JP6438297B2 - Positive electrode active material for lithium ion battery, positive electrode for lithium ion battery, and lithium ion battery - Google Patents
Positive electrode active material for lithium ion battery, positive electrode for lithium ion battery, and lithium ion battery Download PDFInfo
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- JP6438297B2 JP6438297B2 JP2014263356A JP2014263356A JP6438297B2 JP 6438297 B2 JP6438297 B2 JP 6438297B2 JP 2014263356 A JP2014263356 A JP 2014263356A JP 2014263356 A JP2014263356 A JP 2014263356A JP 6438297 B2 JP6438297 B2 JP 6438297B2
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- 239000007774 positive electrode material Substances 0.000 title claims description 123
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims description 44
- 229910001416 lithium ion Inorganic materials 0.000 title claims description 44
- 239000002245 particle Substances 0.000 claims description 98
- 239000000203 mixture Substances 0.000 claims description 24
- 239000011149 active material Substances 0.000 claims description 8
- 238000002156 mixing Methods 0.000 claims description 7
- 229910052782 aluminium Inorganic materials 0.000 claims description 5
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- 229910052725 zinc Inorganic materials 0.000 claims description 4
- 229910052726 zirconium Inorganic materials 0.000 claims description 4
- 230000000052 comparative effect Effects 0.000 description 37
- 239000000843 powder Substances 0.000 description 31
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 21
- VZSRBBMJRBPUNF-UHFFFAOYSA-N 2-(2,3-dihydro-1H-inden-2-ylamino)-N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]pyrimidine-5-carboxamide Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C(=O)NCCC(N1CC2=C(CC1)NN=N2)=O VZSRBBMJRBPUNF-UHFFFAOYSA-N 0.000 description 20
- 229910052751 metal Inorganic materials 0.000 description 20
- 239000002184 metal Substances 0.000 description 20
- 239000011572 manganese Substances 0.000 description 19
- 238000001035 drying Methods 0.000 description 15
- 238000006243 chemical reaction Methods 0.000 description 10
- 238000011156 evaluation Methods 0.000 description 10
- 239000002002 slurry Substances 0.000 description 9
- 239000000243 solution Substances 0.000 description 9
- 239000011888 foil Substances 0.000 description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 7
- 230000007423 decrease Effects 0.000 description 7
- 238000010304 firing Methods 0.000 description 7
- 229910052760 oxygen Inorganic materials 0.000 description 7
- 239000001301 oxygen Substances 0.000 description 7
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 6
- 239000003513 alkali Substances 0.000 description 6
- 238000000975 co-precipitation Methods 0.000 description 6
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 6
- 229910052808 lithium carbonate Inorganic materials 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 239000012266 salt solution Substances 0.000 description 6
- 230000006866 deterioration Effects 0.000 description 5
- 229910052748 manganese Inorganic materials 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 229910052759 nickel Inorganic materials 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 238000005406 washing Methods 0.000 description 5
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 150000002642 lithium compounds Chemical class 0.000 description 4
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- VCUFZILGIRCDQQ-KRWDZBQOSA-N N-[[(5S)-2-oxo-3-(2-oxo-3H-1,3-benzoxazol-6-yl)-1,3-oxazolidin-5-yl]methyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C1O[C@H](CN1C1=CC2=C(NC(O2)=O)C=C1)CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F VCUFZILGIRCDQQ-KRWDZBQOSA-N 0.000 description 3
- FHKPLLOSJHHKNU-INIZCTEOSA-N [(3S)-3-[8-(1-ethyl-5-methylpyrazol-4-yl)-9-methylpurin-6-yl]oxypyrrolidin-1-yl]-(oxan-4-yl)methanone Chemical compound C(C)N1N=CC(=C1C)C=1N(C2=NC=NC(=C2N=1)O[C@@H]1CN(CC1)C(=O)C1CCOCC1)C FHKPLLOSJHHKNU-INIZCTEOSA-N 0.000 description 3
- JAWMENYCRQKKJY-UHFFFAOYSA-N [3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-ylmethyl)-1-oxa-2,8-diazaspiro[4.5]dec-2-en-8-yl]-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]methanone Chemical compound N1N=NC=2CN(CCC=21)CC1=NOC2(C1)CCN(CC2)C(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F JAWMENYCRQKKJY-UHFFFAOYSA-N 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- 229910052758 niobium Inorganic materials 0.000 description 3
- 238000010298 pulverizing process Methods 0.000 description 3
- YLZOPXRUQYQQID-UHFFFAOYSA-N 3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]propan-1-one Chemical compound N1N=NC=2CN(CCC=21)CCC(=O)N1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F YLZOPXRUQYQQID-UHFFFAOYSA-N 0.000 description 2
- DEXFNLNNUZKHNO-UHFFFAOYSA-N 6-[3-[4-[2-(2,3-dihydro-1H-inden-2-ylamino)pyrimidin-5-yl]piperidin-1-yl]-3-oxopropyl]-3H-1,3-benzoxazol-2-one Chemical compound C1C(CC2=CC=CC=C12)NC1=NC=C(C=N1)C1CCN(CC1)C(CCC1=CC2=C(NC(O2)=O)C=C1)=O DEXFNLNNUZKHNO-UHFFFAOYSA-N 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 238000013019 agitation Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 229910000361 cobalt sulfate Inorganic materials 0.000 description 2
- 229940044175 cobalt sulfate Drugs 0.000 description 2
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 229940099596 manganese sulfate Drugs 0.000 description 2
- 235000007079 manganese sulphate Nutrition 0.000 description 2
- 239000011702 manganese sulphate Substances 0.000 description 2
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 239000003595 mist Substances 0.000 description 2
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 2
- 229940053662 nickel sulfate Drugs 0.000 description 2
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 2
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 2
- 235000017557 sodium bicarbonate Nutrition 0.000 description 2
- 238000009423 ventilation Methods 0.000 description 2
- YIWGJFPJRAEKMK-UHFFFAOYSA-N 1-(2H-benzotriazol-5-yl)-3-methyl-8-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carbonyl]-1,3,8-triazaspiro[4.5]decane-2,4-dione Chemical compound CN1C(=O)N(c2ccc3n[nH]nc3c2)C2(CCN(CC2)C(=O)c2cnc(NCc3cccc(OC(F)(F)F)c3)nc2)C1=O YIWGJFPJRAEKMK-UHFFFAOYSA-N 0.000 description 1
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910003548 Li(Ni,Co,Mn)O2 Inorganic materials 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- NIPNSKYNPDTRPC-UHFFFAOYSA-N N-[2-oxo-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 NIPNSKYNPDTRPC-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000002482 conductive additive Substances 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- SFMJNHNUOVADRW-UHFFFAOYSA-N n-[5-[9-[4-(methanesulfonamido)phenyl]-2-oxobenzo[h][1,6]naphthyridin-1-yl]-2-methylphenyl]prop-2-enamide Chemical compound C1=C(NC(=O)C=C)C(C)=CC=C1N1C(=O)C=CC2=C1C1=CC(C=3C=CC(NS(C)(=O)=O)=CC=3)=CC=C1N=C2 SFMJNHNUOVADRW-UHFFFAOYSA-N 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 229910000314 transition metal oxide 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
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- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、リチウムイオン電池用正極活物質、リチウムイオン電池用正極、及び、リチウムイオン電池に関する。 The present invention relates to a positive electrode active material for a lithium ion battery, a positive electrode for a lithium ion battery, and a lithium ion battery.
リチウムイオン電池の正極活物質には、一般にリチウム含有遷移金属酸化物が用いられている。具体的には、コバルト酸リチウム（ＬｉＣｏＯ2）、ニッケル酸リチウム（ＬｉＮｉＯ2）、マンガン酸リチウム（ＬｉＭｎ2Ｏ4）等であり、特性改善（高容量化、サイクル特性、保存特性、内部抵抗低減、レート特性）や安全性を高めるためにこれらを複合化することが進められている。車載用やロードレベリング用といった大型用途におけるリチウムイオン電池には、これまでの携帯電話用やパソコン用とは異なった特性が求められている。 Lithium-containing transition metal oxides are generally used as positive electrode active materials for lithium ion batteries. Specifically, lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), lithium manganate (LiMn 2 O 4 ), etc., improved characteristics (higher capacity, cycle characteristics, storage characteristics, reduced internal resistance) In order to improve the rate characteristics and safety, it is underway to combine them. Lithium ion batteries for large-scale applications such as in-vehicle use and load leveling are required to have different characteristics from those of conventional mobile phones and personal computers.
このようなリチウムイオン電池において求められる電池特性の向上について、従来、種々の研究・開発が行われている。例えば、特許文献１〜５は、異なる粒子径の正極活物質を混合して正極活物質を作製することで、電池特性が向上することについて記載している。 Conventionally, various researches and developments have been made on improving the battery characteristics required for such lithium ion batteries. For example, Patent Documents 1 to 5 describe that battery characteristics are improved by mixing positive electrode active materials having different particle sizes to produce a positive electrode active material.
特許文献１〜５に記載されているように、粒子径の異なる正極活物質を混合して正極活物質を構成することで、正極活物質の体積密度が増し、電池の高容量化が図れる。また、正極活物質において、Ｎｉ組成比を大きくすることで電池を高容量化することができるが、Ｎｉ組成比が大きくなればなるほど、繰り返し充放電した時の容量維持率、いわゆるサイクル特性が悪くなる。このため、特に高電流下で充放電する電気自動車用途においてサイクル特性の改善が常に求められていた。サイクル特性の改善としては、異種金属元素を、単に、組成：Ｌｉ（Ｎｉ、Ｃｏ、Ｍｎ）Ｏ2にドーピングする技術が知られているが、このような技術では異種金属元素をドーピングした分だけ電池の初期容量が低下する問題があった。 As described in Patent Literatures 1 to 5, by mixing positive electrode active materials having different particle diameters to form the positive electrode active material, the volume density of the positive electrode active material is increased and the capacity of the battery can be increased. Further, in the positive electrode active material, the battery can be increased in capacity by increasing the Ni composition ratio. However, the larger the Ni composition ratio, the worse the capacity retention rate when repeatedly charged and discharged, so-called cycle characteristics. Become. For this reason, improvement in cycle characteristics has always been sought, particularly in electric vehicle applications that charge and discharge under high currents. As an improvement of the cycle characteristics, a technique of simply doping a different metal element into a composition: Li (Ni, Co, Mn) O 2 is known. There was a problem that the initial capacity of the battery was lowered.
また、特許文献３では、２種類の正極活物質の粒子を混合したものを用いて電池の正極を構成している。しかしながら、これら２種類の正極活物質には粒子径の大小関係が規定されていないか（請求項１等）、粒子径の大小関係が規定されたものについては粒子径が小さいものについて異種元素を固溶させるという思想が開示されている（請求項２等）。しかしながら、充放電容量及びサイクル特性を両立させることが可能な正極活物質としては未だ改善の余地がある。 Moreover, in patent document 3, the positive electrode of a battery is comprised using what mixed the particle | grains of two types of positive electrode active materials. However, these two types of positive electrode active materials are not defined to have a particle size relationship (Claim 1 etc.), or those having a defined particle size relationship are different elements from those having a small particle size. The idea of solid solution is disclosed (claim 2 etc.). However, there is still room for improvement as a positive electrode active material capable of achieving both charge / discharge capacity and cycle characteristics.
このような問題を鑑みて、本発明は、電極密度、充放電容量及びサイクル特性が良好なリチウムイオン電池用正極活物質を提供することを課題とする。 In view of such a problem, an object of the present invention is to provide a positive electrode active material for a lithium ion battery having good electrode density, charge / discharge capacity, and cycle characteristics.
本発明者は、上記問題を解決するため種々の検討を行った結果、粒子径が異なる２種類の正極活物質を混合し、劣化速度が速い粒子径大の正極活物質のみに異種元素をドーピングする思想に想到した。すなわち、粒子径大及び小の両方の正極活物質に異種元素をドーピングすると、初期容量低下が大きくなるが、粒子径大の活物質のみにドーピングすることで、初期容量低下が最小限に抑えられることを見出した。そして、このように粒子径大の正極活物質に異種元素をドーピングすることで、サイクル評価時の直流抵抗増加率を小さくすることができ、サイクル特性が改善する正極活物質を得ることができることを見出した。 As a result of various studies to solve the above problems, the present inventor mixed two types of positive electrode active materials having different particle diameters, and doped only different types of positive electrode active materials having a high deterioration rate with different elements. I came up with the idea to do. That is, when the positive electrode active material of both large and small particle diameters is doped with a different element, the initial capacity decrease is large, but by doping only the large particle active material, the initial capacity decrease can be minimized. I found out. In addition, by doping the positive electrode active material having a large particle diameter in this way with a different element, the DC resistance increase rate during cycle evaluation can be reduced, and a positive electrode active material with improved cycle characteristics can be obtained. I found it.
上記知見を基礎にして完成した本発明は一側面において、組成式Ｉ：ＬｉaＮｉbＣｏcＭｎdＡeＯ2
（前記式Ｉにおいて、１．００≦ａ≦１．０８、ｂ≧０．４、ｂ＋ｃ＋ｄ＝１、０．００１≦ｅ≦０．０２、ＡはＴｉ、Ｚｎ、Ｚｒ、Ａｌ、Ｎｂ、Ｖ及びＴａから選ばれる少なくとも１種の元素)で表され、平均粒子径（Ｄ５０）が６〜１５μｍである正極活物質（１）と、
組成式ＩＩ：ＬｉgＮｉhＣｏiＭｎjＯ2
（前記式ＩＩにおいて、１．００≦ｇ≦１．０８、ｈ≧０．４、ｈ＋ｉ＋ｊ＝１）で表され、平均粒子径（Ｄ５０）が１〜５μｍである正極活物質（２）とを混合してなるリチウムイオン電池用正極活物質である。
In one aspect, the present invention completed on the basis of the above knowledge has a composition formula I: Li a Ni b Co c Mn d A e O 2
(In Formula I above, 1.00 ≦ a ≦ 1.08, b ≧ 0.4, b + c + d = 1, 0.001 ≦ e ≦ 0.02, A is Ti, Zn, Zr, Al, Nb, V and A positive electrode active material (1) represented by (at least one element selected from Ta) and having an average particle diameter (D50) of 6 to 15 μm;
Composition formula II: Li g Ni h Co i Mn j O 2
(In the formula II, 1.00 ≦ g ≦ 1.08, h ≧ 0.4, h + i + j = 1), and a positive electrode active material (2) having an average particle diameter (D50) of 1 to 5 μm It is a positive electrode active material for lithium ion batteries formed by mixing.
本発明に係るリチウムイオン電池用正極活物質は一実施形態において、重量比で、前記正極活物質（１）：前記正極活物質（２）＝８：２〜６：４である。 In one embodiment, the positive electrode active material for a lithium ion battery according to the present invention is, by weight ratio, the positive electrode active material (1): the positive electrode active material (2) = 8: 2 to 6: 4.
本発明に係るリチウムイオン電池用正極活物質は別の実施形態において、前記正極活物質（２）の平均粒子径（Ｄ５０）に対する前記正極活物質（１）の平均粒子径（Ｄ５０）の比が２〜５である。 In another embodiment, the positive electrode active material for a lithium ion battery according to the present invention has a ratio of the average particle size (D50) of the positive electrode active material (1) to the average particle size (D50) of the positive electrode active material (2). 2-5.
本発明に係るリチウムイオン電池用正極活物質は更に別の実施形態において、前記正極活物質（１）は前記元素Ａに濃度勾配があり、粒子断面において径中心部と、粒子表面から深さ５ｎｍの位置における元素Ａの濃度の濃度差について、(粒子表面から深さ５ｎｍの位置における元素Ａの濃度)／(径中心部の前記元素Ａの濃度）＝２〜１０である。 In still another embodiment of the positive electrode active material for a lithium ion battery according to the present invention, the positive electrode active material (1) has a concentration gradient in the element A, and a diameter cross section of the particle cross section and a depth of 5 nm from the particle surface. The concentration difference of the concentration of element A at the position of (2) is (concentration of element A at a position 5 nm deep from the particle surface) / (concentration of element A at the center of the diameter) = 2-10.
本発明は別の一側面において、本発明のリチウムイオン電池用正極活物質を用いたリチウムイオン電池用正極である。 In another aspect, the present invention is a positive electrode for a lithium ion battery using the positive electrode active material for a lithium ion battery of the present invention.
本発明は更に別の一側面において、本発明のリチウムイオン電池用正極を用いたリチウムイオン電池である。 In still another aspect, the present invention is a lithium ion battery using the positive electrode for a lithium ion battery of the present invention.
本発明によれば、電極密度、充放電容量及びサイクル特性が良好なリチウムイオン電池用正極活物質を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material for lithium ion batteries with favorable electrode density, charging / discharging capacity | capacitance, and cycling characteristics can be provided.
（リチウムイオン電池用正極活物質の構成）
本発明のリチウムイオン電池用正極活物質は、組成式Ｉ：ＬｉaＮｉbＣｏcＭｎdＡeＯ2
（前記式Ｉにおいて、１．００≦ａ≦１．０８、ｂ≧０．４、ｂ＋ｃ＋ｄ＝１、０．００１≦ｅ≦０．０２、ＡはＴｉ、Ｚｎ、Ｚｒ、Ａｌ、Ｎｂ、Ｖ及びＴａから選ばれる少なくとも１種の元素)で表され、平均粒子径（Ｄ５０）が６〜１５μｍである正極活物質（１）と、
組成式ＩＩ：ＬｉgＮｉhＣｏiＭｎjＯ2
（前記式ＩＩにおいて、１．００≦ｇ≦１．０８、ｈ≧０．４、ｈ＋ｉ＋ｊ＝１）で表され、平均粒子径（Ｄ５０）が１〜５μｍである正極活物質（２）とを混合してなる。
なお、正極活物質（１）及び（２）の組成式中のＯ(酸素)の組成は「Ｏ2」と記載するが、酸素含有量をＬＥＣＯ法で測定した場合、測定精度の関係から、測定値は１．８〜２．２の範囲となる。本来は化学量論組成からのズレを持っているが、ＸＲＤからＲ−３ｍの層状構造と考えられるため、ＡＢＯ2型の記載としている。例えばＺｒを添加する場合、本発明の正極活物質中ではＬｉ2ＺｒＯ3になっているものがあると考えられるため、その分、正極活物質（１）及び（２）の組成式中のＯ(酸素)の組成は「Ｏ2」から増えることがある。また、焼成時の雰囲気によっては、部分的に結晶格子中に酸素欠陥が生じるため、その分、正極活物質（１）及び（２）の組成式中のＯ(酸素)の組成は「Ｏ2」から減ることがある。これらのことから総合的に結晶格子中のＯ(酸素)の量が決まるが、概算上はほぼ「Ｏ2」とみなすことができる。
(Configuration of positive electrode active material for lithium ion battery)
The positive electrode active material for a lithium ion battery of the present invention has a composition formula I: Li a Ni b Co c Mn d A e O 2
(In Formula I above, 1.00 ≦ a ≦ 1.08, b ≧ 0.4, b + c + d = 1, 0.001 ≦ e ≦ 0.02, A is Ti, Zn, Zr, Al, Nb, V and A positive electrode active material (1) represented by (at least one element selected from Ta) and having an average particle diameter (D50) of 6 to 15 μm;
Composition formula II: Li g Ni h Co i Mn j O 2
(In the formula II, 1.00 ≦ g ≦ 1.08, h ≧ 0.4, h + i + j = 1), and a positive electrode active material (2) having an average particle diameter (D50) of 1 to 5 μm Mixed.
In addition, although the composition of O (oxygen) in the composition formulas of the positive electrode active materials (1) and (2) is described as “O 2 ”, when the oxygen content is measured by the LECO method, The measured value is in the range of 1.8 to 2.2. Originally, there is a deviation from the stoichiometric composition, but since it is considered to be a layered structure from XRD to R-3m, it is described as ABO 2 type. For example, when Zr is added, it is considered that some of the positive electrode active materials of the present invention are Li 2 ZrO 3 , and accordingly, O in the composition formulas of the positive electrode active materials (1) and (2). The composition of (oxygen) may increase from “O 2 ”. Depending on the firing atmosphere, oxygen defects are partially generated in the crystal lattice, and accordingly, the composition of O (oxygen) in the composition formulas of the positive electrode active materials (1) and (2) is “O 2. May be reduced. From these, the amount of O (oxygen) in the crystal lattice is comprehensively determined, but it can be regarded as almost “O 2 ” on the rough estimate.
一般に、二次電池の使用で充放電が繰り返されることで、正極活物質に表面被膜が生成し、構造劣化が進行する。このため、正極活物質の抵抗値が増加し、直流抵抗も増加する。直流抵抗が増加すると電池の充放電容量が低下し、サイクル特性が悪化する。このような問題に対し、本発明のリチウムイオン電池用正極活物質は、粒子径が異なる２種類の正極活物質である正極活物質（１）及び（２）について、劣化速度が速い粒子径大の正極活物質（１）のみに異種元素Ａをドーピングしている。このように、劣化速度が速い粒子径大の正極活物質（１）の表面を異種元素ドーピングで修飾することで、充電時に電解液との反応を抑制し、被膜の生成が抑制される。また、異種元素ドーピングにより正極活物質の構造を安定化することができ、充放電繰り返しによる構造劣化も抑制でき、活物質粒子の充放電による抵抗上昇を抑制することができる。このため、電池の寿命が長くなる。さらに、粒子径の異なる２種類の正極活物質（１）及び（２）を混合することで、電極密度も向上でき、電池容量を増加させることができる。 In general, when a secondary battery is used and charging and discharging are repeated, a surface film is generated on the positive electrode active material, and structural deterioration proceeds. For this reason, the resistance value of the positive electrode active material increases and the direct current resistance also increases. When the direct current resistance increases, the charge / discharge capacity of the battery decreases and the cycle characteristics deteriorate. In response to such a problem, the positive electrode active material for lithium ion batteries of the present invention has a large particle size with a high deterioration rate for the positive electrode active materials (1) and (2) which are two types of positive electrode active materials having different particle sizes. Only the positive electrode active material (1) is doped with the different element A. Thus, by modifying the surface of the positive electrode active material (1) having a large particle size with a high deterioration rate by doping with a different element, the reaction with the electrolyte during charging is suppressed, and the formation of a coating film is suppressed. Further, the structure of the positive electrode active material can be stabilized by doping with different elements, the structural deterioration due to repeated charge / discharge can be suppressed, and the increase in resistance due to charge / discharge of the active material particles can be suppressed. For this reason, the lifetime of a battery becomes long. Furthermore, by mixing two types of positive electrode active materials (1) and (2) having different particle diameters, the electrode density can be improved and the battery capacity can be increased.
粒子径が異なる２種類の正極活物質である正極活物質（１）及び（２）を、重量比で、正極活物質（１）：正極活物質（２）＝８：２〜６：４となるように混合するのが好ましい。このような構成によれば、より良好に充放電容量及びサイクル特性が良好なリチウムイオン電池用正極活物質を提供することができる。 The positive electrode active materials (1) and (2), which are two types of positive electrode active materials having different particle diameters, are in a weight ratio of positive electrode active material (1): positive electrode active material (2) = 8: 2 to 6: 4. It is preferable to mix so that it becomes. According to such a configuration, a positive electrode active material for a lithium ion battery with better charge / discharge capacity and cycle characteristics can be provided.
正極活物質（２）の平均粒子径（Ｄ５０）に対する正極活物質（１）の平均粒子径（Ｄ５０）の比が２〜５であるのが好ましい。このような構成によれば、より良好に充放電容量及びサイクル特性が良好なリチウムイオン電池用正極活物質を提供することができる。正極活物質（２）の平均粒子径（Ｄ５０）に対する正極活物質（１）の平均粒子径（Ｄ５０）の比は、３〜５であるのがより好ましい。 The ratio of the average particle diameter (D50) of the positive electrode active material (1) to the average particle diameter (D50) of the positive electrode active material (2) is preferably 2 to 5. According to such a configuration, a positive electrode active material for a lithium ion battery with better charge / discharge capacity and cycle characteristics can be provided. The ratio of the average particle size (D50) of the positive electrode active material (1) to the average particle size (D50) of the positive electrode active material (2) is more preferably 3-5.
元素Ａの含有量が、Ｎｉ、Ｃｏ及びＭｎの総含有量に対して、０．１〜２ｍｏｌ％であるのが好ましい。このような構成によれば、より良好に充放電容量及びサイクル特性が良好なリチウムイオン電池用正極活物質を提供することができる。元素Ａの含有量が、Ｎｉ、Ｃｏ及びＭｎの総含有量に対して、０．２〜１ｍｏｌ％であるのがより好ましい。 It is preferable that the content of the element A is 0.1 to 2 mol% with respect to the total content of Ni, Co, and Mn. According to such a configuration, a positive electrode active material for a lithium ion battery with better charge / discharge capacity and cycle characteristics can be provided. The content of the element A is more preferably 0.2 to 1 mol% with respect to the total content of Ni, Co, and Mn.
正極活物質（１）は元素Ａに濃度勾配があり、粒子断面において径中心部（粒子表面から１００ｎｍ以上内側の任意の１点）と、粒子表面から深さ５ｎｍの位置における元素Ａの濃度差について、(粒子表面から深さ５ｎｍの位置における元素Ａの濃度)／(径中心部の前記元素Ａの濃度）＝２〜１０であるのが好ましい。このような構成によれば、活物質表面での電解液との反応抑制による不活性な被膜生成の抑制が可能となる。また、充電時、Ｌｉを引き抜いたときの結晶構造の安定化が可能となる。更に、元素Ａの濃度について、活物質内部よりも表面側の濃度を大きくすることで、活物質と電解液界面での電解液分解を効率よく抑制することができる。従って、電池での充放電サイクルによる抵抗増加の抑制、充放電容量減少の抑制が可能となる。当該濃度差については、(粒子表面から深さ５ｎｍの位置における元素Ａの濃度)／(径中心部の元素Ａの濃度）＝３〜９であるのがより好ましく、４〜８であるのが更により好ましい。 The positive electrode active material (1) has a concentration gradient in the element A, and the concentration difference between the element A at the center of the diameter (any one point 100 nm or more inside from the particle surface) and at a depth of 5 nm from the particle surface in the particle cross section Is preferably (concentration of element A at a position 5 nm deep from the particle surface) / (concentration of element A at the center of the diameter) = 2-10. According to such a configuration, it is possible to suppress generation of an inactive film by suppressing reaction with the electrolytic solution on the active material surface. In addition, it is possible to stabilize the crystal structure when Li is extracted during charging. Furthermore, by increasing the concentration of the element A on the surface side of the active material, decomposition of the electrolyte at the interface between the active material and the electrolyte can be efficiently suppressed. Therefore, it is possible to suppress an increase in resistance due to a charge / discharge cycle in the battery and to suppress a decrease in charge / discharge capacity. The concentration difference is more preferably (concentration of element A at a position 5 nm deep from the particle surface) / (concentration of element A at the center of the diameter) = 3-9, and more preferably 4-8. Even more preferred.
（リチウムイオン電池用正極及びそれを用いたリチウムイオン電池の構成）
本発明の実施形態に係るリチウムイオン電池用正極は、例えば、上述の構成のリチウムイオン電池用正極活物質と、導電助剤と、バインダーとを混合して調製した正極合剤をアルミニウム箔等からなる集電体の片面または両面に設けた構造を有している。また、本発明の実施形態に係るリチウムイオン電池は、このような構成のリチウムイオン電池用正極を備えている。本発明の正極活物質を用いることで、リチウムイオン電池用正極における対極Ｌｉコインセル（ＣＲ２０３２）での直流抵抗増加が１．０〜１．３倍となる粉体を得ることができ、これにより、充放電容量低下を抑えることができる。
(Configuration of positive electrode for lithium ion battery and lithium ion battery using the same)
The positive electrode for a lithium ion battery according to an embodiment of the present invention includes, for example, a positive electrode mixture prepared by mixing a positive electrode active material for a lithium ion battery having the above-described configuration, a conductive additive, and a binder from an aluminum foil or the like. The current collector has a structure provided on one side or both sides. Moreover, the lithium ion battery which concerns on embodiment of this invention is equipped with the positive electrode for lithium ion batteries of such a structure. By using the positive electrode active material of the present invention, it is possible to obtain a powder in which the direct current resistance increase in the counter electrode Li coin cell (CR2032) in the positive electrode for a lithium ion battery is 1.0 to 1.3 times, A decrease in charge / discharge capacity can be suppressed.
（リチウムイオン電池用正極活物質の製造方法）
次に、本発明の実施形態に係るリチウムイオン電池用正極活物質の製造方法について詳細に説明する。
・粒子径大の正極活物質（１）の作製
まず、金属塩溶液を作製する。当該金属は、Ｎｉ、及び、Ｍｎ及びＣｏである。また、金属塩は硫酸塩、塩化物、硝酸塩、酢酸塩等を用いることができる。金属塩に含まれる各金属は、所望のモル比率となるように調整しておく。これにより、正極活物質中の各金属のモル比率が決定する。当該金属塩溶液とアルカリ溶液とを十分攪拌しながら、金属塩溶液とアルカリ溶液とを同一の槽に徐々に添加しながら撹拌して共沈反応させ、ろ過、洗浄を行い、ケーキを得る。反応は常法に従うことができる。
(Method for producing positive electrode active material for lithium ion battery)
Next, the manufacturing method of the positive electrode active material for lithium ion batteries which concerns on embodiment of this invention is demonstrated in detail.
-Preparation of positive electrode active material (1) having a large particle size First, a metal salt solution is prepared. The metals are Ni, Mn and Co. As the metal salt, sulfate, chloride, nitrate, acetate and the like can be used. Each metal contained in the metal salt is adjusted so as to have a desired molar ratio. Thereby, the molar ratio of each metal in the positive electrode active material is determined. While sufficiently stirring the metal salt solution and the alkali solution, the metal salt solution and the alkali solution are stirred and gradually added to the same tank to cause a coprecipitation reaction, followed by filtration and washing to obtain a cake. The reaction can follow conventional methods.
次に、洗浄した後のケーキに、リチウム化合物（例えば、炭酸リチウム、硝酸リチウム、水酸化リチウムなど）と、Ｔｉ、Ｚｎ、Ｚｒ、Ａｌ、Ｎｂ、Ｖ及びＴａから選ばれる少なくとも１種の元素Ａの化合物（例えば、酸化物、水酸化物、炭酸塩、硝酸塩等があるが、特に酸化物が好ましい）と水とを加えてスラリーとし、当該スラリーを乾燥する。このとき添加するリチウム化合物と元素Ａの化合物との量によって、生成する正極活物質中のＬｉ及び元素Ａの含有量を制御することができる。 Next, the cake after washing is added with a lithium compound (for example, lithium carbonate, lithium nitrate, lithium hydroxide) and at least one element A selected from Ti, Zn, Zr, Al, Nb, V, and Ta. These compounds (for example, oxides, hydroxides, carbonates, nitrates, etc. are preferred, but oxides are particularly preferred) and water are added to form a slurry, and the slurry is dried. At this time, the contents of Li and element A in the produced positive electrode active material can be controlled by the amounts of the lithium compound and the element A compound to be added.
次に、乾燥で得られた粉体(乾燥粉)を焼成する。このとき、元素Ａの濃度勾配「(粒子表面から深さ５ｎｍの位置における元素Ａの濃度)／(径中心部の元素Ａの濃度）」は、同じ乾燥粉であれば焼成時間によりコントロールすることができる。例えば、元素Ａの濃度勾配を大きくする（表面側の元素Ａの濃度をより大きくする）場合は、焼成時間を短くし、元素Ａの濃度勾配を小さくする（表面側と内部側の濃度差を小さくする）場合は、焼成時間を長くする。乾燥粉が異なる場合、乾燥粉の性状により、焼成条件（温度、時間）を適宜変化させる必要がある。これは、当業者が実施可能な範囲で検討する。例えば、同一の乾燥粉を何種類か条件を変化させて焼成し、ＳＴＥＭ−ＥＤＸなどから所望の濃度勾配を持つ条件を選び出すことで、当該乾燥粉に合った焼成条件を決定することができる。
次に、焼成した粉(焼成粉)をロールミル、パルベライザー等を用いて解砕し、平均粒子径（Ｄ５０）が６〜１５μｍとなった、粒子径大の正極活物質（１）の粉末を得る。この粒子径の調整方法については後述する。
Next, the powder (dry powder) obtained by drying is fired. At this time, the concentration gradient of element A “(concentration of element A at a position 5 nm deep from the particle surface) / (concentration of element A at the center of the diameter)” should be controlled by the firing time for the same dry powder. Can do. For example, when the concentration gradient of element A is increased (the concentration of element A on the surface side is increased), the firing time is shortened and the concentration gradient of element A is decreased (the concentration difference between the surface side and the inner side is reduced). In the case of reducing), the firing time is lengthened. When the dry powder is different, it is necessary to appropriately change the firing conditions (temperature, time) depending on the properties of the dry powder. This is considered to the extent practicable by those skilled in the art. For example, it is possible to determine the firing conditions suitable for the dry powder by baking the same dry powder with various conditions and selecting a condition having a desired concentration gradient from STEM-EDX or the like.
Next, the fired powder (fired powder) is pulverized using a roll mill, a pulverizer, or the like to obtain a powder of a positive electrode active material (1) having a large particle diameter and an average particle diameter (D50) of 6 to 15 μm. . A method for adjusting the particle diameter will be described later.
・粒子径小の正極活物質（２）の作製
まず、金属塩溶液を作製する。当該金属は、Ｎｉ、及び、Ｍｎ及びＣｏである。また、金属塩は硫酸塩、塩化物、硝酸塩、酢酸塩等を用いることができる。金属塩に含まれる各金属は、所望のモル比率となるように調整しておく。これにより、正極活物質中の各金属のモル比率が決定する。当該金属塩溶液とアルカリ溶液とを十分攪拌しながら、金属塩溶液とアルカリ溶液とを同一の槽に徐々に添加しながら撹拌して共沈反応させ、ろ過、洗浄を行いケーキを得る。反応は常法に従うことができる。
-Preparation of positive electrode active material (2) with a small particle diameter First, a metal salt solution is prepared. The metals are Ni, Mn and Co. As the metal salt, sulfate, chloride, nitrate, acetate and the like can be used. Each metal contained in the metal salt is adjusted so as to have a desired molar ratio. Thereby, the molar ratio of each metal in the positive electrode active material is determined. While sufficiently stirring the metal salt solution and the alkali solution, the metal salt solution and the alkali solution are stirred and gradually added to the same tank to cause a coprecipitation reaction, followed by filtration and washing to obtain a cake. The reaction can follow conventional methods.
次に、洗浄した後のケーキに、リチウム化合物（例えば、炭酸リチウム、硝酸リチウム、水酸化リチウムなど）と水とを加えてスラリーとし、当該スラリーを乾燥する。このとき添加するリチウム化合物の量によって、生成する正極活物質中のＬｉの含有量を制御することができる。 Next, a lithium compound (for example, lithium carbonate, lithium nitrate, lithium hydroxide, and the like) and water are added to the cake after washing to form a slurry, and the slurry is dried. At this time, the content of Li in the produced positive electrode active material can be controlled by the amount of the lithium compound added.
次に、乾燥で得られた粉体(乾燥粉)を焼成して焼成粉とし、これをロールミル、パルベライザー等を用いて解砕し、平均粒子径（Ｄ５０）が１〜５μｍとなった、粒子径小の正極活物質（２）の粉末を得る。この粒子径の調整方法については後述する。 Next, the powder obtained by drying (dry powder) is fired to obtain a fired powder, which is crushed using a roll mill, a pulverizer, etc., and the average particle diameter (D50) is 1 to 5 μm. A small-diameter positive electrode active material (2) powder is obtained. A method for adjusting the particle diameter will be described later.
正極活物質（１）及び（２）の粒子径の調整は、次の３種類の条件の調整により行うことができる。すなわち、〔条件i〕共沈反応時の溶液添加時間(所望の粒径が小さい場合は短く、大きい場合は長くする)、〔条件ii〕焼成時間および温度(所望の粒径が小さい場合は時間を短くするか温度を低くするかその両方を行い、大きい場合は時間を長くするか温度を高くするかその両方を行う)、〔条件iii〕パルベライザーでの解砕時の粉砕および分級回転数、送風量(一般的に所望の粒径が小さい場合は回転数を大きくするか送風量を小さくするかその両方を行い、大きい場合は回転数を小さくするか送風量を大きくするかその両方を行うが、この通りでない場合もある)である。これらの条件は、生成する物質の物性によって適宜変更される。この際、正極活物質（１）の焼成粉に濃度勾配を付与する製造条件については当然考慮されるため、一般的には〔条件i〕により調整し、〔条件ii〕及び〔条件iii〕については〔条件i〕で得られた乾燥粉を用いて条件検討を行い決定するのが好ましい。 Adjustment of the particle diameter of positive electrode active material (1) and (2) can be performed by adjustment of the following three types of conditions. (Condition i) Solution addition time during coprecipitation reaction (short if the desired particle size is small, lengthen if large), (Condition ii) firing time and temperature (time if the desired particle size is small) (If it is larger, increase the time or increase the temperature or both), (Condition iii) Grinding and classifying rotation speed during pulverization with a pulverizer, Air flow (generally, if the desired particle size is small, increase the rotation speed or decrease the air flow, or both, decrease the rotation speed, increase the air flow, or both May not be the case). These conditions are appropriately changed depending on the physical properties of the substance to be generated. At this time, since the manufacturing conditions for imparting a concentration gradient to the fired powder of the positive electrode active material (1) are naturally taken into account, in general, the conditions are adjusted according to [Condition i], and [Condition ii] and [Condition iii]. Is preferably determined by examining conditions using the dry powder obtained in [Condition i].
・リチウムイオン電池用正極活物質の作製
次に、上記で得られた粒子径大の正極活物質（１）及び粒子径小の正極活物質（２）の粉体をそれぞれ所定の割合で混合することで、本発明のリチウムイオン電池用正極活物質が得られる。
Preparation of positive electrode active material for lithium ion battery Next, the powders of the positive electrode active material (1) having a large particle diameter and the positive electrode active material (2) having a small particle diameter obtained above are mixed at a predetermined ratio. Thereby, the positive electrode active material for lithium ion batteries of this invention is obtained.
以下、本発明及びその利点をより良く理解するための実施例を提供するが、本発明はこれらの実施例に限られるものではない。 Examples for better understanding of the present invention and its advantages are provided below, but the present invention is not limited to these examples.
（実施例１−１〜実施例１−５、実施例１−８〜実施例１−１０）
まず、大粒子及び小粒子の２種類の正極活物質を以下のように作製した。
・大粒子の正極活物質の作製
硫酸ニッケル、硫酸コバルト、硫酸マンガンを水溶液として、Ｎｉ／（Ｎｉ＋Ｍｎ＋Ｃｏ）、Ｍｎ／（Ｎｉ＋Ｍｎ＋Ｃｏ）、Ｃｏ／（Ｎｉ＋Ｍｎ＋Ｃｏ）がそれぞれ表に記載のモル比となるように混合し、十分撹拌しながら十分に撹拌したアルカリ（重炭酸ナトリウム）溶液と同一の槽に添加して、撹拌しながら常法に従って共沈反応させ、ろ過、洗浄を実施した後、炭酸リチウムとＺｒＯ2と水とを加えスラリーを作製した。また、共沈反応時の溶液添加時間は２〜１４４時間とした。次に、当該スラリーをマイクロミストドライヤにて噴霧乾燥した。ＺｒＯ2は、Ｚｒ含有量がＮｉ、Ｍｎ、Ｃｏの総量に対して、表に記載のｍｏｌ％となるように調整して加えた。Ｌｉ／（Ｎｉ＋Ｍｎ＋Ｃｏ）は、表に記載のモル比となるようにした。その後、乾燥で得られた粉体をローラーハースキルンで、酸素含有雰囲気下、２時間で９５０℃まで昇温させた後、９５０℃で６時間保持した。その後、ロールミルとパルベライザーを用いて解砕し、活物質粉末を得た。また、パルベライザーでの解砕時の粉砕および分級回転数はそれぞれ１０〜１１０００ｒｐｍ及び１０〜６８００ｒｐｍとし、送風量は、０．１〜１００ｍ3／分とした。このときの粒子径（Ｄ５０）は表に記載の通りである。
・小粒子の正極活物質の作製
硫酸ニッケル、硫酸コバルト、硫酸マンガンを水溶液として、Ｎｉ／（Ｎｉ＋Ｍｎ＋Ｃｏ）、Ｍｎ／（Ｎｉ＋Ｍｎ＋Ｃｏ）、Ｃｏ／（Ｎｉ＋Ｍｎ＋Ｃｏ）がそれぞれ表に記載のモル比となるように混合し、十分撹拌しながら十分に撹拌したアルカリ（重炭酸ナトリウム）溶液と同一の槽に添加して、撹拌しながら常法に従って共沈反応させ、ろ過、洗浄を実施した後、炭酸リチウムと水とを加えスラリーを作製した。また、共沈反応時の溶液添加時間は１〜１２０時間とした。次に、当該スラリーをマイクロミストドライヤにて噴霧乾燥した。Ｌｉ／（Ｎｉ＋Ｍｎ＋Ｃｏ）は、表に記載のモル比となるようにした。その後、乾燥で得られた粉体をローラーハースキルンで焼成し、ロールミルとパルベライザーを用いて解砕し、活物質粉末を得た。また、パルベライザーでの解砕時の粉砕および分級回転数はそれぞれ１００〜１２０００ｒｐｍ及び１００〜７０００ｒｐｍとし、送風量は、０．２〜１１０ｍ3／分とした。このときの粒子径（Ｄ５０）は表に記載の通りである。
こうしてできた大粒子の正極活物質と小粒子の正極活物質とを、表に記載の重量比となるように混合し、正極活物質を得た。
(Example 1-1 to Example 1-5, Example 1-8 to Example 1-10)
First, two types of positive electrode active materials, large particles and small particles, were produced as follows.
Preparation of large-particle positive electrode active material Ni / (Ni + Mn + Co), Mn / (Ni + Mn + Co), and Co / (Ni + Mn + Co) in the aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate have the molar ratios shown in the table. After mixing and adding to the same tank as the well-stirred alkali (sodium bicarbonate) solution with stirring well, coprecipitation reaction was carried out in accordance with the usual method with stirring, and after filtration and washing, lithium carbonate and ZrO 2 and water were added to prepare a slurry. The solution addition time during the coprecipitation reaction was 2 to 144 hours. Next, the slurry was spray-dried with a micro mist dryer. ZrO 2 was added so that the Zr content was adjusted to the mol% described in the table with respect to the total amount of Ni, Mn, and Co. Li / (Ni + Mn + Co) was set to the molar ratio shown in the table. Thereafter, the powder obtained by drying was heated to 950 ° C. in an oxygen-containing atmosphere in a roller hearth kiln over 2 hours, and then held at 950 ° C. for 6 hours. Then, it grind | pulverized using the roll mill and the pulverizer, and obtained active material powder. Moreover, the grinding | pulverization at the time of crushing with a pulverizer and classification rotation speed were 10-11000 rpm and 10-6800 rpm, respectively, and the ventilation volume was 0.1-100 m < 3 > / min. The particle diameter (D50) at this time is as described in the table.
Preparation of small-particle positive electrode active material Ni / (Ni + Mn + Co), Mn / (Ni + Mn + Co), and Co / (Ni + Mn + Co) in the aqueous solution of nickel sulfate, cobalt sulfate, and manganese sulfate so that the molar ratio described in the table is obtained. Add the mixture to the same tank as the well-stirred alkali (sodium bicarbonate) solution with sufficient agitation, co-precipitate in the usual way with agitation, filter and wash, and then add lithium carbonate and water. Were added to prepare a slurry. The solution addition time during the coprecipitation reaction was 1 to 120 hours. Next, the slurry was spray-dried with a micro mist dryer. Li / (Ni + Mn + Co) was set to the molar ratio shown in the table. Then, the powder obtained by drying was fired with a roller hearth kiln and pulverized using a roll mill and a pulverizer to obtain an active material powder. Moreover, the grinding | pulverization at the time of crushing by a pulverizer and classification rotation speed were 100-12000 rpm and 100-7000 rpm, respectively, and the ventilation volume was 0.2-110 m < 3 > / min. The particle diameter (D50) at this time is as described in the table.
The large particle positive electrode active material and the small particle positive electrode active material thus produced were mixed so as to have a weight ratio shown in the table to obtain a positive electrode active material.
（実施例１−６、実施例２−６）
大粒子の正極活物質の作製において、炭酸リチウムとＡｌ2Ｏ3とを加えてスラリーを作製した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 1-6, Example 2-6)
A positive electrode active material was produced in the same manner as in Example 1-1, except that lithium carbonate and Al 2 O 3 were added to produce a large particle positive electrode active material.
（実施例１−７、実施例２−７）
大粒子の正極活物質の作製において、炭酸リチウムとＺｎＯとを加えてスラリーを作製した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 1-7, Example 2-7)
A positive electrode active material was produced in the same manner as in Example 1-1, except that lithium carbonate and ZnO were added to produce a large particle positive electrode active material.
（実施例１−１１〜実施例１−１２）
大粒子の正極活物質の作製において、乾燥で得られた粉体をローラーハースキルンで昇温後、９５０℃で８時間保持した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 1-11 to Example 1-12)
A positive electrode active material was prepared in the same manner as in Example 1-1, except that the powder obtained by drying was heated at a roller hearth kiln and then held at 950 ° C. for 8 hours. .
（実施例１−１３〜実施例１−１４）
大粒子の正極活物質の作製において、乾燥で得られた粉体をローラーハースキルンで昇温後、９５０℃で３時間保持した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 1-13 to Example 1-14)
A positive electrode active material was prepared in the same manner as in Example 1-1, except that the powder obtained by drying was heated at a roller hearth kiln and then held at 950 ° C. for 3 hours. .
（実施例１−１５）
大粒子の正極活物質の作製において、乾燥で得られた粉体をローラーハースキルンで昇温後、９５０℃で１０時間保持した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 1-15)
A positive electrode active material was prepared in the same manner as in Example 1-1, except that the powder obtained by drying was heated at a roller hearth kiln and then held at 950 ° C. for 10 hours. .
（実施例１−１６）
大粒子の正極活物質の作製において、乾燥で得られた粉体をローラーハースキルンで昇温後、９５０℃で２時間保持した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 1-16)
A positive electrode active material was prepared in the same manner as in Example 1-1, except that the powder obtained by drying was heated at a roller hearth kiln and then held at 950 ° C. for 2 hours. .
（比較例１−１、比較例２−１）
大粒子の正極活物質の作製において、異種元素Ａの酸化物を加えなかった以外は、実施例１−１と同様にして正極活物質を作製した。
(Comparative Example 1-1, Comparative Example 2-1)
A positive electrode active material was prepared in the same manner as in Example 1-1 except that in the production of the large particle positive electrode active material, the oxide of the different element A was not added.
（比較例１−２、比較例２−２）
大粒子及び小粒子の正極活物質の作製において、それぞれＺｒ含有量が１．０ｍｏｌ％となるように調整した以外は、実施例１−１と同様にして正極活物質を作製した。
(Comparative Example 1-2, Comparative Example 2-2)
A positive electrode active material was prepared in the same manner as in Example 1-1, except that the large particle and small particle positive electrode active materials were each adjusted to have a Zr content of 1.0 mol%.
（比較例１−３〜比較例１−６、比較例１−１０〜比較例１−１２、比較例２−３〜比較例２−６、比較例２−１０〜比較例２−１２）
表に示す各条件に従って、実施例１−１と同様にして正極活物質を作製した。
(Comparative Example 1-3, Comparative Example 1-6, Comparative Example 1-10, Comparative Example 1-12, Comparative Example 2-3, Comparative Example 2-6, Comparative Example 2-10, Comparative Example 2-12)
A positive electrode active material was produced in the same manner as in Example 1-1 according to each condition shown in the table.
（比較例１−７、比較例２−７）
小粒子の正極活物質を作製しなかった以外は、実施例１−１と同様にして正極活物質を作製した。
(Comparative Example 1-7, Comparative Example 2-7)
A positive electrode active material was produced in the same manner as in Example 1-1 except that the small particle positive electrode active material was not produced.
（比較例１−８、比較例２−８）
大粒子の正極活物質を作製しなかった以外は、実施例１−１と同様にして正極活物質を作製した。
(Comparative Example 1-8, Comparative Example 2-8)
A positive electrode active material was produced in the same manner as in Example 1-1, except that a large particle positive electrode active material was not produced.
（比較例１−９、比較例２−９）
大粒子に異種元素Ａを添加せず、小粒子の正極活物質の作製において、Ｚｒ含有量が１．０ｍｏｌ％となるように調整した以外は、実施例１−１と同様にして正極活物質を作製した。
(Comparative Example 1-9, Comparative Example 2-9)
The positive electrode active material was prepared in the same manner as in Example 1-1, except that the different element A was not added to the large particles, and the Zr content was adjusted to 1.0 mol% in the production of the small particle positive electrode active material. Was made.
（実施例２−１〜実施例２−５、実施例２−８〜実施例２−１０）
大粒子の正極活物質の作製において、乾燥で得られた粉体をローラーハースキルンで昇温後、９００℃で６時間保持した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 2-1 to Example 2-5, Example 2-8 to Example 2-10)
A positive electrode active material was prepared in the same manner as in Example 1-1, except that the powder obtained by drying was heated at a roller hearth kiln and then held at 900 ° C. for 6 hours. .
（実施例２−１１〜実施例２−１２）
大粒子の正極活物質の作製において、乾燥で得られた粉体をローラーハースキルンで昇温後、９００℃で８時間保持した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 2-11 to Example 2-12)
A positive electrode active material was prepared in the same manner as in Example 1-1, except that the powder obtained by drying was heated at a roller hearth kiln and then held at 900 ° C. for 8 hours. .
（実施例２−１３〜実施例２−１４）
大粒子の正極活物質の作製において、乾燥で得られた粉体をローラーハースキルンで昇温後、９００℃で３時間保持した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 2-13 to Example 2-14)
A positive electrode active material was produced in the same manner as in Example 1-1, except that the powder obtained by drying was heated at a roller hearth kiln and then held at 900 ° C. for 3 hours. .
（実施例２−１５）
大粒子の正極活物質の作製において、乾燥で得られた粉体をローラーハースキルンで昇温後、９００℃で１０時間保持した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 2-15)
A positive electrode active material was produced in the same manner as in Example 1-1, except that the powder obtained by drying was heated at a roller hearth kiln and then held at 900 ° C. for 10 hours in the production of a large particle positive electrode active material. .
（実施例２−１６）
大粒子の正極活物質の作製において、乾燥で得られた粉体をローラーハースキルンで昇温後、９００℃で２時間保持した以外は実施例１−１と同様にして正極活物質を作製した。
(Example 2-16)
A positive electrode active material was prepared in the same manner as in Example 1-1, except that the powder obtained by drying was heated at a roller hearth kiln and then held at 900 ° C. for 2 hours. .
（評価）
−正極材組成の評価−
各正極材中の金属含有量は、誘導結合プラズマ発光分光分析装置（ＩＣＰ−ＯＥＳ）で測定し、各金属の組成比（モル比）を算出した。各金属の組成比は、表１、２に記載の通りであることを確認した。
(Evaluation)
-Evaluation of composition of positive electrode material-
The metal content in each positive electrode material was measured with an inductively coupled plasma optical emission spectrometer (ICP-OES), and the composition ratio (molar ratio) of each metal was calculated. It was confirmed that the composition ratio of each metal was as described in Tables 1 and 2.
−異種元素（元素Ａ）の濃度勾配の評価−
ＳＴＥＭ−ＥＤＸ分析装置で粒子断面の線分析を行った。分析結果から元素Ａの濃度(ａｔｍ％)を出し、粒子断面において径中心部（粒子表面から１００ｎｍ以上内側の任意の１点）と、粒子表面から深さ５ｎｍの位置における元素Ａの濃度差について、(粒子表面から深さ５ｎｍの位置における元素Ａの濃度)/（径中心部の前記元素Ａの濃度）を算出した。
-Evaluation of concentration gradient of different elements (element A)-
Line analysis of the cross section of the particle was performed with a STEM-EDX analyzer. From the analysis results, the concentration of element A (atm%) is calculated, and the concentration difference of element A at the center of the diameter (any one point 100 nm or more inside from the particle surface) and at a depth of 5 nm from the particle surface in the particle cross section , (Concentration of element A at a position 5 nm deep from the particle surface) / (concentration of the element A at the center of the diameter) was calculated.
−電池特性（充放電容量、サイクル特性）の評価−
正極活物質と、導電材と、バインダー（ＰＶＤＦ）を９４：３：３の割合で秤量し、バインダーを有機溶媒（Ｎ−メチルピロリドン）に溶解したものに、正極活物質と導電材とを混合してスラリー化し、Ａｌ箔上に塗布して乾燥後にプレスして正極とした。続いて、対極をＬｉとした評価用の対極Ｌｉコインセル(ＣＲ２０３２)を準備し、電解液に１Ｍ−ＬｉＰＦ6をＥＣ−ＤＭＣ（３：７）に溶解したものを用いて、２５℃で１Ｃの放電電流で得られた初期放電容量と１０サイクル後の放電容量とを比較することによってサイクル特性（容量維持率）を測定した。具体的な評価条件及び表に記載の容量維持率と直流抵抗増加率の定義を以下に示す。
・初回充放電：２５℃、充電４．２３Ｖ、０．２Ｃ、２．５ｈ、放電３．０Ｖ、０．２Ｃ
・１Ｃ充放電サイクル：４５℃、充電４．２３Ｖ、１Ｃ、２．５ｈ、放電３．０Ｖ、１Ｃ
・容量維持率：４５℃雰囲気で充放電サイクル評価（充電４．２３Ｖ、１Ｃ、放電１Ｃ、３．０Ｖｃｕｔ）を行ったときの、１サイクル目に対する１０サイクル目の放電容量の割合。
・直流抵抗増加率：４５℃雰囲気で充放電サイクル評価（充電４．２３Ｖ、１Ｃ、放電１Ｃ、３．０Ｖｃｕｔ）を行ったときの、１サイクル目に対する１０サイクル目の直流抵抗値の割合。
電極密度算出方法を以下に示す。
・上記のＡｌ箔上に塗布して乾燥後にプレスした正極および、使用したＡｌ箔を直径１２．５ｍｍのペレット状に打ち抜き、それぞれの重量を測定し、Ａｌ箔を除いた部分の正極の面積密度(ｍｇ／ｃｍ2)・・・(1)を算出する。
・上記のＡｌ箔上に塗布して乾燥後にプレスした正極および、使用したＡｌ箔のそれぞれの厚みを測定し、Ａｌ箔を除いた部分の正極の厚み(μｍ)・・・(2)を算出する
・(1)／(2)が上記正極の電極密度となる。
これらの結果を表１、２に示す。
-Evaluation of battery characteristics (charge / discharge capacity, cycle characteristics)-
A positive electrode active material, a conductive material, and a binder (PVDF) are weighed in a ratio of 94: 3: 3, and the binder is dissolved in an organic solvent (N-methylpyrrolidone), and the positive electrode active material and the conductive material are mixed. Then, it was made into a slurry, applied onto an Al foil, dried and pressed to obtain a positive electrode. Subsequently, a counter electrode Li coin cell (CR2032) for evaluation in which the counter electrode was Li was prepared, and 1C at 25 ° C. was obtained using 1M-LiPF 6 dissolved in EC-DMC (3: 7) as an electrolyte. The cycle characteristics (capacity retention ratio) were measured by comparing the initial discharge capacity obtained with the discharge current with the discharge capacity after 10 cycles. Specific evaluation conditions and definitions of the capacity maintenance rate and the DC resistance increase rate described in the table are shown below.
-Initial charge / discharge: 25 ° C, charge 4.23V, 0.2C, 2.5h, discharge 3.0V, 0.2C
1C charge / discharge cycle: 45 ° C, charge 4.23V, 1C, 2.5h, discharge 3.0V, 1C
-Capacity maintenance ratio: The ratio of the discharge capacity of the 10th cycle to the 1st cycle when the charge / discharge cycle evaluation (charge 4.23V, 1C, discharge 1C, 3.0Vcut) is performed in a 45 ° C atmosphere.
DC resistance increase rate: The ratio of the DC resistance value of the 10th cycle to the 1st cycle when the charge / discharge cycle evaluation (charge 4.23V, 1C, discharge 1C, 3.0Vcut) is performed in a 45 ° C. atmosphere.
The electrode density calculation method is shown below.
-The positive electrode coated on the above Al foil and pressed after drying, and the Al foil used was punched into pellets with a diameter of 12.5 mm, the respective weights were measured, and the area density of the positive electrode in the portion excluding the Al foil (mg / cm 2 ) (1) is calculated.
・ Measure the thickness of the positive electrode coated on the Al foil and pressed after drying, and the thickness of the Al foil used, and calculate the thickness of the positive electrode excluding the Al foil (μm) (2)・ (1) / (2) is the electrode density of the positive electrode.
These results are shown in Tables 1 and 2.
（評価結果）
実施例１−１〜１−１６及び実施例２−１〜２−１６は、いずれも電極密度、充放電容量及びサイクル特性が良好であった。
比較例１−１及び比較例２−１は、大粒子に異種元素を含有しておらず、サイクル特性が不良であった。
比較例１−２及び比較例２−２は、小粒子に異種元素が含まれているため、充放電容量が不良であった。
比較例１−３及び比較例２−３は、大粒子の平均粒子径（Ｄ５０）が１５μｍを超えたため、サイクル特性が不良であった。
比較例１−４及び比較例２−４は、大粒子の平均粒子径（Ｄ５０）が６μｍ未満であったため、電極密度が不良であった。
比較例１−５及び比較例２−５は、小粒子の平均粒子径（Ｄ５０）が１μｍ未満であったため、サイクル特性が不良であった。
比較例１−６及び比較例２−６は、小粒子の平均粒子径（Ｄ５０）が５μｍを超えたため、電極密度が不良であった。
比較例１−７及び比較例２−７は、小粒子を有さないため、電極密度および充放電容量が不良であった。
比較例１−８及び比較例２−８は、大粒子を有さないため、電極密度が不良であった。
比較例１−９及び比較例２−９は、大粒子に異種元素を含有しておらず、小粒子に異種元素が含まれているため、サイクル特性が不良であった。
比較例１−１０及び比較例２−１０は、大粒子の異種元素含有量が２ｍｏｌ％（組成式で示す０．００１≦ｅ≦０．０２の上限値である０．０２）を超えたため、充放電容量が不良であった。
比較例１−１１及び比較例２−１１は、大粒子及び小粒子のＬｉの組成が小さ過ぎたため、サイクル特性が不良であった。
比較例１−１２及び比較例２−１２は、大粒子及び小粒子のＬｉの組成が大き過ぎたため、サイクル特性が不良であった。
(Evaluation results)
In each of Examples 1-1 to 1-16 and Examples 2-1 to 2-16, the electrode density, the charge / discharge capacity, and the cycle characteristics were good.
Comparative Example 1-1 and Comparative Example 2-1 did not contain foreign elements in the large particles, and the cycle characteristics were poor.
Since Comparative Example 1-2 and Comparative Example 2-2 contained different elements in the small particles, the charge / discharge capacity was poor.
In Comparative Examples 1-3 and 2-3, the average particle diameter (D50) of the large particles exceeded 15 μm, so the cycle characteristics were poor.
In Comparative Examples 1-4 and 2-4, the average particle diameter (D50) of the large particles was less than 6 μm, so the electrode density was poor.
Since Comparative Example 1-5 and Comparative Example 2-5 had an average particle diameter (D50) of small particles of less than 1 μm, the cycle characteristics were poor.
In Comparative Examples 1-6 and 2-6, the average particle diameter (D50) of the small particles exceeded 5 μm, so the electrode density was poor.
Since Comparative Example 1-7 and Comparative Example 2-7 did not have small particles, the electrode density and charge / discharge capacity were poor.
Since Comparative Example 1-8 and Comparative Example 2-8 did not have large particles, the electrode density was poor.
In Comparative Examples 1-9 and 2-9, the large particles did not contain the different elements, and the small particles contained the different elements, so the cycle characteristics were poor.
Since Comparative Example 1-10 and Comparative Example 2-10 exceeded 2 mol% (0.02 which is the upper limit of 0.001 ≦ e ≦ 0.02 shown in the composition formula), the content of the different particles in the large particles exceeded 2 mol%. The charge / discharge capacity was poor.
In Comparative Examples 1-11 and 2-11, the composition of large particles and small particles of Li was too small, so that the cycle characteristics were poor.
In Comparative Example 1-12 and Comparative Example 2-12, the composition of large particles and small particles of Li was too large, and thus the cycle characteristics were poor.
Claims (5)
（前記式Ｉにおいて、１．００≦ａ≦１．０８、ｂ≧０．４、ｂ＋ｃ＋ｄ＝１、０．００１≦ｅ≦０．０２、ＡはＴｉ、Ｚｎ、Ｚｒ、Ａｌ、及びＶから選ばれる少なくとも１種の元素)で表され、平均粒子径（Ｄ５０）が６〜１５μｍである正極活物質（１）と、
組成式ＩＩ：ＬｉgＮｉhＣｏiＭｎjＯ2
（前記式ＩＩにおいて、１．００≦ｇ≦１．０８、ｈ≧０．４、ｈ＋ｉ＋ｊ＝１）で表され、平均粒子径（Ｄ５０）が１〜５μｍである正極活物質（２）とを混合してなるリチウムイオン電池用正極活物質であり、
前記正極活物質（１）は前記元素Ａに濃度勾配があり、粒子断面において径中心部と、粒子表面から深さ５ｎｍの位置における元素Ａの濃度の濃度差について、(粒子表面から深さ５ｎｍの位置における元素Ａの濃度)／(径中心部の前記元素Ａの濃度）＝２〜１０であるリチウムイオン電池用正極活物質。 Composition formula I: Li a Ni b Co c Mn d A e O 2
(In the above formula I, 1.00 ≦ a ≦ 1.08, b ≧ 0.4, b + c + d = 1, 0.001 ≦ e ≦ 0.02, A is selected from Ti, Zn, Zr, Al, and V A positive electrode active material (1) having an average particle diameter (D50) of 6 to 15 μm,
Composition formula II: Li g Ni h Co i Mn j O 2
(In the formula II, 1.00 ≦ g ≦ 1.08, h ≧ 0.4, h + i + j = 1), and a positive electrode active material (2) having an average particle diameter (D50) of 1 to 5 μm It is a positive electrode active material for lithium ion batteries formed by mixing ,
The positive electrode active material (1) has a concentration gradient in the element A. Regarding the concentration difference in the concentration of the element A at the center of the diameter in the particle cross section and at a position at a depth of 5 nm from the particle surface, the depth is 5 nm from the particle surface. The positive electrode active material for a lithium ion battery in which the concentration of the element A at the position of (2) / (the concentration of the element A at the center of the diameter) is 2 to 10 .
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