WO2015069853A1 - Improvements for capacitors having conditioned carbon for electrodes - Google Patents
Improvements for capacitors having conditioned carbon for electrodes Download PDFInfo
- Publication number
- WO2015069853A1 WO2015069853A1 PCT/US2014/064275 US2014064275W WO2015069853A1 WO 2015069853 A1 WO2015069853 A1 WO 2015069853A1 US 2014064275 W US2014064275 W US 2014064275W WO 2015069853 A1 WO2015069853 A1 WO 2015069853A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- och
- carbonate
- electrochemical device
- methyl
- solvent system
- Prior art date
Links
- 239000003990 capacitor Substances 0.000 title claims abstract description 64
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims description 43
- 229910052799 carbon Inorganic materials 0.000 title claims description 33
- 230000001143 conditioned effect Effects 0.000 title claims description 12
- 150000003839 salts Chemical class 0.000 claims abstract description 29
- 239000008151 electrolyte solution Substances 0.000 claims abstract description 23
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 10
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 8
- 239000002904 solvent Substances 0.000 claims description 37
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 20
- 239000003125 aqueous solvent Substances 0.000 claims description 16
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 14
- 150000004649 carbonic acid derivatives Chemical class 0.000 claims description 13
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 claims description 12
- 125000001449 isopropyl group Chemical group [H]C([H])([H])C([H])(*)C([H])([H])[H] 0.000 claims description 12
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 claims description 12
- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 claims description 12
- 125000001453 quaternary ammonium group Chemical group 0.000 claims description 12
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 11
- 229910052760 oxygen Inorganic materials 0.000 claims description 9
- 239000001301 oxygen Substances 0.000 claims description 9
- 239000002253 acid Substances 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 6
- 229910052717 sulfur Inorganic materials 0.000 claims description 6
- 239000011593 sulfur Substances 0.000 claims description 6
- 238000007710 freezing Methods 0.000 claims description 5
- 230000008014 freezing Effects 0.000 claims description 5
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 4
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 4
- 229910001416 lithium ion Inorganic materials 0.000 claims description 4
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- STLGQBDVSTWGIP-UHFFFAOYSA-N bis(2-methoxyethyl) carbonate Chemical compound COCCOC(=O)OCCOC STLGQBDVSTWGIP-UHFFFAOYSA-N 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 abstract description 11
- 150000003242 quaternary ammonium salts Chemical class 0.000 abstract description 7
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 abstract description 6
- -1 lithium hexafluorophosphate Chemical compound 0.000 description 39
- 239000003792 electrolyte Substances 0.000 description 34
- 229940021013 electrolyte solution Drugs 0.000 description 16
- 239000000203 mixture Substances 0.000 description 13
- 150000001733 carboxylic acid esters Chemical class 0.000 description 9
- 150000005677 organic carbonates Chemical class 0.000 description 8
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 7
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 6
- WQDUMFSSJAZKTM-UHFFFAOYSA-N Sodium methoxide Chemical compound [Na+].[O-]C WQDUMFSSJAZKTM-UHFFFAOYSA-N 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 229910052744 lithium Inorganic materials 0.000 description 6
- 238000004821 distillation Methods 0.000 description 5
- 239000011888 foil Substances 0.000 description 5
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 4
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 4
- 125000004432 carbon atom Chemical group C* 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 4
- 150000005676 cyclic carbonates Chemical class 0.000 description 4
- 150000002170 ethers Chemical class 0.000 description 4
- XNWFRZJHXBZDAG-UHFFFAOYSA-N 2-METHOXYETHANOL Chemical compound COCCO XNWFRZJHXBZDAG-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 150000002148 esters Chemical class 0.000 description 3
- 239000000706 filtrate Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical compound [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 239000011541 reaction mixture Substances 0.000 description 3
- FVAUCKIRQBBSSJ-UHFFFAOYSA-M sodium iodide Chemical compound [Na+].[I-] FVAUCKIRQBBSSJ-UHFFFAOYSA-M 0.000 description 3
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 2
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 2
- 150000001298 alcohols Chemical class 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 230000001351 cycling effect Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000006056 electrooxidation reaction Methods 0.000 description 2
- 238000011067 equilibration Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000011244 liquid electrolyte Substances 0.000 description 2
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 description 2
- HSZCZNFXUDYRKD-UHFFFAOYSA-M lithium iodide Chemical compound [Li+].[I-] HSZCZNFXUDYRKD-UHFFFAOYSA-M 0.000 description 2
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 description 2
- TZIHFWKZFHZASV-UHFFFAOYSA-N methyl formate Chemical compound COC=O TZIHFWKZFHZASV-UHFFFAOYSA-N 0.000 description 2
- 159000000001 potassium salts Chemical class 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- JHJLBTNAGRQEKS-UHFFFAOYSA-M sodium bromide Chemical compound [Na+].[Br-] JHJLBTNAGRQEKS-UHFFFAOYSA-M 0.000 description 2
- 159000000000 sodium salts Chemical class 0.000 description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 2
- GARJMFRQLMUUDD-UHFFFAOYSA-N 1,1-dimethylpyrrolidin-1-ium Chemical compound C[N+]1(C)CCCC1 GARJMFRQLMUUDD-UHFFFAOYSA-N 0.000 description 1
- XUKSWKGOQKREON-UHFFFAOYSA-N 1,4-diacetoxybutane Chemical compound CC(=O)OCCCCOC(C)=O XUKSWKGOQKREON-UHFFFAOYSA-N 0.000 description 1
- KMADWBKVGYMGTJ-UHFFFAOYSA-N 1-o-ethyl 4-o-methyl 2-methylbutanedioate Chemical compound CCOC(=O)C(C)CC(=O)OC KMADWBKVGYMGTJ-UHFFFAOYSA-N 0.000 description 1
- PMGAWPFOVRBVFC-UHFFFAOYSA-N 1-o-ethyl 5-o-methyl 2-methylpentanedioate Chemical compound CCOC(=O)C(C)CCC(=O)OC PMGAWPFOVRBVFC-UHFFFAOYSA-N 0.000 description 1
- HZNVUJQVZSTENZ-UHFFFAOYSA-N 2,3-dichloro-5,6-dicyano-1,4-benzoquinone Chemical compound ClC1=C(Cl)C(=O)C(C#N)=C(C#N)C1=O HZNVUJQVZSTENZ-UHFFFAOYSA-N 0.000 description 1
- JTXMVXSTHSMVQF-UHFFFAOYSA-N 2-acetyloxyethyl acetate Chemical compound CC(=O)OCCOC(C)=O JTXMVXSTHSMVQF-UHFFFAOYSA-N 0.000 description 1
- FREKRUMBUWKLPT-UHFFFAOYSA-N 2-methoxyethyl methyl carbonate Chemical group COCCOC(=O)OC FREKRUMBUWKLPT-UHFFFAOYSA-N 0.000 description 1
- YHRUNAIXGSNSTP-UHFFFAOYSA-N 5-o-ethyl 1-o-methyl pentanedioate Chemical compound CCOC(=O)CCCC(=O)OC YHRUNAIXGSNSTP-UHFFFAOYSA-N 0.000 description 1
- CWOVOJUKEQPFBA-UHFFFAOYSA-N 6-o-ethyl 1-o-methyl hexanedioate Chemical compound CCOC(=O)CCCCC(=O)OC CWOVOJUKEQPFBA-UHFFFAOYSA-N 0.000 description 1
- JZVUAOCDNFNSGQ-UHFFFAOYSA-N 7-methoxy-2-phenyl-1h-quinolin-4-one Chemical compound N=1C2=CC(OC)=CC=C2C(O)=CC=1C1=CC=CC=C1 JZVUAOCDNFNSGQ-UHFFFAOYSA-N 0.000 description 1
- RZHGLJNKYIEOIA-UHFFFAOYSA-N C(OC)COC.CC(C(C)O)O Chemical compound C(OC)COC.CC(C(C)O)O RZHGLJNKYIEOIA-UHFFFAOYSA-N 0.000 description 1
- 235000013162 Cocos nucifera Nutrition 0.000 description 1
- 244000060011 Cocos nucifera Species 0.000 description 1
- VIZORQUEIQEFRT-UHFFFAOYSA-N Diethyl adipate Chemical compound CCOC(=O)CCCCC(=O)OCC VIZORQUEIQEFRT-UHFFFAOYSA-N 0.000 description 1
- DKMROQRQHGEIOW-UHFFFAOYSA-N Diethyl succinate Chemical compound CCOC(=O)CCC(=O)OCC DKMROQRQHGEIOW-UHFFFAOYSA-N 0.000 description 1
- UDSFAEKRVUSQDD-UHFFFAOYSA-N Dimethyl adipate Chemical compound COC(=O)CCCCC(=O)OC UDSFAEKRVUSQDD-UHFFFAOYSA-N 0.000 description 1
- MUXOBHXGJLMRAB-UHFFFAOYSA-N Dimethyl succinate Chemical compound COC(=O)CCC(=O)OC MUXOBHXGJLMRAB-UHFFFAOYSA-N 0.000 description 1
- HXXRQBBSGZDQNP-UHFFFAOYSA-N Ethyl methyl_succinate Chemical compound CCOC(=O)CCC(=O)OC HXXRQBBSGZDQNP-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 1
- 229920006370 Kynar Polymers 0.000 description 1
- MLHOXUWWKVQEJB-UHFFFAOYSA-N Propyleneglycol diacetate Chemical compound CC(=O)OC(C)COC(C)=O MLHOXUWWKVQEJB-UHFFFAOYSA-N 0.000 description 1
- 229920003182 Surlyn® Polymers 0.000 description 1
- 239000005035 Surlyn® Substances 0.000 description 1
- GRHZLQBPAJAHDM-SPRQWYLLSA-N [(3as,4r,6ar)-2,3,3a,4,5,6a-hexahydrofuro[2,3-b]furan-4-yl] n-[(2s,4s,5s)-5-[[2-(2,6-dimethylphenoxy)acetyl]amino]-4-hydroxy-1,6-diphenylhexan-2-yl]carbamate Chemical compound CC1=CC=CC(C)=C1OCC(=O)N[C@H]([C@@H](O)C[C@H](CC=1C=CC=CC=1)NC(=O)O[C@@H]1[C@@H]2CCO[C@@H]2OC1)CC1=CC=CC=C1 GRHZLQBPAJAHDM-SPRQWYLLSA-N 0.000 description 1
- 125000003158 alcohol group Chemical group 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- 239000000010 aprotic solvent Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000003750 conditioning effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- SHSCLYKFOFTZGZ-UHFFFAOYSA-N diethyl 2-methylpentanedioate Chemical compound CCOC(=O)CCC(C)C(=O)OCC SHSCLYKFOFTZGZ-UHFFFAOYSA-N 0.000 description 1
- OUWSNHWQZPEFEX-UHFFFAOYSA-N diethyl glutarate Chemical compound CCOC(=O)CCCC(=O)OCC OUWSNHWQZPEFEX-UHFFFAOYSA-N 0.000 description 1
- NFOQJNGQQXICBY-UHFFFAOYSA-N dimethyl 2-methylbutanedioate Chemical compound COC(=O)CC(C)C(=O)OC NFOQJNGQQXICBY-UHFFFAOYSA-N 0.000 description 1
- ZWKKRUNHAVNSFW-UHFFFAOYSA-N dimethyl 2-methylpentanedioate Chemical compound COC(=O)CCC(C)C(=O)OC ZWKKRUNHAVNSFW-UHFFFAOYSA-N 0.000 description 1
- XTDYIOOONNVFMA-UHFFFAOYSA-N dimethyl pentanedioate Chemical compound COC(=O)CCCC(=O)OC XTDYIOOONNVFMA-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 150000002240 furans Chemical class 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 239000000499 gel Substances 0.000 description 1
- 235000013773 glyceryl triacetate Nutrition 0.000 description 1
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 1
- 125000000687 hydroquinonyl group Chemical class C1(O)=C(C=C(O)C=C1)* 0.000 description 1
- 150000004693 imidazolium salts Chemical class 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 239000003562 lightweight material Substances 0.000 description 1
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 description 1
- 229940031993 lithium benzoate Drugs 0.000 description 1
- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 description 1
- 229910001486 lithium perchlorate Inorganic materials 0.000 description 1
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 description 1
- IOEDDFFKYCBADJ-UHFFFAOYSA-M lithium;4-methylbenzenesulfonate Chemical compound [Li+].CC1=CC=C(S([O-])(=O)=O)C=C1 IOEDDFFKYCBADJ-UHFFFAOYSA-M 0.000 description 1
- LDJNSLOKTFFLSL-UHFFFAOYSA-M lithium;benzoate Chemical compound [Li+].[O-]C(=O)C1=CC=CC=C1 LDJNSLOKTFFLSL-UHFFFAOYSA-M 0.000 description 1
- MCVFFRWZNYZUIJ-UHFFFAOYSA-M lithium;trifluoromethanesulfonate Chemical compound [Li+].[O-]S(=O)(=O)C(F)(F)F MCVFFRWZNYZUIJ-UHFFFAOYSA-M 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 1
- OYUDDYMUZSIFDB-UHFFFAOYSA-N methyl 2-acetyloxy-2-methylpropanoate Chemical compound COC(=O)C(C)(C)OC(C)=O OYUDDYMUZSIFDB-UHFFFAOYSA-N 0.000 description 1
- WLAKXJVBZHPARL-UHFFFAOYSA-N methyl 4-acetyloxybutanoate Chemical compound COC(=O)CCCOC(C)=O WLAKXJVBZHPARL-UHFFFAOYSA-N 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 229910017464 nitrogen compound Inorganic materials 0.000 description 1
- 150000002830 nitrogen compounds Chemical class 0.000 description 1
- 239000005486 organic electrolyte Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 150000002926 oxygen Chemical class 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 150000002989 phenols Chemical class 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- GLGXXYFYZWQGEL-UHFFFAOYSA-M potassium;trifluoromethanesulfonate Chemical compound [K+].[O-]S(=O)(=O)C(F)(F)F GLGXXYFYZWQGEL-UHFFFAOYSA-M 0.000 description 1
- 150000004053 quinones Chemical class 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000007581 slurry coating method Methods 0.000 description 1
- 235000009518 sodium iodide Nutrition 0.000 description 1
- BAZAXWOYCMUHIX-UHFFFAOYSA-M sodium perchlorate Chemical compound [Na+].[O-]Cl(=O)(=O)=O BAZAXWOYCMUHIX-UHFFFAOYSA-M 0.000 description 1
- 229910001488 sodium perchlorate Inorganic materials 0.000 description 1
- 229910001495 sodium tetrafluoroborate Inorganic materials 0.000 description 1
- XGPOMXSYOKFBHS-UHFFFAOYSA-M sodium;trifluoromethanesulfonate Chemical compound [Na+].[O-]S(=O)(=O)C(F)(F)F XGPOMXSYOKFBHS-UHFFFAOYSA-M 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 239000011885 synergistic combination Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- URAYPUMNDPQOKB-UHFFFAOYSA-N triacetin Chemical compound CC(=O)OCC(OC(C)=O)COC(C)=O URAYPUMNDPQOKB-UHFFFAOYSA-N 0.000 description 1
- 229960002622 triacetin Drugs 0.000 description 1
- ITMCEJHCFYSIIV-UHFFFAOYSA-M triflate Chemical compound [O-]S(=O)(=O)C(F)(F)F ITMCEJHCFYSIIV-UHFFFAOYSA-M 0.000 description 1
- 150000008648 triflates Chemical class 0.000 description 1
- 238000009489 vacuum treatment Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/54—Electrolytes
- H01G11/58—Liquid electrolytes
- H01G11/60—Liquid electrolytes characterised by the solvent
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0568—Liquid materials characterised by the solutes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0569—Liquid materials characterised by the solvents
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/54—Electrolytes
- H01G11/58—Liquid electrolytes
- H01G11/62—Liquid electrolytes characterised by the solute, e.g. salts, anions or cations therein
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
- H01M2300/0028—Organic electrolyte characterised by the solvent
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
- H01M2300/0028—Organic electrolyte characterised by the solvent
- H01M2300/0037—Mixture of solvents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- 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
- Y02E60/13—Energy storage using capacitors
Definitions
- the present invention relates to novel electrolyte solutions for electrochemical devices such as capacitors and having carbon electrodes with conditioned carbon elements. More particularly, there is a synergism found with the use of the electrolyte solutions with the conditioned carbon cathodes which improves the energy density with a conductive salt such as a lithium salt or quaternary ammonium salt.
- a conductive salt such as a lithium salt or quaternary ammonium salt.
- blends of organic carbonates have been used along with the addition of ethers and low molecular weight esters to achieve low temperature (-60°C) freezing points of the mixed solvents containing lithium hexafluorophosphate for low temperature lithium-ion battery performance.
- the use of mixtures of ethylmethyl carbonate with dimethyl carbonate and small quantities of ethylene carbonate have allowed performance down to -20°C and even -30°C in some cases for lithium battery electrolytes.
- the use of tetrahydrofuran (THF) and methyl formate and methyl acetate and dimethyl ethylene glycol (glyme) or dimethoxy ethane (DME) has allowed some battery electrolytes to achieve -40°C or even -50°C performance.
- Propylene carbonate has been used in mixtures with other organic carbonates for capacitor electrolytes but this solvent also limits cell voltage to about 3 V and the solubility of the tetrafluoroborate salt decreases rapidly on cooling and results in low conductivity of the electrolyte at temperatures below -20°C.
- the use of ethylene carbonate (mp 35°C) with cyclic organic carbonate mixtures containing organic quaternary tetrafluoroborate salts for capacitor use gives higher operating cell voltage in ultra capacitors, but these electrolytes freeze before - 20°C is reached.
- Low temperature cycling performance non-freezing
- the temperature desired is down to -40°C.
- these applications desire high temperature performance (>70°C) with low vapor pressure. This means that volatile solvents which are used for low temperature performance cause problems at the high end of the desired performance range.
- Activated carbon is the preferred material for use in preparing electrodes for carbon electrode capacitors.
- This activated carbon is prepared from a number of different sources such as coconut shells, wood, sugar, cellulosics and phenolic resins. After converting these materials to carbon under steam controlled conditions, the carbons are "activated” in a second step using steam or catalyzed with KOH, NaOH and/or carbon dioxide and KOH to increase the surface area to very high surface areas such as 1000 to 2400 m /g.
- These activated carbons usually contain about 2% oxygen after they have been thoroughly dried and traces of inorganic salts. This oxygen is probably present as quinones, hydroquinones, esters, phenols, carboxylic acids, furans and possibly ketones etc. with some nitrogen compounds present— all of which under high voltage conditions greater than 3 V. will undergo electrochemical
- Electrolytic capacitors and electrochemical double layer capacitors also have an electrolyte.
- the electrodes are provided by an oxide or carbon layer formed on metal foil and are separated by a porous non-conducting membrane such as paper, porous polymer, etc.
- the liquid electrolyte provides electrical contact to the opposite electrode through the separator.
- the inherently high resistance of electrolytic capacitors is generally mitigated by rolling a large sheet of the electrode material into a roll to give high surface area.
- the dielectric is provided by the electrolyte.
- the resistance of the electrolyte is a significant factor in the total device resistance.
- the temperature has a major influence on the electrolyte in the performance of the capacitor since the conductivity of the electrolyte decreases with temperature.
- Electrochemical double layer capacitors including super capacitors typically comprise electrodes, electrical contacts to a power supply, separators for electrodes and/or cells, and electrolyte and environmental seals.
- electrolyte typically comprises a combination of a conductive salt and a solvent.
- Desirable electrolytes are typically liquid with low viscosity, low density, and high conductivity over a range of ambient temperature conditions. They should also be commercially inexpensive, chemically and electrochemically stable, and compatible with carbon.
- Aqueous electrolyte systems have been used extensively and provide voltage restricted below 1.8 V. For example, ultra capacitors in Japan are not permitted to use acetonitrile for the electrolyte.
- U.S. Patent No. 6,743,947 to Xu, et al. discloses an electrolyte system comprising a mixture of ethylene carbonate and dimethyl carbonate at a concentration of the electrolyte salt at 0.5 -2.5 M which has poor conductivity at low temperatures.
- U.S. Patent No. 7,924,549 to Smith, et al discloses conditioned carbon electrodes for capacitors and lithium batteries having conditioned carbon electrodes that have also been heat treated and used in an electrolyte comprising a quaternary ammonium tetrafluorobotrate salt in an aprotic solvent.
- U.S. Patent Application Publication No. 20070002522 discloses capacitors having electrodes with alkali-activated carbon electrodes in electrolytic solutions comprising a quaternary ammonium salt and a solvent containing a carboxylic ester.
- Electrochemical double layer capacitors capable of high energy density have been assembled from a variety of materials.
- super-capacitors have been constructed from a variety of materials.
- This type of super-capacitor incorporates electrodes based on carbon that may be prepared from organic gels.
- ammonium salt of hydrogen fluoride with an imidazolium compound in a nitrile solvent which operate at temperatures between -60 and 150 degrees C.
- the tetrafluoroborate salt can be used in the present invention with the present electrolyte solutions.
- lithium ion batteries and capacitors containing carbon electrodes an electrolyte solution which comprises a conductive salt such as a lithium salt or a quaternary ammonium salt and a solvent system comprised of at least 20% by weight (i.e., 25 to 75% by weight) of one or more symmetrical and/or unsymmetrical (asymmetrical) carbonates of the formula:
- R is selected from the group consisting of methyl, ethyl, propyl, isopropyl,
- R 1 is selected from the group consisting of CH 3 OCH 2 CH 2 -, CH 3 OCH 2 CH 2 OCH 2 CH 2 -, CH 3 OCH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 -,
- an electrochemical device e.g., a lithium battery or a capacitor, such as an ultra capacitor or an electrochemical double layer capacitor
- an electrochemical device comprising the combination of a conditioned and heat treated carbon electrode having reduced chemically bound oxygen, nitrogen and sulfur and an electrolyte solution, the electrolyte solution comprising a non-aqueous solvent system comprising 20 to 100% by weight of one or more symmetrical and/or asymmetrical carbonates of the general formula:
- R is selected from the group consisting of methyl, ethyl, isopropyl, propyl,
- R 1 is selected from the group consisting of CH 3 OCH 2 CH 2 -, CH 3 OCH 2 CH 2 OCH 2 CH 2 -, CH 3 OCH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 -,
- R" is methyl, ethyl, propyl or isopropyl, and a conductive salt (e.g., a lithium salt or a quaternary ammonium tetrafluoroborate or triflate) at a concentration of from 0.6 to 3 mol/1.
- a conductive salt e.g., a lithium salt or a quaternary ammonium tetrafluoroborate or triflate
- the novel carbonates of the invention can be mixed with each other or with other organic cyclic or linear carbonates, ethers and carboxylic esters such that they comprise at least 20% by weight of the solvent systems.
- the solvents are utilized in combination with capacitors having carbon electrodes which have been "activated” or post-treated to reduce or remove all chemically bound oxygen, nitrogen and sulfur and preferably heat treated after acid washing at temperatures of 1100-1500°C under an inert atmosphere.
- the surface area of the carbon present in the carbon electrode is >1200 m 2 /g.
- the internal resistance of an ultra capacitor cell is reduced or minimized by lowering the functional Equivalent Series Resistance (ESR) as measured on the RCL meter (Resistance Capacitance and Inductance) which measures the capacitor's impedance in a circuit.
- ESR Equivalent Series Resistance
- the ESR limits the power at which the device can operate from a direct or alternating current.
- capacitor refers to all capacitors which are provided with at least one activated carbon electrode and includes Electric Double Layer Capacitors (EDLC) and Ultra Capacitors (UC).
- EDLC Electric Double Layer Capacitors
- UC Ultra Capacitors
- a yet still further aspect of the invention provides an ultra capacitor having a stable operating cell voltage of about 4V when containing, as part of an electrolyte solution, about 2M of a quaternary ammonium tetrafluoroborate salt at room temperature.
- Also provided by the present invention is a method of making an electrochemical device, comprising the step of combining a carbon electrode with an electrolyte solution comprising a non-aqueous solvent system comprising 20 to 100% by weight of one or more symmetrical and/or asymmetrical carbonates of the general formula:
- R is selected from the group consisting of methyl, ethyl, isopropyl, propyl,
- R 1 is selected from the group consisting of CH 3 OCH 2 CH 2 -, CH 3 OCH 2 CH 2 OCH 2 CH 2 -, CH 3 OCH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 -,
- capacitors having the synergistic combination of at least one activated carbon electrode in an electrolyte solution comprising a conductive salt (e.g., a lithium salt or a quaternary ammonium salt) in a concentration of 0.6 to 3 M wherein the solvent system used for the electrolyte solution is acetonitrile-free and comprises 20 to 100% by weight, preferably 25 to 75%> by weight, of one or more symmetrical and/or unsymmetrical carbonates of the formula:
- a conductive salt e.g., a lithium salt or a quaternary ammonium salt
- R is selected from the group consisting of methyl, ethyl, isopropyl, propyl,
- R 1 is selected from the group consisting of CH 3 OCH 2 CH 2 -, CH 3 OCH 2 CH 2 OCH 2 CH 2 -, CH 3 OCH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 -,
- the carbonate solvents of the invention may be a mixture of themselves or with other linear or cyclic carbonates, esters and/or ethers, preferably ethylene carbonate.
- the solvent system comprises, consists essentially of, or consists of ethylene carbonate (EC) and methyl- (2-methoxyethyl)-carbonate (MMC).
- An amount of MMC may be present in combination with EC which is effective to provide a solvent system having a freezing point of -20°C or lower, - 30°C or lower, -40°C or lower, or even -50°C or lower.
- An EC/MMC solvent system may contain, for example, 10 to 80% by weight EC, with the balance being MMC.
- such a solvent system may contain up to 5% by weight of one or more solvents other than EC and MMC, such as a cyclic or linear carbonate.
- Cyclic carbonates include ethylene carbonate (hereafter designated as EC) and propylene carbonate (PC).
- Linear carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), etc.
- the carboxylic ester optionally used herein preferably has three or more carbon atoms and one or more carboxylic ester bonds.
- the upper limit of the number of carbon atoms in the carboxylic ester is not particularly limited.
- the carboxylic ester preferably has ten or less carbon atoms and more preferably eight or less carbon atoms.
- the number of carboxylic ester bonds in the carboxylic ester is one or more as described above. Since an increase in the number of carboxylic ester bonds generally leads to an increase in the viscosity of the carboxylic ester, the number of carboxylic ester bonds is preferably one or two.
- carboxylic esters examples include dimethyl succinate, ethyl methyl succinate, diethyl succinate, dimethyl 2-methylsuccinate, ethyl methyl 2-methylsuccinate, dimethyl glutarate, ethyl methyl glutarate, diethyl glutarate, dimethyl 2-methylglutarate, ethyl methyl 2-methylglutarate, diethyl 2-methylglutarate, dimethyl adipate, ethyl methyl adipate, diethyl adipate, 1,2-diacetoxyethane, 1 ,2-diacetoxypropane, 1 ,4-diacetoxybutane, glycerin triacetate, methyl 4-acetoxybutyrate, gamma butyrolactone, and methyl 2-acetoxyisobutyrate, ethyl acetate and methyl acetate.
- the electrolyte solutions of the present invention for capacitors comprise the solvent systems of the invention and at least one conductive salt dissolved as an electrolyte.
- the conductive salt may be any that is capable of being used in electrical storage devices, such as lithium secondary cells, lithium ion secondary cells and electrical double-layer capacitors.
- Conductive salts that may be used include alkali metal salts and quaternary ammonium salts. Combinations and mixtures of different conductive salts may be utilized.
- Preferred alkali metal salts are lithium salts, sodium salts and potassium salts. Specific examples include: (1) lithium salts such as lithium tetrafluoroborate, lithium
- lithium perchlorate lithium trifluoromethanesulfonate, sulfonyl imide lithium salts, sulfonyl methide lithium salts, lithium acetate, lithium trifluoroacetate, lithium benzoate, lithium p-toluenesulfonate, lithium nitrate, lithium bromide, lithium iodide and lithium tetraphenylborate;
- sodium salts such as sodium perchlorate, sodium iodide, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium trifluoromethanesulfonate and sodium bromide
- potassium salts such as potassium iodide, potassium tetrafluoroborate, potassium hexafluorophosphate and potassium trifluoromethanesulfonate.
- quaternary ammonium salt useful in the present invention include, but are not limited to, quaternary ammonium tetrafluoroborates and quaternary ammonium triflates such as triethylmethylammonium tetrafluoroborate, diethyldimethylammonium tetrafluoroborate, ethyltrimethylammonium tetrafluoroborate, dimethylpyrrolidinium tetrafluoroborate, diethylpyrrolidinium tetrafluoroborate,
- quaternary ammonium tetrafluoroborate salts preferably have a molecular weight in the range of 178-240.
- tetrafluoroborate and the like are particularly preferable.
- the concentration of the conductive salt in the electrolyte solution of the present invention is preferably from 0.6 to 3 mol/1, particularly preferably from 1 M to 2 M of the electrolytic solution.
- the concentration of the conductive salt is less than 0.6 mol/1, the conductivity may be insufficient; if more than 3 mol/1, the low temperature performance and economical efficiency may be impaired.
- the electrolyte solution should remain liquid with high salt concentrations of salt, e.g., from >1 M up to 2 M.
- the organic carbonates of the invention meet all of these requirements.
- the liquidus range of this solvent is about -65°C to 170°C, providing outstanding low temperature and high temperature performance while dissolving a high level of conductive salt.
- This solvent has a stable operating cell voltage of about 4 V in ultra capacitor performance when containing 2 M diethyldimethyl ammonium tetrafluoroborate at room temperature.
- Other quaternary alkylammonium tetrafluoroborates can also be used for this same stable high operating voltage in this solvent and related solvents.
- the catalyst can be neutralized with an acid or acid salt and the reaction mixture distilled to remove the alcohols and obtain pure organic carbonate components or a useful mixture of organic carbonates.
- Using an excess of the DMC in this case favors more of the desired MMC (asymmetrical component) as opposed to the symmetrical component bis-2-methoxyethyl carbonate (BMC).
- BMC bis-2-methoxyethyl carbonate
- Mixtures of both with the starting material can be used as long as the alcohols are removed.
- the MMC is a preferred solvent of these series of organic carbonates. MMC may be isolated in pure form by distillation.
- the preferred carbon electrodes of the invention can be prepared following the procedure disclosed in U.S. Patent No. 7,924,549 of Smith, et al., incorporated herein by reference in its entirety for all purposes.
- Electrodes may be made of 90% treated carbon and 10% Kynar® binder in an acetone slurry.
- a 1-mil thick sheet of aluminum foil pre-treated with a conductive carbon layer may be trimmed to size and prepared for coating.
- a draw knife may be used to deliver the proper thickness of slurry coating onto the foil.
- the acetone evaporates and then the other side of the aluminum foil may be coated.
- proper sized rectangles may be cut from the aluminum sheet with small plain aluminum tabs still attached to one end. Once cut, the electrodes may be baked under vacuum to remove any residual moisture.
- the ESR of cells was reduced as follows:
- the higher temperature (above 1 100°C) chemically eliminates most (if not all) chemically bound oxygen and nitrogen, which are susceptible to electrochemical oxidation reduction at cell voltages above approximately 3.4 V in the ultra capacitor. Their presence contributes to leakage current (electrochemical oxidation currents on charging the UC and accelerate self discharge) which degrades UC performance, especially at operating voltages above 3.4V.
- conditioning the carbon electrodes according to the present preferred process optimizes the performance of the ultra capacitor when used with the electrolyte solutions of the invention
- the prior art carbon electrodes, for example, which have been alkali conditioned will also be synergistically improved with the electrolyte solutions of the invention.
- the distillate was continuously collected and checked by GC for the presence of products (MMC and bis(2-methoxy ethyl)- carbonate (BMC)). This was continued until the reaction flask reached a temperature of 100°C and the distillation temperature reached 72°C. At this point, the reaction flask contents contained only a small percentage of DMC and no methanol.
- the reaction mixture was allowed to cool to room temperature.
- the reaction mixture was then filtered to remove the sodium methoxide catalyst.
- the slightly yellow filtrate was treated with NaH ⁇ PC ⁇ , mixed, and re-filtered. This step was then repeated and the filtrate checked to assure that no catalyst remained.
- the filtrate was then transferred to a 500 mL 3-necked flask and stirred. This was then vacuum-distilled slowly.
- the first fraction started at a distillation temperature of 28°C and a reaction flask temperature of 35°C. These fractions were mostly DMC.
- the MMC laden fractions were collected under vacuum (24 mm Hg) at a distillation temperature of 43 °C and a reaction flask temperature of 55°C.
- the GC analysis showed a 91% yield of MMC in the final fraction of MMC product collected.
- the remainder of the mix was composed of 6% BMC and 3% 2-methoxy ethanol.
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Abstract
There is provided an improvement for capacitors having activated carbon electrodes by the use of an electrolyte solution containing a carbonate of the formula RO(C=O)OR1 and a conductive salt such as a lithium salt or a quaternary ammonium salt at a concentration of from 0.6 to 3 mol/1.
Description
IMPROVEMENTS FOR CAPACITORS HAVING CONDITIONED CARBON
FOR ELECTRODES
Cross-Reference to Related Applications
This application claims priority to United States Application No. 14/073,302, filed November 6, 2013, and to United States Application No. 14/073,401, filed November 6, 2013, and issued on July 22, 2014, as U.S. Pat. No. 8,785,057, the disclosure of each of which is incorporated herein by reference in its entirety for all purposes.
Field of the Invention
The present invention relates to novel electrolyte solutions for electrochemical devices such as capacitors and having carbon electrodes with conditioned carbon elements. More particularly, there is a synergism found with the use of the electrolyte solutions with the conditioned carbon cathodes which improves the energy density with a conductive salt such as a lithium salt or quaternary ammonium salt.
Background of the Invention
The performance of ultra capacitor and lithium batteries electrolytes at low temperature is a continuing problem since the conductivity of the electrolyte will go to zero if it freezes before a desired low temperature performance is achieved. Various
blends of organic carbonates have been used along with the addition of ethers and low molecular weight esters to achieve low temperature (-60°C) freezing points of the mixed solvents containing lithium hexafluorophosphate for low temperature lithium-ion battery performance. The use of mixtures of ethylmethyl carbonate with dimethyl carbonate and small quantities of ethylene carbonate have allowed performance down to -20°C and even -30°C in some cases for lithium battery electrolytes. The use of tetrahydrofuran (THF) and methyl formate and methyl acetate and dimethyl ethylene glycol (glyme) or dimethoxy ethane (DME) has allowed some battery electrolytes to achieve -40°C or even -50°C performance. The problem is that the performance of these electrolytes at high temperature such as >70°C causes high vapor pressures in the batteries with these volatile low boiling solvents. In the case of ultra capacitors based on organic electrolytes the situation is similar except most current ultra capacitor electrolytes are based on the use of acetonitrile (low boiling with bp 82°C) containing tetraethylammonium tetrafluoroborate.
These ultra capacitor electrolytes have an upper operating voltage limitation of 2.7 V. The use of capacitor electrolyte solvents based on the organic carbonates and containing tetr alky 1 ammonium tetrafluoroborates has also been limited because of solubility limitations
when using propylene carbonate, or by low temperature performance when using mixtures containing ethylene carbonate.
Propylene carbonate has been used in mixtures with other organic carbonates for capacitor electrolytes but this solvent also limits cell voltage to about 3 V and the solubility of the tetrafluoroborate salt decreases rapidly on cooling and results in low conductivity of the electrolyte at temperatures below -20°C. The use of ethylene carbonate (mp 35°C) with cyclic organic carbonate mixtures containing organic quaternary tetrafluoroborate salts for capacitor use gives higher operating cell voltage in ultra capacitors, but these electrolytes freeze before - 20°C is reached. Low temperature cycling performance (non-freezing) is desired (required for the use of ultra capacitor performance in vehicle performance down to -30°C). In aircraft, the temperature desired is down to -40°C. At the same time these applications desire high temperature performance (>70°C) with low vapor pressure. This means that volatile solvents which are used for low temperature performance cause problems at the high end of the desired performance range.
Activated carbon is the preferred material for use in preparing electrodes for carbon electrode capacitors. This activated carbon is prepared from a number of different sources such as coconut shells, wood, sugar, cellulosics and phenolic resins. After converting these materials to carbon under steam controlled conditions, the carbons are "activated" in a second step using steam or catalyzed with KOH, NaOH and/or carbon dioxide and KOH to increase the surface area to very high surface areas such as 1000 to 2400 m /g. These activated carbons usually contain about 2% oxygen after they have been thoroughly dried and traces of inorganic salts. This oxygen is probably present as quinones, hydroquinones, esters, phenols, carboxylic acids, furans and possibly ketones etc. with some nitrogen compounds present— all of which under high voltage conditions greater than 3 V. will undergo electrochemical
oxidation/reduction as the voltage is increased past 3.3 V. At lower voltages, these functional groups actually improve the energy storage capacity of the carbon and are desirable at voltages below 3.2 V.
The basic components of electrical capacitors include conductive electrodes connected to an electric power supply and a dielectric material separating the electrodes. Electrolytic capacitors and electrochemical double layer capacitors also have an electrolyte. In an electrolyte capacitor, the electrodes are provided by an oxide or carbon layer formed on metal foil and are separated by a porous non-conducting membrane such as paper, porous polymer, etc. The liquid electrolyte provides electrical contact to the opposite electrode through the
separator. The inherently high resistance of electrolytic capacitors is generally mitigated by rolling a large sheet of the electrode material into a roll to give high surface area. In an electrochemical double layer capacitor, the dielectric is provided by the electrolyte. In this type of capacitor the resistance of the electrolyte is a significant factor in the total device resistance. In capacitors that use electrolytes, the temperature has a major influence on the electrolyte in the performance of the capacitor since the conductivity of the electrolyte decreases with temperature.
Electrochemical double layer capacitors including super capacitors, typically comprise electrodes, electrical contacts to a power supply, separators for electrodes and/or cells, and electrolyte and environmental seals. As mentioned above, a key component of electrolytic and electrochemical double layer capacitors is the electrolyte, which typically comprises a combination of a conductive salt and a solvent. Desirable electrolytes are typically liquid with low viscosity, low density, and high conductivity over a range of ambient temperature conditions. They should also be commercially inexpensive, chemically and electrochemically stable, and compatible with carbon. Aqueous electrolyte systems have been used extensively and provide voltage restricted below 1.8 V. For example, ultra capacitors in Japan are not permitted to use acetonitrile for the electrolyte. A need exists for improved electrolyte systems that provide optimum capacitance for capacitors to achieve high power density, a wide temperature range, and a long lifetime without memory effects.
The key requirements for the electrolyte in both non-aqueous batteries and capacitors are high voltage stability, low temperature performance and electrochemical stability. U.S. Patent No. 6,743,947 to Xu, et al. discloses an electrolyte system comprising a mixture of ethylene carbonate and dimethyl carbonate at a concentration of the electrolyte salt at 0.5 -2.5 M which has poor conductivity at low temperatures.
U.S. Patent No. 7,924,549 to Smith, et al discloses conditioned carbon electrodes for capacitors and lithium batteries having conditioned carbon electrodes that have also been heat treated and used in an electrolyte comprising a quaternary ammonium tetrafluorobotrate salt in an aprotic solvent.
U.S. Patent Application Publication No. 20070002522 discloses capacitors having electrodes with alkali-activated carbon electrodes in electrolytic solutions comprising a quaternary ammonium salt and a solvent containing a carboxylic ester.
Electrochemical double layer capacitors capable of high energy density, known as "super-capacitors", have been assembled from a variety of materials. In general, it is desirable
to construct super-capacitors with light weight materials and electrolytes that are stable and non-reactive, as described in U.S. Patent No. 5,260,855 issued to Kaschmitter et al., the teachings of which are hereby incorporated by reference. This type of super-capacitor incorporates electrodes based on carbon that may be prepared from organic gels.
U.S. Patent No. 6,902,683 to Smith et al., which is herein incorporated by reference, relates to electrolytes of a complex salt formed by mixing of a tetraalkyl
ammonium salt of hydrogen fluoride with an imidazolium compound in a nitrile solvent which operate at temperatures between -60 and 150 degrees C.
The article of Ue in J. Electrochem. Soc. Vol 141 , No. 11 , November 1994 entitled "Electrochemical Properties of Organic Liquid Electrolytes Based on Quaternary Onium Salts for Electrical Double-Layer Capacitors" which is herein incorporated by reference, discloses high permittivity solvents and onium salts for double-layer capacitors. Specifically studied were quaternary onium tetrafluoroborate salts which showed greater solubility in the solvents with good stability and conductivity.
U.S. Patent No. 6,980,415 to Higono et al, which is herein incorporated by reference, discloses an electrolyte for capacitors comprising dimethyl carbonate and a spiro
tetrafluoroborate salt. The tetrafluoroborate salt can be used in the present invention with the present electrolyte solutions.
Summary of the Invention
According to one embodiment of the invention, there is provided lithium ion batteries and capacitors containing carbon electrodes, an electrolyte solution which comprises a conductive salt such as a lithium salt or a quaternary ammonium salt and a solvent system comprised of at least 20% by weight (i.e., 25 to 75% by weight) of one or more symmetrical and/or unsymmetrical (asymmetrical) carbonates of the formula:
RO(C=0)OR1
wherein R is selected from the group consisting of methyl, ethyl, propyl, isopropyl,
CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-,
R"OCH2CH2- and R"-0-(CH2)n-, n is 2, 3 or 4, R1 is selected from the group consisting of CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-,
CH3CH2OCH2CH2- and R"-0-CH2CH2-, and R" is methyl, ethyl, propyl or isopropyl.
Thus, one aspect of the present invention provides an electrochemical device (e.g., a lithium battery or a capacitor, such as an ultra capacitor or an electrochemical double layer capacitor) comprising the combination of a conditioned and heat treated carbon electrode
having reduced chemically bound oxygen, nitrogen and sulfur and an electrolyte solution, the electrolyte solution comprising a non-aqueous solvent system comprising 20 to 100% by weight of one or more symmetrical and/or asymmetrical carbonates of the general formula:
RO(C=0)ORl
wherein R is selected from the group consisting of methyl, ethyl, isopropyl, propyl,
CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-,
R"OCH2CH2- and R"-0-(CH2)n-, n is 2, 3 or 4, R1 is selected from the group consisting of CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-,
CH3CH2OCH2CH2- and R -0-CH2CH2-, and R" is methyl, ethyl, propyl or isopropyl, and a conductive salt (e.g., a lithium salt or a quaternary ammonium tetrafluoroborate or triflate) at a concentration of from 0.6 to 3 mol/1.
According to another embodiment of the invention, the novel carbonates of the invention can be mixed with each other or with other organic cyclic or linear carbonates, ethers and carboxylic esters such that they comprise at least 20% by weight of the solvent systems. For example, the solvent system employed in the electrolyte solution may be comprised of 20 to 100%o by weight of a carbonate, or a combination of carbonates, meeting the aforementioned formula RO(C=0)ORI, with the balance of the solvent system being one or more solvents selected from the group consisting of cyclic carbonates, linear carbonates not having the formula RO(C=0)OR1, ethers, carboxylic esters, and combinations thereof.
According to an embodiment of the invention, the solvents are utilized in combination with capacitors having carbon electrodes which have been "activated" or post-treated to reduce or remove all chemically bound oxygen, nitrogen and sulfur and preferably heat treated after acid washing at temperatures of 1100-1500°C under an inert atmosphere. Preferably, the surface area of the carbon present in the carbon electrode is >1200 m2/g.
In another embodiment of the invention, the internal resistance of an ultra capacitor cell is reduced or minimized by lowering the functional Equivalent Series Resistance (ESR) as measured on the RCL meter (Resistance Capacitance and Inductance) which measures the capacitor's impedance in a circuit. The lower the ESR the faster at which the capacitor can be charged and discharged. The ESR limits the power at which the device can operate from a direct or alternating current.
The term "capacitors" as used herein refers to all capacitors which are provided with at least one activated carbon electrode and includes Electric Double Layer Capacitors (EDLC) and Ultra Capacitors (UC).
A yet still further aspect of the invention provides an ultra capacitor having a stable operating cell voltage of about 4V when containing, as part of an electrolyte solution, about 2M of a quaternary ammonium tetrafluoroborate salt at room temperature.
Also provided by the present invention is a method of making an electrochemical device, comprising the step of combining a carbon electrode with an electrolyte solution comprising a non-aqueous solvent system comprising 20 to 100% by weight of one or more symmetrical and/or asymmetrical carbonates of the general formula:
RO(C=0)OR1
wherein R is selected from the group consisting of methyl, ethyl, isopropyl, propyl,
CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-,
R"OCH2CH2- and R"-0-(CH2)n-, n is 2, 3 or 4, R1 is selected from the group consisting of CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-,
CH3CH2OCH2CH2- and R -0-CH2CH2-, and R" is methyl, ethyl, propyl or isopropyl, and a conductive salt at a concentration of from 0.6 to 3 mo 1/1, wherein the carbon of the carbon electrode has been conditioned by acid washing and heat treating at a temperature from
1 100°C to 1500°C in an inert atmosphere to reduce or remove chemically bound oxygen, nitrogen and sulfur.
Description of the Preferred Embodiments
According to the present invention there is provided capacitors having the synergistic combination of at least one activated carbon electrode in an electrolyte solution comprising a conductive salt (e.g., a lithium salt or a quaternary ammonium salt) in a concentration of 0.6 to 3 M wherein the solvent system used for the electrolyte solution is acetonitrile-free and comprises 20 to 100% by weight, preferably 25 to 75%> by weight, of one or more symmetrical and/or unsymmetrical carbonates of the formula:
ROCC^OR1
wherein R is selected from the group consisting of methyl, ethyl, isopropyl, propyl,
CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-,
R"OCH2CH2- and R"-0-(CH2)n-, n is 2, 3 or 4, R1 is selected from the group consisting of CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-,
CH3CH2OCH2CH2- and R -0-CH2CH2-, and R" is methyl, ethyl, propyl or isopropyl.
According to another embodiment of the invention the carbonate solvents of the invention may be a mixture of themselves or with other linear or cyclic carbonates, esters and/or ethers, preferably ethylene carbonate. In one embodiment of the invention, the solvent
system comprises, consists essentially of, or consists of ethylene carbonate (EC) and methyl- (2-methoxyethyl)-carbonate (MMC). An amount of MMC may be present in combination with EC which is effective to provide a solvent system having a freezing point of -20°C or lower, - 30°C or lower, -40°C or lower, or even -50°C or lower. An EC/MMC solvent system may contain, for example, 10 to 80% by weight EC, with the balance being MMC. Optionally, such a solvent system may contain up to 5% by weight of one or more solvents other than EC and MMC, such as a cyclic or linear carbonate.
Cyclic carbonates include ethylene carbonate (hereafter designated as EC) and propylene carbonate (PC). Linear carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), etc.
The carboxylic ester optionally used herein preferably has three or more carbon atoms and one or more carboxylic ester bonds. The upper limit of the number of carbon atoms in the carboxylic ester is not particularly limited. In view of the compatibility with the linear carbonate and/or cyclic carbonate, the carboxylic ester preferably has ten or less carbon atoms and more preferably eight or less carbon atoms.
The number of carboxylic ester bonds in the carboxylic ester is one or more as described above. Since an increase in the number of carboxylic ester bonds generally leads to an increase in the viscosity of the carboxylic ester, the number of carboxylic ester bonds is preferably one or two.
Examples of suitable carboxylic esters include dimethyl succinate, ethyl methyl succinate, diethyl succinate, dimethyl 2-methylsuccinate, ethyl methyl 2-methylsuccinate, dimethyl glutarate, ethyl methyl glutarate, diethyl glutarate, dimethyl 2-methylglutarate, ethyl methyl 2-methylglutarate, diethyl 2-methylglutarate, dimethyl adipate, ethyl methyl adipate, diethyl adipate, 1,2-diacetoxyethane, 1 ,2-diacetoxypropane, 1 ,4-diacetoxybutane, glycerin triacetate, methyl 4-acetoxybutyrate, gamma butyrolactone, and methyl 2-acetoxyisobutyrate, ethyl acetate and methyl acetate.
The electrolyte solutions of the present invention for capacitors comprise the solvent systems of the invention and at least one conductive salt dissolved as an electrolyte.
The conductive salt may be any that is capable of being used in electrical storage devices, such as lithium secondary cells, lithium ion secondary cells and electrical double-layer capacitors. Conductive salts that may be used include alkali metal salts and quaternary ammonium salts. Combinations and mixtures of different conductive salts may be utilized.
Preferred alkali metal salts are lithium salts, sodium salts and potassium salts. Specific examples include: (1) lithium salts such as lithium tetrafluoroborate, lithium
hexafluorophosphate, lithium perchlorate, lithium trifluoromethanesulfonate, sulfonyl imide lithium salts, sulfonyl methide lithium salts, lithium acetate, lithium trifluoroacetate, lithium benzoate, lithium p-toluenesulfonate, lithium nitrate, lithium bromide, lithium iodide and lithium tetraphenylborate; (2) sodium salts such as sodium perchlorate, sodium iodide, sodium tetrafluoroborate, sodium hexafluorophosphate, sodium trifluoromethanesulfonate and sodium bromide; and (3) potassium salts such as potassium iodide, potassium tetrafluoroborate, potassium hexafluorophosphate and potassium trifluoromethanesulfonate.
Highly conductive quaternary ammonium and related imidazolium salts and inflates and mixtures thereof as tetrafluoroborates have synergistic effect on their solubilities and conductivities at low temperatures when dissolved in the solvent systems of the invention.
Preferable specific examples of the quaternary ammonium salt useful in the present invention include, but are not limited to, quaternary ammonium tetrafluoroborates and quaternary ammonium triflates such as triethylmethylammonium tetrafluoroborate, diethyldimethylammonium tetrafluoroborate, ethyltrimethylammonium tetrafluoroborate, dimethylpyrrolidinium tetrafluoroborate, diethylpyrrolidinium tetrafluoroborate,
ethylmethylpyrrolidinium tetrafluoroborate, spiro-(l,l 1)-bipyrrolidinium tetrafluoroborate, dimethylpiperidinium tetrafluoroborate, diethyl piperidinium tetrafluoroborate, spiro-(l,l ')- bipiperidinium tetrafluoroborate, piperidine- 1 -spiro- 11 -pyrrolidinium tetrafluoroborate, and the triflates thereof. The quaternary ammonium tetrafluoroborate salts preferably have a molecular weight in the range of 178-240.
Of these, triethylmethylammonium tetrafluoroborate, spiro-(l,l 1)-bipyrrolidimum tetrafluoroborate, diethyl pyrrolidinium tetrafluoroborate, dimethyl pyrrolidinium
tetrafluoroborate, and the like are particularly preferable.
The concentration of the conductive salt in the electrolyte solution of the present invention is preferably from 0.6 to 3 mol/1, particularly preferably from 1 M to 2 M of the electrolytic solution.
If the concentration of the conductive salt is less than 0.6 mol/1, the conductivity may be insufficient; if more than 3 mol/1, the low temperature performance and economical efficiency may be impaired.
What is needed are solvents with high operating voltages greater than 3 V for an ultra capacitor in which conductive salts are very soluble and which have a wide liquidus range,
preferably from -70°C to >150°C. In addition, the electrolyte solution should remain liquid with high salt concentrations of salt, e.g., from >1 M up to 2 M. The organic carbonates of the invention meet all of these requirements. The preferred solvent is methyl methoxyethyl carbonate (CH30(C=0)OCH2CH20CH3), (MMC). The liquidus range of this solvent is about -65°C to 170°C, providing outstanding low temperature and high temperature performance while dissolving a high level of conductive salt. This solvent has a stable operating cell voltage of about 4 V in ultra capacitor performance when containing 2 M diethyldimethyl ammonium tetrafluoroborate at room temperature. Other quaternary alkylammonium tetrafluoroborates can also be used for this same stable high operating voltage in this solvent and related solvents. This same stable solvent with 2 M quaternary ammonium
tetrafluoroborate salt will reversibly charge/discharge cycle at -45°C in an ultra capacitor. Preparation of Novel Carbonate Solvents
A direct synthesis for the symmetrical and asymmetrical members of the family of organic carbonates is the following equilibration:
RO(C=0) OR1 + R'OH <→ RO(C=0)OR" + R"0(C=0)OR1 + R"0(C=0)OR" + R'OH + ROH
(in the presence of basic catalyst such as sodium methoxide)
In the case of dimethyl carbonate and 2-methoxy ethanol this becomes:
CH30(C==0)OCH3 (DMC) + CH3OCH2CH2OH «→ CH30(C=0)OCH2CH2OCH3(MMC) +
CH3OCH2CH20(C=0)OCH2CH2OCH3 (BMC) + CH3OH
After equilibration, the catalyst can be neutralized with an acid or acid salt and the reaction mixture distilled to remove the alcohols and obtain pure organic carbonate components or a useful mixture of organic carbonates. Using an excess of the DMC in this case favors more of the desired MMC (asymmetrical component) as opposed to the symmetrical component bis-2-methoxyethyl carbonate (BMC). Mixtures of both with the starting material can be used as long as the alcohols are removed. The MMC is a preferred solvent of these series of organic carbonates. MMC may be isolated in pure form by distillation.
Preparation of Preferred Carbon Electrodes
The preferred carbon electrodes of the invention can be prepared following the procedure disclosed in U.S. Patent No. 7,924,549 of Smith, et al., incorporated herein by reference in its entirety for all purposes.
The capacitor requires two electrodes. Electrodes may be made of 90% treated carbon and 10% Kynar® binder in an acetone slurry. A 1-mil thick sheet of aluminum foil pre-treated with a conductive carbon layer may be trimmed to size and prepared for coating. A draw knife
may be used to deliver the proper thickness of slurry coating onto the foil. Once coated onto the treated aluminum sheet, the acetone evaporates and then the other side of the aluminum foil may be coated. Once the second side has been coated, proper sized rectangles may be cut from the aluminum sheet with small plain aluminum tabs still attached to one end. Once cut, the electrodes may be baked under vacuum to remove any residual moisture.
Once removed from the baking/vacuum treatment, small squares of Surlyn® resin sheets may be welded to the small plain aluminum tabs. This allows for future secure welding to the assembled flexible foil pouch.
To improve the functioning components in order to increase the performance of the ultra capacitor (UC) at higher voltage, we have been able to have stable cycling at 3.9-4.0 V with selected electrolytes and carbons. An additional aspect for better performance is to minimize the internal resistance of the UC, which depends on the measured ESR of the cell. It was found that one can lower the functional ESR of our UC cells by heat treating at higher temperatures the activated carbons used in the cells. It was found that with cleaned carbons under inert atmosphere one can continue to gain improvement by going from 1 100°C up to 1300°C. However, while going up to about 1400°C may offer further reduction in ESR the effect did not appear to be different than 1300°C, and the surface area (capacity) appeared to start being affected negatively. Therefore, the range of post heat treatment after acid washing of the carbon is 1 100°C to 1500°C, with the preferred range being 1250-1300°C under inert atmosphere.
The ESR of cells was reduced as follows:
Peak Temperature (2 hrs) of treated carbon ESR-ohms mAH Capacity at 3.9V
1 100°C 0.4 3.0 to 3.5
1200°C 0.3 3.4 to 3.7
1250°C 0.2 3.6 to 3.8
1300°C 0.18 3.8 to 4.0
Part of the reason for this improvement is the improvement of carbon conductivity which occurs significantly in going from 1000°C to about 1400°C and then only very slowly increases after that with increases in temperature. At the same time a high surface area carbon such as an activated carbon begins to rearrange and collapses to a more graphitic nature, thus losing its high surface area which is needed for the performance of the ultra capacitor. This surface collapse increases more and rapidly as the temperature is increased starting at about 1200°C and proceeding more rapidly as the temperature is raised past 1400°C. Empirically, it was found that this optimum heating range to achieve maximum conductivity before
degradation of the surface area is harmful to be about 1250°C to 1300°C for two hours with purified activated carbons. In addition to improving the conductivity while preserving the surface area, the higher temperature (above 1 100°C) chemically eliminates most (if not all) chemically bound oxygen and nitrogen, which are susceptible to electrochemical oxidation reduction at cell voltages above approximately 3.4 V in the ultra capacitor. Their presence contributes to leakage current (electrochemical oxidation currents on charging the UC and accelerate self discharge) which degrades UC performance, especially at operating voltages above 3.4V.
It is understood that conditioning the carbon electrodes according to the present preferred process optimizes the performance of the ultra capacitor when used with the electrolyte solutions of the invention, the prior art carbon electrodes, for example, which have been alkali conditioned will also be synergistically improved with the electrolyte solutions of the invention.
EXAMPLE 1
Preparation of Exemplary Electrolyte Solvent
In a 2L 3-necked flask, 1749 g (21.9 moles) of dimethylcarbonate (DMC), 246.14 g (3.24 moles) of 2-methoxy ethanol, and 49.23 g (5 wt. %) of a 25% sodium methoxide in methanol solution were added. A 250°C thermometer was added to the flask and the reaction flask was then fitted to a distillation apparatus containing a thermometer and a collection flask. This was stirred at room temperature for 30 minutes until a cloudy, white suspension began to form. The mixture was then heated slowly to a reaction flask temperature of 73 °C. At this point, the first drop of distillate was collected at 43 °C. The distillate was continuously collected and checked by GC for the presence of products (MMC and bis(2-methoxy ethyl)- carbonate (BMC)). This was continued until the reaction flask reached a temperature of 100°C and the distillation temperature reached 72°C. At this point, the reaction flask contents contained only a small percentage of DMC and no methanol. The reaction mixture was allowed to cool to room temperature. The reaction mixture was then filtered to remove the sodium methoxide catalyst. The slightly yellow filtrate was treated with NaH^PC^, mixed, and re-filtered. This step was then repeated and the filtrate checked to assure that no catalyst remained. The filtrate was then transferred to a 500 mL 3-necked flask and stirred. This was then vacuum-distilled slowly. The first fraction started at a distillation temperature of 28°C and a reaction flask temperature of 35°C. These fractions were mostly DMC. The MMC laden fractions were collected under vacuum (24 mm Hg) at a distillation temperature of 43 °C and a
reaction flask temperature of 55°C. The GC analysis showed a 91% yield of MMC in the final fraction of MMC product collected. The remainder of the mix was composed of 6% BMC and 3% 2-methoxy ethanol.
Claims
1. An electrochemical device comprising the combination of a conditioned and heat treated carbon electrode having reduced chemically bound oxygen, nitrogen and sulfur and an electrolyte solution, the electrolyte solution comprising a non-aqueous solvent system comprising 20 to 100% by weight of one or more symmetrical and/or asymmetrical carbonates of the general formula:
RO(C=0)OR1
wherein R is selected from the group consisting of methyl, ethyl, isopropyl, propyl, CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-, R"OCH2CH2- and R"-0-(CH2)n-, n is 2, 3 or 4, R1 is selected from the group consisting of CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-, CH3CH2OCH2CH2- and R -0-CH2CH2-, and R" is methyl, ethyl, propyl or isopropyl, and a conductive salt at a concentration of from 0.6 to 3 mol/1.
2. The electrochemical device of claim 1 wherein the non-aqueous solvent system is comprised of at least 20% by weight methyl-(2-methoxyethyl)-carbonate.
3. The electrochemical device of claim 1 wherein the non-aqueous solvent system is comprised of at least 20% by weight bis(2-methoxyethyl) carbonate.
4. The electrochemical device of claim 1 wherein the carbon of the carbon electrode has a surface area greater than 1200 m /g.
5. The electrochemical device of claim 1 wherein the conductive salt is selected from the group consisting of quaternary ammonium tetrafluoroborates, quaternary ammonium inflates, and combinations thereof.
6. The electrochemical device of claim 1 wherein the carbon of the carbon electrode has been acid washed and heat treated at a temperature from 1100°C to 1500°C in an inert atmosphere.
7. The electrochemical device of claim 6 wherein the carbon after heat treatment has a surface area greater than 1200 m /g.
8. The electrochemical device of claim 1 wherein the non-aqueous solvent system
includes a solvent selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate and diethyl carbonate.
9. The electrochemical device of claim 1 wherein the electrochemical device is an ultra capacitor.
10. The electrochemical device of claim 1 wherein the electrochemical device is an electrochemical double layer capacitor.
11. The electrochemical device of claim 1 wherein the electrolyte solution has a liquidus range from -70°C to greater than 150°C.
12. The electrochemical device of claim 1 wherein the non-aqueous solvent system consists of methyl-(2-methoxyethyl)-carbonate.
13. The electrochemical device of claim 1 , wherein the electrochemical device is a lithium ion battery and the conductive salt is a lithium salt.
14. The electrochemical device of claim 1, wherein the non-aqueous solvent system is comprised of 25 to 75% by weight of one or more symmetrical and/or asymmetrical carbonates of the general formula:
RO(C=0)OR1
15. The electrochemical device of claim 14, wherein the non-aqueous solvent system is additionally comprised of ethylene carbonate.
16. The electrochemical device of claim 1, wherein the non-aqueous solvent system
consists of ethylene carbonate, methyl-(2-methoxyethyl)-carbonate and, optionally, up to 5% by weight in total of one or more solvents other than ethylene carbonate and methyl-(2-methoxyethyl)-carbonate, wherein an amount of methyl-(2-methoxyethyl)- carbonate is present which is effective to provide the non-aqueous solvent system with a freezing point of -20°C or lower.
17. A method of making an electrochemical device, comprising the step of combining a carbon electrode with an electrolyte solution comprising a non-aqueous solvent system comprising 20 to 100% by weight of one or more symmetrical and/or asymmetrical carbonates of the general formula:
RO(C=0)OR1
wherein R is selected from the group consisting of methyl, ethyl, isopropyl, propyl, CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH2OCH2CH2-, R"OCH2CH2- and Κ"-0-(0¾)η-, n is 2, 3 or 4, R1 is selected from the group consisting of CH3OCH2CH2-, CH3OCH2CH2OCH2CH2-, CH3OCH2CH2OCH2CH20CH2CH2-, CH3CH2OCH2CH2- and R"-0-CH2CH2-, and R" is methyl, ethyl, propyl or isopropyl, and a conductive salt at a concentration of from 0.6 to 3 mol/1, wherein the carbon of the carbon electrode has been conditioned by acid washing and heat treating at a
temperature from 1 100°C to 1500°C in an inert atmosphere to reduce or remove chemically bound oxygen, nitrogen and sulfur.
18. The method of claim 17, wherein the non-aqueous solvent system is comprised of 25 to 75% by weight of one or more symmetrical and/or asymmetrical carbonates of the general formula:
RCKC^OR1
19. The method of claim 18, wherein the non-aqueous solvent system is additionally
comprised of ethylene carbonate.
20. The method of claim 17, wherein the non-aqueous solvent system consists of ethylene carbonate, methyl-(2-methoxyethyl)-carbonate and, optionally, up to 5% by weight in total of one or more solvents other than ethylene carbonate and methyl-(2- methoxyethyl)-carbonate, wherein an amount of methyl-(2-methoxyethyl)-carbonate is present which is effective to provide the non-aqueous solvent system with a freezing point of -20°C or lower.
21. The method of claim 17 wherein the conductive salt is selected from the group
consisting of quaternary ammonium tetrafluoroborates, quaternary ammonium triflates, and combinations thereof.
22. The method of claim 17, wherein the carbon of the carbon electrode has been
conditioned by acid washing and heat treating at a temperature from 1250°C to 1300°C in an inert atmosphere to reduce or remove chemically bound oxygen, nitrogen and sulfur
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