JP2015201432A - Positive electrode active material particle powder for nonaqueous electrolyte secondary battery, method of manufacturing the same, and nonaqueous electrolyte secondary battery - Google Patents

Positive electrode active material particle powder for nonaqueous electrolyte secondary battery, method of manufacturing the same, and nonaqueous electrolyte secondary battery Download PDF

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JP2015201432A
JP2015201432A JP2015033335A JP2015033335A JP2015201432A JP 2015201432 A JP2015201432 A JP 2015201432A JP 2015033335 A JP2015033335 A JP 2015033335A JP 2015033335 A JP2015033335 A JP 2015033335A JP 2015201432 A JP2015201432 A JP 2015201432A
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positive electrode
electrode active
active material
particle powder
lithium
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祐司 三島
Yuji Mishima
祐司 三島
尊久 西尾
Takahisa Nishio
尊久 西尾
琢磨 北條
Takuma Hojo
琢磨 北條
光昭 畑谷
Mitsuaki Hataya
光昭 畑谷
竜太 正木
Ryuta Masaki
竜太 正木
貞村　英昭
Hideaki Sadamura
英昭 貞村
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Toda Kogyo Corp
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Toda Kogyo Corp
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    • 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 positive electrode active material particle powder having high capacity, a high capacity maintenance rate and excellent high temperature overcharge test, and also to provide a manufacturing method therefor, and a secondary battery using the same.SOLUTION: A positive electrode active material particle powder includes: a core particle composed of cobaltic acid lithium having a layered structure containing element M (M is Mg and/or Al); and a surface layer composed of the cobaltic acid lithium having the layered structure in which at least Ti is incorporated into solid solution. The average layer thickness of the surface layer is 0.005 to 1.5 μm, and the BET specific surface area is 0.02 to 0.25 m/g.

Description

本発明は、高エネルギー密度を示す二次電池用の正極活物質として、高温過充電特性、且つ充放電繰り返し特性に優れた正極活物質粒子粉末とその製造方法、及びそれを用いた二次電池を提供する。   The present invention relates to a positive electrode active material particle powder excellent in high temperature overcharge characteristics and charge / discharge repetition characteristics as a positive electrode active material for a secondary battery exhibiting high energy density, a method for producing the same, and a secondary battery using the same I will provide a.

近年、携帯電話やパソコン等の電子機器の小型・軽量化に拍車がかかり、これらの駆動用電源として高エネルギー密度を有する二次電池への要求が高くなっている。このような状況下において、充放電容量が大きく、且つ安全性が高いという長所を有するリチウムイオン二次電池が注目されている。   In recent years, electronic devices such as mobile phones and personal computers have been spurred to be smaller and lighter, and the demand for secondary batteries having high energy density as power sources for driving these devices has increased. Under such circumstances, a lithium ion secondary battery having advantages such as a large charge / discharge capacity and high safety has been attracting attention.

従来、４Ｖ級の電圧をもつ高エネルギー型のリチウムイオン二次電池に有用な正極活物質としては、層状（岩塩型）構造のＬｉＣｏＯ２、Ｌｉ（Ｎｉ、Ｃｏ）Ｏ２、Ｌｉ（Ｎｉ、Ｃｏ、Ｍｎ）Ｏ２、及びスピネル型構造のＬｉＭｎ２Ｏ４が一般的に知られており、なかでも高い結晶性が容易に得られやすく、高密度に充填が可能なコバルト酸リチウムＬｉＣｏＯ２はモバイル機器の駆動電源の正極活物質として２０年以上使われている。しかしながら、前記機器の高性能化に伴い、更なる特性改善が求められている。 Conventionally, as a positive electrode active material useful for a high energy type lithium ion secondary battery having a voltage of 4V class, LiCoO 2 having a layered (rock salt type) structure, Li (Ni, Co) O 2 , Li (Ni, Co) , Mn) O 2 , and LiMn 2 O 4 having a spinel structure are generally known, and among them, lithium cobalt oxide LiCoO 2 that can easily obtain high crystallinity and can be packed at high density is mobile. It has been used for more than 20 years as a positive electrode active material for device drive power. However, further improvement in characteristics has been demanded as the performance of the device has been improved.

特性改善の一つに、二次電池の充電電圧を上げて、高エネルギー密度化を図る方法がある。しかしながら、高充電電圧下、即ち、過充電状態において、充放電繰り返し特性の劣化やガス発生に伴う電池パックの膨れの問題が指摘されている。   One of the characteristic improvements is to increase the charging voltage of the secondary battery to increase the energy density. However, under high charging voltage, that is, in an overcharged state, problems of deterioration of charge / discharge repetition characteristics and swelling of the battery pack due to gas generation have been pointed out.

一般に、コバルト酸リチウムＬｉＣｏＯ２の結晶は一価のＬｉ＋、三価のＣｏ３＋、マイナス二価のＯ２−で構成されており、充電により該結晶からＬｉ＋と電子ｅ−が脱離し、ヤーン・テラー性の不安定なＣｏ４＋を含む脱リチウム状態のＬｉ１−ａＣｏＯ２（ａ＞０）へと変化する。そのため、Ｌｉ＋が半分抜けたＬｉ０．５ＣｏＯ２の組成比付近の脱リチウム状態において、該結晶から電解液へコバルトイオンが溶出すると共に、該結晶の相転移や崩壊が発生するため、電池の充放電繰り返し特性を悪化させる。 In general, a crystal of lithium cobaltate LiCoO 2 is composed of monovalent Li + , trivalent Co 3+ , and minus divalent O 2− , and Li + and electrons e − are desorbed from the crystal by charging, It changes to Li 1-a CoO 2 (a> 0) in a delithiated state containing Co 4+ with unstable yarn-teller properties. Therefore, in the delithiated state in the vicinity of the composition ratio of Li 0.5 CoO 2 from which Li + has been removed by half, cobalt ions are eluted from the crystal into the electrolyte solution, and phase transition and collapse of the crystal occur. It deteriorates the charge / discharge repetition characteristics.

また、脱リチウム状態のＬｉ１−ａＣｏＯ２（ａ＞０）におけるＣｏ３＋／４＋に付随したｄ軌道のエネルギー準位とＯ２−に付随したｐ軌道のエネルギー準位は比較的近いため、電気化学的にＬｉ１−ａＣｏＯ２のコバルトイオンから電子を引き抜くことと酸素イオンから電子を引く抜くことは等価であり、結晶からのコバルトイオン溶出と共にも酸素（イオン）も放出される。電池が高い充電状態にあるとき、正極近傍は電子を奪う高い酸化状態に正極が曝され、また、前述の放出された酸素により更に高い酸化状態となり、正極周囲の電解液やバインダーを酸化させ、ＣＯ２等のガス発生が生じて電池を膨らませる危険が生じる。 In addition, the energy level of the d orbital associated with Co 3 + / 4 + and the energy level of the p orbital associated with O 2− in Li 1-a CoO 2 (a> 0) in the delithiated state are relatively close. Electrochemically extracting electrons from cobalt ions of Li 1-a CoO 2 is equivalent to extracting electrons from oxygen ions, and oxygen (ions) is released along with the elution of cobalt ions from the crystal. When the battery is in a highly charged state, the positive electrode is exposed to a high oxidation state that takes away electrons in the vicinity of the positive electrode, and becomes a higher oxidation state due to the released oxygen, oxidizing the electrolyte and binder around the positive electrode, There is a risk that gas such as CO 2 is generated and the battery is expanded.

特に、高温での高充電圧下では、コバルトイオン溶出に伴った酸素（イオン）と電解液との反応が活性を増し、二次電池としての安全性を確保するためには、脱Ｌｉ状態のコバルト酸リチウム正極活物質の構造がより安定であることが必要とされている。即ち、充電電圧を上げて、充放電に利用可能なＬｉの量を安全に増やすためには、コバルト酸リチウム粒子粉末の改善が必要である。従来、コバルト酸リチウムの脱リチウム状態の安定化に対して、異種元素による置換や被覆の技術が提案されている（特許文献１〜６）。   In particular, under high charge pressure at high temperature, the reaction between oxygen (ion) and the electrolyte accompanying elution of cobalt ions increases the activity, and in order to ensure safety as a secondary battery, cobalt in a de-Li state The structure of the lithium acid positive electrode active material is required to be more stable. That is, in order to increase the charging voltage and safely increase the amount of Li available for charging and discharging, it is necessary to improve the lithium cobalt oxide particle powder. Conventionally, a technique of substitution or covering with a different element has been proposed for stabilizing the delithiated state of lithium cobaltate (Patent Documents 1 to 6).

一般に、Ｌｉ（Ｎｉ２＋、Ｃｏ３＋、Ｍｎ４＋）Ｏ２はＬｉ＋とＮｉ２＋のイオン半径が近いため、Ｌｉ＋が遷移金属のサイトへ入ったり、Ｎｉ２＋がリチウムのサイトへ入ったりして、完全な結晶が作りにくいことが知られている。また、充放電においてＮｉ２＋／４＋に対応した電位をとり、コバルト酸リチウム正極の電池電圧に比べ低くなる。同時に、４価のコバルトイオンＣｏ４＋が生成しない。そのため、コバルト酸リチウムＬｉＣｏＯ２に比べ、高温過充電状態でのコバルトイオンの溶出は極めて少なく、コバルト酸リチウムの表面処理として利用されている（特許文献１〜５）。 In general, Li (Ni 2+ , Co 3+ , Mn 4+ ) O 2 has a close ionic radius between Li + and Ni 2+ , so Li + enters a transition metal site or Ni 2+ enters a lithium site. It is known that perfect crystals are difficult to make. Moreover, the electric potential corresponding to Ni <2 +> / 4+ is taken in charging / discharging, and becomes low compared with the battery voltage of a lithium cobaltate positive electrode. At the same time, tetravalent cobalt ions Co 4+ are not generated. Therefore, compared to lithium cobalt oxide LiCoO 2, elution of cobalt ions is extremely small in a high temperature overcharge state, it is used as the surface treatment of the lithium cobalt oxide (Patent Documents 1 to 5).

また、コバルト酸リチウム作製時にＴｉＯ２を混合すると、得られる粉末にはコバルト酸リチウムの表層にＬｉ２ＴｉＯ３結晶として存在し、二次電池の充放電繰り返し特性やレート特性、並びに非水電解液との反応によるガス発生を抑制することが報告されている。（特許文献６）。 In addition, when TiO 2 is mixed during the preparation of lithium cobalt oxide, the resulting powder exists as Li 2 TiO 3 crystals on the surface of the lithium cobalt oxide, and the charge / discharge repetition characteristics and rate characteristics of the secondary battery, as well as the non-aqueous electrolyte It has been reported to suppress gas generation due to the reaction with. (Patent Document 6).

特表２００２−５２９３６１号公報JP 2002-529361 A 特開２００６−３３１９３９号公報JP 2006-331939 A 特開２００７−０６６７４５号公報JP 2007-066745 A 特開２００７−２５８０９５号公報JP 2007-258095 A 特開２００８−１６２４３号公報JP 2008-16243 A 国際公開第２０１１／０４３２９６号International Publication No. 2011/043296

高エネルギー密度を示す二次電池用の正極活物質として、高温過充電特性と充放電繰り返し特性に優れた正極活物質粒子粉末とその製造方法、及びそれを用いた二次電池について、現在最も要求されているところであるが、未だ確立されていない。   As the positive electrode active material for a secondary battery exhibiting high energy density, currently the most demanded of positive electrode active material particle powder excellent in high-temperature overcharge characteristics and charge / discharge repeatability, its manufacturing method, and a secondary battery using the same. It has been established, but has not been established yet.

即ち、特許文献１に記載された技術では、活物質粒子表面層が精密に制御されておらず、高温過充電特性に優れた正極活物質、及び該製造法が開示されているとは言い難い。   That is, in the technique described in Patent Document 1, it is difficult to say that the active material particle surface layer is not precisely controlled, and a positive electrode active material excellent in high-temperature overcharge characteristics and the production method are not disclosed. .

特許文献２記載の技術はコバルト酸リチウム表面のニッケルやマンガンを含む相の精密制御がなされていないため高容量化が難しく、高エネルギー密度を示す二次電池用の正極活物質の製造方法、及び二次電池が開示されているとは言い難い。   The technology described in Patent Document 2 is difficult to increase the capacity because the phase containing nickel or manganese on the surface of lithium cobaltate is not precisely controlled, and a method for producing a positive electrode active material for a secondary battery exhibiting a high energy density, and It is difficult to say that a secondary battery is disclosed.

特許文献３記載の技術はコバルト酸リチウム中の多量のニッケルの存在のため高容量化が難しく、高エネルギー密度を示す二次電池用の正極活物質、及び二次電池が開示されているとは言い難い。   The technology described in Patent Document 3 is difficult to increase the capacity due to the presence of a large amount of nickel in lithium cobalt oxide, and a positive electrode active material for a secondary battery exhibiting a high energy density and a secondary battery are disclosed. It's hard to say.

特許文献４、及び５記載の技術は、コバルト酸リチウム粒子の被覆層の精密な制御ができているとは言い難く、高温過充電時の安定性に優れている正極活物質及び二次電池が開示されているとは言い難い。   The techniques described in Patent Documents 4 and 5 are difficult to say that precise control of the coating layer of lithium cobalt oxide particles is possible, and positive electrode active materials and secondary batteries that are excellent in stability during high-temperature overcharge are obtained. It is hard to say that it is disclosed.

特許文献６記載の技術は、１度の焼成で偶発的にコバルト酸リチウム粒子の表層にＬｉ２ＴｉＯ３の結晶を作製する方法であり、コバルト酸リチウム粒子の一次粒子が非常に小さく、コバルトイオン溶出抑制ができず、高温過充電時の安定性に優れている正極活物質および二次電池とは言い難い。 The technique described in Patent Document 6 is a method of accidentally producing a Li 2 TiO 3 crystal on the surface layer of lithium cobalt oxide particles by one firing, where the primary particles of the lithium cobalt oxide particles are very small, cobalt ions It cannot be said that it is a positive electrode active material and a secondary battery that cannot suppress elution and are excellent in stability at high temperature overcharge.

そこで、本発明は、コバルト酸リチウムを芯粒子とし、少量の被覆層を精密に制御することで、高容量を維持しつつ、高温過充電特性と充放電繰り返し特性に優れた正極活物質粒子粉末とその製造方法、及びそれを用いた二次電池の提供を技術的課題とする。   Accordingly, the present invention provides a positive electrode active material particle powder having excellent high-temperature overcharge characteristics and charge / discharge repeatability characteristics while maintaining a high capacity by using lithium cobaltate as a core particle and precisely controlling a small amount of a coating layer. And a method of manufacturing the same, and a secondary battery using the same is a technical problem.

前記技術的課題は、次の通りの本発明によって達成できる。   The technical problem can be achieved by the present invention as follows.

即ち、本発明は、元素Ｍ（ＭはＭｇ及び／又はＡｌ）を含む層状構造のコバルト酸リチウムからなる芯粒子と、少なくともＴｉが固溶した層状構造のコバルト酸リチウムからなる表層を有する正極活物質粒子粉末であって、該表層の平均の層厚が０．００５〜１．５μｍであり、ＢＥＴ比表面積が０．０２〜０．２５ｍ２／ｇであることを特徴とする正極活物質粒子粉末である（本発明１）。 That is, the present invention provides a positive electrode active material having core particles made of lithium cobaltate having a layered structure containing the element M (M is Mg and / or Al) and a surface layer made of lithium cobaltate having a layered structure in which at least Ti is dissolved. Positive electrode active material particles, characterized in that the material layer powder has an average layer thickness of 0.005 to 1.5 μm and a BET specific surface area of 0.02 to 0.25 m 2 / g It is a powder (Invention 1).

また、本発明は、前記正極活物質粒子粉末が元素Ａ（ＡはＷ、Ｍｏ、及びＢから選ばれる少なくとも１種の元素）を含む水可溶性のリチウム酸化物からなる最表面を有し、該最表面の含有量が０．０１〜０．５重量％である本発明１に記載の正極活物質粒子粉末である（本発明２）。   In the present invention, the positive electrode active material particle powder has an outermost surface made of water-soluble lithium oxide containing element A (A is at least one element selected from W, Mo, and B), It is positive electrode active material particle powder of this invention 1 whose content of the outermost surface is 0.01 to 0.5 weight% (this invention 2).

また、本発明は、体積基準のメジアン径が１０〜３５μｍである本発明１又は２に記載の正極活物質粒子粉末である（本発明３）。   Moreover, this invention is a positive electrode active material particle powder of this invention 1 or 2 whose volume-based median diameter is 10-35 micrometers (this invention 3).

また、本発明は残存アルカリ成分が８００ｐｐｍ以下、未反応酸化コバルトが５００ｐｐｍ以下である本発明１〜３のいずれかに記載の正極活物質粒子粉末である（本発明４）。   Moreover, this invention is a positive electrode active material particle powder in any one of this invention 1-3 whose residual alkali component is 800 ppm or less and whose unreacted cobalt oxide is 500 ppm or less (this invention 4).

また、本発明は前記表層のＴｉ濃度が０．００１≦Ｔｉ／Ｃｏ（ｍｏｌ比）≦０．０２である本発明１〜４のいずれかに記載の正極活物質粒子粉末である（本発明５）。   Further, the present invention is the positive electrode active material particle powder according to any one of the present inventions 1 to 4, wherein the surface layer has a Ti concentration of 0.001 ≦ Ti / Co (mol ratio) ≦ 0.02. ).

また、本発明は前記表層の前記芯粒子に対する被覆率が８０％以上である本発明１〜５のいずれかに記載の正極活物質粒子粉末である（本発明６）。   Moreover, this invention is a positive electrode active material particle powder in any one of this invention 1-5 whose coverage with respect to the said core particle of the said surface layer is 80% or more (this invention 6).

また、本発明は本発明１〜６のいずれかに記載の正極活物質粒子粉末の製造方法であって、リチウム原料とコバルト原料と元素Ｍ原料（ＭはＭｇ及び／又はＡｌ）を混合後、８００〜１１００℃で焼成を行って層状構造のコバルト酸リチウム粒子粉末を作製する第一工程と、第一工程で得られたコバルト酸リチウム粒子粉末とチタン原料とリチウム原料とを混合後、８００〜１１００℃で焼成を行って表層を形成する第二工程からなることを特徴とする正極活物質粒子粉末の製造方法である（本発明７）。   Moreover, this invention is a manufacturing method of the positive electrode active material particle powder in any one of this invention 1-6, Comprising: After mixing a lithium raw material, a cobalt raw material, and element M raw material (M is Mg and / or Al), A first step of producing a lithium cobaltate particle powder having a layered structure by baking at 800 to 1100 ° C., and after mixing the lithium cobaltate particle powder obtained in the first step, a titanium raw material, and a lithium raw material, It is a manufacturing method of the positive electrode active material particle powder which consists of a 2nd process which forms by baking by 1100 degreeC (this invention 7).

また、本発明は本発明２〜６のいずれかに記載の正極活物質粒子粉末の製造方法であって、リチウム原料とコバルト原料と元素Ｍ原料（ＭはＭｇ及び／又はＡｌ）を混合後、８００〜１１００℃で焼成を行って層状構造のコバルト酸リチウム粒子粉末を作製する第一工程と、第一工程で得られたコバルト酸リチウム粒子粉末とチタン原料と元素Ａ原料（ＡはＷ、Ｍｏ、及びＢから選ばれる少なくとも１種の元素）とリチウム原料とを混合後、８００〜１１００℃で焼成を行って表層及び最表面を形成する第二工程からなることを特徴とする正極活物質粒子粉末の製造方法である（本発明８）。   Further, the present invention is a method for producing a positive electrode active material particle powder according to any one of the present invention 2-6, after mixing a lithium raw material, a cobalt raw material and an element M raw material (M is Mg and / or Al), A first step of producing a layered lithium cobalt oxide particle powder by firing at 800 to 1100 ° C., a lithium cobalt oxide particle powder obtained in the first step, a titanium raw material, and an element A raw material (A is W, Mo And at least one element selected from B) and a lithium raw material, followed by baking at 800 to 1100 ° C. to form a surface layer and an outermost surface, and thereby comprising positive electrode active material particles This is a method for producing a powder (Invention 8).

また、本発明は本発明１〜６のいずれかに記載の正極活物質粒子粉末を正極活物質の少なくとも一部に用いて作製した非水電解液二次電池である（本発明９）。   Further, the present invention is a non-aqueous electrolyte secondary battery produced by using the positive electrode active material particle powder according to any one of the present inventions 1 to 6 as at least a part of the positive electrode active material (Invention 9).

また、本発明は本発明１〜６のいずれかに記載の正極活物質粒子粉末に対し、凝集粒子の体積基準のメジアン径が１〜７μｍのＬｉ（Ｎｉ１−ａ−ｂＣｏａＭｎｂ）Ｏ２（ａ及びｂは０．１５≦ａ≦０．４、０．１５≦ｂ≦０．５）で表わされる正極活物質粒子粉末を３〜２５重量％含む混合物を正極活物質として用いて作製した非水電解液二次電池ある（本発明１０）。 Further, the present invention is to positive electrode active material particles as described in any one of the present invention 1-6, volume-based median diameter of aggregated particles of 1~7μm Li (Ni 1-a- b Co a Mn b) A mixture containing 3 to 25% by weight of positive electrode active material particles represented by O 2 (a and b are 0.15 ≦ a ≦ 0.4, 0.15 ≦ b ≦ 0.5) is used as the positive electrode active material. There is a produced non-aqueous electrolyte secondary battery (Invention 10).

本発明に係る正極活物質粒子粉末は、芯粒子に高容量を示すコバルト酸リチウムを用い、その表層に微量のＴｉを固溶させ、高温過充電時のコバルトイオンの溶出を抑制した正極活物質粒子粉末であるため、これを用いた二次電池は高温過充電特性と充放電繰り返し特性に優れている。従って、本発明に係る正極活物質粒子粉末は、非水電解液二次電池用の正極活物質として好適である。   The positive electrode active material powder according to the present invention is a positive electrode active material in which lithium cobaltate having a high capacity is used as a core particle, a trace amount of Ti is solid-solved on the surface layer, and elution of cobalt ions during high temperature overcharge is suppressed. Since it is a particle powder, a secondary battery using this is excellent in high-temperature overcharge characteristics and charge / discharge repetition characteristics. Therefore, the positive electrode active material particle powder according to the present invention is suitable as a positive electrode active material for a non-aqueous electrolyte secondary battery.

また、本発明に係る正極活物質粒子粉末は、その最表面にコバルト酸リチウムと電解液との反応を抑制する相を形成することができ、高温過充電特性と充放電繰り返し特性に優れた二次電池を製造できる。   In addition, the positive electrode active material particle powder according to the present invention can form a phase that suppresses the reaction between lithium cobalt oxide and the electrolytic solution on the outermost surface, and has excellent high-temperature overcharge characteristics and charge / discharge repetition characteristics. A secondary battery can be manufactured.

本発明の実施例１の各工程で得られる粒子粉末のＳＥＭ写真である。 （１）第一工程で得られたコバルト酸リチウム粒子粉末 （２）二酸化チタンが被覆処理されたコバルト酸リチウム粒子粉末 （３）第二工程で得られた正極活物質粒子粉末It is a SEM photograph of the particle powder obtained at each process of Example 1 of the present invention. (1) Lithium cobaltate particle powder obtained in the first step (2) Lithium cobaltate particle powder coated with titanium dioxide (3) Positive electrode active material particle powder obtained in the second step 実施例１で得られた正極活物質粒子粉末を樹脂包埋後、収束イオンビーム（ＦＩＢ）で薄膜化して撮影したＳＴＥＭ写真とエネルギー分散型Ｘ線（ＥＤＸ）で分析した結果である。＋００５、＋００１、＋００８は粒子の最表面であり、他は粒子内部である。斜体字はＴｉ／Ｃｏ（ｍｏｌ％）である。It is the result of analyzing by the STEM photograph and energy dispersive X-rays (EDX) which image | photographed the positive electrode active material particle powder obtained in Example 1 after embedding resin and making it thin with a focused ion beam (FIB). +005, +001, and +008 are the outermost surfaces of the particles, and the others are inside the particles. The italic character is Ti / Co (mol%). 実施例１で得られた正極活物質粒子粉末を樹脂包埋後、収束イオンビーム（ＦＩＢ）で薄膜化し、ナノビームの電子線回折（ＮＥＤ）で分析した（１）表面から約６００ｎｍの＋００３、（２）表面から約２５０ｎｍの＋００２、（３）粒子最表面の＋００１、における［０，−１，０］ｚｏｎｅの回折パターンである。こられの測定箇所は図２に示した点に対応している。The positive electrode active material particle powder obtained in Example 1 was embedded in a resin, then thinned with a focused ion beam (FIB), and analyzed by nanobeam electron diffraction (NED). (1) +003 of about 600 nm from the surface ( 2) [0, -1, 0] zone diffraction pattern at +002 at approximately 250 nm from the surface, and (3) +001 at the outermost surface of the particle. These measurement points correspond to the points shown in FIG. 実施例１で得られた正極活物質粒子粉末を樹脂包埋後、クロスセクションポリッシャー（ＣＰ）で粒子断面を作製し、電界放射型オージェ電子分光法(ＦＥ‐ＡＥＳ)で点分析した結果である。点分析により、約０．０２μｍの範囲の元素濃度を得た。図に示すＦＥ−ＡＥＳ像のとおり、粒子断面の各地点で粒子表面から点分析を行い、粒子表面からの距離に対し、Ｔｉの微分形式のオージェスペクトル強度をプロットした。FIG. 4 shows the result of embedding the positive electrode active material particle powder obtained in Example 1 with a resin, making a cross section of the particle with a cross section polisher (CP), and performing point analysis with field emission Auger electron spectroscopy (FE-AES). . Point analysis yielded elemental concentrations in the range of about 0.02 μm. As in the FE-AES image shown in the figure, point analysis was performed from the particle surface at each point of the particle cross section, and the Auger spectrum intensity in the differential form of Ti was plotted against the distance from the particle surface. 実施例１で得られた正極活物質粒子粉末のＸ線回折パターンをＲｉｅｔｖｅｌｄ解析した結果である。測定点（＋）に対し実線で計算値を示す。各２θにおける測定値と計算値の差を下段に曲線で示した。Ｘ線回折パターンの下にコバルト酸リチウムのピーク位置を短線（｜）で、Ｔｉが固溶したコバルト酸リチウムのピーク位置を長線（｜）で示した。右上の挿入図はＸ線回折パターンの２θが４３．５から４６．５°までの範囲を拡大した部分であり、縦軸を対数とし、該２相のピークを破線で表わしたものである。It is the result of Rietveld analysis of the X-ray diffraction pattern of the positive electrode active material particle powder obtained in Example 1. The calculated value is indicated by a solid line with respect to the measurement point (+). The difference between the measured value and the calculated value at each 2θ is shown by a curve in the lower part. Under the X-ray diffraction pattern, the peak position of lithium cobaltate is indicated by a short line (|), and the peak position of lithium cobaltate in which Ti is dissolved is indicated by a long line (|). The inset in the upper right is an enlarged portion of the X-ray diffraction pattern 2θ from 43.5 to 46.5 °, with the vertical axis representing the logarithm and the two-phase peaks represented by broken lines. 実施例１で得られた正極活物質粒子粉末を正極化し、コインセルを用いて２５℃、４．４Ｖで充放電試験を行った結果である。It is the result of having made positive electrode active material particle powder obtained in Example 1 into a positive electrode and conducting a charge / discharge test at 25 ° C. and 4.4 V using a coin cell. 実施例１で得られた正極活物質粒子粉末を正極化し、コインセルを用いて２５℃、４．４Ｖで充放電繰り返し試験を行った結果である。横軸に放電回数、縦軸に初期放電容量を１００％とした放電容量維持率を示す。It is the result of having made the positive electrode active material particle powder obtained in Example 1 into a positive electrode and conducting a charge / discharge repeated test at 25 ° C. and 4.4 V using a coin cell. The horizontal axis represents the number of discharges, and the vertical axis represents the discharge capacity retention rate with the initial discharge capacity being 100%. 正極活物質粒子粉末を正極化し、コインセルを用いて６０℃、４．５Ｖで高温過充電試験を行った結果である。時間の原点を０．１Ｃ定電流充電試験開始直後とし、４．５Ｖに達した後、定電圧試験に切り替え、１４〜７２時間の正極活物質重量当たりの積算電流値から漏れ電気量を算出した。It is the result of converting the positive electrode active material particle powder into a positive electrode and conducting a high-temperature overcharge test at 60 ° C. and 4.5 V using a coin cell. The time origin was set immediately after the start of the 0.1 C constant current charge test, and after reaching 4.5 V, the test was switched to the constant voltage test, and the amount of leakage electricity was calculated from the accumulated current value per positive electrode active material weight for 14 to 72 hours. .

本発明の構成をより詳しく説明すれば次の通りである。   The configuration of the present invention will be described in more detail as follows.

まず、本発明に係る正極活物質粒子粉末について述べる。   First, the positive electrode active material particle powder according to the present invention will be described.

本発明に係る正極活物質粒子粉末は元素Ｍ（ＭはＭｇ及び／又はＡｌ）を含む層状構造のコバルト酸リチウムからなる芯粒子と、少なくともチタンが固溶したコバルト酸リチウムからなる表層を有している。   The positive electrode active material particle powder according to the present invention has a core particle made of lithium cobaltate having a layered structure containing the element M (M is Mg and / or Al) and a surface layer made of lithium cobaltate in which at least titanium is dissolved. ing.

本発明に係る正極活物質粒子の芯粒子である層状構造のコバルト酸リチウムの化学式はＬｉ１＋ｘ（Ｃｏ１−ｙＭｙ）Ｏ２（ｘ及びｙは、０＜ｘ≦０．１、０＜ｙ≦０．０３、ＭはＭｇ及び／又はＡｌ）である。芯粒子をコバルト酸リチウムとすることで高いエネルギー密度をもつ正極活物質粒子粉末を得ることができる。 The chemical formula of the lithium cobaltate having a layered structure which is the core particle of the positive electrode active material particle according to the present invention is Li 1 + x (Co 1-y M y ) O 2 (x and y are 0 <x ≦ 0.1, 0 < y ≦ 0.03, M is Mg and / or Al). By using lithium cobalt oxide as the core particle, a positive electrode active material particle powder having a high energy density can be obtained.

コバルト酸リチウム作製時のリチウム量をコバルトと添加元素Ｍのｍｏｌ量に対して過剰にすることで、焼成後の一次粒子径が増大し、電池の高温過充電特性が向上する。ｘの値が０以下の場合、コバルト酸リチウムの一次粒子が小さくなり、電池の高温過充電特性を悪化させる。また、ｘの値が０．１を超える場合、容量が確保できず、高エネルギー密度の電池を設計することができない。また、正極活物質の残存アルカリ成分が増加し、それに起因する充電時の電解液分解によるガス発生が生じる。   By making the amount of lithium at the time of producing lithium cobalt oxide excessive with respect to the molar amount of cobalt and additive element M, the primary particle diameter after firing increases, and the high-temperature overcharge characteristics of the battery are improved. When the value of x is 0 or less, the primary particles of lithium cobalt oxide become small, and the high-temperature overcharge characteristics of the battery are deteriorated. Further, when the value of x exceeds 0.1, the capacity cannot be secured, and a battery having a high energy density cannot be designed. Moreover, the residual alkali component of a positive electrode active material increases, and the gas generation by the electrolyte solution decomposition | disassembly at the time of charge resulting from it arises.

また、添加元素Ｍはコバルト酸リチウムに固溶する、Ｍｇ、Ａｌのうち少なくとも１種である。特に、Ｍｇは放電容量を上げる効果も備えており、添加元素Ｍとしてより好ましい。添加元素Ｍを微量添加することによって電池の高温過充電特性を良好にすることができる。ｙの値が０の場合、電池の高温過充電特性に対する効果が現れない。また、ｙの値が０．０３を超える場合、放電容量が確保できず、高エネルギー密度の電池を設計することができない。   Further, the additive element M is at least one of Mg and Al that are solid-solved in lithium cobalt oxide. In particular, Mg has an effect of increasing the discharge capacity and is more preferable as the additive element M. By adding a small amount of additive element M, the high-temperature overcharge characteristics of the battery can be improved. When the value of y is 0, the effect on the high temperature overcharge characteristic of the battery does not appear. On the other hand, if the value of y exceeds 0.03, the discharge capacity cannot be secured, and a battery with a high energy density cannot be designed.

本発明に係る正極活物質粒子粉末の表層は、少なくともＴｉが固溶した層状構造のコバルト酸リチウムである。   The surface layer of the positive electrode active material particle powder according to the present invention is a lithium cobalt oxide having a layered structure in which at least Ti is dissolved.

本発明に係る正極活物質粒子粉末の表層は、平均の層厚が０．００５〜１．５μｍである。表層の層厚が０．００５μｍ未満の場合、コバルトイオンの溶出を抑制できず、高温過充電特性が不良であった。表層の層厚が１．５μｍを超える場合、容量の確保が難しく、高いエネルギー密度の電池の設計が難しくなる。表層の層厚は、好ましくは０．０１〜１．３μｍ、より好ましくは０．０５〜１．２μｍである。   The surface layer of the positive electrode active material particle powder according to the present invention has an average layer thickness of 0.005 to 1.5 μm. When the surface layer thickness was less than 0.005 μm, the elution of cobalt ions could not be suppressed, and the high-temperature overcharge characteristics were poor. When the thickness of the surface layer exceeds 1.5 μm, it is difficult to ensure the capacity, and it becomes difficult to design a battery having a high energy density. The layer thickness of the surface layer is preferably 0.01 to 1.3 μm, more preferably 0.05 to 1.2 μm.

従来、Ｔｉは電解液の分解を妨げる効果を備えていることが知られていた。今回、Ｔｉをコバルト酸リチウム結晶の表層に固溶させることにより、コバルトイオンの溶出を防ぐ役割を果たすことが分かった。コバルト酸リチウムの表層において三価のＣｏ３＋のサイトに四価のＴｉ４＋が部分的に固溶し、構造欠陥を有するＬｉ（□α/３Ｃｏ１−４α/３Ｔｉα）Ｏ２が生じ、脱Ｌｉ状態での相転移や結晶崩壊を抑制したためと推察している。ここで、□は空孔を意味する。 Conventionally, it has been known that Ti has an effect of preventing the decomposition of the electrolytic solution. This time, it was found that by dissolving Ti in the surface layer of lithium cobaltate crystal, it plays a role of preventing elution of cobalt ions. In the surface layer of lithium cobaltate, tetravalent Ti 4+ partially dissolves at the trivalent Co 3+ site, resulting in Li (□ α / 3 Co 1-4α / 3 Ti α ) O 2 having structural defects. This is presumed to be because the phase transition and crystal collapse in the Li-free state were suppressed. Here, □ means a hole.

表層のＴｉ濃度は０．００１≦Ｔｉ／Ｃｏ（ｍｏｌ比）≦０．０２であることが好ましい。表層のＴｉ濃度がＴｉ／Ｃｏ＜０．００１では高温過充電特性は良好でない。また、０．０２＜Ｔｉ／Ｃｏの場合、表層のコバルト酸リチウムに固溶しきらなかったチタンがＬｉ２ＴｉＯ３を形成し、容量を低下させる。 The Ti concentration of the surface layer is preferably 0.001 ≦ Ti / Co (mol ratio) ≦ 0.02. When the Ti concentration of the surface layer is Ti / Co <0.001, the high temperature overcharge characteristics are not good. Further, in the case of 0.02 <Ti / Co, titanium that did not completely dissolve in the surface lithium cobaltate forms Li 2 TiO 3 and lowers the capacity.

表層の芯粒子に対する被覆率が８０％以上であることが好ましい。被覆率が８０％を下回る場合、高温過充電特性が不良であった。   It is preferable that the coverage of the core particles on the surface layer is 80% or more. When the coverage was less than 80%, the high temperature overcharge characteristics were poor.

本発明に係る正極活物質粒子粉末は元素Ｍ（ＭはＭｇ及び／又はＡｌ）を含む層状構造のコバルト酸リチウムからなる芯粒子と、チタンが固溶したコバルト酸リチウムからなる表層を有する。また、元素Ａ（ＡはＷ、Ｍｏ、及びＢから選ばれる少なくとも１種の元素）を含む水可溶性のリチウム酸化物からなる最表面を有していてもよい。   The positive electrode active material particle powder according to the present invention has core particles made of lithium cobaltate having a layered structure containing the element M (M is Mg and / or Al), and a surface layer made of lithium cobaltate in which titanium is dissolved. Moreover, you may have the outermost surface which consists of a water-soluble lithium oxide containing the element A (A is at least 1 sort (s) of elements chosen from W, Mo, and B).

本発明に係る正極活物質粒子粉末の最表面に存在するリチウム酸化物の化学式はＬｉｚＡＯδ（ＡはＭｏ、Ｗ、Ｂのうち少なくとも１種、ＡがＭｏ又はＷの場合ｚ＝２、δ＝４、ＡがＢの場合ｚ＝３、δ＝３）である。即ち、Ａがモリブデン（Ｍｏ）の場合Ｌｉ２ＭｏＯ４、Ａがタングステン（Ｗ）の場合Ｌｉ２ＷＯ４、Ａがホウ素（Ｂ）の場合Ｌｉ３ＢＯ３である。これらの化合物は後述する可溶性塩とワルダー法による残存アルカリ成分の測定結果から定量化した。 The chemical formula of the lithium oxide present on the outermost surface of the positive electrode active material particle powder according to the present invention is Li z AO δ (A is at least one of Mo, W, and B, z = 2 when A is Mo or W, When δ = 4 and A is B, z = 3 and δ = 3). That is, Li 2 MoO 4 when A is molybdenum (Mo), Li 2 WO 4 when A is tungsten (W), and Li 3 BO 3 when A is boron (B). These compounds were quantified based on the measurement results of the soluble salts described later and the residual alkali components by the Walder method.

該最表面に存在するリチウム酸化物は二酸化炭素や水に対し溶解性を示すため、高温過充電状態で電池内部に生成した二酸化炭素や水を捕捉し、電池のガス膨れや電解液分解を抑制する働きを示すと考えている。また、該酸化物は電池内に残存、或いは生成する水と電解液との反応で生じたフッ酸に対し耐性を示すため、コバルト酸リチウム結晶の崩壊を抑制する働きも示すと考えている。従って、より高容量であり、且つ、より高温過充電特性に優れた電池特性を示すことができる。   Since the lithium oxide present on the outermost surface is soluble in carbon dioxide and water, it captures carbon dioxide and water generated inside the battery in a high-temperature overcharged state, and suppresses gas expansion and electrolyte decomposition of the battery. I think that it shows the work to do. In addition, since the oxide exhibits resistance to hydrofluoric acid remaining in the battery or generated by the reaction between the generated water and the electrolytic solution, it is considered that the oxide also functions to suppress the collapse of the lithium cobalt oxide crystal. Therefore, it is possible to exhibit battery characteristics that are higher in capacity and more excellent in high-temperature overcharge characteristics.

最表面に存在するリチウム化合物の含有量は、０．０１〜０．５重量％であることが好ましい。該最表面の含有量が０．０１重量％未満の場合、その効果は電池特性に見られず、また、０．５重量％を超える場合、容量が低下する場合がある。   The content of the lithium compound present on the outermost surface is preferably 0.01 to 0.5% by weight. When the content of the outermost surface is less than 0.01% by weight, the effect is not seen in the battery characteristics, and when it exceeds 0.5% by weight, the capacity may decrease.

本発明に係る正極活物質粒子粉末は一次粒子が凝集した二次粒子である。一次粒子は大きくなると層状構造特有のエッジが観察でき、結晶子サイズに近いことが分かる。そのため、一次粒子が大きいほど高温過充電試験に対し良好である。また、一次粒子が大きくなるほど、ＢＥＴ比表面積は低下する傾向にあり、電解液との接触面積が低減でき、高温過充電試験に対し良好となる。   The positive electrode active material particle powder according to the present invention is a secondary particle in which primary particles are aggregated. As the primary particles become larger, an edge peculiar to the layered structure can be observed, and it can be seen that it is close to the crystallite size. Therefore, the larger the primary particles, the better the high temperature overcharge test. In addition, as the primary particles become larger, the BET specific surface area tends to decrease, the contact area with the electrolytic solution can be reduced, and the high temperature overcharge test becomes better.

本発明に係る正極活物質粒子粉末の一次粒子は粒径が３μｍ以上であることが好ましい。それ未満の場合、結晶が弱く、高温過充電状態での結晶崩壊を抑制することが難しい。   The primary particles of the positive electrode active material particle powder according to the present invention preferably have a particle size of 3 μm or more. If it is less than that, the crystal is weak and it is difficult to suppress crystal collapse in a high-temperature overcharged state.

本発明に係る正極活物質粒子粉末の二次粒子の体積基準のメジアン径は１０〜３５μｍである。メジアン径が１０μｍ未満の場合、圧縮成型体密度は低くなり、高いエネルギー密度の電池の設計が難しくなる。メジアン径が３５μｍを超えて、他の特性を満たす粒子粉末を得ることは難しい。メジアン径は、より好ましくは１１〜３０μｍであり、さらに好ましくは１２〜２５μｍである。   The volume-based median diameter of the secondary particles of the positive electrode active material particle powder according to the present invention is 10 to 35 μm. When the median diameter is less than 10 μm, the density of the compression molded body becomes low, and it becomes difficult to design a battery having a high energy density. It is difficult to obtain a particle powder having a median diameter exceeding 35 μm and satisfying other characteristics. The median diameter is more preferably 11 to 30 μm, and further preferably 12 to 25 μm.

本発明に係る正極活物質粒子のＢＥＴ比表面積が０．０２〜０．２５ｍ２／ｇである。ＢＥＴ比表面積が０．０２ｍ２／ｇ未満の粒子を作製することは、現時点では困難である。ＢＥＴ比表面積が０．２５ｍ２／ｇを超える場合、電解液との接触面積が広くなり、高温過充電状態で正極活物質からのコバルトイオン溶出やガス発生を抑制できなくなる。ＢＥＴ比表面積は、より好ましくは０．０７〜０．２３ｍ２／ｇであり、さらに好ましくは０．０８〜０．２１ｍ２／ｇである。 The positive electrode active material particles according to the present invention have a BET specific surface area of 0.02 to 0.25 m 2 / g. It is currently difficult to produce particles with a BET specific surface area of less than 0.02 m 2 / g. When the BET specific surface area exceeds 0.25 m 2 / g, the contact area with the electrolytic solution becomes wide, and it becomes impossible to suppress elution of cobalt ions and gas generation from the positive electrode active material in a high temperature overcharged state. The BET specific surface area is more preferably 0.07 to 0.23 m 2 / g, and further preferably 0.08 to 0.21 m 2 / g.

本発明に係る正極活物質粒子粉末における残存アルカリ成分は８００ｐｐｍ以下が望ましい。その値を超える場合、アルカリ性が高くなり、電極スラリー作製時のゲル化の要因となり、電池特性に悪影響を及ぼすためである。   The residual alkali component in the positive electrode active material particle powder according to the present invention is desirably 800 ppm or less. When the value is exceeded, the alkalinity increases, which causes gelation during electrode slurry preparation and adversely affects battery characteristics.

本発明に係る正極活物質粒子粉末における未反応酸化コバルトＣｏ３Ｏ４は５００ｐｐｍ以下が望ましい。その値を超える場合、高温過充電特性が悪くなり、安全な電池の設計が難しくなる。 Unreacted cobalt oxide Co 3 O 4 in the positive electrode active material particles according to the present invention is less desirable 500 ppm. When the value is exceeded, the high-temperature overcharge characteristic is deteriorated, and it is difficult to design a safe battery.

本発明に係る正極活物質粒子粉末における２．５ｔｏｎ／ｃｍ２での圧縮成型体密度は３．５〜４．２ｇ／ｃｃが望ましい。３．５ｇ／ｃｃ未満の場合、高いエネルギー密度の電池の設計が難しくなる。４．２ｇ／ｃｃを超える場合、他の特性を満たす粒子粉末を得ることは難しい。 The density of the compression molded body at 2.5 ton / cm 2 in the positive electrode active material particle powder according to the present invention is preferably 3.5 to 4.2 g / cc. If it is less than 3.5 g / cc, it becomes difficult to design a battery having a high energy density. When it exceeds 4.2 g / cc, it is difficult to obtain a particle powder satisfying other characteristics.

圧縮成型体密度を上げるために、本発明に係る正極活物質粒子粉末に、体積基準のメジアン径が１〜７μｍの正極活物質粒子粉末を３〜２５重量％で混合したものを正極活物質として取り扱っても問題ない。体積基準のメジアン径が１〜７μｍの正極活物質粒子粉末として、望ましくは、ＬｉＣｏＯ２とＬｉ（Ｎｉ、Ｃｏ、Ｍｎ）Ｏ２の少なくとも１種である。体積基準のメジアン径が１〜７μｍの範囲外であれば、圧縮成型体密度を上げることが難しく、高いエネルギー密度の電池が得られない。 In order to increase the density of the compression molded body, the positive electrode active material particle powder according to the present invention mixed with 3 to 25% by weight of a positive electrode active material particle powder having a volume-based median diameter of 1 to 7 μm is used as the positive electrode active material. There is no problem with handling. The positive electrode active material particle powder having a volume-based median diameter of 1 to 7 μm is desirably at least one of LiCoO 2 and Li (Ni, Co, Mn) O 2 . If the volume-based median diameter is outside the range of 1 to 7 μm, it is difficult to increase the density of the compression molded body, and a battery having a high energy density cannot be obtained.

本発明に係る正極活物質粒子粉末に対して、混合する正極活物質はＬｉ（Ｎｉ１−ａ−ｂＣｏａＭｎｂ）Ｏ２（ａ及びｂは０．１５≦ａ≦０．４、０．１５≦ｂ≦０．５）であることが好ましい。ａの値が０．１５未満の場合やｂの値が０．５を超える場合、所望の層状構造が形成されにくくなり、高性能の正極活物質として機能しにくくなる。また、ａの値が０．４を超える場合やｂの値が０．１５未満の場合、高温過充電試験に劣る正極活物質となり、混合する効果が現れない。混合する正極活物質のＬｉとＯの各々の量は僅かに化学量論組成比の１と２の値からずれても構わず、特に限定しない。 With respect to the positive electrode active material particle powder according to the present invention, the positive electrode active material to be mixed is Li (Ni 1-ab Co a Mn b ) O 2 (a and b are 0.15 ≦ a ≦ 0.4, 0 .15 ≦ b ≦ 0.5). When the value of a is less than 0.15 or when the value of b exceeds 0.5, it becomes difficult to form a desired layered structure, and it becomes difficult to function as a high-performance positive electrode active material. Moreover, when the value of a exceeds 0.4 or when the value of b is less than 0.15, it becomes a positive electrode active material inferior to a high temperature overcharge test, and the effect of mixing does not appear. The amount of each of Li and O of the positive electrode active material to be mixed may be slightly deviated from the values of 1 and 2 in the stoichiometric composition ratio, and is not particularly limited.

本発明に係る正極活物質粒子粉末に対して、混合する正極活物質Ｌｉ（Ｎｉ１−ａ−ｂＣｏａＭｎｂ）Ｏ２（ａ及びｂは０．１５≦ａ≦０．４、０．１５≦ｂ≦０．５）は体積基準のメジアン径が１〜７μｍであることが好ましい。１μｍ未満では高温過充電試験に優れる正極活物質は得られず、また、７μｍを超えては圧縮成型体密度が向上した正極活物質は得られない。 The positive electrode active material powder according to the present invention is mixed with the positive electrode active material Li (Ni 1-ab Co a Mn b ) O 2 (a and b are 0.15 ≦ a ≦ 0.4, 0. 15 ≦ b ≦ 0.5) preferably has a volume-based median diameter of 1 to 7 μm. If it is less than 1 μm, a positive electrode active material excellent in the high-temperature overcharge test cannot be obtained, and if it exceeds 7 μm, a positive electrode active material having an improved compression molded body density cannot be obtained.

本発明に係る正極活物質粒子粉末に対して、混合する正極活物質Ｌｉ（Ｎｉ１−ａ−ｂＣｏａＭｎｂ）Ｏ２（ａ及びｂは０．１５≦ａ≦０．４、０．１５≦ｂ≦０．５）は３〜２５重量％であることが好ましい。３重量％未満、又は２５重量％を超えては、圧縮成型体密度が向上した正極活物質は得られない。 The positive electrode active material powder according to the present invention is mixed with the positive electrode active material Li (Ni 1-ab Co a Mn b ) O 2 (a and b are 0.15 ≦ a ≦ 0.4, 0. 15 ≦ b ≦ 0.5) is preferably 3 to 25% by weight. When the amount is less than 3% by weight or exceeds 25% by weight, a positive electrode active material having an improved compression molded body density cannot be obtained.

次に、本発明に係る正極活物質粒子粉末の製造法について述べる。   Next, a method for producing the positive electrode active material particle powder according to the present invention will be described.

本発明に係る正極活物質粒子粉末は該粒子の多層構造を形成させるために２度の焼成を含む固相反応法を基に作製される。固相反応とは構成する元素を含む原料を混合し、高温の熱処理により固体同士の化学反応を促進させ、目的の相を得る方法である。   The positive electrode active material particle powder according to the present invention is produced based on a solid-phase reaction method including two firings in order to form a multilayer structure of the particles. The solid-phase reaction is a method in which raw materials containing constituent elements are mixed and a chemical reaction between solids is promoted by high-temperature heat treatment to obtain a target phase.

本発明に係る正極活物質粒子粉末は１度目の焼成で芯粒子となる層状構造のコバルト酸リチウムを作製し、２度目の焼成でＴｉを固溶させたコバルト酸リチウムからなる表層を該粒子に形成することで製造できる。また、モリブデン、タングステン、ホウ素のうち少なくとも１種を含むリチウム酸化物からなる最表面は、２度目の焼成時に表層と同時に形成することができる。   The positive electrode active material particle powder according to the present invention produces a lithium cobaltate having a layered structure that becomes a core particle in the first firing, and a surface layer made of lithium cobaltate in which Ti is dissolved in the second firing as a particle. It can be manufactured by forming. Further, the outermost surface made of lithium oxide containing at least one of molybdenum, tungsten, and boron can be formed simultaneously with the surface layer during the second firing.

まず、第一工程について説明する。第一工程ではリチウム原料とコバルト原料と元素Ｍ原料（ＭはＭｇ及び／又はＡｌ）を混合後、８００〜１１００℃で焼成を行って層状構造のコバルト酸リチウム粒子粉末を作製する。   First, the first step will be described. In the first step, a lithium raw material, a cobalt raw material, and an element M raw material (M is Mg and / or Al) are mixed and then fired at 800 to 1100 ° C. to produce a lithium cobaltate particle powder having a layered structure.

芯粒子のコバルト酸リチウム粒子粉末の原料には構成元素を有する種々の化合物を用いることができる。   Various compounds having a constituent element can be used as a raw material for the lithium cobalt oxide particle powder of the core particle.

芯粒子の原料の混合は溶媒を用いない乾式法によることが望ましい。原料粉末の混合装置としては、らいかい機、ボールミル、ヘンシェルミキサー、ハイスピードミキサー等を用いることができる。   It is desirable to mix the raw materials for the core particles by a dry method that does not use a solvent. As a mixing device for the raw material powder, a raking machine, a ball mill, a Henschel mixer, a high speed mixer, or the like can be used.

芯粒子のリチウム原料としてはＬｉＯＨ・Ｈ２Ｏ、Ｌｉ２ＣＯ３が好ましい。リチウムの原料粉末は、固相反応中のリチウムの拡散を容易にするために粒径が微細なものを用いることが望ましい。 As a lithium raw material for the core particles, LiOH.H 2 O and Li 2 CO 3 are preferable. It is desirable to use a lithium raw material powder having a fine particle size in order to facilitate diffusion of lithium during the solid-phase reaction.

芯粒子のコバルト原料としてはＣｏ（ＯＨ）２、ＣｏＯＯＨ、Ｃｏ３Ｏ４が好ましい。コバルトの原料粉末は、該粒径が本発明で得られる正極活物質粒子粉末の粒径に強く影響を与えるため、メジアン径Ｄ５０が所望の正極活物質粒子粉末のＤ５０と近い値であることが好ましい。 As the cobalt raw material of the core particles, Co (OH) 2 , CoOOH, and Co 3 O 4 are preferable. Raw material powder cobalt, to provide a strong influence on the particle size of the positive electrode active material particles the particle size is obtained in the present invention, the median diameter D 50 is a value close to the D 50 of the desirable positive electrode active material particles It is preferable.

芯粒子の添加物元素Ｍ（ＭはＭｇ及び／又はＡｌ）はコバルト原料中に含まれていても、元素Ｍの化合物を添加しても構わない。元素Ｍの化合物としては酸化物、水酸化物、炭酸塩が好ましい。添加物元素Ｍの原料粉末は固相反応性の高い微細なものが望ましい。   The additive element M (M is Mg and / or Al) of the core particle may be contained in the cobalt raw material, or a compound of the element M may be added. The compound of the element M is preferably an oxide, hydroxide, or carbonate. The raw material powder of additive element M is preferably a fine powder having high solid phase reactivity.

芯粒子を得る１度目の焼成の温度は８００〜１１００℃である。該温度での焼成時間は５〜１５時間程度であり、焼成の昇温、降温速度は１００〜２００℃／時間程度である。焼成温度が８００℃未満では固相反応が十分でなく、得られた正極活物質での電池の容量は至って低い。一方、焼成温度が１１００℃を超える場合、リチウムの蒸発が抑えきれず、化学組成のずれを引き起し、また、電気炉の劣化を促進させる。焼成温度はより好ましくは９３０〜１０５０℃である。   The temperature of the first firing to obtain core particles is 800-1100 ° C. The firing time at this temperature is about 5 to 15 hours, and the temperature rise and temperature drop rate of firing is about 100 to 200 ° C./hour. When the firing temperature is less than 800 ° C., the solid phase reaction is not sufficient, and the battery capacity of the obtained positive electrode active material is extremely low. On the other hand, when the firing temperature exceeds 1100 ° C., the evaporation of lithium cannot be suppressed, causing a shift in chemical composition and promoting the deterioration of the electric furnace. The firing temperature is more preferably 930 to 1050 ° C.

焼成炉としては、ガス流通式箱型マッフル炉、ガス流通式回転炉、ローラーハースキルン等を用いることができる。   As the firing furnace, a gas flow box muffle furnace, a gas flow rotary furnace, a roller hearth kiln, or the like can be used.

焼成の後に、焼成物の粉砕、分級を行っても構わない。粉砕装置として、らいかい機、衝撃式微粉砕機、流体粉砕機等がある。   After firing, the fired product may be pulverized and classified. Examples of the pulverizer include a rough machine, an impact pulverizer, and a fluid pulverizer.

次に、第二工程について説明する。第二工程では、第一工程で得られたコバルト酸リチウム粒子粉末とチタン原料とリチウム原料とを混合後、８００〜１１００℃で焼成を行って表層を形成して、本発明に係る正極活物質粒子粉末を作製する。   Next, the second step will be described. In the second step, the lithium cobalt oxide particle powder obtained in the first step, the titanium raw material, and the lithium raw material are mixed, and then fired at 800 to 1100 ° C. to form a surface layer, whereby the positive electrode active material according to the present invention A particle powder is prepared.

また、第二工程で、第一工程で得られたコバルト酸リチウム粒子粉末とチタン原料と元素Ａ原料（ＡはＷ、Ｍｏ、及びＢから選ばれる少なくとも１種の元素）とリチウム原料とを混合後、８００〜１１００℃で焼成を行って表層及び最表面を形成してもよい。   In the second step, the lithium cobalt oxide particle powder obtained in the first step, the titanium raw material, the element A raw material (A is at least one element selected from W, Mo, and B) and the lithium raw material are mixed. Then, baking may be performed at 800 to 1100 ° C. to form the surface layer and the outermost surface.

表層と最表面の原料には構成元素を有する種々の化合物を用いることができる。   Various compounds having constituent elements can be used for the surface layer and the outermost surface material.

表層及び最表面の原料の混合は乾式法、湿式法のいずれでも構わない。   Mixing of the surface layer and the raw material on the outermost surface may be either a dry method or a wet method.

表層及び最表面の原料の混合を乾式法で行う場合、原料粉末の混合装置としては、らいかい機、ボールミル、ヘンシェルミキサー、ハイスピードミキサー等を用いることができる。   When mixing the raw material of the surface layer and the outermost surface by a dry method, as a raw material powder mixing apparatus, a raking machine, a ball mill, a Henschel mixer, a high speed mixer, or the like can be used.

表層及び最表面の原料の混合を湿式法で行う場合、水溶媒を用いて、構成元素の酸化物、水酸化物、或いは炭酸塩として共沈させ、水洗、濾別、乾燥をして混合原料粉末を得ることが望ましい。   When mixing the raw material of the surface layer and the outermost surface by a wet method, it is coprecipitated as an oxide, hydroxide, or carbonate of a constituent element using a water solvent, washed with water, filtered and dried, and mixed raw material It is desirable to obtain a powder.

そのため、乾式混合を用いる場合には、酸化物、水酸化物、炭酸塩を原料とすることが望ましく、湿式混合を用いる場合、硫酸塩、硝酸塩、塩化物を原料とすることが望ましい。   Therefore, when dry mixing is used, it is desirable to use oxides, hydroxides, and carbonates as raw materials, and when wet mixing is used, it is desirable to use sulfates, nitrates, and chlorides as raw materials.

表層及び最表面のリチウム原料はＬｉＯＨ・Ｈ２Ｏ、Ｌｉ２ＣＯ３であることが好ましい。 The surface layer and the outermost lithium raw material are preferably LiOH.H 2 O and Li 2 CO 3 .

表層のチタン原料はＴｉＯ２・ｎＨ２Ｏ、Ｔｉ（ＳＯ４）２、ＴｉＣｌ４であることが好ましい。 The titanium material for the surface layer is preferably TiO 2 · nH 2 O, Ti (SO 4 ) 2 , or TiCl 4 .

最表面の添加物元素Ａの原料はモリブデン（Ｍｏ）、タングステン（Ｗ）、ホウ素（Ｂ）の酸化物、水酸化物、炭酸塩、硫酸塩、硝酸塩、塩化物であることが好ましい。   The raw material of the additive element A on the outermost surface is preferably molybdenum (Mo), tungsten (W), boron (B) oxide, hydroxide, carbonate, sulfate, nitrate, or chloride.

表層及び最表面を得る２度目の焼成温度は、８００〜１１００℃である。該温度での焼成時間は５〜１５時間程度であり、焼成の昇温、降温速度は１００〜２００℃／時間程度である。焼成温度が８００℃未満では固相反応が十分でなく、得られた正極活物質での電池の容量は至って低い。一方、焼成温度が１１００℃を超える場合、リチウムの蒸発が抑えきれず、化学組成のずれを引き起し、また、電気炉の劣化を促進させる。焼成温度はより好ましくは８５０〜１０４０℃である。   The second baking temperature for obtaining the surface layer and the outermost surface is 800 to 1100 ° C. The firing time at this temperature is about 5 to 15 hours, and the temperature rise and temperature drop rate of firing is about 100 to 200 ° C./hour. When the firing temperature is less than 800 ° C., the solid phase reaction is not sufficient, and the battery capacity of the obtained positive electrode active material is extremely low. On the other hand, when the firing temperature exceeds 1100 ° C., the evaporation of lithium cannot be suppressed, causing a shift in chemical composition and promoting the deterioration of the electric furnace. The firing temperature is more preferably 850 to 1040 ° C.

焼成炉としては、ガス流通式箱型マッフル炉、ガス流通式回転炉、ローラーハースキルン等を用いることができる。   As the firing furnace, a gas flow box muffle furnace, a gas flow rotary furnace, a roller hearth kiln, or the like can be used.

第一工程で得られたコバルト酸リチウムと表層の原料とを混合し、２度目の焼成を行うことによって、芯粒子表層にＴｉが固溶した結晶相が形成される。また、該コバルト酸リチウムと表層および最表面の原料との混合物を焼成することで、表層と同時に元素Ａを含む水可溶性のリチウム酸化物からなる最表面が形成される。該表層もまた芯粒子表面にＴｉが拡散することで形成される。   The lithium cobaltate obtained in the first step and the raw material for the surface layer are mixed and fired for the second time, whereby a crystalline phase in which Ti is dissolved in the core particle surface layer is formed. Moreover, the outermost surface which consists of a water-soluble lithium oxide containing the element A is formed simultaneously with a surface layer by baking the mixture of this lithium cobaltate, a surface layer, and the raw material of the outermost surface. The surface layer is also formed by diffusion of Ti on the surface of the core particle.

焼成の後に、焼成物の粉砕、篩分けを行っても構わない。粉砕装置として、らいかい機、衝撃式微粉砕機、流体粉砕機等がある。   After firing, the fired product may be pulverized and sieved. Examples of the pulverizer include a rough machine, an impact pulverizer, and a fluid pulverizer.

次に、本発明に係る正極活物質粒子粉末を正極活物質として用いた非水電解液二次電池について述べる。   Next, a non-aqueous electrolyte secondary battery using the positive electrode active material particle powder according to the present invention as a positive electrode active material will be described.

本発明に係る正極活物質粒子粉末を用いて正極シートを製造する場合には、常法に従って、導電剤と結着剤を添加混合する。導電剤としてはカーボンブラック、グラファイト等が好ましい。結着剤としてはポリテトラフルオロエチレン、ポリフッ化ビニリデン等が好ましい。溶媒として、例えば、Ｎ−メチル−ピロリドンを用いることが好ましい。正極活物質粒子粉末と導電材と結着剤該添加物を含むスラリーを蜂蜜状になるまで混練する。得られた正極合剤スラリーを溝が２５μｍ〜５００μｍのドクターブレードで塗布速度は約６０ｃｍ／ｓｅｃで集電体上に塗布し、溶媒除去と結着剤軟化のため８０〜１８０℃で乾燥する。集電体には約２０μｍのＡｌ箔を用いる。正極合剤を塗布した集電体に線圧０．１〜３ｔ／ｃｍのカレンダーロール処理を行って正極シートを得る。   When manufacturing a positive electrode sheet using the positive electrode active material particle powder according to the present invention, a conductive agent and a binder are added and mixed according to a conventional method. As the conductive agent, carbon black, graphite or the like is preferable. As the binder, polytetrafluoroethylene, polyvinylidene fluoride and the like are preferable. For example, N-methyl-pyrrolidone is preferably used as the solvent. The slurry containing the positive electrode active material particle powder, the conductive material and the binder and the additive is kneaded until it becomes honey. The obtained positive electrode mixture slurry is applied onto a current collector with a doctor blade having a groove of 25 μm to 500 μm at a coating speed of about 60 cm / sec, and dried at 80 to 180 ° C. to remove the solvent and soften the binder. An Al foil of about 20 μm is used for the current collector. The current collector coated with the positive electrode mixture is subjected to a calender roll treatment with a linear pressure of 0.1 to 3 t / cm to obtain a positive electrode sheet.

本発明に係る正極活物質粒子粉末は圧縮成型体密度が高く、また、該正極活物質のＢＥＴ比表面積が低いため、正極合剤スラリーへの結着剤添加量を低減でき、結果として密度の高い正極シートが得られる。また、メジアン径が１〜７μｍの小粒径の正極活物質を混合することでより高密度の正極シートを得ることができる。   The positive electrode active material particle powder according to the present invention has a high compression-molded body density, and since the BET specific surface area of the positive electrode active material is low, the amount of binder added to the positive electrode mixture slurry can be reduced. A high positive electrode sheet is obtained. Moreover, a higher-density positive electrode sheet can be obtained by mixing a positive electrode active material having a small particle diameter with a median diameter of 1 to 7 μm.

負極活物質としては、リチウム金属、リチウム／アルミニウム合金、リチウム／スズ合金、黒鉛等を用いることができ、正極と同様のドクターブレード法や金属圧延により負極シートは作製される。   As the negative electrode active material, lithium metal, lithium / aluminum alloy, lithium / tin alloy, graphite or the like can be used, and the negative electrode sheet is produced by the same doctor blade method or metal rolling as the positive electrode.

また、電解液の溶媒としては、炭酸エチレンと炭酸ジエチルの組み合わせ以外に、炭酸プロピレン、炭酸ジメチル等のカーボネート類や、ジメトキシエタン等のエーテル類の少なくとも１種類を含む有機溶媒を用いることができる。   In addition to the combination of ethylene carbonate and diethyl carbonate, an organic solvent containing at least one of carbonates such as propylene carbonate and dimethyl carbonate and ethers such as dimethoxyethane can be used as the solvent for the electrolytic solution.

さらに、電解質としては、六フッ化リン酸リチウム以外に、過塩素酸リチウム、四フッ化ホウ酸リチウム等のリチウム塩の少なくとも１種類を上記溶媒に溶解して用いることができる。   Further, as the electrolyte, in addition to lithium hexafluorophosphate, at least one lithium salt such as lithium perchlorate and lithium tetrafluoroborate can be dissolved in the above solvent and used.

本発明に係る正極活物質を用いて製造した対極Ｌｉの二次電池は、２５℃において、４．４Ｖと４，５Ｖでの充電後の初期放電容量が、各々１７０ｍＡｈ／ｇ、１９０ｍＡｈ／ｇ以上である。また、２５℃において、４．４Ｖと４，５Ｖでの充電、３．０Ｖまでの放電での５１回目の放電容量維持率は、各々８５％、８０％以上である。更に、後述する評価法の高温過充電試験において、６０℃での漏れ電気量は２５ｍＡｈ／ｇ以下であり、優れた電池特性を示す。   The secondary battery of the counter electrode Li manufactured using the positive electrode active material according to the present invention has initial discharge capacities of 170 mAh / g and 190 mAh / g or more at 25 ° C. after charging at 4.4 V and 4, 5 V, respectively. It is. In addition, at 25 ° C., the discharge capacity maintenance ratios at the 51st time in charging at 4.4 V and 4,5 V and discharging to 3.0 V are 85% and 80% or more, respectively. Furthermore, in a high-temperature overcharge test of an evaluation method described later, the amount of electricity leaked at 60 ° C. is 25 mAh / g or less, indicating excellent battery characteristics.

＜作用＞
本発明に係る正極活物質粒子粉末は、芯粒子に高容量を示すコバルト酸リチウムを用いる。該コバルト酸リチウム粒子表面は微量のＴｉが固溶した層を形成しているため、コバルトイオンの溶出を抑制することができ、高容量で、高温過充電試験と充放電繰り返し特性に優れる二次電池を製造できる。 <Action>
The positive electrode active material particle powder according to the present invention uses lithium cobalt oxide having a high capacity as the core particle. Since the surface of the lithium cobalt oxide particles forms a layer in which a small amount of Ti is dissolved, it is possible to suppress elution of cobalt ions, a high capacity, and a secondary that excels in high temperature overcharge test and charge / discharge repeatability. A battery can be manufactured.

また、本発明に係る正極活物質粒子粉末が、粒子の最表面に少量の耐酸化性のモリブデン、タングステン、ホウ素からなるリチウム化合物を有すると電解液の分解を抑制するため、高容量で、高温過充電試験と充放電繰り返し特性に優れる二次電池を製造できる。   In addition, when the positive electrode active material particle powder according to the present invention has a small amount of oxidation-resistant molybdenum, tungsten, or boron compound on the outermost surface of the particle to suppress decomposition of the electrolyte, it has a high capacity and a high temperature. A secondary battery having excellent overcharge test and charge / discharge repetition characteristics can be manufactured.

本発明の具体的な実施の例を以下に示す。   Specific examples of implementation of the present invention are shown below.

炭酸リチウムＬｉ２ＣＯ３は純度９９．４％の東洋ケミカルズ株式会社製を用いた。オキシ水酸化コバルトＣｏＯＯＨは下記参考文献を元に作製し、Ｄ５０＝１７．２μｍの粉末を得た。得られたオキシ水酸化コバルトは、ＥＤＴＡ（エチレンジアミン四酢酸）によるキレート滴定により測定した純度が９４．７％であった。水酸化マグネシウムＭｇ（ＯＨ）２は宇部マテリアルズ株式会社製、及び水酸化アルミニウムＡｌ（ＯＨ）３は日本軽金属株式会社製を用いた。これらの化学式と純度から原料仕込み量を決定した。 Lithium carbonate Li 2 CO 3 manufactured by Toyo Chemicals Co., Ltd. having a purity of 99.4% was used. Cobalt oxyhydroxide CoOOH was prepared based on the following reference, and a powder of D 50 = 17.2 μm was obtained. The obtained cobalt oxyhydroxide had a purity of 94.7% as measured by chelate titration with EDTA (ethylenediaminetetraacetic acid). Magnesium hydroxide Mg (OH) 2 manufactured by Ube Materials Co., Ltd. and aluminum hydroxide Al (OH) 3 manufactured by Nippon Light Metal Co., Ltd. were used. The raw material charge was determined from these chemical formulas and purity.

＜参考文献＞
特許第５２９６９４８号、戸田工業株式会社 <References>
Patent No. 5296948, Toda Industry Co., Ltd.

本発明の正極活物質粒子粉末の粉体評価は以下のように行った。   The powder evaluation of the positive electrode active material particle powder of the present invention was performed as follows.

第一工程と第二工程で得られる試料の主成分元素であるリチウム、コバルト、マグネシウム、アルミニウム、チタン、モリブデン、タングステン、ホウ素の含有量は、該試料粉末を２０％塩酸で完全に溶解後、ＩＣＰ発光分光分析装置（ＩＣＰ−ＯＥＳ）Ｏｐｔｉｍａ８３００［株式会社パーキンエルマージャパン］を用い、検量線法で測定した。   The content of lithium, cobalt, magnesium, aluminum, titanium, molybdenum, tungsten, and boron, which are the main components of the sample obtained in the first step and the second step, is determined by completely dissolving the sample powder with 20% hydrochloric acid. It measured by the analytical curve method using ICP emission-spectral-analysis apparatus (ICP-OES) Optima8300 [Perkin Elmer Japan Co., Ltd.].

試料の表面を観察することと化学組成を分析するためにエネルギー分散型Ｘ線分析装置付き走査電子顕微鏡ＳＥＭのＪＳＭ−７１００［日本電子株式会社］を用いた。   In order to observe the surface of the sample and analyze the chemical composition, JSM-7100 [JEOL Ltd.] of a scanning electron microscope SEM with an energy dispersive X-ray analyzer was used.

ＢＥＴ比表面積は試料を窒素ガス下で１２０℃、４５分間乾燥脱気した後、Ｍａｃｓｏｒｂ［（株）マウンテック］を用いた。また、下記（１）式からＢＥＴ換算粒径を算出した。この際、粒子は真球状であり、コバルト酸リチウムの真密度として、５．１ｇ／ｃｃを用いた。
ＢＥＴ換算粒径（μｍ）＝６／ＢＥＴ値（ｍ２／ｇ）／真密度（ｇ／ｃｃ）・・・（１） For the BET specific surface area, the sample was dried and deaerated under nitrogen gas at 120 ° C. for 45 minutes, and then Macsorb [Co., Ltd., Mountec] was used. Further, the BET equivalent particle diameter was calculated from the following formula (1). At this time, the particles were spherical, and 5.1 g / cc was used as the true density of lithium cobaltate.
BET equivalent particle size (μm) = 6 / BET value (m 2 / g) / true density (g / cc) (1)

試料の表層近辺の結晶構造と組成を確認するために、樹脂包埋処理を行い、ＦＩＢ（収束イオンビーム、Ｆｏｃｕｓｅｄ Ｉｏｎ Ｂｅａｍ）のＪＥＭ−９３２０［日本電子株式会社］で１００ｎｍ以下に薄片化した。透過型電子顕微鏡ＴＥＭのＪＥＭ−２１００［日本電子株式会社］に付随したＮＥＤ（ナノビーム電子線回折、Ｎａｎｏ Ｅｌｅｃｔｒｏｎ Ｄｉｆｆｒａｃｔｉｏｎ）やＥＤＸ（エネルギー分散型Ｘ線分析、Ｅｎｅｒｇｙ Ｄｉｓｐｅｒｓｉｖｅ Ｘ−ｒａｙ ｓｐｅｃｔｒｏｍｅｔｒｙ）を用いて観察した。   In order to confirm the crystal structure and composition in the vicinity of the surface layer of the sample, resin embedding treatment was performed, and it was sliced to 100 nm or less with JEM-9320 (JEOL Ltd.) of FIB (focused ion beam, Focused Ion Beam). Observation using NEM (Nano Electron Diffraction) and EDX (Energy Dispersive X-ray spectroscopy) attached to JEM-2100 [JEOL Ltd.] of transmission electron microscope TEM did.

試料の表層のＴｉの固溶領域、即ちＴｉが固溶した表層の層厚を算出するために、粒子粉末を樹脂に包埋し、クロスセクションポリッシャー（ＣＰ、Ｃｒｏｓｓ Ｓｅｃｔｉｏｎ Ｐｏｌｉｓｈｅｒ）のＳＭ−０９０１０［日本電子株式会社］で粒子を切断後、電界放射型オージェ電子顕微鏡ＦＥ−ＡＥＳのＪＡＭＰ−９５００Ｆ［日本電子株式会社］で観察した。加速電圧２０ｋＶ、照射電流４ｎＡとし、断面箇所の２０ｎｍφの範囲で深さ方向数ｎｍを点分析できるようにした。エネルギー範囲として、Ｔｉは３５５−４３５ｅＶ、Ｃｏは７３０−８００ｅＶ、各々１０回測定し、平均化したスペクトルが得られた。得られたスペクトルは電子のエネルギーＥに対するＥとＮ（Ｅ）の積である。ここで、Ｎ（Ｅ）はエネルギーの分布である。   In order to calculate the solid solution region of Ti on the surface layer of the sample, that is, the layer thickness of the surface layer in which Ti was dissolved, the particle powder was embedded in resin, and SM-09010 [CP, Cross Section Polisher] was used. The particles were cut with JEOL Ltd., and then observed with a JAMP-9500F (JEOL Ltd.) of a field emission Auger electron microscope FE-AES. The acceleration voltage was 20 kV, the irradiation current was 4 nA, and a point analysis of several nm in the depth direction was made possible within the range of 20 nmφ at the cross section. As energy ranges, Ti was measured at 355-435 eV, and Co was measured at 730-800 eV, 10 times each, and an averaged spectrum was obtained. The obtained spectrum is the product of E and N (E) with respect to the electron energy E. Here, N (E) is an energy distribution.

図４（１）に示すように試料断面において、粒子表面から粒子内部へ向かって点分析を直線的に行い、得られたＴｉによる３８５ｅＶ付近を極小とする微分形式のスペクトルの強度ｄ [Ｅ・Ｎ（Ｅ）]／ｄＥを読み取った。即ち、図４（１）では、粒子表面の該スペクトル強度は８２である。粒子内部に進むほど、該スペクトル強度は３３、２０、１８、１６と下がった。図４（２）に示すように、１１地点の粒子表面からの距離に対する該スペクトル強度をプロットし、該スペクトル強度が３０以下をＴｉの検出限界とし、表面からその距離を各々の地点のＴｉが固溶した表層の層厚とした。算術平均により該層厚の平均値を表１に記した。測定地点の数に対するＴｉが検出された数から、芯粒子に対する被覆率として表１に記した。   As shown in FIG. 4 (1), a point analysis is linearly performed from the particle surface toward the inside of the particle in the sample cross section, and the intensity d [E · N (E)] / dE was read. That is, in FIG. 4 (1), the spectral intensity on the particle surface is 82. The spectral intensity decreased to 33, 20, 18, and 16 as it proceeded to the inside of the particle. As shown in FIG. 4 (2), the spectrum intensity with respect to the distance from the particle surface at 11 points is plotted, the spectrum intensity is 30 or less as the Ti detection limit, and the distance from the surface is the Ti at each point. It was set as the layer thickness of the surface layer which carried out solid solution. The average value of the layer thickness is shown in Table 1 by arithmetic mean. From the number of Ti detected with respect to the number of measurement points, the coverage for core particles is shown in Table 1.

これらと同様に、各試料の任意の１０〜１４地点において、図４（１）と同様の点分析と図４（２）のプロットを行い、各試料の表層の平均層厚と被覆率を算出し、表１に記した。   Similarly to these, the point analysis similar to FIG. 4 (1) and the plot of FIG. 4 (2) are performed at arbitrary 10 to 14 points of each sample, and the average layer thickness and coverage of each sample are calculated. And listed in Table 1.

ＩＣＰ発光分光分析で得られた試料のＴｉ／Ｃｏ比は、前述の真球状粒子と仮定したＢＥＴ換算粒径の表層のＴｉ／Ｃｏ比と芯粒子のＣｏ量に対応するとした。前記記載の方法で得られた平均の層厚を形成したとして、芯粒子の体積と表層の体積を割り出し、表層のＴｉ／Ｃｏ（ｍｏｌ比）を算出して、表１に記載した。   The Ti / Co ratio of the sample obtained by ICP emission spectroscopic analysis was assumed to correspond to the Ti / Co ratio of the surface layer of the BET equivalent particle diameter assumed to be the above-mentioned spherical particles and the Co amount of the core particles. The average layer thickness obtained by the method described above was formed, and the volume of the core particles and the volume of the surface layer were calculated, and Ti / Co (mol ratio) of the surface layer was calculated and listed in Table 1.

試料の結晶相の確認のため、粉末Ｘ線回折装置ＳｍａｒｔＬａｂ［株式会社リガク製］を用いて測定した。Ｘ線回折パターンはＣｕ−Ｋα、４５ｋＶ，２００ｍＡの条件下で、モノクロメータ通して測定し、最高ピーク強度のｃｏｕｎｔ数が６０００〜１２０００になるよう、０．０１°のステップで、計数時間１．０秒で２θが１５〜９０°の範囲で測定した。外部標準試料としてＮＩＳＴ（Ｎａｔｉｏｎａｌ Ｉｎｓｔｉｔｕｔｅ ｏｆ Ｓｔａｎｄａｒｄｓ ａｎｄ Ｔｅｃｈｎｏｌｏｇｙ）のＳＲＭ６６０ｂを用い、Ｒｉｅｔｖｅｌｄ解析プログラムにＲＩＥＴＡＮ２０００を用いた。   In order to confirm the crystal phase of the sample, measurement was performed using a powder X-ray diffractometer SmartLab [manufactured by Rigaku Corporation]. The X-ray diffraction pattern was measured through a monochromator under the conditions of Cu-Kα, 45 kV, 200 mA, and the counting time was 1. in steps of 0.01 ° so that the number of counts of the maximum peak intensity was 6000 to 12000. Measurements were made in the range of 2 to 15 ° to 90 ° at 0 seconds. SRM660b of NIST (National Institute of Standards and Technology) was used as an external standard sample, and Rietan2000 was used as a Rietveld analysis program.

水可溶性塩の測定方法として、試料５ｇを１００ｃｃ純水で、２０分間煮沸した溶液を室温まで冷やし、濾別後、ＩＣＰ発光分光分析装置にて分析した。層状構造のコバルト酸リチウムやコバルト・チタン酸リチウムは水に不溶であるから、水可溶性塩の測定によって最表面に露出した水可溶性の化合物の元素量を測定できる。水可溶性塩として、検出されたＬｉ、Ｗ、Ｍｏ、Ｂの量と後述するワルダー法による残存アルカリ成分量から、最表面に形成される化合物は推定できる。即ち、最表面はＬｉｚＡＯδ（ＡはＷ、Ｍｏ、Ｂのうち少なくとも１種、ＡがＷ及び／又Ｍｏの場合ｚ＝２、δ＝４、ＡがＢの場合ｚ＝３、δ＝３）で表される化合物であり、Ｌｉ２ＷＯ４、Ｌｉ２ＭｏＯ４、及びＬｉ３ＢＯ３である。 As a method for measuring water-soluble salts, a solution obtained by boiling 5 g of a sample with 100 cc pure water for 20 minutes was cooled to room temperature, filtered, and then analyzed with an ICP emission spectroscopic analyzer. Since the layered lithium cobaltate and cobalt / lithium titanate are insoluble in water, the amount of the element of the water-soluble compound exposed on the outermost surface can be measured by measuring the water-soluble salt. As the water-soluble salt, the compound formed on the outermost surface can be estimated from the detected amounts of Li, W, Mo, B and the residual alkali component amount by the Walder method described later. That is, the outermost surface is Li z AO δ (A is at least one of W, Mo, and B, z = 2, δ = 4 when A is W and / or Mo, and z = 3, δ when A is B. = 3), Li 2 WO 4 , Li 2 MoO 4 , and Li 3 BO 3 .

残存アルカリ成分として、ワルダー法で得られた水酸化リチウムと炭酸リチウムの量を炭酸リチウム量に換算した数値を用いた。即ち、試料１０．０ｇを水５０ｍｌに１時間分散させ、その後、１時間静置した後、上澄み液を塩酸で滴定した。その際の指示薬はフェノールフタレインとブロモフェノールブルーを用い水酸化リチウムと炭酸リチウムを定量し、全て炭酸リチウム量に換算した。但し、前記Ｌｉ２ＷＯ４、Ｌｉ２ＭｏＯ４、及びＬｉ３ＢＯ３の影響は計算により除外していている。 As the residual alkali component, a numerical value obtained by converting the amount of lithium hydroxide and lithium carbonate obtained by the Walder method into the amount of lithium carbonate was used. That is, 10.0 g of a sample was dispersed in 50 ml of water for 1 hour, then allowed to stand for 1 hour, and then the supernatant was titrated with hydrochloric acid. In this case, phenolphthalein and bromophenol blue were used as indicators, and lithium hydroxide and lithium carbonate were quantified, and all were converted to the amount of lithium carbonate. However, the influence of Li 2 WO 4 , Li 2 MoO 4 , and Li 3 BO 3 is excluded by calculation.

未反応酸化コバルトＣｏ３Ｏ４の定量は、酸化コバルトとコバルト酸リチウムとの硫酸鉄溶液に対する溶解度の違いを利用した。即ち、試料を硫酸鉄溶液に分散し、１時間放置後、未溶解成分を未反応酸化コバルトとみなした。該未溶解成分はフィルターで濾別され、フィルター上の残存物を塩酸に溶かし、コバルト量をＩＣＰ発光分光分析装置で定量し、酸化コバルトＣｏ３Ｏ４に換算した。 Unreacted cobalt oxide Co 3 O 4 was quantified using the difference in solubility between cobalt oxide and lithium cobaltate in an iron sulfate solution. That is, the sample was dispersed in an iron sulfate solution and allowed to stand for 1 hour, and then the undissolved component was regarded as unreacted cobalt oxide. The undissolved component was filtered off with a filter, the residue on the filter was dissolved in hydrochloric acid, the amount of cobalt was quantified with an ICP emission spectroscopic analyzer, and converted to cobalt oxide Co 3 O 4 .

試料のメジアン径Ｄ５０は湿式法のレーザー回折・散乱型粒度分布計のマイクロトラックＨＲＡ［日機装株式会社］を用いて測定した。 Median diameter D 50 of the samples was measured using a Microtrac HRA [Nikkiso Co., Ltd.] in the laser diffraction scattering type particle size distribution meter wet method.

圧縮成型体密度は５ｇの試料を１０ｍｍφの治具で２．５ｔ／ｃｍ２の圧力で圧粉し、成型体の重量と体積から算出した。 The density of the compression molded body was calculated from the weight and volume of the molded body by compacting a 5 g sample with a 10 mmφ jig at a pressure of 2.5 t / cm 2 .

得られた正極活物質粒子粉末を用いて、下記製造方法で正極を調製し、ＣＲ２０３２型コインセルでの二次電池特性を評価した。   Using the obtained positive electrode active material particle powder, a positive electrode was prepared by the following production method, and the secondary battery characteristics in a CR2032-type coin cell were evaluated.

正極活物質と導電剤であるアセチレンブラック、グラファイト及び結着剤のポリフッ化ビニリデンを重量比９４：３：３となるよう精秤し、Ｎ−メチル−２−ピロリドンに分散させ、高速混練装置で十分に混合して正極合剤スラリーを調整した。次に該合剤スラリーを集電体のアルミニウム箔にドクターブレードで塗布し、１２０℃で乾燥して、０．５ｔ／ｃｍに加圧して、約４０μｍの膜厚の正極シートを作製した。正極シートを１６ｍｍφに打ち抜き、正極とした。   The positive electrode active material and the conductive agent acetylene black, graphite, and the binder polyvinylidene fluoride were precisely weighed to a weight ratio of 94: 3: 3, and dispersed in N-methyl-2-pyrrolidone. Thorough mixing was performed to prepare a positive electrode mixture slurry. Next, the mixture slurry was applied to an aluminum foil as a current collector with a doctor blade, dried at 120 ° C., and pressurized to 0.5 t / cm to produce a positive electrode sheet having a thickness of about 40 μm. A positive electrode sheet was punched to 16 mmφ to obtain a positive electrode.

負極として、１６ｍｍφに打ち抜いた金属リチウム箔［本城金属株式会社］を用いた。   As the negative electrode, a metal lithium foil [Honjo Metal Co., Ltd.] punched to 16 mmφ was used.

セパレーターとして、セルガード＃２４００［Ｃｅｌｇａｒｄ，ＬＬＣ］２０ｍｍφを用いた。１ｍｏｌ／ｌのＬｉＰＦ６を溶解したＥＣとＤＭＣ（エチレンカーボネート：ジメチルカーボネート＝１：２体積比）混合溶媒を電解液として用いた。これら部材を組み立て、ＣＲ２０３２型コインセル［株式会社宝泉］を作製した。 As a separator, Celgard # 2400 [Celgard, LLC] 20 mmφ was used. EC and DMC (ethylene carbonate: dimethyl carbonate = 1: 2 volume ratio) mixed solvent in which 1 mol / l LiPF 6 was dissolved was used as an electrolytic solution. These members were assembled to produce a CR2032-type coin cell [Hosen Co., Ltd.].

電解液や金属リチウムが大気により分解されないよう、アルゴン雰囲気のグローブボックス中で電池の組み立てを行った。   The battery was assembled in a glove box in an argon atmosphere so that the electrolyte and metallic lithium were not decomposed by the air.

２５℃における初期放電容量、及び放電容量維持率の測定は、放電電圧下限を３．０Ｖとし、充電上限電圧を４．４Ｖ及び４．５Ｖとした２条件の試験を行った。定電流で充電して各上限電圧に到達後、上限電圧下において充電電流が０．０２５Ｃを下回ったときを充電の終了とした。１、１１、２１、３１、４１、５１回目の充放電を０．２Ｃで、その他の回数の充放電を１Ｃで行い、１回目の放電容量を初期放電容量、５１回目の放電容量を１回目の放電容量で割った値を放電容量維持率として評価した。   The initial discharge capacity at 25 ° C. and the discharge capacity retention rate were measured under two conditions with the discharge voltage lower limit set to 3.0V and the charge upper limit voltage set to 4.4V and 4.5V. After charging with a constant current and reaching each upper limit voltage, when the charge current was lower than 0.025C under the upper limit voltage, charging was terminated. 1, 11, 21, 31, 41, 51st charge / discharge at 0.2C, other number of charge / discharge at 1C, first discharge capacity at initial discharge capacity, 51st discharge capacity at first time The value divided by the discharge capacity was evaluated as the discharge capacity retention rate.

高温過充電試験として、６０℃において、０．１Ｃで４．５Ｖまで定電流で充電後、４．５Ｖを維持したまま、電流値を変動させた。充電開始から１４時間後から７２時間後までの間の電流値を積算し、正極活物質重量当りの漏れ電気量とした。充電開始から７２時間以内に電池に短絡が起こった場合には、短絡した時点で試験を打ち切った。   As a high temperature overcharge test, after charging at a constant current up to 4.5 V at 0.1 C at 60 ° C., the current value was varied while maintaining 4.5 V. The current values from 14 hours to 72 hours after the start of charging were integrated to obtain the amount of electricity leaked per positive electrode active material weight. When a short circuit occurred within 72 hours from the start of charging, the test was terminated when the short circuit occurred.

高温過充電における正極活物質からのＣｏ溶出量を定量化した。即ち、負極グラファイトを用いて電池を組み、６０℃、０．１Ｃ定電流で４．４Ｖまで充電後、同電圧を維持したまま、電流値を変動させ、７２時間後に電池を取り出し、分解した。その後、負極、及びセパレーターに析出したＣｏ量をＩＣＰ発光分光にて定量化した。   The amount of Co elution from the positive electrode active material during high temperature overcharge was quantified. That is, a battery was assembled using negative electrode graphite, charged to 4.4 V at 60 ° C. and a constant current of 0.1 C, the current value was changed while maintaining the same voltage, and the battery was taken out and disassembled after 72 hours. Thereafter, the amount of Co deposited on the negative electrode and the separator was quantified by ICP emission spectroscopy.

［実施例１］
（第一工程）
Ｌｉ２ＣＯ３、ＣｏＯＯＨ、Ｍｇ（ＯＨ）２、Ａｌ（ＯＨ）３がｍｏｌ比でＬｉ／（０．９９０Ｃｏ＋０．００５Ｍｇ＋０．００５Ａｌ）＝１．０５、各原料の総重量が３．０ｋｇになるようとなるように原料を計量した。原料を２０分間混合して、容積内の混合原料にムラがないことを目視にて確認し、ＩＣＰ発光分光分析にて組成ずれがないことを確認した。混合原料を匣鉢に入れ、焼成炉で９８０℃、１０時間焼成した。得られた焼成物を粉砕・分級し、ＭｇとＡｌが固溶したコバルト酸リチウム粒子粉末を作製した。 [Example 1]
(First step)
Li 2 CO 3 , CoOOH, Mg (OH) 2 , and Al (OH) 3 are in a molar ratio of Li / (0.990Co + 0.005Mg + 0.005Al) = 1.05, and the total weight of each raw material is 3.0 kg. The raw materials were weighed so that The raw materials were mixed for 20 minutes, and it was visually confirmed that there was no unevenness in the mixed raw materials in the volume, and it was confirmed that there was no composition shift by ICP emission spectroscopic analysis. The mixed raw material was put in a mortar and fired at 980 ° C. for 10 hours in a firing furnace. The obtained fired product was pulverized and classified to prepare lithium cobalt oxide particle powder in which Mg and Al were dissolved.

ＳＥＭ写真を図１（１）に示すように、得られたコバルト酸リチウム粒子の表面に凹凸はほとんど観察されない。得られたコバルト酸リチウム粒子粉末を酸溶液で溶解後、ＩＣＰ発光分光分析により、各元素の含有量を測定したところ、得られたコバルト酸リチウムの組成はＬｉ１．０５（Ｃｏ０．９９０Ｍｇ０．００５Ａｌ０．００５）Ｏ２であった。これらの値は原料仕込みから予測される値と一致していた。 As shown in FIG. 1A, the SEM photograph shows almost no irregularities on the surface of the obtained lithium cobalt oxide particles. After the obtained lithium cobaltate particles powder was dissolved in an acid solution, the content of each element was measured by ICP emission spectroscopic analysis. As a result, the composition of the obtained lithium cobaltate was Li 1.05 (Co 0.990 Mg 0.005 Al 0.005 ) O 2 . These values were consistent with the values predicted from raw material charging.

（第二工程）
得られたコバルト酸リチウム粒子粉末を１００ｇ計量し、コバルトに対し０．２ｍｏｌ％二酸化チタン（Ｔｉ／Ｃｏ＝０．００２ｍｏｌ比、ミレニアム・インオーガニック・ケミカルズ製、ＰＣ−５００、２５０ｍ２／ｇ）をボールミルにて１時間混合した。 (Second step)
100 g of the obtained lithium cobaltate particle powder was weighed, and 0.2 mol% titanium dioxide (Ti / Co = 0.002 mol ratio, manufactured by Millennium Inorganic Chemicals, PC-500, 250 m 2 / g) with respect to cobalt. Mix for 1 hour in a ball mill.

混合後のＳＥＭ写真を図１（２）に示す。図１（２）から微細な二酸化チタンがコバルト酸リチウム粒子を満遍なく覆い、被覆率が高いことが確認された。   The SEM photograph after mixing is shown in FIG. From FIG. 1 (2), it was confirmed that fine titanium dioxide uniformly covered the lithium cobalt oxide particles and the coverage was high.

被覆処理物を坩堝に入れ、箱型マッフル炉で１０００℃、５時間で再焼成した。メノウ乳鉢で粉砕し、４５μｍのメッシュで篩分けし、本発明の正極活物質粒子粉末を得た（図１（３）参照）。ＩＣＰ発光分光分析装置で元素分析し、仕込み量と一致するＬｉ／Ｃｏ比とＴｉ／Ｃｏ比が得られた。   The coated product was put in a crucible and refired at 1000 ° C. for 5 hours in a box-type muffle furnace. The mixture was pulverized with an agate mortar and sieved with a 45 μm mesh to obtain a positive electrode active material particle powder of the present invention (see FIG. 1 (3)). Elemental analysis was performed with an ICP emission spectroscopic analyzer, and a Li / Co ratio and a Ti / Co ratio that coincided with the charged amount were obtained.

図２及び図３に実施例１の粒子のＳＴＥＭ−ＥＤＸ−ＮＥＤの分析結果を示す。前述したように、Ｔｉはコバルト酸リチウム粒子に拡散し、活物質粒子表面から内部に向かって、Ｔｉの濃度は傾斜していた。即ち、表層にＴｉが固溶した層状構造のコバルト酸リチウムが形成されていることがわかった。   2 and 3 show the STEM-EDX-NED analysis results of the particles of Example 1. FIG. As described above, Ti diffused into the lithium cobalt oxide particles, and the concentration of Ti was inclined from the surface of the active material particles to the inside. That is, it was found that lithium cobaltate having a layered structure in which Ti was dissolved in the surface layer was formed.

図４に実施例１の粒子断面のＦＥ−ＡＥＳ分析結果を示す。図４（１）に示すようにＡ地点における点分析を行ったところ、微分形式のスペクトル強度から粒子表面付近でＴｉは検出可能であった。図４（２）に示すように、Ａ地点の該強度が３０以下となる場所、即ち、粒子表面から１．０５μｍの距離をＴｉ固溶した表層の層厚と見積もった。同様に任意のＢ〜Ｋ地点においても、粒子内部方向に点分析を行い、外挿してＴｉ固溶層の層厚を見積もった。各々の地点における該層厚の平均値は０．９μｍであった。ＢＥＴ換算粒径は９．８μｍであり、該平均の層厚を形成する体積はＢＥＴ換算粒径からなる粒子の体積の４５．６％に相当した。そのため、ＩＣＰ発光分光によるＴｉ／Ｃｏ比から、該層の平均のＴｉ／Ｃｏは０．００４ｍｏｌ比と見積もられた。   FIG. 4 shows the FE-AES analysis result of the particle cross section of Example 1. When point analysis was performed at point A as shown in FIG. 4 (1), Ti was detectable in the vicinity of the particle surface from the spectrum intensity in the differential form. As shown in FIG. 4 (2), the place where the intensity at point A is 30 or less, that is, the distance of 1.05 μm from the particle surface was estimated as the layer thickness of the surface layer in which Ti was dissolved. Similarly, at arbitrary B to K points, point analysis was performed in the particle internal direction, and extrapolated to estimate the layer thickness of the Ti solid solution layer. The average value of the layer thickness at each point was 0.9 μm. The BET equivalent particle size was 9.8 μm, and the volume forming the average layer thickness corresponded to 45.6% of the volume of the particle having the BET equivalent particle size. Therefore, the average Ti / Co of the layer was estimated to be 0.004 mol ratio from the Ti / Co ratio by ICP emission spectroscopy.

図５に示すように、Ｒｉｅｔｖｅｌｄ解析により得られた格子定数から層状構造のコバルト酸リチウムの相とチタンが固溶したコバルト酸リチウムの２相の存在を確認した。第一工程で得られたコバルト酸リチウムの格子定数はａ＝２．８１６４Å、ｃ＝１４．０５７Åであり、第二工程で得られたコバルト酸リチウムの格子定数はａ＝２．８１６１Å、ｃ＝１４．０５６Åであり、第一工程で得られた値とほぼ同じであった。そのため、第一工程で得られた該コバルト酸リチウムの組成を該芯粒子の組成とみなした。また、表層の格子定数はａ＝２．８１９Å、ｃ＝１４．０７Åであって、表層の格子定数ａとｃは芯粒子に比べて長くなっており、表層はチタンが固溶したコバルト酸リチウムであると推定した。   As shown in FIG. 5, the presence of two layers of a lithium cobaltate layer having a layered structure and lithium cobaltate in which titanium was solid-solved was confirmed from the lattice constant obtained by Rietveld analysis. The lattice constant of the lithium cobaltate obtained in the first step is a = 2.8164Å and c = 14.057Å, and the lattice constant of the lithium cobaltate obtained in the second step is a = 2.8161Å, c = It was 14.056 mm and was almost the same as the value obtained in the first step. Therefore, the composition of the lithium cobaltate obtained in the first step was regarded as the composition of the core particles. The surface layer has a lattice constant of a = 2.819 Å and c = 14.07 、, and the surface layer has a lattice constant a and c longer than that of the core particle, and the surface layer is lithium cobalt oxide in which titanium is dissolved. It was estimated that.

表２に示すよう、得られた正極活物質粒子粉末の粉体特性である残存アルカリや未反応酸化コバルトは低く、メジアン径は大きく、高い圧縮成型体密度が得られた。   As shown in Table 2, the residual alkali and unreacted cobalt oxide, which are the powder characteristics of the obtained positive electrode active material particle powder, were low, the median diameter was large, and a high compression-molded body density was obtained.

得られた粒子粉末を正極化し、コインセルにて評価を行った。その結果は、表３に示すように初期の放電容量も高く、充放電繰り返し特性も良好で、高温過充電試験結果も良好であった。６０℃のグラファイト負極を用いたコバルトイオン溶出量は正極活物質に対し０．２０ｗｔ％であり、後述する比較例１に比べ、溶出量は抑制されていた。   The obtained particle powder was converted into a positive electrode and evaluated in a coin cell. As shown in Table 3, the initial discharge capacity was high, the charge / discharge repetition characteristics were good, and the high-temperature overcharge test result was also good. The cobalt ion elution amount using a graphite negative electrode at 60 ° C. was 0.20 wt% with respect to the positive electrode active material, and the elution amount was suppressed as compared with Comparative Example 1 described later.

以下の実施例、及び比較例についても同様に、粉体特性を表１と２に、電池特性を表３に記す。   Similarly, in the following examples and comparative examples, the powder characteristics are shown in Tables 1 and 2, and the battery characteristics are shown in Table 3.

［実施例２〜４］
芯粒子のコバルト酸リチウムの作製の際、Ｌｉ／（０．９９０Ｃｏ＋０．００２５Ｍｇ＋０．００７５Ａｌ）＝１．０２ｍｏｌ比となるように原料を計量した。他の条件は、実施例１同様に処理を行い、第二工程の焼成の温度として、実施例２は１０５０℃、実施例３は１０００℃、実施例４は９５０℃とした。結果、良好な粉体特性と電池特性が得られた。但し、実施例２はＴｉの固溶が進行しすぎたためか、Ｔｉが検出できない粒子表面も存在し、被覆率はやや低下していた。その結果、高温過充電試験による６０℃の漏れ電気量は僅かに高い値を示した。 [Examples 2 to 4]
The raw materials were weighed so that the ratio Li / (0.990Co + 0.0025Mg + 0.0075Al) = 1.02 mol ratio was produced when the core particle lithium cobaltate was prepared. The other conditions were the same as in Example 1. The firing temperature in the second step was 1050 ° C. in Example 2, 1000 ° C. in Example 3, and 950 ° C. in Example 4. As a result, good powder characteristics and battery characteristics were obtained. However, in Example 2, there was a particle surface where Ti could not be detected because the solid solution of Ti progressed too much, and the coverage was slightly reduced. As a result, the amount of electricity leaked at 60 ° C. in the high temperature overcharge test showed a slightly high value.

［実施例５〜７］
芯粒子のコバルト酸リチウムの作製の際、Ｌｉ／（０．９９５Ｃｏ＋０．００５Ｍｇ）＝１．０３ｍｏｌ比となるように原料を計量した。第一工程における他の条件は、実施例１同様に処理を行った。第二工程において、得られたコバルト酸リチウムを１００ｇ計量し、コバルトに対し０．１ｍｏｌ％二酸化チタンをボールミル混合した。実施例５、６、７は最表面の相となり得るＭｏ、Ｗ、Ｂを各々コバルトに対し、０．１ｍｏｌ％となるよう、サブミクロンのＭｏＯ３、ＷＯ３、Ｈ３ＢＯ３と所定量のＬｉ２ＣＯ３をボールミル混合した。ここで、所定量とはＬｉ２ＭｏＯ４、Ｌｉ２ＷＯ４、Ｌｉ３ＢＯ３が形成できるＬｉのｍｏｌ量である。第二工程の焼成温度として、９５０℃とした。得られた正極活物質粒子粉末のＳＥＭ−ＥＤＸ分析により、Ｍｏ、Ｗ、Ｂが粒子表面にいることが分かった。また、ＩＣＰ発光分析により、水可溶性のＭｏ、Ｗ、Ｂは試料中のＭｏ、Ｗ、Ｂ量の８８、９１、８３％であった。表１〜３に示すように良好な粉体特性と電池特性が得られた。 [Examples 5 to 7]
The raw materials were weighed so that the ratio Li / (0.995Co + 0.005Mg) = 1.03 mol was obtained when the core particle lithium cobaltate was prepared. Other conditions in the first step were the same as in Example 1. In the second step, 100 g of the obtained lithium cobaltate was weighed, and 0.1 mol% titanium dioxide was ball-milled with respect to cobalt. In Examples 5, 6, and 7, submicron MoO 3 , WO 3 , H 3 BO 3 and a predetermined amount of Mo, W, and B, which can be the outermost surface phase, are 0.1 mol% with respect to cobalt, respectively. Li 2 CO 3 was ball mill mixed. Here, the predetermined amount is the molar amount of Li that can form Li 2 MoO 4 , Li 2 WO 4 , and Li 3 BO 3 . The firing temperature in the second step was 950 ° C. SEM-EDX analysis of the obtained positive electrode active material particle powder revealed that Mo, W, and B were on the particle surface. Moreover, by ICP emission analysis, water-soluble Mo, W, and B were 88, 91, and 83% of the amount of Mo, W, and B in a sample. As shown in Tables 1 to 3, good powder characteristics and battery characteristics were obtained.

［実施例８］
芯粒子のコバルト酸リチウムの作製の際、Ｌｉ／（０．９９５Ｃｏ＋０．００５Ｍｇ）＝１．０２５ｍｏｌ比となるように原料を計量した。第一工程における他の条件は、実施例１同様に処理を行った。第二工程において、得られたコバルト酸リチウムを１００ｇ計量し、コバルトに対し０．２ｍｏｌ％二酸化チタンをボールミル混合し、９５０℃で焼成した。結果、表１〜３に示すように良好な粉体特性と電池特性が得られた。 [Example 8]
The raw materials were weighed so that Li / (0.995Co + 0.005Mg) = 1.005 mol ratio when producing lithium cobalt oxide as the core particles. Other conditions in the first step were the same as in Example 1. In the second step, 100 g of the obtained lithium cobaltate was weighed, 0.2 mol% titanium dioxide was mixed in a ball mill with respect to cobalt, and fired at 950 ° C. As a result, as shown in Tables 1 to 3, good powder characteristics and battery characteristics were obtained.

［実施例９］
実施例８で得られたコバルト酸リチウムの粒子粉末を８５重量％とし、体積基準のメジアン径が３．４μｍのＬｉ１．０３Ｎｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２を１５重量％となるよう混合し、該混合物を正極活物質とした。圧縮成型体密度は３．９７ｇ／ｃｃと高い値が得られた。電池特性を評価したところ、表４に示すように、高い初期放電容量と低い漏れ電気量を示した。 [Example 9]
The lithium cobaltate particle powder obtained in Example 8 was 85% by weight, and 15% by weight of Li 1.03 Ni 0.5 Co 0.2 Mn 0.3 O 2 having a volume-based median diameter of 3.4 μm. %, And the mixture was used as a positive electrode active material. The compression molded body density was as high as 3.97 g / cc. When the battery characteristics were evaluated, as shown in Table 4, a high initial discharge capacity and a low amount of leakage electricity were shown.

［実施例１０］
実施例８で得られたコバルト酸リチウムの粒子粉末を８５重量％とし、体積基準のメジアン径が３．５μｍのＬｉ１．０６Ｎｉ０．４Ｃｏ０．３Ｍｎ０．３Ｏ２を１５重量％となるよう混合し、該混合物を正極活物質とした。圧縮成型体密度は３．９１ｇ／ｃｃと高い値が得られた。電池特性を評価したところ、表４に示すように、高い放電容量と低い漏れ電気量を示した。 [Example 10]
The lithium cobaltate particle powder obtained in Example 8 was 85% by weight, and 15% by weight of Li 1.06 Ni 0.4 Co 0.3 Mn 0.3 O 2 having a volume-based median diameter of 3.5 μm. %, And the mixture was used as a positive electrode active material. The compression molding density was as high as 3.91 g / cc. When the battery characteristics were evaluated, as shown in Table 4, a high discharge capacity and a low amount of leakage electricity were shown.

［比較例１］
実施例１の第一工程で得られたコバルト酸リチウムを正極活物質とした。即ち、本発明の粒子の表層にチタンを含む層状化合物や最表面にモリブデン、タングステン、ホウ素からなる異相は存在しない。その結果、４．５Ｖの初期放電容量や放電容量維持率は悪く、６０℃の漏れ電気量は高い値を示した。６０℃のグラファイト負極を用いた電池のコバルトイオン溶出量は正極活物質に対し０．３７ｗｔ％と実施例１に比べ高い値を示した。 [Comparative Example 1]
The lithium cobalt oxide obtained in the first step of Example 1 was used as the positive electrode active material. That is, there is no layered compound containing titanium on the surface layer of the particles of the present invention or a heterogeneous phase composed of molybdenum, tungsten, or boron on the outermost surface. As a result, the initial discharge capacity and the discharge capacity retention rate of 4.5V were poor, and the amount of leakage electricity at 60 ° C. was high. The cobalt ion elution amount of the battery using the graphite negative electrode at 60 ° C. was 0.37 wt% with respect to the positive electrode active material, which was higher than that in Example 1.

［比較例２］
Ｌｉ２ＣＯ３、ＣｏＯＯＨ、及びＭｇ（ＯＨ）２をＬｉ／（０．９９６Ｃｏ＋０．００４Ｍｇ）＝０．９９６ｍｏｌ比となるように計量した。ここで、粒成長を抑制するためサブミクロンのＺｒＯ２（Ｚｒ／Ｃｏ＝０．１ｍｏｌ％）を添加した。原料を混合し、９８０℃で焼成後、粉砕、分級を経て、第一工程のみで得られたコバルト酸リチウムを正極活物質粒子粉末とした。得られた正極活物質粒子粉末では、Ｚｒのコバルト酸リチウムへの固溶は観察されなかった。また、ＳＥＭ観察により一次粒子径が２μｍと小さかったため、ＢＥＴ比表面積は高いが、Ｄ５０がやや大きめであった。その結果、初期放電容量や放電容量維持率は高いものの、漏れ電気量は高かった。 [Comparative Example 2]
Li 2 CO 3 , CoOOH, and Mg (OH) 2 were weighed so that the ratio Li / (0.996Co + 0.004Mg) = 0.996 mol. Here, in order to suppress grain growth, submicron ZrO 2 (Zr / Co = 0.1 mol%) was added. The raw materials were mixed, fired at 980 ° C., pulverized and classified, and lithium cobaltate obtained only in the first step was used as the positive electrode active material particle powder. In the obtained positive electrode active material particle powder, solid solution of Zr in lithium cobalt oxide was not observed. Moreover, since the primary particle diameter was small and 2μm by SEM observation, but a high BET specific surface area, D 50 was slightly larger. As a result, although the initial discharge capacity and the discharge capacity maintenance rate were high, the amount of leakage electricity was high.

［比較例３］
Ｌｉ２ＣＯ３、ＣｏＯＯＨ、Ｍｇ（ＯＨ）２及びＴｉＯ２をＬｉ／（０．９８５Ｃｏ＋０．００５Ｍｇ＋０．０１Ｔｉ）＝１．０２ｍｏｌ比となるように計量した。原料を混合し、１０００℃で焼成後、粉砕、分級を経て、第一工程のみで得られたコバルト酸リチウムを正極活物質粒子粉末とした。得られた正極活物質粒子粉末は、ＸＲＤで確認したところ、層状構造単一相が得られ、Ｔｉ固溶によるａ軸が２．８１７６Å、ｃ軸が１４．０６７Åと伸びた格子定数が得られた。また、ＳＥＭ観察による一次粒子径が２μｍと小さかったため、ＢＥＴ比表面積は高いが、Ｄ５０がやや大きめであった。その結果、初期放電容量や放電容量維持率も低く、漏れ電気量は高かった。 [Comparative Example 3]
Li 2 CO 3 , CoOOH, Mg (OH) 2 and TiO 2 were weighed so that the ratio Li / (0.985Co + 0.005Mg + 0.01Ti) = 1.02 mol. The raw materials were mixed, fired at 1000 ° C., pulverized and classified, and lithium cobaltate obtained only in the first step was used as the positive electrode active material particle powder. When the obtained positive electrode active material particle powder was confirmed by XRD, a lamellar structure single phase was obtained, and a lattice constant with an a-axis extending to 2.8176 mm and a c-axis extending to 14.067 mm due to Ti solid solution was obtained. It was. Moreover, since the primary particle diameter determined by SEM observation was as small as 2 [mu] m, but a high BET specific surface area, D 50 was slightly larger. As a result, the initial discharge capacity and discharge capacity maintenance rate were low, and the amount of leakage electricity was high.

［比較例４］
比較例２で得られたコバルト酸リチウム粒子粉末を１００ｇ計量し、コバルトに対し０．２ｍｏｌ％二酸化チタンを混合し、１０００℃で再焼成した。結果、コバルト酸リチウム粒子の表層にチタンが固溶した粒子が得られたものの、一次粒子径の大きさは比較例２とほぼ同じで、改善されなかった。また、一次粒子径が小さいため、二酸化チタンでの表面処理が不十分であり、Ｔｉが固溶した表層の芯粒子に対する被覆率が低下した。結果、電池特性として、初期放電容量、及び放電容量維持率は良好であったが、漏れ電気量が高かった。 [Comparative Example 4]
100 g of the lithium cobaltate particles obtained in Comparative Example 2 were weighed, mixed with 0.2 mol% titanium dioxide with respect to cobalt, and refired at 1000 ° C. As a result, although particles in which titanium was dissolved in the surface layer of lithium cobaltate particles were obtained, the size of the primary particle diameter was almost the same as in Comparative Example 2 and was not improved. Moreover, since the primary particle diameter was small, the surface treatment with titanium dioxide was insufficient, and the coverage of core particles on the surface layer in which Ti was dissolved was lowered. As a result, the initial discharge capacity and the discharge capacity retention rate were good as battery characteristics, but the amount of leakage electricity was high.

［比較例５］
実施例２の第一工程で得られたコバルト酸リチウム１００ｇに、コバルトに対し０．２ｍｏｌ％のＭｏＯ３と所定量のＬｉ２ＣＯ３をボールミル混合後、１０５０℃で焼成した。表面被覆状態が耐酸化性に劣っていたためか、初期放電容量は高いものの、放電容量維持率は低く、漏れ電気量は高かった。 [Comparative Example 5]
To 100 g of lithium cobaltate obtained in the first step of Example 2, 0.2 mol% of MoO 3 and a predetermined amount of Li 2 CO 3 with respect to cobalt were mixed with a ball mill and then fired at 1050 ° C. The initial discharge capacity was high because the surface coating state was inferior in oxidation resistance, but the discharge capacity retention rate was low, and the amount of leakage electricity was high.

［比較例６］
Ｌｉ２ＣＯ３、Ｃｏ３Ｏ４、Ｍｇ（ＯＨ）２及びＡｌ（ＯＨ）３をＬｉ／（０．９９０Ｃｏ＋０．００５Ｍｇ＋０．００５Ａｌ）＝１．０２ｍｏｌ比となるように計量した。ここで、微粒子のＣｏ３Ｏ４（Ｄ５０＝２．４μｍ）を用いた。原料を混合し、９２０℃で焼成後、粉砕、分級を経て、第一工程のみで得られたコバルト酸リチウムを正極活物質粒子粉末とした。得られた正極活物質粒子粉末は、ＢＥＴ比表面積は高く、残存アルカリ成分は高く、未反応酸化コバルトは高く、Ｄ５０が小さく、圧縮成型体密度は低かった。これは焼成温度が低かったためと推察できる。その結果、初期放電容量や放電容量維持率は高いものの、漏れ電気量は高かった。 [Comparative Example 6]
Li 2 CO 3 , Co 3 O 4 , Mg (OH) 2 and Al (OH) 3 were weighed so that the ratio Li / (0.990Co + 0.005Mg + 0.005Al) = 1.02 mol. Here, fine particles of Co 3 O 4 (D 50 = 2.4 μm) were used. The raw materials were mixed, fired at 920 ° C., pulverized and classified, and lithium cobaltate obtained only in the first step was used as the positive electrode active material particle powder. The positive electrode active material particles obtained are, BET specific surface area is high, remaining alkali components is high, unreacted cobalt oxide is high, small D 50, the compressed compact density was low. It can be inferred that this was because the firing temperature was low. As a result, although the initial discharge capacity and the discharge capacity maintenance rate were high, the amount of leakage electricity was high.

［比較例７］
比較例１で得られた正極活物質粒子粉末を８５重量％とし、体積基準のメジアン径が３．４μｍのＬｉ１．０３Ｎｉ０．３３３Ｃｏ０．３３３Ｍｎ０．３３３Ｏ２を１５重量％となるよう混合し、該混合物を正極活物質とした。圧縮成型体密度は３．９１ｇ／ｃｃと高い値が得られた。電池特性を評価したところ、表４に示すように、高い放電容量を示したが、容量維持率は低く、高い漏れ電気量を示した。 [Comparative Example 7]
85% by weight of the positive electrode active material particle powder obtained in Comparative Example 1 and 15% by weight of Li 1.03 Ni 0.333 Co 0.333 Mn 0.333 O 2 having a volume-based median diameter of 3.4 μm. The mixture was used as a positive electrode active material. The compression molding density was as high as 3.91 g / cc. When the battery characteristics were evaluated, as shown in Table 4, a high discharge capacity was shown, but the capacity retention rate was low and a high amount of leakage electricity was shown.

［比較例８］
比較例１で得られた正極活物質粒子粉末を８５重量％とし、体積基準のメジアン径が３．５μｍのＬｉ１．０５Ｎｉ０．４Ｃｏ０．３Ｍｎ０．３Ｏ２を１５重量％となるよう混合し、該混合物を正極活物質とした。圧縮成型体密度は３．９０ｇ／ｃｃと高い値が得られた。電池特性を評価したところ、表４に示すように、高い放電容量を示したが、容量維持率は低く、高い漏れ電気量を示した。 [Comparative Example 8]
85% by weight of the positive electrode active material particle powder obtained in Comparative Example 1 and 15% by weight of Li 1.05 Ni 0.4 Co 0.3 Mn 0.3 O 2 having a volume-based median diameter of 3.5 μm The mixture was used as a positive electrode active material. The compression molded body density was as high as 3.90 g / cc. When the battery characteristics were evaluated, as shown in Table 4, a high discharge capacity was shown, but the capacity retention rate was low and a high amount of leakage electricity was shown.

以上の結果から本発明に係る正極材活物質は、芯粒子に高容量を示すコバルト酸リチウムを用い、コバルト酸リチウム粒子表面には微量のＴｉが固溶した層を形成しているため、コバルトイオンの溶出を抑制することができ、高容量で、高温過充電試験と充放電繰り返し特性においても優れていることが確認された。
From the above results, the positive electrode active material according to the present invention uses lithium cobaltate having a high capacity as the core particle, and forms a layer in which a small amount of Ti is dissolved in the lithium cobaltate particle surface. It was confirmed that ion elution can be suppressed, the capacity is high, and the high-temperature overcharge test and charge / discharge repetition characteristics are also excellent.

本発明は低コストで、環境負荷の少ない製法で作製された正極活物質粒子粉末を二次電池正極活物質として用いることで、体積当りのエネルギー密度が高く、充放電繰り返し特性に優れ、耐高温過充電性を備えた非水溶媒系二次電池を得ることができる。   The present invention uses a positive electrode active material particle powder produced by a low-cost, low environmental load production method as a secondary battery positive electrode active material, which has a high energy density per volume, excellent charge / discharge repeatability, and high temperature resistance. A nonaqueous solvent secondary battery having overchargeability can be obtained.

Claims (10)

元素Ｍ（ＭはＭｇ及び／又はＡｌ）を含む層状構造のコバルト酸リチウムからなる芯粒子と、少なくともＴｉが固溶した層状構造のコバルト酸リチウムからなる表層を有する正極活物質粒子粉末であって、該表層の平均の層厚が０．００５〜１．５μｍであり、ＢＥＴ比表面積が０．０２〜０．２５ｍ２／ｇであることを特徴とする正極活物質粒子粉末。 Positive electrode active material particle powder having core particles made of lithium cobaltate having a layered structure containing element M (M is Mg and / or Al) and a surface layer made of lithium cobaltate having a layered structure in which at least Ti is solid-solved. The positive electrode active material particle powder, wherein the average layer thickness of the surface layer is 0.005 to 1.5 μm, and the BET specific surface area is 0.02 to 0.25 m 2 / g. 前記正極活物質粒子粉末が元素Ａ（ＡはＷ、Ｍｏ、及びＢから選ばれる少なくとも１種の元素）を含む水可溶性のリチウム酸化物からなる最表面を有し、該最表面の含有量が０．０１〜０．５重量％である請求項１に記載の正極活物質粒子粉末。 The positive electrode active material particle powder has an outermost surface made of a water-soluble lithium oxide containing the element A (A is at least one element selected from W, Mo, and B), and the content of the outermost surface is The positive electrode active material particle powder according to claim 1, which is 0.01 to 0.5 wt%. 体積基準のメジアン径が１０〜３５μｍである請求項１又は２に記載の正極活物質粒子粉末。 The positive electrode active material particle powder according to claim 1 or 2, wherein the volume-based median diameter is 10 to 35 µm. 残存アルカリ成分が８００ｐｐｍ以下、未反応酸化コバルトが５００ｐｐｍ以下である請求項１〜３のいずれか一項に記載の正極活物質粒子粉末。 The positive electrode active material particle powder according to any one of claims 1 to 3, wherein the residual alkali component is 800 ppm or less and the unreacted cobalt oxide is 500 ppm or less. 前記表層のＴｉ濃度が０．００１≦Ｔｉ／Ｃｏ（ｍｏｌ比）≦０．０２である請求項１〜４のいずれか一項に記載の正極活物質粒子粉末。 The positive electrode active material particle powder according to claim 1, wherein a Ti concentration of the surface layer is 0.001 ≦ Ti / Co (mol ratio) ≦ 0.02. 前記表層の前記芯粒子に対する被覆率が８０％以上である請求項１〜５のいずれか一項に記載の正極活物質粒子粉末。 The positive electrode active material particle powder according to claim 1, wherein a coverage of the surface layer with respect to the core particles is 80% or more. 請求項１〜６のいずれか一項に記載の正極活物質粒子粉末の製造方法であって、リチウム原料とコバルト原料と元素Ｍ原料（ＭはＭｇ及び／又はＡｌ）を混合後、８００〜１１００℃で焼成を行って層状構造のコバルト酸リチウム粒子粉末を作製する第一工程と、第一工程で得られたコバルト酸リチウム粒子粉末とチタン原料とリチウム原料とを混合後、８００〜１１００℃で焼成を行って表層を形成する第二工程からなることを特徴とする正極活物質粒子粉末の製造方法。 It is a manufacturing method of the positive electrode active material particle powder as described in any one of Claims 1-6, Comprising: After mixing a lithium raw material, a cobalt raw material, and element M raw material (M is Mg and / or Al), 800-1100 The first step of producing a layered lithium cobalt oxide particle powder by firing at ° C., the lithium cobalt oxide particle powder obtained in the first step, the titanium raw material, and the lithium raw material are mixed, and then at 800 to 1100 ° C. The manufacturing method of the positive electrode active material particle powder characterized by including the 2nd process which performs baking and forms a surface layer. 請求項２〜６のいずれか一項に記載の正極活物質粒子粉末の製造方法であって、リチウム原料とコバルト原料と元素Ｍ原料（ＭはＭｇ及び／又はＡｌ）を混合後、８００〜１１００℃で焼成を行って層状構造のコバルト酸リチウム粒子粉末を作製する第一工程と、第一工程で得られたコバルト酸リチウム粒子粉末とチタン原料と元素Ａ原料（ＡはＷ、Ｍｏ、及びＢから選ばれる少なくとも１種の元素）とリチウム原料とを混合後、８００〜１１００℃で焼成を行って表層及び最表面を形成する第二工程からなることを特徴とする正極活物質粒子粉末の製造方法。 It is a manufacturing method of the positive electrode active material particle powder as described in any one of Claims 2-6, Comprising: After mixing a lithium raw material, a cobalt raw material, and element M raw material (M is Mg and / or Al), 800-1100 A first step of producing a layered lithium cobalt oxide particle powder by firing at 0 ° C., a lithium cobaltate particle powder obtained in the first step, a titanium raw material, and an element A raw material (A is W, Mo, and B) A positive electrode active material particle powder comprising a second step of forming a surface layer and an outermost surface by baking at 800 to 1100 ° C. after mixing a lithium raw material with at least one element selected from Method. 請求項１〜６のいずれか一項に記載の正極活物質粒子粉末を正極活物質の少なくとも一部に用いて作製した非水電解液二次電池。 The non-aqueous-electrolyte secondary battery produced using the positive electrode active material particle powder as described in any one of Claims 1-6 for at least one part of a positive electrode active material. 請求項１〜６のいずれか一項に記載の正極活物質粒子粉末に対し、凝集粒子の体積基準のメジアン径が１〜７μｍのＬｉ（Ｎｉ１−ａ−ｂＣｏａＭｎｂ）Ｏ２（ａ及びｂは０．１５≦ａ≦０．４、０．１５≦ｂ≦０．５）で表わされる正極活物質粒子粉末を３〜２５重量％含む混合物を正極活物質として用いて作製した非水電解液二次電池。 To the positive electrode active material particles according to any one of claims 1 to 6, Li of the volume-based median diameter of the aggregated particles 1~7μm (Ni 1-a-b Co a Mn b) O 2 ( a and b were prepared using, as a positive electrode active material, a mixture containing 3 to 25% by weight of a positive electrode active material particle powder represented by 0.15 ≦ a ≦ 0.4 and 0.15 ≦ b ≦ 0.5) Water electrolyte secondary battery.
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