CN113410437A - Negative electrode surface protection method suitable for solid lithium battery and secondary lithium battery - Google Patents
Negative electrode surface protection method suitable for solid lithium battery and secondary lithium battery Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 28
- 239000007787 solid Substances 0.000 title claims description 12
- 229910052751 metal Inorganic materials 0.000 claims abstract description 40
- 239000002184 metal Substances 0.000 claims abstract description 40
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- 229920000642 polymer Polymers 0.000 claims abstract description 24
- 239000003960 organic solvent Substances 0.000 claims abstract description 22
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 21
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 18
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- 238000001035 drying Methods 0.000 claims abstract description 13
- 239000000758 substrate Substances 0.000 claims abstract description 13
- 239000002131 composite material Substances 0.000 claims abstract description 11
- 238000002791 soaking Methods 0.000 claims abstract description 8
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 claims description 22
- -1 polypropylene carbonate Polymers 0.000 claims description 18
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 claims description 15
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 12
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 10
- 229910010272 inorganic material Inorganic materials 0.000 claims description 10
- 239000011147 inorganic material Substances 0.000 claims description 10
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 9
- 239000002202 Polyethylene glycol Substances 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 6
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 6
- 239000004642 Polyimide Substances 0.000 claims description 5
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 claims description 5
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 5
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- 238000005096 rolling process Methods 0.000 claims description 5
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 4
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 4
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 4
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 4
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 4
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 4
- WNXJIVFYUVYPPR-UHFFFAOYSA-N 1,3-dioxolane Chemical compound C1COCO1 WNXJIVFYUVYPPR-UHFFFAOYSA-N 0.000 claims description 3
- IRPGOXJVTQTAAN-UHFFFAOYSA-N 2,2,3,3,3-pentafluoropropanal Chemical compound FC(F)(F)C(F)(F)C=O IRPGOXJVTQTAAN-UHFFFAOYSA-N 0.000 claims description 3
- KLZUFWVZNOTSEM-UHFFFAOYSA-K Aluminum fluoride Inorganic materials F[Al](F)F KLZUFWVZNOTSEM-UHFFFAOYSA-K 0.000 claims description 3
- 229920000459 Nitrile rubber Polymers 0.000 claims description 3
- 239000002033 PVDF binder Substances 0.000 claims description 3
- BTGRAWJCKBQKAO-UHFFFAOYSA-N adiponitrile Chemical compound N#CCCCCC#N BTGRAWJCKBQKAO-UHFFFAOYSA-N 0.000 claims description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 3
- 229910052593 corundum Inorganic materials 0.000 claims description 3
- 150000003983 crown ethers Chemical class 0.000 claims description 3
- 125000004122 cyclic group Chemical group 0.000 claims description 3
- 150000003949 imides Chemical class 0.000 claims description 3
- 238000005470 impregnation Methods 0.000 claims description 3
- 230000008595 infiltration Effects 0.000 claims description 3
- 238000001764 infiltration Methods 0.000 claims description 3
- 229910000664 lithium aluminum titanium phosphates (LATP) Inorganic materials 0.000 claims description 3
- KTQDYGVEEFGIIL-UHFFFAOYSA-N n-fluorosulfonylsulfamoyl fluoride Chemical compound FS(=O)(=O)NS(F)(=O)=O KTQDYGVEEFGIIL-UHFFFAOYSA-N 0.000 claims description 3
- 229920005569 poly(vinylidene fluoride-co-hexafluoropropylene) Polymers 0.000 claims description 3
- 229920001223 polyethylene glycol Polymers 0.000 claims description 3
- 229920000139 polyethylene terephthalate Polymers 0.000 claims description 3
- 239000005020 polyethylene terephthalate Substances 0.000 claims description 3
- 229920000193 polymethacrylate Polymers 0.000 claims description 3
- 229920000379 polypropylene carbonate Polymers 0.000 claims description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 3
- 229920002635 polyurethane Polymers 0.000 claims description 3
- 239000004814 polyurethane Substances 0.000 claims description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 3
- 235000012239 silicon dioxide Nutrition 0.000 claims description 3
- 239000000377 silicon dioxide Substances 0.000 claims description 3
- 229920001897 terpolymer Polymers 0.000 claims description 3
- 239000004408 titanium dioxide Substances 0.000 claims description 3
- 229910001845 yogo sapphire Inorganic materials 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 2
- 238000007654 immersion Methods 0.000 claims 1
- 210000001787 dendrite Anatomy 0.000 abstract description 10
- 230000001351 cycling effect Effects 0.000 abstract description 7
- 230000008569 process Effects 0.000 abstract description 7
- 238000007086 side reaction Methods 0.000 abstract description 4
- 238000007599 discharging Methods 0.000 abstract description 2
- 230000002401 inhibitory effect Effects 0.000 abstract 1
- 238000009736 wetting Methods 0.000 description 13
- 239000002904 solvent Substances 0.000 description 7
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 230000008021 deposition Effects 0.000 description 4
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- 239000010410 layer Substances 0.000 description 2
- 150000002641 lithium Chemical class 0.000 description 2
- 229910003473 lithium bis(trifluoromethanesulfonyl)imide Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000009257 reactivity Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000007614 solvation Methods 0.000 description 2
- 239000002841 Lewis acid Substances 0.000 description 1
- 229910013553 LiNO Inorganic materials 0.000 description 1
- MHABMANUFPZXEB-UHFFFAOYSA-N O-demethyl-aloesaponarin I Natural products O=C1C2=CC=CC(O)=C2C(=O)C2=C1C=C(O)C(C(O)=O)=C2C MHABMANUFPZXEB-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 230000008859 change Effects 0.000 description 1
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- 239000002608 ionic liquid Substances 0.000 description 1
- 150000007517 lewis acids Chemical class 0.000 description 1
- DEUISMFZZMAAOJ-UHFFFAOYSA-N lithium dihydrogen borate oxalic acid Chemical compound B([O-])(O)O.C(C(=O)O)(=O)O.C(C(=O)O)(=O)O.[Li+] DEUISMFZZMAAOJ-UHFFFAOYSA-N 0.000 description 1
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- 239000000126 substance Substances 0.000 description 1
- 238000010023 transfer printing Methods 0.000 description 1
- NDZWKTKXYOWZML-UHFFFAOYSA-N trilithium;difluoro oxalate;borate Chemical compound [Li+].[Li+].[Li+].[O-]B([O-])[O-].FOC(=O)C(=O)OF NDZWKTKXYOWZML-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- 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
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/381—Alkaline or alkaline earth metals elements
- H01M4/382—Lithium
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a method for protecting the surface of a negative electrode of a solid-state lithium battery and a secondary lithium battery, which comprises the following steps: adding the polymer or the composite material into an organic solvent to prepare a film solution; coating the film solution on the surface of a substrate, volatilizing and drying for a period of time to obtain a polymer film; transferring the polymer film to the surface of a lithium metal negative electrode; sequentially adding lithium salt and an additive into an organic solvent according to a certain proportion to prepare a soaking solution; and coating the impregnating solution on the metal lithium cathode with the surface covered with the polymer film, after soaking for a period of time, removing the redundant impregnating solution on the metal lithium cathode, and drying for a period of time to obtain the protective layer. The method has the advantages of effectively inhibiting interface side reaction, homogenizing the current density on the surface of the lithium metal cathode, improving the generation condition of lithium dendrite in the charging and discharging process and improving the cycling stability of the lithium metal cathode.
Description
Technical Field
The invention belongs to the technical field of lithium battery cathode surface protection, and particularly relates to a cathode surface protection method suitable for a solid-state lithium battery and a secondary lithium battery.
Background
With the increasing demand for energy density of batteries for electronic devices, electric tools, electric vehicles, and the like, the energy density of lithium ion batteries using graphite materials as negative electrodes has approached the theoretical upper limit. The metallic lithium cathode has become one of the most promising high specific energy lithium ion battery cathode materials due to its high specific capacity (3861mAh/g) and lowest electrochemical potential (-3.04V).
The core problem of limiting the application of the metal lithium in the high specific energy battery at present is that dead lithium and lithium dendrite generated by a metal lithium cathode in the using process of the battery can cause the problems of reduction of coulombic efficiency, shortened cycle life, poor safety performance and the like of the battery. The main reason for the formation of dead lithium and lithium dendrites is the negative electrode surface lithium ions (Li) during charge and discharge+) The uneven deposition causes the current density distribution on the surface of the electrode to be uneven, lithium dendrites are formed on a plurality of nucleation sites by lithium ions, and the volume effect of the lithium ions in the deposition/dissolution process causes the problems of internal stress change of metal lithium, unstable negative electrode interface, negative electrode pulverization and the like. In addition, dead lithium is formed when minute lithium filaments formed at the nucleation sites are detached from the electrode surface, resulting in loss of a lithium source in the battery, capacity fade, decreased cycle life and increased safety problems; and the deterioration of cycle performance is further aggravated by the additional consumption of electrolyte due to lithium dendrites. Electrochemical on interface, Li+OfAfter the detail study of the bulk deposition behavior and the characteristics of the metallic lithium material, the main solution strategy at present is to suppress lithium dendrites through an artificial SEI film, adjust the current density on the surface of a negative electrode to induce uniform deposition of lithium, and combine the lithium and the negative electrode.
Disclosure of Invention
The invention aims to provide a method for protecting the surface of a negative electrode of a solid lithium battery and a secondary lithium battery, which effectively solves the problems that the coulombic efficiency of the battery is reduced, the cycle life is shortened, the safety performance is deteriorated and the like caused by the fact that side reactions are easily generated after the surface of a metal lithium negative electrode is contacted with an electrolyte and lithium dendrites are generated on the surface; and the problems that the loss of a lithium source in the battery, capacity attenuation, cycle life reduction and safety performance deterioration are caused because dead lithium is formed after micro lithium wires formed at nucleation sites are separated from the surface of an electrode are solved.
In order to solve the technical problems, the invention adopts the technical scheme that: a method for protecting the surface of a negative electrode suitable for a solid-state lithium battery and a secondary lithium battery, comprising:
adding the polymer or the composite material into an organic solvent to prepare a film solution;
coating the film solution on the surface of a substrate, volatilizing and drying to obtain a polymer film;
transferring the polymer film to the surface of a lithium metal negative electrode;
sequentially adding lithium salt and an additive into an organic solvent according to a certain proportion to prepare a soaking solution;
and coating the impregnating solution on the metal lithium cathode with the surface covered with the polymer film for infiltration, removing the redundant impregnating solution on the metal lithium cathode, and drying to obtain the protective layer.
Preferably, the composite material is formed by mixing a polymer and an inorganic material according to a certain proportion, wherein the mass ratio of the polymer to the inorganic material is 3: 97-97: 3.
preferably, after the film solution is coated on the surface of the substrate, the organic solvent is volatilized at the temperature of 30-80 ℃, then the drying is carried out for 4-12h under the conditions of vacuum and the temperature of 40-80 ℃ to obtain the polymer film, and the polymer film is transferred to the surface of the lithium metal negative electrode in a roll-to-roll rolling manner.
Preferably, in the step of sequentially adding a lithium salt and an additive into an organic solvent according to a certain proportion to prepare the impregnating solution, the mass ratio of the lithium salt to the additive is 5:1-2: 1.
Preferably, the impregnating solution is coated on the metal lithium cathode of which the surface is covered with the polymer film, then the metal lithium cathode is placed in vacuum at the temperature of 20-45 ℃ to promote impregnation, after the impregnating solution is impregnated into the polymer film, the redundant impregnating solution on the surface of the metal lithium cathode is removed at the temperature of 30-80 ℃, and then the metal lithium cathode is placed in vacuum at the temperature of 40-60 ℃ to be dried for 4-12 hours to obtain the protective layer.
More preferably, the inorganic material is LATP, LAGP, LLZO, LLZTO, LPS, LGPS, titanium dioxide, Al2O3And silicon dioxide.
More preferably, the polymer is one or more of crown ether polymer, ethylene glycol dimethyl ether terpolymer, ethylene glycol dimethyl ether tetramer, polyethylene glycol, polyethylene oxide, modified polyethylene oxide, polypropylene carbonate, nitrile rubber, polyacrylonitrile, polymethacrylate, polyurethane, PVDF and PVDF-HFP.
More preferably, the organic solvent in the film solution and the impregnating solution is one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran, acetone, acetonitrile, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate and ethylene glycol dimethyl ether.
More preferably, the substrate is one or more of polyimide, polyethylene terephthalate, polytetrafluoroethylene and release paper.
More preferably, the lithium salt is imide lithium salt, such as one or more of bis (trifluoromethanesulfonyl) imide lithium, bis (fluorosulfonyl) imide lithium, cyclic imide lithium, lithium hexafluorophosphate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate and lithium nitrate; the additive is one or more of 1, 3-dioxolane, polymethylsiloxane, fluoroethylene carbonate, aluminum fluoride and adiponitrile.
According to the technical scheme, a polymer which is stable relative to metal lithium or a composite material formed by mixing the polymer and an inorganic material is mixed with an organic solvent to form a film solution, the film solution is volatilized and dried to obtain a polymer film, the polymer film is attached to the surface of a metal lithium cathode through a transfer printing process, and then a wetting solution consisting of a high-concentration lithium salt, an additive and a solvent is prepared and coated on the surface of the polymer film. Utilizes lone pair electrons in polymer molecule and Li in lithium salt+Coordinating to obtain weak Lewis acid complex cation, and combining with weak Lewis basic anion to obtain compound with high thermal stability, low volatility, low flammability and high ionic conductivity, so as to inhibit side reaction of negative electrode interface, improve growth condition of lithium dendrite, and inhibit growth of lithium dendrite by utilizing concentration gradient of high-concentration lithium salt on the surface of the metal lithium negative electrode; solvent molecules in the impregnating solution are all mixed with Li under the solvation effect+Complexing ensures that no free solvent molecules can volatilize in the whole protective layer, reduces the reactivity of the impregnating solution to Li metal, and avoids the risks of leakage and gas generation of the battery.
Drawings
FIG. 1 is a schematic view of a surface protection layer of a lithium metal negative electrode according to an embodiment of the present invention
FIG. 2 is a schematic diagram illustrating the comparison of the cycling stability of a protected lithium metal anode and an unprotected modified lithium metal anode in a symmetric battery according to an embodiment of the present invention
FIG. 3 is a schematic diagram showing the comparison of the cycling stability of a protected lithium metal cathode and an unprotected modified lithium metal cathode in a button half cell according to an embodiment of the present invention
In the figure:
1. metallic lithium negative electrode 2, protective layer
Detailed Description
The invention is further illustrated by the following examples and figures:
in the description of the embodiments of the present invention, it should be understood that the terms "top," "bottom," and the like refer to orientations and positional relationships illustrated in the drawings, which are used for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated, and thus should not be construed as limiting the present invention.
As shown in fig. 1, a schematic diagram of a surface protection layer of a lithium metal negative electrode, a method for protecting a surface of a negative electrode suitable for a solid-state lithium battery and a secondary lithium battery includes:
preparing a film solution: adding a polymer into an organic solvent to prepare a film solution; the polymer is selected from one or more of crown ether polymer, ethylene glycol dimethyl ether terpolymer, ethylene glycol dimethyl ether tetramer, polyethylene glycol, polyethylene oxide, modified polyethylene oxide, polypropylene carbonate, nitrile rubber, polyacrylonitrile, polymethacrylate, polyurethane, PVDF and PVDF-HFP, and is directly mixed with an organic solvent to obtain a film solution.
In some possible embodiments, the composite material is added into an organic solvent to be mixed into a film solution, wherein the composite material is formed by mixing a polymer and an inorganic material according to a certain ratio, and the mass ratio of the polymer to the inorganic material is 3: 97-97: 3. the polymer is selected from the same materials as the above polymer, and the inorganic materials are LATP, LAGP, LLZO, LLZTO, LPS, LGPS, titanium dioxide, and Al2O3And silicon dioxide.
The organic solvent can be one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran, acetone, acetonitrile, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate and ethylene glycol dimethyl ether, and the polymer or the composite material is added into the organic solvent to obtain the film solution.
Coating the film solution on the surface of a substrate, volatilizing and drying for a period of time to obtain a polymer film; after the film solution is coated on the surface of a substrate, volatilizing the organic solvent at the temperature of 30-80 ℃, and drying for 4-12h at the temperature of 40-80 ℃ in vacuum to obtain the polymer film, wherein the thickness of the polymer film is less than or equal to 15 mu m.
The substrate can be selected from one or more of polyimide, polyethylene terephthalate, polytetrafluoroethylene and release paper.
Transfer polymer film: the polymer film is transferred from the substrate to the surface of the lithium metal anode 1 by roll-to-roll rolling.
Preparing an impregnating solution: sequentially adding lithium salt and an additive into an organic solvent according to a certain proportion to prepare a soaking solution; wherein the mass ratio of the lithium salt to the additive is 5:1-2: 1.
The lithium salt can be selected from imide lithium salt, such as one or more of bis (trifluoromethanesulfonyl) imide lithium, bis (fluorosulfonyl) imide lithium, cyclic imide lithium, lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate and lithium nitrate; the additive can be one or more selected from 1, 3-dioxolane, polymethylsiloxane, fluoroethylene carbonate, aluminum fluoride and adiponitrile; the organic solvent can be one or more selected from N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran, acetone, acetonitrile, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate and ethylene glycol dimethyl ether, and the lithium salt and the additive are sequentially added into the organic solvent and mixed to obtain the impregnation liquid.
Preparing a protective layer: and coating the wetting solution on the metal lithium cathode 1 with the surface covered with the polymer film, removing the redundant wetting solution on the metal lithium cathode 1 after wetting for a period of time, and drying for a period of time to obtain the protective layer 2. The method comprises the steps of coating a polymer film on the surface of a lithium metal cathode 1 with a wetting solution, then placing the lithium metal cathode 1 in vacuum at a temperature of 20-45 ℃ to promote wetting, removing the redundant wetting solution on the surface of the lithium metal cathode 1 at a temperature of 30-80 ℃ after the wetting solution is soaked in the polymer film, and then placing in vacuum at a temperature of 40-60 ℃ to dry for 4-12 hours to obtain a protective layer 2.
The lithium salt in the impregnating solution is combined with the polymer in the polymer film in a certain proportion, and lone pair electrons in polymer molecules and Li in the lithium salt are utilized+Coordination can obtain weak Lewis acidThe complex cation is combined with weak Lewis basic anion to obtain the ionic liquid-like compound with similar physical and chemical properties to the traditional ionic liquid. Solvent molecules in the impregnating solution are complexed with the ionic liquid-like compound under the solvation effect, so that no free solvent molecules in the whole protective layer 2 can volatilize, the reactivity of the impregnating solution to Li metal is reduced, and the risks of leakage and gas generation of the battery are avoided.
Several specific examples are listed below:
example 1
In the embodiment, all preparation processes are carried out in a dry environment, and the dew point is less than or equal to 45 ℃.
Preparation of a polymer film: adding 10.5g of PEO into 25g of acetonitrile to prepare a film solution, coating the film solution on the bottom surface of a polyimide base, volatilizing the solvent at 80 ℃, and drying the film for 12 hours at 60 ℃ under a vacuum condition to obtain a PEO polymer film with the thickness of 12 mu m.
Transfer polymer film: the polymer film is then transferred from the substrate to the surface of the lithium metal anode 1 by roll-to-roll rolling.
Preparing an impregnating solution: 13g of LiTFSI and 7g of DOL are sequentially added into 4g of THF and 4g of DME to prepare a soaking solution.
Preparing a protective layer 2: the method comprises the steps of coating the surface of a metal lithium cathode 1 coated with a PEO polymer film with an impregnating solution by adopting a micro-gravure coating process, adjusting the tape speed, the air speed and the temperature of an oven, then placing the metal lithium cathode 1 in vacuum at the temperature of 20 ℃ to promote infiltration, removing the redundant impregnating solution on the surface of the metal lithium cathode 1 at the temperature of 30 ℃ after the impregnating solution is completely infiltrated into the film, and drying the metal lithium cathode 1 at the temperature of 60 ℃ for 12 hours to obtain a protective layer 2.
Example 2
In the embodiment, all preparation processes are carried out in a dry environment, and the dew point is less than or equal to 45 ℃.
Preparation of a polymer film: 4.66g PAN and 6g LLZTO are sequentially added into 20g DMAC to prepare a film solution, the film solution is coated on the bottom surface of the polyimide base, the solvent is volatilized at the temperature of 80 ℃, and then the film is dried in vacuum at the temperature of 60 ℃ for 12h to obtain the PAN and LLZTO composite polymer film (the thickness is 8 mu m).
Transfer polymer film: and then the composite film is transferred from the substrate to the surface of the lithium metal negative electrode 1 in a roll-to-roll rolling mode.
Preparing an impregnating solution: 10g of LiTFSI and 2.8g of LiNO were mixed3And 7g of DOL are sequentially added into 3g of DEC and 4g of DME to prepare a soaking solution.
Preparing a protective layer 2: the method comprises the steps of coating the wetting solution on the metal lithium cathode 1 with the polymer film covered on the surface by adopting an extrusion process, wherein the used coating equipment is modified to have a vacuum function, the metal lithium cathode 1 coated with the wetting solution is firstly placed under a vacuum condition of 35 ℃ to promote wetting, after the wetting solution is soaked in the polymer film, the redundant wetting solution on the surface of the metal lithium cathode 1 is firstly removed at a temperature of 80 ℃, and then the metal lithium cathode is wound and transferred into a vacuum oven to be dried at a temperature of 60 ℃ to obtain the protective layer 2.
As can be seen from a comparison schematic diagram of the cycling stability of the protected metal lithium cathode and the unprotected modified metal lithium cathode in the symmetric battery in fig. 2 and a comparison schematic diagram of the cycling stability of the protected metal lithium cathode and the unprotected modified metal lithium cathode in the button-type half battery in fig. 3, the metal lithium cathode with the protective layer on the surface is more stable in the battery cycling of the symmetric battery and the button-type half battery, so that the interface side reaction can be more effectively inhibited, the current density on the surface of the metal lithium cathode 1 is uniform, the generation condition of lithium dendrite in the charging and discharging process is improved, and the cycling stability of the metal lithium cathode is improved.
The embodiments of the present invention have been described in detail, but the description is only for the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.
Claims (10)
1. A method for protecting the surface of a negative electrode suitable for a solid-state lithium battery and a secondary lithium battery, comprising:
adding the polymer or the composite material into an organic solvent to prepare a film solution;
coating the film solution on the surface of a substrate, volatilizing and drying to obtain a polymer film;
transferring the polymer film to the surface of a lithium metal negative electrode;
sequentially adding lithium salt and an additive into an organic solvent according to a certain proportion to prepare a soaking solution;
and coating the impregnating solution on the metal lithium cathode with the surface covered with the polymer film for infiltration, removing the redundant impregnating solution on the metal lithium cathode, and drying to obtain the protective layer.
2. The method for protecting a surface of a negative electrode for a solid state lithium battery and a secondary lithium battery according to claim 1, wherein: the composite material is formed by mixing a polymer and an inorganic material according to a certain proportion, wherein the mass ratio of the polymer to the inorganic material is 3: 97-97:3.
3. The method for protecting a surface of a negative electrode for a solid state lithium battery and a secondary lithium battery according to claim 1, wherein: after the film solution is coated on the surface of a substrate, volatilizing the organic solvent at the temperature of 30-80 ℃, drying for 4-12h at the temperature of 40-80 ℃ in vacuum to obtain the polymer film, and transferring the polymer film to the surface of the metal lithium cathode in a roll-to-roll rolling manner.
4. The method for protecting a surface of a negative electrode for a solid state lithium battery and a secondary lithium battery according to claim 1, wherein: adding lithium salt and an additive into an organic solvent in sequence according to a certain proportion to prepare a soaking solution, wherein the mass ratio of the lithium salt to the additive is 5:1-2: 1.
5. The method for protecting a surface of a negative electrode for a solid state lithium battery and a secondary lithium battery according to claim 1, wherein: coating the impregnating solution on the metal lithium cathode with the polymer film covered on the surface, then placing the metal lithium cathode in vacuum at the temperature of 20-45 ℃ to promote impregnation, removing the redundant impregnating solution on the surface of the metal lithium cathode at the temperature of 30-80 ℃ after the impregnating solution is impregnated into the polymer film, and then placing in vacuum at the temperature of 40-60 ℃ to dry for 4-12h to obtain the protective layer.
6. The method for protecting a surface of a negative electrode for a lithium solid state battery and a lithium secondary battery according to claim 2, wherein: the inorganic material is LATP, LAGP, LLZO, LLZTO, LPS, LGPS, titanium dioxide, Al2O3And silicon dioxide.
7. The method for protecting a surface of a negative electrode for a solid state lithium battery and a secondary lithium battery as claimed in any one of claims 1 to 5, wherein: the polymer is one or more of crown ether polymer, ethylene glycol dimethyl ether terpolymer, ethylene glycol dimethyl ether tetramer, polyethylene glycol, polyethylene oxide, modified polyethylene oxide, polypropylene carbonate, nitrile rubber, polyacrylonitrile, polymethacrylate, polyurethane, PVDF and PVDF-HFP.
8. The method for protecting a surface of a negative electrode for a solid state lithium battery and a secondary lithium battery as claimed in any one of claims 1 to 5, wherein: the film solution and the organic solvent in the immersion liquid are one or more of N-methyl pyrrolidone, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran, acetone, acetonitrile, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate and ethylene glycol dimethyl ether.
9. The method for protecting a surface of a negative electrode for a solid state lithium battery and a secondary lithium battery as claimed in any one of claims 1 to 5, wherein: the substrate is one or more of polyimide, polyethylene terephthalate, polytetrafluoroethylene and release paper.
10. The method for protecting a surface of a negative electrode for a solid state lithium battery and a secondary lithium battery as claimed in any one of claims 1 to 5, wherein: the lithium salt is imide lithium salt, such as one or more of bis (trifluoromethanesulfonyl) imide lithium, bis (fluorosulfonyl) imide lithium, cyclic imide lithium, lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate and lithium nitrate; the additive is one or more of 1, 3-dioxolane, polymethylsiloxane, fluoroethylene carbonate, aluminum fluoride and adiponitrile.
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