JP2007073382A - Separator for lithium secondary cell and lithium secondary cell using the same - Google Patents
Separator for lithium secondary cell and lithium secondary cell using the same Download PDFInfo
- Publication number
- JP2007073382A JP2007073382A JP2005260021A JP2005260021A JP2007073382A JP 2007073382 A JP2007073382 A JP 2007073382A JP 2005260021 A JP2005260021 A JP 2005260021A JP 2005260021 A JP2005260021 A JP 2005260021A JP 2007073382 A JP2007073382 A JP 2007073382A
- Authority
- JP
- Japan
- Prior art keywords
- separator
- lithium secondary
- secondary battery
- cellulose
- lithium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 62
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 229920002678 cellulose Polymers 0.000 claims abstract description 51
- 239000000839 emulsion Substances 0.000 claims abstract description 25
- 239000012528 membrane Substances 0.000 claims abstract description 24
- 229920005989 resin Polymers 0.000 claims abstract description 24
- 239000011347 resin Substances 0.000 claims abstract description 24
- 239000003960 organic solvent Substances 0.000 claims abstract description 16
- 238000001035 drying Methods 0.000 claims abstract description 13
- 239000011255 nonaqueous electrolyte Substances 0.000 claims abstract description 13
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 8
- 229920003086 cellulose ether Polymers 0.000 claims abstract description 6
- 239000000758 substrate Substances 0.000 claims abstract description 6
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 5
- 159000000002 lithium salts Chemical class 0.000 claims abstract description 5
- 239000000126 substance Substances 0.000 claims abstract description 3
- 239000007774 positive electrode material Substances 0.000 claims description 8
- 239000000243 solution Substances 0.000 abstract description 10
- 239000011248 coating agent Substances 0.000 abstract description 7
- 238000000576 coating method Methods 0.000 abstract description 7
- 239000006182 cathode active material Substances 0.000 abstract 1
- 239000001913 cellulose Substances 0.000 description 43
- WFDIJRYMOXRFFG-UHFFFAOYSA-N Acetic anhydride Chemical compound CC(=O)OC(C)=O WFDIJRYMOXRFFG-UHFFFAOYSA-N 0.000 description 18
- 239000000203 mixture Substances 0.000 description 16
- 238000006243 chemical reaction Methods 0.000 description 15
- 238000004519 manufacturing process Methods 0.000 description 15
- 239000002245 particle Substances 0.000 description 15
- -1 lithium transition metal Chemical class 0.000 description 13
- 239000007789 gas Substances 0.000 description 11
- 239000000463 material Substances 0.000 description 11
- 239000011148 porous material Substances 0.000 description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 11
- 239000003995 emulsifying agent Substances 0.000 description 9
- 229920000098 polyolefin Polymers 0.000 description 9
- 238000003860 storage Methods 0.000 description 9
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 8
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 239000002904 solvent Substances 0.000 description 8
- 230000002427 irreversible effect Effects 0.000 description 7
- 238000006479 redox reaction Methods 0.000 description 7
- 239000011230 binding agent Substances 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- 239000007773 negative electrode material Substances 0.000 description 6
- 229910052723 transition metal Inorganic materials 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 5
- 239000002131 composite material Substances 0.000 description 5
- 239000004020 conductor Substances 0.000 description 5
- 239000008151 electrolyte solution Substances 0.000 description 5
- 239000002905 metal composite material Substances 0.000 description 5
- 238000003756 stirring Methods 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 description 3
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 3
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
- 229910013684 LiClO 4 Inorganic materials 0.000 description 3
- 229910013870 LiPF 6 Inorganic materials 0.000 description 3
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 3
- 239000003575 carbonaceous material Substances 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 239000011737 fluorine Substances 0.000 description 3
- 229910052731 fluorine Inorganic materials 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 238000007086 side reaction Methods 0.000 description 3
- 235000017281 sodium acetate Nutrition 0.000 description 3
- 239000001632 sodium acetate Substances 0.000 description 3
- YEJRWHAVMIAJKC-UHFFFAOYSA-N 4-Butyrolactone Chemical compound O=C1CCCO1 YEJRWHAVMIAJKC-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical group [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 238000010924 continuous production Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000002950 deficient Effects 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 235000014113 dietary fatty acids Nutrition 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 230000032050 esterification Effects 0.000 description 2
- 238000005886 esterification reaction Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 239000000194 fatty acid Substances 0.000 description 2
- 229930195729 fatty acid Natural products 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- RSNHXDVSISOZOB-UHFFFAOYSA-N lithium nickel Chemical compound [Li].[Ni] RSNHXDVSISOZOB-UHFFFAOYSA-N 0.000 description 2
- 239000002931 mesocarbon microbead Substances 0.000 description 2
- LNAZSHAWQACDHT-XIYTZBAFSA-N (2r,3r,4s,5r,6s)-4,5-dimethoxy-2-(methoxymethyl)-3-[(2s,3r,4s,5r,6r)-3,4,5-trimethoxy-6-(methoxymethyl)oxan-2-yl]oxy-6-[(2r,3r,4s,5r,6r)-4,5,6-trimethoxy-2-(methoxymethyl)oxan-3-yl]oxyoxane Chemical compound CO[C@@H]1[C@@H](OC)[C@H](OC)[C@@H](COC)O[C@H]1O[C@H]1[C@H](OC)[C@@H](OC)[C@H](O[C@H]2[C@@H]([C@@H](OC)[C@H](OC)O[C@@H]2COC)OC)O[C@@H]1COC LNAZSHAWQACDHT-XIYTZBAFSA-N 0.000 description 1
- WNXJIVFYUVYPPR-UHFFFAOYSA-N 1,3-dioxolane Chemical compound C1COCO1 WNXJIVFYUVYPPR-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
- JVIPLYCGEZUBIO-UHFFFAOYSA-N 2-(4-fluorophenyl)-1,3-dioxoisoindole-5-carboxylic acid Chemical compound O=C1C2=CC(C(=O)O)=CC=C2C(=O)N1C1=CC=C(F)C=C1 JVIPLYCGEZUBIO-UHFFFAOYSA-N 0.000 description 1
- 229920002799 BoPET Polymers 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- 229920008347 Cellulose acetate propionate Polymers 0.000 description 1
- 229920001425 Diethylaminoethyl cellulose Polymers 0.000 description 1
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 1
- 229920000896 Ethulose Polymers 0.000 description 1
- 239000001856 Ethyl cellulose Substances 0.000 description 1
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 1
- 239000001859 Ethyl hydroxyethyl cellulose Substances 0.000 description 1
- 229910000733 Li alloy Inorganic materials 0.000 description 1
- 229910015015 LiAsF 6 Inorganic materials 0.000 description 1
- 229910013063 LiBF 4 Inorganic materials 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- 229910002995 LiNi0.8Co0.15Al0.05O2 Inorganic materials 0.000 description 1
- 239000000020 Nitrocellulose Substances 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- KLARSDUHONHPRF-UHFFFAOYSA-N [Li].[Mn] Chemical compound [Li].[Mn] KLARSDUHONHPRF-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 150000005215 alkyl ethers Chemical class 0.000 description 1
- 239000004760 aramid Substances 0.000 description 1
- 229920003235 aromatic polyamide Polymers 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 238000010923 batch production Methods 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 229910002091 carbon monoxide 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
- 150000001768 cations Chemical group 0.000 description 1
- 229920002301 cellulose acetate Polymers 0.000 description 1
- 229920006217 cellulose acetate butyrate Polymers 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- CKFRRHLHAJZIIN-UHFFFAOYSA-N cobalt lithium Chemical compound [Li].[Co] CKFRRHLHAJZIIN-UHFFFAOYSA-N 0.000 description 1
- 239000000571 coke Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000011883 electrode binding agent Substances 0.000 description 1
- 230000001804 emulsifying effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000006266 etherification reaction Methods 0.000 description 1
- ZOOODBUHSVUZEM-UHFFFAOYSA-N ethoxymethanedithioic acid Chemical compound CCOC(S)=S ZOOODBUHSVUZEM-UHFFFAOYSA-N 0.000 description 1
- 229920001249 ethyl cellulose Polymers 0.000 description 1
- 235000019325 ethyl cellulose Nutrition 0.000 description 1
- 235000019326 ethyl hydroxyethyl cellulose Nutrition 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 229920001973 fluoroelastomer Polymers 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 230000010220 ion permeability Effects 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 239000001989 lithium alloy Substances 0.000 description 1
- 150000002642 lithium compounds Chemical class 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229920000609 methyl cellulose Polymers 0.000 description 1
- 239000001923 methylcellulose Substances 0.000 description 1
- 235000010981 methylcellulose Nutrition 0.000 description 1
- 239000012982 microporous membrane Substances 0.000 description 1
- 239000004005 microsphere Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 229910021382 natural graphite Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229920001220 nitrocellulos Polymers 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920001230 polyarylate Polymers 0.000 description 1
- 229920006289 polycarbonate film Polymers 0.000 description 1
- 229920006267 polyester film Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920006290 polyethylene naphthalate film Polymers 0.000 description 1
- 229920000139 polyethylene terephthalate Polymers 0.000 description 1
- 239000005020 polyethylene terephthalate Substances 0.000 description 1
- 229920002503 polyoxyethylene-polyoxypropylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000004810 polytetrafluoroethylene Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
- 239000002516 radical scavenger Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 229920002050 silicone resin Polymers 0.000 description 1
- 239000011877 solvent mixture Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- 239000012991 xanthate Substances 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
Description
本発明は、リチウムイオンの吸蔵・脱離現象を利用したリチウム二次電池を構成するセパレータ、およびそれを用いたリチウム二次電池に関する。
The present invention relates to a separator constituting a lithium secondary battery using a lithium ion storage / desorption phenomenon, and a lithium secondary battery using the separator.
リチウムの吸蔵・脱離現象を利用したリチウム二次電池は、高エネルギー密度であることから、携帯電話、パソコン等の小型化に伴い、通信機器、情報関連機器の分野で広く普及するに至っている。また、自動車の分野においても、資源問題、環境問題から電気自動車の開発が急がれており、この電気自動車用の電源としても、リチウム二次電池が検討されている。現在実用化されているリチウム二次電池は、一般に、リチウム遷移金属複合酸化物を正極活物質とした正極と、炭素材料等を負極活物質とした負極と、その正極と負極との間に挟装されたセパレータと、リチウム塩を有機溶媒に溶解した非水系電解液とから構成されており、４Ｖ級の高い電圧を有するものが主流をなしている。ここで、構成要素の一つであるセパレータは、正極と負極とを分離し、それらの間に電解液を保持させる役割を果たすものである。そして、セパレータには、正極、負極および電解液
に対して化学的に安定であること、電解質やイオンの透過性が良好であること等が要求される。このような特性を備えたセパレータとして、セルロース紙（特許文献１）や、それとポリオレフィンからなる薄い多孔質膜とを積層したもの等が挙げられる。
Lithium secondary batteries that use the lithium absorption / desorption phenomenon have a high energy density, and as a result, miniaturization of mobile phones, personal computers, etc. has led to widespread use in the fields of communication equipment and information-related equipment. . In the field of automobiles, the development of electric vehicles has been urgently promoted due to resource issues and environmental issues, and lithium secondary batteries have been studied as power sources for the electric vehicles. Lithium secondary batteries currently in practical use are generally sandwiched between a positive electrode using a lithium transition metal composite oxide as a positive electrode active material, a negative electrode using a carbon material or the like as a negative electrode active material, and the positive electrode and the negative electrode. It is composed of a mounted separator and a non-aqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent, and one having a high voltage of 4 V class is mainstream. Here, the separator which is one of the constituent elements plays a role of separating the positive electrode and the negative electrode and holding the electrolytic solution therebetween. The separator is required to be chemically stable with respect to the positive electrode, the negative electrode, and the electrolytic solution, and to have good electrolyte and ion permeability. Examples of the separator having such characteristics include cellulose paper (Patent Document 1) and a laminate of the paper and a thin porous film made of polyolefin.
しかしながら、上記セルロース紙を含むセパレータを用いたリチウム二次電池は、初回の充電時、あるいは過充電に至った場合に、水素や一酸化炭素等のガスの発生量が多い。ガスの発生量が多いと、電池内部の圧力が上昇するため、安全上好ましくない。ガスが発生するメカニズムは明らかではないが、初回の充電時や過充電時には、電解液が分解することに加え、上記セパレータ自体も反応してガスを生成すると考えられる。また、上記セルロース紙を含むセパレータを用いたリチウム二次電池は、自己放電量が大きく、特に充電状態で高温下に長時間放置した場合にはその程度が大き
い。
However, a lithium secondary battery using a separator containing the cellulose paper generates a large amount of gas such as hydrogen or carbon monoxide during the first charge or when overcharge occurs. If the amount of gas generated is large, the pressure inside the battery increases, which is not preferable for safety. The mechanism by which the gas is generated is not clear, but it is considered that the separator itself reacts to generate gas in addition to the decomposition of the electrolyte during the initial charge or overcharge. Moreover, the lithium secondary battery using the separator containing the cellulose paper has a large self-discharge amount, especially when left in a charged state for a long time at a high temperature.
本発明は、上記問題を解決するためになされたものであり、電気化学的に安定であり、自己放電量の小さいリチウム二次電池を構成し得るセパレータであって、製造コストが安価なセパレータを提供することを課題とする。 The present invention has been made to solve the above problems, and is a separator that is electrochemically stable and can constitute a lithium secondary battery with a small self-discharge amount, and has a low manufacturing cost. The issue is to provide.
本発明のリチウム二次電池用セパレータは、セルロースの水酸基の少なくとも一部がエステル化またはエーテル化されたセルロース誘導体（以下、セルロースエステル、セルロースエーテルを指す。）より選ばれた少なくとも１種の樹脂を主成分するＷ／Ｏ型エマルジョン（Ｗ／Ｏ型は、油相中に水の粒子が分散する型）を基材に塗布、乾燥することにより得られた多孔質膜である。（第１発明）
第２発明は、第１発明のセパレータを正極と負極の間に狭装し、非水電解液を備えたリチウム二時電池である。
The separator for a lithium secondary battery of the present invention comprises at least one resin selected from a cellulose derivative in which at least a part of the hydroxyl group of cellulose is esterified or etherified (hereinafter referred to as cellulose ester or cellulose ether). A W / O emulsion (W / O type is a type in which water particles are dispersed in an oil phase) is applied to a base material and dried, and dried. (First invention)
The second invention is a lithium secondary battery in which the separator of the first invention is sandwiched between a positive electrode and a negative electrode and is provided with a non-aqueous electrolyte.
第３発明は、正極および、または負極に直接前記のＷ／Ｏ型エマルジョンを塗布、乾燥することにより得られた多孔質膜のセパレータを設け、非水電解液を備えたリチウム二時電池である。 The third invention is a lithium secondary battery comprising a porous membrane separator obtained by coating and drying the W / O emulsion directly on the positive electrode and / or the negative electrode, and comprising a non-aqueous electrolyte. .
本発明のセパレータは、セルロース誘導体を主成分とする多孔質膜を含んでなるため、初期充電時等におけるガスの発生量が少ない。すなわち、セルロースは水酸基（−ＯＨ）を有するため電気化学的に安定ではなく、充電時の電位の変化に伴って酸化反応あるいは還元反応を生じる。このセルロースの酸化還元反応が水素等のガスを発生させる要因と考えられる。したがって、セルロースの水酸基の少なくとも一部をエステル化またはエステル化して不活性なものとすることにより、セルロースを電気化学的に安定化させ、その結果、酸化還元反応を抑制することができると考えられる。また、セルロースの酸化還元反応が抑制されると、電池の自己放電量も小さくなる。つまり、自己放電の多くは、セルロースの酸化還元反応により生じた生成物等が、正極および負極において還元剤または酸化剤となることで生じると考えられる。したがって、セルロースを電気化学的に安定化さ
せ、酸化還元反応を抑制することで、電池の自己放電も抑制することができる。さらに、セルロースの反応は、本来の電池反応以外の不可逆的な副反応であるため、その副反応が抑制されることにより、可逆的な電池反応に寄与する電荷が増加して、いわゆる不可逆容量が減少することになる。このように、本発明のリチウム二次電池用セパレータは、電気化学的に安定であり、充電時におけるガスの発生量が少なく、自己放電量および不可逆容
量の小さい二次電池を構成することができる。
Since the separator of the present invention includes a porous film containing a cellulose derivative as a main component, the amount of gas generated during initial charging is small. That is, since cellulose has a hydroxyl group (—OH), it is not electrochemically stable, and an oxidation reaction or a reduction reaction occurs with a change in potential during charging. It is considered that this redox reaction of cellulose generates a gas such as hydrogen. Therefore, it is considered that the cellulose is electrochemically stabilized by esterifying or esterifying at least a part of the hydroxyl groups of cellulose, and as a result, the redox reaction can be suppressed. . Moreover, when the oxidation-reduction reaction of cellulose is suppressed, the self-discharge amount of the battery is also reduced. That is, it is considered that most of self-discharge occurs when a product or the like generated by the redox reaction of cellulose becomes a reducing agent or an oxidizing agent in the positive electrode and the negative electrode. Therefore, by stabilizing the cellulose electrochemically and suppressing the redox reaction, the self-discharge of the battery can also be suppressed. Furthermore, since the cellulose reaction is an irreversible side reaction other than the original battery reaction, by suppressing the side reaction, the charge contributing to the reversible battery reaction increases, so-called irreversible capacity is increased. Will be reduced. As described above, the lithium secondary battery separator of the present invention can form a secondary battery that is electrochemically stable, generates a small amount of gas during charging, and has a small self-discharge amount and small irreversible capacity. .
また、本発明のリチウム二次電池用セパレータは、上記セルロース誘導体を主成分とする多孔質膜とポリオレフィン製多孔質膜とを含み、セルロース誘導体を主成分とする多孔質膜とポリオレフィン製多孔質膜とが積層してなるように構成することができる。 The separator for a lithium secondary battery according to the present invention includes a porous film mainly composed of the cellulose derivative and a polyolefin porous film, and the porous film mainly composed of the cellulose derivative and the polyolefin porous film. And can be configured to be laminated.
一般に、リチウム二次電池が過充電に至った場合には、正極活物質の結晶の崩壊や電解液の分解反応等様々な反応を生じる。特に、電解液の分解反応はガスの発生を伴うものであり、電池の内部圧力は上昇する。さらに、これらの過充電反応の殆どは発熱反応であるため、電池内部の温度は上昇することになる。セパレータとしてポリオレフィンからなる多孔質膜を用いると、電池内部の温度上昇に伴ってポリオレフィンの多孔質膜は軟化して、その多孔が閉塞し、それ以上の過充電反応をシャットダウンする。つまり、ポリオレフィンの多孔質膜は過充電反応を自己抑制するように作用する。しかし、ポリオレフィンは融点が１２５℃〜１８０℃程度と比較的低いため、例えば、温度上昇が急激な場合には、セパレータが溶融してその形状を保持できず、正極と負極とが直接接触する、いわゆる内部短絡を引き起こすおそれがある。よって、リチウム二次電池の過充電時における安全性を向上するためには、セパレータの高温における強度の向上を図ることが必要となる。ここで、セルロース系の膜は、熱分解開始温度が３００℃前後であり、ポリオレフィンからなる膜が溶融する温度範囲であっても形状を保持することができる。したがって、セルロース誘導体を主成分とする多孔質膜と、シャットダウン作用を有するポリオレフィン製多孔質膜とを積層させることで、高温下において形状を維持しつつ、過充電反応を充分に沈静化することができる。すなわち、積層化した本発明のセパレータを用いたリチウム二次電池は、上記電池特性に優れるだけでなく、過充電時における安全性も高いものとなる。 In general, when a lithium secondary battery is overcharged, various reactions such as the collapse of the crystal of the positive electrode active material and the decomposition reaction of the electrolytic solution occur. In particular, the decomposition reaction of the electrolytic solution is accompanied by gas generation, and the internal pressure of the battery increases. Furthermore, since most of these overcharge reactions are exothermic reactions, the temperature inside the battery rises. When a porous membrane made of polyolefin is used as the separator, the porous membrane of polyolefin is softened as the temperature inside the battery rises, and the pores are blocked and further overcharge reaction is shut down. That is, the polyolefin porous membrane acts to self-suppress the overcharge reaction. However, since the polyolefin has a relatively low melting point of about 125 ° C. to 180 ° C., for example, when the temperature rises rapidly, the separator cannot melt and maintain its shape, and the positive electrode and the negative electrode are in direct contact. There is a risk of causing a so-called internal short circuit. Therefore, in order to improve the safety at the time of overcharging of the lithium secondary battery, it is necessary to improve the strength of the separator at a high temperature. Here, the cellulose-based film has a thermal decomposition start temperature of around 300 ° C., and can maintain the shape even in a temperature range in which the polyolefin film melts. Therefore, by laminating a porous membrane mainly composed of a cellulose derivative and a polyolefin porous membrane having a shutdown action, the overcharge reaction can be sufficiently calmed while maintaining the shape at a high temperature. it can. That is, the lithium secondary battery using the laminated separator of the present invention has not only excellent battery characteristics but also high safety during overcharge.
本発明のリチウム二次電池は、リチウムイオンを吸蔵・脱離できる物質を正極活物質とする正極と、負極と、該正極と負極との間に挟装されたセパレータと、リチウム塩を有機溶媒に溶解した非水電解液とを備えてなるリチウム二次電池であって、前記セパレータ
は、セルロースの水酸基の少なくとも一部がエステル化またはエーテル化されたセルロース誘導体を主成分とする多孔質膜を含むことを特徴とする。すなわち、本発明のリチウム二次電池は、上記本発明のセパレータを用いた電池であり、充電時におけるガスの発生量が少なく、自己放電量および不可逆容量の小さい二次電池となる。
The lithium secondary battery of the present invention includes a positive electrode using a substance capable of inserting and extracting lithium ions as a positive electrode active material, a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and a lithium salt as an organic solvent. A lithium secondary battery comprising a non-aqueous electrolyte dissolved in the separator, wherein the separator comprises a porous membrane mainly composed of a cellulose derivative in which at least part of hydroxyl groups of cellulose is esterified or etherified. It is characterized by including. That is, the lithium secondary battery of the present invention is a battery using the separator of the present invention, and is a secondary battery that generates a small amount of gas during charging and has a small self-discharge amount and small irreversible capacity.
本発明のリチウム二次電池用セパレータは、セルロース誘導体を主成分とする多孔質膜を含むものである。セルロースの水酸基の少なくとも一部をエステル化またはエーテル化して不活性なものとすることにより、セルロースを電気化学的に安定化させ、副反応を抑制することができる。したがって、本発明のセパレータを用いることにより、自己放電量および不可逆容量の小さいリチウム二次電池を構成することができる。多孔質膜は、基材面にセルロース誘導体を含むＷ／Ｏ型エマルジョンを塗布、乾燥することで容易に製造でき、製造コストを安価にできる。また、正極および、または負極に直接前記のＷ／Ｏ型エマルジョンを塗布、乾燥することにより得られた多孔質膜のセパレータを設けてなるリチウム二次電池は、さらに安価に製造できる。 The separator for a lithium secondary battery of the present invention includes a porous film mainly composed of a cellulose derivative. By making at least a part of the hydroxyl group of cellulose esterified or etherified to be inactive, the cellulose can be electrochemically stabilized and side reactions can be suppressed. Therefore, by using the separator of the present invention, a lithium secondary battery with a small self-discharge amount and irreversible capacity can be configured. The porous membrane can be easily manufactured by applying and drying a W / O type emulsion containing a cellulose derivative on the substrate surface, and the manufacturing cost can be reduced. Moreover, a lithium secondary battery comprising a porous membrane separator obtained by applying and drying the W / O emulsion directly on the positive electrode and / or the negative electrode can be produced at a lower cost.
以下に、本発明のリチウム二次電池用セパレータおよびそれを用いたリチウム二次電池の実施形態について説明する。なお、説明する実施形態は一実施形態にすぎず、本発明のリチウム二次電池用セパレータおよびリチウム二次電池が、下記の実施形態に限定されるものではない。下記実施形態を始めとして、当業者が行い得る変更、改良等を施した種々の形態にて実施することができる。 Embodiments of a separator for a lithium secondary battery and a lithium secondary battery using the same according to the present invention will be described below. In addition, embodiment described is only one Embodiment, The separator for lithium secondary batteries and lithium secondary battery of this invention are not limited to the following embodiment. The present invention can be implemented in various forms including changes and improvements that can be made by those skilled in the art, including the following embodiment.
第１発明のセパレータは、セルロースの水酸基の少なくとも一部がエステル化またはエーテル化されたセルロース誘導体を主成分とする多孔質膜を含むものである。セルロース誘導体は、セルロースのすべての水酸基がエステル化またはエーテル化されているものの他、一部の水酸基のみを置換したものでもよい。 The separator of the first invention includes a porous film mainly composed of a cellulose derivative in which at least a part of hydroxyl groups of cellulose is esterified or etherified. Cellulose derivatives may be those in which all hydroxyl groups of cellulose are esterified or etherified, or in which only some hydroxyl groups are substituted.
セルロースエステルとしては、セルロースアセテート、セルロースアセテートプロピオネート、セルロースアセテートブチレート、ニトロセルロース、セルロースキサントゲン酸塩等が挙げられる。セルロースエーテルとしては、メチルセルロール、エチルセルロース、ジエチルアミノエチルセルロース、エチルヒドロキシエチルセルロース、カルボキシメチルセルロース等が挙げられる。いずれも市販のセルロース誘導体を使用できる。 Examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, nitrocellulose, and cellulose xanthate. Examples of the cellulose ether include methyl cellulose, ethyl cellulose, diethylaminoethyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose and the like. In any case, a commercially available cellulose derivative can be used.
これらのセルロース誘導体より１種以上を選択した樹脂より多孔質膜を作成する方法は、樹脂をＷ／Ｏ型エマルジョン化した塗液を基材面に塗布、乾燥することにより得られる。Ｗ／Ｏ型エマルジョンは、以下のようにして製造する。 A method for producing a porous film from a resin selected from one or more of these cellulose derivatives can be obtained by applying a coating liquid obtained by emulsifying the resin to a W / O emulsion and drying it. The W / O type emulsion is produced as follows.
前記特定の樹脂を水と不混和性または難混和性の有機溶剤に溶解させる。有機溶剤に対する樹脂の使用量は、樹脂の種類によっても異なるが、Ｗ／Ｏ型エマルジョンを製造する上で適正な溶液粘度をうる観点から、有機溶剤１００部（重量部、以下同様）に対して、樹脂３〜１０部の割合が好ましい。樹脂の使用量がこの範囲より少ないと、安定したエマルジョンがえられない傾向があり、一方多いとえられたエマルジョンの粘度が高くなり、塗工適性が低下する。樹脂の溶解速度を大きくするために、撹拌機による撹拌下および／または加熱下に溶解させてもよい。多孔質膜をうるためには有機溶剤が水より早く揮散する必要があり、この点から沸点が９０℃以下の有機溶剤が好ましい。有機溶剤としては
メチルエチルケトン（沸点７９．６℃）がとくに好ましい。
The specific resin is dissolved in an organic solvent immiscible or poorly miscible with water. The amount of resin used with respect to the organic solvent varies depending on the type of resin, but from the viewpoint of obtaining an appropriate solution viscosity for producing a W / O type emulsion, with respect to 100 parts of organic solvent (parts by weight, the same applies hereinafter). A ratio of 3 to 10 parts of resin is preferred. If the amount of the resin used is less than this range, there is a tendency that a stable emulsion cannot be obtained, while on the other hand, the viscosity of the obtained emulsion becomes high and the coating suitability is lowered. In order to increase the dissolution rate of the resin, the resin may be dissolved under stirring by a stirrer and / or heating. In order to obtain a porous film, the organic solvent needs to be volatilized earlier than water. From this point, an organic solvent having a boiling point of 90 ° C. or less is preferable. As the organic solvent, methyl ethyl ketone (boiling point 79.6 ° C.) is particularly preferable.
水に乳化剤を溶解する。乳化剤は水１００部に対して１〜５部の範囲で使用するのが好ましい。乳化剤の量がこの範囲を外れると、エマルジョンの安定性がわるくなり、エマルジョンの破壊が生じる傾向にある。乳化剤の溶解速度を大きくするため、撹拌機による撹拌下および／または加熱下に溶解させてもよい。乳化剤はＷ／Ｏ型乳化剤から適宜選択され、たとえばポリグリセリン脂肪酸エステル、ポリエチレングリコール脂肪酸エステル、ポリオキシエチレンポリオキシプロピレンアルキルエーテルなどが使用できる。 Dissolve emulsifier in water. The emulsifier is preferably used in the range of 1 to 5 parts with respect to 100 parts of water. When the amount of the emulsifier is outside this range, the stability of the emulsion is deteriorated and the emulsion tends to be broken. In order to increase the dissolution rate of the emulsifier, the emulsifier may be dissolved with stirring and / or heating. The emulsifier is appropriately selected from W / O type emulsifiers. For example, polyglycerin fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene polyoxypropylene alkyl ether and the like can be used.
前記乳化剤を溶解した水溶液と樹脂溶液を混合し、撹拌機で撹拌して乳化を行なう。水溶液と樹脂溶液の混合比は１：９〜４：６（重量比）の範囲が好ましく、水溶液の割合を少なくする。撹拌を続けると、樹脂溶液の中に水の小さな粒子が生じ、乳濁してくる。かくして安定なＷ／Ｏ型エマルジョンがえられる。エマルジョン中の水粒子の平均粒径は、多孔質膜の平均孔径をどの程度に設定するかによって異なるが、０．１〜２．０μｍの範囲とするのが好ましい。 The aqueous solution in which the emulsifier is dissolved and the resin solution are mixed and emulsified by stirring with a stirrer. The mixing ratio of the aqueous solution and the resin solution is preferably in the range of 1: 9 to 4: 6 (weight ratio), and the ratio of the aqueous solution is reduced. When stirring is continued, small particles of water are produced in the resin solution and become milky. Thus, a stable W / O emulsion can be obtained. The average particle size of the water particles in the emulsion varies depending on how much the average pore size of the porous membrane is set, but is preferably in the range of 0.1 to 2.0 μm.
前記Ｗ／Ｏ型エマルジョンを基材面に適宜の塗布機で塗布し、乾燥する。乾燥は熱風
ドライヤーなどで４０〜７０℃で行なえばよく、容易に乾燥する。乾燥後は加熱下にエージングする必要はない。基材より多孔質膜を剥がすことにより多孔質膜がえられる。基材より剥がしにくい場合は、基材に予めシリコーン系樹脂、フッ素系樹脂、ワックス等からなる離型層を設けておくとよい。
The W / O type emulsion is applied to the substrate surface with an appropriate coating machine and dried. Drying may be performed at 40 to 70 ° C. with a hot air dryer or the like, and is easily dried. After drying, it is not necessary to age under heating. A porous film is obtained by peeling the porous film from the substrate. If it is difficult to peel off from the base material, a release layer made of silicone resin, fluorine resin, wax or the like may be provided in advance on the base material.
前記のように適正な材料と材料の配合比および適正な製造条件でえられたＷ／Ｏ型エマルジョンは、その中の水の粒子の粒径および密度がほぼ設計どおりの粒子径および密度となり、かつ保存しても安定である。そしてこの水の粒子は、Ｗ／Ｏ型エマルジョンを塗布、乾燥する際に多孔質膜の孔部分を形成するものであり、Ｗ／Ｏ型エマルジョン中に所定の粒径の水粒子が所定密度で存在するため、所定の孔径および孔密度の多孔質膜がえられる。 As described above, the W / O type emulsion obtained with an appropriate material-to-material mixing ratio and an appropriate production condition has a particle size and density of water particles in the particle size and density almost as designed, It is stable even when stored. The water particles form pores of the porous membrane when the W / O type emulsion is applied and dried, and the water particles having a predetermined particle size have a predetermined density in the W / O type emulsion. Therefore, a porous film having a predetermined pore diameter and density can be obtained.
多孔質膜は、その厚さが特に限定されるものではないが、セパレータとして多孔質膜１枚を単独で用いる場合には、その厚さを１０μｍ以上５０μｍ以下とすることが望ましい。１０μｍ未満の場合には、強度、特に膜厚方向における突刺し強度が充分ではなく、内部短絡の発生率が高くなるからである。さらに強度を向上させるためには２０μｍ以上とすることがより望ましい。一方、５０μｍを超えると、内部抵抗が増加したり放電容量が減少する等、電池性能の低下を招くおそれがある。電池性能を考慮すると４０μｍ以下とすることがより望ましい。なお、後述するように、他の多孔質膜と積層してセパレータとする場合には、積層して形成された膜の全体の厚さを考慮して、それぞれの多孔質膜の厚さを適宜決定すればよい。 The thickness of the porous membrane is not particularly limited, but when a single porous membrane is used alone as a separator, the thickness is desirably 10 μm or more and 50 μm or less. When the thickness is less than 10 μm, the strength, particularly the piercing strength in the film thickness direction is not sufficient, and the occurrence rate of internal short circuit is increased. In order to further improve the strength, it is more desirable that the thickness be 20 μm or more. On the other hand, when the thickness exceeds 50 μm, the battery performance may be deteriorated, for example, the internal resistance may increase or the discharge capacity may decrease. Considering battery performance, it is more desirable to set it as 40 micrometers or less. As will be described later, when the separator is laminated with another porous membrane, the thickness of each porous membrane is appropriately determined in consideration of the total thickness of the laminated membrane. Just decide.
セルロース誘導体を主成分とする多孔質膜の孔径は、特に限定されるものではないが、平均孔径が０．１μｍ以上１μｍ以下であることが望ましい。平均孔径が０．１μｍ未満であると、膜の抵抗が増加し、電池性能が低下するからであり、１μｍを超えると内部短絡し易くなるからである。平均孔径は、例えば、多孔質膜を走査型電子顕微鏡で観察し、その写真を統計的に処理することにより求めればよい。また、空隙率は、２０％以上６０％以下とすることが望ましい。平均孔径の場合と同様、２０％未満の場合には膜の抵抗が増加し、電池性能が低下するからであり、６０％を超えると内部短絡し易くなるからである。空隙率は、例えば、多孔質膜の原料となる材料の真密度、多孔質膜の重量および体積とから求ることができる。さらに、内部短絡の発生を抑制するという観点から、膜厚方向における突刺し強度がある程度以上の値であることが望ましい。突刺し強度は、例えば、テクスチャーアナライザー等の強度試験機を用いて、測定対象となる多孔質膜に金属針（直径１〜２ｍｍ、先端部ｒ＝０．５ｍｍ）を一定速度で突き刺した際の荷重で評価することができる。 The pore diameter of the porous membrane containing a cellulose derivative as a main component is not particularly limited, but the average pore diameter is desirably 0.1 μm or more and 1 μm or less. This is because when the average pore diameter is less than 0.1 μm, the resistance of the film increases and the battery performance is deteriorated. When the average pore diameter exceeds 1 μm, the internal short circuit easily occurs. The average pore diameter may be obtained, for example, by observing the porous film with a scanning electron microscope and statistically processing the photograph. The porosity is preferably 20% or more and 60% or less. This is because, when the average pore size is less than 20%, the resistance of the film increases and the battery performance decreases, and when it exceeds 60%, the internal short circuit easily occurs. The porosity can be determined from, for example, the true density of the material that is the raw material of the porous membrane, the weight and volume of the porous membrane. Furthermore, from the viewpoint of suppressing the occurrence of internal short circuit, it is desirable that the puncture strength in the film thickness direction is a value of a certain level or more. The puncture strength is obtained when, for example, a metal needle (diameter 1 to 2 mm, tip portion r = 0.5 mm) is pierced at a constant speed into a porous film to be measured using a strength tester such as a texture analyzer. It can be evaluated by load.
基材としては、ポリエチレンテレフタレートフィルム、ポリエチレンナフタレートフィルム、ポリアリレートフィルムなどのポリエステルフィルム、ポリカーボネートフィルム、ポリアミドフィルム、アラミドフィルム等のプラステックフィルムが使用できる。また、前記フィルムの材料からなるプラスチック板を使用してもよい。セパレータの連続製造が可能な点からフィルムを使用するのが好ましい。基材フィルムの厚さは製膜のハンドリングを良好にする点から1〜100μｍ程度、なかんづく10〜50μｍ程度が好ましい。 As the base material, polyester films such as polyethylene terephthalate film, polyethylene naphthalate film and polyarylate film, and plastic films such as polycarbonate film, polyamide film and aramid film can be used. Further, a plastic plate made of the film material may be used. It is preferable to use a film because a separator can be continuously produced. The thickness of the base film is preferably about 1 to 100 μm, especially about 10 to 50 μm from the viewpoint of improving the film-forming handling.
従来、セルロースをエステル化した多孔質膜を製造する方法としては、種々のものがある。例えば、セルロースを硫酸と無水酢酸との混合溶液に浸漬する方法、高温下で無水酢酸の蒸気により処理する方法、酢酸ナトリウムを触媒として無水酢酸水溶液に浸漬する、あるいは無水酢酸の蒸気により処理する方法等が挙げられる。特に、エステル化の程度を制御し易いという理由から、酢酸ナトリウムを触媒として無水酢酸の蒸気により処理する方法を採用することが望ましいとされている。 Conventionally, there are various methods for producing a porous membrane obtained by esterifying cellulose. For example, a method of immersing cellulose in a mixed solution of sulfuric acid and acetic anhydride, a method of treating with acetic anhydride vapor at high temperature, a method of immersing in an acetic anhydride aqueous solution using sodium acetate as a catalyst, or a method of treating with acetic anhydride vapor Etc. In particular, for the reason that the degree of esterification is easily controlled, it is desirable to employ a method of treating with sodium acetate as a catalyst with acetic anhydride vapor.
特開２００３−１２３７２４号公報のセパレータ用セルロースエステルの多孔質膜の製造方法は、その実施例によれば次のように記載されている。「セルロース紙に１０ｗｔ％の酢酸ナトリウム水溶液をスプレーコートした後、無水酢酸蒸気を作用させながら５０℃の温度で５時間保持することにより行った。そして、エステル化処理後にイオン交換水で洗浄し、８０℃で２４時間真空乾燥してエステル化セルロースを主成分とする微多孔膜とした。」この方法では、連続製造しにくく、バッチ製造となり製造時間も長くなる。本発明のセパレータの製造は、市販のセルロースエステル等のセルロース誘導体を使用するものである。セルロース誘導体をエマルジョン化した塗工液を基材上に塗布、乾燥する方法のため連続製造が可能であり製造時間も従来の方法に比べて相当短縮することができ、製造コストが安価にできるものである。 According to the Example, the manufacturing method of the porous film | membrane of the cellulose ester for separators of Unexamined-Japanese-Patent No. 2003-123724 is described as follows. “This was performed by spray-coating a 10 wt% aqueous solution of sodium acetate on cellulose paper and then holding it for 5 hours at a temperature of 50 ° C. while allowing acetic anhydride vapor to act. It was vacuum dried at 80 ° C. for 24 hours to form a microporous membrane mainly composed of esterified cellulose. ”In this method, continuous production is difficult, batch production is required, and production time is increased. Manufacture of the separator of this invention uses cellulose derivatives, such as a commercially available cellulose ester. A coating solution in which a cellulose derivative is emulsified is applied to a substrate and dried, so that continuous production is possible, production time can be considerably shortened compared to conventional methods, and production costs can be reduced. It is.
第２発明のリチウム二次電池は、上記本発明のセパレータを備えた二次電池であり、セパレータを除いて他の構成要素は特に限定するものではなく、既に存在する通常のリチウム二次電池に従えばよい。以下、各構成要素ごとに説明する。 The lithium secondary battery of the second invention is a secondary battery provided with the separator of the present invention, and the other components are not particularly limited except for the separator. Just follow. Hereinafter, each component will be described.
正極は、リチウムイオンを吸蔵・脱離できる正極活物質に導電材および結着剤を混合し、適当な溶剤を加えてペースト状の正極合材としたものを、アルミニウム等の金属箔製の集電体表面に塗布乾燥し、必要に応じて電極密度を高めるべく圧縮して形成することができる。この場合の塗布、乾燥、プレス等は通常の方法に従えばよい。 The positive electrode is made by mixing a conductive material and a binder with a positive electrode active material capable of inserting and extracting lithium ions, and adding a suitable solvent to form a paste-like positive electrode mixture made of a metal foil such as aluminum. It can be applied and dried on the surface of the electric body and compressed to increase the electrode density as necessary. Application, drying, pressing, and the like in this case may follow normal methods.
正極活物質は、リチウムイオンを吸蔵・脱離できる物質であれば特に限定されるものではなく、例えば、リチウム遷移金属複合酸化物を用いることができる。リチウム遷移金属複合酸化物としては、例えば、４Ｖ級の二次電池を構成できるという観点から、基本組成をＬｉＣｏＯ2、ＬｉＮｉＯ2とする層状岩塩構造のリチウムコバルト複合酸化物やリチウムニッケル複合酸化物、あるいは基本組成をＬｉＭｎ2Ｏ4とするスピネル構造のリチウムマンガン複合酸化物等を用いることが望ましい。特に、基本組成をＬｉＮｉＯ2とする層状岩塩構造リチウムニッケル複合酸化物は、Ｃｏを中心金属としたリチウム遷移金属複合酸化物に比較して、安価でありまた容量のより大きな二次電池を構成できる点で優れている。なお、「基本組成をＬｉＮｉＯ2とする」とは、組成式ＬｉＮｉＯ2で表される正規組成のものの他、Ｎｉサイトの一部をＣｏ、Ｍｎ等で置換したものや、また、熱的安定性を高めるためＡｌ等で置換したもの、Ｌｉで置換したもの等、他元素置換タイプのものをも含むことを意味する。さらに、必ずしも化学量論組成のものに限定されるわけではなく、例えば、製造上不可避的に生じるリチウムや遷移金属等の陽イオン原子が欠損した、あるいは酸素原子が欠損した非化学量論組成のもの等をも含む。また、上記リチウム遷移金属複合酸化物のうち１種類のものを単独で用いてもよく、また、２種類以上のものを混合して用いることも可能である。２種類以上を混合して用いる場合は、例えば、過充電反応が生じる電位の異なるものを用いることにより、過充電反応を分散させて行わせることができる。つまり、より低い電位で過充電反応を生じる正極活物質が優先的に過充電され、早期に発熱反応を生じるため、セパレータによるシャットダウンの時期を早めることができ、急激な温度上昇を回避することができる。この場合、より低い電位で過充電反応を生じるリチウム遷移金属化合物は、過充電反応を分散して行わせるという効果を充分に発揮させるような割合で混合すればよい。具体的には、その混合割合を１０ｗｔ％以上９０ｗｔ％以下とすることが望ましい。 The positive electrode active material is not particularly limited as long as it is a material that can occlude and desorb lithium ions. For example, a lithium transition metal composite oxide can be used. As the lithium transition metal composite oxide, for example, a lithium cobalt composite oxide or lithium nickel composite oxide having a layered rock salt structure having a basic composition of LiCoO 2 and LiNiO 2 from the viewpoint that a secondary battery of 4V class can be configured, Alternatively, it is desirable to use a spinel structure lithium manganese composite oxide having a basic composition of LiMn 2 O 4 . In particular, a layered rock salt structure lithium nickel composite oxide having a basic composition of LiNiO 2 is cheaper and can constitute a secondary battery having a larger capacity than a lithium transition metal composite oxide having Co as a central metal. Excellent in terms. Note that “the basic composition is LiNiO 2 ” means that the Ni composition has a regular composition represented by the composition formula LiNiO 2 , a Ni site partially substituted with Co, Mn, etc., and thermal stability. It is meant to include other element substitution types, such as those substituted with Al or the like, or those substituted with Li. Furthermore, it is not necessarily limited to that of a stoichiometric composition. For example, a non-stoichiometric composition in which a cation atom such as lithium or a transition metal inevitably produced in production is deficient or an oxygen atom is deficient. Including things. Further, one type of lithium transition metal composite oxide may be used alone, or two or more types may be mixed and used. When two or more types are mixed and used, for example, by using different potentials at which an overcharge reaction occurs, the overcharge reaction can be dispersed. In other words, since the positive electrode active material that causes an overcharge reaction at a lower potential is preferentially overcharged and generates an exothermic reaction at an early stage, it is possible to advance the shutdown timing by the separator and avoid a sudden temperature rise. it can. In this case, the lithium transition metal compound that causes an overcharge reaction at a lower potential may be mixed in such a ratio as to sufficiently exhibit the effect of dispersing and performing the overcharge reaction. Specifically, the mixing ratio is desirably 10 wt% or more and 90 wt% or less.
導電材は、正極の電気伝導性を確保するためのものであり、例えば、カーボンブラック、アセチレンブラック、黒鉛等の炭素物質粉状体の１種又は２種以上を混合したものを用いることができる。結着剤は、活物質粒子および導電材粒子を繋ぎ止める役割を果たすもので、例えば、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、フッ素ゴム等の含フッ素樹脂、ポリプロピレン、ポリエチレン等の熱可塑性樹脂を用いることができる。これら活物質、導電材、結着剤を分散させる溶剤としては、Ｎ−メチル−２−ピロリドン等の有機溶剤を用いることができる。 The conductive material is for securing the electrical conductivity of the positive electrode, and for example, a material obtained by mixing one or more carbon material powders such as carbon black, acetylene black, and graphite can be used. . The binder plays a role of connecting the active material particles and the conductive material particles. For example, a fluorine-containing resin such as polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber, or a thermoplastic resin such as polypropylene or polyethylene is used. be able to. An organic solvent such as N-methyl-2-pyrrolidone can be used as a solvent for dispersing these active material, conductive material, and binder.
正極に対向させる負極は、負極活物質である金属リチウムを、シート状にして、あるいはシート状にしたものをニッケル、ステンレス等の集電体網に圧着して形成することができる。負極活物質には金属リチウムに代え、リチウム合金、またはリチウム化合物をも用
いることができる。ただし、金属リチウム等はデンドライトの析出という問題があるため、これらに代えて、正極同様、リチウムイオンを吸蔵・脱離できる負極活物質に結着剤を混合し、適当な溶剤を加えてペースト状にした負極合材を、銅等の金属箔集電体の表面に塗布乾燥し、必要に応じて電極密度を高めるべく圧縮して形成することができる。この場合、負極活物質として、例えば、天然黒鉛、人造黒鉛、フェノール樹脂等の有機化合物焼成体、コークス等の炭素物質の粉状体を用いることができる。負極結着剤としては、正極同様、ポリフッ化ビニリデン等の含フッ素樹脂等を、溶剤としてはＮ−メチル−２−ピロリドン等の有機溶剤を用いることができる。
The negative electrode opposed to the positive electrode can be formed by forming metallic lithium, which is a negative electrode active material, into a sheet shape, or a sheet-shaped material that is pressure-bonded to a current collector network such as nickel or stainless steel. Instead of metallic lithium, a lithium alloy or a lithium compound can also be used for the negative electrode active material. However, since lithium metal and the like have a problem of precipitation of dendrites, instead of these, like a positive electrode, a binder is mixed with a negative electrode active material capable of inserting and extracting lithium ions, and an appropriate solvent is added to form a paste. The negative electrode mixture can be formed by applying and drying on the surface of a metal foil current collector such as copper and then compressing it to increase the electrode density as necessary. In this case, as the negative electrode active material, for example, a fired organic compound such as natural graphite, artificial graphite, or a phenol resin, or a powdery carbon material such as coke can be used. As the negative electrode binder, as in the positive electrode, a fluorine-containing resin such as polyvinylidene fluoride can be used, and as the solvent, an organic solvent such as N-methyl-2-pyrrolidone can be used.
非水電解液は、有機溶媒に電解質を溶解させたもので、有機溶媒としては、非プロトン性有機溶媒、例えばエチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、γ−ブチロラクトン、アセトニトリル、ジメトキシエタン、テトラヒドロフラン、ジオキソラン、塩化メチレン等の１種またはこれらの２種以上の溶媒を用いることができる。また、溶解させる電解質としては、溶解させることによりリチウムイオンを生じるＬｉＢＦ4、ＬｉＰＦ6、ＬｉＣｌＯ4、ＬｉＡｓＦ6等を用いることができる。なお、非水電解液は、さらにラジカル補足剤、界面活性剤や難燃剤などを含んでいてもよい。上記電解質は、それぞれ単独で用いてもよく、また、２種以上のものを併用することもできる。特に、ＬｉＰＦ6は、比較的電気伝導率が高く、内部抵抗の小さな電池を構成することができるため好適である。さらに、ＬｉＣｌＯ4をも併用することが望ましい。ＬｉＣｌＯ4を併用することで、過充電状態の初期に発熱させることができ、セパレータによるシャットダウンの時期を早め、リチウム二次電池の安全性を高めることができる。 The non-aqueous electrolyte is a solution in which an electrolyte is dissolved in an organic solvent. Examples of the organic solvent include aprotic organic solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, One kind of tetrahydrofuran, dioxolane, methylene chloride or the like, or two or more kinds of these solvents can be used. As the electrolyte to be dissolved, LiBF 4 , LiPF 6 , LiClO 4 , LiAsF 6, etc. that generate lithium ions when dissolved can be used. The non-aqueous electrolyte may further contain a radical scavenger, a surfactant, a flame retardant, and the like. The above electrolytes may be used alone or in combination of two or more. In particular, LiPF 6 is preferable because it has a relatively high electrical conductivity and can form a battery having a low internal resistance. Furthermore, it is desirable to use LiClO 4 together. By using LiClO 4 in combination, heat can be generated in the early stage of the overcharge state, the shutdown timing by the separator can be advanced, and the safety of the lithium secondary battery can be improved.
以上の構成要素によって構成されるリチウム二次電池であるが、その形状は円筒型、積層型、コイン型等、種々のものとすることができる。いずれの形状を採る場合であっても、正極と負極との間にセパレータを挟装させ電極体とする。そして正極集電体および負極
集電体から外部に通ずる正極端子および負極端子までの間を、集電用リード等を用いて接続し、この電極体に上記電解液を含浸させ電池ケースに密閉し、リチウム二次電池を完成する。
Although it is a lithium secondary battery comprised by the above component, the shape can be made into various things, such as a cylindrical type, a laminated type, and a coin type. In any case, a separator is sandwiched between the positive electrode and the negative electrode to form an electrode body. Then, the positive electrode current collector and the negative electrode current collector are connected to the positive electrode terminal and the negative electrode terminal leading to the outside using a current collecting lead or the like, and the electrode body is impregnated with the above electrolyte solution and sealed in a battery case. Complete the lithium secondary battery.
第３発明のリチウム二次電池は、正極および、または負極に直接、セルロースエステル、セルロースエーテルより選ばれた少なくとも１種の樹脂を主成分とするＷ／Ｏ型エマルジョンを塗布、乾燥することにより多孔質膜のセパレータを設けるものである。リチウム二次電池の各部品を組み立て製造するコストをこのように予めセパレータを極部位に設けることで安価になるものである。正極、負極、非水電解液は、第２発明と同じものを使用することができる。 The lithium secondary battery of the third invention is porous by directly applying and drying a W / O emulsion mainly composed of at least one resin selected from cellulose ester and cellulose ether to the positive electrode and / or the negative electrode. A membrane separator is provided. The cost for assembling and manufacturing the components of the lithium secondary battery can be reduced by providing the separator in advance in this way. As the positive electrode, the negative electrode, and the non-aqueous electrolyte, the same ones as in the second invention can be used.
以下、上記実施形態に基づいて、本発明のセパレータを備えたリチウム二次電池を種々作製した。また、比較のため、従来のセパレータを用いてリチウム二次電池を作製した。これら作製したリチウム二次電池について、初回充電時の圧力および放電容量を測定し、さらに保存試験を行った。以下、これらについて詳しく説明する。
（セパレータの製作）
表１に示される処方の樹脂を溶剤に加え、デイスパーで撹拌して溶解させて、樹脂溶液を調製した。溶解しにくい樹脂のばあいは５０℃に加熱して溶解させた。この樹脂溶液中に乳化剤水溶液を加え、前記デイスパーで１時間撹拌してＷ／Ｏ型エマルジョンを調製した。
このＷ／Ｏ型エマルジョン中の水粒子の平均粒径をレーザー回折式粒度分布測定装置（島津製作所（株）製ＳＡＬＤ−２２００）で測定した。結果を表１に示す。
Hereinafter, various lithium secondary batteries including the separator of the present invention were produced based on the above embodiment. For comparison, a lithium secondary battery was fabricated using a conventional separator. About these produced lithium secondary batteries, the pressure and discharge capacity at the time of first charge were measured, and also the storage test was done. These will be described in detail below.
(Manufacture of separator)
Resin having the formulation shown in Table 1 was added to the solvent and dissolved by stirring with a disperser to prepare a resin solution. In the case of a resin that is difficult to dissolve, it was dissolved by heating to 50 ° C. An aqueous emulsifier solution was added to the resin solution, and the mixture was stirred with the disperser for 1 hour to prepare a W / O type emulsion.
The average particle diameter of the water particles in the W / O emulsion was measured with a laser diffraction particle size distribution analyzer (SALD-2200, manufactured by Shimadzu Corporation). The results are shown in Table 1.
前記Ｗ／Ｏ型エマルジョンを基材として、厚み２５μｍのＰＥＴフィルム上に塗布し、４５℃で乾燥させて、乾燥後の厚みが２０μｍとなるように実施例１〜４の多孔質膜を形成した。 Using the W / O type emulsion as a base material, it was applied onto a PET film having a thickness of 25 μm and dried at 45 ° C., and the porous films of Examples 1 to 4 were formed so that the thickness after drying was 20 μm. .
えられた多孔質膜の表面部分を走査型電子顕微鏡（日本電子（株）製ＪＳＭ−５６１０ＬＶ）を用い、倍率２万倍で観察して平均孔径を求めた。結果を表１に示す。
比較例１のセパレータは、セルロース紙のみからなるセパレータを用いた。
The surface portion of the obtained porous film was observed with a scanning electron microscope (JSM-5610LV, manufactured by JEOL Ltd.) at a magnification of 20,000 to determine the average pore diameter. The results are shown in Table 1.
As the separator of Comparative Example 1, a separator made only of cellulose paper was used.
（二次電池の製作）
正極は、まず、正極活物質となるＬｉＮｉ0.8Ｃｏ0.15Ａｌ0.05Ｏ2の９０重量部に、導電材としてのカーボンブラックを５重量部、結着剤としてのポリフッ化ビニリデンを５重量部混合し、溶剤として適量のＮ−メチル−２−ピロリドンを添加し、ペースト状の正極
合材を調製した。次いで、このペースト状の正極合材を、ロールコータを用いて、厚さ１５μｍのアルミニウム箔集電体の両面に塗布、乾燥し、ロールプレスにて圧縮し、シート状の正極を作製した。なお、このシート状の正極は５４ｍｍ×１００ｍｍの大きさに裁断して用いた。
(Production of secondary battery)
First, the positive electrode is prepared by mixing 90 parts by weight of LiNi 0.8 Co 0.15 Al 0.05 O 2 as a positive electrode active material, 5 parts by weight of carbon black as a conductive material, and 5 parts by weight of polyvinylidene fluoride as a binder, An appropriate amount of N-methyl-2-pyrrolidone was added as a solvent to prepare a paste-like positive electrode mixture. Next, this paste-like positive electrode mixture was applied to both surfaces of a 15 μm thick aluminum foil current collector using a roll coater, dried, and compressed by a roll press to produce a sheet-like positive electrode. The sheet-like positive electrode was cut into a size of 54 mm × 100 mm and used.
対向させる負極は、負極活物質に黒鉛化メソフェーズ小球体（ＭＣＭＢ）を採用した。まず、このＭＣＭＢの９５重量部に対して、結着剤としてポリフッ化ビニリデンを５重量部混合し、溶剤として適量のＮ−メチル−２−ピロリドンを添加し、これらを充分に混練
してペースト状の負極合材を調製した。次いで、この負極合材を厚さ１０μｍの銅箔集電体の両面に塗布、乾燥し、ロールプレスにて圧縮し、シート状の負極を作製した。なお、このシート状の負極は５６ｍｍ×１２０ｍｍの大きさに裁断して用いた。
For the negative electrode to be opposed, graphitized mesophase microspheres (MCMB) were used as the negative electrode active material. First, 5 parts by weight of polyvinylidene fluoride as a binder is mixed with 95 parts by weight of MCMB, an appropriate amount of N-methyl-2-pyrrolidone is added as a solvent, and these are sufficiently kneaded to form a paste. A negative electrode composite was prepared. Next, this negative electrode mixture was applied to both sides of a 10 μm thick copper foil current collector, dried, and compressed by a roll press to prepare a sheet-like negative electrode. In addition, this sheet-like negative electrode was cut into a size of 56 mm × 120 mm and used.
上記正極と負極との間に、上記の実施例１〜４、比較例１のセパレータを挟んで捲回し、ロール状の電極体を形成した。そして、その電極体をＳＵＳ３０４製の電池ケースに挿設し、非水電解液を注入した後、電池ケースを密閉して実施例１〜４、比較例１のリチウム二次電池を作製した。 A roll-shaped electrode body was formed by sandwiching the separators of Examples 1 to 4 and Comparative Example 1 between the positive electrode and the negative electrode. And the electrode body was inserted in the battery case made from SUS304, and after injecting a nonaqueous electrolyte, the battery case was sealed and the lithium secondary battery of Examples 1-4 and the comparative example 1 was produced.
なお、非水電解液は、エチレンカーボネートとジエチルカーボネートとを体積比で３：７に混合した混合溶媒に、ＬｉＰＦ6を１Ｍの濃度で溶解したものを用いた。非水電解液の注液量は、１ｃｃとした。なお、電池ケースには、内部圧力が０．８ＭＰａを超えると開弁する安全弁を正極および負極蓋板にそれぞれ設け、さらに、初回充電時における内部圧力を測定するための圧力計を取り付けた。 Incidentally, the non-aqueous electrolyte solution, 3 ethylene carbonate and diethyl carbonate at a volume ratio: a solvent mixture to 7, the LiPF 6 was used at a concentration of 1M. The amount of non-aqueous electrolyte injected was 1 cc. The battery case was provided with safety valves on the positive electrode and the negative electrode cover plate, respectively, that opened when the internal pressure exceeded 0.8 MPa, and a pressure gauge for measuring the internal pressure during the initial charge was attached.
（評価）
（１）リチウム二次電池の放電容量および初回充電時の圧力測定
製作した実施例および比較例の各リチウム二次電池を、初回充放電として、温度２５℃下にて、電流密度１．０ｍＡ／ｃｍ2の定電流で４．１Ｖまで充電した後、電流密度１．０ｍＡ／ｃｍ2の定電流で３．０Ｖまで放電を行った。そして、放電容量を測定し、充電前後の電池内部の圧力を測定することにより充電による圧力増加を求めた。これらの測定結果を表１に示す。
(Evaluation)
(1) Measurement of discharge capacity of lithium secondary battery and pressure at the time of initial charge The lithium secondary batteries of the manufactured examples and comparative examples were subjected to initial charge / discharge at a temperature of 25 ° C. and a current density of 1.0 mA / after charging to 4.1V at a constant current of cm 2, and discharged at a constant current density of 1.0 mA / cm 2 until 3.0 V. And discharge capacity was measured and the pressure increase by charge was calculated | required by measuring the pressure inside the battery before and behind charge. These measurement results are shown in Table 1.
表１に示すように、本発明のセパレータを用いた実施例１〜４の各二次電池は、従来のセルロース紙をセパレータとして用いた比較例１の二次電池と比較して放電容量が大きい。これは、エステル化またはエーテル化することによりセルロースの酸化還元反応が抑制され、電池の不可逆容量が減少したためと考えられる。また、実施例の各二次電池は、充電による圧力増加が小さい。このことは、上記同様にセルロースの酸化還元反応が抑制されたため、ガスの発生が減少したことを示すものである。これより、セルロース誘導体を主成分とする微多孔膜を含むセパレータを用いることで、充電時におけるガスの発生量が少なく、不可逆容量の小さいリチウム二次電池を構成できることが確認できた。 As shown in Table 1, each secondary battery of Examples 1 to 4 using the separator of the present invention has a large discharge capacity compared to the secondary battery of Comparative Example 1 using conventional cellulose paper as a separator. . This is considered to be because the redox reaction of cellulose was suppressed by esterification or etherification, and the irreversible capacity of the battery was reduced. Moreover, each secondary battery of an Example has a small pressure increase by charge. This indicates that the generation of gas was reduced because the redox reaction of cellulose was suppressed as described above. From this, it was confirmed that by using a separator including a microporous film containing a cellulose derivative as a main component, a lithium secondary battery with a small amount of gas generated during charging and a small irreversible capacity can be constructed.
（２）リチウム二次電池の保存試験および自己放電量の測定
次に、実施例および比較例の各リチウム二次電池について保存試験を行った。保存試験は、電流密度１．０ｍＡ／ｃｍ2の定電流で電圧が３．７５Ｖに到達するまで充電を行うことにより各二次電池をＳＯＣ６０％の状態とした後、２５℃の恒温槽に１週間保存することとした。そして、保存試験の前後で各二次電池の放電容量を測定し、それらの値から、式［｛１−（保存後放電容量／保存前放電容量）｝×１００（％）］を用いて自己放電率
（％）を計算した。各二次電池の自己放電率の値を先の表１にまとめて示す。なお、表１には、求めた各二次電池の自己放電率の値を４倍して１ヶ月間の保存における自己放電率とした値を示す。実施例１〜４の二次電池は、比較例１の二次電池に比べ圧力増加、自己放電率が小さいものであった。
(2) Storage test of lithium secondary battery and measurement of self-discharge amount Next, a storage test was performed for each of the lithium secondary batteries of Examples and Comparative Examples. In the storage test, each secondary battery is brought into a SOC 60% state by charging until the voltage reaches 3.75 V at a constant current of 1.0 mA / cm 2 , and then stored in a constant temperature bath at 25 ° C. We decided to save for a week. Then, the discharge capacity of each secondary battery is measured before and after the storage test, and from these values, self-expression is performed using the formula [{1- (discharge capacity after storage / discharge capacity before storage)} × 100 (%)]. The discharge rate (%) was calculated. The values of the self-discharge rate of each secondary battery are summarized in Table 1 above. Table 1 shows values obtained by multiplying the obtained self-discharge rate value of each secondary battery by 4 to obtain a self-discharge rate in storage for one month. The secondary batteries of Examples 1 to 4 had a smaller pressure increase and a lower self-discharge rate than the secondary battery of Comparative Example 1.
（第３発明の二次電池の製作）
前記の正極シート上に、実施例１のエマルジョン塗工液を塗布、乾燥して厚み２０μｍの多孔質膜と形成した。負極、非電解液、電池ケースは前記と同じものを使用して二次電池を製作した。（実施例５）実施例５の二次電池の各項目の評価は、実施例１の値と同じとなり、比較例１に比べ電気化学的に安定であり、自己放電量の小さい二次電池であった。また、製造コストが実施例１〜４に比べさらに安価に製造できた。
(Production of secondary battery of the third invention)
On the positive electrode sheet, the emulsion coating liquid of Example 1 was applied and dried to form a porous film having a thickness of 20 μm. A secondary battery was manufactured using the same negative electrode, non-electrolyte, and battery case as described above. (Example 5) Evaluation of each item of the secondary battery of Example 5 is the same as the value of Example 1, which is electrochemically stable compared to Comparative Example 1, and is a secondary battery with a small self-discharge amount. there were. Moreover, the manufacturing cost was able to be manufactured at a lower cost than in Examples 1 to 4.
Claims (3)
A porous membrane separator is provided by directly applying a W / O emulsion mainly composed of at least one resin selected from cellulose ester and cellulose ether to the positive electrode and / or the negative electrode, and then drying the lithium salt. A lithium secondary battery comprising a non-aqueous electrolyte dissolved in an organic solvent.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2005260021A JP5023261B2 (en) | 2005-09-08 | 2005-09-08 | Lithium secondary battery separator and lithium secondary battery using the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2005260021A JP5023261B2 (en) | 2005-09-08 | 2005-09-08 | Lithium secondary battery separator and lithium secondary battery using the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2007073382A true JP2007073382A (en) | 2007-03-22 |
| JP5023261B2 JP5023261B2 (en) | 2012-09-12 |
Family
ID=37934666
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2005260021A Active JP5023261B2 (en) | 2005-09-08 | 2005-09-08 | Lithium secondary battery separator and lithium secondary battery using the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP5023261B2 (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009054319A (en) * | 2007-08-23 | 2009-03-12 | Toshiba Corp | Nonaqueous electrolyte solution battery |
| WO2013054888A1 (en) * | 2011-10-13 | 2013-04-18 | 特種東海製紙株式会社 | Electrochemical element separator and manufacturing method for same |
| US8735000B2 (en) | 2011-10-13 | 2014-05-27 | Tokushu Tokai Paper Co., Ltd. | Porous membrane and process for preparing the same |
| US8765308B2 (en) | 2011-10-13 | 2014-07-01 | Tokushu Tokai Paper Co., Ltd. | Porous membrane and process for preparing the same |
| US9023535B2 (en) | 2011-10-13 | 2015-05-05 | Tokushu Tokai Paper Co., Ltd. | Porous membrane and process for preparing the same |
| US9142357B2 (en) | 2011-02-24 | 2015-09-22 | Nec Corporation | Separator for electric storage device and electric storage device |
| JP2017010911A (en) * | 2015-06-26 | 2017-01-12 | 三菱樹脂株式会社 | Separator for power storage device and manufacturing method therefor |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0379643A (en) * | 1989-08-23 | 1991-04-04 | Teijin Koodore Kk | Method for forming w/o type emulsion and cellular substance |
| JP2002532853A (en) * | 1998-12-18 | 2002-10-02 | エヴァレディー バッテリー カンパニー インコーポレイテッド | In-situ molded separator for batteries |
| JP2003155371A (en) * | 2001-11-21 | 2003-05-27 | Tohoku Ricoh Co Ltd | Porous membrane, method for preparing the same and sheet having the same |
-
2005
- 2005-09-08 JP JP2005260021A patent/JP5023261B2/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0379643A (en) * | 1989-08-23 | 1991-04-04 | Teijin Koodore Kk | Method for forming w/o type emulsion and cellular substance |
| JP2002532853A (en) * | 1998-12-18 | 2002-10-02 | エヴァレディー バッテリー カンパニー インコーポレイテッド | In-situ molded separator for batteries |
| JP2003155371A (en) * | 2001-11-21 | 2003-05-27 | Tohoku Ricoh Co Ltd | Porous membrane, method for preparing the same and sheet having the same |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009054319A (en) * | 2007-08-23 | 2009-03-12 | Toshiba Corp | Nonaqueous electrolyte solution battery |
| US8728670B2 (en) | 2007-08-23 | 2014-05-20 | Kabushiki Kaisha Toshiba | Nonaqueous-electrolyte battery containing a negative electrode with a coating film formed by an isocyanate-containing compound in the nonaqueous electrolyte |
| US9142357B2 (en) | 2011-02-24 | 2015-09-22 | Nec Corporation | Separator for electric storage device and electric storage device |
| WO2013054888A1 (en) * | 2011-10-13 | 2013-04-18 | 特種東海製紙株式会社 | Electrochemical element separator and manufacturing method for same |
| KR101331481B1 (en) | 2011-10-13 | 2013-11-20 | 도쿠슈 도카이 세이시 가부시키가이샤 | Separator for electrochemical device and process for preparing the same |
| US8735000B2 (en) | 2011-10-13 | 2014-05-27 | Tokushu Tokai Paper Co., Ltd. | Porous membrane and process for preparing the same |
| US8765308B2 (en) | 2011-10-13 | 2014-07-01 | Tokushu Tokai Paper Co., Ltd. | Porous membrane and process for preparing the same |
| US8900758B2 (en) | 2011-10-13 | 2014-12-02 | Tokushu Tokai Paper Co., Ltd. | Separator for electrochemical device and process for preparing the same |
| US9023535B2 (en) | 2011-10-13 | 2015-05-05 | Tokushu Tokai Paper Co., Ltd. | Porous membrane and process for preparing the same |
| JP2017010911A (en) * | 2015-06-26 | 2017-01-12 | 三菱樹脂株式会社 | Separator for power storage device and manufacturing method therefor |
Also Published As
| Publication number | Publication date |
|---|---|
| JP5023261B2 (en) | 2012-09-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP6469879B2 (en) | Gel polymer electrolyte, method for producing the same, and electrochemical device including gel polymer electrolyte | |
| JP4249607B2 (en) | Composite polymer electrolyte for lithium secondary battery containing single ion conductor and method for producing the same | |
| JP5235109B2 (en) | Nonaqueous electrolyte battery separator and nonaqueous electrolyte battery | |
| JP4201308B2 (en) | Lithium secondary battery separator and lithium secondary battery using the same | |
| JP4493513B2 (en) | Organic electrolyte and lithium battery using the same | |
| JP2007207675A (en) | Lithium secondary cell using ionic liquid | |
| JP2012174569A (en) | Preparation method of slurry for forming positive electrode mixture layer, and method of manufacturing nonaqueous electrolyte secondary battery | |
| EP2913879B1 (en) | Nonaqueous electrolyte secondary battery and method for manufacturing same | |
| JP5023261B2 (en) | Lithium secondary battery separator and lithium secondary battery using the same | |
| JP5734708B2 (en) | Nonaqueous electrolyte secondary battery and manufacturing method thereof | |
| CN113574697A (en) | Compositions and methods for prelithiation of energy storage devices | |
| JP6989095B2 (en) | Lithium ion secondary battery | |
| KR101739294B1 (en) | Positive electrode for lithium secondary battery and lithium secondary battery comprising the same | |
| JP6341151B2 (en) | Electrode sheet manufacturing method | |
| JP2018190582A (en) | Method for manufacturing lithium ion secondary battery | |
| JP2005142141A (en) | Organic electrolyte and lithium battery using the same | |
| JP6241911B2 (en) | Active material particles, positive electrode for electricity storage device, electricity storage device, and method for producing active material particles | |
| JP2010015719A (en) | Nonaqueous electrolyte for battery, and nonaqueous electrolyte secondary battery equipped with it | |
| JP2010050021A (en) | Nonaqueous electrolyte for battery and nonaqueous electrolyte secondary battery having the same | |
| KR20130029328A (en) | Non-aqueous electrolyte for electrochemical device and electrochemical device | |
| JP4649692B2 (en) | Positive electrode mixture paste for lithium secondary battery and lithium secondary battery | |
| JP2010015717A (en) | Nonaqueous electrolyte for battery, and nonaqueous electrolyte secondary battery equipped with it | |
| JP2012028086A (en) | Positive electrode for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery and method of manufacturing the same | |
| JP2010050026A (en) | Nonaqueous electrolyte for battery and nonaqueous electrolyte secondary battery having the same | |
| KR20190080697A (en) | Binder for rechargable battery, binder resin composition for rechargable battery, electrode for rechargable battery, and rechargable battery |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20080901 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20110822 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20110830 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20110901 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20120329 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20120410 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20150629 Year of fee payment: 3 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 Ref document number: 5023261 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313531 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |