CN114203963A - Carbon material lithium metal composite negative electrode and preparation method and application thereof - Google Patents

Carbon material lithium metal composite negative electrode and preparation method and application thereof Download PDF

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CN114203963A
CN114203963A CN202111511224.5A CN202111511224A CN114203963A CN 114203963 A CN114203963 A CN 114203963A CN 202111511224 A CN202111511224 A CN 202111511224A CN 114203963 A CN114203963 A CN 114203963A
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carbon material
lithium
lithium metal
metal composite
negative electrode
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穆晓阳
周晶晶
郭炳焜
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University of Shanghai for Science and Technology
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    • H—ELECTRICITY
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    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract

The invention discloses a carbon material lithium metal composite negative electrode and a preparation method and application thereof. The preparation method of the carbon material lithium metal composite negative electrode improves the lithium affinity of a three-dimensional current collector of the carbon material by carrying out surface treatment on the carbon material, so that the cycle stability of the carbon material lithium metal composite negative electrode is improved. The application of the carbon material lithium metal composite negative electrode is characterized in that the carbon material lithium metal composite negative electrode and a positive electrode material are assembled into a lithium metal battery; or the lithium ion battery is applied to various lithium metal battery systems of Li-S batteries and Li-air batteries. The lithium metal composite cathode prepared by the invention also shows excellent cycling stability in full battery cycling, has strong operability, is convenient for industrial production and popularization, and has wide application prospect in the field of high-energy density lithium batteries.

Description

Carbon material lithium metal composite negative electrode and preparation method and application thereof
Technical Field
The invention relates to a composite negative electrode and a preparation method and application thereof, in particular to a carbon material lithium metal composite negative electrode and a preparation method and application thereof, and belongs to the field of preparation of high-energy-density lithium batteries and electrode materials thereof.
Background
With the rapid popularization of electric vehicles and the improvement of environmental protection requirements, the development of a new generation of high-energy-density lithium battery has important significance. Lithium metal has an extremely high theoretical capacity (3860mAh g)-1) And the lowest electrochemical potential (-3.04Vvs. SHE), is an ideal choice for the next generation of high voltage and high specific energy lithium battery negative electrode materials. However, since lithium metal is very active in chemical properties and has a large volume expansion effect in a lithium deposition/stripping cycle process, lithium dendrites are very easily generated, and severe safety problems such as reduction of coulombic efficiency and even short circuit are caused, which greatly limits the practical application of the lithium metal negative electrode.
The specific surface area of the lithium metal negative electrode can be enlarged by constructing the three-dimensional current collector, so that the local current density is reduced to play a role in inhibiting lithium dendrites, and meanwhile, the volume expansion effect in the lithium metal circulation process can be relieved by the pore structure in the three-dimensional current collector frame, so that the method is a measure widely adopted in the field of lithium metal negative electrode modification. Guo et al reduction of Cu (OH) by argon2The nanowire array obtains a copper current collector with a three-dimensional structure, and 2mAh & cm is deposited-2After lithium treatment, the electrode has no significant volume change and shows better cycling stability and higher efficiency than the original copper foil. However, the matrix material such as porous copper or porous nickel generally used does not have an active lithium storage capacity and has a high density, which is disadvantageous in the energy density index of the lithium metal composite negative electrode. Hu et al anchored ultrafine nano silver particles on carbon nanofibers by a rapid Joule heating method for nucleation and growth of lithium metal, and the nano silver particles can guide lithium metal to form a composite cathode without dendrite problems, but the rapid Joule heating method is special in device, harsh in heating condition and high in cost. Therefore, the existing lithium metal composite negative electrode preparation method has the following technical problems:
1. the metal three-dimensional current collector frame has high density, no lithium storage capacity and serious influence on the overall energy density of the lithium metal composite cathode;
2. the metal three-dimensional current collector frame structure has sharp protrusions, so that the risk of short circuit caused by membrane puncture exists in the battery structure, and the safety of the lithium metal composite cathode is seriously influenced;
3. the modification measures adopted for improving the lithium affinity of the three-dimensional current collector frame are complex to operate, harsh in experimental conditions and high in comprehensive cost, and are not beneficial to industrial popularization and application;
the carbon material is a mature lithium ion battery cathode material and has the characteristics of high lithium storage capacity, good conductivity, low density, rich pore structure, good economy and the like; meanwhile, the carbon material can be subjected to surface modification by adopting various means to further improve the lithium affinity of the carbon material, so that the stability of the lithium deposition/stripping process is improved. Therefore, the carbon material has great potential in the aspect of preparing the lithium metal composite negative electrode as an ideal three-dimensional current collector material.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides the carbon material lithium metal composite negative electrode, and the preparation method and the application thereof, so that the stable circulation of the lithium metal negative electrode under the conditions of higher current density and high surface capacity is realized. According to the invention, by adopting surface modification measures such as air oxidation and silver coating, the lithium affinity of the treated carbon material is improved, and the lithium metal is guided to be deposited in the three-dimensional current collector of the carbon material in the lithium deposition/stripping cycle process, so that the effects of relieving volume expansion, inhibiting the growth of lithium dendrite and improving the cycle stability are achieved.
In order to solve the technical problems, the invention adopts the technical scheme that: the carbon material lithium metal composite negative electrode is formed by compounding a carbon material three-dimensional current collector which is constructed on the surface of a copper foil and is subjected to surface modification treatment with lithium metal, and the lithium affinity of the carbon material three-dimensional current collector is improved by performing surface treatment on the carbon material, so that the cycle stability of the carbon material lithium metal composite negative electrode is improved.
According to the invention, common carbon materials such as hard carbon, graphite and the like are used as a three-dimensional current collector frame, the lithium affinity of the carbon materials is improved by adopting surface treatment measures such as air oxidation and the like, and the compounding of lithium metal and the three-dimensional current collector of the carbon materials is realized by electrochemical deposition or molten lithium infusion and the like.
Preferably, the carbon material used is one or more of activated carbon, pitch coke, acetylene black, carbon nanotubes and graphite.
The carbon material used in the present invention is one or more of soft carbon or hard carbon, including but not limited to activated carbon, pitch coke, acetylene black, carbon nanotube, graphite, etc.
Preferably, the carbon material used has a specific surface area of 5m2·g-1-1000m2·g-1；
The thickness of the constructed carbon material three-dimensional current collector is 10-500 mu m;
the adopted surface modification measures comprise one of air oxidation and silver coating.
A preparation method of a carbon material lithium metal composite negative electrode comprises the following steps:
the method comprises the following steps: subjecting the carbon material to surface treatment to obtain a carbon material having improved lithium affinity;
step two: and preparing the carbon material subjected to surface treatment into mixed slurry, and coating the mixed slurry on the surface of the copper foil to construct a three-dimensional carbon material current collector.
Step three: and compounding the lithium metal and the carbon material three-dimensional current collector to finally obtain the carbon material lithium metal composite negative electrode.
Preferably, the surface treatment mode in the step one is air oxidation, wherein the air oxidation temperature is 100-500 ℃, the heat preservation time is 3-9 h, and the heating rate is 1 ℃ min-1-10℃·min-1。
Preferably, the surface treatment in the first step is silver coating, wherein the silver source is silver ammonia solution prepared from silver nitrate, and the reducing agent is one of reducing substances formaldehyde or glucose.
Preferably, the mixed slurry in the second step comprises the following components: a carbon material, a binder;
wherein the carbon material is one or more of activated carbon, pitch coke, acetylene black, carbon nanotube, graphite and carbon cloth;
wherein the binder is one or more of PVDF NMP solution (N-methylpyrrolidone solution of polyvinylidene fluoride), CMC water solution (carboxymethyl cellulose water solution), PTFE suspension (polytetrafluoroethylene suspension) or SBR latex (styrene-butadiene latex).
Preferably, the mixture ratio of the mixed slurry in the step two is as follows: the mass ratio of the carbon material is 80-95 percent, and the mass ratio of the binder is 5-20 percent;
and in the second step, the coating thickness of the mixed slurry is 50-1000 μm, air blowing drying is needed after coating, the drying temperature is 60-100 ℃, and the thickness of the dried carbon material three-dimensional current collector is 10-150 μm.
Preferably, the lithium metal compounding process in the third step adopts electrochemical deposition or molten lithium perfusion, and the deposition amount is 2mAh & cm-2-5mAh·cm-2。
An application of a carbon material lithium metal composite negative electrode is characterized in that the carbon material lithium metal composite negative electrode is matched with one of positive electrode materials LFP (lithium iron phosphate), LCO (lithium cobaltate), NCM (ternary battery) and LMO (lithium manganate) to assemble a lithium metal battery; or the lithium ion battery is applied to various lithium metal battery systems of Li-S batteries and Li-air batteries.
Preferably, the semi-cell assembled by the carbon material three-dimensional current collector subjected to surface treatment and the lithium foil is subjected to a lithium deposition/stripping cycle test, and the test condition area capacity is 4mAh & cm-2Current density 2mA cm-2And a charge cut-off voltage of 0.8V. The result shows that the carbon material three-dimensional current collector subjected to surface modification can stably circulate for more than 40 weeks, the coulombic efficiency reaches more than 99%, and the volume expansion effect and the growth of lithium dendrites are effectively inhibited.
Preferably, the surface-treated carbon material three-dimensional current collector is compounded with lithium metal and then matched with a lithium iron phosphate positive electrode to assemble a full battery, and charging and discharging circulation is carried out between 2.4V and 4.2V, wherein the current density is 1 mA-cm-2The capacity retention after 200 weeks of cycling was still greater than 89%.
Compared with the prior art, the invention has the following remarkable characteristics and advantages:
1. the invention uses carbon material as the raw material of the three-dimensional current collector, has the characteristics of high self lithium storage capacity and low density, can reduce the influence of the three-dimensional current collector material on the energy density loss of the composite lithium metal negative electrode, and gives play to the advantage of high specific energy of the lithium metal negative electrode to the greatest extent;
2. the carbon material is used as the raw material of the three-dimensional current collector, the structure of the three-dimensional current collector is similar to that of a common battery electrode, the risk of damage of a diaphragm caused by the frame bulge does not exist, and the safety of the three-dimensional current collector composite cathode is superior to that of a traditional metal three-dimensional current collector composite cathode;
3. the method adopts surface treatment measures such as air oxidation or silver coating and the like to improve the lithium affinity of the carbon material, has simple implementation condition requirements, strong operability and low economic cost, has considerable industrialized popularization and application prospects, and has important significance for early realizing the application of the lithium metal cathode in the field of high specific energy lithium batteries.
The invention has the beneficial effects that: under the conditions of high current density and high surface capacity circulation, the three-dimensional current collector constructed by the carbon material after surface treatment can reduce the local current density, inhibit the growth of lithium dendrites and relieve the volume expansion, has good lithium affinity, can effectively guide the deposition of lithium in a hard carbon frame, and improves the stability of lithium deposition/stripping circulation; the prepared lithium metal composite cathode also shows excellent cycling stability in full battery cycling and has good practical prospect; the surface treatment measures adopted by the invention have strong operability, are convenient for industrial production and popularization, and have wide application prospect in the field of high-energy density lithium batteries.
Drawings
FIG. 1 shows 4mAh · cm-2@2mA·cm-2Lithium deposition/stripping process under cycling conditions; wherein (a) example 1 capacity-voltage curve; (b) example 2 capacity-voltage curve.
FIG. 2 shows 4mAh · cm-2@2mA·cm-2Lithium deposition/stripping process under cycling conditions; coulombic efficiencies of example 1, example 2, comparative examples 1-1, comparative examples 1-2, comparative examples 1-3.
FIG. 3 shows 1mA · cm-2Cycling capacity retention ratio of lithium iron phosphate full cells of example 1 and comparative examples 1-2 under cycling conditions.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
The preferred embodiments of the invention are surface treated carbon material lithium metal composite negative electrodes, in particular air oxidized hard carbon lithium metal composite negative electrodes. If the surface treatment is needed to be carried out on the carbon material through silver coating, the carbon material is subjected to silver mirror reaction or other reactions capable of coating silver on the surface of the carbon material. If other lithium metal composite cathodes made of carbon materials need to be prepared, the surface treatment method is only used for improving the lithium affinity of the carbon materials. In the aspect of compounding the carbon material three-dimensional current collector and lithium metal, due to the improved lithium affinity, both electrochemical deposition and molten lithium infusion methods can be used. In the aspect of full battery application, the lithium metal composite negative electrode using the carbon material can be matched with LFP, LCO, NCM, LMO and other positive electrode materials or applied to Li-S batteries, Li-air batteries and other various lithium battery systems.
Example 1
In this embodiment, a carbon material lithium metal composite negative electrode is prepared by oxidizing hard carbon with air, and the specific steps are as follows:
1. hard carbon particles with an average particle size of 5 mu m are weighed, placed in a tube furnace and then subjected to gas flow of 100 L.h-1High-purity air is introduced into the furnace.
2. Setting the temperature rise of the tubular furnace to 5 ℃ and min-1Heating the mixture from room temperature to 300 ℃, preserving the heat for 6h, and then naturally cooling the mixture to room temperature to obtain the hard carbon material subjected to air oxidation treatment, which is recorded as a group of 300-6 h.
3. Weighing 300-6 h of hard carbon, acetylene black, sodium polymethyl cellulose and styrene-butadiene latex mixtures according to the mass fractions of 90%, 2%, 4% and 4%, fully and uniformly stirring by using a defoaming stirrer, and adjusting by using deionized water to a state with proper fluidity.
4. The slurry was uniformly coated on a copper foil using a coating die having a thickness of 400 μm, and then the coated copper foil was sufficiently dried and the dried copper foil coated with a hard carbon frame was cut into a pole piece.
5. Assembling the 300-6 h group of air oxidation hard carbon three-dimensional current collector pole pieces and lithium pieces into a half-cell for lithium metal compounding, wherein the electrolyte contains 1 wt% of LiNO3And 5 wt% FEC (fluoroethylene carbonate)Alkenyl ester) 1 mol. L of additive-1LiTFSI electrolyte (lithium bistrifluoromethanesulfonimide electrolyte), solvent DOL DME (1,3 dioxolane: ethylene glycol dimethyl ether) 1:1 (vol%), deposited lithium capacity 4mAh cm-2。
Analysis of experimental test results:
the hard carbon is subjected to air oxidation treatment, so that surface defects increase, the number of oxygen-containing functional groups such as carbonyl (C ═ O) and ether bonds (C — O) increases, the number of micropores per se significantly increases, and the specific surface area increases. The voltage polarization in the lithium deposition/stripping cycle in the electrochemical test is only 73mV, which can be at 4mAh cm-2@2mA·cm-2The volume expansion rate of the stable cycling under the condition of 50 weeks is only 50% after 40 weeks of cycling, and no "dead lithium" is observed outside the hard carbon three-dimensional current collector due to the improvement of lithium affinity. Pre-depositing 4mAh cm-2The 300-6 h group hard carbon composite cathode of lithium is matched with the lithium iron phosphate anode to prepare a full battery which is 1mA cm-2The capacity retention rate is 89.14% after the lithium-carbon material composite negative electrode is cycled for 200 weeks under the condition, and the carbon material lithium-metal composite negative electrode has excellent cycle performance and considerable application prospect.
Comparative examples 1 to 1
In order to prove that the carbon material three-dimensional current collector plays an important role in improving the cycling stability of the lithium metal negative electrode under the conditions of high current density and high surface capacity, the bare copper foil electrode prepared by the comparative example is subjected to a lithium deposition/stripping experiment, and the specific steps are as follows:
1. cleaning the surface of the copper foil by using an absolute ethyl alcohol cotton ball, and cutting into a wafer.
2. Assembling a bare copper foil pole piece and a lithium piece into a half-cell, wherein the electrolyte contains 1 wt% of LiNO3And 5 wt% of FEC additive 1 mol. L-1LiTFSI electrolyte, solvent DOL: DME ═ 1:1 (vol%), deposited lithium capacity 4mAh · cm-2。
Comparative examples 1 to 2
In order to prove that the surface oxidation treatment can improve the lithium affinity of the hard carbon three-dimensional current collector, guide lithium deposition to be carried out in the frame and inhibit dead lithium generation outside the frame, thereby improving the cycle stability, the comparative example uses the hard carbon material without surface treatment to prepare the hard carbon lithium metal composite negative electrode for carrying out a lithium deposition/stripping experiment, and the specific steps are as follows:
1. weighing the mixture of the hard carbon, the acetylene black, the sodium polymethyl cellulose and the styrene-butadiene latex according to the mass fractions of 90%, 2%, 4% and 4%, fully and uniformly stirring by using a defoaming stirrer, and adjusting the mixture to a state with proper fluidity by using deionized water.
2. The slurry was uniformly coated on a copper foil using a coating die having a thickness of 400 μm, and then the coated copper foil was sufficiently dried and the dried copper foil coated with a hard carbon frame was cut into a pole piece.
3. Assembling the original hard carbon three-dimensional current collector pole piece and the lithium piece into a half-cell for lithium metal compounding, wherein the electrolyte contains 1 wt% of LiNO3And 5 wt% of FEC additive 1 mol. L-1LiTFSI electrolyte, solvent DOL: DME ═ 1:1 (vol%), deposited lithium capacity 4mAh · cm-2。
Comparative examples 1 to 3
Compared with example 1, the comparative example only changes the surface treatment conditions, the air oxidation temperature is 450 ℃, and the holding time is 6 h.
1. Hard carbon particles with the average particle size of 5 mu m are weighed and placed in a tube furnace, and then the gas flow rate is 100 L.h-1High-purity air is introduced into the furnace.
2. Setting the temperature rise of the tubular furnace to 5 ℃ and min-1Heating the mixture from room temperature to 450 ℃, preserving the heat for 6h, and then naturally cooling the mixture to room temperature to obtain the hard carbon material subjected to air oxidation treatment, which is recorded as 450-6 h group.
3. Weighing the mixture of 450-6 h hard carbon, acetylene black, sodium polymethyl cellulose and styrene-butadiene latex according to the mass fractions of 90%, 2%, 4% and 4%, fully and uniformly stirring by using a defoaming stirrer, and adjusting by using deionized water to a state with proper fluidity.
4. The slurry was uniformly coated on a copper foil using a coating die having a thickness of 400 μm, and then the coated copper foil was sufficiently dried and the dried copper foil coated with a hard carbon frame was cut into a pole piece.
5. Assembling the 450-6 h air oxidation hard carbon three-dimensional current collector pole piece and the lithium piece into a half battery for lithium metal compounding, and using the electrolyte to ensure thatWith a catalyst containing 1 wt% LiNO3And 5 wt% of FEC additive 1 mol. L-1LiTFSI electrolyte, solvent DOL: DME ═ 1:1 (vol%), deposited lithium capacity 4mAh · cm-2。
Example 2
In this embodiment, a carbon material lithium metal composite negative electrode is prepared by coating silver on the surface of hard carbon, and the specific implementation steps are as follows:
1. hard carbon particles with the average particle size of 5 mu m are weighed, mixed with a surfactant and then ultrasonically dispersed in deionized water.
2. A silver ammonia solution was prepared using a 2 wt% silver nitrate aqueous solution as a silver source, and the silver ammonia solution was sufficiently mixed with the dispersion in step 1.
3. And (3) using a 40% formaldehyde aqueous solution as a reducing agent, adding excessive formaldehyde aqueous solution into the mixed solution obtained in the step (2), heating and stirring for 20min, filtering after the reaction is completed, and drying to obtain the product, thus obtaining the hard carbon material with the surface coated with silver.
4. Weighing the mixture of silver-coated hard carbon, acetylene black, sodium polymethylcellulose and styrene-butadiene latex in the mass fractions of 90%, 2%, 4% and 4%, fully and uniformly stirring by using a defoaming stirrer, and adjusting the mixture to a state with proper fluidity by using deionized water.
5. The slurry was uniformly coated on a copper foil using a coating die having a thickness of 400 μm, and then the coated copper foil was sufficiently dried and the dried copper foil coated with a silver-coated hard carbon frame was cut into pole pieces.
6. Assembling a semi-cell by a surface silver coated hard carbon three-dimensional current collector pole piece and a lithium piece for lithium metal compounding, wherein the electrolyte contains 1 wt% of LiNO3And 5 wt% of FEC additive 1 mol. L-1LiTFSI electrolyte, solvent DOL: DME ═ 1:1 (vol%), deposited lithium capacity 4mAh · cm-2。
Example 3
In this embodiment, a carbon material lithium metal composite negative electrode is prepared by oxidizing graphite with air, and the specific implementation steps are as follows:
1. weighing graphite powder, placing in a tube furnace, and measuring with gas flow rate of 100 L.h-1High-purity air is introduced into the furnace.
2. Setting the temperature rise of the tubular furnace to 5 ℃ and min-1Heating to 400 ℃ from room temperature, preserving the heat for 6h, and then naturally cooling to room temperature to obtain graphite subjected to air oxidation treatment, which is recorded as 400-6 h group.
3. Weighing 400-6 h groups of graphite, acetylene black, sodium polymethyl cellulose and styrene-butadiene latex mixtures according to the mass fractions of 90%, 2%, 4% and 4%, fully and uniformly stirring by using a defoaming stirrer, and adjusting by using deionized water to a state with proper fluidity.
4. The slurry was uniformly coated on a copper foil using a coating die having a thickness of 400 μm, and then the coated copper foil was sufficiently dried and the dried copper foil coated with the oxidation-treated graphite frame was cut into pole pieces.
5. Assembling the 400-6 h air oxidized graphite three-dimensional current collector pole piece and a lithium piece into a half-cell for lithium metal compounding, wherein the electrolyte contains 1 wt% of LiNO3And 5 wt% of FEC additive 1 mol. L-1LiTFSI electrolyte, solvent DOL: DME ═ 1:1 (vol%), deposited lithium capacity 4mAh · cm-2。
Example 4
In this embodiment, a carbon material lithium metal composite negative electrode is prepared by coating silver on the surface of graphite, and the specific implementation steps are as follows:
1. weighing graphite powder, mixing with a surfactant, and ultrasonically dispersing in deionized water.
2. A silver ammonia solution was prepared using a 2 wt% silver nitrate aqueous solution as a silver source, and the silver ammonia solution was sufficiently mixed with the dispersion in step 1.
3. And (3) using a 40% formaldehyde aqueous solution as a reducing agent, adding excessive formaldehyde aqueous solution into the mixed solution obtained in the step (2), heating and stirring for 20min, filtering after the reaction is completed, and drying to obtain a product, thus obtaining the graphite with the surface coated with silver.
4. Weighing the mixture of silver-coated graphite, acetylene black, sodium polymethyl cellulose and styrene-butadiene latex in the mass fractions of 90%, 2%, 4% and 4%, fully and uniformly stirring by using a defoaming stirrer, and adjusting the mixture to a state with proper fluidity by using deionized water.
5. The slurry was uniformly coated on a copper foil using a coating die having a thickness of 400 μm, and then the coated copper foil was sufficiently dried and the dried copper foil coated with a graphite frame was cut into a pole piece.
6. Assembling a half-cell by a three-dimensional current collector pole piece with silver-coated graphite on the surface and a lithium piece for lithium metal compounding, wherein the electrolyte contains 1 wt% of LiNO3And 5 wt% of FEC additive 1 mol. L-1LiTFSI electrolyte, solvent DOL: DME ═ 1:1 (vol%), deposited lithium capacity 4mAh · cm-2。
The following is a statistical table of the test results of the lithium deposition/peeling cycle of the carbon material lithium metal composite negative electrode prepared by the above examples, and the cyclic load current density is 2mA cm-2Flour capacity of 4mAh cm-2。
TABLE 1 statistical table of the results of the cycle tests of the various embodiments of the present invention
Figure BDA0003392971960000101
As can be seen from the above example and comparative example test results, the composite anodes of examples 1 to 4 all exhibited a lithium deposition/exfoliation plateau voltage polarization of less than 100mV and a coulombic efficiency of more than 98%. The lower lithium deposition/stripping plateau voltage polarization represents that the potential barrier of the lithium ion deposition/dissolution process in the circulation process is smaller, which shows that the carbon material subjected to the surface treatment of the invention has good lithium affinity, while the higher coulombic efficiency can ensure that the composite negative electrode maintains longer cycle life, and the characteristics are favorable for realizing long and more stable deposition/stripping circulation of the lithium metal composite negative electrode, so that the examples 1 to 4 can stably circulate for more than 40 weeks. Comparative examples 1-1, which directly performed lithium deposition/exfoliation cycles on the surface of copper foil, showed the worst cycle stability due to no recombination with a three-dimensional current collector of a carbon material, and the coulombic efficiency decreased to 90% or less after only 6 weeks of cycling. In comparative examples 1-2, the common hard carbon three-dimensional current collector can effectively relieve volume expansion and inhibit dendritic crystal growth, thereby showing superior cycle stability to copper foil; however, since no surface treatment was performed, the lithium affinity was inferior to that of example 1, and therefore, the voltage polarization was larger and the stable cycle life was shorter than that of example 1. In comparative examples 1 to 3, the higher surface treatment temperature increased the amount of oxygen-containing functional groups and micropores on the surface of hard carbon more than that of example 1, and thus the voltage polarization was smaller and the lithium affinity was better than that of example 1; however, the overall stability was slightly inferior to that of example 1 because of its low first-week coulombic efficiency.
To further illustrate the advantageous properties of the present invention, examples 1 and 2 of the present invention using hard carbon materials are described below with reference to the accompanying drawings.
As can be seen from fig. 1 and 2 in combination with table 1, the carbon material lithium metal composite negative electrode provided by the invention has good cycle stability, the voltage polarization of a lithium deposition/stripping platform is small in the cycle process, the coulombic efficiency can be maintained at a high level, the problems of poor lithium deposition/stripping cycle stability and low coulombic efficiency directly on the surface of a copper foil under a large-current high-surface-capacity load are effectively solved, and an important reference is provided for putting the lithium metal negative electrode into practical application. Meanwhile, as can be seen from fig. 3, the lithium metal composite negative electrode-lithium iron phosphate all-cell assembled in example 1 of the present invention has an excellent capacity retention rate at 1mA · cm-2The capacity retention rate is still 89.14% after current density charging and discharging circulation is carried out for 200 weeks, and the capacity retention rate is better than that of the same type of full batteries provided by comparative examples 1-2, which shows that the carbon material lithium metal composite cathode provided by the invention can be adapted to common cathode materials, the advantage of high specific energy is fully exerted, the circulation performance is stable and reliable, the operation of the invention is simple, and the industrialized production is facilitated, so that the carbon material lithium metal composite cathode has excellent application and popularization prospects.
The present invention is not limited to the above-described embodiments, and various changes and modifications may be made according to the purpose of the present invention, and any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention should be equivalent substitution patterns, so long as the object of the present invention is met, and the technical principle and inventive concept of improving the lithium affinity of the carbon material by the surface treatment to improve the cycle performance of the lithium metal composite negative electrode of the carbon material by the present invention are not departed from the protection scope of the present invention.
The above embodiments are not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make variations, modifications, additions or substitutions within the technical scope of the present invention.

Claims (10)

1. A lithium metal composite negative electrode of a carbon material, characterized in that: the composite negative electrode is formed by compounding a carbon material three-dimensional current collector which is constructed on the surface of a copper foil and is subjected to surface modification treatment with lithium metal, and the lithium affinity of the carbon material three-dimensional current collector is improved by performing surface treatment on the carbon material, so that the cycle stability of the carbon material lithium metal composite negative electrode is improved.
2. The lithium-on-carbon material-lithium metal composite anode according to claim 1, characterized in that: the carbon material is one or more of active carbon, pitch coke, acetylene black, carbon nanotube and graphite.
3. The lithium-on-carbon material-lithium metal composite anode according to claim 1, characterized in that: the specific surface area of the carbon material used was 5m2·g-1-1000m2·g-1；
The thickness of the constructed carbon material three-dimensional current collector is 10-500 mu m;
the adopted surface modification measures comprise one of air oxidation and silver coating.
4. A method for producing a lithium metal composite anode of carbon material according to any one of claims 1 to 3, characterized in that: the method comprises the following steps:
the method comprises the following steps: subjecting the carbon material to surface treatment to obtain a carbon material having improved lithium affinity;
step two: preparing the carbon material subjected to surface treatment into mixed slurry, and coating the mixed slurry on the surface of a copper foil to construct a carbon material three-dimensional current collector;
step three: and compounding the lithium metal and the carbon material three-dimensional current collector to finally obtain the carbon material lithium metal composite negative electrode.
5. The method for producing a lithium-on-carbon material-lithium metal composite anode according to claim 4, wherein: the surface treatment mode in the step one is air oxidation, wherein the air oxidation temperature is 100-500 ℃, the heat preservation time is 3-9 h, and the heating rate is 1 ℃ per minute-1-10℃·min-1。
6. The method for producing a lithium-on-carbon material-lithium metal composite anode according to claim 4, wherein: the surface treatment mode in the first step is silver coating, wherein the silver source is silver ammonia solution prepared by silver nitrate, and the reducing agent is one of reducing substances formaldehyde or glucose.
7. The method for producing a lithium-on-carbon material-lithium metal composite anode according to claim 4, wherein: the mixed slurry in the second step comprises the following components: a carbon material, a binder;
wherein the carbon material is one or more of activated carbon, pitch coke, acetylene black, carbon nanotube, graphite and carbon cloth;
wherein, the binder is one or more of NMP solution of PVDF, CMC water solution, PTFE suspension or SBR latex.
8. The method for producing a lithium-on-carbon material-lithium metal composite anode according to claim 4, wherein: the mixture ratio of the mixed slurry in the step two is as follows: the mass ratio of the carbon material is 80-95 percent, and the mass ratio of the binder is 5-20 percent;
and in the second step, the coating thickness of the mixed slurry is 50-1000 μm, air blowing drying is needed after coating, the drying temperature is 60-100 ℃, and the thickness of the dried carbon material three-dimensional current collector is 10-150 μm.
9. The method for producing a lithium-on-carbon material-lithium metal composite anode according to claim 4, wherein: the lithium metal compounding process in the third step adopts electrochemical deposition or molten lithium perfusion, and the deposition amount is 2mAh & cm-2-5mAh·cm-2。
10. Use of a lithium metal composite anode of carbon material prepared according to any one of claims 4 to 9, characterized in that: matching and assembling the carbon material lithium metal composite negative electrode with one of positive electrode materials LFP, LCO, NCM and LMO to form a lithium metal battery; or the lithium ion battery is applied to various lithium metal battery systems of Li-S batteries and Li-air batteries.
CN202111511224.5A 2021-12-06 2021-12-06 Carbon material lithium metal composite negative electrode and preparation method and application thereof Pending CN114203963A (en)

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