JP2015162421A - Nonaqueous electrolyte secondary battery - Google Patents
Nonaqueous electrolyte secondary battery Download PDFInfo
- Publication number
- JP2015162421A JP2015162421A JP2014038238A JP2014038238A JP2015162421A JP 2015162421 A JP2015162421 A JP 2015162421A JP 2014038238 A JP2014038238 A JP 2014038238A JP 2014038238 A JP2014038238 A JP 2014038238A JP 2015162421 A JP2015162421 A JP 2015162421A
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- JP
- Japan
- Prior art keywords
- active material
- electrode active
- positive electrode
- secondary battery
- negative electrode
- Prior art date
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- 239000007774 positive electrode material Substances 0.000 claims abstract description 75
- 239000007773 negative electrode material Substances 0.000 claims abstract description 51
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
Description
本発明は、重負荷での放電特性および充放電サイクル特性、並びに貯蔵特性に優れた非水電解質二次電池に関するものである。 The present invention relates to a nonaqueous electrolyte secondary battery excellent in discharge characteristics under heavy load, charge / discharge cycle characteristics, and storage characteristics.
リチウムイオン二次電池などの非水電解質二次電池においては、近年、産業用やアンシラリーサービス用などの蓄電池としての用途への適用が検討されており、その一環として、出力特性、すなわち重負荷での放電特性の向上や、例えば数年程度の非常に長期にわたって容量が維持できる機能、すなわち充放電サイクル特性の向上が求められている。 In recent years, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries have been studied for use as storage batteries for industrial and ancillary services, and as part of this, output characteristics, that is, heavy load Therefore, there is a demand for improvement in discharge characteristics, and a function that can maintain the capacity for a very long time, for example, several years, that is, improvement in charge / discharge cycle characteristics.
非水電解質二次電池の出力特性の向上に関しては、例えば特許文献１に、Ｎ（ＳＯ２Ｆ）２アニオンと、その他の含フッ素無機アニオンとを含有する非水電解質を使用することが提案されている。 Regarding the improvement of the output characteristics of the nonaqueous electrolyte secondary battery, for example, Patent Document 1 proposes the use of a nonaqueous electrolyte containing N (SO 2 F) 2 anion and other fluorine-containing inorganic anions. ing.
しかしながら、非水電解質二次電池を特に前記のような用途に適用する場合を考慮すると、特許文献１に記載されているような従来の技術で確保し得る重負荷放電特性は、未だ十分とはいい難い。 However, in consideration of the case where the nonaqueous electrolyte secondary battery is applied to the above-mentioned application, the heavy load discharge characteristics that can be ensured by the conventional technique as described in Patent Document 1 are still not sufficient. It ’s not good.
本発明は、前記事情に鑑みてなされたものであり、その目的は、重負荷での放電特性および充放電サイクル特性、並びに貯蔵特性に優れた非水電解質二次電池を提供することにある。 This invention is made | formed in view of the said situation, The objective is to provide the nonaqueous electrolyte secondary battery excellent in the discharge characteristic in heavy load, charging / discharging cycling characteristics, and the storage characteristic.
前記目的を達成し得た本発明の非水電解質二次電池は、正極活物質を含有する正極、負極活物質を含有する負極、セパレータおよび非水電解質を用いた非水電解質二次電池であって、前記正極活物質および前記負極活物質のうちの少なくとも一方は、平均粒子径が１２μｍ以下であり、前記非水電解質は、ＬｉＰＦ６およびイミド塩を含有していることを特徴とするものである。 The non-aqueous electrolyte secondary battery of the present invention that has achieved the above object is a non-aqueous electrolyte secondary battery using a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator, and a non-aqueous electrolyte. In addition, at least one of the positive electrode active material and the negative electrode active material has an average particle diameter of 12 μm or less, and the nonaqueous electrolyte contains LiPF 6 and an imide salt. is there.
本発明によれば、重負荷での放電特性および充放電サイクル特性、並びに貯蔵特性に優れた非水電解質二次電池を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte secondary battery excellent in the discharge characteristic in heavy load, charging / discharging cycling characteristics, and the storage characteristic can be provided.
本発明の非水電解質二次電池は、正極活物質および負極活物質のうちの少なくとも一方に、粒径の小さいものを使用すると共に、非水電解質に、ＬｉＰＦ６とイミド塩とを含有するものを使用する。 The non-aqueous electrolyte secondary battery of the present invention uses a small particle size as at least one of a positive electrode active material and a negative electrode active material, and contains LiPF 6 and an imide salt in the non-aqueous electrolyte. Is used.
粒径が小さく充放電時の反応面積が大きい正極活物質または負極活物質を使用することで、放電時の電流値を大きくしても、十分な容量を引き出すことができるようになる。よって、ＬｉＰＦ６およびイミド塩を含有する非水電解質と、粒径の小さい正極活物質や負極活物質とを使用することで、この非水電解質による大電流での放電時に引き出し得る容量を高める作用と、正極活物質や負極活物質による前記の作用とが相俟って、電池の重負荷での放電特性を高めることができる。 By using a positive electrode active material or a negative electrode active material having a small particle size and a large reaction area during charge / discharge, a sufficient capacity can be extracted even when the current value during discharge is increased. Therefore, by using a non-aqueous electrolyte containing LiPF 6 and an imide salt, and a positive electrode active material and a negative electrode active material having a small particle size, the capacity that can be extracted at the time of discharging with a large current by this non-aqueous electrolyte is increased. In combination with the above-described effects of the positive electrode active material and the negative electrode active material, the discharge characteristics under heavy load of the battery can be improved.
また、理由は定かではないが、粒径が小さい正極活物質または負極活物質を使用すると共に、ＬｉＰＦ６およびイミド塩を含有する非水電解質を使用することで、非常に長期にわたって重負荷での充放電を繰り返しても、容量低下が生じ難い非水電解質二次電池（すなわち、重負荷での充放電サイクル特性が優れた非水電解質二次電池）とすることができる。 In addition, although the reason is not clear, by using a positive electrode active material or a negative electrode active material having a small particle size and using a nonaqueous electrolyte containing LiPF 6 and an imide salt, Even if charging / discharging is repeated, it is possible to obtain a non-aqueous electrolyte secondary battery in which capacity reduction is unlikely to occur (that is, a non-aqueous electrolyte secondary battery excellent in charge / discharge cycle characteristics under heavy load).
ところで、一般に、粒径が小さい正極活物質または負極活物質を使用した非水電解質二次電池では、非水電解質の分解反応が生じやすく、例えば充電状態で長期間貯蔵すると、容量低下が生じやすい。しかしながら、ＬｉＰＦ６およびイミド塩を含有する非水電解質を使用した場合には、前記の容量低下を抑制することができ、電池の貯蔵特性を高めることができる。 By the way, in general, in a non-aqueous electrolyte secondary battery using a positive electrode active material or a negative electrode active material having a small particle size, a decomposition reaction of the non-aqueous electrolyte is likely to occur. . However, when a nonaqueous electrolyte containing LiPF 6 and an imide salt is used, the capacity reduction can be suppressed, and the storage characteristics of the battery can be enhanced.
本発明の非水電解質二次電池は、これらの作用によって、重負荷での放電特性および充放電サイクル特性、並びに貯蔵特性に優れたものとなる。 The nonaqueous electrolyte secondary battery of the present invention has excellent discharge characteristics under heavy load, charge / discharge cycle characteristics, and storage characteristics due to these actions.
本発明の非水電解質二次電池に係る非水電解質には、例えば、リチウム塩を有機溶媒に溶解した溶液（非水電解液）が用いられる。 For the nonaqueous electrolyte according to the nonaqueous electrolyte secondary battery of the present invention, for example, a solution (nonaqueous electrolyte) in which a lithium salt is dissolved in an organic solvent is used.
そして、前記非水電解質は、リチウム塩として、イミド塩およびＬｉＰＦ６を含有している。前記の通り、このような非水電解質を使用することで、粒径の小さい正極活物質や負極活物質を用いても、優れた貯蔵特性を有する電池とすることができ、また、粒径の小さい正極活物質や負極活物質を共に使用することで、重負荷での充放電サイクル特性を高めることができる。 The nonaqueous electrolyte contains an imide salt and LiPF 6 as a lithium salt. As described above, by using such a non-aqueous electrolyte, a battery having excellent storage characteristics can be obtained even when a positive electrode active material or a negative electrode active material having a small particle size is used. By using both a small positive electrode active material and a negative electrode active material, charge / discharge cycle characteristics under heavy load can be enhanced.
イミド塩としては、例えば、ＬｉＮ（ＳＯ２Ｆ）２、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＮ（Ｃ２Ｆ５ＳＯ２）２などのリチウムイミド塩が挙げられる。イミド塩は、前記例示のもののうちの１種のみを用いてもよく、２種以上を併用してもよい。これらのイミド塩の中でも、電池の重負荷での放電特性を高める作用がより強いことから、ＬｉＮ（ＳＯ２Ｆ）２を使用することが好ましい。 Examples of the imide salt include lithium imide salts such as LiN (SO 2 F) 2 , LiN (CF 3 SO 2 ) 2 , and LiN (C 2 F 5 SO 2 ) 2 . As the imide salt, only one of the above examples may be used, or two or more may be used in combination. Among these imide salts, LiN (SO 2 F) 2 is preferably used because it has a stronger effect of enhancing the discharge characteristics under heavy load of the battery.
本発明の非水電解質二次電池で使用する非水電解質は、リチウム塩として、イミド塩と共にＬｉＰＦ６を使用する。非水電解質二次電池の正極には、通常、アルミニウム（アルミニウム合金を含む）製の集電体が使用されるが、イミド塩を含有する非水電解質を用いた場合には、アルミニウムの腐食が生じやすく、正極が早期に劣化するようになる。しかしながら、非水電解質にＬｉＰＦ６も含有させた場合には、イミド塩によるアルミニウムの腐食を抑制して、正極の劣化を抑え、信頼性や充放電サイクル特性に優れた非水電解質二次電池とすることができる。 The nonaqueous electrolyte used in the nonaqueous electrolyte secondary battery of the present invention uses LiPF 6 together with an imide salt as a lithium salt. As the positive electrode of the nonaqueous electrolyte secondary battery, a current collector made of aluminum (including an aluminum alloy) is usually used. However, when a nonaqueous electrolyte containing an imide salt is used, corrosion of aluminum is caused. It tends to occur and the positive electrode deteriorates early. However, when LiPF 6 is also contained in the non-aqueous electrolyte, the corrosion of the aluminum by the imide salt is suppressed, the deterioration of the positive electrode is suppressed, and the non-aqueous electrolyte secondary battery excellent in reliability and charge / discharge cycle characteristics can do.
非水電解質二次電池に使用する非水電解質は、イミド塩およびＬｉＰＦ６以外の他のリチウム塩を、イミド塩およびＬｉＰＦ６と共に含有していてもよい。このような他のリチウム塩としては、例えば、ＬｉＣｌＯ４、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＳｂＦ６などの無機リチウム塩；ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、Ｌｉ２Ｃ２Ｆ４（ＳＯ３）２、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＣｎＦ２ｎ＋１ＳＯ３（ｎ≧２）などの有機リチウム塩；が挙げられる。 Non-aqueous electrolyte used in the nonaqueous electrolyte secondary batteries, other lithium salts other than the imide salt and LiPF 6, may contain together with the imide salt and LiPF 6. Such other lithium salts, for example, LiClO 4, LiBF 4, LiAsF 6, LiSbF 6 inorganic lithium salts such as; LiCF 3 SO 3, LiCF 3 CO 2, Li 2 C 2 F 4 (SO 3) 2 And organic lithium salts such as LiC (CF 3 SO 2 ) 3 and LiC n F 2n + 1 SO 3 (n ≧ 2).
非水電解質に係る有機溶媒としては、イミド塩やＬｉＰＦ６などのリチウム塩を溶解し、電池として使用される電圧範囲で分解などの副反応を起こさないものであれば特に限定されない。例えば、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、ビニレンカーボネートなどの環状カーボネート；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などの鎖状カーボネート；プロピオン酸メチルなどの鎖状エステル；γ−ブチロラクトンなどの環状エステル；ジメトキシエタン、ジエチルエーテル、１，３−ジオキソラン、ジグライム、トリグライム、テトラグライムなどの鎖状エーテル；ジオキサン、テトラヒドロフラン、２−メチルテトラヒドロフランなどの環状エーテル；アセトニトリル、プロピオニトリル、メトキシプロピオニトリルなどのニトリル類；エチレングリコールサルファイトなどの亜硫酸エステル類；などが挙げられ、これらは２種以上混合して用いることもできる。なお、より良好な特性の電池とするためには、エチレンカーボネートと鎖状カーボネートの混合溶媒など、高い導電率を得ることができる組み合わせで用いることが望ましい。 The organic solvent related to the non-aqueous electrolyte is not particularly limited as long as it dissolves a lithium salt such as an imide salt or LiPF 6 and does not cause a side reaction such as decomposition in a voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; Chain ethers such as dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile and methoxypropionitrile Sulfites such as ethylene glycol sulfite; etc., and these should be used as a mixture of two or more. It can be. In order to obtain a battery with better characteristics, it is desirable to use a combination that can obtain high conductivity, such as a mixed solvent of ethylene carbonate and chain carbonate.
非水電解質二次電池に使用する非水電解質（非水電解液）におけるイミド塩の濃度は、イミド塩による正極集電体の腐食をより良好に抑えて、電池の信頼性や充放電サイクル特性をより高める観点から、０．２ｍｏｌ／ｌ未満であることが好ましく、０．１５ｍｏｌ／ｌ以下であることがより好ましい。また、イミド塩の使用による前記の効果を良好に確保する観点からは、非水電解質二次電池に使用する非水電解質（非水電解液）におけるイミド塩の濃度は、０．０１ｍｏｌ／ｌ以上であることが好ましく、０．０５ｍｏｌ／ｌ以上であることがより好ましい。 The concentration of the imide salt in the non-aqueous electrolyte (non-aqueous electrolyte) used in the non-aqueous electrolyte secondary battery suppresses the corrosion of the positive electrode current collector due to the imide salt better, and the battery reliability and charge / discharge cycle characteristics From the viewpoint of further improving the ratio, it is preferably less than 0.2 mol / l, more preferably 0.15 mol / l or less. In addition, from the viewpoint of ensuring the above-mentioned effects by using the imide salt satisfactorily, the concentration of the imide salt in the non-aqueous electrolyte (non-aqueous electrolyte) used for the non-aqueous electrolyte secondary battery is 0.01 mol / l or more. It is preferable that it is 0.05 mol / l or more.
更に、非水電解質二次電池に使用する非水電解質（非水電解液）におけるＬｉＰＦ６の濃度は、イミド塩による正極集電体の腐食をより良好に抑えて、電池の信頼性や充放電サイクル特性をより高める観点から、０．３ｍｏｌ／ｌ以上であることが好ましく、０．５ｍｏｌ／ｌ以上であることがより好ましい。また、非水電解質二次電池に使用する非水電解質（非水電解液）におけるＬｉＰＦ６の濃度は、１．１ｍｏｌ／ｌ以下であることが好ましく、０．９ｍｏｌ／ｌ以下であることがより好ましい。 Further, the concentration of LiPF 6 in the non-aqueous electrolyte (non-aqueous electrolyte) used in the non-aqueous electrolyte secondary battery can better suppress the corrosion of the positive electrode current collector due to the imide salt, thereby improving the reliability and charge / discharge of the battery. From the viewpoint of further improving the cycle characteristics, it is preferably 0.3 mol / l or more, and more preferably 0.5 mol / l or more. The concentration of LiPF 6 in the non-aqueous electrolyte (non-aqueous electrolyte) used for the non-aqueous electrolyte secondary battery is preferably 1.1 mol / l or less, and more preferably 0.9 mol / l or less. preferable.
なお、非水電解質二次電池に使用する非水電解質（非水電解液）におけるリチウム塩の合計濃度は、０．８〜１．２ｍｏｌ／ｌであることが好ましい。よって、イミド塩およびＬｉＰＦ６以外のリチウム塩も使用する場合には、イミド塩およびＬｉＰＦ６の濃度、並びにリチウム塩の合計濃度が、それぞれ前記の好適値を満たし得る量で使用することが好ましい。 In addition, it is preferable that the total density | concentration of the lithium salt in the nonaqueous electrolyte (nonaqueous electrolyte) used for a nonaqueous electrolyte secondary battery is 0.8-1.2 mol / l. Therefore, when a lithium salt other than an imide salt and LiPF 6 is also used, it is preferable that the concentration of the imide salt and LiPF 6 and the total concentration of the lithium salt are used in amounts that can satisfy the above-described preferred values.
また、非水電解質二次電池に使用する非水電解質は、ビニレンカーボネート（ＶＣ）を含有していることが好ましい。ＶＣを使用することで、イミド塩およびＬｉＰＦ６を用いることによる電池の貯蔵特性を高める作用がより向上する。 Moreover, it is preferable that the nonaqueous electrolyte used for a nonaqueous electrolyte secondary battery contains vinylene carbonate (VC). The use of VC, effect of improving the storage characteristics of a battery by using an imide salt and LiPF 6 is more improved.
非水電解質二次電池に使用する非水電解質（非水電解液）におけるＶＣの含有量は、その使用による前記の効果を良好に確保する観点から、１質量％以上であることが好ましく、３質量％以上であることがより好ましい。ただし、非水電解質中のＶＣの量が多すぎると、電池内でのガス発生の要因となって、電池の貯蔵特性向上効果が小さくなる虞がある。よって、非水電解質二次電池に使用する非水電解質（非水電解液）におけるＶＣの含有量は、８質量％以下であることが好ましく、５質量％以下であることがより好ましい。 The content of VC in the non-aqueous electrolyte (non-aqueous electrolyte solution) used for the non-aqueous electrolyte secondary battery is preferably 1% by mass or more from the viewpoint of ensuring the above-described effects due to its use. More preferably, it is at least mass%. However, if the amount of VC in the non-aqueous electrolyte is too large, it may cause gas generation in the battery, and the effect of improving the storage characteristics of the battery may be reduced. Therefore, the content of VC in the nonaqueous electrolyte (nonaqueous electrolyte solution) used for the nonaqueous electrolyte secondary battery is preferably 8% by mass or less, and more preferably 5% by mass or less.
また、前記の非水電解質（非水電解液）には、電池の安全性や充放電サイクル性、高温貯蔵特性といった特性を更に向上させる目的で、４−フルオロ−１，３−ジオキソラン−２−オン（ＦＥＣ）などのハロゲン置換された環状カーボネート、トリエチルホスホノアセテート（ＴＥＰＡ）などのホスホノアセテート類、１，３−プロパンサルトン、ジフェニルジスルフィド、シクロヘキシルベンゼン、ビフェニル、フルオロベンゼン、ｔ−ブチルベンゼンなどの添加剤を適宜加えることもできる。 In addition, the non-aqueous electrolyte (non-aqueous electrolyte) includes 4-fluoro-1,3-dioxolane-2-2, for the purpose of further improving characteristics such as battery safety, charge / discharge cycle performance, and high-temperature storage characteristics. Halogen-substituted cyclic carbonates such as ON (FEC), phosphonoacetates such as triethylphosphonoacetate (TEPA), 1,3-propane sultone, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, t-butylbenzene Additives such as can also be added as appropriate.
更に、前記の非水電解液は、ポリマーなどの公知のゲル化剤を加えてゲル状（ゲル状電解質）として用いてもよい。 Furthermore, the non-aqueous electrolyte may be used as a gel (gel electrolyte) by adding a known gelling agent such as a polymer.
本発明の非水電解質二次電池においては、正極活物質および負極活物質の少なくとも一方の平均粒子径が１２μｍ以下である。前記の通り、このようなサイズの正極活物質または負極活物質を使用することで、ＬｉＰＦ６およびイミド塩を含有する非水電解質の使用による作用と相俟って、電池の重負荷での放電特性および重負荷での充放電サイクル特性を高めることができる。 In the nonaqueous electrolyte secondary battery of the present invention, the average particle diameter of at least one of the positive electrode active material and the negative electrode active material is 12 μm or less. As described above, by using a positive electrode active material or a negative electrode active material of such a size, combined with the effect of using a non-aqueous electrolyte containing LiPF 6 and an imide salt, discharge under heavy load of the battery Characteristics and charge / discharge cycle characteristics under heavy load can be improved.
なお、本発明の非水電解質二次電池においては、正極活物質および負極活物質のうちのいずれか一方の平均粒子径が前記の値を満たしていればよいが、電池の重負荷での放電特性および重負荷での充放電サイクル特性を高める効果をより良好に確保する観点からは、正極活物質および負極活物質の両方の平均粒子径が前記の値を満たしていることが、より好ましい。 In the nonaqueous electrolyte secondary battery of the present invention, it is sufficient that the average particle diameter of either the positive electrode active material or the negative electrode active material satisfies the above value. From the viewpoint of better ensuring the characteristics and the effect of enhancing the charge / discharge cycle characteristics under heavy load, it is more preferable that the average particle diameters of both the positive electrode active material and the negative electrode active material satisfy the above values.
正極活物質の平均粒子径は、１０μｍ以下であることがより好ましく、７μｍ以下であることが更に好ましく、また、３μｍ以上であることが好ましい。 The average particle diameter of the positive electrode active material is more preferably 10 μm or less, further preferably 7 μm or less, and preferably 3 μm or more.
更に、負極活物質の平均粒子径は、１０μｍ以下であることがより好ましく、また、５μｍ以上であることが好ましい。 Furthermore, the average particle diameter of the negative electrode active material is more preferably 10 μm or less, and preferably 5 μm or more.
本明細書でいう正極活物質および負極活物質の平均粒子径は、レーザー散乱粒度分布計（例えば、日機装社製「マイクロトラックＨＲＡ」）を用い、測定対象物を溶解しない媒体に分散させて測定した体積基準の積算分率５０％における粒子直径の値であるＤ５０％を意味している。 The average particle diameter of the positive electrode active material and the negative electrode active material as used in the present specification is measured by dispersing a measurement object in a medium that does not dissolve, using a laser scattering particle size distribution meter (for example, “Microtrack HRA” manufactured by Nikkiso Co., Ltd.). D 50% , which is the value of the particle diameter at a volume-based cumulative fraction of 50%.
本発明の非水電解質二次電池に係る正極には、例えば、正極活物質、導電助剤およびバインダなどを含有する正極合剤層を、集電体の片面または両面に有する構造のものが使用できる。 For the positive electrode according to the non-aqueous electrolyte secondary battery of the present invention, for example, a positive electrode mixture layer containing a positive electrode active material, a conductive additive and a binder is used on one or both sides of the current collector. it can.
正極活物質については特に制限はなく、従来から知られている非水電解質二次電池の正極活物質として使用されているものと同じもの、すなわち、Ｌｉイオンを吸蔵放出可能な正極活物質を用いることができる。具体的には、例えば、Ｌｉ１＋ｘＭ１Ｏ２（−０．１＜ｘ＜０．１、Ｍ１：Ｃｏ、Ｎｉ、Ｍｎ、Ａｌ、Ｍｇなど）で表される層状構造のリチウム含有遷移金属酸化物、ＬｉＭｎ２Ｏ４やその元素の一部を他元素で置換したスピネル構造のリチウムマンガン酸化物、ＬｉＭ２ＰＯ４（Ｍ２：Ｃｏ、Ｎｉ、Ｍｎ、Ｆｅなど）で表されるオリビン型化合物などのリチウム含有複合酸化物などが挙げられる。前記層状構造のリチウム含有遷移金属酸化物の具体例としては、ＬｉＣｏＯ２やＬｉＮｉ１−ａＣｏａ−ｂＡｌｂＯ２（０．１≦ａ≦０．３、０．０１≦ｂ≦０．２）などのほか、少なくともＮｉ、ＣｏおよびＭｎを含む酸化物（ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２、ＬｉＮｉ５／１２Ｃｏ１／６Ｍｎ５／１２Ｏ２、ＬｉＮｉ１／２Ｃｏ２／１０Ｍｎ３／１０Ｏ２、ＬｉＮｉ３／５Ｃｏ１／５Ｍｎ１／５Ｏ２など）などを例示することができる。 There is no particular limitation on the positive electrode active material, and the same positive electrode active material that is conventionally used as a positive electrode active material of a nonaqueous electrolyte secondary battery, that is, a positive electrode active material capable of occluding and releasing Li ions is used. be able to. Specifically, for example, a lithium-containing transition metal having a layered structure represented by Li 1 + x M 1 O 2 (−0.1 <x <0.1, M 1 : Co, Ni, Mn, Al, Mg, etc.) Olivine type represented by oxide, LiMn 2 O 4 and spin manganese lithium manganese oxide in which some of its elements are substituted with other elements, LiM 2 PO 4 (M 2 : Co, Ni, Mn, Fe, etc.) Examples thereof include lithium-containing composite oxides such as compounds. Specific examples of the lithium-containing transition metal oxide having a layered structure include LiCoO 2 and LiNi 1-a Co ab Al b O 2 (0.1 ≦ a ≦ 0.3, 0.01 ≦ b ≦ 0. 2) and other oxides containing at least Ni, Co and Mn (LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiNi 5/12 Co 1/6 Mn 5/12 O 2 , LiNi 1 / 2 Co 2/10 Mn 3/10 O 2 , LiNi 3/5 Co 1/5 Mn 1/5 O 2, etc.).
正極活物質には、前記例示のリチウム含有複合酸化物（粒子）の表面に、Ｚｒ酸化物を有するものを使用することもできる。Ｚｒ酸化物を表面に有するリチウム含有複合酸化物を正極活物質として使用した場合には、正極の抵抗を低減し得るため、電池の重負荷での充放電サイクル特性を更に高めることができる。また、Ｚｒ酸化物の添加によって、正極活物質の放電時の電位が高くなり、電池の平均作動電圧が高くなる。作動電圧がわずか０．１Ｖ異なるだけでも、エネルギー密度に換算すると大きな差を生じるため、正極活物質自体の放電電位をできるだけ高くすることが好ましい。 As the positive electrode active material, one having a Zr oxide on the surface of the lithium-containing composite oxide (particles) exemplified above can also be used. When a lithium-containing composite oxide having a Zr oxide on the surface is used as the positive electrode active material, the resistance of the positive electrode can be reduced, and therefore the charge / discharge cycle characteristics under heavy load of the battery can be further improved. In addition, the addition of Zr oxide increases the potential of the positive electrode active material during discharge, thereby increasing the average operating voltage of the battery. Even if the operating voltage differs by only 0.1 V, a large difference occurs when converted to energy density. Therefore, it is preferable to increase the discharge potential of the positive electrode active material itself as much as possible.
Ｚｒ酸化物を表面に有するリチウム含有複合酸化物は、例えば以下の製造方法により得ることができる。まず、ニッケル化合物、コバルト化合物、マンガン化合物などの、リチウム含有複合酸化物を構成するための遷移金属を含む化合物から調製した所定量の遷移金属イオンを含有する水溶液を、攪拌している純水中に滴下する。更に、この水溶液の温度を４０〜８０℃とし、攪拌しながら、この水溶液中に、ｐＨが８〜１２となるようにアルカリ水溶液を滴下して、前記遷移金属を含有する沈殿物を得る。なお、前記水溶液に滴下するアルカリ水溶液には、水酸化ナトリウム水溶液、炭酸水素アンモニウム水溶液、炭酸水素ナトリウム水溶液、水酸化カリウム水溶液、水酸化リチウム水溶液などを使用することができる。 The lithium-containing composite oxide having a Zr oxide on the surface can be obtained, for example, by the following production method. First, an aqueous solution containing a predetermined amount of transition metal ions prepared from a compound containing a transition metal for constituting a lithium-containing composite oxide, such as a nickel compound, a cobalt compound, or a manganese compound, is stirred in pure water. Dripping into. Further, the temperature of the aqueous solution is set to 40 to 80 ° C., and while stirring, an alkaline aqueous solution is dropped into the aqueous solution so that the pH becomes 8 to 12 to obtain a precipitate containing the transition metal. In addition, sodium hydroxide aqueous solution, ammonium hydrogencarbonate aqueous solution, sodium hydrogencarbonate aqueous solution, potassium hydroxide aqueous solution, lithium hydroxide aqueous solution etc. can be used for the alkaline aqueous solution dripped at the said aqueous solution.
次に、前記水溶液をろ過して生成した沈殿物を回収し、これを水洗した後に、８０℃〜４００℃の酸素含有気流中で攪拌しながら熱処理する。これにより、前記遷移金属を含有する酸化物（前記遷移金属を複数種含有する場合は、複合酸化物。以下、「前記遷移金属を含む酸化物」には、前記遷移金属を複数種含有する複合酸化物を含む。）が得られる。前記遷移金属を含有する酸化物は、平均粒子径が、１２μｍ以下であることが好ましく、１０μｍ以下であることが更に好ましい。前記遷移金属を含有する酸化物の比表面積は、沈殿条件や沈殿物の熱処理条件によって、任意に調整することができる。 Next, the precipitate formed by filtering the aqueous solution is recovered, washed with water, and then heat-treated while stirring in an oxygen-containing air stream at 80 ° C to 400 ° C. Thereby, the oxide containing the transition metal (in the case of containing a plurality of the transition metals, a composite oxide. Hereinafter, the “oxide containing the transition metal” is referred to as a composite containing a plurality of the transition metals. Including oxides). The oxide containing the transition metal preferably has an average particle size of 12 μm or less, and more preferably 10 μm or less. The specific surface area of the oxide containing the transition metal can be arbitrarily adjusted depending on the precipitation conditions and the heat treatment conditions of the precipitate.
前記のようにして得られた前記遷移金属を含有する酸化物にリチウム化合物およびジルコニウム化合物を混合して原料混合物を調製し、この原料混合物を焼成する。この焼成によって、前記遷移金属を含有する酸化物とリチウム化合物とからリチウム含有複合酸化物が生成し、そのリチウム含有複合酸化物（粒子）の表面に、Ｚｒ酸化物が生成する。焼成は、大気中で行ってもよいが、酸素雰囲気中で行うこともできる。焼成温度は６５０℃〜１１００℃であることが好ましく、より好ましくは、８５０℃〜１０５０℃である。焼成温度が低すぎると、未反応の原料が正極活物質中に残留し、単位質量当たりの放電容量の低下や充放電サイクル特性の低下、作動電圧の低下を招く虞がある。また、焼成温度が高すぎると、副生成物が生成しやすくなり、単位質量当たりの放電容量の低下や充放電サイクル特性の低下、作動電圧の低下を招く虞がある。焼成の時間は、５時間以上とすることが好ましく、これにより混合物の粒子間の拡散反応を十分に進行させることができる。また、焼成の時間は、３０時間以下とすることが好ましく、これにより正極活物質の生産性を高めることができる。 A lithium compound and a zirconium compound are mixed with the oxide containing the transition metal obtained as described above to prepare a raw material mixture, and this raw material mixture is fired. By this firing, a lithium-containing composite oxide is generated from the oxide containing the transition metal and the lithium compound, and a Zr oxide is generated on the surface of the lithium-containing composite oxide (particles). Firing may be performed in the air, but can also be performed in an oxygen atmosphere. The firing temperature is preferably 650 ° C to 1100 ° C, more preferably 850 ° C to 1050 ° C. If the firing temperature is too low, unreacted raw materials remain in the positive electrode active material, which may cause a decrease in discharge capacity per unit mass, a decrease in charge / discharge cycle characteristics, and a decrease in operating voltage. On the other hand, if the firing temperature is too high, a by-product is likely to be generated, which may cause a decrease in discharge capacity per unit mass, a decrease in charge / discharge cycle characteristics, and a decrease in operating voltage. The firing time is preferably 5 hours or longer, whereby the diffusion reaction between the particles of the mixture can sufficiently proceed. In addition, the firing time is preferably 30 hours or less, which can increase the productivity of the positive electrode active material.
また、前記のような、前記遷移金属を含有する沈殿物の生成を経て正極活物質の原料を得る工程を含む以外にも、リチウム含有複合酸化物を構成するための遷移金属を含有する化合物とジルコニウム化合物とリチウム化合物とを混合、焼成して、Ｚｒ酸化物を表面に有するリチウム含有複合酸化物を製造することも可能である。 In addition to the step of obtaining the raw material of the positive electrode active material through the generation of the precipitate containing the transition metal as described above, the compound containing the transition metal for constituting the lithium-containing composite oxide; It is also possible to produce a lithium-containing composite oxide having a Zr oxide on the surface by mixing and baking a zirconium compound and a lithium compound.
前記方法により得られるＺｒ酸化物は、酸化ジルコニウム：ＺｒＯ２、または一部にリチウムとの複合酸化物（Ｌｉ２ＺｒＯ３など）を含む酸化物の混合体であり、リチウム含有複合酸化物の表面がそのような酸化物で覆われることにより、高い電圧が印加された場合の活物質の安定性が向上し、その結果、非水電解質の分解反応や正極活物質の結晶構造の破壊が生じ難くなり、優れた充放電サイクル特性および保存特性を示す正極活物質となる。 The Zr oxide obtained by the above method is zirconium oxide: ZrO 2 , or a mixture of oxides partially including a complex oxide with lithium (such as Li 2 ZrO 3 ), and the surface of the lithium-containing complex oxide Is covered with such an oxide, the stability of the active material when a high voltage is applied is improved, and as a result, the decomposition reaction of the nonaqueous electrolyte and the destruction of the crystal structure of the positive electrode active material are unlikely to occur. Thus, a positive electrode active material exhibiting excellent charge / discharge cycle characteristics and storage characteristics is obtained.
前記方法により得られるリチウム含有複合酸化物の表面にＺｒ酸化物が存在することは、例えば、走査型電子顕微鏡（ＳＥＭ）像、走査型イオン顕微鏡（ＳＩＭ）像、透過型電子顕微鏡（ＴＥＭ）像、走査透過型電子顕微鏡（ＳＴＥＭ）像などで確認することができる。また、リチウム遷移金属複合酸化物の断面をＳＥＭ像、ＳＩＭ像、ＴＥＭ像、ＳＴＥＭ像などで確認してもよい。 The presence of a Zr oxide on the surface of the lithium-containing composite oxide obtained by the above method is, for example, a scanning electron microscope (SEM) image, a scanning ion microscope (SIM) image, or a transmission electron microscope (TEM) image. It can be confirmed with a scanning transmission electron microscope (STEM) image or the like. Moreover, you may confirm the cross section of lithium transition metal complex oxide by a SEM image, a SIM image, a TEM image, a STEM image, etc.
Ｚｒ酸化物が正極活物質の表面に存在することにより前記特性が改善される詳細な作用機構については不明であるが、ジルコニウム化合物中のＺｒの一部が、焼成時にリチウム含有複合酸化物中に拡散してリチウム含有複合酸化物の遷移金属サイトを置換することによって、結晶構造を強化していると考えられる。更に、リチウム含有複合酸化物の表面に形成されるＺｒ酸化物は、被膜的な作用を有するとも考えられる。つまり、Ｚｒ酸化物の形成過程で、Ｚｒが拡散することによる結晶構造の安定化、および形成されたＺｒ酸化物の被膜効果によって、リチウム含有複合酸化物を構成する金属イオンの溶出が減少し、電圧降下が抑制されると考えられる。このような効果は、リチウム含有複合酸化物とＺｒ酸化物とを単に混合するだけでは得ることができず、従って、リチウム化合物と遷移金属を含有する化合物とを焼成する際に、ジルコニウム化合物との混合物を作製し、これを焼成することが好ましい。 Although the detailed mechanism of action that improves the above-described characteristics by the presence of the Zr oxide on the surface of the positive electrode active material is unknown, a part of Zr in the zirconium compound is not contained in the lithium-containing composite oxide during firing. It is considered that the crystal structure is strengthened by diffusing and replacing the transition metal sites of the lithium-containing composite oxide. Furthermore, it is considered that the Zr oxide formed on the surface of the lithium-containing composite oxide has a film-like action. In other words, in the formation process of the Zr oxide, the elution of the metal ions constituting the lithium-containing composite oxide is reduced by the stabilization of the crystal structure due to the diffusion of Zr and the coating effect of the formed Zr oxide, It is considered that the voltage drop is suppressed. Such an effect cannot be obtained by simply mixing the lithium-containing composite oxide and the Zr oxide. Therefore, when the lithium compound and the compound containing the transition metal are fired, It is preferable to prepare a mixture and to fire it.
これらの方法で得られた、Ｚｒ酸化物を表面に有するリチウム含有複合酸化物は、必要に応じて、乳鉢、ボールミル、振動ミル、ピンミル、ジェットミルなどを用いて粉砕し、目的とする粒度に調整することもできる。得られる正極活物質は、平均粒子径が、１２μｍ以下であることが好ましく、１０μｍ以下であることが更に好ましい。また、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く、０．３〜０．８ｍ２／ｇであることがより好ましい。 The lithium-containing composite oxide having a Zr oxide on the surface obtained by these methods is pulverized as necessary using a mortar, ball mill, vibration mill, pin mill, jet mill, etc. It can also be adjusted. The obtained positive electrode active material preferably has an average particle size of 12 μm or less, and more preferably 10 μm or less. The specific surface area of the positive electrode active material is preferably 0.2~1.5m 2 / g, more preferably 0.3~0.8m 2 / g.
Ｚｒ酸化物を表面に有するリチウム含有複合酸化物においては、リチウム含有複合酸化物の結晶子界面に十分な量のＺｒ酸化物を存在させて、その効果を良好に確保する観点から、リチウム含有複合酸化物とその表面に存在するＺｒ酸化物とを構成している全元素の合計量を１００ｍｏｌ％としたときに、Ｚｒ酸化物を構成しているジルコニウムの量が、０．０１ｍｏｌ％以上であることが好ましく、０．０２ｍｏｌ％以上であることがより好ましく、０．０４ｍｏｌ％以上であることが更に好ましい。また、Ｚｒ酸化物を表面に有するリチウム含有複合酸化物においては、Ｚｒ酸化物の量が多くなることで生じ得る放電容量の低下を良好に抑制する観点から、リチウム含有複合酸化物とその表面に存在するＺｒ酸化物とを構成している全元素の合計量を１００ｍｏｌ％としたときに、Ｚｒ酸化物を構成しているジルコニウムの量が、２ｍｏｌ％以下であることが好ましく、０．３ｍｏｌ％以下であることがより好ましく、０．２５ｍｏｌ％以下であることが更に好ましい。 In a lithium-containing composite oxide having a Zr oxide on the surface, a lithium-containing composite oxide is used from the viewpoint of ensuring a sufficient effect by having a sufficient amount of Zr oxide present at the crystallite interface of the lithium-containing composite oxide. When the total amount of all elements constituting the oxide and the Zr oxide existing on the surface is 100 mol%, the amount of zirconium constituting the Zr oxide is 0.01 mol% or more. It is preferably 0.02 mol% or more, and more preferably 0.04 mol% or more. Further, in the lithium-containing composite oxide having a Zr oxide on the surface, from the viewpoint of satisfactorily suppressing a decrease in discharge capacity that may be caused by an increase in the amount of Zr oxide, the lithium-containing composite oxide and the surface thereof When the total amount of all elements constituting the Zr oxide present is 100 mol%, the amount of zirconium constituting the Zr oxide is preferably 2 mol% or less, and 0.3 mol% More preferably, it is more preferably 0.25 mol% or less.
正極合剤層に係るバインダには、従来から知られている非水電解質二次電池用の正極に係る正極合剤層で使用されているバインダと同じものが使用できる。具体的には、例えば、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、スチレンブタジエンゴム（ＳＢＲ）、カルボキシメチルセルロース（ＣＭＣ）などが好ましいものとして挙げられる。 As the binder related to the positive electrode mixture layer, the same binder as that used in the positive electrode mixture layer related to the positive electrode known for the nonaqueous electrolyte secondary battery can be used. Specifically, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC) and the like are preferable.
正極合剤層に係る導電助剤としては、例えば、天然黒鉛（鱗片状黒鉛など）、人造黒鉛などの黒鉛；アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラック、サーマルブラックなどのカ−ボンブラック；炭素繊維；などが挙げられる。 Examples of the conductive aid for the positive electrode mixture layer include graphite such as natural graphite (eg, scaly graphite) and artificial graphite; carbon such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. -Bon black; carbon fiber;
正極は、例えば、正極活物質、バインダおよび導電助剤などをＮＭＰなどの溶剤に分散させたペースト状やスラリー状の正極合剤層形成用組成物を調製し（ただし、バインダは溶剤に溶解していてもよい）、これを集電体の片面または両面に塗布し、乾燥した後に、必要に応じてカレンダ処理を施す工程を経て製造される。ただし、正極は、前記の製造方法で製造されたものに限定される訳ではなく、他の方法で製造したものであってもよい。 For the positive electrode, for example, a paste-form or slurry-form composition for forming a positive electrode mixture layer in which a positive electrode active material, a binder, a conductive auxiliary agent, and the like are dispersed in a solvent such as NMP is prepared (however, the binder is dissolved in the solvent). It may be manufactured through a step of applying a calender treatment as necessary after applying it to one or both sides of the current collector and drying it. However, the positive electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other methods.
また、正極には、必要に応じて、非水電解質二次電池内の他の部材と電気的に接続するためのリード体を、常法に従って形成してもよい。 Moreover, you may form the lead body for electrically connecting with the other member in a nonaqueous electrolyte secondary battery according to a conventional method as needed.
正極合剤層の厚みは、例えば、集電体の片面あたり１０〜１００μｍであることが好ましい。また、正極合剤層の組成としては、例えば、正極活物質の量が６０〜９５質量％であることが好ましく、バインダの量が１〜１５質量％であることが好ましく、導電助剤の量が３〜２０質量％であることが好ましい。 The thickness of the positive electrode mixture layer is preferably, for example, 10 to 100 μm per one side of the current collector. Moreover, as a composition of a positive mix layer, it is preferable that the quantity of a positive electrode active material is 60-95 mass%, for example, it is preferable that the quantity of a binder is 1-15 mass%, and the quantity of a conductive support agent. Is preferably 3 to 20% by mass.
正極の集電体は、従来から知られている非水電解質二次電池の正極に使用されているものと同様のものが使用でき、例えば、厚みが１０〜３０μｍのアルミニウム箔が好ましい。 As the current collector for the positive electrode, the same one as used for the positive electrode of a conventionally known non-aqueous electrolyte secondary battery can be used. For example, an aluminum foil having a thickness of 10 to 30 μm is preferable.
本発明の非水電解質二次電池に係る負極には、例えば、負極活物質およびバインダ、更には必要に応じて導電助剤などを含有する負極合剤層を、集電体の片面または両面に有する構造のものが使用できる。 In the negative electrode according to the nonaqueous electrolyte secondary battery of the present invention, for example, a negative electrode active material and a binder, and further, a negative electrode mixture layer containing a conductive auxiliary agent as necessary, are provided on one side or both sides of the current collector. The thing of the structure which has can be used.
負極活物質には、従来から知られている非水電解質二次電池の負極に使用されている負極活物質、すなわち、リチウムイオンを吸蔵放出可能な活物質を用いることができる。このような負極活物質の具体例としては、例えば、黒鉛（天然黒鉛；熱分解炭素類、ＭＣＭＢ、炭素繊維などの易黒鉛化炭素を２８００℃以上で黒鉛化処理した人造黒鉛；など）、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、活性炭などの炭素材料；リチウムと合金化可能な金属（Ｓｉ、Ｓｎなど）や、これらの金属を含む材料（合金など）；などの粒子が挙げられる。負極には、前記例示の負極活物質のうち、１種のみを使用してもよく、２種以上を併用してもよい。 As the negative electrode active material, a conventionally known negative electrode active material used for a negative electrode of a nonaqueous electrolyte secondary battery, that is, an active material capable of occluding and releasing lithium ions can be used. Specific examples of such a negative electrode active material include, for example, graphite (natural graphite; artificial graphite obtained by graphitizing graphitized carbon such as pyrolytic carbons, MCMB, and carbon fiber at 2800 ° C. or higher), heat Carbon materials such as decomposed carbons, cokes, glassy carbons, fired organic polymer compounds, mesocarbon microbeads, carbon fibers and activated carbon; metals that can be alloyed with lithium (Si, Sn, etc.), and these And other particles containing a metal (such as an alloy). In the negative electrode, only one type of the above illustrated negative electrode active materials may be used, or two or more types may be used in combination.
負極合剤層に係るバインダには、正極合剤層に使用し得るものとして先に例示した各種バインダと同じものが使用できる。また、負極合剤層に導電助剤を含有させる場合、その導電助剤には、正極合剤層に使用し得るものとして先に例示した各種導電助剤と同じものが使用できる。 As the binder for the negative electrode mixture layer, the same binders as those exemplified above as those that can be used for the positive electrode mixture layer can be used. Moreover, when making a negative electrode mixture layer contain a conductive support agent, the same thing as the various conductive support agents illustrated previously as what can be used for a positive mix layer can be used for the conductive support agent.
負極は、例えば、負極活物質およびバインダ、更には必要に応じて導電助剤などをＮＭＰなどの有機溶剤や水といった溶剤に分散させたペースト状やスラリー状の負極合剤層形成用組成物を調製し（ただし、バインダは溶剤に溶解していてもよい）、これを集電体の片面または両面に塗布し、乾燥した後に、必要に応じてカレンダ処理を施す工程を経て製造される。ただし、負極は、前記の製造方法で製造されたものに限定される訳ではなく、他の方法で製造したものであってもよい。 The negative electrode is, for example, a paste-form or slurry-form composition for forming a negative electrode mixture layer in which a negative electrode active material and a binder, and further, if necessary, a conductive additive or the like is dispersed in an organic solvent such as NMP or a solvent such as water. The binder is prepared (however, the binder may be dissolved in a solvent), applied to one or both sides of the current collector, dried, and then subjected to a calendering process as necessary. However, the negative electrode is not limited to those manufactured by the above manufacturing method, and may be manufactured by other methods.
また、負極には、必要に応じて、非水電解質二次電池内の他の部材と電気的に接続するためのリード体を、常法に従って形成してもよい。 Moreover, you may form in the negative electrode the lead body for electrically connecting with the other member in a nonaqueous electrolyte secondary battery according to a conventional method as needed.
負極合剤層の厚みは、例えば、集電体の片面あたり１０〜１００μｍであることが好ましい。負極合剤層の組成としては、例えば、負極活物質の量が８５〜９９質量％であることが好ましく、バインダの量が１．０〜１０質量％とすることが好ましい。また、負極合剤層に導電助剤を含有させる場合には、負極合剤層中における導電助剤の量は０．５〜１０質量％であることが好ましい。 The thickness of the negative electrode mixture layer is preferably 10 to 100 μm per one surface of the current collector, for example. As the composition of the negative electrode mixture layer, for example, the amount of the negative electrode active material is preferably 85 to 99% by mass, and the amount of the binder is preferably 1.0 to 10% by mass. Moreover, when making a negative electrode mixture layer contain a conductive support agent, it is preferable that the quantity of the conductive support agent in a negative mix layer is 0.5-10 mass%.
負極の集電体には、銅製や銅合金製、ニッケル製、ニッケル合金製の箔、パンチングメタル、網、エキスパンドメタルなどを用い得るが、通常、銅箔が用いられる。負極集電体の厚みは、例えば、５〜３０μｍであることが好ましい。 For the current collector of the negative electrode, foil made of copper, copper alloy, nickel, nickel alloy, punching metal, net, expanded metal, or the like can be used, but copper foil is usually used. The thickness of the negative electrode current collector is preferably, for example, 5 to 30 μm.
なお、本発明の非水電解質二次電池において、正極活物質および負極活物質のうちの少なくとも一方には、シランカップリング処理を施したものを使用することもできる。シランカップリング処理を施した正極活物質や負極活物質を使用することで、電池の貯蔵特性を更に高めることができる。 In the nonaqueous electrolyte secondary battery of the present invention, at least one of the positive electrode active material and the negative electrode active material can be used after silane coupling treatment. By using a positive electrode active material or a negative electrode active material that has been subjected to silane coupling treatment, the storage characteristics of the battery can be further enhanced.
本発明の非水電解質二次電池において、シランカップリング処理された活物質を使用する際には、正極活物質および負極活物質のうちのいずれか一方のみが、シランカップリング処理されたものであってもよく、両方がシランカップリング処理されたものであってもよい。 In the nonaqueous electrolyte secondary battery of the present invention, when an active material subjected to silane coupling treatment is used, only one of the positive electrode active material and the negative electrode active material is subjected to silane coupling treatment. Both of them may be silane-coupled.
正極活物質や負極活物質のシランカップリング処理に使用し得るシランカップリング剤としては、例えば、ビニルトリクロルシラン、ビニルトリメトキシシラン、ビニルトリエトキシシランなどのビニル基を有するシランカップリング剤；２−（３，４−エポキシシクロヘキシル）エチルトリメトキシシラン、３−グリシドキシプロピルトリメトキシシラン、３−グリシドキシプロピルメチルジエトキシシラン、３−グリシドキシプロピルトリエトキシシランなどのエポキシ基を有するシランカップリング剤；ｐ−スチリルトリメトキシシランなどのスチリル基を有するシランカップリング剤；３−メタクリロキシプロピルメチルジメトキシシラン、３−メタクリロキシプロピルトリメトキシシラン、３−メタクリロキシプロピルメチルジメトキシシラン、３−メタクリロキシプロピルトリエトキシシランなどのメタクロキシ基を有するシランカップリング剤；３−アクリロキシプロピルトリメトキシシランなどのアクリロキシ基を有するシランカップリング剤；Ｎ−２−（アミノエチル）−３−アミノプロピルメチルジメトキシシラン、Ｎ−２−（アミノエチル）−３−アミノプロピルトリメトキシシラン、３−アミノプロピルトリエトキシシラン、３−アミノプロピルトリメトキシシラン、３−アミノプロピルトリエトキシシラン、３−トリエトキシシリル−Ｎ−（１，３−ジメチル−ブチリデン）プロピルアミン、Ｎ−フェニル−３−アミノプロピルトリメトキシシラン、Ｎ−（ビニルベンジル）−２−アミノエチル−３−アミノプロピルトリメトキシシランの塩酸塩などのアミノ基を有するシランカップリング剤；３−ウレイドプロピルトリエトキシシランなどのウレイド基を有するシランカップリング剤；３−クロロプロピルトリメトキシシランなどのクロロプロピル基を有するシランカップリング剤；３−メルカプトプロピルメチルジメトキシシラン、３−メルカプトプロピルトリメトキシシランなどのメルカプト基を有するシランカップリング剤；ビス（トリエトキシシリルプロピル）テトラスルフィドなどのスルフィド基を有するシランカップリング剤；３−イソシアネートプロピルトリエトキシシランなどのイソシアネート基を有するシランカップリング剤；などが挙げられる。活物質のシランカップリング処理には、前記例示のシランカップリング剤のうちの１種のみを用いてもよく、２種以上を併用してもよい。 Examples of the silane coupling agent that can be used for the silane coupling treatment of the positive electrode active material and the negative electrode active material include silane coupling agents having a vinyl group such as vinyltrichlorosilane, vinyltrimethoxysilane, and vinyltriethoxysilane; 2 -Having an epoxy group such as (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane Silane coupling agent; Silane coupling agent having a styryl group such as p-styryltrimethoxysilane; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethyl Silane coupling agents having a methacryloxy group such as xyloxysilane and 3-methacryloxypropyltriethoxysilane; Silane coupling agents having an acryloxy group such as 3-acryloxypropyltrimethoxysilane; N-2- (aminoethyl) -3 -Aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3- Of triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane Such as hydrochloride Silane coupling agent having a mino group; Silane coupling agent having a ureido group such as 3-ureidopropyltriethoxysilane; Silane coupling agent having a chloropropyl group such as 3-chloropropyltrimethoxysilane; 3-mercaptopropyl Silane coupling agents having mercapto groups such as methyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; Silane coupling agents having sulfide groups such as bis (triethoxysilylpropyl) tetrasulfide; 3-isocyanatopropyltriethoxysilane and the like Silane coupling agents having an isocyanate group of In the silane coupling treatment of the active material, only one kind of the exemplified silane coupling agents may be used, or two or more kinds may be used in combination.
正極活物質や負極活物質をシランカップリング処理する方法としては、例えば、正極活物質や負極活物質とシランカップリング剤とを混合して、シランカップリング剤が正極活物質や負極活物質の表面に付着した混合物とし、この混合物を正極活物質や負極活物質として用いて、前記の方法で正極や負極を製造する方法が挙げられる。この方法では、正極合剤層や負極合剤層を形成するための乾燥時に、正極活物質や負極活物質の表面に付着しているシランカップリング剤が反応して重合物などを形成し、正極活物質や負極活物質の表面が処理される。 As a method for silane coupling treatment of the positive electrode active material or the negative electrode active material, for example, the positive electrode active material or the negative electrode active material and the silane coupling agent are mixed, and the silane coupling agent is mixed with the positive electrode active material or the negative electrode active material. A method of producing a positive electrode or a negative electrode by the above-described method using a mixture adhering to the surface and using the mixture as a positive electrode active material or a negative electrode active material can be mentioned. In this method, when drying to form the positive electrode mixture layer or the negative electrode mixture layer, the silane coupling agent attached to the surface of the positive electrode active material or the negative electrode active material reacts to form a polymer, The surface of the positive electrode active material or the negative electrode active material is treated.
正極活物質や負極活物質とシランカップリング剤とは、例えば、ミキサーやディスパーなどの混合機で混合したり、スプレードライヤーを用いたスプレードライ法によって混合したりすればよい。混合時の条件は、例えば、温度２５〜６０℃で、混合時間を１５〜６０分とすることが好ましく、また、混合は、真空中で行うことが好ましい。 The positive electrode active material, the negative electrode active material, and the silane coupling agent may be mixed, for example, with a mixer such as a mixer or a disper, or may be mixed by a spray drying method using a spray dryer. The mixing condition is, for example, preferably at a temperature of 25 to 60 ° C. and a mixing time of 15 to 60 minutes, and the mixing is preferably performed in a vacuum.
正極活物質や負極活物質の処理に使用するシランカップリング剤の量は、正極活物質または負極活物質１００質量部に対して、０．０５質量部以上であることが好ましく、０．１質量部以上であることがより好ましく、また、３質量部以下であることが好ましく、２質量部以下であることがより好ましい。 The amount of the silane coupling agent used for the treatment of the positive electrode active material or the negative electrode active material is preferably 0.05 parts by mass or more with respect to 100 parts by mass of the positive electrode active material or the negative electrode active material. More preferably, the amount is 3 parts by mass or less, and more preferably 2 parts by mass or less.
また、正極活物質や負極活物質の表面にシランカップリング剤を付着させた混合物を用い、正極合剤層や負極合剤層の形成時の乾燥によって処理を行う場合には、正極合剤層や負極合剤層の形成時の乾燥条件を、例えば６０〜１２０℃で５〜１５分程度とすることが好ましい。 In the case of using a mixture in which a silane coupling agent is attached to the surface of the positive electrode active material or the negative electrode active material and performing the treatment by drying at the time of forming the positive electrode mixture layer or the negative electrode mixture layer, the positive electrode mixture layer It is preferable that the drying conditions at the time of forming the negative electrode mixture layer are, for example, about 60 to 120 ° C. and about 5 to 15 minutes.
前記の正極と前記の負極とは、セパレータを介在させて重ねた積層電極体や、更にこれを渦巻状に巻回した巻回電極体の形態で本発明の非水電解質二次電池に使用することができる。 The positive electrode and the negative electrode are used in the non-aqueous electrolyte secondary battery of the present invention in the form of a laminated electrode body with a separator interposed therebetween or a wound electrode body obtained by winding the separator in a spiral shape. be able to.
本発明の非水電解質二次電池に係るセパレータは、８０℃以上（より好ましくは１００℃以上）１７０℃以下（より好ましくは１５０℃以下）において、その孔が閉塞する性質（すなわちシャットダウン機能）を有していることが好ましく、通常のリチウムイオン二次電池などの非水電解質二次電池で使用されているセパレータ、例えば、ポリエチレン（ＰＥ）やポリプロピレン（ＰＰ）などのポリオレフィン製の微多孔膜を用いることができる。セパレータを構成する微多孔膜は、例えば、ＰＥのみを使用したものやＰＰのみを使用したものであってもよく、また、ＰＥ製の微多孔膜とＰＰ製の微多孔膜との積層体であってもよい。セパレータの厚みは、例えば、１０〜３０μｍであることが好ましい。 The separator according to the non-aqueous electrolyte secondary battery of the present invention has a property that the pores are blocked at 80 ° C. or higher (more preferably 100 ° C. or higher) and 170 ° C. or lower (more preferably 150 ° C. or lower) (ie, shutdown function). It is preferable to have a separator used in a nonaqueous electrolyte secondary battery such as a normal lithium ion secondary battery, for example, a microporous membrane made of polyolefin such as polyethylene (PE) or polypropylene (PP) Can be used. The microporous film constituting the separator may be, for example, one using only PE or one using PP, or a laminate of a PE microporous film and a PP microporous film. There may be. The thickness of the separator is preferably 10 to 30 μm, for example.
本発明の非水電解質二次電池の形態としては、スチール缶やアルミニウム缶などを外装体として使用した筒形（角筒形や円筒形など）などが挙げられる。また、金属を蒸着したラミネートフィルムを外装体としたソフトパッケージ電池とすることもできる。 Examples of the form of the non-aqueous electrolyte secondary battery of the present invention include a tubular shape (such as a square tubular shape or a cylindrical shape) using a steel can or an aluminum can as an exterior body. Moreover, it can also be set as the soft package battery which used the laminated film which vapor-deposited the metal as an exterior body.
本発明の非水電解質二次電池は、重負荷での放電特性および充放電サイクル特性、並びに貯蔵特性が良好であることから、こうした特性を活かして、産業用やアンシラリーサービス用などの蓄電池などの用途をはじめとして、従来の非水電解質二次電池が使用されている各種の用途に適用することができる。 Since the non-aqueous electrolyte secondary battery of the present invention has good discharge characteristics under heavy loads, charge / discharge cycle characteristics, and storage characteristics, taking advantage of these characteristics, storage batteries for industrial and ancillary services, etc. It can be applied to various uses where conventional non-aqueous electrolyte secondary batteries are used.
以下、実施例に基づいて本発明を詳細に述べる。ただし、下記実施例は、本発明を制
限するものではない。
Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.
実施例１
＜正極の作製＞
正極活物質であるＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２（平均粒子径：７μｍ）：９３質量部と、導電助剤であるアセチレンブラック：３．５質量部と、バインダであるＰＶＤＦ：３．２質量部と、分散剤であるポリビニルピロリドン（ＰＶＰ）：０．３質量部とを混合し、更に適量のＮＭＰを添加し、プラネタリーミキサーを用いて混合・分散を行って、正極合剤層形成用スラリーを調製した。
Example 1
<Preparation of positive electrode>
LiNi 0.5 Co 0.2 Mn 0.3 O 2 which is a positive electrode active material (average particle diameter: 7 μm): 93 parts by mass, acetylene black which is a conductive auxiliary agent: 3.5 parts by mass, and a binder PVDF: 3.2 parts by mass and polyvinyl pyrrolidone (PVP): 0.3 part by mass as a dispersant are mixed, and an appropriate amount of NMP is added, followed by mixing and dispersion using a planetary mixer. A slurry for forming a positive electrode mixture layer was prepared.
次に、正極集電体となる厚みが１５μｍのアルミニウム箔の片面に、前記正極合剤層形成用スラリーを一定厚みで塗布し、８５℃で乾燥した後、更に１００℃で８時間真空乾燥し、その後にロールプレス機を用いてプレス処理を施して、厚みが５０μｍの正極合剤層を集電体の片面に有する正極を得た。なお、正極合剤層の形成に際しては、集電体の一部が露出するように、正極合剤層が存在しない部分を設けた。 Next, the positive electrode mixture layer forming slurry is applied at a constant thickness on one surface of an aluminum foil having a thickness of 15 μm to be a positive electrode current collector, dried at 85 ° C., and further vacuum dried at 100 ° C. for 8 hours. Then, press treatment was performed using a roll press machine to obtain a positive electrode having a positive electrode mixture layer having a thickness of 50 μm on one side of the current collector. In forming the positive electrode mixture layer, a portion where the positive electrode mixture layer does not exist was provided so that a part of the current collector was exposed.
前記の正極を、正極合剤層の面積が３０ｍｍ×３０ｍｍで、かつ集電体の露出部を含むように切断し、更に、電流を取り出すためのアルミニウム製のリード体を集電体の露出部に溶接した。 The positive electrode is cut so that the area of the positive electrode mixture layer is 30 mm × 30 mm and includes the exposed portion of the current collector, and an aluminum lead body for taking out current is further exposed to the exposed portion of the current collector. Welded to.
＜負極の作製＞
負極活物質である黒鉛（平均粒子径：１０μｍ）：９７．８質量％、およびバインダであるＳＢＲ：２．２質量％からなる負極合剤に、適量の水を添加し、十分に混合して負極合剤層形成用スラリーを調製した。
<Production of negative electrode>
An appropriate amount of water was added to a negative electrode mixture composed of graphite (average particle size: 10 μm): 97.8% by mass and SBR: 2.2% by mass as a binder, and mixed thoroughly. A slurry for forming a negative electrode mixture layer was prepared.
次に、負極集電体となる厚みが１０μｍの銅箔の片面に、前記負極合剤層形成用スラリーを一定厚みで塗布し、１００℃で乾燥した後、更に１００℃で１５時間真空乾燥し、その後にロールプレス機を用いてプレス処理を施して、厚みが６０μｍの負極合剤層を集電体の片面に有する負極を得た。負極合剤層の形成に際しては、集電体の一部が露出するように、負極合剤層が存在しない部分を設けた。 Next, the negative electrode mixture layer-forming slurry was applied to one side of a copper foil having a thickness of 10 μm serving as a negative electrode current collector at a constant thickness, dried at 100 ° C., and further vacuum dried at 100 ° C. for 15 hours. Then, press treatment was performed using a roll press machine to obtain a negative electrode having a negative electrode mixture layer having a thickness of 60 μm on one side of the current collector. In forming the negative electrode mixture layer, a portion where the negative electrode mixture layer does not exist was provided so that a part of the current collector was exposed.
前記の負極を、負極合剤層の面積が３５ｍｍ×３５ｍｍで、かつ集電体の露出部を含むように裁断し、更に、電流を取り出すためのニッケル製のリード体を集電体の露出部に溶接した。 The negative electrode is cut so that the area of the negative electrode mixture layer is 35 mm × 35 mm and includes the exposed portion of the current collector, and a nickel lead body for taking out current is further exposed to the current collector. Welded to.
＜非水電解液の調製＞
エチレンカーボネートとジエチルカーボネートとを３：７の体積比で混合した溶媒に、ＬｉＮ（ＳＯ２Ｆ）２を０．１５ｍｏｌ／ｌの濃度で溶解させ、かつＬｉＰＦ６を１．０５ｍｏｌ／ｌの濃度で溶解させて、非水電解液を調製した。
<Preparation of non-aqueous electrolyte>
LiN (SO 2 F) 2 is dissolved at a concentration of 0.15 mol / l in a solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 3: 7, and LiPF 6 is dissolved at a concentration of 1.05 mol / l. A non-aqueous electrolyte was prepared by dissolving.
＜電池の組み立て＞
前記の負極と前記との正極とを、ＰＥ製微多孔膜セパレータ（厚み１８μｍ）を介して重ね合わせて積層電極体とし、この積層電極体を、９０ｍｍ×１８０ｍｍのアルミニウムラミネートフィルムからなる外装体に収容した。次に、前記の非水電解液を外装体内に注入した後、外装体を封止して、図１に示す外観で、図２に示す断面構造の非水電解質二次電池を得た。
<Battery assembly>
The negative electrode and the positive electrode are overlapped via a PE microporous membrane separator (thickness 18 μm) to form a laminated electrode body, and this laminated electrode body is formed into an exterior body made of an aluminum laminate film of 90 mm × 180 mm. Accommodated. Next, after injecting the non-aqueous electrolyte solution into the exterior body, the exterior body was sealed to obtain a non-aqueous electrolyte secondary battery having a cross-sectional structure shown in FIG. 2 with the appearance shown in FIG.
ここで、図１および図２について説明すると、図１は非水電解質二次電池を模式的に表す平面図であり、図２は、図１のＡ−Ａ線断面図である。非水電解質液二次電池１は、２枚のラミネートフィルムで構成した外装体２内に、正極５と負極６とをセパレータ７を介して積層して構成した積層電極体と、非水電解液（図示しない）とを収容しており、外装体２は、その外周部において、上下のラミネートフィルムを熱融着することにより封止されている。なお、図２では、図面が煩雑になることを避けるために、外装体２を構成している各層、並びに正極５および負極６の各層を区別して示していない。 Here, FIG. 1 and FIG. 2 will be described. FIG. 1 is a plan view schematically showing a nonaqueous electrolyte secondary battery, and FIG. 2 is a cross-sectional view taken along line AA of FIG. The nonaqueous electrolyte secondary battery 1 includes a laminated electrode body formed by laminating a positive electrode 5 and a negative electrode 6 with a separator 7 in an exterior body 2 constituted by two laminated films, and a nonaqueous electrolytic solution. (Not shown) is housed, and the outer package 2 is sealed by heat-sealing the upper and lower laminate films at the outer periphery thereof. In FIG. 2, each layer constituting the exterior body 2 and each layer of the positive electrode 5 and the negative electrode 6 are not shown separately in order to avoid the drawing from becoming complicated.
正極５は、電池１内でリード体を介して正極外部端子３と接続しており、また、図示していないが、負極６も、電池１内でリード体を介して負極外部端子４と接続している。そして、正極外部端子３および負極外部端子４は、外部の機器などと接続可能なように、片端側がラミネートフィルム外装体２の外側に引き出されている。 The positive electrode 5 is connected to the positive electrode external terminal 3 in the battery 1 through a lead body. Although not shown, the negative electrode 6 is also connected to the negative electrode external terminal 4 in the battery 1 through a lead body. doing. The positive electrode external terminal 3 and the negative electrode external terminal 4 are drawn out to the outside of the laminate film exterior body 2 so that they can be connected to an external device or the like.
実施例２
非水電解液におけるＬｉＮ（ＳＯ２Ｆ）２およびＬｉＰＦ６の濃度を、それぞれ、０．１ｍｏｌ／ｌ、０．９ｍｏｌ／ｌに変更した以外は、実施例１と同様にして非水電解液を調製し、これらの非水電解液を用いた以外は実施例１と同様にして非水電解質二次電池を作製した。
Example 2
The nonaqueous electrolytic solution was changed in the same manner as in Example 1 except that the concentrations of LiN (SO 2 F) 2 and LiPF 6 in the nonaqueous electrolytic solution were changed to 0.1 mol / l and 0.9 mol / l, respectively. A non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 1 except that these non-aqueous electrolytes were prepared.
実施例３
非水電解液におけるＬｉＮ（ＳＯ２Ｆ）２およびＬｉＰＦ６の濃度を、それぞれ、０．１５ｍｏｌ／ｌ、０．８５ｍｏｌ／ｌに変更した以外は、実施例１と同様にして非水電解液を調製し、これらの非水電解液を用いた以外は実施例１と同様にして非水電解質二次電池を作製した。
Example 3
The nonaqueous electrolyte solution was changed in the same manner as in Example 1 except that the concentrations of LiN (SO 2 F) 2 and LiPF 6 in the nonaqueous electrolyte solution were changed to 0.15 mol / l and 0.85 mol / l, respectively. A non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 1 except that these non-aqueous electrolytes were prepared.
実施例４
正極活物質を、平均粒子径が１０μｍのＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２に変更した以外は、実施例１と同様にして正極を作製し、この正極を用いた以外は実施例１と同様にして非水電解質二次電池を作製した。
Example 4
A positive electrode was produced in the same manner as in Example 1 except that the positive electrode active material was changed to LiNi 0.5 Co 0.2 Mn 0.3 O 2 having an average particle diameter of 10 μm, and this positive electrode was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.
実施例５
反応槽に、硫酸ニッケル、硫酸コバルトおよび硫酸マンガンから調製したコバルトイオン、ニッケルイオン、マンガンイオンを含有する水溶液を用意した。水溶液中のコバルト、ニッケルおよびマンガンのモル比（コバルト：ニッケル：マンガン）は、５：２：３となるようにした。この水溶液の温度を５０℃にした上で、この水溶液中に、ｐＨが９．５となるように水酸化ナトリウム水溶液を滴下して、コバルト、ニッケルおよびマンガンを含む沈殿物を得た。前記の沈殿物をろ過によって水溶液から取り出して水洗した後に、３００℃の酸素含有気流中で熱処理して、ニッケルとコバルトとマンガンの複合酸化物〔（Ｎｉ０．５Ｃｏ０．２Ｍｎ０．３）３Ｏ４〕を得た。
Example 5
An aqueous solution containing cobalt ions, nickel ions, and manganese ions prepared from nickel sulfate, cobalt sulfate, and manganese sulfate was prepared in a reaction vessel. The molar ratio of cobalt, nickel and manganese (cobalt: nickel: manganese) in the aqueous solution was set to 5: 2: 3. After the temperature of this aqueous solution was set to 50 ° C., a sodium hydroxide aqueous solution was dropped into this aqueous solution so that the pH was 9.5 to obtain a precipitate containing cobalt, nickel and manganese. The precipitate is taken out from the aqueous solution by filtration, washed with water, and then heat-treated in an oxygen-containing gas stream at 300 ° C. to obtain a composite oxide of nickel, cobalt, and manganese [(Ni 0.5 Co 0.2 Mn 0.3 ) 3 O 4 ] was obtained.
得られた複合酸化物に、酸化ジルコニウムと炭酸リチウム（Ｌｉ２ＣＯ３）とを混合した。このときの酸化ジルコニウムの添加量は、ニッケル、コバルトおよびマンガンのモル総和に対するモル比が、ジルコニウム換算で０．０１に相当する量とした。また、炭酸リチウムの添加量は、ニッケル、コバルトおよびマンガンのモル総和に対するモル比が、リチウム換算で１．１５となる量とした。前記の混合物を大気中にて９８０℃で１５時間焼成し、その後に篩いにかけて、正極活物質〔Ｚｒ酸化物を表面に有するリチウム含有複合酸化物（リチウム−ニッケル−コバルト−マンガン複合酸化物）〕を得た。なお、得られた正極活物質の表面にＺｒ酸化物が存在していることは、ＳＥＭによる断面観察および元素分析によって確認した。 Zirconium oxide and lithium carbonate (Li 2 CO 3 ) were mixed with the obtained composite oxide. At this time, the amount of zirconium oxide added was such that the molar ratio to the total molar amount of nickel, cobalt and manganese was equivalent to 0.01 in terms of zirconium. The amount of lithium carbonate added was such that the molar ratio to the total molar amount of nickel, cobalt and manganese was 1.15 in terms of lithium. The mixture was calcined in the atmosphere at 980 ° C. for 15 hours, and then sieved to form a positive electrode active material [lithium-containing composite oxide having a Zr oxide on the surface (lithium-nickel-cobalt-manganese composite oxide)] Got. The presence of Zr oxide on the surface of the obtained positive electrode active material was confirmed by cross-sectional observation by SEM and elemental analysis.
正極活物質を前記のものに変更した以外は実施例１と同様にして正極を作製し、この正極を用いた以外は実施例３と同様にして非水電解質二次電池を作製した。 A positive electrode was produced in the same manner as in Example 1 except that the positive electrode active material was changed to that described above, and a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 3 except that this positive electrode was used.
実施例６
正極活物質であるＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２（平均粒子径：７μｍ）：９２．７質量部と信越シリコーン社製のシランカップリング剤「ＫＢＥ８４６（商品名）」：０．３質量部とをプラネタリーミキサーで温度２５℃、混合時間６０分の条件で混合して、シランカップリング剤を正極活物質表面に付着させた混合物を得た。この混合物と、導電助剤であるアセチレンブラック：３．５質量部と、バインダであるＰＶＤＦ：３．２質量部と、分散剤であるポリビニルピロリドン（ＰＶＰ）：０．３質量部とを混合し、更に適量のＮＭＰを添加し、プラネタリーミキサーを用いて混合・分散を行って、正極合剤層形成用スラリーを調製した。
Example 6
LiNi 0.5 Co 0.2 Mn 0.3 O 2 (average particle diameter: 7 μm) as a positive electrode active material: 92.7 parts by mass and a silane coupling agent “KBE846 (trade name)” manufactured by Shin-Etsu Silicone Co., Ltd .: 0.3 parts by mass was mixed with a planetary mixer under the conditions of a temperature of 25 ° C. and a mixing time of 60 minutes to obtain a mixture in which the silane coupling agent was adhered to the surface of the positive electrode active material. This mixture was mixed with 3.5 parts by mass of acetylene black as a conductive additive, 3.2 parts by mass of PVDF as a binder, and 0.3 parts by mass of polyvinylpyrrolidone (PVP) as a dispersant. Further, an appropriate amount of NMP was added and mixed and dispersed using a planetary mixer to prepare a positive electrode mixture layer forming slurry.
前記の正極合剤層形成用スラリーを用いた以外は実施例１と同様にして正極を作製し、この正極を用いた以外は実施例１と同様にして非水電解質二次電池を作製した。 A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer forming slurry was used, and a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.
比較例１
正極活物質を、平均粒子径：１４μｍのＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２に変更した以外は、実施例１と同様にして正極を作製した。また、負極活物質を、平均粒子径が２０μｍの黒鉛に変更した以外は、実施例１と同様にして負極を作製した。そして、前記の正極と前記の負極とを用いた以外は、実施例１と同様にして非水電解質二次電池を作製した。
Comparative Example 1
A positive electrode was produced in the same manner as in Example 1 except that the positive electrode active material was changed to LiNi 0.5 Co 0.2 Mn 0.3 O 2 having an average particle size of 14 μm. A negative electrode was produced in the same manner as in Example 1 except that the negative electrode active material was changed to graphite having an average particle diameter of 20 μm. And the nonaqueous electrolyte secondary battery was produced like Example 1 except having used the said positive electrode and the said negative electrode.
比較例２
ＬｉＮ（ＳＯ２Ｆ）２を添加せず、ＬｉＰＦ６の濃度を１．２ｍｏｌ／ｌに変更した以外は、実施例１と同様にして非水電解液を調製し、これらの非水電解液を用いた以外は実施例６と同様にして非水電解質二次電池を作製した。
Comparative Example 2
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that LiN (SO 2 F) 2 was not added and the concentration of LiPF 6 was changed to 1.2 mol / l. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 6 except that it was used.
比較例３
ＬｉＮ（ＳＯ２Ｆ）２を添加せず、ＬｉＰＦ６の濃度を１．２ｍｏｌ／ｌに変更した以外は、実施例１と同様にして非水電解液を調製し、これらの非水電解液を用いた以外は実施例１と同様にして非水電解質二次電池を作製した。
Comparative Example 3
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that LiN (SO 2 F) 2 was not added and the concentration of LiPF 6 was changed to 1.2 mol / l. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that it was used.
比較例４
ＬｉＮ（ＳＯ２Ｆ）２を添加せず、ＬｉＰＦ６の濃度を１．２ｍｏｌ／ｌに変更した以外は、実施例１と同様にして非水電解液を調製し、これらの非水電解液を用いた以外は比較例１と同様にして非水電解質二次電池を作製した。
Comparative Example 4
A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that LiN (SO 2 F) 2 was not added and the concentration of LiPF 6 was changed to 1.2 mol / l. A nonaqueous electrolyte secondary battery was produced in the same manner as in Comparative Example 1 except that it was used.
比較例５
非水電解液におけるＬｉＮ（ＳＯ２Ｆ）２およびＬｉＰＦ６の濃度を、それぞれ、０．５ｍｏｌ／ｌ、０．５ｍｏｌ／ｌに変更した以外は、実施例１と同様にして非水電解液を調製し、これらの非水電解液を用いた以外は比較例１と同様にして非水電解質二次電池を作製した。
Comparative Example 5
The nonaqueous electrolytic solution was changed in the same manner as in Example 1 except that the concentrations of LiN (SO 2 F) 2 and LiPF 6 in the nonaqueous electrolytic solution were changed to 0.5 mol / l and 0.5 mol / l, respectively. A non-aqueous electrolyte secondary battery was prepared in the same manner as Comparative Example 1 except that these non-aqueous electrolytes were prepared.
実施例および比較例の非水電解質二次電池について、下記の各評価を行った。 The following evaluations were performed on the nonaqueous electrolyte secondary batteries of Examples and Comparative Examples.
＜重負荷での放電特性評価＞
実施例および比較例の非水電解質二次電池について、０．２Ｃの電流値で４．２Ｖまで定電流充電し、続いて、４．２Ｖで電流値が０．０５Ｃになるまで定電圧充電を行い、その後、０．２Ｃの電流値で２．５Ｖまで定電流放電を行って、放電容量（０．２Ｃ容量）を求めた。
<Evaluation of discharge characteristics under heavy load>
About the nonaqueous electrolyte secondary battery of an Example and a comparative example, constant current charge to 4.2V was carried out with the electric current value of 0.2C, and then constant voltage charge was carried out until the electric current value was set to 0.05C at 4.2V. Thereafter, a constant current discharge was performed to 2.5 V at a current value of 0.2 C, and a discharge capacity (0.2 C capacity) was obtained.
次に、各電池について、２Ｃの電流値で４．２Ｖまで定電流充電し、続いて、４．２Ｖで電流値が０．０５Ｃになるまで定電圧充電を行い、その後、２Ｃの電流値で２．５Ｖまで定電流放電を行って、放電容量（２Ｃ容量）を求めた。 Next, each battery is charged at a constant current of up to 4.2V at a current value of 2C, and then is charged at a constant voltage of 4.2V until the current value reaches 0.05C, and then at a current value of 2C. A constant current discharge was performed up to 2.5 V to obtain a discharge capacity (2C capacity).
そして、各電池について、２Ｃ容量を０．２Ｃ容量で除した値を百分率で表して、容量維持率（２Ｃ容量維持率）を求めた。すなわち、この２Ｃ容量維持率が高いほど、電池の重負荷での放電特性が優れているといえる。 And about each battery, the value which remove | divided 2C capacity | capacitance by 0.2C capacity | capacitance was represented by the percentage, and the capacity | capacitance maintenance factor (2C capacity | capacitance maintenance factor) was calculated | required. That is, it can be said that the higher the 2C capacity retention rate, the better the discharge characteristics under heavy load of the battery.
＜重負荷での充放電サイクル特性評価＞
実施例および比較例の非水電解質二次電池について、２Ｃの電流値で４．２Ｖまで定電流充電し、続いて、４．２Ｖで電流値が０．０５Ｃになるまで定電圧充電を行い、その後、２Ｃの電流値で２．５Ｖまで定電流放電を行う一連の操作を１サイクルとして、これを１５００サイクル繰り返し、サイクル毎の放電容量を求めた。そして、各電池について、１５００サイクル目の放電容量を１サイクル目の放電容量で除した値を百分率で表して、２Ｃでの充放電サイクル時の容量維持率を求めた。すなわち、この容量維持率が高いほど、電池の重負荷での充放電サイクル特性が優れているといえる。
<Charge / discharge cycle characteristics evaluation under heavy load>
About the nonaqueous electrolyte secondary battery of an Example and a comparative example, it carries out the constant current charge to 4.2V with the electric current value of 2C, followed by the constant voltage charge until the electric current value becomes 0.05C at 4.2V, Thereafter, a series of operations for performing constant current discharge to 2.5 V at a current value of 2C was taken as one cycle, and this was repeated 1500 cycles, and the discharge capacity for each cycle was determined. And about each battery, the value which remove | divided the discharge capacity of 1500th cycle by the discharge capacity of 1st cycle was represented by percentage, and the capacity | capacitance maintenance factor at the time of the charging / discharging cycle in 2C was calculated | required. That is, it can be said that the higher the capacity retention rate, the better the charge / discharge cycle characteristics under heavy load of the battery.
＜貯蔵特性評価＞
実施例および比較例の非水電解質二次電池について、１Ｃの電流値で４．２Ｖまで定電流充電し、続いて、４．２Ｖで電流値が０．０５Ｃになるまで定電圧充電を行い、その後、１Ｃの電流値で２．５Ｖまで定電流放電を行って、放電容量（初期放電容量）を求めた。
<Storage characteristics evaluation>
About the nonaqueous electrolyte secondary battery of an Example and a comparative example, it carries out constant current charge to 4.2V with the electric current value of 1C, and then performs constant voltage charging until the electric current value becomes 0.05C with 4.2V, Thereafter, a constant current discharge was performed up to 2.5 V at a current value of 1 C, and a discharge capacity (initial discharge capacity) was obtained.
初期放電容量測定後の各電池について、初期放電容量測定時と同じ条件で定電流充電および定電圧充電を行った。そして、充電後の各電池を６０℃の恒温槽内で貯蔵し、９０日後に取り出して、１Ｃの電流値で２．５Ｖまで定電流放電した。 About each battery after initial stage discharge capacity measurement, constant current charge and constant voltage charge were performed on the same conditions as the time of initial stage discharge capacity measurement. Each battery after charging was stored in a constant temperature bath at 60 ° C., taken out after 90 days, and discharged at a constant current up to 2.5 V at a current value of 1C.
更に、貯蔵後の定電流放電を行った各電池について、初期放電容量測定時と同じ条件で定電流充電、定電圧充電および定電流放電を行って、放電容量（貯蔵後放電容量）を求めた。そして、各電池について、貯蔵後放電容量を初期放電容量で除した値を百分率で表して、容量回復率を求めた。すなわち、この容量回復率が高いほど、電池の貯蔵特性が優れているといえる。 Furthermore, for each battery that was subjected to constant current discharge after storage, constant current charge, constant voltage charge, and constant current discharge were performed under the same conditions as at the time of initial discharge capacity measurement, and the discharge capacity (discharge capacity after storage) was determined. . And about each battery, the value which remove | divided the discharge capacity after storage by the initial stage discharge capacity was represented by the percentage, and the capacity | capacitance recovery rate was calculated | required. That is, it can be said that the higher the capacity recovery rate, the better the storage characteristics of the battery.
実施例および比較例の非水電解質二次電池に使用した非水電解質、正極活物質および負極活物質の構成を表１に示し、前記の各評価結果を表２に示す。 Table 1 shows the structures of the nonaqueous electrolyte, the positive electrode active material, and the negative electrode active material used in the nonaqueous electrolyte secondary batteries of Examples and Comparative Examples, and Table 2 shows the evaluation results.
表１および表２に示す通り、適正な平均粒子径の正極活物質や負極活物質を使用し、かつＬｉＰＦ６とイミド塩とを含有する非水電解液を用いた実施例１〜６の非水電解質二次電池は、重負荷での放電特性評価時の容量維持率（２Ｃ放電容量維持率）、重負荷での充放電サイクル特性時の容量維持率、および貯蔵特性評価時の容量回復率のいずれもが高く、重負荷での放電特性および充放電サイクル特性、並びに貯蔵特性が優れていた。 As shown in Tables 1 and 2, the non-aqueous electrolytes of Examples 1 to 6 using a positive electrode active material or a negative electrode active material having an appropriate average particle diameter and using a nonaqueous electrolyte solution containing LiPF 6 and an imide salt. The water electrolyte secondary battery has a capacity retention rate (2C discharge capacity maintenance rate) at the time of discharge characteristics evaluation under heavy load, a capacity maintenance rate at the time of charge / discharge cycle characteristics under heavy load, and a capacity recovery rate at the time of storage characteristics evaluation. All of these were high, and discharge characteristics under heavy load, charge / discharge cycle characteristics, and storage characteristics were excellent.
なお、正極活物質の平均粒子径が異なる以外は同じ構成の実施例１の電池と実施例４の電池とを比較すると、より平均粒子径の小さい正極活物質を用いた実施例１の電池の方が、重負荷での放電特性のみならず、重負荷での充放電サイクル特性も優れていた。 In addition, when the battery of Example 1 and the battery of Example 4 having the same configuration except that the average particle diameter of the positive electrode active material is different, the battery of Example 1 using the positive electrode active material having a smaller average particle diameter is compared. However, not only the discharge characteristics under heavy load but also the charge / discharge cycle characteristics under heavy load were superior.
また、Ｚｒ酸化物を表面に有するリチウム含有複合酸化物を使用した実施例５の電池は、実施例３の電池（Ｚｒ酸化物を含有していないリチウム含有複合酸化物を使用した以外は実施例５の電池と同じ構成の電池）に比べて、重負荷での充放電サイクル特性が優れていた。 Further, the battery of Example 5 using the lithium-containing composite oxide having a Zr oxide on the surface is the same as that of Example 3 except that the lithium-containing composite oxide containing no Zr oxide is used. Compared with the battery having the same structure as the battery of No. 5), the charge / discharge cycle characteristics under heavy load were excellent.
更に、シランカップリング処理を施した正極活物質を使用した実施例６の電池は、実施例１の電池（シランカップリング処理を施していない正極活物質を使用した以外は実施例６の電池と同じ構成の電池）に比べて、貯蔵特性が優れていた。 Furthermore, the battery of Example 6 using the positive electrode active material subjected to the silane coupling treatment was the same as the battery of Example 1 except that the positive electrode active material not subjected to the silane coupling treatment was used. Compared with the battery having the same configuration, the storage characteristics were excellent.
一方、平均粒子径が大きい正極活物質および負極活物質を使用した比較例１の電池は、重負荷での放電特性が劣っているのみならず、重負荷での充放電サイクル特性も劣っていた。前記の実施例１の電池および実施例４の電池との評価結果と、この比較例１の電池の評価結果とから、ＬｉＰＦ６とイミド塩とを含有する非水電解液の使用に加えて、適度に小さい平均粒子径の正極活物質や負極活物質を使用することが、電池の重負荷での充放電サイクル特性の向上に大きく寄与することが判明した。 On the other hand, the battery of Comparative Example 1 using the positive electrode active material and the negative electrode active material having a large average particle size was not only inferior in discharge characteristics under heavy load, but also in charge / discharge cycle characteristics under heavy load. . From the evaluation results of the battery of Example 1 and the battery of Example 4 and the evaluation result of the battery of Comparative Example 1, in addition to the use of a non-aqueous electrolyte containing LiPF 6 and an imide salt, It has been found that the use of a positive electrode active material or a negative electrode active material having a moderately small average particle size greatly contributes to improvement of charge / discharge cycle characteristics under heavy load of the battery.
また、比較例２〜４の電池は、イミド塩を含有していない非水電解液を用いた例であるが、これらのうち、比較例２、３の電池は、平均粒子径が適度に小さい正極活物質および負極活物質を使用したにも関わらず重負荷での放電特性が劣っており、貯蔵特性も劣っていた。そして、平均粒子径が大きい正極活物質および負極活物質を使用した比較例４の電池は、重負荷での放電特性および重負荷での充放電サイクル特性が劣っていた。 The batteries of Comparative Examples 2 to 4 are examples using a non-aqueous electrolyte solution that does not contain an imide salt. Among these, the batteries of Comparative Examples 2 and 3 have a moderately small average particle diameter. Despite the use of the positive electrode active material and the negative electrode active material, the discharge characteristics under heavy load were inferior and the storage characteristics were also inferior. And the battery of the comparative example 4 using the positive electrode active material and negative electrode active material with a large average particle diameter was inferior in the discharge characteristic in heavy load, and the charge / discharge cycle characteristic in heavy load.
更に、ＬｉＰＦ６とイミド塩とを含有する非水電解液を使用した一方で、平均粒子径が大きい正極活物質および負極活物質を使用した比較例５の電池は、重負荷での放電特性および重負荷での充放電サイクル特性が劣っていた。 Furthermore, while using a non-aqueous electrolyte containing LiPF 6 and an imide salt, the battery of Comparative Example 5 using a positive electrode active material and a negative electrode active material having a large average particle size had discharge characteristics under heavy load and The charge / discharge cycle characteristics under heavy load were inferior.
１ 非水電解質二次電池
２ 外装体
５ 正極
６ 負極
７ セパレータ
DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte secondary battery 2 Exterior body 5 Positive electrode 6 Negative electrode 7 Separator
Claims (8)
前記正極活物質および前記負極活物質のうちの少なくとも一方は、平均粒子径が１２μｍ以下であり、
前記非水電解質は、ＬｉＰＦ６およびイミド塩を含有していることを特徴とする非水電解質二次電池。 A non-aqueous electrolyte secondary battery using a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, a separator and a non-aqueous electrolyte,
At least one of the positive electrode active material and the negative electrode active material has an average particle size of 12 μm or less,
The non-aqueous electrolyte secondary battery includes LiPF 6 and an imide salt.
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