CN114725500A - Polymer composite solid electrolyte and preparation method thereof - Google Patents
Polymer composite solid electrolyte and preparation method thereof Download PDFInfo
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- CN114725500A CN114725500A CN202210372709.9A CN202210372709A CN114725500A CN 114725500 A CN114725500 A CN 114725500A CN 202210372709 A CN202210372709 A CN 202210372709A CN 114725500 A CN114725500 A CN 114725500A
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- lithium
- polyvinyl formal
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- solid electrolyte
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- 229920000642 polymer Polymers 0.000 title claims abstract description 178
- 239000007784 solid electrolyte Substances 0.000 title claims abstract description 92
- 239000002131 composite material Substances 0.000 title claims abstract description 57
- 238000002360 preparation method Methods 0.000 title abstract description 13
- 229920002554 vinyl polymer Polymers 0.000 claims abstract description 162
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 60
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 58
- 239000000463 material Substances 0.000 claims abstract description 38
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 29
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 29
- RJEIKIOYHOOKDL-UHFFFAOYSA-N [Li].[La] Chemical compound [Li].[La] RJEIKIOYHOOKDL-UHFFFAOYSA-N 0.000 claims abstract description 28
- 239000002033 PVDF binder Substances 0.000 claims abstract description 27
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims abstract description 27
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 69
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 42
- 238000003756 stirring Methods 0.000 claims description 40
- 238000000034 method Methods 0.000 claims description 28
- 238000002156 mixing Methods 0.000 claims description 27
- UPMLOUAZCHDJJD-UHFFFAOYSA-N 4,4'-Diphenylmethane Diisocyanate Chemical compound C1=CC(N=C=O)=CC=C1CC1=CC=C(N=C=O)C=C1 UPMLOUAZCHDJJD-UHFFFAOYSA-N 0.000 claims description 25
- 239000002002 slurry Substances 0.000 claims description 24
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims description 23
- 239000004327 boric acid Substances 0.000 claims description 23
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 23
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 23
- 235000006408 oxalic acid Nutrition 0.000 claims description 23
- 239000011259 mixed solution Substances 0.000 claims description 22
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 claims description 21
- 239000000243 solution Substances 0.000 claims description 20
- 239000011248 coating agent Substances 0.000 claims description 16
- 238000000576 coating method Methods 0.000 claims description 16
- 238000001035 drying Methods 0.000 claims description 16
- 239000003960 organic solvent Substances 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 239000011268 mixed slurry Substances 0.000 claims description 10
- 239000011521 glass Substances 0.000 claims description 9
- -1 lithium tetrafluoroborate Chemical compound 0.000 claims description 9
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- 150000003949 imides Chemical class 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 8
- 239000002994 raw material Substances 0.000 claims description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 7
- 238000003760 magnetic stirring Methods 0.000 claims description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 6
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 6
- 238000004108 freeze drying Methods 0.000 claims description 6
- ZCSHNCUQKCANBX-UHFFFAOYSA-N lithium diisopropylamide Chemical compound [Li+].CC(C)[N-]C(C)C ZCSHNCUQKCANBX-UHFFFAOYSA-N 0.000 claims description 6
- 238000001556 precipitation Methods 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 238000007711 solidification Methods 0.000 claims description 5
- 230000008023 solidification Effects 0.000 claims description 5
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 4
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 4
- FWLUTJHBRZTAMP-UHFFFAOYSA-N B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+] Chemical compound B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.B([O-])([O-])F.[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+].[Li+] FWLUTJHBRZTAMP-UHFFFAOYSA-N 0.000 claims description 3
- 229910001500 lithium hexafluoroborate Inorganic materials 0.000 claims description 3
- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 claims description 3
- 229910001486 lithium perchlorate Inorganic materials 0.000 claims description 3
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 claims description 3
- LCLRSXLTUQFGEC-UHFFFAOYSA-N lithium;1,2,3,4,5-pentamethylcyclopenta-1,3-diene Chemical compound [Li].CC1C(C)=C(C)C(C)=C1C LCLRSXLTUQFGEC-UHFFFAOYSA-N 0.000 claims description 3
- XKLXIRVJABJBLQ-UHFFFAOYSA-N lithium;2-(trifluoromethyl)-1h-imidazole-4,5-dicarbonitrile Chemical compound [Li].FC(F)(F)C1=NC(C#N)=C(C#N)N1 XKLXIRVJABJBLQ-UHFFFAOYSA-N 0.000 claims description 3
- UBJFKNSINUCEAL-UHFFFAOYSA-N lithium;2-methylpropane Chemical compound [Li+].C[C-](C)C UBJFKNSINUCEAL-UHFFFAOYSA-N 0.000 claims description 3
- UTLRZTUJSMCBHB-UHFFFAOYSA-M lithium;3-oxobutanoate Chemical compound [Li+].CC(=O)CC([O-])=O UTLRZTUJSMCBHB-UHFFFAOYSA-M 0.000 claims description 3
- 230000001376 precipitating effect Effects 0.000 claims description 2
- 238000009777 vacuum freeze-drying Methods 0.000 claims description 2
- 239000007787 solid Substances 0.000 abstract description 38
- 239000011159 matrix material Substances 0.000 abstract description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 38
- 229910001416 lithium ion Inorganic materials 0.000 description 38
- 239000002245 particle Substances 0.000 description 21
- 230000000052 comparative effect Effects 0.000 description 19
- 239000010416 ion conductor Substances 0.000 description 13
- 230000005540 biological transmission Effects 0.000 description 10
- 210000001787 dendrite Anatomy 0.000 description 10
- 239000000203 mixture Substances 0.000 description 9
- 230000009286 beneficial effect Effects 0.000 description 6
- 239000013310 covalent-organic framework Substances 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- SMBQBQBNOXIFSF-UHFFFAOYSA-N dilithium Chemical compound [Li][Li] SMBQBQBNOXIFSF-UHFFFAOYSA-N 0.000 description 4
- 238000010494 dissociation reaction Methods 0.000 description 4
- 230000005593 dissociations Effects 0.000 description 4
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical group [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000005518 polymer electrolyte Substances 0.000 description 4
- 229920006254 polymer film Polymers 0.000 description 4
- 230000002195 synergetic effect Effects 0.000 description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical group [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 3
- DHKHKXVYLBGOIT-UHFFFAOYSA-N acetaldehyde Diethyl Acetal Natural products CCOC(C)OCC DHKHKXVYLBGOIT-UHFFFAOYSA-N 0.000 description 3
- 125000002777 acetyl group Chemical class [H]C([H])([H])C(*)=O 0.000 description 3
- 238000010382 chemical cross-linking Methods 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 125000004430 oxygen atom Chemical group O* 0.000 description 3
- 229920006324 polyoxymethylene Polymers 0.000 description 3
- 229910000846 In alloy Inorganic materials 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000000498 ball milling Methods 0.000 description 2
- 239000006229 carbon black Substances 0.000 description 2
- 210000004027 cell Anatomy 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- LHJOPRPDWDXEIY-UHFFFAOYSA-N indium lithium Chemical compound [Li].[In] LHJOPRPDWDXEIY-UHFFFAOYSA-N 0.000 description 2
- 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 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 239000002861 polymer material Substances 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000015271 coagulation Effects 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 235000019441 ethanol Nutrition 0.000 description 1
- RTZKZFJDLAIYFH-UHFFFAOYSA-N ether Substances CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 238000001879 gelation Methods 0.000 description 1
- 238000001453 impedance spectrum Methods 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 239000005486 organic electrolyte Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 229910001251 solid state electrolyte alloy Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- 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
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0065—Solid electrolytes
- H01M2300/0082—Organic polymers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0085—Immobilising or gelification of electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0088—Composites
- H01M2300/0091—Composites in the form of mixtures
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention discloses a polymer composite solid electrolyte and a preparation method thereof, and relates to the technical field of solid electrolytes, wherein the polymer composite solid electrolyte comprises a lithiated polyvinyl formal polymer, a lithium salt, polyvinylidene fluoride, a porous organic covalent material and lanthanum lithium zirconate, and the mass ratio of the lithiated polyvinyl formal polymer to the lithium salt to the polyvinylidene fluoride to the porous organic covalent material to the lanthanum lithium zirconate is 50-70: 5-10: 1-5: 3-5: 10-30. Compared with pure polyvinyl formal solid electrolyte, the polymer composite solid electrolyte adopting the multi-component matrix can not only remarkably improve the room-temperature conductivity and mechanical elasticity of the solid electrolyte, but also greatly improve the rate discharge performance and cycle life of the all-solid lithium battery.
Description
Technical Field
The invention relates to the technical field of solid electrolytes, in particular to a polymer composite solid electrolyte and a preparation method thereof.
Background
At present, the lithium-ion secondary battery has the advantages of high working voltage, long cycle life, small environmental pollution and the like, and becomes a green chemical energy source with very common application. A new generation of high-specific-energy lithium battery is the development direction of future energy storage devices, but because the high-energy-density lithium battery uses organic electrolyte, a series of potential safety hazards such as easy liquid leakage, ignition and explosion exist, and the application of the secondary battery in the field of long-cycle and high-safety energy storage is severely limited. In order to solve these problems, some all-solid-state electrolytes for lithium ion batteries have been developed in succession. Among solid electrolytes, Solid Polymer Electrolytes (SPEs) have advantages of no electrolyte leakage, low flammability, good flexibility, easy processing, and the like, and are widely used.
Among the materials for preparing Solid Polymer Electrolytes (SPEs), polyvinyl formal (PVFM) polymers have the advantages of low crystallinity, good film-forming property, adjustable intramolecular structure and the like, and the contained ether cyclic groups have high solubility and good lithium salt resolution, so that the PVFM polymers become ideal materials for preparing Solid Polymer Electrolytes (SPEs). For example, chinese patent document, granted publication No. CN103804892B, application No. CN201310231733.1, a method for preparing the same, and an application thereof in a gel polymer electrolyte disclose that gelation of a polyvinyl acetal polymer PVFM system is achieved by adsorbing a swelling electrolyte, mechanical properties and compatibility with an electrode are improved, and safety of a solid battery is improved. And chinese patent publication No. CN101176233A, application No. CN200680016615.7, which discloses improvement of electrolyte leakage and battery performance by polymerization using polyvinyl acetal alcohol and its derivatives. However, the polyvinyl acetal (PVFM) polymer solid electrolyte prepared in these patent documents has the problems of single material and low conductivity of the solid electrolyte at room temperature, which is not favorable for optimizing the performance of the solid electrolyte and the solid battery, and further affects the rate discharge performance and cycle life of the all-solid lithium battery.
Disclosure of Invention
1. Technical problem to be solved by the invention
Aiming at the technical problems of single material and low room temperature conductivity of a solid electrolyte prepared based on a polyvinyl formal (PVFM) polymer in the prior art, the invention provides a polymer composite solid electrolyte and a preparation method thereof, which can obviously improve the room temperature conductivity and mechanical elasticity of the solid electrolyte, and greatly improve the rate discharge performance and cycle life of an all-solid lithium battery.
2. Technical scheme
In order to solve the problems, the technical scheme provided by the invention is as follows:
a polymer composite solid electrolyte comprises a lithiated polyvinyl formal polymer, a lithium salt, polyvinylidene fluoride, a porous organic covalent material and lanthanum lithium zirconate, wherein the mass ratio of the lithiated polyvinyl formal polymer to the lithium salt to the polyvinylidene fluoride to the porous organic covalent material to the lanthanum lithium zirconate is 50-70: 5-10: 1-5: 3-5: 10-30.
According to the application, by utilizing the synergistic effect of the components of the lithiated polyvinyl formal polymer, the lithium salt, the polyvinylidene fluoride, the porous organic covalent material and the lanthanum lithium zirconate, the room-temperature conductivity and the mechanical elasticity of the solid electrolyte can be obviously improved, and the rate discharge performance and the cycle life of the all-solid lithium battery are greatly improved. The lithiated polyvinyl formal polymer can be used as a single lithium ion conductor and is compounded with lithium salt to form a dilithium polymer, and a lithium source is added; meanwhile, the added porous organic covalent material is taken as a proton-philic material, has excellent affinity with lithium ions, and has high specific surface area, so that the addition of the porous organic covalent material can accelerate the further dissociation of the lithium ions in the lithiated polyvinyl formal polymer and obviously enhance the transmission channel of the lithium ions, thereby obviously reducing the interface internal resistance; in addition, the addition of the polyvinylidene fluoride can effectively improve the mechanical elasticity of the polymer film layer, increase the film layer stability and the surface smoothness in the circulating process, and the lanthanum lithium zirconate is used as an excellent lithium ion conductor, so that the mechanical strength and the lithium ion transmission performance of the polymer solid electrolyte can be further enhanced. Therefore, compared with pure polyvinyl formal solid electrolyte, the polymer composite solid electrolyte adopting the multi-component matrix can not only remarkably improve the room-temperature conductivity and mechanical elasticity of the solid electrolyte, but also greatly improve the rate discharge performance and cycle life of the all-solid lithium battery.
Optionally, the raw materials of the lithiated polyvinyl formal polymer include polyvinyl formal polymer, dimethyl sulfoxide, boric acid, lithium carbonate and oxalic acid; wherein the mass ratio of the polyvinyl formal polymer to the dimethyl sulfoxide is 0.5-1: 8-12; the molar ratio of the boric acid to the lithium carbonate to the oxalic acid is 0.8-1.0: 0.5-1.5: 1.5-2.0. The mechanical elasticity and the lithium dendrite resistance of the polyvinyl formal can be improved by adopting the polyvinyl formal polymer, the improvement of the cycle life and the safety of a solid battery are facilitated, meanwhile, the polyvinyl formal polymer is dissolved in dimethyl sulfoxide and gradually reacts with boric acid, lithium carbonate and oxalic acid to form a polyvinyl acetal polymer as a main chain, a lithium monoacetate structure is directly grafted on a polymer molecular chain to realize chemical crosslinking, and the conduction of lithium ions is realized by utilizing the coordination process and the de-coordination process between an oxygen atom group contained on the polymer main chain and a boron atom group in the lithium monoacetate structure on the side chain, so that the lithiated polyvinyl formal polymer can be used as a single lithium ion conductor, and the conductivity of a solid electrolyte is improved.
Optionally, the raw materials of the polyvinyl formal polymer include polyvinyl formal and 4, 4 '-diphenylmethane diisocyanate, and the concentrations of the polyvinyl formal and the 4, 4' -diphenylmethane diisocyanate are 0.5-4.5mol/L and 0.05-0.5mol/L, respectively. Compared with polyvinyl formal, the polyvinyl formal polymer prepared by adopting the raw materials with the concentration setting has very high molecular weight, and the improvement of the molecular weight is beneficial to improving the mechanical elasticity and the lithium dendrite resistance of the polyvinyl formal and improving the cycle life and the safety of a solid battery.
Optionally, the molecular weight of the polyvinyl formal is 50000-70000, and the molecular weight of the polyvinyl formal polymer is 200000-500000. Generally, if the molecular weight of the polyvinyl formal polymer is lower than 200000, the viscosity of the material is too high, which significantly increases the difficulty of assembling the solid battery and increases the manufacturing cost; if the hardness is higher than 500000, the hardness of the polyvinyl formal polymer material is too high, so that the brittleness of the polymer composite solid electrolyte membrane is high, the contact performance with the positive and negative electrode interfaces is reduced, and the safety problem of the battery is caused. The molecular weight of the polyvinyl formal polymer is 200000-500000, so that the mechanical elasticity and lithium dendrite resistance of the solid electrolyte are ensured.
Optionally, the lithium salt is selected from one or more of lithium bistrifluoromethanesulfonylimide, lithium bistrifolimate, lithium bisoxalatoborate, lithium tetrafluoroborate, lithium hexafluoroborate, lithium perchlorate, lithium difluorobisoxalatoborate, lithium triethylborohydride, lithium diisopropylamide, lithium acetoacetate, lithium bistrimethylsilyl, lithium pentamethylcyclopentadiene, lithium 4, 5-dicyano-2-trifluoromethylimidazole, (lithium fluorosulfonyl) (n-perfluorobutylsulfonyl) imide, and tert-butyllithium.
Meanwhile, the application also provides a preparation method of the polymer composite solid electrolyte, which is used for preparing the polymer composite solid electrolyte and comprises the following steps:
s1, dissolving a lithiated polyvinyl formal polymer, lithium salt, polyvinylidene fluoride, a porous organic covalent material and lanthanum lithium zirconate in an organic solvent, stirring and mixing, and performing ultrasonic dispersion to obtain mixed slurry;
and S2, coating the mixed slurry obtained in the S1 on a glass plate, and drying in vacuum to obtain the polymer composite solid electrolyte.
Optionally, the mass ratio of the lithiated polyvinyl formal polymer to the lithium salt to the polyvinylidene fluoride to the porous organic covalent material to the lanthanum lithium zirconate is 50-70: 5-10: 1-5: 3-5: 10-30 parts of lithium salt, namely lithium bistrifluoromethanesulfonylimide, the organic solvent is anhydrous acetonitrile, the stirring time is 1-3h, the ultrasonic time is 1-2h, the drying temperature is 60-80, the drying time at the temperature of 20-30h, and the coating thickness is 50-200 mu m. By limiting each parameter, the prepared polymer composite solid electrolyte has higher room temperature conductivity and mechanical elasticity, and the rate discharge performance and the cycle life of the all-solid lithium battery can be greatly improved.
Optionally, in the step S1, the method for preparing the lithiated polyvinyl formal polymer includes the following steps:
a. dissolving polyvinyl formal in an organic solvent, stirring and mixing, adding 4, 4' -diphenylmethane diisocyanate, continuously stirring and mixing, adding deionized water, continuously stirring and uniformly mixing to obtain slurry, and finally precipitating the obtained slurry to obtain a polyvinyl formal polymer;
b. and c, dissolving the polyvinyl formal polymer obtained in the step a in an organic solvent, adding boric acid, stirring and mixing, sequentially adding lithium carbonate and oxalic acid, ultrasonically mixing to obtain a mixed solution, and finally freeze-drying the obtained mixed solution to obtain the lithiated polyvinyl formal polymer.
Optionally, the step a specifically includes: dissolving polyvinyl formal in N-methyl pyrrolidone, magnetically stirring for 1-2h, continuously stirring for 20-60min at the temperature of 65-85 ℃, then adding 4, 4 ' -diphenylmethane diisocyanate, and continuously stirring for 1-2h at the temperature of 40-55 ℃ to enable the polyvinyl formal and the 4, 4 ' -diphenylmethane diisocyanate to be completely dissolved, wherein the concentrations of the polyvinyl formal and the 4, 4 ' -diphenylmethane diisocyanate are respectively 0.5-4.5mol/L and 0.05-0.5mol/L, then adding deionized water, continuously stirring and uniformly mixing to obtain slurry, and finally placing the obtained slurry in a solidification tank for precipitation to obtain the polyvinyl formal polymer. Compared with polyvinyl formal, the polyvinyl formal polymer prepared by the method has very high molecular weight, and the improvement of the molecular weight is beneficial to improving the mechanical elasticity and the lithium dendrite resistance of the polyvinyl formal and improving the cycle life and the safety of a solid battery.
Optionally, the step b specifically includes: dissolving the polyvinyl formal polymer obtained in the step a in dimethyl sulfoxide, wherein the mass ratio of the polyvinyl formal polymer to the dimethyl sulfoxide is 0.5-1:8-12, so as to obtain a light yellow uniform transparent solution, adding boric acid with the concentration of 0.05-0.3mol/L, placing the solution at the temperature of 70-90 ℃ for magnetic stirring for 3-5h, after uniform mixing, sequentially adding lithium carbonate and oxalic acid, placing the solution at the temperature of 50-90 ℃ for ultrasonic mixing for 4-8h, so as to obtain a mixed solution, wherein the molar ratio of the boric acid, the lithium carbonate and the oxalic acid is 0.8-1.0: 0.5-1.5: 1.5-2.0; and finally washing the obtained mixed solution by using absolute ethyl alcohol or isopropanol for 3-4 times, drying at the temperature of 50-70 ℃ for 3-5h, and carrying out vacuum freeze drying for 3-6h to obtain the lithiated polyvinyl formal polymer. The lithiated polyvinyl formal polymer can be used as a single lithium ion conductor, thereby improving the conductivity of the solid electrolyte.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) according to the polymer composite solid electrolyte provided by the embodiment of the application, the room-temperature conductivity and the mechanical elasticity of the solid electrolyte can be remarkably improved by utilizing the synergistic effect among the components of the lithiated polyvinyl formal polymer, the lithium salt, the polyvinylidene fluoride, the porous organic covalent material and the lanthanum lithium zirconate, and the rate discharge performance and the cycle life of the all-solid lithium battery are greatly improved. The lithiated polyvinyl formal polymer can be used as a single lithium ion conductor and is compounded with lithium salt to form a dilithium polymer, and a lithium source is added; meanwhile, the added porous organic covalent material is taken as a proton-philic material, has excellent affinity with lithium ions, and has high specific surface area, so that the addition of the porous organic covalent material can accelerate the further dissociation of the lithium ions in the lithiated polyvinyl formal polymer and obviously enhance the transmission channel of the lithium ions, thereby obviously reducing the interface internal resistance; in addition, the addition of the polyvinylidene fluoride can effectively improve the mechanical elasticity of the polymer film layer, increase the film layer stability and the surface smoothness in the circulating process, and the lanthanum lithium zirconate is used as an excellent lithium ion conductor, so that the mechanical strength and the lithium ion transmission performance of the polymer solid electrolyte can be further enhanced. Therefore, compared with pure polyvinyl formal solid electrolyte, the polymer composite solid electrolyte adopting the multi-component matrix can not only remarkably improve the room-temperature conductivity and mechanical elasticity of the solid electrolyte, but also greatly improve the rate discharge performance and cycle life of the all-solid lithium battery.
(2) The polymer composite solid electrolyte provided by the embodiment of the application can improve the mechanical elasticity and the lithium dendrite resistance of polyvinyl formal by adopting the polyvinyl formal polymer, is beneficial to improving the cycle life and the safety of a solid battery, simultaneously, the polyvinyl formal polymer is dissolved in dimethyl sulfoxide and gradually reacts with boric acid, lithium carbonate and oxalic acid to form a polymer with polyvinyl acetal as a main chain, a lithium monoacetate borate structure is directly grafted on a polymer molecular chain to realize chemical crosslinking, and the conduction of lithium ions is realized by utilizing the oxygen atom group contained on the polymer main chain and the coordination and de-coordination processes between the boron atom group in the lithium monoacetate borate structure on the side chain and the lithium ions, so that the lithiated polyvinyl formal polymer can be used as a single lithium ion conductor, thereby improving the conductivity of the solid electrolyte.
(3) According to the polymer composite solid electrolyte, the polyvinyl formal polymer prepared by the polymer composite solid electrolyte is higher in molecular weight compared with polyvinyl formal by limiting the adoption of the concentration, the improvement of the molecular weight is favorable for improving the mechanical elasticity and the lithium dendrite resistance of the polyvinyl formal, and the cycle life and the safety of a solid battery are favorably improved.
(4) The polymer composite solid electrolyte provided by the embodiment of the application can obtain the molecular weight of the polyvinyl formal polymer of 200000-500000 by limiting the molecular weight of the polyvinyl formal, and ensures the mechanical elasticity and the lithium dendrite resistance of the solid electrolyte.
(5) According to the preparation method of the polymer composite solid electrolyte, the polymer composite solid electrolyte prepared by the method has higher room-temperature conductivity and mechanical elasticity, and the rate discharge performance and the cycle life of an all-solid lithium battery can be greatly improved.
Detailed Description
For further understanding of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The application provides a polymer composite solid electrolyte, including lithiated polyvinyl formal polymer, lithium salt, polyvinylidene fluoride, porous organic covalent material and lanthanum lithium zirconate, the mass ratio of lithiated polyvinyl formal polymer, lithium salt, polyvinylidene fluoride, porous organic covalent material and lanthanum lithium zirconate is 50-70: 5-10: 1-5: 3-5: 10-30. By utilizing the synergistic effect among the components of the lithiated polyvinyl formal polymer, the lithium salt, the polyvinylidene fluoride, the porous organic covalent material and the lanthanum lithium zirconate, the room-temperature conductivity and the mechanical elasticity of the solid electrolyte can be obviously improved, and the rate discharge performance and the cycle life of the all-solid lithium battery are greatly improved. The lithiated polyvinyl formal polymer can be used as a single lithium ion conductor and is compounded with lithium salt to form a dilithium polymer, and a lithium source is added; meanwhile, the added porous organic covalent material is taken as a proton-philic material, has excellent affinity with lithium ions, and has high specific surface area, so that the addition of the porous organic covalent material can accelerate the further dissociation of the lithium ions in the lithiated polyvinyl formal polymer and obviously enhance the transmission channel of the lithium ions, thereby obviously reducing the interface internal resistance; in addition, the addition of the polyvinylidene fluoride can effectively improve the mechanical elasticity of the polymer film layer, increase the film layer stability and the surface smoothness in the circulating process, and the lanthanum lithium zirconate is used as an excellent lithium ion conductor, so that the mechanical strength and the lithium ion transmission performance of the polymer solid electrolyte can be further enhanced. Therefore, compared with pure polyvinyl formal solid electrolyte, the polymer composite solid electrolyte adopting the multi-component matrix can not only remarkably improve the room-temperature conductivity and mechanical elasticity of the solid electrolyte, but also greatly improve the rate discharge performance and cycle life of the all-solid lithium battery.
Specifically, the raw materials of the lithiated polyvinyl formal polymer comprise a polyvinyl formal polymer, dimethyl sulfoxide, boric acid, lithium carbonate and oxalic acid; wherein the mass ratio of the polyvinyl formal polymer to the dimethyl sulfoxide is 0.5-1: 8-12; the molar ratio of the boric acid to the lithium carbonate to the oxalic acid is 0.8-1.0: 0.5-1.5: 1.5-2.0. The polyvinyl formal polymer is dissolved in dimethyl sulfoxide and reacts with boric acid, lithium carbonate and oxalic acid step by step to form a main chain which takes the polyvinyl acetal polymer as a main chain, a lithium monoacetate structure is directly grafted on a polymer molecular chain to realize chemical crosslinking, and the processes of coordination and decomplexing between an oxygen atom group contained on the polymer main chain and a boron atom group in the lithium monoacetate structure on the side chain and lithium ions are utilized to realize the conduction of the lithium ions, so that the lithiated polyvinyl formal polymer can be used as a single lithium ion conductor, thereby improving the conductivity of a solid electrolyte. In addition, the molecular weight of the polyvinyl formal polymer is 200000-500000, generally, if the molecular weight of the polyvinyl formal polymer is less than 200000, the viscosity of the material is too high, which significantly increases the assembly difficulty of the solid battery and increases the manufacturing cost; if the hardness is higher than 500000, the hardness of the polyvinyl formal polymer material is too high, so that the brittleness of the polymer composite solid electrolyte membrane is high, the contact performance with the positive and negative electrode interfaces is reduced, and the safety performance of the battery is caused. The molecular weight of the polyvinyl formal polymer is 200000-500000, so that the mechanical elasticity and lithium dendrite resistance of the solid electrolyte are ensured.
Specifically, the raw materials of the polyvinyl formal polymer comprise polyvinyl formal and 4, 4 '-diphenylmethane diisocyanate, the concentrations of the polyvinyl formal and the 4, 4' -diphenylmethane diisocyanate are respectively 0.5-4.5mol/L and 0.05-0.5mol/L, and the molecular weight of the polyvinyl formal is 50000-70000. Compared with polyvinyl formal, the polyvinyl formal polymer prepared by adopting the raw materials with the concentration setting has very high molecular weight, and the improvement of the molecular weight is beneficial to improving the mechanical elasticity and the lithium dendrite resistance of the polyvinyl formal and improving the cycle life and the safety of a solid battery.
The lithium salt is selected from one or more of lithium bistrifluoromethanesulfonimide, lithium bistriflurosulfonate, lithium bisoxalato borate, lithium tetrafluoroborate, lithium hexafluoroborate, lithium perchlorate, lithium difluorobisoxalato borate, lithium triethylborohydride, lithium diisopropylamide, lithium acetoacetate, lithium bistrimethylsilyl, lithium pentamethylcyclopentadiene, lithium 4, 5-dicyano-2-trifluoromethylimidazole, (lithium fluorosulfonyl) (n-perfluorobutylsulfonyl) imide and tert-butyllithium.
Meanwhile, the application also provides a preparation method of the polymer composite solid electrolyte, which is used for preparing the polymer composite solid electrolyte and comprises the following steps:
s1, dissolving a lithiated polyvinyl formal polymer, lithium salt, polyvinylidene fluoride, a porous organic covalent material and lanthanum lithium zirconate in an organic solvent, stirring and mixing, and performing ultrasonic dispersion to obtain mixed slurry; wherein the mass ratio of the lithiated polyvinyl formal polymer to the lithium salt to the polyvinylidene fluoride to the porous organic covalent material to the lanthanum lithium zirconate is 50-70: 5-10: 1-5: 3-5: 10-30 parts of lithium salt, namely bis (trifluoromethanesulfonyl) imide lithium, wherein the organic solvent is anhydrous acetonitrile, the stirring time is 1-3 hours, and the ultrasonic time is 1-2 hours. Through the limitation of each parameter, the prepared polymer composite solid electrolyte has higher room temperature conductivity and mechanical elasticity, and the rate discharge performance and the cycle life of the all-solid lithium battery can be greatly improved.
Specifically, the preparation method of the lithiated polyvinyl formal polymer comprises the following steps:
a. dissolving polyvinyl formal in N-methyl pyrrolidone, magnetically stirring for 1-2 hr, continuously stirring for 20-60min at 65-85 deg.C, adding 4, 4' -diphenylmethane diisocyanate, and continuously stirring for 1-2h at the temperature of 40-55 ℃ to completely dissolve the mixture, wherein the concentration of the polyvinyl formal and the concentration of the 4, 4' -diphenylmethane diisocyanate are respectively 0.5-4.5mol/L and 0.05-0.5mol/L, then deionized water is added as a non-organic solvent to precipitate white particles, stirring is continued until the precipitated turbid liquid becomes a transparent and viscous slurry, namely obtaining slurry, and finally placing the obtained slurry in a coagulation pool for precipitation to obtain the polyvinyl formal polymer with the molecular weight of 50000-70000. Compared with polyvinyl formal, the polyvinyl formal polymer prepared by the method has very high molecular weight, and the improvement of the molecular weight is beneficial to improving the mechanical elasticity and the lithium dendrite resistance of the polyvinyl formal and improving the cycle life and the safety of a solid battery.
b. Dissolving the polyvinyl formal polymer obtained in the step a in dimethyl sulfoxide, wherein the mass ratio of the polyvinyl formal polymer to the dimethyl sulfoxide is 0.5-1:8-12, so as to obtain a light yellow uniform transparent solution, adding boric acid with the concentration of 0.05-0.3mol/L, placing the solution at the temperature of 70-90 ℃ for magnetic stirring for 3-5h, after uniform mixing, sequentially adding lithium carbonate and oxalic acid, placing the solution at the temperature of 50-90 ℃ for ultrasonic mixing for 4-8h, so as to obtain a mixed solution, wherein the molar ratio of the boric acid to the lithium carbonate to the oxalic acid is 0.8-1.0: 0.5-1.5: 1.5-2.0; finally, washing the obtained mixed solution by using absolute ethyl alcohol or isopropanol for 3-4 times, drying the mixed solution for 3-5h at the temperature of 50-70 ℃, and then carrying out freeze drying for 3-6h in a vacuum environment cold pump to obtain the lithiated polyvinyl formal polymer with the molecular weight of 200000-500000. The lithiated polyvinyl formal polymer can be used as a single lithium ion conductor, thereby improving the conductivity of the solid electrolyte.
And S2, coating the mixed slurry obtained in the S1 on a glass plate by a scraper method, wherein the coating thickness is 50-200 mu m, drying the glass plate in a vacuum oven at the temperature of 60-80 ℃ for 20-30h, completely removing the solvent, and drying in vacuum to obtain the polymer composite solid electrolyte. Generally, the coating thickness is too low, so that the actual energy density of the solid battery is reduced, and the battery cost is too high; the coating thickness is too high, the lithium ion transmission path is increased, the internal resistance of the solid battery is increased, and the performance of power performance is not facilitated. In the present application, by defining the coating thickness, the energy density of the solid-state battery and the smoothness of lithium ion transmission can be ensured.
In addition, the present application also provides a method for manufacturing a solid-state battery, the method comprising: lanthanum lithium zirconate particles (the particle size is 100-500nm), a positive electrode active material and a carbon black conductive agent are mixed according to the mass ratio of (0.5-1.0: 1-2.5): 0.05-0.1, adding the mixture into a high-energy vibration ball mill, carrying out ball milling for 30-45min at normal temperature to obtain a mixture, transferring the mixture into a molybdenum-based alloy die, and pressing the mixture into a film under the standard atmospheric pressure of 300 plus 400 to serve as a composite positive plate, wherein the used positive material is any one of lithium iron phosphate LFP, lithium cobaltate LCO and a layered ternary material NCM; and then, taking the obtained composite positive plate as a positive plate, taking a lithium-indium alloy as a negative plate (the atomic percentage of lithium is 40-60%), and respectively pressing the positive plate and the negative plate on two sides of the prepared polymer composite solid electrolyte under 20-40 standard atmospheric pressures to prepare the solid battery.
Example 1
Preparation of lithiated polyvinyl formal polymers: dissolving polyvinyl formal in N-methyl pyrrolidone, stirring for 1.5h by magnetic force, continuing to stir at 75 ℃ for 45min, then adding 4, 4 ' -diphenylmethane diisocyanate, and continuing to stir at 45 ℃ for 1.5h to dissolve all the polyvinyl formal and the 4, 4 ' -diphenylmethane diisocyanate, wherein the concentrations of the polyvinyl formal and the 4, 4 ' -diphenylmethane diisocyanate are respectively 2.8mol/L and 0.22mol/L, then adding deionized water as a non-organic solvent to precipitate white particles, and continuing to stir until the precipitated turbid liquid becomes transparent and viscous slurry, namely slurry is obtained, and finally placing the obtained slurry in a solidification tank for precipitation to obtain a polyvinyl formal polymer with the molecular weight of 50000; then dissolving the obtained polyvinyl formal polymer in dimethyl sulfoxide, wherein the mass ratio of the polyvinyl formal polymer to the dimethyl sulfoxide is 0.8:10, so as to obtain a light yellow uniform transparent solution, then adding boric acid with the concentration of 0.16mol/L, placing the solution at the temperature of 80 ℃ for magnetic stirring for 4 hours, after uniformly mixing, sequentially adding lithium carbonate and oxalic acid, placing the solution at the temperature of 70 ℃ for ultrasonic mixing for 6 hours, so as to obtain a mixed solution, wherein the molar ratio of the boric acid, the lithium carbonate and the oxalic acid is 0.9: 0.9: 1.7; and finally, washing the obtained mixed solution by using absolute ethyl alcohol for 3 times, then drying the mixed solution for 4 hours at the temperature of 65 ℃, and then carrying out freeze drying for 5 hours in a vacuum environment cold pump to obtain the lithiated polyvinyl formal polymer with the molecular weight of 200000.
Preparing a polymer composite solid electrolyte: the obtained lithiated polyvinyl formal polymer, lithium bistrifluoromethylenesulfonate imide, polyvinylidene fluoride, porous COFs particles and lanthanum lithium zirconate particles (the particle size is 500nm) are mixed according to the mass ratio of 65: 8: 3: 4: 17 is dissolved in anhydrous acetonitrile, firstly, the mixture is magnetically stirred for 2 hours at normal temperature, then the mixture is continuously ultrasonically dispersed for 1.5 hours at normal temperature to obtain evenly mixed slurry, the slurry is coated on a glass plate by a scraper method, the coating thickness is 120 mu m, the mixture is dried for 26 hours in a vacuum oven at 70 ℃, and the polymer composite solid electrolyte is obtained after the solvent is completely removed. (Water and oxygen contents of the above production process need to be controlled to 10ppm or less)
Example 2
Preparation of lithiated polyvinyl formal polymers: dissolving polyvinyl formal in N-methyl pyrrolidone, stirring for 2 hours under magnetic force, continuing to stir for 20 minutes at the temperature of 75 ℃, then adding 4, 4 ' -diphenylmethane diisocyanate, and continuing to stir for 2 hours at the temperature of 55 ℃ to dissolve all the polyvinyl formal and the 4, 4 ' -diphenylmethane diisocyanate, wherein the concentrations of the polyvinyl formal and the 4, 4 ' -diphenylmethane diisocyanate are respectively 4.5mol/L and 0.05mol/L, then adding deionized water as a non-organic solvent to precipitate white particles, and continuing to stir until the precipitated turbid liquid becomes transparent and viscous slurry, so as to obtain slurry, and finally placing the obtained slurry in a solidification tank for precipitation, so as to obtain a polyvinyl formal polymer with the molecular weight of 60000; then dissolving the obtained polyvinyl formal polymer in dimethyl sulfoxide, wherein the mass ratio of the polyvinyl formal polymer to the dimethyl sulfoxide is 1:8, so as to obtain a light yellow uniform transparent solution, then adding boric acid with the concentration of 0.3mol/L, placing the solution at the temperature of 80 ℃ for magnetic stirring for 4 hours, after uniform mixing, sequentially adding lithium carbonate and oxalic acid, placing the solution at the temperature of 70 ℃ for ultrasonic mixing for 6 hours, so as to obtain a mixed solution, wherein the molar ratio of the boric acid to the lithium carbonate to the oxalic acid is 0.8: 1.5: 1.5; and finally, washing the obtained mixed solution with absolute ethyl alcohol for 4 times, drying the mixed solution at the temperature of 70 ℃ for 3 hours, and freeze-drying the dried mixed solution in a vacuum environment cold pump for 3 hours to obtain the lithiated polyvinyl formal polymer with the molecular weight of 350000.
Preparing a polymer composite solid electrolyte: the obtained lithiated polyvinyl formal polymer, lithium bistrifluoromethylenesulfonate imide, polyvinylidene fluoride, porous COFs particles and lanthanum lithium zirconate particles (the particle size is 500nm) are mixed according to the mass ratio of 50: 6: 2: 3: 12, dissolving in anhydrous acetonitrile, magnetically stirring for 1.5h at normal temperature, then continuing to ultrasonically disperse for 1h at normal temperature to obtain uniformly mixed slurry, coating the slurry on a glass plate by using a scraper method, wherein the coating thickness is 80 mu m, drying for 22h in a vacuum oven at 65 ℃, and completely removing the solvent to obtain the polymer composite solid electrolyte. (the water and oxygen content in the above production process need to be controlled to 10ppm or less).
Example 3
Preparation of lithiated polyvinyl formal polymers: dissolving polyvinyl formal in N-methyl pyrrolidone, magnetically stirring for 1h, continuing to stir at 75 ℃ for 60min, then adding 4, 4 ' -diphenylmethane diisocyanate, and continuing to stir at 40 ℃ for 1.5h to dissolve all the polyvinyl formal and the 4, 4 ' -diphenylmethane diisocyanate, wherein the concentrations of the polyvinyl formal and the 4, 4 ' -diphenylmethane diisocyanate are respectively 0.5mol/L and 0.5mol/L, then adding deionized water as a non-organic solvent to precipitate white particles, and continuing to stir until the precipitated turbid liquid becomes transparent and viscous slurry, so as to obtain slurry, and finally placing the obtained slurry in a solidification tank for precipitation, so as to obtain a polyvinyl formal polymer with the molecular weight of 70000; then dissolving the obtained polyvinyl formal polymer in dimethyl sulfoxide, wherein the mass ratio of the polyvinyl formal polymer to the dimethyl sulfoxide is 0.5:12, so as to obtain a light yellow uniform transparent solution, then adding boric acid with the concentration of 0.05mol/L, placing the solution at the temperature of 80 ℃ for magnetic stirring for 4 hours, after uniformly mixing, sequentially adding lithium carbonate and oxalic acid, placing the solution at the temperature of 50 ℃ for ultrasonic mixing for 8 hours, so as to obtain a mixed solution, wherein the molar ratio of the boric acid, the lithium carbonate and the oxalic acid is 1.0: 0.5: 2.0; and finally, washing the obtained mixed solution by using absolute ethyl alcohol for 3 times, then drying the mixed solution for 5 hours at the temperature of 50 ℃, and then carrying out freeze drying on the dried mixed solution for 6 hours in a vacuum environment cold pump to obtain the lithiated polyvinyl formal polymer with the molecular weight of 400000.
Preparation of polymer composite solid electrolyte: the obtained lithiated polyvinyl formal polymer, lithium bistrifluoromethylenesulfonate imide, polyvinylidene fluoride, porous COFs particles and lanthanum lithium zirconate particles (the particle size is 700nm) are mixed according to the mass ratio of 70: 10: 5: 5: 25 is dissolved in anhydrous acetonitrile, magnetic stirring is carried out for 3 hours at normal temperature, then normal-temperature ultrasonic dispersion is carried out for 2 hours to obtain evenly mixed slurry, the slurry is coated on a glass plate by a scraper method, the coating thickness is 130 micrometers, the glass plate is dried for 30 hours in a vacuum oven at 80 ℃, and the polymer composite solid electrolyte is obtained after the solvent is completely removed. (the water and oxygen content in the above production process need to be controlled to 10ppm or less).
Example 4
Compared with example 1, the difference is that the polymer composite solid electrolyte is prepared: the lithiated polyvinyl formal polymer obtained in step 1 obtained in example 1, lithium bistrifluoromethylenesulfonate imide, polyvinylidene fluoride, porous COFs particles, and lanthanum lithium zirconate particles (particle size of 700nm) were mixed in a mass ratio of 70: 5: 1: 3: dissolving 10 in anhydrous acetonitrile, magnetically stirring for 1 hour at normal temperature, then continuing to ultrasonically disperse for 1 hour at normal temperature to obtain uniformly mixed slurry, coating the slurry on a glass plate by using a scraper method, wherein the coating thickness is 200 mu m, drying for 20 hours in a vacuum oven at 60 ℃, and completely removing the solvent to obtain the polymer composite solid electrolyte. (the water and oxygen content in the above production process need to be controlled to 10ppm or less).
Comparative example 1
The difference compared to example 1 is that in comparative example 1 unlithiated polyvinyl formal is used, and the other conditions are the same as in example 1.
Comparative example 2
The difference from example 1 is that in comparative example 2, lithium bistrifluoromethylenesulfonamide was not added, and the other conditions were the same as in example 1.
Comparative example 3
The difference compared to example 1 is that in comparative example 3 no porous COFs particles are added, and the remaining conditions are the same as in example 1.
Comparative example 4
The difference from example 1 is that comparative example 4 has no polyvinylidene fluoride added, and the other conditions are the same as example 1.
Comparative example 5
The difference from example 1 is that comparative example 5 uses polyvinyl formal to prepare a polymer solid electrolyte, and the other conditions are the same as example 1.
Comparative example 6
The difference compared to example 1 is that the molecular weight of the lithiated polyvinyl formal polymer of comparative example 6 is 800000, and the rest of the conditions are the same as in example 1.
Comparative example 7
The difference from example 1 is that the coating thickness in comparative example 7 is 200 μm, and the other conditions are the same as example 1.
Evaluation of various performance tests
In the present application, lanthanum lithium zirconate particles (particle size of 300nm), lithium cobaltate and a carbon black conductive agent are mixed in a mass ratio of 0.8: 1.7: 0.09 is added into a high-energy vibration ball mill, ball milling is carried out for 37min at normal temperature, and then the mixture is transferred into a molybdenum-based alloy die and is pressed into a film under 350 standard atmospheric pressures to be used as a composite positive plate. Then, the composite positive electrode sheet obtained as described above was used as a positive electrode sheet, a lithium indium alloy was used as a negative electrode sheet (lithium atomic percentage: 50%), and the positive and negative electrode sheets were pressed on both sides of the three-dimensional polymer composite solid electrolyte prepared in examples 1 to 3 and the solid electrolyte prepared in comparative examples 1 to 6, respectively, under 35 standard atmospheric pressures, to prepare corresponding solid full cells. Then testing the alternating current internal resistance of the solid full cell prepared by the method by using an alternating current impedance spectrum at 30 ℃ and 60 ℃ respectively, wherein the amplitude of the applied voltage is 5-10mV, and the frequency range is 1-10 mV6HZ; within the voltage range of 2.5-4.0V, the multiplying power discharge performance of the battery is tested;meanwhile, the battery cycle life is tested by testing the continuous charge-discharge cycle at the temperature of 30 ℃ and 60 ℃ and the charge-discharge multiplying power of 0.3C and the voltage range of 2.5-4.0V until the voltage is short-circuited (the voltage drop speed is more than 5 mV/S). As shown in Table 1, the three-dimensional polymer composite solid electrolytes obtained in examples 1 to 4 were compared with the solid electrolytes obtained in comparative examples 1 to 6 in terms of electrochemical properties at normal temperature and high temperature.
Table 1: comparison of Normal temperature and high temperature electrochemical Properties of solid electrolytes prepared in examples 1 to 4 and comparative examples 1 to 7
As shown in table 1, the lithiated polyvinyl formal polymer and polymer composite solid electrolyte prepared by the present application can significantly improve the rate performance and cycle life of the polymer solid battery by combining the data of examples 1 to 4, wherein the effect of example 1 is the best. Specifically, by combining the data of example 1 and comparative examples 1 to 5, it can be seen that the room temperature conductivity and the mechanical elasticity of the solid electrolyte can be significantly improved and the rate discharge performance and the cycle life of the all-solid lithium battery can be greatly improved by utilizing the synergistic effect among the components of the lithiated polyvinyl formal polymer, the lithium salt, the polyvinylidene fluoride, the porous organic covalent material and the lanthanum lithium zirconate. The lithiated polyvinyl formal polymer can be used as a single lithium ion conductor and is compounded with lithium salt to form a dilithium polymer, and a lithium source is added; meanwhile, the added porous organic covalent material is taken as a proton-philic material, has excellent affinity with lithium ions, and has high specific surface area, so that the addition of the porous organic covalent material can accelerate the further dissociation of the lithium ions in the lithiated polyvinyl formal polymer and obviously enhance the transmission channel of the lithium ions, thereby obviously reducing the interface internal resistance; in addition, the addition of the polyvinylidene fluoride can effectively improve the mechanical elasticity of the polymer film layer, increase the film layer stability and the surface smoothness in the circulating process, and the lanthanum lithium zirconate is used as an excellent lithium ion conductor, so that the mechanical strength and the lithium ion transmission performance of the polymer solid electrolyte can be further enhanced. Compared with pure polyvinyl formal solid electrolyte, the polymer composite solid electrolyte adopting the multi-component matrix can not only remarkably improve the room-temperature conductivity and mechanical elasticity of the solid electrolyte, but also greatly improve the rate discharge performance and cycle life of the all-solid lithium battery.
It can be seen from the data of example 1 and comparative examples 6 to 7 that limiting the molecular weight of the lithiated polyvinyl formal polymer and the thickness of the prepared polymer composite solid electrolyte membrane can greatly improve the rate discharge performance and cycle life of the all-solid lithium battery. Therefore, the polymer composite solid electrolyte prepared by the method can obviously improve the room-temperature conductivity and mechanical elasticity of the solid electrolyte, greatly improve the rate discharge performance and cycle life of the all-solid lithium battery, obviously improve the performance of the all-solid lithium battery at normal temperature and high temperature, and provide effective technical support for developing high-performance solid sizing.
While the invention has been described with respect to a preferred embodiment, it will be understood by those skilled in the art that the foregoing and other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention. Those skilled in the art can make various changes, modifications and equivalent arrangements, which are equivalent to the embodiments of the present invention, without departing from the spirit and scope of the present invention, and which may be made by utilizing the techniques disclosed above; meanwhile, any changes, modifications and variations of the above-described embodiments, which are equivalent to those of the technical spirit of the present invention, are within the scope of the technical solution of the present invention.
Claims (10)
1. The polymer composite solid electrolyte is characterized by comprising a lithiated polyvinyl formal polymer, a lithium salt, polyvinylidene fluoride, a porous organic covalent material and lanthanum lithium zirconate, wherein the mass ratio of the lithiated polyvinyl formal polymer to the lithium salt to the polyvinylidene fluoride to the porous organic covalent material to the lanthanum lithium zirconate is 50-70: 5-10: 1-5: 3-5: 10-30.
2. The polymer composite solid electrolyte according to claim 1, wherein the raw material of the lithiated polyvinyl formal polymer includes polyvinyl formal polymer, dimethyl sulfoxide, boric acid, lithium carbonate, and oxalic acid; wherein the mass ratio of the polyvinyl formal polymer to the dimethyl sulfoxide is 0.5-1: 8-12; the molar ratio of the boric acid to the lithium carbonate to the oxalic acid is 0.8-1.0: 0.5-1.5: 1.5-2.0.
3. The polymer composite solid electrolyte according to claim 2, wherein the raw material of the polyvinyl formal polymer comprises polyvinyl formal and 4, 4 '-diphenylmethane diisocyanate, and the concentrations of the polyvinyl formal and the 4, 4' -diphenylmethane diisocyanate are 0.5 to 4.5mol/L and 0.05 to 0.5mol/L, respectively.
4. The polymer composite solid electrolyte as claimed in claim 3, wherein the molecular weight of the polyvinyl formal is 50000-70000, and the molecular weight of the polyvinyl formal polymer is 200000-500000.
5. The polymer composite solid electrolyte according to claim 1, wherein the lithium salt is selected from one or more of lithium bistrifluoromethylsulfonyl imide, lithium bistrifluorosulfonate, lithium bisoxalato borate, lithium tetrafluoroborate, lithium hexafluoroborate, lithium perchlorate, lithium difluorobisoxalato borate, lithium triethylborohydride, lithium diisopropylamide, lithium acetoacetate, lithium bistrimethylsilyl, lithium pentamethylcyclopentadiene, lithium 4, 5-dicyano-2-trifluoromethylimidazole, (fluorosulfonyl) (n-perfluorobutylsulfonyl) imide, and t-butyllithium.
6. A method for producing a polymer composite solid electrolyte according to any one of claims 1 to 5, comprising the steps of:
s1, dissolving lithiated polyvinyl formal polymer, lithium salt, polyvinylidene fluoride, a porous organic covalent material and lanthanum lithium zirconate in an organic solvent, stirring and mixing, and performing ultrasonic dispersion to obtain mixed slurry;
and S2, coating the mixed slurry obtained in the S1 on a glass plate, and drying in vacuum to obtain the polymer composite solid electrolyte.
7. The method for preparing a polymer composite solid electrolyte according to claim 6, wherein the mass ratio of the lithiated polyvinyl formal polymer to the lithium salt to the polyvinylidene fluoride to the porous organic covalent material to the lanthanum lithium zirconate is 50 to 70: 5-10: 1-5: 3-5: 10-30 parts of lithium salt, namely lithium bistrifluoromethanesulfonylimide, the organic solvent is anhydrous acetonitrile, the stirring time is 1-3h, the ultrasonic time is 1-2h, the drying temperature is 60-80, the drying time at the temperature of 20-30h, and the coating thickness is 50-200 mu m.
8. The method of claim 6, wherein the method of preparing the lithiated polyvinyl formal polymer in the step of S1 comprises the steps of:
a. dissolving polyvinyl formal in an organic solvent, stirring and mixing, adding 4, 4' -diphenylmethane diisocyanate, continuously stirring and mixing, adding deionized water, continuously stirring and uniformly mixing to obtain slurry, and finally precipitating the obtained slurry to obtain a polyvinyl formal polymer;
b. and c, dissolving the polyvinyl formal polymer obtained in the step a in an organic solvent, adding boric acid, stirring and mixing, sequentially adding lithium carbonate and oxalic acid, ultrasonically mixing to obtain a mixed solution, and finally freeze-drying the obtained mixed solution to obtain the lithiated polyvinyl formal polymer.
9. The method for preparing a polymer composite solid electrolyte according to claim 8, wherein the step a is as follows: dissolving polyvinyl formal in N-methyl pyrrolidone, magnetically stirring for 1-2h, continuously stirring for 20-60min at the temperature of 65-85 ℃, then adding 4, 4 ' -diphenylmethane diisocyanate, and continuously stirring for 1-2h at the temperature of 40-55 ℃ to enable the polyvinyl formal and the 4, 4 ' -diphenylmethane diisocyanate to be completely dissolved, wherein the concentrations of the polyvinyl formal and the 4, 4 ' -diphenylmethane diisocyanate are respectively 0.5-4.5mol/L and 0.05-0.5mol/L, then adding deionized water, continuously stirring and uniformly mixing to obtain slurry, and finally placing the obtained slurry in a solidification tank for precipitation to obtain the polyvinyl formal polymer.
10. The method of claim 8, wherein step b comprises the steps of: dissolving the polyvinyl formal polymer obtained in the step a in dimethyl sulfoxide, wherein the mass ratio of the polyvinyl formal polymer to the dimethyl sulfoxide is 0.5-1:8-12, so as to obtain a light yellow uniform transparent solution, adding boric acid with the concentration of 0.05-0.3mol/L, placing the solution at the temperature of 70-90 ℃ for magnetic stirring for 3-5h, after uniform mixing, sequentially adding lithium carbonate and oxalic acid, placing the solution at the temperature of 50-90 ℃ for ultrasonic mixing for 4-8h, so as to obtain a mixed solution, wherein the molar ratio of the boric acid, the lithium carbonate and the oxalic acid is 0.8-1.0: 0.5-1.5: 1.5-2.0; and finally washing the obtained mixed solution by using absolute ethyl alcohol or isopropanol for 3-4 times, drying at the temperature of 50-70 ℃ for 3-5h, and carrying out vacuum freeze drying for 3-6h to obtain the lithiated polyvinyl formal polymer.
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