CN116779870B - Negative electrode material for lithium metal battery, preparation method and application - Google Patents
Negative electrode material for lithium metal battery, preparation method and application Download PDFInfo
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- CN116779870B CN116779870B CN202311033986.8A CN202311033986A CN116779870B CN 116779870 B CN116779870 B CN 116779870B CN 202311033986 A CN202311033986 A CN 202311033986A CN 116779870 B CN116779870 B CN 116779870B
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 123
- 239000007773 negative electrode material Substances 0.000 title claims abstract description 68
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 79
- 239000002041 carbon nanotube Substances 0.000 claims abstract description 79
- 229910021393 carbon nanotube Inorganic materials 0.000 claims abstract description 79
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 55
- 229920000877 Melamine resin Polymers 0.000 claims abstract description 55
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims abstract description 55
- 239000002033 PVDF binder Substances 0.000 claims abstract description 47
- 239000002105 nanoparticle Substances 0.000 claims abstract description 40
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 29
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 26
- 238000001035 drying Methods 0.000 claims description 16
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 12
- 239000010405 anode material Substances 0.000 claims description 12
- 239000010406 cathode material Substances 0.000 claims description 12
- 239000011889 copper foil Substances 0.000 claims description 12
- 239000011888 foil Substances 0.000 claims description 12
- 239000002002 slurry Substances 0.000 claims description 12
- 238000000227 grinding Methods 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 6
- 239000011248 coating agent Substances 0.000 claims description 6
- 238000000576 coating method Methods 0.000 claims description 6
- 238000009713 electroplating Methods 0.000 claims description 6
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 6
- 239000010931 gold Substances 0.000 claims description 6
- 229910052737 gold Inorganic materials 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- 239000001301 oxygen Substances 0.000 claims description 6
- 239000000843 powder Substances 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 34
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 34
- 239000003792 electrolyte Substances 0.000 abstract description 20
- 210000001787 dendrite Anatomy 0.000 abstract description 15
- 238000007086 side reaction Methods 0.000 abstract description 9
- 238000001556 precipitation Methods 0.000 abstract description 8
- 230000005540 biological transmission Effects 0.000 abstract description 6
- 230000007704 transition Effects 0.000 abstract description 4
- YZSKZXUDGLALTQ-UHFFFAOYSA-N [Li][C] Chemical compound [Li][C] YZSKZXUDGLALTQ-UHFFFAOYSA-N 0.000 abstract 2
- 230000000052 comparative effect Effects 0.000 description 24
- 238000000034 method Methods 0.000 description 23
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 12
- 210000004027 cell Anatomy 0.000 description 11
- 229920000767 polyaniline Polymers 0.000 description 9
- 125000000524 functional group Chemical group 0.000 description 8
- 230000008569 process Effects 0.000 description 6
- 230000002829 reductive effect Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000001000 micrograph Methods 0.000 description 5
- 230000008859 change Effects 0.000 description 4
- 230000002427 irreversible effect Effects 0.000 description 4
- 230000010287 polarization Effects 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 239000006260 foam Substances 0.000 description 3
- 230000037427 ion transport Effects 0.000 description 3
- 125000003277 amino group Chemical group 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000007784 solid electrolyte Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000000452 restraining effect Effects 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The application discloses a negative electrode material for a lithium metal battery, a preparation method and application thereof, and relates to the technical field of batteries, wherein the negative electrode material comprises melamine nano particles, lithiated carbon nano tubes and polyvinylidene fluoride binder; the mass ratio of the melamine nano particles to the lithiated carbon nano tubes to the polyvinylidene fluoride binder is (4-8): (1-4): (1-2). The lithium carbon nanotube is used as a transition layer between lithium metal and electrolyte, and can keep electrochemical stability when the transition layer is contacted with the electrolyte and the lithium metal, so that side reactions of the electrolyte and the lithium metal can be avoided, meanwhile, the lithium carbon nanotube can conduct lithium ions, a lithium ion transmission channel is formed in the negative electrode, good electrochemical dynamic performance is provided for the negative electrode, the melamine has polarity, and electrochemical precipitation of the lithium ions can be controlled, so that growth of lithium dendrites is inhibited, and the negative electrode material for the lithium metal battery has higher cycle life and safety.
Description
Technical Field
The application relates to the technical field of batteries, in particular to a negative electrode material for a lithium metal battery, a preparation method and application thereof.
Background
The energy density of lithium batteries is increasingly demanded, but lithium ion batteries using graphite as a negative electrode reach theoretical limits, and it is difficult to further improve the energy density. Even though lithium metal can replace graphite, the energy density of the battery can be greatly improved, but the electrochemical behavior of lithium ions of the lithium metal in the charge and discharge process is uncontrolled, lithium dendrites are easy to form, the lithium dendrites can puncture an SEI film, the cycle life is reduced, and along with the growth of dendrites, a diaphragm can be even punctured, so that a short circuit is caused, and the safety problem occurs. In addition, lithium metal has active chemical property, and can generate irreversible side reaction when contacting with electrolyte, thus forming a solid electrolyte interface film (SEI film) and consuming precious electrolyte and lithium metal. And the lithium metal can generate volume change in the charge and discharge process, so that the pressure is formed in the battery in the charge and discharge process, and the service life and safety of the battery are affected.
Patent CN201810079938.5 discloses a negative electrode material for a lithium metal battery, a preparation method and application thereof, and proposes that the interaction of functional groups in melamine and lithium ions is used for realizing stable deposition of lithium ions, and simultaneously, volume expansion is restrained, and internal stress of the battery is relieved, so that the purpose of restraining growth of lithium dendrites is achieved. However, the porosity of the melamine foam in the technical scheme is above 90%, although the gaps can provide space for electrochemical precipitation of lithium ions, the electrolyte is also led into the gaps, the problem of side reaction caused by contact of lithium metal and the electrolyte is not solved, the framework in the melamine foam can damage the integrity of a solid electrolyte interface film (SEI film) generated by reaction of the lithium metal and the electrolyte, the SEI film is continuously broken in the charging and discharging process, further irreversible side reaction of the lithium metal and the electrolyte is continuously caused, and finally the internal resistance of the battery is increased and the service life is reduced.
Patent CN202011437477.8 discloses a lithium metal negative electrode, a preparation method and application thereof, and proposes a buffer layer for preparing the lithium metal negative electrode by using melamine foam and polyaniline, wherein the buffer layer can adapt to volume change in a charge-discharge process by using elasticity of melamine, and can disperse dendrite tip current by using weak conductivity of polyaniline, homogenize lithium ion concentration and inhibit dendrite growth. However, in the technical scheme, only the elastic performance of melamine is utilized, and the weak conductivity of polyaniline in the technical scheme can disperse dendrite tip current, homogenize lithium ion concentration and inhibit dendrite growth, but the weak conductivity of polyaniline enables electrochemical reaction to occur on the surface of a buffer layer, so that a battery is easier to short-circuit, and the technical scheme still does not isolate lithium metal from electrolyte, and side reaction still cannot be avoided.
Therefore, the existing lithium metal as a negative electrode material has the problems of unstable electrode/electrolyte interface, easy volume change and easy generation of lithium dendrite.
Disclosure of Invention
The application aims to provide a negative electrode material for a lithium metal battery, a preparation method and application thereof, and solves the problems that the interface of an electrode/electrolyte is unstable, the volume is easy to change and lithium dendrite is easy to generate when the current lithium metal is used as the negative electrode material.
The application is realized by the following technical scheme:
in a first aspect, the application provides a negative electrode material for a lithium metal battery, comprising melamine nanoparticles, lithiated carbon nanotubes and a polyvinylidene fluoride binder; the mass ratio of the melamine nano particles to the lithiated carbon nano tubes to the polyvinylidene fluoride binder is (4-8): (1-4): (1-2).
The principle of improving the electrochemical performance of the lithium metal anode material according to the technical scheme of the application is as follows:
the amine group in the melamine has polarity, the adsorption of the amine group in the melamine to lithium ions is utilized, an electrochemical active space is built in a lithium metal negative electrode, the lithiated carbon nano tube has good lithium ion conduction capability, meanwhile, the lithiated carbon nano tube can keep electrochemical stability when in contact with lithium, lithium metal is isolated from electrolyte by the lithiated carbon nano tube, side reaction is reduced, polyvinylidene fluoride binder and electrolyte are not mutually dissolved, melamine nano particles and the lithiated carbon nano tube are combined into a whole by the polyvinylidene fluoride binder, lithium ions reach melamine crystal lattice through the lithiated carbon nano tube when being charged, and are adsorbed by polar functional groups of the melamine after being combined with electrons from a current collector, along with the progress of charging, lithium atoms start growing from the current collector, so that uniform electrochemical precipitation of lithium ions is realized, lithium dendrite growth is inhibited, and meanwhile, the lithiated carbon nano tube and polyvinylidene fluoride isolate the electrolyte from the lithium metal, and irreversible side reaction of the electrolyte and the lithium metal is avoided.
Further, the preparation method of the lithiated carbon nanotube comprises the following steps: and heating the lithium foil to a molten state, and then placing the carbon nano tube on the surface of the molten state lithium metal until the carbon nano tube is changed from black to gold, so as to obtain the lithiated carbon nano tube.
Further, the lithium foil is heated under the condition that the water content is less than or equal to 0.01ppm and the oxygen content is less than or equal to 0.01 ppm.
In a second aspect, the present application provides a method for preparing a negative electrode material for a lithium metal battery, comprising the steps of:
step 1: preparing lithiated carbon nanotubes;
step 2: grinding the lithiated carbon nanotubes and the melamine nanoparticles prepared in the step 1 to form a uniform mixture of the lithiated carbon nanotubes and the melamine nanoparticles;
step 3: dissolving polyvinylidene fluoride powder in N-methyl pyrrolidone solution to form N-methyl pyrrolidone solution containing polyvinylidene fluoride;
step 4: adding the mixture of the uniform lithiated carbon nanotubes and the melamine nanoparticles obtained in the step 2 into the N-methylpyrrolidone solution containing polyvinylidene fluoride prepared in the step 3, and grinding to form uniform slurry;
step 5: uniformly coating the slurry obtained in the step 4 on a copper foil, and then drying to form a layer of film on the copper foil;
step 6: cutting the film obtained in the step 5 into a pole piece shape to obtain a cathode material without lithium;
step 7: and (3) carrying out electroplating treatment on the cathode material which does not contain lithium and is obtained in the step (6).
Further, the preparation method of the lithiated carbon nanotube in the step 1 comprises the following steps: and heating the lithium foil to a molten state, and then placing the carbon nano tube on the surface of the molten state lithium metal until the carbon nano tube is changed from black to gold, so as to obtain the lithiated carbon nano tube.
Further, the lithium foil is heated under the condition that the water content is less than or equal to 0.01ppm and the oxygen content is less than or equal to 0.01 ppm.
Further, the concentration of polyvinylidene fluoride in the N-methylpyrrolidone solution containing polyvinylidene fluoride in the step 3 is 5mg/ml to 15mg/ml.
Further, the film thickness in step 5 is 30 μm to 100. Mu.m.
Further, the drying method in step 5 is as follows: drying in a non-vacuum environment to volatilize the N-methyl pyrrolidone solution, and then drying in a vacuum environment.
In a third aspect, the application provides an anode material for a lithium metal battery and an application of the anode material for the lithium metal battery prepared by the preparation method in preparation of a lithium metal solid-state battery and a lithium metal liquid-state battery.
Compared with the prior art, the application has the following advantages and beneficial effects:
according to the application, the lithiated carbon nanotube is used as a transition layer between lithium metal and electrolyte, and the transition layer can keep electrochemical stability when being contacted with the electrolyte and the lithium metal, so that side reactions of the electrolyte and the lithium metal can be avoided, meanwhile, the lithiated carbon nanotube can conduct lithium ions, a lithium ion transmission channel is formed in the negative electrode, good electrochemical dynamic performance is provided for the negative electrode, the melamine has polarity, and electrochemical precipitation of the lithium ions can be controlled, so that growth of lithium dendrites is inhibited, and the negative electrode material for the lithium metal battery prepared by adopting the technical scheme of the application has higher cycle life and safety.
Drawings
In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present application, the drawings that are needed in the examples will be briefly described below, it being understood that the following drawings only illustrate some examples of the present application and therefore should not be considered as limiting the scope, and that other related drawings may be obtained from these drawings without inventive effort for a person skilled in the art. In the drawings:
fig. 1 is a scanning electron microscope image of a negative electrode material for a lithium metal battery in example 1 of the present application;
FIG. 2 is a scanning electron microscope image of the negative electrode material for lithium metal batteries in example 2 of the present application;
FIG. 3 is a scanning electron microscope image of the negative electrode material for lithium metal batteries in example 3 of the present application;
fig. 4 is a scanning electron microscope image of the anode material for lithium metal batteries in example 4 of the present application;
FIG. 5 is a scanning electron microscope image of the negative electrode material for lithium metal batteries in example 5 of the present application;
fig. 6 is a 100 th charge-discharge curve of a full cell composed of a negative electrode material and lithium cobaltate in comparative example 1 of the present application;
fig. 7 is a 100 th charge-discharge curve of a full cell composed of a negative electrode material and lithium cobaltate in comparative example 2 of the present application;
FIG. 8 is a 100 th charge/discharge curve of a full cell composed of the negative electrode material and lithium cobaltate in example 1 of the present application;
fig. 9 is a 100 th charge-discharge curve of a full cell composed of a negative electrode material and lithium iron phosphate in comparative example 3 of the present application;
fig. 10 is a 100 th charge-discharge curve of a full cell composed of a negative electrode material and lithium iron phosphate in example 1 of the present application.
Fig. 11 is a 100 th charge-discharge curve of a full cell composed of a negative electrode material and lithium iron phosphate in example 2 of the present application.
Fig. 12 is a 100 th charge-discharge curve of a full cell composed of a negative electrode material and lithium iron phosphate in example 3 of the present application.
Fig. 13 is a 100 th charge-discharge curve of a full cell composed of a negative electrode material and lithium iron phosphate in example 4 of the present application.
Fig. 14 is a 100 th charge-discharge curve of a full cell composed of a negative electrode material and lithium iron phosphate in example 5 of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
Example 1
The embodiment provides a negative electrode material for a lithium metal battery, which comprises melamine nano-particles, lithiated carbon nano-tubes and polyvinylidene fluoride binder; the mass ratio of the melamine nano-particles to the lithiated carbon nano-tubes to the polyvinylidene fluoride binder is 8:1:1.
The preparation method of the anode material for lithium metal batteries in this example is as follows:
step 1: heating 0.2g of lithium foil at 400 ℃ under the conditions that the water content is less than or equal to 0.01ppm and the oxygen content is less than or equal to 0.01ppm to enable the lithium foil to be in a molten state, and placing 2g of carbon nano tubes on the surface of molten lithium metal until the carbon nano tubes are changed from black to gold to obtain lithiated carbon nano tubes;
step 2: grinding 1g of the lithiated carbon nanotubes obtained in the step 1 and 8g of melamine nanoparticles for 1 hour to form a uniform mixture of the lithiated carbon nanotubes and the melamine nanoparticles;
step 3: dissolving 1g of polyvinylidene fluoride powder in 100ml of N-methylpyrrolidone solution to form N-methylpyrrolidone solution containing polyvinylidene fluoride;
step 4: adding the mixture of the lithiated carbon nanotubes and the melamine nanoparticles obtained in the step 2 into the N-methylpyrrolidone solution containing polyvinylidene fluoride obtained in the step 3, and grinding for 2 hours to form uniform slurry;
step 5: uniformly coating the slurry obtained in the step 4 on a copper foil, drying at 60 ℃ for 12 hours to volatilize an N-methyl pyrrolidone solution, and drying at 60 ℃ for 24 hours again to form a layer of film containing melamine nano particles, lithiated carbon nano tubes and polyvinylidene fluoride on the copper foil, wherein the thickness of the film is 35 mu m;
step 6: cutting the film obtained in the step 5 into a pole piece shape to obtain a cathode material without lithium;
step 7: the negative electrode material without lithium obtained in the step 6 was subjected to a treatment of 0.2 mA cm -2 Electroplating for 20 hours at the current density of (2) to obtain the lithium-containing surface with the capacity of 4mAh cm -2 Is a negative electrode material of (a).
The negative electrode material for lithium metal battery prepared by the preparation method is detected by using an electronic scanning mirror, and an electronic scanning diagram of the internal structure is shown in fig. 1.
From the figure, lithium enters the melamine nano particles, melamine and the lithiated carbon nano tubes are uniformly distributed and stably contacted, which indicates that the polar functional groups in the melamine can adsorb lithium ions, and the lithiated carbon nano tubes can provide a transmission channel for the lithium ions.
Example 2
Based on example 1, this example differs from example 1 in that the mass ratio of melamine nanoparticles, lithiated carbon nanotubes and polyvinylidene fluoride binder in this example is 4:1:1.
The negative electrode material for lithium metal battery prepared by the technical scheme of example 2 was detected by using an electronic scanning mirror, and an electronic scanning diagram of the internal structure thereof is shown in fig. 2.
From the figure, lithium enters the melamine nano particles, melamine and the lithiated carbon nano tubes are uniformly distributed and stably contacted, which indicates that the polar functional groups in the melamine can adsorb lithium ions, and the lithiated carbon nano tubes can provide a transmission channel for the lithium ions.
Example 3
Based on example 1, this example differs from example 1 in that the mass ratio of melamine nanoparticles, lithiated carbon nanotubes and polyvinylidene fluoride binder in this example is 4:2:1.
The negative electrode material for lithium metal battery prepared by the technical scheme of example 3 was detected by using an electronic scanning mirror, and an electronic scanning diagram of the internal structure thereof is shown in fig. 3.
From the figure, lithium enters the melamine nano particles, melamine and the lithiated carbon nano tubes are uniformly distributed and stably contacted, which indicates that the polar functional groups in the melamine can adsorb lithium ions, and the lithiated carbon nano tubes can provide a transmission channel for the lithium ions.
Example 4
Based on embodiment 1, this embodiment differs from embodiment 1 in that: the film thickness in step 5 was 30. Mu.m.
The negative electrode material for lithium metal batteries prepared by the technical scheme of example 4 was detected by using an electronic scanning mirror, and an electronic scanning diagram of a cross section thereof is shown in fig. 4.
The graph shows that the lithium metal is distributed compactly and has uniform thickness, which indicates that the lithiated carbon nano tube can conduct lithium ions into the cathode material, and the polar functional group of melamine can induce electrochemical precipitation of lithium ions.
Example 5
Based on embodiment 1, this embodiment differs from embodiment 1 in that: the film thickness in step 5 was 100. Mu.m.
The negative electrode material for lithium metal batteries prepared by the technical scheme of example 5 was detected by using an electronic scanning mirror, and an electronic scanning diagram of a cross section thereof is shown in fig. 5.
From the figure, it can be seen that when the thickness is increased to 100 μm, lithium metal can still fill the whole cathode material, the thickness is still relatively uniform, which means that when the thickness of the cathode material is increased, the lithiated carbon nanotube can still conduct lithium ions into the cathode material, and the polar functional group of melamine can still induce electrochemical precipitation of lithium ions.
Comparative example 1
This comparative example contains no lithiated carbon nanotubes and only melamine nanoparticles and polyvinylidene fluoride binder, wherein the mass ratio of melamine nanoparticles to polyvinylidene fluoride binder is 8:1, as compared to example 1.
The preparation method comprises the following steps:
step 1: dissolving 1g of polyvinylidene fluoride powder in 100ml of N-methylpyrrolidone solution to form N-methylpyrrolidone solution containing polyvinylidene fluoride;
step 2: adding melamine nano-particles into the N-methyl pyrrolidone solution with polyvinylidene fluoride obtained in the step 1, and grinding for 2 hours to form uniform slurry;
step 3: uniformly coating the slurry obtained in the step 2 on a copper foil, drying at 60 ℃ for 12 hours to volatilize the N-methyl pyrrolidone solution, and drying at 60 ℃ for 24 hours again to form a film containing melamine nano particles and polyvinylidene fluoride on the copper foil, wherein the thickness of the film is 35 mu m;
step 4: cutting the film obtained in the step 3 into a pole piece shape to obtain a cathode material without lithium;
step 5: the negative electrode material without lithium obtained in the step 4 is subjected to a temperature of 0.2 mA cm -2 Electroplating for 20 hours at the current density of (2) to obtain the lithium-containing surface with the capacity of 4mAh cm -2 Is a negative electrode material of (a).
The full battery composed of the negative electrode material prepared by the method of comparative example 1 and lithium cobaltate was tested, and the 100 th charge-discharge curve was, as shown in fig. 6, tested at a rate of 1C and a test temperature of 25 ℃. As can be seen from the graph, the specific discharge capacity of the anode material prepared by the method of comparative example 1 was 101 mAh.g -1 。
Comparative example 2
This comparative example contains no melamine nanoparticles and only lithiated carbon nanotubes and polyvinylidene fluoride binder, compared to example 1, wherein the mass ratio of lithiated carbon nanotubes to polyvinylidene fluoride binder is 1:1.
The preparation method comprises the following steps:
step 1: heating 0.2g of lithium foil at 400 ℃ under the conditions that the water content is less than or equal to 0.01ppm and the oxygen content is less than or equal to 0.01ppm to enable the lithium foil to be in a molten state, and placing 2g of carbon nano tubes on the surface of molten lithium metal until the carbon nano tubes are changed from black to gold to obtain lithiated carbon nano tubes;
step 2: dissolving 1g of polyvinylidene fluoride powder in 100ml of N-methylpyrrolidone solution to form N-methylpyrrolidone solution containing polyvinylidene fluoride;
step 3: adding 1g of the lithiated carbon nanotube obtained in the step 1 into the N-methyl pyrrolidone solution with polyvinylidene fluoride obtained in the step 2, and grinding for 2 hours to form uniform slurry;
step 4: uniformly coating the slurry obtained in the step 3 on a copper foil, drying at 60 ℃ for 12 hours to volatilize the N-methyl pyrrolidone solution, and drying at 60 ℃ for 24 hours again to form a film containing lithiated carbon nano tubes and polyvinylidene fluoride on the copper foil, wherein the thickness of the film is 35 mu m;
step 6: cutting the film obtained in the step 5 into a pole piece shape to obtain a cathode material without lithium;
step 7: the negative electrode material without lithium obtained in the step 6 was subjected to a treatment of 0.2 mA cm -2 Electroplating for 20 hours at the current density of (2) to obtain the lithium-containing surface with the capacity of 4mAh cm -2 Is a negative electrode material of (a).
The full battery composed of the negative electrode material prepared by the method of comparative example 2 and lithium cobaltate was tested, and the 100 th charge-discharge curve was, as shown in fig. 7, tested at a rate of 1C and a test temperature of 25 ℃. As can be seen from the graph, the specific discharge capacity of the anode material prepared by the method of comparative example 2 was 122 mAh.g -1 。
The full cell composed of the negative electrode material prepared by the method of example 1 and lithium cobaltate was tested, and the 100 th charge-discharge graph was shown in fig. 8. As can be seen from the graph, the method of example 1 was usedThe specific discharge capacity of the anode material prepared by the method is 138 mAh.g -1 。
By comparing the 100 th charge-discharge graphs of comparative examples 1 and 2 with the 100 th charge-discharge graph of example 1, it can be seen that the discharge capacity of the negative electrode material prepared by containing lithiated carbon nanotubes in the middle of comparative example 1 is minimized after 100 times of charge-discharge, because lithium in the negative electrode material directly contacts with the electrolyte after no lithiated carbon nanotubes are present in the negative electrode material, and irreversible side reactions occur, thereby reducing active lithium in the negative electrode material and decreasing specific capacity. In contrast, in comparative example 2, although the lithiated carbon nanotubes were contained, electrochemical precipitation of lithium ions was not controlled after the melamine nanoparticles were not present, lithium dendrites were easily generated, and part of lithium was deactivated during repeated charge and discharge processes, so that the active lithium inside the negative electrode material was reduced, and the specific capacity was lowered. Meanwhile, it can be seen that the discharge specific capacity of the anode material prepared by the preparation method of the embodiment 1 is highest, because the melamine nano-particles, the lithiated carbon nano-tubes and the polyvinylidene fluoride have synergistic effect, the melamine nano-particles have polar functional groups, can induce electrochemical precipitation of lithium ions, inhibit growth of lithium dendrites, the lithiated carbon nano-tubes can protect lithium, simultaneously provide a channel for transmission of lithium ions, and the polyvinylidene fluoride is used as a binder to bond the melamine nano-particles and the lithiated carbon nano-tubes into a whole.
Comparative example 3
This comparative example differs from example 1 in that melamine nanoparticles are replaced with polyaniline nanoparticles.
The preparation method of the negative electrode material for lithium metal batteries in this comparative example is as follows:
step 1: heating 0.2g of lithium foil at 400 ℃ under the conditions that the water content is less than or equal to 0.01ppm and the oxygen content is less than or equal to 0.01ppm to enable the lithium foil to be in a molten state, and placing 2g of carbon nano tubes on the surface of molten lithium metal until the carbon nano tubes are changed from black to gold to obtain lithiated carbon nano tubes;
step 2: grinding 1g of the lithiated carbon nanotubes obtained in the step 1 and 8g of polyaniline nanoparticles for 1 hour to form a uniform mixture of the lithiated carbon nanotubes and the polyaniline nanoparticles;
step 3: dissolving 1g of polyvinylidene fluoride powder in 100ml of N-methylpyrrolidone solution to form N-methylpyrrolidone solution containing polyvinylidene fluoride;
step 4: adding the mixture of the lithiated carbon nanotubes and polyaniline nano particles obtained in the step 2 into the N-methylpyrrolidone solution with polyvinylidene fluoride obtained in the step 3, and grinding for 2 hours to form uniform slurry;
step 5: uniformly coating the slurry obtained in the step 4 on a copper foil, drying at 60 ℃ for 12 hours to volatilize an N-methyl pyrrolidone solution, and drying at 60 ℃ for 24 hours again to form a layer of film containing polyaniline nano particles, lithiated carbon nano tubes and polyvinylidene fluoride on the copper foil, wherein the thickness of the film is 35 mu m;
step 6: cutting the film obtained in the step 5 into a pole piece shape to obtain a cathode material without lithium;
step 7: the negative electrode material without lithium obtained in the step 6 was subjected to a treatment of 0.2 mA cm -2 Electroplating for 20 hours at the current density of (2) to obtain the lithium-containing surface with the capacity of 4mAh cm -2 Is a negative electrode material of (a).
The full battery composed of the negative electrode material prepared by the method of comparative example 3 and lithium iron phosphate was tested, and the 100 th charge-discharge curve was, as shown in fig. 9, tested at a rate of 0.5C and a test temperature of 25 ℃. As can be seen from the graph, the specific discharge capacity of the anode material prepared by the method of comparative example 3 was 108mAhg -1 。
The full battery composed of the negative electrode material prepared by the preparation method of example 1 and lithium iron phosphate was tested, the test rate was 0.5C, the test temperature was 25℃, and the 100 th charge-discharge curve was shown in FIG. 10, as can be seen from the curve, the specific discharge capacity of the negative electrode material prepared by the preparation method of example 1 was 122 mAhg -1 . From the graphs of both, it can be seen that the discharge specific capacity of the anode material prepared by the method of example 1 is greater than that of the anode prepared by the method of comparative example 3A material.
The full battery composed of the negative electrode material prepared by the preparation method of example 2 and lithium iron phosphate was tested, the test rate was 0.5C, the test temperature was 25 ℃, and the 100 th charge-discharge curve was shown in fig. 11, it can be seen that the discharge specific capacity was reduced to 118 mAhg as the ratio of lithiated carbon nanotubes to polyvinylidene fluoride binder was increased -1 The negative electrode material prepared by the method in example 2 has a discharge specific capacity greater than that of the negative electrode material prepared by the method of comparative example 3, and voltage polarization becomes large, mainly due to the decrease in active sites of lithium ions caused by the decrease in the proportion of melamine nanoparticles.
The full cell composed of the negative electrode material prepared by the preparation method of example 3 and lithium iron phosphate was tested, the test rate was 0.5C, the test temperature was 25℃, and the 100 th charge-discharge curve was shown in fig. 12, it can be seen that the discharge specific capacity was 120 mAhg as the ratio of lithiated carbon nanotubes to polyvinylidene fluoride binder was increased -1 There was a slight increase in voltage polarization compared to example 2, mainly due to the increase in the proportion of lithiated carbon nanotubes, increased lithium ion transport channels inside the electrode, decreased battery internal, and greater specific discharge capacity than the negative electrode material prepared by the method of comparative example 3.
The full battery composed of the negative electrode material prepared by the preparation method of example 4 and lithium iron phosphate was tested, the test rate was 0.5C, the test temperature was 25 ℃, the 100 th charge-discharge curve was shown in FIG. 13, and the specific discharge capacity was 120 mAhg -1 It can be seen that the reduction in electrode thickness, and the voltage polarization, is further reduced mainly due to the reduction in thickness, the reduction in electron and lithium ion transport distance, the reduction in ohmic resistance, and the discharge specific capacity of the negative electrode material prepared by the method of comparative example 3.
The full battery composed of the negative electrode material prepared by the preparation method of example 5 and lithium iron phosphate was tested, the test rate was 0.5C, the test temperature was 25 ℃, the 100 th charge-discharge curve was shown in FIG. 14, and the specific discharge capacity was 112mAhg -1 It can be seen that the thickness of the electrode increases and the voltage polarization becomesThis is mainly due to the increased thickness, increased electron and lithium ion transport distance, increased ohmic resistance, and greater specific discharge capacity than the negative electrode material prepared by the method of comparative example 3.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the application, and is not meant to limit the scope of the application, but to limit the application to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the application are intended to be included within the scope of the application.
Claims (7)
1. The negative electrode material for the lithium metal battery is characterized by comprising melamine nano particles, lithiated carbon nano tubes and polyvinylidene fluoride binder; the mass ratio of the melamine nano particles to the lithiated carbon nano tubes to the polyvinylidene fluoride binder is (4-8): (1-4): (1-2);
the preparation method of the anode material for the lithium metal battery comprises the following steps:
step 1: preparing lithiated carbon nanotubes;
step 2: grinding the lithiated carbon nanotubes and the melamine nanoparticles prepared in the step 1 to form a uniform mixture of the lithiated carbon nanotubes and the melamine nanoparticles;
step 3: dissolving polyvinylidene fluoride powder in N-methyl pyrrolidone solution to form N-methyl pyrrolidone solution containing polyvinylidene fluoride;
step 4: adding the mixture of the uniform lithiated carbon nanotubes and the melamine nanoparticles obtained in the step 2 into the N-methylpyrrolidone solution containing polyvinylidene fluoride prepared in the step 3, and grinding to form uniform slurry;
step 5: uniformly coating the slurry obtained in the step 4 on a copper foil, and then drying to form a layer of film on the copper foil;
step 6: cutting the film obtained in the step 5 into a pole piece shape to obtain a cathode material without lithium;
step 7: and (3) carrying out electroplating treatment on the cathode material which does not contain lithium and is obtained in the step (6).
2. The negative electrode material for lithium metal batteries according to claim 1, wherein the preparation method of the lithiated carbon nanotubes comprises the following steps: and heating the lithium foil to a molten state, and then placing the carbon nano tube on the surface of the molten state lithium metal until the carbon nano tube is changed from black to gold, so as to obtain the lithiated carbon nano tube.
3. The negative electrode material for lithium metal batteries according to claim 2, wherein the lithium foil is heated under conditions of a water content of 0.01ppm or less and an oxygen content of 0.01ppm or less.
4. The negative electrode material for lithium metal batteries according to claim 1, wherein the concentration of polyvinylidene fluoride in the N-methylpyrrolidone solution containing polyvinylidene fluoride in step 3 is 5mg/ml to 15mg/ml.
5. The negative electrode material for lithium metal batteries according to claim 1, wherein the film thickness in step 5 is 30 μm to 100 μm.
6. The negative electrode material for lithium metal batteries according to claim 1, wherein the drying method in step 5 is as follows: drying in a non-vacuum environment to volatilize the N-methyl pyrrolidone solution, and then drying in a vacuum environment.
7. Use of the negative electrode material for lithium metal batteries according to any one of claims 1 to 6 for preparing lithium metal solid-state batteries and lithium metal liquid-state batteries.
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