JP6607388B2 - Positive electrode for lithium ion secondary battery and method for producing the same - Google Patents
Positive electrode for lithium ion secondary battery and method for producing the same Download PDFInfo
- Publication number
- JP6607388B2 JP6607388B2 JP2015237152A JP2015237152A JP6607388B2 JP 6607388 B2 JP6607388 B2 JP 6607388B2 JP 2015237152 A JP2015237152 A JP 2015237152A JP 2015237152 A JP2015237152 A JP 2015237152A JP 6607388 B2 JP6607388 B2 JP 6607388B2
- Authority
- JP
- Japan
- Prior art keywords
- positive electrode
- active material
- electrode active
- lithium ion
- ion secondary
- 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.)
- Active
Links
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims description 64
- 229910001416 lithium ion Inorganic materials 0.000 title claims description 64
- 238000004519 manufacturing process Methods 0.000 title claims description 9
- 239000007774 positive electrode material Substances 0.000 claims description 244
- 239000011163 secondary particle Substances 0.000 claims description 107
- 239000002002 slurry Substances 0.000 claims description 13
- 239000011149 active material Substances 0.000 claims description 9
- 239000011164 primary particle Substances 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 5
- 229920000447 polyanionic polymer Polymers 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 239000010450 olivine Substances 0.000 claims description 4
- 229910052609 olivine Inorganic materials 0.000 claims description 4
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 239000011248 coating agent Substances 0.000 claims description 2
- 238000000576 coating method Methods 0.000 claims description 2
- 230000008569 process Effects 0.000 claims description 2
- 239000010410 layer Substances 0.000 description 121
- 238000012360 testing method Methods 0.000 description 74
- 229910013210 LiNiMnCoO Inorganic materials 0.000 description 40
- 239000007773 negative electrode material Substances 0.000 description 19
- 238000001878 scanning electron micrograph Methods 0.000 description 18
- 239000000463 material Substances 0.000 description 15
- 230000001186 cumulative effect Effects 0.000 description 12
- 239000011255 nonaqueous electrolyte Substances 0.000 description 11
- 150000003839 salts Chemical class 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 9
- 229910052744 lithium Inorganic materials 0.000 description 9
- 239000011159 matrix material Substances 0.000 description 9
- -1 LiMnFePO 4 Inorganic materials 0.000 description 8
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 8
- 239000000956 alloy Substances 0.000 description 8
- 230000009257 reactivity Effects 0.000 description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 7
- 229910045601 alloy Inorganic materials 0.000 description 7
- 239000011230 binding agent Substances 0.000 description 7
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 6
- 239000006182 cathode active material Substances 0.000 description 6
- 239000004020 conductor Substances 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- 239000003960 organic solvent Substances 0.000 description 6
- 229910052710 silicon Inorganic materials 0.000 description 6
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 238000003825 pressing Methods 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 4
- 239000002033 PVDF binder Substances 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 239000003575 carbonaceous material Substances 0.000 description 4
- 238000007600 charging Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 4
- 239000000203 mixture 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
- 239000010703 silicon Substances 0.000 description 4
- 239000002344 surface layer Substances 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 3
- 229910010707 LiFePO 4 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
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 3
- 239000006230 acetylene black Substances 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 238000009792 diffusion process Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 238000012423 maintenance Methods 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000007769 metal material Substances 0.000 description 3
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 3
- 239000004810 polytetrafluoroethylene Substances 0.000 description 3
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 2
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 description 2
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 2
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 238000004220 aggregation Methods 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000003125 aqueous solvent Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 2
- 239000008151 electrolyte solution Substances 0.000 description 2
- 150000002170 ethers Chemical class 0.000 description 2
- 239000011737 fluorine Substances 0.000 description 2
- 229910052731 fluorine Inorganic materials 0.000 description 2
- 229910021382 natural graphite Inorganic materials 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 229920000058 polyacrylate Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 238000011076 safety test Methods 0.000 description 2
- 239000003566 sealing material Substances 0.000 description 2
- 229910052596 spinel Inorganic materials 0.000 description 2
- 239000011029 spinel Substances 0.000 description 2
- 238000000992 sputter etching Methods 0.000 description 2
- 229920003048 styrene butadiene rubber Polymers 0.000 description 2
- 239000002562 thickening agent Substances 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- VAYTZRYEBVHVLE-UHFFFAOYSA-N 1,3-dioxol-2-one Chemical compound O=C1OC=CO1 VAYTZRYEBVHVLE-UHFFFAOYSA-N 0.000 description 1
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 1
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical compound C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 description 1
- 229910001200 Ferrotitanium Inorganic materials 0.000 description 1
- 229910012425 Li3Fe2 (PO4)3 Inorganic materials 0.000 description 1
- 229910015015 LiAsF 6 Inorganic materials 0.000 description 1
- 229910013063 LiBF 4 Inorganic materials 0.000 description 1
- 229910013684 LiClO 4 Inorganic materials 0.000 description 1
- 229910011281 LiCoPO 4 Inorganic materials 0.000 description 1
- 229910010743 LiFeSi Inorganic materials 0.000 description 1
- 229910015645 LiMn Inorganic materials 0.000 description 1
- 229910014689 LiMnO Inorganic materials 0.000 description 1
- 229910013528 LiN(SO2 CF3)2 Inorganic materials 0.000 description 1
- 229910013385 LiN(SO2C2F5)2 Inorganic materials 0.000 description 1
- 229910013392 LiN(SO2CF3)(SO2C4F9) Inorganic materials 0.000 description 1
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 1
- 229910013086 LiNiPO Inorganic materials 0.000 description 1
- 229910012424 LiSO 3 Inorganic materials 0.000 description 1
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- OFOBLEOULBTSOW-UHFFFAOYSA-N Propanedioic acid Natural products OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000005856 abnormality Effects 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 1
- 229920000800 acrylic rubber Polymers 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 229920001940 conductive polymer Polymers 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 229910021469 graphitizable carbon Inorganic materials 0.000 description 1
- 239000011357 graphitized carbon fiber Substances 0.000 description 1
- 239000002946 graphitized mesocarbon microbead Substances 0.000 description 1
- 150000008282 halocarbons Chemical class 0.000 description 1
- 229910021385 hard carbon Inorganic materials 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 239000003273 ketjen black Substances 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 150000002596 lactones Chemical class 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 238000007561 laser diffraction method Methods 0.000 description 1
- SWAIALBIBWIKKQ-UHFFFAOYSA-N lithium titanium Chemical compound [Li].[Ti] SWAIALBIBWIKKQ-UHFFFAOYSA-N 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- VZCYOOQTPOCHFL-UPHRSURJSA-N maleic acid Chemical compound OC(=O)\C=C/C(O)=O VZCYOOQTPOCHFL-UPHRSURJSA-N 0.000 description 1
- 239000011976 maleic acid Substances 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 239000011302 mesophase pitch Substances 0.000 description 1
- 239000002905 metal composite material Substances 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 238000009782 nail-penetration test Methods 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 229910021470 non-graphitizable carbon Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 125000002467 phosphate group Chemical class [H]OP(=O)(O[H])O[*] 0.000 description 1
- 239000011295 pitch Substances 0.000 description 1
- 229920002239 polyacrylonitrile Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- HNJBEVLQSNELDL-UHFFFAOYSA-N pyrrolidin-2-one Chemical compound O=C1CCCN1 HNJBEVLQSNELDL-UHFFFAOYSA-N 0.000 description 1
- 239000005060 rubber Substances 0.000 description 1
- 238000000790 scattering method Methods 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 229910021384 soft carbon Inorganic materials 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 150000007984 tetrahydrofuranes Chemical class 0.000 description 1
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 1
- 229910001887 tin oxide Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- VZCYOOQTPOCHFL-UHFFFAOYSA-N trans-butenedioic acid Natural products OC(=O)C=CC(O)=O VZCYOOQTPOCHFL-UHFFFAOYSA-N 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、リチウムイオン二次電池に用いられる正極及びその製造方法に関する。 The present invention relates to a positive electrode used for a lithium ion secondary battery and a method for producing the same.
ノート型コンピュータ、携帯電話、デジタルカメラ等電子機器の普及に伴い、これら電子機器を駆動するための二次電池の需要が拡大している。近年、これら電子機器においては、高機能化の進展に伴い消費電力が増大していることや、小型化が期待されていることから、二次電池の高容量化が求められている。二次電池の中でも、例えば非水電解質二次電池（特に、リチウムイオン二次電池）は、高容量化及び高出力化が可能であることから種々の電子機器への利用が進められている。また最近では、高容量化及び高出力化が可能なリチウムイオン二次電池は、その特徴を利用して電気自動車、ハイブリッド自動車に至る大型電池用途にも用いられており、高容量化及び高出力化と併せて、高安全性化の要求も非常に高まっている。 With the widespread use of electronic devices such as notebook computers, mobile phones, and digital cameras, the demand for secondary batteries for driving these electronic devices is increasing. In recent years, these electronic devices have been required to have a high capacity secondary battery because power consumption has increased with the progress of higher functionality and miniaturization is expected. Among secondary batteries, for example, non-aqueous electrolyte secondary batteries (particularly lithium ion secondary batteries) are being used in various electronic devices because of their high capacity and high output. Recently, lithium-ion secondary batteries capable of higher capacity and higher output are also used for large-sized battery applications such as electric vehicles and hybrid cars using their characteristics. Along with this trend, the demand for higher safety is also increasing.
リチウムイオン二次電池では、一般に、正極活物質に代表される正極材料からなる正極活物質層を正極集電体の表面に形成した正極と、負極活物質に代表される負極材料からなる負極活物質層を負極集電体の表面に形成した負極とが、セパレータを介在させて電極体を構成している。そして、電極体の正極及び負極は、非水電解質（非水電解液）を介して接続され、電池ケースに収納されている。 Generally, in a lithium ion secondary battery, a positive electrode in which a positive electrode active material layer made of a positive electrode material typified by a positive electrode active material is formed on the surface of a positive electrode current collector, and a negative electrode active material made of a negative electrode material typified by a negative electrode active material. A negative electrode having a material layer formed on the surface of the negative electrode current collector constitutes an electrode body with a separator interposed therebetween. And the positive electrode and negative electrode of an electrode body are connected via the non-aqueous electrolyte (non-aqueous electrolyte), and are accommodated in the battery case.
リチウムイオン二次電池の正極材料に使用される正極活物質としては、一般に、リチウムイオンの拡散速度が速く電子伝導性に優れている、層状構造を有するＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＭｎＯ２等の酸化物、あるいは、これらの複合酸化物が用いられている。しかしながら、これらの酸化物系正極活物質は熱安定性が低いことが知られており、過充電等の電池異常時における安全性に問題がある。そこで、正極活物質として、比較的熱安定性の高いスピネル構造を有するＬｉＭｎ２Ｏ４や、オリビン構造を有するＬｉＦｅＰＯ４等のリチウム含有リン酸化合物の開発が進められている。 As a positive electrode active material used for a positive electrode material of a lithium ion secondary battery, generally, oxidation of LiCoO 2 , LiNiO 2 , LiMnO 2, etc. having a layered structure with a high diffusion rate of lithium ions and excellent electron conductivity Or a composite oxide of these. However, these oxide-based positive electrode active materials are known to have low thermal stability, and there is a problem in safety in the event of battery abnormality such as overcharging. Therefore, development of lithium-containing phosphate compounds such as LiMn 2 O 4 having a spinel structure with relatively high thermal stability and LiFePO 4 having an olivine structure has been promoted as a positive electrode active material.
ところが、スピネル構造を有するＬｉＭｎ２Ｏ４や、オリビン構造を有するＬｉＦｅＰＯ４は、ＬｉＣｏＯ２等に比べて熱安定性は高いものの、リチウムイオンの拡散速度が遅く、また、電子伝導性がＬｉＣｏＯ２等に比べて劣っているため、高容量化及び高出力化の実現に問題があった。このように、リチウムイオン二次電池の正極において、高容量化及び高出力化の実現と、高安全性化の実現とはトレードオフの関係にあり、高容量化及び高出力化と高安全性化を共に実現できるリチウムイオン二次電池の正極が望まれている。 However, LiMn 2 O 4 having a spinel structure and LiFePO 4 having an olivine structure have higher thermal stability than LiCoO 2 or the like, but have a slow diffusion rate of lithium ions and an electron conductivity of LiCoO 2 or the like. Therefore, there was a problem in realizing high capacity and high output. Thus, in the positive electrode of a lithium ion secondary battery, the realization of high capacity and high output and the realization of high safety are in a trade-off relationship, and high capacity and high output and high safety are achieved. A positive electrode for a lithium ion secondary battery that can be realized together is desired.
このような実情に鑑みて近年では、リチウムイオン二次電池の正極において、異なる複数の正極活物質を混合して形成した正極活物質層や、正極活物質の種類が異なる複数の層からなる正極活物質層等が提案されており、これによって、高容量化及び高出力化と共に高安全性化を図っている。 In view of such circumstances, in recent years, in a positive electrode of a lithium ion secondary battery, a positive electrode active material layer formed by mixing a plurality of different positive electrode active materials, or a positive electrode comprising a plurality of layers having different types of positive electrode active materials An active material layer or the like has been proposed, thereby achieving higher safety as well as higher capacity and higher output.
例えば特許文献１では、正極活物質層が２種類の異なる正極活物質からなる層（２層）で構成されている。この正極活物質層は、正極集電体に接する第１正極活物質層と第１正極活物質層の上に形成された第２正極活物質層とからなる。そして、第１正極活物質層には電池反応性が高いものの熱安定性が低い材料（ＬｉＣｏＯ２）が用いられており、第２正極活物質層には熱安定性が高い材料（ＬｉＭｎ２Ｏ４）が用いられている。すなわち、特許文献１の正極活物質層では、過充電時に最初に高温となる正極表面側に熱安定性が高い材料からなる第２正極活物質層を形成することで、正極集電体側に配置された熱安定性の低い材料（第１正極活物質層）の充電反応の進行を抑制している。 For example, in patent document 1, the positive electrode active material layer is comprised by the layer (two layers) which consists of two types of different positive electrode active materials. The positive electrode active material layer includes a first positive electrode active material layer in contact with the positive electrode current collector and a second positive electrode active material layer formed on the first positive electrode active material layer. The first positive electrode active material layer uses a material having high battery reactivity but low thermal stability (LiCoO 2 ), and the second positive electrode active material layer has high thermal stability (LiMn 2 O). 4 ) is used. That is, in the positive electrode active material layer of Patent Document 1, the second positive electrode active material layer made of a material having high thermal stability is formed on the positive electrode surface side that first becomes a high temperature during overcharging, so that the positive electrode active material layer is disposed on the positive electrode current collector side. The progress of the charging reaction of the material with low thermal stability (first positive electrode active material layer) is suppressed.
しかしながら、特許文献１に開示されている正極活物質層では、ＬｉＣｏＯ２とＬｉＭｎ２Ｏ４とが２層構造となっている。このような正極活物質層が２層構造となった正極において、集電体側では電子抵抗が下がる反面、イオン抵抗が上がる。一方で、集電体側と反対側の電極表面側では電子抵抗が上がる反面、イオン抵抗が下がる。そのため、電子抵抗とイオン抵抗の分布が大きくなりすぎると、反応部分に偏りが生じ、劣化が促進される。 However, in the positive electrode active material layer disclosed in Patent Document 1, LiCoO 2 and LiMn 2 O 4 have a two-layer structure. In the positive electrode in which such a positive electrode active material layer has a two-layer structure, the electron resistance decreases on the current collector side, but the ionic resistance increases. On the other hand, while the electron resistance increases on the electrode surface side opposite to the current collector side, the ionic resistance decreases. Therefore, if the distribution of the electronic resistance and the ionic resistance becomes too large, the reaction part is biased and the deterioration is accelerated.
このように反応性の異なる正極活物質が別々の層として形成された正極活物質層では、反応性の高い正極活物質が優先的に電池反応に寄与され、結果としてこの正極活物質の層が先に劣化してしまう。すなわち、ＬｉＣｏＯ２の層とＬｉＭｎ２Ｏ４の層とで電池反応量に相違が生じ、これに起因する正極劣化が生じることが考えられ得る。つまり、電池寿命の向上を図ることが困難であることが考えられ得る。 In the positive electrode active material layer in which the positive electrode active materials having different reactivities are formed as separate layers in this way, the positive electrode active material having high reactivity is preferentially contributed to the battery reaction, and as a result, the positive electrode active material layer is It will deteriorate first. That is, it can be considered that there is a difference in the amount of battery reaction between the LiCoO 2 layer and the LiMn 2 O 4 layer, resulting in deterioration of the positive electrode. That is, it may be difficult to improve the battery life.
このような現象は、低温や高レートでの電池使用時に顕著に生じる。また、正極活物質として電子伝導性の低いポリアニオン系正極活物質を混合する場合は、電子伝導性の分布も大きくなり、反応分布が生じやすく、劣化が起こりやすい。 Such a phenomenon remarkably occurs when the battery is used at a low temperature or at a high rate. Further, when a polyanionic positive electrode active material having low electron conductivity is mixed as the positive electrode active material, the distribution of electron conductivity is increased, reaction distribution is likely to occur, and deterioration is likely to occur.
そこで、本発明は高容量化及び高出力化と高安全性化を実現させると共に、さらに電池寿命を向上させることができるリチウムイオン二次電池用正極及びその製造方法を提供することを目的とする。 SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a positive electrode for a lithium ion secondary battery and a method for manufacturing the same, which can realize high capacity, high output and high safety, and can further improve battery life. .
上記課題を解決するための本発明のリチウムイオン二次電池用正極は、正極集電体と、正極集電体の表面に設けられ正極材料からなる正極活物質層と、を有するリチウムイオン二次電池用正極であって、正極材料には、ポリアニオン構造を有する第１正極活物質と酸化物系の活物質である第２正極活物質とが、第１活物質の質量が第２活物質の質量よりも多くなるように含有されており、正極活物質層において、第１正極活物質及び第２正極活物質は一次粒子が凝集した二次粒子の形態を有し、第１正極活物質の体積基準とした平均二次粒子径Ｒ １ と第２正極活物質の体積基準とした平均二次粒子径Ｒ ２ とが、Ｒ １ ＜Ｒ ２ の関係（ただし、Ｒ １ ≦（０．５０７）Ｒ ２ の範囲を除く）を満たし、正極集電体の一方の表面に設けられた正極活物質層の層厚Ｄを基準としたときに、正極活物質層において正極集電体と反対側の表面である正極表面から１５％の厚さの範囲に分散されている第２正極活物質が、第２正極活物質全体に対して、０体積％を超え１０体積％以下で含まれることを特徴とする。 A positive electrode for a lithium ion secondary battery according to the present invention for solving the above-mentioned problems is a lithium ion secondary battery having a positive electrode current collector and a positive electrode active material layer formed on the surface of the positive electrode current collector and made of a positive electrode material. A positive electrode for a battery, wherein the positive electrode material includes a first positive electrode active material having a polyanion structure and a second positive electrode active material that is an oxide-based active material, wherein the mass of the first active material is the second active material. In the positive electrode active material layer, the first positive electrode active material and the second positive electrode active material have a form of secondary particles in which primary particles are aggregated, and the first positive electrode active material The relationship between the average secondary particle diameter R 1 based on volume and the average secondary particle diameter R 2 based on volume of the second positive electrode active material is R 1 <R 2 (where R 1 ≦ (0.507)) met except to the extent of R 2), provided on one surface of the positive electrode current collector a positive electrode When relative to the thickness D of the material layer, a second cathode active material is dispersed in a range from the positive electrode surface of 15% of the thickness of the opposite side surface of the positive electrode current collector in the positive electrode active material layer , the second overall positive active material, characterized in that contained less than 10% by volume more than 0% by volume.
本発明者らはリチウムイオン二次電池における正極を鋭意検討した結果、正極活物質に代表される正極活物質層において、熱安定性の高い正極活物質（第１正極活物質）をマトリックス又はマトリックス様（以下、単に「マトリックス」と称する）とし、熱安定性が低く電池反応性の高い正極活物質（第２正極活物質）をこのマトリックスに分散させ、かつ、正極表面から所定の厚みに分散される第２正極活物質の量を制御することに想到した。これにより、リチウムイオン二次電池の正極における高安全性化を実現できると共に、リチウムイオン二次電池の寿命を向上させることが可能となった。 As a result of intensive studies on the positive electrode in a lithium ion secondary battery, the present inventors have found that a positive active material layer (first positive active material) having high thermal stability is used as a matrix or matrix in a positive active material layer typified by a positive active material. (Hereinafter simply referred to as “matrix”), a positive electrode active material (second positive electrode active material) having low thermal stability and high battery reactivity is dispersed in this matrix, and is dispersed from the positive electrode surface to a predetermined thickness. The inventors have conceived of controlling the amount of the second positive electrode active material. As a result, it is possible to improve the safety of the positive electrode of the lithium ion secondary battery and improve the life of the lithium ion secondary battery.
すなわち、本発明の構成によれば、第１正極活物質によって熱安定性を向上させることができる。また、正極表面から所定の厚みに分散されている第２正極活物質の量を制御することにより、第１正極活物質と第２正極活物質との電池反応量を近づけることができ、つまり、優先的に第２正極活物質が電池反応に寄与することにより起こり得る電池劣化を抑制することができる。結果として、電池寿命を向上させることができる。
上記課題を解決するための本発明のリチウムイオン二次電池用正極の製造方法は、第１正極活物質及び第２正極活物質を含む正極材料スラリーを調製する工程において、第１正極活物質及び第２正極活物質は一次粒子が凝集した二次粒子の形態を有し、第１正極活物質の体積基準とした平均二次粒子径Ｒ １ と第２正極活物質の体積基準とした平均二次粒子径Ｒ ２ とが、Ｒ １ ＜Ｒ ２ の関係（ただし、Ｒ １ ≦（０．５０７）Ｒ ２ の範囲を除く）を満たし、下記（ａ）及び（ｂ）のうちの少なくとも一方の条件を満たし、調製した正極材料スラリーを正極集電体に塗布する工程を有する請求項１〜５の何れか一項に記載のリチウムイオン二次電池用正極を製造する方法である。（ａ）前記平均二次粒子径Ｒ １ は、Ｒ １ ＜（１／２）Ｄである。（ｂ）前記平均二次粒子径Ｒ ２ は、Ｒ ２ ＜（１／２）Ｄである。
That is, according to the structure of this invention, thermal stability can be improved with the 1st positive electrode active material. Further, by controlling the amount of the second positive electrode active material dispersed in a predetermined thickness from the positive electrode surface, the amount of battery reaction between the first positive electrode active material and the second positive electrode active material can be made closer, that is, Battery degradation that may occur when the second positive electrode active material preferentially contributes to the battery reaction can be suppressed. As a result, battery life can be improved.
The method for producing a positive electrode for a lithium ion secondary battery according to the present invention for solving the above-described problems includes the step of preparing a positive electrode material slurry containing a first positive electrode active material and a second positive electrode active material, second positive electrode active material has the form of secondary particles formed by aggregation of primary particles, average secondary to a volumetric basis of the first positive electrode active material was an average secondary particle diameter R 1 and to a volume standard of the second positive electrode active material The secondary particle size R 2 satisfies the relationship of R 1 <R 2 ( excluding the range of R 1 ≦ (0.507) R 2 ), and at least one of the following (a) and (b) It is the method of manufacturing the positive electrode for lithium ion secondary batteries as described in any one of Claims 1-5 which has the process of satisfy | filling conditions and apply | coating the prepared positive electrode material slurry to a positive electrode electrical power collector. (A) The average secondary particle diameter R 1 is R 1 <(1/2) D. (B) the average secondary particle diameter R 2 is R 2 <(1/2) D.
以下、本発明のリチウムイオン二次電池用正極及びその製造方法における好適な実施形態を説明する。ただし、本発明はこの実施形態に限定されるものではなく、その要旨を変更しない範囲において適宜変更して実施することが可能なものである。なお、本明細書において特に言及している事項以外の事柄であって本発明の実施に必要な事項は、当該分野における従来技術に基づく当業者の設計事項として把握され得る。本発明は、本明細書に開示されている内容と当該分野における技術常識とに基づいて実施することができる。 Hereinafter, preferred embodiments of the positive electrode for a lithium ion secondary battery and the method for producing the same of the present invention will be described. However, the present invention is not limited to this embodiment, and can be appropriately modified and implemented without departing from the scope of the invention. It should be noted that matters other than matters specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.
図１に当該実施形態に係る正極を適応したリチウムイオン二次電池の概略断面図を示す。図１で例示するリチウムイオン二次電池は、コイン型リチウムイオン二次電池１である。後述する試験例においては、リチウムイオン二次電池を用いる。 FIG. 1 is a schematic cross-sectional view of a lithium ion secondary battery to which the positive electrode according to the embodiment is applied. The lithium ion secondary battery illustrated in FIG. 1 is a coin-type lithium ion secondary battery 1. In a test example to be described later, a lithium ion secondary battery is used.
当該実施形態に係る正極１４を適応したリチウムイオン二次電池１は、正極ケース１１、シール材（ガスケット）１２、非水電解質１３、正極１４、正極集電体１４０、正極活物質層１４１、セパレータ１５、負極ケース１６、負極１７、負極集電体１７０、負極集電体層１７１、保持部材１８等を有する。 A lithium ion secondary battery 1 to which the positive electrode 14 according to the embodiment is applied includes a positive electrode case 11, a sealing material (gasket) 12, a nonaqueous electrolyte 13, a positive electrode 14, a positive electrode current collector 140, a positive electrode active material layer 141, and a separator. 15, a negative electrode case 16, a negative electrode 17, a negative electrode current collector 170, a negative electrode current collector layer 171, a holding member 18, and the like.
（正極）
正極１４は、正極集電体１４０と、正極集電体１４０の表面に設けられた正極活物質層１４１とを有する。正極１４の製造方法は、特に限定されるものではなく、例えば次のように作製される。
(Positive electrode)
The positive electrode 14 includes a positive electrode current collector 140 and a positive electrode active material layer 141 provided on the surface of the positive electrode current collector 140. The manufacturing method of the positive electrode 14 is not specifically limited, For example, it produces as follows.
まず、リチウムイオンを可逆的に吸蔵・脱離し得る複数の正極活物質、導電材、及び結着材とを含む正極材料を適切な溶媒に懸濁させ混合して正極材料スラリーを得る。正極材料を溶媒に混合する手段としては、せん断力が比較的強いプラネタリーミキサ、ディスパーミキサ、自転・公転ミキサ等の攪拌機を用いることが望ましい。 First, a positive electrode material including a plurality of positive electrode active materials capable of reversibly occluding and desorbing lithium ions, a conductive material, and a binder is suspended and mixed in an appropriate solvent to obtain a positive electrode material slurry. As a means for mixing the positive electrode material with the solvent, it is desirable to use a stirrer such as a planetary mixer, a disper mixer, or a rotation / revolution mixer having a relatively strong shearing force.
次に、得られた正極材料スラリーを正極集電体１４０の片面または両面に塗布する。正極材料スラリーを正極集電体１４０に塗工する手段としては、ダイコーター、グラビアコータ―、ドクターブレード等の一般的な塗工機器を用いることが望ましい。そして、これを乾燥し、正極活物質層１４１を正極集電体１４０の表面に形成する。 Next, the obtained positive electrode material slurry is applied to one side or both sides of the positive electrode current collector 140. As a means for applying the positive electrode material slurry to the positive electrode current collector 140, it is desirable to use a general application device such as a die coater, a gravure coater, or a doctor blade. Then, this is dried to form the positive electrode active material layer 141 on the surface of the positive electrode current collector 140.
正極活物質層１４１が形成された正極集電体１４０は、ロールプレス等により所定の圧力を付加して圧縮成形した後、所望の形状に裁断又は打ち抜くことでリチウムイオン二次電池用正極とする。 The positive electrode current collector 140 on which the positive electrode active material layer 141 is formed is compression-molded by applying a predetermined pressure by a roll press or the like, and then cut or punched into a desired shape to form a positive electrode for a lithium ion secondary battery. .
当該実施形態における正極材料の正極活物質は、ポリアニオン構造を有する第１正極活物質と、層状構造を有する酸化物系の第２正極活物質を有する。ポリアニオン構造を有する正極活物質は、結晶構造中にＸＯ４四面体（Ｘ＝Ｐ，Ａｓ，Ｓｉ，Ｂ等）を含む。このＸＯ４四面体では、酸素は強固な共有結合によってＸと結合しているため、酸素が放出されにくい構造となっている。したがって、ポリアニオン構造を有する第１正極活物質は、熱安定性が高く、リチウムイオン二次電池の高安全性化を実現させることができる。 The positive electrode active material of the positive electrode material in the embodiment includes a first positive electrode active material having a polyanion structure and an oxide-based second positive electrode active material having a layered structure. The positive electrode active material having a polyanion structure contains an XO 4 tetrahedron (X = P, As, Si, B, etc.) in the crystal structure. This XO 4 tetrahedron has a structure in which oxygen is difficult to be released because oxygen is bonded to X by a strong covalent bond. Therefore, the 1st positive electrode active material which has a polyanion structure has high thermal stability, and can implement | achieve the high safety | security of a lithium ion secondary battery.
このような第１正極活物質としては、一般式：ＬｉαＭβＸＯ４−γ（０≦α≦２、０≦β≦１、０≦γ≦１、ＭはＭｇ，Ａｌ，Ｔｉ，Ｖ，Ｃｒ，Ｍｎ，Ｆｅ，Ｃｏ，Ｎｉ，Ｃｕ，Ｚｎ，Ｇａ，Ｚｒ,Ｎｂ，Ｍｏより選ばれる一種以上、ＸはＰ，Ｓｉ，Ｂより選ばれる一種）で表されるものが望ましい。より望ましくは、ＬｉＦｅＰＯ4、ＬｉＭｎＦｅＰＯ４、ＬｉＣｏＰＯ４、ＬｉＭｎＣｏＰＯ４、ＬｉＮｉＰＯ４、ＬｉＭｎＮｉＰＯ４、Ｌｉ３Ｖ２（ＰＯ４）３、Ｌｉ３Ｆｅ２（ＰＯ４）３、ＬｉＭｎＳｉ２Ｏ６、ＬｉＦｅＳｉ２Ｏ６、ＬｉＣｏＳｉ２Ｏ６、Ｌｉ２ＭｎＳｉＯ４、Ｌｉ２ＦｅＳｉＯ４、Ｌｉ２ＣｏＳｉＯ４、Ｌｉ２ＮｉＳｉＯ４が挙げられる。これらのうち、特にＭｎを含有するオリビン構造を備える材料がより好ましい。 As such a first positive electrode active material, a general formula: Li α M β XO 4-γ (0 ≦ α ≦ 2, 0 ≦ β ≦ 1, 0 ≦ γ ≦ 1, M is Mg, Al, Ti, V , Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Nb, and Mo, and X is preferably selected from P, Si, and B). More preferably, LiFePO 4, LiMnFePO 4, LiCoPO 4, LiMnCoPO 4, LiNiPO 4, LiMnNiPO 4, Li 3 V 2 (PO 4) 3, Li 3 Fe 2 (PO 4) 3, LiMnSi 2 O 6, LiFeSi 2 O 6 , LiCoSi 2 O 6 , Li 2 MnSiO 4 , Li 2 FeSiO 4 , Li 2 CoSiO 4 , Li 2 NiSiO 4 . Among these, a material having an olivine structure containing Mn is more preferable.
層状構造を有する酸化物系の正極材料は、理論容量が大きく、リチウムイオンの拡散速度及び電子伝導性に優れることが知られている。したがって、層状構造を有する酸化物系の第２正極活物質は、リチウムイオン二次電池の高容量化及び高出力化を実現させることができる。 It is known that an oxide-based positive electrode material having a layered structure has a large theoretical capacity and is excellent in lithium ion diffusion rate and electronic conductivity. Therefore, the oxide-based second positive electrode active material having a layered structure can realize higher capacity and higher output of the lithium ion secondary battery.
このような第２正極活物質としては、一般式：Ｌｉ１＋ｘＭ１−ｙＯ２（ＭはＦｅ,Ｎｉ,Ｍｎ,Ｃｏ等から選択される１種以上の遷移金属元素、０≦ｘ＜１／３、０≦ｙ＜１／３）で表されるものが望ましい。より望ましくは、ＬｉＮｉＭｎＣｏＯ２等の三元系リチウム複合酸化物である。第２正極活物質としては、表面処理を行ったものでもよい。 As such a second positive electrode active material, a general formula: Li 1 + x M 1-y O 2 (M is one or more transition metal elements selected from Fe, Ni, Mn, Co, etc., 0 ≦ x <1 / 3, 0 ≦ y <1/3) is desirable. More desirably, a ternary lithium composite oxide such as LiNiMnCoO 2 is used. The second positive electrode active material may be subjected to surface treatment.
第１正極活物質は、第１正極活物質及び第２正極活物質の総量（体積）を基準として５０％以上１００％未満の含有量で有り、７０％以上とすることが好ましく、８０％以上の含有量（体積）とすることが更に好ましい。すなわち、当該実施形態における正極活物質層１４１では、第１正極活物質が第２正極活物質よりも多く含有されている。更には、第１正極活物質及び第２正極活物質は、正極活物質層１４１を形成する際に第１正極活物質がマトリックスとなり、第２正極活物質が第１正極活物質に分散されるような海島構造を形成することが好ましい。 The first positive electrode active material has a content of 50% or more and less than 100% based on the total amount (volume) of the first positive electrode active material and the second positive electrode active material, preferably 70% or more, and 80% or more. The content (volume) is more preferable. That is, in the positive electrode active material layer 141 in the embodiment, the first positive electrode active material is contained more than the second positive electrode active material. Furthermore, the first positive electrode active material and the second positive electrode active material are dispersed in the first positive electrode active material by forming the positive electrode active material layer 141 into the first positive electrode active material as a matrix. It is preferable to form such a sea-island structure.
ここで本発明者等は、第１正極活物質を含有する層と第２正極活物質を含有する層とが積層するようにして正極活物質層が形成されるよりも、当該実施形態の正極活物質層１４１のように、第１正極活物質を含有する層に第２正極活物質が分散されて正極活物質層が形成されることの方が、電池寿命の向上に有利であることを知見した。特に、安全性に優れた正極活物質をマトリックスとして、このマトリックスに高容量化及び高出力化を図ることができる正極活物質を分散させて構成された正極活物質層１４１の方が、電池寿命の向上に有利であった。 In this case, the inventors of the present invention do not form the positive electrode active material layer by laminating the layer containing the first positive electrode active material and the layer containing the second positive electrode active material. Like the active material layer 141, it is more advantageous for improving the battery life that the positive electrode active material layer is formed by dispersing the second positive electrode active material in the layer containing the first positive electrode active material. I found out. In particular, the positive electrode active material layer 141 formed by dispersing a positive electrode active material capable of increasing the capacity and output in the matrix using a positive electrode active material excellent in safety as a matrix has a longer battery life. It was advantageous for improvement.
さらに、本発明者等は鋭意検討の結果、第１正極活物質を含有する層に第２正極活物質が単に分散されているのではなく、正極表面から所定の厚みの範囲に存在する第２正極活物質の量を制御することが、高安全性化と電池寿命の向上とを共に実現させることに必要であることを見い出した。ここで、「正極表面」とは、正極集電体１４０の一方の面に形成された正極活物質層１４１において、正極集電体１４０と反対側の表面、すなわち、正極集電体１４０から正極活物質層１４１の層厚方向に最も離れた表面、を意味する。 Further, as a result of intensive studies, the present inventors have found that the second positive electrode active material is not simply dispersed in the layer containing the first positive electrode active material, but is present in the second thickness range from the positive electrode surface to a predetermined thickness. It has been found that controlling the amount of the positive electrode active material is necessary to achieve both high safety and improved battery life. Here, the “positive electrode surface” refers to the surface opposite to the positive electrode current collector 140 in the positive electrode active material layer 141 formed on one surface of the positive electrode current collector 140, that is, from the positive electrode current collector 140 to the positive electrode. The surface farthest in the layer thickness direction of the active material layer 141 is meant.
電池寿命が向上する要因としては、正極活物質層において電池反応性の高い第２正極活物質を、第２正極活物質と比べて電池反応性が低い第１正極活物質の層に分散させることにより、第２正極活物質と第１正極活物質との電池反応量を近づけることができるためであると考えられる。一般に、正極活物質層において、正極集電体１４０側よりも負極に近い正極表面側では、正極活物質の電池反応性が活性化される。つまり、正極表面から所定の厚みの範囲に存在する第２正極活物質の量を制御することにより、電池反応性が高い第２正極活物質が先に電池反応に寄与し劣化してしまうことを抑制できると考えられる。 As a factor for improving the battery life, the second positive electrode active material having high battery reactivity in the positive electrode active material layer is dispersed in the layer of the first positive electrode active material having lower battery reactivity than the second positive electrode active material. This is considered to be because the amount of battery reaction between the second positive electrode active material and the first positive electrode active material can be made closer. In general, in the positive electrode active material layer, the battery reactivity of the positive electrode active material is activated on the positive electrode surface side closer to the negative electrode than on the positive electrode current collector 140 side. That is, by controlling the amount of the second positive electrode active material existing within a predetermined thickness range from the positive electrode surface, the second positive electrode active material having high battery reactivity contributes to the battery reaction first and deteriorates. It can be suppressed.
さらに、当該実施形態では、正極表面から所定の厚みの範囲に存在する第２正極活物質の量を制御することにより、正極表面側には熱安定性の高い第１正極活物質が多く存在するようにして、高安全性化を実現している。 Furthermore, in this embodiment, by controlling the amount of the second positive electrode active material existing within a predetermined thickness range from the positive electrode surface, there are many first positive electrode active materials with high thermal stability on the positive electrode surface side. In this way, high safety is realized.
当該実施形態における正極活物質層１４１では、正極活物質層１４１の層厚Ｄを基準として正極表面から１５％の厚みの範囲に存在する第２正極活物質の二次粒子の量（体積基準）を、正極活物質層１４１全体に含まれる第２正極活物質の二次粒子の量（体積基準）に対して０体積％を超え１０体積％以下に制御している。 In the positive electrode active material layer 141 in the embodiment, the amount of secondary particles of the second positive electrode active material existing in a range of 15% from the positive electrode surface with respect to the layer thickness D of the positive electrode active material layer 141 (volume basis) Is controlled to be more than 0 volume% and 10 volume% or less with respect to the amount (volume basis) of secondary particles of the second cathode active material contained in the entire cathode active material layer 141.
正極表面から１５％の厚みの範囲に存在する第２正極活物質の二次粒子の総体積量を、正極活物質層１４１全体に含まれる第２正極活物質の二次粒子の総体積量に対して上記範囲内に制御することにより、高容量化及び高出力化の実現を可能とさせると共に、高安全性化及び電池寿命の向上を図ることが可能となる。 The total volume of secondary particles of the second positive electrode active material existing in a range of 15% thickness from the surface of the positive electrode is changed to the total volume of secondary particles of the second positive electrode active material contained in the entire positive electrode active material layer 141. On the other hand, by controlling within the above range, it is possible to realize high capacity and high output, as well as high safety and improvement of battery life.
正極表面から１５％の厚みの範囲に存在する第２正極活物質の二次粒子の量（体積基準）は、正極活物質層１４１全体に含有される第２正極活物質の二次粒子の量（体積基準）に対して０体積％を超え９．５体積％以下であることがより望ましく、０体積％を超え９．０体積％以下、０体積％を超え８．０体積％以下であることが望ましい。 The amount (second volume basis) of secondary particles of the second positive electrode active material existing in the range of 15% thickness from the positive electrode surface is the amount of secondary particles of the second positive electrode active material contained in the entire positive electrode active material layer 141. More preferably, it is more than 0 volume% and 9.5 volume% or less with respect to (volume basis), more than 0 volume% and 9.0 volume% or less, more than 0 volume% and 8.0 volume% or less. It is desirable.
また、正極活物質層１４１の層厚Ｄを基準として正極表面から１０％の厚みの範囲に存在する第２正極活物質の二次粒子の量（体積基準）は、正極活物質層１４１全体に含有される第２正極活物質の二次粒子の量（体積基準）に対して０体積％を超え１０体積％以下であることがより望ましく、０体積％を超え９．０体積％以下、または、０体積％を超え８．０体積％以下であることが望ましい。 Further, the amount of secondary particles (volume basis) of the second positive electrode active material existing in a range of 10% from the positive electrode surface with respect to the layer thickness D of the positive electrode active material layer 141 is the total amount of the positive electrode active material layer 141. More preferably, it is more than 0 volume% and 10 volume% or less, more than 0 volume% and 9.0 volume% or less with respect to the amount (volume basis) of secondary particles of the second positive electrode active material contained, or It is desirable that the amount be more than 0% by volume and not more than 8.0% by volume.
正極活物質層１４１において、正極活物質層１４１の層厚Ｄを基準として正極表面から１５％の厚みに存在する第２正極活物質の二次粒子の量を制御する手段は、特に限定されるものでない。例えば、正極の製造後の正極活物質層１４１において、〈１〉第１正極活物質の一次粒子が凝集して形成される二次粒子の平均二次粒子径Ｒ１と、第２正極活物質の一次粒子が凝集して形成される二次粒子の平均二次粒子径Ｒ２との関係が、Ｒ１＜Ｒ２となることが望ましい。より望ましくは、（１／４）Ｒ２＜Ｒ１＜（４／５）Ｒ２、（１／３）Ｒ２＜Ｒ１＜（３／４）Ｒ２である。 In the positive electrode active material layer 141, the means for controlling the amount of secondary particles of the second positive electrode active material present at a thickness of 15% from the surface of the positive electrode based on the layer thickness D of the positive electrode active material layer 141 is particularly limited. Not a thing. For example, in the positive electrode active material layer 141 after fabrication of the cathode, the average secondary particle diameter R 1 of the secondary particles <1> primary particles of the first cathode active material is formed by aggregation, the second positive electrode active material It is desirable that the relationship between the secondary particles formed by agglomeration of primary particles and the average secondary particle diameter R 2 is R 1 <R 2 . More desirably, (1/4) R 2 <R 1 <(4/5) R 2 and (1/3) R 2 <R 1 <(3/4) R 2 .
第１正極活物質の平均二次粒子径Ｒ１と第２正極活物質の平均二次粒子径Ｒ２との関係が上記関係にあれば、第２正極活物質がマトリックスとなる第１正極活物質を含む層に効果的に分散され得る。また、第１正極活物質の平均二次粒子径Ｒ１と第２正極活物質の平均二次粒子径Ｒ２との関係が上記関係にあれば、正極活物質層１４１の正極表面から所望とする厚みに存在する第２正極活物質の二次粒子の量（体積基準）を、正極活物質層１４１全体に含まれる第２正極活物質の二次粒子の量（体積基準）に対して０体積％を超え１０体積％以下に効果的に制御できる。よって、電池寿命の向上により有利なものとなる。 If the relationship between the average secondary particle diameter R 2 of average secondary particle diameter R 1 and the second positive active material in the first positive electrode active material is the above relationship, the first positive electrode active the second positive electrode active material is the matrix It can be effectively dispersed in the layer containing the substance. Further, if the relationship between the average secondary particle diameter R 2 of average secondary particle diameter R 1 and the second positive active material in the first positive electrode active material is the above relationship, the desired from the positive electrode surface of the positive electrode active material layer 141 The amount (secondary volume) of secondary particles of the second positive electrode active material present in the thickness of the positive electrode active material layer 141 is 0 with respect to the amount (secondary volume) of secondary particles of the second positive electrode active material contained in the whole positive electrode active material layer 141 It can be effectively controlled to exceed 10% by volume. Therefore, it becomes advantageous by improving the battery life.
また、〈２〉正極活物質層１４１の層厚Ｄと第１正極活物質の平均二次粒子径Ｒ１の関係が、Ｒ１＜（１／２）Ｄであることが望ましい。これにより、上記した〈２〉と同様の効果を奏する。 Moreover, <2> layer thickness D and an average relationship of the secondary particle diameter R 1 of the first positive electrode active material of the positive electrode active material layer 141, R 1 <(1/2) is desirably D. Thereby, there exists an effect similar to above-mentioned <2>.
また、〈３〉正極活物質層１４１の層厚Ｄと第２正極活物質の平均二次粒子径Ｒ２の関係が、Ｒ２＜（１／２）Ｄであることが望ましい。これにより、上記した〈１〉と同様の効果を奏する。さらに、上記〈１〉〜〈３〉は、適宜組み合わせることにより、〈１〉と同様もしくは更なる効果を奏することが期待できる。 Further, <3> relationship of the layer thickness D and an average secondary particle diameter R 2 of the second positive electrode active material of the positive electrode active material layer 141 is, R 2 <(1/2) is desirably D. Thereby, there exists an effect similar to above-mentioned <1>. Furthermore, it can be expected that the above <1> to <3> have the same or further effects as <1> by combining them appropriately.
第１正極活物質と第２正極活物質のそれぞれの平均二次粒子径は、例えば、正極集電体表面に対して垂直な断面を走査型電子顕微鏡（ＳＥＭ）又は透過型電子顕微鏡（ＴＥＭ）によって該粒子を観察することにより測定することができる。具体的には、断面をイオンミリング装置を用いて処理した断面観察サンプルを作製し、ＳＥＭ又はＴＥＭによりこの断面観察を行う。そして、異なる複数の位置で反射電子像を取得することにより、第１正極活物質と第２正極活物質それぞれの二次粒子の形状が観察できる。第１正極活物質と第２正極活物質は、コントラストの相違などに両者の性状の相違に基づき差異が生ずるもとのして選択された指標により識別することが可能である。 The average secondary particle diameter of each of the first positive electrode active material and the second positive electrode active material is, for example, a cross section perpendicular to the surface of the positive electrode current collector, a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Can be measured by observing the particles. Specifically, a cross-sectional observation sample whose cross-section is processed using an ion milling apparatus is prepared, and this cross-sectional observation is performed by SEM or TEM. And the shape of the secondary particle of each of the 1st positive electrode active material and the 2nd positive electrode active material can be observed by acquiring a backscattered electron image in a plurality of different positions. The first positive electrode active material and the second positive electrode active material can be distinguished from each other by an index selected based on the difference in properties due to the difference in contrast.
この手法により、それぞれの二次粒子をランダムに１００個観察して算出できる。具体的には、各粒子の面積をそれぞれ算出し、算出した面積をもつ円の径をそれぞの粒子の粒子径としたときの体積基準の平均粒子径を算出して、平均二次粒子径とする。 This method can be calculated by observing 100 secondary particles at random. Specifically, calculate the area of each particle, calculate the volume-based average particle diameter when the diameter of the circle with the calculated area is the particle diameter of each particle, and calculate the average secondary particle diameter And
また、正極材料を溶媒に混合して正極材料スラリーを調製する工程において、第１正極活物質と第２正極活物質との平均二次粒子径を上記した関係になるように調製してもよい。この場合それぞれの平均二次粒子径は、例えば、レーザー回折・散乱法により求めた体積基準の平均二次粒子径とすることができる。 In addition, in the step of preparing the positive electrode material slurry by mixing the positive electrode material in a solvent, the average secondary particle diameter of the first positive electrode active material and the second positive electrode active material may be adjusted so as to have the above-described relationship. . In this case, each average secondary particle diameter can be set to, for example, a volume-based average secondary particle diameter determined by a laser diffraction / scattering method.
導電材は、通常リチウム二次電池に用いられるものであれば特に限定されない。例えば、炭素材料、金属材料、導電性ポリマー等を用いることができる。導電性と安定性の観点から、アセチレンブラック、ケッチェンブラック、カーボンブラック等の炭素材料を使用することが好ましい。 A conductive material will not be specifically limited if it is normally used for a lithium secondary battery. For example, a carbon material, a metal material, a conductive polymer, or the like can be used. From the viewpoint of conductivity and stability, it is preferable to use a carbon material such as acetylene black, ketjen black, or carbon black.
結着材は、通常リチウム二次電池に用いられるものであれば特に限定されない。例えば、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）、四フッ化エチレン・六フッ化プロピレン共重合体等のフッ素樹脂共重合体、スチレンブタジエンゴム（ＳＢＲ）、アクリル系ゴム、フッ素系ゴム、ポリビニルアルコール（ＰＶＡ）、スチレン・マレイン酸樹脂、ポリアクリル酸塩、カルボキシルメチルセルロース（ＣＭＣ）等を用いることができる。 The binder is not particularly limited as long as it is usually used for a lithium secondary battery. For example, fluorine resin copolymers such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene / hexafluoropropylene copolymer, styrene butadiene rubber (SBR), acrylic rubber, fluorine Rubber, polyvinyl alcohol (PVA), styrene / maleic acid resin, polyacrylate, carboxymethyl cellulose (CMC) and the like can be used.
正極活物質等が分散する溶媒は、通常結着材を溶解乃至分散する有機溶剤が使用される。例えば、Ｎ−メチルピロリドン（ＮＭＰ）、ジメチルホルムアミド、ジメチルアセトアミド、メチルエチルケトン、シクロヘキサノン、酢酸メチル、アクリル酸メチル、ジエチルトリアミン、Ｎ−Ｎ−ジメチルアミノプロピルアミン、エチレンオキシド、テトラヒドロフランなどを挙げることができるが、これらに限定されない。また、水に分散剤、増粘剤などを加えてＰＴＦＥなどで活物質をスラリー化する場合もある。 As the solvent in which the positive electrode active material and the like are dispersed, an organic solvent that normally dissolves or disperses the binder is used. For example, N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like can be mentioned. It is not limited to these. In some cases, the active material is slurried with PTFE or the like by adding a dispersant, a thickener or the like to water.
正極集電体１４０は、通常リチウム二次電池に用いられるものであれば特に限定されない。例えば、銅、アルミニウム、ニッケル、チタン、ステンレス鋼等のように導電性の良い金属を主体に構成された部材を使用することができる。正極集電体１４０の形状は、得られた電極を用いて構築される電池の形状等に応じて異なり得るため特に限定されず、棒状、板状、箔状、網状、パンチングメタル状、エキスパンドメタル状等を用いることができる。正極集電体１４０は、１０μｍ〜５０μｍに薄箔状に形成された矩形状のものを用いる。 The positive electrode current collector 140 is not particularly limited as long as it is normally used for a lithium secondary battery. For example, a member mainly composed of a metal having good conductivity such as copper, aluminum, nickel, titanium, and stainless steel can be used. The shape of the positive electrode current collector 140 is not particularly limited because it can be different depending on the shape of the battery constructed using the obtained electrode, and is not limited to a rod shape, plate shape, foil shape, net shape, punching metal shape, expanded metal. A shape or the like can be used. As the positive electrode current collector 140, a rectangular one formed in a thin foil shape with a thickness of 10 μm to 50 μm is used.
（負極）
本実施形態のリチウムイオン二次電池用正極１４を適用したリチウムイオン二次電池１では、以下に記載する負極１７、セパレータ１５、非水電解質１３等を用いることが望ましい。負極１７は、負極集電体１７０と、負極集電体１７０の表面に設けられ且つ負極活物質を含む負極活物質層１７１とからなる。負極１７は、例えば次のように作製される。まず、リチウムイオンを可逆的に吸蔵・脱離し得る負極活物質、結着材、及び必要に応じて混合される導電材とを含む負極材料を適切な溶媒に懸濁させて混合し負極材料スラリーを得る。次に、得られた負極材料スラリーを負極集電体１７０の片面または両面に塗布する。そして、これを乾燥し、負極集電体１７０の表面に負極活物質層１７１を設けることで、負極１７は作製される。
(Negative electrode)
In the lithium ion secondary battery 1 to which the positive electrode 14 for the lithium ion secondary battery of the present embodiment is applied, it is desirable to use the negative electrode 17, the separator 15, the nonaqueous electrolyte 13, and the like described below. The negative electrode 17 includes a negative electrode current collector 170 and a negative electrode active material layer 171 provided on the surface of the negative electrode current collector 170 and containing a negative electrode active material. The negative electrode 17 is produced as follows, for example. First, a negative electrode material slurry is prepared by suspending and mixing a negative electrode material containing a negative electrode active material capable of reversibly occluding and desorbing lithium ions, a binder, and a conductive material to be mixed if necessary. Get. Next, the obtained negative electrode material slurry is applied to one side or both sides of the negative electrode current collector 170. And this is dried and the negative electrode 17 is produced by providing the negative electrode active material layer 171 on the surface of the negative electrode current collector 170.
負極活物質は、リチウムを可逆的に吸蔵及び放出できるものであれば特に制限されず、従来公知の負極活物質をいずれも使用できる。例えば、炭素材料、ケイ素・スズ等を含有する合金系材料、リチウム金属等の金属材料、リチウム−チタン複合酸化物等のリチウム−遷移金属複合酸化物が挙げられる。また、金属材料、合金系材料など導電性をもち且つ機械的特性をそれ自身で確保できる材料を負極活物質として採用する場合には、活物質をそのまま成形して負極にすることもできる。 The negative electrode active material is not particularly limited as long as it can reversibly occlude and release lithium, and any conventionally known negative electrode active material can be used. Examples thereof include carbon materials, alloy materials containing silicon and tin, metal materials such as lithium metal, and lithium-transition metal composite oxides such as lithium-titanium composite oxides. Further, when a material having conductivity and mechanical properties such as a metal material or an alloy-based material is employed as the negative electrode active material, the active material can be molded as it is to form a negative electrode.
炭素材料は難黒鉛化性炭素（ハードカーボン）、易黒鉛化性炭素（ソフトカーボン）、黒鉛（グラファイト）等が用いられ得るが、特に黒鉛が好ましい。黒鉛としては、天然黒鉛、人造黒鉛、黒鉛化メソカーボンマイクロビーズを始めとして、ピッチ系、ポリアクリロニトリル系、メソフェーズピッチ系、気相成長系の黒鉛化炭素繊維を粉末状に加工したものも用いることができる。 As the carbon material, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), graphite (graphite) and the like can be used, and graphite is particularly preferable. For graphite, natural graphite, artificial graphite, graphitized mesocarbon microbeads, pitch-based, polyacrylonitrile-based, mesophase pitch-based, and vapor-phase-grown graphitized carbon fibers should also be used. Can do.
合金系材料とは、リチウムが合金形成可能な元素を含む材料のことである。リチウムが合金形成可能な元素としては、例えばケイ素・スズ等が挙げられる。ケイ素・スズ等を含有する合金系材料は、ケイ素酸化物、ケイ素窒化物、及びケイ素含有合金等のケイ素含有化合物や、スズ酸化物、スズ窒化物、及びスズ含有合金等のスズ含有化合物が好ましい。上記負極活物質は、単独で使用しても又は２種以上の混合物の形態で使用しても良い。 The alloy-based material is a material containing an element capable of forming an alloy with lithium. Examples of elements that can form an alloy with lithium include silicon and tin. The alloy-based material containing silicon / tin is preferably a silicon-containing compound such as silicon oxide, silicon nitride, and a silicon-containing alloy, or a tin-containing compound such as tin oxide, tin nitride, and a tin-containing alloy. . The negative electrode active material may be used alone or in the form of a mixture of two or more.
導電材、結着材、負極活物質等が分散する溶媒、負極集電体１７０は、それぞれ上記正極で例示したものから適宜選択することができる。 The conductive material, the binder, the solvent in which the negative electrode active material and the like are dispersed, and the negative electrode current collector 170 can be appropriately selected from those exemplified for the positive electrode.
（セパレータ）
本実施形態のリチウムイオン二次電池用正極１４を適用したリチウムイオン二次電池１のセパレータ１５は、正極活物質層１４１と負極活物質層１７１とを電気的に絶縁し、非水電解質１３を保持するものであれば、特に限定されるものではないが、電池の安全性を高める上で、１２０〜１５０℃の温度でいわゆるシャットダウン機能を発現させるものであることが望ましい。このような観点からセパレータ１５は、多孔性合成樹脂膜、特にポリオレフィン系高分子（ポリエチレン、ポリプロピレン）の多孔膜を用いることが望ましい。セパレータ１５の厚さは、５０〜３００μｍであることが望ましい。
(Separator)
The separator 15 of the lithium ion secondary battery 1 to which the positive electrode 14 for the lithium ion secondary battery of the present embodiment is applied electrically insulates the positive electrode active material layer 141 and the negative electrode active material layer 171, and the nonaqueous electrolyte 13 Although it will not specifically limit if it hold | maintains, in order to improve the safety | security of a battery, it is desirable to express what is called a shutdown function at the temperature of 120-150 degreeC. From such a viewpoint, the separator 15 is desirably a porous synthetic resin film, particularly a porous film of a polyolefin polymer (polyethylene or polypropylene). The thickness of the separator 15 is desirably 50 to 300 μm.
（非水電解質）
非水電解質１３は、支持塩が有機溶媒に溶解してなるものを用いる。非水電解質１３の支持塩は、その種類が特に限定されるものではないが、ＬｉＰＦ６，ＬｉＢＦ４，ＬｉＣｌＯ４及びＬｉＡｓＦ６から選ばれる無機塩，これらの無機塩の誘導体，ＬｉＳＯ３ＣＦ３，ＬｉＣ（ＳＯ３ＣＦ３）３及びＬｉＮ（ＳＯ２ＣＦ３）２，ＬｉＮ（ＳＯ２Ｃ２Ｆ５）２，ＬｉＮ（ＳＯ２ＣＦ３）（ＳＯ２Ｃ４Ｆ９），から選ばれる有機塩、並びにこれらの有機塩の誘導体の少なくとも１種であることが望ましい。これらの支持塩は、電池性能を更に優れたものとすることができ、かつその電池性能を室温以外の温度域においても更に高く維持することができる。支持塩の濃度についても特に限定されるものではなく、用途に応じ、支持塩及び有機溶媒の種類を考慮して適切に選択することが好ましい。
(Nonaqueous electrolyte)
The non-aqueous electrolyte 13 is formed by dissolving a supporting salt in an organic solvent. The supporting salt of the non-aqueous electrolyte 13 is not particularly limited in kind, but an inorganic salt selected from LiPF 6 , LiBF 4 , LiClO 4 and LiAsF 6 , derivatives of these inorganic salts, LiSO 3 CF 3 , Organic salt selected from LiC (SO 3 CF 3 ) 3 and LiN (SO 2 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 , LiN (SO 2 CF 3 ) (SO 2 C 4 F 9 ) And at least one of these organic salt derivatives. These supporting salts can further improve the battery performance, and can maintain the battery performance higher even in a temperature range other than room temperature. The concentration of the supporting salt is not particularly limited, and it is preferable to appropriately select the supporting salt and the organic solvent in consideration of the use.
支持塩が溶解する有機溶媒（非水溶媒）は、通常の非水電解質に用いられる有機溶媒であれば特に限定されるものではなく、例えばカーボネート類，ハロゲン化炭化水素，エーテル類，ケトン類，ニトリル類，ラクトン類，オキソラン化合物等を用いることができる。特に、プロピレンカーボネート，エチレンカーボネート，１，２−ジメトキシエタン，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，ビニレンカーボネート等及びそれらの混合溶媒が適当である。例に挙げたこれらの有機溶媒のうち、特にカーボネート類，エーテル類からなる群より選ばれた１種以上の非水溶媒を用いることにより、支持塩の溶解性、誘電率及び粘度において優れ、電池の充放電効率が高いので、好ましい。 The organic solvent (non-aqueous solvent) in which the supporting salt dissolves is not particularly limited as long as it is an organic solvent used in ordinary non-aqueous electrolytes. For example, carbonates, halogenated hydrocarbons, ethers, ketones, Nitriles, lactones, oxolane compounds and the like can be used. In particular, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate and the like, and mixed solvents thereof are suitable. Among these organic solvents mentioned in the examples, in particular, by using one or more non-aqueous solvents selected from the group consisting of carbonates and ethers, the solubility of the supporting salt, the dielectric constant and the viscosity are excellent, and the battery The charge / discharge efficiency is preferable.
（その他の形態）
本実施形態のリチウムイオン二次電池１の形状は、特に限定されるものではなく、コイン型、円筒型、角型等、種々の形状の電池とすることができる。また、正極１４、セパレータ１５、及び負極１７からなる電極群の形状も積層型であっても巻回型であってもその他の形状であってもよい。また、本実施形態のリチウムイオン二次電池１は、上述した各部材を用いて公知の方法によって製造できる。
(Other forms)
The shape of the lithium ion secondary battery 1 of the present embodiment is not particularly limited, and batteries having various shapes such as a coin shape, a cylindrical shape, and a square shape can be used. The shape of the electrode group composed of the positive electrode 14, the separator 15, and the negative electrode 17 may be a laminated type, a wound type, or other shapes. Moreover, the lithium ion secondary battery 1 of this embodiment can be manufactured by a well-known method using each member mentioned above.
（試験例）
以下、試験例を用いて具体的に説明する。
(Test example)
Hereinafter, it demonstrates concretely using a test example.
本発明の効果についてより具体的に説明するため、試験例１〜６のリチウムイオン二次電池を準備した。 In order to more specifically explain the effects of the present invention, lithium ion secondary batteries of Test Examples 1 to 6 were prepared.
（試験例１）
正極は以下のように作製した。
(Test Example 1)
The positive electrode was produced as follows.
ＬｉＭｎＦｅＰＯ４（第１正極活物質）とＬｉＮｉＭｎＣｏＯ２（第２正極活物質）が質量比として７：３となるように混合された正極活物質と、導電材としてアセチレンブラック（ＡＢ）と、結着材としてポリフッ化ビニリデン（ＰＶＤＦ）とを、これらの材料の質量比が正極活物質：導電材：結着材＝９０：５：５となるように混合した正極材料を、Ｎ−メチル−２−ピロリドン（ＮＭＰ）に分散させて正極材料スラリーを調製した。この正極材料スラリーをアルミニウム箔の正極集電体表面に塗布し乾燥させた後、プレスすることにより正極活物質層の層厚を２５μｍとして正極シートを作製した。そして、所望の大きさに形成してリチウムイオン二次電池用の正極を得た。 A positive electrode active material in which LiMnFePO 4 (first positive electrode active material) and LiNiMnCoO 2 (second positive electrode active material) are mixed so as to have a mass ratio of 7: 3, acetylene black (AB) as a conductive material, and binding A positive electrode material obtained by mixing polyvinylidene fluoride (PVDF) as a material so that the mass ratio of these materials is positive electrode active material: conductive material: binder = 90: 5: 5, N-methyl-2- A positive electrode material slurry was prepared by dispersing in pyrrolidone (NMP). This positive electrode material slurry was applied to the surface of the positive electrode current collector of aluminum foil, dried, and then pressed to prepare a positive electrode sheet with a positive electrode active material layer thickness of 25 μm. And it formed in the desired magnitude | size and the positive electrode for lithium ion secondary batteries was obtained.
プレス後の正極シートを、イオンミリング装置（日立ハイテクノロジーズ社製）を用いて断面観察サンプルを作製し、この断面観察サンプルから反射電子像を取得してＳＥＭ観察を行った。結果を図３に示す。図３に示すように、コントラストの異なる２種類の二次粒子が観察でき、コントラストの濃い二次粒子がＬｉＭｎＦｅＰＯ４であり、白く観察できる二次粒子がＬｉＮｉＭｎＣｏＯ２である。 A cross-sectional observation sample was produced from the pressed positive electrode sheet using an ion milling device (manufactured by Hitachi High-Technologies Corporation), a reflected electron image was obtained from the cross-sectional observation sample, and SEM observation was performed. The results are shown in FIG. As shown in FIG. 3, two types of secondary particles having different contrasts can be observed, the secondary particles having a high contrast are LiMnFePO 4 , and the secondary particles that can be observed in white are LiNiMnCoO 2 .
図３に表すＳＥＭ画像より、ＬｉＭｎＦｅＰＯ４とＬｉＮｉＭｎＣｏＯ２の平均二次粒子径を算出すると、ＬｉＭｎＦｅＰＯ４の平均二次粒子は７．０μｍであり、ＬｉＮｉＭｎＣｏＯ２の平均二次粒子は１０μｍであった。 When the average secondary particle diameter of LiMnFePO 4 and LiNiMnCoO 2 was calculated from the SEM image shown in FIG. 3, the average secondary particle of LiMnFePO 4 was 7.0 μm, and the average secondary particle of LiNiMnCoO 2 was 10 μm.
また、図３に表すＳＥＭ画像よりＬｉＮｉＭｎＣｏＯ２の二次粒子の総体積量を算出し、正極活物質層の層厚を基準とした正極表面からの厚みの範囲に存在するＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）を求めた。結果を図２に示す。 Further, the total volume of secondary particles of LiNiMnCoO 2 is calculated from the SEM image shown in FIG. 3, and the secondary particles of LiNiMnCoO 2 existing in the thickness range from the positive electrode surface based on the layer thickness of the positive electrode active material layer. The cumulative ratio (volume basis) was determined. The results are shown in FIG.
図２より、正極表面から正極活物質層全体の１５％の厚みの範囲に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）は、正極活物質層に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子全体の総量（体積）に対して７．８％であった。 From FIG. 2, LiNiMnCoO cumulative percentage of LiNiMnCoO 2 of secondary particles from the surface of the positive electrode is dispersed in a range of the positive electrode active material layer overall 15% of the thickness (volume basis) are dispersed in the positive electrode active material layer 2 The total amount (volume) of the secondary particles was 7.8%.
負極は以下のように作製した。 The negative electrode was produced as follows.
負極活物質として天然黒鉛と、結着剤としてスチレンブタジエンゴム（ＳＢＲ）と、増粘剤としてカルボキシメチルセルロース（ＣＭＣ）とを、これらの材料の質量比が９８：１：１となるように水で混合して、負極材料スラリーを調製した。この組成物を、厚さ１５μｍの銅箔（負極集電体）に塗付した。その塗付物を乾燥させ、プレスすることにより、該負極集電体上に負極活物質層が形成されてなる負極シートを作製した。 Natural graphite as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener are added with water so that the mass ratio of these materials becomes 98: 1: 1. The negative electrode material slurry was prepared by mixing. This composition was applied to a copper foil (negative electrode current collector) having a thickness of 15 μm. The coated material was dried and pressed to prepare a negative electrode sheet in which a negative electrode active material layer was formed on the negative electrode current collector.
得られた負極と正極との間にポリプロピレンからなるセパレータを介在させ、電解液を用いて、ドライボックス中で本実施例のコイン型のリチウムイオン二次電池を組み立てた。なお、電解液は、エチレンカーボネート（ＥＣ）３０体積％とジメチルカーボネート（ＤＭＣ）３０体積％とエチルメチルカーボネート（ＥＭＣ）４０体積％との混合溶媒に、ＬｉＰＦ６を１モル／リットルとなるように溶解させて調製されている。 A separator made of polypropylene was interposed between the obtained negative electrode and the positive electrode, and a coin-type lithium ion secondary battery of this example was assembled in a dry box using an electrolytic solution. The electrolyte solution was mixed with 30% by volume of ethylene carbonate (EC), 30% by volume of dimethyl carbonate (DMC) and 40% by volume of ethyl methyl carbonate (EMC), and LiPF 6 was 1 mol / liter. It is prepared by dissolving.
以上により、試験例１のリチウムイオン二次電池を製造した。 Thus, the lithium ion secondary battery of Test Example 1 was manufactured.
（試験例２）
試験例２では、正極活物質層の層厚を７０μｍとして正極シートを作製した。
(Test Example 2)
In Test Example 2, a positive electrode sheet was produced with a positive electrode active material layer thickness of 70 μm.
プレス後の正極シートを、試験例１と同様にして断面観察サンプルを作製し、ＳＥＭ観察を行った。結果を図４に示す。 A cross-sectional observation sample of the positive electrode sheet after pressing was prepared in the same manner as in Test Example 1, and SEM observation was performed. The results are shown in FIG.
図４に表すＳＥＭ画像より、ＬｉＭｎＦｅＰＯ４とＬｉＮｉＭｎＣｏＯ２の平均二次粒子径を算出すると、ＬｉＭｎＦｅＰＯ４の平均二次粒子は１８．１μｍであり、ＬｉＮｉＭｎＣｏＯ２の平均二次粒子は３０μｍであった。 When the average secondary particle diameter of LiMnFePO 4 and LiNiMnCoO 2 was calculated from the SEM image shown in FIG. 4, the average secondary particle of LiMnFePO 4 was 18.1 μm, and the average secondary particle of LiNiMnCoO 2 was 30 μm.
また、図４に表すＳＥＭ画像よりＬｉＮｉＭｎＣｏＯ２の二次粒子の総体積量を算出し、正極表面からの厚みの範囲に存在するＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）を求めた。結果を図２に示す。 Further, the total volume of secondary particles of LiNiMnCoO 2 was calculated from the SEM image shown in FIG. 4, and the cumulative ratio (volume basis) of secondary particles of LiNiMnCoO 2 existing in the thickness range from the positive electrode surface was obtained. The results are shown in FIG.
図２より、正極表面から正極活物質層全体の１５％の厚みの範囲に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）は、正極活物質層に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子全体の総量（体積）に対して９．８％であった。 From FIG. 2, LiNiMnCoO cumulative percentage of LiNiMnCoO 2 of secondary particles from the surface of the positive electrode is dispersed in a range of the positive electrode active material layer overall 15% of the thickness (volume basis) are dispersed in the positive electrode active material layer 2 The total amount (volume) of the secondary particles was 9.8%.
上記以外については、試験例１と同様の方法により試験例２のリチウムイオン二次電池を製造した。 Except for the above, the lithium ion secondary battery of Test Example 2 was produced in the same manner as in Test Example 1.
（試験例３）
試験例３では、正極活物質層の層厚を４３μｍとして正極シートを作製した。
(Test Example 3)
In Test Example 3, a positive electrode sheet was produced with a positive electrode active material layer thickness of 43 μm.
プレス後の正極シートを、試験例１と同様にして断面観察サンプルを作製し、ＳＥＭ観察を行った。結果を図５に示す。 A cross-sectional observation sample of the positive electrode sheet after pressing was prepared in the same manner as in Test Example 1, and SEM observation was performed. The results are shown in FIG.
図５に表すＳＥＭ画像より、ＬｉＭｎＦｅＰＯ４とＬｉＮｉＭｎＣｏＯ２の平均二次粒子径を算出すると、ＬｉＭｎＦｅＰＯ４の平均二次粒子は１７．３μｍであり、ＬｉＮｉＭｎＣｏＯ２の平均二次粒子は３０μｍであった。 When the average secondary particle diameter of LiMnFePO 4 and LiNiMnCoO 2 was calculated from the SEM image shown in FIG. 5, the average secondary particle of LiMnFePO 4 was 17.3 μm, and the average secondary particle of LiNiMnCoO 2 was 30 μm.
また、図５に表すＳＥＭ画像よりＬｉＮｉＭｎＣｏＯ２の二次粒子の総体積量を算出し、正極活物質層における正極表面からの厚みの範囲に存在するＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）を求めた。結果を図２に示す。 Further, the total volume of secondary particles of LiNiMnCoO 2 is calculated from the SEM image shown in FIG. 5, and the cumulative ratio of secondary particles of LiNiMnCoO 2 existing in the thickness range from the positive electrode surface in the positive electrode active material layer (volume basis). ) The results are shown in FIG.
図２より、正極表面から正極活物質層全体の１５％の厚みの範囲に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）は、正極活物質層に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子全体の総量（体積）に対して９．５％であった。 From FIG. 2, LiNiMnCoO cumulative percentage of LiNiMnCoO 2 of secondary particles from the surface of the positive electrode is dispersed in a range of the positive electrode active material layer overall 15% of the thickness (volume basis) are dispersed in the positive electrode active material layer 2 The total amount (volume) of the secondary particles was 9.5%.
上記以外については、試験例１と同様の方法により試験例３のリチウムイオン二次電池を製造した。 Except for the above, the lithium ion secondary battery of Test Example 3 was produced in the same manner as in Test Example 1.
（試験例４）
試験例４では、正極活物質層の層厚を３９μｍとして正極シートを作製した。
(Test Example 4)
In Test Example 4, a positive electrode sheet was produced with a positive electrode active material layer thickness of 39 μm.
プレス後の正極シートを、試験例１と同様にして断面観察サンプルを作製し、ＳＥＭ観察を行った。結果を図６に示す。 A cross-sectional observation sample of the positive electrode sheet after pressing was prepared in the same manner as in Test Example 1, and SEM observation was performed. The results are shown in FIG.
図６に表すＳＥＭ画像より、ＬｉＭｎＦｅＰＯ４とＬｉＮｉＭｎＣｏＯ２の平均二次粒子径を算出すると、ＬｉＭｎＦｅＰＯ４の平均二次粒子は３６．４μｍであり、ＬｉＮｉＭｎＣｏＯ２の平均二次粒子は３０μｍであった。 When the average secondary particle diameter of LiMnFePO 4 and LiNiMnCoO 2 was calculated from the SEM image shown in FIG. 6, the average secondary particle of LiMnFePO 4 was 36.4 μm, and the average secondary particle of LiNiMnCoO 2 was 30 μm.
また、図６に表すＳＥＭ画像よりＬｉＮｉＭｎＣｏＯ２の二次粒子の総体積量を算出し、正極表面からの厚みの範囲に存在するＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）を求めた。結果を図２に示す。 Further, the total volume of secondary particles of LiNiMnCoO 2 was calculated from the SEM image shown in FIG. 6, and the cumulative ratio (volume basis) of secondary particles of LiNiMnCoO 2 existing in the thickness range from the positive electrode surface was obtained. The results are shown in FIG.
図６より、正極表面から正極活物質層全体の１５％の厚みの範囲に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）は、正極活物質層に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子全体の総量（体積）に対して８．９％であった。 Fig than 6, the cumulative percentage (by volume) of the secondary particles of LiNiMnCoO 2 from the surface of the positive electrode is dispersed in a range of the positive electrode active material layer overall 15% thickness, LiNiMnCoO 2 are dispersed in the positive electrode active material layer The total amount (volume) of the secondary particles was 8.9%.
上記以外については、試験例１と同様の方法により試験例４のリチウムイオン二次電池を製造した。 Except for the above, the lithium ion secondary battery of Test Example 4 was produced in the same manner as in Test Example 1.
（試験例５）
試験例５では、正極活物質層の層厚を４３μｍとして正極シートを作製した。
(Test Example 5)
In Test Example 5, a positive electrode sheet was produced with a positive electrode active material layer thickness of 43 μm.
プレス後の正極シートを、試験例１と同様にして断面観察サンプルを作製し、ＳＥＭ観察を行った。結果を図７に示す。 A cross-sectional observation sample of the positive electrode sheet after pressing was prepared in the same manner as in Test Example 1, and SEM observation was performed. The results are shown in FIG.
図７に表すＳＥＭ画像より、ＬｉＭｎＦｅＰＯ４とＬｉＮｉＭｎＣｏＯ２の平均二次粒子径を算出すると、ＬｉＭｎＦｅＰＯ４の平均二次粒子は３５．３μｍであり、ＬｉＮｉＭｎＣｏＯ２の平均二次粒子は８μｍであった。 When the average secondary particle diameter of LiMnFePO 4 and LiNiMnCoO 2 was calculated from the SEM image shown in FIG. 7, the average secondary particle of LiMnFePO 4 was 35.3 μm, and the average secondary particle of LiNiMnCoO 2 was 8 μm.
また、図７に表すＳＥＭ画像よりＬｉＮｉＭｎＣｏＯ２の二次粒子の総体積量を算出し、正極表面からの厚みの範囲に存在するＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）を求めた。結果を図２に示す。 Further, the total volume of the secondary particles of LiNiMnCoO 2 was calculated from the SEM image shown in FIG. 7, and the cumulative ratio (volume basis) of the secondary particles of LiNiMnCoO 2 existing in the thickness range from the positive electrode surface was obtained. The results are shown in FIG.
図２より、正極表面から正極活物質層全体の１５％の厚みの範囲に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）は、正極活物質層に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子全体の総量（体積）に対して１５．６％であった。 From FIG. 2, LiNiMnCoO cumulative percentage of LiNiMnCoO 2 of secondary particles from the surface of the positive electrode is dispersed in a range of the positive electrode active material layer overall 15% of the thickness (volume basis) are dispersed in the positive electrode active material layer 2 The total amount (volume) of the secondary particles was 15.6%.
上記以外については、試験例１と同様の方法により試験例５のリチウムイオン二次電池を製造した。 Except for the above, the lithium ion secondary battery of Test Example 5 was produced in the same manner as in Test Example 1.
（試験例６）
試験例６では、正極活物質層の層厚を２５μｍとして正極シートを作製した。
(Test Example 6)
In Test Example 6, a positive electrode sheet was produced with a positive electrode active material layer thickness of 25 μm.
プレス後の正極シートを、試験例１と同様にして断面観察サンプルを作製し、ＳＥＭ観察を行った。結果を図８に示す。 A cross-sectional observation sample of the positive electrode sheet after pressing was prepared in the same manner as in Test Example 1, and SEM observation was performed. The results are shown in FIG.
図８に表すＳＥＭ画像より、ＬｉＭｎＦｅＰＯ４とＬｉＮｉＭｎＣｏＯ２の平均二次粒子径を算出すると、ＬｉＭｎＦｅＰＯ４の平均二次粒子は３．５μｍであり、ＬｉＮｉＭｎＣｏＯ２の平均二次粒子は１５μｍであった。 When the average secondary particle diameter of LiMnFePO 4 and LiNiMnCoO 2 was calculated from the SEM image shown in FIG. 8, the average secondary particle of LiMnFePO 4 was 3.5 μm, and the average secondary particle of LiNiMnCoO 2 was 15 μm.
また、図８に表すＳＥＭ画像よりＬｉＮｉＭｎＣｏＯ２の二次粒子の総体積量を算出し、正極表面からの厚みの範囲に存在するＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）を求めた。結果を図２に示す。 Further, the total volume of the secondary particles of LiNiMnCoO 2 was calculated from the SEM image shown in FIG. 8, and the cumulative ratio (volume basis) of the secondary particles of LiNiMnCoO 2 existing in the thickness range from the positive electrode surface was obtained. The results are shown in FIG.
図２より、正極表面から正極活物質層全体の１５％の厚みの範囲に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子の累積比率（体積基準）は、正極活物質層に分散されているＬｉＮｉＭｎＣｏＯ２の二次粒子全体の総量（体積）に対して２９．０％であった。 From FIG. 2, LiNiMnCoO cumulative percentage of LiNiMnCoO 2 of secondary particles from the surface of the positive electrode is dispersed in a range of the positive electrode active material layer overall 15% of the thickness (volume basis) are dispersed in the positive electrode active material layer 2 The total amount (volume) of the secondary particles was 29.0%.
上記以外については、試験例１と同様の方法により試験例６のリチウムイオン二次電池を製造した。以上の条件を表１に示す。なお、表１においてＬＭＦＰとはＬｉＭｎＦｅＰＯ４を意味し、ＬＮＭＣとはＬｉＮｉＭｎＣｏＯ２を意味する。 Except for the above, the lithium ion secondary battery of Test Example 6 was produced in the same manner as in Test Example 1. The above conditions are shown in Table 1. In Table 1, LMFP means LiMnFePO 4 and LNMC means LiNiMnCoO 2 .
［安全性試験］
表１に示す異なる条件によって作製された試験例１〜６のリチウムイオン二次電池において、安全性の評価として釘刺し試験を行った。
[Safety test]
In the lithium ion secondary batteries of Test Examples 1 to 6 produced under different conditions shown in Table 1, a nail penetration test was performed as safety evaluation.
まず、各試験例のリチウムイオン二次電池を、電流値を１／３Ｃとし、充電上限電圧を４．２Ｖとして定電流充電を行った。そののち、定電圧で電流値が１／１０Ｃになるまで充電を行った。そして、満充電状態になった各試験例のリチウムイオン二次電池に対して、２５℃の試験温度の下、電池中央付近に直径３ｍｍの鉄製の釘を１０ｍｍ／ｓｅｃの速度で貫通させた。 First, the lithium ion secondary battery of each test example was subjected to constant current charging with a current value of 1/3 C and a charging upper limit voltage of 4.2 V. After that, the battery was charged at a constant voltage until the current value became 1 / 10C. Then, an iron nail having a diameter of 3 mm was passed through the lithium ion secondary battery of each test example in a fully charged state near the center of the battery at a speed of 10 mm / sec at a test temperature of 25 ° C.
このときの各試験例におけるリチウムイオン二次電池の電池外表面温度を熱電対で測定し、最高温度を測定した。最高温度が２００℃未満を○、最高温度が２００℃以上を×として、結果を表１に示す。 The battery outer surface temperature of the lithium ion secondary battery in each test example at this time was measured with a thermocouple, and the maximum temperature was measured. The results are shown in Table 1, where the maximum temperature is less than 200 ° C. and the maximum temperature is 200 ° C. or more as x.
［サイクル特性試験］
表１に示す異なる条件によって作製された試験例１〜６のリチウムイオン二次電池において、サイクル特性試験を行った。
[Cycle characteristic test]
In the lithium ion secondary batteries of Test Examples 1 to 6 produced under different conditions shown in Table 1, a cycle characteristic test was performed.
２５℃と４５℃の試験温度の下、電流値を２Ｃ、上限電圧を４．２ＶとしてＣＣ／ＣＶモードにて充電を行い、１／１０Ｃの電流値でＣＶ充電を終了した。放電はＣＣモードにて下限電圧２．６Ｖまで行った。これを５００回繰り返し、１回目の放電容量と５００回目の放電容量との比をサイクル特性（放電容量維持率）とし、放電容量維持率（％）＝（５００回目の放電容量／１回目の放電容量）×１００の式によりサイクル特性（放電容量維持率）を算出した。結果を表１に示す。 Under the test temperatures of 25 ° C. and 45 ° C., the current value was 2 C, the upper limit voltage was 4.2 V, and charging was performed in the CC / CV mode, and the CV charging was terminated with a current value of 1/10 C. Discharge was performed up to a lower limit voltage of 2.6 V in the CC mode. This is repeated 500 times, and the ratio of the first discharge capacity to the 500th discharge capacity is defined as cycle characteristics (discharge capacity maintenance rate), and the discharge capacity maintenance rate (%) = (500th discharge capacity / first discharge). The cycle characteristics (discharge capacity retention rate) were calculated by the formula of (capacity) × 100. The results are shown in Table 1.
表１に示すように、安全性試験において試験例１〜６のいずれにおいても良好な結果が得られた。すなわち、本発明に係る試験例１〜４は、従来からの試験例５及び６と同様に高安全性化を実現できるリチウムイオン二次電池用正極であることが理解できる。 As shown in Table 1, good results were obtained in any of Test Examples 1 to 6 in the safety test. That is, it can be understood that Test Examples 1 to 4 according to the present invention are positive electrodes for lithium ion secondary batteries that can realize high safety in the same manner as the conventional Test Examples 5 and 6.
また、表１に示すようにサイクル特性試験では、２５℃及び４５℃のどちらにおいても本発明に係る試験例１〜４の方が、試験例５及び６よりも放電容量維持率が優れていた。すなわち、本発明に係る試験例１〜４の方が、従来からの試験例５及び６よりも電池寿命の向上に有利なリチウムイオン二次電池用正極であることが理解できる。つまり、正極活物質層において、正極表面から１５％の厚みに存在する第２正極活物質の二次粒子の量（体積）を第２正極活物質全体の１０％以下に制御することにより、電池寿命の向上に有利な正極となることがわかった。 Further, as shown in Table 1, in the cycle characteristic test, the test examples 1 to 4 according to the present invention were superior to the test examples 5 and 6 in the discharge capacity maintenance rate at both 25 ° C. and 45 ° C. . That is, it can be understood that Test Examples 1 to 4 according to the present invention are positive electrodes for lithium ion secondary batteries that are more advantageous for improving the battery life than conventional Test Examples 5 and 6. That is, in the positive electrode active material layer, by controlling the amount (volume) of secondary particles of the second positive electrode active material present at a thickness of 15% from the positive electrode surface to 10% or less of the entire second positive electrode active material, the battery It turned out that it becomes a positive electrode advantageous for the improvement of a lifetime.
（第１正極活物質の平均二次粒子径Ｒ１と第２正極活物質の平均二次粒子Ｒ２との関係について）
試験例１〜３、及び、試験例３と試験例５との比較により、第２正極活物質の平均二次粒子径Ｒ２が第１正極活物質の平均二次粒子径Ｒ１よりも大きいことが、正極活物質層の表層（正極表面）側に存在する第２正極活物質の二次粒子を少なくすることに有利であると考えられる。試験例３と試験例５は共に正極活物質層の層厚Ｄは同じであるが、Ｒ１とＲ２との大小関係が異なっている。すなわち、Ｒ１＜Ｒ２の方が、正極活物質層の表層（正極最面）側に存在する第２正極活物質の二次粒子を少なくすることに有利となり、電池寿命の向上において優れた結果となっている。
(The average secondary particle diameter R 1 of the first positive electrode active material for the relationship between the average secondary particle R 2 of the second positive electrode active material)
Test Examples 1 to 3, and, by comparison with the test example 3 in Test Example 5, the average secondary particle diameter R 2 of the second positive electrode active material is larger than the average secondary particle diameter R 1 of the first positive electrode active material This is considered advantageous for reducing the secondary particles of the second positive electrode active material present on the surface layer (positive electrode surface) side of the positive electrode active material layer. Both Test Example 3 and Test Example 5 have the same positive electrode active material layer thickness D, but the magnitude relationship between R 1 and R 2 is different. That is, R 1 <R 2 is advantageous in reducing the secondary particles of the second positive electrode active material present on the surface layer (positive electrode outermost surface) side of the positive electrode active material layer, and is excellent in improving the battery life. It is the result.
また、層厚Ｄが同じ試験例１と試験例６の結果を検討すると、試験例６では、Ｒ１がＲ２に比べて試験例１よりも小さくなっている。換言すると、試験例１に比べて試験例６では、正極活物質層のマトリックスとなる第１正極活物質の平均二次粒子径Ｒ１が、正極活物質層に分散する第２正極活物質の平均二次粒子径Ｒ２よりも小さくなりすぎている。このため試験例６では試験例１に比べて、第２正極活物質が正極活物質層において正極表面側により多く存在してしまったものと考えられる。このことより、Ｒ１とＲ２の関係は、（１／４）Ｒ２＜Ｒ１＜（４／５）Ｒ２が望ましく、より望ましくは（１／３）Ｒ２＜Ｒ１＜（３／４）Ｒ２であると考えられる。 Further, when the results of Test Example 1 and Test Example 6 having the same layer thickness D are examined, in Test Example 6, R 1 is smaller than Test Example 1 compared to R 2 . In other words, in Test Example 6 in comparison to Test Example 1, the average secondary particle diameter R 1 of the first positive electrode active material comprising a matrix of the positive electrode active material layer, the second positive electrode active material dispersed in the positive electrode active material layer It is too small than the average secondary particle diameter R 2. Therefore, in Test Example 6, it is considered that a larger amount of the second positive electrode active material was present on the positive electrode surface side in the positive electrode active material layer than in Test Example 1. Accordingly, the relationship between R 1 and R 2 is preferably (1/4) R 2 <R 1 <(4/5) R 2 , more preferably (1/3) R 2 <R 1 <(3 / 4) is considered to be R 2.
（正極活物質層の層厚Ｄに対する第１正極活物質の平均二次粒子径Ｒ１、又は第２正極活物質の平均二次粒子Ｒ２との関係について）
試験例１〜３の結果より、層厚Ｄに対してＲ１が小さく、また、Ｒ１＜（１／２）Ｄであることが、正極活物質層の表層（正極表面）側に存在する第２正極活物質の二次粒子を少なくすることに有利であると考えられる。
(Regarding the relationship with the average secondary particle diameter R 1 of the first positive electrode active material or the average secondary particle R 2 of the second positive electrode active material with respect to the layer thickness D of the positive electrode active material layer)
From the results of Test Examples 1 to 3, R 1 is smaller than the layer thickness D, and R 1 <(1/2) D exists on the surface layer (positive electrode surface) side of the positive electrode active material layer. It is considered advantageous to reduce the secondary particles of the second positive electrode active material.
また、試験例１と試験例６を比較すると、共に層厚Ｄは同じであるが、試験例６の方はＲ１が小さい。このため、試験例６の方が試験例１よりも、正極表面側の正極活物質層に第２正極活物質の二次粒子が多く存在してしまったものと考えられる。このことより、（１／５）Ｄ＜Ｒ１＜（１／２）Ｄであることがより望ましいと考えられる。 Moreover, when the test example 1 and the test example 6 are compared with each other, the layer thickness D is the same, but the test example 6 has a smaller R 1 . For this reason, it is considered that Test Example 6 had more secondary particles of the second positive electrode active material in the positive electrode active material layer on the positive electrode surface side than Test Example 1. From this, it is considered that (1/5) D <R 1 <(1/2) D is more desirable.
また、試験例１及び２の結果より、正極活物質層の層厚Ｄに対して第２正極活物質の平均二次粒子径Ｒ２が小さく、かつ、Ｒ２＜（１／２）Ｄであることが、正極活物質層の表層（正極表面）側に存在する第２正極活物質の二次粒子を少なくすることに有利であると考えられる。 Further, from the results of Test Examples 1 and 2, the average secondary particle diameter R 2 of the second positive electrode active material is smaller than the layer thickness D of the positive electrode active material layer, and R 2 <(1/2) D. It is considered that it is advantageous to reduce the secondary particles of the second positive electrode active material present on the surface layer (positive electrode surface) side of the positive electrode active material layer.
１：リチウムイオン二次電池 １１：正極ケース １２：シール材（ガスケット）
１３：非水電解質 １４：正極 １４０：正極集電体
１４１：正極合剤層 １５：セパレータ １６：負極ケース
１７：負極 １７０：負極集電体 １７１：負極合剤層
１８：保持部材
1: Lithium ion secondary battery 11: Positive electrode case 12: Sealing material (gasket)
13: nonaqueous electrolyte 14: positive electrode 140: positive electrode current collector 141: positive electrode mixture layer 15: separator 16: negative electrode case 17: negative electrode 170: negative electrode current collector 171: negative electrode mixture layer 18: holding member
Claims (6)
前記正極材料には、ポリアニオン構造を有する第１正極活物質と酸化物系の活物質である第２正極活物質とが、前記第１正極活物質の質量が前記第２正極活物質の質量よりも多くなるように含有されており、
前記正極活物質層において、前記第１正極活物質及び前記第２正極活物質は一次粒子が凝集した二次粒子の形態を有し、
前記第１正極活物質の体積基準とした平均二次粒子径Ｒ １ と前記第２正極活物質の体積基準とした平均二次粒子径Ｒ ２ とが、Ｒ １ ＜Ｒ ２ の関係（ただし、Ｒ １ ≦（０．５０７）Ｒ ２ の範囲を除く）を満たし、
前記正極集電体の一方の表面に設けられた前記正極活物質層の層厚Ｄを基準としたときに、前記正極活物質層において前記正極集電体と反対側の正極表面から１５％の厚さの範囲に分散されている前記第２正極活物質が、前記第２正極活物質全体に対して、０体積％を超え１０体積％以下で含まれるリチウムイオン二次電池用正極。 A positive electrode (14) for a lithium ion secondary battery comprising a positive electrode current collector (140) and a positive electrode active material layer (141) made of a positive electrode material provided on the surface of the positive electrode current collector,
The positive electrode material includes a first positive electrode active material having a polyanion structure and a second positive electrode active material that is an oxide-based active material, wherein the mass of the first positive electrode active material is greater than the mass of the second positive electrode active material. Is contained so as to increase
In the positive electrode active material layer, the first positive electrode active material and the second positive electrode active material have a form of secondary particles in which primary particles are aggregated,
The average secondary particle diameter R 2 in which a volume basis of the average secondary particle diameter R 1 and the second positive electrode active material to a volume standard of the first positive electrode active material, the relationship of R 1 <R 2 (where R 1 ≦ (0.507) R 2 is excluded),
When the thickness D of the positive electrode active material layer provided on one surface of the positive electrode current collector is used as a reference, 15% of the positive electrode active material layer from the positive electrode surface opposite to the positive electrode current collector is 15%. The positive electrode for a lithium ion secondary battery, wherein the second positive electrode active material dispersed in a thickness range is contained in an amount of more than 0% by volume and 10% by volume or less with respect to the entire second positive electrode active material.
前記第１正極活物質及び前記第２正極活物質は一次粒子が凝集した二次粒子の形態を有し、
前記第１正極活物質の体積基準とした平均二次粒子径Ｒ １ と前記第２正極活物質の体積基準とした平均二次粒子径Ｒ ２ とが、Ｒ １ ＜Ｒ ２ の関係（ただし、Ｒ １ ≦（０．５０７）Ｒ ２ の範囲を除く）を満たし、
下記（ａ）及び（ｂ）のうちの少なくとも一方の条件を満たし、
調製した前記正極材料スラリーを前記正極集電体に塗布する工程を有する請求項１〜５の何れか一項に記載のリチウムイオン二次電池用正極を製造する方法である、リチウムイオン二次電池用正極の製造方法。
（ａ）前記平均二次粒子径Ｒ１は、Ｒ１＜（１／２）Ｄである。
（ｂ）前記平均二次粒子径Ｒ２は、Ｒ２＜（１／２）Ｄである。 In the step of preparing a positive electrode material slurry containing the first positive electrode active material and the second positive electrode active material,
The first positive electrode active material and the second positive electrode active material have a form of secondary particles in which primary particles are aggregated,
The average secondary particle diameter R 2 in which a volume basis of the average secondary particle diameter R 1 and the second positive electrode active material to a volume standard of the first positive electrode active material, the relationship of R 1 <R 2 (where R 1 ≦ (0.507) R 2 is excluded),
Satisfy at least one of the following conditions (a) and (b):
The lithium ion secondary battery which is a method of manufacturing the positive electrode for lithium ion secondary batteries as described in any one of Claims 1-5 which has the process of apply | coating the prepared said positive electrode material slurry to the said positive electrode electrical power collector. For producing a positive electrode for an automobile.
(A) the average secondary particle diameter R 1 is R 1 <(1/2) D.
(B) the average secondary particle diameter R 2 is R 2 <(1/2) D.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015237152A JP6607388B2 (en) | 2015-12-04 | 2015-12-04 | Positive electrode for lithium ion secondary battery and method for producing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015237152A JP6607388B2 (en) | 2015-12-04 | 2015-12-04 | Positive electrode for lithium ion secondary battery and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2017103170A JP2017103170A (en) | 2017-06-08 |
| JP6607388B2 true JP6607388B2 (en) | 2019-11-20 |
Family
ID=59016850
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2015237152A Active JP6607388B2 (en) | 2015-12-04 | 2015-12-04 | Positive electrode for lithium ion secondary battery and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP6607388B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR102237952B1 (en) | 2017-07-28 | 2021-04-08 | 주식회사 엘지화학 | Positive electorde for secondary battery and lithium secondary battery including the same |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5032800B2 (en) * | 2005-07-14 | 2012-09-26 | パナソニック株式会社 | Positive electrode for lithium secondary battery and lithium secondary battery using the same |
| US8367253B2 (en) * | 2006-02-02 | 2013-02-05 | U Chicago Argonne Llc | Lithium-ion batteries with intrinsic pulse overcharge protection |
| JP5250948B2 (en) * | 2006-07-28 | 2013-07-31 | 株式会社Ｇｓユアサ | Nonaqueous electrolyte secondary battery |
| JP2009252497A (en) * | 2008-04-04 | 2009-10-29 | Nissan Motor Co Ltd | Electrode for battery and battery |
| US20120231341A1 (en) * | 2011-03-09 | 2012-09-13 | Jun-Sik Kim | Positive active material, and electrode and lithium battery containing the positive active material |
| KR101863094B1 (en) * | 2011-09-16 | 2018-07-05 | 삼성에스디아이 주식회사 | Composite cathode active material, and cathode and lithium battery containing the material |
| WO2013052494A1 (en) * | 2011-10-03 | 2013-04-11 | A123 Systems, Inc. | Cathode materials including an oxygen-gettering compound and an ion-storage compound |
| KR101623451B1 (en) * | 2012-02-29 | 2016-05-24 | 히타치가세이가부시끼가이샤 | Lithium-ion cell |
| JP2014192142A (en) * | 2013-03-28 | 2014-10-06 | Shin Kobe Electric Mach Co Ltd | Lithium ion battery |
| JP6287707B2 (en) * | 2014-09-08 | 2018-03-07 | トヨタ自動車株式会社 | Nonaqueous electrolyte secondary battery |
| WO2016163114A1 (en) * | 2015-04-10 | 2016-10-13 | 株式会社豊田自動織機 | Positive electrode for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery |
-
2015
- 2015-12-04 JP JP2015237152A patent/JP6607388B2/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| JP2017103170A (en) | 2017-06-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US8486566B2 (en) | Positive electrode for lithium-ion secondary battery, manufacturing method thereof, and lithium-ion secondary battery | |
| US8178238B2 (en) | Positive-electrode active material for lithium-ion secondary battery, positive electrode, manufacturing method thereof, and lithium-ion secondary battery | |
| JP5219387B2 (en) | Nonaqueous electrolyte secondary battery | |
| WO2015111710A1 (en) | Non-aqueous secondary battery | |
| WO2010131401A1 (en) | Electrode for lithium ion secondary battery, and lithium ion secondary battery | |
| JPWO2015152113A1 (en) | Graphite negative electrode active material, negative electrode and lithium ion secondary battery | |
| JP3868231B2 (en) | Carbon material, negative electrode for lithium ion secondary battery and lithium ion secondary battery | |
| JP2008262768A (en) | Lithium ion secondary battery | |
| JP2009117159A (en) | Positive electrode and lithium ion secondary battery | |
| TW201330350A (en) | Lithium battery | |
| WO2019168035A1 (en) | Positive electrode material for lithium ion secondary battery, positive electrode active material layer, and lithium ion secondary battery | |
| JPWO2017057123A1 (en) | Negative electrode for lithium ion secondary battery and lithium ion secondary battery | |
| JP6115361B2 (en) | Nonaqueous electrolyte secondary battery | |
| JP6995738B2 (en) | Positive electrode for lithium-ion secondary battery and lithium-ion secondary battery | |
| WO2017138382A1 (en) | Positive electrode for lithium ion secondary battery, lithium ion secondary battery, and method of producing and method of evaluating positive electrode for lithium ion secondary battery | |
| JP2017520892A (en) | Positive electrode for lithium battery | |
| US20140011083A1 (en) | Electrode for non-aqueous electrolyte secondary batteries and non-aqueous electrolyte secondary battery including the same | |
| JP2021157925A (en) | Lithium ion secondary battery | |
| WO2012127548A1 (en) | Negative electrode for lithium ion secondary battery, and lithium ion secondary battery | |
| WO2015152115A1 (en) | Lithium ion secondary battery | |
| JP6229333B2 (en) | Nonaqueous electrolyte secondary battery | |
| KR20180028797A (en) | Anode with improved swelling phenomenon and Lithium secondary battery comprising the anode | |
| JP2014165038A (en) | Electrode material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery using the same | |
| US20230387384A1 (en) | Method for Manufacturing Positive Electrode for Lithium Secondary Battery and Positive Electrode for Lithium Secondary Battery Manufactured Thereby | |
| JP6607388B2 (en) | Positive electrode for lithium ion secondary battery and method for producing the same |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20180216 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20190116 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20190305 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20190423 |
|
| 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: 20190926 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20191009 |
|
| R151 | Written notification of patent or utility model registration |
Ref document number: 6607388 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R151 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |