JP7409923B2 - Positive electrode active material for multilayer lithium ion secondary battery and method for producing the same - Google Patents
Positive electrode active material for multilayer lithium ion secondary battery and method for producing the same Download PDFInfo
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- JP7409923B2 JP7409923B2 JP2020047900A JP2020047900A JP7409923B2 JP 7409923 B2 JP7409923 B2 JP 7409923B2 JP 2020047900 A JP2020047900 A JP 2020047900A JP 2020047900 A JP2020047900 A JP 2020047900A JP 7409923 B2 JP7409923 B2 JP 7409923B2
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- lithium
- carbon
- positive electrode
- particles
- active material
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 131
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- 239000011572 manganese Substances 0.000 claims description 26
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- -1 phosphoric acid compound Chemical class 0.000 claims description 21
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- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 description 1
- SQQMAOCOWKFBNP-UHFFFAOYSA-L manganese(II) sulfate Chemical compound [Mn+2].[O-]S([O-])(=O)=O SQQMAOCOWKFBNP-UHFFFAOYSA-L 0.000 description 1
- SCVOEYLBXCPATR-UHFFFAOYSA-L manganese(II) sulfate pentahydrate Chemical compound O.O.O.O.O.[Mn+2].[O-]S([O-])(=O)=O SCVOEYLBXCPATR-UHFFFAOYSA-L 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 150000002772 monosaccharides Chemical class 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- RRIWRJBSCGCBID-UHFFFAOYSA-L nickel sulfate hexahydrate Chemical compound O.O.O.O.O.O.[Ni+2].[O-]S([O-])(=O)=O RRIWRJBSCGCBID-UHFFFAOYSA-L 0.000 description 1
- 229940116202 nickel sulfate hexahydrate Drugs 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 229920001282 polysaccharide Polymers 0.000 description 1
- 239000005017 polysaccharide Substances 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- ULWHHBHJGPPBCO-UHFFFAOYSA-N propane-1,1-diol Chemical compound CCC(O)O ULWHHBHJGPPBCO-UHFFFAOYSA-N 0.000 description 1
- 229940005657 pyrophosphoric acid Drugs 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000008107 starch Substances 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 235000002906 tartaric acid Nutrition 0.000 description 1
- 239000011975 tartaric acid Substances 0.000 description 1
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 description 1
- 150000007984 tetrahydrofuranes Chemical class 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- UNXRWKVEANCORM-UHFFFAOYSA-N triphosphoric acid Chemical compound OP(O)(=O)OP(O)(=O)OP(O)(O)=O UNXRWKVEANCORM-UHFFFAOYSA-N 0.000 description 1
- 229940048102 triphosphoric acid Drugs 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
- Inorganic Compounds Of Heavy Metals (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、優れた電池特性と安全性を兼ね備えた多層型リチウムイオン二次電池用正極活物質及びその製造方法に関する。 The present invention relates to a positive electrode active material for multilayer lithium ion secondary batteries that has both excellent battery characteristics and safety, and a method for manufacturing the same.
層状型リチウム・ニッケル・コバルト・マンガン複合酸化物（ＮＭＣ）や層状型リチウム・ニッケル・コバルト・アルミニウム複合酸化物（ＮＣＡ）等の層状型リチウム複合酸化物は、リチウム原子層と遷移金属原子層とが、酸素原子層を介して交互に積み重なった層状結晶構造となっている。かかる層状型リチウム複合酸化物は、高出力及び高容量のリチウムイオン二次電池を構成できる正極活物質として使用されている。 Layered lithium composite oxides, such as layered lithium-nickel-cobalt-manganese composite oxide (NMC) and layered lithium-nickel-cobalt-aluminum composite oxide (NCA), have a lithium atomic layer and a transition metal atomic layer. have a layered crystal structure in which they are stacked alternately with oxygen atomic layers interposed in between. Such layered lithium composite oxides are used as positive electrode active materials that can constitute high-output and high-capacity lithium ion secondary batteries.
こうした層状型リチウム複合酸化物を正極活物質として用いたリチウムイオン二次電池では、リチウムイオンが層状型リチウム複合酸化物に脱離・挿入されることによって充電・放電が行われるが、充放電サイクルを重ねるにつれて容量低下が生じ、特に長期間使用すると、電池の容量低下が著しくなるおそれがある。これは、充電時にリチウム複合酸化物の遷移金属成分が電解液へ溶出することにより、かかる結晶構造の崩壊が生じやすくなることが原因であると考えられている。特に高温になるほど遷移金属の溶出量は多くなり、サイクル特性に与える影響は大きい。また、リチウム複合酸化物の結晶構造の崩壊が生じると、リチウム複合酸化物の遷移金属成分が周囲の電解液へ溶出し、熱的安定性が低下して安全性が損なわれるおそれもある。 In a lithium ion secondary battery using such a layered lithium composite oxide as a positive electrode active material, charging and discharging are performed by desorption and insertion of lithium ions into the layered lithium composite oxide. The battery capacity decreases as the batteries are used over a long period of time, and especially when used for a long period of time, there is a risk that the battery capacity decreases significantly. This is thought to be because the transition metal component of the lithium composite oxide is eluted into the electrolyte during charging, making the crystal structure more likely to collapse. In particular, the higher the temperature, the more transition metals are eluted, which has a large effect on cycle characteristics. Furthermore, if the crystal structure of the lithium composite oxide collapses, the transition metal component of the lithium composite oxide will be eluted into the surrounding electrolyte, which may reduce thermal stability and impair safety.
車載用電池に使用される電池材料には、１０００サイクル以上もの多数回にわたる充放電サイクルを経ても、一定以上の電池容量を維持できるような優れた耐久性を有することが要求されており、これに応じるべく種々の開発がなされている。例えば、特許文献１には、リチウム複合酸化物粒子からなる層状型リチウム複合酸化物二次粒子の表面の一部のみにおいて、特定のリチウム系ポリアニオン粒子とリチウム複合酸化物粒子とが複合化してなるリチウムイオン二次電池用正極活物質が開示されており、これを用いたリチウムイオン二次電池において、優れた放電特性の発現を試みている。 Battery materials used in automotive batteries are required to have excellent durability so that they can maintain a certain level of battery capacity even after being charged and discharged many times over 1,000 cycles. Various developments have been made to meet these demands. For example, Patent Document 1 discloses that specific lithium-based polyanion particles and lithium composite oxide particles are composited only on a part of the surface of layered lithium composite oxide secondary particles made of lithium composite oxide particles. A positive electrode active material for lithium ion secondary batteries has been disclosed, and efforts are being made to develop excellent discharge characteristics in lithium ion secondary batteries using this material.
しかしながら、上記特許文献１に記載のようなリチウムイオン二次電池用正極活物質においては、層状型リチウム複合酸化物二次粒子とリチウム系ポリアニオン粒子とが強固に複合化されていないと、低温から高温にわたる幅広い温度変化に対応し得る安定した電池特性を発揮できないおそれがあり、さらなる改善を要する状況にある。 However, in the positive electrode active material for lithium ion secondary batteries as described in Patent Document 1, if the layered lithium composite oxide secondary particles and lithium-based polyanion particles are not strongly composited, There is a risk that stable battery characteristics that can withstand wide temperature changes over high temperatures may not be exhibited, and further improvements are required.
したがって、本発明の課題は、リチウム複合酸化物二次粒子とリチウム系ポリアニオン粒子との強固な複合化を可能とする構造を有した多層型リチウムイオン二次電池用正極活物質を提供することにある。 Therefore, an object of the present invention is to provide a positive electrode active material for a multilayer lithium ion secondary battery that has a structure that enables a strong composite of lithium composite oxide secondary particles and lithium-based polyanion particles. be.
そこで本発明者は、上記課題を解決すべく鋭意検討を行った結果、リチウム複合酸化物二次粒子（ａ）からなるコア部（Ａ）と、これを被覆してなるリチウム系ポリアニオン粒子（ｂ）からなる内層（Ｂ）と、さらに内層（Ｂ）を被覆してなる水不溶性炭素粉末（ｃ）からなる外層（Ｃ）なる堅固な多層構造を有することにより、幅広い温度変化に晒されても安定して優れた電池特性を発現することのできる多層型リチウムイオン二次電池用正極活物質が得られることを見出した。 Therefore, as a result of intensive studies to solve the above problems, the present inventors discovered a core part (A) made of lithium composite oxide secondary particles (a) and a lithium-based polyanion particle (b) coated with the core part (A). ) and an outer layer (C) made of water-insoluble carbon powder (c) that covers the inner layer (B), so it can withstand a wide range of temperature changes. It has been found that a positive electrode active material for multilayer lithium ion secondary batteries that can stably exhibit excellent battery characteristics can be obtained.
すなわち、本発明は、平均粒径３μｍ～３０μｍのコア部（Ａ）と、
コア部（Ａ）を被覆してなる、層厚み６００ｎｍ～５０００ｎｍの内層（Ｂ）と、さらに内層（Ｂ）を被覆してなる、層厚み２ｎｍ～８０ｎｍの外層（Ｃ）
を有する多層型リチウムイオン二次電池用正極活物質であって、
コア部（Ａ）が、下記式（Ｉ）又は式（II）：
ＬｉＮｉａＣｏｂＭｎｃＭ１
ｘＯ２・・・（Ｉ）
（式（Ｉ）中、Ｍ１はＭｇ、Ｔｉ、Ｎｂ、Ｆｅ、Ｃｒ、Ｓｉ、Ａｌ、Ｇａ、Ｖ、Ｚｎ、Ｃｕ、Ｓｒ、Ｍｏ、Ｚｒ、Ｓｎ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｂ、Ｂｉ及びＧｅから選ばれる１種又は２種以上の元素を示す。ａ、ｂ、ｃ、ｘは、０．３≦ａ＜１、０＜ｂ≦０．７、０＜ｃ≦０．７、０≦ｘ≦０．３、かつ３ａ＋３ｂ＋３ｃ＋（Ｍ１の価数）×ｘ＝３を満たす数を示す。）
ＬｉＮｉｄＣｏｅＡｌｆＭ２
ｙＯ２・・・（II）
（式（II）中、Ｍ２はＭｇ、Ｔｉ、Ｎｂ、Ｆｅ、Ｃｒ、Ｓｉ、Ｇａ、Ｖ、Ｚｎ、Ｃｕ、Ｓｒ、Ｍｏ、Ｚｒ、Ｓｎ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｂ、Ｂｉ及びＧｅから選ばれる１種又は２種以上の元素を示す。ｄ、ｅ、ｆ、ｙは、０．４≦ｄ＜１、０＜ｅ≦０．６、０＜ｆ≦０．３、０≦ｙ≦０．３、かつ３ｄ＋３ｅ＋３ｆ＋（Ｍ２の価数）×ｙ＝３を満たす数を示す。）
で表されるリチウム複合酸化物二次粒子（ａ）からなり、
内層（Ｂ）が、下記式（III）又は式（III）'：
ＬｉｇＭｎｈＦｅｉＭ３
ｚＰＯ４・・・（III）
（式（III）中、Ｍ３はＣｏ、Ｎｉ、Ｍｇ、Ｃａ、Ｓｒ、Ｙ、Ｚｒ、Ｍｏ、Ｂａ、Ｐｂ、Ｂｉ、Ｌａ、Ｃｅ、Ｎｄ又はＧｄを示す。ｇ、ｈ、ｉ、及びｚは、０＜ｇ≦１．２、０≦ｈ≦１．２、０≦ｉ≦１．２、０≦ｚ≦０．３、及びｈ＋ｉ≠０を満たし、かつｇ＋（Ｍｎの価数）×ｈ＋（Ｆｅの価数）×ｉ＋（Ｍ３の価数）×ｚ＝３を満たす数を示す。）
Ｍｎｈ’Ｆｅｉ’Ｍ３
ｚ'ＰＯ４・・・（III）'
（式（III）'中、Ｍ３は式（III）と同義である。ｈ'、ｉ'、及びｚ'は、０≦ｈ'≦１．２、０≦ｉ'≦１．２、０≦ｚ'≦０．３、及びｈ'＋ｉ'≠０を満たし、かつ（Ｍｎの価数）×ｈ'＋（Ｆｅの価数）×ｉ'＋（Ｍ３の価数）×ｚ'＝３を満たす数を示す。）で表され、かつ表面に炭素（ｘ）が担持してなるリチウム系ポリアニオン粒子（ｂ）からなり、
外層（Ｃ）が、グラファイト、グラフェン、カーボンブラック、及びカーボンナノファイバーから選ばれる水不溶性炭素粉末（ｃ）からなり、
表面に炭素（ｘ）が担持してなるリチウム系ポリアニオン粒子（ｂ）の含有量と、リチウム複合酸化物二次粒子（ａ）の含有量との質量比（（ｂ）：（ａ））が、５：９５～５５：４５である多層型リチウムイオン二次電池用正極活物質を提供するものである。
That is, the present invention provides a core portion (A) having an average particle diameter of 3 μm to 30 μm,
An inner layer (B) with a layer thickness of 600 nm to 5000 nm, which covers the core part (A), and an outer layer (C) with a layer thickness of 2 nm to 80 nm, which further covers the inner layer (B).
A positive electrode active material for a multilayer lithium ion secondary battery having
The core part (A) has the following formula (I) or formula (II):
LiNi a Co b Mn c M 1 x O 2 ...(I)
(In formula (I), M1 is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Represents one or more elements selected from Bi and Ge. a, b, c, x are 0.3≦a<1, 0<b≦0.7, 0<c≦0.7, Indicates a number that satisfies 0≦x≦0.3 and 3a+3b+3c+(M valence of 1 )×x=3.)
LiNi d Co e Al f M 2 y O 2 ...(II)
(In formula (II), M2 is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and Represents one or more elements selected from Ge. d, e, f, y are 0.4≦d<1, 0<e≦0.6, 0<f≦0.3, 0≦ Indicates a number that satisfies y≦0.3 and 3d+3e+3f+(valence of M2 )×y=3.)
Consisting of lithium composite oxide secondary particles (a) represented by
The inner layer (B) has the following formula (III) or formula (III)':
Li g Mn h Fe i M 3 z PO 4 ...(III)
(In formula (III), M3 represents Co, Ni, Mg, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. g, h, i, and z satisfies 0<g≦1.2, 0≦h≦1.2, 0≦i≦1.2, 0≦z≦0.3, and h+i≠0, and g+(valence of Mn)× Indicates the number that satisfies h + (valence of Fe) x i + (valence of M 3 ) x z = 3.)
Mn h' Fe i' M 3 z' PO 4 ...(III)'
(In formula (III)', M3 has the same meaning as in formula (III). h', i', and z' are 0≦h'≦1.2, 0≦i'≦1.2, 0 ≦z'≦0.3 and h'+i'≠0, and (valence of Mn)×h'+(valence of Fe)×i'+(valence of M3 )×z'= (indicates a number that satisfies 3.), and consists of lithium-based polyanion particles (b) on which carbon (x) is supported on the surface,
The outer layer (C) is made of water-insoluble carbon powder (c) selected from graphite, graphene, carbon black, and carbon nanofibers,
The mass ratio ((b):(a)) of the content of the lithium-based polyanion particles (b) having carbon (x) supported on the surface and the content of the lithium composite oxide secondary particles (a) is , 5:95 to 55:45.
また、本発明は、次の工程（Ｐ１）～（Ｐ２）：
（Ｐ１）リチウム化合物と、少なくとも鉄化合物又はマンガン化合物を含む金属化合物とリン酸化合物とから水熱反応物を得た後、或いは少なくとも鉄化合物又はマンガン化合物を含む金属化合物とリン酸化合物とから水熱反応物を得た後、炭素（ｘ）源を混合して噴霧乾燥し、表面に炭素（ｘ）を担持してなるリチウム系ポリアニオン粒子（ｂ）から形成されてなる造粒体（Ｚ）を得る工程
（Ｐ２）圧縮力及びせん断力を付加した混合を行いながら、リチウム複合酸化物二次粒子（ａ）に造粒体（Ｚ）を添加し、次いで水不溶性炭素粉末（ｃ）を添加する工程
を備える上記多層型リチウムイオン二次電池用正極活物質の製造方法を提供するものである。
Further, the present invention provides the following steps (P1) to (P2):
(P1) After obtaining a hydrothermal reaction product from a lithium compound, a metal compound containing at least an iron compound or a manganese compound, and a phosphoric acid compound, or after obtaining a hydrothermal reaction product from a phosphoric acid compound and a metal compound containing at least an iron compound or a manganese compound, After obtaining the thermal reactant, a carbon (x) source is mixed and spray-dried to obtain a granule (Z) formed from lithium-based polyanion particles (b) carrying carbon (x) on the surface. (P2) Adding the granules (Z) to the lithium composite oxide secondary particles (a) while performing mixing while applying compressive force and shear force, and then adding the water-insoluble carbon powder (c). The present invention provides a method for producing the above-mentioned positive electrode active material for a multilayer lithium ion secondary battery, comprising the step of:
本発明の多層型リチウムイオン二次電池用正極活物質によれば、リチウム複合酸化物二次粒子とリチウム系ポリアニオン粒子とが強固に複合化しつつコア部及び内層を形成し、かつ特定の水不溶性炭素粉末からなる外層がこれらを被覆してなる多層構造を有するため、低温環境下に晒されても高温環境下に晒されても、変動することなく優れた電池特性を発現するリチウムイオン二次電池を実現することができる。 According to the positive electrode active material for a multilayer lithium ion secondary battery of the present invention, the lithium composite oxide secondary particles and the lithium-based polyanion particles form a core part and an inner layer while being strongly composited, and have a specific water-insoluble property. Because it has a multilayer structure in which an outer layer made of carbon powder covers these, the lithium ion secondary battery exhibits excellent battery characteristics without fluctuation even when exposed to low-temperature or high-temperature environments. A battery can be realized.
以下、本発明について詳細に説明する。
本発明の多層型リチウムイオン二次電池用正極活物質は、平均粒径３μｍ～３０μｍの上記コア部（Ａ）と、
コア部（Ａ）を被覆してなる、層厚み６００ｎｍ～５０００ｎｍの上記内層（Ｂ）と、
さらに内層（Ｂ）を被覆してなる、層厚み２ｎｍ～８０ｎｍの上記外層（Ｃ）
を有する多層構造、いわゆるコア部（内部）とシェル部（表層部）とを有するコア－シェル構造の粒子である。
このように、本発明の多層型リチウムイオン二次電池用正極活物質の中核としてのコア部（Ａ）をリチウム複合酸化物二次粒子（ａ）が形成するなか、中間層としての内層（Ｂ）をリチウム系ポリアニオン粒子（ｂ）が形成しながら、これらの最外殻として水不溶性炭素粉末（ｃ）が外層（Ｃ）を形成してなる堅固な多層構造を呈しており、リチウム複合酸化物二次粒子とリチウム系ポリアニオン粒子とが強固に複合化しつつ、これらを堅固に外層（Ｃ）が被覆してなる。そのため、過酷な温度変化に対しても、リチウム複合酸化物二次粒子とリチウム系ポリアニオン粒子との複合化が乱されるのを有効に抑制することが可能になるとともに、堅固に被覆された外層（Ｃ）の存在とも相まって、高い導電率を保持することも可能となり、低温から高温にわたる幅広い温度変化に対応し得る安定した電池特性を示すことができる。
The present invention will be explained in detail below.
The positive electrode active material for a multilayer lithium ion secondary battery of the present invention includes the above core portion (A) having an average particle size of 3 μm to 30 μm,
the inner layer (B) having a layer thickness of 600 nm to 5000 nm, which covers the core part (A);
The above outer layer (C) having a layer thickness of 2 nm to 80 nm is further coated with the inner layer (B).
It is a particle with a multilayer structure having a so-called core-shell structure having a core part (inside) and a shell part (surface layer part).
In this way, while the lithium composite oxide secondary particles (a) form the core part (A) as the nucleus of the positive electrode active material for a multilayer lithium ion secondary battery of the present invention, the inner layer (B ) are formed by lithium-based polyanion particles (b), and water-insoluble carbon powder (c) forms the outer layer (C) as the outermost shell of these, forming a solid multilayer structure, and the lithium composite oxide The secondary particles and the lithium-based polyanion particles are strongly composited and are tightly coated with the outer layer (C). Therefore, even under severe temperature changes, it is possible to effectively suppress the disturbance of the composite of lithium composite oxide secondary particles and lithium-based polyanion particles, and the outer layer is tightly coated. Coupled with the presence of (C), it is also possible to maintain high electrical conductivity, and it is possible to exhibit stable battery characteristics that can respond to a wide range of temperature changes from low to high temperatures.
本発明の多層型リチウムイオン二次電池用正極活物質が有するコア部（Ａ）は、平均粒径３μｍ～３０μｍであって、下記式（Ｉ）又は式（II）：
ＬｉＮｉａＣｏｂＭｎｃＭ１
ｘＯ２・・・（Ｉ）
（式（Ｉ）中、Ｍ１はＭｇ、Ｔｉ、Ｎｂ、Ｆｅ、Ｃｒ、Ｓｉ、Ａｌ、Ｇａ、Ｖ、Ｚｎ、Ｃｕ、Ｓｒ、Ｍｏ、Ｚｒ、Ｓｎ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｂ、Ｂｉ及びＧｅから選ばれる１種又は２種以上の元素を示す。ａ、ｂ、ｃ、ｘは、０．３≦ａ＜１、０＜ｂ≦０．７、０＜ｃ≦０．７、０≦ｘ≦０．３、かつ３ａ＋３ｂ＋３ｃ＋（Ｍ１の価数）×ｘ＝３を満たす数を示す。）
ＬｉＮｉｄＣｏｅＡｌｆＭ２
ｙＯ２・・・（II）
（式（II）中、Ｍ２はＭｇ、Ｔｉ、Ｎｂ、Ｆｅ、Ｃｒ、Ｓｉ、Ｇａ、Ｖ、Ｚｎ、Ｃｕ、Ｓｒ、Ｍｏ、Ｚｒ、Ｓｎ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｂ、Ｂｉ及びＧｅから選ばれる１種又は２種以上の元素を示す。ｄ、ｅ、ｆ、ｙは、０．４≦ｄ＜１、０＜ｅ≦０．６、０＜ｆ≦０．３、０≦ｙ≦０．３、かつ３ｄ＋３ｅ＋３ｆ＋（Ｍ２の価数）×ｙ＝３を満たす数を示す。）
で表されるリチウム複合酸化物二次粒子（ａ）からなる。
The core portion (A) of the positive electrode active material for a multilayer lithium ion secondary battery of the present invention has an average particle size of 3 μm to 30 μm, and has the following formula (I) or formula (II):
LiNi a Co b Mn c M 1 x O 2 ...(I)
(In formula (I), M1 is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Represents one or more elements selected from Bi and Ge. a, b, c, x are 0.3≦a<1, 0<b≦0.7, 0<c≦0.7, Indicates a number that satisfies 0≦x≦0.3 and 3a+3b+3c+(M valence of 1 )×x=3.)
LiNi d Co e Al f M 2 y O 2 ...(II)
(In formula (II), M2 is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and Represents one or more elements selected from Ge. d, e, f, y are 0.4≦d<1, 0<e≦0.6, 0<f≦0.3, 0≦ Indicates a number that satisfies y≦0.3 and 3d+3e+3f+(valence of M2 )×y=3.)
It consists of lithium composite oxide secondary particles (a) represented by:
上記式（Ｉ）で表されるリチウムニッケル複合酸化物（いわゆるＬｉ－Ｎｉ－Ｃｏ－Ｍｎ酸化物であり、以後「ＮＣＭ系複合酸化物」とも称する。）粒子、並びに上記式（II）で表されるリチウムニッケル複合酸化物（いわゆるＬｉ－Ｎｉ－Ｃｏ－Ａｌ酸化物であり、以後「ＮＣＡ系複合酸化物」とも称する。）粒子は、いずれも層状岩塩構造を有する粒子である。
これらの粒子は、一次粒子が凝集することによって形成される。したがって、かかるリチウム複合酸化物二次粒子（ａ）についても、同様に「ＮＣＭ系複合酸化物二次粒子（ａ）」、「ＮＣＡ系複合酸化物二次粒子（ａ）」とも称する。
Lithium-nickel composite oxide (so-called Li-Ni-Co-Mn oxide, hereinafter also referred to as "NCM composite oxide") particles represented by the above formula (I), and particles represented by the above formula (II). All of the lithium-nickel composite oxide (so-called Li-Ni-Co-Al oxide, hereinafter also referred to as "NCA-based composite oxide") particles have a layered rock salt structure.
These particles are formed by agglomeration of primary particles. Therefore, the lithium composite oxide secondary particles (a) are also referred to as "NCM composite oxide secondary particles (a)" and "NCA composite oxide secondary particles (a)."
上記式（Ｉ）中のＭ１は、Ｍｇ、Ｔｉ、Ｎｂ、Ｆｅ、Ｃｒ、Ｓｉ、Ａｌ、Ｇａ、Ｖ、Ｚｎ、Ｃｕ、Ｓｒ、Ｍｏ、Ｚｒ、Ｓｎ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｂ、Ｂｉ及びＧｅから選ばれる１種又は２種以上の元素を示す。
また、上記式（Ｉ）中のａ、ｂ、ｃ、ｘは、０．３≦ａ＜１、０＜ｂ≦０．７、０＜ｃ≦０．７、０≦ｘ≦０．３、かつ３ａ＋３ｂ＋３ｃ＋（Ｍ１の価数）×ｘ＝３を満たす数である。
M 1 in the above formula (I) is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb , Bi, and Ge.
In addition, a, b, c, and x in the above formula (I) are 0.3≦a<1, 0<b≦0.7, 0<c≦0.7, 0≦x≦0.3, And it is a number that satisfies 3a+3b+3c+(valence of M1 )×x=3.
上記ＮＣＭ系複合酸化物二次粒子（ａ）において、Ｎｉ、Ｃｏ及びＭｎは、電子伝導性に優れ、電池容量及び出力特性に寄与することが知られている。また、サイクル特性の観点からは、かかる遷移元素の一部が他の金属元素Ｍ１により置換されていることが好ましい。 In the NCM-based composite oxide secondary particles (a), Ni, Co, and Mn are known to have excellent electronic conductivity and contribute to battery capacity and output characteristics. Further, from the viewpoint of cycle characteristics, it is preferable that a part of the transition element is replaced by another metal element M1 .
上記ＮＣＭ系複合酸化物二次粒子（ａ）としては、具体的には、例えばＬｉＮｉ0.33Ｃｏ0.33 Ｍｎ0.34Ｏ2、ＬｉＮｉ0.8Ｃｏ0.1Ｍｎ 0.1Ｏ2、ＬｉＮｉ0.6Ｃｏ0.2Ｍｎ 0.2Ｏ2、ＬｉＮｉ0.33Ｃｏ0.31Ｍｎ0.33Ｍｇ0.045Ｏ2、又はＬｉＮｉ0.33Ｃｏ0.31Ｍｎ0.33Ｚｎ0.045Ｏ2等が挙げられる。なかでも、放電容量を重視する場合には、ＬｉＮｉ0.8Ｃｏ0.1Ｍｎ 0.1Ｏ2、ＬｉＮｉ0.6Ｃｏ0.2Ｍｎ 0.2Ｏ2等のＮｉ量の多い組成からなる粒子が好ましく、サイクル特性を重視する場合には、ＬｉＮｉ0.33Ｃｏ0.33 Ｍｎ0.34Ｏ2、ＬｉＮｉ0.33Ｃｏ0.31Ｍｎ0.33Ｍｇ0.045Ｏ2等のＮｉ量の少ない組成からなる粒子が好ましい。 Specifically, the NCM-based composite oxide secondary particles (a) include, for example, LiNi 0.33 Co 0.33 Mn 0.34 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.33 Examples include Co 0.31 Mn 0.33 Mg 0.045 O 2 or LiNi 0.33 Co 0.31 Mn 0.33 Zn 0.045 O 2 . Among these, particles having a composition with a large amount of Ni such as LiNi 0.8 Co 0.1 Mn 0.1 O 2 and LiNi 0.6 Co 0.2 Mn 0.2 O 2 are preferable when emphasis is placed on discharge capacity, and when emphasis is placed on cycle characteristics. , LiNi 0.33 Co 0.33 Mn 0.34 O 2 , LiNi 0.33 Co 0.31 Mn 0.33 Mg 0.045 O 2 and the like are preferred.
上記式（II）中のＭ２は、Ｍｇ、Ｔｉ、Ｎｂ、Ｆｅ、Ｃｒ、Ｓｉ、Ｇａ、Ｖ、Ｚｎ、Ｃｕ、Ｓｒ、Ｍｏ、Ｚｒ、Ｓｎ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｂ、Ｂｉ及びＧｅから選ばれる１種又は２種以上の元素を示す。
また、上記式（II）中のｄ、ｅ、ｆ、ｙは、０．４≦ｄ＜１、０＜ｅ≦０．６、０＜ｆ≦０．３、０≦ｙ≦０．３、かつ３ｄ＋３ｅ＋３ｆ＋（Ｍ２の価数）×ｙ＝３を満たす数である。
M2 in the above formula (II) is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and Ge.
In addition, d, e, f, and y in the above formula (II) are 0.4≦d<1, 0<e≦0.6, 0<f≦0.3, 0≦y≦0.3, And it is a number that satisfies 3d+3e+3f+(valence of M2 )×y=3.
上記ＮＣＡ系複合酸化物二次粒子（ａ）は、式（Ｉ）で表されるＮＣＭ系複合酸化物粒子よりも、さらに電池容量及び出力特性に優れている。加えて、Ａｌの含有により、雰囲気中の湿分による変質も生じ難く、安全性にも優れている。
上記ＮＣＡ系複合酸化物二次粒子（ａ）としては、具体的には、例えばＬｉＮｉ0.8Ｃｏ0.1Ａｌ0.1Ｏ2、ＬｉＮｉ0.8Ｃｏ0.15Ａｌ0.03Ｍｇ0.03Ｏ2、ＬｉＮｉ0.8Ｃｏ0.15Ａｌ0.03Ｚｎ0.03Ｏ2等からなる粒子が挙げられる。なかでもＬｉＮｉ0.8Ｃｏ0.15Ａｌ0.03Ｍｇ0.03Ｏ2からなる粒子が好ましい。
The NCA-based composite oxide secondary particles (a) have even better battery capacity and output characteristics than the NCM-based composite oxide particles represented by formula (I). In addition, due to the Al content, deterioration due to moisture in the atmosphere is less likely to occur, and it is also excellent in safety.
As for the above NCA -based composite oxide secondary particles (a), for example, Lini 0.8 CO 0.1 AL 0.1 O 2 , LINI 0.8 CO 0.03 MG 0.03 O2 , Lini 0.8 CO 0.15 AL 0.03 ZN 0.03 Examples include particles consisting of 2 etc. Among these, particles made of LiNi 0.8 Co 0.15 Al 0.03 Mg 0.03 O 2 are preferred.
リチウム複合酸化物二次粒子（ａ）の一次粒子としての平均粒径は、好ましくは２０００ｎｍ以下であり、より好ましくは１０００ｎｍ以下である。また、上記一次粒子の平均粒径の下限値は特に限定されないが、ハンドリングの観点から、５０ｎｍ以上が好ましい。
なお、リチウム複合酸化物二次粒子（ａ）の一次粒子の平均粒径は、ＳＥＭ又はＴＥＭの電子顕微鏡による観察において、１００個の多層型リチウムイオン二次電池用正極活物質から測定されるリチウム複合酸化物二次粒子（ａ）の一次粒子の平均値を意味する。
The average particle size of the lithium composite oxide secondary particles (a) as primary particles is preferably 2000 nm or less, more preferably 1000 nm or less. Further, the lower limit of the average particle diameter of the primary particles is not particularly limited, but from the viewpoint of handling, it is preferably 50 nm or more.
In addition, the average particle diameter of the primary particles of lithium composite oxide secondary particles (a) is the lithium particle size measured from 100 positive electrode active materials for multilayer lithium ion secondary batteries in observation using an SEM or TEM electron microscope. It means the average value of the primary particles of the composite oxide secondary particles (a).
本発明の多層型リチウムイオン二次電池用正極活物質が有するコア部（Ａ）は、上記一次粒子が凝集して形成するリチウム複合酸化物二次粒子（ａ）からなり、コア部（Ａ）の平均粒径は、リチウム複合酸化物二次粒子（ａ）と同義である。すなわち、コア部（Ａ）の平均粒径は、３μｍ～３０μｍであって、好ましくは４μｍ～２５μｍであり、より好ましくは５μｍ～２５μｍである。
なお、リチウム複合酸化物二次粒子（ａ）の平均粒径（Ｄ50）は、レーザ回折・散乱法に基づく体積基準の粒度分布により得られる値であって、累積５０％での粒径を意味する。
The core part (A) of the positive electrode active material for a multilayer lithium ion secondary battery of the present invention is composed of lithium composite oxide secondary particles (a) formed by agglomeration of the above-mentioned primary particles, and the core part (A) The average particle diameter is the same as that of the lithium composite oxide secondary particles (a). That is, the average particle size of the core portion (A) is 3 μm to 30 μm, preferably 4 μm to 25 μm, and more preferably 5 μm to 25 μm.
The average particle size (D 50 ) of the lithium composite oxide secondary particles (a) is a value obtained from a volume-based particle size distribution based on a laser diffraction/scattering method, and the particle size at 50% cumulative means.
本発明の多層型リチウムイオン二次電池用正極活物質は、上記コア部（Ａ）を被覆してなる、層厚み６００ｎｍ～５０００ｎｍの内層（Ｂ）を有し、かかる内層（Ｂ）は、下記式（III）又は式（III）'：
ＬｉｇＭｎｈＦｅｉＭ３
ｚＰＯ４・・・（III）
（式（III）中、Ｍ３は、Ｃｏ、Ｎｉ、Ｍｇ、Ｃａ、Ｓｒ、Ｙ、Ｚｒ、Ｍｏ、Ｂａ、Ｐｂ、Ｂｉ、Ｌａ、Ｃｅ、Ｎｄ又はＧｄを示す。ｇ、ｈ、ｉ、及びｚは、０＜ｇ≦１．２、０≦ｈ≦１．２、０≦ｉ≦１．２、０≦ｚ≦０．３、及びｈ＋ｉ≠０を満たし、かつｇ＋（Ｍｎの価数）×ｈ＋（Ｆｅの価数）×ｉ＋（Ｍ３の価数）×ｚ＝３を満たす数を示す。）
Ｍｎｈ’Ｆｅｉ’Ｍ３
ｚ'ＰＯ４・・・（III）'
（式（III）'中、Ｍ３は式（III）と同義である。ｈ'、ｉ'、及びｚ'は、０≦ｈ'≦１．２、０≦ｉ'≦１．２、０≦ｚ'≦０．３、及びｈ'＋ｉ'≠０を満たし、かつ（Ｍｎの価数）×ｈ'＋（Ｆｅの価数）×ｉ'＋（Ｍ３の価数）×ｚ'＝３を満たす数を示す。）で表され、前者はＬｉ含有の粒子である一方、後者はＬｉを含有しない粒子ではあるものの、双方ともオリビン型構造を有するリチウム系ポリアニオン粒子（ｂ）であり、その表面には、リチウム系ポリアニオン粒子（ｂ）を被覆するように炭素（ｘ）が担持してなる。
The positive electrode active material for a multilayer lithium ion secondary battery of the present invention has an inner layer (B) with a layer thickness of 600 nm to 5000 nm, which covers the core part (A), and the inner layer (B) is as follows: Formula (III) or formula (III)':
Li g Mn h Fe i M 3 z PO 4 ...(III)
(In formula (III), M3 represents Co, Ni, Mg, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. g, h, i, and z satisfies 0<g≦1.2, 0≦h≦1.2, 0≦i≦1.2, 0≦z≦0.3, and h+i≠0, and g+ (valence of Mn) ×h+(valence of Fe)×i+(valence of M3 )×z=3.)
Mn h' Fe i' M 3 z' PO 4 ...(III)'
(In formula (III)', M3 has the same meaning as in formula (III). h', i', and z' are 0≦h'≦1.2, 0≦i'≦1.2, 0 ≦z'≦0.3 and h'+i'≠0, and (valence of Mn)×h'+(valence of Fe)×i'+(valence of M3 )×z'= The former is a Li-containing particle, while the latter is a Li-free particle, but both are lithium-based polyanion particles (b) having an olivine-type structure, Carbon (x) is supported on the surface so as to cover the lithium-based polyanion particles (b).
上記式（III）で表されるリチウム系ポリアニオン粒子（ｂ）としては、平均放電電圧の観点から、０．５≦ｈ≦１．２が好ましく、０．６≦ｈ≦１．１がより好ましく、０．６５≦ｈ≦１．０５がさらに好ましい。また、式（III）’で表されるリチウム系ポリアニオン粒子（ｂ）としては、同様の観点から、０．５≦ｈ≦１．２が好ましく、０．６≦ｈ≦１．１がより好ましく、０．６５≦ｈ≦１．０５がさらに好ましい。
具体的には、例えばＬｉＭｎＰＯ４、ＬｉＭｎ0.9Ｆｅ0.1ＰＯ４、ＬｉＭｎ0.8Ｆｅ0.2ＰＯ４、ＬｉＭｎ0.75Ｆｅ0.15Ｍｇ0.1ＰＯ４、ＬｉＭｎ0.75Ｆｅ0.19Ｚｒ0.015ＰＯ４、ＬｉＭｎ0.7Ｆｅ0.3ＰＯ４、ＬｉＭｎ0.6Ｆｅ0.4ＰＯ４、ＬｉＭｎ0.5Ｆｅ0.5ＰＯ４、Ｌｉ1.2Ｍｎ0.63Ｆｅ0.27ＰＯ４、Ｌｉ0.6Ｍｎ0.84Ｆｅ0.36ＰＯ４、Ｍｎ0.7Ｆｅ0.3ＰＯ４等が挙げられる。なかでも、ＬｉＭｎ0.7Ｆｅ0.3ＰＯ４、ＬｉＭｎ0.8Ｆｅ0.2ＰＯ４、Ｌｉ1.2Ｍｎ0.63Ｆｅ0.27ＰＯ４、Ｌｉ0.6Ｍｎ0.84Ｆｅ0.36ＰＯ４、又はＭｎ0.7Ｆｅ0.3ＰＯ４が好ましい。
From the viewpoint of average discharge voltage, the lithium-based polyanion particles (b) represented by the above formula (III) preferably have a value of 0.5≦h≦1.2, more preferably 0.6≦h≦1.1. , 0.65≦h≦1.05 is more preferable. From the same viewpoint, the lithium-based polyanion particles (b) represented by formula (III)' preferably have a value of 0.5≦h≦1.2, more preferably 0.6≦h≦1.1. , 0.65≦h≦1.05 is more preferable.
Specifically, for example, LiMnPO 4 , LiMn 0.9 Fe 0.1 PO 4 , LiMn 0.8 Fe 0.2 PO 4 , LiMn 0.75 Fe 0.15 Mg 0.1 PO 4 , LiMn 0.75 Fe 0.19 Zr 0.015 PO 4 , LiMn 0.7 Fe 0.3 PO 4 , LiMn 0.6 Examples include Fe 0.4 PO 4 , LiMn 0.5 Fe 0.5 PO 4 , Li 1.2 Mn 0.63 Fe 0.27 PO 4 , Li 0.6 Mn 0.84 Fe 0.36 PO 4 , Mn 0.7 Fe 0.3 PO 4 and the like. Among them, LiMn 0.7 Fe 0.3 PO 4 , LiMn 0.8 Fe 0.2 PO 4 , Li 1.2 Mn 0.63 Fe 0.27 PO 4 , Li 0.6 Mn 0.84 Fe 0.36 PO 4 , or Mn 0.7 Fe 0.3 PO 4 is preferred.
リチウム系ポリアニオン粒子（ｂ）の平均粒径は、好ましくは５０ｎｍ～２００ｎｍであり、より好ましくは７０ｎｍ～１５０ｎｍである。
なお、リチウム系ポリアニオン粒子（ｂ）の平均粒径は、一次粒子の平均粒径であり、ＳＥＭ又はＴＥＭの電子顕微鏡による観察において測定される平均値を意味する。
The average particle size of the lithium-based polyanion particles (b) is preferably 50 nm to 200 nm, more preferably 70 nm to 150 nm.
Note that the average particle size of the lithium-based polyanion particles (b) is the average particle size of primary particles, and means the average value measured by observation using an SEM or TEM electron microscope.
上記リチウム系ポリアニオン粒子（ｂ）は、その表面に炭素（ｘ）が担持されてなる。かかる炭素（ｘ）としては、具体的には、セルロースナノファイバー由来の炭素（ｘ１）又は水溶性炭素材料由来の炭素（ｘ２）が挙げられ、これらが炭素源となってリチウム系ポリアニオン粒子（ｂ）の表面に堅固に担持されてなる。 The lithium-based polyanion particles (b) have carbon (x) supported on their surfaces. Specific examples of such carbon (x) include carbon (x1) derived from cellulose nanofibers or carbon (x2) derived from water-soluble carbon materials, which serve as carbon sources to form lithium-based polyanion particles (b). ) is firmly supported on the surface.
炭素（ｘ１）源となり得る上記セルロースナノファイバーとは、全ての植物細胞壁の約５割を占める骨格成分であって、かかる細胞壁を構成する植物繊維をナノサイズまで解繊等することにより得ることができる軽量高強度繊維であり、セルロースナノファイバー由来の炭素は、周期的構造を有する。かかるセルロースナノファイバーの繊維径は、１ｎｍ～１００ｎｍであり、水への良好な分散性も有している。また、セルロースナノファイバーを構成するセルロース分子鎖では、炭素による周期的構造が形成されていることから、これが炭化されつつ、上記リチウム系ポリアニオン粒子（ｂ）の表面に堅固に担持されることにより、これらリチウム系ポリアニオン粒子（ｂ）に電子伝導性を付与し、電池特性に優れる有用な多層型リチウムイオン二次電池用正極活物質を得ることができる。 The above-mentioned cellulose nanofiber, which can be a source of carbon (x1), is a skeletal component that accounts for about 50% of all plant cell walls, and can be obtained by fibrillating the plant fibers that make up the cell wall to nano-size. Carbon derived from cellulose nanofibers has a periodic structure. The fiber diameter of such cellulose nanofibers is 1 nm to 100 nm, and they also have good dispersibility in water. In addition, since the cellulose molecular chains constituting cellulose nanofibers have a periodic structure of carbon, this is carbonized and firmly supported on the surface of the lithium-based polyanion particles (b). By imparting electronic conductivity to these lithium-based polyanion particles (b), a useful positive electrode active material for multilayer lithium ion secondary batteries with excellent battery characteristics can be obtained.
炭素（ｘ２）源となり得る上記水溶性炭素材料とは、２５℃の水１００ｇに、水溶性炭素材料の炭素原子換算量で０．４ｇ以上、好ましくは１．０ｇ以上溶解する炭素材料を意味し、炭化されることで炭素として上記リチウム系ポリアニオン粒子（ｂ）の表面に存在することとなる。かかる水溶性炭素材料としては、例えば、糖類、ポリオール、ポリエーテル、及び有機酸から選ばれる１種又は２種以上が挙げられる。より具体的には、例えば、グルコース、フルクトース、ガラクトース、マンノース等の単糖類；マルトース、スクロース、セロビオース等の二糖類；デンプン、デキストリン等の多糖類；エチレングリコール、プロピレングリコール、ジエチレングリコール、ポリエチレングリコール、ブタンジオール、プロパンジオール、ポリビニルアルコール、グリセリン等のポリオールやポリエーテル；クエン酸、酒石酸、アスコルビン酸等の有機酸が挙げられる。なかでも、溶媒への溶解性及び分散性を高めて炭素材料として効果的に機能させる観点から、グルコース、フルクトース、スクロース、デキストリンが好ましく、グルコースがより好ましい。 The above-mentioned water-soluble carbon material that can be a carbon (x2) source means a carbon material that dissolves in 100 g of water at 25 ° C. in terms of carbon atom equivalent amount of 0.4 g or more, preferably 1.0 g or more. By being carbonized, it exists as carbon on the surface of the lithium-based polyanion particles (b). Examples of such water-soluble carbon materials include one or more selected from saccharides, polyols, polyethers, and organic acids. More specifically, for example, monosaccharides such as glucose, fructose, galactose, and mannose; disaccharides such as maltose, sucrose, and cellobiose; polysaccharides such as starch and dextrin; ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, and butane. Examples include polyols and polyethers such as diol, propanediol, polyvinyl alcohol, and glycerin; and organic acids such as citric acid, tartaric acid, and ascorbic acid. Among these, glucose, fructose, sucrose, and dextrin are preferred, and glucose is more preferred, from the viewpoint of improving solubility and dispersibility in solvents and functioning effectively as a carbon material.
炭素（ｘ）の担持量は、炭素（ｘ）が担持されてなるリチウム系ポリアニオン粒子（ｂ）全量１００質量％中に、好ましくは０．１質量％以上１８質量％未満であり、より好ましくは０．２質量％～１０質量％であり、さらに好ましくは０．３質量％～５質量％である。 The amount of carbon (x) supported is preferably 0.1% by mass or more and less than 18% by mass, more preferably It is 0.2% by mass to 10% by mass, more preferably 0.3% by mass to 5% by mass.
なお、この場合、リチウム系ポリアニオン粒子（ｂ）中における炭素（ｘ）の担持量とは、セルロースナノファイバー由来の炭素（ｘ１）及び水溶性炭素材料由来の炭素（ｘ２）の合計担持量であり、上記炭素源であるセルロースナノファイバー又は水溶性炭素材料の炭素原子換算量に相当する。かかるセルロースナノファイバー又は水溶性炭素材料の炭素原子換算量（炭素の担持量）は、内層（Ｂ）を形成してなるリチウム系ポリアニオン粒子（ｂ）について、炭素・硫黄分析装置を用いて測定した炭素量として、確認することができる。 In this case, the amount of carbon (x) supported in the lithium-based polyanion particles (b) is the total amount of carbon (x1) derived from cellulose nanofibers and carbon (x2) derived from the water-soluble carbon material. , corresponds to the carbon atom equivalent amount of the cellulose nanofiber or water-soluble carbon material that is the carbon source. The carbon atom equivalent amount (carrying amount) of the cellulose nanofiber or water-soluble carbon material was measured using a carbon/sulfur analyzer for the lithium-based polyanion particles (b) forming the inner layer (B). It can be confirmed as carbon content.
表面に炭素（ｘ）が担持してなるリチウム系ポリアニオン粒子（ｂ）からなる内層（Ｂ）の層厚みは、堅固な多層構造を形成させる観点から、６００ｎｍ～５０００ｎｍであって、６５０ｎｍ～５０００ｎｍが好ましく、７００ｎｍ～５０００ｎｍがより好ましい。
ここで、内層（Ｂ）の層厚みとは、ＳＥＭ又はＴＥＭの電子顕微鏡による観察において、１００個の多層型リチウムイオン二次電池用正極活物質から測定される内層（Ｂ）の層厚みの平均値を意味する。
The thickness of the inner layer (B) made of lithium-based polyanion particles (b) with carbon (x) supported on the surface is 600 nm to 5000 nm, preferably 650 nm to 5000 nm, from the viewpoint of forming a strong multilayer structure. Preferably, 700 nm to 5000 nm is more preferable.
Here, the layer thickness of the inner layer (B) is the average layer thickness of the inner layer (B) measured from 100 positive electrode active materials for multilayer lithium ion secondary batteries in observation using an SEM or TEM electron microscope. means value.
本発明の多層型リチウムイオン二次電池用正極活物質において、表面に炭素（ｘ）が担持してなるリチウム系ポリアニオン粒子（ｂ）の含有量（炭素（ｘ）の担持量を含む）と、リチウム複合酸化物二次粒子（ａ）の含有量との質量比（（ｂ）：（ａ））は、リチウム複合酸化物二次粒子とリチウム系ポリアニオン粒子との複合化を強固なものとする観点から、５：９５～５５：４５であって、（表面に炭素（ｘ）が担持してなるリチウム系ポリアニオン粒子（ｂ）の含有量基準でみて）好ましくは７：９３～５０：５０であり、より好ましくは１０：９０～５０：５０である。 In the positive electrode active material for a multilayer lithium ion secondary battery of the present invention, the content of the lithium-based polyanion particles (b) having carbon (x) supported on the surface (including the amount of carbon (x) supported); The mass ratio ((b):(a)) of the content of the lithium composite oxide secondary particles (a) strengthens the composite of the lithium composite oxide secondary particles and the lithium-based polyanion particles. From this point of view, the ratio is 5:95 to 55:45, preferably 7:93 to 50:50 (based on the content of lithium-based polyanion particles (b) having carbon (x) supported on the surface). The ratio is more preferably 10:90 to 50:50.
本発明の多層型リチウムイオン二次電池用正極活物質は、さらに上記内層（Ｂ）を被覆してなる、層厚み２ｎｍ～８０ｎｍの外層（Ｃ）を有し、かかる外層（Ｃ）は、グラファイト、グラフェン、カーボンブラック、及びカーボンナノファイバーから選ばれる水不溶性炭素粉末（ｃ）からなる。上記コア部（Ａ）に被覆してなる内層（Ｂ）を、さらに堅固に被覆してなる外層（Ｃ）が存在することにより、リチウム複合酸化物二次粒子とリチウム系ポリアニオン粒子との複合化を一層強固なものとし、本発明の多層型リチウムイオン二次電池用正極活物質全体としての強度をも増強することが可能となる。また、水不溶性炭素粉末（ｃ）によって堅固に形成された外層（Ｃ）により、温度変化への耐性を高めつつ高い導電率を確保することができ、電解液への金属の溶出をも効果的に抑制し、低温から高温にわたる幅広い温度変化に対応し得る安定した電池特性を示すことが可能となる。 The positive electrode active material for a multilayer lithium ion secondary battery of the present invention further has an outer layer (C) with a layer thickness of 2 nm to 80 nm, which coats the inner layer (B), and the outer layer (C) is made of graphite. , graphene, carbon black, and carbon nanofiber (c). Due to the presence of the inner layer (B) coated on the core part (A) and the outer layer (C) coated more firmly, the lithium composite oxide secondary particles and the lithium-based polyanion particles are combined. This makes it possible to further strengthen the strength of the positive electrode active material for a multilayer lithium ion secondary battery of the present invention as a whole. In addition, the outer layer (C) made of water-insoluble carbon powder (c) can ensure high electrical conductivity while increasing resistance to temperature changes, and is also effective in preventing metal elution into the electrolyte. This makes it possible to exhibit stable battery characteristics that can withstand a wide range of temperature changes from low to high temperatures.
水不溶性炭素粉末（ｃ）としては、グラファイト、グラフェン、カーボンブラック、及びカーボンナノファイバーから選ばれる１種であってもよく、２種以上組み合わせて用いてもよい。なかでも、内層（Ｂ）により強固に複合化させる観点から、グラファイト、カーボンブラック、グラフェンが好ましく、グラファイト、カーボンブラックがより好ましい。 The water-insoluble carbon powder (c) may be one selected from graphite, graphene, carbon black, and carbon nanofiber, or may be used in combination of two or more. Among these, graphite, carbon black, and graphene are preferred, and graphite and carbon black are more preferred, from the viewpoint of making the inner layer (B) more strongly composite.
水不溶性炭素粉末（ｃ）の平均粒径は、１０ｎｍ～１０μｍが好ましく、１０ｎｍ～５μｍがより好ましい。なお、水不溶性炭素粉末（ｂ）の平均粒径とは、一次粒子が凝集した二次粒子の平均粒径であり、ＳＥＭ又はＴＥＭの電子顕微鏡による観察において測定される平均値を意味する。 The average particle size of the water-insoluble carbon powder (c) is preferably 10 nm to 10 μm, more preferably 10 nm to 5 μm. The average particle size of the water-insoluble carbon powder (b) is the average particle size of secondary particles obtained by agglomerating primary particles, and means an average value measured by observation using an SEM or TEM electron microscope.
水不溶性炭素粉末（ｃ）からなる外層（Ｃ）の層厚みは、堅固な多層構造を形成させる観点から、２ｎｍ～８０ｎｍであって、２ｎｍ～７０ｎｍが好ましく、２ｎｍ～４０ｎｍがより好ましい。
ここで、外層（Ｃ）の層厚みとは、内層（Ｂ）と同様、ＳＥＭ又はＴＥＭの電子顕微鏡による観察において、１００個の多層型リチウムイオン二次電池用正極活物質から測定される内層（Ｃ）の層厚みの平均値を意味する。
The layer thickness of the outer layer (C) made of water-insoluble carbon powder (c) is 2 nm to 80 nm, preferably 2 nm to 70 nm, and more preferably 2 nm to 40 nm, from the viewpoint of forming a strong multilayer structure.
Here, the layer thickness of the outer layer (C), like the inner layer (B), is the inner layer ( Means the average value of the layer thickness of C).
本発明の多層型リチウムイオン二次電池用正極活物質において、水不溶性炭素粉末（ｃ）の含有量は、リチウム複合酸化物二次粒子とリチウム系ポリアニオン粒子とを強固に複合化しつつ、かかる複合化を阻害し得る不要な微粒子の発生を有効に抑制する観点から、リチウム複合酸化物二次粒子（ａ）と、後述する表面に炭素（ｘ）が担持してなるリチウム系ポリアニオン粒子（ｂ）との合計含有量１００質量部（炭素（ｘ）の担持量を含む）に対し、好ましくは０．０５質量部～１．７質量部であり、より好ましくは０．０７質量部～１．６５質量部であり、さらに好ましくは０．１質量部～１．６質量部である。 In the positive electrode active material for a multilayer lithium ion secondary battery of the present invention, the content of the water-insoluble carbon powder (c) is such that the content of the water-insoluble carbon powder (c) is such that the lithium composite oxide secondary particles and the lithium-based polyanion particles are strongly composited, and From the viewpoint of effectively suppressing the generation of unnecessary fine particles that may inhibit the chemical reaction, lithium composite oxide secondary particles (a) and lithium-based polyanion particles (b) having carbon (x) supported on the surface described below are used. It is preferably 0.05 parts by mass to 1.7 parts by mass, more preferably 0.07 parts by mass to 1.65 parts by mass, based on 100 parts by mass of the total content (including the supported amount of carbon (x)). Parts by mass, more preferably 0.1 parts by mass to 1.6 parts by mass.
本発明の多層型リチウムイオン二次電池用正極活物質の平均粒径は、好ましくは４μｍ～３０μｍであり、より好ましくは５μｍ～３０μｍである。
なお、多層型リチウムイオン二次電池用正極活物質の平均粒径は、レーザ回折・散乱法に基づく体積基準の粒度分布により得られる値であって、累積５０％での粒径を意味する。
The average particle size of the positive electrode active material for a multilayer lithium ion secondary battery of the present invention is preferably 4 μm to 30 μm, more preferably 5 μm to 30 μm.
Note that the average particle size of the positive electrode active material for a multilayer lithium ion secondary battery is a value obtained from a volume-based particle size distribution based on a laser diffraction/scattering method, and means a particle size at 50% cumulative particle size.
また、本発明の多層型リチウムイオン二次電池用正極活物質のＢＥＴ比表面積は、好ましくは０．１ｍ２／ｇ～３０ｍ２／ｇであり、より好ましくは０．３ｍ２／ｇ～２０ｍ２／ｇである。 Further, the BET specific surface area of the positive electrode active material for a multilayer lithium ion secondary battery of the present invention is preferably 0.1 m 2 /g to 30 m 2 /g, more preferably 0.3 m 2 /g to 20 m 2 /g.
本発明の多層型リチウムイオン二次電池用正極活物質は、コア部（Ａ）とこれを被覆してなる内層（Ｂ）とが、リチウム複合酸化物二次粒子とリチウム系ポリアニオン粒子との複合化を強固なものとしつつ、これらをさらに導電性に優れる水不溶性炭素粉末（ｃ）からなる外層（Ｃ）が全体を覆うように存在する特異な多層構造を有している。そのため、リチウムイオンの挿入及び脱離に伴う正極活物質の体積変化を物理的に抑制するとともに、正極活物質から溶出する遷移金属成分を正極活物質内部に有効に閉じ込め、さらに良好な電気伝導性を有している。
具体的には、本発明の多層型リチウムイオン二次電池用正極活物質の電気伝導度は、２５℃での２０ＭＰａ加圧時において、好ましくは５ｅ－６Ｓ／ｃｍ～５ｅ－２Ｓ／ｃｍであり、より好ましくは１ｅ－５Ｓ／ｃｍ～５ｅ－２Ｓ／ｃｍである。
In the positive electrode active material for a multilayer lithium ion secondary battery of the present invention, the core part (A) and the inner layer (B) covering the core part are composed of a composite of lithium composite oxide secondary particles and lithium-based polyanion particles. It has a unique multi-layered structure in which an outer layer (C) made of water-insoluble carbon powder (c) which has excellent conductivity exists so as to cover the entire structure while making the structure strong. Therefore, the volume change of the positive electrode active material due to the insertion and desorption of lithium ions is physically suppressed, and the transition metal components eluted from the positive electrode active material are effectively confined inside the positive electrode active material, resulting in even better electrical conductivity. have.
Specifically, the electrical conductivity of the positive electrode active material for a multilayer lithium ion secondary battery of the present invention is preferably 5e -6 S/cm to 5e -2 S/cm when pressurized at 20 MPa at 25°C. and more preferably 1e −5 S/cm to 5e −2 S/cm.
本発明の多層型リチウムイオン二次電池用正極活物質における外層（Ｃ）の被覆の度合いは、ラマン分光法を用いて、本発明の多層型リチウムイオン二次電池用正極活物質の表面状態を分析することによって確認することができる。
具体的には、ラマン分光法によって求められるラマンスペクトルにおいて、水不溶性炭素粉末（ｃ）由来の炭素に関わるＤバンドのピーク強度（Ｉ（Ｄ）、ピーク位置：１３５０ｃｍ-1付近）とＰＯ4
3-に関わるピーク強度（Ｉ（ＰＯ4）、ピーク位置：９５０ｃｍ-1付近）との強度比（Ｉ（ＰＯ4）／Ｉ（Ｄ））が、好ましくは０．００１～０．０６であり、より好ましくは０．００２～０．０６である。したがって、強度比（Ｉ（ＰＯ4）／Ｉ（Ｄ））がかかる範囲内であれば、コア部（Ａ）を被覆してなる内層（Ｂ）の表面が、外層（Ｃ）により良好に被覆されていることを示す。
The degree of coverage of the outer layer (C) in the positive electrode active material for multilayer lithium ion secondary batteries of the present invention can be determined using Raman spectroscopy. This can be confirmed by analysis.
Specifically, in the Raman spectrum obtained by Raman spectroscopy, the peak intensity of the D band related to carbon derived from the water-insoluble carbon powder (c) (I (D) , peak position: around 1350 cm -1 ) and PO 4 3 - The intensity ratio (I ( PO4) /I (D) ) to the peak intensity (I (PO4 ), peak position: around 950 cm -1 ) is preferably 0.001 to 0.06, more preferably is 0.002 to 0.06. Therefore, if the intensity ratio (I (PO4) /I (D) ) is within this range, the surface of the inner layer (B) covering the core part (A) will be well covered by the outer layer (C). Indicates that
本発明の多層型リチウムイオン二次電池用正極活物質は、強固な多層構造を有していることから、リチウム複合酸化物二次粒子からのリチウム系ポリアニオン粒子の不要な剥離が有効に抑制され、微粒子が過度に発生するのを有効に抑制されてなる。具体的には、本発明の多層型リチウムイオン二次電池用正極活物質は、レーザ回折・散乱式粒子径分布測定において、粒子径１μｍ以下の微粒子量が、好ましくは５体積％以下であり、より好ましくは４．５体積％以下であり、さらに好ましくは４体積％以下である。 Since the positive electrode active material for multilayer lithium ion secondary batteries of the present invention has a strong multilayer structure, unnecessary peeling of lithium-based polyanion particles from lithium composite oxide secondary particles can be effectively suppressed. , the excessive generation of fine particles is effectively suppressed. Specifically, in the positive electrode active material for a multilayer lithium ion secondary battery of the present invention, the amount of fine particles with a particle size of 1 μm or less is preferably 5% by volume or less in laser diffraction/scattering particle size distribution measurement, More preferably it is 4.5% by volume or less, and still more preferably 4% by volume or less.
本発明の多層型リチウムイオン二次電池用正極活物質の製造方法は、次の工程（Ｐ１）～（Ｐ２）：
（Ｐ１）リチウム化合物と、少なくとも鉄化合物又はマンガン化合物を含む金属化合物とリン酸化合物とから水熱反応物を得た後、或いは少なくとも鉄化合物又はマンガン化合物を含む金属化合物とリン酸化合物とから水熱反応物を得た後、炭素（ｘ）源を混合して噴霧乾燥し、表面に炭素（ｘ）を担持してなるリチウム系ポリアニオン粒子（ｂ）から形成されてなる造粒体（Ｚ）を得る工程
（Ｐ２）圧縮力及びせん断力を付加した混合を行いながら、リチウム複合酸化物二次粒子（ａ）に造粒体（Ｚ）を添加し、次いで水不溶性炭素粉末（ｃ）を添加する工程
を備える。
The method for producing a positive electrode active material for a multilayer lithium ion secondary battery of the present invention includes the following steps (P1) to (P2):
(P1) After obtaining a hydrothermal reaction product from a lithium compound, a metal compound containing at least an iron compound or a manganese compound, and a phosphoric acid compound, or after obtaining a hydrothermal reaction product from a phosphoric acid compound and a metal compound containing at least an iron compound or a manganese compound, After obtaining the thermal reactant, a carbon (x) source is mixed and spray-dried to obtain a granule (Z) formed from lithium-based polyanion particles (b) carrying carbon (x) on the surface. (P2) Adding the granules (Z) to the lithium composite oxide secondary particles (a) while performing mixing while applying compressive force and shear force, and then adding the water-insoluble carbon powder (c). It includes a process of
本発明の製造方法が備える工程（Ｐ１）は、リチウム化合物と、少なくとも鉄化合物又はマンガン化合物を含む金属化合物とリン酸化合物とから水熱反応物を得た後、或いは少なくとも鉄化合物又はマンガン化合物を含む金属化合物とリン酸化合物とから水熱反応物を得た後、炭素（ｘ）源を混合して噴霧乾燥し、表面に炭素（ｘ）を担持してなるリチウム系ポリアニオン粒子（ｂ）から形成されてなる造粒体（Ｚ）を得る工程である。すなわち、本発明の多層型リチウムイオン二次電池用正極活物質が有する内層（Ｂ）を形成するリチウム系ポリアニオン粒子（ｂ）を得るための、リチウム系ポリアニオン粒子（ｂ）の前駆体に相当する造粒体（Ｚ）を得る工程である。かかる造粒体（Ｚ）は、後述する工程（Ｐ２）を経ることにより、内層（Ｂ）を形成することとなる。 The step (P1) included in the production method of the present invention is performed after obtaining a hydrothermal reaction product from a lithium compound, a metal compound containing at least an iron compound or a manganese compound, and a phosphoric acid compound, or after obtaining a hydrothermal reaction product from a lithium compound, a metal compound containing at least an iron compound or a manganese compound, and a phosphoric acid compound. After obtaining a hydrothermal reaction product from a metal compound and a phosphoric acid compound, a carbon (x) source is mixed and spray-dried, and carbon (x) is supported on the surface of the lithium-based polyanion particles (b). This is a step of obtaining the formed granules (Z). That is, it corresponds to a precursor of lithium-based polyanion particles (b) for obtaining lithium-based polyanion particles (b) forming the inner layer (B) of the positive electrode active material for a multilayer lithium ion secondary battery of the present invention. This is a step of obtaining granules (Z). This granule (Z) will form an inner layer (B) by passing through a step (P2) described later.
工程（Ｐ１）では、まずリチウム化合物と、少なくとも鉄化合物又はマンガン化合物を含む金属化合物とリン酸化合物とから、或いは少なくとも鉄化合物又はマンガン化合物を含む金属化合物とリン酸化合物とから水熱反応物を得る。前者は上記式（III）で表されるリチウム系ポリアニオン粒子（ｂ）を得る場合であり、後者は上記式（III）'で表されるリチウム系ポリアニオン粒子（ｂ）を得る場合である。
これら所定の原料化合物から水熱反応物を得るには、具体的には、これらの原料化合物を含有するスラリー水を調製し、水熱反応に付せばよい。
In step (P1), a hydrothermal reaction product is first obtained from a lithium compound, a metal compound containing at least an iron compound or a manganese compound, and a phosphoric acid compound, or from a metal compound containing at least an iron compound or a manganese compound and a phosphoric acid compound. obtain. The former is a case in which lithium-based polyanion particles (b) represented by the above formula (III) are obtained, and the latter is a case in which lithium-based polyanion particles (b) represented by the above formula (III)' are obtained.
In order to obtain a hydrothermal reaction product from these predetermined raw material compounds, specifically, slurry water containing these raw material compounds may be prepared and subjected to a hydrothermal reaction.
用い得るリチウム化合物としては、水酸化リチウム（例えばＬｉＯＨ、ＬｉＯＨ・Ｈ２Ｏ）、炭酸リチウム、硫酸リチウム、酢酸リチウムが挙げられる。 Lithium compounds that can be used include lithium hydroxide (eg, LiOH, LiOH.H 2 O), lithium carbonate, lithium sulfate, and lithium acetate.
用い得る鉄化合物としては、酢酸鉄、硝酸鉄、硫酸鉄等が挙げられる。これらは１種単独で用いてもよく、２種以上組み合わせて用いてもよい。 Examples of iron compounds that can be used include iron acetate, iron nitrate, iron sulfate, and the like. These may be used alone or in combination of two or more.
用い得るマンガン化合物としては、酢酸マンガン、硝酸マンガン、硫酸マンガン等が挙げられる。これらは１種単独で用いてもよく、２種以上組み合わせて用いてもよい。 Manganese compounds that can be used include manganese acetate, manganese nitrate, manganese sulfate, and the like. These may be used alone or in combination of two or more.
用いる金属化合物として、上記化合物のほか、式（III）又は式（III）'に応じて適宜金属（Ｍ３）化合物（Ｍ３は、上記式（III）と同義である）を用いてもよい。かかる金属（Ｍ３）化合物として、硫酸塩、ハロゲン化合物、有機酸塩、及びこれらの水和物等を用いることができる。これらは１種単独で用いてもよく、２種以上用いてもよい。 As the metal compound used, in addition to the above compounds, a metal (M 3 ) compound (M 3 is synonymous with the above formula (III)) may be used as appropriate according to formula (III) or formula (III)'. . As such metal (M 3 ) compounds, sulfates, halogen compounds, organic acid salts, hydrates thereof, and the like can be used. These may be used alone or in combination of two or more.
リン酸化合物としては、オルトリン酸（Ｈ３ＰＯ４、リン酸）、メタリン酸、ピロリン酸、三リン酸、四リン酸、リン酸アンモニウム、リン酸水素アンモニウム等が挙げられる。
なかでもリン酸を用い、これを混合物に滴下して少量ずつ加えながら混合するのが好ましく、混合した後に窒素をパージするのが好ましい。また、リン酸化合物を混合した後の混合物中における溶存酸素濃度を０．５ｍｇ／Ｌ以下とするのが好ましい。
Examples of the phosphoric acid compound include orthophosphoric acid (H 3 PO 4 , phosphoric acid), metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid, ammonium phosphate, ammonium hydrogen phosphate, and the like.
Among these, it is preferable to use phosphoric acid and add it dropwise to the mixture little by little while mixing, and it is preferable to purge with nitrogen after mixing. Moreover, it is preferable that the dissolved oxygen concentration in the mixture after mixing the phosphoric acid compound is 0.5 mg/L or less.
水熱反応の温度は、１００℃以上であればよく、１３０℃～１８０℃が好ましく、圧力は０．３ＭＰａ～０．９ＭＰａであるのが好ましく、水熱反応時間は０．１時間～４８時間が好ましい。 The temperature of the hydrothermal reaction may be 100°C or higher, preferably 130°C to 180°C, the pressure is preferably 0.3 MPa to 0.9 MPa, and the hydrothermal reaction time is 0.1 hour to 48 hours. is preferred.
工程（Ｐ１）では、次いで得られた水熱反応物に炭素（ｘ）源を混合して噴霧乾燥することにより、造粒体（Ｚ）を得る。得られた造粒体（Ｚ）は、焼成するのがよい。これにより、炭素（ｘ）源が炭化されて、造粒体（Ｚ）につき、リチウム系ポリアニオン粒子（ａ）の一次粒子の表面に炭素（ｘ）が担持してなる焼成物とすることができる。用いる炭素（ｘ）源としては、上記セルロースナノファイバー又は水溶性炭素材料が挙げられる。 In step (P1), a carbon (x) source is then mixed with the obtained hydrothermal reaction product and the mixture is spray-dried to obtain granules (Z). The obtained granules (Z) are preferably fired. As a result, the carbon (x) source is carbonized, and the granules (Z) can be made into a fired product in which carbon (x) is supported on the surface of the primary particles of the lithium-based polyanion particles (a). . Examples of the carbon (x) source used include the above cellulose nanofibers or water-soluble carbon materials.
噴霧乾燥により得られる造粒体（Ｚ）の粒径は、レーザ回折・散乱法に基づく粒度分布におけるＤ50値で、１～２０μｍであるのが好ましい。
得られた造粒体（Ｚ）は還元雰囲気又は不活性雰囲気中において焼成するのがよい。焼成条件としては、焼成温度が４００℃～８００℃であり、焼成時間が１０分～３時間であるのが好ましい。
The particle size of the granules (Z) obtained by spray drying is preferably 1 to 20 μm in D 50 value in particle size distribution based on laser diffraction/scattering method.
The obtained granules (Z) are preferably fired in a reducing atmosphere or an inert atmosphere. As for the firing conditions, it is preferable that the firing temperature is 400° C. to 800° C. and the firing time is 10 minutes to 3 hours.
本発明の製造方法が備える工程（Ｐ２）は、圧縮力及びせん断力を付加した混合を行いながら、リチウム複合酸化物二次粒子（ａ）に工程（Ｐ１）で得られた造粒体（Ｚ）を添加し、次いで水不溶性炭素粉末（ｃ）を添加する工程である。すなわちかかる工程（Ｐ２）は、まずリチウム複合酸化物二次粒子（ａ）に工程（Ｐ１）で得られた造粒体（Ｚ）を添加して圧縮力及びせん断力を付加した混合を行い、続いて水不溶性炭素粉末（ｃ）を添加して圧縮力及びせん断力を付加した混合を行う工程、いわゆる多段工程である。 Step (P2) included in the production method of the present invention is to mix the lithium composite oxide secondary particles (a) with the granules (Z ), and then water-insoluble carbon powder (c) is added. That is, in this step (P2), first, the granules (Z) obtained in step (P1) are added to the lithium composite oxide secondary particles (a) and mixed with compressive force and shear force, Subsequently, the water-insoluble carbon powder (c) is added and mixed under compressive force and shear force, which is a so-called multi-stage process.
用いるリチウム複合酸化物二次粒子（ａ）としては、例えば、
リチウム化合物、ニッケル化合物、コバルト化合物、及びマンガン化合物を含有する混合粉体を焼成し（製法ａ１）、得られたＮＣＭ系複合酸化物二次粒子（ａ）を用いてもよく、或いは
リチウム化合物、ニッケル化合物、コバルト化合物、及びアルミニウム化合物を含有する混合粉体を焼成し（製法ａ２）、得られたＮＣＡ系複合酸化物二次粒子（ａ）を用いてもよい。
As the lithium composite oxide secondary particles (a) used, for example,
A mixed powder containing a lithium compound, a nickel compound, a cobalt compound, and a manganese compound may be fired (manufacturing method a1), and the obtained NCM-based composite oxide secondary particles (a) may be used, or a lithium compound, A mixed powder containing a nickel compound, a cobalt compound, and an aluminum compound may be fired (manufacturing method a2), and the obtained NCA-based composite oxide secondary particles (a) may be used.
具体的には、製法ａ１の場合、まず原料化合物、例えば、ニッケル化合物、コバルト化合物、及びマンガン化合物を、所望する複合酸化物の組成となるように水に溶解させて水溶液ａを得る。
次に、上記水溶液ａに、水酸化ナトリウムや水酸化カリウム等のアルカリ剤を添加して水溶液ｂとし、溶解している金属成分を中和反応によって共沈させ、金属複合水酸化物を得る。次いで水溶液ｂを３０℃～６０℃の温度で３０分間～１２０分間撹拌して、金属複合水酸化物を生成させる。
Specifically, in the case of production method a1, raw material compounds, for example, a nickel compound, a cobalt compound, and a manganese compound, are first dissolved in water to obtain a desired composite oxide composition to obtain an aqueous solution a.
Next, an alkali agent such as sodium hydroxide or potassium hydroxide is added to the aqueous solution a to obtain an aqueous solution b, and the dissolved metal components are co-precipitated by a neutralization reaction to obtain a metal composite hydroxide. Next, the aqueous solution b is stirred at a temperature of 30° C. to 60° C. for 30 minutes to 120 minutes to produce a metal composite hydroxide.
撹拌後、水溶液ｂを濾過して金属複合水酸化物を回収し、水で洗浄後、乾燥するのが好ましい。
次いで、所望する複合酸化物の組成となるように、上記金属複合水酸化物とリチウム化合物を乾式混合し、酸素雰囲気下で焼成することにより、ＮＣＭ系複合酸化物を得る。
最後に、得られた焼成物を水洗した後、濾過、及び乾燥してＮＣＭ系複合酸化物粒子（ａ）を得る。
After stirring, the aqueous solution b is preferably filtered to recover the metal composite hydroxide, washed with water, and then dried.
Next, the metal composite hydroxide and the lithium compound are dry mixed to obtain a desired composite oxide composition, and the mixture is fired in an oxygen atmosphere to obtain an NCM-based composite oxide.
Finally, the obtained fired product is washed with water, filtered, and dried to obtain NCM-based composite oxide particles (a).
なお、製法ａ２の場合、原料化合物としてリチウム化合物、ニッケル化合物、コバルト化合物、及びアルミニウム化合物を用いる以外、製法ａ１と同様にしてＮＣＡ系複合酸化物二次粒子（ａ）を得ることができる。 In the case of production method a2, the NCA-based composite oxide secondary particles (a) can be obtained in the same manner as production method a1, except that a lithium compound, a nickel compound, a cobalt compound, and an aluminum compound are used as raw material compounds.
リチウム複合酸化物二次粒子（ａ）に工程（Ｐ１）で得られた造粒体（Ｚ）を添加して行う、圧縮力及びせん断力を付加した混合は、インペラを備える密閉容器で行うのが好ましい。かかるインペラの周速度は、コア部（Ａ）を良好かつ堅固に被覆してなる内層（Ｂ）を有効に形成させる観点から、好ましくは１５ｍ／ｓ～４５ｍ／ｓであり、より好ましくは１５ｍ／ｓ～３５ｍ／ｓである。また、混合時間は、好ましくは３分間～９０分間であり、より好ましくは５分間～６０分間である。
なお、インペラの周速度とは、回転式攪拌翼（インペラ）の最外端部の速度を意味し、下記式（１）により表すことができ、また圧縮力及びせん断力を付加しながら混合する処理を行う時間は、インペラの周速度が遅いほど長くなるように、インペラの周速度によっても変動し得る。
インペラの周速度（ｍ／ｓ）＝
インペラの半径（ｍ）×２×π×回転数（ｒｐｍ）÷６０・・・（１）
なお、インペラを備える密閉容器を有した装置としては、例えば乾式粒子複合化装置であるノビルタ（ホソカワミクロン社製）が挙げられる。
The granules (Z) obtained in step (P1) are added to the lithium composite oxide secondary particles (a), and the mixing with the addition of compressive force and shear force is performed in a closed container equipped with an impeller. is preferred. The circumferential speed of such an impeller is preferably 15 m/s to 45 m/s, more preferably 15 m/s, from the viewpoint of effectively forming the inner layer (B) that covers the core part (A) well and firmly. s~35m/s. Further, the mixing time is preferably 3 minutes to 90 minutes, more preferably 5 minutes to 60 minutes.
Incidentally, the peripheral speed of the impeller means the speed at the outermost end of the rotary stirring blade (impeller), and can be expressed by the following formula (1), and is mixed while applying compressive force and shear force. The processing time can also vary depending on the circumferential speed of the impeller, such that the slower the circumferential speed of the impeller, the longer it takes.
Impeller circumferential speed (m/s) =
Impeller radius (m) x 2 x π x rotation speed (rpm) ÷ 60... (1)
An example of a device having a closed container equipped with an impeller is Nobilta (manufactured by Hosokawa Micron), which is a dry particle compounding device.
工程（Ｐ２）では、次いで水不溶性炭素粉末（ｃ）を添加して、圧縮力及びせん断力を付加した混合を行う。
用いる水不溶性炭素粉末（ｃ）としては、上記のとおり、グラファイト、グラフェン、カーボンブラック、及びカーボンナノファイバーから選ばれる１種又は２種以上が挙げられる。
In step (P2), water-insoluble carbon powder (c) is then added and mixed under compressive force and shear force.
As described above, the water-insoluble carbon powder (c) to be used includes one or more selected from graphite, graphene, carbon black, and carbon nanofiber.
水不溶性炭素粉末（ｃ）の添加量は、本発明の多層型リチウムイオン二次電池用正極活物質において、上記水不溶性炭素粉末（ｃ）の含有量を満たすような量であればよく、具体的には、リチウム複合酸化物二次粒子（ａ）と、表面に炭素（ｘ）が担持してなるリチウム系ポリアニオン粒子（ｂ）との合計添加量１００質量部（炭素（ｘ）の担持量を含む）に対し、好ましくは０．０５質量部～１．７質量部であり、より好ましくは０．０７質量部～１．７質量部であり、さらに好ましくは０．０８質量部～１．７質量部である。 The amount of the water-insoluble carbon powder (c) to be added may be such that it satisfies the content of the water-insoluble carbon powder (c) in the positive electrode active material for a multilayer lithium ion secondary battery of the present invention. Specifically, the total addition amount of lithium composite oxide secondary particles (a) and lithium-based polyanion particles (b) having carbon (x) supported on the surface is 100 parts by mass (supported amount of carbon (x) ), the amount is preferably 0.05 parts by mass to 1.7 parts by mass, more preferably 0.07 parts by mass to 1.7 parts by mass, even more preferably 0.08 parts by mass to 1.7 parts by mass. 7 parts by mass.
水不溶性炭素粉末（ｃ）を添加した際における混合は、上記と同様の装置を続いて用いればよい。
具体的には、ここでのインペラの周速度は、リチウム複合酸化物二次粒子（ａ）に対して効果的に外層（Ｃ）を被覆し、得られる多層型リチウムイオン二次電池用正極活物質の内層（Ｂ）及び外層（Ｃ）の剥離を抑止する観点から、好ましくは１５ｍ／ｓ～４５ｍ／ｓであり、より好ましくは１５ｍ／ｓ～３５ｍ／ｓである。また、混合時間は、好ましくは３分間～９０分間であり、より好ましくは５分間～６０分間である。
For mixing when adding the water-insoluble carbon powder (c), the same apparatus as above may be used subsequently.
Specifically, the circumferential speed of the impeller here is such that the outer layer (C) is effectively coated on the lithium composite oxide secondary particles (a), and the resulting positive electrode active for a multilayer lithium ion secondary battery is adjusted. From the viewpoint of preventing peeling of the inner layer (B) and outer layer (C) of the substance, the speed is preferably 15 m/s to 45 m/s, more preferably 15 m/s to 35 m/s. Further, the mixing time is preferably 3 minutes to 90 minutes, more preferably 5 minutes to 60 minutes.
本発明の多層型リチウムイオン二次電池用正極活物質を正極材料として適用し、これを含むリチウムイオン二次電池としては、正極と負極と電解液とセパレータ、若しくは正極と負極と固体電解質を必須構成とするものであれば特に限定されない。 The positive electrode active material for multilayer lithium ion secondary batteries of the present invention is applied as a positive electrode material, and a lithium ion secondary battery containing the same requires a positive electrode, a negative electrode, an electrolyte, and a separator, or a positive electrode, a negative electrode, and a solid electrolyte. It is not particularly limited as long as it has a configuration.
ここで、負極については、リチウムイオンを充電時には吸蔵し、かつ放電時には放出することができれば、その材料構成で特に限定されるものではなく、公知の材料構成のものを用いることができる。たとえば、リチウム金属、グラファイト、シリコン系（Ｓｉ、ＳｉＯｘ）、チタン酸リチウム又は非晶質炭素等の炭素材料等を用いることができる。そしてリチウムイオンを電気化学的に吸蔵・放出し得るインターカレート材料で形成された電極、特に炭素材料を用いることが好ましい。さらに、２種以上の上記の負極材料を併用してもよく、たとえばグラファイトとシリコン系の組み合わせを用いることができる。 Here, the material composition of the negative electrode is not particularly limited as long as it can occlude lithium ions during charging and release them during discharging, and any known material composition can be used. For example, lithium metal, graphite, silicon-based (Si, SiO x ), lithium titanate, carbon materials such as amorphous carbon, etc. can be used. It is preferable to use an electrode made of an intercalating material that can electrochemically absorb and release lithium ions, particularly a carbon material. Furthermore, two or more of the above negative electrode materials may be used in combination; for example, a combination of graphite and silicon may be used.
電解液は、有機溶媒に支持塩を溶解させたものである。有機溶媒は、通常リチウムイオン二次電池の電解液の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。 The electrolytic solution is one in which a supporting salt is dissolved in an organic solvent. The organic solvent is not particularly limited as long as it is an organic solvent that is normally used in electrolytes of lithium ion secondary batteries, and examples include carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, and lactones. , oxolane compounds, etc. can be used.
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、該無機塩の誘導体、ＬｉＳＯ３ＣＦ３、ＬｉＣ（ＳＯ３ＣＦ３）２及びＬｉＮ（ＳＯ３ＣＦ３）２、ＬｉＮ（ＳＯ２Ｃ２Ｆ５）２及びＬｉＮ（ＳＯ２ＣＦ３）（ＳＯ２Ｃ４Ｆ９）から選ばれる有機塩、並びに該有機塩の誘導体の少なくとも１種であることが好ましい。 The supporting salt is not particularly limited in type, but includes inorganic salts selected from LiPF 6 , LiBF 4 , LiClO 4 and LiAsF 6 , derivatives of the inorganic salts, LiSO 3 CF 3 , LiC(SO 3 CF 3 ) 2 and an organic salt selected from LiN(SO 3 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 and LiN(SO 2 CF 3 ) (SO 2 C 4 F 9 ), and a derivative of the organic salt It is preferable that it is at least one kind of.
セパレータは、正極及び負極を電気的に絶縁し、電解液を保持する役割を果たすものである。たとえば、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）の多孔膜を用いればよい。 The separator serves to electrically insulate the positive electrode and the negative electrode and to retain the electrolyte. For example, a porous synthetic resin membrane, particularly a porous membrane of polyolefin polymer (polyethylene, polypropylene) may be used.
固体電解質は、正極及び負極を電気的に絶縁し、高いリチウムイオン伝導性を示すものである。たとえば、Ｌａ０．５１Ｌｉ０．３４ＴｉＯ２．９４、Ｌｉ１．３Ａｌ０．３Ｔｉ１．７（ＰＯ４）３、Ｌｉ７Ｌａ３Ｚｒ２Ｏ１２、５０Ｌｉ４ＳｉＯ４・５０Ｌｉ３ＢＯ３、Ｌｉ２．９ＰＯ３．３Ｎ０．４６、Ｌｉ３．６Ｓｉ０．６Ｐ０．４Ｏ４、Ｌｉ１．０７Ａｌ０．６９Ｔｉ１．４６（ＰＯ４）３、Ｌｉ１．５Ａｌ０．５Ｇｅ１．５（ＰＯ４）３、Ｌｉ１０ＧｅＰ２Ｓ１２、Ｌｉ３．２５Ｇｅ０．２５Ｐ０．７５Ｓ４、３０Ｌｉ２Ｓ・２６Ｂ２Ｓ３・４４ＬｉＩ、６３Ｌｉ２Ｓ・３６ＳｉＳ２・１Ｌｉ３ＰＯ４、５７Ｌｉ２Ｓ・３８ＳｉＳ２・５Ｌｉ４ＳｉＯ４、７０Ｌｉ２Ｓ・３０Ｐ２Ｓ５、５０Ｌｉ２Ｓ・５０ＧｅＳ２、Ｌｉ７Ｐ３Ｓ１１、Ｌｉ３．２５Ｐ０．９５Ｓ４を用いればよい。 A solid electrolyte electrically insulates a positive electrode and a negative electrode and exhibits high lithium ion conductivity. For example, La 0.51 Li 0.34 TiO 2.94 , Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 , Li 7 La 3 Zr 2 O 12 , 50Li 4 SiO 4.50Li 3 BO 3 , Li 2.9 PO 3.3 N 0.46 , Li 3.6 Si 0.6 P 0.4 O 4 , Li 1.07 Al 0.69 Ti 1.46 (PO 4 ) 3 , Li 1 .5 Al 0.5 Ge 1.5 (PO 4 ) 3 , Li 10 GeP 2 S 12 , Li 3.25 Ge 0.25 P 0.75 S 4 , 30Li 2 S・26B 2 S 3・44LiI, 63Li 2S・36SiS 2・1Li 3 PO 4 , 57Li 2 S・38SiS 2・5Li 4 SiO 4 , 70Li 2 S・30P 2 S 5 , 50Li 2 S・50GeS 2 , Li 7 P 3 S 11 , Li 3.25 P 0.95 S 4 may be used.
上記の構成を有するリチウムイオン二次電池の形状としては、特に制限を受けるものではなく、コイン型、円筒型，角型等種々の形状や、ラミネート外装体に封入した不定形状であってもよい。 The shape of the lithium ion secondary battery having the above structure is not particularly limited, and may be various shapes such as a coin shape, a cylindrical shape, a square shape, or an irregular shape enclosed in a laminate exterior body. .
以下、本発明について、実施例に基づき具体的に説明するが、本発明はこれら実施例に限定されるものではない。 Hereinafter, the present invention will be specifically explained based on Examples, but the present invention is not limited to these Examples.
［製造例１：リチウム複合酸化物二次粒子（ａ）の製造］
Ｎｉ：Ｃｏ：Ｍｎのモル比が１：１：１となるように、硫酸ニッケル六水和物 ２６３ｇ、硫酸コバルト七水和物 ２８１ｇ、硫酸マンガン五水和物 ２４１ｇ、及び水 ３Ｌを混合した後、かかる混合液に、滴下速度３００ｍｌ／分で２５％アンモニア水を滴下して、ｐＨが１１の金属複合水酸化物を含むスラリーａ１を得た。
次いで、スラリーａ１をろ過、乾燥して、金属複合水酸化物の混合物ａ２を得た後、かかる混合物ａ２に炭酸リチウム３７gをボールミルで混合して粉末混合物ａ３を得た。
得られた粉末混合物ａ３を、空気雰囲気下で８００℃×５時間仮焼成して解砕した後、本焼成として空気雰囲気下で８００℃×１０時間焼成し、リチウム複合酸化物二次粒子（ＬｉＮｉ0.33Ｃｏ0.33Ｍｎ0.34Ｏ2、平均粒径：１０μｍ）を得た。
[Production Example 1: Production of lithium composite oxide secondary particles (a)]
After mixing 263 g of nickel sulfate hexahydrate, 281 g of cobalt sulfate heptahydrate, 241 g of manganese sulfate pentahydrate, and 3 L of water so that the molar ratio of Ni:Co:Mn was 1:1:1. 25% ammonia water was added dropwise to the mixed solution at a dropping rate of 300 ml/min to obtain a slurry a1 containing a metal composite hydroxide having a pH of 11.
Next, the slurry a1 was filtered and dried to obtain a metal composite hydroxide mixture a2, and then 37 g of lithium carbonate was mixed with the mixture a2 using a ball mill to obtain a powder mixture a3.
The obtained powder mixture a3 was pre-calcined in an air atmosphere at 800°C for 5 hours to be crushed, and then main calcination was performed in an air atmosphere at 800°C for 10 hours to form lithium composite oxide secondary particles (LiNi 0.33 Co 0.33 Mn 0.34 O 2 , average particle size: 10 μm) was obtained.
［製造例２：表面に炭素（ｘ）が担持してなるリチウム系ポリアニオン粒子（ｂ）の製造］
ＬｉＯＨ・Ｈ2Ｏ ４０７１ｇ、及び水９．６５７Ｌを混合してスラリーｂ１を得た。次いで、得られたスラリーｂ１を、２５℃の温度に保持しながら３分間撹拌しつつ７５％のリン酸水溶液４２０４ｇを４０ｍＬ／分で滴下して、Ｌｉ3ＰＯ4を含むスラリーｂ２を得た。
得られたスラリーｂ２に窒素パージして、スラリーｂ２の溶存酸素濃度を０．１ｍｇ／Ｌとした後、スラリーｂ２全量に対し、ＭｎＳＯ4・５Ｈ2Ｏ ３８０７ｇ、ＦｅＳＯ4・７Ｈ2Ｏ ２６８４ｇを添加してスラリーｂ３を得た。添加したＭｎＳＯ4とＦｅＳＯ4のモル比（マンガン化合物：鉄化合物）は、７０：３０であった。
次いで、得られたスラリーｂ３をオートクレーブに投入し、１６０℃で１時間水熱反応を行った。オートクレーブ内の圧力は０．８ＭＰａであった。水熱反応後、生成した結晶をろ過し、次いで結晶１質量部に対し１２質量部の水により洗浄した。その後フィルタープレス装置で脱水し、脱水ケーキｂ４を得た。
脱水ケーキｂ４中のリチウム系ポリアニオン粒子の平均粒径は、１００ｎｍであった。
得られた脱水ケーキｂ４を８０００ｇ分取し、セルロースナノファイバー（ＦＤ１００Ｆ、ダイセルファインケム社製）１２００ｇ、水８．５Ｌを添加して、固形分濃度３０％のスラリーｂ５を得た。得られたスラリーｂ５を超音波攪拌機（Ｔ２５、ＩＫＡ社製）で１０分間分散処理して全体を均一に混合させた後、スプレードライ装置（ＭＤＬ－０５０Ｍ、藤崎電機株式会社製）を用いて乾燥温度１３０℃で噴霧乾燥し、造粒体ｂ６を得た。
得られた造粒体ｂ６を、アルゴン水素雰囲気下（水素濃度３％）、７００℃で１時間焼成して、２．０質量％のセルロースナノファイバー由来の炭素が担持されたリン酸マンガン鉄リチウム二次粒子（ＬｉＭｎ0.7Ｆｅ0.3ＰＯ4、炭素（ｘ）の担持量：２．０質量％、平均粒径：１２μｍ）を得た。
[Production Example 2: Production of lithium-based polyanion particles (b) with carbon (x) supported on the surface]
Slurry b1 was obtained by mixing 4071 g of LiOH.H 2 O and 9.657 L of water. Next, 4204 g of a 75% phosphoric acid aqueous solution was added dropwise to the obtained slurry b1 at a rate of 40 mL/min while stirring for 3 minutes while maintaining the temperature at 25° C. to obtain a slurry b2 containing Li 3 PO 4 .
After purging the obtained slurry b2 with nitrogen to make the dissolved oxygen concentration of slurry b2 0.1 mg/L, 3807 g of MnSO 4 .5H 2 O and 2684 g of FeSO 4 .7H 2 O were added to the total amount of slurry b2. Slurry b3 was obtained. The molar ratio of added MnSO 4 and FeSO 4 (manganese compound: iron compound) was 70:30.
Next, the obtained slurry b3 was put into an autoclave, and a hydrothermal reaction was performed at 160° C. for 1 hour. The pressure inside the autoclave was 0.8 MPa. After the hydrothermal reaction, the produced crystals were filtered and then washed with 12 parts by weight of water per 1 part by weight of the crystals. Thereafter, it was dehydrated using a filter press to obtain a dehydrated cake b4.
The average particle size of the lithium-based polyanion particles in dehydrated cake b4 was 100 nm.
8,000 g of the obtained dehydrated cake b4 was collected, and 1,200 g of cellulose nanofibers (FD100F, manufactured by Daicel FineChem) and 8.5 L of water were added to obtain slurry b5 with a solid content concentration of 30%. The obtained slurry b5 was dispersed for 10 minutes using an ultrasonic stirrer (T25, manufactured by IKA) to mix the whole uniformly, and then dried using a spray dryer (MDL-050M, manufactured by Fujisaki Electric Co., Ltd.). Spray drying was performed at a temperature of 130°C to obtain granules b6.
The obtained granules b6 were fired at 700°C for 1 hour in an argon-hydrogen atmosphere (hydrogen concentration 3%) to produce lithium manganese iron phosphate on which 2.0% by mass of carbon derived from cellulose nanofibers was supported. Secondary particles (LiMn 0.7 Fe 0.3 PO 4 , carbon (x) supported amount: 2.0% by mass, average particle size: 12 μm) were obtained.
［製造例３：リチウム複合酸化物二次粒子（ｄ）の製造］
ボールミルの混合時間を３時間とした以外、製造例１と同様にしてリチウム複合酸化物二次粒子（ＬｉＮｉ0.33Ｃｏ0.33Ｍｎ0.34Ｏ2、平均粒径（Ｄ５０）：３μｍ）を得た。
[Production Example 3: Production of lithium composite oxide secondary particles (d)]
Lithium composite oxide secondary particles (LiNi 0.33 Co 0.33 Mn 0.34 O 2 , average particle size (D 50 ): 3 μm) were obtained in the same manner as in Production Example 1, except that the mixing time in the ball mill was 3 hours.
［製造例４：リチウム複合酸化物二次粒子（ｅ）の製造］
ボールミルの混合時間を１０分間とした以外、製造例１と同様にしてリチウム複合酸化物二次粒子（ＬｉＮｉ0.33Ｃｏ0.33Ｍｎ0.34Ｏ2、平均粒径（Ｄ５０）：２５μｍ）を得た。
[Production Example 4: Production of lithium composite oxide secondary particles (e)]
Lithium composite oxide secondary particles (LiNi 0.33 Co 0.33 Mn 0.34 O 2 , average particle size (D 50 ): 25 μm) were obtained in the same manner as in Production Example 1, except that the mixing time in the ball mill was changed to 10 minutes.
［実施例１］
製造例１で得られたリチウム複合酸化物二次粒子（ａ）４５０ｇと製造例２で得られたリチウム系ポリアニオン粒子（ｂ）５０ｇをノビルタ(ホソカワミクロン社製、ＮＯＢ－１３０)を用いて２０００ｒｐｍで１０分間の複合化処理を行い、コア部（Ａ）とこれを被覆してなる内層（Ｂ）とを有した予備粒子を得た。続けて、グラファイト（日本黒鉛社製、ＵＰ－５Ｎ）２．５ｇを添加し、２０００ｒｐｍで５分間の複合化処理を行い、さらに内層（Ｂ）を被覆してなる外層（Ｃ）を有した多層型リチウムイオン二次電池用正極活物質を得た。
[Example 1]
450 g of lithium composite oxide secondary particles (a) obtained in Production Example 1 and 50 g of lithium-based polyanion particles (b) obtained in Production Example 2 were heated at 2000 rpm using Nobilta (manufactured by Hosokawa Micron Corporation, NOB-130). A composite treatment was performed for 10 minutes to obtain preliminary particles having a core portion (A) and an inner layer (B) covering the core portion. Subsequently, 2.5 g of graphite (manufactured by Nippon Graphite Co., Ltd., UP-5N) was added, and a composite treatment was performed at 2000 rpm for 5 minutes to form a multilayer structure having an outer layer (C) covering the inner layer (B). A positive electrode active material for type lithium ion secondary batteries was obtained.
［実施例２］
リチウム複合酸化物二次粒子（ａ）を３５０ｇ、リチウム系ポリアニオン粒子（ｂ）を１５０ｇとした以外、実施例１と同様にして多層型リチウムイオン二次電池用正極活物質を得た。
[Example 2]
A positive electrode active material for a multilayer lithium ion secondary battery was obtained in the same manner as in Example 1, except that the lithium composite oxide secondary particles (a) were 350 g and the lithium polyanion particles (b) were 150 g.
［実施例３］
リチウム複合酸化物二次粒子（ａ）を２５０ｇ、リチウム系ポリアニオン粒子（ｂ）を２５０ｇとした以外、実施例１と同様にして多層型リチウムイオン二次電池用正極活物質を得た。
[Example 3]
A positive electrode active material for a multilayer lithium ion secondary battery was obtained in the same manner as in Example 1, except that the lithium composite oxide secondary particles (a) were 250 g and the lithium polyanion particles (b) were 250 g.
［実施例４］
リチウム複合酸化物二次粒子（ａ）を３５０ｇ、リチウム系ポリアニオン粒子（ｂ）を１５０ｇとし、グラファイトの代わりにカーボンブラック（ＥＣ－６００ＪＤ、ライオン・スペシャリティ・ケミカルズ社 一次粒子径３４ｎｍ）２．５ｇを添加した以外、実施例１と同様にして多層型リチウムイオン二次電池用正極活物質を得た。
[Example 4]
350 g of lithium composite oxide secondary particles (a), 150 g of lithium polyanion particles (b), and 2.5 g of carbon black (EC-600JD, Lion Specialty Chemicals, primary particle diameter 34 nm) instead of graphite. A positive electrode active material for a multilayer lithium ion secondary battery was obtained in the same manner as in Example 1, except that the above components were added.
［実施例５］
リチウム複合酸化物二次粒子（ａ）を３５０ｇ、リチウム系ポリアニオン粒子（ｂ）を１５０ｇとし、グラファイトの代わりにグラフェン（ＸＧ ｓｃｉｅｎｃｅｓ社製、ｘＧＮＰ、平均粒径３０μｍ）２．５ｇを添加した以外、実施例１と同様にして多層型リチウムイオン二次電池用正極活物質を得た。
[Example 5]
The lithium composite oxide secondary particles (a) were 350 g, the lithium-based polyanion particles (b) were 150 g, and 2.5 g of graphene (manufactured by XG sciences, xGNP, average particle size 30 μm) was added instead of graphite. A positive electrode active material for a multilayer lithium ion secondary battery was obtained in the same manner as in Example 1.
［実施例６］
リチウム複合酸化物二次粒子（ａ）を３５０ｇ、リチウム系ポリアニオン粒子（ｂ）を１５０ｇ、グラファイトを０．５ｇとした以外、実施例１と同様にして多層型リチウムイオン二次電池用正極活物質を得た。
[Example 6]
A positive electrode active material for a multilayer lithium ion secondary battery was prepared in the same manner as in Example 1, except that the lithium composite oxide secondary particles (a) were 350 g, the lithium polyanion particles (b) were 150 g, and the graphite was 0.5 g. I got it.
［実施例７］
リチウム複合酸化物二次粒子（ａ）を３５０ｇ、リチウム系ポリアニオン粒子（ｂ）を１５０ｇ、グラファイトを７．５ｇとした以外、実施例１と同様にして多層型リチウムイオン二次電池用正極活物質を得た。
[Example 7]
A positive electrode active material for a multilayer lithium ion secondary battery was prepared in the same manner as in Example 1, except that the lithium composite oxide secondary particles (a) were 350 g, the lithium polyanion particles (b) were 150 g, and the graphite was 7.5 g. I got it.
［実施例８］
リチウム複合酸化物二次粒子（ｄ）を３５０ｇとし、リチウム系ポリアニオン粒子（ｂ）を１５０ｇ添加した以外、実施例１と同様にして多層型リチウムイオン二次電池用正極活物質を得た。
[Example 8]
A positive electrode active material for a multilayer lithium ion secondary battery was obtained in the same manner as in Example 1, except that 350 g of lithium composite oxide secondary particles (d) and 150 g of lithium-based polyanion particles (b) were added.
［実施例９］
リチウム複合酸化物二次粒子（ｅ）を３５０ｇとし、リチウム系ポリアニオン粒子（ｂ）を１５０ｇ添加した以外、実施例１と同様にして多層型リチウムイオン二次電池用正極活物質を得た。
[Example 9]
A positive electrode active material for a multilayer lithium ion secondary battery was obtained in the same manner as in Example 1, except that 350 g of lithium composite oxide secondary particles (e) and 150 g of lithium-based polyanion particles (b) were added.
［比較例１］
リチウム複合酸化物二次粒子（ａ）を３５０ｇ、リチウム系ポリアニオン粒子（ｂ）を１５０ｇ、グラファイトを１０ｇとした以外、実施例１と同様にして多層型リチウムイオン二次電池用正極活物質を得た。
[Comparative example 1]
A positive electrode active material for a multilayer lithium ion secondary battery was obtained in the same manner as in Example 1, except that 350 g of lithium composite oxide secondary particles (a), 150 g of lithium-based polyanion particles (b), and 10 g of graphite were used. Ta.
［比較例２］
リチウム複合酸化物二次粒子（ａ）を３５０ｇ、リチウム系ポリアニオン粒子（ｂ）を１５０ｇ、グラファイトを５０ｇとした以外、実施例１と同様にして多層型リチウムイオン二次電池用正極活物質を得た。
[Comparative example 2]
A positive electrode active material for a multilayer lithium ion secondary battery was obtained in the same manner as in Example 1, except that 350 g of lithium composite oxide secondary particles (a), 150 g of lithium-based polyanion particles (b), and 50 g of graphite were used. Ta.
［比較例３］
リチウム複合酸化物二次粒子（ａ）を３５０ｇ、リチウム系ポリアニオン粒子（ｂ）を１５０ｇとし、グラファイトを添加することなく複合化処理を行った以外、実施例１と同様にして、コア部（Ａ）と内層（Ｂ）のみを有する多層型リチウムイオン二次電池用正極活物質を得た。
[Comparative example 3]
A core part (A ) and an inner layer (B), a positive electrode active material for a multilayer lithium ion secondary battery was obtained.
［比較例４］
製造例１で得られたリチウム複合酸化物二次粒子（ａ）３５０ｇ、製造例２で得られたリチウム系ポリアニオン粒子（ｂ）１５０ｇ、及びグラファイト（日本黒鉛社製、ＵＰ－５Ｎ）２．５ｇをノビルタ(ホソカワミクロン社製、ＮＯＢ－１３０)を用いて２０００ｒｐｍで１０分間の一括した複合化処理を行い、リチウムイオン二次電池用正極活物質を得た。
[Comparative example 4]
350 g of lithium composite oxide secondary particles (a) obtained in Production Example 1, 150 g of lithium-based polyanion particles (b) obtained in Production Example 2, and 2.5 g of graphite (manufactured by Nippon Graphite Co., Ltd., UP-5N) A composite treatment was performed using Nobilta (manufactured by Hosokawa Micron, NOB-130) at 2000 rpm for 10 minutes to obtain a positive electrode active material for a lithium ion secondary battery.
《リチウムイオン二次電池用正極活物質が有する各層の層厚みの測定》
実施例及び比較例で得られた各正極活物質について、内層（Ｂ）の層厚みはＳＥＭの電子顕微鏡を用い、外層（Ｃ）の層厚みはＳＥＭの電子顕微鏡を用いて観察し、１００個の粒子の層厚みを測定して平均値を求めた。
《Measurement of the layer thickness of each layer of the positive electrode active material for lithium ion secondary batteries》
For each positive electrode active material obtained in Examples and Comparative Examples, the layer thickness of the inner layer (B) was observed using an SEM electron microscope, and the layer thickness of the outer layer (C) was observed using an SEM electron microscope. The layer thickness of the particles was measured and the average value was determined.
《リチウムイオン二次電池用正極活物質の粒度分布測定》
実施例及び比較例で得られた各正極活物質について、マイクロトラック・ベル社のＭＴ３３００ＥＸ ＩＩを用いて粒度分布測定を行い、１μｍ以下の微粒子量（体積％）と平均粒径（Ｄ50）を求めた。
《Particle size distribution measurement of positive electrode active material for lithium ion secondary batteries》
For each positive electrode active material obtained in Examples and Comparative Examples, particle size distribution was measured using Microtrac Bell's MT3300EX II, and the amount of fine particles (volume %) of 1 μm or less and average particle diameter (D 50 ) were determined. I asked for it.
《２５℃での２０ＭＰａ加圧時における電気伝導度の算出》
実施例及び比較例で得られた各正極活物質について、粉体抵抗装置（三菱ケミカルアナリティック社、ＭＣＰ－ＰＤ５１型）を用い、２５℃での２０ＭＰａ加圧時における電気伝導度（Ｓ／ｃｍ）を算出した。
《Calculation of electrical conductivity when pressurized at 20 MPa at 25°C》
For each positive electrode active material obtained in Examples and Comparative Examples, the electrical conductivity (S/cm ) was calculated.
《ラマン分光法による強度比（Ｉ（ＰＯ4）／Ｉ（Ｄ））の測定》
実施例及び比較例で得られた各正極活物質について、ラマン分光光度計（ＮＲＳ－１０００、日本分光社製）を用いてラマン分光スペクトルを測定し、ピーク強度（Ｉ（Ｄ）、ピーク位置：１３５０ｃｍ-1付近）とＰＯ4
3-に関わるピーク強度（Ｉ（ＰＯ4）、ピーク位置：９５０ｃｍ-1付近）を測定し、強度比（Ｉ（ＰＯ4）／Ｉ（Ｄ））を求めた。
《Measurement of intensity ratio (I (PO4) /I (D) ) by Raman spectroscopy》
For each positive electrode active material obtained in Examples and Comparative Examples, Raman spectra were measured using a Raman spectrophotometer (NRS-1000, manufactured by JASCO Corporation), and the peak intensity (I (D) , peak position: The peak intensity related to PO 4 3- (I (PO4) , peak position: around 950 cm -1 ) was measured , and the intensity ratio (I (PO4) /I (D) ) was determined.
《正極スラリーの評価》
上記リチウムイオン二次電池の作製中において調製した正極スラリーにつき、２５０℃における粘度を粘度計（ＬＶＤＩ－Ｉ＋， Ｂｒｏｏｋｆｉｅｌｄ Ｅｎｇｉｎｅｅｒｉｎｇ Ｌａｂｏｒａｔｏｒｉｅｓ社）にて測定した。
なお、かかる２５℃における粘度が、１０００～５５００ｍＰａ・ｓｅｃ（好ましくは１５００～５０００ｍＰａ・ｓｅｃ）であれば、用いた正極活物質において微粒子の発生が有効に低減されており、集電体への塗工性に優れた正極スラリーであると評価することができる。
《Evaluation of positive electrode slurry》
The viscosity of the positive electrode slurry prepared during the production of the lithium ion secondary battery at 250° C. was measured using a viscometer (LVDI-I+, Brookfield Engineering Laboratories).
Note that if the viscosity at 25°C is 1000 to 5500 mPa·sec (preferably 1500 to 5000 mPa·sec), the generation of fine particles in the positive electrode active material used is effectively reduced, and the coating on the current collector is It can be evaluated that the positive electrode slurry has excellent workability.
《リチウムイオン二次電池の作製１》
実施例及び比較例で得られた各正極活物質を用いて正極スラリーを調製した。具体的には、正極活物質、アセチレンブラック、ポリフッ化ビニリデンを質量比９８：１：１の配合割合で混合し、得られた混合物１００質量部に対して、Ｎ－メチル－２－ピロリドンを１質量部加えて充分混練し、正極スラリーを調製した。
次に、上記正極スラリーを厚さ２０μｍのアルミニウム箔からなる集電体に塗工機を用いて塗布し、８０℃で１２時間の真空乾燥を行った。その後、φ１４ｍｍの円盤状に打ち抜いてハンドプレスを用いて１６ＭＰａで２分間プレスし、正極とした。
次いで、上記正極を用いてコイン型二次電池を構築した。負極には、φ１５ｍｍに打ち抜いたリチウム箔を用いた。電解液には、エチレンカーボネート及びエチルメチルカーボネートを体積比３：７の割合で混合した混合溶媒に、ＬｉＰＦ6を１ｍｏｌ／Ｌの濃度で溶解したものを用いた。セパレータには、ポリプロピレンを用いた。これらの電池部品を露点が－５０℃以下の雰囲気中にて常法により組み込み収容し、コイン型二次電池１（ＣＲ－２０３２）を得た。
《Preparation of lithium ion secondary battery 1》
A positive electrode slurry was prepared using each positive electrode active material obtained in Examples and Comparative Examples. Specifically, the positive electrode active material, acetylene black, and polyvinylidene fluoride were mixed at a mass ratio of 98:1:1, and 1 part of N-methyl-2-pyrrolidone was added to 100 parts by mass of the resulting mixture. A positive electrode slurry was prepared by adding 1 part by mass and sufficiently kneading.
Next, the positive electrode slurry was applied to a current collector made of aluminum foil with a thickness of 20 μm using a coating machine, and vacuum-dried at 80° C. for 12 hours. Thereafter, it was punched out into a disk shape of φ14 mm and pressed using a hand press at 16 MPa for 2 minutes to obtain a positive electrode.
Next, a coin-type secondary battery was constructed using the above positive electrode. A lithium foil punched to a diameter of 15 mm was used as the negative electrode. The electrolytic solution was prepared by dissolving LiPF 6 at a concentration of 1 mol/L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate at a volume ratio of 3:7. Polypropylene was used for the separator. These battery parts were assembled and housed in an atmosphere with a dew point of −50° C. or lower by a conventional method to obtain a coin-type secondary battery 1 (CR-2032).
《電池特性の評価》
得られたコイン型二次電池１を用い、放電容量測定装置（ＨＪ－１００１ＳＤ８、北斗電工社製）にて気温４５℃環境での、０．２Ｃ（３４ｍＡｈ／ｇ）、３Ｃ（５１０ｍＡｈ／ｇ）の放電容量を測定した。
さらに、気温４５℃環境での１Ｃでの充放電の３０回繰り返しによる、下記式（２）による容量維持率（サイクル特性）を求めた。
容量維持率（％）＝（３０サイクル後の放電容量）／（１サイクル後の放電容量）
×１００ ・・・（２）
《Evaluation of battery characteristics》
Using the obtained coin-type secondary battery 1, the discharge capacity measuring device (HJ-1001SD8, manufactured by Hokuto Denko Co., Ltd.) was used to measure 0.2C (34mAh/g) and 3C (510mAh/g) at a temperature of 45°C. The discharge capacity was measured.
Furthermore, the capacity retention rate (cycle characteristics) was determined by the following formula (2) by repeating charging and discharging at 1C 30 times in an environment with an air temperature of 45°C.
Capacity retention rate (%) = (Discharge capacity after 30 cycles) / (Discharge capacity after 1 cycle)
×100...(2)
《リチウムイオン二次電池の作製２》
実施例及び比較例で得られた各正極活物質を用いて正極スラリーを調製した。具体的には、正極活物質、アセチレンブラック、ポリフッ化ビニリデンを質量比９０：５：５の配合割合で混合し、得られた混合物１００質量部に対して、Ｎ－メチル－２－ピロリドンを１質量部加えて充分混練し、正極スラリーを調製した。
次いで、リチウムイオン二次電池の作製１と同様にして、コイン型二次電池２（ＣＲ－２０３２）を得た。
《Preparation of lithium ion secondary battery 2》
A positive electrode slurry was prepared using each positive electrode active material obtained in Examples and Comparative Examples. Specifically, the positive electrode active material, acetylene black, and polyvinylidene fluoride were mixed at a mass ratio of 90:5:5, and 1 part of N-methyl-2-pyrrolidone was added to 100 parts by mass of the resulting mixture. A positive electrode slurry was prepared by adding 1 part by mass and sufficiently kneading.
Next, coin type secondary battery 2 (CR-2032) was obtained in the same manner as Lithium ion secondary battery production 1.
《電極密度及び０℃環境下の正極体積エネルギー密度の算出》
得られたコイン型二次電池２を用い、０℃における５Ｃの放電容量を測定した。次いで、下記式（３）から電極密度を算出するとともに、下記式（４）から０℃環境下の正極体積エネルギー密度を算出した。
電極密度（ｇ／ｃｍ３）＝
正極中の正極活物質質量（ｍｇ）／電極体積（φ１４ｍｍ×厚さ（μｍ））
・・・（３）
０℃環境下の正極体積エネルギー密度（Ｗｈ／ｇ）＝
０℃における放電容量（ｍＡｈ／ｇ）×平均電圧（Ｖ）×電極密度（ｇ／ｃｍ３） ・・・（４）
《Calculation of electrode density and positive electrode volume energy density in 0℃ environment》
Using the obtained coin-type secondary battery 2, the discharge capacity of 5C at 0° C. was measured. Next, the electrode density was calculated from the following equation (3), and the positive electrode volume energy density in a 0° C. environment was calculated from the following equation (4).
Electrode density (g/cm 3 )=
Mass of positive electrode active material in positive electrode (mg)/electrode volume (φ14 mm x thickness (μm))
...(3)
Positive electrode volume energy density (Wh/g) in 0°C environment =
Discharge capacity at 0°C (mAh/g) x average voltage (V) x electrode density (g/cm 3 )...(4)
実施例で得られた多層型リチウムイオン二次電池用正極活物質は、強度比（Ｉ（ＰＯ4）／Ｉ（Ｄ））の値により、リチウム複合酸化物二次粒子とリチウム系ポリアニオン粒子とが堅固に複合化されつつ、外層（Ｃ）が良好に被覆してなる強固な多層構造が形成されていることが示された。また、電気伝導度も高い値を示すことも確認された。
そのため、比較例で得られた正極活物質に比して、電極密度及び０℃環境下の正極体積エネルギー密度及び４５℃環境高温下での容量維持率について高い値を示しており、幅広い温度変化に晒されても安定して優れた電池特性を発現できることがわかる。
In the positive electrode active material for a multilayer lithium ion secondary battery obtained in the example, the lithium composite oxide secondary particles and the lithium-based polyanion particles were separated by the value of the intensity ratio (I (PO4) /I (D) ). It was shown that a strong multilayer structure was formed, which was well covered by the outer layer (C) while being firmly composited. It was also confirmed that the electrical conductivity was also high.
Therefore, compared to the positive electrode active material obtained in the comparative example, it shows higher values for electrode density, positive electrode volume energy density in a 0°C environment, and capacity retention rate at a high temperature of 45°C, and can be used over a wide range of temperature changes. It can be seen that the battery can stably exhibit excellent battery characteristics even when exposed to
Claims (7)
コア部（Ａ）を被覆してなる、層厚み６００ｎｍ～５０００ｎｍの内層（Ｂ）と、
さらに内層（Ｂ）を被覆してなる、層厚み２ｎｍ～８０ｎｍの外層（Ｃ）
を有する多層型リチウムイオン二次電池用正極活物質であって、
コア部（Ａ）が、下記式（Ｉ）又は式（II）：
ＬｉＮｉａＣｏｂＭｎｃＭ１ ｘＯ２・・・（Ｉ）
（式（Ｉ）中、Ｍ１はＭｇ、Ｔｉ、Ｎｂ、Ｆｅ、Ｃｒ、Ｓｉ、Ａｌ、Ｇａ、Ｖ、Ｚｎ、Ｃｕ、Ｓｒ、Ｍｏ、Ｚｒ、Ｓｎ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｂ、Ｂｉ及びＧｅから選ばれる１種又は２種以上の元素を示す。ａ、ｂ、ｃ、ｘは、０．３≦ａ＜１、０＜ｂ≦０．７、０＜ｃ≦０．７、０≦ｘ≦０．３、かつ３ａ＋３ｂ＋３ｃ＋（Ｍ１の価数）×ｘ＝３を満たす数を示す。）
ＬｉＮｉｄＣｏｅＡｌｆＭ２ ｙＯ２・・・（II）
（式（II）中、Ｍ２はＭｇ、Ｔｉ、Ｎｂ、Ｆｅ、Ｃｒ、Ｓｉ、Ｇａ、Ｖ、Ｚｎ、Ｃｕ、Ｓｒ、Ｍｏ、Ｚｒ、Ｓｎ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｂ、Ｂｉ及びＧｅから選ばれる１種又は２種以上の元素を示す。ｄ、ｅ、ｆ、ｙは、０．４≦ｄ＜１、０＜ｅ≦０．６、０＜ｆ≦０．３、０≦ｙ≦０．３、かつ３ｄ＋３ｅ＋３ｆ＋（Ｍ２の価数）×ｙ＝３を満たす数を示す。）
で表されるリチウム複合酸化物二次粒子（ａ）からなり、
内層（Ｂ）が、下記式（III）又は式（III）'：
ＬｉｇＭｎｈＦｅｉＭ３ ｚＰＯ４・・・（III）
（式（III）中、Ｍ３はＣｏ、Ｎｉ、Ｍｇ、Ｃａ、Ｓｒ、Ｙ、Ｚｒ、Ｍｏ、Ｂａ、Ｐｂ、Ｂｉ、Ｌａ、Ｃｅ、Ｎｄ又はＧｄを示す。ｇ、ｈ、ｉ、及びｚは、０＜ｇ≦１．２、０≦ｈ≦１．２、０≦ｉ≦１．２、０≦ｚ≦０．３、及びｈ＋ｉ≠０を満たし、かつｇ＋（Ｍｎの価数）×ｈ＋（Ｆｅの価数）×ｉ＋（Ｍ３の価数）×ｚ＝３を満たす数を示す。）
Ｍｎｈ’Ｆｅｉ’Ｍ３ ｚ'ＰＯ４・・・（III）'
（式（III）'中、Ｍ３は式（III）と同義である。ｈ'、ｉ'、及びｚ'は、０≦ｈ'≦１．２、０≦ｉ'≦１．２、０≦ｚ'≦０．３、及びｈ'＋ｉ'≠０を満たし、かつ（Ｍｎの価数）×ｈ'＋（Ｆｅの価数）×ｉ'＋（Ｍ３の価数）×ｚ'＝３を満たす数を示す。）で表され、かつ表面に炭素（ｘ）が担持してなるリチウム系ポリアニオン粒子（ｂ）からなり、
外層（Ｃ）が、グラファイト、グラフェン、カーボンブラック、及びカーボンナノファイバーから選ばれる水不溶性炭素粉末（ｃ）からなり、
表面に炭素（ｘ）が担持してなるリチウム系ポリアニオン粒子（ｂ）の含有量と、リチウム複合酸化物二次粒子（ａ）の含有量との質量比（（ｂ）：（ａ））が、５：９５～５５：４５である多層型リチウムイオン二次電池用正極活物質。 A core part (A) with an average particle diameter of 3 μm to 30 μm,
an inner layer (B) with a layer thickness of 600 nm to 5000 nm, which covers the core part (A);
Furthermore, an outer layer (C) with a layer thickness of 2 nm to 80 nm is formed by covering the inner layer (B).
A positive electrode active material for a multilayer lithium ion secondary battery having
The core part (A) has the following formula (I) or formula (II):
LiNi a Co b Mn c M 1 x O 2 ...(I)
(In formula (I), M1 is Mg, Ti, Nb, Fe, Cr, Si, Al, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Represents one or more elements selected from Bi and Ge. a, b, c, x are 0.3≦a<1, 0<b≦0.7, 0<c≦0.7, Indicates a number that satisfies 0≦x≦0.3 and 3a+3b+3c+(M valence of 1 )×x=3.)
LiNi d Co e Al f M 2 y O 2 ...(II)
(In formula (II), M2 is Mg, Ti, Nb, Fe, Cr, Si, Ga, V, Zn, Cu, Sr, Mo, Zr, Sn, Ta, W, La, Ce, Pb, Bi and Represents one or more elements selected from Ge. d, e, f, y are 0.4≦d<1, 0<e≦0.6, 0<f≦0.3, 0≦ Indicates a number that satisfies y≦0.3 and 3d+3e+3f+(valence of M2 )×y=3.)
Consisting of lithium composite oxide secondary particles (a) represented by
The inner layer (B) has the following formula (III) or formula (III)':
Li g Mn h Fe i M 3 z PO 4 ...(III)
(In formula (III), M3 represents Co, Ni, Mg, Ca, Sr, Y, Zr, Mo, Ba, Pb, Bi, La, Ce, Nd, or Gd. g, h, i, and z satisfies 0<g≦1.2, 0≦h≦1.2, 0≦i≦1.2, 0≦z≦0.3, and h+i≠0, and g+(valence of Mn)× Indicates the number that satisfies h + (valence of Fe) x i + (valence of M 3 ) x z = 3.)
Mn h' Fe i' M 3 z' PO 4 ...(III)'
(In formula (III)', M3 has the same meaning as in formula (III). h', i', and z' are 0≦h'≦1.2, 0≦i'≦1.2, 0 ≦z'≦0.3 and h'+i'≠0, and (valence of Mn)×h'+(valence of Fe)×i'+(valence of M3 )×z'= (indicates a number that satisfies 3.), and consists of lithium-based polyanion particles (b) on which carbon (x) is supported on the surface,
The outer layer (C) is made of water-insoluble carbon powder (c) selected from graphite, graphene, carbon black, and carbon nanofibers,
The mass ratio ((b):(a)) of the content of the lithium-based polyanion particles (b) having carbon (x) supported on the surface and the content of the lithium composite oxide secondary particles (a) is , 5:95 to 55:45, a positive electrode active material for a multilayer lithium ion secondary battery.
（Ｐ１）リチウム化合物と、少なくとも鉄化合物又はマンガン化合物を含む金属化合物とリン酸化合物とから水熱反応物を得た後、或いは少なくとも鉄化合物又はマンガン化合物を含む金属化合物とリン酸化合物とから水熱反応物を得た後、炭素（ｘ）源を混合して噴霧乾燥し、表面に炭素（ｘ）を担持してなるリチウム系ポリアニオン粒子（ｂ）から形成されてなる造粒体（Ｚ）を得る工程
（Ｐ２）圧縮力及びせん断力を付加した混合を行いながら、リチウム複合酸化物二次粒子（ａ）に造粒体（Ｚ）を添加し、次いで水不溶性炭素粉末（ｃ）を添加する工程
を備える請求項１～６のいずれか１項に記載の多層型リチウムイオン二次電池用正極活物質の製造方法。 Next steps (P1) to (P2):
(P1) After obtaining a hydrothermal reaction product from a lithium compound, a metal compound containing at least an iron compound or a manganese compound, and a phosphoric acid compound, or after obtaining a hydrothermal reaction product from a phosphoric acid compound and a metal compound containing at least an iron compound or a manganese compound, After obtaining the thermal reactant, a carbon (x) source is mixed and spray-dried to obtain a granule (Z) formed from lithium-based polyanion particles (b) carrying carbon (x) on the surface. (P2) Adding the granules (Z) to the lithium composite oxide secondary particles (a) while performing mixing while applying compressive force and shear force, and then adding the water-insoluble carbon powder (c). The method for producing a positive electrode active material for a multilayer lithium ion secondary battery according to any one of claims 1 to 6, comprising the step of:
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