CN116344943B - Lithium iron manganese phosphate battery electrolyte - Google Patents
Lithium iron manganese phosphate battery electrolyte Download PDFInfo
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- CN116344943B CN116344943B CN202310617712.7A CN202310617712A CN116344943B CN 116344943 B CN116344943 B CN 116344943B CN 202310617712 A CN202310617712 A CN 202310617712A CN 116344943 B CN116344943 B CN 116344943B
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 63
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 title claims abstract description 8
- 239000000654 additive Substances 0.000 claims abstract description 29
- 230000000996 additive effect Effects 0.000 claims abstract description 23
- -1 crown ether compounds Chemical class 0.000 claims abstract description 13
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 13
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 13
- 229910007991 Si-N Inorganic materials 0.000 claims abstract description 9
- 229910006294 Si—N Inorganic materials 0.000 claims abstract description 9
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 claims description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 10
- 229910052744 lithium Inorganic materials 0.000 claims description 10
- XQQZRZQVBFHBHL-UHFFFAOYSA-N 12-crown-4 Chemical compound C1COCCOCCOCCO1 XQQZRZQVBFHBHL-UHFFFAOYSA-N 0.000 claims description 8
- 150000001875 compounds Chemical class 0.000 claims description 7
- FSSPGSAQUIYDCN-UHFFFAOYSA-N 1,3-Propane sultone Chemical compound O=S1(=O)CCCO1 FSSPGSAQUIYDCN-UHFFFAOYSA-N 0.000 claims description 6
- ZRZFJYHYRSRUQV-UHFFFAOYSA-N phosphoric acid trimethylsilane Chemical compound C[SiH](C)C.C[SiH](C)C.C[SiH](C)C.OP(O)(O)=O ZRZFJYHYRSRUQV-UHFFFAOYSA-N 0.000 claims description 6
- DKGVLWUCRGFFMN-UHFFFAOYSA-N pyridine;trifluoroborane Chemical compound FB(F)F.C1=CC=NC=C1 DKGVLWUCRGFFMN-UHFFFAOYSA-N 0.000 claims description 6
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 4
- 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 claims description 4
- 239000003960 organic solvent Substances 0.000 claims description 4
- AUKCYOUETBBMFV-UHFFFAOYSA-N 3-trimethylsilyl-1,3-oxazolidin-2-one Chemical compound C[Si](C)(C)N1CCOC1=O AUKCYOUETBBMFV-UHFFFAOYSA-N 0.000 claims description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 3
- 229910019142 PO4 Inorganic materials 0.000 claims description 3
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 3
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 3
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 claims description 2
- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 claims 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 claims description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 2
- 239000010452 phosphate Substances 0.000 claims description 2
- 239000011572 manganese Substances 0.000 abstract description 25
- 150000002500 ions Chemical class 0.000 abstract description 18
- 238000003860 storage Methods 0.000 abstract description 14
- 230000005012 migration Effects 0.000 abstract description 5
- 238000013508 migration Methods 0.000 abstract description 5
- 239000002904 solvent Substances 0.000 abstract description 5
- 230000002195 synergetic effect Effects 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 10
- 238000004090 dissolution Methods 0.000 description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 101150058243 Lipf gene Proteins 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 239000007774 positive electrode material Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 229910052723 transition metal Inorganic materials 0.000 description 5
- 150000003624 transition metals Chemical class 0.000 description 5
- 229910013188 LiBOB Inorganic materials 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 238000000354 decomposition reaction Methods 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 4
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000002360 preparation method Methods 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 125000000524 functional group Chemical group 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 238000007614 solvation Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000006230 acetylene black Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000009472 formulation Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 239000012046 mixed solvent Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- OGWVYCFORNDBRE-UHFFFAOYSA-N n,n-bis(trimethylsilyl)ethanamine Chemical compound CCN([Si](C)(C)C)[Si](C)(C)C OGWVYCFORNDBRE-UHFFFAOYSA-N 0.000 description 2
- ZSMNRKGGHXLZEC-UHFFFAOYSA-N n,n-bis(trimethylsilyl)methanamine Chemical compound C[Si](C)(C)N(C)[Si](C)(C)C ZSMNRKGGHXLZEC-UHFFFAOYSA-N 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- PHIMQSCHTGNBCG-UHFFFAOYSA-N 3-trimethylsilyl-1,3-oxazolidin-2-id-4-one Chemical compound C[Si](N1[CH-]OCC1=O)(C)C PHIMQSCHTGNBCG-UHFFFAOYSA-N 0.000 description 1
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 230000005536 Jahn Teller effect Effects 0.000 description 1
- 239000002841 Lewis acid Substances 0.000 description 1
- 229910015645 LiMn Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 238000005280 amorphization Methods 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 235000011089 carbon dioxide Nutrition 0.000 description 1
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
- 238000003421 catalytic decomposition reaction Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000004807 desolvation Methods 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 239000002608 ionic liquid Substances 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 150000007517 lewis acids Chemical class 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000011268 mixed slurry Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 229920000447 polyanionic polymer Polymers 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 229940094989 trimethylsilane Drugs 0.000 description 1
- 238000010200 validation analysis Methods 0.000 description 1
- 238000003466 welding Methods 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
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The application discloses a lithium iron manganese phosphate battery electrolyte. The electrolyte comprises lithium salt, a solvent and an additive, so that the problems of high-temperature circulation and poor storage performance of the LMFP battery can be well solved, the additive comprises crown ether compounds, the residual quantity of Mn ions in the electrolyte can be obviously reduced, a complex can be formed with the Mn ions due to the strong coordination environment of the structure, the migration of the dissolved Mn ions in the solution can be well inhibited, the Mn ions in the electrolyte can be effectively removed, and the thermal stability of the electrolyte can be improved. In addition, the additive containing the Si-N characteristic structure is selected, HF can be removed, and the battery cycle performance is comprehensively improved by combining the synergistic effect of the low-impedance additive, meanwhile, the interface impedance is reduced, and the conductivity is improved.
Description
Technical Field
The application belongs to the technical field of secondary battery electrolyte, and particularly relates to a lithium iron manganese phosphate battery electrolyte.
Background
Under the drive of environmental protection and carbon emission pressure, research on novel energy sources is actively conducted. Among them, lithium ion batteries are attracting attention in the fields of energy storage and power because of their high specific energy, long cycle life, less self-discharge, good safety performance, etc. The LFP (lithium iron phosphate) battery is widely applied to the fields of energy storage and power due to the advantages of low cost, long cycle, high safety performance and the like, but has the defects of insufficient energy density, low conductivity, poor low-temperature performance and the like, and further breakthrough in market application is limited. The LFP and the LMFP belong to polyanion salt, the olivine structure ensures that the two have higher safety, the manganese element in the LMFP material is added to ensure that the voltage platform is high (4.1V) so as to improve the energy density, the energy density is 15-20% higher than that of the LFP under the equivalent condition, the energy density basically reaches the NCM523 level, the LMFP (lithium iron manganese phosphate) not only maintains the characteristics of low cost, high safety, environmental friendliness and the like of the lithium iron, but also has the advantages of high energy density and good low-temperature performance of the ternary material, and has great application prospect. However, the LMFP battery still has a plurality of problems at the present stage, which limit the large-scale application of the LMFP battery, (1) the LMFP battery comprises a Jahn-Teller effect, so that Mn ions are dissolved out seriously, and SEI is destroyed; (2) Mn/Fe split phase promotes the internal stress accumulation of the material, leads to amorphization and structural collapse fracture of the material, and promotes reaction with electrolyte; (3) The continuous destruction and repair of the electrolyte results in the loss of active lithium to aggravate the problems of double-voltage platform, mn dissolution and the like, and the capacity of the battery, the structural stability, the cycle performance and the like cannot be expected.
Through the research of a high-temperature circulation and storage failure mechanism of the LMFP battery, the dissolution of the transition metal Mn is a main cause of rapid decay of the high-temperature performance of the LMFP battery, wherein (1) the dissolution of the transition metal Mn can cause the defect of the positive electrode material structure and collapse when serious; (2) The dissolved Mn ions are partially deposited on the cathode to catalyze and decompose the SEI film; (3) The other part of the ionic liquid can remain in the electrolyte, and the solvation structure of Mn ions in the electrolyte can catalyze PF 6-decomposition, so that the thermal stability of the electrolyte is reduced. In summary, solving the problem of dissolution of transition metal Mn is critical to improving the performance of LMFP batteries, and electrolyte optimization is an economical, effective and rapid way to be of great interest to researchers.
Disclosure of Invention
The application aims to provide a lithium iron manganese phosphate battery electrolyte for solving the problem of a large amount of transition metal Mn
Dissolution causes the problem of rapid deterioration of cycle performance, and battery kinetics is improved and rate performance is improved through the synergistic use of additives.
The application mainly provides a lithium iron manganese phosphate battery electrolyte which comprises lithium salt, an organic solvent and an additive, wherein the additive comprises crown ether compounds, compounds containing Si-N bonds and boron trifluoride-pyridine.
Further, the crown ether compound is 12-crown-4 ether; the Si-N bond-containing compound is one or more of 3- (trimethylsilyl) -2-oxazolidone, N, N-diethyl trimethyl silane amine, heptamethyl disilazane or ethyl hexamethyldisilazane.
Further, the mass percentage of the crown ether compound in the electrolyte is 0.1% -1%; the mass percentage of the compound containing Si-N bonds in the electrolyte is 0.1% -1%; the mass percentage of the boron trifluoride-pyridine in the electrolyte is 0.1-1%.
Further, the mass percentage of the crown ether compound in the electrolyte is 0.1% -0.3%; the mass percentage of the Si-N bond-containing compound in the electrolyte is 0.1-0.5%; the mass percentage of the boron trifluoride-pyridine in the electrolyte is 0.1-0.6%.
Further, the organic solvent comprises one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate or diethyl carbonate;
further, the lithium salt is at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisoxalato borate, lithium difluorooxalato borate, lithium difluorobisoxalato phosphate, lithium bis (fluorosulfonyl) imide, or lithium bis (trifluoromethylsulfonyl) imide; the lithium salt accounts for 10-15% of the total mass of the electrolyte.
Further, the additive also includes vinylene carbonate, 1, 3-propane sultone, tris (trimethylsilane) phosphate, and lithium dioxaborate.
Further, the vinylene carbonate accounts for 0.5% -2% of the total mass of the electrolyte; the 1, 3-propane sultone accounts for 0.5-1.5% of the total mass of the electrolyte; the tris (trimethylsilane) phosphate accounts for 0.2-1% of the total mass of the electrolyte; the lithium dioxalate borate accounts for 0.1 to 0.3 percent of the total mass of the electrolyte.
The application provides a secondary battery, which comprises a positive electrode plate, a negative electrode plate, a separation film and the electrolyte.
The application also provides electric equipment, which comprises the secondary battery, wherein the secondary battery is used as a power supply of the electric equipment.
The application has the beneficial effects that the crown ether compound additive is adopted in the electrolyte, so that the residual amount of Mn ions in the electrolyte can be obviously reduced, a complex can be formed with Mn ions due to the strong coordination environment, the migration of dissolved Mn ions in the solution can be well inhibited, the Mn ions in the electrolyte can be effectively removed, and the thermal stability of the electrolyte can be improved. In addition, the LMFP positive electrode is extremely sensitive to moisture and HF, and the electrolyte is 3- (trimethylsilyl) -2-oxazolidinone (TMS-ON) which contains Si-N characteristic functional groups and can not only remove HF, but also carbonyl and Li existing in the structure + Can enhance LiPF coordination 6 And the dissociation of the ion conductivity is improved. Meanwhile, in order to inhibit Mn ions from reducing on the surface of a negative electrode and catalyze the decomposition of electrolyte, boron trifluoride-Pyridine (PBF) is selected and comprises two functional groups of organic alkali pyridine-Py and-PF 3, wherein-Py can coordinate with metal Mn to form a gridThe structure is deposited on the surface of the anode to form SEI, which inhibits the SEI from being reduced on the surface of the anode, and the acidic substances PF5 and HF in the electrolyte are neutralized. BF3 acts as Lewis acid and as anion acceptor, can dissolve LiF and reduce interface impedance. The method combines the synergistic effect of several additives such as Vinylene Carbonate (VC), 1, 3-Propane Sultone (PS), tris (trimethylsilane) phosphate (TMSP), lithium dioxalate borate (LiBOB) and the like, comprehensively improves the cycle performance of the battery, reduces interface impedance and improves conductivity, meanwhile, the dosage of the additive also needs to be in a certain range, the content of the additive is too low to exert the characteristic advantages of the additive, the content of the additive is too much, the problems of impedance increase, obvious polarization and the like are caused, and the cost is increased.
Detailed Description
The application is described in further detail below in connection with specific examples which are not to be construed as limiting the scope of the application as claimed.
Short description of the following reagents: ethylene carbonate (abbreviated EC), propylene carbonate (abbreviated PC), ethylmethyl carbonate (abbreviated EMC), diethyl carbonate (abbreviated DEC), vinylene Carbonate (VC), 1, 3-Propane Sultone (PS), tris (trimethylsilane) phosphate (TMSP), lithium dioxaborate (LiBOB), 3- (trimethylsilyl) -2-oxazolidinone (TMS-ON), N-diethyltrimethylsilane amine (EMSA), heptamethyldisilazane (H7 DMS), ethylhexamethyldisilazane (EHMDS).
Example 1
Preparation of electrolyte:
at room temperature, in a glove box filled with argon (H 2 O<1ppm，O 2 <1 ppm), solvent: EC. PC, EMC, DEC the mass ratio is 25:5:50:20, removing water by using a 4A molecular sieve to obtain a mixed solvent, and adding lithium salt: liPF (LiPF) 6 Adding into the obtained mixed solvent successively, continuously stirring, cooling with dry ice to ensure that LiPF can be continuously added when the temperature of the electrolyte rises to 2 deg.C 6 Controlling the LiPF in the electrolyte 6 The mass fraction of (2) is 12.5%, colorless transparent liquid is finally obtained, and the additive is added: 12-crown-4 ether 0.2%, TMS-ON:0.3%, PBF:0.3%, VC:1.5%, PS:1 percent of TMSP, 0.5 percent of LiBOB and 0.3 percent of LiBOB, and stirring uniformly to obtain electrolyte.
The preparation methods of the electrolytes described in examples 2 to 13 and comparative examples 1 to 3 were substantially the same as those of example 1, and the formulation of the electrolytes is shown in table 1.
Preparing a positive electrode plate:
LiMn as a positive electrode active material x Fe 1-x PO4 (x is more than or equal to 0.5 and less than or equal to 0.7), conductive agent acetylene black (Super P) and binder polyvinylidene fluoride (PVDF) are uniformly mixed according to the mass ratio of LMFP to Super P to PVDF=92.5 to 3.5 to 4, uniformly dispersed in 1-methyl-2-pyrrolidone (NMP) to prepare uniform black slurry, and the mixed black slurry is coated on two sides of an aluminum foil, baked, rolled and cut into pieces to obtain the positive pole piece.
Preparing a negative electrode plate:
uniformly mixing graphite serving as a negative electrode active material, acetylene black serving as a conductive agent (Super P) and SBR serving as a binder according to the mass ratio of graphite to Super P to SBR=94:3:3, uniformly dispersing the mixture in deionized water to prepare uniform black slurry, coating the mixed slurry on two sides of a copper foil, baking, rolling and cutting to obtain a negative electrode plate.
Manufacturing a soft package battery:
and stacking the prepared positive plate, the diaphragm and the negative plate in sequence, enabling the diaphragm to be positioned between the positive plate and the negative plate, carrying out lamination process, hot pressing and shaping, welding the electrode lugs to obtain a bare cell, placing the bare cell in an outer packaging aluminum plastic film formed by punching holes, placing in an oven at 80+/-10 ℃ for baking for 48 hours, injecting the prepared electrolyte into a dried battery, standing, forming and capacity-dividing, and thus completing the preparation of the lithium ion soft package battery.
Cell performance test:
high temperature cycle performance test: the soft pack batteries obtained in each of the examples and comparative examples were subjected to a charge-discharge cycle test at 45.+ -. 2 ℃ at a charge-discharge rate of 1C/C in the range of 2.5-4.2V, and the first-week discharge specific capacity and the discharge specific capacity after 500-week cycle of the batteries were recorded. Capacity retention for 500 weeks = specific discharge capacity for 500 weeks/specific discharge capacity for first week 100%, and the recorded data are shown in table 1.
High temperature storage performance test: the soft pack batteries obtained in each of the examples and comparative examples were subjected to a charge-discharge test at a charge-discharge rate of 1C/1C in a range of 2.5 to 4.2V at 60±2 ℃ and the first week discharge specific capacity of the battery was recorded, and then stored at 60±2 ℃ for 35 days, and again subjected to the charge-discharge test and the discharge specific capacity was recorded. High temperature storage capacity retention = discharge specific capacity after 7 days/first week discharge specific capacity 100%, recorded data are given in table 1.
Normal temperature DCR test: the secondary batteries 1C obtained in each of the examples and comparative examples were charged to 4.2V at 25±2 ℃, discharged at 1C capacity for 30min, adjusted to 50% SOC, and then subjected to 5C constant current pulse discharge for 10s, and after 50% SOC was adjusted by the above-mentioned SOC adjustment method, the secondary batteries were recharged for 10s, and dcr= (voltage before pulse discharge-voltage after pulse discharge)/discharge current of 100% was calculated.
Wherein SOC (state of charge) refers to the current capacity state of the secondary battery. 100% SOC is fully charged within the design operating range.
Low temperature DCR test: the secondary batteries 1C obtained in each of the examples and comparative examples were charged to 4.2V at-20±2 ℃, discharged at 1C capacity for 30min, adjusted to 50% SOC, and then subjected to 0.5C constant current pulse discharge for 10s, and 50% SOC was adjusted according to the above-mentioned SOC adjustment method, and then charged for 10s, to calculate dcr= (voltage before pulse discharge-voltage after pulse discharge)/discharge current of 100%.
The preparation methods of the electrolytes described in examples 2 to 13 and comparative examples 1 to 3 were substantially the same as those of example 1, and the formulations are shown in table 1.
Analysis of experimental results:
as can be seen from the experimental results of comparative examples 1, 2, 3, 4 and 5 and comparative examples 1, 2 and 3, the addition of the 12-crown-4 ether, TMS-ON and PBF additives ON the basis of VC, PS, TMSP, liBOB conventional additives significantly improves the cycle and storage properties. Compared with a blank group, the traditional additive combination is obviously improved in circulation and storage, but still is in a poor level, the actual application requirements cannot be met, the additive scheme is introduced, and high-temperature circulation and storage are obviously improved, mainly because the problems of dissolution, migration and deposition of transition metal Mn ions can be solved in a targeted manner by the 12-crown-4 ether, TMS-ON and PBF additives, meanwhile, corrosion of moisture and HF ON a positive electrode material is inhibited, and excellent electrical performance is realized by combining and using all the additives. Further, as can be seen from comparative examples 1, 2, 3, 4, and 5, only one of the 12-crown-4 ether, TMS-ON, and PBF was used alone, although the cycle and storage performance could be improved as compared with the blank group, the effect was more general, which is mainly due to Mn dissolution of the LMFP positive electrode material during the cycle and storage, as described above, mn dissolution not only caused the structural destruction of the positive electrode material, but also accelerated electrolyte decomposition of the dissolved Mn ions, and further the catalytic decomposition of the Mn ions deposited ON the surface of the negative electrode, accelerated active lithium loss. Therefore, in order to comprehensively improve the battery performance, negative effects ON various levels of the battery are required to be inhibited against Mn ion dissolution before and after the occurrence of the phenomenon, the decomposition of the electrolyte by Mn dissolution can be well inhibited by the 12-crown-4 ether, the deposition of the negative electrode by Mn ions can be inhibited by the PBF additive, the SEI film is catalytically decomposed, HF is assisted to be removed by the TMS-ON characteristic functional group, the acidity of the electrolyte is reduced, and the selected additive is comprehensively used, so that the synergistic advantage can be better exerted, and the comprehensive performance of the battery is improved.
As can be seen from comparing the experimental results of examples 1, 7 and 8, replacing part of DEC with a lower viscosity solvent EMC, both normal temperature and low temperature DCR are improved, because the use of lower viscosity solvents can improve the kinetic performance, promote the lithium ion migration rate, but the high temperature cycle and storage performance are deteriorated, mainly because DEC has better thermal stability, can improve the stability of the electrolyte at high temperature, but further increase DEC usage, and the high temperature cycle and storage performance are not further improved, because after DEC usage is increased, the viscosity of the electrolyte is increased, while facilitating improvement of thermal stability, excessive viscosity inhibits the lithium ion migration rate, and polarization is increased. Considering the performance in combination, the example 1 scheme performs best.
As can be seen from the experimental results of comparative examples 1, 9, and 10, the partial substitution of EC with PC solvent can significantly lower the low temperature DCR, mainly because PC has a lower melting point and exhibits better low temperature performance than EC, and as the PC content further increases, cycle and storage performance deteriorate, because a certain degree of graphite peeling phenomenon may occur with a high PC content.
As can be seen from comparing the experimental results of embodiments 1, 11, and 12, the too high or too low lithium salt content can cause performance deterioration, wherein the too low lithium salt content makes the electrolyte conductivity lower, the too high lithium salt content increases the viscosity of the electrolyte, and the change of the lithium salt content can also cause the difference of solvation structures, affect the solvation energy barrier, and simultaneously affect film formation in the desolvation process, thereby changing the interfacial film component, so that the lithium salt content needs to be optimized.
As can be seen from comparing the experimental results of examples 1, 13, 14 and 15, the further increase of the amounts of TMS-ON and PBF of the 12-crown-4 ether, respectively, has no beneficial effect ON the cycle and storage properties, mainly because the resistance of the adopted additive is larger, and the polarization is increased due to the excessive use. Example 1 is the preferred content of each additive after DOE validation to achieve the optimum combination of properties.
According to the application, the additive content is combined and matched in a preferred range, and meanwhile, DOE experiments are carried out on the additive combination mode, so that the result shows that the embodiment 1 is the optimal combination, and the rest combinations are not listed in the embodiment one by one. By combining the effects, the electrolyte solution scheme for the LMFP battery provided by the application realizes excellent high-temperature circulation and storage performance and has better dynamic performance.
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (5)
1. The lithium iron manganese phosphate battery electrolyte is characterized by comprising lithium salt, an organic solvent and an additive, wherein the additive comprises crown ether compounds, compounds containing Si-N bonds, boron trifluoride-pyridine, vinylene carbonate, 1, 3-propane sultone, tris (trimethylsilane) phosphate and lithium dioxalate borate; the crown ether compound is 12-crown-4 ether; the Si-N bond-containing compound is 3- (trimethylsilyl) -2-oxazolidinone; the mass percentage of the crown ether compound in the electrolyte is 0.1-0.3%; the mass percentage of the Si-N bond-containing compound in the electrolyte is 0.1-0.5%; the mass percentage of the boron trifluoride-pyridine in the electrolyte is 0.1-0.6%; the vinylene carbonate accounts for 0.5% -2% of the total mass of the electrolyte; the 1, 3-propane sultone accounts for 0.5-1.5% of the total mass of the electrolyte; the tris (trimethylsilane) phosphate accounts for 0.2-1% of the total mass of the electrolyte; the lithium dioxalate borate accounts for 0.1 to 0.3 percent of the total mass of the electrolyte.
2. The electrolyte of claim 1 wherein the organic solvent comprises one or more of ethylene carbonate, propylene carbonate, ethylmethyl carbonate, or diethyl carbonate.
3. The electrolyte of claim 1, wherein the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, lithium bis (fluorosulfonyl) imide, or lithium bis (trifluoromethylsulfonyl) imide; the lithium salt accounts for 10-15% of the total mass of the electrolyte.
4. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and the electrolyte according to any one of claims 1 to 3.
5. An electric device comprising the secondary battery according to claim 4 as a power supply source of the electric device.
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