CN117855604A - High-power electrolyte for lithium metal secondary battery, preparation method and application - Google Patents
High-power electrolyte for lithium metal secondary battery, preparation method and application Download PDFInfo
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- CN117855604A CN117855604A CN202311868324.2A CN202311868324A CN117855604A CN 117855604 A CN117855604 A CN 117855604A CN 202311868324 A CN202311868324 A CN 202311868324A CN 117855604 A CN117855604 A CN 117855604A
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 109
- 239000003792 electrolyte Substances 0.000 title claims abstract description 80
- 238000002360 preparation method Methods 0.000 title abstract description 16
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000003085 diluting agent Substances 0.000 claims abstract description 22
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000000654 additive Substances 0.000 claims abstract description 20
- 230000000996 additive effect Effects 0.000 claims abstract description 20
- 229910052751 metal Inorganic materials 0.000 claims abstract description 20
- 239000002184 metal Substances 0.000 claims abstract description 20
- 239000003960 organic solvent Substances 0.000 claims abstract description 19
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910003002 lithium salt Inorganic materials 0.000 claims description 28
- 159000000002 lithium salts Chemical class 0.000 claims description 28
- -1 nonenyl trifluoro ethyl ether Chemical compound 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 9
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 claims description 8
- 239000002131 composite material Substances 0.000 claims description 7
- 239000010410 layer Substances 0.000 claims description 6
- ZUHZGEOKBKGPSW-UHFFFAOYSA-N tetraglyme Chemical compound COCCOCCOCCOCCOC ZUHZGEOKBKGPSW-UHFFFAOYSA-N 0.000 claims description 6
- HVLLSGMXQDNUAL-UHFFFAOYSA-N triphenyl phosphite Chemical compound C=1C=CC=CC=1OP(OC=1C=CC=CC=1)OC1=CC=CC=C1 HVLLSGMXQDNUAL-UHFFFAOYSA-N 0.000 claims description 6
- 229910000838 Al alloy Inorganic materials 0.000 claims description 5
- JFBZPFYRPYOZCQ-UHFFFAOYSA-N [Li].[Al] Chemical compound [Li].[Al] JFBZPFYRPYOZCQ-UHFFFAOYSA-N 0.000 claims description 5
- 239000011261 inert gas Substances 0.000 claims description 5
- YFNKIDBQEZZDLK-UHFFFAOYSA-N triglyme Chemical compound COCCOCCOCCOC YFNKIDBQEZZDLK-UHFFFAOYSA-N 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 4
- 238000005524 ceramic coating Methods 0.000 claims description 4
- 239000012046 mixed solvent Substances 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 239000002985 plastic film Substances 0.000 claims description 4
- 229920006255 plastic film Polymers 0.000 claims description 4
- ZPFAVCIQZKRBGF-UHFFFAOYSA-N 1,3,2-dioxathiolane 2,2-dioxide Chemical compound O=S1(=O)OCCO1 ZPFAVCIQZKRBGF-UHFFFAOYSA-N 0.000 claims description 3
- FSSPGSAQUIYDCN-UHFFFAOYSA-N 1,3-Propane sultone Chemical compound O=S1(=O)CCCO1 FSSPGSAQUIYDCN-UHFFFAOYSA-N 0.000 claims description 3
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 claims description 3
- RRQYJINTUHWNHW-UHFFFAOYSA-N 1-ethoxy-2-(2-ethoxyethoxy)ethane Chemical compound CCOCCOCCOCC RRQYJINTUHWNHW-UHFFFAOYSA-N 0.000 claims description 3
- KIAMPLQEZAMORJ-UHFFFAOYSA-N 1-ethoxy-2-[2-(2-ethoxyethoxy)ethoxy]ethane Chemical compound CCOCCOCCOCCOCC KIAMPLQEZAMORJ-UHFFFAOYSA-N 0.000 claims description 3
- 229910000521 B alloy Inorganic materials 0.000 claims description 3
- NEILRVQRJBVMSK-UHFFFAOYSA-N B(O)(O)O.C[SiH](C)C.C[SiH](C)C.C[SiH](C)C Chemical compound B(O)(O)O.C[SiH](C)C.C[SiH](C)C.C[SiH](C)C NEILRVQRJBVMSK-UHFFFAOYSA-N 0.000 claims description 3
- 229910000861 Mg alloy Inorganic materials 0.000 claims description 3
- 239000004698 Polyethylene Substances 0.000 claims description 3
- 239000004743 Polypropylene Substances 0.000 claims description 3
- PPTSBERGOGHCHC-UHFFFAOYSA-N boron lithium Chemical compound [Li].[B] PPTSBERGOGHCHC-UHFFFAOYSA-N 0.000 claims description 3
- 229940019778 diethylene glycol diethyl ether Drugs 0.000 claims description 3
- SBZXBUIDTXKZTM-UHFFFAOYSA-N diglyme Chemical compound COCCOCCOC SBZXBUIDTXKZTM-UHFFFAOYSA-N 0.000 claims description 3
- GCICAPWZNUIIDV-UHFFFAOYSA-N lithium magnesium Chemical compound [Li].[Mg] GCICAPWZNUIIDV-UHFFFAOYSA-N 0.000 claims description 3
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 0.000 claims description 3
- 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 3
- 229920000573 polyethylene Polymers 0.000 claims description 3
- 229920001155 polypropylene Polymers 0.000 claims description 3
- 239000002356 single layer Substances 0.000 claims description 3
- 125000002733 (C1-C6) fluoroalkyl group Chemical group 0.000 claims description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 239000011572 manganese Substances 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- ZXMGHDIOOHOAAE-UHFFFAOYSA-N 1,1,1-trifluoro-n-(trifluoromethylsulfonyl)methanesulfonamide Chemical compound FC(F)(F)S(=O)(=O)NS(=O)(=O)C(F)(F)F ZXMGHDIOOHOAAE-UHFFFAOYSA-N 0.000 claims 1
- RFGOKUXULFJHDS-UHFFFAOYSA-N FN=S(F)F.FN=S(F)F.[Li] Chemical compound FN=S(F)F.FN=S(F)F.[Li] RFGOKUXULFJHDS-UHFFFAOYSA-N 0.000 claims 1
- 239000003795 chemical substances by application Substances 0.000 claims 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 3
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 3
- 238000007086 side reaction Methods 0.000 abstract description 3
- 239000000126 substance Substances 0.000 abstract description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 abstract 1
- 239000011737 fluorine Substances 0.000 abstract 1
- 229910052731 fluorine Inorganic materials 0.000 abstract 1
- 238000013508 migration Methods 0.000 abstract 1
- 230000005012 migration Effects 0.000 abstract 1
- 230000002035 prolonged effect Effects 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 11
- 230000014759 maintenance of location Effects 0.000 description 9
- 239000000243 solution Substances 0.000 description 7
- 230000008569 process Effects 0.000 description 6
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 5
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 description 4
- 238000011056 performance test Methods 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000005457 optimization Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 239000007784 solid electrolyte Substances 0.000 description 3
- 229910052723 transition metal Inorganic materials 0.000 description 3
- 150000003624 transition metals Chemical class 0.000 description 3
- 229910000572 Lithium Nickel Cobalt Manganese Oxide (NCM) Inorganic materials 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 239000012300 argon atmosphere Substances 0.000 description 2
- 210000004027 cell Anatomy 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000012360 testing method Methods 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
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- FBDMTTNVIIVBKI-UHFFFAOYSA-N [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] Chemical compound [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] FBDMTTNVIIVBKI-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000010835 comparative analysis Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 150000002148 esters Chemical group 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 125000003709 fluoroalkyl group Chemical group 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 150000003949 imides Chemical class 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 125000005463 sulfonylimide group Chemical group 0.000 description 1
- 230000009469 supplementation Effects 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 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
Landscapes
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a high-power electrolyte for a lithium metal secondary battery, a preparation method and application thereof, and belongs to the technical field of chemical power supplies. By adopting the electrolyte, in a lithium secondary battery system with the metal lithium as a negative electrode, the nickel cobalt lithium manganate and the lithium cobaltate as a positive electrode, the discharge rate performance of the lithium secondary battery can be obviously improved, and the cycle life of the lithium secondary battery can be effectively prolonged. According to the invention, through the use of the ether organic solvent, the fluorine-containing ether diluent and the additive, the performance parameters such as the conductivity and the lithium ion migration number of the electrolyte are improved, and a stable electrolyte interface film is formed on the positive electrode and the negative electrode of the lithium metal battery, so that the increase of internal resistance caused by side reaction between the lithium metal negative electrode and the electrolyte is effectively inhibited, and the discharge rate performance and the cycle stability of the lithium metal battery are improved.
Description
Technical Field
The invention belongs to the technical field of chemical power supplies, and particularly relates to a high-power electrolyte for a lithium metal secondary battery, a preparation method and application thereof.
Background
In recent years, with the development of diversification of energy demands, higher demands are being made on energy storage systems with high energy density and long cycle life. The metallic lithium has the highest theoretical capacity (3860 mAh/g) and the most negative electrochemical potential (-3.04V). Compared with the existing lithium ion battery anode material, the metal lithium anode has great potential in meeting the requirement of high energy density. Although metallic lithium negative electrodes exhibit superior theoretical capacity and energy density, they have the following problems during application due to interfacial instability: (1) safety problems with lithium dendrite growth; (2) Irreversible side reactions lead to rapid loss of active materials and rapid increase of battery impedance, and lithium metal secondary batteries have poor rate capability; (3) The "host-free" nature of metallic lithium results in pulverization of the electrode, and lithium metal secondary batteries have a low cycle life. For the research work of the interface stability of the lithium metal anode, scientific researchers respectively conduct researches on electrolyte modification, interface protection layers, structured electrodes and the like. The implementation process of manually constructing the interface protection layer and the structured electrode is generally complex, and related researches at present are all stopped at the level of the cathode of the small-area button cell, so that large-area engineering application is difficult to realize. The current optimization of the electrolyte for the lithium metal secondary battery is an effective means for improving the multiplying power performance and the cycle performance of the lithium metal secondary battery, engineering application is easy to realize through the optimization of the electrolyte, and the lithium metal secondary battery has great potential in the application aspect of a high specific energy metal lithium system battery in the future.
Disclosure of Invention
Aiming at the problems existing in the prior art, the invention provides a high-power electrolyte for a lithium metal secondary battery, a preparation method and application thereof. The electrolyte consists of an ether organic solvent, an electrolyte, an additive and a diluent. The electrolyte generates a fluoride solid electrolyte interface film (SEI) rich in inorganic lithium salt on a metal lithium negative electrode, and the rate capability and the cycle stability of the lithium metal secondary battery are effectively improved through the protection effect of the inorganic interface layer of the electrolyte. The electrolyte generates a high-potential stable electrolyte interface film (CEI) on the surface of a high-voltage positive electrode such as lithium nickel cobalt manganese oxide, lithium cobalt oxide and the like through the introduction of the additive, and the interface film has good ion transmission capacity, so that the rate performance of the battery is effectively improved.
The invention aims to solve the technical problems of high-rate discharge and the like of a lithium metal secondary battery, and adopts the following technical scheme: a high-power electrolyte for lithium metal secondary battery is composed of ether organic solvent, lithium salt electrolyte, additive and diluent, and has lithium salt concentration of 1.5-4 mol/L and ionic conductivity of 1-10 mS/cm.
The additive is one or more of 1, 3-propane sultone, 1, 3-propylene sultone, ethylene sulfate, ethylene carbonate, triphenyl phosphite, tris (trimethylsilane) phosphate and tris (trimethylsilane) borate.
The ether organic solvent is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether and triethylene glycol diethyl ether.
The diluent is R 1 —O—R 2 Wherein R is 1 And R is 2 Is a C1-C6 fluoroalkyl group.
The diluent is 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether, perfluor nonenyl trifluoro ethyl ether 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether one or more of 1h,5 h-octafluoropentyl-1, 2-tetrafluoroethyl ether.
The lithium salt electrolyte is one or a mixture of two of lithium difluorophosphate, lithium hexafluorophosphate, lithium bistrifluoromethane sulfonyl imide, lithium bistrifluoro sulfonyl imide, lithium difluorooxalato borate and lithium dioxaato borate.
According to the preparation method of the high-power electrolyte for the lithium metal secondary battery, a certain weight of electrolyte lithium salt is added into an ether organic solvent and a diluent which are uniformly mixed in proportion under the protection of inert gas, and the mixture is stirred for 0.5 to 3 hours at the temperature of between 25 and 40 ℃, and after the lithium salt is dissolved, a certain weight of additive with the proportion of 0.2 to 1.0 percent is added into the electrolyte, and the mixture is stirred for 0.5 to 3 hours at the temperature of between 25 and 40 ℃.
The method specifically comprises the following steps:
step one, under the protection of inert gas, stirring ether organic solvent and diluent in a certain proportion for 0.2 to 0.5 hour at the temperature of 20 to 25 ℃ and uniformly mixing;
adding a certain weight of lithium salt electrolyte into the uniformly mixed solvent, and stirring for 0.5-3 h at the temperature of 25-40 ℃;
and thirdly, adding a certain weight of additive into the electrolyte after the lithium salt electrolyte is dissolved, and stirring for 0.5-3 h at the temperature of 25-40 ℃.
The lithium metal secondary battery adopting the electrolyte comprises a positive electrode, a negative electrode, a diaphragm and an aluminum plastic film, and is characterized in that the positive electrode is one of nickel cobalt lithium manganate, lithium cobaltate and lithium-rich manganese-based oxide positive electrode; the negative electrode is one of a metal lithium belt, a metal lithium magnesium alloy, a metal lithium aluminum alloy and a metal lithium boron alloy; the diaphragm is one of a single-layer polypropylene diaphragm, a three-layer polypropylene-polyethylene composite diaphragm and a polypropylene-alumina ceramic coating composite diaphragm.
The invention has the beneficial effects that: the electrolyte forms an interfacial film on the surfaces of the positive electrode and the negative electrode of the lithium metal secondary battery by the combined action of the additive with the organic solvent, the diluent, the lithium salt and the additive. Wherein:
(1) The electrolyte interface film (CEI) with stable high potential generated on the surface of the positive electrode can effectively inhibit the dissolution of the positive electrode transition metal of the lithium metal secondary battery in the long-life cycle process, effectively improve the capacity retention rate of the battery and improve the cycle stability of the battery;
(2) The fluoride (LiF) solid electrolyte interface film (SEI) rich in inorganic lithium salt is generated on the surface of the metal lithium negative electrode in situ through the optimization of the electrolyte formula, liF has higher surface energy, lithium is promoted to be densely deposited along the surface, dendritic and spongy lithium deposition is reduced, and the SEI film can reduce the internal resistance of the lithium metal secondary battery in the cycle process, so that the multiplying power discharge performance of the lithium metal secondary battery is improved.
In addition, the electrolyte provided by the invention has the advantages of simple and convenient preparation process and high preparation efficiency, provides an engineering scheme in practical application of the lithium metal secondary battery, greatly improves the overall performance of the lithium metal secondary battery, is beneficial to improving the market application prospect of the battery, and has great production practice significance.
Drawings
Fig. 1 is a graph showing the rate discharge performance of lithium metal secondary batteries using the electrolytes of example 1 and comparative example;
fig. 2 is a graph showing the cycle capacity retention ratio of lithium metal secondary batteries using the electrolytes of example 1 and comparative example.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
The embodiment of the invention provides an electrolyte for a lithium metal secondary battery, which is used for inhibiting volume expansion of the lithium metal secondary battery in a circulating process. The electrolyte comprises: the organic solvent, the diluent, the additive and the lithium salt, wherein the organic solvent and the diluent are ethers, the diluent contains fluoroalkyl with 1-10 carbon atoms, and the additive is esters; in the electrolyte, the mass fraction of the additive is 0.5-10%, and the concentration of the lithium salt is 1.5-4 mol/L. The additive is used to blend an organic solvent, a diluent, and a lithium salt to form an interfacial film on the electrode surface of a lithium metal secondary battery.
The ionic conductivity of the electrolyte is 1mS/cm to 10mS/cm.
The organic solvent comprises at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether and triethylene glycol diethyl ether. Preferably, the organic solvent is selected from ethylene glycol dimethyl ether and triethylene glycol dimethyl ether.
The diluent comprises 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether, perfluor nonenyl trifluoroethyl ether 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether at least one of 1H, 5H-octafluoropentyl-1, 2-tetrafluoroethyl ether. Preferred diluents are 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether. The electrolyte containing the diluent generates a fluoride (LiF) solid electrolyte interface film (SEI) rich in inorganic lithium salt on a metallic lithium negative electrode, liF has higher surface energy, can promote the compact deposition of lithium along the surface of the negative electrode, reduces the deposition of dendritic and spongy lithium, can effectively improve the interface stability of the negative electrode, reduces the interface resistance, and effectively improves the discharge rate performance and the cycle stability of a lithium metal secondary battery.
The additive comprises at least one of 1, 3-propane sultone, 1, 3-propylene sultone, ethylene sulfate, vinylene carbonate, triphenyl phosphite, tris (trimethylsilane) phosphate and tris (trimethylsilane) borate. Under the combined action of the additive, an organic solvent, a diluent and lithium salt, an interface film is formed on the surfaces of the positive electrode and the negative electrode of the lithium metal secondary battery, wherein the electrolyte interface film (CEI) with stable high potential is generated on the surface of the positive electrode, so that the dissolution of the positive electrode transition metal of the lithium metal secondary battery in the long-life cycle process can be effectively inhibited, the capacity retention rate of the battery can be effectively improved, and the cycle stability of the battery can be improved.
The lithium salt comprises one or two of lithium difluorophosphate, lithium hexafluorophosphate, lithium bistrifluoromethane sulfonyl imide, lithium bistrifluorosulfonyl imide, lithium difluorooxalato borate and lithium dioxaato borate.
The invention also provides a preparation method of the electrolyte for the lithium metal secondary battery, which comprises the following steps:
s1, adding lithium salt into an organic solvent and a diluent under the protection of inert gas, and fully stirring until the lithium salt is clear and transparent;
and S2, adding an additive into the solution obtained in the step S1, and fully stirring until the solution is clear and transparent.
The volume ratio of the organic solvent to the diluent is 1:1.5.
Since lithium salts are susceptible to thermal decomposition, the temperature of the electrolyte and the duration of stirring should be controlled when preparing the electrolyte. In some embodiments, the electrolyte is prepared at a temperature of 25℃to 40℃and stirred for a period of 0.5h to 3h.
The embodiment of the invention also provides a lithium metal secondary battery, which comprises a positive electrode, a negative electrode, a diaphragm, an aluminum plastic film and the electrolyte for the lithium metal secondary battery.
The positive electrode of the secondary battery is a nickel cobalt lithium manganate positive electrode and a lithium cobaltate positive electrode; the negative electrode is a metal lithium belt, a metal lithium magnesium alloy, a metal lithium aluminum alloy or a metal lithium boron alloy; the diaphragm is a single-layer polypropylene diaphragm, a three-layer polypropylene-polyethylene composite diaphragm or a polypropylene-alumina ceramic coating composite diaphragm.
The invention has been subjected to a plurality of experiments in succession, and the invention is further described in detail by referring to some experimental results, and the detailed description is provided below in connection with specific examples.
Example 1:
preparing an electrolyte for a metal lithium ion battery:
s1, magnetically stirring triethylene glycol dimethyl ether and 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether for 0.5h at 25 ℃ according to the volume ratio of 1:1.5 in an argon atmosphere glove box, adding lithium bistrifluoromethane sulfonyl imide into a mixed solvent at the molar concentration of 4.0mol/L, and stirring for 2h at 30 ℃ by using a magnetic stirrer until lithium salt is completely dissolved, wherein the solution is clear and transparent;
and s2, adding vinylene carbonate which accounts for 2% of the total mass of the prepared electrolyte into the solution obtained in the step s1, and stirring for 1h at 25 ℃ by using a magnetic stirrer until the solution is clear and transparent, thus obtaining the electrolyte for the lithium metal secondary battery.
Preparation of lithium metal secondary battery:
s1, preparation of an anode: uniformly dispersing 97wt% of positive electrode active material nickel cobalt lithium manganate (NCM 811), 1wt% of conductive carbon black, a conductive agent consisting of 0.5wt% of conductive agent carbon nano tube and 1.5wt% of binder PVDF in a proper amount of NMP solvent through a refiner, wherein the PVDF accounts for 5wt% in the NMP solvent; and coating the uniformly dispersed slurry on an aluminum foil current collector to prepare a positive electrode, and slitting and rolling to obtain a positive electrode plate.
s2, preparation of a negative electrode: cutting a metal lithium aluminum alloy belt with the thickness of 0.04mm into a proper size, pressing a copper tab on a lithium sheet at a fixed position by using an oil press, and pressing a lithium aluminum alloy belt with the same size and thickness on one side of the lithium belt covered by the copper tab for lithium supplementation so as to avoid capacity loss at the covered position of the copper tab and obtain a negative electrode plate of the lithium metal secondary battery.
And s3, sequentially stacking corresponding sheets according to the sequence of a metal lithium negative electrode, a polypropylene-alumina ceramic coating composite diaphragm and a positive electrode in a lamination manner to obtain a 17Ah lithium metal secondary battery cell, packaging by using a lithium battery grade aluminum-plastic film, and preparing the lithium metal secondary soft-package battery through the technological processes of liquid injection (the injection amount of the electrolyte for the lithium metal secondary battery prepared by the preparation is 1.5 g/Ah), infiltration, formation, gas removal and the like.
Performance test:
and (3) multiplying power performance test: charging to 4.4V was performed at a rate of 0.2C using a charging and discharging apparatus, and then discharging to 2.75V at a rate of 3C.
And (3) testing the cycle performance: the charge-discharge cycle performance test was performed at a rate of 0.2C using a charge-discharge apparatus, with a charge cutoff voltage of 4.4V and a discharge cutoff voltage of 2.75V.
Comparative examples:
the difference from example 1 is in the preparation of an electrolyte for a lithium metal secondary battery. The preparation and performance test of the lithium metal secondary battery in this comparative example were identical to those of example 1.
In this comparative example, the step of preparing an electrolyte for a lithium metal secondary battery includes: in an argon atmosphere glove box, lithium hexafluorophosphate was added to a mixed solvent of fluoroethylene carbonate and methylethyl carbonate (volume ratio 1:2) at a molar concentration of 1.0mol/L, and stirred using a magnetic stirrer at 30 ℃ for 1 hour until the lithium salt was completely dissolved, and the solution was clear and transparent. 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether was then added to the above solution at 10% by weight, and stirred using a magnetic stirrer at 25℃for 1 hour.
The test results of example 1 and comparative example were subjected to comparative analysis, and the comparative results are referred to fig. 1-2.
Comparison of rate discharge performance of lithium metal secondary battery: as can be seen from fig. 1, under the same charge-discharge regime, the battery using the electrolyte in example 1 has excellent rate discharge performance compared with the battery using the electrolyte in comparative example, and the 3C discharge capacity of the battery is higher than the 0.2C discharge capacity retention rate; the battery 3C using the electrolyte of example 1 was discharged at a discharge capacity retention rate of 96.03% compared to 0.2C, and the battery 3C using the electrolyte of the comparative example was discharged at a discharge capacity retention rate of 72.55% compared to 0.2C. The results show that the electrolyte in the embodiment 1 has the function of generating a compact SEI film with small interface resistance on the surface of the lithium metal negative electrode, so that the internal resistance of the battery is effectively reduced, and the rate discharge performance of the battery is improved.
Lithium metal secondary battery cycle capacity retention ratio comparison: as can be seen from fig. 2, example 1 has more excellent cycle stability than the battery using the electrolyte of the comparative example under the same charge-discharge system, and the life performance of the lithium metal secondary battery is improved to some extent by optimizing the electrolyte. The battery using the electrolyte of example 1 still has a capacity retention rate of 80% or more after being stably circulated for 155 weeks in a lean state, whereas the battery using the electrolyte of comparative example has a capacity jump phenomenon after being circulated for only 54 weeks. This is because the electrolyte of example 1 forms a high potential stable CEI film on the surface of the positive electrode of the battery and forms a high interface stability SEI film on the surface of the negative electrode of the lithium metal, which can effectively inhibit side reactions caused by dissolution of the transition metal of the positive electrode during long-life cycle of the lithium metal secondary battery, and inhibit volume expansion due to pulverization of the lithium metal, thereby effectively improving the capacity retention rate of the battery and the cycle stability of the battery.
Compared with the prior art, the electrolyte for improving the multiplying power performance of the lithium metal secondary battery has obvious effects of improving the interface stability of the positive electrode and the negative electrode of the lithium metal secondary battery and reducing the discharge internal resistance of the lithium metal secondary battery, and can effectively improve the cycle stability of the lithium metal secondary battery; the preparation method of the high-power electrolyte for the lithium metal secondary battery and the lithium metal secondary battery provided by the invention provide an engineering scheme in the practical application of the lithium metal secondary battery, greatly improve the overall performance of the lithium metal secondary battery, are beneficial to improving the market application prospect of the battery, and have great production practice significance. It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explanation of the principles of the present invention and are in no way limiting of the invention. Accordingly, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present invention should be included in the scope of the present invention. Furthermore, the appended claims are intended to cover all such changes and modifications that fall within the true scope and boundary of the claims, or equivalents of such scope and boundary.
Claims (9)
1. The high-power electrolyte for the lithium metal secondary battery is characterized by comprising an ether organic solvent, a lithium salt electrolyte, an additive and a diluent, wherein the concentration of the lithium salt of the electrolyte is 1.5-4 mol/L, and the ionic conductivity is 1-10 mS/cm.
2. The high-power electrolyte for lithium metal secondary batteries according to claim 1, wherein the additive is one or more of 1, 3-propane sultone, ethylene sulfate, vinylene carbonate, triphenyl phosphite, tris (trimethylsilane) phosphate, tris (trimethylsilane) borate.
3. The high-power electrolyte for lithium metal secondary batteries according to claim 1, wherein the ether-type organic solvent is one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, and triethylene glycol diethyl ether.
4. The high-power electrolyte for a lithium metal secondary battery according to claim 1, wherein the diluteThe releasing agent is R 1 —O—R 2 Wherein R is 1 And R is 2 Is a C1-C6 fluoroalkyl group.
5. The high-power electrolyte for a lithium metal secondary battery according to claim 4, wherein, the diluent is 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether, perfluor nonenyl trifluoro ethyl ether 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether one or more of 1h,5 h-octafluoropentyl-1, 2-tetrafluoroethyl ether.
6. The high-power electrolyte for a lithium metal secondary battery according to claim 1, wherein the lithium salt electrolyte is one or a mixture of two of lithium difluorophosphate, lithium hexafluorophosphate, lithium bistrifluoro-methanesulfonimide, lithium bistrifluoro-sulfimide, lithium difluorooxalato-borate, and lithium bisoxalato-borate.
7. The method for preparing a high-power electrolyte for a lithium metal secondary battery according to any one of claims 1 to 6, wherein a certain weight of electrolyte lithium salt is added to an ether organic solvent and a diluent which are uniformly mixed in proportion under the protection of inert gas, and stirred for 0.5 to 3 hours at a temperature of between 25 and 40 ℃, and after the lithium salt is dissolved, a certain weight of additive is added to the electrolyte at a ratio of between 0.2 and 1.0 percent, and stirred for 0.5 to 3 hours at a temperature of between 25 and 40 ℃.
8. The method for preparing a high-power electrolyte for a lithium metal secondary battery according to claim 7, comprising the steps of:
step one, under the protection of inert gas, stirring ether organic solvent and diluent in a certain proportion for 0.2 to 0.5 hour at the temperature of 20 to 25 ℃ and uniformly mixing;
adding a certain weight of lithium salt electrolyte into the uniformly mixed solvent, and stirring for 0.5-3 h at the temperature of 25-40 ℃;
and thirdly, adding a certain weight of additive into the electrolyte after the lithium salt electrolyte is dissolved, and stirring for 0.5-3 h at the temperature of 25-40 ℃.
9. A lithium metal secondary battery adopting the electrolyte of any one of claims 1-7, comprising a positive electrode, a negative electrode, a diaphragm and an aluminum plastic film, wherein the positive electrode is one of nickel cobalt lithium manganate, lithium cobaltate and lithium-rich manganese-based oxide positive electrodes; the negative electrode is one of a metal lithium belt, a metal lithium magnesium alloy, a metal lithium aluminum alloy and a metal lithium boron alloy; the diaphragm is one of a single-layer polypropylene diaphragm, a three-layer polypropylene-polyethylene composite diaphragm and a polypropylene-alumina ceramic coating composite diaphragm.
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