
The present invention is illustrated below by way of specific examples, which are intended to be illustrative only and not to limit the scope of the present invention in any way, and reagents and materials used therein are commercially available, unless otherwise specified, and conditions or steps thereof are not specifically described.
Example 1
Preparing a palladium-ruthenium alloy material: 1g of RuCl3·3H2Adding O into water, stirring and dissolving to obtain RuCl3Adding 4.2g of Pd/C particles (Tanaka Kikinzoku Kogyo, TKK,29 wt.%, wherein 29 wt.% means that the mass fraction of Pd in the Pd/C particles is 29%) into the solution, stirring at normal temperature for 4h, and stirring in a water bath at 90 ℃ for evaporation to dryness to obtain black precursor powder;
calcining black precursor powder in a tubular furnace at high temperature, wherein the atmosphere is argon, the calcining temperature is 600 ℃, the heating rate is 5 ℃/min, and the time is 4h, so that palladium-ruthenium alloy nanoparticle Pd is obtained3Ru；
Preparing slurry: grinding the obtained palladium-ruthenium alloy particles in a mortar, adding a PVDF solution into the particles, and uniformly stirring;
preparing a lithium metal negative electrode: and coating the slurry on a copper foil by using a 30-micrometer scraper, wherein the coating thickness is 5 micrometers, and hot-pressing a protective layer on the copper foil onto a lithium foil to obtain the lithium metal negative electrode.
Example 2
This example differs from example 1 in that: the mass of the added Pd/C particles is 1.4g, and PdRu, the palladium ruthenium alloy nano particles are obtained.
Example 3
This example differs from example 1 in that: addition of RuCl3·3H2The mass of O is 1.5g, the mass of the added Pd/C is 0.7g, and the palladium ruthenium alloy nano-particles PdRu are obtained3。
Example 4
This example differs from example 1 in that: the calcining temperature is 400 ℃, and palladium ruthenium alloy nano-particle Pd is obtained3Ru。
Example 5
This example differs from example 1 in that: the calcining temperature is 200 ℃, and the palladium ruthenium alloy nano-particle Pd is obtained3Ru。
Example 6
This example differs from example 1 in that: the mass of the added Pt/C particles was 4.2g, and platinum-ruthenium alloy particles were obtained.
Example 7
This example differs from example 1 in that: the mass of the added AgCl is 1g, and the silver ruthenium alloy particles are obtained.
Example 8
This example differs from example 1 in that: added NiNO3The mass is 1g, and the nickel-palladium-ruthenium alloy particles are obtained.
Example 9
This example differs from example 1 in that: the coating thickness was 7 um.
Example 10
This example differs from example 1 in that: the coating thickness was 10 um.
Example 11
This example differs from example 1 in that: the mass of the added Pd/C particles is 7.0g, and Pd is obtained5Ru particles.
Example 12
This example differs from example 1 in that: the calcining temperature is 700 ℃, and palladium ruthenium alloy nano-particle Pd is obtained3Ru。
Example 13
This example differs from example 1 in that: the coating thickness was 1 um.
Example 14
This example differs from example 1 in that: the coating thickness was 15 um.
Comparative example 1
This comparative example differs from example 1 in that: 4.2g of the Pd/C particles were directly weighed and ground in a mortar to obtain Pd/C particles.
Comparative example 2
This comparative example differs from example 1 in that: 4.2g of Pd/C particles were replaced with 3g of carbon black, and no Pd/C particles were added to obtain Ru/C particles.
It should be noted that the above embodiments are all single variable adjustments:
for example: in the embodiments 1, 2, 3 and 11, other variables are consistent, and the atomic ratio of palladium and ruthenium in the palladium ruthenium alloy is adjusted by controlling the addition amount of Pd/C;
the other variables of the embodiment 1, the embodiment 4, the embodiment 5 and the embodiment 12 are consistent, and the average diameter of alloy particles is controlled by the heat treatment temperature; wherein the average diameter of the palladium ruthenium alloy particles prepared in example 1 is 10nm, the average diameter of the palladium ruthenium alloy particles prepared in example 12 is 5nm, the average diameter of the palladium ruthenium alloy particles prepared in example 6 is 15nm, and the average diameter of the palladium ruthenium alloy particles prepared in example 7 is 1nm, which are obtained by electron microscopy characterization.
The other variables in the embodiments 1, 9, 10, 13 and 14 are consistent, and the thickness of the protective layer is adjusted by controlling the coating thickness;
examples 6, 7 and 8 prepared different alloy materials, platinum ruthenium alloy, silver ruthenium alloy and nickel palladium ruthenium alloy.
Comparative example 1 a single metal palladium protective layer was prepared with otherwise identical variables;
comparative example 2 a single metal ruthenium protective layer was prepared with otherwise identical variables.
Preparing the alloy materials prepared in the examples 1 to 14 and the metal materials prepared in the comparative examples 1 to 2 into a lithium ion battery, and performing performance test on the lithium ion battery;
the Li vs Cu button cell was prepared and tested as follows:
cutting the copper foil into pole pieces with the diameter of 17mm, adding two PE diaphragms with the diameter of 19mm, adding lithium foil with the diameter of 15mm, applying pressure of 0.1-1 Mpa to compress the two PE diaphragms, and packaging the two PE diaphragms in a button cell shell to obtain the Li vs Cu cell.
Using 1mA cm-2The lithium deposition is carried out at the current density, the coulombic efficiency of the battery is tested by using the cyclic charge-discharge cycle, and the average coulombic efficiency of every 10 cycles of charge-discharge cycles is calculated until 100 cycles, so that the influence of the protective layer on the stability of the metal lithium cathode is evaluated.
The positive electrode vs Li laminated cell was prepared and tested as follows:
and (3) replacing the copper foil with a lithium foil, carrying out hot pressing on the protective layer on the lithium foil to obtain a lithium cathode with the protective layer, assembling the lithium cathode with the ternary material into a laminated battery, testing cyclic charge and discharge, evaluating the cycle life of the battery, and researching the influence of the protective layer on the service life of the battery.
The cell test results are shown in table 1:
TABLE 1 TABLE OF TEST RESULTS FOR BATTERY PERFORMANCE OF EXAMPLES 1-14 AND COMPARATIVE EXAMPLES 1-2
From the results of table 1, it can be derived:
example 1 preparation of palladium ruthenium alloy particles as Pd3Ru, comparative example 1 gave a single metal palladium protective layer and comparative example 2 gave a single metal ruthenium protective layer. As can be seen from table 1, the palladium ruthenium alloy of example 1 effectively improves the coulombic efficiency and cycle performance of the lithium ion battery, compared to a single metal palladium or ruthenium protective layer. The analysis shows that the lithium affinity of a single noble metal is reduced by the alloy material, so that the protective layer has moderate lithium affinity, the deposition and the extraction of lithium are balanced, and the coulomb efficiency and the cycle performance of the lithium ion battery are improved.
Example 1 preparation of palladium ruthenium alloy particles as Pd3Ru, the palladium ruthenium alloy particles prepared in example 2 are PdRu, and the palladium ruthenium alloy particles prepared in example 3 are PdRu3The palladium ruthenium alloy particles prepared in example 5 are Pd5Ru. Comparing the results of the battery performance tests of example 1, example 2, example 3 and example 11 gives: when the atomic ratio of palladium to ruthenium in the palladium-ruthenium alloy meets the range of 3:1, the average coulombic efficiency and the cycle performance of the lithium ion battery are highest. Within the range that the atomic ratio of palladium to ruthenium satisfies 1 (0.3-3), the coulombic efficiency and the cycle performance of the lithium ion battery are relatively excellent, but as the atomic weight of ruthenium increases, the coulombic efficiency and the cycle performance of the lithium ion battery decrease. When the atomic ratio of palladium and ruthenium exceeds this range, Pd as shown in example 115And Ru particles, wherein the atomic ratio of palladium in the alloy is far greater than that of ruthenium, and the coulombic efficiency and the cyclicity of the lithium ion battery are also reduced. The analysis may be that the ratio of palladium atoms or ruthenium atoms in the alloy is unbalanced, so that the lithium affinity of the alloy material is relatively high, and lithium dendrites may be generated on the negative electrode along with the cyclic charge and discharge of the battery, and a large amount of electrolyte is consumed, thereby reducing the cycle performance of the lithium ion battery. Therefore, it can be seen that: the atomic ratio of palladium to ruthenium is 1 (0.3-3), and the protective layer has appropriate lithium affinity, thereby being beneficial to improving the coulombic efficiency and the cycle life of the lithium ion battery.
The average diameter of the palladium ruthenium alloy prepared in example 1 was 10nm, the average diameter of the palladium ruthenium alloy prepared in example 4 was 5nm, the average diameter of the palladium ruthenium alloy prepared in example 6 was 15nm, and the average diameter of the palladium ruthenium alloy prepared in example 7 was 1 nm. It is known that as the heat treatment temperature increases, the average diameter of the alloy material increases because the high temperature is favorable for the alloy material to grow. From table 1, it can be seen that: when the average diameter of the palladium-ruthenium alloy is within the range of 1-10 nm, the coulombic efficiency and the cycle performance of the lithium ion battery are relatively excellent, and the coulombic efficiency and the cycle performance of the lithium ion battery are slightly reduced along with the increase of the average diameter of the alloy within the range. However, when the diameter exceeds 10um, as in example 12, the diameter of the metal particle of the palladium ruthenium alloy is 15nm, the coulombic efficiency and the cycle performance of the lithium ion battery are very obviously reduced, which may be caused by that the diameter is too large due to local accumulation of alloy particles caused by high temperature, the number of active sites is large, the lithium affinity is high, and the lithium is not easy to be extracted due to more local lithium deposition, so that lithium dendrite is generated. The average diameter range of the lithium ion battery is 1-10 nm, the alloy metal particles are uniformly distributed, the deposition and the separation of lithium are balanced, the uniform deposition of the lithium is facilitated, and the generation of lithium dendrites is inhibited, so that the coulombic efficiency and the cycle performance of the lithium ion battery are improved.
The thickness of the protective layer in example 1 was 5um, the thickness of the protective layer in example 9 was 7um, the thickness of the protective layer in example 10 was 10um, the thickness of the protective layer in example 13 was 1um, and the thickness of the protective layer in example 14 was 15 um. As can be seen from table 1, when the thickness of the protective layer is 5um to 10um, the coulombic efficiency and the cycle performance of the lithium ion battery are relatively excellent, and there is no significant gap. When the thickness of the protective layer is reduced to 1um, the coulombic efficiency and the cycle performance of the lithium ion battery are obviously and greatly reduced, and analysis possibly shows that the protective effect is inhibited because the thickness of the protective layer is too small; when the protective layer is increased to 15um, the kunlun efficiency and cycle performance of the lithium ion battery also decrease substantially, and analysis may be that the thickness of the protective layer is too large, sacrificing the overall energy density of the battery. Therefore, the thickness of the protective layer according to the embodiment of the invention is beneficial to improving the charge and discharge capacity of the lithium ion battery, and is also beneficial to improving the cycle stability and the cycle life of the battery.
Example 6 a platinum ruthenium alloy was prepared, example 7 a silver ruthenium alloy, and example 8 a nickel palladium ruthenium alloy. As can be seen from table 1, in comparative examples 6 to 8 and comparative examples 1 to 2, the silver ruthenium alloy, the platinum ruthenium alloy, and the nickel palladium ruthenium alloy all improved the coulombic efficiency and the cycle performance of the lithium ion battery with respect to the single metal ruthenium or metal palladium. The analysis is that the lithium affinity of the single noble metal is too high, the lithium deposition is not uniform and the lithium is difficult to remove, the coulombic efficiency of the battery is reduced, the lithium affinity of the single metal is reduced by the alloy material, the lithium deposition is uniform, the deposition and the removal of the lithium are balanced, and the coulombic efficiency and the cycle performance of the lithium ion battery are further improved.
The foregoing description is only exemplary of the preferred embodiments of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.
Claims (10)
1. A lithium metal anode, comprising:
a lithium metal matrix;
and the protective layer is coated on one side of the lithium metal matrix, which is close to the electrolyte, and comprises a metal alloy material, wherein the metal alloy material comprises any two or three elements of palladium, platinum, gold, silver, ruthenium and nickel.
2. The negative electrode according to claim 1, wherein the metal alloy material is uniformly distributed in the protective layer, and an average diameter of the metal alloy material is 1nm to 10 nm.
3. The negative electrode according to claim 1, wherein the protective layer has a thickness of 5 to 10 um.
4. The cathode according to claim 1, wherein the metal alloy material is palladium ruthenium alloy, and the atomic ratio of palladium to ruthenium in the palladium ruthenium alloy is 1 (0.3-3).
5. The negative electrode according to claim 1, wherein the metal alloy material is an alloy of nickel and any one of platinum, gold, and silver.
6. The anode according to claim 1, wherein the metal alloy material is an alloy of any one or two of platinum, gold, silver and nickel with palladium ruthenium.
7. A method for preparing a lithium metal anode according to any one of claims 1 to 6, comprising the steps of:
preparing a metal alloy material, wherein the metal alloy material is prepared by mixing any two or three or four of palladium carbon particles, platinum carbon particles, gold carbon particles, silver salt solution, ruthenium salt solution and nickel salt solution uniformly, drying, and performing heat treatment;
preparing slurry, wherein the slurry is prepared by grinding the metal alloy material, adding an adhesive and uniformly stirring;
and preparing a lithium metal negative electrode, wherein the lithium metal negative electrode is prepared by uniformly coating the slurry on a lithium metal matrix.
8. The method of claim 7, wherein the heat treatment conditions are: under inert atmosphere, the temperature is 200-600 ℃, and the time is 3-5 h.
9. A lithium ion battery comprising the lithium metal negative electrode according to any one of claims 1 to 6.
10. A vehicle comprising the lithium ion battery of claim 9.
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