CN115842165A - Electrolyte additive, electrolyte and lithium secondary battery - Google Patents
Electrolyte additive, electrolyte and lithium secondary battery Download PDFInfo
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- CN115842165A CN115842165A CN202211458492.XA CN202211458492A CN115842165A CN 115842165 A CN115842165 A CN 115842165A CN 202211458492 A CN202211458492 A CN 202211458492A CN 115842165 A CN115842165 A CN 115842165A
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- Prior art keywords
- electrolyte
- lithium
- additive
- group
- equal
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- 239000003792 electrolyte Substances 0.000 title claims abstract description 83
- 239000002000 Electrolyte additive Substances 0.000 title claims abstract description 71
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 39
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 239000000654 additive Substances 0.000 claims description 46
- 230000000996 additive effect Effects 0.000 claims description 34
- 229910052731 fluorine Inorganic materials 0.000 claims description 25
- 239000011737 fluorine Substances 0.000 claims description 25
- 125000004432 carbon atom Chemical group C* 0.000 claims description 24
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims description 21
- 150000001875 compounds Chemical class 0.000 claims description 21
- -1 lithium hexafluorophosphate Chemical compound 0.000 claims description 19
- VEWLDLAARDMXSB-UHFFFAOYSA-N ethenyl sulfate;hydron Chemical compound OS(=O)(=O)OC=C VEWLDLAARDMXSB-UHFFFAOYSA-N 0.000 claims description 10
- 229910003002 lithium salt Inorganic materials 0.000 claims description 10
- 159000000002 lithium salts Chemical class 0.000 claims description 10
- 229910019142 PO4 Inorganic materials 0.000 claims description 8
- 239000010452 phosphate Substances 0.000 claims description 8
- 125000000217 alkyl group Chemical group 0.000 claims description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 6
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 6
- 239000003960 organic solvent Substances 0.000 claims description 6
- 125000005843 halogen group Chemical group 0.000 claims description 5
- 125000001424 substituent group Chemical group 0.000 claims description 5
- 125000003118 aryl group Chemical group 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 125000001188 haloalkyl group Chemical group 0.000 claims description 4
- IGILRSKEFZLPKG-UHFFFAOYSA-M lithium;difluorophosphinate Chemical compound [Li+].[O-]P(F)(F)=O IGILRSKEFZLPKG-UHFFFAOYSA-M 0.000 claims description 4
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 3
- 125000003342 alkenyl group Chemical group 0.000 claims description 3
- 125000003545 alkoxy group Chemical group 0.000 claims description 3
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 239000007774 positive electrode material Substances 0.000 claims description 3
- KOMNUTZXSVSERR-UHFFFAOYSA-N 1,3,5-tris(prop-2-enyl)-1,3,5-triazinane-2,4,6-trione Chemical compound C=CCN1C(=O)N(CC=C)C(=O)N(CC=C)C1=O KOMNUTZXSVSERR-UHFFFAOYSA-N 0.000 claims description 2
- FSSPGSAQUIYDCN-UHFFFAOYSA-N 1,3-Propane sultone Chemical compound O=S1(=O)CCCO1 FSSPGSAQUIYDCN-UHFFFAOYSA-N 0.000 claims description 2
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 claims description 2
- GWAOOGWHPITOEY-UHFFFAOYSA-N 1,5,2,4-dioxadithiane 2,2,4,4-tetraoxide Chemical compound O=S1(=O)CS(=O)(=O)OCO1 GWAOOGWHPITOEY-UHFFFAOYSA-N 0.000 claims description 2
- 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 2
- SBLRHMKNNHXPHG-UHFFFAOYSA-N 4-fluoro-1,3-dioxolan-2-one Chemical compound FC1COC(=O)O1 SBLRHMKNNHXPHG-UHFFFAOYSA-N 0.000 claims description 2
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 claims description 2
- 229910000733 Li alloy Inorganic materials 0.000 claims description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 2
- 229910000681 Silicon-tin Inorganic materials 0.000 claims description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 2
- SYRDSFGUUQPYOB-UHFFFAOYSA-N [Li+].[Li+].[Li+].[O-]B([O-])[O-].FC(=O)C(F)=O Chemical compound [Li+].[Li+].[Li+].[O-]B([O-])[O-].FC(=O)C(F)=O SYRDSFGUUQPYOB-UHFFFAOYSA-N 0.000 claims description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 2
- 125000004216 fluoromethyl group Chemical group [H]C([H])(F)* 0.000 claims description 2
- 125000000262 haloalkenyl group Chemical group 0.000 claims description 2
- 125000004438 haloalkoxy group Chemical group 0.000 claims description 2
- 125000003106 haloaryl group Chemical group 0.000 claims description 2
- 239000001989 lithium alloy Substances 0.000 claims description 2
- DEUISMFZZMAAOJ-UHFFFAOYSA-N lithium dihydrogen borate oxalic acid Chemical compound B([O-])(O)O.C(C(=O)O)(=O)O.C(C(=O)O)(=O)O.[Li+] DEUISMFZZMAAOJ-UHFFFAOYSA-N 0.000 claims description 2
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 claims description 2
- YKYONYBAUNKHLG-UHFFFAOYSA-N n-Propyl acetate Natural products CCCOC(C)=O YKYONYBAUNKHLG-UHFFFAOYSA-N 0.000 claims description 2
- 239000007773 negative electrode material Substances 0.000 claims description 2
- 229940090181 propyl acetate Drugs 0.000 claims description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 2
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 2
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 2
- 229910001887 tin oxide Inorganic materials 0.000 claims description 2
- XHGIFBQQEGRTPB-UHFFFAOYSA-N tris(prop-2-enyl) phosphate Chemical compound C=CCOP(=O)(OCC=C)OCC=C XHGIFBQQEGRTPB-UHFFFAOYSA-N 0.000 claims description 2
- NQPDZGIKBAWPEJ-UHFFFAOYSA-N valeric acid Chemical compound CCCCC(O)=O NQPDZGIKBAWPEJ-UHFFFAOYSA-N 0.000 claims description 2
- 230000001588 bifunctional effect Effects 0.000 abstract description 3
- 229910052760 oxygen Inorganic materials 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 33
- 230000014759 maintenance of location Effects 0.000 description 23
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 12
- 230000008859 change Effects 0.000 description 12
- 125000004185 ester group Chemical group 0.000 description 12
- 238000011084 recovery Methods 0.000 description 12
- 150000001733 carboxylic acid esters Chemical class 0.000 description 9
- 238000003860 storage Methods 0.000 description 9
- 238000012360 testing method Methods 0.000 description 9
- IQPQWNKOIGAROB-UHFFFAOYSA-N isocyanate group Chemical group [N-]=C=O IQPQWNKOIGAROB-UHFFFAOYSA-N 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 150000002148 esters Chemical class 0.000 description 7
- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 description 7
- 238000000354 decomposition reaction Methods 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 239000012948 isocyanate Substances 0.000 description 6
- 229910052759 nickel Inorganic materials 0.000 description 6
- 150000007942 carboxylates Chemical class 0.000 description 5
- 230000003247 decreasing effect Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 230000002195 synergetic effect Effects 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- OWIKHYCFFJSOEH-UHFFFAOYSA-N Isocyanic acid Chemical group N=C=O OWIKHYCFFJSOEH-UHFFFAOYSA-N 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000008151 electrolyte solution Substances 0.000 description 4
- 125000001153 fluoro group Chemical group F* 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 229910001428 transition metal ion Inorganic materials 0.000 description 4
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 3
- 229910013870 LiPF 6 Inorganic materials 0.000 description 3
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 description 3
- 239000010405 anode material Substances 0.000 description 3
- 239000007795 chemical reaction product Substances 0.000 description 3
- 238000004090 dissolution Methods 0.000 description 3
- 230000005611 electricity Effects 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 239000011255 nonaqueous electrolyte Substances 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 238000006467 substitution reaction Methods 0.000 description 3
- HTSGKJQDMSTCGS-UHFFFAOYSA-N 1,4-bis(4-chlorophenyl)-2-(4-methylphenyl)sulfonylbutane-1,4-dione Chemical compound C1=CC(C)=CC=C1S(=O)(=O)C(C(=O)C=1C=CC(Cl)=CC=1)CC(=O)C1=CC=C(Cl)C=C1 HTSGKJQDMSTCGS-UHFFFAOYSA-N 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical class N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- KXDHJXZQYSOELW-UHFFFAOYSA-M Carbamate Chemical compound NC([O-])=O KXDHJXZQYSOELW-UHFFFAOYSA-M 0.000 description 2
- 101150058243 Lipf gene Proteins 0.000 description 2
- 125000000484 butyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
- 239000002041 carbon nanotube Substances 0.000 description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 description 2
- 150000004651 carbonic acid esters Chemical class 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 125000004093 cyano group Chemical group *C#N 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- NLFBCYMMUAKCPC-KQQUZDAGSA-N ethyl (e)-3-[3-amino-2-cyano-1-[(e)-3-ethoxy-3-oxoprop-1-enyl]sulfanyl-3-oxoprop-1-enyl]sulfanylprop-2-enoate Chemical compound CCOC(=O)\C=C\SC(=C(C#N)C(N)=O)S\C=C\C(=O)OCC NLFBCYMMUAKCPC-KQQUZDAGSA-N 0.000 description 2
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 125000004051 hexyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- RBQRWNWVPQDTJJ-UHFFFAOYSA-N methacryloyloxyethyl isocyanate Chemical compound CC(=C)C(=O)OCCN=C=O RBQRWNWVPQDTJJ-UHFFFAOYSA-N 0.000 description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 2
- 125000001147 pentyl group Chemical group C(CCCC)* 0.000 description 2
- 229920000570 polyether Polymers 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- 230000001629 suppression Effects 0.000 description 2
- ALQLPWJFHRMHIU-UHFFFAOYSA-N 1,4-diisocyanatobenzene Chemical compound O=C=NC1=CC=C(N=C=O)C=C1 ALQLPWJFHRMHIU-UHFFFAOYSA-N 0.000 description 1
- BPOLDGAHSFNTON-UHFFFAOYSA-N 1,8-diisocyanooctane Chemical compound [C-]#[N+]CCCCCCCC[N+]#[C-] BPOLDGAHSFNTON-UHFFFAOYSA-N 0.000 description 1
- RMSGQZDGSZOJMU-UHFFFAOYSA-N 1-butyl-2-phenylbenzene Chemical group CCCCC1=CC=CC=C1C1=CC=CC=C1 RMSGQZDGSZOJMU-UHFFFAOYSA-N 0.000 description 1
- WVXMNBDPVYOPLX-UHFFFAOYSA-N 2-isocyanoethyl prop-2-enoate Chemical compound C=CC(=O)OCC[N+]#[C-] WVXMNBDPVYOPLX-UHFFFAOYSA-N 0.000 description 1
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 1
- FKLJPTJMIBLJAV-UHFFFAOYSA-N Compound IV Chemical compound O1N=C(C)C=C1CCCCCCCOC1=CC=C(C=2OCCN=2)C=C1 FKLJPTJMIBLJAV-UHFFFAOYSA-N 0.000 description 1
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical group C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 description 1
- 239000005057 Hexamethylene diisocyanate Substances 0.000 description 1
- 229910013716 LiNi Inorganic materials 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 1
- KAEZJNCYNQVWRB-UHFFFAOYSA-K P(=O)([O-])([O-])[O-].[Li+].C(C(=O)F)(=O)F.[Li+].[Li+] Chemical compound P(=O)([O-])([O-])[O-].[Li+].C(C(=O)F)(=O)F.[Li+].[Li+] KAEZJNCYNQVWRB-UHFFFAOYSA-K 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000002174 Styrene-butadiene Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 125000004450 alkenylene group Chemical group 0.000 description 1
- 125000003302 alkenyloxy group Chemical group 0.000 description 1
- 125000002947 alkylene group Chemical group 0.000 description 1
- 125000000304 alkynyl group Chemical group 0.000 description 1
- 125000005133 alkynyloxy group Chemical group 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 125000004104 aryloxy group Chemical group 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 125000004369 butenyl group Chemical group C(=CCC)* 0.000 description 1
- 125000004106 butoxy group Chemical group [*]OC([H])([H])C([H])([H])C(C([H])([H])[H])([H])[H] 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000003869 coulometry Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 125000001301 ethoxy group Chemical group [H]C([H])([H])C([H])([H])O* 0.000 description 1
- WUDNUHPRLBTKOJ-UHFFFAOYSA-N ethyl isocyanate Chemical compound CCN=C=O WUDNUHPRLBTKOJ-UHFFFAOYSA-N 0.000 description 1
- VPASWAQPISSKJP-UHFFFAOYSA-N ethyl prop-2-enoate;isocyanic acid Chemical compound N=C=O.CCOC(=O)C=C VPASWAQPISSKJP-UHFFFAOYSA-N 0.000 description 1
- 235000019256 formaldehyde Nutrition 0.000 description 1
- 125000004968 halobutyl group Chemical group 0.000 description 1
- 125000004969 haloethyl group Chemical group 0.000 description 1
- 125000004970 halomethyl group Chemical group 0.000 description 1
- 125000005446 heptyloxy group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])O* 0.000 description 1
- RRAMGCGOFNQTLD-UHFFFAOYSA-N hexamethylene diisocyanate Chemical compound O=C=NCCCCCCN=C=O RRAMGCGOFNQTLD-UHFFFAOYSA-N 0.000 description 1
- 125000006038 hexenyl group Chemical group 0.000 description 1
- 125000003707 hexyloxy group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])O* 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 150000002513 isocyanates Chemical class 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 150000002641 lithium Chemical group 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 1
- HAMGRBXTJNITHG-UHFFFAOYSA-N methyl isocyanate Chemical compound CN=C=O HAMGRBXTJNITHG-UHFFFAOYSA-N 0.000 description 1
- HNHVTXYLRVGMHD-UHFFFAOYSA-N n-butyl isocyanate Chemical compound CCCCN=C=O HNHVTXYLRVGMHD-UHFFFAOYSA-N 0.000 description 1
- 229910001453 nickel ion Inorganic materials 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 238000006864 oxidative decomposition reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 125000002255 pentenyl group Chemical group C(=CCCC)* 0.000 description 1
- 125000004115 pentoxy group Chemical group [*]OC([H])([H])C([H])([H])C([H])([H])C(C([H])([H])[H])([H])[H] 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 1
- DGTNSSLYPYDJGL-UHFFFAOYSA-N phenyl isocyanate Chemical compound O=C=NC1=CC=CC=C1 DGTNSSLYPYDJGL-UHFFFAOYSA-N 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000003918 potentiometric titration Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 125000004368 propenyl group Chemical group C(=CC)* 0.000 description 1
- 125000002572 propoxy group Chemical group [*]OC([H])([H])C(C([H])([H])[H])([H])[H] 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 125000000472 sulfonyl group Chemical group *S(*)(=O)=O 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 125000004434 sulfur atom Chemical group 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 125000003944 tolyl group Chemical group 0.000 description 1
- 238000009966 trimming Methods 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
- 238000003466 welding 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 relates to the field of lithium secondary batteries, in particular to an electrolyte additive, which is used as a bifunctional electrolyte additive and has excellent film-forming property and can effectively remove H in electrolyte 2 O and HF, improve the stability of the electrode/electrolyte interface, thereby improving battery performance. Also disclosed are an electrolyte and a lithium secondary battery.
Description
Technical Field
The application relates to the field of lithium secondary batteries, in particular to an electrolyte additive, an electrolyte and a lithium secondary battery.
Background
With the development of electric vehicles, it is urgent to further improve the energy density of power lithium secondary batteries (LIBs) because LIBs are required to provide more powerThe high energy supports the higher driving range of the electric automobile. The development of high specific capacity and high voltage anode materials is an effective way to improve the specific energy of the lithium secondary battery. Wherein, the high nickel ternary layered oxide LiNi x Co y Mn z O 2 (NCM,0.5<x, x + y + z = 1) is of great interest because of its high specific capacity. However, the high nickel NCM positive electrode has a technical problem to be solved in the existing commercial electrolyte system due to its strong oxidizing ability and poor structural stability. In addition, with global warming, particularly in the hot summer season, the internal temperature of automobiles often reaches 60 ℃ or more, and therefore there is a demand for an electric vehicle power storage device that has no safety problem and does not exhibit significant deterioration in battery performance even when operated at high temperatures. However, in general, the electrolyte in the existing battery is decomposed at high temperature to generate gas, which causes the battery to expand and brings about potential safety hazard.
In the high-nickel anode material, the stability of the material gradually deteriorates along with the increase of the nickel content, and the high-valence nickel ions catalyze the oxidative decomposition of the electrolyte. In addition, during battery cycling, transition metal ions are eluted from the electrode material, causing the destruction of the electrode structure and the continuous decomposition of the electrolyte. The decomposition products are accumulated on the surface of the electrode, resulting in an increase in interfacial resistance and a decrease in battery capacity. In addition to the problems caused by the inherent characteristics of the electrode materials described above, lithium salt LiPF in commercial electrolytes 6 For residual H 2 O is very sensitive. Minute amount of H 2 O will also react with LiPF 6 The reaction generates HF, the high-nickel NCM anode material is corroded, the dissolution of transition metal ions is increased, and the stability of an electrode-electrolyte interface is reduced, so that the capacity attenuation of the battery is aggravated.
Among the various strategies to solve the above problems, the addition of multifunctional additives to the electrolyte is the most efficient and economically viable method. Especially commonly used additives, including VC and FEC, are commonly used as film forming additives for graphite and Si cathodes, but they have poor compatibility with nickel-rich ternary cathodes. Therefore, how to optimize the electrolyte additive is still worth thinking.
Chinese patent No. 201980023321.4 discloses an additive for nonaqueous electrolytic solutions, a nonaqueous electrolytic solution, and an electricity storage device, each of which comprises a compound represented by the following formula (1 a) or formula (1 b), wherein in the formula (1 a) or formula (1 b), X represents an alkylene group having 3 to 7 carbon atoms which may be substituted or an alkenylene group having 3 to 7 carbon atoms which may be substituted, which forms a cyclic structure together with a sulfur atom of a sulfonyl group, n represents an integer of 1 to 7, Z represents a monovalent group represented by the following formula (2 a), formula (2 b), or formula (2 c), and m represents 0 or 1; r2a, R2b and R2c in the formulae (2 a), (2 b) and (2 c) each independently represent an alkyl group having 1 to 4 carbon atoms which may be substituted, an alkenyl group having 2 to 4 carbon atoms which may be substituted, an alkynyl group having 2 to 4 carbon atoms which may be substituted, an aryl group which may be substituted, an alkoxy group having 1 to 4 carbon atoms which may be substituted, an alkenyloxy group having 2 to 4 carbon atoms which may be substituted, an alkynyloxy group having 2 to 4 carbon atoms which may be substituted, an aryloxy group which may be substituted, a hydroxyl group, a lithium alkoxide group or a lithium atom, and two R2c in the same molecule may be the same or different.
The scheme is mentioned in the 77 th paragraph of the specification that the electrolyte additive in the scheme comprises isocyanate compounds including isocyanate ethyl acrylate and isocyano ethyl methacrylate, and the scheme can inhibit initial resistance, improve long-term cycle characteristics and inhibit gas generation by using the additives in a matching way.
Chinese patent No. 202080024217.X discloses a nonaqueous electrolyte solution for an electricity storage device and an electricity storage device using the same, wherein in the nonaqueous electrolyte solution in which an electrolyte salt is dissolved, a polyether polymer having an ethylene oxide unit and a weight average molecular weight of 10 to 250 ten thousand contains 0 to 50 mol% of a repeating unit derived from the following formula (1), 30 to 100 mol% of a repeating unit derived from the following formula (2) and 0 to 20 mol% of a repeating unit derived from the following formula (3), the concentration of the polyether polymer is 0.01 to 2% by mass of the nonaqueous electrolyte solution, and R is an alkyl group having 1 to 12 carbon atoms or-CH 2 O(CR 1 R 2 R 3 )；R 1 、R 2 、R 3 Is a hydrogen atom or-CH 2 O(CH 2 CH 2 O)nR 4 At R 1 、R 2 、R 3 N and R 4 Optionally different; r 4 Is alkyl with 1 to 12 carbon atoms or aryl with optional substituent, and n is an integer of 0 to 12; wherein R5 is a group having an ethylenically unsaturated group.
This embodiment mentions in paragraph 49 of the specification that the electrolyte additive in this embodiment contains other additives such as one or more isocyanate compounds of methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate, 1, 4-diisothiocyanobutyl ester, hexamethylene diisocyanate, 1, 8-diisocyanooctane, 1, 4-phenylene diisocyanate, isocyanoethyl acrylate, and isocyanoethyl methacrylate and thereby achieves the object of being able to suppress gas generation even when stored at high temperatures without lowering the initial discharge capacity of the power storage device.
The problem that this application needs to solve: on the basis of inhibiting gas, the performance of the electrolyte under the conditions of high temperature and high pressure is further improved.
Disclosure of Invention
The purpose of the application is to provide an electrolyte additive, an electrolyte and a lithium secondary battery, wherein the electrolyte additive is used as a bifunctional electrolyte additive, has excellent film-forming property, and can effectively remove H in the electrolyte 2 O and HF, improve the stability of the electrode/electrolyte interface and thus improve battery performance.
Without specific explanation of this application: nM for nanomole/liter,. Mu.M for micromole/liter,. Mu.M for millimole/liter, M for mol/liter;
in order to achieve the above purpose, the present application provides the following technical solutions:
an electrolyte additive, which has a general structural formula shown in formula (I):
wherein n is more than or equal to 1 and less than or equal to 6, and n is an integer; r1 and R2 are each independently any of a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and a haloalkoxy group having 1 to 10 carbon atoms;
r3 is an alkyl group or a haloalkyl group having 1 to 6 carbon atoms, an alkenyl group or a haloalkenyl group having 2 to 6 carbon atoms, or an aryl group or a haloaryl group having 6 to 12 carbon atoms;
and at least one substituent in the three substituents of R1, R2 and R3 contains fluorine element.
More preferably, R1 and R2 are each independently any one of a hydrogen atom, a halogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a halomethyl group, a haloethyl group, a halopropyl group, a halobutyl group, a halopentyl group, a halohexyl group, a haloheptyl group, a halooctyl group, a halononyl group, a halodecyl group, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, a hexyloxy group, a heptyloxy group, a haloethoxy group, a halopropoxy group, a halobutoxy group, a halopentyloxy group, a halohexyloxy group, a haloheptyloxy group, a halooctyloxy group, a halononyloxy group, and a halodecyloxy group.
R3 is selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, ethenyl, propenyl, butenyl, pentenyl, hexenyl, haloethenyl, halopropenyl, halobutenyl, halopentenyl, halohexenyl, phenyl, tolyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl.
Preferably, n =1 or 2;
r1, R2 and R3 are each independently a hydrogen atom, a halogen atom or a fluoromethyl group.
Preferably, compounds shown below are included:
as known to those skilled in the art, liPF 6 Is particularly sensitive to moisture in the electrolyte, and trace water can react with LiPF 6 The reaction produces HF, which can corrode the positive electrode, destroying the electrode structure, and affecting the cell performance.
In the scheme of the application, the inventor finds that the addition of the compound can effectively prevent LiPF 6 And H 2 O, thereby reducing HF production; further, the above compound itself can consume HF in the electrolyte.
The possible reaction mechanisms and processes are presumed to be as follows:
taking compound V as an example, as shown above, compound V can effectively capture trace amount of water in the electrolyte, and reacts with water to generate unstable carbamate, and carbamate is rapidly decomposed into ammonia compounds and CO 2 The ammonia compound can further react with the compound V to polymerize to form a polymer, and the polymer can cover the surfaces of the positive electrode and the negative electrode to form a compact and stable interfacial film, so that the direct contact between the electrodes and the electrolyte is prevented, the continuous decomposition of the electrolyte and the dissolution of transition metal ions are inhibited, the cycle performance and the high-temperature performance of the battery are improved, and the gas generation of the battery is inhibited;meanwhile, the compound V can consume HF in the electrolyte, so that the HF is prevented from corroding the electrode.
In addition, as the carboxylate has higher dielectric constant and lower viscosity than the conventional carbonate, the conductivity of the electrolyte can be improved, the low-temperature characteristic of the battery is improved, but the stability is poor; aiming at the problem, after the F is introduced for substitution, the stability of the carboxylic ester can be improved, the oxidation resistance is obviously improved, and the uniformity and the stability of the film can be further improved. Therefore, the performance of the battery under high-temperature and high-pressure conditions is unexpectedly improved after the additive introduces fluorine.
Specifically, the compounds employed herein have a synergy between F, ester groups and isocyanate groups, and the possible principles are presumed to be as follows:
1) Ester group: the carboxylic acid ester has higher dielectric constant and lower viscosity than the conventional carbonic acid ester. Compared with a material without the carboxylate group, the material containing the carboxylate group can improve the conductivity of the electrolyte and improve the low-temperature characteristic of the battery; however, the stability of the carboxylic acid ester to the negative electrode is slightly weaker than that of the carbonate.
2) F: after F substitution is introduced, the stability of the carboxylic ester can be improved, particularly, conventional carbonic ester or carboxylic ester is easy to oxidize and decompose at high temperature and high voltage, and the oxidation resistance of the fluorine substituted ester can be obviously improved by introducing the fluorine substituted ester.
3) Isocyanate group: trace water and HF in the electrolyte can be removed, a reaction product forms a stable interface film on an electrode interface, decomposition of the electrolyte and introduction of F are effectively inhibited, and uniformity and stability of the film are further improved.
Therefore, under the synergistic effect of the groups, the electrolyte can effectively improve the high-low temperature performance of the battery under high voltage.
In addition, the application also discloses an electrolyte, which contains the electrolyte additive.
Preferably, the electrolyte additive is used in an amount of 0.05 to 1.5% based on the total amount of the electrolyte.
More preferably, the electrolyte additive is used in an amount of 0.3 to 1.0% based on the total amount of the electrolyte.
It should be understood that the ester group-containing isocyanate compound is used in an amount including, but not limited to, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0% by weight based on the total weight of the electrolyte.
Preferably, the composite material further comprises a second additive, wherein the second additive is any one or more of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, 1, 3-propane sultone, triallyl isocyanurate, methylene methanedisulfonate, vinyl sulfate, triallyl phosphate, tripropyl alkynyl phosphate and lithium bis-fluorosulfonylimide;
the dosage of the second additive is 0.5-13.5% of the total amount of the electrolyte.
It is to be understood that the second additive is used in an amount including, but not limited to, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, 11.0%, 12.0%, 13.0% by weight of the total electrolyte.
Preferably, the second additive is selected from one or two of lithium bis (fluorosulfonyl) imide and vinyl sulfate.
Preferably, the lithium salt in the electrolyte is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluorophosphate, lithium difluorooxalato phosphate, lithium tetrafluorooxalato phosphate, lithium difluorobis (oxalato) phosphate and lithium bis (fluorosulfonyl imide);
the organic solvent in the electrolyte is a mixture of at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl propionate and propyl acetate;
the concentration of the lithium salt in the organic solvent is 0.8-1.5mol/L.
It is to be understood that the concentration of the lithium salt in the organic solvent includes, but is not limited to, 0.8mol/L, 0.9mol/L, 1.0mol/L, 1.1mol/L, 1.2mol/L, 1.3mol/L, 1.4mol/L, 1.5mol/L.
In addition, the application also discloses a lithium secondary battery, which comprises the electrolyte, a positive electrode, a negative electrode and a diaphragm;
the positive electrode material is selected from Li 1+a (Ni x Co y M 1-x-y )O 2 、Li(Ni n Mn m Co 2-n-m )O 4 、LiM p (PO 4 ) q Any one of (1); wherein a is more than or equal to 0 and less than or equal to 0.3, x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, x + y is more than or equal to 0 and less than or equal to 1, n is more than or equal to 0 and less than or equal to 2, m is more than or equal to 0 and less than or equal to 2, n + m is more than or equal to 0 and less than or equal to 2, M is selected from any one of Al, fe, ni, co, mn and V, p is more than 0 and less than 5, q is more than 0 and less than 5;
the negative electrode material is selected from any one of graphite, lithium metal, lithium alloy, silicon oxide, tin and tin oxide.
The beneficial effect of this application is:
the electrolyte additive provided by the application, as a bifunctional electrolyte additive, not only has excellent film-forming property, but also can effectively remove H in electrolyte 2 O and HF, improve the stability of the electrode/electrolyte interface, thereby improving battery performance. Compared with the known organic compound containing-N = C = O group, the isocyanate compound containing ester group as a functional electrolyte additive has higher oxidation potential and lower reduction potential than solvent molecules, and can perform oxidation-reduction reaction on the surfaces of the positive electrode and the negative electrode in preference to the solvent. Isocyanate compound containing ester group and H 2 The reaction product generated by the O reaction and the polymer cover the surface of the electrode together, so that a high-quality and stable interface film can be formed, the decomposition of electrolyte and the dissolution of transition metal ions are inhibited, the cycle performance and the high-temperature performance of the battery are improved, the gas generation of the battery is inhibited, and unexpectedly, when the additive contains fluorine elements, the performance of the battery under the conditions of high temperature and high pressure is improved unexpectedly.
Detailed Description
The present application will now be described more fully hereinafter with reference to the accompanying examples.
In the description of the present application, it is to be noted that those whose specific conditions are not specified in the examples are performed according to the conventional conditions or the conditions suggested by the manufacturers. The reagents or instruments used are conventional products which are not indicated by manufacturers and are commercially available.
The lithium secondary batteries of comparative examples and examples in the present application were prepared as follows:
preparing an electrolyte: in a glove box protected by argon or nitrogen atmosphere, dissolving ethylene carbonate, methyl ethyl carbonate and diethyl carbonate in a solvent of 1:1:1, adding an electrolyte additive and a lithium salt, wherein the lithium salt comprises lithium hexafluorophosphate, lithium difluorosulfonimide and lithium difluorooxalate phosphate, and the mass ratio of the lithium hexafluorophosphate to the lithium difluorosulfonimide is 1:1: and 1, fully and uniformly stirring to obtain the electrolyte.
Preparing a positive plate: liCo serving as a positive electrode material 2 O 4 The conductive agent SuperP, the adhesive PVDF and the Carbon Nano Tubes (CNT) are uniformly mixed according to the mass ratio of 95 2 Drying at 85 ℃ and then carrying out cold pressing; then trimming, cutting into pieces, slitting, drying for 4 hours at 85 ℃ under the vacuum condition after slitting, and welding the tabs to prepare the lithium secondary battery positive plate meeting the requirements.
Preparing a negative plate: preparing graphite, a conductive agent SuperP, a thickening agent CMC and a binding agent SBR (styrene butadiene rubber emulsion) into slurry according to the mass ratio of 95.5.
Preparation of lithium secondary battery: the positive plate, the negative plate and the diaphragm prepared by the process are manufactured into a lithium secondary battery with the thickness of 4.7mm, the width of 55mm and the length of 60mm by a lamination process, the lithium secondary battery is baked for 10 hours in vacuum at the temperature of 75 ℃, and the electrolyte is injected. After standing for 24 hours, the mixture was charged to 4.5V with a constant current of 0.lC (180 mA), and then charged at a constant voltage of 4.5V until the current dropped to 0.05C (90 mA); then discharging to 3.0V with 0.2C (180 mA), repeating the charging and discharging for 2 times, finally charging the battery to 3.8V with 0.2C (180 mA), and finishing the manufacture of the battery.
Example 1
The lithium secondary battery is prepared according to the method, wherein the electrolyte additive is specifically a compound V, the lithium salt is lithium bis (fluorosulfonyl) imide, the electrolyte additive accounts for 0.5 percent of the total mass of the electrolyte, the concentration of the lithium salt in an organic solvent is 1.2mol/L,
example 2
Essentially the same as example 1, except that the electrolyte additive is specifically compound ii,
example 3
Essentially the same as in example 1, except that the electrolyte additive is in particular compound III,
example 4
Essentially the same as in example 1, except that the electrolyte additive is specifically compound I,
example 5
Essentially the same as example 1, except that the electrolyte additive is specifically compound XIX,
example 6
Essentially the same as example 1, except that the electrolyte additive is specifically compound XXII,
example 7
The electrolyte additive was substantially the same as in example 1 except that the electrolyte additive was 0.05% by mass of the total mass of the electrolyte.
Example 8
The electrolyte additive was substantially the same as in example 1 except that the electrolyte additive was 0.3% by mass of the total electrolyte.
Example 9
Substantially the same as in example 1 except that the electrolyte additive was 0.8% by mass of the total mass of the electrolyte.
Example 10
The electrolyte additive was substantially the same as in example 1 except that the electrolyte additive was 1% of the total mass of the electrolyte.
Example 11
The electrolyte additive was substantially the same as in example 1 except that the electrolyte additive was 1.5% of the total mass of the electrolyte.
Example 12
Substantially the same as in example 1 except that a second additive comprising vinyl sulfate was further included, the second additive corresponding to 1% of the total amount of the electrolyte.
Example 13
Substantially the same as in example 1 except that the second additive includes lithium bis (fluorosulfonyl) imide, and the second additive corresponds to 1% of the total amount of the electrolyte.
Example 14
Substantially the same as in example 12 except that the second additive includes lithium bis (fluorosulfonyl) imide and vinyl sulfate, and the mass ratio of lithium bis (fluorosulfonyl) imide to vinyl sulfate is 1:1.
comparative example 1
Essentially the same as example 1, except that the electrolyte additive is specifically a comparative compound I,
comparative example 2
Essentially the same as example 1, except that the electrolyte additive was specifically a comparative compound II,
comparative example 3
Essentially the same as example 1, except that the electrolyte additive was specifically comparative compound III,
comparative example 4
Essentially the same as example 1, except that the electrolyte additive was specifically a comparative compound IV,
comparative example 5
Essentially the same as in example 1, except that the electrolyte additive was specifically a comparative compound V,
comparative example 6
Substantially the same as in example 1, except that the electrolyte additive is vinyl sulfate.
Comparative example 7
Essentially the same as example 1, except that the electrolyte additive was not added.
And (3) electrochemical performance testing:
the batteries prepared in examples 1 to 14 and comparative examples 1 to 7 were subjected to a charge-discharge cycle test 5 times at a charge-discharge rate of 1C at room temperature, and finally charged to a full charge state at a rate of 1C. The 1C capacity Q, the internal resistance R of the cell and the thickness T were recorded separately.
Battery high temperature storage experiment: the battery in the full-charge state in the embodiment is stored for 30 days at 60 ℃, the internal resistance R1, the thickness T1 and the 1C discharge capacity Q1 of the battery are recorded, the battery is charged and discharged for 5 weeks at room temperature at the rate of 1C, the discharge capacity Q2 is recorded at the time with the highest discharge capacity, experimental data such as the high-temperature storage capacity retention rate, the capacity recovery rate, the internal resistance change rate, the volume expansion rate and the like of the battery are obtained through calculation, and the recording results are shown in table 1.
Battery low temperature discharge experiment: the battery in the full-charge state in the embodiment is placed in a test cabinet at-20 ℃ for standing for 4h, then the battery is discharged to 2.5V at the rate of 0.5C, the discharge capacity Q3 of the battery is recorded, the low-temperature discharge capacity retention rate of the battery is obtained by calculation, and the recording result is shown in table 1.
Table 1: battery performance test result table
And (4) analyzing results:
1. as can be seen from examples 1 to 6, when the electrolyte additive is the compound v, the internal resistance change rate, the volume expansion rate, the capacity retention rate, the capacity recovery rate, and the low-temperature discharge capacity retention rate of the battery are all optimal, and meanwhile, from three angles of the chain length of the electrolyte additive, the content of the fluorine element, and the position where the fluorine element appears, each optional case of the present application can effectively improve the electrical properties of the lithium secondary battery.
2. It can be seen from examples 7 to 11 that the electrolyte additive improves the battery performance more significantly when the electrolyte additive accounts for 0.3 to 1.0% of the total mass of the electrolyte, wherein the electrolyte additive with the most significant performance improvement is added in an amount of 0.5 to 0.8% of the total mass of the electrolyte.
3. As can be seen by examples 12-14, when the second additive is lithium bis-fluorosulfonylimide and vinyl sulfate and both are present in a ratio of 1:1, the second additive has more obvious improvement on the change rate of internal resistance, the reduction of volume expansion rate, the capacity retention rate, the capacity recovery rate and the low-temperature discharge capacity retention rate compared with the improvement of singly adding the lithium bis (fluorosulfonyl) imide or the vinyl sulfate.
4. As can be seen from the examples 1 and 12 to 14, when the electrolyte additive and the second additive are used in a compounding manner, the volume expansion rate and the capacity retention rate of the battery are both significantly inhibited, the corresponding capacity recovery rate and the low-temperature discharge capacity retention rate are both significantly improved, but when the second additive is lithium bis (fluorosulfonyl) imide, the internal resistance change rate is increased, and the stability of the internal resistance is reduced to a certain extent.
5. It can be seen from example 4 and comparative example 1 that when the electrolyte additive does not contain fluorine, the internal resistance change rate and the volume expansion rate are obviously increased, and the capacity retention rate, the capacity recovery rate and the low-temperature discharge capacity retention rate are obviously reduced.
6. It can be seen from example 5 and comparative example 2 that when the electrolyte additive does not contain fluorine, the internal resistance change rate and the volume expansion rate are obviously increased, and the capacity retention rate, the capacity recovery rate and the low-temperature discharge capacity retention rate are obviously reduced.
7. It can be seen from example 6 and comparative example 3 that when the electrolyte additive does not contain fluorine, the internal resistance change rate and the volume expansion rate are obviously increased, and the capacity retention rate, the capacity recovery rate and the low-temperature discharge capacity retention rate are obviously reduced.
8. It can be seen from example 1 and comparative example 4 that when no ester group is contained in the electrolyte additive, the internal resistance change rate and the volume expansion rate are significantly increased, and the capacity retention rate, the capacity recovery rate, and the low-temperature discharge capacity retention rate are significantly decreased.
9. It can be seen from example 1 and comparative example 5 that, when no cyano group is contained in the electrolyte additive, the internal resistance change rate and the volume expansion rate are significantly increased, and the capacity retention rate, the capacity recovery rate, and the low-temperature discharge capacity retention rate are significantly decreased.
10. As can be seen from example 12 and comparative example 6, when only the second additive was added to the electrolyte, the internal resistance change rate and the volume expansion rate were significantly increased, and the capacity retention rate, the capacity recovery rate, and the low-temperature discharge capacity retention rate were significantly decreased, as compared to when the electrolyte additive and the second additive were added simultaneously.
11. It can be seen from example 1 and comparative example 7 that when no electrolyte additive is added to the electrolyte, the internal resistance change rate and the volume expansion rate of the battery are obviously increased, and the capacity retention rate, the capacity recovery rate and the low-temperature discharge capacity retention rate are obviously reduced.
12. As can be seen from comparative examples 1 to 3 and comparative example 5, when the additive contains fluorine element and has no isocyanic acid group, the internal resistance change rate and the volume expansion rate of the battery in a high-temperature state are obviously increased, and the capacity retention rate and the capacity recovery rate are obviously reduced, and in conclusion, after the additive containing fluorine element and having no isocyanic acid group is added, the high-temperature performance of the battery is deteriorated, and meanwhile, the additives of examples 1 to 14 are observed to be additives containing fluorine element, while the high-temperature performance of examples 1 to 14 is better than that of comparative examples 1 to 3, and the additives of examples 1 to 14 and comparative example 5 are different in that the additives used in examples 1 to 14 contain not only fluorine element but also contain isocyanic acid group, so that the theory that the synergistic principle exists between fluorine and isocyanic acid group is inferred;
meanwhile, it can be seen from observing examples 1-14 and comparative example 4 that when the additive contains fluorine element, ester group and isocyanate group at the same time, the high temperature performance is better than that of the additive containing only fluorine element and isocyanate group, therefore, we conclude that there is a synergistic principle between fluorine and ester group;
further observation of examples 1-14 and comparative examples 1-3 shows that when the additive contains fluorine, an ester group and an isocyanate group at the same time, the high temperature performance is better than that of an additive containing only an ester group and an isocyanate group;
therefore, by the above reasoning we further conclude that there is a synergistic principle between fluorine and the ester and isocyanate groups and that the principle may be:
1. ester group: the carboxylic acid ester has higher dielectric constant and lower viscosity than the conventional carbonic acid ester. Compared with a material without the carboxylate group, the material containing the carboxylate group can improve the conductivity of the electrolyte and improve the low-temperature characteristic of the battery; however, the stability of the carboxylic acid ester to the negative electrode is slightly weaker than that of the carbonate.
2. Fluorine: after fluorine substitution is introduced, the stability of the carboxylic ester can be improved, particularly, under high temperature and high voltage, the conventional carbonic ester or carboxylic ester is easy to oxidize and decompose, and the oxidation resistance of the introduced fluorine substituted ester can be obviously improved.
3. Isocyanate group: trace water and HF in the electrolyte can be removed, and a reaction product forms a stable interface film on an electrode interface, so that the decomposition of the electrolyte is effectively inhibited.
Therefore, under the synergistic effect of the three components, the high-temperature performance and the low-temperature performance of the battery under high voltage can be effectively improved.
In conclusion, compared with the traditional additive, the additive disclosed by the application has better performance; the additive of the present application has a remarkable effect in the above properties.
Testing the moisture and acidity of the electrolyte:
the electrolytes of the lithium secondary batteries of examples 1 to 14 and comparative examples 1 to 7 were used for normal temperature storage, and the electrolytes were tested for moisture and acidity for 7 days, 15 days, 30 days, and 60 days of storage, respectively; the moisture testing instrument is a Switzerland moisture meter, and the moisture testing method is a Karl Fischer coulometry method; the instrument for testing the acidity is a potentiometric titrator, and the method for testing the acidity is a triethylamine potentiometric titration method; the moisture and acidity are reported in table 2.
Table 2: electrolyte moisture and acidity test results table
And (4) analyzing results:
1. as can be seen from examples 1-6, the difference between the battery moisture at 0 days was not large for the electrolyte additives of examples 1-6, and the moisture at 30 days was significantly lower for example 1 than for the other examples, while the electrolyte additive of example 1 was compound v, and thus the suppression of the battery moisture by compound v was more significant than for the electrolyte additives of examples 2-5;
electrolyte additives used in examples 1 and 2 were the same: compared with the electrolyte additives in other embodiments, the compound V and the compound II have stronger acidity inhibition capability.
2. As can be seen from examples 7 to 11, as the content of the electrolyte additive in the electrolyte solution gradually increases, the water-suppressing ability and the acidity-suppressing ability of the electrolyte solution gradually increase.
3. As can be seen from example 1 and examples 12 to 14, the suppression ability of the electrolyte against moisture and acidity gradually decreased with the addition of the second additive.
4. As can be seen from example 1 and comparative examples 1 to 3, when the electrolyte additive does not contain fluorine element, the electrolyte has a remarkably decreased ability to suppress moisture and acidity.
5. As can be seen from example 1 and comparative example 4, when an ester group is not included in the electrolyte additive, the electrolyte has a significantly reduced ability to suppress moisture and acidity.
6. As can be seen from example 1 and comparative example 5, when no cyano group is included in the electrolyte additive, the electrolyte has a significantly reduced ability to suppress moisture and acidity.
7. As can be seen from example 12 and comparative example 6, when only the second additive was added to the electrolyte, the electrolyte had a significantly reduced ability to suppress moisture and acidity.
8. As can be seen from example 12 and comparative example 7, when no electrolyte additive was added to the electrolyte, the electrolyte had a significantly reduced ability to suppress moisture and acidity.
In summary, the additive of the present application has significant advantages in suppressing moisture and acidity over conventional additives, as well as isocyanate, F-containing additives and F-containing ester additives.
Claims (10)
1. An electrolyte additive, which is characterized by having a general structural formula shown as formula (I):
wherein n is more than or equal to 1 and less than or equal to 6, and n is an integer; r1 and R2 are each independently any of a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and a haloalkoxy group having 1 to 10 carbon atoms;
r3 is an alkyl group or a haloalkyl group having 1 to 6 carbon atoms, an alkenyl group or a haloalkenyl group having 2 to 6 carbon atoms, or an aryl group or a haloaryl group having 6 to 12 carbon atoms;
and at least one substituent in the three substituents of R1, R2 and R3 contains fluorine element.
2. The electrolyte additive of claim 1 wherein n =1 or 2;
r1, R2 and R3 are each independently a hydrogen atom, a halogen atom or a fluoromethyl group.
3. The electrolyte additive of claim 1, comprising the compound of:
4. an electrolyte comprising the electrolyte additive according to any one of claims 1 to 3.
5. The electrolyte of claim 4, wherein the electrolyte additive is used in an amount of 0.05 to 1.5% based on the total amount of the electrolyte.
6. The electrolyte of claim 5, wherein the electrolyte additive is used in an amount of 0.5 to 1.5% based on the total amount of the electrolyte.
7. The electrolyte of claim 4, further comprising a second additive that is any one or combination of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, lithium dioxalate borate, lithium difluorooxalate borate, 1, 3-propane sultone, triallyl isocyanurate, methylene methanedisulfonate, vinyl sulfate, triallyl phosphate, tripropynyl phosphate, lithium bis-fluorosulfonylimide;
the dosage of the second additive is 0.5-13.5% of the total amount of the electrolyte.
8. The electrolyte of claim 7, wherein the second additive is selected from one or a combination of two of lithium bis-fluorosulfonylimide and vinyl sulfate.
9. The electrolyte according to claim 4, wherein the lithium salt in the electrolyte is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluorophosphate, lithium difluorooxalato phosphate, lithium tetrafluorooxalato phosphate, lithium difluorobis (oxalato) phosphate, and lithium bis (fluorosulfonylimide);
the organic solvent in the electrolyte is selected from a mixture of at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl propionate and propyl acetate;
the concentration of the lithium salt in the organic solvent is 0.8-1.5mol/L.
10. A lithium secondary battery comprising the electrolyte according to any one of claims 4 to 9, and further comprising a positive electrode, a negative electrode and a separator;
the positive electrode material is selected from Li 1+a (Ni x Co y M 1-x-y )O 2 、Li(Ni n Mn m Co 2-n-m )O 4 、LiM p (PO 4 ) q Any one of (1); wherein a is more than or equal to 0 and less than or equal to 0.3, x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, x + y is more than or equal to 0 and less than or equal to 1, n is more than or equal to 0 and less than or equal to 2, m is more than or equal to 0 and less than or equal to 2, n + m is more than or equal to 0 and less than or equal to 2, M is selected from any one of Al, fe, ni, co, mn and V, p is more than 0 and less than 5, q is more than 0 and less than 5;
the negative electrode material is selected from any one of graphite, lithium metal, lithium alloy, silicon oxide, tin and tin oxide.
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