CA2193935C - Binder solution and electrode-forming composition for non-aqueous-type battery - Google Patents
Binder solution and electrode-forming composition for non-aqueous-type battery Download PDFInfo
- Publication number
- CA2193935C CA2193935C CA002193935A CA2193935A CA2193935C CA 2193935 C CA2193935 C CA 2193935C CA 002193935 A CA002193935 A CA 002193935A CA 2193935 A CA2193935 A CA 2193935A CA 2193935 C CA2193935 C CA 2193935C
- Authority
- CA
- Canada
- Prior art keywords
- acid
- vinylidene fluoride
- electrode
- binder solution
- group
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000011230 binding agent Substances 0.000 title claims abstract description 61
- 239000000203 mixture Substances 0.000 title claims abstract description 47
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 claims abstract description 106
- 239000000243 solution Substances 0.000 claims abstract description 93
- 229920000642 polymer Polymers 0.000 claims abstract description 64
- 239000002253 acid Substances 0.000 claims abstract description 46
- 239000003960 organic solvent Substances 0.000 claims abstract description 32
- 150000007524 organic acids Chemical class 0.000 claims abstract description 27
- 239000007772 electrode material Substances 0.000 claims abstract description 22
- 229920005596 polymer binder Polymers 0.000 claims abstract description 18
- 239000002491 polymer binding agent Substances 0.000 claims abstract description 18
- 239000008367 deionised water Substances 0.000 claims abstract description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 11
- 239000003381 stabilizer Substances 0.000 claims abstract 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical group CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 47
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 39
- 239000002002 slurry Substances 0.000 claims description 29
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 claims description 27
- 229920001577 copolymer Polymers 0.000 claims description 23
- 229920001519 homopolymer Polymers 0.000 claims description 21
- 239000013543 active substance Substances 0.000 claims description 19
- 239000008151 electrolyte solution Substances 0.000 claims description 18
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 claims description 16
- 239000002904 solvent Substances 0.000 claims description 16
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 15
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 12
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 12
- 229910052751 metal Inorganic materials 0.000 claims description 12
- 239000002184 metal Substances 0.000 claims description 12
- 239000002131 composite material Substances 0.000 claims description 11
- 238000001035 drying Methods 0.000 claims description 11
- 239000000758 substrate Substances 0.000 claims description 11
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 10
- 239000000178 monomer Substances 0.000 claims description 10
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 10
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 8
- LCTONWCANYUPML-UHFFFAOYSA-N Pyruvic acid Chemical compound CC(=O)C(O)=O LCTONWCANYUPML-UHFFFAOYSA-N 0.000 claims description 8
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 claims description 8
- HNEGQIOMVPPMNR-IHWYPQMZSA-N citraconic acid Chemical compound OC(=O)C(/C)=C\C(O)=O HNEGQIOMVPPMNR-IHWYPQMZSA-N 0.000 claims description 8
- 229940018557 citraconic acid Drugs 0.000 claims description 8
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 claims description 8
- 239000004310 lactic acid Substances 0.000 claims description 8
- 235000014655 lactic acid Nutrition 0.000 claims description 8
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims description 8
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 7
- 239000003575 carbonaceous material Substances 0.000 claims description 7
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 claims description 7
- 239000011976 maleic acid Substances 0.000 claims description 7
- 229910044991 metal oxide Inorganic materials 0.000 claims description 7
- 150000004706 metal oxides Chemical class 0.000 claims description 7
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 claims description 7
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 6
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 6
- 239000007822 coupling agent Substances 0.000 claims description 6
- 229910052744 lithium Inorganic materials 0.000 claims description 6
- AVQQQNCBBIEMEU-UHFFFAOYSA-N 1,1,3,3-tetramethylurea Chemical compound CN(C)C(=O)N(C)C AVQQQNCBBIEMEU-UHFFFAOYSA-N 0.000 claims description 5
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 claims description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 5
- 235000011054 acetic acid Nutrition 0.000 claims description 5
- 125000003700 epoxy group Chemical group 0.000 claims description 5
- GNOIPBMMFNIUFM-UHFFFAOYSA-N hexamethylphosphoric triamide Chemical compound CN(C)P(=O)(N(C)C)N(C)C GNOIPBMMFNIUFM-UHFFFAOYSA-N 0.000 claims description 5
- 229910001416 lithium ion Inorganic materials 0.000 claims description 5
- 239000002798 polar solvent Substances 0.000 claims description 5
- 230000000087 stabilizing effect Effects 0.000 claims description 5
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 5
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 claims description 4
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 claims description 4
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims description 4
- KDYFGRWQOYBRFD-UHFFFAOYSA-N Succinic acid Natural products OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 claims description 4
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 claims description 4
- 239000011888 foil Substances 0.000 claims description 4
- 235000019253 formic acid Nutrition 0.000 claims description 4
- 238000000034 method Methods 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 235000006408 oxalic acid Nutrition 0.000 claims description 4
- 235000019260 propionic acid Nutrition 0.000 claims description 4
- 229940107700 pyruvic acid Drugs 0.000 claims description 4
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 claims description 4
- DQWPFSLDHJDLRL-UHFFFAOYSA-N triethyl phosphate Chemical compound CCOP(=O)(OCC)OCC DQWPFSLDHJDLRL-UHFFFAOYSA-N 0.000 claims description 4
- WVLBCYQITXONBZ-UHFFFAOYSA-N trimethyl phosphate Chemical compound COP(=O)(OC)OC WVLBCYQITXONBZ-UHFFFAOYSA-N 0.000 claims description 4
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 claims description 4
- 229920002554 vinyl polymer Polymers 0.000 claims description 4
- 229910013108 LiMY2 Inorganic materials 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 239000000843 powder Substances 0.000 claims description 3
- 229910052723 transition metal Inorganic materials 0.000 claims description 3
- 150000003624 transition metals Chemical class 0.000 claims description 3
- 239000006087 Silane Coupling Agent Substances 0.000 claims description 2
- 125000003277 amino group Chemical group 0.000 claims description 2
- 229910052798 chalcogen Inorganic materials 0.000 claims description 2
- 150000004770 chalcogenides Chemical class 0.000 claims description 2
- 150000001787 chalcogens Chemical class 0.000 claims description 2
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 238000007865 diluting Methods 0.000 claims description 2
- 229910003002 lithium salt Inorganic materials 0.000 claims description 2
- 159000000002 lithium salts Chemical class 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 125000003396 thiol group Chemical group [H]S* 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims 4
- 238000006243 chemical reaction Methods 0.000 claims 4
- 239000003495 polar organic solvent Substances 0.000 claims 4
- 229910000077 silane Inorganic materials 0.000 claims 4
- BUPLCMMXKFWTTA-UHFFFAOYSA-N 4-methylidene-1,3-dioxetan-2-one Chemical compound C=C1OC(=O)O1 BUPLCMMXKFWTTA-UHFFFAOYSA-N 0.000 claims 3
- 235000015165 citric acid Nutrition 0.000 claims 3
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 claims 3
- 239000006185 dispersion Substances 0.000 claims 1
- 229910052727 yttrium Inorganic materials 0.000 claims 1
- 238000010790 dilution Methods 0.000 abstract description 13
- 239000012895 dilution Substances 0.000 abstract description 13
- 230000000052 comparative effect Effects 0.000 description 19
- 230000008961 swelling Effects 0.000 description 15
- 230000015572 biosynthetic process Effects 0.000 description 9
- 239000000654 additive Substances 0.000 description 8
- 230000000694 effects Effects 0.000 description 8
- 230000000996 additive effect Effects 0.000 description 7
- -1 e.g. Substances 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 6
- 239000006229 carbon black Substances 0.000 description 6
- 238000005259 measurement Methods 0.000 description 6
- 238000003860 storage Methods 0.000 description 6
- 239000011889 copper foil Substances 0.000 description 5
- 230000001747 exhibiting effect Effects 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 3
- 229920006369 KF polymer Polymers 0.000 description 3
- 230000002579 anti-swelling effect Effects 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 238000007598 dipping method Methods 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 238000006116 polymerization reaction Methods 0.000 description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 229910032387 LiCoO2 Inorganic materials 0.000 description 2
- 229910001290 LiPF6 Inorganic materials 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000005796 dehydrofluorination reaction Methods 0.000 description 2
- FKRCODPIKNYEAC-UHFFFAOYSA-N ethyl propionate Chemical compound CCOC(=O)CC FKRCODPIKNYEAC-UHFFFAOYSA-N 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- NKHAVTQWNUWKEO-UHFFFAOYSA-N fumaric acid monomethyl ester Natural products COC(=O)C=CC(O)=O NKHAVTQWNUWKEO-UHFFFAOYSA-N 0.000 description 2
- 238000010348 incorporation Methods 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- 229910001486 lithium perchlorate Inorganic materials 0.000 description 2
- NKHAVTQWNUWKEO-IHWYPQMZSA-N methyl hydrogen fumarate Chemical compound COC(=O)\C=C/C(O)=O NKHAVTQWNUWKEO-IHWYPQMZSA-N 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- LZDKZFUFMNSQCJ-UHFFFAOYSA-N 1,2-diethoxyethane Chemical compound CCOCCOCC LZDKZFUFMNSQCJ-UHFFFAOYSA-N 0.000 description 1
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 description 1
- ZFFMLCVRJBZUDZ-UHFFFAOYSA-N 2,3-dimethylbutane Chemical group CC(C)C(C)C ZFFMLCVRJBZUDZ-UHFFFAOYSA-N 0.000 description 1
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 1
- 229910001558 CF3SO3Li Inorganic materials 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 229910007966 Li-Co Inorganic materials 0.000 description 1
- 229910013292 LiNiO Inorganic materials 0.000 description 1
- 229910002097 Lithium manganese(III,IV) oxide Inorganic materials 0.000 description 1
- 229910008295 Li—Co Inorganic materials 0.000 description 1
- 229910006421 Li—Ni—Co Inorganic materials 0.000 description 1
- RJUFJBKOKNCXHH-UHFFFAOYSA-N Methyl propionate Chemical compound CCC(=O)OC RJUFJBKOKNCXHH-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 150000008064 anhydrides Chemical class 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000011218 binary composite Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 125000005587 carbonate group Chemical group 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 238000007334 copolymerization reaction Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 238000001879 gelation Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- 229910001540 lithium hexafluoroarsenate(V) Inorganic materials 0.000 description 1
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229920000609 methyl cellulose Polymers 0.000 description 1
- 229940017219 methyl propionate Drugs 0.000 description 1
- 239000001923 methylcellulose Substances 0.000 description 1
- 235000010981 methylcellulose Nutrition 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 229920000620 organic polymer Polymers 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 235000021317 phosphate Nutrition 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 235000011962 puddings Nutrition 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 238000010186 staining Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 238000010557 suspension polymerization reaction Methods 0.000 description 1
- 239000011206 ternary composite Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/24—Acids; Salts thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M6/00—Primary cells; Manufacture thereof
- H01M6/14—Cells with non-aqueous electrolyte
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/09—Carboxylic acids; Metal salts thereof; Anhydrides thereof
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Medicinal Chemistry (AREA)
- Organic Chemistry (AREA)
- Polymers & Plastics (AREA)
- Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Secondary Cells (AREA)
Abstract
A vinylidene fluoride polymer binder solution for forming an electrode for a non-aqueous-type battery is formed by adding an acid, preferably an organic acid, as a stabilizer to a solution of a vinylidene fluoride polymer in an organic solvent.
The acid is preferably added in an amount sufficient to ensure a pH of at most 9 when measured with respect to a 10-times dilution of the binder solution with deionized water. The acid addition is effective for preventing a problematic viscosity increase in the binder solution and also gelling of an electrode-forming composition formed by adding a powdery electrode material in the binder solution.
The acid is preferably added in an amount sufficient to ensure a pH of at most 9 when measured with respect to a 10-times dilution of the binder solution with deionized water. The acid addition is effective for preventing a problematic viscosity increase in the binder solution and also gelling of an electrode-forming composition formed by adding a powdery electrode material in the binder solution.
Description
2 ~ 93935 ,, BINDER SOLUTION AND ELECTRODE-FORMING COMPOSITION
FOR NON-AQUEOUS-TYPE BATTERY
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a solution of a binder comprising a vinylidene fluoride polymer (i.e:, a vinylidene fluoride polymer binder solution) for stably fixing a powdery electrode material (principally comprising an electrode active substance and an optionally added electroconductivity-imparting additive) onto an electrode substrate to form an electrode structure for a non-aqueous battery, particularly a lithium ion battery. The present invention further relates to an electrode-forming composition comprising a mizture of such a binder solution and a powdery electrode material dispersed therein, an electrode structure obtained therefrom, and a non-aqueous-type battery including such an electrode structure.
In recent years, remarkable development has been made in electronic technology, and various apparatus and devices have been reduced in size and weight. Accompanying the reduction in size and weight of electronic apparatus and devices, there has been a remarkably increasing demand for reduction in size and weight of a battery as a power supply for such electronic apparatus and devices. In order to 2~ 93935 generate a larger energy from a battery of small volume and weight, it is desirable to generate a higher voltage from one battery. From this viewpoint, much attention has been called to a battery using a non-aqueous electrolytic solution in combination with a negative electrode substance comprising, e.g., lithium or a carbonaceous material capable of being doped with lithium ions, and a positive electrode active substance comprising, e.g., a lithium-cobalt oxide.
However, in such a non-aqueous-type battery, the non-aqueous electrolytic solution shows only a low ionic conductivity on the order of 10-2 - 10 4 S/cm compared with an ordinary level ionic conductivity of ca. 10-1 S/cm in an aqueous electrolytic solution, so that it becomes essential to use an electrode (layer) in a small thickness of several pn to several hundred pm and in a large area. As a method of economically obtaining such a thin and large-area electrode, it has been known to disperse a powdery electrode material comprising an electrode active substance in a binder solution obtained by dissolving an organic polymer functioning as a binder for the powdery electrode material to form an electrode-forming composition and applying the composition onto an electroconductive substrate, such as a metal foil or a metal net, followed by drying to form an electrode. As such a binder solution for a non-aqueous-type battery, those obtained by dissolving various grades of vinylidene fluoride polymers in polar solvents, uch as N-methyl-2-pyrrolidone, dimethylformamide, N,N-dimethylacetamide have been known as disclosed in Japanese Laid-Open Patent Application (JP-A) 6-93025 and JP-A 6-172452. This is because a vinylidene fluoride polymer is excellent in chemical resistance, weatherability, anti-staining property, etc., is soluble in a polar solvent as described above but is stable against a non-aqueous electrolytic solution while it is swollen to some extent within such a non-aqueous electrolytic solution. Further, a vinylidene fluoride polymer can retain a good adhesion onto a ~ substrate of metal, etc., by copolymerization or modification.
There has been found a problematic phenomenon that a binder solution obtained by dissolving such a vinylidene fluoride polymer in a polar solvent exhibits a remarkably increased solution viscosity depending on a production lot of the solvent used.
Such an increased solution viscosity makes it difficult to obtain a uniform thickness of film in the electrode formation step by application and causes ~ gelling at the time of kneading with the active substance so that the film formation per se becomes difficult. Even if the film formation is possible, 2~ ~393~
FOR NON-AQUEOUS-TYPE BATTERY
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a solution of a binder comprising a vinylidene fluoride polymer (i.e:, a vinylidene fluoride polymer binder solution) for stably fixing a powdery electrode material (principally comprising an electrode active substance and an optionally added electroconductivity-imparting additive) onto an electrode substrate to form an electrode structure for a non-aqueous battery, particularly a lithium ion battery. The present invention further relates to an electrode-forming composition comprising a mizture of such a binder solution and a powdery electrode material dispersed therein, an electrode structure obtained therefrom, and a non-aqueous-type battery including such an electrode structure.
In recent years, remarkable development has been made in electronic technology, and various apparatus and devices have been reduced in size and weight. Accompanying the reduction in size and weight of electronic apparatus and devices, there has been a remarkably increasing demand for reduction in size and weight of a battery as a power supply for such electronic apparatus and devices. In order to 2~ 93935 generate a larger energy from a battery of small volume and weight, it is desirable to generate a higher voltage from one battery. From this viewpoint, much attention has been called to a battery using a non-aqueous electrolytic solution in combination with a negative electrode substance comprising, e.g., lithium or a carbonaceous material capable of being doped with lithium ions, and a positive electrode active substance comprising, e.g., a lithium-cobalt oxide.
However, in such a non-aqueous-type battery, the non-aqueous electrolytic solution shows only a low ionic conductivity on the order of 10-2 - 10 4 S/cm compared with an ordinary level ionic conductivity of ca. 10-1 S/cm in an aqueous electrolytic solution, so that it becomes essential to use an electrode (layer) in a small thickness of several pn to several hundred pm and in a large area. As a method of economically obtaining such a thin and large-area electrode, it has been known to disperse a powdery electrode material comprising an electrode active substance in a binder solution obtained by dissolving an organic polymer functioning as a binder for the powdery electrode material to form an electrode-forming composition and applying the composition onto an electroconductive substrate, such as a metal foil or a metal net, followed by drying to form an electrode. As such a binder solution for a non-aqueous-type battery, those obtained by dissolving various grades of vinylidene fluoride polymers in polar solvents, uch as N-methyl-2-pyrrolidone, dimethylformamide, N,N-dimethylacetamide have been known as disclosed in Japanese Laid-Open Patent Application (JP-A) 6-93025 and JP-A 6-172452. This is because a vinylidene fluoride polymer is excellent in chemical resistance, weatherability, anti-staining property, etc., is soluble in a polar solvent as described above but is stable against a non-aqueous electrolytic solution while it is swollen to some extent within such a non-aqueous electrolytic solution. Further, a vinylidene fluoride polymer can retain a good adhesion onto a ~ substrate of metal, etc., by copolymerization or modification.
There has been found a problematic phenomenon that a binder solution obtained by dissolving such a vinylidene fluoride polymer in a polar solvent exhibits a remarkably increased solution viscosity depending on a production lot of the solvent used.
Such an increased solution viscosity makes it difficult to obtain a uniform thickness of film in the electrode formation step by application and causes ~ gelling at the time of kneading with the active substance so that the film formation per se becomes difficult. Even if the film formation is possible, 2~ ~393~
there has been observed a phenomenon that the binder film after the applying and drying exhibits a large degree of swelling in a non-aqueous electrolytic solution. A Large degree of swelling,of the binder in a non-aqueous electrolytic solution leads to an increase in contact resistance between the powdery electrode material, particularly the active substance, and the metal foil or metal net, and an increase in contact resistance between the active substance particles themselves, thus resulting in an increased internal resistance in the battery. In the case of a secondary battery capable of repetitive charging and discharging, the increased internal resistance leads to an inferior charge-discharge cycle performance and is liable to result in a shorter battery life.
The. gelling during mixing with an active substance is rather remarkably caused in the step of forming a positive electrode-forming slurry composition than in the step of forming a negative electrode-forming slurry composition using carbon as a powdery electrode material. From this fact, it is assumed that the gelling of a vinylidene fluoride polymer in the positive electrode-forming slurry composition is attributable to the function of a lithium-based complex metal oxide as a positive electrode active substance, and it has been also found that this tendency is particularly promoted in the case of adding carbon black as an electro-conductivity-imparting additive.
SUI~lARY OF THE INVENTION
Accordingly, a principal object of the present invention is to provide a vinylidene fluoride polymer binder solution which per se is stable without causing a viscosity increase and allows the formation ~ of a battery electrode which is stable and free from excessive swelling in a non-aqueous electrolytic solution, and also an electrode-forming composition formed by dispersing a powdery electrode material in such a binder solution.
~5 Another object of the present invention is~to stabilize a positive electrode-forming composition in which the gelling of a vinylidene fluoride polymer is liable to be promoted.
A further object of the present invention is 2~ to provide an electrode structure formed from the above-mentioned electrode-forming composition, and a non-aqueous-type battery including such an electrode structure.
According to the present invention, there is 25 provided a vinylidene fluoride polymer binder solution, comprising: a solution of a vinylidene fluoride polymer in an organic solvent, stabilized by addition of an acid. It is preferred that the acid has been added in such an amount as to provide the binder solution; a portion of which will provide a 10-times dilution thereof with deionized water exhibiting a pH of at most J. The acid may preferably be an organic acid.
According to another aspect of the present invention, there is provided an electrode-forming composition comprising a powdery electrode material dispersed in a vinylidene fluoride polymer binder solution as described above.
According to the present invention, there are further provided an electrode structure, comprising:
an electroconductive substrate, and a composite electrode layer disposed on at least one sarface of the substrate comprising a powdery electrode material and a vinylidene fluoride polymer stabilized by an organic acid; and a non-aqueous-type battery including such an electrode structure-as a positive or a negative electrode.
Some explanation is added regarding the function and effect of the present invention.. As a result of our study, it has been found that the above-mentioned abnormal viscosity increase in a vinylidene fluoride polymer binder solution is associated with an acidity or alkalinity of the system. It is difficult to directly measure the acidity or alkalinity of the _7-solution of a vinylidene fluoride polymer in an organic solvent, but a measure may be obtained by diluting a portion thereof with ten times in amount of deionized water and measuring a pH of the resultant llC~uld. As a result of such a measurement, it has been found that the solution system having caused a viscosity increase shows a pH exceeding 9 of such a 10-times dilution liquid. Further knowledge or assumptions have been obtained, such that the viscosity increase is related with dehydrofluorination of a vinylidene fluoride polymer in an alkaline medium which per se is a known phenomenon and is directly related with the binder performance thereof; many of polar solvents exhibiting a good dissolving power for a vinylidene fluoride polymer are nitrogen-containing organic solvents, such as N-methylpyrrolidone and dimethylformamide; and whether the viscosity increases or not and how much it increases are depending on the production lot of a solvent, and are related with an increase of alkalinity of the solvent due to an alkaline substance, such as amine, which remains, or is generated or liberated during the production or the storage thereafter of such a nitrogen-containing organic solvent. Incidentally, it is assumed that the binder performance, such as a solvent resistance or anti-swelling property, of a vinylidene fluoride polymer is lowered by the dehydrofluorination because 2 ~ 93935 the dehydrofluorinated site is liable to be bonded with oxygen to consequently increase the affinity with a non-aqueous electrolytic solution, or the resultant increase of different kinds of bond in polymer molecular structure lowers the crystallinity of the polymer which is an effective factor for providing a good solvent resistance. The present invention is based on such analysis and also based on a knowledge that the above-mentioned difficulty of a vinylidene fluoride polymer binder solution accompanied with a viscosity increase can be effectively suppressed by the addition of an acid for providing a pH of the system at 9 or less.
Further, it has been also confirmed that the above-mentioned stabilization effect of acid addition is also remarkably observed in a positive electrode-forming slurry composition, and the use of an organic acid is particularly preferable.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a partial sectional view of an 21 9 3 9~3 5 _ g -electrode structure which may be adopted in a non-aqueous-type battery.
Figure 2 is a partially exploded perspective view of a non-aqueous-type secondary battery which can be constituted according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The vinylidene fluoride polymer used in the present invention may include vinylidene fluoride homopolymer, vinylidene fluoride copolymer and modification products of these. Vinylidene fluoride homopolymer is preferred in view of resistance to a non-aqueous electrolytic solution, particularly anti-swelling property. However, the homopolymer is liable to exhibit a somewhat low adhesion onto an electrode substrate, e.g., metal, so that it is preferred to use a copolymer of vinylidene fluoride with another monomer, preferably containing at least 95 mold of vinylidene fluoride.
Particularly preferred copolymer is one with an unsaturated dibasic acid monoester, a vinylene carbonate, an epoxy group-containing vinyl monomer, etc., to obtain a copolymer having a polar group, such as a carboxyl group, a carbonate group or an epoxy group (e.g., JP-A 6-172452). It is also preferred to use a modified vinylidene fluoride polymer obtained by treating such a vinylidene fluoride homopolymer or copolymer in a solvent capable of dissolving or swelling such a vinylidene fluoride polymer with a silane coupling agent or titanate coupling agent having a group reactive with the vinylidene fluoride polymer, such as an amino group or a mercapto group, and a hydrolyzable group in combination (as disclosed in JP-A 6-93025).
In order to retain a good anti-swelling resistance against a non-aqueous electrolytic solution as a whole, however, the vinylidene fluoride polymer may preferably retain at least 90 mol. %, particularly at least 95 mol. %, of untreated vinylidene fluoride units .
The vinylidene fluoride polymer may preferably have an inherent viscosity (logarithmic viscosity number at 30 °C of a solution obtained by dissolving 4 g of resin in 1 liter of N,N-dimethylformamide) of 0.5 or higher, more preferably 0.5 - 2.0, particularly preferably 0.8 - 1.5.
The organic solvent used for dissolving the vinylidene fluoride polymer to provide the binder solution according to the present invention may preferably be a polar one, examples of which may include: N-methyl-2-pyrrolidone, dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, and trimethyl phosphate. These organic solvents may be used singly or in mixture of two or more species. As described above, many of good solvents for vinylidene fluoride ~ 93935 polymer are nitrogen-containing solvents, which are also liable to generate an alkaline substance causing a viscosity increase of the binder solution. It is preferred to use a nitrogen-containing organic solvent in the present invention. However, even for a non-nitrogen-containing organic solvent, it is preferred to add an acid for pH control according to the present invention because it becomes possible to obviate a difficulty accompanying a pH increase possibly caused for some reason thereafter. Examples of such non-nitrogen-containing good solvents include dioxane, tetrahydrofuran and trialkyl phosphates, which can suitably be used singly or in mixture'with a nitrogen-containing organic solvent.
~ For obtaining the binder solution according to the present invention, it is preferred to dissolve 0.1 - 20 wt. parts, particularly 1 - 15 wt. parts, of the above-mentioned vinylidene fluoride polymer in 100 wt. parts of such an organic solvent. Below 0.1 wt.
part, the polymer occupies too small a proportion in the solvent, thus being liable to fail in exhibiting a sufficient binder performance. Above 20 wt, parts, the resultant solution is liable to have an excessively high viscosity, thus making It difficult to prepare an electrode-forming composition.
It is preferred to add an acid to the binder solution so that a portion of the binder solution 1~9~~95 after the acid addition is diluted with 10-times in amount of deionized water to provide a liquid which exhibits a pH of at most 9.
The acid to be added is not basically restricted in species. It is however preferred to use such an acid that is removed by decomposition or vaporization during the steps of applying and drying the resultant electrode-forming composition to be free from remaining in the shaped electrode. It is also preferred to use an acid little reactive with an electrode active substance. In this respect, an inorganic acid, such as hydrochloric acid or sulfuric acid, is liable to react with an electrode active substance, thus being not necessarily preferred.
Particularly, in the case of using an electrode active substance, such as graphite, liable to form an intercalation compound with an inorganic substance., it is preferred to use an organic acid having a large molecular diameter and thus being less liable to form an intercalation compound. It is preferred to use an organic acid which has a high vapor pressure, or is susceptible of decomposition to be scattered in a temperature region of the drying step (ordinarily at or below 175 °C which is the melting point of PVDF
(vinylidene fluoride homopolymer)). Examples of the organic acid preferred from such viewpoints may include: acrylic acid, formic acid, citric acid, w.
2~ 93935 acetic acid, oxalic acid, lactic acid, pyruvic acid, malonic acid, succinic acid, propionic acid, malefic acid, malefic anhydride, citraconic acid, and lactic acid. Among these, it is particularly preferred to use malonic acid, or a dibasic acid forming or capable of taking a cis-form, such as malefic acid or citraconic acid.
The incorporation of such an acid in a vinylidene fluoride polymer solution may preferably be performed by adding the acid to an organic solvent in __ advance for solvent pH adjustment and then dissolving the polymer in the solvent. It is however also possible to simultaneously add an acid at the time of dissolving the polymer in an organic solvent or to first dissolve the polymer in an organic solvent and then add an acid to the polymer solution.
The acid may preferably be added in an amount sufficient to provide a binder solution, a portion of which will provide a 10-times dilution thereof with deionized water exhibiting a pH of at most 9.0, (the pH being substantially equal to that of a 10-times dilution of an organic solvent to which an acid has been added in advance according to the,preferred embodiment). The lower limit of the pH is not particularly restricted but may ordinarily be down to ca. 3 as a particular improvement cannot be expected by the addition of a further amount of acid. However, in the case of using an organic acid according to a preferred embodiment, the organic acid is decomposed or evaporated during the applying and drying steps for electrode formation, so that an excessive addition thereof is not harmful. Even in case where the organic solvent or the binder solution before the acid addition already exhibits the dilution pH of 9 or below, it is preferred to add a certain amount of the acid so as to exhibit a buffer effect of resisting a possible pH increase thereafter for some reason, such as decomposition of the solvent. In this instance, the acid may preferably be added in an amount of at least 100 wt. ppm, more preferably 300 - 10,000 wt.
ppm, in the resultant binder solution: In this mode, it is particularly preferred to use an organic acid which results in almost no harm even if it remains thereafter. Such an organic acid even exhibits a tendency of improving the electrode performances through stabilization of the vinylidene fluoride polymer by remaining thereof in the electrode.
An electrode-forming composition may be obtained by adding and dispersing a powdery electrode material (an active substance and optional additives, such as an electroconductivity-imparting additive) into the thus-obtained vinylidene fluoride polymer binder solution according to the present invention.
In the case of forming a positive electrode, ~1939~
the active substance may comprise a composite metal chalcogenide represented by a general formula of LiMY2, wherein M denotes at least one species of transition metals such as Co, Ni, Fe, Mn, Cr and V;
and Y denotes a chalcogen, such as O or S. Among these, it is preferred to use a lithium-based composite metal oxide represented by a general formula of LiM02, wherein M is the same as above. Preferred examples thereof may include: LiCo02,'LiNi02, LiNixCol-x02, and spinel-structured LiMn2O4. Among these, it is particularly preferred to use a Li-Co or Li-Ni binary composite metal oxide or Li-Ni-Co ternary composite metal oxide inclusively represented by a formula of LiNigCol-x02 (0 S x s 1) in view of a high charge-discharge potential and excellent cycle characteristic.
In the case of forming a negative electrode, the active substance may preferably comprise a carbonaceous material, such as graphite, activated carbon or a carbonaceous material obtained by carbonization of phenolic resin, pitch, etc.
An electroconductivity-imparting additive may be added in order to improve the conductivity of a resultant composite electrode layer formed by applying and drying of the electrode-forming composition of the present invention, particularly in case of using an active substance, such as LiCo02, showing a small electron-conductivity in a positive electrode. Examples thereof may include: carbonaceous materials, such as carbon black, graphite fine powder and fiber, and fine powder and fiber of metals, such as nickel and aluminum. The effect of stabilizing the positive electrode-forming composition according to the present invention is particularly pronounced in the case of using electroconductive carbon black (preferably one having an average particle size (diameter) of ca. 10 - 100 nm as measured by observation through an electron microscope) which has a large electroconductivity-improving effect but also is liable to exhibit a remarkable effect of promoting gelation of vinylidene fluoride polymer, singly or in combination with another electroconductivity-imparting w additive. Such an electroconductivity-imparting additive may preferably be used in an amount of 0.1 -l0 wt. parts per 100 wt. parts of a composite metal oxide constituting the positive electrode. In the case of using a carbonaceous material exhibiting a large electroconductivity, such an electro-conductivity-imparting additive need not be added.
In formulating the electrode-forming composition according to the present invention, it is preferred to blend 0.1 - 50 wt. parts, particularly I
- 20 wt. parts of vinylidene fluoride polymer with 100 wt. parts of a powdery electrode material.
z1 ~3~~5 The incorporation of an organic acid for stabilizing vinylidene fluoride polymer in the positive electrode-forming composition may be performed in any arbitrary manner. For example, it is possible to blend the acid simultaneously with blending of a positive electrode active substance, carbon black, a vinylidene fluoride polymer and an organic solvent. It is however preferred to form a vinylidene fluoride polymer solution containing an organic acid added thereto (more preferably by dissolving a vinylidene fluoride polymer in an organic solvent already containing an organic acid) and then blending the vinylidene fluoride polymer solution with a powdery electrode material, such as a positive 25 electrode active substance.
The thus-prepared positive or negative electrode-forming slurry composition may be used for forming an electrode structure having a partial sectional structure as shown in Figure 1. More specifically, referring to Figure I, the slurry composition may be applied onto at least one surface, preferably both surfaces, of an electroconductive substrate 11 comprising a foil or wire net of a metal, such as iron, stainless steel, steel, copper, aluminum, nickel or titanium and having a thickness of, e.g., 5 - 100 um, or 5 - 20 um for a small-sized battery, and dried at, e.g., 50 - 170 °C, to form a -1$_ 1, g ~ 9 3 5 composite electrode layer (12a, 12b) of, e.g., 10 -1000 pn, preferably 10 - 200 ~.un, in thickness for a small-sized battery, thereby providing an electrode structure 10 for a non-aqueous-type battery.
Figure 2 is a partially exploded perspective view of a lithium secondary battery as an embodiment of a non-aqueous-type battery according to the present invention, including an electrode structure prepared in the above-described manner. -More specifically, the secondary battery basically includes a laminate structure including a positive electrode 1, a negative electrode 2 and a separator 3 disposed between the positive and negative electrodes land 2 and comprising a fine porous film of a polymeric material, such as polyethylene or polypropylene, impregnated with an electrolytic solution. The laminate structure is wound in a vortex shape to form an electricity-generating element which is housed within a metal casing 5 having a bottom constituting a negative electrode terminal 5a. In the secondary battery, the negative electrode 2 is electrically connected to the negative electrode terminal 5a, and the uppermost portion of the battery is constituted by disposing a gasket 6 and a safety valve 7 covered with a top plate 8 having a projection constituting a positive electrode terminal 8a electrically connected to the positive electrode.
2 ~ 93935 Further, the uppermost rim 5b of the casing 5 is crimped toward the inner side to form an entirely sealed cell structure enclosing the electricity-generating element. The positive electrode l and the negative electrode 2 may have a structure of the electrode structure 10 shown in Figure 1.
The non-aqueous electrolyte solution impregnating the separator 3 may comprise a solution of an electrolyte, such as a lithium salt, in a non-aqueous solvent (organic solvent).
Examples of the electrolyte may include:
LiPF6, LiAsF6, LiCl04, LiBF4, CH3S03Li, CF3S03Li, LfN(S02CF3)2, LiC(S02CF3)3, LiCl, and Liar. Examples of the organic solvent for such an electrolyte may include: propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, -butyrolactone, methyl propionate, ethyl propionate, and mixtures of these, but they are not exhaustive.
In the above, a cylindrical battery has been described as an embodiment of the non-aqueous-type battery according to the present invention. However, the non-aqueous-type battery according to the present invention can basically have any other shapes, such as those of a coin, a rectangular_parallelepiped, or a paper or sheet.
[Egamples~
Hereinbelow, the present invention will be described more specifically based Examples and Comparative Examples.
(Preparation of vinylidene fluoride polymer) A carboxyl group-containing vinylidene fluoride polymer was prepared in the following manner.
Into a 2 liter-autoclave, 1040 g of deionized water, 0.8 g of methyl cellulose, 2.5 g of ethyl acetate, 4 g of diisopropyl perosydicarbonate, 396 g of vinylidene fluoride and 4 g of monomethyl maleate {i.e., vinylidene fluoride/monomethyl maleate =
100/1.01 (by weight)) were added and subjected to suspension polymerization at 28 oC for 47 hours.
After completion of the polymerization, the ~ polymerization slurry was de-watered, washed with water and dried at 80 °C for 20 hours to obtain a powdery polymer.
The polymerization yield was 90 wt. ~, and the resultant polymer showed an inherent viscosity of 1.1, and a carbonyl group content of 1.2$10-4 mol/g.
(Organic solvent}
20 lots of commercially available N-methyl-2-pyrrolidone (hereinafter abbreviated as "NMP") were stored at room temperature for ca. 3 months and then used for the following tests. The NMP in 20 lots provided 10-times dilutions with de-ionized water showing pH ranging from 6.5 to 11Ø
Comparative Example 1 Into a :Lot of NMP having provided a 10-times dilution with de-ionized water showing a pH of 9.5, the above-prepared carboxyl group-containing vinylidene fluoride polymer was dissolved at 50 oC so as to provide a concentration of 13 wt. % to obtain a binder solution.
Example 1 1000 ppm of malefic acid was added to the same lot of NMP as used in Comparative Example 1, and the solution was also diluted with ten times of deionized water, whereby the dilution showed a pH of 3.2. Then, into the NMP containing malefic acid, the above-mentioned vinylidene fluoride polymer'was dissolved similarly as in Comparative Example l to prepare a binder solution at a concentration of l3 wt. ~.
(Viscosity and Fluorine ion concentration measurement) The binder solutions prepared in Comparative Example 1 and Example 1 were subjected to measurement of viscosity by using a rotating viscometer (according to JIS K7117) and measurement of fluorine ion (F-) concentration.
(Film formation and Swelling test) Each of the binder solutions: prepared in Comparative Example 1 and Example 1 was cast onto a glass plate and dried at 130 oC for 2 hours, followed by peeling, to form a ca. 200 p.m-thick film.
-22- 21 9 3 9 3 5 .
Then, each film thus obtained was dipped at 70 °C for 72 hours in an electrolytic solution formed by dissolving 8.8 wt. parts of LiCl04 into a liquid mixture of 53.6 wt. parts of propylene carbonate and 37.6 v,rt. parts of dimethoxyethane. In the meantime, each film was taken out at 24 hours each to evaluate the degree of swelling in terms of a cast film weight increase percentage (increased weight/weight of the film before dipping x 100).
The results of the above measurement are summarized in the following Table 1:
Table 1 Comparative Example 1 Example I
Binder solution Amount of maleic acid added 0 1000 ppm 10-times dilution pH 9.5 3.2 Viscosity (mPa.s) 1010 870 Fluorine (F-) concentration 200-500 ppm <100 ppm Degree of film swelling (wt.~) 24 hours 28'~ 20 48 hours 29 21 72 hours 29 22 The results in the above Table 1 show that, compared with the vinylidene fluoride polymer binder solution of Comparative Example 1 using NMP as it was, the vinylidene fluoride polymer binder solution of Example 1 obtained by adding 1000 ppm of malefic acid was stabler in view of low viscosity increase and low fluorine ion concentration and showed a remarkably improved swelling resistance against an electrolytic solution for non-aqueous-type battery.
Comparative Example 2 Into a lot of NMP showing a 10-times dilution pH of 10.9, the above-mentioned carboxyl group-containing vinylidene fluoride polymer was dissolved to form a binder solution at a concentration of l3 wt. o.
Example 2 1000 ppm of malonic acid was added to the same lot of NMP as used in Comparative Example 2, and then the carboxyl group-containing vinylidene fluoride polymer was dissolved to form a binder solution at a concentration of 13 wt. ~.
The binder solutions of the above Comparative Example 2 and Example 2 were respectively used for formation of a cast film similarly as in Example 1, and the resultant films were subjected to dipping in the electrolytic solution at 70 °C for 72 hours similarly as in Example 1. As a result, the films exhibited swelling degrees after 72 hours as shown below.
Table 2 Comparative Example 2 Example 2 Amount of malonic acid 0 1000 ppm Swelling degree after 72 hrs. 25 wt.~ 18 wt.~
Comparative Example 3 Into a lot of NMP showing a 10-times dilution of pH of 9.5, vinylidene fluoride homopolymer ("KF Polymer #1100", available from Kureha Kagaku Kogyo K.K.) was dissolved at 50 °C to form a binder solution at a concentration of 13 wt. $.
Example 3 1000 ppm of maleic acid was added to the same lot of NMP as used in Comparative Example 3, and then the vinylidene fluoride homopolymer used in Comparative Example 3 was dissolved therein to form a binder solution at a concentration of 13 wt. ~.
The thus-formed binder solutions were subjected to measurement of viscosity and degree of film swelling similarly as in Example 1. The results are shown in Table 3 below.
*Trade-mark Table 3 Comparative Example 1 Example l Binder solution Amount of malefic acid added 0 1000 ppm 10-times dilution pH 9.5 3.2 Viscosity (mPa.s) 9$0 717 Degree of f i lm swel l inc_r ( wt . ~ ) 72 hours 20 15 Also in this case, the addition of malefic acid provided a binder solution showing a good viscosity increase-preventing effect and an improved film swelling resistance.
Example 4 and Comparative Example 4 The films prepared in the above Example 1 and Comparative Egampie I were respectively dipped in an electrolytic solution comprising 11.6 wt. ~ of LiPF6, 510 wt. ~ of ethylene carbonate and 37.4 wt. ~ of diethyl carbonate at 70 °C for 72 hours. After the dipping, the films showed swelling degrees (weight increases due to swelling) of 1$ wt. g and 24 wt. ~, respectively.
Example 5 9 wt. parts of LiNiO.$Co0.202 (active substance, Dav. (average particle diameter) - 15 pn), 2 i 93935 0.7 wt. part of electroconductive carbon black (Dav.
ca. 40 nm, specific surface area = 30 m2/g, oii absorption = 129 ml/g), 0.3 wt. part of vinylidene fluoride homopolymer ("KF Polymer #1300", available from Kureha Kagaku Kogyo K.K.), and 6 wt. parts of NMP
containing 0.1 wt. ~ of malefic acid were blended with each other and uniformly dispersed at 50 °C to prepare a positive electrode-forming slurry composition. The slurry showed substantially identical viscosities before and after storage for 24 hours at room temperature. The slurry was applied onto one surface of a 10 pm-thick copper foil and dried at 130 °C to form a totally 100 dun-thick electrode structure having a smooth positive electrode layer.
Example 6 9 wt. parts of LiNi0.9Co0.102 (Dav. - 15 ~.un), 0'.7 wt. part of electroconductive carbon black, 0.3 wt. part of vinylidene fluoride homopolymer ("KF
Polymer ##1300") and 6 wt. parts of NMP containing 0.1 wt. ~ of citraconic acid were blended with each other and uniformly dispersed at 50 °C to prepare a positive electrode-forming slurry composition. The slurry showed substantially identical viscosities before and after storage for 24 hours at room temperature. The slurry was applied onto one surface of a ZO pm-thick copper foil and dried at 130 ~C to farm a totally 105 ~.un-thick electrode structure having a smooth positive electrode layer.
Example 7 A positive electrode-forming slurry composition was prepared in the same manner as in Example 5 except for using 6 wt. parts of NMP
containing 0.1 wt. ~ of malonic acid instead of the 0.1 wt. ~ of malefic acid. The slurry; showed substantially identical viscosities before and after storage for 24 hours at room temperature. The slurry was applied onto one surface of a 10 um-thick copper foil and dried at 130 oC to form a totally 102 pm-thick electrode structure having a smooth positive electrode layer.
Example 8 ' A positive electrode-forming slurry composition was prepared in the same manner as in Example 5 except for using 6 wt. parts of NMP
containing 0.1 wt. ~ of acetic acid instead of the 0.1 wt. ~ of malefic acid. The slurry showed substantially identical viscosities before and after storage for 24 hours at room temperature. The slurry was applied onto one surface of a l0 um-thick copper foil and dried at 130 oC to form a totally 106 Wn-thick electrode structure having a smooth positive electrode layer.
Comparative Example 5 A positive electrode-forming slurry ,,,~"', composition was prepared in the same manner as in Example 5 except for using 6 wt. parts of NMP
containing no malefic acid.
After the preparation, the slurry caused severe gelling when it was stored for 2 - 3 hours at room temperature, thus making it difficult to apply the slurry onto a copper foil. After 24 hours of storage at room temperature, the slurry became a rather hard pudding state and could not be used.
As described above, according to the present __ invention, an acid, preferably an organic acid, is added during formation of a binder solution for a non-aqueous-type battery electrode by dissolving a vinylidene fluoride polymer in an organic solvent, 25 whereby it is possible to effectively obviate a viscosity increase of the binder solution, a lowering of binder effect in the resultant electrode due to swelling of the binder with an electrolyte solution, and gelling of an electrode-forming slurry, particularly a positive electrode-forming slurry, which are problematic but have been frequently caused heretofore in non-aqueous-type battery electrode formation.
The. gelling during mixing with an active substance is rather remarkably caused in the step of forming a positive electrode-forming slurry composition than in the step of forming a negative electrode-forming slurry composition using carbon as a powdery electrode material. From this fact, it is assumed that the gelling of a vinylidene fluoride polymer in the positive electrode-forming slurry composition is attributable to the function of a lithium-based complex metal oxide as a positive electrode active substance, and it has been also found that this tendency is particularly promoted in the case of adding carbon black as an electro-conductivity-imparting additive.
SUI~lARY OF THE INVENTION
Accordingly, a principal object of the present invention is to provide a vinylidene fluoride polymer binder solution which per se is stable without causing a viscosity increase and allows the formation ~ of a battery electrode which is stable and free from excessive swelling in a non-aqueous electrolytic solution, and also an electrode-forming composition formed by dispersing a powdery electrode material in such a binder solution.
~5 Another object of the present invention is~to stabilize a positive electrode-forming composition in which the gelling of a vinylidene fluoride polymer is liable to be promoted.
A further object of the present invention is 2~ to provide an electrode structure formed from the above-mentioned electrode-forming composition, and a non-aqueous-type battery including such an electrode structure.
According to the present invention, there is 25 provided a vinylidene fluoride polymer binder solution, comprising: a solution of a vinylidene fluoride polymer in an organic solvent, stabilized by addition of an acid. It is preferred that the acid has been added in such an amount as to provide the binder solution; a portion of which will provide a 10-times dilution thereof with deionized water exhibiting a pH of at most J. The acid may preferably be an organic acid.
According to another aspect of the present invention, there is provided an electrode-forming composition comprising a powdery electrode material dispersed in a vinylidene fluoride polymer binder solution as described above.
According to the present invention, there are further provided an electrode structure, comprising:
an electroconductive substrate, and a composite electrode layer disposed on at least one sarface of the substrate comprising a powdery electrode material and a vinylidene fluoride polymer stabilized by an organic acid; and a non-aqueous-type battery including such an electrode structure-as a positive or a negative electrode.
Some explanation is added regarding the function and effect of the present invention.. As a result of our study, it has been found that the above-mentioned abnormal viscosity increase in a vinylidene fluoride polymer binder solution is associated with an acidity or alkalinity of the system. It is difficult to directly measure the acidity or alkalinity of the _7-solution of a vinylidene fluoride polymer in an organic solvent, but a measure may be obtained by diluting a portion thereof with ten times in amount of deionized water and measuring a pH of the resultant llC~uld. As a result of such a measurement, it has been found that the solution system having caused a viscosity increase shows a pH exceeding 9 of such a 10-times dilution liquid. Further knowledge or assumptions have been obtained, such that the viscosity increase is related with dehydrofluorination of a vinylidene fluoride polymer in an alkaline medium which per se is a known phenomenon and is directly related with the binder performance thereof; many of polar solvents exhibiting a good dissolving power for a vinylidene fluoride polymer are nitrogen-containing organic solvents, such as N-methylpyrrolidone and dimethylformamide; and whether the viscosity increases or not and how much it increases are depending on the production lot of a solvent, and are related with an increase of alkalinity of the solvent due to an alkaline substance, such as amine, which remains, or is generated or liberated during the production or the storage thereafter of such a nitrogen-containing organic solvent. Incidentally, it is assumed that the binder performance, such as a solvent resistance or anti-swelling property, of a vinylidene fluoride polymer is lowered by the dehydrofluorination because 2 ~ 93935 the dehydrofluorinated site is liable to be bonded with oxygen to consequently increase the affinity with a non-aqueous electrolytic solution, or the resultant increase of different kinds of bond in polymer molecular structure lowers the crystallinity of the polymer which is an effective factor for providing a good solvent resistance. The present invention is based on such analysis and also based on a knowledge that the above-mentioned difficulty of a vinylidene fluoride polymer binder solution accompanied with a viscosity increase can be effectively suppressed by the addition of an acid for providing a pH of the system at 9 or less.
Further, it has been also confirmed that the above-mentioned stabilization effect of acid addition is also remarkably observed in a positive electrode-forming slurry composition, and the use of an organic acid is particularly preferable.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 is a partial sectional view of an 21 9 3 9~3 5 _ g -electrode structure which may be adopted in a non-aqueous-type battery.
Figure 2 is a partially exploded perspective view of a non-aqueous-type secondary battery which can be constituted according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The vinylidene fluoride polymer used in the present invention may include vinylidene fluoride homopolymer, vinylidene fluoride copolymer and modification products of these. Vinylidene fluoride homopolymer is preferred in view of resistance to a non-aqueous electrolytic solution, particularly anti-swelling property. However, the homopolymer is liable to exhibit a somewhat low adhesion onto an electrode substrate, e.g., metal, so that it is preferred to use a copolymer of vinylidene fluoride with another monomer, preferably containing at least 95 mold of vinylidene fluoride.
Particularly preferred copolymer is one with an unsaturated dibasic acid monoester, a vinylene carbonate, an epoxy group-containing vinyl monomer, etc., to obtain a copolymer having a polar group, such as a carboxyl group, a carbonate group or an epoxy group (e.g., JP-A 6-172452). It is also preferred to use a modified vinylidene fluoride polymer obtained by treating such a vinylidene fluoride homopolymer or copolymer in a solvent capable of dissolving or swelling such a vinylidene fluoride polymer with a silane coupling agent or titanate coupling agent having a group reactive with the vinylidene fluoride polymer, such as an amino group or a mercapto group, and a hydrolyzable group in combination (as disclosed in JP-A 6-93025).
In order to retain a good anti-swelling resistance against a non-aqueous electrolytic solution as a whole, however, the vinylidene fluoride polymer may preferably retain at least 90 mol. %, particularly at least 95 mol. %, of untreated vinylidene fluoride units .
The vinylidene fluoride polymer may preferably have an inherent viscosity (logarithmic viscosity number at 30 °C of a solution obtained by dissolving 4 g of resin in 1 liter of N,N-dimethylformamide) of 0.5 or higher, more preferably 0.5 - 2.0, particularly preferably 0.8 - 1.5.
The organic solvent used for dissolving the vinylidene fluoride polymer to provide the binder solution according to the present invention may preferably be a polar one, examples of which may include: N-methyl-2-pyrrolidone, dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, and trimethyl phosphate. These organic solvents may be used singly or in mixture of two or more species. As described above, many of good solvents for vinylidene fluoride ~ 93935 polymer are nitrogen-containing solvents, which are also liable to generate an alkaline substance causing a viscosity increase of the binder solution. It is preferred to use a nitrogen-containing organic solvent in the present invention. However, even for a non-nitrogen-containing organic solvent, it is preferred to add an acid for pH control according to the present invention because it becomes possible to obviate a difficulty accompanying a pH increase possibly caused for some reason thereafter. Examples of such non-nitrogen-containing good solvents include dioxane, tetrahydrofuran and trialkyl phosphates, which can suitably be used singly or in mixture'with a nitrogen-containing organic solvent.
~ For obtaining the binder solution according to the present invention, it is preferred to dissolve 0.1 - 20 wt. parts, particularly 1 - 15 wt. parts, of the above-mentioned vinylidene fluoride polymer in 100 wt. parts of such an organic solvent. Below 0.1 wt.
part, the polymer occupies too small a proportion in the solvent, thus being liable to fail in exhibiting a sufficient binder performance. Above 20 wt, parts, the resultant solution is liable to have an excessively high viscosity, thus making It difficult to prepare an electrode-forming composition.
It is preferred to add an acid to the binder solution so that a portion of the binder solution 1~9~~95 after the acid addition is diluted with 10-times in amount of deionized water to provide a liquid which exhibits a pH of at most 9.
The acid to be added is not basically restricted in species. It is however preferred to use such an acid that is removed by decomposition or vaporization during the steps of applying and drying the resultant electrode-forming composition to be free from remaining in the shaped electrode. It is also preferred to use an acid little reactive with an electrode active substance. In this respect, an inorganic acid, such as hydrochloric acid or sulfuric acid, is liable to react with an electrode active substance, thus being not necessarily preferred.
Particularly, in the case of using an electrode active substance, such as graphite, liable to form an intercalation compound with an inorganic substance., it is preferred to use an organic acid having a large molecular diameter and thus being less liable to form an intercalation compound. It is preferred to use an organic acid which has a high vapor pressure, or is susceptible of decomposition to be scattered in a temperature region of the drying step (ordinarily at or below 175 °C which is the melting point of PVDF
(vinylidene fluoride homopolymer)). Examples of the organic acid preferred from such viewpoints may include: acrylic acid, formic acid, citric acid, w.
2~ 93935 acetic acid, oxalic acid, lactic acid, pyruvic acid, malonic acid, succinic acid, propionic acid, malefic acid, malefic anhydride, citraconic acid, and lactic acid. Among these, it is particularly preferred to use malonic acid, or a dibasic acid forming or capable of taking a cis-form, such as malefic acid or citraconic acid.
The incorporation of such an acid in a vinylidene fluoride polymer solution may preferably be performed by adding the acid to an organic solvent in __ advance for solvent pH adjustment and then dissolving the polymer in the solvent. It is however also possible to simultaneously add an acid at the time of dissolving the polymer in an organic solvent or to first dissolve the polymer in an organic solvent and then add an acid to the polymer solution.
The acid may preferably be added in an amount sufficient to provide a binder solution, a portion of which will provide a 10-times dilution thereof with deionized water exhibiting a pH of at most 9.0, (the pH being substantially equal to that of a 10-times dilution of an organic solvent to which an acid has been added in advance according to the,preferred embodiment). The lower limit of the pH is not particularly restricted but may ordinarily be down to ca. 3 as a particular improvement cannot be expected by the addition of a further amount of acid. However, in the case of using an organic acid according to a preferred embodiment, the organic acid is decomposed or evaporated during the applying and drying steps for electrode formation, so that an excessive addition thereof is not harmful. Even in case where the organic solvent or the binder solution before the acid addition already exhibits the dilution pH of 9 or below, it is preferred to add a certain amount of the acid so as to exhibit a buffer effect of resisting a possible pH increase thereafter for some reason, such as decomposition of the solvent. In this instance, the acid may preferably be added in an amount of at least 100 wt. ppm, more preferably 300 - 10,000 wt.
ppm, in the resultant binder solution: In this mode, it is particularly preferred to use an organic acid which results in almost no harm even if it remains thereafter. Such an organic acid even exhibits a tendency of improving the electrode performances through stabilization of the vinylidene fluoride polymer by remaining thereof in the electrode.
An electrode-forming composition may be obtained by adding and dispersing a powdery electrode material (an active substance and optional additives, such as an electroconductivity-imparting additive) into the thus-obtained vinylidene fluoride polymer binder solution according to the present invention.
In the case of forming a positive electrode, ~1939~
the active substance may comprise a composite metal chalcogenide represented by a general formula of LiMY2, wherein M denotes at least one species of transition metals such as Co, Ni, Fe, Mn, Cr and V;
and Y denotes a chalcogen, such as O or S. Among these, it is preferred to use a lithium-based composite metal oxide represented by a general formula of LiM02, wherein M is the same as above. Preferred examples thereof may include: LiCo02,'LiNi02, LiNixCol-x02, and spinel-structured LiMn2O4. Among these, it is particularly preferred to use a Li-Co or Li-Ni binary composite metal oxide or Li-Ni-Co ternary composite metal oxide inclusively represented by a formula of LiNigCol-x02 (0 S x s 1) in view of a high charge-discharge potential and excellent cycle characteristic.
In the case of forming a negative electrode, the active substance may preferably comprise a carbonaceous material, such as graphite, activated carbon or a carbonaceous material obtained by carbonization of phenolic resin, pitch, etc.
An electroconductivity-imparting additive may be added in order to improve the conductivity of a resultant composite electrode layer formed by applying and drying of the electrode-forming composition of the present invention, particularly in case of using an active substance, such as LiCo02, showing a small electron-conductivity in a positive electrode. Examples thereof may include: carbonaceous materials, such as carbon black, graphite fine powder and fiber, and fine powder and fiber of metals, such as nickel and aluminum. The effect of stabilizing the positive electrode-forming composition according to the present invention is particularly pronounced in the case of using electroconductive carbon black (preferably one having an average particle size (diameter) of ca. 10 - 100 nm as measured by observation through an electron microscope) which has a large electroconductivity-improving effect but also is liable to exhibit a remarkable effect of promoting gelation of vinylidene fluoride polymer, singly or in combination with another electroconductivity-imparting w additive. Such an electroconductivity-imparting additive may preferably be used in an amount of 0.1 -l0 wt. parts per 100 wt. parts of a composite metal oxide constituting the positive electrode. In the case of using a carbonaceous material exhibiting a large electroconductivity, such an electro-conductivity-imparting additive need not be added.
In formulating the electrode-forming composition according to the present invention, it is preferred to blend 0.1 - 50 wt. parts, particularly I
- 20 wt. parts of vinylidene fluoride polymer with 100 wt. parts of a powdery electrode material.
z1 ~3~~5 The incorporation of an organic acid for stabilizing vinylidene fluoride polymer in the positive electrode-forming composition may be performed in any arbitrary manner. For example, it is possible to blend the acid simultaneously with blending of a positive electrode active substance, carbon black, a vinylidene fluoride polymer and an organic solvent. It is however preferred to form a vinylidene fluoride polymer solution containing an organic acid added thereto (more preferably by dissolving a vinylidene fluoride polymer in an organic solvent already containing an organic acid) and then blending the vinylidene fluoride polymer solution with a powdery electrode material, such as a positive 25 electrode active substance.
The thus-prepared positive or negative electrode-forming slurry composition may be used for forming an electrode structure having a partial sectional structure as shown in Figure 1. More specifically, referring to Figure I, the slurry composition may be applied onto at least one surface, preferably both surfaces, of an electroconductive substrate 11 comprising a foil or wire net of a metal, such as iron, stainless steel, steel, copper, aluminum, nickel or titanium and having a thickness of, e.g., 5 - 100 um, or 5 - 20 um for a small-sized battery, and dried at, e.g., 50 - 170 °C, to form a -1$_ 1, g ~ 9 3 5 composite electrode layer (12a, 12b) of, e.g., 10 -1000 pn, preferably 10 - 200 ~.un, in thickness for a small-sized battery, thereby providing an electrode structure 10 for a non-aqueous-type battery.
Figure 2 is a partially exploded perspective view of a lithium secondary battery as an embodiment of a non-aqueous-type battery according to the present invention, including an electrode structure prepared in the above-described manner. -More specifically, the secondary battery basically includes a laminate structure including a positive electrode 1, a negative electrode 2 and a separator 3 disposed between the positive and negative electrodes land 2 and comprising a fine porous film of a polymeric material, such as polyethylene or polypropylene, impregnated with an electrolytic solution. The laminate structure is wound in a vortex shape to form an electricity-generating element which is housed within a metal casing 5 having a bottom constituting a negative electrode terminal 5a. In the secondary battery, the negative electrode 2 is electrically connected to the negative electrode terminal 5a, and the uppermost portion of the battery is constituted by disposing a gasket 6 and a safety valve 7 covered with a top plate 8 having a projection constituting a positive electrode terminal 8a electrically connected to the positive electrode.
2 ~ 93935 Further, the uppermost rim 5b of the casing 5 is crimped toward the inner side to form an entirely sealed cell structure enclosing the electricity-generating element. The positive electrode l and the negative electrode 2 may have a structure of the electrode structure 10 shown in Figure 1.
The non-aqueous electrolyte solution impregnating the separator 3 may comprise a solution of an electrolyte, such as a lithium salt, in a non-aqueous solvent (organic solvent).
Examples of the electrolyte may include:
LiPF6, LiAsF6, LiCl04, LiBF4, CH3S03Li, CF3S03Li, LfN(S02CF3)2, LiC(S02CF3)3, LiCl, and Liar. Examples of the organic solvent for such an electrolyte may include: propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, -butyrolactone, methyl propionate, ethyl propionate, and mixtures of these, but they are not exhaustive.
In the above, a cylindrical battery has been described as an embodiment of the non-aqueous-type battery according to the present invention. However, the non-aqueous-type battery according to the present invention can basically have any other shapes, such as those of a coin, a rectangular_parallelepiped, or a paper or sheet.
[Egamples~
Hereinbelow, the present invention will be described more specifically based Examples and Comparative Examples.
(Preparation of vinylidene fluoride polymer) A carboxyl group-containing vinylidene fluoride polymer was prepared in the following manner.
Into a 2 liter-autoclave, 1040 g of deionized water, 0.8 g of methyl cellulose, 2.5 g of ethyl acetate, 4 g of diisopropyl perosydicarbonate, 396 g of vinylidene fluoride and 4 g of monomethyl maleate {i.e., vinylidene fluoride/monomethyl maleate =
100/1.01 (by weight)) were added and subjected to suspension polymerization at 28 oC for 47 hours.
After completion of the polymerization, the ~ polymerization slurry was de-watered, washed with water and dried at 80 °C for 20 hours to obtain a powdery polymer.
The polymerization yield was 90 wt. ~, and the resultant polymer showed an inherent viscosity of 1.1, and a carbonyl group content of 1.2$10-4 mol/g.
(Organic solvent}
20 lots of commercially available N-methyl-2-pyrrolidone (hereinafter abbreviated as "NMP") were stored at room temperature for ca. 3 months and then used for the following tests. The NMP in 20 lots provided 10-times dilutions with de-ionized water showing pH ranging from 6.5 to 11Ø
Comparative Example 1 Into a :Lot of NMP having provided a 10-times dilution with de-ionized water showing a pH of 9.5, the above-prepared carboxyl group-containing vinylidene fluoride polymer was dissolved at 50 oC so as to provide a concentration of 13 wt. % to obtain a binder solution.
Example 1 1000 ppm of malefic acid was added to the same lot of NMP as used in Comparative Example 1, and the solution was also diluted with ten times of deionized water, whereby the dilution showed a pH of 3.2. Then, into the NMP containing malefic acid, the above-mentioned vinylidene fluoride polymer'was dissolved similarly as in Comparative Example l to prepare a binder solution at a concentration of l3 wt. ~.
(Viscosity and Fluorine ion concentration measurement) The binder solutions prepared in Comparative Example 1 and Example 1 were subjected to measurement of viscosity by using a rotating viscometer (according to JIS K7117) and measurement of fluorine ion (F-) concentration.
(Film formation and Swelling test) Each of the binder solutions: prepared in Comparative Example 1 and Example 1 was cast onto a glass plate and dried at 130 oC for 2 hours, followed by peeling, to form a ca. 200 p.m-thick film.
-22- 21 9 3 9 3 5 .
Then, each film thus obtained was dipped at 70 °C for 72 hours in an electrolytic solution formed by dissolving 8.8 wt. parts of LiCl04 into a liquid mixture of 53.6 wt. parts of propylene carbonate and 37.6 v,rt. parts of dimethoxyethane. In the meantime, each film was taken out at 24 hours each to evaluate the degree of swelling in terms of a cast film weight increase percentage (increased weight/weight of the film before dipping x 100).
The results of the above measurement are summarized in the following Table 1:
Table 1 Comparative Example 1 Example I
Binder solution Amount of maleic acid added 0 1000 ppm 10-times dilution pH 9.5 3.2 Viscosity (mPa.s) 1010 870 Fluorine (F-) concentration 200-500 ppm <100 ppm Degree of film swelling (wt.~) 24 hours 28'~ 20 48 hours 29 21 72 hours 29 22 The results in the above Table 1 show that, compared with the vinylidene fluoride polymer binder solution of Comparative Example 1 using NMP as it was, the vinylidene fluoride polymer binder solution of Example 1 obtained by adding 1000 ppm of malefic acid was stabler in view of low viscosity increase and low fluorine ion concentration and showed a remarkably improved swelling resistance against an electrolytic solution for non-aqueous-type battery.
Comparative Example 2 Into a lot of NMP showing a 10-times dilution pH of 10.9, the above-mentioned carboxyl group-containing vinylidene fluoride polymer was dissolved to form a binder solution at a concentration of l3 wt. o.
Example 2 1000 ppm of malonic acid was added to the same lot of NMP as used in Comparative Example 2, and then the carboxyl group-containing vinylidene fluoride polymer was dissolved to form a binder solution at a concentration of 13 wt. ~.
The binder solutions of the above Comparative Example 2 and Example 2 were respectively used for formation of a cast film similarly as in Example 1, and the resultant films were subjected to dipping in the electrolytic solution at 70 °C for 72 hours similarly as in Example 1. As a result, the films exhibited swelling degrees after 72 hours as shown below.
Table 2 Comparative Example 2 Example 2 Amount of malonic acid 0 1000 ppm Swelling degree after 72 hrs. 25 wt.~ 18 wt.~
Comparative Example 3 Into a lot of NMP showing a 10-times dilution of pH of 9.5, vinylidene fluoride homopolymer ("KF Polymer #1100", available from Kureha Kagaku Kogyo K.K.) was dissolved at 50 °C to form a binder solution at a concentration of 13 wt. $.
Example 3 1000 ppm of maleic acid was added to the same lot of NMP as used in Comparative Example 3, and then the vinylidene fluoride homopolymer used in Comparative Example 3 was dissolved therein to form a binder solution at a concentration of 13 wt. ~.
The thus-formed binder solutions were subjected to measurement of viscosity and degree of film swelling similarly as in Example 1. The results are shown in Table 3 below.
*Trade-mark Table 3 Comparative Example 1 Example l Binder solution Amount of malefic acid added 0 1000 ppm 10-times dilution pH 9.5 3.2 Viscosity (mPa.s) 9$0 717 Degree of f i lm swel l inc_r ( wt . ~ ) 72 hours 20 15 Also in this case, the addition of malefic acid provided a binder solution showing a good viscosity increase-preventing effect and an improved film swelling resistance.
Example 4 and Comparative Example 4 The films prepared in the above Example 1 and Comparative Egampie I were respectively dipped in an electrolytic solution comprising 11.6 wt. ~ of LiPF6, 510 wt. ~ of ethylene carbonate and 37.4 wt. ~ of diethyl carbonate at 70 °C for 72 hours. After the dipping, the films showed swelling degrees (weight increases due to swelling) of 1$ wt. g and 24 wt. ~, respectively.
Example 5 9 wt. parts of LiNiO.$Co0.202 (active substance, Dav. (average particle diameter) - 15 pn), 2 i 93935 0.7 wt. part of electroconductive carbon black (Dav.
ca. 40 nm, specific surface area = 30 m2/g, oii absorption = 129 ml/g), 0.3 wt. part of vinylidene fluoride homopolymer ("KF Polymer #1300", available from Kureha Kagaku Kogyo K.K.), and 6 wt. parts of NMP
containing 0.1 wt. ~ of malefic acid were blended with each other and uniformly dispersed at 50 °C to prepare a positive electrode-forming slurry composition. The slurry showed substantially identical viscosities before and after storage for 24 hours at room temperature. The slurry was applied onto one surface of a 10 pm-thick copper foil and dried at 130 °C to form a totally 100 dun-thick electrode structure having a smooth positive electrode layer.
Example 6 9 wt. parts of LiNi0.9Co0.102 (Dav. - 15 ~.un), 0'.7 wt. part of electroconductive carbon black, 0.3 wt. part of vinylidene fluoride homopolymer ("KF
Polymer ##1300") and 6 wt. parts of NMP containing 0.1 wt. ~ of citraconic acid were blended with each other and uniformly dispersed at 50 °C to prepare a positive electrode-forming slurry composition. The slurry showed substantially identical viscosities before and after storage for 24 hours at room temperature. The slurry was applied onto one surface of a ZO pm-thick copper foil and dried at 130 ~C to farm a totally 105 ~.un-thick electrode structure having a smooth positive electrode layer.
Example 7 A positive electrode-forming slurry composition was prepared in the same manner as in Example 5 except for using 6 wt. parts of NMP
containing 0.1 wt. ~ of malonic acid instead of the 0.1 wt. ~ of malefic acid. The slurry; showed substantially identical viscosities before and after storage for 24 hours at room temperature. The slurry was applied onto one surface of a 10 um-thick copper foil and dried at 130 oC to form a totally 102 pm-thick electrode structure having a smooth positive electrode layer.
Example 8 ' A positive electrode-forming slurry composition was prepared in the same manner as in Example 5 except for using 6 wt. parts of NMP
containing 0.1 wt. ~ of acetic acid instead of the 0.1 wt. ~ of malefic acid. The slurry showed substantially identical viscosities before and after storage for 24 hours at room temperature. The slurry was applied onto one surface of a l0 um-thick copper foil and dried at 130 oC to form a totally 106 Wn-thick electrode structure having a smooth positive electrode layer.
Comparative Example 5 A positive electrode-forming slurry ,,,~"', composition was prepared in the same manner as in Example 5 except for using 6 wt. parts of NMP
containing no malefic acid.
After the preparation, the slurry caused severe gelling when it was stored for 2 - 3 hours at room temperature, thus making it difficult to apply the slurry onto a copper foil. After 24 hours of storage at room temperature, the slurry became a rather hard pudding state and could not be used.
As described above, according to the present __ invention, an acid, preferably an organic acid, is added during formation of a binder solution for a non-aqueous-type battery electrode by dissolving a vinylidene fluoride polymer in an organic solvent, 25 whereby it is possible to effectively obviate a viscosity increase of the binder solution, a lowering of binder effect in the resultant electrode due to swelling of the binder with an electrolyte solution, and gelling of an electrode-forming slurry, particularly a positive electrode-forming slurry, which are problematic but have been frequently caused heretofore in non-aqueous-type battery electrode formation.
Claims (21)
1. A vinylidene fluoride polymer binder solution for preparing an electrode-forming composition, the binder solution consisting essentially of:
an organic solvent, a vinylidene fluoride polymer in an amount of 0.1-20 wt. parts per 100 wt. parts of the organic solvent, and an organic acid in a stabilizing amount such that the solution, when diluted 10 times with deionized water, exhibits a pH of 3-9, wherein the vinylidene fluoride polymer has an inherent viscosity of at least 0.5, as measured at 30°C at a concentration of 4 g/liter in N,N-dimethylformamide, and is at least one member selected from the group consisting of (A) a copolymer of at least 95 mol% of vinylidene fluoride with another copolymerizable monomer; (B) a modified product of a vinylidene fluoride homopolymer or the copolymer (A) modified by reaction with a silane or titanate coupling agent having both (1) a group reactive with the vinylidene fluoride homopolymer or copolymer and (2) a hydrolyzable group; and (C) a carboxy group-containing vinylidene fluoride homopolymer or copolymer, and wherein the organic acid is one that is decomposes or evaporated during steps of applying and drying the electrode-forming composition for forming an electrode and is absent in the electrode formed from the electrode-forming composition.
an organic solvent, a vinylidene fluoride polymer in an amount of 0.1-20 wt. parts per 100 wt. parts of the organic solvent, and an organic acid in a stabilizing amount such that the solution, when diluted 10 times with deionized water, exhibits a pH of 3-9, wherein the vinylidene fluoride polymer has an inherent viscosity of at least 0.5, as measured at 30°C at a concentration of 4 g/liter in N,N-dimethylformamide, and is at least one member selected from the group consisting of (A) a copolymer of at least 95 mol% of vinylidene fluoride with another copolymerizable monomer; (B) a modified product of a vinylidene fluoride homopolymer or the copolymer (A) modified by reaction with a silane or titanate coupling agent having both (1) a group reactive with the vinylidene fluoride homopolymer or copolymer and (2) a hydrolyzable group; and (C) a carboxy group-containing vinylidene fluoride homopolymer or copolymer, and wherein the organic acid is one that is decomposes or evaporated during steps of applying and drying the electrode-forming composition for forming an electrode and is absent in the electrode formed from the electrode-forming composition.
2. The binder solution according to claim 1, wherein the organic acid is contained at a concentration of at least 100 wt. ppm.
3. The binder solution according to claim 1 or 2, wherein the organic acid is selected from the group consisting of acrylic acid, formic acid, citric acid, acetic acid, oxalic acid, lactic acid, pyruvic acid, malonic acid, succinic acid, propionic acid, maleic acid, maleic anhydride, citraconic acid, lactic acid and mixtures thereof.
4. The binder solution according to claim 1 or 2, wherein the organic acid is maleic acid, malonic acid or citraconic acid.
5. The binder solution according to any one of claims 1 to 4, wherein the vinylidene fluoride polymer is (A) a copolymer of at least 95 mol% of vinylidene fluoride with another copolymerizable monomer selected from the group consisting of an unsaturated dibasic acid monoester, vinylidene carbonate and an epoxy group-containing vinyl monomer.
6. The binder solution according to any one of claims 1 to 4, wherein the vinylidene fluoride polymer is a modified product of a vinylidene fluoride homopolymer or a copolymer of at least 95 mol% of vinylidene fluoride with another monomer selected from the group consisting of an unsaturated dibasic acid monoester, vinylidene carbonate and an epoxy group-containing vinyl monomer, modified by reaction with a silane or titanate coupling agent having both (1) a group reactive with the vinylidene-fluoride homopolymer or copolymer selected from the group consisting of an amino group and a mercapto group and (2) a hydrolyzable group.
7. The binder solution according to any one of claims 1 to 6, wherein the organic solvent is a nitrogen-containing polar organic solvent.
8. The binder solution according to claim 7, wherein the nitrogen-containing polar organic solvent is N-methyl-2-pyrrolidone.
9. The binder solution according to any one of claims 1 to 8, wherein the organic acid is contained at a concentration of 300-10,000 wt. ppm.
10. A binder solution for dispersing a powder electrode material containing an electrode active substance for forming an electrode of a non-aqueous-type battery, which solution comprises:
(i) a vinylidene fluoride polymer;
(ii) a polar organic solvent selected from the group consisting of N-methyl-2-pyrrolidone, dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, trimethyl phosphate and mixtures thereof; and (iii) an organic acid in such an amount that a solution obtained by diluting 10 times the binder solution with deionized water has a pH value of at most 9, wherein the vinylidene fluoride polymer (i) has an inherent viscosity of at least 0.5, as measured at 30°C at a concentration of 4 g/liter in N,N-dimethylformamide and is contained in an amount of 1 to 20 wt. parts per 100 wt.
parts of the solvent;
wherein the vinylidene fluoride polymer is at least one member selected from the group consisting of (A) a copolymer of at least 95 mol% of vinylidene fluoride with an unsaturated dibasic acid monoester, vinylidene carbonate or an epoxy group-containing vinyl monomer and (B) a modified product of a vinylidene fluoride homopolymer or the vinylidene fluoride copolymer with a silane coupling agent or titanate coupling agent having both (1) a group reactive with the vinylidene fluoride homo- or co-polymer and (2) a hydrolyzable group, the modified product retaining at least 95 mol% of untreated vinylidene fluoride units; and wherein the organic acid is one that is decomposed or evaporated during steps of applying and drying the electrode-forming composition for forming an. electrode and is absent in the electrode formed from the electrode-forming composition.
(i) a vinylidene fluoride polymer;
(ii) a polar organic solvent selected from the group consisting of N-methyl-2-pyrrolidone, dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, trimethyl phosphate and mixtures thereof; and (iii) an organic acid in such an amount that a solution obtained by diluting 10 times the binder solution with deionized water has a pH value of at most 9, wherein the vinylidene fluoride polymer (i) has an inherent viscosity of at least 0.5, as measured at 30°C at a concentration of 4 g/liter in N,N-dimethylformamide and is contained in an amount of 1 to 20 wt. parts per 100 wt.
parts of the solvent;
wherein the vinylidene fluoride polymer is at least one member selected from the group consisting of (A) a copolymer of at least 95 mol% of vinylidene fluoride with an unsaturated dibasic acid monoester, vinylidene carbonate or an epoxy group-containing vinyl monomer and (B) a modified product of a vinylidene fluoride homopolymer or the vinylidene fluoride copolymer with a silane coupling agent or titanate coupling agent having both (1) a group reactive with the vinylidene fluoride homo- or co-polymer and (2) a hydrolyzable group, the modified product retaining at least 95 mol% of untreated vinylidene fluoride units; and wherein the organic acid is one that is decomposed or evaporated during steps of applying and drying the electrode-forming composition for forming an. electrode and is absent in the electrode formed from the electrode-forming composition.
11. The binder solution according to claim 10, wherein the organic acid is selected from the group consisting of acrylic acid, formic acid, citric acid, acetic acid, oxalic acid, lactic acid, pyruvic acid, malonic acid, succinic acid, propionic acid, maleic acid, maleic anhydride, citraconic acid, lactic acid and mixtures thereof.
12. The binder solution according to claim 10 or 11, wherein the solvent is at least one nitrogen containing solvent selected from the group consisting of N-methyl-2-pyrrolidone, dimethylformamide, N,N-dimethylacetamide, hexamethylphosphamide and tetramethylurea.
13. A dispersion for forming an electrode of a non-aqueous-type battery, which comprises:
(a) the binder solution as defined in any one of claims 10 to 12, and (b) a powdery electrode material dispersed in the binder solution (a), wherein the electrode is a positive electrode and the powdery electrode material comprises a composite metal chalcogenide of the formula: LiMY2 (wherein M is at least one transition metal and Y is O
or S).
(a) the binder solution as defined in any one of claims 10 to 12, and (b) a powdery electrode material dispersed in the binder solution (a), wherein the electrode is a positive electrode and the powdery electrode material comprises a composite metal chalcogenide of the formula: LiMY2 (wherein M is at least one transition metal and Y is O
or S).
14. ~A vinylidene fluoride polymer binder solution, comprising a solution of a vinylidene fluoride polymer in an organic solvent, and an acid added to the solution as a stabilizer, which binder solution has been prepared by first adding the acid to the organic solvent and then dissolving the vinylidene fluoride polymer in the organic solvent, wherein the vinylidene fluoride polymer has an inherent viscosity of at least 0.5, as measured at 30°C at a concentration of 4 g/liter in N,N-dimethylformamide.
15. ~An electrode-forming composition, comprising a powdery electrode material dispersed in a vinylidene fluoride polymer binder solution, wherein the vinylidene fluoride polymer binder solution is:
the solution according to any one of claims 1 to 12 or claim 14, or a vinylidene fluoride polymer binder solution consisting essentially of:
an organic solvent, a vinylidene fluoride polymer in an amount of 0.1-20 wt. parts per 100 wt. parts of the organic solvent, and an acid in a stabilizing amount such that the solution, when diluted 10 times with deionized water, exhibits a pH of 3-9, wherein the vinylidene fluoride polymer has an inherent viscosity of at least 0.5, as measured at 30°C at a concentration of 4 g/liter in N,N-dimethylformamide; and is at least one member selected from the group consisting of (A) a copolymer of at least 95 mol% of vinylidene fluoride with another copolymerizable monomer; (B) a modified product of a vinylidene fluoride homopolymer or the copolymer (A) modified by reaction with a silane or titanate coupling agent having both (1) a group reactive with the vinylidene fluoride homopolymer or copolymer and (2) a hydrolyzable group; and (C) a carboxy group-containing vinylidene fluoride homopolymer or copolymer.
the solution according to any one of claims 1 to 12 or claim 14, or a vinylidene fluoride polymer binder solution consisting essentially of:
an organic solvent, a vinylidene fluoride polymer in an amount of 0.1-20 wt. parts per 100 wt. parts of the organic solvent, and an acid in a stabilizing amount such that the solution, when diluted 10 times with deionized water, exhibits a pH of 3-9, wherein the vinylidene fluoride polymer has an inherent viscosity of at least 0.5, as measured at 30°C at a concentration of 4 g/liter in N,N-dimethylformamide; and is at least one member selected from the group consisting of (A) a copolymer of at least 95 mol% of vinylidene fluoride with another copolymerizable monomer; (B) a modified product of a vinylidene fluoride homopolymer or the copolymer (A) modified by reaction with a silane or titanate coupling agent having both (1) a group reactive with the vinylidene fluoride homopolymer or copolymer and (2) a hydrolyzable group; and (C) a carboxy group-containing vinylidene fluoride homopolymer or copolymer.
16. ~An electrode structure, comprising:
an electroconductive substrate, and a composite electrode layer disposed on at least one surface of the substrate, the composite electrode layer comprising a powdery electrode material and a vinylidene fluoride polymer and being formed by applying onto the electroconductive substrate and drying the electrode-forming composition according to claim 15.
an electroconductive substrate, and a composite electrode layer disposed on at least one surface of the substrate, the composite electrode layer comprising a powdery electrode material and a vinylidene fluoride polymer and being formed by applying onto the electroconductive substrate and drying the electrode-forming composition according to claim 15.
17. ~The binder solution as defined in claim 10, 11 or 12, wherein the acid is maleic acid, malonic acid or citraconic acid.
18. ~The binder solution according to any one of claims 1 to 6, wherein the organic solvent is a polar solvent selected from the group consisting of N-methyl-2-pyrrolidone, dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, trimethyl phosphate and mixtures thereof.
19. ~The binder solution according to claim 18, wherein the organic acid is contained at a concentration of 300 to 10,000 wt. ppm.
20. ~A process for producing an electrode structure to be used as a positive or negative electrode in a non-aqueous lithium ion battery which comprises (i) the negative electrode comprising a carbonaceous material capable of being doped with lithium ions, (ii) the positive electrode comprising a lithium composite metal oxide and (iii) a non-aqueous electrolytic solution comprising a lithium salt between the negative electrode (i) and the positive electrode (ii), which process comprises:
(A) providing a vinylidene fluoride polymer binder solution consisting essentially of:
a polar organic solvent selected from the group consisting of N-methyl-2-pyrrolidone, dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, trimethyl phosphate and a mixture thereof, a vinylidene fluoride polymer in an amount of 0.1-20 wt. parts per 100 wt. parts of the organic solvent, and an organic acid in a stabilizing amount such that the solution, when diluted 10 times with deionized water, exhibits a pH of 3-9, wherein the vinylidene fluoride polymer has an inherent viscosity of at least 0.5, as measured at 30°C at a concentration of 4 g/liter in N,N-dimethylformamide, and is at least one member selected from the group consisting of (A) a copolymer of at least 95 mol% of vinylidene fluoride with another copolymerizable monomer; (B) a modified product of a vinylidene fluoride homopolymer or the copolymer (A) modified by reaction with a silane or titanate coupling agent having both (1) a group reactive with the vinylidene fluoride homopolymer or copolymer and (2) a hydrolyzable group; and (C) a carboxy group-containing vinylidene fluoride homopolymer or copolymer;
(B) dispersing a powdery electrode material into the vinylidene fluoride polymer binder solution, to form an electrode-forming slurry composition, wherein the powdery electrode material comprises the lithium composite metal oxide of the formula LiMY2 (in which M is at least one transition metal selected from Co, Ni, Fe, Mn, Cr and V and Y is a chalcogen) when the positive electrode is to be formed and the powdery electrode material comprises the carbonaceous material capable of being doped with lithium ions when the negative electrode is to be formed, and wherein the vinylidene fluoride polymer binder solution is used in such an amount that 1 to 20 wt. parts of the vinylidene fluoride polymer is present per 100 wt. parts of the powdery electrode material in the resulting electrode-forming slurry composition; and (C) applying the electrode-forming slurry onto at least one surface of an electroconductive substrate that is a foil or wire net of a metal, and then drying the applied slurry at 50-170°C, thereby producing the electrode structure.
(A) providing a vinylidene fluoride polymer binder solution consisting essentially of:
a polar organic solvent selected from the group consisting of N-methyl-2-pyrrolidone, dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate, trimethyl phosphate and a mixture thereof, a vinylidene fluoride polymer in an amount of 0.1-20 wt. parts per 100 wt. parts of the organic solvent, and an organic acid in a stabilizing amount such that the solution, when diluted 10 times with deionized water, exhibits a pH of 3-9, wherein the vinylidene fluoride polymer has an inherent viscosity of at least 0.5, as measured at 30°C at a concentration of 4 g/liter in N,N-dimethylformamide, and is at least one member selected from the group consisting of (A) a copolymer of at least 95 mol% of vinylidene fluoride with another copolymerizable monomer; (B) a modified product of a vinylidene fluoride homopolymer or the copolymer (A) modified by reaction with a silane or titanate coupling agent having both (1) a group reactive with the vinylidene fluoride homopolymer or copolymer and (2) a hydrolyzable group; and (C) a carboxy group-containing vinylidene fluoride homopolymer or copolymer;
(B) dispersing a powdery electrode material into the vinylidene fluoride polymer binder solution, to form an electrode-forming slurry composition, wherein the powdery electrode material comprises the lithium composite metal oxide of the formula LiMY2 (in which M is at least one transition metal selected from Co, Ni, Fe, Mn, Cr and V and Y is a chalcogen) when the positive electrode is to be formed and the powdery electrode material comprises the carbonaceous material capable of being doped with lithium ions when the negative electrode is to be formed, and wherein the vinylidene fluoride polymer binder solution is used in such an amount that 1 to 20 wt. parts of the vinylidene fluoride polymer is present per 100 wt. parts of the powdery electrode material in the resulting electrode-forming slurry composition; and (C) applying the electrode-forming slurry onto at least one surface of an electroconductive substrate that is a foil or wire net of a metal, and then drying the applied slurry at 50-170°C, thereby producing the electrode structure.
21. ~The process according to claim 20, wherein the organic acid is one that is decomposed or evaporated during applying and drying steps for forming the electrode (C) and is selected from the group consisting of acrylic acid, formic acid, citric acid, acetic acid, oxalic acid, lactic acid, pyruvic acid, malonic acid, succinic acid, propionic acid, maleic acid, maleic anhydride, citraconic acid, lactic acid and mixtures thereof.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35078295A JP3540080B2 (en) | 1995-12-26 | 1995-12-26 | Battery binder solution and electrode mixture |
| JP350782/1995 | 1995-12-26 | ||
| JP146473/1996 | 1996-05-17 | ||
| JP14647396A JP3540097B2 (en) | 1996-05-17 | 1996-05-17 | Electrode mixture for non-aqueous battery and non-aqueous battery |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2193935A1 CA2193935A1 (en) | 1997-06-27 |
| CA2193935C true CA2193935C (en) | 2007-02-20 |
Family
ID=26477306
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002193935A Expired - Fee Related CA2193935C (en) | 1995-12-26 | 1996-12-24 | Binder solution and electrode-forming composition for non-aqueous-type battery |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US6200703B1 (en) |
| EP (1) | EP0782208B1 (en) |
| KR (1) | KR100263735B1 (en) |
| CA (1) | CA2193935C (en) |
| DE (1) | DE69635888T8 (en) |
Families Citing this family (24)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2309703B (en) * | 1996-01-31 | 1999-06-16 | Aea Technology Plc | Polymer electrolyte |
| FR2802021A1 (en) * | 1999-12-07 | 2001-06-08 | Atofina | PROMOTER OF ADHESION AND COHESION IN A CATHODE OF LITHIUM-ION BATTERY |
| US6432586B1 (en) | 2000-04-10 | 2002-08-13 | Celgard Inc. | Separator for a high energy rechargeable lithium battery |
| KR101170172B1 (en) | 2004-07-15 | 2012-07-31 | 파나소닉 주식회사 | Process of preparing coatings for positive electrode materials for lithium secondary batteries and positive electrodes for lithium secondary batteries |
| JP4626568B2 (en) * | 2005-07-29 | 2011-02-09 | ソニー株式会社 | Lithium ion secondary battery |
| CN101855752B (en) * | 2007-11-14 | 2014-07-23 | 株式会社吴羽 | Positive electrode mixture for nonaqueous battery and positive electrode structure |
| US8642210B2 (en) * | 2008-09-26 | 2014-02-04 | Mitsuyasu Sakuma | Negative electrode mixture for nonaqueous electrolyte secondary batteries, negative electrode for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery |
| US20120015246A1 (en) | 2010-05-27 | 2012-01-19 | Arkema Inc. | Waterborne fluoropolymer composition |
| AU2010254037B2 (en) * | 2009-05-29 | 2014-05-01 | Arkema Inc. | Aqueous polyvinylidene fluoride composition |
| JP5836933B2 (en) * | 2011-08-25 | 2015-12-24 | 日立マクセル株式会社 | Method for producing positive electrode mixture-containing composition and method for producing non-aqueous secondary battery |
| JP4957932B1 (en) * | 2011-08-30 | 2012-06-20 | Ｊｓｒ株式会社 | Binder composition for power storage device electrode, slurry for power storage device electrode, power storage device electrode, and power storage device |
| KR101754611B1 (en) | 2012-11-05 | 2017-07-06 | 삼성에스디아이 주식회사 | Composition for positive electrode of rechargable lithium battery and rechargable lithium battery using the same |
| KR101711986B1 (en) | 2012-11-20 | 2017-03-03 | 삼성에스디아이 주식회사 | Positive active material composition for lithium secondary battery and lithium secondary battery |
| CN106104872B (en) * | 2014-03-31 | 2020-07-07 | 住友化学株式会社 | Electrode compound slurry for sodium secondary battery, positive electrode for sodium secondary battery, and sodium secondary battery |
| JP6745587B2 (en) | 2014-05-29 | 2020-08-26 | 株式会社半導体エネルギー研究所 | Electrode manufacturing method |
| CN113889658B (en) | 2014-06-03 | 2025-01-07 | 阿科玛股份有限公司 | Fabrication of Solvent-Free Electrodes |
| US10230093B2 (en) | 2015-09-25 | 2019-03-12 | Semiconductor Energy Laboratory Co., Ltd. | Method for manufacturing storage battery electrode |
| WO2017138192A1 (en) | 2016-02-08 | 2017-08-17 | 国立研究開発法人産業技術総合研究所 | Non-aqueous electrolyte secondary battery positive electrode slurry production method and non-aqueous electrolyte secondary battery positive electrode slurry |
| JP6951177B2 (en) | 2017-02-09 | 2021-10-20 | 日本スピンドル製造株式会社 | Slurry production equipment and slurry production method |
| CN106935865B (en) * | 2017-05-12 | 2023-04-18 | 中塑新材料技术(吉林)有限公司 | Battery cathode, preparation method thereof and zinc-nickel battery |
| KR102261504B1 (en) * | 2017-08-10 | 2021-06-07 | 주식회사 엘지에너지솔루션 | Pre-lithiation Method of Anode Electrodes for secondary battery |
| WO2019093313A1 (en) | 2017-11-08 | 2019-05-16 | 株式会社Ｇｓユアサ | Positive electrode, nonaqueous electrolyte electricity storage element, method for producing positive electrode, and method for producing nonaqueous electrolyte electricity storage element |
| US20230016014A1 (en) | 2019-12-23 | 2023-01-19 | Arkema Inc. | Coated electrode with polymeric binders for lithium ion battery |
| DE102022212170B4 (en) | 2022-11-16 | 2025-07-24 | Volkswagen Aktiengesellschaft | Process for producing a slurry for a cathode and a battery cell |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5923461A (en) | 1982-07-28 | 1984-02-06 | Shin Kobe Electric Mach Co Ltd | Manufacture of positive plate for lead storage battery |
| JPH0268855A (en) | 1988-09-03 | 1990-03-08 | Sony Corp | Manufacture of electrode for cell |
| DE3904544A1 (en) | 1989-02-15 | 1990-08-16 | Fraunhofer Ges Forschung | POLYMINE MEMBRANES BASED ON POLYVINYLIDENE FLUORIDE, METHOD FOR THE PRODUCTION AND USE THEREOF |
| JPH0693025A (en) | 1992-09-11 | 1994-04-05 | Kureha Chem Ind Co Ltd | Modified polyvinylidene fluoride-based resin composition and its production |
| JP3121943B2 (en) | 1992-12-02 | 2001-01-09 | 呉羽化学工業株式会社 | Vinylidene fluoride copolymer |
| JPH0773882A (en) * | 1993-08-31 | 1995-03-17 | Haibaru:Kk | Secondary battery |
-
1996
- 1996-12-23 US US08/779,955 patent/US6200703B1/en not_active Expired - Lifetime
- 1996-12-24 DE DE69635888T patent/DE69635888T8/en active Active
- 1996-12-24 EP EP96309481A patent/EP0782208B1/en not_active Expired - Lifetime
- 1996-12-24 CA CA002193935A patent/CA2193935C/en not_active Expired - Fee Related
- 1996-12-26 KR KR1019960072262A patent/KR100263735B1/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DE69635888T8 (en) | 2007-03-29 |
| DE69635888T2 (en) | 2006-12-07 |
| KR100263735B1 (en) | 2000-08-01 |
| CA2193935A1 (en) | 1997-06-27 |
| EP0782208A1 (en) | 1997-07-02 |
| EP0782208B1 (en) | 2006-03-08 |
| KR970054750A (en) | 1997-07-31 |
| DE69635888D1 (en) | 2006-05-04 |
| US6200703B1 (en) | 2001-03-13 |
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