JP5686041B2 - Nonaqueous electrolyte secondary battery - Google Patents

Nonaqueous electrolyte secondary battery Download PDF

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JP5686041B2
JP5686041B2 JP2011122612A JP2011122612A JP5686041B2 JP 5686041 B2 JP5686041 B2 JP 5686041B2 JP 2011122612 A JP2011122612 A JP 2011122612A JP 2011122612 A JP2011122612 A JP 2011122612A JP 5686041 B2 JP5686041 B2 JP 5686041B2
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JP2012252806A (en
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毅 千葉
毅 千葉
大輔 池田
大輔 池田
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Sanyo Electric Co Ltd
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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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Description

本発明は、正極活物質にリチウムコバルト複合酸化物を用いた非水電解質二次電池に関し、さらに詳しくは、高温保存時の膨化が抑制され、サイクル特性にも優れた非水電解質二次電池に関する。   The present invention relates to a non-aqueous electrolyte secondary battery using a lithium-cobalt composite oxide as a positive electrode active material, and more particularly to a non-aqueous electrolyte secondary battery in which expansion during high-temperature storage is suppressed and excellent in cycle characteristics. .

近年、携帯電話機、携帯型音楽プレイヤーやノートパソコンといった携帯型の電子機器の駆動電源として、軽量で、高エネルギー密度を有する非水電解質二次電池が広く利用されている。これら電子機器の普及に伴い、非水電解質二次電池のさらなる高容量化が強く望まれている。   In recent years, non-aqueous electrolyte secondary batteries that are lightweight and have a high energy density have been widely used as driving power sources for portable electronic devices such as mobile phones, portable music players, and notebook computers. With the widespread use of these electronic devices, it is strongly desired to further increase the capacity of nonaqueous electrolyte secondary batteries.

非水電解質二次電池の負極活物質としては、Ｌｉイオンを層間に吸蔵、放出することができる炭素質材料や、Ｌｉと合金化することができるケイ素やスズ又はこれらを含む合金が用いられている。また、正極活物質としては、Ｌｉイオンを可逆的に吸蔵、放出することができるＬｉ含有遷移金属複合酸化物が用いられており、特に、リチウムコバルト複合酸化物が、電池特性のバランスに優れていることから広く利用されている。   As the negative electrode active material of the nonaqueous electrolyte secondary battery, a carbonaceous material that can occlude and release Li ions between layers, silicon and tin that can be alloyed with Li, or an alloy containing these is used. Yes. Further, as the positive electrode active material, a Li-containing transition metal composite oxide capable of reversibly occluding and releasing Li ions is used, and in particular, the lithium cobalt composite oxide has an excellent balance of battery characteristics. Widely used.

非水電解質二次電池の負極極板及び正極極板は、活物質と、導電剤と、結着剤とを分散媒中で混合、攪拌して得られる活物質合剤スラリーを、集電体となる金属箔上に塗布して活物質合剤層を形成し、乾燥、圧延を経た後に所定の寸法に切断して作製される。   The negative electrode plate and the positive electrode plate of the nonaqueous electrolyte secondary battery are prepared by mixing an active material mixture slurry obtained by mixing and stirring an active material, a conductive agent, and a binder in a dispersion medium. An active material mixture layer is formed by coating on a metal foil to be formed, dried and rolled, and then cut to a predetermined size.

高容量の非水電解質二次電池を得るためには、活物質合剤層の充填密度を高める必要がある。しかし、活物質合剤層の充填密度を高めようとすると、極板の圧延時の荷重が大きくなるため、極板の製造中に極板の破断や集電体からの活物質合剤層の剥離といった問題が生じることがある。   In order to obtain a high-capacity nonaqueous electrolyte secondary battery, it is necessary to increase the packing density of the active material mixture layer. However, if an attempt is made to increase the packing density of the active material mixture layer, the load during rolling of the electrode plate increases, so the electrode plate breaks during the production of the electrode plate and the active material mixture layer from the current collector Problems such as peeling may occur.

特許文献１には、正極活物質として平均粒子径が０．１〜５０μｍの範囲内にあるリチウム複合酸化物粒子であって、その粒度分布にピークが２個以上存在するものを用いた非水電解質二次電池が開示されており、このような正極活物質を用いることで活物質の最密充填が可能になることが記載されている。この技術によれば、活物質の充填性を向上させ、正極の圧延時の荷重を低減させることができるため、上述の課題が改善されることになる。しかし、この技術は活物質と非水電解液との反応を抑制するものではないため、サイクル特性や高温保存時の電池の膨れの抑制については改善の余地が残されている。   Patent Document 1 discloses a non-aqueous solution using a lithium composite oxide particle having an average particle diameter in the range of 0.1 to 50 μm as a positive electrode active material and having two or more peaks in its particle size distribution. An electrolyte secondary battery is disclosed, and it is described that the use of such a positive electrode active material enables closest packing of the active material. According to this technique, it is possible to improve the fillability of the active material and reduce the load during the rolling of the positive electrode, so that the above-described problems are improved. However, since this technique does not suppress the reaction between the active material and the non-aqueous electrolyte, there remains room for improvement in terms of cycle characteristics and suppression of battery swelling during high-temperature storage.

特許文献２及び３には、正極活物質と非水電解質との副反応を抑制するために、非水電解質中にジニトリル化合物を添加した非水電解質二次電池が開示されている。これらの特許文献には、ジニトリル化合物が正極活物質の表面に作用することで、非水電解液の分解によるガス発生が抑制されることが記載されている。   Patent Documents 2 and 3 disclose a non-aqueous electrolyte secondary battery in which a dinitrile compound is added to a non-aqueous electrolyte in order to suppress a side reaction between the positive electrode active material and the non-aqueous electrolyte. These patent documents describe that the dinitrile compound acts on the surface of the positive electrode active material, thereby suppressing gas generation due to decomposition of the nonaqueous electrolytic solution.

特許文献４には、希土類元素の水酸化物及びオキシ水酸化物の少なくとも１種の化合物の微粒子が分散した状態で表面に付着している正極活物質を用いることで、高温保存時の非水電解液の分解や電池の膨れが抑制されることが記載されている。   In Patent Document 4, a positive electrode active material adhered to the surface in a state where fine particles of at least one compound of a rare earth element hydroxide and an oxyhydroxide are dispersed is used. It is described that the decomposition of the electrolytic solution and the swelling of the battery are suppressed.

特開２０００−８２４６６号公報JP 2000-82466 A 特開２００８−１０８５８６号公報JP 2008-108586 A 特開２０１０−１５９６８号公報JP 2010-15968 A ＷＯ２０１０／００４９７３号公報WO2010 / 004973

特許文献２及び３に記載されているように、非水電解質中にジニトリル化合物を添加した場合、高温保存特性は改善されるものの、サイクル特性が低下してしまうとの課題を有している。これは、ジニトリル化合物が正極活物質表面に吸着して非水電解質との副反応を抑制する一方、正極活物質の充放電反応を阻害する作用も有しているためであると考えられる。   As described in Patent Documents 2 and 3, when a dinitrile compound is added to the non-aqueous electrolyte, the high-temperature storage characteristics are improved, but the cycle characteristics are deteriorated. This is presumably because the dinitrile compound is adsorbed on the surface of the positive electrode active material and suppresses side reactions with the nonaqueous electrolyte, while also having an action of inhibiting the charge / discharge reaction of the positive electrode active material.

また、希土類元素の水酸化物及びオキシ水酸化物少なくとも１種の化合物の微粒子を正極活物質粒子の表面に分散した状態で付着させた場合においても、正極活物質と非水電解質との反応が抑制されるものの、サイクル特性の改善効果は十分ではないとの課題を有している。   In addition, even when fine particles of at least one kind of rare earth element hydroxide and oxyhydroxide compound are attached in a dispersed state on the surface of the positive electrode active material particles, the reaction between the positive electrode active material and the non-aqueous electrolyte does not occur. Although suppressed, there is a problem that the effect of improving the cycle characteristics is not sufficient.

ところが、発明者が検討したところ、正極活物質として粒径の異なる２種の活物質を用い、非水電解質中にジニトリル化合物が添加された非水電解質二次電池において、粒径の大きな活物質の粒子表面のみに希土類元素化合物を選択的に付着させた場合に、高温保存時の電池の膨化が抑制されるとともに、サイクル特性が改善されるとの知見を得た。   However, as a result of investigation by the inventors, in a non-aqueous electrolyte secondary battery in which two active materials having different particle sizes are used as the positive electrode active material and a dinitrile compound is added to the non-aqueous electrolyte, an active material having a large particle size is used. It has been found that when a rare earth element compound is selectively adhered only to the surface of the particles, expansion of the battery during high temperature storage is suppressed and cycle characteristics are improved.

すなわち本発明は、正極活物質として粒径の異なる２つの活物質を用いた非水電解質二次電池であって、高温保存時の膨化が抑制されるとともに、サイクル特性にも優れた非水電解質二次電池を提供することを目的とするものである。   That is, the present invention is a non-aqueous electrolyte secondary battery using two active materials having different particle diameters as a positive electrode active material, which suppresses expansion during high-temperature storage and has excellent cycle characteristics. The object is to provide a secondary battery.

上記目的を達成するために本発明に係る非水電解質二次電池は、正極活物質を含む正極極板と、負極活物質を含む負極極板と、非水溶媒中に電解質塩を含む非水電解質を備える非水電解質二次電池であって、前記正極活物質は一般式ＬｉaＣｏ1-xＭxＯ２（０＜ａ≦１．１、０≦ｘ≦０．１、Ｍ：ジルコニウム（Ｚｒ）、チタン（Ｔｉ）、マグネシウム（Ｍｇ）及びアルミニウム（Ａｌ）の少なくとも１種）で表される正極活物質Ａ及び正極活物質Ｂを含み、前記非水電解質は、一般式ＣＮ−Ｒ−ＣＮ（Ｒは炭素数２〜８の直鎖状の炭化水素基）で表されるジニトリル化合物を０．０５質量％以上０．２質量％以下含み、前記正極活物質Ａの平均粒径は、前記正極活物質Ｂの平均粒径よりも大きく、前記正極活物質のうち前記正極活物質Ａの表面に希土類元素の水酸化物及びオキシ水酸化物の少なくとも１種の化合物（以下、「希土類元素化合物」という）が０．０１ｍｏｌ％以上０．２ｍｏｌ％以下付着していることを特徴とするものである。 In order to achieve the above object, a nonaqueous electrolyte secondary battery according to the present invention includes a positive electrode plate containing a positive electrode active material, a negative electrode plate containing a negative electrode active material, and a nonaqueous solution containing an electrolyte salt in a nonaqueous solvent. A non-aqueous electrolyte secondary battery comprising an electrolyte, wherein the positive electrode active material has a general formula Li a Co 1-x M x O 2 (0 <a ≦ 1.1, 0 ≦ x ≦ 0.1, M: zirconium (Zr), titanium (Ti), magnesium (Mg), and aluminum (Al), and the non-aqueous electrolyte has a general formula CN-R. Containing 0.05% by mass or more and 0.2% by mass or less of a dinitrile compound represented by —CN (R is a linear hydrocarbon group having 2 to 8 carbon atoms), and the average particle size of the positive electrode active material A is , Larger than the average particle diameter of the positive electrode active material B, the positive electrode active material A of the positive electrode active materials At least one compound of a rare earth element hydroxide and an oxyhydroxide (hereinafter referred to as “rare earth element compound”) is adhered to the surface of the substrate in an amount of 0.01 mol% to 0.2 mol%. Is.

本発明では正極活物質として一般式ＬｉaＣｏ1-xＭxＯ2（０＜ａ≦１．１、０≦ｘ≦０．１、Ｍ：Ｚｒ、Ｔｉ、Ｍｇ及びＡｌの少なくとも１種）で表されるリチウムコバルト複合酸化物を用いる。コバルトの一部をＺｒ、Ｔｉ、Ｍｇ及びＡｌの少なくとも１種で置換することで、リチウムコバルト複合酸化物の結晶構造の安定性を高めることができる。 In the present invention, the positive electrode active material has a general formula Li a Co 1-x M x O 2 (0 <a ≦ 1.1, 0 ≦ x ≦ 0.1, M: at least one of Zr, Ti, Mg, and Al). The lithium cobalt composite oxide represented by these is used. By substituting a part of cobalt with at least one of Zr, Ti, Mg, and Al, stability of the crystal structure of the lithium cobalt composite oxide can be improved.

さらに、前記リチウムコバルト複合酸化物は粒径の異なる２種の正極活物質Ａ及び正極活物質Ｂから構成される。正極活物質Ａ及びＢは、同一の組成であることが好ましいが、前記一般式を満たすものであれば互いに異なる組成のものを使用することもできる。正極活物質Ａの平均粒径を正極活物質Ｂの平均粒径よりも大きくすることにより、正極活物質の充填性が向上し、高容量の非水電解質二次電池が得られることになる。正極活物質Ａの平均粒径は２０μｍ以上３０μｍ以下、正極活物質Ｂの平均粒径は４μｍ以上１０μ以下であることが好ましく、正極活物質Ａ及びＢの混合比（質量比）は８：２〜５：５であることが好ましい。正極活物質Ａ及びＢの平均粒径及び混合比がこの範囲内にあれば、正極活物質の充填性を効果的に向上させることができるからである。ここで平均粒径とは、レーザー回折式粒度分布測定装置(島津製作所製ＳＡＬＤ−２０００Ｊ)を用いて測定された、体積基準での積算粒子量が５０％となる粒子径を意味するものである。   Further, the lithium cobalt composite oxide is composed of two types of positive electrode active materials A and B having different particle sizes. The positive electrode active materials A and B preferably have the same composition, but may have different compositions so long as they satisfy the above general formula. By making the average particle size of the positive electrode active material A larger than the average particle size of the positive electrode active material B, the filling property of the positive electrode active material is improved, and a high capacity non-aqueous electrolyte secondary battery is obtained. The average particle size of the positive electrode active material A is preferably 20 μm or more and 30 μm or less, and the average particle size of the positive electrode active material B is preferably 4 μm or more and 10 μm or less, and the mixing ratio (mass ratio) of the positive electrode active materials A and B is 8: 2. It is preferably ˜5: 5. This is because if the average particle diameter and mixing ratio of the positive electrode active materials A and B are within this range, the filling property of the positive electrode active material can be effectively improved. Here, the average particle diameter means a particle diameter measured by using a laser diffraction particle size distribution measuring apparatus (SALD-2000J manufactured by Shimadzu Corporation) so that an integrated particle amount on a volume basis is 50%. .

前記正極活物質Ａの表面には、希土類元素化合物が付着している。希土類元素化合物を正極活物質Ａのみに選択的に付着させることで、非水電解質中に含まれるジニトリル化合物との相乗的な効果が奏され、優れた高温保存特性とサイクル特性の両立を図ることが可能となる。正極活物質Ａの表面に付着した希土類元素化合物の付着量は、正極活物質Ａに対して希土類元素換算で０．０１〜０．２ｍｏｌ％であることが好ましい。希土類元素化合物の付着量がこの範囲内にあれば、高温保存時の電池の膨化が効果的に抑制されるからである。希土類元素化合物の付着量が０．０１〜０．１ｍｏｌ％以下であれば電池の容量低下が見られないためさらに好ましい。   A rare earth element compound adheres to the surface of the positive electrode active material A. By selectively attaching the rare earth element compound only to the positive electrode active material A, a synergistic effect with the dinitrile compound contained in the non-aqueous electrolyte is achieved, and both excellent high-temperature storage characteristics and cycle characteristics are achieved. Is possible. The amount of the rare earth element compound attached to the surface of the positive electrode active material A is preferably 0.01 to 0.2 mol% with respect to the positive electrode active material A in terms of rare earth elements. This is because if the amount of the rare earth element compound is within this range, the expansion of the battery during high temperature storage is effectively suppressed. If the amount of the rare earth element compound is 0.01 to 0.1 mol% or less, the battery capacity is not lowered, which is more preferable.

なお、希土類元素化合物を正極活物質Ａに付着させる方法として、正極活物質Ａの粉末粒子を分散させた水溶液中で、希土類元素の水酸化物を活物質表面に析出させる工程と、水洗、乾燥後に熱処理を行う工程を含む方法を用いることができる。   In addition, as a method of attaching the rare earth element compound to the positive electrode active material A, a step of depositing a rare earth element hydroxide on the active material surface in an aqueous solution in which the powder particles of the positive electrode active material A are dispersed, washing with water, and drying A method including a step of performing heat treatment later can be used.

熱処理の温度としては、８０〜６００℃の範囲であることが好ましく、１００〜４００℃の範囲であることがより好ましい。また、熱処理の時間としては３〜７時間の範囲であることが好ましい。上述の条件で熱処理を行うことで、活物質表面に付着した希土類元素の水酸化物の一部がオキシ水酸化物に変化して希土類元素化合物が生成し、正極活物質と非水電解質との副反応を効果的に抑制することができる。   As temperature of heat processing, it is preferable that it is the range of 80-600 degreeC, and it is more preferable that it is the range of 100-400 degreeC. The heat treatment time is preferably in the range of 3 to 7 hours. By performing the heat treatment under the above-mentioned conditions, a part of the rare earth element hydroxide adhering to the active material surface is changed to an oxyhydroxide to form a rare earth element compound, and the positive electrode active material and the nonaqueous electrolyte Side reactions can be effectively suppressed.

本発明で使用する希土類元素としては、ランタン（Ｌａ）、セリウム（Ｃｅ）、プラセオジム（Ｐｒ）、ネオジム（Ｎｄ）、サマリウム（Ｓｍ）、ユウロピウム（Ｅｕ）、ガドリニウム（Ｇｄ）、テルビウム（Ｔｂ）、ジスプロシウム（Ｄｙ）、ホルミウム（Ｈｏ）、エルビウム（Ｅｒ）、ツリウム（Ｔｍ）、イッテルビウム（Ｙｂ）及びルテチウム（Ｌｕ）から選択される少なくとも１種が挙げられる。中でも、Ｅｒ、Ｙｂ、Ｔｂ、Ｈｏ及びＬｕから選択される少なくとも１種が好ましい。   As rare earth elements used in the present invention, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), Examples thereof include at least one selected from dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Among these, at least one selected from Er, Yb, Tb, Ho, and Lu is preferable.

本発明では非水電解質として、一般式ＣＮ−Ｒ−ＣＮ（Ｒは炭素数２〜８の直鎖状の炭化水素基）で表されるジニトリル化合物を含むものを用いている。この一般式を満たすジニトリル化合物として、スクシノニトリル、グルタロニトリル、アジポニトリル、ピメロニトリル、スベロニトリル、アゼラニトリル、セバコニトリルが挙げられる。これらの化合物は、正極活物質の活性な表面に吸着して、正極活物質と非水電解質の副反応を抑制する作用を有している。この作用は、ジニトリル化合物の直鎖状の炭化水素基の両端に存在するニトリル基に起因するものと考えられる。非水電解質中に含まれるジニトリル化合物の量は、０．０５質量％以上０．２質量％以下であることが好ましい。   In the present invention, a nonaqueous electrolyte containing a dinitrile compound represented by the general formula CN-R-CN (wherein R is a linear hydrocarbon group having 2 to 8 carbon atoms) is used. Examples of dinitrile compounds satisfying this general formula include succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azeronitrile, and sebacononitrile. These compounds have an action of adsorbing on the active surface of the positive electrode active material and suppressing side reactions between the positive electrode active material and the nonaqueous electrolyte. This action is considered to be caused by the nitrile groups present at both ends of the linear hydrocarbon group of the dinitrile compound. The amount of the dinitrile compound contained in the nonaqueous electrolyte is preferably 0.05% by mass or more and 0.2% by mass or less.

本発明の非水電解質に使用する非水溶媒として、環状カーボネート及び鎖状カーボネートを含む混合溶媒を使用することが好ましい。環状カーボネートとしては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、フルオロエチレンカーボネート（ＦＥＣ）などが挙げられ、鎖状カーボネートとしては、ジメチルカーボネート（ＤＭＣ）、メチルエチルカーボネート（ＭＥＣ）、ジエチルカーボネート（ＤＥＣ）、メチルプロピルカーボネート（ＭＰＣ）、メチルブチルカーボネート（ＭＢＣ）などが挙げられる。溶媒の粘度、イオン伝導度の観点から、環状カーボネートと鎖状カーボネートを体積比５：９５〜４０：６０の範囲で使用することが好ましい。さらに非水溶媒として、γ−ブチロラクトン（ＢＬ）、γ−バレロラクトン（ＶＬ）などの環状カルボン酸エステルやピバリン酸メチル、ピバリン酸エチル、メチルイソブチレート、メチルプロピオネートなどの鎖状カルボン酸エステルを使用することもできる。   As the nonaqueous solvent used in the nonaqueous electrolyte of the present invention, a mixed solvent containing a cyclic carbonate and a chain carbonate is preferably used. Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and fluoroethylene carbonate (FEC). Examples of the chain carbonate include dimethyl carbonate (DMC), methyl ethyl carbonate ( MEC), diethyl carbonate (DEC), methyl propyl carbonate (MPC), methyl butyl carbonate (MBC) and the like. From the viewpoint of the viscosity and ionic conductivity of the solvent, it is preferable to use a cyclic carbonate and a chain carbonate in a volume ratio of 5:95 to 40:60. Further, as non-aqueous solvents, cyclic carboxylic acid esters such as γ-butyrolactone (BL) and γ-valerolactone (VL), and chain carboxylic acids such as methyl pivalate, ethyl pivalate, methyl isobutyrate, and methyl propionate. Esters can also be used.

本発明の非水電解質に使用する電解質塩としてはＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＣｌＯ4、ＬｉＣＦ3ＳＯ3、ＬｉＮ(ＣＦ3ＳＯ2)2、ＬｉＮ(Ｃ2Ｆ5ＳＯ2)2等を使用することができる。特に、ＬｉＰＦ6又はＬｉＢＦ4の少なくとも一方を電解質塩とし、その濃度が０．５〜２ｍｏｌ／Ｌであることが好ましい。 Examples of the electrolyte salt used in the non-aqueous electrolyte of the present invention include LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 and the like. Can be used. In particular, it is preferable that at least one of LiPF 6 or LiBF 4 is an electrolyte salt and the concentration thereof is 0.5 to 2 mol / L.

さらに、本発明の非水電解質には、電極保護剤としてビニレンカーボネート（ＶＣ）を添加することもできる。   Furthermore, vinylene carbonate (VC) can also be added to the nonaqueous electrolyte of the present invention as an electrode protective agent.

なお、本発明の負極活物質としては、リチウムイオンを電気化学的に吸蔵、放出できるものなら特に限定されず使用することができ、具体的には天然黒鉛、人造黒鉛などの炭素質材料や、Ｌｉと合金化することができるケイ素、スズ又はこれらを含む合金を使用することができる。   The negative electrode active material of the present invention can be used without particular limitation as long as it can electrochemically occlude and release lithium ions, specifically, carbonaceous materials such as natural graphite and artificial graphite, Silicon, tin or alloys containing these that can be alloyed with Li can be used.

以下、本発明を実施するための最良の形態を実施例及び比較例を用いて詳細に説明する。ただし、以下に示す実施例は、本発明の技術思想を具体化するための非水電解質二次電池の製造方法の一例を例示するものであって、本発明をこの実施例に限定することを意図するものではなく、本発明は特許請求の範囲に示した技術思想を逸脱することなく種々の変更を行ったものにも均しく適用し得るものである。   Hereinafter, the best mode for carrying out the present invention will be described in detail using Examples and Comparative Examples. However, the following examples illustrate one example of a method for manufacturing a nonaqueous electrolyte secondary battery for embodying the technical idea of the present invention, and the present invention is limited to this example. The present invention is not intended, and the present invention can be equally applied to various modifications without departing from the technical idea shown in the claims.

（実施例）
（実施例１）
（正極活物質の作製）
硫酸コバルト（ＣｏＳＯ4）水溶液に、硫酸マグネシウム（ＭｇＳＯ4）、硫酸アルミニウム（Ａｌ2（ＳＯ4）3）及び硫酸ジルコニウム（Ｚｒ（ＳＯ4）2）をコバルトに対してそれぞれ１ｍｏｌ％、１ｍｏｌ％及び０．０４ｍｏｌ％となるように添加した後、炭酸水素ナトリウム（ＮａＨＣＯ3）を添加することで、Ｍｇ、Ａｌ及びＺｒを含む炭酸コバルトとして共沈させた。そして、Ｍｇ、Ａｌ及びＺｒを含む炭酸コバルトの熱分解反応により、Ｍｇ、Ａｌ及びＺｒを含む四酸化三コバルトを得た。 (Example)
(Example 1)
(Preparation of positive electrode active material)
In a cobalt sulfate (CoSO 4 ) aqueous solution, magnesium sulfate (MgSO 4 ), aluminum sulfate (Al 2 (SO 4 ) 3 ), and zirconium sulfate (Zr (SO 4 ) 2 ) are respectively added at 1 mol%, 1 mol%, and cobalt. After adding to 0.04 mol%, sodium bicarbonate (NaHCO 3 ) was added to cause coprecipitation as cobalt carbonate containing Mg, Al and Zr. And the tricobalt tetroxide containing Mg, Al, and Zr was obtained by the thermal decomposition reaction of the cobalt carbonate containing Mg, Al, and Zr.

上記のようにして得られた四酸化三コバルトをコバルト源とし、炭酸リチウム（Ｌｉ2ＣＯ3）をリチウム源として、これらをコバルトとリチウムが１：１（モル比）となるように乳鉢で混合し、得られた混合物を空気中で８５０℃で２０時間焼成してＭｇ、Ａｌ及びＺｒを含むコバルト酸リチウムを作製した。このコバルト酸リチウムを粉砕、分級して大きな平均粒径を有する正極活物質Ａ及び小さな平均粒径を有する正極活物質Ｂを得た。得られた正極活物質Ａの平均粒径は２５μｍ、正極活物質Ｂの平均粒径は６μｍであった。 Tricobalt tetroxide obtained as described above is used as a cobalt source, lithium carbonate (Li 2 CO 3 ) is used as a lithium source, and these are mixed in a mortar so that cobalt and lithium are 1: 1 (molar ratio). Then, the obtained mixture was fired in air at 850 ° C. for 20 hours to produce lithium cobalt oxide containing Mg, Al, and Zr. The lithium cobalt oxide was pulverized and classified to obtain a positive electrode active material A having a large average particle size and a positive electrode active material B having a small average particle size. The average particle diameter of the obtained positive electrode active material A was 25 μm, and the average particle diameter of the positive electrode active material B was 6 μm.

（正極活物質表面への希土類元素化合物の付着）
３リットルの純水に、正極活物質Ａを１０００ｇ添加、攪拌して、正極活物質Ａが分散した懸濁液を調製した。そして、三硝酸エルビウム・５水和物（Ｅｒ（ＮＯ3）3・５Ｈ2Ｏ）の水溶液を、エルビウム元素量が正極活物質Ａに対して０．１ｍｏｌ％となるまで懸濁液に添加した。このとき、水酸化ナトリウム水溶液を適宜添加して、懸濁液のｐＨが９で保たれるようにした。 (Rare earth element compound adhesion to the surface of the positive electrode active material)
1000 g of the positive electrode active material A was added to 3 liters of pure water and stirred to prepare a suspension in which the positive electrode active material A was dispersed. Then, an aqueous solution of erbium trinitrate pentahydrate (Er (NO 3 ) 3 .5H 2 O) was added to the suspension until the amount of erbium element was 0.1 mol% with respect to the positive electrode active material A. . At this time, an aqueous sodium hydroxide solution was appropriately added so that the pH of the suspension was maintained at 9.

次いで、この懸濁液を濾過、水洗して、粒子表面にエルビウムの水酸化物が付着した正極活物質Ａを得た。さらに、この正極活物質Ａを空気雰囲気下で３００℃、５時間の熱処理を行うことで、粒子表面に付着したエルビウムの水酸化物の一部をオキシ水酸化物に変化させ、希土類元素化合物としてのエルビウム化合物が表面に付着した正極活物質Ａを得た。   Next, this suspension was filtered and washed with water to obtain a positive electrode active material A in which erbium hydroxide adhered to the particle surface. Further, by subjecting this positive electrode active material A to heat treatment at 300 ° C. for 5 hours in an air atmosphere, a part of the erbium hydroxide adhering to the particle surface is changed to oxyhydroxide, and as a rare earth element compound A positive electrode active material A having an erbium compound attached to the surface was obtained.

上記のようにして得られた正極活物質Ａについて、エルビウム化合物の付着量をＩＣＰ(Inductively Coupled Plasma：誘導結合プラズマ)発光分析法により測定した結果、エルビウム元素換算で、正極活物質Ａに対して０．１ｍｏｌ％であることが確認された。   About the positive electrode active material A obtained as described above, the adhesion amount of the erbium compound was measured by ICP (Inductively Coupled Plasma) emission spectrometry, and as a result, the positive electrode active material A was converted to the positive electrode active material A in terms of erbium element. It was confirmed to be 0.1 mol%.

（正極極板の作製）
上記のようにして得られた正極活物質Ａと正極活物質Ｂを質量比で６：４となるように混合したものを実施例１に係る正極活物質とした。この正極活物質が９４質量部、導電剤としての炭素粉末が３質量部、結着剤としてのポリフッ化ビニリデン（ＰＶｄＦ）が３質量部となるように混合して、これを分散媒としてのＮ−メチルピロリドン（ＮＭＰ）溶液と混合、攪拌して正極活物質合剤スラリーとした。このスラリーを厚さ１５μｍのアルミニウム製の集電体の両面にドクターブレード法により塗布し、乾燥及び圧延した後、所定寸法に切断して実施例１に係る正極極板を作製した。 (Preparation of positive electrode plate)
The positive electrode active material according to Example 1 was prepared by mixing the positive electrode active material A and the positive electrode active material B obtained as described above in a mass ratio of 6: 4. This positive electrode active material was mixed so that 94 parts by mass, carbon powder as a conductive agent was 3 parts by mass, and polyvinylidene fluoride (PVdF) as a binder was 3 parts by mass, and this was mixed with N as a dispersion medium. -It mixed with the methylpyrrolidone (NMP) solution, and stirred, and it was set as the positive electrode active material mixture slurry. This slurry was applied to both sides of an aluminum current collector having a thickness of 15 μm by a doctor blade method, dried and rolled, and then cut into predetermined dimensions to produce a positive electrode plate according to Example 1.

（負極極板の作製）
負極活物質としての黒鉛が９７．５質量部、増粘剤としてのカルボキシメチルセルロース（ＣＭＣ）が１質量部と、結着剤としてのスチレンブタジエンゴム（ＳＢＲ）が１．５質量部となるように混合して、これを分散媒としての水と混合、攪拌して負極活物質合剤スラリーとした。このスラリーを厚さ１０μｍの銅製集電体の両面にドクターブレード法により塗布し、乾燥及び圧延後に所定寸法に切断して実施例１に係る負極極板を作製した。 (Preparation of negative electrode plate)
The graphite as the negative electrode active material is 97.5 parts by mass, the carboxymethyl cellulose (CMC) as the thickener is 1 part by mass, and the styrene butadiene rubber (SBR) as the binder is 1.5 parts by mass. The mixture was mixed with water as a dispersion medium and stirred to obtain a negative electrode active material mixture slurry. This slurry was applied to both sides of a copper current collector having a thickness of 10 μm by a doctor blade method, dried and rolled, and then cut into predetermined dimensions to produce a negative electrode plate according to Example 1.

なお、正極極板と負極極板のそれぞれの活物質の塗布量は、設計基準となる正極活物質の電位において、正極と負極の充電容量比（負極充電容量／正極充電容量）が１．１となるように調整した。   The amount of the active material applied to each of the positive electrode plate and the negative electrode plate is such that the charge capacity ratio of the positive electrode to the negative electrode (negative electrode charge capacity / positive electrode charge capacity) is 1.1 at the potential of the positive electrode active material as a design standard. It adjusted so that it might become.

（非水電解質の調製）
エチレンカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）及びメチルエチルカーボネート（ＭＥＣ）を体積比３５：２０：４５で混合した非水溶媒に、電解質塩としてのＬｉＰＦ6を１．０ｍｏｌ／Ｌとなるように溶解させ、アジポニトリル（ＡＮ）を０．１質量％及びビニレンカーボネート（ＶＣ）を１質量％添加して、実施例１に係る非水電解質とした。 (Preparation of non-aqueous electrolyte)
In a non-aqueous solvent in which ethylene carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (MEC) are mixed at a volume ratio of 35:20:45, LiPF 6 as an electrolyte salt is adjusted to 1.0 mol / L. The non-aqueous electrolyte according to Example 1 was prepared by adding 0.1% by mass of adiponitrile (AN) and 1% by mass of vinylene carbonate (VC).

（非水電解質二次電池の作製）
上記のように作製した正極極板と負極極板との間にポリエチレン製微多孔膜からなるセパレータを介在させ、巻回して電極体とした。この電極体をアルミニウム製角形外装缶に収納した後、上記のようにして作製した非水電解質を注液して、実施例１に係る角形非水電解質二次電池（厚み５ｍｍ×幅３４ｍｍ×高さ４３ｍｍ）を作製した。この非水電解質二次電池の設計容量は９００ｍＡｈである。 (Preparation of non-aqueous electrolyte secondary battery)
A separator made of a polyethylene microporous film was interposed between the positive electrode plate and the negative electrode plate produced as described above, and wound to obtain an electrode body. After this electrode body was housed in an aluminum rectangular outer can, the nonaqueous electrolyte produced as described above was injected to form a rectangular nonaqueous electrolyte secondary battery according to Example 1 (thickness 5 mm × width 34 mm × high 43 mm). The design capacity of this non-aqueous electrolyte secondary battery is 900 mAh.

（実施例２）
エルビウム化合物が表面に付着した正極活物質Ａに代えて、イッテルビウム化合物が表面に付着した正極活物質Ａを用いたことを除いては、実施例１と同様にして実施例２に係る非水電解質二次電池を作製した。なお、イッテルビウム化合物の正極活物質Ａへの付着は、三硝酸エルビウム・５水和物（Ｅｒ（ＮＯ３）３・５Ｈ２Ｏ）に代えて三硝酸イッテルビウム３水和物（Ｙｂ（ＮＯ３）３・３Ｈ２Ｏ）を用いたことを除いては、実施例１と同様にして行った。イッテルビウム化合物の付着量は、イッテルビウム元素換算で正極活物質Ａに対して０．１ｍｏｌ％であった。 (Example 2)
The nonaqueous electrolyte according to Example 2 is the same as Example 1 except that the positive electrode active material A having the ytterbium compound adhered to the surface is used instead of the positive electrode active material A having the erbium compound adhered to the surface. A secondary battery was produced. In addition, adhesion of the ytterbium compound to the positive electrode active material A is performed by replacing erbium trinitrate pentahydrate (Er (NO 3 ) 3 .5H 2 O) with ytterbium trinitrate trihydrate (Yb (NO 3 )). This was carried out in the same manner as in Example 1 except that 3.3H 2 O) was used. The adhesion amount of the ytterbium compound was 0.1 mol% with respect to the positive electrode active material A in terms of ytterbium element.

(実施例３)
エルビウム化合物が表面に付着した正極活物質Ａに代えて、テルビウム化合物が表面に付着した正極活物質Ａを用いたことを除いては、実施例１と同様にして実施例２に係る非水電解質二次電池を作製した。なお、テルビウム化合物の正極活物質Ａへの付着は、三硝酸エルビウム・５水和物（Ｅｒ（ＮＯ３）３・５Ｈ２Ｏ）に代えて三硝酸テルビウム６水和物（Ｔｂ（ＮＯ３）３・６Ｈ２Ｏ）を用いたことを除いては、実施例１と同様にして行った。テルビウム化合物の付着量は、テルビウム元素換算で正極活物質Ａに対して０．１ｍｏｌ％であった。 Example 3
The nonaqueous electrolyte according to Example 2 is the same as Example 1, except that the positive electrode active material A having the terbium compound adhered to the surface is used instead of the positive electrode active material A having the erbium compound adhered to the surface. A secondary battery was produced. The terbium compound adhered to the positive electrode active material A was replaced with terbium trinitrate hexahydrate (Tb (NO 3 ) instead of erbium trinitrate pentahydrate (Er (NO 3 ) 3 .5H 2 O). This was carried out in the same manner as in Example 1 except that 3.6H 2 O) was used. The adhesion amount of the terbium compound was 0.1 mol% with respect to the positive electrode active material A in terms of terbium element.

(実施例４)
エルビウム化合物が表面に付着した正極活物質Ａに代えて、ホルミウム化合物が表面に付着した正極活物質Ａを用いたことを除いては、実施例１と同様にして実施例２に係る非水電解質二次電池を作製した。なお、テルビウム化合物の正極活物質Ａへの付着は、三硝酸エルビウム・５水和物（Ｅｒ（ＮＯ３）３・５Ｈ２Ｏ）に代えて三硝酸ホルミウム５水和物（Ｈｏ（ＮＯ３）３・５Ｈ２Ｏ）を用いたことを除いては、実施例１と同様にして行った。ホルミウム化合物の付着量は、ホルミウム元素換算で正極活物質Ａに対して０．１ｍｏｌ％であった。 Example 4
The nonaqueous electrolyte according to Example 2 is the same as Example 1 except that the positive electrode active material A having a holmium compound adhered to the surface is used instead of the positive electrode active material A having the erbium compound adhered to the surface. A secondary battery was produced. The terbium compound is attached to the positive electrode active material A by holmium trinitrate pentahydrate (Ho (NO 3 ) instead of erbium trinitrate pentahydrate (Er (NO 3 ) 3 .5H 2 O). The same procedure as in Example 1 except that 3.5H 2 O) was used. The adhesion amount of the holmium compound was 0.1 mol% with respect to the positive electrode active material A in terms of holmium element.

(実施例５)
エルビウム化合物が表面に付着した正極活物質Ａに代えて、ルテチウム化合物が表面に付着した正極活物質Ａを用いたことを除いては、実施例１と同様にして実施例２に係る非水電解質二次電池を作製した。なお、ルテチウム化合物の正極活物質Ａへの付着は、三硝酸エルビウム・５水和物（Ｅｒ（ＮＯ３）３・５Ｈ２Ｏ）に代えて三硝酸ルテチウム３水和物（Ｌｕ（ＮＯ３）３・３Ｈ２Ｏ）を用いたことを除いては、実施例１と同様にして行った。ルテチウム化合物の付着量は、ルテチウム元素換算で正極活物質Ａに対して０．１ｍｏｌ％であった。 (Example 5)
The nonaqueous electrolyte according to Example 2 is the same as Example 1 except that the positive electrode active material A having the lutetium compound adhered to the surface is used instead of the positive electrode active material A having the erbium compound adhered to the surface. A secondary battery was produced. In addition, adhesion of the lutetium compound to the positive electrode active material A is performed by replacing erbium trinitrate pentahydrate (Er (NO 3 ) 3 .5H 2 O) with lutetium trinitrate trihydrate (Lu (NO 3 )). This was carried out in the same manner as in Example 1 except that 3.3H 2 O) was used. The adhesion amount of the lutetium compound was 0.1 mol% with respect to the positive electrode active material A in terms of lutetium element.

（比較例１）
正極活物質Ｂにも実施例１と同様の方法によりエルビウム化合物を付着させたことを除いては、実施例１と同様にして比較例１に係る非水電解質二次電池を作製した。 (Comparative Example 1)
A nonaqueous electrolyte secondary battery according to Comparative Example 1 was produced in the same manner as in Example 1 except that the erbium compound was adhered to the positive electrode active material B in the same manner as in Example 1.

（比較例２）
非水電解質にアジポニトリルを添加しなかったことを除いては、比較例１と同様にして比較例２に係る非水電解質二次電池を作製した。 (Comparative Example 2)
A nonaqueous electrolyte secondary battery according to Comparative Example 2 was produced in the same manner as Comparative Example 1 except that adiponitrile was not added to the nonaqueous electrolyte.

（比較例３）
正極活物質Ａにエルビウム化合物を付着させず、正極活物質Ｂのみにエルビウム化合物を付着させたことを除いては、実施例１と同様にして比較例３に係る非水電解質二次電池を作製した。 (Comparative Example 3)
A nonaqueous electrolyte secondary battery according to Comparative Example 3 was produced in the same manner as in Example 1 except that the erbium compound was not attached to the positive electrode active material A and the erbium compound was attached only to the positive electrode active material B. did.

（比較例４）
正極活物質Ａにエルビウム化合物を付着させなかったことを除いては、実施例１と同様にして比較例４に係る非水電解質二次電池を作製した。 (Comparative Example 4)
A nonaqueous electrolyte secondary battery according to Comparative Example 4 was produced in the same manner as in Example 1 except that the erbium compound was not attached to the positive electrode active material A.

（比較例５）
非水電解質にアジポニトリルを添加しなかったことを除いては、実施例１と同様にして比較例５に係る非水電解質二次電池を作製した。 (Comparative Example 5)
A nonaqueous electrolyte secondary battery according to Comparative Example 5 was produced in the same manner as in Example 1 except that adiponitrile was not added to the nonaqueous electrolyte.

（比較例６）
正極活物質Ａにエルビウム化合物を付着させなかったことを除いては、比較例５と同様にして比較例６に係る非水電解質二次電池を作製した。 (Comparative Example 6)
A nonaqueous electrolyte secondary battery according to Comparative Example 6 was produced in the same manner as Comparative Example 5 except that the erbium compound was not attached to the positive electrode active material A.

（比較例７）
正極活物質として正極活物質Ｂを用いなかったこと除いては、比較例６と同様にして比較例７に係る非水電解質二次電池を作製した。 (Comparative Example 7)
A nonaqueous electrolyte secondary battery according to Comparative Example 7 was produced in the same manner as Comparative Example 6 except that the positive electrode active material B was not used as the positive electrode active material.

（比較例８）
正極活物質として正極活物質Ａを用いなかったこと除いては、比較例６と同様にして比較例８に係る非水電解質二次電池を作製した。 (Comparative Example 8)
A nonaqueous electrolyte secondary battery according to Comparative Example 8 was produced in the same manner as Comparative Example 6 except that the positive electrode active material A was not used as the positive electrode active material.

（実施例６〜８及び比較例９）
正極活物質Ａに付着させるエルビウム化合物の量を表２に示す値としたことを除いては、実施例１と同様にして実施例６〜８及び比較例９に係る非水電解質二次電池を作製した。 (Examples 6 to 8 and Comparative Example 9)
The nonaqueous electrolyte secondary batteries according to Examples 6 to 8 and Comparative Example 9 were the same as Example 1 except that the amount of the erbium compound attached to the positive electrode active material A was set to the value shown in Table 2. Produced.

（実施例９〜１１及び比較例１０）
非水電解質に添加するアジポニトリル（ＡＮ）の量を表３に示す値としたことを除いては、実施例１と同様にして実施例９〜１１及び比較例１０に係る非水電解質二次電池を作製した。 (Examples 9 to 11 and Comparative Example 10)
Nonaqueous electrolyte secondary batteries according to Examples 9 to 11 and Comparative Example 10 except that the amount of adiponitrile (AN) added to the nonaqueous electrolyte was changed to the values shown in Table 3. Was made.

（サイクル特性の評価）
上記のようにして作製した実施例及び比較例に係る各電池について、２５℃で、１Ｉｔ（９００ｍＡ）の定電流で充電し、電圧が４．２Ｖに達した後は、４．２Ｖの定電圧で、電流が２０ｍＡとなるまで充電した。その後、１Ｉｔの定電流で、電圧が２．７Ｖになるまで放電し、１サイクル目の放電容量を求めた。さらに、この充放電サイクルを３００サイクルまで繰り返して行い、１サイクル目の放電容量に対する３００サイクル目の放電容量の比率を容量維持率（％）として算出した。 (Evaluation of cycle characteristics)
About each battery which concerns on the Example and the comparative example which were produced as mentioned above, it charged with the constant current of 1 It (900 mA) at 25 degreeC, and after the voltage reached 4.2V, it was a constant voltage of 4.2V The battery was charged until the current reached 20 mA. Thereafter, the battery was discharged at a constant current of 1 It until the voltage reached 2.7 V, and the discharge capacity at the first cycle was determined. Further, this charge / discharge cycle was repeated up to 300 cycles, and the ratio of the discharge capacity at the 300th cycle to the discharge capacity at the 1st cycle was calculated as the capacity retention rate (%).

（高温保存時の膨化率の評価）
上記のようにして作製した実施例及び比較例に係る各電池について、２５℃で、１Ｉｔ（９００ｍＡｈ）の定電流で充電し、電圧が４．２Ｖに達した後は、４．２Ｖの定電圧で、電流が２０ｍＡとなるまで充電した。このときの電池の厚みをノギスで測定し、保存前の電池厚みとした。厚みの測定後、各電池を８０℃の恒温槽に投入して、２日間保存した。そして、恒温槽から各電池を取り出し、各電池の温度が室温（２５℃）になるまで放冷した後の電池の厚みをノギスで測定した。このときの電池厚みを保存後の電池厚みとした。保存前の電池厚みに対する保存後の電池厚みの比率を膨化率（％）として算出した。 (Evaluation of expansion rate during high temperature storage)
About each battery which concerns on the Example and the comparative example which were produced as mentioned above, it charged with the constant current of 1 It (900 mAh) at 25 degreeC, and after the voltage reached to 4.2V, the constant voltage of 4.2V The battery was charged until the current reached 20 mA. The thickness of the battery at this time was measured with a vernier caliper and used as the battery thickness before storage. After measuring the thickness, each battery was put into a constant temperature bath at 80 ° C. and stored for 2 days. And each battery was taken out from the thermostat, and the thickness of the battery after standing to cool until the temperature of each battery became room temperature (25 degreeC) was measured with the caliper. The battery thickness at this time was defined as the battery thickness after storage. The ratio of the battery thickness after storage to the battery thickness before storage was calculated as the expansion ratio (%).

上記のようにして評価したサイクル特性及び高温保存時の膨化率の結果を表１〜３にまとめて示す。   The results of the cycle characteristics evaluated as described above and the expansion rate during high-temperature storage are summarized in Tables 1 to 3.

比較例６に比べて、比較例２の膨化率は１４０％から１３３％に抑えられているが、容量維持率が８４％から８１％に若干低下している。これは、正極活物質へのエルビウム化合物の付着が電池の膨化抑制に効果的ではあるものの、サイクル特性の改善にはあまり寄与していないことを示している。同様に、比較例６に比べて、比較例４の膨化率は１４０％から１３１％に抑えられているが、容量維持率が８４％から７７％と大きく低下している。これは、アジポニトリルの非水電解質への添加が電池の膨化抑制に効果的ではあるものの、サイクル特性を低下させてしまうことを示している。また、これらの技術を単に組み合わせた比較例１を比較例６と比べると、膨化率は１４０％から１２５％に抑えられているものの、容量維持率は８４％から８２％と若干低下している。この結果は、正極活物質への希土類元素化合物の付着と非水電解質へのジニトリル化合物の添加を単に組み合わせただけでは、電池の膨化の抑制には効果的であるが、サイクル特性はほとんど改善されていないことを示している。   Compared with Comparative Example 6, the expansion rate of Comparative Example 2 is suppressed from 140% to 133%, but the capacity retention rate is slightly reduced from 84% to 81%. This indicates that the adhesion of the erbium compound to the positive electrode active material is effective in suppressing the expansion of the battery, but does not contribute much to the improvement of the cycle characteristics. Similarly, compared with Comparative Example 6, the expansion rate of Comparative Example 4 is suppressed from 140% to 131%, but the capacity retention rate is greatly reduced from 84% to 77%. This indicates that the addition of adiponitrile to the non-aqueous electrolyte is effective in suppressing the expansion of the battery, but the cycle characteristics are deteriorated. Further, when Comparative Example 1 in which these techniques are simply combined is compared with Comparative Example 6, the expansion rate is suppressed from 140% to 125%, but the capacity retention rate is slightly reduced from 84% to 82%. . As a result, simply combining the adhesion of the rare earth element compound to the positive electrode active material and the addition of the dinitrile compound to the nonaqueous electrolyte is effective in suppressing the expansion of the battery, but the cycle characteristics are almost improved. Indicates that it is not.

ところが、非水電解質にアジポニトリルを添加し、エルビウム化合物を正極活物質Ａのみに付着させた実施例１は、比較例６に比べて膨化率が１４０％から１２６％に抑えられるとともに、容量維持率も８４％から８８％へ向上している。また、エルビウム化合物に代えて他の希土類元素化合物を正極活物質Ａの表面に付着させた実施例２〜５においても同様な結果が得られている。一方、エルビウム化合物を正極活物質Ｂのみに付着させた比較例３は、比較例６に比べて、膨化率は抑えられているものの、容量維持率が８４％から７８％と大きく低下している。これらの結果から、電池の膨化とサイクル特性の双方を改善させる効果は、本発明の構成によってのみ奏される特異的なものであることがわかる。   However, in Example 1 in which adiponitrile was added to the nonaqueous electrolyte and the erbium compound was adhered only to the positive electrode active material A, the expansion rate was suppressed from 140% to 126% as compared with Comparative Example 6, and the capacity retention rate was Also improved from 84% to 88%. In addition, similar results were obtained in Examples 2 to 5 in which another rare earth element compound was deposited on the surface of the positive electrode active material A instead of the erbium compound. On the other hand, in Comparative Example 3 in which the erbium compound was adhered only to the positive electrode active material B, the capacity retention rate was greatly reduced from 84% to 78%, although the expansion rate was suppressed as compared with Comparative Example 6. . From these results, it can be seen that the effect of improving both the swelling and cycle characteristics of the battery is a specific effect that can be achieved only by the configuration of the present invention.

正極活物質Ａへの希土類元素化合物の付着量の影響を確認するために、実施例１、６〜８及び比較例９の容量維持率と膨化率の結果をまとめて表２に示す。   In order to confirm the influence of the amount of the rare earth element compound adhering to the positive electrode active material A, the results of capacity retention rates and expansion rates of Examples 1, 6 to 8 and Comparative Example 9 are shown together in Table 2.

表２から、正極活物質Ａへの希土類元素化合物の付着量としては０．０１ｍｏｌ％以上０．２ｍｏｌ％以下の範囲であることが好ましいことがわかる。なお、希土類元素化合物付着量が増加すると電池容量が低下するため、０．０１ｍｏｌ％以上０．１ｍｏｌ％以下であることがより好ましい。   From Table 2, it can be seen that the amount of the rare earth element compound attached to the positive electrode active material A is preferably in the range of 0.01 mol% to 0.2 mol%. In addition, since battery capacity will fall when the rare earth element compound adhesion amount increases, it is more preferable that it is 0.01 mol% or more and 0.1 mol% or less.

非水電解質へのアジポニトリルの添加量の影響を確認するために、実施例１、９〜１１及び比較例１０の容量維持率と膨化率の結果をまとめて表３に示す。   In order to confirm the influence of the amount of adiponitrile added to the nonaqueous electrolyte, Table 3 shows the results of the capacity retention ratio and the expansion ratio of Examples 1, 9 to 11 and Comparative Example 10.

表３から、非水電解質へのアジポニトリルの添加量としては０．０２質量％以上０．２質量％以下の範囲であることが好ましいことがわかる。なお、ジニトリル化合物の実施例としては上記のアジポニトリルについての実施例を示したが、本発明の効果は主に直鎖状の炭化水素基の両端に２つのニトリル基によって奏されるものであり、一般式ＣＮ−Ｒ−ＣＮ（Ｒは炭素数２〜８の直鎖状の炭化水素基）で表されるジニトリル化合物であれば特に限定することなくアジポニトリルに代えて使用しても同様の効果が奏されるものと考えられる。   From Table 3, it can be seen that the amount of adiponitrile added to the nonaqueous electrolyte is preferably in the range of 0.02 mass% or more and 0.2 mass% or less. In addition, although the example about said adiponitrile was shown as an Example of a dinitrile compound, the effect of this invention is mainly show | played by two nitrile groups at the both ends of a linear hydrocarbon group, If it is a dinitrile compound represented by the general formula CN-R-CN (R is a linear hydrocarbon group having 2 to 8 carbon atoms), the same effect can be obtained even if it is used in place of adiponitrile without any particular limitation. It is thought to be played.

（正極活物質混合粉末の作製）
正極活物質Ａ及びＢの平均粒径並びにそれらの混合質量比が充填性に与える影響について調べるために、表４に示す平均粒径及び混合質量比を有する活物質の混合粉末を作製した。これらの活物質はいずれも実施例１と同様の方法で作製したものである。これらの平均粒子径は活物質の実施例１の粉砕、分級条件を変更することで調整した。そして、表４に記載した質量比となるように正極活物質Ａ及びＢを混合して、実施例１２〜１４、１６、１７、２０、２１及び参考例１５、１８、１９、２２に係る正極活物質の混合粉末を得た。 (Preparation of positive electrode active material mixed powder)
In order to investigate the influence of the average particle diameters of the positive electrode active materials A and B and the mixing mass ratio thereof on the filling properties, mixed powders of active materials having the average particle diameters and mixing mass ratios shown in Table 4 were prepared. All of these active materials were produced by the same method as in Example 1. These average particle diameters were adjusted by changing the pulverization and classification conditions of Example 1 of the active material. And positive electrode active material A and B were mixed so that it might become mass ratio described in Table 4, and the positive electrode which concerns on Examples 12-14, 16, 17, 20, 21 and Reference Examples 15 , 18 , 19, and 22 A mixed powder of the active material was obtained.

（正極活物質の充填性評価）
実施例１及び実施例１２〜２２に係る正極活物質の混合粉末を、試料充填部の直径が２ｃｍであるペレッタに充填し、０．３ｔｏｎ／ｃｍ2の荷重をかけた後の充填密度を測定した。このとき得られた実施例１２〜１４、１６、１７、２０、２１及び参考例１５、１８、１９、２２の充填密度を、実施例１の充填密度を１００とした場合の相対的な指数として算出した。その結果を表４に示す。 (Fillability evaluation of positive electrode active material)
The mixed powder of the positive electrode active material according to Example 1 and Examples 12 to 22 was filled in a pelleter having a sample filling part diameter of 2 cm, and the packing density after applying a load of 0.3 ton / cm 2 was measured. did. The packing density of Examples 12 to 14, 16, 17, 20, 21 and Reference Examples 15 , 18 , 19, and 22 obtained at this time is a relative index when the packing density of Example 1 is 100. Calculated. The results are shown in Table 4.

表４から、正極活物質の充填性を効果的に向上させるためには、正極活物質Ａの平均粒径が２０μｍ以上３０μｍ以下であること、正極活物質Ｂの平均粒径が４μｍ以上１０μｍ以下であることが好ましいことがわかる。正極活物質Ａ及びＢの混合質量比については、５：５〜８：２が好ましく、６：４〜８：２がさらに好ましい範囲であることがわかる。   From Table 4, in order to effectively improve the filling property of the positive electrode active material, the average particle size of the positive electrode active material A is 20 μm or more and 30 μm or less, and the average particle size of the positive electrode active material B is 4 μm or more and 10 μm or less. It turns out that it is preferable. It can be seen that the mixing mass ratio of the positive electrode active materials A and B is preferably 5: 5 to 8: 2, and more preferably 6: 4 to 8: 2.

Claims (3)

正極活物質を含む正極極板と、負極活物質を含む負極極板と、非水溶媒中に電解質塩を含む非水電解質を備える非水電解質二次電池であって、
前記正極活物質は一般式ＬｉａＣｏ１−ｘＭｘＯ２（０＜ａ≦１．１、０≦ｘ≦０．１、Ｍ：Ｚｒ、Ｔｉ、Ｍｇ及びＡｌの少なくとも１種）で表される正極活物質Ａ及び正極活物質Ｂを含み、
前記非水電解質は、一般式ＣＮ−Ｒ−ＣＮ（Ｒは炭素数２〜８の直鎖状の炭化水素基）で表されるジニトリル化合物を０．０５質量％以上０．２質量％以下含み、
前記正極活物質Ａの平均粒径は２０μｍ以上３０μｍ以下、前記正極活物質Ｂの平均粒径は４μｍ以上１０μｍ以下であり、
前記正極活物質のうち前記正極活物質Ａの表面にのみ希土類元素の水酸化物及びオキシ水酸化物の少なくとも１種の化合物が前記正極活物質に対して０．０１ｍｏｌ％以上０．２ｍｏｌ％以下付着していることを特徴とする、
非水電解質二次電池。 A nonaqueous electrolyte secondary battery comprising a positive electrode plate containing a positive electrode active material, a negative electrode plate containing a negative electrode active material, and a nonaqueous electrolyte containing an electrolyte salt in a nonaqueous solvent,
The positive electrode active material is represented by the general formula Li a Co 1-x M x O 2 (0 <a ≦ 1.1, 0 ≦ x ≦ 0.1, M: at least one of Zr, Ti, Mg, and Al). A positive electrode active material A and a positive electrode active material B,
The non-aqueous electrolyte contains 0.05% by mass or more and 0.2% by mass or less of a dinitrile compound represented by the general formula CN—R—CN (where R is a linear hydrocarbon group having 2 to 8 carbon atoms). ,
The positive electrode active material A has an average particle size of 20 μm or more and 30 μm or less , and the positive electrode active material B has an average particle size of 4 μm or more and 10 μm or less .
Among the positive electrode active materials, at least one compound of a rare earth element hydroxide and oxyhydroxide is only 0.01 mol% to 0.2 mol% of the positive electrode active material only on the surface of the positive electrode active material A. It is characterized by adhering,
Non-aqueous electrolyte secondary battery. 前記正極活物質Ａと前記正極活物質Ｂの質量比は５：５〜８：２である請求項１に記載の非水電解質二次電池。   The non-aqueous electrolyte secondary battery according to claim 1, wherein a mass ratio of the positive electrode active material A to the positive electrode active material B is 5: 5 to 8: 2. 前記ジニトリル化合物がアジポニトリルである請求項１又は２に記載の非水電解質二次電池。   The nonaqueous electrolyte secondary battery according to claim 1, wherein the dinitrile compound is adiponitrile.
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