CN117712488A - Electrolyte, secondary battery containing same, battery pack and electric equipment - Google Patents
Electrolyte, secondary battery containing same, battery pack and electric equipment Download PDFInfo
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- CN117712488A CN117712488A CN202410154079.7A CN202410154079A CN117712488A CN 117712488 A CN117712488 A CN 117712488A CN 202410154079 A CN202410154079 A CN 202410154079A CN 117712488 A CN117712488 A CN 117712488A
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 102
- 150000001875 compounds Chemical class 0.000 claims abstract description 82
- 125000001153 fluoro group Chemical group F* 0.000 claims abstract description 9
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 7
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims abstract description 7
- 125000000217 alkyl group Chemical group 0.000 claims abstract description 5
- 125000004469 siloxy group Chemical group [SiH3]O* 0.000 claims abstract description 5
- 125000003342 alkenyl group Chemical group 0.000 claims abstract description 4
- 125000003545 alkoxy group Chemical group 0.000 claims abstract description 4
- 125000004185 ester group Chemical group 0.000 claims abstract description 4
- LMBFAGIMSUYTBN-MPZNNTNKSA-N teixobactin Chemical compound C([C@H](C(=O)N[C@@H]([C@@H](C)CC)C(=O)N[C@@H](CO)C(=O)N[C@H](CCC(N)=O)C(=O)N[C@H]([C@@H](C)CC)C(=O)N[C@@H]([C@@H](C)CC)C(=O)N[C@@H](CO)C(=O)N[C@H]1C(N[C@@H](C)C(=O)N[C@@H](C[C@@H]2NC(=N)NC2)C(=O)N[C@H](C(=O)O[C@H]1C)[C@@H](C)CC)=O)NC)C1=CC=CC=C1 LMBFAGIMSUYTBN-MPZNNTNKSA-N 0.000 claims description 21
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 claims description 14
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 10
- FKRCODPIKNYEAC-UHFFFAOYSA-N ethyl propionate Chemical compound CCOC(=O)CC FKRCODPIKNYEAC-UHFFFAOYSA-N 0.000 claims description 10
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 6
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 5
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 5
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 claims description 4
- UHOPWFKONJYLCF-UHFFFAOYSA-N 2-(2-sulfanylethyl)isoindole-1,3-dione Chemical compound C1=CC=C2C(=O)N(CCS)C(=O)C2=C1 UHOPWFKONJYLCF-UHFFFAOYSA-N 0.000 claims description 4
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 48
- 229910001416 lithium ion Inorganic materials 0.000 description 47
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- 239000010410 layer Substances 0.000 description 18
- 238000002360 preparation method Methods 0.000 description 14
- 238000006243 chemical reaction Methods 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 11
- -1 lithium hexafluorophosphate Chemical compound 0.000 description 11
- 238000000034 method Methods 0.000 description 11
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 5
- 239000004698 Polyethylene Substances 0.000 description 5
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- 239000006183 anode active material Substances 0.000 description 5
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- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 4
- 229910013870 LiPF 6 Inorganic materials 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
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- 239000006245 Carbon black Super-P Substances 0.000 description 2
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-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
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 239000004642 Polyimide Substances 0.000 description 2
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
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- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
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- 239000011889 copper foil Substances 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000005684 electric field Effects 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 2
- 238000002955 isolation Methods 0.000 description 2
- 125000001449 isopropyl group Chemical group [H]C([H])([H])C([H])(*)C([H])([H])[H] 0.000 description 2
- 239000004816 latex Substances 0.000 description 2
- 229920000126 latex Polymers 0.000 description 2
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
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- 239000011574 phosphorus Substances 0.000 description 2
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- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
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- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 description 2
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000007784 solid electrolyte Substances 0.000 description 2
- 238000007614 solvation Methods 0.000 description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- IXPNQXFRVYWDDI-UHFFFAOYSA-N 1-methyl-2,4-dioxo-1,3-diazinane-5-carboximidamide Chemical compound CN1CC(C(N)=N)C(=O)NC1=O IXPNQXFRVYWDDI-UHFFFAOYSA-N 0.000 description 1
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 239000002028 Biomass Substances 0.000 description 1
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910018119 Li 3 PO 4 Inorganic materials 0.000 description 1
- 229910010710 LiFePO Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004962 Polyamide-imide Substances 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 125000005396 acrylic acid ester group Chemical group 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 239000006256 anode slurry Substances 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
- 239000006182 cathode active material Substances 0.000 description 1
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- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 230000005518 electrochemistry Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910021385 hard carbon Inorganic materials 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000016507 interphase Effects 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 239000004005 microsphere Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000002048 multi walled nanotube Substances 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000011356 non-aqueous organic solvent Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 125000004437 phosphorous atom Chemical group 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920002312 polyamide-imide Polymers 0.000 description 1
- 229920000139 polyethylene terephthalate Polymers 0.000 description 1
- 239000005020 polyethylene terephthalate Substances 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000002633 protecting effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000005060 rubber Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- 239000002109 single walled nanotube Substances 0.000 description 1
- 239000000661 sodium alginate Substances 0.000 description 1
- 235000010413 sodium alginate Nutrition 0.000 description 1
- 229940005550 sodium alginate Drugs 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000002335 surface treatment layer Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 125000000026 trimethylsilyl group Chemical group [H]C([H])([H])[Si]([*])(C([H])([H])[H])C([H])([H])[H] 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 238000009461 vacuum packaging 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)
Abstract
The application provides an electrolyte, a secondary battery, a battery pack and electric equipment containing the electrolyte, wherein the electrolyte comprises a compound shown as a formula I and a compound shown as a formula II, wherein R 1 、R 2 、R 3 、R 4 Each selected from any one of fluorine atom, alkyl group, alkoxy group, alkenyl group, phenyl group and ester group; in the formula II, R 5 、R 6 、R 7 Each independently selected from substituted or unsubstituted siloxyl; based on the mass of the electrolyte, the mass percentage of the compound of the formula I is a, the mass percentage of the compound of the formula II is b, and the following conditions are satisfied: a is more than or equal to 0.1% and less than or equal to 5%, and b is more than or equal to 0.1% and less than or equal to 1%.
Description
Technical Field
The application relates to the technical field of electrochemistry, in particular to electrolyte, a secondary battery containing the electrolyte, a battery pack and electric equipment.
Background
Secondary batteries (e.g., lithium ion batteries) have advantages of high energy density, small self-discharge, light weight, and the like, and thus are widely used in the fields of energy storage devices and the like.
With the improvement of the performance requirements of the secondary battery, for example, the performance requirements of the secondary battery in the wind power generation and solar power generation energy storage scenes, the secondary battery is required to have high energy density and stable cycle performance, so that the long-term stable operation requirements of the energy storage device in the energy storage application scenes are met.
Disclosure of Invention
In order to solve the technical problems, the application discloses an electrolyte, a secondary battery containing the electrolyte, a battery pack and electric equipment, and the cycle performance of the secondary battery is improved while the impedance of the secondary battery is reduced.
In a first aspect, the present application provides an electrolyte comprising a compound of formula i and a compound of formula ii:
；
in the formula I, R 1 、R 2 、R 3 、R 4 Each selected from any one of fluorine atom, alkyl group, alkoxy group, alkenyl group, phenyl group and ester group;
in the formula II, R 5 、R 6 、R 7 Each independently selected from substituted or unsubstituted siloxyl;
based on the mass of the electrolyte, the mass percentage of the compound of the formula I is a, the mass percentage of the compound of the formula II is b, and the following conditions are satisfied: a is more than or equal to 0.1% and less than or equal to 5%, and b is more than or equal to 0.1% and less than or equal to 1%.
In some embodiments of the present application, the following are satisfied between a and b: a/b is more than or equal to 5 and less than or equal to 50.
In some embodiments of the present application, the compound of formula i is selected from at least one of the following compounds:
、/>、/>、/>、/>、、/>、/>、/>、/>、/>、、/>、/>、/>、/>。
in some embodiments of the present application, the compound of formula ii is selected from at least one of the following compounds:
、/>、/>、/>。
in some embodiments of the present application, the electrolyte further comprises fluoroethylene carbonate, the mass percent content of the fluoroethylene carbonate is c, based on the mass of the electrolyte, satisfying: c is more than or equal to 2% and less than or equal to 4%.
In some embodiments of the present application, the viscosity of the electrolyte is 1.50 mPa-s to 3.00 mPa-s.
In some embodiments of the present application, the electrolyte further comprises at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, methylethyl carbonate, dimethyl carbonate, and ethylene carbonate.
In a second aspect, the present application provides a secondary battery comprising the electrolyte of the first aspect.
In a third aspect, the present application provides a battery pack comprising a case and at least one secondary battery according to the second aspect, the secondary battery being housed in the case.
In a fourth aspect, the present application provides an electric device, including the secondary battery according to the second aspect or the battery pack according to the third aspect. Compared with the prior art, the application has at least the following beneficial effects:
the application provides an electrolyte, a secondary battery, a battery pack and electric equipment containing the electrolyte, and the electrolyteWherein the electrolyte comprises a compound of formula I and a compound of formula II, the mass percentage of the compound of formula I is a, the mass percentage of the compound of formula II is b, based on the mass of the electrolyte, and the electrolyte meets the following conditions: a is more than or equal to 0.1% and less than or equal to 5%, and b is more than or equal to 0.1% and less than or equal to 1%. The electrolyte comprises a compound shown in a formula I and a compound shown in a formula II, and the content of the compound shown in the formula I can be regulated and controlled, so that the viscosity of the electrolyte can be reduced, and the conductivity of the electrolyte can be improved; wherein the silicon-oxygen bond in the compound of formula II can react with hydrogen fluoride to generate organic phosphorus which can participate in the construction of SEI (Solid Electrolyte Interphase, solid electrolyte interface) film to generate Li-containing compound 3 PO 4 The SEI film has excellent stability and can reduce the decomposition of electrolyte. After the compound of the formula I and lithium ions form a solvation structure, strong electricity of fluorine atoms in the compound of the formula I attracts the compound of the formula II through dipole moment action outside a solvation structure shell, and the compound of the formula II can be transferred to the surface of a negative electrode plate to participate in constructing an SEI film under the action of an electric field through the attraction of the compound of the formula I to the compound of the formula II, so that the decomposition of electrolyte is inhibited. The application improves the conductivity of the electrolyte through the synergistic effect of the compound shown in the formula I and the compound shown in the formula II, can inhibit the decomposition of the electrolyte, reduces the impedance of the secondary battery, improves the cycle performance of the secondary battery, and is more suitable for the energy storage device with high requirement on the long-term cycle performance of the secondary battery.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a household energy storage system according to one embodiment of the present application;
FIG. 2 is a schematic diagram of an energy storage system according to one embodiment of the present application;
FIG. 3 is a schematic structural diagram of an Ubbelohde viscometer in the method for testing the viscosity of an electrolyte.
Reference numerals illustrate: 1-energy storage device, 2-electric energy conversion device, 3-first user load, 4-second user load, 11-A pipe, 12-B pipe, 13-C pipe, 121-B ball, 131-C ball, 132-A ball, 400-energy storage system, 410-high voltage cable, 420-first electric energy conversion device, 430-second electric energy conversion device.
Detailed Description
The following description of the technical solutions in the embodiments of the present application will be made clearly and completely with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
In the present application, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate an azimuth or a positional relationship based on that shown in the drawings. These terms are used primarily to better describe the present application and its embodiments and are not intended to limit the indicated device, element or component to a particular orientation or to be constructed and operated in a particular orientation.
Also, some of the terms described above may be used to indicate other meanings in addition to orientation or positional relationships, for example, the term "upper" may also be used to indicate some sort of attachment or connection in some cases. The specific meaning of these terms in this application will be understood by those of ordinary skill in the art as appropriate.
Furthermore, the terms "mounted," "configured," "provided," "connected," and "connected" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; may be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements, or components. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art as the case may be.
Furthermore, the terms "first," "second," and the like, are used primarily to distinguish between different devices, elements, or components (the particular species and configurations may be the same or different), and are not used to indicate or imply the relative importance and number of devices, elements, or components indicated. Unless otherwise indicated, the meaning of "a plurality" is two or more.
In the present application, a lithium ion battery is used as an example of a secondary battery, but the secondary battery of the present application is not limited to a lithium ion battery.
In the related art, in the field of energy storage, a mixed carbonate solvent, such as ethylene carbonate, is mostly used as an electrolyte of a lithium ion battery. The addition of ethylene carbonate causes an increase in the viscosity of the electrolyte, which is liable to cause the following problems: 1. adverse to the increase of the conductivity of the electrolyte; 2. the compatibility between the electrolyte and the negative electrode plate and the separator is poor; 3. the dynamic performance of the lithium ion battery is affected, so that the lithium is easier to separate out from the negative electrode plate; 4. the diffusion coefficient of lithium ions in the active material is reduced, and the charge transfer resistance is increased. Therefore, how to reduce the impedance of the electrolyte and improve the cycle performance of the lithium ion battery is a problem to be solved.
In view of this, the present application provides an electrolyte comprising a compound of formula i and a compound of formula ii:
；
in the formula I, R 1 、R 2 、R 3 、R 4 Each selected from any one of fluorine atom, alkyl group, alkoxy group, alkenyl group, phenyl group and ester group;
in the formula II, R 5 、R 6 、R 7 Each independently selected from substituted or unsubstituted siloxyl;
based on the mass of the electrolyte, the mass percentage of the compound of the formula I is a, the mass percentage of the compound of the formula II is b, and the following conditions are satisfied: a is more than or equal to 0.1% and less than or equal to 5%, and b is more than or equal to 0.1% and less than or equal to 1%. For example, a is 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.5%, 2%, 3%, 5% or any range therebetween; b is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1% or any range therebetween.
In the present application, the siloxy group has the general formula-OSiR 8 R 9 R 10 . The application is directed to R 8 、R 9 、R 10 The kind of the group is not particularly limited, and may be any group. Illustratively, R is 8 、R 9 、R 10 Each independently selected from alkyl groups, phenyl groups, fluorine atoms, and the like.
The inventor of the application researches find that when the content of the compound of the formula I is too low (for example, lower than 0.1 percent), the viscosity improvement effect of the compound of the formula I on the electrolyte is not obvious, the improvement of the conductivity of the electrolyte is not facilitated, meanwhile, the attraction effect on the compound of the formula II is limited, and the compound of the formula II is difficult to effectively exert a synergistic effect with the compound of the formula II; when the content of the compound of the formula I is too high (for example, higher than 5 percent), the lithium ion battery is easier to generate gas in the circulating process due to the lower boiling point of the compound of the formula I, so that the circulating life of the lithium ion battery is influenced; when the content of the compound of formula II is too low (e.g., less than 0.1%), it is difficult to generate a compound containing Li 3 PO 4 Meanwhile, the SEI film is difficult to effectively play a synergistic effect with the compound shown in the formula I, and the SEI film has poor stability; when the content of the compound of formula II is too high (for example, higher than 1%), the SEI film thickness is too large, so that the impedance of the lithium ion battery is increased, and the cycle performance of the lithium ion battery is affected. When the contents of the compound shown in the formula I and the compound shown in the formula II are regulated and controlled within the range, the impedance of the lithium ion battery can be effectively reduced, and the cycle performance of the lithium ion battery can be improved. This is probably due to the fact that the compound of formula I contains both fluorine and silicon, the strong electronegativity of fluorine atoms and the large dipole moment of silicon-fluorine bonds, and the low space volume property, silane can reduce the viscosity of the electrolyte after fluoro, and the dielectric constant of the electrolyte is increased to improve the conductivity of the electrolyte; silicon in the compound of formula IIThe oxygen bond can react with hydrogen fluoride to generate organic phosphorus which can participate in the construction of SEI film to generate Li-containing film 3 PO 4 The SEI film has excellent stability, can reduce the decomposition of electrolyte and is beneficial to the improvement of the cycle performance of the lithium ion battery. In addition, through the synergistic effect of the compound shown in the formula I and the compound shown in the formula II, the electrolyte conductivity is improved, and meanwhile, the decomposition of the electrolyte can be inhibited. This is probably because, after the compound of formula i forms a solvated structure with lithium ions, the strong electronegativity of the fluorine atom in the compound of formula i and the electrically neutral phosphorus atom in the compound of formula ii have a dipole action outside the solvated structure shell, so that the compound of formula ii can be transferred to the surface of the negative electrode sheet to participate in constructing the SEI film under the action of an electric field by attracting the compound of formula ii through the dipole moment, thereby inhibiting the decomposition of the electrolyte.
Therefore, under the synergistic effect of the compound shown in the formula I and the compound shown in the formula II, the impedance of the lithium ion battery is reduced, the cycle performance of the lithium ion battery is improved, and the lithium ion battery is more suitable for the energy storage device with high requirement on the long-term cycle performance of the lithium ion battery, so that the operation cost of the energy storage device is reduced.
In some embodiments of the present application, the following are satisfied between a and b: a/b is more than or equal to 5 and less than or equal to 50. For example, a/b=5, a/b=10, a/b=15, a/b=20, a/b=30, a/b=50, or any range therebetween. The content of the compound shown in the formula I and the content of the compound shown in the formula II are regulated to meet the proportion relation, and the compound shown in the formula I and the compound shown in the formula II can better play a synergistic effect, so that the compound shown in the formula II can more fully participate in the construction of the SEI film by utilizing the attraction effect of the compound shown in the formula I to the compound shown in the formula II, the decomposition of electrolyte is further inhibited, and the cycle performance of the lithium ion battery is further improved.
In some embodiments of the present application, the compound of formula i is selected from at least one of the following compounds:
、/>、/>、/>、/>、、/>、/>、/>、/>、/>、、/>、/>、/>、/>。
wherein Me represents methyl; ph represents phenyl. By selecting at least one of the compounds of the formulas I-1 to I-16, the electrolyte conductivity is improved, and meanwhile, the decomposition of the electrolyte can be inhibited, so that the lithium ion battery with low impedance and excellent cycle performance is obtained.
In some embodiments of the present application, the compound of formula ii is selected from at least one of the following compounds:
、/>、/>、/>。
wherein TMS represents a trimethylsilyl group;i-Pr represents isopropyl; ph represents phenyl. By selecting the compounds II-1 to II-4, the SEI film with excellent stability is formed by being cooperated with the compound of the formula I, and the decomposition of electrolyte is inhibited, so that the improvement of the cycle performance of the lithium ion battery is facilitated.
In some embodiments of the present application, the electrolyte further comprises fluoroethylene carbonate, the mass percent of fluoroethylene carbonate based on the mass of the electrolyte is c, satisfying: c is more than or equal to 2% and less than or equal to 4%. For example, c is 2%, 2.5%, 3%, 3.5%, 4% or any range therebetween. The cyclic performance of the lithium ion battery is further improved by regulating and controlling the content of fluoroethylene carbonate in the range.
In some embodiments of the present application, the viscosity of the electrolyte is 1.50 mPa-s to 3.00 mPa-s; in other embodiments of the present application, the viscosity of the electrolyte is 2.00 mPas to 2.50 mPas. For example, the viscosity of the electrolyte is 1.50 mPas, 1.70 mPas, 2.00 mPas, 2.20 mPas, 2.50 mPas, 2.70 mPas, 3.00 mPas or any range therebetween. By regulating the viscosity of the electrolyte within the above range, it is advantageous to obtain an electrolyte having high conductivity, thereby facilitating the obtaining of a lithium ion battery having excellent cycle performance.
In some embodiments of the present application, at least one of Ethylene Carbonate (EC), diethyl carbonate (DEC), ethyl Propionate (EP), propyl Propionate (PP), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), and Vinylene Carbonate (VC) may also be included in the electrolyte of the present application.
The electrolyte preparation process is not particularly limited, and for example, at least one of ethylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, methyl ethyl carbonate, dimethyl carbonate and vinylene carbonate may be mixed in a certain mass ratio or volume ratio to obtain a nonaqueous organic solvent, and then the compound of formula I, the compound of formula II and fluoroethylene carbonate (FEC) may be added, followed by addition of lithium hexafluorophosphate (LiPF 6 ) Dissolving and mixing uniformly.
The application relates to LiPF 6 The concentration in the electrolyte is not particularly limited as long as the object of the present application can be achieved. For example, liPF 6 At a concentration of 0.6mol/L to 2.0mol/L, liPF 6 The concentration of (C) is 0.6mol/L, 0.8mol/L, 1.0mol/L, 1.5mol/L, 2.0mol/L or any range therebetween.
The present application also provides a secondary battery comprising the electrolyte according to any of the embodiments of the present application.
The secondary battery further comprises a positive electrode plate, a negative electrode plate and a diaphragm, wherein the diaphragm is positioned between the positive electrode plate and the negative electrode plate, and plays a role in isolation.
The present application is not particularly limited as long as the object of the present application can be achieved, for example, a positive electrode sheet generally includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer may be provided on one surface in the thickness direction of the positive electrode current collector, or may be provided on both surfaces in the thickness direction of the positive electrode current collector. The positive electrode active material layer in the application is arranged on the surface of the positive electrode current collector, namely, the positive electrode active material layer can be arranged in a partial area of one surface of the positive electrode current collector, and can also be arranged in all areas of one surface of the positive electrode current collector. The present application is not particularly limited as long as the object of the present application can be achieved, and may include, for example, but not limited to, aluminum foil, aluminum alloy foil, composite current collector, or the like. In the present application, the thickness of the positive electrode current collector is not particularly limited as long as the object of the present application can be achieved, for example, the thickness is 8 μm to 13 μm. The single-sided coating weight of the positive electrode active material layer can be 250 mg/1540.25mm to 330 mg/1540.25 mm.
In the present application, the positive electrode active material layer includes a positive electrode active material, and the present application is not particularly limited as long as the object of the present application can be achieved, and may include, for example, at least one of lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide, lithium manganate, and lithium manganese iron phosphate.
In the present application, a positive electrode conductive agent may be further included in the positive electrode active material layer, and the present application is not particularly limited as long as the object of the present application can be achieved, and may include, for example, at least one of conductive carbon black (Super P), carbon Nanotubes (CNTs), carbon fibers, acetylene black, and graphene. The carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and/or multi-walled carbon nanotubes. In the present application, the positive electrode active material layer may further include a positive electrode binder, which is not particularly limited as long as the object of the present application can be achieved, and may include, for example, but not limited to, at least one of a fluorine-containing resin, a polypropylene resin, a fiber-type binder, a rubber-type binder, or a polyimide-type binder.
The negative electrode tab is not particularly limited as long as the object of the present application can be achieved, for example, the negative electrode tab generally includes a negative electrode current collector and a negative electrode active material layer. The anode active material layer may be provided on one surface or both surfaces in the thickness direction of the anode current collector. The negative electrode active material layer in the application is arranged on the surface of the negative electrode current collector, namely, the negative electrode active material layer can be arranged in a partial area of one surface of the negative electrode current collector, and can also be arranged in all areas of one surface of the negative electrode current collector. The negative electrode current collector is not particularly limited as long as the object of the present application can be achieved, and may include, for example, but not limited to, copper foil, copper alloy foil, nickel foil, composite current collector, or the like. In the present application, the thickness of the negative electrode current collector is not particularly limited as long as the object of the present application can be achieved, for example, the thickness is 4 μm to 12 μm. The single-sided coating weight of the negative electrode active material layer can be 130 mg/1540.25mm to 160 mg/1540.25 mm.
In the present application, the anode active material layer includes an anode active material, wherein the anode active material is not particularly limited as long as the object of the present application can be achieved, and for example, may include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, silicon carbon.
In the present application, a negative electrode binder may also be included in the negative electrode active material layer. The negative electrode binder is not particularly limited as long as the object of the present application can be achieved, and may include at least one of acrylic acid ester, polyamide, polyimide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, and sodium carboxymethyl cellulose, for example.
The separator is not particularly limited in this application, and those skilled in the art can select according to actual needs as long as the object of the present application can be achieved. For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected.
The secondary battery of the present application further includes a case, and the present application is not particularly limited to the case, and may be selected according to actual needs by those skilled in the art as long as the object of the present application can be achieved. For example, the housing may comprise an aluminium plastic film.
The method of manufacturing the secondary battery is not particularly limited, and a manufacturing method known in the art may be selected as long as the object of the present application can be achieved. For example, the method of manufacturing the secondary battery includes, but is not limited to, the steps of: and stacking the positive electrode plate, the diaphragm and the negative electrode plate in sequence, winding and folding the positive electrode plate, the diaphragm and the negative electrode plate according to the need to obtain a bare cell with a winding structure, placing the bare cell into a packaging bag, injecting electrolyte into the packaging bag, and sealing to obtain the secondary battery.
The present application also provides a battery pack comprising a case and at least one secondary battery of any one of the above embodiments, the secondary battery being housed in the case. The battery pack with the two batteries has excellent performance and is beneficial to the use of the battery pack. The battery is accommodated in the box body, so that the fixing and protecting effects on the battery can be improved, and the service life of the battery pack is prolonged. It is understood that the battery pack may have one or more secondary batteries therein, and when the battery pack includes a plurality of secondary batteries, the plurality of secondary batteries may be connected in at least one of parallel and series.
The application also provides electric equipment, which comprises the secondary battery or the battery pack in any embodiment, so that the product competitiveness and the service performance of the electric equipment are improved. In an alternative embodiment, the powered device includes a powered device body, and the secondary battery or battery pack is used to power the powered device body. In an alternative embodiment, the powered device body includes a device anode and a device cathode, the positive electrode piece of the secondary battery or the battery pack is used for electrically connecting the device anode of the powered device body, and the negative electrode piece of the secondary battery or the battery pack is used for electrically connecting the device cathode of the powered device body to supply power to the powered device.
The powered device of the present application may include, but is not limited to: containers, household energy storage systems, battery cars, electric cars, ships, spacecraft, electric toys, electric tools, and the like, wherein spacecraft is, for example, an airplane, rocket, space shuttle, space spacecraft, and the like, electric toys include, for example, fixed or mobile electric toys, specifically, for example, electric car toys, electric ship toys, and electric airplane toys, and the like, and electric tools include, for example, metal cutting electric tools, grinding electric tools, assembling electric tools, and railway electric tools, specifically, for example, electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact electric drills, concrete vibrators, and electric planers.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a household energy storage system according to an embodiment of the present application, and the embodiment of fig. 1 of the present application is illustrated by taking a household energy storage scenario in a user side energy storage as an example, and the energy storage device of the present application is not limited to the household energy storage scenario.
The application provides a household energy storage system, this household energy storage system include electric energy conversion device 2 (photovoltaic board), first user load 3 (street lamp), second user load 4 (for example household appliances such as air conditioner) etc. and energy storage device 1, and energy storage device 1 is small-size tank, and accessible hanging mode is installed in outdoor wall. In particular, the photovoltaic panel may convert solar energy into electrical energy during low electricity prices, and the energy storage device 1 is used to store the electrical energy and supply the electrical energy to street lamps and household appliances for use during peak electricity prices, or to supply power during power outage/outage of the power grid.
Referring to fig. 2, fig. 2 is a schematic structural diagram of an energy storage system 400 according to an embodiment of the present application, and the embodiment of fig. 2 of the present application is illustrated by taking a power generation/distribution side shared energy storage scenario as an example, and the energy storage device 1 of the present application is not limited to the power generation/distribution side energy storage scenario.
The present application provides an energy storage system 400, the energy storage system 400 comprising: the high-voltage cable 410, the first electric energy conversion device 420, the second electric energy conversion device 430 and the energy storage device 1 provided by the application, under the power generation condition, the first electric energy conversion device 420 and the second electric energy conversion device 430 are used for converting other forms of energy into electric energy, are connected with the high-voltage cable 410 and are supplied to the power distribution network power utilization side for use, and when the power load is lower, the first electric energy conversion device 420 and the second electric energy conversion device 430 store multiple generated electric energy into the energy storage device 1 when the power generation is excessive, so that the wind abandoning and the light abandoning rate are reduced, and the problem of power generation and consumption of new energy is improved; when the power consumption load is high, the power grid gives an instruction, the electric quantity stored by the energy storage device 1 is cooperated with the high-voltage cable 410 to transmit electric energy to the power consumption side for use in a grid-connected mode, so that various services such as peak regulation, frequency modulation and standby are provided for the operation of the power grid, the peak regulation effect of the power grid is fully exerted, peak clipping and valley filling of the power grid are promoted, and the power supply pressure of the power grid is relieved.
Alternatively, the first and second power conversion devices 420 and 430 may convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, mechanical energy, and the like into electric energy.
The number of the energy storage devices 1 may be plural, and the plurality of energy storage devices 1 may be connected in series or in parallel, and the plurality of energy storage devices 1 may be supported and electrically connected by using a separator (not shown). In the present embodiment, "a plurality of" means two or more. The energy storage device 1 may be further provided with an energy storage box for accommodating the energy storage device 1.
Alternatively, the energy storage device 1 may include, but is not limited to, a battery cell, a battery module, a battery pack, a battery system, and the like. The practical application form of the energy storage device 1 provided in the embodiment of the present application may be, but is not limited to, the listed products, and may also be other application forms, and the embodiment of the present application does not strictly limit the application form of the energy storage device 1. The embodiment of the present application will be described by taking the energy storage device 1 as a multi-core battery as an example. When the energy storage device 1 is a single battery, the energy storage device 1 may be at least one of a cylindrical battery, a prismatic battery, and the like.
Examples
Hereinafter, embodiments of the present application will be described in more detail with reference to preparation examples, examples and comparative examples. The various tests and evaluations were carried out according to the following methods.
Example 1-1
< preparation of Positive electrode sheet >
Lithium iron phosphate (LiFePO) as a cathode active material 4 ) Mixing conductive carbon black (Super-P) and a binder PVDF according to the mass ratio of 94:3:3; then N-methyl pyrrolidone (NMP) is added as a solvent to prepare positive electrode slurry with the solid content of 60wt%, the positive electrode slurry is uniformly stirred, and then the positive electrode slurry is uniformly coated on one surface of a positive electrode current collector aluminum foil with the thickness of 13 mu m, wherein the single-sided coating weight of the positive electrode slurry is 300 mg/1540.25 mm. And then drying, cold pressing, slitting and cutting to obtain the positive pole piece.
< preparation of negative electrode sheet >
Mixing the anode active material hard carbon, conductive carbon black (Super-P) serving as a conductive agent, sodium carboxymethyl cellulose (CMC) serving as a thickener and styrene-butadiene rubber (SBR) serving as a binder according to a mass ratio of 96:2:1:1, adding deionized water, preparing into anode slurry with a solid content of 50wt%, and uniformly stirring. The negative electrode slurry was uniformly coated on one surface of a negative electrode current collector copper foil having a thickness of 8 μm, and the single-sided coating weight of the negative electrode slurry was 144 mg/1540.25 mm. And drying, cold pressing, slitting and cutting to obtain the negative electrode plate.
< preparation of electrolyte >
Mixing Ethylene Carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) according to a mass ratio of 1:1:1 in an argon atmosphere glove box with a water content of less than or equal to 1ppm, and then adding lithium salt LiPF 6 And dissolving the mixture into the solvent, adding the compound shown in the formula I, the compound shown in the formula II and fluoroethylene carbonate (FEC), and uniformly mixing to obtain the electrolyte. Wherein the compound of formula I is selected from the group consisting of compound I-1, the compound of formula II is selected from the group consisting of compound II-1, based on the mass of the electrolyte, the mass percent of the compound of formula I is 0.1%, the mass percent of the compound of formula II is 0.1%, the mass percent of FEC in the electrolyte is 3%, and LiPF 6 The molar concentration in the electrolyte was 1mol/L.
< preparation of separator >
A Polyethylene (PE) porous polymeric film having a thickness of 16 μm was used as a separator.
< preparation of lithium ion Battery >
And sequentially stacking the prepared positive electrode plate, the diaphragm and the negative electrode plate, so that the diaphragm is positioned between the positive electrode and the negative electrode to play a role in isolation, and winding to obtain the bare cell. And placing the bare cell in an aluminum plastic film packaging bag, vacuum drying, injecting electrolyte, and performing vacuum packaging, standing, formation and other procedures to obtain the lithium ion battery.
Examples 1 to 2 to 1 to 24
The procedure of example 1-1 was repeated except that the types and contents of the compounds of formula I and the compounds of formula II were adjusted in accordance with Table 1-1 in < preparation of electrolyte >.
Examples 2-1 to 2-3
The procedure of examples 1-21 was repeated except that the FEC content was adjusted in accordance with Table 2-1 in < preparation of electrolyte >.
Comparative example 1
The procedure of example 1-1 was repeated except that the compound of formula I and the compound of formula II were not added in < preparation of electrolyte >.
Comparative examples 2 to 5
The procedure of example 1-1 was repeated except that the types and contents of the compounds of formula I and the compounds of formula II were adjusted in accordance with Table 1-1 in < preparation of electrolyte >.
Test method and apparatus:
and (3) testing the viscosity of an electrolyte:
an Ubbelohde viscometer with an inner diameter of 0.5mm was prepared, and the temperature for the ear-washing ball was 25 ℃. Referring to fig. 3, electrolyte to be measured is injected into the B pipe 12 of the Ubbelohde viscometer to the center of the scale mark of the B ball 121, the latex tube of the A pipe 11 is clamped, the ear washing ball is used for blowing air from the B pipe 12, the electrolyte slowly rises above the C ball 131 of the C pipe 13, the B pipe 12 is quickly plugged by a rubber plug, and the latex tubes on the A pipe 11 and the C pipe 13 are clamped; then the tube A, the tube B and the tube C are released, so that the electrolyte slowly flows down from the upper part of the ball C131 to the scale mark m 1 Time recording time t 1 The electrolyte continues to slowly flow down from above the A ball 132 to the scale mark m 2 Time recording time t 2 The method comprises the steps of carrying out a first treatment on the surface of the The electrolyte flow-out time is t=t 2 -t 1 Electrolyte kinematic viscosity=outflow time×viscometer constant α, i.e., electrolyte viscosity=t×α, unit mpa·s; wherein alpha is 0006869mm 2 /s 2 。
The test viscosity data was averaged three times in three repetitions (the numerical fluctuation of the outflow time of the electrolyte for three times did not exceed 0.2s, otherwise the test was continued three to five times).
And (3) testing the cycle performance:
the test temperature was 25 ℃, the lithium ion battery was charged to 3.65V at a constant current of 0.5 rate (C), charged to 0.05C at a constant voltage, and discharged to 2.5V at 0.5C after standing for 10 min. The capacity obtained in this step was taken as the initial discharge capacity C 0 The cycle test (cycles) of 0.5C charge/0.5C discharge was performed 1000 times, and the 1000 th cycle was recordedDischarge capacity. Cycle capacity retention = (discharge capacity at 1000 th cycle/initial discharge capacity C 0 )×100%。
Direct current impedance (DCR) test:
the testing temperature is 25 ℃, the lithium ion battery after formation is charged to 3.65V at a constant current of 0.5C, then charged to 0.05C at a constant voltage of 3.65V, and kept stand for 10min; then discharging to 2.5V with constant current of 0.5C, standing for 10min, and taking the capacity of the step as a reference. Charging to 3.65V at 25deg.C under constant current of 0.5C, charging to 0.05C under constant voltage of 3.65V, and standing for 10min; discharging for 0.5min at constant current of 0.5C, and recording the voltage at the moment as V1; and then discharging for 0.5min with a constant current of 0.5C, recording the voltage at the moment as V2, and calculating the direct current impedance corresponding to the 50% State of Charge (SOC) State of the lithium ion battery. Dcr= (V1-V2)/0.5C in mΩ.
TABLE 1-1 preparation parameters for examples 1-1, examples 1-24 and comparative examples 1-5
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Note that: in Table 1-1, "/" indicates that no relevant preparation parameters are present.
TABLE 1-2 Performance data for examples 1-1, examples 1-24 and comparative examples 1-5
As can be seen from examples 1-1 to 1-4 and comparative examples 1 to 5 in combination with table 1-2, when the electrolyte is a simple carbonate mixed system (e.g., comparative example 1), the capacity retention rate of the lithium ion battery is low, which may be due to the fact that during the cycling of the lithium ion battery, the SEI film is continuously damaged and repaired as it expands and contracts in the electrochemical process of charging and discharging the lithium ion battery, and the SEI film is generated as the electrolyte component loses electrons on the surface of the active material, which is accompanied by the loss of active lithium and is an irreversible loss, and the charge-discharge cycle ability of the lithium ion battery is deteriorated due to the decrease in the content of active lithium; when only the compound of formula i is added to the electrolyte (e.g., comparative example 2), the cycle performance of the lithium ion battery is low, which may be because the compound of formula i cannot act synergistically with the compound of formula ii to form an SEI film having a stable interface, thereby affecting the cycle performance of the lithium ion battery; when only the compound of the formula II is added in the electrolyte (for example, comparative example 3), the viscosity of the electrolyte is high, so that the electrolyte in the lithium ion battery is easily insufficiently soaked, the risk of lithium precipitation is generated, and the improvement of the cycle performance of the lithium ion battery is not facilitated; when the content of the compound of formula i is too high (e.g., comparative example 4), the cycle performance of the lithium ion battery tends to decrease, probably because the boiling point of the compound of formula i is lower, the lithium ion battery is more prone to generate gas during the cycle process, and the cycle performance of the lithium ion battery is affected; when the content of the compound of formula ii is too high (e.g., comparative example 5), the cycle performance of the lithium ion battery is poor, which may be due to the fact that too much compound of formula ii may cause the SEI film thickness to be too large, resulting in an increase in the impedance of the lithium ion battery, affecting the cycle performance of the lithium ion battery.
It can be seen from examples 1-1 to 1-8, examples 1-9 to 1-15 and examples 1-16 to 1-22 that the cycle performance of the lithium ion battery is further improved by adjusting a/b within the scope of the application.
The type and amount of the compounds of formula I and formula II, and the viscosity of the electrolyte, will also typically affect the performance of the lithium ion battery. It can be further seen from examples 1-1 to 1-24 that by adjusting the types and contents of the compounds of formula I and formula II and the viscosity of the electrolyte within the range of the application, a lithium ion battery with excellent cycle performance and low DCR can be advantageously obtained.
TABLE 2-1 preparation parameters for examples 1-21, examples 2-1-2-3
TABLE 2-2 Performance data for examples 1-21, examples 2-1-2-3
By combining tables 2-2, it can be seen from examples 1-21 and examples 2-1 to 2-3 that the lithium ion battery with excellent cycle performance is advantageously obtained by controlling the content of FEC within the range of the application.
The above describes in detail an electrolyte, a secondary battery including the electrolyte, a battery pack and electric equipment disclosed in the embodiments of the present application, and specific examples are applied to illustrate principles and embodiments of the present application, where the description of the above embodiments is only used to help understand the technical solutions and core inventions of the embodiments of the present application: meanwhile, as those skilled in the art will vary in the specific embodiments and application scope according to the ideas of the present application, the contents of the present specification should not be construed as limiting the present application in summary.
Claims (10)
1. An electrolyte comprising a compound of formula i and a compound of formula ii:
；
in the formula I, R 1 、R 2 、R 3 、R 4 Each selected from any one of fluorine atom, alkyl group, alkoxy group, alkenyl group, phenyl group and ester group;
in the formula II, R 5 、R 6 、R 7 Each independently selected from substituted or unsubstituted siloxyl;
based on the mass of the electrolyte, the mass percentage of the compound of the formula I is a, the mass percentage of the compound of the formula II is b, and the following conditions are satisfied: a is more than or equal to 0.1% and less than or equal to 5%, and b is more than or equal to 0.1% and less than or equal to 1%.
2. The electrolyte of claim 1, wherein the following is satisfied between a and b: a/b is more than or equal to 5 and less than or equal to 50.
3. The electrolyte of claim 1 wherein the compound of formula i is selected from at least one of the following:
、/>、/>、/>、/>、、/>、/>、/>、/>、/>、、/>、/>、/>、/>。
4. the electrolyte of claim 1 wherein the compound of formula ii is selected from at least one of the following:
、/>、/>、/>。
5. the electrolyte of claim 1, further comprising fluoroethylene carbonate, wherein the fluoroethylene carbonate is present in an amount of c by mass based on the mass of the electrolyte, satisfying: c is more than or equal to 2% and less than or equal to 4%.
6. The electrolyte according to any one of claims 1 to 5, wherein the viscosity of the electrolyte is 1.50 mPa-s to 3.00 mPa-s.
7. The electrolyte according to any one of claims 1 to 5, further comprising at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, methyl ethyl carbonate, dimethyl carbonate, and vinylene carbonate.
8. A secondary battery comprising the electrolyte as defined in any one of claims 1 to 7.
9. A battery pack comprising a case and at least one secondary battery according to claim 8, the secondary battery being accommodated in the case.
10. A powered device comprising the secondary battery of claim 8 or comprising the battery pack of claim 9.
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| CN117712488B (en) | 2024-05-24 |
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