JP2006156032A - Positive electrode active material for nonaqueous electrolyte secondary battery and its manufacturing method - Google Patents

Positive electrode active material for nonaqueous electrolyte secondary battery and its manufacturing method Download PDF

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JP2006156032A
JP2006156032A JP2004342544A JP2004342544A JP2006156032A JP 2006156032 A JP2006156032 A JP 2006156032A JP 2004342544 A JP2004342544 A JP 2004342544A JP 2004342544 A JP2004342544 A JP 2004342544A JP 2006156032 A JP2006156032 A JP 2006156032A
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zirconia
lithium
composite oxide
positive electrode
active material
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Atsushi Yamanaka
厚志 山中
Hajime Miyashiro
一 宮代
Akira Kobayashi
陽 小林
Shiro Seki
志朗 関
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Sumitomo Metal Mining Co Ltd
Central Research Institute of Electric Power Industry
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Central Research Institute of Electric Power Industry
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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
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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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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    • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

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Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium-containing composite oxide excellent in a charge/discharge cycle property and a high-temperature storage property and usable for manufacturing a nonaqueous electrolyte secondary battery. <P>SOLUTION: Lithium-containing composite oxide powder is put into a predetermined device and heating air is supplied for holding a temperature of the powder at 35°C or more and forming a powder fluidized bed at the same time. A zirconia sol water solution is added to the lithium-containing composite oxide powder forming the fluidized bed, and a zirconia coating layer of 1.5-8.5 mass% to total mass of the lithium-containing composite oxide powder is formed. The zirconia coating layer uniformly covers the surface of the lithium-containing composite oxide powder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、負極にリチウム、リチウム合金またはカーボンを用いる非水系電解質二次電池用の正極活物質およびその製造方法に関し、特に非水系電解質二次電池の熱安定性およびサイクル安定性の向上に寄与する正極活物質およびその製造方法に関するものである。   The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery using lithium, a lithium alloy, or carbon as a negative electrode and a method for producing the same, and particularly contributes to an improvement in thermal stability and cycle stability of the non-aqueous electrolyte secondary battery. The present invention relates to a positive electrode active material and a manufacturing method thereof.

近年、携帯電話やノート型パソコンなどの携帯機器の普及にともない、小型、軽量で容量の大きい二次電池の開発が強く望まれている。この要請を満たすためには、エネルギー密度のより大きい二次電池を開発することが必要である。   In recent years, with the widespread use of mobile devices such as mobile phones and laptop computers, development of secondary batteries that are small, light, and large in capacity is strongly desired. In order to satisfy this requirement, it is necessary to develop a secondary battery having a higher energy density.

エネルギー密度の大きい二次電池としては、リチウム、リチウム合金あるいはカーボンを負極として用い、リチウム含有複合酸化物などを正極として用いたリチウムイオン二次電池がある。リチウムイオン二次電池は、高電圧で、かつ、高いエネルギー密度を有するため、今後も市場が大きく成長していくものと期待されている二次電池である。   As a secondary battery having a high energy density, there is a lithium ion secondary battery using lithium, a lithium alloy or carbon as a negative electrode and using a lithium-containing composite oxide or the like as a positive electrode. The lithium ion secondary battery is a secondary battery that is expected to grow greatly in the future because of its high voltage and high energy density.

リチウムイオン二次電池にはいくつかの種類があるが、実用化されているものとしては、リチウムコバルト複合酸化物（ＬｉＣｏＯ2）を正極活物質に用いたリチウムイオン二次電池があり、現在では広く利用されるようになってきている。しかし、コバルト（Ｃｏ）は、地球上に偏在し、かつ希少な資源であるためコストが高くつく。また、Ｃｏには安定供給が難しいという問題もある。このため、Ｃｏに代わる正極活物質用の材料の出現が望まれており、資源として豊富に存在し、安価なニッケル（Ｎｉ）やマンガン（Ｍｎ）をベースにした正極活物質の開発が進められている。 There are several types of lithium ion secondary batteries, but ones that have been put to practical use include lithium ion secondary batteries that use lithium cobalt composite oxide (LiCoO 2 ) as a positive electrode active material. It is becoming widely used. However, since cobalt (Co) is unevenly distributed on the earth and is a scarce resource, the cost is high. In addition, there is a problem that stable supply is difficult for Co. Therefore, the appearance of materials for positive electrode active materials that replace Co is desired, and development of positive electrode active materials based on nickel (Ni) and manganese (Mn) that are abundant in resources and inexpensive is promoted. ing.

しかし、ＬｉＮｉＯ2を使用した正極材料は、理論容量が大きく、かつ高放電電位を有するものの、充放電サイクルの進行に伴ってＬｉＮｉＯ2の結晶構造に崩壊が生じ、放電容量の低下を引き起こすという問題や、熱安定性に劣るという問題等がある。 However, although the positive electrode material using LiNiO 2 has a large theoretical capacity and a high discharge potential, the crystal structure of LiNiO 2 collapses as the charge / discharge cycle progresses, causing a decrease in discharge capacity. In addition, there are problems such as poor thermal stability.

開発が進められているもう１つの正極活物質用の材料であるＬｉＭｎ2Ｏ4は、正スピネル型構造を持ち、空間群Ｆｄ３ｍを有しており、対リチウム電極で４Ｖ級というＬｉＣｏＯ2と同等の高い電位を有するという特長がある。これに加えて、ＬｉＭｎ2Ｏ4は、合成が容易であり、かつ、高い電池容量を有するという特長がある。このため、ＬｉＭｎ2Ｏ4は、非常に有望視されており、実用化もされている。しかし、実際にＬｉＭｎ2Ｏ4を用いて構成された電池には、高温保存時における容量劣化が大きいといった問題や、Ｍｎが電解液に溶解してしまうといった問題があり、安定性についての問題やサイクル特性が充分でないといった問題が残されている。 LiMn 2 O 4 , which is another positive electrode active material being developed, has a positive spinel structure, has a space group of Fd3m, and is equivalent to LiCoO 2 of 4V class with respect to the lithium electrode. It has the feature of having a high potential. In addition to this, LiMn 2 O 4 is characterized by being easy to synthesize and having a high battery capacity. For this reason, LiMn 2 O 4 is very promising and has been put into practical use. However, batteries actually configured using LiMn 2 O 4 have problems such as large capacity degradation during storage at high temperatures and problems that Mn dissolves in the electrolyte, There remains a problem that the cycle characteristics are not sufficient.

一方、リチウムイオン二次電池の主用途の一つであるノート型パソコンにおいては、演算チップ速度の向上、主記憶容量の増大、補助記憶装置の高容量・高速化にともない消費電力が増大しており、その結果、電源であるリチウムイオン電池は機器使用時には常に高温状態に置かれてしまっている。充電状態の電池がこのような高温状態に置かれてしまった場合においては、電池内部にガスが発生することがあり、電池ケースの変形や電池容量の低下さらには電池自体の安全性の低下といった問題まで発生する可能性がある。このため、安全性に対する配慮から、携帯電話用の電池パックあるいはノート型パソコン用電池の回収・交換が行われることもある。したがって、リチウムイオン二次電池の高温状態での特性の向上がますます望まれるようになってきている。なお、ガス発生の機構については、詳しくは解明されていないものの、電解液と活物質の界面反応により生ずるものと考えられている。   On the other hand, notebook computers, which are one of the main uses of lithium ion secondary batteries, have increased power consumption due to increased computing chip speed, increased main memory capacity, and increased capacity and speed of auxiliary storage devices. As a result, the lithium ion battery as a power source is always kept in a high temperature state when the device is used. When a charged battery is placed in such a high temperature state, gas may be generated inside the battery, and the battery case may be deformed, the battery capacity may be reduced, and the safety of the battery itself may be reduced. There is a possibility of problems. For this reason, in consideration of safety, a battery pack for a mobile phone or a battery for a laptop computer may be collected and replaced. Therefore, improvement in the characteristics of the lithium ion secondary battery at a high temperature has been increasingly desired. Although the mechanism of gas generation has not been elucidated in detail, it is considered to be caused by an interfacial reaction between the electrolyte and the active material.

また、市販されているリチウムイオン電池においては、リチウムコバルト複合酸化物の持つ理論容量の５０％程度しか実際の使用では用いられていないのが現状である。これは、コバルト酸リチウム（Ｌｉ1-xＣｏＯ2）において、ｘ≧０．５の領域まで含めて充放電を繰り返すと、結晶構造の安定性に問題が生じ、サイクル特性が悪化することが原因の一つであるとされている。 Moreover, in the commercially available lithium ion battery, only about 50% of the theoretical capacity of the lithium cobalt composite oxide is actually used. This is because in lithium cobaltate (Li 1-x CoO 2 ), when charging and discharging are repeated including the region of x ≧ 0.5, a problem occurs in the stability of the crystal structure, and the cycle characteristics deteriorate. It is said that it is one of.

これを解決するために、Ｍｇ、Ａｌ、Ｃｏ、Ｋ、Ｎａ、Ｃａ、Ｓｉ、Ｔｉ、Ｖ、Ｇｅ、Ｇａ、Ｂ、Ａｓ及びＺｒからなる群より選択されるコーティング元素を含む酸化物、または前記コーティング元素を含む水酸化物、オキシヒドロキシド（oxyhydroxide）、オキシカーボネート（oxycarbonate）、ヒドロキシカーボネート（hydroxycarbonate）、またはこれらの混合物を含む表面処理層を含むリチウム二次電池用正極活物質が提案されており、製造方法としては、コーティング溶液に正極活物質を添加して混合した後に取り出して熱処理する方法が記載されている（特許文献１参照）。   In order to solve this, an oxide containing a coating element selected from the group consisting of Mg, Al, Co, K, Na, Ca, Si, Ti, V, Ge, Ga, B, As and Zr, or A positive electrode active material for a lithium secondary battery including a surface treatment layer including a hydroxide containing a coating element, oxyhydroxide, oxycarbonate, hydroxycarbonate, or a mixture thereof has been proposed. As a manufacturing method, a method is described in which a positive electrode active material is added to a coating solution, mixed, and then taken out and heat-treated (see Patent Document 1).

他に、活物質表面を化学的に安定なＡｌ2Ｏ3、ＴｉＯ2あるいはＺｒＯ2などの酸化物で被覆して改質することが試みられており、実電池の過充電領域（４．２Ｖ以上）まで含めて充放電を繰り返した場合のサイクル特性が向上することが報告されている（非特許文献１参照）。非特許文献１では、具体的には、ＬｉＣｏＯ2粒子を分散させた被覆原料液を含有する溶液を中和／加水分解することにより、コート元素の水酸化物を生成させてＬｉＣｏＯ2粒子の表面をコートし、その後空気中で温度３００℃で４時間熱処理を行い、３質量％程度のアルミナ（粒径約３ｎｍ、一部ＡｌＯＯＨ含有）、チタニア（粒径約６ｎｍ、非晶質）またはジルコニア（粒径約２ｎｍ、非晶質）を被覆することが記載されている。
しかし、前記のような含浸法による被覆処理では、非特許文献１中の図４のＴＥＭ写真に示されているように、被覆層を構成する酸化物粒子のＬｉＣｏＯ2粒子表面への被覆率は低く、被覆されていない部分も多く認められていた。 In addition, it has been attempted to modify the surface of the active material by coating it with a chemically stable oxide such as Al 2 O 3 , TiO 2, or ZrO 2. It has been reported that the cycle characteristics are improved when charging and discharging are repeated including the above (see Non-Patent Document 1). In Non-Patent Document 1, specifically, a solution containing a coating raw material liquid in which LiCoO 2 particles are dispersed is neutralized / hydrolyzed to generate a hydroxide of a coat element, thereby generating a surface of LiCoO 2 particles. Then, heat treatment is performed in air at a temperature of 300 ° C. for 4 hours, and about 3% by mass of alumina (particle size: about 3 nm, partially containing AlOOH), titania (particle size: about 6 nm, amorphous) or zirconia ( Coating with a particle size of about 2 nm, amorphous).
However, in the coating treatment by the impregnation method as described above, as shown in the TEM photograph of FIG. 4 in Non-Patent Document 1, the coverage ratio of the oxide particles constituting the coating layer to the LiCoO 2 particle surface is Low and many uncovered parts were also observed.

特開２００２−１５８０１１号公報JP 2002-158011 A

A.M. Kannan et al, Electrochemical and Solid-Sate Letters, Vol. 6(1) A16-A18 (2003).A.M.Kannan et al, Electrochemical and Solid-Sate Letters, Vol. 6 (1) A16-A18 (2003).

本発明は、かかる問題点に鑑みてなされたものであって、充放電のサイクル特性および高温保存特性に優れた非水系電解質二次電池の製造に用いることができるリチウム含有複合酸化物およびその製造方法を提供することを目的とする。   The present invention has been made in view of such problems, and is a lithium-containing composite oxide that can be used for the manufacture of a nonaqueous electrolyte secondary battery excellent in charge / discharge cycle characteristics and high-temperature storage characteristics, and the manufacture thereof. It aims to provide a method.

本発明に係る非水系電解質二次電池用正極活物質は、一般式ＬｉxＭＯy（式中のＭは、主として遷移金属からなり、Ｃｏ、Ｍｎ、Ｎｉ、Ｖ、Ｆｅの少なくとも一種を含む。また、式中のｘ、ｙの値の範囲はｘ＝０．０２〜２．２、ｙ＝１．４〜３である。）で表されるリチウム含有複酸化物粉末の表面にジルコニア被覆層を形成した非水系電解質二次電池用正極活物質であって、該ジルコニア被覆層は前記リチウム含有複合酸化物粉末全質量に対して１．５〜８．５質量％の割合で形成され、かつ、該ジルコニア被覆層は均一に前記リチウム含有複合酸化物粉末の表面を覆っていることを特徴とする。 The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention has a general formula Li x MO y (M in the formula is mainly composed of a transition metal and contains at least one of Co, Mn, Ni, V, and Fe. In addition, the ranges of the values of x and y in the formula are x = 0.02 to 2.2 and y = 1.4 to 3. The zirconia coating layer is formed on the surface of the lithium-containing double oxide powder represented by A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the zirconia coating layer is formed at a ratio of 1.5 to 8.5% by mass with respect to the total mass of the lithium-containing composite oxide powder, and The zirconia coating layer uniformly covers the surface of the lithium-containing composite oxide powder.

前記非水系電解質二次電池用正極活物質の比表面積は０．２〜１．５ｍ2／ｇであることが好ましい。また、前記ジルコニウム被覆層はジルコニア粒子で形成されており、該ジルコニア粒子の結晶構造は立方晶であり、かつ、該ジルコニア粒子の形状は球状であって、外径が５〜２０ｎｍであることが好ましい。 The specific surface area of the positive electrode active material for a non-aqueous electrolyte secondary battery is preferably 0.2 to 1.5 m 2 / g. The zirconium coating layer is formed of zirconia particles, the crystal structure of the zirconia particles is cubic, and the shape of the zirconia particles is spherical, and the outer diameter is 5 to 20 nm. preferable.

本発明に係る非水系電解質二次電池用正極活物質の製造方法は、一般式ＬｉxＭＯy（式中のＭは、主として遷移金属からなり、Ｃｏ、Ｍｎ、Ｎｉ、Ｖ、Ｆｅの少なくとも一種を含む。また、式中のｘ、ｙの値の範囲はｘ＝０．０２〜２．２、ｙ＝１．４〜３である。）で表されるリチウム含有複合酸化物粉末を所定の容器に入れ、加熱空気を送り込み、該粉末を３５℃以上に予熱するとともに該粉末の流動層を形成する工程と、該粉末の流動層にジルコニア粒子を含むジルコニアゾル溶液を添加して、該粉末の全質量に対してジルコニアが１．５〜８．５質量％含まれるように該粉末の表面にジルコニア被覆層を形成させ、ジルコニア被覆リチウム含有複合酸化物粉末を得る工程と、該ジルコニア被覆リチウム含有複合酸化物粉末を４００〜６５０℃で焼成して、非水系電解質二次電池用正極活物質を得る工程と、を有することを特徴とする。 The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention has a general formula Li x MO y (where M is mainly composed of a transition metal and is at least one of Co, Mn, Ni, V, and Fe). In addition, the ranges of the values of x and y in the formula are x = 0.02 to 2.2 and y = 1.4 to 3). Putting into a container, feeding heated air, preheating the powder to 35 ° C. or higher and forming a fluidized bed of the powder, adding a zirconia sol solution containing zirconia particles to the fluidized bed of the powder, Forming a zirconia coating layer on the surface of the powder so that zirconia is contained in an amount of 1.5 to 8.5% by mass based on the total mass of the zirconia, and obtaining a zirconia-coated lithium-containing composite oxide powder; and the zirconia-coated lithium 400 containing composite oxide powder And fired at 650 ° C., and having a step of obtaining a positive electrode active material for a non-aqueous electrolyte secondary battery, a.

前記ジルコニアゾル溶液中のジルコニア粒子の濃度は１．０〜８．０質量％であり、かつ、該ジルコニアゾル溶液は前記流動層の側面の底部近傍から接線方向に噴霧して添加され、さらに、添加されるジルコニアゾル溶液の量が前記リチウム含有複合酸化物粉末１００質量部に対して１８〜５００質量部であることが好ましい。   The concentration of zirconia particles in the zirconia sol solution is 1.0 to 8.0% by mass, and the zirconia sol solution is added by spraying in the tangential direction from the vicinity of the bottom of the side surface of the fluidized bed. The amount of the zirconia sol solution added is preferably 18 to 500 parts by mass with respect to 100 parts by mass of the lithium-containing composite oxide powder.

また、前記ジルコニアゾル溶液の噴霧速度が、前記リチウム含有複合酸化物粉末１００質量部に対して、０．２〜０．４５質量部／ｍｉｎであることが好ましい。   Moreover, it is preferable that the spray rate of the said zirconia sol solution is 0.2-0.45 mass part / min with respect to 100 mass parts of said lithium containing complex oxide powder.

さらに、前記加熱空気の温度が７０〜１１０℃であり、該加熱空気を前記所定の装置内に送り込む送量が、前記リチウム含有複合酸化物粉末１００ｇに対して２０〜４２Ｌ／ｍｉｎであることが好ましい。   Furthermore, the temperature of the heated air is 70 to 110 ° C., and the feed rate for feeding the heated air into the predetermined apparatus is 20 to 42 L / min with respect to 100 g of the lithium-containing composite oxide powder. preferable.

さらにまた、前記リチウム含有複合酸化物粉末の比表面積は０．２〜０．７ｍ2／ｇであることが好ましい。 Furthermore, the specific surface area of the lithium-containing composite oxide powder is preferably 0.2 to 0.7 m 2 / g.

本発明に係る非水系電解質二次電池用正極活物質は、リチウム含有複合酸化物粉末の表面に適切な量のジルコニア被覆層が設けられてなり、かつ、該ジルコニア被覆層は均一に前記リチウム含有複合酸化物粉末の表面を覆っているので、本発明に係る非水系電解質二次電池用正極活物質を用いて製造された二次電池は、充放電のサイクル特性および高温保存特性に優れる。したがって、消費電力が増大している携帯電話やノート型パソコンなどの携帯用電子機器の二次電池に好適に用いることができる。   The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is provided with an appropriate amount of a zirconia coating layer on the surface of a lithium-containing composite oxide powder, and the zirconia coating layer is evenly mixed Since the surface of the composite oxide powder is covered, the secondary battery manufactured using the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is excellent in charge / discharge cycle characteristics and high-temperature storage characteristics. Therefore, it can be suitably used for a secondary battery of a portable electronic device such as a mobile phone or a notebook personal computer whose power consumption is increasing.

本発明者は、非水系電解質二次電池用正極活物質の製造方法において、所定の組成のリチウム含有複酸化物粉末にジルコニアゾル水溶液を添加しながら加熱空気を送り込み、上記リチウム含有複合酸化物粉末を３５℃以上に保持するとともに流動層を形成させ、該リチウム含有複合酸化物粉末の粒度分布状態を維持しつつ該粒子表面に被覆層を形成させ、さらに４００〜６５０℃で該表面被覆層を乾燥させることによって、リチウム含有複合酸化物粉末の表面にジルコニア酸化物層を形成することができることを見出した。そして、前記ジルコニア酸化物層で被覆されたリチウム含有複合酸化物粉末を正極活物質として用いて非水系電解質二次電池を製造すれば、充放電におけるサイクル安定性および高温保存特性に優れた非水系電解質二次電池が得られることを見出し、本発明に至った。   In the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, the inventor sends heated air while adding an aqueous zirconia sol solution to a lithium-containing double oxide powder having a predetermined composition, and the lithium-containing composite oxide powder. Is maintained at 35 ° C. or higher and a fluidized layer is formed, and a coating layer is formed on the particle surface while maintaining the particle size distribution state of the lithium-containing composite oxide powder. Further, the surface coating layer is formed at 400 to 650 ° C. It was found that a zirconia oxide layer can be formed on the surface of the lithium-containing composite oxide powder by drying. If a non-aqueous electrolyte secondary battery is manufactured using the lithium-containing composite oxide powder coated with the zirconia oxide layer as a positive electrode active material, the non-aqueous system has excellent cycle stability and high-temperature storage characteristics in charge and discharge. The inventors have found that an electrolyte secondary battery can be obtained and have reached the present invention.

［１．リチウム含有複合酸化物粉末］
本発明に係る非水系電解質二次電池用正極活物質の製造に用いるリチウム含有複合酸化物粉末は、一般式ＬｉxＭＯyで表される。ここで、式中のＭは、主として遷移金属からなり、Ｃｏ、Ｍｎ、Ｎｉ、Ｖ、Ｆｅの少なくとも一種を含む。また、式中のｘ、ｙの値の範囲はｘ＝０．０２〜２．２、ｙ＝１．４〜３である。なお、式中のＭは主として遷移金属からなるが、遷移金属以外にＡｌ、Ｇａ、Ｉｎ、Ｇｅ、Ｓｎ、Ｐｂ、Ｓｂ、Ｂｉ、Ｓｉ、Ｐ、Ｂなどが添加されていてもよい。これらの元素の添加量は遷移金属に対して０〜３０モル％が好ましい。３０モル％を超えると電池容量が低下してしまうため好ましくない。 [1. Lithium-containing composite oxide powder]
The lithium-containing composite oxide powder used for the production of the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is represented by the general formula Li x MO y . Here, M in the formula is mainly composed of a transition metal and includes at least one of Co, Mn, Ni, V, and Fe. Moreover, the ranges of the values of x and y in the formula are x = 0.02 to 2.2 and y = 1.4 to 3. M in the formula is mainly composed of a transition metal, but Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, B, etc. may be added in addition to the transition metal. The addition amount of these elements is preferably 0 to 30 mol% with respect to the transition metal. If it exceeds 30 mol%, the battery capacity will decrease, such being undesirable.

好ましいリチウム含有複合酸化物粉末としては、具体的には、層状岩塩型構造を持つＬｉxＣｏＯ2、ＬｉxＮｉＯ2、ＬｉxＭｎＯ2、ＬｉxＣｏaＮｉ1-aＯ2、ＬｉxＣｏbＶ1-bＯz、ＬｉxＣｏbＦｅ1-bＯ2、およびスピネル型構造を持つＬｉxＭｎ2Ｏ4、ＬｉxＭｎcＣｏ2-cＯ4、ＬｉxＭｎcＮｉ2-cＯ4、ＬｉxＭｎcＶ2-cＯ4、ＬｉxＭｎcＦｅ2-cＯ4をあげることができる。ここで、ｘ＝０．０２〜２．２、ａ＝０．１〜０．９、ｂ＝０．８〜０．９８、ｃ＝１．６〜１．９６、ｚ＝２．０１〜２．３である。また、前記好ましいリチウム含有複合酸化物粉末のうち、より好ましいリチウム含有複合酸化物粉末としては、具体的には、ＬｉxＣｏＯ2、ＬｉxＮｉＯ2、ＬｉxＭｎＯ2、ＬｉxＣｏaＮｉ1-aＯ2 、ＬｉxＭｎ2Ｏ4、ＬｉxＣｏbＶ1-bＯzをあげることができる。ここで、ｘ＝０．０２〜２．２、ａ＝０．１〜０．９、ｂ＝０．９〜０．９８、ｚ＝２．０１〜２．３である。なお、上記のｘの値は、充放電開始前の値であり、充放電により増減する。 Specific examples of preferable lithium-containing composite oxide powders include Li x CoO 2 , Li x NiO 2 , Li x MnO 2 , Li x Co a Ni 1-a O 2 , and Li x Co having a layered rock salt structure. b V 1-b O z , Li x Co b Fe 1-b O 2 , and Li x Mn 2 O 4 having a spinel structure, Li x Mn c Co 2 -c O 4 , Li x Mn c Ni 2- c O 4, Li x Mn c V 2-c O 4, can be mentioned Li x Mn c Fe 2-c O 4. Here, x = 0.02 to 2.2, a = 0.1 to 0.9, b = 0.8 to 0.98, c = 1.6 to 1.96, z = 2.1-2. .3. Among the preferable lithium-containing composite oxide powders, more preferable lithium-containing composite oxide powders are specifically Li x CoO 2 , Li x NiO 2 , Li x MnO 2 , and Li x Co a Ni 1. -a O 2, can be mentioned Li x Mn 2 O 4, Li x Co b V 1-b O z. Here, x = 0.02 to 2.2, a = 0.1 to 0.9, b = 0.9 to 0.98, and z = 2.01 to 2.3. In addition, said value of x is a value before charge / discharge start, and increases / decreases by charge / discharge.

［２．リチウム含有複合酸化物粉末の作製方法］
一般式ＬｉxＭＯyにおいて所定の組成になるように、Ｌｉおよび元素Ｍの酸化物、炭酸塩等を、１次粒子が１０μｍ以下となるように粉砕した後に精秤し、混合粉とする。１次粒子の大きさが１０μｍより大きいと、均一な複合酸化物を得るためにはより長時間の焼成が必要となり生産性が悪くなる。その後、造粒するが、造粒においては混合造粒機を用いてもよい。混合造粒機を用いる場合、装置底部の回転羽の回転数を調整することで造粒物の大きさを調整する。造粒物の大きさは１〜３ｍｍの範囲内が好ましい。造粒物の大きさが１ｍｍよりも小さいと、造粒した効果が十分に得られず、焼成を行っても均一な組成のリチウム含有複合酸化物粉末とはならないおそれがある。３ｍｍよりも大きいと、後工程の粉砕に時間を要し、条件によっては粉砕装置からの不純物の混入を招くおそれがある。得られた造粒物は温度：１００〜１４０℃で、時間：１〜５時間乾燥させる。さらにマグネシア焼成容器等を用いて酸素雰囲気中で昇温させ、温度：８５０〜１０００℃で時間：５〜１５時間程度保持して反応を進めることが好ましい。 [2. Method for producing lithium-containing composite oxide powder]
Li, the oxide of M, element M, and the like are pulverized so that the primary particles are 10 μm or less so as to have a predetermined composition in the general formula Li x MO y , and then precisely weighed to obtain a mixed powder. If the size of the primary particles is larger than 10 μm, a longer time is required to obtain a uniform composite oxide, resulting in poor productivity. Thereafter, granulation is carried out, but in the granulation, a mixed granulator may be used. When using a mixing granulator, the magnitude | size of a granulated material is adjusted by adjusting the rotation speed of the rotary blade of an apparatus bottom part. The size of the granulated product is preferably in the range of 1 to 3 mm. If the size of the granulated product is smaller than 1 mm, the effect of granulation cannot be sufficiently obtained, and there is a possibility that a lithium-containing composite oxide powder having a uniform composition will not be obtained even if firing is performed. If it is larger than 3 mm, it takes time for the pulverization in the subsequent process, and depending on the conditions, there is a risk of introducing impurities from the pulverizer. The obtained granulated product is dried at a temperature of 100 to 140 ° C. for a time of 1 to 5 hours. Furthermore, it is preferable to raise the temperature in an oxygen atmosphere using a magnesia firing container or the like and keep the temperature at 850 to 1000 ° C. for about 5 to 15 hours and advance the reaction.

このようにして作製されたリチウムコバルト複合酸化物は造粒物の形状を保っているか、造粒物同士が結着している場合もあるため、通常は２０〜４０μｍ以下の大きさとなるようにピンミル等の粉砕機を用いて解砕して、その後所望の粒度分布になるように分級機等を用いて分級することが好ましい。   Since the lithium cobalt composite oxide thus produced maintains the shape of the granulated product or the granulated product may be bound to each other, the size is usually 20 to 40 μm or less. It is preferable to crush using a pulverizer such as a pin mill and then classify using a classifier so that the desired particle size distribution is obtained.

得られるリチウム含有複合酸化物粉末の比表面積は、０．２〜０．７ｍ2／ｇであることが好ましい。比表面積が０．２〜０．７ｍ2／ｇから外れると、電池の安全性が低下するおそれがあるため好ましくない。すなわち、比表面積が０．２ｍ2／ｇより小さいと最終的に得られる二次電池の特性が不安定となるおそれがあり、比表面積が０．７ｍ2／ｇより大きいと電解液との反応性が増加し、電池の安全性が低下するおそれがある。 The specific surface area of the obtained lithium-containing composite oxide powder is preferably 0.2 to 0.7 m 2 / g. If the specific surface area deviates from 0.2 to 0.7 m 2 / g, the safety of the battery may be lowered, which is not preferable. That is, if the specific surface area is smaller than 0.2 m 2 / g, the characteristics of the finally obtained secondary battery may be unstable, and if the specific surface area is larger than 0.7 m 2 / g, the reaction with the electrolytic solution may occur. May increase the battery safety.

［３．被覆処理液の調製方法］
分子内にエーテル結合を有するアルコールに金属イソプロポキシドを溶解させた後、酸および蒸留水を加え、加水分解・重合反応をさせるとジルコニアゾル微粒子が溶液中に生成し、ジルコニアゾル溶液が得られる。次に、得られた溶液を蒸留水で希釈することで、被覆処理液であるジルコニアゾル水溶液を得ることができる。 [3. Preparation method of coating solution]
After dissolving metal isopropoxide in alcohol having an ether bond in the molecule, adding acid and distilled water, followed by hydrolysis and polymerization reaction, zirconia sol fine particles are generated in the solution, and a zirconia sol solution is obtained. . Next, by diluting the obtained solution with distilled water, a zirconia sol aqueous solution that is a coating treatment liquid can be obtained.

前記ジルコニアゾル水溶液中のジルコニアの含有量は、前記ジルコニアゾル溶液を蒸留水で希釈して１．０〜８．０質量％とすればよく、より好ましくは、２．５〜６．５質量％とするのがよい。前記ジルコニアゾル水溶液中のジルコニアの含有量が、１．０質量％未満では被覆処理が効率よく行われず、処理時間が長くなるため生産性に劣り不経済である。また、８．０質量％を超える場合は、液の粘性が高くなるため、ジルコニア被覆層形成時にリチウム含有複合酸化物粉末が造粒され、二次粒子となるおそれがある。リチウム含有複合酸化物粉末が二次粒子となると、形成される被覆層の均一性を保つことが困難となる。   The content of zirconia in the zirconia sol aqueous solution may be 1.0 to 8.0% by mass by diluting the zirconia sol solution with distilled water, and more preferably 2.5 to 6.5% by mass. It is good to do. When the content of zirconia in the zirconia sol aqueous solution is less than 1.0% by mass, the coating treatment is not performed efficiently, and the treatment time becomes long, resulting in poor productivity and uneconomical. Moreover, when it exceeds 8.0 mass%, since the viscosity of a liquid becomes high, there exists a possibility that lithium containing complex oxide powder may be granulated at the time of zirconia coating layer formation, and it may become a secondary particle. When the lithium-containing composite oxide powder becomes secondary particles, it becomes difficult to maintain the uniformity of the coating layer to be formed.

［４．ジルコニア被覆層形成］
上記のようにして得られたリチウム含有複合酸化物粉末を所定の装置に投入し、加熱空気を送り込むことにより該粉末の温度を３５℃以上に保持するとともに該粉末の流動層を形成する。該粉末を３５℃以上に保持することは良好なジルコニア被覆層を形成するために必要である。３５℃未満では、前記ジルコニアゾル水溶液を該粉末に噴霧した後の乾燥速度が遅くなり、流動層の維持が困難となる。流動層の維持ができないと、リチウム含有複合酸化物粉末同士で二次粒子を形成してしまい、被覆処理自体が困難となる。前記ジルコニアゾル水溶液の噴霧速度を遅くすれば該粉末の温度が３５℃未満でも被覆処理をすることは可能となるが、被覆処理に要する時間が長くなり、生産性が低下してしまう。 [4. Zirconia coating layer formation]
The lithium-containing composite oxide powder obtained as described above is put into a predetermined apparatus, and heated air is sent in to maintain the temperature of the powder at 35 ° C. or higher and form a fluidized bed of the powder. It is necessary to keep the powder at 35 ° C. or higher in order to form a good zirconia coating layer. If it is less than 35 degreeC, the drying rate after spraying the said zirconia sol aqueous solution to this powder will become slow, and it will become difficult to maintain a fluidized bed. If the fluidized bed cannot be maintained, secondary particles are formed between the lithium-containing composite oxide powders, and the coating process itself becomes difficult. If the spray rate of the zirconia sol aqueous solution is slowed, the coating process can be performed even if the temperature of the powder is less than 35 ° C., but the time required for the coating process becomes longer and the productivity is lowered.

そして、流動層を形成している該リチウム含有複合酸化物粉末に前記ジルコニアゾル水溶液を添加し、該リチウム含有複合酸化物粉末全質量に対して１．５〜８．５質量％のジルコニア被覆層を形成させる。被覆層を形成するジルコニア量が１．５質量％未満では、電解液と活物質の界面反応を防止する効果が不十分となってしまう。一方、８．５質量％を超えると、被覆の効果としては十分であるが、被覆物質の増加により相対的に活物質量が減少してしまうため得られる電池の容量が低下してしまう。より好ましくは、被覆層を形成するジルコニア量は該リチウム含有複合酸化物粉末全質量に対して１．５〜６．０質量％である。被覆層を形成するジルコニア量を１．５〜６．０質量％とすることにより、電池容量の低下は極力抑えられ、電解液と活物質との界面反応を十分に抑制することが可能となる。   Then, the zirconia sol aqueous solution is added to the lithium-containing composite oxide powder forming the fluidized bed, and the zirconia coating layer is 1.5 to 8.5% by mass with respect to the total mass of the lithium-containing composite oxide powder. To form. If the amount of zirconia forming the coating layer is less than 1.5% by mass, the effect of preventing the interface reaction between the electrolytic solution and the active material will be insufficient. On the other hand, if it exceeds 8.5% by mass, the effect of the coating is sufficient, but the amount of the active material is relatively decreased due to the increase in the coating material, so that the capacity of the obtained battery is reduced. More preferably, the amount of zirconia forming the coating layer is 1.5 to 6.0% by mass with respect to the total mass of the lithium-containing composite oxide powder. By setting the amount of zirconia forming the coating layer to 1.5 to 6.0% by mass, a decrease in battery capacity can be suppressed as much as possible, and the interface reaction between the electrolytic solution and the active material can be sufficiently suppressed. .

前記の被覆層形成処理に用いる装置としては、転動流動造粒コーティング装置が好ましい。前記ジルコニアゾル水溶液をリチウム含有複合酸化物粉末へ添加している際の状況を図１に示す。   As the apparatus used for the coating layer forming process, a rolling fluidized granulation coating apparatus is preferable. FIG. 1 shows the situation when the zirconia sol aqueous solution is added to the lithium-containing composite oxide powder.

転動流動造粒コーティング装置は、図１に示すように、上方部分が円錐筒状、下方部分が円筒状をなす流動層容器１、流動層容器１の上方に設置されるフィルター２、流動層容器１の下方に設置されるディスクローター４、ディスクローター４を回転駆動させる回転駆動軸５、加熱空気を流動層容器１に供給する際の通り道となる通気部３、リチウム含有複合酸化物粉末流動層へジルコニアゾル水溶液を噴霧するためのスプレーガン７からなる。   As shown in FIG. 1, the rolling fluidized granulation coating apparatus includes a fluidized bed container 1 in which an upper portion has a conical cylinder shape and a lower portion in a cylindrical shape, a filter 2 installed above the fluidized bed container 1, a fluidized bed A disk rotor 4 installed below the container 1, a rotary drive shaft 5 that rotationally drives the disk rotor 4, a vent portion 3 that serves as a passage for supplying heated air to the fluidized bed container 1, and a lithium-containing composite oxide powder flow It consists of a spray gun 7 for spraying a zirconia sol aqueous solution onto the layer.

加熱空気は通気部３を介して流動層容器１内に供給され、供給された加熱空気によりリチウム含有複合酸化物粉末６は流動層容器１の側壁に沿って上昇するが、ある程度上昇して上昇気流の通り道から外れると、流動層容器１の中央部付近を下に降りていく。そして、ディスクロータ４に達すると、ディスクロータ４の回転によりリチウム含有複合酸化物粉末６はディスクロータ４の外周部に移動して、通気部３から供給される加熱空気の上昇気流にもどされ、再度流動層容器１の側壁に沿って上昇する。このようにして、リチウム含有複合酸化物粉末６の流動層が形成される。   The heated air is supplied into the fluidized bed container 1 through the ventilation part 3, and the lithium-containing composite oxide powder 6 rises along the side wall of the fluidized bed container 1 by the supplied heated air, but rises to some extent and rises. When it deviates from the passage of the air current, it descends near the center of the fluidized bed container 1. When reaching the disk rotor 4, the lithium-containing composite oxide powder 6 is moved to the outer periphery of the disk rotor 4 by the rotation of the disk rotor 4, and is returned to the rising air current of the heated air supplied from the aeration unit 3, It rises again along the side wall of the fluidized bed container 1. In this way, a fluidized bed of the lithium-containing composite oxide powder 6 is formed.

リチウム含有複合酸化物粉末６の流動層へのジルコニアゾル水溶液の添加は、図１に示すように、リチウム含有複合酸化物粉末の流動層側面の底部近傍から流動層の接線方向にジルコニアゾル水溶液を噴霧し、ミストとして添加することで行う。ジルコニアゾル水溶液の添加量は前記リチウム含有複合酸化物粉末１００質量部に対して１８〜５００質量部となるようにすればよい。ジルコニアゾル水溶液の添加量が１８質量部未満では、添加されるジルコニア量が不足し、形成されるジルコニア被覆層を均一に形成することが困難となるおそれがある。均一に形成するためにはジルコニア水溶液中のジルコニア濃度を高くする必要があるが、ジルコニア濃度を高くしすぎすると水溶液中のジルコニアを一次粒子の状態で保存することが困難となる。さらに、ジルコニアゾル水溶液の添加量が５００質量部を超える場合は、被覆層の形成処理時間が長くなり生産性が低くなり不経済となる。   As shown in FIG. 1, the addition of the zirconia sol aqueous solution to the fluidized bed of the lithium-containing composite oxide powder 6 is performed by adding the zirconia sol aqueous solution from the vicinity of the bottom of the fluidized bed side surface of the lithium-containing composite oxide powder in the tangential direction of the fluidized bed. Spray and add as mist. What is necessary is just to make it the addition amount of zirconia sol aqueous solution be 18-500 mass parts with respect to 100 mass parts of said lithium containing complex oxide powder. If the amount of the zirconia sol aqueous solution added is less than 18 parts by mass, the amount of zirconia added may be insufficient, and it may be difficult to form a uniform zirconia coating layer. In order to form it uniformly, it is necessary to increase the zirconia concentration in the zirconia aqueous solution. However, if the zirconia concentration is too high, it becomes difficult to store the zirconia in the aqueous solution in the form of primary particles. Furthermore, when the added amount of the zirconia sol aqueous solution exceeds 500 parts by mass, the formation processing time of the coating layer becomes long and the productivity becomes low, which is uneconomical.

前記ジルコニアゾル水溶液の噴霧速度は、リチウム含有複合酸化物粉末１００質量部に対して０．２〜０．４５質量部／ｍｉｎとすることが好ましい。噴霧速度が０．２質量部／ｍｉｎよりも小さいと処理時間が長くなり経済的でない。また、０．４５質量部／ｍｉｎよりも多くなると、流動層の維持が困難となり原料のリチウム含有複合酸化物自体が造粒されてしまうおそれがある。   The spray rate of the zirconia sol aqueous solution is preferably 0.2 to 0.45 parts by mass / min with respect to 100 parts by mass of the lithium-containing composite oxide powder. When the spraying speed is less than 0.2 parts by mass / min, the treatment time becomes long and it is not economical. Moreover, when it exceeds 0.45 mass part / min, maintenance of a fluidized bed will become difficult and there exists a possibility that the raw material lithium containing complex oxide itself may be granulated.

また、流動層を形成するために送り込む加熱空気の温度は７０〜１１０℃とすることが好ましく、送り込む加熱空気の送量は、前記リチウム含有複合酸化物粉末１００ｇに対して２０〜４２Ｌ／ｍｉｎとすることが好ましい。   Moreover, it is preferable that the temperature of the heated air sent in in order to form a fluidized bed shall be 70-110 degreeC, and the amount of the heated air sent in is 20-42 L / min with respect to 100 g of said lithium containing complex oxide powder. It is preferable to do.

送り込む加熱空気の温度を７０〜１１０℃とするのは、加熱空気の温度が７０℃未満では被覆処理中のリチウム含有複合酸化物粉末の乾燥が不十分となり流動層を維持できなくなるおそれがあるからであり、１１０℃を超えるとリチウム含有複合酸化物表面でのジルコニアゾル水溶液の乾燥が速くなり良好な被覆層を形成できず比表面積が増大してしまうおそれがあるからである。また、送り込む加熱空気の送量を、上記リチウム含有複酸化物粉末１００ｇに対して２０〜４２Ｌ／ｍｉｎとするのは、この範囲を外れると、被覆処理に好適な流動層を維持できなくなるおそれがあるからである。   The reason why the temperature of the heated air to be fed is set to 70 to 110 ° C. is that if the temperature of the heated air is less than 70 ° C., the lithium-containing composite oxide powder during the coating treatment may not be sufficiently dried and the fluidized bed may not be maintained. If the temperature exceeds 110 ° C., the drying of the zirconia sol aqueous solution on the surface of the lithium-containing composite oxide is accelerated, and a favorable coating layer cannot be formed, which may increase the specific surface area. Moreover, if the amount of heated air to be fed is set to 20 to 42 L / min with respect to 100 g of the lithium-containing double oxide powder, if it is out of this range, a fluidized bed suitable for coating treatment may not be maintained. Because there is.

［５．被覆層の乾燥］
前記被覆層を乾燥させるために、４００〜６５０℃で、前記被覆層を有するリチウム含有複合酸化物粉末を焼成する。焼成の際の雰囲気は乾燥空気あるいは酸素気流中が望ましい。焼成温度が４００℃未満では、通常の焼成処理時間内では、ゾル中に含まれる水分を除去することが不十分となり、電池内部に多量の水分を持ち込むことになるため電池の活物質として適さない。焼成温度が６５０℃を超えると、表面のジルコニア層からジルコニア元素が活物質内部へ拡散するため電池特性が劣化するばかりでなく、ジルコニアの結晶層が単斜晶系へと転移し、ジルコニア微粒子自体が焼結して粒成長するため均一な連続層を形成させることが困難となり、被覆の効果が十分には得られなくなる。 [5. Drying of coating layer]
In order to dry the coating layer, the lithium-containing composite oxide powder having the coating layer is fired at 400 to 650 ° C. The atmosphere during firing is preferably in dry air or an oxygen stream. If the firing temperature is less than 400 ° C., the moisture contained in the sol is insufficient to be removed within a normal firing time, and a large amount of moisture is brought into the battery. . When the firing temperature exceeds 650 ° C., the zirconia element diffuses from the surface zirconia layer into the active material, so that not only the battery characteristics deteriorate, but also the zirconia crystal layer transitions to a monoclinic system, and the zirconia fine particles themselves Since it sinters and grain grows, it becomes difficult to form a uniform continuous layer, and the effect of coating cannot be obtained sufficiently.

前述のようにして得られるジルコニア被覆層はジルコニア粒子から形成されているが、該ジルコニア粒子は、立方晶で、かつ、５〜２０ｎｍの概ね球状の粒子であることが好ましい。該ジルコニア粒子の結晶相は、前述のような適切な焼成温度で焼成を行った場合には立方晶となる。外径５ｎｍよりも小さいジルコニア粒子を得ることは通常のゾルゲル溶液を用いる方法では困難であり実用的でない。また、ジルコニア粒子の外形が２０ｎｍを超えると、均一な被覆層を得ることが難しくなる。また、ジルコニア粒子の形状が異形状であると均一な被覆層を得ることが難しくなる。   The zirconia coating layer obtained as described above is formed of zirconia particles, and the zirconia particles are preferably cubic and generally spherical particles of 5 to 20 nm. The crystal phase of the zirconia particles becomes cubic when fired at an appropriate firing temperature as described above. Obtaining zirconia particles having an outer diameter smaller than 5 nm is difficult and impractical by a method using a normal sol-gel solution. Moreover, when the external shape of a zirconia particle exceeds 20 nm, it will become difficult to obtain a uniform coating layer. In addition, if the shape of the zirconia particles is different, it is difficult to obtain a uniform coating layer.

また、以上のようにして得られるジルコニアが被覆された本発明に係る正極活物質の比表面積は０．２〜１．５ｍ2／ｇの範囲内であることが好ましい。比表面積は０．２ｍ2／ｇ未満では、活物質表面で生じるリチウムイオンの挿入・脱離が制限を受け、電池反応がスムーズに行われなくなってしまうおそれがある。一方、比表面積が１．５ｍ2／ｇを超えると、ジルコニアの被覆量がリチウム含有複合酸化物粉末全質量に対して８．５質量％を超え、電池容量が低下することや、ジルコニア被覆層の膜質が不均一となり、電池の安全性が低下することが懸念される。 The specific surface area of the positive electrode active material according to the present invention coated with zirconia obtained as described above is preferably in the range of 0.2 to 1.5 m 2 / g. If the specific surface area is less than 0.2 m 2 / g, the insertion / extraction of lithium ions occurring on the active material surface is limited, and the battery reaction may not be performed smoothly. On the other hand, when the specific surface area exceeds 1.5 m 2 / g, the coating amount of zirconia exceeds 8.5% by mass with respect to the total mass of the lithium-containing composite oxide powder, the battery capacity decreases, and the zirconia coating layer There is a concern that the film quality of the battery becomes non-uniform and the safety of the battery decreases.

［６．正極］
前述のようにして作製したジルコニア被覆層を有するリチウム複合酸化物を正極活物質として用いた正極は、たとえば、次のようにして作製する。まず、この正極活物質に、必要に応じて導電助剤、バインダーなどを適宜添加して混合し、溶剤でペースト状にする。バインダーはあらかじめ溶剤に溶解させた状態にしておき正極活物質と混合してもよい。得られた正極合剤含有ペーストをアルミニウム箔などからなる正極集電体に塗布し、乾燥させて正極合剤層を形成し、必要に応じて加圧成形する工程を経て正極を作製する。なお、正極の作製方法は、前記例示のものに限られることなく、任意の方法を採用できる。 [6. Positive electrode]
The positive electrode using the lithium composite oxide having the zirconia coating layer produced as described above as the positive electrode active material is produced, for example, as follows. First, a conductive additive, a binder, and the like are appropriately added to the positive electrode active material as necessary, and mixed to form a paste with a solvent. The binder may be previously dissolved in a solvent and mixed with the positive electrode active material. The obtained positive electrode mixture-containing paste is applied to a positive electrode current collector made of aluminum foil or the like, dried to form a positive electrode mixture layer, and a positive electrode is produced through a step of pressure molding as necessary. In addition, the manufacturing method of a positive electrode is not restricted to the said illustration thing, Arbitrary methods are employable.

前記正極の作製にあたって、導電助剤としては、黒鉛（天然黒鉛、人造黒鉛、膨張黒鉛など）やアセチレンブラック、ケッチェンブラックなどのカーボンブラック系材料などを用いることができる。また、バインダーとしては、ポリフッ化ビニリデン、ポリテトラフルオロエチレン、エチレンプロピレンジエンゴム、フッ素ゴム、スチレンブタジエン、セルロース系樹脂、ポリアクリル酸などを用いることができる。   In producing the positive electrode, as the conductive auxiliary agent, graphite (natural graphite, artificial graphite, expanded graphite, etc.), carbon black-based material such as acetylene black, ketjen black, or the like can be used. As the binder, polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluororubber, styrene butadiene, cellulose resin, polyacrylic acid, or the like can be used.

［７．負極］
前記正極活物質を含有する正極に対して対極となる負極の活物質としては、リチウム、リチウム−アルミニウムで代表されるリチウム合金、黒鉛、熱分解炭素類、コークス類、ガラス状炭素類、有機高分子化合物の焼成体、メソカーボンマイクロビーズ、炭素繊維、活性炭などの、リチウムイオンを可逆的に吸蔵・放出できる炭素系材料、Ｓｉ、Ｓｎ、Ｉｎなどの合金、またはＬｉに近い低電位で充放電できる酸化物や窒化物などの化合物も負極活物質として用いることができる。 [7. Negative electrode]
Examples of the negative electrode active material that is a counter electrode with respect to the positive electrode containing the positive electrode active material include lithium, lithium alloys represented by lithium-aluminum, graphite, pyrolytic carbons, cokes, glassy carbons, organic high Charge and discharge at low potential close to carbon-based materials that can reversibly store and release lithium ions, alloys such as Si, Sn, and In, or Li, such as calcined molecular compounds, mesocarbon microbeads, carbon fibers, and activated carbon Compounds such as oxides and nitrides that can be used can also be used as the negative electrode active material.

負極活物質がリチウムやリチウム合金の場合は、そのまま負極として用いることもできるし、集電体に圧着させて負極として用いることもできる。負極活物質が炭素系材料の場合は、必要に応じて正極の場合と同様のバインダーを負極活物質に添加して混合し、溶剤を用いてペースト状にする。バインダーはあらかじめ溶剤に溶解させた状態にしておき負極活物質と混合してもよい。得られた負極合剤含有ペーストを銅箔などからなる負極集電体に塗布し、乾燥させて負極合剤層を形成し、必要に応じて加圧成形する工程を経て負極を作製する。なお、負極の作製方法は、前記例示のものに限られることなく、任意の方法を採用できる。   When the negative electrode active material is lithium or a lithium alloy, it can be used as a negative electrode as it is, or it can be used as a negative electrode after being pressure-bonded to a current collector. When the negative electrode active material is a carbon-based material, the same binder as in the case of the positive electrode is added to the negative electrode active material and mixed as necessary, and a paste is formed using a solvent. The binder may be previously dissolved in a solvent and mixed with the negative electrode active material. The obtained negative electrode mixture-containing paste is applied to a negative electrode current collector made of copper foil or the like, dried to form a negative electrode mixture layer, and a negative electrode is produced through a step of pressure molding as necessary. In addition, the preparation methods of a negative electrode are not restricted to the said illustration thing, Arbitrary methods are employable.

［８．電解質］
電解質としては、非水系の液状電解質、ゲル状ポリマー電解質のいずれも用いることができるが、本発明に係る正極活物質を有する正極を用いて二次電池を形成する場合、汎用性やコストの面から、電解液と呼ばれる液状電解質を用いるのがよい。 [8. Electrolytes]
As the electrolyte, either a non-aqueous liquid electrolyte or a gel polymer electrolyte can be used. However, when a secondary battery is formed using a positive electrode having a positive electrode active material according to the present invention, versatility and cost are considered. Therefore, it is preferable to use a liquid electrolyte called an electrolytic solution.

液状電解質（電解液）は、有機溶媒を主材とする非水溶媒にリチウム塩などの電解質塩を溶解させることによって調製するが、その溶媒としては、ジメチルカーボネート、ジエチルカーボネート、メチルエチルカーボネート、プロピオン酸メチルなどの鎖状エステル、リン酸トリメチルなどの鎖状リン酸トリエステル、１，２−ジメトキシエタン、１，３−ジオキソラン、テトラヒドロフラン、２−メチル−テトラヒドロフラン、ジエチルエーテルなどを用いることができる。そのほか、アミンイミド系有機溶媒やスルホランなどのイオウ系有機溶媒なども用いることができる。   A liquid electrolyte (electrolyte) is prepared by dissolving an electrolyte salt such as a lithium salt in a non-aqueous solvent mainly composed of an organic solvent. Examples of the solvent include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and propion. A chain ester such as methyl acid, a chain phosphate triester such as trimethyl phosphate, 1,2-dimethoxyethane, 1,3-dioxolane, tetrahydrofuran, 2-methyl-tetrahydrofuran, diethyl ether and the like can be used. In addition, amine organic solvents, sulfur organic solvents such as sulfolane, and the like can also be used.

さらに、誘電率の高いエステル（誘電率３０以上）を上記溶媒に添加して用いることが、電池特性、特に負荷特性を向上させる点で好ましい。誘電率の高いエステルの具体例としては、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、γ−ブチロラクトンなどのほかに、エチレングリコールサルファイトなどのイオウ系エステルもあげることができるが、環状構造のエステルが好ましく、特にエチレンカーボネートのような環状カーボネートが好ましい。これらの溶媒はそれぞれ単独で、または２種以上混合して用いることができる。   Furthermore, it is preferable to use an ester having a high dielectric constant (dielectric constant of 30 or more) added to the above solvent from the viewpoint of improving battery characteristics, particularly load characteristics. Specific examples of the ester having a high dielectric constant include, in addition to ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and sulfur-based esters such as ethylene glycol sulfite, but esters having a cyclic structure are preferred. In particular, cyclic carbonates such as ethylene carbonate are preferred. These solvents can be used alone or in combination of two or more.

リチウム塩などの電解質塩としては、たとえば、ＬｉＣｌＯ4、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＳｂＦ6、ＬｉＣＦ3ＳＯ3、ＬｉＣ4Ｆ9ＳＯ3、ＬｉＣＦ3ＣＯ2、Ｌｉ2Ｃ2Ｆ4（ＳＯ3）2 、ＬｉＮ（Ｒｆ1ＳＯ2）（Ｒｆ2ＳＯ2）〔ここで、Ｒｆ1、Ｒｆ2はフルオロアルキル基を含む置換基である〕、ＬｉＮ（Ｒｆ3ＯＳＯ2）（Ｒｆ4ＯＳＯ2）〔ここで、Ｒｆ3 、Ｒｆ4はフルオロアルキル基である〕、ＬｉＣnＦ2n+1ＳＯ3（ｎ≧２）、ＬｉＣ（Ｒｆ5ＳＯ2）2、ＬｉＮ（Ｒｆ6ＯＳＯ2）2〔ここでＲｆ5、Ｒｆ6はフルオロアルキル基である〕、ポリマータイプイミドリチウム塩などが単独または２種以上混合して用いられる。電解液中における電解質塩の濃度は、特に限定されるものではないが、濃度を０．１〜２．０ｍｏｌ／Ｌにすることが好ましい。 As an electrolyte salt such as lithium salt, for example, LiClO 4, LiPF 6, LiBF 4, LiAsF 6, LiSbF 6, LiCF 3 SO 3, LiC 4 F 9 SO 3, LiCF 3 CO 2, Li 2 C 2 F 4 ( SO 3 ) 2 , LiN (Rf 1 SO 2 ) (Rf 2 SO 2 ) [where Rf 1 and Rf 2 are substituents containing a fluoroalkyl group], LiN (Rf 3 OSO 2 ) (Rf 4 OSO 2 ) [where Rf 3 and Rf 4 are fluoroalkyl groups], LiC n F 2n + 1 SO 3 (n ≧ 2), LiC (Rf 5 SO 2 ) 2 , LiN (Rf 6 OSO 2 ) 2 [Wherein Rf 5 and Rf 6 are fluoroalkyl groups], polymer type imidolithium salts and the like are used alone or in admixture of two or more. The concentration of the electrolyte salt in the electrolytic solution is not particularly limited, but the concentration is preferably 0.1 to 2.0 mol / L.

ゲル状ポリマー電解質は、たとえば上記電解液をゲル化剤によってゲル化したものであるが、ゲル化にあたっては、たとえば、ポリフッ化ビニリデン、ポリエチレンオキサイド、ポリアクリルニトリルなどの直鎖状ポリマーまたはそれらのコポリマー、紫外線や電子線などの活性光線の照射によりポリマー化する多官能モノマー（たとえば、ペンタエリスリトールテトラアクリレート、ジトリメチロールプロパンテトラアクリレート、エトキシ化ペンタエリスリトールテトラアクリレート、ジペンタエリスリトールヘキサアクリレートなどの四官能以上のアクリレートおよび上記アクリレートと同様の四官能以上のメタクリレートなど）などが用いられる。ただし、モノマーの場合、モノマーそのものが電解液をゲル化させるのではなく、上記モノマーがポリマー化したポリマーがゲル化剤として作用する。   The gel polymer electrolyte is obtained by, for example, gelling the above electrolytic solution with a gelling agent. For gelation, for example, a linear polymer such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or a copolymer thereof is used. , Polyfunctional monomers that polymerize by irradiation with actinic rays such as ultraviolet rays and electron beams (for example, tetrafunctional or higher functional groups such as pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, etc. An acrylate and a tetrafunctional or higher methacrylate similar to the above acrylate) are used. However, in the case of a monomer, the monomer itself does not gel the electrolyte solution, but a polymer obtained by polymerizing the monomer acts as a gelling agent.

上記のように多官能モノマーを用いて電解液をゲル化させる場合、必要であれば、重合開始剤として、ベンゾイル類、ベンゾインアルキルエーテル類、ベンゾフェノン類、ベンゾイルフェニルフォスフィンオキサイド類、アセトフェノン類、チオキサントン類、アントラキノン類、アミノエステルなども使用することもできる。   When the electrolyte is gelled using a polyfunctional monomer as described above, if necessary, as a polymerization initiator, benzoyls, benzoin alkyl ethers, benzophenones, benzoylphenylphosphine oxides, acetophenones, thioxanthone , Anthraquinones, aminoesters and the like can also be used.

以下、本発明の実施例について説明する。   Examples of the present invention will be described below.

（実施例１）
＜リチウムコバルト複合酸化物粉末の製造＞
まず、炭酸リチウム（Ｌｉ2ＣＯ3；純度９９％；比表面積０．５〜３ｍ2／ｇ程度、本荘ケミカル製）、酸化コバルト（Ｃｏ3Ｏ4；Ｃｏ含有量７３．５質量％；比表面積１〜５ｍ2／ｇ程度、住友金属鉱山製）の１次粒子を１０μｍ以下に粉砕し、リチウムとコバルトとの原子数比が１．０２となるように精秤し、混合して混合粉とした。 Example 1
<Manufacture of lithium cobalt composite oxide powder>
First, lithium carbonate (Li 2 CO 3 ; purity 99%; specific surface area 0.5-3 m 2 / g, manufactured by Honjo Chemical), cobalt oxide (Co 3 O 4 ; Co content 73.5% by mass; specific surface area) Primary particles of about 1 to 5 m 2 / g, manufactured by Sumitomo Metal Mining) are pulverized to 10 μm or less, precisely weighed so that the atomic ratio of lithium and cobalt is 1.02, and mixed to obtain a mixed powder. did.

得られた混合粉は、混合造粒機（深江工業株式会社製；ハイスピードミキサー）を用いて造粒した。まず、底部回転羽を回転させて予備混合を行った。次に、前記予備混合よりも回転数を少なくして４質量％のＰＶＡ（ポリビニルアルコール）水溶液を加え、その後回転数を再び上げ、１ｍｍ程度の種粒子を作製した。さらに回転数を調整して造粒し、１〜３ｍｍの造粒物を作製した。   The obtained mixed powder was granulated using a mixing granulator (Fukae Kogyo Co., Ltd .; high speed mixer). First, preliminary mixing was performed by rotating the bottom rotary blade. Next, the number of rotations was made lower than that of the preliminary mixing, and a 4% by mass PVA (polyvinyl alcohol) aqueous solution was added. Thereafter, the number of rotations was increased again to produce seed particles of about 1 mm. Furthermore, the number of rotations was adjusted and granulated to produce a granulated product of 1 to 3 mm.

得られた造粒物を温度１００℃で２時間乾燥させ、さらにマグネシア焼成容器を用いて酸素雰囲気中で昇温して、温度９５０℃で１５時間保持して反応を進めた。   The obtained granulated product was dried at a temperature of 100 ° C. for 2 hours, further heated in an oxygen atmosphere using a magnesia firing container, and kept at a temperature of 950 ° C. for 15 hours to proceed the reaction.

このようにして作製したリチウムコバルト複合酸化物をピンミルの粉砕機を用いて解砕して、粒径を４０μｍ以下とした。次に、粒径が１〜４０μｍの範囲となるように分級機を用いて分級した。得られたリチウム含有複合酸化物粉末の比表面積は、０．６２ｍ2／ｇであった。 The lithium cobalt composite oxide thus produced was pulverized using a pin mill pulverizer, and the particle size was adjusted to 40 μm or less. Next, it classified using the classifier so that a particle size might be in the range of 1-40 micrometers. The specific surface area of the obtained lithium-containing composite oxide powder was 0.62 m 2 / g.

＜被覆処理液の調製＞
６０℃に保持したエチレングリコールモノエチルエーテル（和光純薬工業製、試薬特級）０．５Ｌにジルコニウムイソプロポキシド（高純度化学研究所製）２５０ｇを溶解させた後、０．００１Ｍの試薬特級酢酸水溶液（和光純薬工業製）５００ｍｌを３０分間かけてゆっくりと滴下し、加水分解・重合反応させることによりジルコニアゾル微粒子を溶液中に生成させた。次に、得られた溶液を蒸留水で希釈し、ジルコニアの含有量を、５．０質量％として、被覆処理液であるジルコニアゾル水溶液を調製した。 <Preparation of coating treatment solution>
After dissolving 250 g of zirconium isopropoxide (manufactured by High Purity Chemical Laboratory) in 0.5 L of ethylene glycol monoethyl ether (manufactured by Wako Pure Chemical Industries, Ltd., maintained at 60 ° C.), 0.001M reagent-grade acetic acid 500 ml of an aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) was slowly dropped over 30 minutes, and zirconia sol fine particles were produced in the solution by hydrolysis and polymerization reaction. Next, the obtained solution was diluted with distilled water, and the content of zirconia was set to 5.0% by mass to prepare a zirconia sol aqueous solution as a coating treatment liquid.

＜被覆処理＞
被覆処理装置として、株式会社パウレック製の流動転動コーティング装置マルチプレックスＭＰ−０１を用いた。 <Coating treatment>
As a coating processing apparatus, a fluid rolling coating apparatus multiplex MP-01 manufactured by POWREC Co., Ltd. was used.

上記のようにして作製したリチウムコバルト複合酸化物粉末（比表面積０．６２ｍ2／ｇ）１．２ｋｇを上記装置槽内に投入し、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込み、流動層を形成させた。そして、リチウムコバルト複合酸化物粉末が４５℃に予熱された段階で、上記のようにして作製したジルコニアゾル水溶液を噴霧した。該噴霧は、該流動層の側面底部近傍から接線方向に、５質量％ジルコニアゾル水溶液５００ｇを４．２ｇ／ｍｉｎ（リチウムコバルト複合酸化物粉末１００質量部に対し噴霧されるジルコニアゾル水溶液量は０．３５質量部／ｍｉｎ）の噴霧速度で１２０分間行った。噴霧終了後も、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込む状態を５分間保持し、乾燥を行った。次に、リチウムコバルト複合酸化物粉末を装置から取り出し、該粉末を電気炉を用いて酸素気流中において、温度５５０℃で１５時間の焼成を行った。 1.2 kg of the lithium cobalt composite oxide powder (specific surface area 0.62 m 2 / g) produced as described above was put into the apparatus tank, and air heated to 80 ° C. was fed at 0.3 m 3 / min. A fluidized bed was formed. Then, when the lithium cobalt composite oxide powder was preheated to 45 ° C., the zirconia sol aqueous solution prepared as described above was sprayed. The spraying is performed in a tangential direction from the vicinity of the bottom of the side surface of the fluidized bed in an amount of 500 g of a 5% by mass zirconia sol aqueous solution by 4.2 g / min (the amount of the zirconia sol aqueous solution sprayed on 100 parts by mass of the lithium cobalt composite oxide powder is 0). .35 parts by mass / min) for 120 minutes. Even after the spraying was finished, the air heated to 80 ° C. was fed at 0.3 m 3 / min for 5 minutes and dried. Next, the lithium cobalt composite oxide powder was taken out from the apparatus, and the powder was fired at a temperature of 550 ° C. for 15 hours in an oxygen stream using an electric furnace.

得られた粉末について、粒度分布および比表面積の測定を行った。また、被覆されたジルコニアの量は、得られたジルコニア被覆リチウムコバルト複合酸化物を硫酸で溶解し、通常の内標準法によりＩＣＰを用いて化学分析を行い、求めた。それらの測定結果を表１に示す。   The particle size distribution and specific surface area of the obtained powder were measured. The amount of the coated zirconia was obtained by dissolving the obtained zirconia-coated lithium cobalt composite oxide with sulfuric acid and performing chemical analysis using ICP by a normal internal standard method. The measurement results are shown in Table 1.

＜電池容量の評価＞
１）容量確認試験
得られた活物質を用いて、以下のように正極容量規制のコイン電池（図２参照）を作製し、充放電容量を測定した。 <Evaluation of battery capacity>
1) Capacity Confirmation Test Using the obtained active material, a positive electrode capacity-restricted coin battery (see FIG. 2) was produced as follows, and the charge / discharge capacity was measured.

得られた活物質粉末４５ｍｇにアセチレンブラック１０．５ｍｇおよびＰＴＦＥ（ポリテトラフッ化エチレン樹脂）４．５ｍｇを混合して、正極合剤含有ペーストとした。得られた正極合剤含有ペーストを直径１８ｍｍのアルミメッシュに塗布し、２００ＭＰａの圧力でアルミメッシュとともにプレス成型した。得られた成型物を真空乾燥器中において１２０℃で真空乾燥を行い、正極とした。   45 mg of the obtained active material powder was mixed with 10.5 mg of acetylene black and 4.5 mg of PTFE (polytetrafluoroethylene resin) to obtain a positive electrode mixture-containing paste. The obtained positive electrode mixture-containing paste was applied to an aluminum mesh having a diameter of 18 mm and press-molded together with the aluminum mesh at a pressure of 200 MPa. The obtained molded product was vacuum-dried at 120 ° C. in a vacuum dryer to obtain a positive electrode.

負極としては、リチウムフォイル（本城金属（株）製）を用い、電解液としては、１ＭのＬｉＰＦ6を支持塩とするエチレンカボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）の等量混合溶液を用いて、図２に示すコイン電池にＡｒ雰囲気のグローブボックス中で組み立てた。なお、セパレータとしては、膜厚２５μｍのポリエチレン多孔膜を２枚重ねて用いた。 Lithium foil (manufactured by Honjo Metal Co., Ltd.) is used as the negative electrode, and an equivalent mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) using 1M LiPF 6 as a supporting salt is used as the electrolyte. The coin battery shown in FIG. 2 was assembled in an Ar atmosphere glove box. As the separator, two polyethylene porous films having a film thickness of 25 μm were used.

作製した電池は数時間程度放置し、開回路電圧ＯＣＶ（Open Circuit Voltage）が安定した後、正極に対する電流密度を０．２ｍＡ／ｃｍ2として、カットオフ電圧４．６Ｖまで充電した。このときの容量を初期充電容量とし、１時間の休止後にカットオフ電圧３．０Ｖまで放電したときの容量を初期放電容量とした。また前記と同じ条件で充放電試験を繰り返して、５０回目の放電容量の維持率Ａを下記数式１により求めた。その結果を表１に示す。 The produced battery was left to stand for several hours, and after the open circuit voltage OCV (Open Circuit Voltage) was stabilized, the current density with respect to the positive electrode was set to 0.2 mA / cm 2 and charged to a cutoff voltage of 4.6 V. The capacity at this time was defined as the initial charge capacity, and the capacity when discharged to a cut-off voltage of 3.0 V after a one-hour pause was defined as the initial discharge capacity. In addition, the charge / discharge test was repeated under the same conditions as described above, and the 50th discharge capacity retention ratio A was determined by the following formula 1. The results are shown in Table 1.

２）高温保存特性
前記の容量確認試験を行った場合と同様に図２に示すコイン電池を作製し、４０℃、４．２Ｖの状態に保存し、２００時間ごとに容量の確認試験を行った。その結果、４０℃、４．２Ｖの状態に保存する時間が長くなるほど、電池の内部抵抗が高くなった。また、４０℃、４．２Ｖの状態に１０００時間保存した後の放電容量の維持率Ｂを下記数式２により求めた。その結果を表１に示す。 2) High-temperature storage characteristics The coin battery shown in FIG. 2 was produced in the same manner as in the capacity check test described above, stored at 40 ° C. and 4.2 V, and the capacity check test was performed every 200 hours. . As a result, the longer the time for storage in the state of 40 ° C. and 4.2 V, the higher the internal resistance of the battery. Moreover, the retention rate B of the discharge capacity after being stored at 40 ° C. and 4.2 V for 1000 hours was obtained by the following formula 2. The results are shown in Table 1.

＜ＴＥＭ観察＞
被覆層の状態を観察するため以下に示すようにＴＥＭ観察を行った。得られたジルコニア被覆粉末をアクリル樹脂で固化させた後、集束イオンビーム法（ＦＩＢ（Focused Ion Beam））により薄片に加工し、粒子断面用のサンプルとした。図３に粒子断面のＴＥＭ観察像を示し、図４に被覆層断面のＴＥＭ観察像を示す。図４からわかるように、粒子表面は、数ｎｍ程度のジルコニア微粒子により被覆されている。 <TEM observation>
In order to observe the state of the coating layer, TEM observation was performed as follows. The obtained zirconia-coated powder was solidified with an acrylic resin, and then processed into a thin piece by a focused ion beam method (FIB (Focused Ion Beam)) to obtain a sample for particle cross section. FIG. 3 shows a TEM observation image of the particle cross section, and FIG. 4 shows a TEM observation image of the coating layer cross section. As can be seen from FIG. 4, the particle surface is covered with zirconia fine particles of about several nm.

＜ＸＲＤ測定＞
被覆層を形成しているジルコニアの結晶形態を調べるためＸＲＤ測定を行った。図５にその測定結果を示す。図５に示す測定結果から、被覆層を形成している微粒子ジルコニアは立方晶であることがわかる。 <XRD measurement>
XRD measurement was performed to examine the crystal form of zirconia forming the coating layer. FIG. 5 shows the measurement results. From the measurement results shown in FIG. 5, it can be seen that the fine zirconia particles forming the coating layer are cubic.

（実施例２）
実施例１と同様にして得られたリチウムコバルト複酸化物粉末１．２ｋｇを前記装置槽内に投入し、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込み、流動層を形成させた。そして、リチウムコバルト複合酸化物粉末が３５℃に予熱された段階で、ジルコニアゾル水溶液を噴霧した。該噴霧は、該流動層の側面底部近傍から接線方向に、４．０質量％ジルコニアゾル水溶液７７５ｇを３．０ｇ／ｍｉｎ（リチウムコバルト複合酸化物粉末１００質量部に対し噴霧されるジルコニアゾル水溶液量は０．２５質量部／ｍｉｎ）の噴霧速度で約２５８分間行った。噴霧終了後も、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込む状態を５分間保持し、乾燥を行った。次に、リチウムコバルト複合酸化物粉末を装置から取り出し、該粉末を電気炉を用いて酸素気流中において、温度５００℃で１５時間の焼成を行った。 (Example 2)
1.2 kg of lithium cobalt complex oxide powder obtained in the same manner as in Example 1 was put into the apparatus tank, and air heated to 80 ° C. was fed at 0.3 m 3 / min to form a fluidized bed. . Then, when the lithium cobalt composite oxide powder was preheated to 35 ° C., an aqueous zirconia sol solution was sprayed. The spraying is performed in the tangential direction from the vicinity of the bottom of the side surface of the fluidized bed at 3.0 g / min (amount of zirconia sol aqueous solution sprayed on 100 parts by mass of lithium cobalt composite oxide powder). Was performed at a spray rate of 0.25 parts by mass / min) for about 258 minutes. Even after the spraying was finished, the air heated to 80 ° C. was fed at 0.3 m 3 / min for 5 minutes and dried. Next, the lithium cobalt composite oxide powder was taken out from the apparatus, and the powder was fired at a temperature of 500 ° C. for 15 hours in an oxygen stream using an electric furnace.

得られた粉末について、粒度分布および比表面積の測定を行った。また、被覆されたジルコニアの量は、得られたジルコニア被覆リチウムコバルト複合酸化物を硫酸で溶解し、通常の内標準法によりＩＣＰを用いて化学分析を行い、求めた。それらの測定結果を表１に示す。   The particle size distribution and specific surface area of the obtained powder were measured. The amount of the coated zirconia was obtained by dissolving the obtained zirconia-coated lithium cobalt composite oxide with sulfuric acid and performing chemical analysis using ICP by a normal internal standard method. The measurement results are shown in Table 1.

また、図２に示すコイン電池を実施例１と同様に作製し、実施例１と同様に電池容量の評価を行った。   Also, the coin battery shown in FIG. 2 was produced in the same manner as in Example 1, and the battery capacity was evaluated in the same manner as in Example 1.

（実施例３）
実施例１と同様にして得られたリチウムコバルト複酸化物粉末１．２ｋｇを前記装置槽内に投入し、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込み、流動層を形成させた。そして、リチウムコバルト複合酸化物粉末が３５℃に予熱された段階で、ジルコニアゾル水溶液を噴霧した。該噴霧は、該流動層の側面底部近傍から接線方向に、４．９質量％ジルコニアゾル水溶液１３２５ｇを３．０ｇ／ｍｉｎ（リチウムコバルト複合酸化物粉末１００質量部に対し噴霧されるジルコニアゾル水溶液量は０．２５質量部／ｍｉｎ）の噴霧速度で約４４２分間行った。噴霧終了後も、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込む状態を５分間保持し、乾燥を行った。次に、リチウムコバルト複合酸化物粉末を装置から取り出し、該粉末を電気炉を用いて酸素気流中において、温度５００℃で１５時間の焼成を行った。 (Example 3)
1.2 kg of lithium cobalt complex oxide powder obtained in the same manner as in Example 1 was put into the apparatus tank, and air heated to 80 ° C. was fed at 0.3 m 3 / min to form a fluidized bed. . Then, when the lithium cobalt composite oxide powder was preheated to 35 ° C., an aqueous zirconia sol solution was sprayed. The spraying is performed in the tangential direction from the vicinity of the bottom of the side surface of the fluidized bed at a rate of 3.0 g / min of 1325 g of a 4.9% by mass zirconia sol aqueous solution (amount of zirconia sol aqueous solution sprayed on 100 parts by mass of lithium cobalt composite oxide powder). Was performed at a spray rate of 0.25 parts by mass / min) for about 442 minutes. Even after the spraying was finished, the air heated to 80 ° C. was fed at 0.3 m 3 / min for 5 minutes and dried. Next, the lithium cobalt composite oxide powder was taken out from the apparatus, and the powder was fired at a temperature of 500 ° C. for 15 hours in an oxygen stream using an electric furnace.

得られた粉末について、粒度分布および比表面積の測定を行った。また、被覆されたジルコニアの量は、得られたジルコニア被覆リチウムコバルト複合酸化物を硫酸で溶解し、通常の内標準法によりＩＣＰを用いて化学分析を行い、求めた。それらの測定結果を表１に示す。   The particle size distribution and specific surface area of the obtained powder were measured. The amount of the coated zirconia was obtained by dissolving the obtained zirconia-coated lithium cobalt composite oxide with sulfuric acid and performing chemical analysis using ICP by a normal internal standard method. The measurement results are shown in Table 1.

また、図２に示すコイン電池を実施例１と同様に作製し、実施例１と同様に電池容量の評価を行った。   Also, the coin battery shown in FIG. 2 was produced in the same manner as in Example 1, and the battery capacity was evaluated in the same manner as in Example 1.

（実施例４）
実施例１と同様にして得られたリチウムコバルト複酸化物粉末１．２ｋｇを前記装置槽内に投入し、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込み、流動層を形成させた。そして、リチウムコバルト複合酸化物粉末が３５℃に予熱された段階で、ジルコニアゾル水溶液を噴霧した。該噴霧は、該流動層の側面底部近傍から接線方向に、４．９質量％ジルコニアゾル水溶液１７８０ｇを４．０ｇ／ｍｉｎ（リチウムコバルト複合酸化物粉末１００質量部に対し噴霧されるジルコニアゾル水溶液量は０．３３質量部／ｍｉｎ）の噴霧速度で約４４５分間行った。噴霧終了後も、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込む状態を５分間保持し、乾燥を行った。次に、リチウムコバルト複合酸化物粉末を装置から取り出し、該粉末を電気炉を用いて酸素気流中において、温度５００℃で１５時間の焼成を行った。 Example 4
1.2 kg of lithium cobalt complex oxide powder obtained in the same manner as in Example 1 was put into the apparatus tank, and air heated to 80 ° C. was fed at 0.3 m 3 / min to form a fluidized bed. . Then, when the lithium cobalt composite oxide powder was preheated to 35 ° C., an aqueous zirconia sol solution was sprayed. The spraying is performed in the tangential direction from the vicinity of the bottom of the side surface of the fluidized bed at 1780 g of a 4.9% by mass zirconia sol aqueous solution (4.0 g / min) Was carried out at a spray rate of 0.33 parts by mass / min) for about 445 minutes. Even after the spraying was finished, the air heated to 80 ° C. was fed at 0.3 m 3 / min for 5 minutes and dried. Next, the lithium cobalt composite oxide powder was taken out from the apparatus, and the powder was fired at a temperature of 500 ° C. for 15 hours in an oxygen stream using an electric furnace.

得られた粉末について、粒度分布および比表面積の測定を行った。また、被覆されたジルコニアの量は、得られたジルコニア被覆リチウムコバルト複合酸化物を硫酸で溶解し、通常の内標準法によりＩＣＰを用いて化学分析を行い、求めた。それらの測定結果を表１に示す。   The particle size distribution and specific surface area of the obtained powder were measured. The amount of the coated zirconia was obtained by dissolving the obtained zirconia-coated lithium cobalt composite oxide with sulfuric acid and performing chemical analysis using ICP by a normal internal standard method. The measurement results are shown in Table 1.

また、図２に示すコイン電池を実施例１と同様に作製し、実施例１と同様に電池容量の評価を行った。   Also, the coin battery shown in FIG. 2 was produced in the same manner as in Example 1, and the battery capacity was evaluated in the same manner as in Example 1.

（比較例１）
実施例１で原料として使用したリチウムコバルト複合酸化物粉末を、被覆処理を行わずに用いて、図２に示すコイン電池を実施例１と同様に作製し、実施例１と同様に電池容量の評価を行った。 (Comparative Example 1)
The lithium-cobalt composite oxide powder used as a raw material in Example 1 was used without performing a coating process, and the coin battery shown in FIG. 2 was produced in the same manner as in Example 1. Evaluation was performed.

（比較例２）
実施例１と同様にして得られたリチウムコバルト複酸化物粉末１．２ｋｇを前記装置槽内に投入し、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込み、流動層を形成させた。そして、リチウムコバルト複合酸化物粉末が３０℃に予熱された段階で、ジルコニアゾル水溶液を噴霧した。該噴霧は、該流動層の側面底部近傍から接線方向に、１０質量％ジルコニアゾル水溶液５９０ｇを６．５ｇ／ｍｉｎ（リチウムコバルト複合酸化物粉末１００質量部に対し噴霧されるジルコニアゾル水溶液量は０．５４質量部／ｍｉｎ）の噴霧速度で９０分間行った。 (Comparative Example 2)
1.2 kg of lithium cobalt complex oxide powder obtained in the same manner as in Example 1 was put into the apparatus tank, and air heated to 80 ° C. was fed at 0.3 m 3 / min to form a fluidized bed. . Then, when the lithium cobalt composite oxide powder was preheated to 30 ° C., a zirconia sol aqueous solution was sprayed. The spraying is performed in a tangential direction from the vicinity of the bottom of the side surface of the fluidized bed to 590 g of a 10% by mass zirconia sol aqueous solution at 6.5 g / min (the amount of the zirconia sol aqueous solution sprayed on 100 parts by mass of the lithium cobalt composite oxide powder is 0). .54 parts by mass / min) for 90 minutes.

しかし、比較例２の条件では、リチウムコバルト複酸化物粉末に噴霧されたジルコニアゾル水溶液の乾燥が不十分となり、リチウムコバルト複酸化物粉末の流動層の維持が不可能となり、途中で製造を中止した。リチウムコバルト複合酸化物粉末は造粒物となりジルコニア被覆の粉末を得ることができなかった。   However, under the conditions of Comparative Example 2, drying of the zirconia sol aqueous solution sprayed on the lithium cobalt double oxide powder becomes insufficient, and it becomes impossible to maintain the fluidized bed of the lithium cobalt double oxide powder. did. The lithium cobalt composite oxide powder became a granulated product, and a zirconia-coated powder could not be obtained.

（比較例３）
実施例１と同様にして得られたリチウムコバルト複酸化物粉末１．２ｋｇを前記装置槽内に投入し、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込み、流動層を形成させた。そして、リチウムコバルト複合酸化物粉末が３５℃に予熱された段階で、ジルコニアゾル水溶液を噴霧した。該噴霧は、該流動層の側面底部近傍から接線方向に、８．２質量％ジルコニアゾル水溶液１６６０ｇを６．０ｇ／ｍｉｎ（リチウムコバルト複合酸化物粉末１００質量部に対し噴霧されるジルコニアゾル水溶液量は０．５質量部／ｍｉｎ）の噴霧速度で約２７７分間行った。噴霧終了後も、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込む状態を１０分間保持し、乾燥を行った。次に、リチウムコバルト複合酸化物粉末を装置から取り出し、該粉末を電気炉を用いて酸素気流中において、温度５５０℃で１５時間の焼成を行った。 (Comparative Example 3)
1.2 kg of lithium cobalt complex oxide powder obtained in the same manner as in Example 1 was put into the apparatus tank, and air heated to 80 ° C. was fed at 0.3 m 3 / min to form a fluidized bed. . Then, when the lithium cobalt composite oxide powder was preheated to 35 ° C., an aqueous zirconia sol solution was sprayed. The spraying is performed in a tangential direction from the vicinity of the bottom of the side surface of the fluidized bed in an amount of 1660 g of a 8.2% by mass zirconia sol aqueous solution to 6.0 g / min (the amount of the zirconia sol aqueous solution sprayed on 100 parts by mass of the lithium cobalt composite oxide powder). Was carried out at a spray rate of 0.5 parts by mass / min) for about 277 minutes. Even after the completion of spraying, the air heated to 80 ° C. was fed at 0.3 m 3 / min for 10 minutes and dried. Next, the lithium cobalt composite oxide powder was taken out from the apparatus, and the powder was fired at a temperature of 550 ° C. for 15 hours in an oxygen stream using an electric furnace.

得られた粉末について、粒度分布および比表面積の測定を行った。また、被覆されたジルコニアの量は、得られたジルコニア被覆リチウムコバルト複合酸化物を硫酸で溶解し、通常の内標準法によりＩＣＰを用いて化学分析を行い、求めた。それらの測定結果を表１に示す。   The particle size distribution and specific surface area of the obtained powder were measured. The amount of the coated zirconia was obtained by dissolving the obtained zirconia-coated lithium cobalt composite oxide with sulfuric acid and performing chemical analysis using ICP by a normal internal standard method. The measurement results are shown in Table 1.

また、図２に示すコイン電池を実施例１と同様に作製し、実施例１と同様に電池容量の評価を行った。   Also, the coin battery shown in FIG. 2 was produced in the same manner as in Example 1, and the battery capacity was evaluated in the same manner as in Example 1.

（比較例４）
実施例１と同様にして得られたリチウムコバルト複酸化物粉末１．２ｋｇを前記装置槽内に投入し、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込み、流動層を形成させた。そして、リチウムコバルト複合酸化物粉末が３５℃に予熱された段階で、ジルコニアゾル水溶液を噴霧した。該噴霧は、該流動層の側面底部近傍から接線方向に、５．０質量％ジルコニアゾル水溶液３０２ｇを４．０ｇ／ｍｉｎ（リチウムコバルト複合酸化物粉末１００質量部に対し噴霧されるジルコニアゾル水溶液量は０．３３質量部／ｍｉｎ）の噴霧速度で約７６分間行った。噴霧終了後も、８０℃に加熱した空気を０．３ｍ3／ｍｉｎで送り込む状態を５分間保持し、乾燥を行った。次に、リチウムコバルト複合酸化物粉末を装置から取り出し、該粉末を電気炉を用いて酸素気流中において、温度５５０℃で１５時間の焼成を行った。 (Comparative Example 4)
1.2 kg of lithium cobalt complex oxide powder obtained in the same manner as in Example 1 was put into the apparatus tank, and air heated to 80 ° C. was fed at 0.3 m 3 / min to form a fluidized bed. . Then, when the lithium cobalt composite oxide powder was preheated to 35 ° C., an aqueous zirconia sol solution was sprayed. The spraying is performed in a tangential direction from the vicinity of the bottom of the side surface of the fluidized bed in an amount of 302 g of 5.0% by mass of zirconia sol aqueous solution (4.0 g / min). Was carried out at a spray rate of 0.33 parts by mass / min) for about 76 minutes. Even after the spraying was finished, the air heated to 80 ° C. was fed at 0.3 m 3 / min for 5 minutes and dried. Next, the lithium cobalt composite oxide powder was taken out from the apparatus, and the powder was fired at a temperature of 550 ° C. for 15 hours in an oxygen stream using an electric furnace.

得られた粉末について、粒度分布および比表面積の測定を行った。また、被覆されたジルコニアの量は、得られたジルコニア被覆リチウムコバルト複合酸化物を硫酸で溶解し、通常の内標準法によりＩＣＰを用いて化学分析を行い、求めた。それらの測定結果を表１に示す。   The particle size distribution and specific surface area of the obtained powder were measured. The amount of the coated zirconia was obtained by dissolving the obtained zirconia-coated lithium cobalt composite oxide with sulfuric acid and performing chemical analysis using ICP by a normal internal standard method. The measurement results are shown in Table 1.

また、図２に示すコイン電池を実施例１と同様に作製し、実施例１と同様に電池容量の評価を行った。   Also, the coin battery shown in FIG. 2 was produced in the same manner as in Example 1, and the battery capacity was evaluated in the same manner as in Example 1.

（比較例５）
実施例４と同じ条件で流動層装置を用いて、リチウムコバルト複合酸化物粉末にジルコニアゾル液を被覆した後、該粉末を電気炉を用いて酸素気流中において、温度９００℃で１５時間焼成を行った。 (Comparative Example 5)
Using a fluidized bed apparatus under the same conditions as in Example 4, the zirconia sol solution was coated on the lithium cobalt composite oxide powder, and then the powder was calcined at 900 ° C. for 15 hours in an oxygen stream using an electric furnace. went.

得られた粉末について、粒度分布および比表面積の測定を行った。また、被覆されたジルコニアの量は、得られたジルコニア被覆リチウムコバルト複合酸化物を硫酸で溶解し、通常の内標準法によりＩＣＰを用いて化学分析を行い、求めた。それらの測定結果を表１に示す。   The particle size distribution and specific surface area of the obtained powder were measured. The amount of the coated zirconia was obtained by dissolving the obtained zirconia-coated lithium cobalt composite oxide with sulfuric acid and performing chemical analysis using ICP by a normal internal standard method. The measurement results are shown in Table 1.

また、図２に示すコイン電池を実施例１と同様に作製し、実施例１と同様に電池容量の評価を行った。   Also, the coin battery shown in FIG. 2 was produced in the same manner as in Example 1, and the battery capacity was evaluated in the same manner as in Example 1.

また、実施例１と同様にＴＥＭ観察用のサンプルを調製し、ＴＥＭ観察を行った。得られた粒子断面のＴＥＭ写真を図６に示す。表面層に存在するジルコニアは焼結により粒成長しており、均一な連続膜を形成していないことがわかる。   Moreover, the sample for TEM observation was prepared similarly to Example 1, and TEM observation was performed. A TEM photograph of the obtained particle cross section is shown in FIG. It can be seen that the zirconia present in the surface layer is grain-grown by sintering and does not form a uniform continuous film.

さらに、被覆層のＸＲＤ測定も行った。図７にその測定結果を示す。図７に示す測定結果から、被覆層のジルコニア粒子の結晶構造は単斜晶であり、粒成長とともに結晶構造も変化していることがわかる。   Furthermore, the XRD measurement of the coating layer was also performed. FIG. 7 shows the measurement results. From the measurement results shown in FIG. 7, it can be seen that the crystal structure of the zirconia particles in the coating layer is monoclinic, and the crystal structure changes with grain growth.

表１からわかるように、実施例１〜４に係る正極活物質は、ジルコニア被覆量が、リチウム含有複合酸化物粉末全質量に対して２．５１〜７．５２質量％であり、本発明に係る正極活物質のジルコニア被覆量の規定値（１．５〜８．５質量％）を満たしている。また、実施例１〜４に係る正極活物質は、比表面積が、０．５６〜１．３９ｍ2／g であり、本発明に係る正極活物質の比表面積の好ましい値の範囲（０．２〜１．５ｍ2／g）の条件を満たしている。このため、実施例１〜４に係る正極活物質は、初期放電容量がいずれも２００ｍＡｈ／ｇを上回っており、良好な結果となっている。また、放電容量維持率Ａが８７．８〜９０．５％と大きく、良好な結果となっている。さらに、実施例１については放電容量維持率Ｂも測定しているが、９３％と大きく、良好な結果となっている。 As can be seen from Table 1, in the positive electrode active materials according to Examples 1 to 4, the zirconia coating amount is 2.51 to 7.52% by mass with respect to the total mass of the lithium-containing composite oxide powder. The specified value (1.5 to 8.5% by mass) of the zirconia coating amount of the positive electrode active material is satisfied. In addition, the positive electrode active materials according to Examples 1 to 4 have a specific surface area of 0.56 to 1.39 m 2 / g, and a preferable range of the specific surface area of the positive electrode active material according to the present invention (0.2 To 1.5 m 2 / g). For this reason, all of the positive electrode active materials according to Examples 1 to 4 have an initial discharge capacity exceeding 200 mAh / g, which is a favorable result. Moreover, the discharge capacity maintenance rate A is as large as 87.8 to 90.5%, which is a favorable result. Further, for Example 1, the discharge capacity retention ratio B was also measured, but it was as large as 93%, which is a good result.

これに対して、比較例１に係る正極活物質は、ジルコニア被覆量が０であるため、放電容量維持率Ａが６３．４％と小さく、また、放電容量維持率Ｂも７６％と小さくなっている。   On the other hand, since the positive electrode active material according to Comparative Example 1 has a zirconia coating amount of 0, the discharge capacity retention ratio A is as small as 63.4%, and the discharge capacity retention ratio B is also as small as 76%. ing.

比較例３に係る正極活物質は、ジルコニア被覆量が１０．２質量％と大きく、本発明に係る正極活物質のジルコニア被覆量の規定値（１．５〜８．５質量％）の上限値を超えている。また、比較例３に係る正極活物質は、比表面積が、１．９７ｍ2／g であり、本発明に係る正極活物質の比表面積の好ましい値の範囲（０．２〜１．５ｍ2／g）の条件も満たしていない。さらに、被覆に用いたジルコニアゾル水溶液中のジルコニア濃度が８．２質量％と大きく、本発明に係る正極活物質の製造方法における被覆に用いるジルコニアゾル水溶液のジルコニア濃度の規定値（１．０〜８．０質量％）を上回っており、形成されたジルコニア被覆の均一性も十分ではないと考えられる。このため、初期放電容量、５０サイクル目放電容量とも実施例１〜４に係る正極活物質よりも１０％程度小さくなっている。 The positive electrode active material according to Comparative Example 3 has a large zirconia coating amount of 10.2% by mass, and the upper limit of the specified value (1.5 to 8.5% by mass) of the zirconia coating amount of the positive electrode active material according to the present invention. Is over. The positive active material according to Comparative Example 3, the ratio surface area is 1.97m 2 / g, the range of preferable values of the specific surface area of the positive electrode active material according to the present invention (0.2~1.5m 2 / The condition of g) is not satisfied. Furthermore, the zirconia concentration in the zirconia sol aqueous solution used for coating is as large as 8.2% by mass, and the zirconia concentration of the zirconia sol aqueous solution used for coating in the method for producing a positive electrode active material according to the present invention (1.0 to 8.0% by mass), and the uniformity of the formed zirconia coating is considered to be insufficient. For this reason, both the initial discharge capacity and the 50th cycle discharge capacity are about 10% smaller than the positive electrode active materials according to Examples 1 to 4.

比較例４に係る正極活物質は、ジルコニア被覆量が１．２４質量％と小さく、本発明に係る正極活物質のジルコニア被覆量の規定値（１．５〜８．５質量％）の下限値を下回っている。このため、初期放電容量は大きいものの、５０サイクル目放電容量が１５２．１ｍＡｈ／ｇと小さく、放電容量維持率Ａは７１．０％と小さくなっている。   The positive electrode active material according to Comparative Example 4 has a small zirconia coating amount of 1.24% by mass, and the lower limit of the prescribed value (1.5 to 8.5% by mass) of the zirconia coating amount of the positive electrode active material according to the present invention. Is below. For this reason, although the initial discharge capacity is large, the 50th cycle discharge capacity is as small as 152.1 mAh / g, and the discharge capacity retention ratio A is as small as 71.0%.

比較例２に係る正極活物質は、リチウムコバルト複合酸化物粉末が３０℃に予熱された段階で、ジルコニアゾル水溶液が噴霧されており、本発明に係る正極活物質の製造方法における予熱温度の規定値（３５℃以上）を下回っている。このため、リチウムコバルト複合酸化物粉末に噴霧されたジルコニアゾル水溶液の乾燥が不十分となり、流動層の維持が不可能となった。このため、リチウムコバルト複合酸化物粉末は造粒物となり、ジルコニアが被覆された粉末を得ることができなかった。   In the positive electrode active material according to Comparative Example 2, the aqueous solution of zirconia sol is sprayed when the lithium cobalt composite oxide powder is preheated to 30 ° C., and the preheating temperature is defined in the method for producing a positive electrode active material according to the present invention. Below the value (above 35 ° C). For this reason, drying of the zirconia sol aqueous solution sprayed on the lithium cobalt composite oxide powder becomes insufficient, and the fluidized bed cannot be maintained. For this reason, the lithium cobalt composite oxide powder became a granulated product, and a powder coated with zirconia could not be obtained.

比較例５に係る正極活物質は、９００℃で焼成されており、本発明に係る正極活物質の製造方法における焼成温度の規定値（４５０〜６００℃）の上限値を上回っている。このため、図６のＴＥＭ写真に示すように、表面層に存在するジルコニアは焼結により粒成長しており、均一な連続膜を形成していない。このため、初期放電容量は大きいものの、５０サイクル目放電容量が１５３．３ｍＡｈ／ｇと小さく、放電容量維持率Ａは７５．９％と小さくなっている。   The positive electrode active material according to Comparative Example 5 is fired at 900 ° C., which exceeds the upper limit value of the firing temperature (450 to 600 ° C.) in the method for producing a positive electrode active material according to the present invention. For this reason, as shown in the TEM photograph of FIG. 6, the zirconia present in the surface layer is grown by sintering and does not form a uniform continuous film. For this reason, although the initial discharge capacity is large, the 50th cycle discharge capacity is as small as 153.3 mAh / g, and the discharge capacity maintenance ratio A is as small as 75.9%.

リチウム含有複合酸化物粉末の流動層に、ジルコニアゾル水溶液を噴霧している状況を示す図である。It is a figure which shows the condition which sprays the zirconia sol aqueous solution to the fluidized bed of lithium containing complex oxide powder. 電池試験に用いた２０３２型コイン電池の一部破断斜視図である。It is a partially broken perspective view of a 2032 type coin battery used for a battery test. 実施例１で得られたジルコニア被覆リチウムコバルト複合酸化物粒子の断面ＴＥＭ写真である。2 is a cross-sectional TEM photograph of zirconia-coated lithium cobalt composite oxide particles obtained in Example 1. FIG. 実施例１で得られたジルコニア被覆リチウムコバルト複合酸化物粒子の被覆層の断面ＴＥＭ写真である。2 is a cross-sectional TEM photograph of a coating layer of zirconia-coated lithium cobalt composite oxide particles obtained in Example 1. FIG. 実施例１で得られたジルコニア被覆リチウムコバルト複合酸化物粒子のＸＲＤ測定結果である。2 is an XRD measurement result of zirconia-coated lithium cobalt composite oxide particles obtained in Example 1. FIG. 比較例５で得られたジルコニア被覆リチウムコバルト複合酸化物粒子の断面ＴＥＭ写真である。6 is a cross-sectional TEM photograph of zirconia-coated lithium cobalt composite oxide particles obtained in Comparative Example 5. 比較例５で得られたジルコニア被覆リチウムコバルト複合酸化物粒子のＸＲＤ測定結果である。6 is an XRD measurement result of zirconia-coated lithium cobalt composite oxide particles obtained in Comparative Example 5.

符号の説明Explanation of symbols

１ 流動層容器
２ フィルター
３ 通気部
４ ディスクロータ（回転体）
５ 回転駆動軸
６ リチウム含有複合酸化物粉末
７ スプレーガン
８ 回転駆動室
９ リチウム金属ペレット
１０ セパレータ
１１ 正極ペレット
１２ ガスケット
１３ 負極缶
１４ 正極缶 DESCRIPTION OF SYMBOLS 1 Fluidized bed container 2 Filter 3 Ventilation part 4 Disc rotor (rotary body)
DESCRIPTION OF SYMBOLS 5 Rotation drive shaft 6 Lithium containing complex oxide powder 7 Spray gun 8 Rotation drive chamber 9 Lithium metal pellet 10 Separator 11 Positive electrode pellet 12 Gasket 13 Negative electrode can 14 Positive electrode can

Claims (9)

一般式ＬｉxＭＯy（式中のＭは、主として遷移金属からなり、Ｃｏ、Ｍｎ、Ｎｉ、Ｖ、Ｆｅの少なくとも一種を含む。また、式中のｘ、ｙの値の範囲はｘ＝０．０２〜２．２、ｙ＝１．４〜３である。）で表されるリチウム含有複酸化物粉末の表面にジルコニア被覆層を形成した非水系電解質二次電池用正極活物質であって、該ジルコニア被覆層は前記リチウム含有複合酸化物粉末全質量に対して１．５〜８．５質量％の割合で形成され、かつ、該ジルコニア被覆層は均一に前記リチウム含有複合酸化物粉末の表面を覆っていることを特徴とする非水系電解質二次電池用正極活物質。 General formula Li x MO y (M in the formula is mainly composed of a transition metal and includes at least one of Co, Mn, Ni, V, and Fe. The range of values of x and y in the formula is x = 0. 0.02-2.2, y = 1.4-3)), a positive electrode active material for a non-aqueous electrolyte secondary battery in which a zirconia coating layer is formed on the surface of the lithium-containing double oxide powder represented by The zirconia coating layer is formed at a ratio of 1.5 to 8.5% by mass with respect to the total mass of the lithium-containing composite oxide powder, and the zirconia coating layer is uniformly formed of the lithium-containing composite oxide powder. A positive electrode active material for a non-aqueous electrolyte secondary battery, characterized by covering the surface. 前記非水系電解質二次電池用正極活物質の比表面積が０．２〜１．５ｍ2／ｇであることを特徴とする請求項１に記載の非水系電解質二次電池用正極活物質。 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein a specific surface area of the positive electrode active material for the non-aqueous electrolyte secondary battery is 0.2 to 1.5 m 2 / g. 前記ジルコニウム被覆層はジルコニア粒子で形成されており、該ジルコニア粒子の結晶構造は立方晶であり、かつ、該ジルコニア粒子の形状は球状であって、外径が５〜２０ｎｍであることを特徴とする請求項１または２に記載の非水系電解質二次電池用正極活物質。 The zirconium coating layer is formed of zirconia particles, the crystal structure of the zirconia particles is cubic, the shape of the zirconia particles is spherical, and the outer diameter is 5 to 20 nm, The positive electrode active material for non-aqueous electrolyte secondary batteries according to claim 1 or 2. 一般式ＬｉxＭＯy（式中のＭは、主として遷移金属からなり、Ｃｏ、Ｍｎ、Ｎｉ、Ｖ、Ｆｅの少なくとも一種を含む。また、式中のｘ、ｙの値の範囲はｘ＝０．０２〜２．２、ｙ＝１．４〜３である。）で表されるリチウム含有複合酸化物粉末を所定の容器に入れ、加熱空気を送り込み、該粉末を３５℃以上に予熱するとともに該粉末の流動層を形成する工程と、該粉末の流動層にジルコニア粒子を含むジルコニアゾル溶液を添加して、該粉末の全質量に対してジルコニアが１．５〜８．５質量％含まれるように該粉末の表面にジルコニア被覆層を形成させ、ジルコニア被覆リチウム含有複合酸化物粉末を得る工程と、該ジルコニア被覆リチウム含有複合酸化物粉末を４００〜６５０℃で焼成して、非水系電解質二次電池用正極活物質を得る工程と、を有することを特徴とする非水系電解質二次電池用正極活物質の製造方法。 General formula Li x MO y (M in the formula is mainly composed of a transition metal and includes at least one of Co, Mn, Ni, V, and Fe. The range of values of x and y in the formula is x = 0. 0.02 to 2.2, y = 1.4 to 3) is put in a predetermined container, heated air is fed, and the powder is preheated to 35 ° C. or higher. A step of forming a fluidized bed of the powder, and a zirconia sol solution containing zirconia particles are added to the fluidized bed of the powder, so that zirconia is contained in an amount of 1.5 to 8.5% by mass with respect to the total mass of the powder. Thus, a step of forming a zirconia coating layer on the surface of the powder to obtain a zirconia-coated lithium-containing composite oxide powder, and firing the zirconia-coated lithium-containing composite oxide powder at 400 to 650 ° C. Obtain positive electrode active material for secondary battery The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery characterized by having a step. 前記ジルコニアゾル溶液中のジルコニア粒子の濃度は１．０〜８．０質量％であり、かつ、該ジルコニアゾル溶液は前記流動層の側面の底部近傍から接線方向に噴霧して添加され、さらに、添加されるジルコニアゾル溶液の量が前記リチウム含有複合酸化物粉末１００質量部に対して１８〜５００質量部であることを特徴とする請求項４に記載の非水系電解質二次電池用正極活物質の製造方法。 The concentration of zirconia particles in the zirconia sol solution is 1.0 to 8.0% by mass, and the zirconia sol solution is added by spraying in the tangential direction from the vicinity of the bottom of the side surface of the fluidized bed. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 4, wherein the amount of the zirconia sol solution added is 18 to 500 parts by mass with respect to 100 parts by mass of the lithium-containing composite oxide powder. Manufacturing method. 前記ジルコニアゾル溶液の噴霧速度が、前記リチウム含有複合酸化物粉末１００質量部に対して、０．２〜０．４５質量部／ｍｉｎであることを特徴とする請求項４または５に記載の非水系電解質二次電池用正極活物質の製造方法。 The spray rate of the zirconia sol solution is 0.2 to 0.45 parts by mass / min with respect to 100 parts by mass of the lithium-containing composite oxide powder. A method for producing a positive electrode active material for an aqueous electrolyte secondary battery. 前記加熱空気の温度が７０〜１１０℃であり、該加熱空気を前記所定の装置内に送り込む送量が、前記リチウム含有複合酸化物粉末１００ｇに対して２０〜４２Ｌ／ｍｉｎであることを特徴とする請求項４〜６のいずれかに記載の非水系電解質二次電池用正極活物質の製造方法。 The temperature of the heated air is 70 to 110 ° C., and the feed rate for feeding the heated air into the predetermined apparatus is 20 to 42 L / min with respect to 100 g of the lithium-containing composite oxide powder. The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries in any one of Claims 4-6. 前記リチウム含有複合酸化物粉末の比表面積が０．２〜０．７ｍ2／ｇであることを特徴とする請求項４〜７のいずれかに記載の非水系電解質二次電池用正極活物質の製造方法。 8. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 4, wherein the lithium-containing composite oxide powder has a specific surface area of 0.2 to 0.7 m 2 / g. Production method. 請求項４〜８のいずれかの製造方法により製造された非水系電解質二次電池用正極活物質。 The positive electrode active material for non-aqueous electrolyte secondary batteries manufactured by the manufacturing method in any one of Claims 4-8.
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