JP5583998B2 - Polyolefin microporous membrane, non-aqueous secondary battery separator and non-aqueous secondary battery - Google Patents
Polyolefin microporous membrane, non-aqueous secondary battery separator and non-aqueous secondary battery Download PDFInfo
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- JP5583998B2 JP5583998B2 JP2010068116A JP2010068116A JP5583998B2 JP 5583998 B2 JP5583998 B2 JP 5583998B2 JP 2010068116 A JP2010068116 A JP 2010068116A JP 2010068116 A JP2010068116 A JP 2010068116A JP 5583998 B2 JP5583998 B2 JP 5583998B2
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- secondary battery
- separator
- aqueous secondary
- orientation
- microporous membrane
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- 229920000098 polyolefin Polymers 0.000 title claims description 103
- 239000012982 microporous membrane Substances 0.000 title claims description 64
- 239000011256 inorganic filler Substances 0.000 claims description 22
- 229910003475 inorganic filler Inorganic materials 0.000 claims description 22
- 229920006015 heat resistant resin Polymers 0.000 claims description 18
- 239000013078 crystal Substances 0.000 claims description 12
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 11
- 229910052744 lithium Inorganic materials 0.000 claims description 11
- 238000005259 measurement Methods 0.000 claims description 9
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical group [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 6
- 239000004760 aramid Substances 0.000 claims description 5
- 229920003235 aromatic polyamide Polymers 0.000 claims description 5
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 claims description 5
- 239000000347 magnesium hydroxide Substances 0.000 claims description 5
- 229910001862 magnesium hydroxide Inorganic materials 0.000 claims description 5
- 229920005989 resin Polymers 0.000 claims description 3
- 239000011347 resin Substances 0.000 claims description 3
- 239000004962 Polyamide-imide Substances 0.000 claims description 2
- 239000004642 Polyimide Substances 0.000 claims description 2
- 229920002678 cellulose Polymers 0.000 claims description 2
- 229920001643 poly(ether ketone) Polymers 0.000 claims description 2
- 229920002492 poly(sulfone) Polymers 0.000 claims description 2
- 229920002312 polyamide-imide Polymers 0.000 claims description 2
- 229920001601 polyetherimide Polymers 0.000 claims description 2
- 229920001721 polyimide Polymers 0.000 claims description 2
- 229920001470 polyketone Polymers 0.000 claims description 2
- 239000004697 Polyetherimide Substances 0.000 claims 1
- 239000001913 cellulose Substances 0.000 claims 1
- 238000000034 method Methods 0.000 description 56
- 239000002904 solvent Substances 0.000 description 28
- 239000007788 liquid Substances 0.000 description 27
- -1 polyethylene Polymers 0.000 description 27
- 230000008569 process Effects 0.000 description 23
- 229910052782 aluminium Inorganic materials 0.000 description 19
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 19
- 239000000203 mixture Substances 0.000 description 17
- 239000000243 solution Substances 0.000 description 17
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 15
- 239000012528 membrane Substances 0.000 description 15
- 239000004698 Polyethylene Substances 0.000 description 14
- 239000011888 foil Substances 0.000 description 14
- 229920000573 polyethylene Polymers 0.000 description 14
- 230000000694 effects Effects 0.000 description 13
- 239000002002 slurry Substances 0.000 description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 12
- 238000000576 coating method Methods 0.000 description 12
- LCZVSXRMYJUNFX-UHFFFAOYSA-N 2-[2-(2-hydroxypropoxy)propoxy]propan-1-ol Chemical compound CC(O)COC(C)COC(C)CO LCZVSXRMYJUNFX-UHFFFAOYSA-N 0.000 description 11
- 230000001112 coagulating effect Effects 0.000 description 11
- 238000001816 cooling Methods 0.000 description 11
- 239000011248 coating agent Substances 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 10
- NNBZCPXTIHJBJL-UHFFFAOYSA-N decalin Chemical compound C1CCCC2CCCCC21 NNBZCPXTIHJBJL-UHFFFAOYSA-N 0.000 description 10
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- 238000002844 melting Methods 0.000 description 9
- 230000008018 melting Effects 0.000 description 9
- 239000007774 positive electrode material Substances 0.000 description 9
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 8
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- 239000006255 coating slurry Substances 0.000 description 8
- 229910001416 lithium ion Inorganic materials 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 239000007773 negative electrode material Substances 0.000 description 8
- 239000000758 substrate Substances 0.000 description 8
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
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- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- CXWXQJXEFPUFDZ-UHFFFAOYSA-N tetralin Chemical compound C1=CC=C2CCCCC2=C1 CXWXQJXEFPUFDZ-UHFFFAOYSA-N 0.000 description 6
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 5
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 5
- 239000011230 binding agent Substances 0.000 description 5
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 5
- 229920000642 polymer Polymers 0.000 description 5
- PXXNTAGJWPJAGM-UHFFFAOYSA-N vertaline Natural products C1C2C=3C=C(OC)C(OC)=CC=3OC(C=C3)=CC=C3CCC(=O)OC1CC1N2CCCC1 PXXNTAGJWPJAGM-UHFFFAOYSA-N 0.000 description 5
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 4
- 229910013063 LiBF 4 Inorganic materials 0.000 description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
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- 229910000000 metal hydroxide Inorganic materials 0.000 description 4
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- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 4
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- 238000004804 winding Methods 0.000 description 4
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 3
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 239000004699 Ultra-high molecular weight polyethylene Substances 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
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- 239000004745 nonwoven fabric Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
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- 239000002994 raw material Substances 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
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- 229920000785 ultra high molecular weight polyethylene Polymers 0.000 description 3
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 2
- 229910010205 LiAl0.25 Ni0.75 O2 Inorganic materials 0.000 description 2
- 229910013595 LiCo0.5Ni0.5O2 Inorganic materials 0.000 description 2
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 2
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 239000003125 aqueous solvent Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- XFWJKVMFIVXPKK-UHFFFAOYSA-N calcium;oxido(oxo)alumane Chemical compound [Ca+2].[O-][Al]=O.[O-][Al]=O XFWJKVMFIVXPKK-UHFFFAOYSA-N 0.000 description 2
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 2
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- 150000002170 ethers Chemical class 0.000 description 2
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 2
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- 229930195733 hydrocarbon Natural products 0.000 description 2
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- 229910003002 lithium salt Inorganic materials 0.000 description 2
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- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 239000012046 mixed solvent Substances 0.000 description 2
- 229920000620 organic polymer Polymers 0.000 description 2
- 239000002798 polar solvent Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
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- 239000000377 silicon dioxide Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- 229910000314 transition metal oxide Inorganic materials 0.000 description 2
- BIKXLKXABVUSMH-UHFFFAOYSA-N trizinc;diborate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]B([O-])[O-].[O-]B([O-])[O-] BIKXLKXABVUSMH-UHFFFAOYSA-N 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 description 1
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 description 1
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 1
- 238000012935 Averaging Methods 0.000 description 1
- XKGKLYUXFRFGKU-UHFFFAOYSA-N CC.F.F.F Chemical compound CC.F.F.F XKGKLYUXFRFGKU-UHFFFAOYSA-N 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 1
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 1
- 229910013684 LiClO 4 Inorganic materials 0.000 description 1
- 229910013733 LiCo Inorganic materials 0.000 description 1
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 1
- 229910016087 LiMn0.5Ni0.5O2 Inorganic materials 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
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- 239000006087 Silane Coupling Agent Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910006913 SnSb Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
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- 150000001298 alcohols Chemical class 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
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- VCNTUJWBXWAWEJ-UHFFFAOYSA-J aluminum;sodium;dicarbonate Chemical compound [Na+].[Al+3].[O-]C([O-])=O.[O-]C([O-])=O VCNTUJWBXWAWEJ-UHFFFAOYSA-J 0.000 description 1
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- 239000001506 calcium phosphate Substances 0.000 description 1
- 229910000389 calcium phosphate Inorganic materials 0.000 description 1
- 235000011010 calcium phosphates Nutrition 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000001768 carboxy methyl cellulose Substances 0.000 description 1
- 235000010948 carboxy methyl cellulose Nutrition 0.000 description 1
- 239000008112 carboxymethyl-cellulose Substances 0.000 description 1
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- 229910001647 dawsonite Inorganic materials 0.000 description 1
- 238000004807 desolvation Methods 0.000 description 1
- 125000004177 diethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- JVSWJIKNEAIKJW-UHFFFAOYSA-N dimethyl-hexane Natural products CCCCCC(C)C JVSWJIKNEAIKJW-UHFFFAOYSA-N 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
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- 239000004744 fabric Substances 0.000 description 1
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- 239000010419 fine particle Substances 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 235000011187 glycerol Nutrition 0.000 description 1
- ZEMPKEQAKRGZGQ-XOQCFJPHSA-N glycerol triricinoleate Natural products CCCCCC[C@@H](O)CC=CCCCCCCCC(=O)OC[C@@H](COC(=O)CCCCCCCC=CC[C@@H](O)CCCCCC)OC(=O)CCCCCCCC=CC[C@H](O)CCCCCC ZEMPKEQAKRGZGQ-XOQCFJPHSA-N 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910021385 hard carbon Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
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- 229910000625 lithium cobalt oxide 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
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Description
本発明は、ポリオレフィン微多孔膜に関わるものであり、特に非水系二次電池の安全性および電池特性を向上させる技術に関するものである。 The present invention relates to a polyolefin microporous membrane, and particularly relates to a technique for improving the safety and battery characteristics of a non-aqueous secondary battery.
正極にコバルト酸リチウムに代表されるリチウム含有遷移金属酸化物、負極にリチウムをドープ・脱ドープ可能な炭素材料を用いたリチウムイオン二次電池を代表とする非水系二次電池は、高エネルギー密度を有するという特徴から携帯電話に代表される携帯電子機器の電源として重要なものであり、これら携帯電子機器の急速な普及に伴いその需要は高まる一方である。 Non-aqueous secondary batteries such as lithium-ion secondary batteries, which use lithium-containing transition metal oxides typified by lithium cobaltate as the positive electrode and carbon materials that can be doped or dedoped with lithium as the negative electrode, have high energy density. It is important as a power source for portable electronic devices typified by mobile phones because of its characteristics, and demand for these portable electronic devices is increasing with the rapid spread of these portable electronic devices.
また、ハイブリッド自動車など、環境対応を意識した自動車が数多く開発されているが、搭載される電源の一つとして、高エネルギー密度を有するリチウムイオン二次電池が大きく注目されている。 In addition, many automobiles that are environmentally conscious, such as hybrid cars, have been developed, but lithium ion secondary batteries having a high energy density have attracted a great deal of attention as one of the power sources to be mounted.
リチウムイオン二次電池の多くは、正極、電解液を含むセパレータ、負極の積層体から構成されている。セパレータは、主たる機能として正極と負極の短絡防止を担っているが、要求特性として、リチウムイオンの移動度、強度、耐久性などがある。 Many lithium ion secondary batteries are composed of a laminate of a positive electrode, a separator containing an electrolytic solution, and a negative electrode. The separator is responsible for preventing a short circuit between the positive electrode and the negative electrode as a main function, but as required characteristics, there are mobility, strength, durability, and the like of lithium ions.
現在、リチウムイオン二次電池セパレータ用途に適するフィルムとして各種のポリオレフィン微多孔膜が数多く提案されている。ポリオレフィン微多孔膜は、上述にある要求特性を満たし、かつ高温時の安全機能として、高温による孔の閉塞から電流を遮断する事による熱暴走防止機能、いわゆるシャットダウン機能を有している事もあり、リチウムイオン二次電池のセパレータとして幅広く使用されている。 At present, various polyolefin microporous membranes have been proposed as films suitable for lithium ion secondary battery separator applications. Polyolefin microporous membrane satisfies the above-mentioned required characteristics, and as a safety function at high temperatures, it may have a thermal runaway prevention function by shutting off current from hole blockage due to high temperature, so-called shutdown function It is widely used as a separator for lithium ion secondary batteries.
しかしながら、温度上昇により微多孔膜の孔が閉塞されて電流が一旦遮断されても、電池温度が微多孔膜を構成するポリエチレンの融点を超えて、ポリエチレンの耐熱性の限界を超えると、微多孔膜自体が溶融してシャットダウン機能が失われる。その結果、電極間の短絡をきっかけとして電池の熱暴走がおこり、リチウムイオン二次電池を組み込んだ装置の破壊や、発火による事故発生などを招くおそれがある。このため、さらなる安全性確保のために、高温時でもシャットダウン機能を維持できるセパレータが求められている。 However, even if the pores of the microporous membrane are blocked due to the temperature rise and the current is interrupted once, if the battery temperature exceeds the melting point of polyethylene constituting the microporous membrane and exceeds the heat resistance limit of polyethylene, the microporous membrane The membrane itself melts and the shutdown function is lost. As a result, a short circuit between the electrodes causes a thermal runaway of the battery, which may cause destruction of a device incorporating the lithium ion secondary battery or occurrence of an accident due to ignition. For this reason, in order to ensure further safety, there is a demand for a separator that can maintain a shutdown function even at high temperatures.
そこで、特許文献１には、ポリエチレン微多孔膜の表面に、全芳香族ポリアミド等の耐熱性ポリマーからなる耐熱性多孔質層を被覆した非水系二次電池用セパレータが提案されている。また、特許文献２には、耐熱性多孔質層中にアルミナ等の無機微粒子を含ませて、シャットダウン機能に加えて耐熱性の向上を図った構成が示されている。また、特許文献３には、耐熱性多孔質層中に水酸化アルミニウム等の金属水酸化物粒子を含ませて、シャットダウン機能および耐熱性に加えて難燃性の向上を図った構成が示されている。これらの構成はいずれも、シャットダウン機能と耐熱性を両立させた点において、電池の安全性という観点において優れた効果が期待できる。 Therefore, Patent Document 1 proposes a separator for a nonaqueous secondary battery in which the surface of a polyethylene microporous membrane is covered with a heat resistant porous layer made of a heat resistant polymer such as wholly aromatic polyamide. Patent Document 2 discloses a configuration in which inorganic fine particles such as alumina are included in a heat-resistant porous layer to improve heat resistance in addition to a shutdown function. Patent Document 3 shows a structure in which metal hydroxide particles such as aluminum hydroxide are included in the heat-resistant porous layer to improve the flame retardancy in addition to the shutdown function and heat resistance. ing. Any of these configurations can be expected to have an excellent effect in terms of battery safety in terms of both a shutdown function and heat resistance.
しかし、非水系二次電池用セパレータはポリオレフィン微多孔膜を耐熱性多孔質層でコーティングするという構造のため、ポリオレフィン微多孔膜の有するシャットダウン機能を抑制する傾向にあり、ポリオレフィン微多孔膜に匹敵するシャットダウン機能を有する非水系二次電池用セパレータが望まれていた。また、上述した従来技術においては耐熱性多孔質層は塗工法で作成するため、機械強度はあまり優れるものとはならず、機械強度はポリオレフィン微多孔膜に大きく依存していた。そのため、ポリオレフィン微多孔膜の機械強度が、非水系二次電池用セパレータ及び非水系二次電池の製造工程における工程通過性に大きく影響していた。 However, the separator for non-aqueous secondary batteries has a structure in which the polyolefin microporous membrane is coated with a heat-resistant porous layer, and therefore tends to suppress the shutdown function of the polyolefin microporous membrane, comparable to the polyolefin microporous membrane. A separator for a non-aqueous secondary battery having a shutdown function has been desired. In the above-described prior art, since the heat-resistant porous layer is formed by a coating method, the mechanical strength is not so excellent, and the mechanical strength largely depends on the polyolefin microporous membrane. For this reason, the mechanical strength of the polyolefin microporous membrane has greatly influenced the process passability in the manufacturing process of the separator for nonaqueous secondary batteries and the nonaqueous secondary battery.
ところで、リチウムイオン電池の高容量化という点では、近年、様々な高容量タイプの正極材料や負極材料の開発が行われている。しかし、このような高容量タイプの正・負極材料には、充放電時における体積変化が大きなものが多く存在するため、電極の大きな体積変化によって電池特性が低下してしまうといった問題が生じてくる。 By the way, in terms of increasing the capacity of lithium ion batteries, in recent years, various high capacity type positive electrode materials and negative electrode materials have been developed. However, such high-capacity positive and negative electrode materials often have large volume changes during charging and discharging, and thus a problem arises in that battery characteristics deteriorate due to large volume changes in electrodes. .
すなわち、セパレータは、電池内においては正極と負極の間に配置されているため、電池の充放電が行われた場合、電極の膨張・収縮によってセパレータの厚み方向に圧縮力や回復力が作用する。従来のコバルト酸リチウムやハードカーボンなどの低容量タイプの正負極材料の場合は、電極の体積変化が小さいため、セパレータの厚み方向への変形も小さく、電池特性への影響も特にはない。ところが、高容量タイプの正・負極活物質など、充放電時における体積変化率が大きい電極材料を用いた場合、電極からセパレータに与えられる作用力も大きくなる。そして、電極の体積変化にセパレータが追随できず、セパレータの多孔質構造が圧縮された状態から回復できなくなると、セパレータの空孔内に十分な量の電解液が保持されなくなると言った、いわゆる液枯れの問題が発生するおそれがある。この液枯れ現象は、結果として電池の繰り返し充放電特性（サイクル特性）を低下させてしまうおそれがある。 That is, since the separator is disposed between the positive electrode and the negative electrode in the battery, when the battery is charged / discharged, a compressive force or a restoring force acts in the thickness direction of the separator due to the expansion / contraction of the electrode. . In the case of conventional low-capacity positive and negative electrode materials such as lithium cobaltate and hard carbon, since the volume change of the electrode is small, the deformation in the thickness direction of the separator is small, and the battery characteristics are not particularly affected. However, when an electrode material having a large volume change rate during charge / discharge, such as a high-capacity positive / negative active material, is used, the acting force applied from the electrode to the separator also increases. And, when the separator cannot follow the volume change of the electrode and the porous structure of the separator cannot be recovered from the compressed state, a sufficient amount of electrolyte is not retained in the pores of the separator, so-called There is a possibility that the problem of withering may occur. As a result, this liquid withdrawing phenomenon may deteriorate the repeated charge / discharge characteristics (cycle characteristics) of the battery.
この液枯れの問題を解決するために、ポリオレフィン微多孔膜の弾性等の物性を制御することが考えられるが、上述したようにポリオレフィン微多孔膜には良好なシャットダウン特性と機械強度も求められており、ポリオレフィン微多孔膜の一方の物性を制御すれば必然的に他の物性にも影響が生じてくる。よって、これらの諸特性をバランス良く向上できる技術が望まれている。 In order to solve this problem of liquid drainage, it is conceivable to control physical properties such as elasticity of the polyolefin microporous membrane. However, as described above, the polyolefin microporous membrane is also required to have good shutdown characteristics and mechanical strength. Therefore, if one physical property of the polyolefin microporous film is controlled, the other physical property is inevitably affected. Therefore, a technique that can improve these characteristics in a well-balanced manner is desired.
本発明の目的は、耐熱性多孔質層と複合した時に、優れたシャットダウン機能と工程通過性を付与でき、かつ、電解液の液枯れを防止可能なポリオレフィン微多孔膜を提供することにある。 An object of the present invention is to provide a polyolefin microporous membrane that can provide an excellent shutdown function and process passability when combined with a heat-resistant porous layer, and can prevent the electrolyte from draining.
本発明者らは、上記課題を解決すべく鋭意検討を重ねた結果、以下の構成により解決可能である事を見出し、本発明に到達した。 As a result of intensive studies to solve the above problems, the present inventors have found that the problem can be solved by the following configuration, and have reached the present invention.
すなわち、本発明は、Ｘ線測定により得られたポリオレフィンの結晶構造で、配向軸が２本あり、それぞれ配向軸１、配向軸２とした時、配向軸１が機械方向に対し０〜２０度、配向軸２が機械方向に対し６０〜９０度であり、配向軸１の配向度が６５〜８０％、配向軸２の配向度が６５〜８０％であり、配向全体の積分値に占める配向軸１の積分値が２０〜４０％である事を特徴とするポリオレフィン微多孔膜である。 That is, the present invention is a polyolefin crystal structure obtained by X-ray measurement and has two orientation axes. When the orientation axis is 1 and the orientation axis is 2, respectively, the orientation axis 1 is 0 to 20 degrees with respect to the machine direction. The orientation axis 2 is 60 to 90 degrees with respect to the machine direction, the orientation degree of the orientation axis 1 is 65 to 80%, the orientation degree of the orientation axis 2 is 65 to 80%, and the orientation occupies the integrated value of the whole orientation. The polyolefin microporous film is characterized in that the integral value of the shaft 1 is 20 to 40%.
また、本発明は前記ポリオレフィン微多孔膜を耐熱性多孔質層で被覆した非水系二次電池用セパレータである。また、本発明はリチウムのドープ・脱ドープにより起電力を得る非水系二次電池であって、前記非水系二次電池用セパレータを用いたことを特徴とする非水系二次電池である。 The present invention also provides a separator for a non-aqueous secondary battery in which the polyolefin microporous membrane is coated with a heat resistant porous layer. In addition, the present invention is a non-aqueous secondary battery that obtains an electromotive force by doping or dedoping lithium, wherein the non-aqueous secondary battery separator is used.
本発明では、耐熱性多孔質層と複合した時に、優れたシャットダウン機能と工程通過性を付与でき、かつ、電解液の液枯れを防止可能なポリオレフィン微多孔膜を提供することができる。このような本発明のポリオレフィン微多孔膜あるいはこれを用いた非水系二次電池用セパレータによれば、非水系二次電池の安全性および電池特性を向上させる事ができる。 The present invention can provide a microporous polyolefin membrane that can provide an excellent shutdown function and process passability when combined with a heat-resistant porous layer, and can prevent the electrolyte from draining. According to the polyolefin microporous membrane of the present invention or the separator for a non-aqueous secondary battery using the same, the safety and battery characteristics of the non-aqueous secondary battery can be improved.
以下に、本発明の実施の形態について順次説明する。なお、これらの説明及び実施例は本発明を例示するものであり、本発明の範囲を制限するものではない。 Hereinafter, embodiments of the present invention will be sequentially described. In addition, these description and Examples illustrate this invention, and do not restrict | limit the scope of the present invention.
［ポリオレフィン微多孔膜］
本発明のポリオレフィン微多孔膜において、微多孔膜とは、内部に多数の微細孔を有し、これら微細孔が連結された構造となっており、一方の面から他方の面へと気体あるいは液体が通過可能となった膜を言う。
[Polyolefin microporous membrane]
In the polyolefin microporous membrane of the present invention, the microporous membrane has a structure in which a large number of micropores are connected to each other, and these micropores are connected to each other. Refers to a membrane that can pass through.
本発明で用いられるポリオレフィン微多孔膜の原料としては、ポリオレフィン、すなわち例えばポリエチレン、ポリプロピレン、ポリメチルペンテン及びその共重合体等が挙げられる。中でもポリエチレンが好ましく、より好ましくは高密度ポリエチレン、高密度ポリエチレンと超高分子量ポリエチレンの混合物が、強度、耐熱性等の観点から好ましい。ポリエチレンの分子量は重量平均分子量で５０万〜５００万のものが好適であり、重量平均分子量１００万以上の超高分子量ポリエチレンを１重量％以上含むポリエチレンの組成物が特に好ましい。さらに、重量平均分子量１００万以上の超高分子量ポリエチレンを１０〜９０重量％含むポリエチレン組成物が好適である。また、高密度ポリエチレンの密度は０．９４２ｇ／ｃｍ３（ＪＩＳ Ｋ ６７４８−１９８１）以上であることが好ましい。なお、本発明で用いるポリオレフィン微多孔膜は、９０重量％以上がポリオレフィンからなるものであればよく、１０重量％以下の電池特性に影響を与えない他の成分を含んでいても構わない。 Examples of the raw material for the polyolefin microporous membrane used in the present invention include polyolefins, for example, polyethylene, polypropylene, polymethylpentene and copolymers thereof. Among these, polyethylene is preferable, and high-density polyethylene and a mixture of high-density polyethylene and ultrahigh molecular weight polyethylene are more preferable from the viewpoints of strength, heat resistance, and the like. The molecular weight of polyethylene is preferably 500,000 to 5,000,000 in terms of weight average molecular weight, and a polyethylene composition containing 1% by weight or more of ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more is particularly preferred. Furthermore, a polyethylene composition containing 10 to 90% by weight of ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more is suitable. The density of the high density polyethylene is preferably 0.942 g / cm 3 (JIS K 6748-1981) or more. The polyolefin microporous membrane used in the present invention is not limited as long as 90% by weight or more is made of polyolefin, and may contain 10% by weight or less of other components that do not affect the battery characteristics.
本発明のポリオレフィン微多孔膜は、Ｘ線測定により得られたポリオレフィンの結晶構造で、配向軸が２本あり、それぞれを配向軸１、配向軸２とした時、配向軸１が機械方向に対し０〜２０度、配向軸２が機械方向に対し６０〜９０度の角度であり、配向軸１の配向度が６５〜８０％、配向軸２の配向度が６５〜８０％であり、配向全体の積分値に占める配向軸１の積分値が２０〜４０％である事を特徴とする。 The polyolefin microporous membrane of the present invention is a polyolefin crystal structure obtained by X-ray measurement, and has two orientation axes. When the orientation axis is 1 and the orientation axis is 2, respectively, the orientation axis 1 is relative to the machine direction. 0 to 20 degrees, the orientation axis 2 is at an angle of 60 to 90 degrees with respect to the machine direction, the orientation degree of the orientation axis 1 is 65 to 80%, the orientation degree of the orientation axis 2 is 65 to 80%, and the whole orientation The integral value of the orientation axis 1 occupying the integral value is 20 to 40%.
ポリオレフィンの結晶性パラメータがこの範囲にある時、本発明のポリオレフィン微多孔膜を使用した非水系二次電池用セパレータの工程通過性が優れたものとなり、非水系二次電池用セパレータの本来有するシャットダウン特性、耐熱性と合わせて、安全性に優れたものとなる。さらに、電解液の液枯れを防止する効果にも優れたものとなる。なお、本発明における「工程通過性」とは、非水系二次電池用セパレータを捲回し、非水系二次電池を製作する際に、非水系二次電池用セパレータに変形や破損が無い事を意味する。 When the polyolefin crystallinity parameter is within this range, the non-aqueous secondary battery separator using the polyolefin microporous membrane of the present invention has excellent process passability, and the non-aqueous secondary battery separator inherently shuts down. Combined with characteristics and heat resistance, it has excellent safety. Furthermore, it is excellent in the effect of preventing the electrolyte from withstanding. In the present invention, “process passability” means that the nonaqueous secondary battery separator is not deformed or damaged when the nonaqueous secondary battery separator is wound to manufacture the nonaqueous secondary battery. means.
本発明のポリオレフィン微多孔膜は製造過程において、機械方向及び機械垂直方向に延伸して得るため、配向軸は２本となる。それぞれ配向軸１、配向軸２とした時、工程通過性の観点から、配向軸１が機械方向に対し０〜２０度、配向軸２が機械方向に対し６０〜９０度の角度にあることが好ましい。この事から実質的に、配向軸１は機械方向への延伸に対応した配向軸、配向軸２は機械垂直方向への延伸に対応した配向軸という事になる。なお、配向軸とはポリオレフィン結晶が全体としてどの方向に向いているかを意味する。配向軸１が機械方向に対し大きくずれていると、ポリオレフィン微多孔膜を用いて非水系二次電池用セパレータとし、これを電極と積層して非水系二次電池を捲回して作成する際に、セパレータの変形が均一でなくなり、工程通過性が低下する事になる。配向軸２が配向軸１に対し、非常に近い場合もしくは非常に遠い場合には、捲回の張力により機械垂直方向へのセパレータの変形が均一でなくなり、工程通過性が低下することになる。また、配向軸１は機械方向であるため、より正確であることが求められる。従って、配向軸１が機械方向に対し０〜２０度、配向軸２が機械方向に対し６０〜９０度の角度にあることが好ましい。より好ましくは配向軸１が機械方向に対し０〜１０度、配向軸２が機械方向に対し７５〜９０度の角度にあることが好ましい。
配向軸１、２の方向は、例えば図１に示すように、Ｘ線の回折像で強くピークが現れた２つの方向に対して、９０度ずらした方向を配向軸の方向として求める。
Since the polyolefin microporous film of the present invention is obtained by stretching in the machine direction and the machine vertical direction in the production process, the number of orientation axes is two. When the orientation axis 1 and the orientation axis 2 are used, respectively, the orientation axis 1 is at an angle of 0 to 20 degrees with respect to the machine direction and the orientation axis 2 is at an angle of 60 to 90 degrees with respect to the machine direction from the viewpoint of process passability. preferable. From this fact, the orientation axis 1 is substantially the orientation axis corresponding to stretching in the machine direction, and the orientation axis 2 is the orientation axis corresponding to stretching in the machine vertical direction. The orientation axis means in which direction the polyolefin crystal is oriented as a whole. When the orientation axis 1 is greatly deviated with respect to the machine direction, a polyolefin microporous membrane is used as a separator for a non-aqueous secondary battery, and this is laminated with an electrode to form a non-aqueous secondary battery by winding. The deformation of the separator is not uniform, and the process passability is reduced. When the alignment axis 2 is very close to or very far from the alignment axis 1, the deformation of the separator in the machine vertical direction is not uniform due to the winding tension, and the process passability decreases. Further, since the orientation axis 1 is in the machine direction, it is required to be more accurate. Therefore, the orientation axis 1 is preferably at an angle of 0 to 20 degrees with respect to the machine direction, and the orientation axis 2 is at an angle of 60 to 90 degrees with respect to the machine direction. More preferably, the orientation axis 1 is at an angle of 0 to 10 degrees with respect to the machine direction, and the orientation axis 2 is at an angle of 75 to 90 degrees with respect to the machine direction.
For example, as shown in FIG. 1, the directions of the orientation axes 1 and 2 are determined as directions of the orientation axes by shifting by 90 degrees with respect to two directions where strong peaks appear in the X-ray diffraction image.
本発明では、シャットダウン特性の観点から、配向全体の積分値に占める配向軸１の積分値の割合が２０〜４０％である事が好ましい。ポリオレフィン結晶の配向は基本的に配向軸１もしくは配向軸２のどちらかに分配されるが、配向全体の積分値に占める配向軸１の積分値の割合とは、配向軸１に沿って配向するポリオレフィン結晶の割合を示す。 In the present invention, from the viewpoint of shutdown characteristics, the ratio of the integrated value of the alignment axis 1 to the integrated value of the entire alignment is preferably 20 to 40%. The orientation of the polyolefin crystal is basically distributed to either the orientation axis 1 or the orientation axis 2, and the ratio of the integral value of the orientation axis 1 to the integral value of the whole orientation is oriented along the orientation axis 1. The ratio of polyolefin crystals is shown.
本発明のポリオレフィン微多孔膜は高温においては先に配向軸１に沿って収縮し、後に配向軸２に沿って収縮する。そのため、シャットダウン特性には機械方向の熱収縮率に大きく依存する。熱収縮率を支配するパラメータの一つとして、ポリオレフィン高分子鎖の結晶配向がある。この配向割合が、ある程度小さい方が、シャットダウン特性に優れる傾向にある。しかし、配向軸１へのポリオレフィン結晶の配向割合が小さいと、非水系二次電池用セパレータを電極と積層して非水系二次電池を捲回して作成する際に、非水系二次電池用セパレータが変形しやすくなり、工程通過性が低下することになる。そのため、配向全体の積分値に占める配向軸１の積分値の割合が２０〜４０％が好ましい。 The polyolefin microporous membrane of the present invention first shrinks along the orientation axis 1 at a high temperature, and later shrinks along the orientation axis 2. Therefore, the shutdown characteristic greatly depends on the heat shrinkage rate in the machine direction. One of the parameters governing the heat shrinkage rate is the crystal orientation of the polyolefin polymer chain. When this orientation ratio is small to some extent, the shutdown characteristics tend to be excellent. However, when the orientation ratio of the polyolefin crystal to the orientation axis 1 is small, a separator for a non-aqueous secondary battery is formed when a non-aqueous secondary battery separator is laminated with an electrode and wound to make a non-aqueous secondary battery. Will be easily deformed, and process passability will be reduced. Therefore, the ratio of the integrated value of the alignment axis 1 to the integrated value of the entire alignment is preferably 20 to 40%.
配向全体の積分値に占める配向軸１の積分値の割合は、２θ＝２１．３、２３．７、２９．８付近のピークを配向軸１、配向軸２においてスキャンして得られた強度分布のピークの積分強度から下記式（１）により算出した。
（配向全体の積分値に占める配向軸１の積分値の割合）＝（配向軸１の積分強度）／［（配向軸１の積分強度）＋（配向軸２の積分強度）］×１００ …（１）
The ratio of the integral value of the orientation axis 1 to the integral value of the whole orientation is the intensity distribution obtained by scanning the peaks around 2θ = 21.3, 23.7, 29.8 in the orientation axis 1 and the orientation axis 2. From the integrated intensity of the peak, the following formula (1) was used.
(Ratio of the integrated value of the alignment axis 1 to the integrated value of the entire alignment) = (integrated intensity of the alignment axis 1) / [(integrated intensity of the alignment axis 1) + (integrated intensity of the alignment axis 2)] × 100 ( 1)
更に本発明では、配向軸１の配向度が６５〜８０％、配向軸２の配向度が６５〜８０％であることが好ましい。配向度とは、ポリオレフィン結晶の１個１個が配向軸方向にどの程度揃っているかを意味する。配向度が高いほど、配向軸方向への機械強度が高い事を示し、工程通過性が優れたものとなる。しかし、配向度が大きすぎると熱収縮に由来するシャットダウン特性が低下する事になり、バランスをとることが必要となる。そのため、配向軸１の配向度が６５〜８０％、配向軸２の配向度が６５〜８０％であることが好ましい。 Furthermore, in the present invention, the orientation degree of the orientation axis 1 is preferably 65 to 80%, and the orientation degree of the orientation axis 2 is preferably 65 to 80%. The degree of orientation means how much each of the polyolefin crystals is aligned in the orientation axis direction. The higher the degree of orientation, the higher the mechanical strength in the direction of the orientation axis, and the better the process passability. However, if the degree of orientation is too large, the shutdown characteristics due to heat shrinkage will be reduced, and it will be necessary to balance. Therefore, the orientation degree of the orientation axis 1 is preferably 65 to 80%, and the orientation degree of the orientation axis 2 is preferably 65 to 80%.
配向度は、２θ＝２１．３、２３．７、２９．８付近のピークを配向軸１、配向軸２においてスキャンして得られた強度分布のピークの半値幅から下記式（２）により算出した。
配向度＝［（１８０−Ｈ）／１８０］×１００ …（２）
ここで、上記式（２）において、Ｈは強度分布のピークの半値幅を意味する。
The degree of orientation is calculated by the following formula (2) from the half-value width of the peak of the intensity distribution obtained by scanning the peaks in the vicinity of 2θ = 21.3, 23.7, 29.8 on the orientation axis 1 and the orientation axis 2. did.
Degree of orientation = [(180−H) / 180] × 100 (2)
Here, in the above formula (2), H means the half width of the peak of the intensity distribution.
なお、これら結晶性パラメータを制御する方法に特に限定は無いが、具体的には例えばポリオレフィン微多孔膜の延伸条件やアニール条件の制御、原料に用いるポリオレフィンの分子量分布や分岐構造の制御、以下において説明する縦延伸工程と横延伸工程の間に冷却工程を設けること等が挙げられる。基本的には、分子量が下がるほど、分岐構造が減るほど、延伸条件を強くするほど、アニール温度を下げるほど、結晶化度は向上する傾向にある。 The method for controlling these crystallinity parameters is not particularly limited. Specifically, for example, control of the stretching conditions and annealing conditions of the polyolefin microporous film, control of the molecular weight distribution and branch structure of the polyolefin used as a raw material, For example, a cooling process may be provided between the longitudinal stretching process and the lateral stretching process described. Basically, the lower the molecular weight, the smaller the branched structure, the stronger the stretching conditions, and the lower the annealing temperature, the higher the degree of crystallinity.
本発明のポリオレフィン微多孔膜の膜厚は、非水系二次電池のエネルギー密度、負荷特性、機械強度およびハンドリング性の観点から、５〜２５μｍであることが好ましい。
本発明のポリオレフィン微多孔膜の空孔率は、透過性、機械強度およびハンドリング性の観点から、３０〜６０％であることが好ましい。更に好ましくは、４０％〜６０％である。
The film thickness of the polyolefin microporous membrane of the present invention is preferably 5 to 25 μm from the viewpoint of energy density, load characteristics, mechanical strength and handling properties of the non-aqueous secondary battery.
The porosity of the polyolefin microporous membrane of the present invention is preferably 30 to 60% from the viewpoints of permeability, mechanical strength and handling properties. More preferably, it is 40% to 60%.
本発明のポリオレフィン微多孔膜のガーレ値（ＪＩＳ・Ｐ８１１７）は、機械強度と膜抵抗をバランス良く得るという観点から、５０〜５００ｓｅｃ／１００ｃｃであることが好ましい。
本発明のポリオレフィン微多孔膜の膜抵抗は、非水系二次電池の負荷特性の観点から、０．５〜５ｏｈｍ・ｃｍ２であることが好ましい。
The Gurley value (JIS P8117) of the microporous polyolefin membrane of the present invention is preferably 50 to 500 sec / 100 cc from the viewpoint of obtaining a good balance between mechanical strength and membrane resistance.
The membrane resistance of the polyolefin microporous membrane of the present invention is preferably 0.5 to 5 ohm · cm 2 from the viewpoint of load characteristics of the non-aqueous secondary battery.
本発明のポリオレフィン微多孔膜の突刺強度は２５０ｇ以上であることが好ましい。２５０ｇを下回ると、非水系二次電池を作成した場合、電極の凹凸や衝撃等でセパレータにピンホール等が発生し、非水系二次電池が短絡する可能性が高くなるため、好ましくない場合がある。 The puncture strength of the polyolefin microporous membrane of the present invention is preferably 250 g or more. If it is less than 250 g, when a nonaqueous secondary battery is produced, pinholes and the like are generated in the separator due to unevenness or impact of the electrode, and the possibility of a short circuit of the nonaqueous secondary battery increases. is there.
本発明のポリオレフィン微多孔膜の引張強度は１５Ｎ以上であることが好ましい。１５Ｎを下回ると、非水系二次電池を作成する時にセパレータを捲回する際に、セパレータが破損する可能性が高くなるため、好ましくない場合がある。 The tensile strength of the polyolefin microporous membrane of the present invention is preferably 15N or more. If it is less than 15N, there is a possibility that the separator will be damaged when winding the separator when producing a non-aqueous secondary battery, which may not be preferable.
本発明のポリオレフィン微多孔膜のシャットダウン温度は１３０〜１５０℃であることが好ましい。シャットダウン温度は、抵抗値が１０３ｏｈｍ・ｃｍ２となった温度を差す。シャットダウン温度が１３０℃より小さい場合、シャットダウン現象が低温で発現するのと同じく、ポリオレフィン微多孔膜が完全溶融し短絡現象が発生するメルトダウンと呼ばれる現象も低温で発生する事になり、安全上好ましくない場合がある。また、シャットダウン温度が１５０℃より大きいと、高温時の十分な安全機能が期待できず、好ましくない場合がある。好ましくは１３５〜１４５℃である。 The shutdown temperature of the polyolefin microporous membrane of the present invention is preferably 130 to 150 ° C. The shutdown temperature is the temperature at which the resistance value is 10 3 ohm · cm 2 . When the shutdown temperature is lower than 130 ° C., the phenomenon called meltdown, in which the polyolefin microporous membrane completely melts and the short circuit phenomenon occurs, is generated at a low temperature. There may not be. On the other hand, if the shutdown temperature is higher than 150 ° C., a sufficient safety function at a high temperature cannot be expected, which is not preferable. Preferably it is 135-145 degreeC.
本発明のポリオレフィン微多孔膜の１０５℃における熱収縮率は５〜４０％以下であることが好ましい。熱収縮率がこの範囲にある時、ポリオレフィン微多孔膜を加工して得た非水系二次電池用セパレータの形状安定性とシャットダウン特性のバランスがとれたものとなる。 The heat shrinkage rate at 105 ° C. of the polyolefin microporous membrane of the present invention is preferably 5 to 40% or less. When the thermal shrinkage is in this range, the shape stability and shutdown characteristics of the separator for a non-aqueous secondary battery obtained by processing the polyolefin microporous membrane are balanced.
［ポリオレフィン微多孔膜の製造法］
本発明のポリオレフィン微多孔膜の製造法に、特に制限は無いが、具体的には下記（１）〜（６）の工程を経て製造することが好ましい。なお、原料に用いるポリオレフィンについては上述のとおりである。
[Polyolefin microporous membrane production method]
Although there is no restriction | limiting in particular in the manufacturing method of the polyolefin microporous membrane of this invention, Specifically, manufacturing through the following (1)-(6) processes is preferable. The polyolefin used as a raw material is as described above.
（１）ポリオレフィン溶液の調整
ポリオレフィンを溶剤に溶解させた溶液を調整する。この時、溶剤を混合して溶液を作成しても構わない。溶剤としては、例えばパラフィン、流動パラフィン、パラフィン油、鉱油、ひまし油、テトラリン、エチレングリコール、グリセリン、デカリン、トルエン、キシレン、ジエチルトリアミン、エチルジアミン、ジメチルスルホキシド、ヘキサン等が挙げられる。ポリオレフィン溶液の濃度は１〜３５重量％が好ましく、より好ましくは１０〜３０重量％である。ポリオレフィン溶液の濃度が１重量％未満では、冷却ゲル化して得られるゲル状成形物が溶媒で高度に膨潤されるため変形し易く、取扱いに支障をきたす場合がある。一方、３５重量％を超えると押し出しの際の圧力が高くなるため吐出量が低くなり生産性が上げられない場合があり、また押し出し工程での配向が進み、延伸性や均一性が確保できなくなる場合がある。
(1) Preparation of polyolefin solution A solution in which polyolefin is dissolved in a solvent is prepared. At this time, a solution may be prepared by mixing solvents. Examples of the solvent include paraffin, liquid paraffin, paraffin oil, mineral oil, castor oil, tetralin, ethylene glycol, glycerin, decalin, toluene, xylene, diethyltriamine, ethyldiamine, dimethyl sulfoxide, hexane, and the like. The concentration of the polyolefin solution is preferably 1 to 35% by weight, more preferably 10 to 30% by weight. When the concentration of the polyolefin solution is less than 1% by weight, the gel-like molded product obtained by cooling and gelation is highly swollen with a solvent, so that it is easily deformed, which may hinder handling. On the other hand, if it exceeds 35% by weight, the pressure at the time of extrusion increases, so the discharge amount may decrease and the productivity may not be increased. Further, the orientation in the extrusion process proceeds, and stretchability and uniformity cannot be ensured. There is a case.
（２）ポリオレフィン溶液の押出
調整した溶液を一軸押出機、もしくは二軸押出機で混練し、融点以上かつ融点＋６０℃以下の温度でＴダイもしくはＩダイで押し出す。好ましくは二軸押出機を用いる。そして、押し出した溶液をチルロールまたは冷却浴に通過させて、ゲル状組成物を形成する。この際、ゲル化温度以下に急冷しゲル化することが好ましい。
(2) Extrusion of polyolefin solution The adjusted solution is kneaded with a single screw extruder or a twin screw extruder, and extruded with a T die or an I die at a temperature not lower than the melting point and not higher than the melting point + 60 ° C. A twin screw extruder is preferably used. Then, the extruded solution is passed through a chill roll or a cooling bath to form a gel composition. At this time, it is preferable to rapidly cool below the gelation temperature to cause gelation.
（３）脱溶媒処理
次いで、ゲル状組成物から溶媒を除去する。揮発性溶剤を使用する場合、予熱工程も兼ねて加熱等により蒸発させゲル状組成物から溶媒を除くこともできる。また不揮発性溶媒の場合は圧力をかけて絞り出すなどして溶媒を除くことができる。なお溶媒は完全に除く必要はない。
(3) Desolvation treatment Next, the solvent is removed from the gel composition. When a volatile solvent is used, the solvent can also be removed from the gel composition by evaporating by heating or the like, which also serves as a preheating step. In the case of a non-volatile solvent, the solvent can be removed by squeezing out under pressure. The solvent need not be completely removed.
（４）ゲル状組成物の延伸
脱溶媒処理に次いで、ゲル状組成物を延伸する。ここで、延伸処理の前に弛緩処理を行っても良い。延伸処理は、ゲル状成形物を加熱し、通常のテンター法、ロール法、圧延法もしくはこれらの方法の組合せによって所定の倍率で２軸延伸する。２軸延伸は、同時または逐次のどちらであってもよい。また縦多段延伸や３、４段延伸とすることもできる。
延伸温度は、９０℃〜ポリオレフィンの融点未満であることが好ましく、さらに好ましくは１００〜１２０℃である。加熱温度が融点を越える場合は、ゲル状成形物が溶解するために延伸できない。又、加熱温度が９０℃未満の場合は、ゲル状成形物の軟化が不十分で延伸において破膜し易く高倍率の延伸が困難となる場合がある。特に本発明においては、ポリオレフィンの結晶を制御するために、縦延伸工程と横延伸工程の間に冷却工程を設けることが好ましい。この場合、冷却方法としては、シートを縦延伸温度よりも低い雰囲気中に暴露する処理や、冷風を吹きつける処理等が挙げられる。また、冷却工程における温度は、縦延伸温度マイナス１０〜７０℃の範囲に設定することが好ましい。
また、延伸倍率は、原反の厚さによって異なるが、１軸方向で少なくとも２倍以上、好ましくは４〜２０倍で行うことが好ましい。特に、結晶パラメータを制御するという観点では、延伸倍率が機械方向に４〜１０倍、また機械垂直方向に６〜１５倍であることが好ましい。
延伸後、必要に応じて熱固定を行い、熱寸法安定性を持たせる。
(4) Stretching of the gel-like composition After the solvent removal treatment, the gel-like composition is stretched. Here, a relaxation treatment may be performed before the stretching treatment. In the stretching treatment, the gel-like molded product is heated and biaxially stretched at a predetermined magnification by a normal tenter method, roll method, rolling method, or a combination of these methods. Biaxial stretching may be simultaneous or sequential. Moreover, it can also be set as longitudinal multistage extending | stretching, 3 or 4 steps | stretching.
The stretching temperature is preferably 90 ° C. to less than the melting point of the polyolefin, more preferably 100 to 120 ° C. When the heating temperature exceeds the melting point, it cannot be stretched because the gel-like molded product is dissolved. On the other hand, when the heating temperature is less than 90 ° C., the gel-like molded product is not sufficiently softened, and the film is likely to be broken during stretching, making it difficult to stretch at a high magnification. In particular, in the present invention, in order to control polyolefin crystals, it is preferable to provide a cooling step between the longitudinal stretching step and the transverse stretching step. In this case, examples of the cooling method include a process of exposing the sheet to an atmosphere lower than the longitudinal stretching temperature, a process of blowing cool air, and the like. Moreover, it is preferable to set the temperature in a cooling process in the range of the longitudinal stretch temperature minus 10-70 degreeC.
Moreover, although a draw ratio changes with thickness of an original fabric, it is preferable to carry out by at least 2 times or more in a uniaxial direction, Preferably it is 4-20 times. In particular, from the viewpoint of controlling crystal parameters, the draw ratio is preferably 4 to 10 times in the machine direction and 6 to 15 times in the machine vertical direction.
After stretching, heat setting is performed as necessary to provide thermal dimensional stability.
（５）溶剤の抽出・除去
延伸後のゲル状組成物を抽出溶剤に浸漬して、溶媒を抽出する。抽出溶剤としては、例えばペンタン、ヘキサン、ヘプタン、シクロヘキサン、デカリン、テトラリンなどの炭化水素、塩化メチレン、四塩化炭素、メチレンクロライドなどの塩素化炭化水素、三フッ化エタンなどのフッ化炭化水素、ジエチルエーテル、ジオキサン等のエーテル類など易揮発性のものを用いることができる。これらの溶剤はポリオレフィン組成物の溶解に用いた溶媒に応じて適宜選択し、単独もしくは混合して用いることができる。溶媒の抽出は、微多孔膜中の溶媒を１重量％未満に迄除去する。
(5) Extraction and removal of solvent The stretched gel composition is immersed in an extraction solvent to extract the solvent. Examples of the extraction solvent include hydrocarbons such as pentane, hexane, heptane, cyclohexane, decalin, and tetralin, chlorinated hydrocarbons such as methylene chloride, carbon tetrachloride, and methylene chloride, fluorinated hydrocarbons such as ethane trifluoride, diethyl, and the like. Easily volatile compounds such as ethers and ethers such as dioxane can be used. These solvents are appropriately selected according to the solvent used for dissolving the polyolefin composition, and can be used alone or in combination. Solvent extraction removes the solvent in the microporous membrane to less than 1% by weight.
（６）微多孔膜のアニール
微多孔膜をアニールにより熱セットする。アニールは８０〜１５０℃で実施する。本発明においては、所定の熱収縮率を有するという観点から、アニール温度が１１５〜１３５℃であることが好ましい。
(6) Annealing of microporous film The microporous film is heat-set by annealing. Annealing is performed at 80 to 150 ° C. In this invention, it is preferable that annealing temperature is 115-135 degreeC from a viewpoint that it has a predetermined | prescribed heat shrinkage rate.
［非水系二次電池用セパレータ］
本発明の非水系二次電池用セパレータは、上述したポリオレフィン微多孔膜と、耐熱性樹脂を含んで形成され前記ポリオレフィン微多孔膜の片面又は両面に積層された耐熱性多孔質層とを備えた非水系二次電池用セパレータであることを特徴とする。
[Separator for non-aqueous secondary battery]
A separator for a non-aqueous secondary battery according to the present invention includes the above-described polyolefin microporous membrane and a heat-resistant porous layer formed by including a heat-resistant resin and laminated on one or both sides of the polyolefin microporous membrane. It is a separator for non-aqueous secondary batteries.
このような本発明の非水系二次電池用セパレータによれば、ポリオレフィン微多孔膜によりシャットダウン機能が得られると共に、耐熱性多孔質層によりシャットダウン温度以上の温度においてもポリオレフィンが保持されるため、メルトダウンが生じ難く、高温時の安全性を確保できる。従って、本発明のセパレータによれば、安全性に優れた非水系二次電池を得ることができる。 According to such a separator for a non-aqueous secondary battery of the present invention, the polyolefin microporous membrane provides a shutdown function, and the heat-resistant porous layer holds the polyolefin even at a temperature higher than the shutdown temperature. It is hard to cause down and secures safety at high temperatures. Therefore, according to the separator of the present invention, a non-aqueous secondary battery excellent in safety can be obtained.
本発明の非水系二次電池用セパレータは、非水系二次電池のエネルギー密度の観点から、全体の膜厚が３０μｍ以下であることが好ましい。
本発明の非水系二次電池用セパレータの空孔率は、透過性、機械強度およびハンドリング性の観点から、３０〜７０％であることが好ましい。更に好ましくは、４０％〜６０％である。
The separator for a non-aqueous secondary battery of the present invention preferably has a total film thickness of 30 μm or less from the viewpoint of the energy density of the non-aqueous secondary battery.
The porosity of the non-aqueous secondary battery separator of the present invention is preferably 30 to 70% from the viewpoints of permeability, mechanical strength, and handling properties. More preferably, it is 40% to 60%.
本発明の非水系二次電池用セパレータのガーレ値（ＪＩＳ・Ｐ８１１７）は、機械強度と膜抵抗のバランスが良くなるという観点から、１００〜５００ｓｅｃ／１００ｃｃであることが好ましい。
本発明の非水系二次電池用セパレータの膜抵抗は、非水系二次電池の負荷特性の観点から、１．５〜１０ｏｈｍ・ｃｍ２であることが好ましい。
The Gurley value (JIS P8117) of the non-aqueous secondary battery separator of the present invention is preferably 100 to 500 sec / 100 cc from the viewpoint of improving the balance between mechanical strength and membrane resistance.
The membrane resistance of the non-aqueous secondary battery separator of the present invention is preferably 1.5 to 10 ohm · cm 2 from the viewpoint of load characteristics of the non-aqueous secondary battery.
本発明の非水系二次電池用セパレータの突刺強度は２５０〜１０００ｇであることが好ましい。突刺強度が２５０ｇ未満の場合、非水系二次電池を作成した場合、電極の凹凸や衝撃等でセパレータにピンホール等が発生し、非水系二次電池が短絡する可能性があり好ましくない場合がある。 The puncture strength of the separator for a non-aqueous secondary battery of the present invention is preferably 250 to 1000 g. When the puncture strength is less than 250 g, when a non-aqueous secondary battery is produced, pinholes or the like may be generated in the separator due to electrode unevenness or impact, etc., which may cause a short circuit of the non-aqueous secondary battery. is there.
本発明の非水系二次電池用セパレータの引張強度は１５Ｎ以上であることが好ましい。１５Ｎ未満の場合、非水系二次電池を作成する時にセパレータを捲回する際に、セパレータが破損する可能性が高くなるため、好ましくない場合がある。 The tensile strength of the nonaqueous secondary battery separator of the present invention is preferably 15 N or more. If it is less than 15N, there is a possibility that the separator is damaged when winding the separator when producing a non-aqueous secondary battery, which may not be preferable.
本発明の非水系二次電池用セパレータのシャットダウン温度は１３０〜１５５℃であることが好ましい。シャットダウン温度が１３０℃未満の場合、メルトダウンが低温で発生する事になり、安全上好ましくない場合がある。また、シャットダウン温度が１５５℃より大きい場合、高温時の十分な安全機能が期待できず、好ましくない場合がある。好ましくは１３５〜１５０℃である。 The shutdown temperature of the separator for a non-aqueous secondary battery of the present invention is preferably 130 to 155 ° C. When the shutdown temperature is lower than 130 ° C., meltdown occurs at a low temperature, which may be unfavorable for safety. On the other hand, when the shutdown temperature is higher than 155 ° C., a sufficient safety function at a high temperature cannot be expected, which is not preferable. Preferably it is 135-150 degreeC.
本発明の非水系二次電池用セパレータの１０５℃における熱収縮率は０．５〜１０％であることが好ましい。熱収縮率がこの範囲にある時、非水系二次電池用セパレータの形状安定性とシャットダウン特性のバランスがとれたものとなる。更に好ましくは０．５〜５％である。 The thermal contraction rate at 105 ° C. of the separator for a non-aqueous secondary battery of the present invention is preferably 0.5 to 10%. When the heat shrinkage rate is within this range, the shape stability and shutdown characteristics of the non-aqueous secondary battery separator are balanced. More preferably, it is 0.5 to 5%.
［耐熱性多孔質層］
本発明において、耐熱性多孔質層としては、微多孔膜状、不織布状、紙状、その他三次元ネットーワーク状の多孔質構造を有した層を挙げることができるが、より優れた耐熱性が得られる点で、微多孔膜状の層であることが好ましい。ここで、微多孔膜状の層とは、内部に多数の微細孔を有し、これら微細孔が連結された構造となっており、一方の面から他方の面へと気体あるいは液体が通過可能となった層のことを言う。
[Heat-resistant porous layer]
In the present invention, examples of the heat-resistant porous layer include microporous film-like, non-woven fabric, paper-like, and other layers having a three-dimensional network-like porous structure. From the viewpoint of being obtained, the layer is preferably a microporous film. Here, the microporous film-like layer has a large number of micropores inside, and has a structure in which these micropores are connected. Gas or liquid can pass from one surface to the other. It says the layer that became.
本発明で用いられる耐熱性樹脂は、融点２００℃以上のポリマー、あるいは融点を有しないが分解温度が２００℃以上のポリマーが適当である。このような耐熱性樹脂の好ましい例としては、全芳香族ポリアミド、ポリイミド、ポリアミドイミド、ポリスルホン、ポリケトン、ポリエーテルケトン、ポリエーテルイミドおよびセルロースからなる群から選ばれる少なくとも１種の樹脂が挙げられる。特に、耐久性の観点から全芳香族ポリアミドが好適であり、多孔質層を形成しやすく耐酸化還元性に優れるという観点から、メタ型全芳香族ポリアミドであるポリメタフェニレンイソフタルアミドがさらに好適である。 The heat-resistant resin used in the present invention is suitably a polymer having a melting point of 200 ° C. or higher, or a polymer having no melting point but having a decomposition temperature of 200 ° C. or higher. Preferable examples of such heat-resistant resins include at least one resin selected from the group consisting of wholly aromatic polyamides, polyimides, polyamideimides, polysulfones, polyketones, polyether ketones, polyether imides, and celluloses. In particular, wholly aromatic polyamides are preferable from the viewpoint of durability, and polymetaphenylene isophthalamide, which is a meta-type wholly aromatic polyamide, is more preferable from the viewpoint of easy formation of a porous layer and excellent redox resistance. is there.
本発明において、耐熱性多孔質層はポリオレフィン微多孔膜の両面または片面に形成すればよいが、ハンドリング性、耐久性および熱収縮の抑制効果の観点から、基材の表裏両面に形成した方が好ましい。なお、耐熱性多孔質層を基材上に固定するためには、耐熱性多孔質層を塗工法により基材上に直接形成する手法が好ましいが、これに限らず、別途製造した耐熱性多孔質層のシートを基材上に接着剤等を用いて接着する手法や、熱融着や圧着などの手法も採用することができる。 In the present invention, the heat-resistant porous layer may be formed on both surfaces or one surface of the polyolefin microporous membrane. However, from the viewpoint of handling properties, durability, and the effect of suppressing heat shrinkage, it is preferable to form the heat-resistant porous layer on both surfaces of the substrate. preferable. In order to fix the heat-resistant porous layer on the substrate, a method in which the heat-resistant porous layer is directly formed on the substrate by a coating method is preferable. A technique of adhering the quality layer sheet on the base material using an adhesive or the like, a technique such as heat fusion or pressure bonding can also be employed.
本発明において、耐熱性多孔質層の厚みについては、耐熱性多孔質層が基材の両面に形成されている場合は、耐熱性多孔質層の厚みの合計が３μｍ以上１２μｍ以下であることが好ましく、耐熱性多孔質層が基材の片面にのみ形成されている場合は耐熱性多孔質層の厚みが３μｍ以上１２μｍ以下であることが好ましい。このような膜厚の範囲は、液枯れの防止効果の観点からも好ましい。
本発明において、耐熱性多孔質層の空孔率は、液枯れの防止効果の観点から、３０〜９０％の範囲が好適である。より好ましくは３０〜７０％である。
In the present invention, regarding the thickness of the heat resistant porous layer, when the heat resistant porous layer is formed on both surfaces of the substrate, the total thickness of the heat resistant porous layer may be 3 μm or more and 12 μm or less. Preferably, when the heat resistant porous layer is formed only on one side of the substrate, the thickness of the heat resistant porous layer is preferably 3 μm or more and 12 μm or less. Such a range of the film thickness is also preferable from the viewpoint of the effect of preventing liquid withstand.
In the present invention, the porosity of the heat-resistant porous layer is preferably in the range of 30 to 90% from the viewpoint of the effect of preventing liquid withstand. More preferably, it is 30 to 70%.
［無機フィラー］
本発明において、耐熱性多孔質層には無機フィラーが含まれていることが好ましい。無機フィラーとしては、特に限定はないが、具体的にはアルミナ、チタニア、シリカ、ジルコニアなどの金属酸化物、炭酸カルシウムなどの金属炭酸塩、リン酸カルシウムなどの金属リン酸塩、水酸化アルミニウム、水酸化マグネシウムなどの金属水酸化物などが好適に用いられる。このような無機フィラーは、不純物の溶出や耐久性の観点から結晶性の高いものが好ましい。
[Inorganic filler]
In the present invention, the heat resistant porous layer preferably contains an inorganic filler. The inorganic filler is not particularly limited, but specifically, metal oxides such as alumina, titania, silica, zirconia, metal carbonates such as calcium carbonate, metal phosphates such as calcium phosphate, aluminum hydroxide, hydroxide A metal hydroxide such as magnesium is preferably used. Such an inorganic filler is preferably highly crystalline from the viewpoints of impurity elution and durability.
中でも、無機フィラーとしては、２００〜４００℃において吸熱反応を生じるものであるものが好ましい。この様な特性を有する無機フィラーとして、特に限定されないが、金属水酸化物、硼素塩化合物または粘土鉱物等からなる無機フィラーであって、２００〜４００℃において吸熱反応を生じるものが挙げられる。具体的には、例えば、水酸化アルミニウムや水酸化マグネシウム、アルミン酸カルシウム、ドーソナイト、硼酸亜鉛等が挙げられ、これらは単独若しくは２種以上を組合せて用いることができる。また、これらの難燃性の無機フィラーには、アルミナやジルコニア、シリカ、マグネシア、チタニア等の金属酸化物、金属窒化物、金属炭化物、金属炭酸塩などの他の無機フィラーを適宜混合して用いることもできる。 Especially, as an inorganic filler, what produces an endothermic reaction in 200-400 degreeC is preferable. Although it does not specifically limit as an inorganic filler which has such a characteristic, It is an inorganic filler which consists of a metal hydroxide, a boron salt compound, or a clay mineral, Comprising: What produces an endothermic reaction in 200-400 degreeC is mentioned. Specific examples include aluminum hydroxide, magnesium hydroxide, calcium aluminate, dosonite, zinc borate and the like, and these can be used alone or in combination of two or more. In addition, these flame retardant inorganic fillers are appropriately mixed with other inorganic fillers such as metal oxides such as alumina, zirconia, silica, magnesia, and titania, metal nitrides, metal carbides, and metal carbonates. You can also.
ここで、非水系二次電池では、正極の分解に伴う発熱が最も危険と考えられており、この分解は３００℃近傍で起こる。このため、吸熱反応の発生温度が２００℃〜４００℃の範囲であれば、非水系二次電池の発熱を防ぐ上で有効である。例えば、水酸化アルミニウムやドーソナイト、アルミン酸カルシウムは２００〜３００℃の範囲において脱水反応が起こり、また、水酸化マグネシウムや硼酸亜鉛は３００〜４００℃の範囲において脱水反応が起こるため、これらの無機フィラーのうち少なくともいずれか一種を用いることが好ましい。 Here, in the non-aqueous secondary battery, heat generation accompanying the decomposition of the positive electrode is considered to be the most dangerous, and this decomposition occurs in the vicinity of 300 ° C. For this reason, if the generation | occurrence | production temperature of endothermic reaction is the range of 200 to 400 degreeC, it is effective in preventing the heat_generation | fever of a non-aqueous secondary battery. For example, aluminum hydroxide, dawsonite, and calcium aluminate undergo a dehydration reaction in the range of 200 to 300 ° C, and magnesium hydroxide and zinc borate undergo a dehydration reaction in the range of 300 to 400 ° C. It is preferable to use at least one of them.
特に本発明では、無機フィラーは難燃性の向上効果、ハンドリング性、除電効果、電池の耐久性の改善効果の観点から、金属水酸化物からなることが好ましい。中でも水酸化アルミニウムまたは水酸化マグネシウムであることが好ましい。 In particular, in the present invention, the inorganic filler is preferably made of a metal hydroxide from the viewpoints of flame retardancy improving effect, handling property, charge eliminating effect, and battery durability improving effect. Of these, aluminum hydroxide or magnesium hydroxide is preferred.
本発明において、無機フィラーの平均粒子径は、高温時の耐短絡性や成形性等の観点から、０．１〜２μｍの範囲が好ましい。
本発明において、耐熱性多孔質層における無機フィラーの含有量は、耐熱性向上効果、透過性およびハンドリング性の観点から、５０〜９５重量％であることが好ましい。
In the present invention, the average particle diameter of the inorganic filler is preferably in the range of 0.1 to 2 μm from the viewpoint of short circuit resistance at high temperature, moldability, and the like.
In this invention, it is preferable that content of the inorganic filler in a heat resistant porous layer is 50 to 95 weight% from a heat resistant improvement effect, a permeability, and a viewpoint of handling property.
なお、耐熱性多孔質層中の無機フィラーは、耐熱性多孔質層が微多孔膜状である場合は耐熱性樹脂に捕捉された状態で存在しており、耐熱性多孔質層が不織布等の場合は構成繊維中に存在するか、樹脂などのバインダーにより不織布表面等に固定されていればよい。 In addition, the inorganic filler in the heat resistant porous layer is present in a state of being trapped by the heat resistant resin when the heat resistant porous layer is in the form of a microporous film, and the heat resistant porous layer is a nonwoven fabric or the like. In such a case, it may be present in the constituent fibers or fixed to the nonwoven fabric surface or the like with a binder such as a resin.
［耐熱性多孔質層の製造法］
本発明において、非水系二次電池用セパレータの製造法は、上述した構成の本発明のセパレータが製造できれば特に限定されないが、例えば下記（１）〜（５）の工程を経て製造することが可能である。
[Method for producing heat-resistant porous layer]
In the present invention, the method for producing a separator for a non-aqueous secondary battery is not particularly limited as long as the separator of the present invention having the above-described configuration can be produced. For example, it can be produced through the following steps (1) to (5). It is.
（１）塗工用スラリーの作製
耐熱性樹脂を溶剤に溶かし、塗工用スラリーを作製する。溶剤は耐熱性樹脂を溶解するものであればよく、特に限定は無いが、具体的には極性溶剤が好ましく、例えばＮ−メチルピロリドン、ジメチルアセトアミド、ジメチルホルムアミド、ジメチルスルホキシドなどが挙げられる。また、当該溶剤はこれらの極性溶剤に加えて耐熱性樹脂に対して貧溶剤となる溶剤も加えることができる。このような貧溶剤を適用することでミクロ相分離構造が誘発され、耐熱性多孔質層を形成する上で多孔化が容易となる。貧溶剤としては、アルコールの類が好適であり、特にグリコールのような多価アルコールが好適である。塗工用スラリー中の耐熱性樹脂の濃度は４〜９重量％が好ましい。また必要に応じ、これに無機フィラーを分散させて塗工用スラリーとする。塗工用スラリー中に無機フィラーを分散させるに当たって、無機フィラーの分散性が好ましくないときは、無機フィラーをシランカップリング剤などで表面処理し、分散性を改善する手法も適用可能である。
(1) Preparation of coating slurry A heat-resistant resin is dissolved in a solvent to prepare a coating slurry. The solvent is not particularly limited as long as it dissolves the heat-resistant resin, but specifically, a polar solvent is preferable, and examples thereof include N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and dimethylsulfoxide. Moreover, the said solvent can add the solvent used as a poor solvent with respect to heat resistant resin in addition to these polar solvents. By applying such a poor solvent, a microphase separation structure is induced and the formation of a heat-resistant porous layer is facilitated. As the poor solvent, alcohols are preferable, and polyhydric alcohols such as glycol are particularly preferable. The concentration of the heat resistant resin in the coating slurry is preferably 4 to 9% by weight. Moreover, an inorganic filler is disperse | distributed to this as needed, and it is set as the slurry for coating. In dispersing the inorganic filler in the coating slurry, when the dispersibility of the inorganic filler is not preferable, a method of improving the dispersibility by surface-treating the inorganic filler with a silane coupling agent or the like is also applicable.
（２）スラリーの塗工
スラリーをポリオレフィン微多孔膜の少なくとも一方の表面に塗工する。ポリオレフィン微多孔膜の両面に耐熱性多孔質層を形成する場合は、基材の両面に同時に塗工することが、工程の短縮という観点で好ましい。塗工用スラリーを塗工する方法としては、ナイフコーター法、グラビアコーター法、スクリーン印刷法、マイヤーバー法、ダイコーター法、リバースロールコーター法、インクジェット法、スプレー法、ロールコーター法などが挙げられる。この中でも、塗膜を均一に形成するという観点において、リバースロールコーター法が好適である。基材の両面に同時に塗工する場合は、例えば、基材を一対のマイヤーバーの間に通すことで基材の両面に過剰な塗工用スラリーを塗布し、これを一対のリバースロールコーターの間に通して過剰なスラリーを掻き落すことで精密計量するという方法が挙げられる。
(2) Coating of slurry The slurry is coated on at least one surface of the polyolefin microporous membrane. When forming a heat-resistant porous layer on both surfaces of a polyolefin microporous film, it is preferable from a viewpoint of shortening of a process to apply simultaneously on both surfaces of a base material. Examples of the method for coating the slurry for coating include a knife coater method, a gravure coater method, a screen printing method, a Meyer bar method, a die coater method, a reverse roll coater method, an ink jet method, a spray method, and a roll coater method. . Among these, the reverse roll coater method is preferable from the viewpoint of uniformly forming a coating film. When applying simultaneously to both sides of the base material, for example, by passing the base material between a pair of Meyer bars, an excess coating slurry is applied to both sides of the base material, and this is applied to a pair of reverse roll coaters. There is a method of precise measurement by scraping off excess slurry in between.
（３）スラリーの凝固
スラリーが塗工された基材を、前記耐熱性樹脂を凝固させることが可能な凝固液で処理する。塗工用スラリーを塗工した基材を、当該耐熱性樹脂を凝固させることが可能な凝固液で処理することにより、耐熱性樹脂を凝固させて、耐熱性多孔質層を形成する。凝固液で処理する方法としては、塗工用スラリーを塗工した基材に対して凝固液をスプレーで吹き付ける方法や、当該基材を凝固液の入った浴（凝固浴）中に浸漬する方法などが挙げられる。ここで、凝固浴を設置する場合は、塗工装置の下方に設置することが好ましい。凝固液としては、当該耐熱性樹脂を凝固できるものであれば特に限定されないが、水、または、スラリーに用いた溶剤に水を適当量混合させたものが好ましい。ここで、水の混合量は凝固液に対して４０〜８０重量％が好適である。水の量が４０重量％より少ないと、耐熱性樹脂を凝固するのに必要な時間が長くなったり、凝固が不十分になったりという問題が生じる。また、水の量が８０重量％より多いと、溶剤回収においてコスト高となったり、凝固液と接触する表面の凝固が速くなりすぎて表面が十分に多孔化されなかったりという問題が生じる。
(3) Solidification of slurry The base material on which the slurry is applied is treated with a coagulating liquid capable of coagulating the heat-resistant resin. The substrate coated with the coating slurry is treated with a coagulating liquid capable of coagulating the heat resistant resin, so that the heat resistant resin is solidified to form a heat resistant porous layer. As a method of treating with the coagulating liquid, a method of spraying the coagulating liquid on the substrate coated with the coating slurry, or a method of immersing the substrate in a bath (coagulating bath) containing the coagulating liquid. Etc. Here, when installing a coagulation bath, it is preferable to install it below the coating apparatus. The coagulation liquid is not particularly limited as long as it can coagulate the heat-resistant resin, but water or a solution obtained by mixing an appropriate amount of water with the solvent used in the slurry is preferable. Here, the mixing amount of water is preferably 40 to 80% by weight with respect to the coagulation liquid. When the amount of water is less than 40% by weight, there arises a problem that the time required for solidifying the heat-resistant resin becomes long or the solidification becomes insufficient. On the other hand, when the amount of water is more than 80% by weight, there arises a problem that the cost for solvent recovery becomes high, or the surface that comes into contact with the coagulation liquid is solidified too quickly and the surface is not sufficiently porous.
（４）凝固液の除去
凝固液を水洗することによって除去する。
(4) Removal of coagulating liquid The coagulating liquid is removed by washing with water.
（５）乾燥
シートから水を乾燥して除去する。乾燥方法は特に限定は無いが、乾燥温度は５０〜８０℃が好適であり、高い乾燥温度を適用する場合は熱収縮による寸法変化が起こらないようにするためにロールに接触させるような方法を適用することが好ましい。
(5) Drying Dry and remove water from the sheet. Although there is no particular limitation on the drying method, the drying temperature is preferably 50 to 80 ° C. When a high drying temperature is applied, a method of contacting with a roll to prevent dimensional change due to heat shrinkage. It is preferable to apply.
［非水系二次電池］
本発明の非水系二次電池は、リチウムのドープ・脱ドープにより起電力を得る非水系二次電池であって、上述した構成の非水系二次電池用セパレータを用いたことを特徴とする。非水系二次電池は、負極と正極がセパレータを介して対向している電池要素に電解液が含浸され、これが外装に封入された構造となっている。
[Non-aqueous secondary battery]
The non-aqueous secondary battery of the present invention is a non-aqueous secondary battery that obtains an electromotive force by doping or dedoping lithium, and is characterized by using the separator for a non-aqueous secondary battery having the above-described configuration. The non-aqueous secondary battery has a structure in which a battery element in which a negative electrode and a positive electrode face each other with a separator interposed therebetween is impregnated with an electrolytic solution, and this is enclosed in an exterior.
負極は、負極活物質、導電助剤およびバインダーからなる負極合剤が、集電体上に成形された構造となっている。負極活物質としては、リチウムを電気化学的にドープすることが可能な材料が挙げられ、例えば炭素材料、シリコン、アルミニウム、スズ、ウッド合金などが挙げられる。特に本発明のセパレータによる液枯れ防止効果を活かすという観点では、負極活物質としてはリチウムを脱ドープする過程における体積変化率が３％以上となるものを用いることが好ましい。かかる負極活物質としては、例えばＳｎ、ＳｎＳｂ、Ａｇ３Ｓｎ、人造黒鉛、グラファイト、Ｓｉ、ＳｉＯ、Ｖ５Ｏ４等が挙げられる。導電助剤は、アセチレンブラック、ケッチェンブラックといった炭素材料が挙げられる。バインダーは有機高分子からなり、例えばポリフッ化ビニリデン、カルボキシメチルセルロースなどが挙げられる。集電体には銅箔、ステンレス箔、ニッケル箔などを用いることが可能である。 The negative electrode has a structure in which a negative electrode mixture composed of a negative electrode active material, a conductive additive and a binder is formed on a current collector. Examples of the negative electrode active material include materials capable of electrochemically doping lithium, and examples thereof include carbon materials, silicon, aluminum, tin, and wood alloys. In particular, from the viewpoint of utilizing the effect of preventing the liquid withering by the separator of the present invention, it is preferable to use a negative electrode active material having a volume change rate of 3% or more in the process of dedoping lithium. Examples of the negative electrode active material include Sn, SnSb, Ag 3 Sn, artificial graphite, graphite, Si, SiO, V 5 O 4 and the like. Examples of the conductive assistant include carbon materials such as acetylene black and ketjen black. The binder is made of an organic polymer, and examples thereof include polyvinylidene fluoride and carboxymethyl cellulose. As the current collector, a copper foil, a stainless steel foil, a nickel foil, or the like can be used.
正極は、正極活物質、導電助剤およびバインダーからなる正極合剤が、集電体上に成形された構造となっている。正極活物質としては、リチウム含有遷移金属酸化物等が挙げられ、具体的にはＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＭｎ０．５Ｎｉ０．５Ｏ２、ＬｉＣｏ１／３Ｎｉ１／３Ｍｎ１／３Ｏ２、ＬｉＭｎ２Ｏ４、ＬｉＦｅＰＯ４、ＬｉＣｏ０．５Ｎｉ０．５Ｏ２、ＬｉＡｌ０．２５Ｎｉ０．７５Ｏ２等が挙げられる。特に本発明のセパレータによる液枯れ防止効果を活かすという観点では、正極活物質としてはリチウムを脱ドープする過程における体積変化率が１％以上となるものを用いることが好ましい。かかる正極活物質としては、例えばＬｉＭｎ２Ｏ４、ＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＣｏ０．５Ｎｉ０．５Ｏ２、ＬｉＡｌ０．２５Ｎｉ０．７５Ｏ２等が挙げられる。導電助剤はアセチレンブラック、ケッチェンブラックといった炭素材料が挙げられる。バインダーは有機高分子からなり、例えばポリフッ化ビニリデンなどが挙げられる。集電体にはアルミ箔、ステンレス箔、チタン箔などを用いることが可能である。 The positive electrode has a structure in which a positive electrode mixture composed of a positive electrode active material, a conductive additive and a binder is formed on a current collector. Examples of the positive electrode active material include lithium-containing transition metal oxides. Specifically, LiCoO 2 , LiNiO 2 , LiMn 0.5 Ni 0.5 O 2 , LiCo 1/3 Ni 1/3 Mn 1/3 Examples include O 2 , LiMn 2 O 4 , LiFePO 4 , LiCo 0.5 Ni 0.5 O 2 , LiAl 0.25 Ni 0.75 O 2, and the like. In particular, from the viewpoint of utilizing the effect of preventing liquid withering by the separator of the present invention, it is preferable to use a positive electrode active material having a volume change rate of 1% or more in the process of dedoping lithium. Examples of such a positive electrode active material include LiMn 2 O 4 , LiCoO 2 , LiNiO 2 , LiCo 0.5 Ni 0.5 O 2 , LiAl 0.25 Ni 0.75 O 2 and the like. Examples of the conductive assistant include carbon materials such as acetylene black and ketjen black. The binder is made of an organic polymer, and examples thereof include polyvinylidene fluoride. As the current collector, aluminum foil, stainless steel foil, titanium foil, or the like can be used.
電解液は、リチウム塩を非水系溶媒に溶解した構成である。リチウム塩としては、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４などが挙げられる。非水系溶媒としては、プロピレンカーボネート、エチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、γ−ブチロラクトン、ビニレンカーボネートなどが挙げられ、これらは単独で用いても混合して用いてもよい。 The electrolytic solution has a structure in which a lithium salt is dissolved in a non-aqueous solvent. Examples of the lithium salt include LiPF 6 , LiBF 4 , LiClO 4 and the like. Examples of the non-aqueous solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, vinylene carbonate, and the like. These may be used alone or in combination.
外装材は、金属缶またはアルミラミネートパック等が挙げられる。電池の形状は角型、円筒型、コイン型などがあるが、本発明のセパレータはいずれの形状においても好適に適用することが可能である。 Examples of the exterior material include a metal can or an aluminum laminate pack. The shape of the battery includes a square shape, a cylindrical shape, a coin shape, and the like, but the separator of the present invention can be suitably applied to any shape.
以下に実施例を示すが、本発明はこれらに制限されるものではない。
［測定方法］
本実施例における各値は、以下の方法に従って求めた。
（１）ポリオレフィン微多孔膜及び非水系二次電池用セパレータの膜厚は、接触式の膜厚計（ミツトヨ社製）にて２０点測定し、これを平均することで求めた。ここで接触端子は底面が直径０．５ｃｍの円柱状のものを用いた。
Examples are shown below, but the present invention is not limited thereto.
[Measuring method]
Each value in this example was determined according to the following method.
(1) The film thickness of the polyolefin microporous membrane and the separator for a non-aqueous secondary battery was determined by measuring 20 points with a contact-type film thickness meter (manufactured by Mitutoyo Corporation) and averaging them. Here, the contact terminal used was a cylindrical one having a bottom surface of 0.5 cm in diameter.
（２）ポリオレフィン微多孔膜及び非水系二次電池用セパレータの目付は、サンプルを１０ｃｍ×１０ｃｍに切り出し重量を測定する。この重量を面積で割ることで１ｍ２当たりの重量である目付を求めた。 (2) The basis weight of the polyolefin microporous membrane and the separator for a non-aqueous secondary battery is obtained by cutting a sample into 10 cm × 10 cm and measuring the weight. By dividing this weight by the area, the basis weight which is the weight per 1 m 2 was obtained.
（３）ポリオレフィン微多孔膜及び非水系二次電池用セパレータの空孔率は、下記式から求めた。
ε＝｛１−Ｗｓ／（ｄｓ・ｔ）｝×１００
ここで、ε：空隙率（％）、Ｗｓ：目付（ｇ／ｍ２）、ｄｓ：真密度（ｇ／ｃｍ３）、ｔ：膜厚（μｍ）である。
(3) The porosity of the polyolefin microporous membrane and the non-aqueous secondary battery separator was determined from the following formula.
ε = {1-Ws / (ds · t)} × 100
Here, ε: porosity (%), Ws: basis weight (g / m 2 ), ds: true density (g / cm 3 ), and t: film thickness (μm).
（４）ポリオレフィン微多孔膜及び非水系二次電池用セパレータのガーレ値はＪＩＳ Ｐ８１１７に従って求めた。 (4) The Gurley values of the polyolefin microporous membrane and the non-aqueous secondary battery separator were determined according to JIS P8117.
（５）ポリオレフィン微多孔膜及び非水系二次電池用セパレータの膜抵抗は、以下の方法で求めた。
まず、サンプルを２．６ｃｍ×２．０ｃｍのサイズに切り出す。非イオン性界面活性剤（花王社製エマルゲン２１０Ｐ）を３重量％溶解したメタノール溶液（メタノール：和光純薬社製）に切り出したサンプルを浸漬し、風乾する。厚さ２０μｍのアルミ箔を２．０ｃｍ×１．４ｃｍに切り出しリードタブを付ける。このアルミ箔を２枚用意して、アルミ箔間に切り出したサンプルをアルミ箔が短絡しないように挟む。サンプルに電解液である１ＭのＬｉＢＦ４ プロピレンカーボネート／エチレンカーボネート（１／１重量比）を含浸させる。これをアルミラミネートパック中にタブがアルミパックの外に出るようにして減圧封入する。このようなセルをアルミ箔中にセパレータが１枚、２枚、３枚となるようにそれぞれ作製する。該セルを２０℃の恒温槽中に入れ、交流インピーダンス法で振幅１０ｍＶ、周波数１００ｋＨｚにて該セルの抵抗を測定する。測定されたセルの抵抗値をセパレータの枚数に対してプロットし、このプロットを線形近似し傾きを求める。この傾きに電極面積である２．０ｃｍ×１．４ｃｍを乗じてセパレータ１枚当たりの膜抵抗（ｏｈｍ・ｃｍ２）を求めた。
(5) The membrane resistance of the polyolefin microporous membrane and the non-aqueous secondary battery separator was determined by the following method.
First, a sample is cut out to a size of 2.6 cm × 2.0 cm. A sample cut out in a methanol solution (methanol: manufactured by Wako Pure Chemical Industries, Ltd.) in which 3% by weight of a nonionic surfactant (Emalgen 210P manufactured by Kao Corporation) is dissolved is immersed and air-dried. A 20 μm thick aluminum foil is cut into 2.0 cm × 1.4 cm and a lead tab is attached. Two aluminum foils are prepared, and a sample cut between the aluminum foils is sandwiched so that the aluminum foils are not short-circuited. The sample is impregnated with 1M LiBF 4 propylene carbonate / ethylene carbonate (1/1 weight ratio) as an electrolyte. This is sealed under reduced pressure in an aluminum laminate pack so that the tab comes out of the aluminum pack. Such cells are prepared so that there are one, two, and three separators in the aluminum foil, respectively. The cell is placed in a constant temperature bath at 20 ° C., and the resistance of the cell is measured by an AC impedance method at an amplitude of 10 mV and a frequency of 100 kHz. The measured resistance value of the cell is plotted against the number of separators, and the plot is linearly approximated to obtain the slope. The film resistance (ohm · cm 2 ) per separator was determined by multiplying the inclination by 2.0 cm × 1.4 cm which is the electrode area.
（６）ポリオレフィン微多孔膜及び非水系二次電池用セパレータの突刺強度は、カトーテック社製ＫＥＳ−Ｇ５ハンディー圧縮試験器を用いて、針先端の曲率半径０．５ｍｍ、突刺速度２ｍｍ／ｓｅｃの条件で突刺試験を行い、最大突刺荷重を突刺強度とした。ここでサンプルはΦ１１．３ｍｍの穴があいた金枠（試料ホルダー）にシリコンゴム製のパッキンも一緒に挟み固定した。 (6) The piercing strength of the polyolefin microporous membrane and the separator for the non-aqueous secondary battery was measured using a KES-G5 handy compression tester manufactured by Kato Tech Co., with a radius of curvature of the needle tip of 0.5 mm and a piercing speed of 2 mm / sec. The puncture test was performed under the conditions, and the maximum puncture load was defined as the puncture strength. Here, the sample was fixed by sandwiching a silicon rubber packing in a metal frame (sample holder) having a hole of Φ11.3 mm.
（７）ポリオレフィン微多孔膜及び非水系二次電池用セパレータの引張強度は、１０×１００ｍｍに調整したサンプルを引張試験機（Ａ＆Ｄ社製、ＲＴＣ−１２２５Ａ）を用い、ロードセル荷重５ｋｇｆ、チャック間距離５０ｍｍの条件で測定した。 (7) Tensile strength of polyolefin microporous membrane and non-aqueous secondary battery separator was adjusted to 10 × 100 mm using a tensile tester (A & D, RTC-1225A), load cell load 5 kgf, distance between chucks Measurement was performed under the condition of 50 mm.
（８）ポリオレフィン微多孔膜の結晶性パラメータは、Ｘ線解析装置（リガク社製、ＲＡＤ−Ｂ型）を用いて測定した。
具体的に、ポリオレフィンの配向軸１、配向軸２の機械方向に対する角度は、Ｘ線の回折像で強くピークが現れた２つの方向に向かい、９０度ずらした方向を配向軸の方向として求めた。
配向全体の積分値に占める配向軸１の積分値の割合は、２θ＝２１．３、２３．７、２９．８付近のピークを配向軸１、配向軸２においてスキャンして得られた強度分布のピークの積分強度から下記式により算出した。
（配向全体の積分値に占める配向軸１の積分値の割合）＝（配向軸１の積分強度）／［（配向軸１の積分強度）＋（配向軸２の積分強度）］×１００
配向軸１、配向軸２の配向度は、配向度は、２θ＝２１．３、２３．７、２９．８付近のピークを配向軸１、配向軸２においてスキャンして得られた強度分布のピークの半値幅から下記式により算出した。なお、Ｈは強度分布のピークの半値幅を意味する。
配向度＝［（１８０−Ｈ）／１８０］×１００
(8) The crystallinity parameter of the microporous polyolefin membrane was measured using an X-ray analyzer (RAD-B type, manufactured by Rigaku Corporation).
Specifically, the angles of the orientation axis 1 and the orientation axis 2 of the polyolefin with respect to the machine direction were found in two directions where strong peaks appeared in the X-ray diffraction image, and the direction shifted by 90 degrees was obtained as the orientation axis direction. .
The ratio of the integral value of the orientation axis 1 to the integral value of the whole orientation is the intensity distribution obtained by scanning the peaks around 2θ = 21.3, 23.7, 29.8 in the orientation axis 1 and the orientation axis 2. From the integrated intensity of the peak, the following formula was used.
(Ratio of the integrated value of the alignment axis 1 to the integrated value of the entire alignment) = (integral intensity of the alignment axis 1) / [(integral intensity of the alignment axis 1) + (integral intensity of the alignment axis 2)] × 100
The orientation degree of the orientation axis 1 and the orientation axis 2 is the intensity distribution obtained by scanning the orientation axis 1 and the orientation axis 2 for peaks near 2θ = 21.3, 23.7 and 29.8. It calculated from the following formula from the half width of the peak. Note that H means the half width of the peak of the intensity distribution.
Degree of orientation = [(180−H) / 180] × 100
（９）ポリオレフィン微多孔膜及び非水系二次電池用セパレータのシャットダウン温度は、以下の方法で求めた。
まず、サンプルを直径１９ｍｍに打ち抜き、非イオン性界面活性剤（花王社製エマルゲン２１０Ｐ）を３重量％溶解したメタノール溶液（メタノール：和光純薬社製）に切り出したサンプルを浸漬し、風乾した。サンプルを直径１５．５ｍｍのＳＵＳ板に挟んだ。サンプルに電解液である１ＭのＬｉＢＦ４ プロピレンカーボネート／エチレンカーボネート（１／１重量比）（キシダ化学社製）を含浸させた。これを２０３２型コインセルに封入した。コインセルからリード線をとり、熱電対を付けてオーブンの中に入れた。昇温速度１．６℃／分で昇温させ、同時に交流インピーダンス法で振幅１０ｍＶ、周波数１００ｋＨｚにて該セルの抵抗を測定した。抵抗値が１０３ｏｈｍ・ｃｍ２以上となった温度をシャットダウン温度とした。
(9) The shutdown temperature of the polyolefin microporous membrane and the non-aqueous secondary battery separator was determined by the following method.
First, a sample was punched into a diameter of 19 mm, and the sample cut out in a methanol solution (methanol: manufactured by Wako Pure Chemical Industries, Ltd.) in which 3% by weight of a nonionic surfactant (Emulgen 210P manufactured by Kao Co., Ltd.) was dissolved was immersed and air-dried. The sample was sandwiched between SUS plates having a diameter of 15.5 mm. The sample was impregnated with 1M LiBF 4 propylene carbonate / ethylene carbonate (1/1 weight ratio) (manufactured by Kishida Chemical Co., Ltd.) as an electrolyte. This was enclosed in a 2032 type coin cell. I took the lead from the coin cell, put a thermocouple, and put it in the oven. The temperature of the cell was increased at a rate of temperature increase of 1.6 ° C./min, and the resistance of the cell was measured at the same time by the AC impedance method at an amplitude of 10 mV and a frequency of 100 kHz. The temperature at which the resistance value reached 10 3 ohm · cm 2 or more was taken as the shutdown temperature.
（１０）非水系二次電池用セパレータの耐熱性は、上記（９）のシャットダウン温度を測定した際に、シャットダウンが発現してからセル温度が２００℃になるまでに、抵抗値が１０３ｏｈｍ・ｃｍ２以上を維持し続けるかどうかにより評価した。抵抗値が１０３ｏｈｍ・ｃｍ２以上を維持し続ければ耐熱性が良好（〇）と判断し、抵抗値が１０３ｏｈｍ・ｃｍ２を下回れば耐熱性が不良（×）と判断した。 (10) The heat resistance of the non-aqueous secondary battery separator is such that when the shutdown temperature of (9) is measured, the resistance value is 10 3 ohms until the cell temperature reaches 200 ° C. after the shutdown occurs. -Evaluated by whether or not to continue to maintain cm 2 or more. When the resistance value was kept at 10 3 ohm · cm 2 or more, the heat resistance was judged as good (◯), and when the resistance value was below 10 3 ohm · cm 2 , the heat resistance was judged as poor (×).
（１１）ポリオレフィン微多孔膜及び非水系二次電池用セパレータの熱収縮率は、サンプル１０５℃で１時間加熱することによって測定した。なお、測定方向は機械方向である。 (11) The thermal shrinkage of the polyolefin microporous membrane and the non-aqueous secondary battery separator was measured by heating at 105 ° C. for 1 hour. Note that the measurement direction is the machine direction.
（１２）ポリオレフィン微多孔膜及び非水系二次電池用セパレータの液枯れ防止効果は、以下の加圧回復率を測定して評価した。
まず、サンプル２．６ｃｍ×２．０ｃｍのサイズに切り出した。非イオン性界面活性剤（花王社製；エマルゲン２１０Ｐ）を３重量％溶解したメタノール溶液に、切り出したサンプルを浸漬し、風乾した。厚さ２０μｍのアルミ箔を、２．０ｃｍ×１．４ｃｍに切り出しリードタブを付けた。このアルミ箔を２枚用意して、アルミ箔間に切り出したセパレータを、アルミ箔が短絡しないように挟んだ。電解液には、プロピレンカーボネートとエチレンカーボネートが１対１の重量比で混合された溶媒中にＬｉＢＦ４を１Ｍ溶解させたものを用い、この電解液を上記サンプルに含浸させた。これをアルミラミネートパック中に、タブがアルミパックの外に出るようにして減圧封入した。このセルの抵抗を交流インピーダンス法で、振幅１０ｍＶ、周波数１００ｋＨｚにて測定し、加圧前の抵抗値（A）（ｏｈｍ・ｃｍ２）を求めた。次にこのセルを平板プレス機で４０MPaとなるように５分間加圧し、続いて圧力を開放した。この操作を５回繰り返し、加圧後圧力を開放したセルの抵抗値（Ｂ）（ｏｈｍ・ｃｍ２）を測定した。そして、下式により加圧回復率を求めた。なお、加圧回復率が高いほど、液枯れ防止効果に優れているといえる。
加圧回復率＝抵抗値（Ｂ）／抵抗値（A）×１００（％）
(12) The effect of preventing liquid withering of the polyolefin microporous membrane and the non-aqueous secondary battery separator was evaluated by measuring the following pressure recovery rate.
First, the sample was cut into a size of 2.6 cm × 2.0 cm. The cut sample was immersed in a methanol solution in which 3% by weight of a nonionic surfactant (manufactured by Kao Corporation; Emulgen 210P) was dissolved and air-dried. A 20 μm thick aluminum foil was cut into 2.0 cm × 1.4 cm, and a lead tab was attached. Two aluminum foils were prepared, and a separator cut between the aluminum foils was sandwiched between the aluminum foils so that the aluminum foils were not short-circuited. As the electrolytic solution, a solution in which 1M LiBF 4 was dissolved in a solvent in which propylene carbonate and ethylene carbonate were mixed at a weight ratio of 1: 1 was used, and the above sample was impregnated with the electrolytic solution. This was sealed in an aluminum laminate pack under reduced pressure so that the tabs came out of the aluminum pack. The resistance of this cell was measured by an alternating current impedance method at an amplitude of 10 mV and a frequency of 100 kHz, and a resistance value (A) (ohm · cm 2 ) before pressurization was obtained. Next, this cell was pressurized with a flat plate press to 40 MPa for 5 minutes, and then the pressure was released. This operation was repeated 5 times, and the resistance value (B) (ohm · cm 2 ) of the cell whose pressure was released after pressurization was measured. And the pressure recovery rate was calculated | required by the following Formula. In addition, it can be said that the higher the pressure recovery rate is, the better the effect of preventing liquid withering.
Pressure recovery rate = resistance value (B) / resistance value (A) × 100 (%)
（１３）非水系二次電池用セパレータの工程通過性は、以下のようにして評価した。
まず、上記（７）と同様のサンプルを直径１ｍｍのステンレス製の棒にたるみが無いように１．５Ｎの張力で巻きつけた。そして、機械方向及び機械垂直方向へのサンプルの変形が共に５％以内にあるサンプルを良好（○）と判断し、５％を超えたサンプルを不良（×）と判断した。
(13) The process passability of the non-aqueous secondary battery separator was evaluated as follows.
First, a sample similar to the above (7) was wound around a stainless steel rod having a diameter of 1 mm with a tension of 1.5 N so as not to sag. A sample in which the deformation of the sample in both the machine direction and the machine vertical direction was within 5% was judged as good (◯), and a sample exceeding 5% was judged as bad (x).
［実施例１］
ポリエチレンパウダーとしてＴｉｃｏｎａ社製ＧＵＲ２１２６（重量平均分子量４１５万、融点１４１℃）とＧＵＲＸ１４３（重量平均分子量５６万、融点１３５℃）を用いた。ＧＵＲ２１２６とＧＵＲＸ１４３を３０：７０（重量比）となる様にして、ポリエチレン濃度が３０重量％となるように流動パラフィン（松村石油研究所社製スモイルＰ−３５０：沸点４８０℃）とデカリン（和光純薬社製、沸点１９３℃）の混合溶媒中に溶解させ、ポリエチレン溶液を作製した。該ポリエチレン溶液の組成はポリエチレン：流動パラフィン：デカリン＝３０：６０：１０（重量比）である。
このポリエチレン溶液を１４８℃でダイから押し出し、水浴中で冷却してゲル状テープ（ベーステープ）を作製した。該ベーステープを６０℃で８分、９５℃で１５分乾燥し、該ベーステープを縦延伸、横延伸を逐次行う２軸延伸にて延伸した。ここで、縦延伸５．５倍、延伸温度は９０℃、横延伸は延伸倍率１１倍、延伸温度は１０５℃とし、縦延伸と横延伸の間に３０℃の冷却工程を設けた。横延伸の後に１３２℃で熱固定を行った。次にこれを塩化メチレン浴に浸漬し、流動パラフィンとデカリンを抽出した。その後、５０℃で乾燥し、１２０℃でアニール処理することでポリオレフィン微多孔膜を得た。得られたポリオレフィン微多孔膜はフィブリル状ポリオレフィンが網目状に交絡し、細孔を構成する構造を有するものであった。
得られたポリオレフィン微多孔膜の特性（膜厚、目付、空孔率、ガーレ値、膜抵抗、突刺強度、引張強度、各種結晶物性、シャットダウン（ＳＤ）温度、熱収縮率、加圧回復率）の測定結果を表１に示す。なお、以下の実施例２，３および比較例１，２についても同様に表１に示す。
[Example 1]
Ticona's GUR2126 (weight average molecular weight 4150,000, melting point 141 ° C.) and GURX143 (weight average molecular weight 560,000, melting point 135 ° C.) were used as polyethylene powder. Liquid paraffin (Smoyl P-350, boiling point 480 ° C. by Matsumura Oil Research Co., Ltd.) and decalin (Wako Pure) so that GUR2126 and GURX143 become 30:70 (weight ratio) and the polyethylene concentration becomes 30% by weight. A polyethylene solution was prepared by dissolving in a mixed solvent having a boiling point of 193 ° C. manufactured by Yakuhin Co., Ltd. The composition of the polyethylene solution is polyethylene: liquid paraffin: decalin = 30: 60: 10 (weight ratio).
This polyethylene solution was extruded from a die at 148 ° C. and cooled in a water bath to prepare a gel tape (base tape). The base tape was dried at 60 ° C. for 8 minutes and at 95 ° C. for 15 minutes, and the base tape was stretched by biaxial stretching in which longitudinal stretching and lateral stretching were sequentially performed. Here, the longitudinal stretching was 5.5 times, the stretching temperature was 90 ° C., the transverse stretching was 11 times the stretching ratio, the stretching temperature was 105 ° C., and a cooling step of 30 ° C. was provided between the longitudinal stretching and the lateral stretching. After transverse stretching, heat setting was performed at 132 ° C. Next, this was immersed in a methylene chloride bath to extract liquid paraffin and decalin. Then, the polyolefin microporous film was obtained by drying at 50 degreeC and annealing at 120 degreeC. The resulting polyolefin microporous membrane had a structure in which fibrillar polyolefins were entangled in a network and constituted pores.
Properties of the resulting microporous polyolefin membrane (film thickness, basis weight, porosity, Gurley value, membrane resistance, puncture strength, tensile strength, various crystal properties, shutdown (SD) temperature, thermal shrinkage, pressure recovery rate) The measurement results are shown in Table 1. The following Examples 2 and 3 and Comparative Examples 1 and 2 are similarly shown in Table 1.
［実施例２］
実施例１において、横延伸倍率を１２倍にし、縦延伸と横延伸の間の冷却温度を５０℃に設定した以外は、実施例１と同様にしてポリオレフィン微多孔膜を得た。
[Example 2]
In Example 1, a polyolefin microporous membrane was obtained in the same manner as in Example 1 except that the transverse stretching ratio was set to 12 and the cooling temperature between longitudinal stretching and transverse stretching was set to 50 ° C.
［実施例３］
実施例１において、縦延伸倍率を７倍にし、横延伸倍率を８．５倍にし、縦延伸と横延伸の間の冷却温度を４０℃に設定した以外は、実施例１と同様にしてポリオレフィン微多孔膜を得た。
[Example 3]
In Example 1, except that the longitudinal stretch ratio was 7 times, the lateral stretch ratio was 8.5 times, and the cooling temperature between the longitudinal stretch and the lateral stretch was set to 40 ° C., the polyolefin was treated in the same manner as in Example 1. A microporous membrane was obtained.
［比較例１］
実施例１において、縦延伸倍率を４倍、横延伸倍率を４倍にし、縦延伸工程から横延伸工程までの間に冷却工程を設けずに９０℃のまま維持した以外は、実施例１と同様にしてポリオレフィン微多孔膜を得た。
[Comparative Example 1]
In Example 1, the longitudinal stretching ratio was 4 times, the lateral stretching ratio was 4 times, and it was maintained at 90 ° C. without providing a cooling step between the longitudinal stretching step and the lateral stretching step. Similarly, a polyolefin microporous membrane was obtained.
［比較例２］
実施例１において、縦延伸倍率を１５倍にし、横延伸倍率を１５倍にし、縦延伸と横延伸の間の冷却温度を８８℃に設定した以外は、実施例１と同様にしてポリオレフィン微多孔膜を得た。
[Comparative Example 2]
In Example 1, the microporous polyolefin was formed in the same manner as in Example 1 except that the longitudinal stretching ratio was 15 times, the lateral stretching ratio was 15 times, and the cooling temperature between the longitudinal stretching and the transverse stretching was set to 88 ° C. A membrane was obtained.
［実施例４］
実施例１で得られたポリオレフィン微多孔膜を用い、これに耐熱性樹脂と無機フィラーからなる耐熱性多孔質層を積層させて、本発明の非水系二次電池用セパレータを製造した。
具体的に、耐熱性樹脂として、ポリメタフェニレンイソフタルアミド（帝人テクノプロダクツ社製、コーネックス）を用いた。この耐熱性樹脂を、ジメチルアセトアミド（ＤＭＡｃ）とトリプロピレングリコール（ＴＰＧ）が重量比５０：５０となっている混合溶媒に溶解させた。このポリマー溶液に、無機フィラーとしての水酸化マグネシウム（協和化学工業社製、キスマ−５Ｐ、平均粒子径１．０μｍ）を分散させて、塗工用スラリーを作製した。なお、塗工用スラリーにおけるポリメタフェニレンイソフタルアミドの濃度は５．５重量％となるようにし、かつ、ポリメタフェニレンイソフタルアミドと無機フィラーの重量比は２５：７５となるように調整した。そして、マイヤーバーを２本対峙させ、その間に塗工液を適量のせた。この後、ポリオレフィン微多孔膜を、塗工液がのっているマイヤーバー間を通過させて、ポリオレフィン微多孔膜の表裏面に塗工液を塗工した。ここで、マイヤーバー間のクリアランスは２０μｍに設定し、マイヤーバーの番手は２本とも＃６を用いた。これを重量比で水：ＤＭＡｃ：ＴＰＧ＝５０：２５：２５で４０℃となっている凝固液中に浸漬し、次いで水洗・乾燥を行った。これにより、ポリオレフィン微多孔膜の表裏両面に耐熱性多孔質層が形成された非水系二次電池用セパレータを得た。
得られた非水系二次電池用セパレータの特性（膜厚、目付、空孔率、ガーレ値、膜抵抗、突刺強度、引張強度、シャットダウン温度、耐熱性、熱収縮率、加圧回復率）の測定結果を表２に示す。なお、以下の実施例５〜１１および比較例３，４についても同様に、表２に示す。
[Example 4]
The polyolefin microporous membrane obtained in Example 1 was used, and a heat-resistant porous layer made of a heat-resistant resin and an inorganic filler was laminated thereon to produce the non-aqueous secondary battery separator of the present invention.
Specifically, polymetaphenylene isophthalamide (manufactured by Teijin Techno Products, Conex) was used as the heat resistant resin. This heat resistant resin was dissolved in a mixed solvent of dimethylacetamide (DMAc) and tripropylene glycol (TPG) in a weight ratio of 50:50. In this polymer solution, magnesium hydroxide as an inorganic filler (Kyowa Chemical Industry Co., Ltd., Kisuma-5P, average particle size: 1.0 μm) was dispersed to prepare a slurry for coating. The concentration of polymetaphenylene isophthalamide in the coating slurry was adjusted to 5.5% by weight, and the weight ratio of polymetaphenylene isophthalamide to inorganic filler was adjusted to 25:75. Then, two Meyer bars were opposed to each other, and an appropriate amount of coating liquid was put between them. Thereafter, the polyolefin microporous film was passed between Mayer bars on which the coating liquid was placed, and the coating liquid was applied to the front and back surfaces of the polyolefin microporous film. Here, the clearance between the Meyer bars was set to 20 μm, and # 6 was used for both the Mayer bars. This was immersed in a coagulating liquid having a weight ratio of water: DMAc: TPG = 50: 25: 25 and 40 ° C., followed by washing and drying. This obtained the separator for non-aqueous secondary batteries in which the heat resistant porous layer was formed in the both surfaces of the polyolefin microporous film.
Characteristics of the obtained non-aqueous secondary battery separator (film thickness, basis weight, porosity, Gurley value, membrane resistance, puncture strength, tensile strength, shutdown temperature, heat resistance, heat shrinkage rate, pressure recovery rate) The measurement results are shown in Table 2. The following Examples 5 to 11 and Comparative Examples 3 and 4 are similarly shown in Table 2.
［実施例５］
ポリオレフィン微多孔膜として実施例２で作製したものを使用した以外は、実施例４と同様にして非水系二次電池用セパレータを得た。
[Example 5]
A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 4 except that the polyolefin microporous film prepared in Example 2 was used.
［実施例６］
ポリオレフィン微多孔膜として実施例３で作製したものを使用した以外は、実施例４と同様にして非水系二次電池用セパレータを得た。
[Example 6]
A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 4 except that the polyolefin microporous film prepared in Example 3 was used.
［実施例７］
実施例４において、マイヤーバー間のクリアランスを７μｍに設定した以外は、実施例４と同様にして非水系二次電池用セパレータを得た。
[Example 7]
In Example 4, a separator for a nonaqueous secondary battery was obtained in the same manner as in Example 4 except that the clearance between Mayer bars was set to 7 μm.
［実施例８］
実施例４において、ＤＭＡｃとＴＰＧの混合比を４０：６０（重量比）にし、マイヤーバー間のクリアランスを６０μｍに設定し、凝固液の組成を水：ＤＭＡｃ：ＴＰＧ＝５０：３０：２０に調整した以外は、実施例４と同様にして非水系二次電池用セパレータを得た。
[Example 8]
In Example 4, the mixing ratio of DMAc and TPG was set to 40:60 (weight ratio), the clearance between the Meyer bars was set to 60 μm, and the composition of the coagulation liquid was adjusted to water: DMAc: TPG = 50: 30: 20 A separator for a nonaqueous secondary battery was obtained in the same manner as in Example 4 except that.
［実施例９］
実施例４において、ＤＭＡｃとＴＰＧの混合比を４０：６０（重量比）にし、マイヤーバー間のクリアランスを７５μｍに設定し、凝固液の組成を水：ＤＭＡｃ：ＴＰＧ＝５０：３０：２０に調整した以外は、実施例４と同様にして非水系二次電池用セパレータを得た。
[Example 9]
In Example 4, the mixing ratio of DMAc and TPG was set to 40:60 (weight ratio), the clearance between Mayer bars was set to 75 μm, and the composition of the coagulation liquid was adjusted to water: DMAc: TPG = 50: 30: 20 A separator for a nonaqueous secondary battery was obtained in the same manner as in Example 4 except that.
［実施例１０］
実施例４において、ＤＭＡｃとＴＰＧの混合比を３５：６５（重量比）にし、マイヤーバー間のクリアランスを６０μｍに設定し、凝固液の組成を水：ＤＭＡｃ：ＴＰＧ＝５０：３２：１８に調整した以外は、実施例４と同様にして非水系二次電池用セパレータを得た。
[Example 10]
In Example 4, the mixing ratio of DMAc and TPG was set to 35:65 (weight ratio), the clearance between the Meyer bars was set to 60 μm, and the composition of the coagulation liquid was adjusted to water: DMAc: TPG = 50: 32: 18 A separator for a nonaqueous secondary battery was obtained in the same manner as in Example 4 except that.
［実施例１１］
実施例４において、ＤＭＡｃとＴＰＧの混合比を７０：３０（重量比）にし、凝固液の組成を水：ＤＭＡｃ：ＴＰＧ＝５０：１５：３５に調整した以外は、実施例４と同様にして非水系二次電池用セパレータを得た。
[Example 11]
In Example 4, the mixing ratio of DMAc and TPG was set to 70:30 (weight ratio), and the composition of the coagulation liquid was adjusted to water: DMAc: TPG = 50: 15: 35. A separator for a non-aqueous secondary battery was obtained.
［比較例３］
ポリオレフィン微多孔膜として比較例１で作製したものを使用した以外は、実施例４と同様にして非水系二次電池用セパレータを得た。
[Comparative Example 3]
A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 4 except that the polyolefin microporous film prepared in Comparative Example 1 was used.
［比較例４］
ポリオレフィン微多孔膜として比較例２で作製したものを使用した以外は、実施例４と同様にして非水系二次電池用セパレータを得た。
[Comparative Example 4]
A separator for a non-aqueous secondary battery was obtained in the same manner as in Example 4 except that the polyolefin microporous film prepared in Comparative Example 2 was used.
［サイクル特性］
コバルト酸リチウム（ＬｉＣｏＯ２：日本化学工業社製）８９．５重量部、アセチレンブラック（電気化学工業社製デンカブラック）４．５重量部、ポリフッ化ビニリデン（クレハ化学社製）６重量部となるように、Ｎ−メチル−ピロリドンを用いてこれらを混練し、スラリーを作製した。得られたスラリーを厚さが２０μｍのアルミ箔上に塗布乾燥後プレスし、１００μｍの正極を得た。
メソフェーズカーボンマイクロビーズ（ＭＣＭＢ：大阪瓦斯化学社製）８７重量部、アセチレンブラック（電気化学工業社製商品名デンカブラック）３重量部、ポリフッ化ビニリデン（クレハ化学社製）１０重量部となるようにＮ−メチル−２ピロリドンを用いてこれらを混練し、スラリーを作製した。得られたスラリーを厚さが１８μｍの銅箔上に塗布乾燥後プレスし、９０μｍの負極を得た。
[Cycle characteristics]
Lithium cobalt oxide (LiCoO 2 : manufactured by Nippon Chemical Industry Co., Ltd.) 89.5 parts by weight, acetylene black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd.) 4.5 parts by weight, polyvinylidene fluoride (manufactured by Kureha Chemical Co., Ltd.) 6 parts by weight Thus, these were kneaded using N-methyl-pyrrolidone to prepare a slurry. The obtained slurry was applied onto an aluminum foil having a thickness of 20 μm, dried and pressed to obtain a positive electrode having a thickness of 100 μm.
87 parts by weight of mesophase carbon micro beads (MCMB: manufactured by Osaka Gas Chemical Co., Ltd.), 3 parts by weight of acetylene black (trade name Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.) and 10 parts by weight of polyvinylidene fluoride (manufactured by Kureha Chemical Co., Ltd.) These were kneaded using N-methyl-2pyrrolidone to prepare a slurry. The obtained slurry was applied onto a copper foil having a thickness of 18 μm, dried and pressed to obtain a negative electrode having a thickness of 90 μm.
上記正極及び負極の間に、実施例１〜１１および比較例１〜４で作製したポリオレフィン微多孔膜あるいは非水系二次電池用セパレータをそれぞれ挟んだ。これに電解液を含浸させアルミラミネートフィルムからなる外装に封入して、実施例１２〜２２および比較例５〜８の非水系二次電池を作製した。ここで、電解液には１Ｍ ＬｉＰＦ６ エチレンカーボネート／エチルメチルカーボネート（３／７重量比）（キシダ化学社製）を用いた。
ここで、この試作電池は正極面積が２×１．４ｃｍ２、負極面積は２．２×１．６ｃｍ２で、設定容量は８ｍＡｈ（４．２Ｖ−２．７５Ｖの範囲）とした。
このようにして得た各非水系二次電池について、４．０Ｖの定電流・定電圧充電と、２．７５Ｖの定電流放電を１００サイクル繰り返した後に、その放電容量を測定した。そして、１００サイクル後の放電容量を３サイクル後の放電容量で割り、得られた放電容量保持率（％）をサイクル特性の指標とした。測定結果を表３にまとめて示す。
Between the positive electrode and the negative electrode, the polyolefin microporous membrane or non-aqueous secondary battery separator prepared in Examples 1 to 11 and Comparative Examples 1 to 4 was sandwiched, respectively. This was impregnated with an electrolytic solution and sealed in an exterior made of an aluminum laminate film, and non-aqueous secondary batteries of Examples 12 to 22 and Comparative Examples 5 to 8 were produced. Here, 1M LiPF 6 ethylene carbonate / ethyl methyl carbonate (3/7 weight ratio) (manufactured by Kishida Chemical Co., Ltd.) was used as the electrolytic solution.
Here, this prototype battery had a positive electrode area of 2 × 1.4 cm 2 , a negative electrode area of 2.2 × 1.6 cm 2 , and a set capacity of 8 mAh (in the range of 4.2V-2.75V).
For each non-aqueous secondary battery thus obtained, 4.0 V constant current / constant voltage charging and 2.75 V constant current discharging were repeated 100 cycles, and then the discharge capacity was measured. The discharge capacity after 100 cycles was divided by the discharge capacity after 3 cycles, and the obtained discharge capacity retention rate (%) was used as an index of cycle characteristics. The measurement results are summarized in Table 3.
本発明のポリオレフィン微多孔膜は、ポリオレフィンの結晶性を制御する事で、耐熱性多孔質層と複合した時に優れたシャットダウン特性及び工程通過性を付与し、かつ、電解液の液枯れを防止する事を可能にせしめている。これを用いた非水系二次電池用セパレータ及び非水系二次電池の安全性を確かなものとする。 The polyolefin microporous membrane of the present invention provides excellent shutdown characteristics and process passability when combined with a heat-resistant porous layer by controlling the crystallinity of the polyolefin, and prevents the electrolyte from draining. It makes things possible. The safety of the non-aqueous secondary battery separator and the non-aqueous secondary battery using this is assured.
Claims (6)
配向軸１が機械方向に対し０〜２０度、配向軸２が機械方向に対し６０〜９０度であり、
配向軸１の配向度が６５〜８０％、配向軸２の配向度が６５〜８０％であり、
配向全体の積分値に占める配向軸１の積分値の割合が２０〜４０％であり、
シャットダウン温度が１３５〜１４５℃であることを特徴とするポリオレフィン微多孔膜。 In the polyolefin crystal structure obtained by X-ray measurement, there are two orientation axes. When the orientation axis is 1 and the orientation axis is 2, respectively,
The orientation axis 1 is 0 to 20 degrees with respect to the machine direction, the orientation axis 2 is 60 to 90 degrees with respect to the machine direction,
The orientation degree of the orientation axis 1 is 65 to 80%, the orientation degree of the orientation axis 2 is 65 to 80%,
The ratio of the integral value of the orientation axis 1 to the integral value of the entire orientation is 20 to 40% ,
A polyolefin microporous membrane having a shutdown temperature of 135 to 145 ° C.
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| JP5969683B1 (en) * | 2015-11-30 | 2016-08-17 | 住友化学株式会社 | Nonaqueous electrolyte secondary battery separator, nonaqueous electrolyte secondary battery laminate separator, nonaqueous electrolyte secondary battery member, and nonaqueous electrolyte secondary battery |
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| JP4876387B2 (en) * | 2003-11-05 | 2012-02-15 | 東レ株式会社 | Biaxially oriented microporous film and method for producing the same |
| WO2008156033A1 (en) * | 2007-06-19 | 2008-12-24 | Teijin Limited | Separator for nonaqueous secondary battery, method for producing the same, and nonaqueous secondary battery |
| JP5214999B2 (en) * | 2008-02-28 | 2013-06-19 | 帝人株式会社 | Nonaqueous electrolyte battery separator, manufacturing method thereof, and nonaqueous electrolyte secondary battery using the same |
| JP5366426B2 (en) * | 2008-04-04 | 2013-12-11 | 東芝機械株式会社 | Method for forming porous film and sequential biaxial stretching apparatus for forming porous film |
| JP2010053245A (en) * | 2008-08-28 | 2010-03-11 | Teijin Ltd | Polyolefin microporous membrane |
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| JP5969683B1 (en) * | 2015-11-30 | 2016-08-17 | 住友化学株式会社 | Nonaqueous electrolyte secondary battery separator, nonaqueous electrolyte secondary battery laminate separator, nonaqueous electrolyte secondary battery member, and nonaqueous electrolyte secondary battery |
| KR101685882B1 (en) | 2015-11-30 | 2016-12-12 | 스미또모 가가꾸 가부시키가이샤 | Nonaqueous electrolyte secondary battery separator, laminated separator for nonaqueous electrolyte secondary battery, member for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery |
| US10014503B2 (en) | 2015-11-30 | 2018-07-03 | Sumitomo Chemical Company, Limited | Nonaqueous electrolyte secondary battery separator, nonaqueous electrolyte secondary battery laminated separator, nonaqueous electrolyte secondary battery member, and nonaqueous electrolyte secondary battery |
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