CN117638233A - Flame-retardant lithium-rich manganese-based lithium ion battery high-voltage electrolyte - Google Patents
Flame-retardant lithium-rich manganese-based lithium ion battery high-voltage electrolyte Download PDFInfo
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 96
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 65
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 64
- 239000011572 manganese Substances 0.000 title claims abstract description 49
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 title claims abstract description 45
- 229910052748 manganese Inorganic materials 0.000 title claims abstract description 45
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 43
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 43
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 title claims abstract description 14
- 239000003063 flame retardant Substances 0.000 title claims abstract description 14
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 26
- 239000010452 phosphate Substances 0.000 claims abstract description 26
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 24
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 22
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 20
- 238000013329 compounding Methods 0.000 claims abstract description 5
- ABDBNWQRPYOPDF-UHFFFAOYSA-N carbonofluoridic acid Chemical compound OC(F)=O ABDBNWQRPYOPDF-UHFFFAOYSA-N 0.000 claims abstract description 3
- 125000000217 alkyl group Chemical group 0.000 claims description 16
- -1 fluoro carboxylic ester Chemical class 0.000 claims description 11
- 150000002148 esters Chemical class 0.000 claims description 9
- 125000001153 fluoro group Chemical group F* 0.000 claims description 7
- 239000002253 acid Substances 0.000 claims description 6
- 125000003342 alkenyl group Chemical group 0.000 claims description 6
- GZKHDVAKKLTJPO-UHFFFAOYSA-N ethyl 2,2-difluoroacetate Chemical compound CCOC(=O)C(F)F GZKHDVAKKLTJPO-UHFFFAOYSA-N 0.000 claims description 5
- DQWPFSLDHJDLRL-UHFFFAOYSA-N triethyl phosphate Chemical compound CCOP(=O)(OCC)OCC DQWPFSLDHJDLRL-UHFFFAOYSA-N 0.000 claims description 5
- WVLBCYQITXONBZ-UHFFFAOYSA-N trimethyl phosphate Chemical compound COP(=O)(OC)OC WVLBCYQITXONBZ-UHFFFAOYSA-N 0.000 claims description 5
- STSCVKRWJPWALQ-UHFFFAOYSA-N TRIFLUOROACETIC ACID ETHYL ESTER Chemical compound CCOC(=O)C(F)(F)F STSCVKRWJPWALQ-UHFFFAOYSA-N 0.000 claims description 4
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 4
- IRWIXUQVVIFUPL-UHFFFAOYSA-N propyl 2-fluoroacetate Chemical compound CCCOC(=O)CF IRWIXUQVVIFUPL-UHFFFAOYSA-N 0.000 claims description 4
- QLCATRCPAOPBOP-UHFFFAOYSA-N tris(1,1,1,3,3,3-hexafluoropropan-2-yl) phosphate Chemical compound FC(F)(F)C(C(F)(F)F)OP(=O)(OC(C(F)(F)F)C(F)(F)F)OC(C(F)(F)F)C(F)(F)F QLCATRCPAOPBOP-UHFFFAOYSA-N 0.000 claims description 4
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 3
- 150000001733 carboxylic acid esters Chemical class 0.000 claims description 3
- 125000002015 acyclic group Chemical group 0.000 claims description 2
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 claims description 2
- 150000003949 imides Chemical class 0.000 claims 1
- 230000014759 maintenance of location Effects 0.000 abstract description 8
- 230000007774 longterm Effects 0.000 abstract description 4
- 230000001351 cycling effect Effects 0.000 abstract description 2
- 230000003111 delayed effect Effects 0.000 abstract description 2
- 230000001681 protective effect Effects 0.000 abstract description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 abstract 1
- 238000012360 testing method Methods 0.000 description 14
- 238000002156 mixing Methods 0.000 description 12
- 238000000034 method Methods 0.000 description 11
- 239000007774 positive electrode material Substances 0.000 description 11
- 230000008569 process Effects 0.000 description 8
- 239000002904 solvent Substances 0.000 description 7
- 229910013872 LiPF Inorganic materials 0.000 description 6
- 101150058243 Lipf gene Proteins 0.000 description 6
- 230000000704 physical effect Effects 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 230000001965 increasing effect Effects 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 3
- 229910013188 LiBOB Inorganic materials 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000003960 organic solvent Substances 0.000 description 3
- 238000006864 oxidative decomposition reaction Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- 229920001774 Perfluoroether Polymers 0.000 description 2
- ABLZXFCXXLZCGV-UHFFFAOYSA-N Phosphorous acid Chemical class OP(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000003064 anti-oxidating effect Effects 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- GVBWFXWJTVAKMW-UHFFFAOYSA-N butyl 2,2-difluoroacetate Chemical compound CCCCOC(=O)C(F)F GVBWFXWJTVAKMW-UHFFFAOYSA-N 0.000 description 2
- JHRWWRDRBPCWTF-OLQVQODUSA-N captafol Chemical compound C1C=CC[C@H]2C(=O)N(SC(Cl)(Cl)C(Cl)Cl)C(=O)[C@H]21 JHRWWRDRBPCWTF-OLQVQODUSA-N 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 229910021382 natural graphite Inorganic materials 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 2
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 description 1
- 235000009161 Espostoa lanata Nutrition 0.000 description 1
- 240000001624 Espostoa lanata Species 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000007983 Tris buffer Substances 0.000 description 1
- KLARSDUHONHPRF-UHFFFAOYSA-N [Li].[Mn] Chemical compound [Li].[Mn] KLARSDUHONHPRF-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000004807 desolvation Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- DEUISMFZZMAAOJ-UHFFFAOYSA-N lithium dihydrogen borate oxalic acid Chemical compound B([O-])(O)O.C(C(=O)O)(=O)O.C(C(=O)O)(=O)O.[Li+] DEUISMFZZMAAOJ-UHFFFAOYSA-N 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 150000003014 phosphoric acid esters Chemical class 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000002468 redox effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- 238000007614 solvation Methods 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 229910001428 transition metal ion Inorganic materials 0.000 description 1
- 125000002023 trifluoromethyl group Chemical group FC(F)(F)* 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a flame-retardant lithium-rich manganese-based lithium ion battery high-voltage electrolyte which is prepared by compounding fluorocarboxylate, phosphate and lithium salt. The fluoro-carboxylate can improve the high-voltage resistance of the electrolyte, form an electrode/electrolyte interface film rich in fluoride on the surface of the electrode, and stabilize the long-term circulation of the battery; the ignition time is delayed by introducing the phosphate, the safety performance of the electrolyte is improved, and the high-pressure resistance of the electrolyte is not influenced. The electrolyte provided by the invention can form compact and stable protective films on the surfaces of the positive electrode and the negative electrode, the capacity retention rate of the LLO I Li half battery in 200 circles in a voltage interval of 2.0-4.8V reaches 90%, and the high-voltage cycling stability and the battery safety of the lithium-rich manganese-based lithium ion battery can be obviously improved by using the electrolyte.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery electrolyte, and particularly relates to a flame-retardant lithium-rich manganese-based lithium ion battery high-voltage electrolyte.
Background
The lithium ion battery has the advantages of high specific energy, high working voltage, long cycle life and the like, is suitable for consumer electronic products such as mobile phones, tablets, computers and the like, and is gradually applied to electric automobiles along with the increasing reduction of traditional fossil fuels and the deterioration of environments. However, the endurance mileage of an electric vehicle becomes a major obstacle for realizing the large-scale application of the electric vehicle at present. The lithium-rich manganese-based positive electrode material has higher theoretical specific capacity and working voltage, and becomes a current research hot spot. However, its higher operating voltage also increases the need for high voltage resistance of the electrolyte. The current commercial electrolyte mainly adopts a mixed solution of carbonic ester and lithium salt, the antioxidation potential of the commercial electrolyte is about 4.5V, and the commercial electrolyte hardly meets the working requirement of high voltage 4.7V of a lithium-rich battery. In addition, lithium-rich materials can also cause thermal runaway safety issues under extreme conditions such as overcharging and overdischarging, with capacity fade and structural failure during long-term cycling.
The current method for solving the problems is mainly focused on the aspects of optimizing an electrolyte formula and improving a positive electrode material, and the optimized electrolyte formula improves the antioxidation capability of the electrolyte, so that the continuous oxidization of the electrolyte in the circulating process can be reduced, and the long-term circulating stability of the battery is improved.
The lithium-rich manganese-based positive electrode material is characterized by high specific discharge capacity (250 mAh/g), easily available material composition, environmental friendliness and low cost, and is considered to be a preferable material for the positive electrode of a next-generation lithium ion battery. However, the lithium-rich manganese-based positive electrode material is rearranged in a Li layer and mixed with transition metal ions under high voltage, so that the structure is converted from a layer state to a spinel phase, and meanwhile, lattice oxygen on the surface of the lithium-rich manganese-based positive electrode is removed under high voltage, so that high-oxidability oxygen anions are formed to attack an organic solvent to decompose an electrolyte, the long-cycle capacity of the lithium-rich manganese-based positive electrode material battery is reduced, and the discharge capacity is seriously degraded.
For high-voltage lithium ion batteries, increasing the working voltage of the battery can certainly improve the discharge capacity of the battery, but the electrolyte is inevitably subjected to severe oxidative decomposition, and meanwhile, the decomposed byproducts are covered on the surfaces of the positive electrode material and the negative electrode material of the battery, so that the charge transfer impedance and Li of the battery are increased + Traversing solid electrolyte membraneImpedance, so that battery performance is rapidly declined, and therefore development of an electrolyte which can adapt to high working voltage is important for development of lithium-rich manganese-based lithium ion batteries.
Patent document publication No. CN111313094a discloses a lithium-rich manganese-based lithium ion battery high-voltage electrolyte containing fluoroethylene carbonate, which effectively improves the high-voltage performance of the battery, and has good compatibility with a lithium-rich manganese-based positive electrode and shows very good performance. However, the working voltage of the electrolyte is only about 4.4V, and it is still difficult to meet the requirements of high-voltage electrolyte in the market, so that the working voltage still needs to be increased to obtain higher energy release.
Patent document CN115763977a discloses a phosphate-containing high-voltage lithium battery additive, which effectively improves the high-voltage performance of the battery, and has good compatibility with graphite negative electrode, silicon oxide 450 and the like. However, the addition amount of the phosphate is only 2% of the content of the electrolyte, so that the electrolyte is still more flammable, and the potential safety hazard still exists.
Patent document with publication number of CN113571770A discloses an electrolyte for a natural graphite negative electrode lithium ion battery, which comprises the following components in percentage by weight: 3-20% of lithium salt, 2-50% of additive and 30-95% of organic solvent; the additive comprises phosphate and phosphonate compounds, sulfate compounds, fluoroether and fluorocarboxylate, wherein the content of the phosphate and phosphonate compounds in the electrolyte accounts for 0.1-10 wt% of the total mass of the electrolyte, the content of the sulfate compounds accounts for 0.1-10 wt% of the total mass of the electrolyte, and the content of the fluoroether and fluorocarboxylate accounts for 1-20 wt% of the total mass of the electrolyte. In a natural graphite negative electrode system, the first efficiency of the lithium ion battery can be improved to 90%, the cycle times are more than 800, and the first efficiency and the cycle life of the lithium ion battery are effectively improved. However, the electrolyte in the technical scheme of the patent document uses a large amount of organic solvent, which is not beneficial to environmental protection and is also not beneficial to improving the flame retardant property.
Based on the above, it is important to develop an electrolyte with high safety, excellent electrochemical performance and good electrode/electrolyte interface.
Disclosure of Invention
The invention solves the technical problem of providing a flame-retardant lithium-rich manganese-based lithium ion battery high-voltage electrolyte, which takes phosphate as a solvent, forms a specific solvation structure with lithium salt according to a certain proportion, takes fluorocarboxylate as a main solvent, and decomposes on the surfaces of a lithium-rich manganese-based positive electrode and a negative electrode to form a stable protective film in the charging and discharging process, so as to prevent the continuous occurrence of side reaction between the electrolyte and the electrode, realize long-term stable circulation of the lithium-rich manganese-based battery under high pressure and not sacrifice higher specific capacity of the battery. In addition, the phosphate can capture free radicals, so that the ignition time of the electrolyte can be remarkably delayed, most performance and safety requirements of the market are met, and meanwhile, active oxygen released by the lithium-rich manganese base in the high-pressure circulation process can be captured, so that continuous oxidative decomposition of the electrolyte under high pressure is avoided.
The invention adopts the following technical scheme to solve the technical problems, and is characterized in that: the electrolyte is prepared by compounding fluoro carboxylic ester, phosphate and lithium salt;
the structural formula of the phosphate is as follows:
wherein R is 1 Is C 1-10 Branched or straight-chain alkyl, fluoro substituted C 2-10 Branched or straight-chain alkyl or C 2-10 Branched or straight chain alkenyl; r is R 2 Is C 1-10 Branched or straight-chain alkyl, fluoro substituted C 2-10 Branched or straight-chain alkyl or C 2-10 Branched or straight chain alkenyl; r is R 3 Is C 1-10 Branched or straight-chain alkyl, fluoro substituted C 2-10 Branched or straight-chain alkyl or C 2-10 Branched or straight chain alkenyl;
the fluorocarboxylic acid ester is acyclic fluorocarboxylic acid ester, and the fluorocarboxylic acid ester has a structural formula:
wherein R is 4 Is fluorineSubstitution C 2-10 Branched or straight chain alkyl; r is R 5 Is F instead of C 2-10 Branched or straight chain alkyl;
the lithium salt is lithium hexafluorophosphate (LiPF) 6 ) Lithium difluorooxalato borate (LiDFOB), lithium tetrafluoroborate (LiBF) 4 ) Lithium dioxalate borate (LiBOB), lithium bis (trifluoromethyl) sulfonimide (LiTFSI), lithium bis (fluoro) sulfonimide (LiLSI) or lithium nitrate (LiNO) 3 ) One or more of the following.
Further defined, the volume ratio of the fluorocarboxylic ester to the phosphoric ester is 1-10:1, preferably 4-8:1.
Further defined, the concentration of lithium salt in the electrolyte is 0.5 to 3mol/L, preferably 0.5 to 1.2mol/L.
Further defined, the phosphate is one or more of trimethyl phosphate, triethyl phosphate, tris (2, 2-trifluoroethyl) phosphate, or tris (hexafluoroisopropyl) phosphate.
Further defined, the fluorocarboxylate is one or more of ethyl trifluoroacetate, ethyl difluoroacetate, or propyl monofluoroacetate.
The specific action mechanism of introducing the fluorinated carboxylic ester into the high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery is as follows: (1) The fluoro-carboxylic ester is decomposed in the first circle to form LiF and covers Yu Fuli manganese-based positive electrode material and the surface of the negative electrode to form a stable interfacial film so as to stabilize the cycle performance of the battery; (2) The fluorocarboxylate imparts highly stable redox properties to the electrolyte and can withstand high voltages. The specific action mechanism of introducing phosphate into the high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery is as follows: (1) phosphate esters are capable of enhancing the solubility of lithium salts; (2) The phosphate captures oxygen anions which are removed from the surface circulation process of the lithium-rich manganese-based positive electrode at high temperature to block electrolyte decomposition reaction which may occur subsequently; (3) Phosphate is decomposed to form a phosphorus-containing interfacial film before recycling to cause Li + Rapidly passes through the interface film. Through reasonable proportion optimization of the fluoro-carboxylic acid ester and the phosphate, the synergistic effect between solvents is realized, and the characteristics of high specific energy and high capacity of the lithium-rich manganese-based positive electrode material are exerted to the greatest extent.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the fluorocarboxylate in the high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery has moderate dielectric constant and desolvation energy, and has very good oxidation-reduction stability, but poor lithium salt dissolving capacity; the phosphate has excellent flame retardance and good lithium salt dissolving capacity. The two solvents are combined and mixed for use, so that the working voltage interval of the lithium ion battery can be met and improved, and the lithium ion battery is compatible with the lithium-rich manganese-based positive electrode material to achieve higher discharge capacity. The discharge specific capacity of the lithium ion battery sold in the market at present is more than 150-200 mAh/g, and the high-voltage electrolyte and the lithium-rich manganese-based positive electrode material can exert the specific capacity exceeding 250mAh/g when combined, so that the requirements of high specific energy and high safety lithium batteries can be met.
The high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery replaces Ethylene Carbonate (EC), ethylmethyl carbonate (DMC) and the like which are commonly used in the market and have flammable working voltage, and the fluorocarboxylate with high oxidation potential and the flame-retardant phosphate are used, so that the working voltage range of the electrolyte is greatly improved, the combustion of the electrolyte can be well prevented, and safer performance is provided for the battery.
The high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery solves the problem of non-ideal long-cycle performance due to the loss of irreversible capacity of the lithium-rich manganese-based positive electrode material in the first cycle.
The high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery is remarkably inhibited from oxidative decomposition under high voltage, and the problem of serious degradation of battery performance is avoided to the greatest extent.
Drawings
Fig. 1 is a comparison of the cycle data of example 1 and comparative example 1 electrolyte applied to 3.0-4.5v 0.5c in NCM 811 Li battery systems.
Fig. 2 is a graph of the initial charge and discharge of 2.0-4.8v 0.5c for the electrolyte of example 1 applied to a lithium-rich manganese-based positive electrode-to-lithium half-cell system.
Detailed Description
The above-described matters of the present invention will be described in further detail by way of examples, but it should not be construed that the scope of the above-described subject matter of the present invention is limited to the following examples, and all techniques realized based on the above-described matters of the present invention are within the scope of the present invention.
The test method adopted by the invention is 2025 button battery test, and the electrolyte is used for assembling the high-nickel ternary positive electrode pair lithium half battery or the graphite negative electrode pair lithium half battery.
Assembling a lithium battery: the button half cell was fabricated in an argon filled glove box. The diaphragm is Celgard2500, the half cell is a pole piece pair lithium piece, the positive pole is rich in lithium manganese base, and the negative pole is a lithium piece.
The flammability of the electrolyte was measured: the quartz cotton ball with the diameter of 0.3 cm to 0.5cm is used for dipping the sufficient electrolyte, and the lighter is used for igniting, so that the combustibility of different electrolytes is observed.
Example 1
A high-voltage electrolyte of lithium-enriched Mn-based lithium ion battery is prepared from lithium salt LiPF 6 The preparation method comprises the steps of: mixing trimethyl phosphate and ethyl difluoroacetate according to a volume ratio of 4:1, and adding LiPF with corresponding mass according to a molar concentration of 0.5mol/L 6 Fully stirring and uniformly mixing to obtain the high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery. The electrolyte system is used for physical property and electrochemical cycle tests of a half cell of LLO I Li, and the test shows that the cell can be cycled for 200 circles under the high pressure of 4.8V, and the capacity retention rate is more than 80%; and the electrolyte is non-flammable.
Example 2
The high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery is prepared by compounding lithium salt LiDFOB, solvent triethyl phosphate and ethyl difluoroacetate, and the preparation method comprises the following steps: and mixing trimethyl phosphate and ethyl difluoroacetate according to a volume ratio of 5:1, adding LiDFOB with corresponding mass according to a molar concentration of 0.6mol/L, and fully stirring and uniformly mixing to obtain the lithium-rich manganese-based lithium ion battery high-voltage electrolyte. The electrolyte system is used for physical property and electrochemical cycle tests of a half cell of LLO I Li, and the test shows that the cell can be cycled for 200 circles under the high pressure of 4.8V, and the capacity retention rate is more than 80%; and the electrolyte is non-flammable.
Example 3
The high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery is prepared by compounding lithium salt LiTFSI, solvent tri (2, 2-trifluoroethyl) phosphate and ethyl trifluoroacetate, and the preparation method comprises the following steps: mixing tri (2, 2-trifluoroethyl) phosphate and ethyl trifluoroacetate according to the volume ratio of 6:1, adding LiTFSI with corresponding mass according to the molar concentration of 0.8mol/L, and fully stirring and uniformly mixing to obtain the lithium-rich manganese-based lithium ion battery high-voltage electrolyte. The electrolyte system is used for physical property and electrochemical cycle tests of a half cell of LLO||Li, and the test shows that the cell can be cycled for 200 circles under the high pressure of 4.8V, and the capacity retention rate is more than 90%; and the electrolyte is non-flammable.
Example 4
A high-voltage electrolyte of lithium-enriched Mn-based lithium ion battery is prepared from LiBOB and LiPF as lithium salts 6 The solvent is compounded by tri (hexafluoroisopropyl) phosphate and propyl monofluoroacetate, and the preparation method comprises the following steps: mixing tri (hexafluoroisopropyl) phosphate and propyl monofluoroacetate according to a volume ratio of 7:1, and adding LiPF with corresponding mass according to a molar concentration of 1mol/L 6 And adding LiBOB with corresponding mass according to the molar concentration of 0.5mol/L, and fully stirring and uniformly mixing to obtain the high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery. The electrolyte system is used for physical property and electrochemical cycle tests of a half cell of LLO I Li, and the test shows that the cell can be cycled for 200 circles under the high pressure of 4.8V, and the capacity retention rate is more than 80%; and the electrolyte is non-flammable.
Example 5
A high-voltage electrolyte of lithium-rich Mn-based lithium ion battery is prepared from lithium salt (LiNO) 3 And LiDFOB, triethyl phosphate and butyl difluoroacetate, and the preparation method comprises the following steps: mixing triethyl phosphate and butyl difluoroacetate according to a volume ratio of 8:1, adding LiDFOB with corresponding mass according to a molar concentration of 0.9mol/L, and adding LiNO with corresponding mass according to a molar concentration of 0.2mol/L 3 Fully stirring and uniformly mixing to obtain the high-voltage electrolyte of the lithium-rich manganese-based lithium ion battery. The method comprisesThe electrolyte is used for physical property and electrochemical cycle tests of a half cell of LLO Li, and the test shows that the cell can be cycled at a high pressure of 4.8V for 200 circles, and the capacity retention rate is more than 70%; and the electrolyte is non-flammable.
Comparative example 1
1M LiPF using the currently conventional commercial electrolyte 6 EC/DMC (3:7, v/v), the electrolyte was tested for flammability, indicating that the commercial electrolyte was flammable. The electrolyte is applied to an LLO||Li half cell for electrochemical performance test, and the test voltage range is as follows: the capacity retention after 200 cycles of 0.5C was 25% at 2.0-4.8V.
Comparative example 2
A lithium-rich Mn-based lithium ion battery electrolyte is prepared from lithium salt LiPF 6 The preparation method comprises the steps of: mixing trimethyl phosphate and ethyl acetate according to a volume ratio of 4:1, and adding LiPF with corresponding mass according to a molar concentration of 0.5mol/L 6 Fully stirring and uniformly mixing to obtain the lithium-rich manganese-based lithium ion battery electrolyte. The electrolyte system is used for physical property and electrochemical cycle tests of a half cell of LLO||Li, and the tests show that the cell can be cycled for 200 circles under the high pressure of 4.8V, and the capacity retention rate is 50%; the electrolyte is non-flammable.
The detailed process equipment and process flow of the present invention are described by the above embodiments, but the present invention is not limited to, i.e., it does not mean that the present invention must be practiced depending on the detailed process equipment and process flow. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.
Claims (7)
1. A flame-retardant lithium-rich manganese-based lithium ion battery high-voltage electrolyte is characterized in that: the electrolyte is prepared by compounding fluoro carboxylic ester, phosphate and lithium salt;
the structural formula of the phosphate is as follows:wherein R is 1 Is C 1-10 Branched or straight-chain alkyl, fluoro substituted C 2-10 Branched or straight-chain alkyl or C 2-10 Branched or straight chain alkenyl; r is R 2 Is C 1-10 Branched or straight-chain alkyl, fluoro substituted C 2-10 Branched or straight-chain alkyl or C 2-10 Branched or straight chain alkenyl; r is R 3 Is C 1-10 Branched or straight-chain alkyl, fluoro substituted C 2-10 Branched or straight-chain alkyl or C 2-10 Branched or straight chain alkenyl;
the fluorocarboxylic acid ester is acyclic fluorocarboxylic acid ester, and the fluorocarboxylic acid ester has a structural formula:wherein R is 4 Is F instead of C 2-10 Branched or straight chain alkyl; r is R 5 Is F instead of C 2-10 Branched or straight chain alkyl;
the lithium salt is one or more of lithium hexafluorophosphate, lithium difluorooxalato borate, lithium tetrafluoroborate, lithium dioxaato borate, lithium bistrifluoromethylsulfonimide, lithium bisfluorosulfonyl imide or lithium nitrate.
2. The flame retardant lithium-rich manganese-based lithium ion battery high voltage electrolyte according to claim 1, wherein: the volume ratio of the fluorinated carboxylic ester to the phosphate ester is 1-10:1.
3. The flame retardant lithium-rich manganese-based lithium ion battery high voltage electrolyte according to claim 1, wherein: the volume ratio of the fluorinated carboxylic ester to the phosphate ester is 4-8:1.
4. The flame retardant lithium-rich manganese-based lithium ion battery high voltage electrolyte according to claim 1, wherein: the concentration of lithium salt in the electrolyte is 0.5-3 mol/L.
5. The flame retardant lithium-rich manganese-based lithium ion battery high voltage electrolyte according to claim 1, wherein: the concentration of lithium salt in the electrolyte is 0.5-1.2mol/L.
6. The flame retardant lithium-rich manganese-based lithium ion battery high voltage electrolyte according to claim 1, wherein: the phosphate is one or more of trimethyl phosphate, triethyl phosphate, tri (2, 2-trifluoroethyl) phosphate or tri (hexafluoroisopropyl) phosphate.
7. The flame retardant lithium-rich manganese-based lithium ion battery high voltage electrolyte according to claim 1, wherein: the fluoro carboxylic acid ester is one or more of ethyl trifluoroacetate, ethyl difluoroacetate or propyl monofluoroacetate.
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