CN115763950A - Electrolyte of lithium-sulfur battery without negative electrode and application thereof - Google Patents
Electrolyte of lithium-sulfur battery without negative electrode and application thereof Download PDFInfo
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 68
- JDZCKJOXGCMJGS-UHFFFAOYSA-N [Li].[S] Chemical compound [Li].[S] JDZCKJOXGCMJGS-UHFFFAOYSA-N 0.000 title claims abstract description 56
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 54
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 43
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000002904 solvent Substances 0.000 claims abstract description 14
- BZLVMXJERCGZMT-UHFFFAOYSA-N Methyl tert-butyl ether Chemical compound COC(C)(C)C BZLVMXJERCGZMT-UHFFFAOYSA-N 0.000 claims description 50
- WNXJIVFYUVYPPR-UHFFFAOYSA-N 1,3-dioxolane Chemical compound C1COCO1 WNXJIVFYUVYPPR-UHFFFAOYSA-N 0.000 claims description 17
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 16
- 229910003002 lithium salt Inorganic materials 0.000 claims description 15
- 159000000002 lithium salts Chemical class 0.000 claims description 15
- 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 15
- 229910052717 sulfur Inorganic materials 0.000 claims description 15
- 239000011593 sulfur Substances 0.000 claims description 15
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 claims description 14
- JWUJQDFVADABEY-UHFFFAOYSA-N 2-methyltetrahydrofuran Chemical compound CC1CCCO1 JWUJQDFVADABEY-UHFFFAOYSA-N 0.000 claims description 13
- -1 lithium hexafluorophosphate Chemical compound 0.000 claims description 13
- 239000012528 membrane Substances 0.000 claims description 10
- 239000000203 mixture Substances 0.000 claims description 10
- 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 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 6
- 239000000919 ceramic Substances 0.000 claims description 6
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 claims description 5
- GLNWILHOFOBOFD-UHFFFAOYSA-N lithium sulfide Chemical compound [Li+].[Li+].[S-2] GLNWILHOFOBOFD-UHFFFAOYSA-N 0.000 claims description 5
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- 239000004743 Polypropylene Substances 0.000 claims description 4
- 150000002170 ethers Chemical class 0.000 claims description 4
- 229920001155 polypropylene Polymers 0.000 claims description 4
- ZUHZGEOKBKGPSW-UHFFFAOYSA-N tetraglyme Chemical compound COCCOCCOCCOCCOC ZUHZGEOKBKGPSW-UHFFFAOYSA-N 0.000 claims description 4
- 239000004698 Polyethylene Substances 0.000 claims description 3
- 239000002131 composite material Substances 0.000 claims description 3
- 239000011889 copper foil Substances 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 229920000573 polyethylene Polymers 0.000 claims description 3
- 239000007774 positive electrode material Substances 0.000 claims description 3
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 2
- 239000004760 aramid Substances 0.000 claims description 2
- 229920003235 aromatic polyamide Polymers 0.000 claims description 2
- 229910052799 carbon Inorganic materials 0.000 claims description 2
- 229920002678 cellulose Polymers 0.000 claims description 2
- 239000001913 cellulose Substances 0.000 claims description 2
- SBZXBUIDTXKZTM-UHFFFAOYSA-N diglyme Chemical compound COCCOCCOC SBZXBUIDTXKZTM-UHFFFAOYSA-N 0.000 claims description 2
- 239000003365 glass fiber Substances 0.000 claims description 2
- 239000010439 graphite Substances 0.000 claims description 2
- 229910002804 graphite Inorganic materials 0.000 claims description 2
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 claims description 2
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 2
- 239000010703 silicon Substances 0.000 claims description 2
- 229910052710 silicon Inorganic materials 0.000 claims description 2
- 229910019142 PO4 Inorganic materials 0.000 claims 1
- 239000007773 negative electrode material Substances 0.000 claims 1
- 239000010452 phosphate Substances 0.000 claims 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims 1
- 239000005077 polysulfide Substances 0.000 abstract description 23
- 229920001021 polysulfide Polymers 0.000 abstract description 23
- 150000008117 polysulfides Polymers 0.000 abstract description 23
- 230000000694 effects Effects 0.000 abstract description 16
- 238000007599 discharging Methods 0.000 abstract description 10
- 238000006243 chemical reaction Methods 0.000 abstract description 8
- 239000013078 crystal Substances 0.000 abstract description 8
- 238000000034 method Methods 0.000 abstract description 8
- 230000008569 process Effects 0.000 abstract description 7
- 150000001450 anions Chemical group 0.000 abstract description 6
- 238000004090 dissolution Methods 0.000 abstract description 5
- 238000013461 design Methods 0.000 abstract description 4
- 238000000354 decomposition reaction Methods 0.000 abstract 1
- 239000011241 protective layer Substances 0.000 abstract 1
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 description 26
- 239000000243 solution Substances 0.000 description 15
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 8
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 description 8
- 229910052760 oxygen Inorganic materials 0.000 description 8
- 239000001301 oxygen Substances 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 6
- 239000010949 copper Substances 0.000 description 5
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 229910017539 Cu-Li Inorganic materials 0.000 description 3
- 229910013553 LiNO Inorganic materials 0.000 description 3
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 239000010405 anode material Substances 0.000 description 3
- 239000006258 conductive agent Substances 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 230000001351 cycling effect Effects 0.000 description 3
- 210000001787 dendrite Anatomy 0.000 description 3
- 238000000151 deposition Methods 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000005303 weighing Methods 0.000 description 3
- LDXJRKWFNNFDSA-UHFFFAOYSA-N 2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]ethanone Chemical compound C1CN(CC2=NNN=C21)CC(=O)N3CCN(CC3)C4=CN=C(N=C4)NCC5=CC(=CC=C5)OC(F)(F)F LDXJRKWFNNFDSA-UHFFFAOYSA-N 0.000 description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 2
- 101150058243 Lipf gene Proteins 0.000 description 2
- 239000013543 active substance Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 230000008021 deposition Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229910003473 lithium bis(trifluoromethanesulfonyl)imide Inorganic materials 0.000 description 2
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 description 2
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000007614 solvation Methods 0.000 description 2
- JQMFQLVAJGZSQS-UHFFFAOYSA-N 2-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]piperazin-1-yl]-N-(2-oxo-3H-1,3-benzoxazol-6-yl)acetamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)N1CCN(CC1)CC(=O)NC1=CC2=C(NC(O2)=O)C=C1 JQMFQLVAJGZSQS-UHFFFAOYSA-N 0.000 description 1
- 239000002000 Electrolyte additive Substances 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 229910018091 Li 2 S Inorganic materials 0.000 description 1
- 229910001216 Li2S Inorganic materials 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical group [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000009920 chelation Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- OPHUWKNKFYBPDR-UHFFFAOYSA-N copper lithium Chemical compound [Li].[Cu] OPHUWKNKFYBPDR-UHFFFAOYSA-N 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000000635 electron micrograph Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000013538 functional additive Substances 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000000543 intermediate Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 239000011244 liquid electrolyte Substances 0.000 description 1
- 238000006138 lithiation reaction Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000007784 solid electrolyte Substances 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
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- 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
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Abstract
The invention discloses electrolyte of a cathode-free lithium-sulfur battery and application thereof, aiming at solving the problems of shuttle effect and dendritic crystal growth of a lithium cathode caused by dissolution of polysulfide formed by reaction in the electrolyte during charge and discharge of the cathode-free lithium-sulfur battery. The electrolyte designed by the invention can reduce the solubility to polysulfide and eliminate shuttle effect by reasonably introducing the ether solvent with steric hindrance; and the decomposition of anions can be promoted, and a protective layer rich in LiF is generated, so that the growth of dendritic crystals of the lithium cathode is inhibited, and finally the cathode-free lithium-sulfur battery can keep good capacity exertion in the charging and discharging process. Therefore, the electrolyte for the lithium-sulfur battery without the negative electrode and the application thereof have great significance for the design and large-scale application of the high-energy-density secondary battery.
Description
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to an electrolyte of a lithium-sulfur battery without a negative electrode and application of the electrolyte.
Background
Energy crisis and environmental pollution have made people attach importance to the development of clean energy, and new batteries have become the target of people's development. The lithium battery has the advantages of playing a great role in establishing a safe and stable new energy power system and an energy storage system by virtue of excellent performances of large energy density, high working voltage, long cycle life, low self-heat release rate, large output power, wider charge-discharge multiplying power, green safety, environmental protection and the like, and enters the field of the public. However, currently, the mainstream positive electrode materials, such as lithium iron phosphate, lithium cobaltate and high nickel ternary positive electrode materials, have relatively limited specific capacity, and the lithium sulfur battery has relatively high specific capacity due to the active substance sulfur. The lithium-sulfur battery is a lithium battery with sulfur as a battery positive electrode and metal lithium as a battery negative electrode. The elemental sulfur has rich reserves in the earth, has the characteristics of low price, environmental friendliness, low price and the like, and can be prepared into a light multi-electron reaction anode material. The lithium-sulfur battery using sulfur as the anode material has higher material theoretical specific capacity and battery theoretical specific energy which respectively reach 1675mAh/g and 2600Wh/kg, and is far higher than the capacity (150 mAh/g) of a lithium cobaltate battery widely applied commercially. And the active substance sulfur is friendly to the environment, has abundant natural reserves, can be developed and used as a next-generation novel lithium secondary battery, thus receiving wide attention and being considered as the next-generation secondary lithium ion battery with great potential. There are still some problems that greatly hinder the commercialization progress, such as poor conductivity of sulfur and its discharge products; volume changes caused by sulfur reactions lead to electrode "chalking"; polysulfide formed by reaction is dissolved in electrolyte, penetrates through a diaphragm to corrode a lithium negative electrode to cause a shuttle effect, and the cycling stability is influenced; the kinetics of polysulfide conversion is slow, and the dendritic crystal growth of the lithium cathode seriously reduces the safety of the whole system and other problems, so that the capacity of the lithium-sulfur battery is continuously attenuated in the charging and discharging processes.
The anode of the lithium-sulfur battery without the cathode is Li 2 S or organic sulfide after lithiation, the negative electrode is copper foil or other current collectors, lithium is provided by depositing the positive electrode to the side of the negative electrode, metal lithium is not required to be directly used, and the lithium can be applied to the batteryThe processability is better, and the large-scale application can be carried out. And Li 2 The conductivity of S is better than that of S, and meanwhile, the problem of electrode pulverization caused by volume change can be solved to a certain extent in the lithium-sulfur battery without the negative electrode. However, for the lithium sulfur battery without a negative electrode, the problems of polysulfide dissolution and lithium negative electrode dendrite faced by the lithium sulfur battery are more difficult to solve. During the charging and discharging processes, polysulfide intermediates generated by the positive electrode are dissolved in electrolyte, pass through the diaphragm and diffuse to the negative electrode, and the irreversible loss of effective substances in the battery, the attenuation of the service life of the battery and low coulombic efficiency are caused by a shuttle effect caused by direct reaction with metal lithium of the negative electrode; in the charging and discharging process, the lithium metal is dissolved and then cannot be smoothly deposited on a negative current collector, but the lithium metal layer is uneven due to uneven deposition or a tip effect, so that a solid electrolyte layer on the surface of a lithium metal negative electrode is continuously cracked, the fresh lithium inside is contacted with the electrolyte, the electrolyte is consumed in an accelerating manner, and the coulomb efficiency and the cycling stability of the battery are reduced. And dendritic crystals similar to dendrites are generated, and the dendrites generated after multiple depositions easily pierce through the diaphragm to cause short circuit of the positive electrode and the negative electrode, so that high temperature is caused and even the battery is ignited and burnt. Therefore, the invention provides the electrolyte which can well prevent the shuttle effect of lithium polysulfide and the dendritic crystal growth of a lithium metal negative electrode, so that the lithium sulfur battery without the negative electrode has stable electrochemical performance.
The electrolyte is used as an important component of the battery and is simultaneously contacted with the positive electrode and the negative electrode, so that the overall performance of the battery is directly influenced. For example: long cycle life, rate, internal resistance, capacity and safety of the battery, and the liquid electrolyte is generally made of lithium salt (LiTFSI, liPF) 6 、LiC1O 4 Etc.), organic solvents (DOL, DME, etc.), and additives. The ideal electrolyte should also have some basic properties, such as stable electrochemical performance, wide electrochemical window, good electronic insulation, high ion conductivity, and stable electrochemical activity of positive and negative electrodes. The shuttle effect of lithium polysulfide and the dendritic crystal growth of a lithium metal negative electrode can be well prevented by optimizing the components of the electrolyte, so that the lithium sulfur battery without the negative electrode has stable electrochemistryAnd the electrolyte has high chemical performance, so that the optimization of the electrolyte of the lithium-sulfur battery without the negative electrode has great research value.
Therefore, the electrolyte for the cathode-free lithium sulfur battery and the application thereof prevent the shuttle effect of polysulfide, protect the stability of the cathode, have great significance and have wide prospect for large-scale application of the cathode-free lithium sulfur battery.
Disclosure of Invention
The invention aims to overcome the 'shuttle effect' and dendritic crystal growth of a lithium cathode caused by dissolution of polysulfide formed by reaction in electrolyte during charging and discharging of a lithium sulfur battery without a cathode in the prior art, so that the capacity of the lithium sulfur battery without the cathode is continuously attenuated during charging and discharging. According to the electrolyte disclosed by the invention, the molecular structure of the solvent is reasonably regulated and controlled, and the components of the lithium salt and the solution are designed, so that the solubility of polysulfide is reduced, the shuttle effect is inhibited, the growth of dendritic crystals of a lithium cathode is inhibited, and the purpose that a lithium sulfur battery without the cathode can keep good chemical properties in the charging and discharging processes is realized.
Compared with the traditional electrolyte, on one hand, the single lithium salt used in the electrolyte is preferably a fluorine-rich lithium salt which can generate lithium fluoride-rich SEI on a lithium negative electrode more easily, so that the SEI can form Li < + > -anion pairs more easily, and more anions can be decomposed during reduction. On the other hand, the molecular structure of the solvent selected by the electrolyte is one oxygen less than that of the traditional electrolyte, so that the coordination capacity of the solvent is reduced, and the molecular structure of the selected solvent only contains single oxygen, so that the selected solvent has steric hindrance and weaker solvation capacity. Thereby allowing anions in a lithium sulfur battery without a negative electrode to generate SEI while allowing the solubility of polysulfides to be significantly reduced. The design can effectively inhibit the shuttle effect of polysulfide, so that the lithium negative electrode has excellent stability. Therefore, the electrolyte for the non-negative-electrode lithium-sulfur battery and the application thereof have great significance in large-scale commercial application of the non-negative-electrode lithium-sulfur battery in the future.
The purpose of the invention can be realized by the following technical scheme:
an electrolyte for a lithium-sulfur battery having no negative electrode, the electrolyte comprising a single lithium salt and a mixture comprising two or more sterically hindered ethers.
According to the scheme, the single lithium salt is lithium bis (fluorosulfonyl) imide (LiFSI) and lithium hexafluorophosphate (LiPF) 6 ) Lithium difluorooxalato borate (LiDFOB), lithium bistrifluoromethylsulfonimide (LiTFSI), lithium tetrafluoroborate (LiBF) 4 ) Lithium difluorophosphate (LiPO) 2 F 2 ) And one of lithium bis (oxalato) borate (LiBOB), preferably lithium bis (fluorosulfonyl) imide (LiFSI), wherein the concentration of a single lithium salt in the electrolyte is 0.5mol/L to 3mol/L.
According to the scheme, the ether mixture is at least two of methyl tert-butyl ether (MTBE), dioxolane (DOL), 2-methyl tetrahydrofuran (Me-THF), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (G2) and tetraethylene glycol dimethyl ether (G4) solvents, preferably methyl tert-butyl ether (MTBE) and 2-methyl tetrahydrofuran (Me-THF), wherein the volume ratio of the two ethers is (0.1-2): 1, and the volume ratio is preferably 1:1.
another aspect of the invention provides the use of the electrolyte in a cathode-free lithium sulfur battery.
According to the scheme, the diaphragm of the applied non-negative electrode lithium-sulfur battery is a ceramic diaphragm, a polypropylene diaphragm, a polyethylene diaphragm, a composite diaphragm of polypropylene and polyethylene, and Al 2 O 3 A coated membrane, a glass fiber membrane, a polytetrafluoroethylene membrane, a cellulose membrane or an aramid membrane. Preferably a ceramic diaphragm, the diameter of the ceramic diaphragm is 18-20 mm.
According to the scheme, the cathode material of the applied cathode-free lithium-sulfur battery is a copper foil, a titanium foil, graphite, silicon and a nickel net, and the anode material is one of lithium sulfide, lithiated polyacrylonitrile sulfide, a compound of lithium sulfide and sulfur/carbon and lithiated organic sulfide. Lithium sulfide is preferred.
Furthermore, the ratio of the ether mixture to the single lithium salt is (1-10) to 1.
The single lithium salt used in the electrolyte is preferably a fluorine-rich lithium salt which is more easily generated to be rich in lithium at the lithium negative electrodeLithium fluoride containing SEI, making it more susceptible to Li formation + Anion pairs, more anions are decomposed during reduction. Meanwhile, compared with the traditional electrolyte, the molecular structure of the solvent selected by the electrolyte is one oxygen less, so that the coordination capacity of the solvent is reduced, and the molecular structure of the selected solvent only contains single oxygen, so that the selected solvent has steric hindrance, and the solvent has weaker solvation capacity. Thereby allowing the anions in the non-negative lithium sulfur battery to generate SEI while allowing the solubility of polysulfides to be significantly reduced. The design can effectively inhibit the shuttle effect of polysulfide, so that the lithium negative electrode has excellent stability. Therefore, the electrolyte for the cathode-free lithium-sulfur battery and the application thereof have great significance in large-scale commercial application of the cathode-free lithium-sulfur battery in the future.
The invention has the beneficial effects that:
at present, the research on the electrolyte system of the liquid lithium-sulfur battery mainly aims at reducing the shuttle effect of lithium polysulfide and selects a proper solvent or a proper functional additive. In a lithium-sulfur battery without a negative electrode, the reaction between lithium polysulfide and metal lithium is reduced or the solubility of the lithium polysulfide in an electrolyte is reduced, active metal lithium is easy to reduce with the electrolyte, a passivated SEI film is generated on the surface of an electrode, the electrolyte is consumed, and the interface stability of the negative electrode and the electrolyte is damaged.
1M LiFSI DOL/DME +1wt% LiN0 compared to the conventional electrolyte 3 The electrolyte for the lithium-sulfur battery without the negative electrode is characterized in that the mixed ether electrolyte is preferably methyl tert-butyl ether (MTBE) and tetrahydrofuran (Me-THF), ethylene glycol dimethyl ether (DME) and has a simple structure formula
Dioxolane (DOL) having the structural formula
Methyl tert-butyl ether (MTBE) with the structure simple formula
2-firstTetrahydrofuran (Me-THF), the structural formula is
Compared with the traditional electrolyte and the electrolyte composition mentioned in the invention, MTBE has one more oxygen in DME, has stronger binding capacity to Li ions and has chelation effect compared with DME. In contrast MTBE contains only one oxygen, is less solvating and also has the steric hindrance of trimethyl. MTBE is therefore less solvating than DME and is less prone to binding Li ions. Compared with DOL, me-THF has only one oxygen in the molecular formula, so that the coordination capability is greatly reduced. And the multiple methyl groups beside oxygen make it sterically hindered and thus not readily available to Li + Are combined together. The design can effectively inhibit the shuttle effect of polysulfide, so that the lithium negative electrode has excellent stability. Therefore, the invention provides an electrolyte for a lithium-sulfur battery without a negative electrode and application thereof.
Drawings
The invention will be further described with reference to the accompanying drawings.
FIG. 1 is a schematic diagram showing the ether comparison between the experimental group and the control group in example 1.
FIG. 2 is a diagram showing the state of lithium polysulfide in example 2 after it has been dissolved in a DME solution.
Fig. 3 is a diagram showing the state of lithium polysulfide of example 2 after dissolution in a 1M LiFSI MTBE/Me-THF (v: v = 1.
FIG. 4 is a diagram showing the state of example 2 after lithium polysulfide has been dissolved in Me-THF solution.
FIG. 5 is a graph of Cu-Li in the control group set forth in example 3 2 The first circle 0.1C charge-discharge curve of the S battery is shown schematically.
FIG. 6 is the Cu-Li in the experimental group presented in example 3 2 The first circle 0.1C charge-discharge curve of the S battery is shown schematically.
Fig. 7 is an internal resistance test chart of EIS of the experimental group and the control group proposed in example 4.
FIG. 8 is a Cu-Li plot of the control and experimental groups set forth in example 5 2 And (3) a schematic diagram of a cycle curve of the S battery.
Fig. 9 is a schematic diagram of the cycle curves of the Li-Cu batteries of the control group and the experimental group proposed in example 6.
Fig. 10 is a schematic view of the charge and discharge curves of the Li-LFP batteries of the control group and the experimental group proposed in example 7.
FIG. 11 is an electron micrograph of the ceramic separator of the control group of example 8 under a scanning electron microscope.
FIG. 12 is a characterization of the ceramic separator of the experimental group of example 8 under a scanning electron microscope.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
1M LiFSI MTBE/Me-THF (v: v = 1) was prepared as an electrolyte of the present invention, 1M LiFSI DOL/DME +1wt% LiNO was added as an electrolyte of the control group 3 ；
Wherein, the structure of the ethylene glycol dimethyl ether (DME) is shown as the simple formula
Dioxolane (DOL) having the structural formula
Methyl tert-butyl ether (MTBE) with the structure simple formula
2-methyltetrahydrofuran (Me-THF), the structural formula is
The ether comparison scheme of the experimental and control groups is shown in figure 1.
Example 2
960mg of S8 and 138mg of Li2S were mixed uniformly, and the mixture was put into a glycol dimethyl ether (DME) solution, a 1M LiFSI MTBE/Me-THF (v: v = 1) solution, and a 2-methyltetrahydrofuran (Me-THF) solution, and the mixture was left to stand to observe the experimental phenomenon as shown in FIG. 2, FIG. 3, and FIG. 4, respectively. In which fig. 2 is completely dissolved, fig. 3 is partially dissolved, and fig. 4 is completely insoluble.
Example 3
Preparing a hand-coated sulfur sheet, weighing sulfur, super P (conductive agent) and an adhesive respectively, wherein the mass ratio of the sulfur to the super P is 63. In an inert atmosphere, 1M lithium bis (trifluoromethanesulfonylimide) (LiFSI) was dissolved in methyl tert-butyl ether (MTBE) and 2-methyltetrahydrofuran (Me-THF) (v: v = 1). Injecting electrolyte to be used into a positive battery shell, a hand-coated sulfur sheet, a diaphragm, a lithium metal pole piece and a negative battery shell in sequence, assembling a lithium-sulfur full battery in a glove box, and testing the first-circle charging and discharging efficiency of the battery of the well-assembled lithium-sulfur battery under the charging and discharging condition of 0.1C. As shown in fig. 5 and fig. 6, wherein fig. 5 is a control group, and fig. 6 is an experimental group. The experimental group underwent the solid-to-solid process, the control group (electrolyte of control group 1M LiFSI DOL/DME +1wt% 3 ) The process goes from solid to liquid to solid, thereby demonstrating that the present invention can effectively prevent the dissolution loss of lithium polysulfide in a lithium sulfur battery without a negative electrode.
Example 4
When the internal resistance test was performed, fig. 7 was obtained using the EIS test platform. As can be seen from FIG. 7, a lithium sulfur battery without negative electrode prepared by dissolving 1M lithium bistrifluoromethanesulfonimide in a solution of methyl t-butyl ether and 2-methyltetrahydrofuran (1 volume ratio) was compared to LiFSI 1M dissolved in dioxolane and glyme and adding 1wt% of an additive to LiNO 3 The lithium sulfur battery without the negative electrode prepared by the lithium (nitrate) solution has smaller internal resistance. For the battery, the smaller the internal resistance is, the less the electric energy is wasted, and the battery is helpful for heat generation, multiplying power and the like.
Example 5
Preparing a hand-coated sulfur piece, weighing sulfur, a super P (conductive agent) and an adhesive respectively according to a mass ratio of 63. Dissolving 1M lithium bis (trifluoromethanesulfonyl) imide in methyl tert-butyl ether and 2-methyltetrahydrofuran (volume ratio is 1. Injecting electrolyte to be used into a positive electrode battery shell, a hand-coated sulfur sheet, a copper sheet, a diaphragm, a lithium metal pole piece and a negative electrode battery shell in sequence, assembling the lithium-sulfur full battery in a glove box, and performing a density cycle test under the condition of 1+1 current; the electrolyte of the control group is 1M dimethyl glycol dimethyl ether, dioxolane and 1wt% lithium nitrate solution of lithium bistrifluoromethanesulfonimide, and the volume ratio is 1:1 (with its battery configuration and parameter settings held constant) and subjected to a density cycling test at a current of 1+1, as shown in fig. 8. It can be shown from the figure that the electrolyte additive can obviously improve the cycle performance of the lithium-sulfur battery without the negative electrode.
Example 6
In an inert atmosphere, 1M lithium bis (trifluoromethanesulfonyl) imide is dissolved in methyl tert-butyl ether and 2-methyltetrahydrofuran (volume ratio is 1). The electrolyte of the control group is 1M dimethyl glycol dimethyl ether, dioxolane and 1wt% lithium nitrate solution of lithium bis (trifluoromethane) sulfonimide, and the volume ratio is 1:1 (the battery structure and parameter settings are kept unchanged), and electrolyte of an experimental group and electrolyte of a control group are injected according to the sequence of a positive battery shell, a copper sheet, a diaphragm, a lithium metal pole piece and a negative battery shell, and are assembled into a lithium-copper half battery in a glove box, and a density cycle test is carried out under the current condition of 1+1, as shown in figure 9, the Li-Cu battery assembled by the electrolyte used in the invention has excellent cycle performance.
Example 7
Preparing a hand-coated LFP, respectively weighing LFP (lithium iron phosphate), PVDF (polyvinylidene fluoride) and SuperP (conductive agent) according to a mass ratio of 8. 1M lithium bis (trifluoromethanesulfonylimide) (LiFSI) was dissolved in methyl tert-butyl ether (MTBE) and 2-methyltetrahydrofuran (Me-THF) (v: v = 1. The electrolyte of the control group is 1M glycol dimethyl ether, dioxolane and 1wt% of lithium nitrate solution of lithium bistrifluoromethanesulfonimide, and the volume ratio is 1:1 (the battery structure and parameter setting are kept unchanged), injecting electrolyte of an experimental group and electrolyte of a control group into a positive battery case, lithium iron phosphate, a copper sheet, a diaphragm, a lithium metal pole piece and a negative battery case in sequence, assembling the lithium-LFP full battery in a glove box, and carrying out charging and discharging tests on the lithium-LFP full battery. The cycle curve is shown in fig. 10, and the Li-LFP battery assembled with the electrolyte solution used in the present invention is excellent in cycle performance.
Example 8
A lithium sulfur battery (experimental group) without negative electrode prepared by scanning a solution of 1M lithium bistrifluoromethanesulfonylimide in methyl t-butyl ether and 2-methyltetrahydrofuran (1 in volume ratio) and a solution of 1M LiFSI in dioxolane and ethylene glycol dimethyl ether with a scanning electron microscope and adding 1wt% of an additive LiNO 3 Images of lithium sulfur batteries (control) without negative electrode made of lithium (nitrate) solution, wherein fig. 11 and 12 are respectively the scanning electron microscope characterization images of the separator of the two batteries.
The above description of the embodiments specifically describes the analysis method according to the present invention. It should be noted that the above description is only for the purpose of helping those skilled in the art better understand the method and idea of the present invention, and not for the purpose of limiting the relevant contents. The present invention may be appropriately adjusted or modified by those skilled in the art without departing from the principle of the present invention, and the adjustment and modification also fall within the scope of the present invention.
Claims (10)
1. An electrolyte for a non-negative electrode lithium-sulfur battery, characterized in that the electrolyte contains a single lithium salt and a mixture containing two or more sterically hindered ethers.
2. The electrolyte for a lithium sulfur battery without a negative electrode according to claim 1, wherein the single lithium salt is one of lithium bis (fluorosulfonyl) imide, lithium hexafluorophosphate, lithium difluoro (oxalato) borate, lithium bis (trifluoromethylsulfonyl) imide, lithium tetrafluoroborate, lithium difluoro (oxalato) phosphate, and lithium bis (oxalato) borate.
3. The electrolyte for a lithium-sulfur battery without a negative electrode of claim 2, wherein the single lithium salt is lithium bis-fluorosulfonylimide, and wherein the concentration of the single lithium salt in the electrolyte is 0.5mol/L to 3mol/L.
4. The electrolyte for a cathode-free lithium sulfur battery according to claim 1, wherein the ether mixture is at least two of methyl t-butyl ether, dioxolane, 2-methyltetrahydrofuran, glyme, diglyme, and tetraglyme solvents.
5. The electrolyte for a non-negative electrode lithium sulfur battery according to claim 4, wherein the ether mixture is methyl tert-butyl ether and 2-methyl tetrahydrofuran, and the volume ratio of the two ethers is (0.1-2): 1.
6. The electrolyte for a cathode-less lithium sulfur battery according to claim 5, wherein the volume ratio of the methyl t-butyl ether to the 2-methyltetrahydrofuran is 1.
7. The electrolyte for a non-negative electrode lithium-sulfur battery according to claim 1, wherein the ratio of the ether mixture to the single lithium salt is (1-10) to 1.
8. Use of the electrolyte of claim 1 in a non-negative electrode lithium sulfur battery.
9. The use of claim 8, wherein the separator of the non-negative electrode lithium-sulfur battery is a ceramic separator, a polypropylene separator, or polyethyleneDiaphragm, composite diaphragm of polypropylene and polyethylene, and Al 2 O 3 A coated membrane, a glass fiber membrane, a polytetrafluoroethylene membrane, a cellulose membrane or an aramid membrane.
10. The use of claim 8, wherein the negative electrode material of the non-negative electrode lithium-sulfur battery is copper foil, titanium foil, graphite, silicon, nickel mesh, and the positive electrode material is one of lithium sulfide, lithiated polyacrylonitrile sulfide, a composite of lithium sulfide and sulfur/carbon, and lithiated organic sulfide.
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| CN110754009A (en) * | 2017-08-28 | 2020-02-04 | 株式会社Lg化学 | Lithium secondary battery |
| US20220077490A1 (en) * | 2020-09-08 | 2022-03-10 | Global Graphene Group, Inc. | Flame-resistant quasi-solid hybrid electrolyte for safe anode-less lithium batteries and production method |
| CN114464891A (en) * | 2020-11-09 | 2022-05-10 | 中国科学院物理研究所 | Ultralow-density electrolyte and lithium-sulfur battery |
| US20220376247A1 (en) * | 2021-05-21 | 2022-11-24 | Zeta Energy Llc | Anode-Free Electrochemical Cell |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110754009A (en) * | 2017-08-28 | 2020-02-04 | 株式会社Lg化学 | Lithium secondary battery |
| US20220077490A1 (en) * | 2020-09-08 | 2022-03-10 | Global Graphene Group, Inc. | Flame-resistant quasi-solid hybrid electrolyte for safe anode-less lithium batteries and production method |
| CN114464891A (en) * | 2020-11-09 | 2022-05-10 | 中国科学院物理研究所 | Ultralow-density electrolyte and lithium-sulfur battery |
| US20220376247A1 (en) * | 2021-05-21 | 2022-11-24 | Zeta Energy Llc | Anode-Free Electrochemical Cell |
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