JP2012074390A - Method for producing positive electrode active material - Google Patents

Method for producing positive electrode active material Download PDF

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JP2012074390A
JP2012074390A JP2011255418A JP2011255418A JP2012074390A JP 2012074390 A JP2012074390 A JP 2012074390A JP 2011255418 A JP2011255418 A JP 2011255418A JP 2011255418 A JP2011255418 A JP 2011255418A JP 2012074390 A JP2012074390 A JP 2012074390A
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positive electrode
active material
electrode active
lithium ion
ion secondary
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JP2012074390A5 (en
JP5464717B2 (en
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Takao Noda
孝男 野田
Akihiko Shirakawa
彰彦 白川
Joseph Gaze
ジョセフ ガゼ
Yoshiaki Yamauchi
慶昭 山内
Fumiyoshi Ono
文善 小野
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Resonac Holdings Corp
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Showa Denko KK
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a positive electrode active material for a lithium ion secondary battery, excellent in filling properties, high in initial capacity and less in decrease of capacity (high in capacity retention rate) in repeating charging and discharging.SOLUTION: A method for manufacturing a positive electrode active material for a lithium ion secondary battery, the material mainly consisting of a Li-Mn composite oxide having a spinel structure, includes a step of adding an oxide, an element convertible into an oxide or a compound containing the element, which fuse at a temperature of 550 to 900°C, or an oxide, an element convertible into an oxide or a compound containing the element, which form solid solution with lithium or manganese or react and fuse with lithium or manganese, to a crushed material of a Li-Mn composite oxide having the spinel structure, and mixing to be granulated.

Description

本発明は、リチウムイオン二次電池用正極活物質、その製造方法及びその正極活物質を用いたリチウムイオン二次電池に関する。   The present invention relates to a positive electrode active material for a lithium ion secondary battery, a method for producing the same, and a lithium ion secondary battery using the positive electrode active material.

リチウムイオン二次電池用正極活物質としては、安全性に優れ、かつ資源も豊富なリチウムマンガン複合酸化物（以下Ｌｉ−Ｍｎ系複合酸化物という。）が注目されている。しかしながら、Ｌｉ−Ｍｎ系複合酸化物は、リチウムコバルト複合酸化物（Ｌｉ−Ｃｏ系複酸化物と略する。）と比較して活物質当たりの容量が低く、二次粒子内に多くの空隙を含むので、二次粒子が軽く、吸油量が大きいために大きさが制限される電池内に仕込める活物質質量が少なくなってしまう。その結果、単位電池あたりの電気容量が小さいという問題がある。   As a positive electrode active material for a lithium ion secondary battery, a lithium manganese composite oxide (hereinafter referred to as a Li-Mn composite oxide) that is excellent in safety and has abundant resources has attracted attention. However, the Li—Mn composite oxide has a lower capacity per active material than a lithium cobalt composite oxide (abbreviated as Li—Co composite oxide), and has many voids in the secondary particles. Accordingly, the mass of the active material charged in the battery whose size is limited because the secondary particles are light and the oil absorption is large is reduced. As a result, there is a problem that the electric capacity per unit battery is small.

その改善策として、近年、マンガン化合物とリチウム化合物との混合物を５００ｋｇ／ｃｍ2以上の圧力で加圧成形後、加熱処理し解砕を行うことにより、タップ密度（一定の条件で容器を振動させて得られる粉末の見掛け密度）が１.７ｇ／ｍｌ以上のＬｉ−Ｍｎ複合酸化物を得ようとする提案がある（米国特許第５８０７６４６号：特許文献１，特開平９−８６９３３号：特許文献２）。しかしながら、開示されている具体的なタップ密度は、高々１.９ｇ／ｍｌに過ぎず満足のいくレベルではなかった。 In recent years, tap density (vibrating the container under certain conditions) has been improved by pressing and molding a mixture of a manganese compound and a lithium compound at a pressure of 500 kg / cm 2 or higher, followed by heat treatment and crushing. Have been proposed to obtain a Li—Mn composite oxide having an apparent density of 1.7 g / ml or more (US Pat. No. 5,807,646: Patent Document 1, JP-A-9-86933: Patent Document). 2). However, the specific tap density disclosed is only 1.9 g / ml at most, which is not a satisfactory level.

また、前記公報には、Ｌｉ−Ｍｎ系複合酸化物の１次粒子が凝集した二次粒子の平均粒子径が開示されているが、二次粒子は１次粒子間の相互作用を利用して充填性を向上させても、電極材料の調合工程の際に塗料化（電極ペースト化）する段階でその凝集がなくなり、本質的な改善策になっていない。   Further, the above publication discloses the average particle diameter of secondary particles in which primary particles of Li—Mn-based composite oxide are aggregated, but secondary particles use the interaction between primary particles. Even if the filling property is improved, the aggregation does not occur at the stage of forming a paint (electrode paste) during the preparation process of the electrode material, which is not an essential improvement measure.

また、スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の製造方法としては、マンガン化合物とリチウム化合物の混合物を高温（例えば２５０℃から８５０℃の温度下）で焼成して製造する方法（特開平９−８６９３３号公報：特許文献２）や、マンガン化合物とリチウム化合物にさらにマンガンと置換し得る硼素元素の酸化物を混合し、高温で焼成してＭｎをＢで一部置換したＬｉ−Ｍｎ−Ｂ系酸化物の正極活物質を製造する方法（特開平４−２３７９７０号公報：特許文献３）が開示されている。   In addition, as a method for producing a Li-Mn composite oxide having a spinel structure, a method of producing a mixture of a manganese compound and a lithium compound by firing at a high temperature (for example, at a temperature of 250 ° C. to 850 ° C.) -86933 gazette: Patent Document 2) or Li-Mn-B in which a manganese compound and a lithium compound are further mixed with an oxide of a boron element that can be substituted with manganese, fired at high temperature, and Mn is partially substituted with B A method for producing a positive electrode active material of a system oxide (Japanese Patent Laid-Open No. 4-237970: Patent Document 3) is disclosed.

しかしながら、これらの原料を大気中または酸素ガスフロー中、高温で焼成した場合には、解砕後の二次粒子は、平均空隙率が大きく（１５％以上）、タップ密度が低く（１.９ｇ／ｍｌ以下）、このため電極に仕込める正極活物質の質量を多くして高容量化を図ることはできない。   However, when these raw materials are fired at high temperature in the atmosphere or in an oxygen gas flow, the secondary particles after pulverization have a high average porosity (15% or more) and a low tap density (1.9 g). For this reason, the mass of the positive electrode active material charged into the electrode cannot be increased to increase the capacity.

また、特開平４−１４７５２号公報（特許文献４）には、スピネル型リチウムマンガン酸化物に酸化チタンを配合、焼結したマンガン系酸化物の正極活物質への使用が開示されているが、酸化チタンは９５０℃〜１０００℃以上でないとリチウムとマンガンと反応して融液を生成せず、さらには酸化チタンを１０質量％も添加しないとタップ密度は１.６０ｇ／ｍｌしか得られないとの問題があった。   JP-A-4-14752 (Patent Document 4) discloses the use of a manganese-based oxide obtained by blending and sintering titanium oxide in a spinel type lithium manganese oxide for a positive electrode active material. If titanium oxide is not 950 ° C. to 1000 ° C. or higher, lithium and manganese will not react to form a melt, and if titanium oxide is not added in an amount of 10% by mass, the tap density is only 1.60 g / ml. There was a problem.

米国特許第５８０７６４６号US Pat. No. 5,807,646 特開平９−８６９３３号公報JP-A-9-86933 特開平４−２３７９７０号公報JP-A-4-237970 特開平４−１４７５２号公報JP-A-4-14752

本発明の課題は、充填性に優れ、初期容量が高く、充放電を繰り返した時の容量の低下が少ない（容量維持率が高い）リチウムイオン二次電池用正極活物質、その製造方法及びその正極活物質を用いたリチウムイオン二次電池を提供することにある。   An object of the present invention is to provide a positive electrode active material for a lithium ion secondary battery that has excellent filling properties, a high initial capacity, and a small decrease in capacity when charging and discharging are repeated (a high capacity retention rate), a method for producing the same, and a method for producing the same An object of the present invention is to provide a lithium ion secondary battery using a positive electrode active material.

本発明者らは、鋭意検討した結果、スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の焼成品を解砕後、これらの粉砕粒子に焼結促進助剤を添加し、造粒及び焼成することにより粒子の緻密化を図ることに成功して前記課題を解決した。
すなわち、本発明は、以下のリチウムイオン二次電池用正極活物質、その製造方法、その正極活物質を含む電極用ペースト及びリチウムイオン二次電池用正極、及びリチウムイオン二次電池を提供する。 As a result of intensive studies, the present inventors have crushed a fired product of Li-Mn composite oxide having a spinel structure, and then added a sintering accelerator to these pulverized particles, and granulated and fired. As a result, the above-mentioned problems were solved by succeeding in densifying the particles.
That is, the present invention provides the following positive electrode active material for a lithium ion secondary battery, a production method thereof, an electrode paste containing the positive electrode active material, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary battery.

［１］スピネル構造を有するＬｉ−Ｍｎ系複合酸化物粒子を主体とするリチウムイオン二次電池用正極活物質において、下記式
空隙率（％）＝（Ａ／Ｂ）×１００ （１）
（Ａは二次粒子１個の断面に含まれるポアの総断面積であり、Ｂは二次粒子１個の断面積である。）で示される前記粒子の空隙率の平均値が１５％以下であることを特徴とするリチウムイオン二次電池用正極活物質。
［２］前記平均空隙率の値が１０％以下であり、かつ一次粒子の平均粒子径が０.２〜３μｍである前記［１］に記載のリチウムイオン二次電池用正極活物質。
［３］正極活物質のタップ密度が、１.９ｇ／ｍｌ以上である前記［１］に記載のリチウムイオン二次電池用正極活物質。
［４］正極活物質のタップ密度が、２.２ｇ／ｍｌ以上である前記［３］に記載のリチウムイオン二次電池用正極活物質。
［５］正極活物質の結晶子サイズが、４００〜９６０オングストロームである前記［１］に記載のリチウムイオン二次電池用正極活物質。
［６］正極活物質の格子定数が、８.２４０オングストローム以下である前記［１］に記載のリチウムイオン二次電池用正極活物質。
［７］正極活物質が、スピネル構造を有するＬｉ−Ｍｎ系複合酸化物を主体とし、その酸化物が５５０℃〜９００℃の温度で溶融する酸化物または酸化物になり得る元素または元素を含む化合物、またはリチウムまたはマンガンと固溶するか反応して溶融する酸化物または酸化物になり得る元素または元素を含む化合物からなり、造粒及び焼結されている活物質である前記［１］に記載のリチウムイオン二次電池用正極活物質。
［８］５５０℃〜９００℃の温度で溶融する酸化物または酸化物になり得る元素または元素を含む化合物、またはリチウムまたはマンガンと固溶するか反応して溶融する酸化物または酸化物になり得る元素または元素を含む化合物が、Ｂｉ、Ｂ、Ｗ、Ｍｏ、Ｐｂからなる群より選ばれる少なくとも１種の元素または元素を含む化合物、またはＢ2Ｏ3とＬｉＦを組み合わせた化合物またはＭｎＦ2とＬｉＦを組み合わせた化合物である前記［７］に記載のリチウムイオン二次電池用正極活物質。
［９］スピネル構造を有するＬｉ−Ｍｎ系複合酸化物を主体とするリチウムイオン二次電池用正極活物質の製造方法において、スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の粉砕物に、５５０℃〜９００℃の温度で溶融する酸化物または酸化物になり得る元素または元素を含む化合物、またはリチウムまたはマンガンと固溶するか反応して溶融する酸化物または酸化物になり得る元素または元素を含む化合物を添加し混合して造粒する工程を有することを特徴とするリチウムイオン二次電池用正極活物質の製造方法。
［１０］造粒工程以外に、前記造粒物を焼結する工程を有する前記［９］に記載のリチウムイオン二次電池用正極活物質の製造方法。
［１１］造粒工程以外に、前記造粒物を焼結収縮開始温度から少なくとも１００℃以上高い温度まで少なくとも１００℃／ｍｉｎの速度で昇温してその温度に１分〜１０分間保持した後、少なくとも１００℃／ｍｉｎの速度で焼結開始温度まで降温して焼結させる工程を有する前記［９］に記載のリチウムイオン二次電池用正極活物質の製造方法。
［１２］ロータリーキルンを用いて焼結させる前記［１１］に記載のリチウムイオン二次電池用正極活物質の製造方法。
［１３］前記焼結工程が、Ｌｉ−Ｍｎ系複合酸化物粒子の表面でＢｉ、Ｂ、Ｗ、Ｍｏ、Ｐｂからなる群より選ばれる少なくとも１種の元素または元素を含む化合物、またはＢ2Ｏ3とＬｉＦを組み合わせた化合物またはＭｎＦ2とＬｉＦを組み合わせた化合物を溶融し焼結して行われる前記［１０］に記載のリチウムイオン二次電池用正極活物質の製造方法。
［１４］スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の粉砕物の平均粒子径が、５μｍ以下である前記［９］に記載のリチウムイオン二次電池用正極活物質の製造方法。
［１５］スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の粉砕物の平均粒子径が、３μｍ以下である前記［９］に記載のリチウムイオン二次電池用正極活物質の製造方法。
［１６］前記造粒工程が、噴霧造粒方法、撹拌造粒方法、圧縮造粒方法または流動造粒方法で行われる前記［９］に記載のリチウムイオン二次電池用正極活物質の製造方法。
［１７］前記造粒工程において、造粒助剤として、アクリル系樹脂、イソブチレンと無水マレイン酸との共重合物、ポリビニルアルコール、ポリエチレングリコール、ポリビニルピロリデン、ハイドロキシプロピルセルロース、メチルセルロース、コーンスターチ、ゼラチン、リグニンからなる群より選ばれる少なくとも１種の有機化合物を使用する前記［９］に記載のリチウムイオン二次電池用正極活物質の製造方法。
［１８］大気中または酸素を含有するガスフロー雰囲気中、３００℃〜５５０℃の温度下で脱脂工程を有する前記［１７］に記載のリチウムイオン二次電池用正極活物質の製造方法。
［１９］前記［９］乃至［１８］のいずれかの項に記載の方法で得られたリチウムイオン二次電池用正極活物質。
［２０］前記［１］乃至［８］のいずれかの項に記載のリチウムイオン二次電池用正極活物質を含む電極用ペースト。
［２１］前記［１］乃至［８］のいずれかの項または前記［１９］に記載のリチウムイオン二次電池用正極活物質を含むリチウムイオン二次電池用正極。
［２２］前記［２１］に記載のリチウムイオン二次電池用正極を備えたリチウムイオン二次電池。
［２３］リチウムイオン二次電池が、コイン型電池、巻回型電池、円筒型、角型電池または積層型電池である前記［２２］に記載のリチウムイオン二次電池。 [1] In a positive electrode active material for a lithium ion secondary battery mainly composed of Li-Mn composite oxide particles having a spinel structure, the following formula
Porosity (%) = (A / B) × 100 (1)
(A is the total cross-sectional area of the pores included in the cross section of one secondary particle, and B is the cross-sectional area of one secondary particle.) The average value of the porosity of the particles shown in FIG. A positive electrode active material for a lithium ion secondary battery.
[2] The positive electrode active material for a lithium ion secondary battery according to [1], wherein the average porosity is 10% or less, and the average particle diameter of primary particles is 0.2 to 3 μm.
[3] The positive electrode active material for a lithium ion secondary battery according to [1], wherein the positive electrode active material has a tap density of 1.9 g / ml or more.
[4] The positive electrode active material for a lithium ion secondary battery according to [3], wherein the positive electrode active material has a tap density of 2.2 g / ml or more.
[5] The positive electrode active material for a lithium ion secondary battery according to the above [1], wherein the crystallite size of the positive electrode active material is 400 to 960 Å.
[6] The positive electrode active material for a lithium ion secondary battery according to [1], wherein the positive electrode active material has a lattice constant of 8.240 angstroms or less.
[7] The positive electrode active material is mainly composed of a Li-Mn composite oxide having a spinel structure, and the oxide contains an element or an element that can be an oxide or oxide that melts at a temperature of 550 ° C to 900 ° C. In the above [1], which is a compound, or an active material that is granulated and sintered, consisting of a compound, or an element that can be dissolved or reacted with lithium or manganese, or an oxide that can be melted by reaction or an oxide The positive electrode active material for lithium ion secondary batteries as described.
[8] An element or a compound containing an element that can be an oxide or oxide that melts at a temperature of 550 ° C. to 900 ° C., or an oxide or oxide that melts or reacts with lithium or manganese. An element or a compound containing an element is at least one element selected from the group consisting of Bi, B, W, Mo, and Pb, or a compound that combines B 2 O 3 and LiF, or MnF 2 and LiF The positive electrode active material for a lithium ion secondary battery according to [7], which is a compound in which
[9] In a method for producing a positive electrode active material for a lithium ion secondary battery mainly composed of a Li-Mn composite oxide having a spinel structure, the pulverized product of the Li-Mn composite oxide having a spinel structure is 550 ° C. Contains an element or compound that can be an oxide or oxide that melts at a temperature of ˜900 ° C., or an element or element that can be dissolved or reacts with lithium or manganese to become an oxide or oxide that melts The manufacturing method of the positive electrode active material for lithium ion secondary batteries characterized by having the process of adding a compound, mixing, and granulating.
[10] The method for producing a positive electrode active material for a lithium ion secondary battery according to [9], which includes a step of sintering the granulated product in addition to the granulating step.
[11] In addition to the granulation step, the granulated product is heated at a rate of at least 100 ° C./min from the sintering shrinkage start temperature to a temperature higher by at least 100 ° C. and held at that temperature for 1 to 10 minutes. The method for producing a positive electrode active material for a lithium ion secondary battery according to the above [9], comprising a step of lowering the temperature to the sintering start temperature at a rate of at least 100 ° C./min and sintering.
[12] The method for producing a positive electrode active material for a lithium ion secondary battery according to [11], wherein sintering is performed using a rotary kiln.
[13] The sintering step includes at least one element selected from the group consisting of Bi, B, W, Mo, and Pb on the surface of the Li—Mn composite oxide particles, or a compound containing the element, or B 2 O [3 ] The method for producing a positive electrode active material for a lithium ion secondary battery according to [10], wherein the method is performed by melting and sintering a compound combining 3 and LiF or a compound combining MnF 2 and LiF.
[14] The method for producing a positive electrode active material for a lithium ion secondary battery according to [9], wherein the average particle size of the pulverized product of the Li-Mn composite oxide having a spinel structure is 5 μm or less.
[15] The method for producing a positive electrode active material for a lithium ion secondary battery according to [9], wherein the average particle size of the pulverized product of the Li—Mn composite oxide having a spinel structure is 3 μm or less.
[16] The method for producing a positive electrode active material for a lithium ion secondary battery according to [9], wherein the granulation step is performed by a spray granulation method, a stirring granulation method, a compression granulation method or a fluidized granulation method. .
[17] In the granulation step, an acrylic resin, a copolymer of isobutylene and maleic anhydride, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidene, hydroxypropyl cellulose, methyl cellulose, corn starch, gelatin, The method for producing a positive electrode active material for a lithium ion secondary battery according to the above [9], wherein at least one organic compound selected from the group consisting of lignin is used.
[18] The method for producing a positive electrode active material for a lithium ion secondary battery according to the above [17], which has a degreasing step at a temperature of 300 ° C. to 550 ° C. in a gas flow atmosphere containing air or oxygen.
[19] A positive electrode active material for a lithium ion secondary battery obtained by the method according to any one of [9] to [18].
[20] An electrode paste containing the positive electrode active material for a lithium ion secondary battery according to any one of [1] to [8].
[21] A positive electrode for a lithium ion secondary battery comprising the positive electrode active material for a lithium ion secondary battery according to any one of [1] to [8] or [19].
[22] A lithium ion secondary battery comprising the positive electrode for a lithium ion secondary battery according to [21].
[23] The lithium ion secondary battery according to [22], wherein the lithium ion secondary battery is a coin battery, a wound battery, a cylindrical battery, a prismatic battery, or a stacked battery.

本発明により造粒・焼成・整粒された正極活物質の一例（実施例１４）の走査電子顕微鏡写真（×15,000倍）である。It is a scanning electron micrograph (x15,000 times) of an example (Example 14) of the positive electrode active material granulated, fired, and sized according to the present invention. 本発明により造粒・焼成・整粒された正極活物質の一例（実施例１４）の粒径分布である。It is a particle size distribution of an example (Example 14) of the positive electrode active material granulated, fired, and sized according to the present invention.

以下、本発明を具体的に説明する。
本発明は、二次粒子の空隙率を従来品に比べ大きく減少させ１５％以下とした、スピネル構造を有するＬｉ−Ｍｎ系複合酸化物正極活物質に関する。また、本発明は、二次粒子の平均空隙率が１０％以下であり、従来品と比べそのサイクル特性の特に優れたスピネル構造を有するＬｉ−Ｍｎ系複合酸化物に関する。 Hereinafter, the present invention will be specifically described.
The present invention relates to a Li—Mn based composite oxide positive electrode active material having a spinel structure in which the porosity of secondary particles is greatly reduced to 15% or less compared to conventional products. In addition, the present invention relates to a Li—Mn composite oxide having a spinel structure in which the average porosity of secondary particles is 10% or less and the cycle characteristics are particularly excellent compared to conventional products.

すなわち、本発明におけるスピネル構造を有するリチウム−マンガン（Ｌｉ−Ｍｎ）系複合酸化物の正極活物質は、化学式ＬｉＭｎ2Ｏ4、Ｌｉ1+xＭｎ2-xＯ4（式中ｘは０＜ｘ＜０.２の範囲である。）または前記Ｍｎを、クロム、コバルト、アルミニウム、ニッケル、鉄、マグネシウムからなる群より選ばれる少なくとも１種の元素（化学式ではＭと略する）で置換した化学式Ｌｉ1+xＭｎ2-x-yＭyＯ4（式中ｘは０＜ｘ＜０.２の範囲であり、ｙは０＜ｙ＜０.４である。）で示される化合物を総称するものである。 That is, the positive electrode active material of a lithium-manganese (Li-Mn) based composite oxide having a spinel structure in the present invention has chemical formulas LiMn 2 O 4 , Li 1 + x Mn 2−x O 4 (where x is 0 < x <0.2) or a chemical formula in which Mn is substituted with at least one element selected from the group consisting of chromium, cobalt, aluminum, nickel, iron, and magnesium (abbreviated as M in the chemical formula). li 1 + x Mn 2-xy M y O 4 ( wherein x is in the range of 0 <x <0.2, y is 0 <y <0.4.) a general term of a compound represented by It is.

本発明においては、リチウムイオン二次電池用正極活物質は、前記スピネル構造を有するＬｉ−Ｍｎ系複合酸化物を主体とするものであって、二次粒子１個の空隙率が下記式（１）
空隙率（％）＝（Ａ／Ｂ）×１００ （１）
（Ａは二次粒子１個の断面に含まれるポアの総断面積であり、Ｂは二次粒子１個の断面積である。）で算出され、その平均空隙率が１５％以下であるものが使用される。 In the present invention, the positive electrode active material for a lithium ion secondary battery is mainly composed of the Li-Mn composite oxide having the spinel structure, and the porosity of one secondary particle is represented by the following formula (1 )
Porosity (%) = (A / B) × 100 (1)
(A is the total cross-sectional area of pores included in the cross section of one secondary particle, and B is the cross-sectional area of one secondary particle), and the average porosity is 15% or less Is used.

また、前記Ｌｉ−Ｍｎ系複合酸化物としては、好ましくは前記正極活物質の平均空隙率は１０％以下であって、一次粒子の平均粒子径が０.２〜３μｍであるものが使用される。
すなわち、正極活物質としてタップ密度が１.９ｇ／ｍｌを超えるためには、二次粒子の平均空隙率が１５％以下であることが必要である。二次粒子の平均空隙率は好ましくは１３％以下であり、さらに好ましくは１０％以下である。 Further, as the Li—Mn based composite oxide, those having an average porosity of 10% or less and an average primary particle diameter of 0.2 to 3 μm are preferably used. .
That is, in order for the tap density to exceed 1.9 g / ml as the positive electrode active material, the average porosity of secondary particles needs to be 15% or less. The average porosity of the secondary particles is preferably 13% or less, more preferably 10% or less.

一般的に複合酸化物の製造方法において、焼結温度を高くかつ焼結時間を長くして焼結収縮させて二次粒子の平均空隙率をできるだけ低減しようとすると、一次粒子は焼結収縮に伴い粒成長して大きくなってしまい、この材料を電池正極活物質に使用すると容量維持率が低下する。その結果、電池組立後の電池特性が悪化してしまう。   In general, in the composite oxide manufacturing method, if the sintering temperature is increased and the sintering time is increased to cause the shrinkage of the secondary particles to reduce the average porosity of the secondary particles as much as possible, the primary particles cause the sintering shrinkage. Accompanying this, the grains grow and become large, and when this material is used as a battery positive electrode active material, the capacity retention rate decreases. As a result, battery characteristics after battery assembly are deteriorated.

本発明者らは、粒成長を抑制して焼結収縮させる方法を鋭意研究した結果、熱機械試験機（Thermo-mechanical analysis）で測定した焼結収縮開始温度よりも少なくとも１００℃以上高い温度まで少なくとも１００℃／ｍｉｎの速度で昇温した後、１分〜１０分の時間保持後、該焼結収縮開始温度まで少なくとも１００℃／ｍｉｎの速度で降温することにより粒成長を抑制して焼結収縮できることを見出した。   As a result of diligent research on a method for suppressing grain growth and sintering shrinkage, the present inventors have achieved a temperature at least 100 ° C. higher than the sintering shrinkage initiation temperature measured by a thermo-mechanical analysis. After raising the temperature at a rate of at least 100 ° C./min, holding for 1 minute to 10 minutes, and then lowering the temperature to the sintering shrinkage start temperature at a rate of at least 100 ° C./min to suppress grain growth and sinter It was found that it can shrink.

ここで、焼結収縮開始温度とは、熱機械試験機で求めた収縮開始温度をいう。前記保持温度としては、焼結収縮開始温度よりも少なくとも１００℃以上高い温度であることが必要である。保持温度を焼結開始温度よりも１００℃未満に高くした程度では、焼結収縮速度が遅いため焼結時間が長く必要となり、その結果粒成長して一次粒子径が０.５μｍよりも大きくなってしまう。   Here, the sintering shrinkage start temperature refers to the shrinkage start temperature obtained with a thermomechanical tester. The holding temperature needs to be at least 100 ° C. higher than the sintering shrinkage start temperature. When the holding temperature is made lower than 100 ° C. below the sintering start temperature, the sintering shrinkage rate is slow, so that a longer sintering time is required. As a result, the grains grow and the primary particle diameter becomes larger than 0.5 μm. End up.

また、前記焼結工程において該焼結収縮開始温度よりも少なくとも１００℃以上の高い温度において、一次粒子径が０.２μｍ以上、かつ０.５μｍ以下であって、かつ優れた電池特性が得られる保持時間は、少なくとも１分以上、１０分以内である。保持時間が１分未満では熱伝達時間が短すぎて一次粒子径が０.２μｍ未満と小さく、結晶化も不十分となり、初期容量が小さくなる。保持時間が１０分を越えると、焼結収縮後も粒成長が進行するので、一次粒子が大きくなり容量維持率が低下する。   Further, in the sintering step, the primary particle diameter is 0.2 μm or more and 0.5 μm or less at a temperature at least 100 ° C. higher than the sintering shrinkage start temperature, and excellent battery characteristics are obtained. The holding time is at least 1 minute and within 10 minutes. If the holding time is less than 1 minute, the heat transfer time is too short, the primary particle size is as small as less than 0.2 μm, crystallization is insufficient, and the initial capacity is reduced. When the holding time exceeds 10 minutes, grain growth proceeds even after sintering shrinkage, so that the primary particles become large and the capacity retention rate decreases.

本発明においては、好ましくは保持時間は２分から８分、さらに好ましくは２分から５分とする。
焼結開始温度から保持温度までの温度領域において昇温速度と降温速度を少なくとも１００℃／分と限定したのは、粒成長が進行する温度領域での保持時間をできるだけ短くすることにより焼結収縮のみを進行させて粒成長を抑制するためである。
また、正極活物質のタップ密度が２.２ｇ／ｍｌを越えるためには、二次粒子の平均空隙率が１０％以下であることが必要であり、好ましくは７％以下、さらに好ましくは５％以下である。 In the present invention, the holding time is preferably 2 to 8 minutes, more preferably 2 to 5 minutes.
In the temperature range from the sintering start temperature to the holding temperature, the rate of temperature increase and the rate of temperature decrease was limited to at least 100 ° C./minute because the holding time in the temperature range where grain growth proceeds is made as short as possible. This is because the grain growth is suppressed only by proceeding.
Further, in order for the tap density of the positive electrode active material to exceed 2.2 g / ml, the average porosity of the secondary particles needs to be 10% or less, preferably 7% or less, more preferably 5%. It is as follows.

本発明における前記正極活物質の結晶子サイズは、４００〜９６０オングストロームが好ましい。結晶子サイズが４００オングストローム未満の場合では、結晶性が不十分のために電池における初期容量が低く、容量維持率が低くなる。一方、結晶子サイズが９６０オングストロームを超える場合には、容量維持率の低下が激しくなる。さらに具体的に好ましい結晶子サイズは５００〜９２０オングストロームであり、さらに望ましくは７００〜９２０オングストロームである。   The crystallite size of the positive electrode active material in the present invention is preferably 400 to 960 Å. When the crystallite size is less than 400 angstroms, the initial capacity of the battery is low because of insufficient crystallinity, and the capacity retention rate is low. On the other hand, when the crystallite size exceeds 960 angstroms, the capacity retention rate is drastically reduced. More specifically, the preferred crystallite size is 500 to 920 angstroms, and more desirably 700 to 920 angstroms.

また、本発明のスピネル構造を有するＬｉ−Ｍｎ系複合酸化物の正極活物質は、その格子定数が８.２４０オングストローム以下であることが好ましい。格子定数が８.２４０オングストロームを超えると電池の容量維持率の低下が激しくなる。従って、格子定数の好ましい範囲は、８.２３５オングストローム以下であり、さらに好ましくは８.２３３オングストローム以下である。   In addition, the positive electrode active material of the Li—Mn composite oxide having a spinel structure of the present invention preferably has a lattice constant of 8.240 angstroms or less. When the lattice constant exceeds 8.240 angstroms, the capacity retention rate of the battery is drastically reduced. Therefore, the preferable range of the lattice constant is 8.235 angstroms or less, and more preferably 8.233 angstroms or less.

スピネル構造を有するＬｉ−Ｍｎ系複合酸化物を主体とする本発明の正極活物質は、スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の焼成品を解砕後、得られる粉砕粒子（これは１次粒子の集合した二次粒子であり、好ましくは平均粒子径が０.５μｍ以下である。）に焼結促進助剤（造粒促進剤）を添加混合して造粒焼成した緻密な造粒粒子が使用される。ここで、緻密な造粒粒子とは、その酸化物の１次粒子間に空隙がないか、または少ないことを意味する。本発明の正極活物質は前記の緻密な造粒粒子であり、後記する焼結促進助剤を使用して形成される。   The positive electrode active material of the present invention mainly composed of a Li-Mn composite oxide having a spinel structure is obtained by crushing a fired product of a Li-Mn composite oxide having a spinel structure and then obtaining pulverized particles (this is 1 Dense particles obtained by adding and mixing a sintering acceleration aid (granulation accelerator) to secondary particles in which secondary particles are aggregated, preferably having an average particle size of 0.5 μm or less. Particles are used. Here, the dense granulated particles mean that there are no or few voids between the primary particles of the oxide. The positive electrode active material of the present invention is the above-mentioned dense granulated particles, and is formed using a sintering acceleration aid described later.

以下、本発明の正極活物質の製造方法について説明する。
スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の製造方法は、マンガン化合物とリチウム化合物の混合物、またはさらにマンガンと置換し得る異種元素を含む化合物を添加した混合物を大気中または酸素ガスフロー中において、３００〜８５０℃の温度で少なくとも１時間以上焼成すればよい。 Hereinafter, the manufacturing method of the positive electrode active material of this invention is demonstrated.
In a method for producing a Li-Mn composite oxide having a spinel structure, a mixture of a manganese compound and a lithium compound, or a mixture to which a compound containing a different element that can be substituted with manganese is further added in the atmosphere or in an oxygen gas flow. The baking may be performed at a temperature of 300 to 850 ° C. for at least 1 hour.

スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の結晶性については特に制限はなく、未反応のリチウム化合物とマンガン酸化物が残留していてもかまわない。結晶性の高いスピネル構造を有するＬｉ−Ｍｎ系複合酸化物を使用する場合、格子定数について特に制約はないが、格子定数が８.２４０オングストローム以下となる正極活物質に使用すると、容量維持率の低下が抑えられる。   There is no restriction | limiting in particular about the crystallinity of Li-Mn type complex oxide which has a spinel structure, The unreacted lithium compound and manganese oxide may remain | survive. When using a Li—Mn composite oxide having a spinel structure with high crystallinity, there is no particular limitation on the lattice constant, but when used for a positive electrode active material having a lattice constant of 8.240 angstroms or less, the capacity retention rate is reduced. Reduction is suppressed.

スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の原料は、特に制限を受けないが、好ましくは公知のマンガン化合物、例えば二酸化マンガン、三二酸化マンガン、四三酸化マンガン、水和マンガン酸化物、炭酸マンガン、硝酸マンガンなどが使用でき、またリチウム化合物としては水酸化リチウム、炭酸リチウム、硝酸リチウムなどが使用できる。
また望ましくは、前記マンガン化合物としては、正極活物質に適応させた時の電池特性が優れているリチウム化合物と低温で反応しやすい炭酸マンガンが好ましい。 The raw material of the Li-Mn composite oxide having a spinel structure is not particularly limited, but is preferably a known manganese compound such as manganese dioxide, manganese sesquioxide, manganese trioxide, hydrated manganese oxide, manganese carbonate. Manganese nitrate can be used, and lithium hydroxide, lithium carbonate, lithium nitrate and the like can be used as the lithium compound.
Desirably, the manganese compound is preferably manganese carbonate that easily reacts at a low temperature with a lithium compound having excellent battery characteristics when applied to a positive electrode active material.

マンガン置換型のＬｉ1+xＭｎ2-x-yＭyＯ4で示されるＬｉ−Ｍｎ−Ｍ（異種元素）系複合酸化物の製造には、前記マンガン化合物と前記リチウム化合物の原料と共にクロム、コバルト、アルミニウム、ニッケル、鉄、マグネシウムからなる群より選ばれる少なくとも１種の元素が使用される。そして、この異種元素Ｍを含む化合物としては、加熱反応によって前記酸化物を形成し得る化合物なら何でもよく、前記加熱反応の際にリチウム化合物やマンガン化合物と共に添加すればよい。 The preparation of manganese substituted for Li 1 + x Mn Li-Mn -M ( different element) indicated by the 2-xy M y O 4 based complex oxide, chromium together with the raw material of the manganese compound and the lithium compound, a cobalt At least one element selected from the group consisting of aluminum, nickel, iron and magnesium is used. The compound containing the different element M may be any compound that can form the oxide by a heating reaction, and may be added together with a lithium compound or a manganese compound in the heating reaction.

前記のスピネル構造を有するＬｉ−Ｍｎ系複合酸化物の二次粒子の解砕・粉砕方法については特に制限はなく公知の解砕機や粉砕機が使用できる。例えば、媒体撹拌式粉砕機、ボールミル、ペイントシェーカー、ジェットミル、ローラーミルなどが挙げられる。解砕・粉砕方式は乾式でもよいし、湿式でもよい。湿式の際に使用できる溶媒についても特に制限はなく、例えば水、アルコールなどが使用される。   The method for crushing and crushing secondary particles of the Li—Mn composite oxide having the spinel structure is not particularly limited, and known crushers and crushers can be used. Examples thereof include a medium agitating pulverizer, a ball mill, a paint shaker, a jet mill, and a roller mill. The crushing and pulverizing method may be dry or wet. There is no restriction | limiting in particular also about the solvent which can be used in the case of wet, For example, water, alcohol, etc. are used.

焼結収縮を促進させるという観点から、解砕・粉砕後のスピネル構造を有するＬｉ−Ｍｎ系複合酸化物の粒度が重要である。
粒度はレーザー式粒度分布測定器で測定した時の平均粒子径が５μｍ以下であることが好ましい。さらに好ましくは、５μｍ以上の粗大粒子を含まず平均粒子径が２μｍ以下のものである。さらに好ましくは、３μｍを越える粗大粒子を含まず平均粒子径が１.５μｍ以下のもの、さらには、０.５μｍ以下、さらに好ましくは０.３μｍ以下、特に好ましくは０.２μｍ以下のものである。 From the viewpoint of promoting sintering shrinkage, the particle size of the Li—Mn based composite oxide having a spinel structure after pulverization and pulverization is important.
The particle size is preferably 5 μm or less in average particle size as measured with a laser particle size distribution analyzer. More preferably, the average particle diameter is 2 μm or less without including coarse particles of 5 μm or more. More preferably, it does not contain coarse particles exceeding 3 μm and has an average particle size of 1.5 μm or less, more preferably 0.5 μm or less, still more preferably 0.3 μm or less, and particularly preferably 0.2 μm or less. .

解砕・粉砕したＬｉ−Ｍｎ系複合酸化物粒子と焼結促進助剤との混合方法には特に制限はなく、例えば前記した媒体撹拌式粉砕機、ボールミル、ペイントシェーカー、混合ミキサーなどが使用できる。混合方式についても乾式、湿式どちらでもよい。Ｌｉ−Ｍｎ系複合酸化物を解砕・粉砕する際に焼結促進助剤を添加して混合を同時に行ってもよい。
焼結促進助剤は、Ｌｉ−Ｍｎ系複合酸化物粒子の解砕・粉砕粒子を造粒のために焼結できるものであればよく、より好ましくは、９００℃以下の温度で溶融する化合物、例えば５５０℃〜９００℃の温度で溶融可能な酸化物または酸化物になり得る前駆体、もしくはリチウムまたはマンガンと固溶するかまたは反応して溶融する酸化物または酸化物になり得る化合物であればよい。 There are no particular limitations on the method of mixing the pulverized and pulverized Li-Mn composite oxide particles and the sintering accelerating aid. For example, the above-mentioned medium agitating pulverizer, ball mill, paint shaker, mixing mixer, etc. can be used. . The mixing method may be either dry or wet. When pulverizing and pulverizing the Li—Mn-based composite oxide, a sintering promoting aid may be added and mixed at the same time.
The sintering promoting auxiliary agent only needs to be capable of sintering the pulverized / pulverized particles of Li-Mn composite oxide particles for granulation, more preferably a compound that melts at a temperature of 900 ° C. or lower, For example, a precursor capable of becoming an oxide or oxide that can be melted at a temperature of 550 ° C. to 900 ° C., or a compound that can be dissolved or reacted with lithium or manganese to become an oxide or oxide that melts by reaction. Good.

焼結促進助剤としては、例えばＢｉ、Ｂ、Ｗ、Ｍｏ、Ｐｂなどの元素を含む化合物が挙げられ、またこれらの化合物を任意に組み合わせて使用してもよい。また、Ｂ2Ｏ3とＬｉＦを組み合わせた化合物またはＭｎＦ2とＬｉＦを組み合わせた化合物も使用される。中でも、Ｂｉ、Ｂ、Ｗの元素を含む化合物は焼結収縮効果が大きいので好ましい。 Examples of the sintering acceleration aid include compounds containing elements such as Bi, B, W, Mo, and Pb, and these compounds may be used in any combination. A compound in which B 2 O 3 and LiF are combined or a compound in which MnF 2 and LiF are combined is also used. Among these, compounds containing Bi, B, and W elements are preferable because they have a large sintering shrinkage effect.

Ｂｉ化合物としては、例えば三酸化ビスマス、硝酸ビスマス、安息臭酸ビスマス、オキシ酢酸ビスマス、オキシ炭酸ビスマス、クエン酸ビスマス、水酸化ビスマスなどが挙げられる。また、Ｂ化合物としては、三二酸化硼素、炭化硼素、窒化硼素、硼酸などが挙げられる。Ｗ化合物としては、二酸化タングステン、三酸化タングステンなどが挙げられる。   Examples of the Bi compound include bismuth trioxide, bismuth nitrate, bismuth benzoate, bismuth oxyacetate, bismuth oxycarbonate, bismuth citrate, and bismuth hydroxide. Examples of the B compound include boron trioxide, boron carbide, boron nitride, and boric acid. Examples of the W compound include tungsten dioxide and tungsten trioxide.

焼結促進助剤の添加量は、添加金属元素換算でＬｉ−Ｍｎ系複合酸化物中のＭｎ１モルに対して、０.０００１〜０.０５モルの範囲内が好ましい。添加金属元素換算での添加量が、０.０００１モル未満では焼結収縮効果が得られず、０.０５モルを超えると活物質の初期容量が小さくなる。好ましい添加量は０.００５〜０.０３モルである。   The addition amount of the sintering accelerating aid is preferably in the range of 0.0001 to 0.05 mol with respect to 1 mol of Mn in the Li-Mn composite oxide in terms of added metal element. If the added amount in terms of added metal element is less than 0.0001 mol, the sintering shrinkage effect cannot be obtained, and if it exceeds 0.05 mol, the initial capacity of the active material becomes small. A preferable addition amount is 0.005 to 0.03 mol.

焼結促進助剤は、粉末状態で使用しても溶媒に溶解した液体状態で使用しても構わない。粉末状態で添加する場合、焼結促進助剤の平均粒子径は５０μｍ以下が好ましく、さらに１０μｍ以下が好ましく、３μｍ以下が一層好ましい。焼結促進助剤は造粒／焼結前に添加することが好ましいが、造粒後焼結促進助剤が溶融できる温度で造粒物に含浸させ、焼結させても構わない。   The sintering aid may be used in a powder state or in a liquid state dissolved in a solvent. When added in a powder state, the average particle size of the sintering accelerator aid is preferably 50 μm or less, more preferably 10 μm or less, and even more preferably 3 μm or less. The sintering promoting aid is preferably added before granulation / sintering, but the granulated product may be impregnated and sintered at a temperature at which the sintering promoting aid can be melted after granulation.

焼結促進助剤は、焼成後において電池に使用される正極材料中に残存されることが多く、例えば本発明における製造方法において使用される前記焼結促進助剤が正極活物質に残存していることが分析により検知される。   In many cases, the sintering accelerator aid remains in the positive electrode material used in the battery after firing. For example, the sintering accelerator assistant used in the production method of the present invention remains in the cathode active material. It is detected by analysis.

次に造粒方法について説明する。
造粒方法としては、前記焼結促進助剤を使用して噴霧造粒方法、流動造粒方法、圧縮造粒方法、撹拌造粒方法などが挙げられ、また媒体流動乾燥や媒体振動乾燥などの併用をしてもよい。 Next, the granulation method will be described.
Examples of the granulation method include spray granulation method, fluidized granulation method, compression granulation method, stirring granulation method and the like using the above-mentioned sintering acceleration aid, and also include medium fluidized drying and medium vibration drying. You may use together.

本発明においては緻密な二次粒子（造粒粒子も含む）が形成できればよく、特に造粒の形成方法に制約はない。撹拌造粒と圧縮造粒は、二次粒子の密度が高くなるため、また噴霧造粒は造粒粒子形状が真球状となるため特に好ましい。撹拌造粒器の例としては、パウレック（株）社製バーチィカルグラニュレーターや不二パウダル（株）社製スパルタンリューザーなどが挙げられ、圧縮造粒器の例としては、栗本鉄工（株）製ローラーコンパクターＭＲＣＰ−２００型などが挙げられる。噴霧造粒器の例としては、アシザワニロアトマイザー（株）モービルマイナー型スプレードライヤーなどが挙げられる。   In the present invention, it is sufficient that dense secondary particles (including granulated particles) can be formed, and there is no particular limitation on the granulation formation method. Agitation granulation and compression granulation are particularly preferred because the density of secondary particles is high, and spray granulation is particularly preferred because the granulated particle shape is a true sphere. Examples of the agitating granulator include a vertical granulator manufactured by Paulek Co., Ltd. and a Spartan Luther manufactured by Fuji Paudal Co., Ltd. Examples of the compression granulator include Kurimoto Tekko Co., Ltd. Examples thereof include a roller compactor MRCP-200 type. As an example of a spray granulator, Ashizawairo atomizer Co., Ltd. Mobile minor type spray dryer etc. are mentioned.

造粒する二次粒子のサイズには特に制約はない。造粒した二次粒子の平均粒子径が大きすぎる場合には、造粒直後または焼結後に軽く解砕・粉砕し分級する等して整粒し、希望する粒度にすればよい。一般的には、平均粒子径１０〜２０μｍのサイズの二次粒子が好まれる。   There are no particular restrictions on the size of the secondary particles to be granulated. When the average particle size of the granulated secondary particles is too large, the particles may be crushed, pulverized and classified immediately after granulation or after sintering, and the particle size may be adjusted to a desired particle size. In general, secondary particles having an average particle size of 10 to 20 μm are preferred.

造粒効率を高めるためには、有機物系の造粒助剤を添加してもよい。
このような造粒助剤としては、アクリル系樹脂、イソブチレンと無水マレイン酸との共重合体、ポリビニルアルコール、ポリエチレングリコール、ポリビニルピロリデン、ハイドロキシプロピルセルロース、メチルセルロース、コーンスターチ、ゼラチン、リグニンなどが挙げられる。 In order to increase the granulation efficiency, an organic granulation aid may be added.
Examples of such granulation aids include acrylic resins, copolymers of isobutylene and maleic anhydride, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidene, hydroxypropyl cellulose, methyl cellulose, corn starch, gelatin, and lignin. .

造粒助剤の添加方法は、粉末状態で添加するよりも、水やアルコールなどの有機溶媒に溶解して噴霧するなどの方法で添加し造粒する方が効率がよい。造粒助剤の添加量としては、スピネル構造を有するＬｉ−Ｍｎ系複合酸化物及び焼結促進助剤１００質量部に対して５質量部以下が好ましく、さらに好ましくは２質量部以下である。   The method of adding the granulation aid is more efficient than adding it in a powdered state by adding and granulating it by dissolving it in an organic solvent such as water or alcohol. The addition amount of the granulation aid is preferably 5 parts by mass or less, more preferably 2 parts by mass or less, with respect to 100 parts by mass of the Li-Mn composite oxide having a spinel structure and the sintering acceleration aid.

次に造粒した二次粒子の焼成方法について説明する。
造粒した粒子の脱脂方法は、大気中または酸素を含有するガスフロー中で３００〜５５０℃の温度範囲で１０分以上保持することにより行う。脱脂した造粒物のカーボン残留量は、０.１％以下であることが好ましい。 Next, a method for firing the granulated secondary particles will be described.
The method for degreasing the granulated particles is carried out by holding for 10 minutes or more in the temperature range of 300 to 550 ° C. in the air or in a gas flow containing oxygen. The carbon residue in the degreased granulated product is preferably 0.1% or less.

脱脂後の造粒粒子の焼成は、粒成長を抑制して焼結収縮を進行させるために、大気中または酸素を含有するガスフロー中、５５０℃〜９００℃の温度範囲で１分間以上、焼結促進助剤がＬｉ−Ｍｎ系複合酸化物粒子表面で溶融した状態で保持して焼結収縮させ二次粒子の緻密化をはかることができる。   Firing of the granulated particles after degreasing is performed for 1 minute or more in the temperature range of 550 ° C. to 900 ° C. in the air or in a gas flow containing oxygen in order to suppress grain growth and advance sintering shrinkage. The sintering promoting aid can be held in a molten state on the surface of the Li—Mn composite oxide particles, sintered and shrunk, and the secondary particles can be densified.

また、本発明では、脱脂後の造粒粒子の焼成は、粒成長を抑制して焼結収縮を進行させるために大気中または酸素を含有するガスフロー中で熱機械試験機で測定した焼結収縮開始温度よりも、少なくとも１００℃高い温度まで、少なくとも１００℃／ｍｉｎの速度で昇温して１分〜１０分間保持した後、少なくとも１００℃／ｍｉｎの速度で焼結収縮開始温度まで降温して焼結収縮させ、二次粒子の緻密化をはかる。常温と焼結収縮開始温度との間の昇温速度と降温速度については、従来通り１０℃／ｍｉｎ以下でも構わない。   Further, in the present invention, the calcination of the granulated particles after degreasing is the sintering measured by a thermomechanical tester in the atmosphere or in a gas flow containing oxygen in order to suppress the grain growth and advance the sintering shrinkage. After raising the temperature at a rate of at least 100 ° C./min to a temperature that is at least 100 ° C. higher than the shrinkage start temperature and holding for 1 to 10 minutes, the temperature is lowered to the sintering shrinkage start temperature at a rate of at least 100 ° C./min. Sintering shrinks to densify the secondary particles. About the temperature increase rate and temperature decrease rate between normal temperature and sintering shrinkage start temperature, it may be 10 degrees C / min or less as usual.

また、前述の有機物系の造粒助剤を使用しない造粒物の粒子の焼成も、大気中または酸素を含有するガスフロー雰囲気中で同様に焼結収縮させ、二次粒子の緻密化をはかることができる。
本発明の正極活物質及び本発明の製造方法から得られる正極活物質は、従来のＬｉ−Ｍｎ系複合酸化物と同様の方法に準じてリチウムイオン二次電池用正極に加工され、電池の評価に供される。 In addition, the firing of the granulated particles without using the above-mentioned organic-based granulating aid is similarly performed by sintering and shrinking in the air or in a gas flow atmosphere containing oxygen, thereby densifying the secondary particles. be able to.
The positive electrode active material of the present invention and the positive electrode active material obtained from the production method of the present invention are processed into a positive electrode for a lithium ion secondary battery according to the same method as a conventional Li-Mn composite oxide, and evaluation of the battery To be served.

以下、本発明の前記正極活物質を非水二次電池の正極材料として使用する例について説明する。
先ず正極材料は、前記正極活物質とカーボンブラックまたは黒鉛などの導電性付与剤、及びポリフツ化ビニリデンなどのバインダー（結合材）を溶解した溶液（例えば、Ｎ−メチルピロリドンなど）を所定割合で混練して、電極ペーストとして集電体に塗布し、次いで乾燥後にロールプレスなどで加圧して製造される。集電体には、アルミニウム、ステンレス、チタン等の公知の金属製集電体が使用される。 Hereinafter, the example which uses the said positive electrode active material of this invention as a positive electrode material of a non-aqueous secondary battery is demonstrated.
First, as a positive electrode material, a solution (for example, N-methylpyrrolidone) in which a positive electrode active material, a conductivity imparting agent such as carbon black or graphite, and a binder (binding material) such as polyvinylidene fluoride are dissolved is kneaded at a predetermined ratio. The electrode paste is applied to the current collector, and then dried and pressed by a roll press or the like. As the current collector, a known metal current collector such as aluminum, stainless steel or titanium is used.

本発明の非水二次電池において使用される電解液中の電解質塩としては、フッ素を含有する公知のリチウム塩が使用できる。例えば、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＡｓＦ6、ＬｉＣＦ3ＳＯ3、ＬｉＣ4Ｆ9ＳＯ3などが使用できる。非水二次電池の電解液は、前記フッ素を含有する公知のリチウム塩の少なくとも１種の電解質を非水系電解液に溶解して用いる。前記非水系電解液の非水溶媒には、化学的及び電気化学的に安定な非プロトン性のものが使用できる。 As the electrolyte salt in the electrolytic solution used in the nonaqueous secondary battery of the present invention, a known lithium salt containing fluorine can be used. For example, LiPF 6 , LiBF 4 , LiN (CF 3 SO 2 ) 2 , LiAsF 6 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 can be used. The electrolyte solution of the non-aqueous secondary battery is used by dissolving at least one electrolyte of a known lithium salt containing fluorine in a non-aqueous electrolyte solution. As the non-aqueous solvent of the non-aqueous electrolyte solution, a chemically and electrochemically stable aprotic solvent can be used.

例えば、炭酸ジメチル、炭酸プロピレン、炭酸エチレン、炭酸メチルエチル、炭酸メチルプロピル、炭酸メチルイソプロピル、炭酸メチルブチル、炭酸ジエチル、炭酸エチルプロピル、炭酸ジイソプロピル、炭酸ジブチル、炭酸１，２−ブチレン、炭酸エチルイソプロピル、炭酸エチルブチル等の炭酸エステル類が挙げられる。また、トリエチレングリコールメチルエーテル、テトラエチレングリコールジメチルエーテル等のオリゴエーテル類、プロピオン酸メチル、蟻酸メチル等の脂肪族エステル類、ベンゾニトリル、トルニトリル等の芳香族ニトリル類、ジメチルホルムアミド等のアミド類、ジメチルスルホキシド等のスルホキシド類、γ−ブチロラクトン等のラクトン類、スルホラン等の硫黄化合物、Ｎ−ビニルピロリドン、Ｎ−メチルピロリドン、リン酸エステル類等も例示できる。中でも、炭酸エステル類、脂肪族エステル類、エーテル類が好ましい。   For example, dimethyl carbonate, propylene carbonate, ethylene carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, diethyl carbonate, ethyl propyl carbonate, diisopropyl carbonate, dibutyl carbonate, 1,2-butylene carbonate, ethyl isopropyl carbonate, Examples thereof include carbonates such as ethylbutyl carbonate. Also, oligoethers such as triethylene glycol methyl ether and tetraethylene glycol dimethyl ether, aliphatic esters such as methyl propionate and methyl formate, aromatic nitriles such as benzonitrile and tolunitrile, amides such as dimethylformamide, dimethyl Examples include sulfoxides such as sulfoxide, lactones such as γ-butyrolactone, sulfur compounds such as sulfolane, N-vinylpyrrolidone, N-methylpyrrolidone, and phosphate esters. Of these, carbonic acid esters, aliphatic esters, and ethers are preferable.

本発明の非水二次電池において使用される負極としては、リチウムイオンを可逆的に吸蔵放出可能な材料であれば特に制限はなく、例えば、リチウム金属、リチウム合金、炭素材料（黒鉛を含む）、金属カルコゲン等が使用できる。   The negative electrode used in the nonaqueous secondary battery of the present invention is not particularly limited as long as it is a material capable of reversibly occluding and releasing lithium ions. For example, lithium metal, lithium alloy, carbon material (including graphite) Metal chalcogen etc. can be used.

次に、電極特性の評価方法について説明する。
正極活物質、導電材としてキャボット製バルカンＸＣ−７２、結着剤として四フッ化エチレン樹脂を質量比で、５０：３４：１６の割合で混合し、その混合物をトルエンで１２時間膨潤する。膨潤した混合物をアルミニウムエキスバンドメタルからなる集電体上に塗り、２ｔ／ｃｍ2で加圧成形し、トルエンを乾燥して正極とする。一方、負極としては、リチウム箔を用いる。 Next, a method for evaluating electrode characteristics will be described.
A positive electrode active material, Cabot Vulcan XC-72 as a conductive material, and tetrafluoroethylene resin as a binder are mixed in a mass ratio of 50:34:16, and the mixture is swollen with toluene for 12 hours. The swollen mixture is applied onto a current collector made of aluminum expanded metal, and pressure-molded at 2 t / cm 2 , and toluene is dried to form a positive electrode. On the other hand, lithium foil is used as the negative electrode.

電解液としては、炭酸プロピレンと炭酸ジメチルを体積比で１対２の割合で混合した混合液にＬｉＰＦ6を１モル／リットルの濃度で溶解したものを用いる。セパレーターとしては、ポリプロピレン製のものを用い、負極のデンドライト生成が原因のマイクロショートを防止する目的で、補強材としてシリカ繊維ろ紙（例えば、アドバンテック東洋（株）製のＱＲ−１００）をも併用する。これら正極、負極、電解液、セパレーターと補強材を用いて、２０１６型コイン電池を作製し、６０℃に設定した恒温槽内で５００回の充電・放電サイクル試験を行う。測定条件は、定電流定電圧充電−定電流放電、充電及び放電レート１Ｃ（充電開始から２.５時間で充電休止）、走査電圧３.１Ｖ〜４.３Ｖである。 As an electrolytic solution, a solution obtained by dissolving LiPF 6 at a concentration of 1 mol / liter in a mixed solution in which propylene carbonate and dimethyl carbonate are mixed at a volume ratio of 1: 2 is used. A separator made of polypropylene is used, and silica fiber filter paper (for example, QR-100 manufactured by Advantech Toyo Co., Ltd.) is also used as a reinforcing material for the purpose of preventing micro shorts caused by dendrite formation of the negative electrode. . Using these positive electrode, negative electrode, electrolytic solution, separator and reinforcing material, a 2016 coin battery is prepared and subjected to 500 charge / discharge cycle tests in a thermostat set at 60 ° C. The measurement conditions are constant current constant voltage charge-constant current discharge, charge and discharge rate 1C (charge suspend in 2.5 hours from the start of charge), and scanning voltage 3.1V to 4.3V.

以下、実施例および比較例を挙げて本発明を説明するが、本発明は下記の記載により何ら限定されるものではない。
なお、下記の例及び表１〜３に示す正極活物質の特性は以下の方法により測定した。
１）平均粒子径及び比表面積
レーザー式粒度測定器としてCILAS社製GRANULOMETER（HR850型）を使用して、界面活性剤（花王製デモールＰ）０.２％水溶液中に超音波で粉体を分散して粒度分布を測定して求めた。
２）タップ密度
（株）蔵持科学機器製作所製タップピングマシン（KRS-409型）を使用して、振幅８ｍｍで２０００回タッピング後測定した。 EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated, this invention is not limited at all by the following description.
In addition, the characteristic of the positive electrode active material shown to the following example and Tables 1-3 was measured with the following method.
1) Average particle size and specific surface area Disperse the powder by ultrasonic wave in 0.2% aqueous solution of surfactant (Kao Demol P) using CILAS GRANULOMETER (HR850 type) as a laser particle sizer. Then, the particle size distribution was measured and determined.
2) Tap density Measured after tapping 2000 times with an amplitude of 8 mm using a tapping machine (KRS-409 type) manufactured by Kuramochi Scientific Instruments.

３）空隙率
正極活物質と熱硬化性樹脂と混合、硬化することにより正極活物質を樹脂中に埋め込み、ミクロトームで切断し、鏡面研磨して、研磨面を走査電子顕微鏡（ＳＥＭ）で写真撮影した。得られたＳＥＭ写真中の二次粒子１個の断面積Ｂとその二次粒子断面中に含まれる全ポアの総断面積Ａを画像解析装置で計測し、以下の式で二次粒子１個の空隙率Ｃ（％）を計算し、ランダムに選択した二次粒子５０個の空隙率の平均値を平均空隙率とした。
Ｃ（％）＝（Ａ／Ｂ）×１００
４）結晶子サイズ
以下の条件にて測定した（１１１）面のＸ線回折ピークからScherrerの式を用いて算出した。 3) Porosity The positive electrode active material and thermosetting resin are mixed and cured to embed the positive electrode active material in the resin, cut with a microtome, mirror polished, and photograph the polished surface with a scanning electron microscope (SEM) did. The cross-sectional area B of one secondary particle in the obtained SEM photograph and the total cross-sectional area A of all the pores contained in the cross-section of the secondary particle are measured with an image analyzer, and one secondary particle is expressed by the following formula. The porosity C (%) was calculated, and the average value of the porosity of 50 randomly selected secondary particles was defined as the average porosity.
C (%) = (A / B) × 100
4) Crystallite size It calculated using the Scherrer formula from the X-ray diffraction peak of the (111) plane measured under the following conditions.

すなわち、結晶子の外形が立方体で大きさの分布を持たないと仮定して、結晶子の大きさによる回折線の広がりを半値幅より算出した値を使用した。なお、単結晶シリコンを炭化タングステン製サンプルミルで粉砕後、４４μｍ以下に篩い分けした粉末を外部標準として、装置定数更正曲線を作成した。   That is, assuming that the outer shape of the crystallite is a cube and does not have a size distribution, a value obtained by calculating the diffraction line broadening due to the crystallite size from the half width was used. In addition, after pulverizing the single crystal silicon with a sample mill made of tungsten carbide and using a powder obtained by sieving to 44 μm or less as an external standard, an apparatus constant correction curve was prepared.

［測定装置及び方法］
理学電機（株）製Ｒａｄタイプゴニオメータ、測定モードとして連続測定、解析ソフトには理学電機（株）RINT2000シリーズのアプリケーションソフトを使用し、結晶子の大きさの解析を行った。
測定条件は、Ｘ線（ＣｕＫα線）、出力５０ｋＶ、１８０ｍＡ、スリット幅（３ケ所）は１／２゜、１／２゜、０.１５ｍｍ、スキャン方法には２θ／θ法、スキャン速度は１゜／ｍｉｎ、測定範囲（２θ）は１７〜２０゜、ステップは０.００４゜である。なお、この方法で得られる結晶子サイズの精度は、±３０オングストロームである。 [Measurement apparatus and method]
Rad type goniometer manufactured by Rigaku Corporation, continuous measurement as measurement mode, and RINT2000 series application software was used as analysis software, and the size of crystallites was analyzed.
The measurement conditions are X-ray (CuKα ray), output 50 kV, 180 mA, slit width (3 places) 1/2 °, 1/2 °, 0.15 mm, scan method 2θ / θ method, scan speed 1 The measurement range (2θ) is 17 to 20 °, and the step is 0.004 °. The accuracy of the crystallite size obtained by this method is ± 30 angstroms.

５）格子定数
J. B. Nelson，D. P. Rileyの方法（Proc. Phys. Soc., 57, 160（1945））で求めた。
６）比表面積
ＢＥＴ法で測定した。
７）造粒粒子の形状
正極活物質の造粒品をＳＥＭで写真撮影し、画像解析して、二次粒子の円形度（円形度＝４π［面積／（周囲長さ）2］）と針状比（針状比＝針絶対最大長／対角幅）を求めた。各サンプルについて、それぞれ二次粒子２００個を計測し、その平均値を求めた。 5) Lattice constant
JB Nelson and DP Riley's method (Proc. Phys. Soc., 57 , 160 (1945)).
6) Specific surface area Measured by the BET method.
7) Shape of granulated particles Photographed granulated product of positive electrode active material with SEM, image analysis, secondary particle circularity (circularity = 4π [area / (perimeter length) 2 ]) and needle The shape ratio (needle ratio = needle absolute maximum length / diagonal width) was determined. For each sample, 200 secondary particles were measured, and the average value was obtained.

実施例１
Ｌｉ／Ｍｎ原子比が０.５１の組成となるように、比表面積２２ｍ2／ｇの炭酸マンガン（中央電気工業（株）製、Ｃ２−１０）と炭酸リチウム（本庄ケミカル（株）製、３Ｎ）をボールミルで混合し、大気雰囲気中加熱速度２００℃／ｈｒで室温から６５０℃まで昇温してその温度に４時間保持してＬｉ−Ｍｎ系複合酸化物を合成した。合成物中には、Ｌｉ−Ｍｎ系複合酸化物以外にごく微量の三二酸化マンガンがＸ線解析装置（ＸＲＤ）で検出された。レーザー式粒度分布測定器で測定した合成物の平均粒子径は１０μｍであり、比表面積は７.７ｍ2／ｇであった。 Example 1
Manganese carbonate (Chuo Electric Industry Co., Ltd., C2-10) having a specific surface area of 22 m 2 / g and lithium carbonate (Honjo Chemical Co., Ltd. 3N) so that the Li / Mn atomic ratio is 0.51. ) Was mixed with a ball mill, and the temperature was raised from room temperature to 650 ° C. at a heating rate of 200 ° C./hr in an air atmosphere and kept at that temperature for 4 hours to synthesize a Li—Mn-based composite oxide. In the composite, a very small amount of manganese sesquioxide other than the Li—Mn composite oxide was detected by an X-ray analyzer (XRD). The average particle size of the synthesized product measured with a laser particle size distribution analyzer was 10 μm, and the specific surface area was 7.7 m 2 / g.

得られたスピネル構造を有するＬｉ−Ｍｎ系複合酸化物をエタノール溶媒に分散して湿式ボールミルで粉砕して、平均粒子径を０.５μｍにした。測定の結果、粉砕粉には３μｍ以上の大きな粒子は含まれておらず、比表面積は２７.８ｍ2／ｇであった。この粉砕粉に、Ｂｉ／Ｍｎの原子比が０.００２６の割合となるように平均粒子径が２μｍの酸化ビスマスを添加混合して、不二パウダル（株）社製スパルタンリューザーＲＭＯ−６Ｈで撹拌造粒した。 The obtained Li-Mn composite oxide having a spinel structure was dispersed in an ethanol solvent and pulverized with a wet ball mill to make the average particle size 0.5 μm. As a result of the measurement, the pulverized powder did not contain large particles of 3 μm or more, and the specific surface area was 27.8 m 2 / g. To this pulverized powder, bismuth oxide having an average particle diameter of 2 μm was added and mixed so that the atomic ratio of Bi / Mn was 0.0026, and the mixture was mixed with Fuji Powder Co., Ltd. Spartan Luzer RMO-6H. Agitation granulation was performed.

Ｌｉ−Ｍｎ系複合酸化物と酸化ビスマスの混合粉１００質量部に対して造粒助剤としてポリビニルアルコール１.５質量部を水溶液に溶かして添加し、１６分間造粒した。得られた造粒物をミキサーで軽く解砕・粉砕し、風力分級機で平均粒子径１５μｍに整粒した。整粒後の造粒物のタップ密度は１.６５ｇ／ｍｌであった。   As a granulation aid, 1.5 parts by mass of polyvinyl alcohol was dissolved in an aqueous solution and added to 100 parts by mass of the mixed powder of Li-Mn composite oxide and bismuth oxide, and granulated for 16 minutes. The obtained granulated material was lightly crushed and pulverized with a mixer, and sized with an air classifier to an average particle size of 15 μm. The tap density of the granulated product after the sizing was 1.65 g / ml.

得られた造粒物を大気中５００℃で２時間保持して脱脂処理（ポリビニルアルコールを分解）後、大気中２００℃／ｈｒで昇温し７５０℃に２０時間保持して正極活物質を得た。ここで製造された正極活物質は、ＩＣＰ−ＡＥＳ法（誘導結合プラズマ発光分析法）により前記酸化ビスマスのＢｉ元素を仕込み組成比相当含むことが確認された。   The obtained granulated product is kept in the atmosphere at 500 ° C. for 2 hours and degreased (polyvinyl alcohol is decomposed), then heated in the atmosphere at 200 ° C./hr and kept at 750 ° C. for 20 hours to obtain a positive electrode active material. It was. The positive electrode active material produced here was confirmed to contain the Bi element of the bismuth oxide by an ICP-AES method (inductively coupled plasma emission analysis method) and to contain the composition ratio.

得られた正極活物質の平均空隙率は１１.２％であった。また、正極活物質のタップ密度は１.９６ｇ／ｍｌであり、結晶子サイズは８８０オングストロームであり、格子定数は８.２３３オングストロームであった。
上記の正極活物質を用いてコイン型電池を次のようにして作製した。正極活物質、導電材であるカーボンブラック、Ｎ−メチル−２−ピロリドンに溶解したポリフッ化ビニリデンを質量比で８０：１０：１０の割合で混練し、アルミニウム箔上に塗布し加圧プレスして正極とした。負極としては所定厚みのリチウム箔を用いた。電解液としては、炭酸プロピレンと炭酸ジメチルを体積比で１：２の割合で混合した混合液に、ＬｉＰＦ6を１モル／リットルの濃度で溶解したものを用いた。これらの正極と負極、ポリプロピレン製のセパレーター、電解液及びガラスフィルターを用い、２０１６型のコイン型電池を作製した。 The obtained positive electrode active material had an average porosity of 11.2%. Further, the tap density of the positive electrode active material was 1.96 g / ml, the crystallite size was 880 angstroms, and the lattice constant was 8.233 angstroms.
Using the above positive electrode active material, a coin-type battery was produced as follows. A positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride dissolved in N-methyl-2-pyrrolidone are kneaded at a mass ratio of 80:10:10, applied onto an aluminum foil, and pressed. A positive electrode was obtained. A lithium foil having a predetermined thickness was used as the negative electrode. As the electrolytic solution, a solution obtained by dissolving LiPF 6 at a concentration of 1 mol / liter in a mixed solution in which propylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 2 was used. Using these positive and negative electrodes, a polypropylene separator, an electrolytic solution and a glass filter, a 2016 type coin-type battery was produced.

上記方法で作製した電池の６０℃での充放電サイクル試験を、充放電レート１Ｃ（充電開始から２.５時間で充電休止）、電圧範囲３.０〜４.２Ｖの条件で１００サイクル充放電を繰り返した。初期の放電容量と１００サイクル経過後の容量維持率（％）を、他の測定結果と共に表１に示す。   A charge / discharge cycle test at 60 ° C. of the battery produced by the above method was performed with a charge / discharge rate of 1C (charge stopped in 2.5 hours from the start of charge) and a charge / discharge cycle of 100 cycles under the conditions of a voltage range of 3.0 to 4.2V. Was repeated. Table 1 shows the initial discharge capacity and the capacity retention rate (%) after 100 cycles, together with other measurement results.

実施例２
Ｌｉ−Ｍｎ系複合酸化物合成条件中のマンガン原料を電解二酸化マンガンとしたこと以外は実施例１と同様に操作を行い、二次粒子の空隙率、タップ密度、結晶子サイズ、格子定数、電極特性の評価を行った。結果を表１に示す。 Example 2
The same procedure as in Example 1 was carried out except that the manganese raw material in the Li-Mn composite oxide synthesis conditions was electrolytic manganese dioxide, the porosity of the secondary particles, the tap density, the crystallite size, the lattice constant, the electrode The characteristics were evaluated. The results are shown in Table 1.

実施例３
Ｌｉ／Ｍｎ／Ａｌの原子比が１.０２：１.９６７：０.０１３の組成となるように、炭酸マンガンと炭酸リチウムと水酸化アルミニウムをボールミルで混合し、大気雰囲気中加熱速度２００℃／ｈｒで室温から６５０℃まで昇温し、６５０℃に４時間保持して、Ｌｉ−Ｍｎ系複合酸化物を合成した。合成物中には、Ｌｉ−Ｍｎ系複合酸化物以外にごく微量の三二酸化マンガンがＸＲＤで検出された。レーザー式粒度分布測定器で測定した合成物の平均粒子径は１０μｍであった。
得られたＬｉ−Ｍｎ系複合酸化物を平均粒子径０.５μｍに粉砕し、Ｂ／Ｍｎの原子比が０.０２０８となるように酸化硼素を添加し造粒した。次に、脱脂後の造粒物を７５０℃で０.５ｈｒ焼成したこと以外は、実施例１と同様に実施した。その結果を表１に示す。 Example 3
Manganese carbonate, lithium carbonate and aluminum hydroxide were mixed with a ball mill so that the atomic ratio of Li / Mn / Al was 1.02: 1.967: 0.013, and the heating rate in the atmosphere was 200 ° C. / The temperature was raised from room temperature to 650 ° C. with hr and held at 650 ° C. for 4 hours to synthesize a Li—Mn-based composite oxide. In the synthesized product, a very small amount of manganese sesquioxide other than the Li—Mn composite oxide was detected by XRD. The average particle size of the synthesized product measured with a laser particle size distribution analyzer was 10 μm.
The obtained Li—Mn composite oxide was pulverized to an average particle size of 0.5 μm, and boron oxide was added and granulated so that the atomic ratio of B / Mn was 0.0208. Next, the same procedure as in Example 1 was performed except that the granulated product after degreasing was fired at 750 ° C. for 0.5 hr. The results are shown in Table 1.

実施例４
Ｂ／Ｍｎの原子比を０.００９にしたこと、及び脱脂後の造粒物を７６０℃で０.５ｈｒ焼成したこと以外は、実施例３と同様に実施した。その結果を表１に示す。 Example 4
The same procedure as in Example 3 was performed except that the B / Mn atomic ratio was 0.009 and the degreased granulated product was calcined at 760 ° C. for 0.5 hr. The results are shown in Table 1.

実施例５
Ｂ／Ｍｎの原子比を０.００６にしたこと、及び脱脂後の造粒物を７７０℃で０.５ｈｒ焼成したこと以外は、実施例３と同様に実施した。その結果を表１に示す。 Example 5
The same procedure as in Example 3 was performed except that the B / Mn atomic ratio was 0.006 and the degreased granulated product was calcined at 770 ° C. for 0.5 hr. The results are shown in Table 1.

実施例６
脱脂後の造粒物を７６０℃で２０ｈｒ焼成したこと以外は、実施例１と同様に実施した。その結果を表１に示す。 Example 6
It was carried out in the same manner as in Example 1 except that the granulated product after degreasing was fired at 760 ° C. for 20 hours. The results are shown in Table 1.

実施例７
酸化ビスマスを三酸化タングステンに変更して、Ｗ／Ｍｎの原子比が０.０２０８の割合で三酸化タングステンを添加したこと、及び脱脂後の造粒物を７５０℃で２０ｈｒ焼成したこと以外は、実施例１と同様に実施した。その結果を表１に示す。 Example 7
Except for changing the bismuth oxide to tungsten trioxide, adding tungsten trioxide at an atomic ratio of W / Mn of 0.0208, and firing the degreased granulated product at 750 ° C. for 20 hours, The same operation as in Example 1 was performed. The results are shown in Table 1.

実施例８
実施例１で合成したＬｉ−Ｍｎ系複合酸化物を、さらに大気中加熱速度が２００℃／ｈｒで室温から７５０℃まで昇温し、７５０℃で２０ｈｒ保持して結晶化した。その後は、実施例１で結晶化したＬｉ−Ｍｎ系複合酸化物を使用したこと、酸化ビスマスを酸化硼素に変更して、Ｂ／Ｍｎの原子比が０.０２０８の割合で酸化硼素を添加したこと、及び脱脂後の造粒物を７５０℃で０.５ｈｒ焼成したこと以外は、実施例１と同様に実施した。その結果を表１に示す。 Example 8
The Li—Mn-based composite oxide synthesized in Example 1 was further crystallized by raising the temperature from room temperature to 750 ° C. at a heating rate in the atmosphere of 200 ° C./hr and holding at 750 ° C. for 20 hours. Thereafter, the Li-Mn composite oxide crystallized in Example 1 was used, bismuth oxide was changed to boron oxide, and boron oxide was added at a B / Mn atomic ratio of 0.0208. This was carried out in the same manner as in Example 1 except that the granulated product after degreasing was calcined at 750 ° C. for 0.5 hr. The results are shown in Table 1.

実施例９
造粒前のＬｉ−Ｍｎ系複合酸化物として平均粒子径が３.５μｍ、比表面積が１０ｍ2／ｇのものを使用したこと以外は、実施例３と同様に実施した。その結果を表１に示す。 Example 9
The same procedure as in Example 3 was performed except that the Li—Mn composite oxide before granulation had an average particle size of 3.5 μm and a specific surface area of 10 m 2 / g. The results are shown in Table 1.

実施例１０
Ｌｉ／Ｍｎ／Ａｌの原子比が１.０３：１.９６７：０.０１３の組成となるように、炭酸マンガンと炭酸リチウムと水酸化アルミニウムをボールミルで混合して合成したＬｉ−Ｍｎ系複合酸化物を使用したこと以外は、実施例３と同様に実施した。その結果を表１に示す。 Example 10
Li-Mn based composite oxidation synthesized by mixing manganese carbonate, lithium carbonate and aluminum hydroxide with a ball mill so that the atomic ratio of Li / Mn / Al is 1.03: 1.967: 0.013. The same procedure as in Example 3 was performed except that the product was used. The results are shown in Table 1.

Figure 2012074390
Figure 2012074390

実施例１１
脱脂後の造粒物を８３０℃で２０ｈｒ焼成したこと以外は、実施例１と同様に実施した。その結果を表２に示す。 Example 11
It was carried out in the same manner as in Example 1 except that the granulated product after degreasing was fired at 830 ° C. for 20 hours. The results are shown in Table 2.

実施例１２
Ｌｉ／Ｍｎ／Ａｌの原子比が０.９９：１.９６７：０.０１３の組成となるように、炭酸マンガンと炭酸リチウムと水酸化アルミニウムをボールミルで混合して合成したＬｉ−Ｍｎ系複合酸化物を使用したこと以外は、実施例３と同様に実施した。その結果を表２に示す。 Example 12
Li-Mn based composite oxidation synthesized by mixing manganese carbonate, lithium carbonate and aluminum hydroxide with a ball mill so that the atomic ratio of Li / Mn / Al is 0.99: 1.967: 0.013. The same procedure as in Example 3 was performed except that the product was used. The results are shown in Table 2.

実施例１３
造粒後の平均粒子径を６５μｍに整粒したこと以外は、実施例３と同様に実施した。その結果を表２に示す。 Example 13
The same procedure as in Example 3 was performed except that the average particle size after granulation was adjusted to 65 μm. The results are shown in Table 2.

実施例１４
Ｂｉ／Ｍｎの原子比が０.００２０の割合にしたこと以外は、実施例１と同様に実施した。その結果を表２に示す。ここで得られた造粒・焼成・整粒された正極活物質を走査電子顕微鏡（×15,000倍）で観察した結果、図１に示すように丸い形状の粒子であることがわかった。この粒子の粒度分布を図２に示す。 Example 14
The same operation as in Example 1 was carried out except that the Bi / Mn atomic ratio was 0.0019. The results are shown in Table 2. As a result of observing the granulated, fired and sized positive electrode active material obtained here with a scanning electron microscope (× 15,000 times), it was found that the particles were round particles as shown in FIG. The particle size distribution of the particles is shown in FIG.

比較例１
造粒前のＬｉ−Ｍｎ系複合酸化物の平均粒子径を６.０μｍとしたこと以外は、実施例１と同様に実施した。その結果を表２に示す。 Comparative Example 1
The same operation as in Example 1 was performed except that the average particle diameter of the Li—Mn composite oxide before granulation was 6.0 μm. The results are shown in Table 2.

比較例２
Ｌｉ／Ｍｎの原子比が０.５１の配合組成で、平均粒子径が２０μｍの電解二酸化マンガンと炭酸リチウムをボールミルで混合し、大気中加熱速度１００℃／ｈｒで７６０℃まで昇温し、７６０℃で２４ｈｒ保持して正極活物質を合成した。得られた正極活物質について実施例１と同様に評価した。その結果を表２に示す。 Comparative Example 2
Electrolytic manganese dioxide having an Li / Mn atomic ratio of 0.51 and an average particle size of 20 μm was mixed with lithium carbonate by a ball mill, and the temperature was raised to 760 ° C. at a heating rate of 100 ° C./hr in the atmosphere. The positive electrode active material was synthesized by maintaining at 24 ° C. for 24 hours. The obtained positive electrode active material was evaluated in the same manner as in Example 1. The results are shown in Table 2.

比較例３
焼結促進剤を添加せずに造粒したこと以外は、実施例１と同様に実施した。その結果を表２に示す。 Comparative Example 3
The same procedure as in Example 1 was performed except that granulation was performed without adding a sintering accelerator. The results are shown in Table 2.

比較例４
造粒物を７５０℃で２０ｈｒ焼成したこと以外は、実施例３と同様に実施した。その結果を表２に示す。 Comparative Example 4
It was carried out in the same manner as in Example 3 except that the granulated material was fired at 750 ° C. for 20 hours. The results are shown in Table 2.

Figure 2012074390
Figure 2012074390

造粒粒子の形状測定結果の解析
表１〜２に示す実施例１〜１４及び比較例１〜４で製造された二次粒子の円形度（円形度＝４π［面積／（周囲長さ）2］）と針状比（針状比＝針絶対最大長／対角幅）の測定結果から実施例で製造された正極活物質は、円形度が０.７以上で、かつ針状比が１.３５以下に特徴があることが分かる。 Analysis of Shape Measurement Results of Granulated Particles Circularity of the secondary particles produced in Examples 1 to 14 and Comparative Examples 1 to 4 shown in Tables 1 to 2 (circularity = 4π [area / (perimeter length) 2] ] And the acicular ratio (needle ratio = needle absolute maximum length / diagonal width), the positive electrode active material produced in the example has a circularity of 0.7 or more and an acicular ratio of 1 It can be seen that there are features below .35.

本発明の正極活物質は、従来既知の凝集力を利用する二次粒子と比べ、造粒及び焼結を行っている点で本質的に異なり、従来方法で得られる正極活物質に比較して粒子が緻密でありかつ球状であり、電極への充填性に優れ、また二次電池として高温環境の下においても初期容量及び容量維持率が高くなるという効果を奏する。   The positive electrode active material of the present invention is essentially different in that it is granulated and sintered as compared with the conventionally known secondary particles utilizing cohesive force, compared with the positive electrode active material obtained by the conventional method. The particles are dense and spherical, have excellent filling properties to the electrode, and have an effect of increasing the initial capacity and capacity retention rate even in a high temperature environment as a secondary battery.

本発明の正極活物質の製造方法によれば、高温域で融液を生成する焼結促進助剤をＬｉ−Ｍｎ系複合酸化物に添加することで、二次粒子の緻密化を図ると共に、従来の方法では初期容量とサイクル特性が悪化してしまうような結晶子サイズに成長させても優れた電池性能が得られる。従来法の二次粒子の緻密化を図る際に一次粒子サイズが０.５μｍよりも大きく粒成長してしまい初期容量とサイクル特性が悪化するという問題が、高温域で融液を生成する焼結促進助剤をＬｉ−Ｍｎ系複合酸化物に添加する本発明の方法により解決され、高充填性でかつ優れた電池性能を有する正極活物質が得られる。   According to the method for producing a positive electrode active material of the present invention, by adding a sintering acceleration aid that generates a melt in a high temperature range to the Li-Mn composite oxide, the secondary particles are densified, In the conventional method, excellent battery performance can be obtained even when grown to a crystallite size that deteriorates initial capacity and cycle characteristics. In the conventional method, when the secondary particles are densified, the primary particle size grows larger than 0.5 μm and the initial capacity and cycle characteristics are deteriorated. This is solved by the method of the present invention in which an accelerator aid is added to the Li—Mn composite oxide, and a positive electrode active material having high filling properties and excellent battery performance is obtained.

本発明のリチウムイオン二次電池は、充填性に優れた正極活物質を使用しているために、高温での初期容量と容量維持率に優れている。   Since the lithium ion secondary battery of the present invention uses a positive electrode active material excellent in filling properties, it is excellent in initial capacity and capacity retention at a high temperature.

Claims (10)

スピネル構造を有するＬｉ−Ｍｎ系複合酸化物を主体とするリチウムイオン二次電池用正極活物質の製造方法において、スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の粉砕物に、５５０℃〜９００℃の温度で溶融する酸化物または酸化物になり得る元素または元素を含む化合物、またはリチウムまたはマンガンと固溶するか反応して溶融する酸化物または酸化物になり得る元素または元素を含む化合物を添加し混合して造粒する工程を有することを特徴とするリチウムイオン二次電池用正極活物質の製造方法。   In the method for producing a positive electrode active material for a lithium ion secondary battery mainly composed of a Li-Mn composite oxide having a spinel structure, the pulverized product of the Li-Mn composite oxide having a spinel structure is 550 ° C to 900 ° C. Add an element or compound containing an element or element that can become an oxide or oxide that melts at a temperature, or a compound containing an element or element that can be dissolved or reacted with lithium or manganese to become an oxide or oxide that melts And a method for producing a positive electrode active material for a lithium ion secondary battery, comprising a step of granulating the mixture. 造粒工程以外に、前記造粒物を焼結する工程を有する請求項１に記載のリチウムイオン二次電池用正極活物質の製造方法。   The manufacturing method of the positive electrode active material for lithium ion secondary batteries of Claim 1 which has the process of sintering the said granulated material other than a granulation process. 造粒工程以外に、前記造粒物を焼結収縮開始温度から少なくとも１００℃以上高い温度まで少なくとも１００℃／ｍｉｎの速度で昇温してその温度に１分〜１０分間保持した後、少なくとも１００℃／ｍｉｎの速度で焼結開始温度まで降温して焼結させる工程を有する請求項１に記載のリチウムイオン二次電池用正極活物質の製造方法。   In addition to the granulation step, the granulated product is heated at a rate of at least 100 ° C./min from the sintering shrinkage start temperature to a temperature higher by at least 100 ° C. and held at that temperature for 1 minute to 10 minutes, and then at least 100 The manufacturing method of the positive electrode active material for lithium ion secondary batteries of Claim 1 which has the process of falling and sintering to a sintering start temperature at the speed | rate of (degreeC / min). ロータリーキルンを用いて焼結させる請求項３に記載のリチウムイオン二次電池用正極活物質の製造方法。   The manufacturing method of the positive electrode active material for lithium ion secondary batteries of Claim 3 made to sinter using a rotary kiln. 前記焼結工程が、Ｌｉ−Ｍｎ系複合酸化物粒子の表面でＢｉ、Ｂ、Ｗ、Ｍｏ、Ｐｂからなる群より選ばれる少なくとも１種の元素または元素を含む化合物、またはＢ2Ｏ3とＬｉＦを組み合わせた化合物またはＭｎＦ2とＬｉＦを組み合わせた化合物を溶融し焼結して行われる請求項２に記載のリチウムイオン二次電池用正極活物質の製造方法。 In the sintering step, at least one element selected from the group consisting of Bi, B, W, Mo, and Pb on the surface of the Li—Mn composite oxide particles or a compound containing the element, or B 2 O 3 and LiF the method for producing a positive electrode active material for a lithium ion secondary battery as claimed in claim 2 which is performed by melting and sintering the combination compound or compounds that combine MnF 2 and LiF a. スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の粉砕物の平均粒子径が、５μｍ以下である請求項１に記載のリチウムイオン二次電池用正極活物質の製造方法。   2. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 1, wherein an average particle size of the pulverized product of the Li—Mn composite oxide having a spinel structure is 5 μm or less. スピネル構造を有するＬｉ−Ｍｎ系複合酸化物の粉砕物の平均粒子径が、３μｍ以下である請求項１に記載のリチウムイオン二次電池用正極活物質の製造方法。   2. The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 1, wherein the average particle size of the pulverized product of the Li—Mn composite oxide having a spinel structure is 3 μm or less. 前記造粒工程が、噴霧造粒方法、撹拌造粒方法、圧縮造粒方法または流動造粒方法で行われる請求項１に記載のリチウムイオン二次電池用正極活物質の製造方法。   The manufacturing method of the positive electrode active material for lithium ion secondary batteries of Claim 1 with which the said granulation process is performed by the spray granulation method, the stirring granulation method, the compression granulation method, or the fluidized granulation method. 前記造粒工程において、造粒助剤として、アクリル系樹脂、イソブチレンと無水マレイン酸との共重合物、ポリビニルアルコール、ポリエチレングリコール、ポリビニルピロリデン、ハイドロキシプロピルセルロース、メチルセルロース、コーンスターチ、ゼラチン、リグニンからなる群より選ばれる少なくとも１種の有機化合物を使用する請求項１に記載のリチウムイオン二次電池用正極活物質の製造方法。   In the granulation step, as a granulation aid, an acrylic resin, a copolymer of isobutylene and maleic anhydride, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidene, hydroxypropyl cellulose, methyl cellulose, corn starch, gelatin, lignin The method for producing a positive electrode active material for a lithium ion secondary battery according to claim 1, wherein at least one organic compound selected from the group is used. 大気中または酸素を含有するガスフロー雰囲気中、３００℃〜５５０℃の温度下で脱脂工程を有する請求項９に記載のリチウムイオン二次電池用正極活物質の製造方法。   The manufacturing method of the positive electrode active material for lithium ion secondary batteries of Claim 9 which has a degreasing process under the temperature of 300 to 550 degreeC in air | atmosphere or the gas flow atmosphere containing oxygen.
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