JP6258641B2 - Non-aqueous electrolyte secondary battery - Google Patents
Non-aqueous electrolyte secondary battery Download PDFInfo
- Publication number
- JP6258641B2 JP6258641B2 JP2013184567A JP2013184567A JP6258641B2 JP 6258641 B2 JP6258641 B2 JP 6258641B2 JP 2013184567 A JP2013184567 A JP 2013184567A JP 2013184567 A JP2013184567 A JP 2013184567A JP 6258641 B2 JP6258641 B2 JP 6258641B2
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- JP
- Japan
- Prior art keywords
- negative electrode
- electrode mixture
- electrolyte secondary
- secondary battery
- polyacrylic acid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Images
Classifications
-
- 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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- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Description
本発明は、高容量の負極材料を使用し、かつ優れた充放電サイクル特性を有する非水電解液二次電池に関するものである。 The present invention relates to a non-aqueous electrolyte secondary battery that uses a high-capacity negative electrode material and has excellent charge / discharge cycle characteristics.
リチウムイオン二次電池などの非水電解液二次電池は、パーソナルコンピューターや携帯電話などのポータブル機器用に普及しており、これらの各種機器に合わせた要求特性を備えている。特に今後も更に市場が伸びると予測される携帯電話については、その高機能化が進むことに伴って、その電源に使用される非水電解液二次電池にも、それに応じた高容量化が要求されると考えられる。 Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are widely used for portable devices such as personal computers and mobile phones, and have required characteristics tailored to these various devices. In particular, as mobile phones, which are expected to grow further in the future, become more sophisticated, non-aqueous electrolyte secondary batteries used in their power supplies will also have higher capacities. It is considered to be required.
現在市販されている非水電解液二次電池は、一部を除いて正極活物質としてＬｉＣｏＯ２が使用され、負極活物質として黒鉛が使用されているが、特に黒鉛に関しては既に理論容量である３７２ｍＡｈ／ｇに極めて近い利用率での電池設計がなされており、更なる高容量化には、これに代わる負極材料（高容量負極材料）が必要となる。 The non-aqueous electrolyte secondary batteries currently on the market use LiCoO 2 as the positive electrode active material and graphite as the negative electrode active material, except for some parts, but especially with respect to graphite, it is already theoretical capacity. Batteries are designed at a utilization rate very close to 372 mAh / g, and a further negative electrode material (high capacity negative electrode material) is required for further increase in capacity.
このような高容量負極材料として、Ｓｎ合金、Ｓｉ合金、Ｓｉ酸化物、Ｌｉ窒化物、Ｌｉ金属などが検討されているが、現時点では、いずれも電池に用いたときの充放電サイクル特性が、黒鉛に比して劣っている。この原因は、黒鉛が層状構造を有しており、電池の充放電時にリチウムイオンがこの層間にドープまたはアンドープされる際の膨張量が、層間距離の１０％程度であるのに対し、前記の高容量負極材料では、充放電時のＬｉ含有量が多いことから膨張量が非常に大きくなるために、結果として負極材料の膨張収縮が繰り返されることになる電池の充放電サイクルでは、負極材料を含む負極合剤層の強度や負極合剤層内の電子伝導性が低下してしまうからであり、高容量負極材料を用いた電池では、このような理由から、充放電サイクル特性、すなわち初期容量に対する充放電サイクル後の容量維持率が、黒鉛を用いた電池に比して悪くなってしまう。 As such high-capacity negative electrode materials, Sn alloys, Si alloys, Si oxides, Li nitrides, Li metals and the like have been studied, but at present, the charge / discharge cycle characteristics when used in batteries are as follows: It is inferior to graphite. This is because graphite has a layered structure, and the amount of expansion when lithium ions are doped or undoped between the layers during charging and discharging of the battery is about 10% of the interlayer distance. In a high capacity negative electrode material, since the Li content at the time of charge / discharge is large, the expansion amount becomes very large. As a result, in the charge / discharge cycle of the battery in which the expansion / contraction of the negative electrode material is repeated, This is because the strength of the negative electrode mixture layer and the electron conductivity in the negative electrode mixture layer are lowered, and in a battery using a high capacity negative electrode material, charge / discharge cycle characteristics, that is, initial capacity As a result, the capacity retention rate after the charge / discharge cycle becomes worse than that of a battery using graphite.
こうした事情の下、高容量負極材料を使用することによる非水電解液二次電池の充放電サイクル特性の低下を抑える技術の提案もある。例えば、特許文献１には、負極活物質に、ＳｉＯｘで表される高容量負極材料と黒鉛とを特定比率で併用することで、高容量負極材料の使用量を抑えて電池の充放電時の負極合剤層の体積変化を抑えつつ、高容量負極材料の使用量の低減に伴う容量低下を黒鉛で補うことで、電池の高容量化と充放電サイクル特性の低下抑制とを達成し得た技術が開示されている。
Under such circumstances, there is also a proposal of a technique for suppressing deterioration in charge / discharge cycle characteristics of a non-aqueous electrolyte secondary battery by using a high-capacity negative electrode material. For example,
また、高容量負極材料を含む負極合剤層の機械的強度を向上させることで、負極合剤層内の電子伝導性の低下を抑制する技術も提案されている。 In addition, a technique for suppressing a decrease in electron conductivity in the negative electrode mixture layer by improving the mechanical strength of the negative electrode mixture layer containing a high capacity negative electrode material has been proposed.
非水電解液二次電池の負極合剤層に係るバインダには、ポリフッ化ビニリデン（ＰＶＤＦ）を使用したり、スチレンブタジエンゴム（ＳＢＲ）などのゴム系バインダとカルボキシメチルセルロース（ＣＭＣ）とを併用したりすることが一般的であるが、特許文献２には、Ｓｉなどと黒鉛とを含む負極合剤層のバインダにポリアクリル酸を使用することで、電池の充放電サイクル特性を高め得ることが開示されている。
For the binder related to the negative electrode mixture layer of the non-aqueous electrolyte secondary battery, polyvinylidene fluoride (PVDF) is used, or a rubber binder such as styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are used in combination. However, in
また、ポリアクリル酸についてはリチウム塩の存在が知られており、非特許文献１には、Ｓｉを負極活物質とする負極合剤層において、ポリアクリル酸のリチウム塩をバインダに使用することで、電池の充放電サイクル特性を高め得ることが報告されている。
In addition, the presence of a lithium salt is known for polyacrylic acid, and Non-Patent
この他、高容量負極材料を用いた電池の充放電サイクル特性の向上が目的ではないが、特許文献３には、ポリアクリル酸のリチウム塩とＣＭＣのナトリウム塩とを併用することで、電極の合剤層を形成するためのスラリーの、集電体への塗布性が向上することが報告されている。
In addition, although the purpose is not to improve the charge / discharge cycle characteristics of a battery using a high-capacity negative electrode material,
特許文献１に記載の技術によれば、高容量負極材料を使用することによる非水電解液二次電池の高容量化効果を確保しつつ、その充放電サイクル特性も良好にできる。しかしながら、その一方で、高容量負極材料を使用した非水電解液二次電池における充放電サイクル特性に要求されるレベルは、今後益々高まることも予想され、これに対応し得る技術の開発も求められる。
According to the technique described in
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、高容量の負極材料を使用し、かつ優れた充放電サイクル特性を有する非水電解液二次電池を提供することにある。 The present invention has been made in view of the above circumstances, and an object thereof is to provide a non-aqueous electrolyte secondary battery using a high-capacity negative electrode material and having excellent charge / discharge cycle characteristics. .
前記目的を達成し得た本発明の非水電解液二次電池は、リチウムを含む遷移金属複合酸化物を活物質として含有する正極と、リチウムイオンを吸蔵および脱離可能な活物質を含有する負極と、セパレータと、非水電解液とを有する非水電解液二次電池であって、前記負極は、前記活物質およびバインダを含有する負極合剤層を、集電体の片面または両面に有しており、前記負極合剤層は、前記バインダとして、ポリアクリル酸のアルカリ塩と、カルボキシメチルセルロースおよびポリビニルアルコールより選ばれる少なくとも１種とを含有しており、ポリアクリル酸のアルカリ塩１００質量部に対し、カルボキシメチルセルロースおよびポリビニルアルコールより選ばれる少なくとも１種の比率が１０質量部以上８０質量部以下であり、前記負極合剤層は、前記活物質として、黒鉛と、組成式ＳｉＯｘで表される材料（ただし、Ｓｉに対するＯの原子比ｘは０．５≦ｘ≦１．５である）、ＳｉまたはＳｉ合金と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 includes a positive electrode containing a transition metal composite oxide containing lithium as an active material, and an active material capable of inserting and extracting lithium ions. A non-aqueous electrolyte secondary battery having a negative electrode, a separator, and a non-aqueous electrolyte, wherein the negative electrode has a negative electrode mixture layer containing the active material and a binder on one side or both sides of a current collector. The negative electrode mixture layer contains, as the binder, an alkali salt of polyacrylic acid and at least one selected from carboxymethylcellulose and polyvinyl alcohol, and an alkali salt of polyacrylic acid 100 mass The proportion of at least one selected from carboxymethyl cellulose and polyvinyl alcohol is 10 parts by mass or more and 80 parts by mass or less with respect to parts, Electrode mixture layer, as the active material, and graphite, a material represented by a composition formula SiO x (where the atomic ratio x of O to Si is 0.5 ≦ x ≦ 1.5), Si or Si It is characterized by containing an alloy.
本発明によれば、高容量の負極材料を使用し、かつ優れた充放電サイクル特性を有する非水電解液二次電池を提供することができる。 According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery that uses a high-capacity negative electrode material and has excellent charge / discharge cycle characteristics.
本発明の非水電解液二次電池に係る負極は、リチウムイオンを吸蔵および脱離可能な活物質を含有する負極合剤層を、集電体の片面または両面に有している。 The negative electrode according to the nonaqueous electrolyte secondary battery of the present invention has a negative electrode mixture layer containing an active material capable of inserting and extracting lithium ions on one side or both sides of a current collector.
本発明の非水電解液二次電池では、活物質として、組成式ＳｉＯｘで表される材料（ただし、Ｓｉに対するＯの原子比ｘは０．５≦ｘ≦１．５である。以下、当該材料を単に「ＳｉＯｘ」と記載する。）、ＳｉまたはＳｉ合金（以下、これらを纏めて「高容量負極材料」という場合がある）を使用して、高容量化を図っている。 In the non-aqueous electrolyte secondary battery of the present invention, as an active material, a material represented by the composition formula SiO x (however, the atomic ratio x of O to Si is 0.5 ≦ x ≦ 1.5. The material is simply referred to as “SiO x ”), Si or Si alloy (hereinafter, these may be collectively referred to as “high capacity negative electrode material”) to increase the capacity.
そして、本発明の非水電解液二次電池では、負極活物質に前記高容量負極材料と共に黒鉛を使用することで、高容量負極材料の使用量を低減すると共に、特定のバインダを複数種組み合わせることで、前記高容量負極材料を使用した場合に生じ得る充放電サイクル特性の低下を抑えている。 In the non-aqueous electrolyte secondary battery of the present invention, graphite is used together with the high capacity negative electrode material for the negative electrode active material, thereby reducing the amount of the high capacity negative electrode material used and combining a plurality of specific binders. This suppresses the deterioration of charge / discharge cycle characteristics that may occur when the high-capacity negative electrode material is used.
負極活物質には、ＳｉＯｘ、ＳｉまたはＳｉ合金を使用する。これらの高容量負極材料は、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, SiO x , Si or Si alloy is used. These high capacity negative electrode materials may use only 1 type and may use 2 or more types together.
Ｓｉ合金としては、例えば、ＳｉＳｎ、ＳｉＣｕ、ＳｉＣｒ、ＳｉＴｉなどが挙げられる。 Examples of the Si alloy include SiSn, SiCu, SiCr, and SiTi.
ＳｉＯｘは、Ｓｉの微結晶または非晶質相を含んでいてもよく、この場合、ＳｉとＯの原子比は、Ｓｉの微結晶または非晶質相のＳｉを含めた比率となる。すなわち、ＳｉＯｘには、非晶質のＳｉＯ２マトリックス中に、Ｓｉ（例えば、微結晶Ｓｉ）が分散した構造のものが含まれ、この非晶質のＳｉＯ２と、その中に分散しているＳｉを合わせて、前記の原子比ｘが０．５≦ｘ≦１．５を満足していればよい。例えば、非晶質のＳｉＯ２マトリックス中に、Ｓｉが分散した構造で、ＳｉＯ２とＳｉのモル比が１：１の材料の場合、ｘ＝１であるので、構造式としてはＳｉＯで表記される。このような構造の材料の場合、例えば、Ｘ線回折分析では、Ｓｉ（微結晶Ｓｉ）の存在に起因するピークが観察されない場合もあるが、透過型電子顕微鏡で観察すると、微細なＳｉの存在が確認できる。 The SiO x may contain Si microcrystal or amorphous phase. In this case, the atomic ratio of Si and O is a ratio including Si microcrystal or amorphous phase Si. That is, SiO x includes a structure in which Si (for example, microcrystalline Si) is dispersed in an amorphous SiO 2 matrix, and this amorphous SiO 2 is dispersed in the SiO 2 matrix. It is sufficient that the atomic ratio x satisfies 0.5 ≦ x ≦ 1.5 in combination with Si. For example, in the case of a material in which Si is dispersed in an amorphous SiO 2 matrix and the material has a molar ratio of SiO 2 to Si of 1: 1, x = 1, so that the structural formula is represented by SiO. The In the case of a material having such a structure, for example, in X-ray diffraction analysis, a peak due to the presence of Si (microcrystalline Si) may not be observed, but when observed with a transmission electron microscope, the presence of fine Si Can be confirmed.
ＳｉＯｘは、炭素材料と複合化した複合体として使用することができ、例えば、ＳｉＯｘの表面が炭素材料で被覆されていることが好ましい。ＳｉＯｘは導電性が乏しいため、これを負極活物質として用いる際には、良好な電池特性確保の観点から、導電性材料（導電助剤）を使用し、負極内におけるＳｉＯｘと導電性材料との混合・分散を良好にして、優れた導電ネットワークを形成する必要がある。ＳｉＯｘを炭素材料と複合化した複合体であれば、例えば、単にＳｉＯｘと炭素材料などの導電性材料とを混合して得られた材料を用いた場合よりも、負極における導電ネットワークが良好に形成される。 SiO x can be used as a composite compounded with a carbon material. For example, the surface of SiO x is preferably covered with a carbon material. Since SiO x has poor conductivity, when it is used as a negative electrode active material, from the viewpoint of securing good battery characteristics, a conductive material (conductive aid) is used, and SiO x and conductive material in the negative electrode are used. Therefore, it is necessary to form a good conductive network by mixing and dispersing with each other. If complexes complexed with carbon material SiO x, for example, simply than with a material obtained by mixing a conductive material such as SiO x and the carbon material, good conductive network in the negative electrode Formed.
負極にＳｉＯｘと炭素材料との複合体を使用する場合、ＳｉＯｘと炭素材料との比率は、炭素材料との複合化による作用を良好に発揮させる観点から、ＳｉＯｘ：１００質量部に対して、炭素材料が、５質量部以上であることが好ましく、１０質量部以上であることがより好ましい。また、前記複合体において、ＳｉＯｘと複合化する炭素材料の比率が多すぎると、負極合剤層中のＳｉＯｘ量の低下に繋がり、高容量化の効果が小さくなる虞があることから、ＳｉＯｘ：１００質量部に対して、炭素材料は、５０質量部以下であることが好ましく、４０質量部以下であることがより好ましい。 When a composite of SiO x and a carbon material is used for the negative electrode, the ratio of SiO x and the carbon material is based on SiO x : 100 parts by mass from the viewpoint of satisfactorily exerting the effect of the composite with the carbon material. The carbon material is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more. Further, in the composite, if the ratio of the carbon material to be combined with SiO x is too large, it may lead to a decrease in the amount of SiO x in the negative electrode mixture layer, and the effect of increasing the capacity may be reduced. SiO x: relative to 100 parts by weight, the carbon material, and more preferably preferably not more than 50 parts by weight, more than 40 parts by weight.
負極活物質には、前記高容量負極材料と共に、黒鉛を使用する。黒鉛は、非水電解液二次電池の負極活物質として汎用されており、比較的容量が大きい一方で、電池の充放電に伴う体積変化量が前記高容量負極材料に比べて小さい。よって、負極活物質に前記高容量負極材料と黒鉛とを併用することで、高容量負極材料の使用量の低減に伴って電池の容量向上効果が小さくなることと、電池の充放電に伴う負極合剤層の体積変化量とを可及的に抑制することができる。 As the negative electrode active material, graphite is used together with the high capacity negative electrode material. Graphite is widely used as a negative electrode active material for non-aqueous electrolyte secondary batteries, and has a relatively large capacity, while its volume change accompanying charging / discharging of the battery is smaller than that of the high capacity negative electrode material. Therefore, by using the high-capacity negative electrode material and graphite in combination with the negative electrode active material, the effect of improving the capacity of the battery is reduced as the amount of the high-capacity negative electrode material used is reduced. The volume change amount of the mixture layer can be suppressed as much as possible.
負極活物質として使用する黒鉛としては、例えば、鱗片状黒鉛などの天然黒鉛；熱分解炭素類、メソフェーズカーボンマイクロビーズ（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；などが挙げられる。 As the graphite used as the negative electrode active material, for example, natural graphite such as flaky graphite; graphitized carbon such as pyrolytic carbons, mesophase carbon microbeads (MCMB), and carbon fiber was graphitized at 2800 ° C. or higher. Artificial graphite; and the like.
全負極活物質中における前記高容量負極材料の含有量（ＳｉＯｘ、ＳｉおよびＳｉ合金のうちのいずれか１種のみを用いる場合には、その量であり、これらのうちの２種以上を使用する場合には、それらの合計量である。全負極活物質中における前記高容量負極材料の含有量について、以下同じ。）は、前記高容量負極材料を使用することによる高容量化の効果を良好に確保する観点から、０．０１質量％以上であることが好ましく、１質量％以上であることがより好ましく、３質量％以上であることがより好ましい。また、充放電に伴う前記高容量負極材料の体積変化による問題をより良好に回避する観点から、全負極活物質中における前記高容量負極材料の含有量は、２０質量％以下であることが好ましく、１５質量％以下であることがより好ましい。 Content of the high-capacity negative electrode material in all negative electrode active materials (when only one of SiO x , Si and Si alloy is used, this is the amount, and two or more of these are used) In this case, the content of the high-capacity negative electrode material in the whole negative electrode active material is the same hereinafter.) Is the effect of increasing the capacity by using the high-capacity negative electrode material. From the viewpoint of ensuring good, it is preferably 0.01% by mass or more, more preferably 1% by mass or more, and more preferably 3% by mass or more. Further, from the viewpoint of better avoiding the problem due to the volume change of the high-capacity negative electrode material accompanying charge / discharge, the content of the high-capacity negative electrode material in the total negative electrode active material is preferably 20% by mass or less. More preferably, it is 15 mass% or less.
負極活物質には、ＳｉＯｘ、Ｓｉ、Ｓｉ合金および黒鉛の他に、他の活物質を、これらの活物質と共に使用してもよい。このような他の活物質としては、例えば、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、ＭＣＭＢ、炭素繊維、活性炭、リチウムと合金化可能な金属（Ｓｎなど）またはその合金、酸化物などが挙げられる。ただし、これらの他の活物質の使用量は、全負極活物質中、１０質量％以下とすることが好ましい。 As the negative electrode active material, in addition to SiO x , Si, Si alloy and graphite, other active materials may be used together with these active materials. Examples of such other active materials include pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, MCMB, carbon fibers, activated carbon, metals that can be alloyed with lithium (Sn, etc. ) Or an alloy or oxide thereof. However, the amount of these other active materials used is preferably 10% by mass or less in the total negative electrode active material.
負極合剤層に係るバインダには、ポリアクリル酸のアルカリ塩と、カルボキシメチルセルロース（ＣＭＣ）およびポリビニルアルコール（ＰＶＡ）より選ばれる少なくとも１種とを使用する。 For the binder related to the negative electrode mixture layer, an alkali salt of polyacrylic acid and at least one selected from carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) are used.
負極合剤層は、通常、負極活物質およびバインダなどを溶媒に分散させて調製した負極合剤含有組成物を、集電体表面に塗布し乾燥する工程を経て形成されるが、この負極合剤含有組成物の溶媒に水を用いる場合には、スチレンブタジエンゴム（ＳＢＲ）とＣＭＣとを併用することが一般的である。このうち、特にＣＭＣは、負極活物質粒子間の接着と共に、一般に集電体として用いられている銅箔と負極合剤層（負極活物質粒子）との接着も担っている。 The negative electrode mixture layer is usually formed through a process in which a negative electrode mixture-containing composition prepared by dispersing a negative electrode active material and a binder in a solvent is applied to the surface of the current collector and dried. When water is used as the solvent of the agent-containing composition, it is common to use styrene butadiene rubber (SBR) and CMC in combination. Among these, CMC, in particular, is responsible for adhesion between the negative electrode active material particles and copper foil generally used as a current collector and negative electrode mixture layer (negative electrode active material particles).
ここで、非水電解液二次電池の負極活物質として一般的な黒鉛を用いる場合には、リチウムイオンの吸蔵時の膨張は１０体積％程度と見積もられ、ＳＢＲとＣＭＣとの使用比率を調整することで、こうした黒鉛の膨張による負極合剤層の膨張を抑制している。 Here, when general graphite is used as the negative electrode active material of the non-aqueous electrolyte secondary battery, the expansion at the time of occlusion of lithium ions is estimated to be about 10% by volume, and the usage ratio between SBR and CMC is By adjusting, the expansion of the negative electrode mixture layer due to the expansion of the graphite is suppressed.
ところが、リチウムイオンの吸蔵時の膨張量がより大きい高容量負極材料を使用する場合に、この膨張による負極合剤層の膨張を抑制するために、負極合剤層におけるＣＭＣの使用量を多くすると、ＣＭＣが絶縁性物質であることから、例えば電池の負荷特性が低下してしまう。 However, when a high-capacity negative electrode material with a larger expansion amount during occlusion of lithium ions is used, in order to suppress the expansion of the negative electrode mixture layer due to this expansion, the amount of CMC used in the negative electrode mixture layer is increased. Since CMC is an insulating material, for example, the load characteristics of the battery are degraded.
これに対し、ポリアクリル酸のアルカリ塩を使用すると、ＣＭＣに対して同質量比率でのリチウムイオン吸蔵時の負極合剤層の膨張量が低減することが明らかとなり、負極合剤層の機械的強度が向上することが判明した。 On the other hand, when an alkali salt of polyacrylic acid is used, it becomes clear that the amount of expansion of the negative electrode mixture layer at the time of occlusion of lithium ions at the same mass ratio with respect to CMC is reduced. It was found that the strength was improved.
これは、ポリアクリル酸のアルカリ塩は、ＣＭＣに比べて、負極活物質粒子の表面をより均一に被覆する作用を有することが報告されており、このことが結果的に負極活物質粒子間の接着性を向上させたものと考えている。実際に、負極活物質に黒鉛だけでなく、ＳｉＯｘ、ＳｉまたはＳｉ合金を共に使用した場合には、例えばＳｉＯｘであれば１０００ｍＡｈ／ｇ以上と黒鉛の３倍以上の容量が確保できる反面、リチウムイオン吸蔵時の膨張量も大きくなる。ところが、このような場合でも、ポリアクリル酸のアルカリ塩の使用によって負極合剤層の機械的強度が改善され、リチウムイオン吸蔵時の負極合剤層の膨張量をより低減できる。 It has been reported that the alkali salt of polyacrylic acid has a function of covering the surface of the negative electrode active material particles more uniformly than CMC, and as a result, between the negative electrode active material particles. It is considered that the adhesiveness has been improved. Actually, when not only graphite but also SiO x , Si or Si alloy are used as the negative electrode active material, for example, if it is SiO x , a capacity of 1000 mAh / g or more and 3 times or more of graphite can be secured, The amount of expansion during lithium ion storage also increases. However, even in such a case, the mechanical strength of the negative electrode mixture layer is improved by using an alkali salt of polyacrylic acid, and the expansion amount of the negative electrode mixture layer during occlusion of lithium ions can be further reduced.
しかしながら、その一方で、負極合剤層のバインダにＣＭＣを使用した非水電解液二次電池において、充放電を繰り返すと、そのサイクル初期で容量低下が生じるものの、充放電サイクル数を多くしても容量の低下の程度が減少して比較的大きな容量が長期にわたって維持されるのに対し、負極合剤層のバインダにポリアクリル酸のアルカリ塩を用いた非水電解液二次電池では、充放電サイクル数を多くすると容量の低下が大きく、サイクル初期ではＣＭＣを用いた電池よりも容量が大きくても、充放電サイクルが進むことで容量が小さくなってしまう。 However, on the other hand, in a non-aqueous electrolyte secondary battery using CMC as the binder of the negative electrode mixture layer, repeated charge / discharge causes a decrease in capacity at the beginning of the cycle, but the number of charge / discharge cycles is increased. However, the degree of decrease in capacity is reduced and a relatively large capacity is maintained over a long period of time, whereas in a non-aqueous electrolyte secondary battery using a polyacrylic acid alkali salt as the binder of the negative electrode mixture layer, When the number of discharge cycles is increased, the capacity is greatly reduced. At the initial stage of the cycle, even if the capacity is larger than that of the battery using CMC, the capacity decreases as the charge / discharge cycle proceeds.
負極合剤層のバインダにポリアクリル酸のアルカリ塩を用いた非水電解液二次電池において生じ得る前記の充放電サイクル劣化は、負極合剤層と集電体との接着性が、ＣＭＣをバインダに用いた場合より劣っていることが主因であると考えられる。 The charge / discharge cycle deterioration that may occur in a non-aqueous electrolyte secondary battery using an alkali salt of polyacrylic acid as the binder of the negative electrode mixture layer is caused by the adhesion between the negative electrode mixture layer and the current collector being CMC. The main reason is that it is inferior to that used in the binder.
そこで、本発明では、負極合剤層と集電体との接着性を高め得る作用を有するＣＭＣまたはＰＶＡを、負極合剤層のバインダとしてポリアクリル酸のアルカリ塩と共に使用することで、負極活物質がリチウムイオンを吸蔵することで生じ得る負極合剤層の膨張を抑え得る機械的強度と、集電体との間の高い接着強度とを兼ね備えた負極合剤層を形成できるようにして、高容量の負極材料を使用し、かつ優れた充放電サイクル特性を有する非水電解液二次電池の提供を可能とした。 Therefore, in the present invention, CMC or PVA having an action capable of improving the adhesion between the negative electrode mixture layer and the current collector is used together with an alkali salt of polyacrylic acid as a binder for the negative electrode mixture layer. It is possible to form a negative electrode mixture layer that combines the mechanical strength that can suppress the expansion of the negative electrode mixture layer that can be generated by occlusion of lithium ions and the high adhesive strength between the current collector and A non-aqueous electrolyte secondary battery using a high-capacity negative electrode material and having excellent charge / discharge cycle characteristics can be provided.
ポリアクリル酸のアルカリ塩としては、ポリアクリル酸のナトリウム塩、ポリアクリル酸のリチウム塩、ポリアクリル酸のアンモニウム塩などが挙げられ、これらのうちの１種のみを用いてもよく、２種以上を併用してもよい。これらのポリアクリル酸のアルカリ塩の中でも、ポリアクリル酸のアルカリ金属塩（ナトリウム塩、リチウム塩）がより好ましく、ポリアクリル酸におけるカルボキシル基の置換比率（ポリアクリル酸が有するカルボキシル基のうち、塩へ変換している基の比率）が同一の場合には、ナトリウム塩の方が他のアルカリ金属塩よりも、非水電解液二次電池の充放電サイクル特性を高める作用が大きいことから、ポリアクリル酸のナトリウム塩が更に好ましい。 Examples of the alkali salt of polyacrylic acid include sodium salt of polyacrylic acid, lithium salt of polyacrylic acid, ammonium salt of polyacrylic acid, etc., and only one of them may be used. May be used in combination. Among these alkali salts of polyacrylic acid, alkali metal salts (sodium salt, lithium salt) of polyacrylic acid are more preferable, and the substitution ratio of carboxyl groups in polyacrylic acid (of the carboxyl groups possessed by polyacrylic acid, the salt In the case where the ratio of the groups converted to) is the same, the sodium salt has a greater effect on enhancing the charge / discharge cycle characteristics of the non-aqueous electrolyte secondary battery than the other alkali metal salts. More preferred is the sodium salt of acrylic acid.
ＣＭＣとＰＶＡとは、いずれか一方のみを使用してもよく、両者を併用してもよい。 Only one of CMC and PVA may be used, or both may be used in combination.
ポリアクリル酸のアルカリ塩と、ＣＭＣおよびＰＶＡより選ばれる少なくとも１種との使用比率は、負極合剤層と集電体との接着性を良好に高める観点から、ポリアクリル酸のアルカリ塩１００質量部に対するＣＭＣおよびＰＶＡより選ばれる少なくとも１種の比率（ＣＭＣおよびＰＶＡのうちのいずれか一方のみ使用する場合は、その比率であり、両者を併用する場合は、それらの合計比率。以下同じ。）が、１０質量部以上であり、２０質量部以上であることが好ましい。 The use ratio of the alkali salt of polyacrylic acid and at least one selected from CMC and PVA is 100 masses of alkali salt of polyacrylic acid from the viewpoint of improving the adhesion between the negative electrode mixture layer and the current collector. Ratio of at least one selected from CMC and PVA with respect to part (when only one of CMC and PVA is used, this is the ratio, and when both are used together, the total ratio thereof. The same applies hereinafter.) Is 10 parts by mass or more, and preferably 20 parts by mass or more.
また、ＣＭＣやＰＶＡによって負極活物質粒子の表面が被覆されることを抑制して、ポリアクリル酸のアルカリ塩の使用による負極活物質粒子同士の接着性を高め、負極合剤層の機械的強度を良好に高める観点から、ポリアクリル酸のアルカリ塩１００質量部に対するＣＭＣおよびＰＶＡより選ばれる少なくとも１種の比率は、８０質量部以下であり、５０質量部以下であることが好ましい。 Moreover, it suppresses that the surface of negative electrode active material particle is coat | covered with CMC and PVA, improves the adhesiveness of negative electrode active material particles by use of the alkali salt of polyacrylic acid, and the mechanical strength of a negative mix layer From the standpoint of improving the ratio, the ratio of at least one selected from CMC and PVA to 100 parts by mass of the alkali salt of polyacrylic acid is 80 parts by mass or less, and preferably 50 parts by mass or less.
負極合剤層のバインダには、ポリアクリル酸のアルカリ塩、ＣＭＣおよびＰＶＡ以外のバインダを、これらのバインダと共に使用することもできる。 For the binder of the negative electrode mixture layer, a binder other than the alkali salt of polyacrylic acid, CMC and PVA can be used together with these binders.
現在の非水電解液二次電池では、例えば、携帯機器用の電源用途のように、厚みの薄い角筒形の電池ケースが使用されることがあり、このような形態の場合には、正極と負極とをセパレータを介して重ね、渦巻状に巻回すると共に横断面が扁平状になるように成形した形状の巻回電極体が使用されることがあるが、このような形状の巻回電極体を構成する負極においては、負極合剤層が高い柔軟性を有していることが望ましい。 In the current non-aqueous electrolyte secondary battery, for example, a thin cylindrical battery case may be used, such as a power supply for portable devices. And a negative electrode are stacked via a separator, wound in a spiral shape, and a wound electrode body having a shape with a flat cross section may be used. In the negative electrode constituting the electrode body, it is desirable that the negative electrode mixture layer has high flexibility.
そこで、特に横断面が扁平状の巻回電極体とする場合には、負極合剤層のバインダに、前記の各バインダに加えて、負極合剤層の柔軟性を高め得るバインダを使用することが好ましい。前記の各バインダと共に使用して、負極合剤層の柔軟性を高め得るバインダとしては、例えば、ＳＢＲ、フッ素ゴム、アクリル樹脂、ポリアミド樹脂、ポリアミドイミド樹脂、ポリオレフィン（ポリエチレン、ポリプロピレンなど）などが挙げられ、これらのうちの１種または２種以上を使用することができる。 Therefore, in particular, in the case of a wound electrode body with a flat cross section, in addition to the above binders, a binder that can increase the flexibility of the negative electrode mixture layer is used as the binder of the negative electrode mixture layer. Is preferred. Examples of the binder that can be used together with each of the above-mentioned binders to increase the flexibility of the negative electrode mixture layer include SBR, fluororubber, acrylic resin, polyamide resin, polyamideimide resin, polyolefin (polyethylene, polypropylene, etc.), and the like. Of these, one or more of these can be used.
ただし、ポリアクリル酸のアルカリ塩、ＣＭＣおよびＰＶＡ以外のバインダについては、その使用量が多すぎると、ポリアクリル酸のアルカリ塩、ＣＭＣおよびＰＶＡを使用することによる前記の効果が小さくなる虞があることから、負極合剤層における全バインダ中の、ポリアクリル酸のアルカリ塩、ＣＭＣおよびＰＶＡ以外のバインダの量は、４０質量％以下であることが好ましい。他方、例えば、負極合剤層の柔軟性を高め得る前記のバインダを使用する場合、その効果を良好に確保する観点からは、負極合剤層における全バインダ中の、負極合剤層の柔軟性を高め得る前記のバインダの量は、５質量％以上であることが好ましく、１０質量％以上であることがより好ましく、２０質量％以上であることが更に好ましい。 However, if the amount of the binder other than the alkali salt of polyacrylic acid, CMC, and PVA is too large, the above-described effect due to the use of the alkali salt of polyacrylic acid, CMC, and PVA may be reduced. Therefore, the amount of binder other than alkali salt of polyacrylic acid, CMC and PVA in all binders in the negative electrode mixture layer is preferably 40% by mass or less. On the other hand, for example, when using the above-mentioned binder that can improve the flexibility of the negative electrode mixture layer, the flexibility of the negative electrode mixture layer in all the binders in the negative electrode mixture layer from the viewpoint of ensuring the effect of the binder. The amount of the binder capable of increasing the viscosity is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 20% by mass or more.
負極合剤層には、必要に応じて導電助剤を含有させることもできる。負極合剤層に使用可能な導電助剤としては、後述する正極合剤層に係る導電助剤と同じものが挙げられる。 The negative electrode mixture layer may contain a conductive additive as necessary. As a conductive support agent which can be used for a negative mix layer, the same thing as the conductive support agent which concerns on the positive mix layer mentioned later is mentioned.
負極は、例えば、前述した負極活物質およびバインダ、更には必要に応じて使用する導電助剤を、水などの溶媒に分散させたペースト状やスラリー状の負極合剤含有組成物を調製し（ただし、バインダは溶媒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などのプレス処理を施す工程を経て製造される。ただし、負極の製造方法は、前記の方法に制限される訳ではなく、他の製造方法で製造してもよい。 The negative electrode is prepared, for example, by preparing a paste-like or slurry-like negative electrode mixture-containing composition in which the above-described negative electrode active material and binder, and further a conductive auxiliary agent used as necessary are dispersed in a solvent such as water ( However, the binder may be dissolved in a solvent), and this is applied to one or both sides of the current collector, dried, and then subjected to a press treatment such as a calender treatment as necessary. However, the manufacturing method of the negative electrode is not limited to the above method, and may be manufactured by other manufacturing methods.
負極合剤含有組成物の調製手順については、特に制限はないが、ＣＭＣやＰＶＡよりも先に、ポリアクリル酸のアルカリ塩を負極活物質粒子の表面に付着させることが好ましいため、先に負極活物質とポリアクリル酸のアルカリ塩（例えば、その水溶液）とを混合し、その後にＣＭＣやＰＶＡ（これらの水溶液）を添加し、混合する手順で、負極合剤層形成用組成物を調製することがより好ましい。 The preparation procedure of the negative electrode mixture-containing composition is not particularly limited, but it is preferable to attach the alkali salt of polyacrylic acid to the surface of the negative electrode active material particles before CMC and PVA. A composition for forming a negative electrode mixture layer is prepared by mixing an active material and an alkali salt of polyacrylic acid (for example, an aqueous solution thereof) and then adding and mixing CMC and PVA (an aqueous solution thereof). It is more preferable.
負極の集電体としては、銅製やニッケル製の箔、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。この負極集電体は、高エネルギー密度の電池を得るために負極全体の厚みを薄くする場合、厚みの上限は３０μｍであることが好ましく、機械的強度を確保するために下限は５μｍであることが望ましい。 As the current collector for the negative electrode, a foil made of copper or nickel, a punching metal, a net, an expanded metal, or the like can be used, but a copper foil is usually used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is 5 μm in order to ensure mechanical strength. Is desirable.
負極合剤層の組成としては、例えば、負極活物質の量が８０〜９９質量％であることが好ましく、バインダの量が１〜２０質量％であることが好ましい。また、負極合剤層に導電助剤を含有させる場合には、導電助剤は、負極活物質の量およびバインダの量が、前記の好適値を満足する範囲内で使用することが好ましい。更に、負極合剤層の厚みは、集電体の片面あたり、１０〜１００μｍであることが好ましい。 As a composition of a negative mix layer, it is preferable that the quantity of a negative electrode active material is 80-99 mass%, for example, and it is preferable that the quantity of a binder is 1-20 mass%. In addition, when the conductive additive is contained in the negative electrode mixture layer, it is preferable to use the conductive assistant within a range in which the amount of the negative electrode active material and the amount of the binder satisfy the above-described preferable values. Furthermore, the thickness of the negative electrode mixture layer is preferably 10 to 100 μm per one side of the current collector.
本発明の非水電解液二次電池に係る正極は、リチウムを含む遷移金属複合酸化物を活物質として含有しており、例えば、前記活物質、バインダおよび導電助剤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である。 The positive electrode according to the non-aqueous electrolyte secondary battery of the present invention contains a transition metal composite oxide containing lithium as an active material, for example, a positive electrode mixture layer containing the active material, a binder, and a conductive additive. Is provided on one side or both sides of the current collector.
正極活物質としては、リチウムイオンを吸蔵放出可能な、リチウムを含む遷移金属複合酸化物（リチウム含有遷移金属複合酸化物）が使用される。リチウム含有遷移金属複合酸化物としては、従来から知られているリチウムイオン二次電池などの非水電解液二次電池に使用されているもの、具体的には、ＬｉｙＣｏＯ２（ただし、０≦ｙ≦１．１である。）、ＬｉｚＮｉＯ２（ただし、０≦ｚ≦１．１である。）、ＬｉｅＭｎＯ２（ただし、０≦ｅ≦１．１である。）、ＬｉａＣｏｂＭ１ １-ｂＯ２（ただし、Ｍ１は、Ｍｇ、Ｍｎ、Ｆｅ、Ｎｉ、Ｃｕ、Ｚｎ、Ａｌ、Ｔｉ、ＧｅおよびＣｒよりなる群から選択される少なくとも１種の金属元素であり、０≦ａ≦１．１、０＜ｂ＜１．０である。）、ＬｉｃＮｉ１−ｄＭ２ ｄＯ２（ただし、Ｍ２は、Ｍｇ、Ｍｎ、Ｆｅ、Ｃｏ、Ｃｕ、Ｚｎ、Ａｌ、Ｔｉ、ＧｅおよびＣｒよりなる群から選択される少なくとも１種の金属元素であり、０≦ｃ≦１．１、０＜ｄ＜１．０である。）、ＬｉｆＭｎｇＮｉｈＣｏ１−ｇ−ｈＯ２（ただし、０≦ｆ≦１．１、０＜ｇ＜１．０、０＜ｈ＜１．０である。）などの層状構造を有するリチウム含有遷移金属複合酸化物などが挙げられ、これらのうちの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 positive electrode active material, a transition metal composite oxide containing lithium (lithium-containing transition metal composite oxide) that can occlude and release lithium ions is used. Examples of the lithium-containing transition metal composite oxide include those conventionally used in non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, specifically, Li y CoO 2 (however, 0 ≦ y ≦ 1.1.), Li z NiO 2 (where 0 ≦ z ≦ 1.1), Li e MnO 2 (where 0 ≦ e ≦ 1.1), Li a Co b M 1 1-b O 2 (where M 1 is at least one metal element selected from the group consisting of Mg, Mn, Fe, Ni, Cu, Zn, Al, Ti, Ge and Cr) Yes, 0 ≦ a ≦ 1.1, 0 <b <1.0), Li c Ni 1-d M 2 d O 2 (where M 2 is Mg, Mn, Fe, Co, Cu, At least one metal element selected from the group consisting of Zn, Al, Ti, Ge and Cr And is a 0 ≦ c ≦ 1.1,0 <d < 1.0.), Li f Mn g Ni h Co 1-g-h O 2 ( however, 0 ≦ f ≦ 1.1,0 < g <1.0, 0 <h <1.0.) and the like, and lithium-containing transition metal composite oxides having a layered structure such as 1) may be used, and only one of these may be used. More than one species may be used in combination.
正極合剤層に係るバインダとしては、例えば、でんぷん、ポリビニルアルコール、ポリアクリル酸、ＣＭＣ、ヒドロキシプロピルセルロース、再生セルロース、ジアセチルセルロースなどの多糖類やそれらの変成体；ポリビニルクロリド、ポリビニルピロリドン、ポリテトラフルオロエチレン（ＰＴＦＥ）、ＰＶＤＦ、ポリエチレン、ポリプロピレン、ポリアミドイミド、ポリアミドなどの熱可塑性樹脂やそれらの変成体；ポリイミド；エチレン−プロピレン−ジエンターポリマー（ＥＰＤＭ）、スルホン化ＥＰＤＭ、ＳＢＲ、ブタジエンゴム、ポリブタジエン、フッ素ゴム、ポリエチレンオキシドなどのゴム状弾性を有するポリマーやそれらの変成体；などが挙げられ、これらのうちの１種のみを使用してもよく、２種以上を併用してもよい。 Examples of the binder for the positive electrode material mixture layer include polysaccharides such as starch, polyvinyl alcohol, polyacrylic acid, CMC, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, and modified products thereof; polyvinyl chloride, polyvinyl pyrrolidone, polytetra Thermoplastic resins such as fluoroethylene (PTFE), PVDF, polyethylene, polypropylene, polyamideimide, polyamide and their modified products; polyimide; ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, SBR, butadiene rubber, polybutadiene , Polymers having rubbery elasticity such as fluororubber and polyethylene oxide, and their modified products, etc., and only one of them may be used, or two or more may be used in combination. .
正極合剤層に係る導電助剤には、例えば、アセチレンブラック、ケッチェンブラック（商品名）、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ーボンブラック；炭素繊維、金属繊維などの導電性繊維；アルミニウム粉、ニッケル粉、銅粉、銀粉などの金属粉末；フッ化炭素；酸化亜鉛；チタン酸カリウムなどからなる導電性ウィスカー；酸化チタンなどの導電性金属酸化物；ポリフェニレン誘導体（特開昭５９−２０９７１号公報に記載のもの）などの有機導電性材料；などが挙げられ、これらの１種または２種以上を使用することができる。 Examples of the conductive auxiliary agent related to the positive electrode mixture layer include carbon blacks such as acetylene black, ketjen black (trade name), channel black, furnace black, lamp black, and thermal black; and conductive materials such as carbon fiber and metal fiber. Fiber: Metal powder such as aluminum powder, nickel powder, copper powder, silver powder; Fluorinated carbon; Zinc oxide; Conductive whisker made of potassium titanate; Conductive metal oxide such as titanium oxide; Organic conductive materials such as those described in Japanese Patent No. 59-20971), and one or more of these may be used.
正極は、例えば、正極活物質や、バインダ、導電助剤などを、Ｎ−メチル−２−ピロリドン（ＮＭＰ）などの溶媒に分散させたペースト状やスラリー状の正極合剤含有組成物を調製し（ただし、バインダは溶媒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などのプレス処理を施す工程を経て製造される。ただし、正極の製造方法は、前記の方法に制限される訳ではなく、他の製造方法で製造してもよい。 For the positive electrode, for example, a paste-like or slurry-like positive electrode mixture-containing composition in which a positive electrode active material, a binder, a conductive auxiliary agent, and the like are dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) is prepared. (However, the binder may be dissolved in a solvent.) After being applied to one or both sides of the current collector and dried, the binder is manufactured through a step of performing a pressing process such as a calendering process as necessary. . However, the manufacturing method of the positive electrode is not limited to the above method, and may be manufactured by other manufacturing methods.
正極集電体としては、従来から知られている非水電解液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、正極集電体の材質は、構成された非水電解液二次電池において化学的に安定な電子伝導体であれば特に限定されない。例えば、アルミニウムまたはアルミニウム合金、ステンレス鋼、ニッケル、チタン、炭素、導電性樹脂などの他に、アルミニウム、アルミニウム合金またはステンレス鋼の表面に炭素層またはチタン層を形成した複合材などを用いることができる。これらの中でも、アルミニウムまたはアルミニウム合金が特に好ましい。これらは、軽量で電子伝導性が高いからである。正極集電体には、例えば、前記材質からなるフォイル、フィルム、シート、ネット、パンチングシート、ラス体、多孔質体、発泡体、繊維群の成形体などが使用される。また、正極集電体の表面に、表面処理を施して凹凸を付けることもできる。正極集電体の厚みは特に限定されないが、通常１〜５００μｍである。 As the positive electrode current collector, the same as those used for the positive electrode of the conventionally known non-aqueous electrolyte secondary battery can be used, and the material of the positive electrode current collector is the non-aqueous electrolysis that is configured. If it is a chemically stable electronic conductor in a liquid secondary battery, it will not be specifically limited. For example, in addition to aluminum or aluminum alloy, stainless steel, nickel, titanium, carbon, conductive resin, etc., a composite material in which a carbon layer or a titanium layer is formed on the surface of aluminum, aluminum alloy, or stainless steel can be used. . Among these, aluminum or an aluminum alloy is particularly preferable. This is because they are lightweight and have high electron conductivity. For the positive electrode current collector, for example, a foil, a film, a sheet, a net, a punching sheet, a lath body, a porous body, a foamed body, a molded body of a fiber group, or the like made of the above materials is used. Further, the surface of the positive electrode current collector can be roughened by surface treatment. Although the thickness of a positive electrode electrical power collector is not specifically limited, Usually, it is 1-500 micrometers.
正極合剤層の組成としては、例えば、正極活物質の量が６０〜９８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１〜２５質量％であることが好ましい。また、正極合剤層の厚みは、例えば、正極集電体の片面あたり１０〜１００μｍであることが好ましい。 As the composition of the positive electrode mixture layer, for example, the amount of the positive electrode active material is preferably 60 to 98% by mass, the amount of the binder is preferably 1 to 15% by mass, and the amount of the conductive auxiliary agent is 1. It is preferably ˜25% by mass. Moreover, it is preferable that the thickness of a positive mix layer is 10-100 micrometers per single side | surface of a positive electrode electrical power collector, for example.
本発明の非水電解液二次電池は、正極、負極、セパレータ、および非水電解液を有しており、負極が前記の負極であって、正極が前記の正極であればよく、その他の構成および構造に関しては特に制限はなく、従来から知られている非水電解液二次電池で採用されている各種構成および構造を適用することができる。 The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The negative electrode is the negative electrode, and the positive electrode is the positive electrode. There is no restriction | limiting in particular regarding a structure and a structure, The various structures and structures employ | adopted by the conventionally known nonaqueous electrolyte secondary battery are applicable.
非水電解液には、有機溶媒にリチウム塩（無機リチウム塩もしくは有機リチウム塩またはその両者）を溶解させることによって調製した電解液を使用することができる。 As the non-aqueous electrolyte, an electrolyte prepared by dissolving a lithium salt (inorganic lithium salt or organic lithium salt or both) in an organic solvent can be used.
非水電解液に係る有機溶媒としては、例えば、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）、ビニレンカーボネート（ＶＣ），ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、メチルエチルカーボネート（ＭＥＣ）、γ−ブチロラクトン、１，２−ジメトキシエタン、テトラヒドロフラン、２−メチルテトラヒドロフラン、ジメチルスルフォキシド、１，３−ジオキソラン、ホルムアミド、ジメチルホルムアミド、ジオキソラン、アセトニトリル、ニトロメタン、蟻酸メチル、酢酸メチル、燐酸トリエステル、トリメトキシメタン、ジオキソラン誘導体、スルホラン、３−メチル−２−オキサゾリジノン、プロピレンカーボネート誘導体、テトラヒドロフラン誘導体、ジエチルエーテル、１，３−プロパンサルトンなどの非プロトン性有機溶媒が挙げられ、これらを１種単独で用いてもよいし、２種以上を併用してもよい。また、アミンイミド系有機溶媒や、含イオウまたは含フッ素系有機溶媒なども用いることができる。これらの中でも、ＥＣとＭＥＣとＤＥＣとの混合溶媒が好ましく、この場合、混合溶媒の全容量に対して、ＤＥＣを１５体積％以上８０体積％以下の量で含むことがより好ましい。このような混合溶媒であれば、電池の低温特性や充放電サイクル特性を高く維持しつつ、高電圧充電時における溶媒の安定性を高めることができるからである。 Examples of the organic solvent related to the non-aqueous electrolyte include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl. Ethyl carbonate (MEC), γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, acetic acid Methyl, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative , Diethyl ether, include aprotic organic solvents such as 1,3-propane sultone, it may be used those either alone, or in combination of two or more. Also, amine imide organic solvents, sulfur-containing or fluorine-containing organic solvents, and the like can be used. Among these, a mixed solvent of EC, MEC, and DEC is preferable. In this case, it is more preferable to include DEC in an amount of 15% by volume to 80% by volume with respect to the total volume of the mixed solvent. This is because such a mixed solvent can enhance the stability of the solvent during high-voltage charging while maintaining the low temperature characteristics and charge / discharge cycle characteristics of the battery high.
非水電解液を構成するための無機リチウム塩としては、ＬｉＣｌＯ４、ＬｉＢＦ４、ＬｉＰＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＢ１０Ｃｌ１０、低級脂肪族カルボン酸Ｌｉ、ＬｉＡｌＣｌ４、ＬｉＣｌ、ＬｉＢｒ、ＬｉＩ、クロロボランＬｉ、四フェニルホウ酸Ｌｉなどが挙げられ、これらのうちの１種または２種以上を用いることができる。
Examples of the inorganic lithium salt for constituting the
非水電解液を構成するための有機リチウム塩としては、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、Ｌｉ２Ｃ２Ｆ４（ＳＯ３）２、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＣｎＦ２ｎ＋１ＳＯ３（２≦ｎ≦７）、ＬｉＮ（ＲｆＯＳＯ２）２〔ここでＲｆはフルオロアルキル基を示す。〕などが挙げられ、これらのうちの１種または２種以上を用いることができる。 Examples of the organic lithium salt for constituting the non-aqueous electrolyte include LiCF 3 SO 3 , LiCF 3 CO 2 , Li 2 C 2 F 4 (SO 3 ) 2 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiC n F 2n + 1 SO 3 (2 ≦ n ≦ 7), LiN (RfOSO 2 ) 2 [wherein Rf represents a fluoroalkyl group. Etc., and one or more of these can be used.
これらの非水電解液の中でも、ジメチルカーボネート、ジエチルカーボネートおよびメチルエチルカーボネートより選ばれる少なくとも１種の鎖状カーボネートと、エチレンカーボネートおよびプロピレンカーボネートより選ばれる少なくとも１種の環状カーボネートとを含む溶媒に、ＬｉＰＦ６を溶解した電解液が好ましい。 Among these non-aqueous electrolytes, a solvent containing at least one chain carbonate selected from dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate, and at least one cyclic carbonate selected from ethylene carbonate and propylene carbonate, An electrolytic solution in which LiPF 6 is dissolved is preferable.
非水電解液中のリチウム塩の濃度は、例えば、０．２〜３．０ｍｏｌ／Ｌであることが適当であり、０．８〜２．０ｍｏｌ／Ｌであることが好ましく、０．９〜１．６ｍｏｌ／Ｌであることがより好ましい。 The concentration of the lithium salt in the non-aqueous electrolyte is, for example, suitably 0.2 to 3.0 mol / L, preferably 0.8 to 2.0 mol / L, 0.9 to More preferably, it is 1.6 mol / L.
また、充放電サイクル特性の更なる改善や、高温貯蔵性や過充電防止などの安全性を向上させる目的で、前記の非水電解液に、例えば、無水酸、スルホン酸エステル、ジニトリル、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、ビニレンカーボネート（ＶＣ）、ビフェニル、フルオロベンゼン、ｔ−ブチルベンゼン、環状フッ素化カーボネート〔トリフルオロプロピレンカーボネート（ＴＦＰＣ）、フルオロエチレンカーボネート（ＦＥＣ）など〕、または、鎖状フッ素化カーボネート〔トリフルオロジメチルカーボネート（ＴＦＤＭＣ）、トリフルオロジエチルカーボネート（ＴＦＤＥＣ）、トリフルオロエチルメチルカーボネート（ＴＦＥＭＣ）など〕など（前記の各化合物の誘導体も含む）を適宜含有させることもできる。なお、前記環状フッ素化カーボネートおよび鎖状フッ素化カーボネートは、エチレンカーボネートなどのように、溶媒として用いることもできる。 Further, for the purpose of further improving the charge / discharge cycle characteristics and improving the safety such as high temperature storage and prevention of overcharge, the non-aqueous electrolyte includes, for example, acid anhydride, sulfonate ester, dinitrile, 1, 3-propane sultone, diphenyl disulfide, cyclohexylbenzene, vinylene carbonate (VC), biphenyl, fluorobenzene, t-butylbenzene, cyclic fluorinated carbonate [trifluoropropylene carbonate (TFPC), fluoroethylene carbonate (FEC), etc.], Alternatively, a chain fluorinated carbonate [trifluorodimethyl carbonate (TFDMC), trifluorodiethyl carbonate (TFDEC), trifluoroethylmethyl carbonate (TFEMC), etc.] (including derivatives of the above-mentioned respective compounds) is appropriately included. It can also be. The cyclic fluorinated carbonate and the chain fluorinated carbonate can also be used as a solvent, such as ethylene carbonate.
また、前記の非水電解液に公知のポリマーなどのゲル化剤を添加してゲル状としたもの（ゲル状電解質）を、本発明の非水電解液二次電池に使用してもよい。 Moreover, you may use for the nonaqueous electrolyte secondary battery of this invention what added gelatinizers, such as a well-known polymer, to the said nonaqueous electrolyte solution, and was made into the gel form (gel electrolyte).
本発明の非水電解液二次電池に係るセパレータとしては、強度が十分で、かつ非水電解液を多く保持できるものがよく、例えば、厚みが５〜５０μｍで開口率が３０〜７０％の、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、エチレン−プロピレン共重合体を含んでいてもよく、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。 As the separator according to the non-aqueous electrolyte secondary battery of the present invention, a separator having sufficient strength and capable of holding a large amount of non-aqueous electrolyte is preferable. For example, the thickness is 5 to 50 μm and the aperture ratio is 30 to 70%. A microporous membrane made of polyolefin such as polyethylene (PE) or polypropylene (PP) can be used. The microporous membrane constituting the separator may be, for example, one using only PE or one using only PP, may contain an ethylene-propylene copolymer, and may be made of PE. A laminate of a membrane and a PP microporous membrane may be used.
更に、セパレータには、融点が１４０℃以下の樹脂を主体とした多孔質層と、融点が１５０℃以上の樹脂または耐熱温度が１５０℃以上の無機フィラーを主体として含む多孔質層とから構成された積層型のセパレータを使用することができる。ここで、「融点」とは日本工業規格（ＪＩＳ） Ｋ ７１２１の規定に準じて、示差走査熱量計（ＤＳＣ）を用いて測定される融解温度を意味し、「耐熱温度が１５０℃以上」とは、少なくとも１５０℃において軟化などの変形が見られないことを意味している。 Furthermore, the separator is composed of a porous layer mainly composed of a resin having a melting point of 140 ° C. or lower and a porous layer mainly including a resin having a melting point of 150 ° C. or higher or an inorganic filler having a heat resistant temperature of 150 ° C. or higher. A laminated separator can be used. Here, “melting point” means a melting temperature measured using a differential scanning calorimeter (DSC) in accordance with the provisions of Japanese Industrial Standard (JIS) K 7121, and “heat resistance is 150 ° C. or higher”. Means that no deformation such as softening is observed at least at 150 ° C.
セパレータ（ポリオレフィン製の微多孔膜からなるセパレータや、前記積層型のセパレータ）の厚みは、１０〜３０μｍであることがより好ましい。 The thickness of the separator (a separator made of a polyolefin microporous film or the laminated separator) is more preferably 10 to 30 μm.
本発明の非水電解液二次電池の形態としては、特に制限はない。例えば、コイン形、ボタン形、シート形、積層形、円筒形、扁平形、角形、電気自動車などに用いる大型のものなど、いずれであってもよい。 There is no restriction | limiting in particular as a form of the nonaqueous electrolyte secondary battery of this invention. For example, any of a coin shape, a button shape, a sheet shape, a laminated shape, a cylindrical shape, a flat shape, a square shape, a large size used for an electric vehicle, etc. may be used.
また、非水電解液二次電池に正極、負極およびセパレータを導入するにあたっては、電池の形態に応じて、複数の正極と複数の負極とをセパレータを介して積層した積層電極体や、正極と負極とをセパレータを介して積層し、更にこれを渦巻状に巻回した巻回電極体として使用することができる。 Further, when introducing the positive electrode, the negative electrode, and the separator into the non-aqueous electrolyte secondary battery, depending on the form of the battery, a laminated electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are stacked via the separator, It can be used as a wound electrode body obtained by laminating a negative electrode with a separator and winding it in a spiral shape.
本発明の非水電解液二次電池は、高容量の負極材料を使用し、かつ優れた充放電サイクル特性を有していることから、これらの特性を生かして、小型で多機能な携帯機器の電源を始めとして、従来から知られている非水電解液二次電池が適用されている各種用途に好ましく用いることができる。 Since the non-aqueous electrolyte secondary battery of the present invention uses a high-capacity negative electrode material and has excellent charge / discharge cycle characteristics, these characteristics are utilized to make a small and multifunctional portable device. It can be preferably used for various applications to which conventionally known non-aqueous electrolyte secondary batteries are applied.
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ＬｉＣｏＯ２：９３質量部、導電助剤であるカーボンブラック：３質量部、およびバインダであるＰＶＤＦ：４質量部を、溶媒であるＮＭＰを用いて均一になるように混合して正極合剤含有スラリーを調製した。この正極合剤含有スラリーを、厚みが１５μｍのアルミニウム箔からなる正極集電体の片面に塗布し、乾燥した後、ローラープレス機により加圧成形することにより、正極集電体の片面に厚みが７０μｍの正極合剤層を形成した。その後、これを２５ｍｍ×３５ｍｍに切断して短冊状の正極を得た。
Example 1
<Preparation of positive electrode>
LiCoO 2 as a positive electrode active material: 93 parts by mass, carbon black as a conductive auxiliary agent: 3 parts by mass, and PVDF as a binder: 4 parts by mass are mixed uniformly using NMP as a solvent. A positive electrode mixture-containing slurry was prepared. The positive electrode mixture-containing slurry is applied to one side of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm, dried, and then subjected to pressure molding with a roller press, whereby the thickness of one side of the positive electrode current collector is increased. A 70 μm positive electrode mixture layer was formed. Then, this was cut | disconnected to 25 mm x 35 mm, and the strip-shaped positive electrode was obtained.
＜負極の作製＞
ポリアクリル酸：１００ｇを純水：５００ｇに投入して攪拌溶解させた後、ＮａＯＨ：７０ｇを加えてｐＨが７以下になるまで攪拌溶解させた。この水溶液を一部採取し、１００℃で真空乾燥し、残渣の質量を測定して固形分比を求めた。そして、残りの水溶液に純水を添加して、ポリアクリル酸のナトリウム塩の５質量％濃度水溶液を得た。また、ＣＭＣを純水に投入し、攪拌溶解させてＣＭＣの２質量％濃度水溶液を調製した。
<Production of negative electrode>
After adding 100 g of polyacrylic acid to 500 g of pure water and stirring and dissolving, NaOH: 70 g was added and stirring and dissolving until the pH became 7 or less. A part of this aqueous solution was collected and dried in vacuum at 100 ° C., and the mass of the residue was measured to determine the solid content ratio. And the pure water was added to the remaining aqueous solution, and the 5 mass% concentration aqueous solution of the sodium salt of polyacrylic acid was obtained. Moreover, CMC was put into pure water and dissolved by stirring to prepare a 2% by weight aqueous solution of CMC.
負極活物質として、ＳｉＯ（非晶質のＳｉＯ２マトリックス中にＳｉが分散した構造で、ＳｉＯ２とＳｉとのモル比が１：１である材料）と黒鉛とを、４：１の質量比で含む混合物を用意した。この負極活物質と導電助剤であるカーボンブラックとを、前記のポリアクリル酸のナトリウム塩の水溶液に投入して十分攪拌した後、ここに前記のＣＭＣの水溶液を加え、更に純水を投入して粘度を調整して負極合剤含有スラリーを得た。この負極合剤含有スラリーにおいて、負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとの組成比（質量比）は、９４：１．５：３：１．５とした。 As a negative electrode active material, SiO (a material in which Si is dispersed in an amorphous SiO 2 matrix and a molar ratio of SiO 2 to Si is 1: 1) and graphite are mass ratio of 4: 1. A mixture containing was prepared. The negative electrode active material and the carbon black as a conductive additive are added to the aqueous solution of sodium salt of polyacrylic acid and sufficiently stirred. Then, the aqueous solution of CMC is added thereto, and pure water is further added. The viscosity was adjusted to obtain a negative electrode mixture-containing slurry. In this negative electrode mixture-containing slurry, the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, and CMC was 94: 1.5: 3: 1.5.
前記の負極合剤含有スラリーを、厚みが１０μｍの銅箔からなる負極集電体の片面に塗布し、乾燥した後、ローラープレス機により加圧成形することにより、負極集電体の片面に厚みが５０μｍの負極合剤層を形成した。その後、これを３０ｍｍ×３５ｍｍに切断して短冊状の負極を得た。 The negative electrode mixture-containing slurry is applied to one side of a negative electrode current collector made of a copper foil having a thickness of 10 μm, dried, and then press-molded with a roller press to obtain a thickness on one side of the negative electrode current collector. Formed a negative electrode mixture layer having a thickness of 50 μm. Then, this was cut | disconnected to 30 mm x 35 mm, and the strip-shaped negative electrode was obtained.
＜電池の組み立て＞
前記の正極と前記の負極とを、ＰＥ製微多孔膜セパレータ（厚み２５μｍ、空孔率４５％）を介在させつつ重ね合わせて積層電極体とした。この積層電極体を１０ｃｍ×２０ｃｍのアルミニウムラミネートフィルムからなる外装体内に挿入した。次に、ＥＣとＤＥＣとＭＥＣとを１：１：１の体積比で混合した溶液にＬｉＰＦ６を１ｍｏｌ／Ｌの濃度で溶解させた後、更にＶＣを１質量％となる量で溶解させて調製した非水電解液を外装体内に注入した。その後、外装体の開口部を封口して、図１に示す外観で、図２に示す断面構造の非水電解液二次電池を作製した。
<Battery assembly>
The positive electrode and the negative electrode were overlapped with a PE microporous membrane separator (thickness 25 μm, porosity 45%) to form a laminated electrode body. This laminated electrode body was inserted into an exterior body made of a 10 cm × 20 cm aluminum laminate film. Next, after dissolving LiPF 6 at a concentration of 1 mol / L in a solution in which EC, DEC and MEC are mixed at a volume ratio of 1: 1: 1, VC is further dissolved in an amount of 1% by mass. The prepared non-aqueous electrolyte was injected into the exterior body. Then, the opening part of the exterior body was sealed and the nonaqueous electrolyte secondary battery of the cross-sectional structure shown in FIG. 2 was produced with the external 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は非水電解液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 non-aqueous electrolyte secondary battery, and FIG. 2 is a cross-sectional view taken along line AA of FIG. The nonaqueous electrolyte
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
実施例２
負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとの組成比（質量比）を、９４：１．５：４．０９：０．４１に変更した以外は、実施例１と同様にして負極合剤含有スラリーを調製した。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Example 2
Except that the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, and CMC was changed to 94: 1.5: 4.09: 0.41, the same as in Example 1. Thus, a negative electrode mixture-containing slurry was prepared. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例３
負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとの組成比（質量比）を、９４：１．５：２．５：２に変更した以外は、実施例１と同様にして負極合剤含有スラリーを調製した。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Example 3
The negative electrode was prepared in the same manner as in Example 1 except that the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, and CMC was changed to 94: 1.5: 2.5: 2. A mixture-containing slurry was prepared. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例４
負極活物質を、黒鉛とＳｉとを４：１の質量比で含む混合物に変更した以外は、実施例１と同様にして負極合剤含有スラリーを調製した。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Example 4
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 1 except that the negative electrode active material was changed to a mixture containing graphite and Si at a mass ratio of 4: 1. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例５
ＣＭＣの水溶液の添加後にＳＢＲの水分散液を添加し、その後に純水を投入して粘度を調整した以外は実施例１と同様にして負極合剤含有スラリーを調製した。この負極合剤含有スラリーにおいて、負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとＳＢＲとの組成比（質量比）は、９４：１．５：２．７：１．３：０．５とした。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Example 5
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 1 except that an aqueous dispersion of SBR was added after the addition of the aqueous solution of CMC, and then the viscosity was adjusted by adding pure water. In this negative electrode mixture-containing slurry, the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, CMC, and SBR was 94: 1.5: 2.7: 1.3: 0. .5. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例６
ＳＢＲの水分散液に代えてフッ素ゴムの水分散液を用いた以外は、実施例５と同様にして負極合剤含有スラリーを調製した。この負極合剤含有スラリーにおいて、負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとフッ素ゴムとの組成比（質量比）は、９４：１．５：２．７：１．３：０．５とした。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Example 6
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 5 except that a fluororubber aqueous dispersion was used instead of the SBR aqueous dispersion. In this negative electrode mixture-containing slurry, the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, CMC, and fluororubber was 94: 1.5: 2.7: 1.3: 0.5. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例７
ＳＢＲの水分散液に代えてアクリル樹脂の水分散液を用いた以外は、実施例５と同様にして負極合剤含有スラリーを調製した。この負極合剤含有スラリーにおいて、負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとアクリル樹脂との組成比（質量比）は、９４：１．５：２．７：１．３：０．５とした。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Example 7
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 5 except that an acrylic resin aqueous dispersion was used instead of the SBR aqueous dispersion. In this negative electrode mixture-containing slurry, the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, CMC, and acrylic resin was 94: 1.5: 2.7: 1.3: 0.5. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例８
ＳＢＲの水分散液に代えてポリイミド樹脂の水分散液を用いた以外は、実施例５と同様にして負極合剤含有スラリーを調製した。この負極合剤含有スラリーにおいて、負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとポリイミド樹脂との組成比（質量比）は、９４：１．５：２．７：１．３：０．５とした。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Example 8
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 5 except that a polyimide resin aqueous dispersion was used instead of the SBR aqueous dispersion. In this negative electrode mixture-containing slurry, the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, CMC, and polyimide resin was 94: 1.5: 2.7: 1.3: 0.5. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例９
ＳＢＲの水分散液に代えてポリアミドイミド樹脂の水分散液を用いた以外は、実施例５と同様にして負極合剤含有スラリーを調製した。この負極合剤含有スラリーにおいて、負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとポリアミドイミド樹脂との組成比（質量比）は、９４：１．５：２．７：１．３：０．５とした。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Example 9
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 5 except that an aqueous dispersion of polyamideimide resin was used instead of the aqueous dispersion of SBR. In this negative electrode mixture-containing slurry, the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, CMC, and polyamideimide resin was 94: 1.5: 2.7: 1.3. : 0.5. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例１０
ＳＢＲの水分散液に代えてＰＰの水分散液を用いた以外は、実施例５と同様にして負極合剤含有スラリーを調製した。この負極合剤含有スラリーにおいて、負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとＰＰとの組成比（質量比）は、９４：１．５：２．７：１．３：０．５とした。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Example 10
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 5 except that the PP aqueous dispersion was used instead of the SBR aqueous dispersion. In this negative electrode mixture-containing slurry, the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, CMC and PP was 94: 1.5: 2.7: 1.3: 0. .5. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例１１
ポリアクリル酸：１００ｇを純水：５００ｇに投入して攪拌溶解させた後、ＬｉＯＨ：４０ｇを加えてｐＨが７以下になるまで攪拌溶解させた。この水溶液を一部採取し、１００℃で真空乾燥し、残渣の質量を測定して固形分比を求めた。そして、残りの水溶液に純水を添加して、ポリアクリル酸のリチウム塩の５質量％濃度水溶液を得た。
Example 11
After adding 100 g of polyacrylic acid to 500 g of pure water and stirring and dissolving, LiOH: 40 g was added and stirring and dissolving until the pH was 7 or less. A part of this aqueous solution was collected and dried in vacuum at 100 ° C., and the mass of the residue was measured to determine the solid content ratio. And the pure water was added to the remaining aqueous solution, and 5 mass% concentration aqueous solution of the lithium salt of polyacrylic acid was obtained.
ポリアクリル酸のナトリウム塩の水溶液に代えて、前記のポリアクリル酸のリチウム塩の水溶液を用いた以外は、実施例１と同様にして負極合剤含有スラリーを調製した。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。 A negative electrode mixture-containing slurry was prepared in the same manner as in Example 1 except that the aqueous solution of lithium salt of polyacrylic acid was used instead of the aqueous solution of sodium salt of polyacrylic acid. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例１２
ポリアクリル酸：１００ｇを純水：５００ｇに投入して攪拌溶解させた後、ＮａＯＨ：５０ｇを加えてｐＨが７以上８以下になるまで攪拌溶解させてアルカリ置換反応を停止させた。この水溶液を一部採取し、１００℃で真空乾燥し、残渣の質量を測定して固形分比を求めた。そして、残りの水溶液に純水を添加して、ポリアクリル酸のナトリウム塩の５質量％濃度水溶液を得た。
Example 12
After adding polyacrylic acid: 100 g to pure water: 500 g and stirring and dissolving, NaOH: 50 g was added and stirring and dissolving until pH became 7 or more and 8 or less to stop the alkali substitution reaction. A part of this aqueous solution was collected and dried in vacuum at 100 ° C., and the mass of the residue was measured to determine the solid content ratio. And the pure water was added to the remaining aqueous solution, and the 5 mass% concentration aqueous solution of the sodium salt of polyacrylic acid was obtained.
ポリアクリル酸のナトリウム塩の水溶液を前記のものに変更した以外は、実施例１と同様にして負極合剤含有スラリーを調製した。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。 A negative electrode mixture-containing slurry was prepared in the same manner as in Example 1 except that the aqueous solution of the sodium salt of polyacrylic acid was changed to that described above. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例１３
ポリアクリル酸：１００ｇを純水：５００ｇに投入して攪拌溶解させた後、ＬｉＯＨ：３０ｇを加えてｐＨが７以上８以下になるまで攪拌溶解させてアルカリ置換反応を停止させた。この水溶液を一部採取し、１００℃で真空乾燥し、残渣の質量を測定して固形分比を求めた。そして、残りの水溶液に純水を添加して、ポリアクリル酸のリチウム塩の５質量％濃度水溶液を得た。
Example 13
After adding polyacrylic acid: 100 g to pure water: 500 g and stirring and dissolving, LiOH: 30 g was added and stirred and dissolved until the pH became 7 or more and 8 or less to stop the alkali substitution reaction. A part of this aqueous solution was collected and dried in vacuum at 100 ° C., and the mass of the residue was measured to determine the solid content ratio. And the pure water was added to the remaining aqueous solution, and 5 mass% concentration aqueous solution of the lithium salt of polyacrylic acid was obtained.
ポリアクリル酸のナトリウム塩の水溶液に代えて、前記のポリアクリル酸のリチウム塩の水溶液を用いた以外は、実施例１と同様にして負極合剤含有スラリーを調製した。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。 A negative electrode mixture-containing slurry was prepared in the same manner as in Example 1 except that the aqueous solution of lithium salt of polyacrylic acid was used instead of the aqueous solution of sodium salt of polyacrylic acid. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例１４
ＣＭＣの水溶液に代えてＰＶＡの２質量％濃度の水溶液を用いた以外は、実施例１と同様にして負極合剤含有スラリーを調製した。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Example 14
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 1 except that a 2% by mass aqueous solution of PVA was used instead of the CMC aqueous solution. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
比較例１
ＣＭＣの水溶液を添加しなかった以外は、実施例１と同様にして負極合剤含有スラリーを調製した。この負極合剤含有スラリーにおいて、負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩との組成比（質量比）は、９４：１．５：４．５とした。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Comparative Example 1
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 1 except that the CMC aqueous solution was not added. In this negative electrode mixture-containing slurry, the composition ratio (mass ratio) of the negative electrode active material, carbon black, and sodium salt of polyacrylic acid was 94: 1.5: 4.5. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
比較例２
ポリアクリル酸のナトリウム塩の水溶液を添加しなかった以外は、実施例１と同様にして負極合剤含有スラリーを調製した。この負極合剤含有スラリーにおいて、負極活物質とカーボンブラックとＣＭＣとの組成比（質量比）は、９４：１．５：４．５とした。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Comparative Example 2
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 1 except that the aqueous solution of sodium salt of polyacrylic acid was not added. In this negative electrode mixture-containing slurry, the composition ratio (mass ratio) of the negative electrode active material, carbon black, and CMC was 94: 1.5: 4.5. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
比較例３
負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとの組成比（質量比）が、９４：１．５：４．２９：０．２１となるようにした以外は、実施例１と同様にして負極合剤含有スラリーを調製した。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Comparative Example 3
Example 1 except that the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, and CMC was 94: 1.5: 4.29: 0.21. Similarly, a negative electrode mixture-containing slurry was prepared. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
比較例４
負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩とＣＭＣとの組成比（質量比）が、９４：１．５：１．８：２．７となるようにした以外は、実施例１と同様にして負極合剤含有スラリーを調製した。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Comparative Example 4
Example 1 except that the composition ratio (mass ratio) of the negative electrode active material, carbon black, sodium salt of polyacrylic acid, and CMC was 94: 1.5: 1.8: 2.7. Similarly, a negative electrode mixture-containing slurry was prepared. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
比較例５
ＣＭＣの水溶液を添加しなかった以外は、実施例４と同様にして負極合剤含有スラリーを調製した。この負極合剤含有スラリーにおいて、負極活物質とカーボンブラックとポリアクリル酸のナトリウム塩との組成比（質量比）は、９４：１．５：４．５とした。そして、前記の負極合剤含有スラリーを用いた以外は実施例１と同様にして負極を作製し、この負極を用いた以外は実施例１と同様にして非水電解液二次電池を作製した。
Comparative Example 5
A negative electrode mixture-containing slurry was prepared in the same manner as in Example 4 except that the CMC aqueous solution was not added. In this negative electrode mixture-containing slurry, the composition ratio (mass ratio) of the negative electrode active material, carbon black, and sodium salt of polyacrylic acid was 94: 1.5: 4.5. A negative electrode was produced in the same manner as in Example 1 except that the above negative electrode mixture-containing slurry was used. A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this negative electrode was used. .
実施例および比較例の各非水電解液二次電池、およびこれらの電池に使用した負極について、以下の各評価を行った。 Each non-aqueous electrolyte secondary battery of Examples and Comparative Examples and the negative electrodes used in these batteries were evaluated as follows.
＜充放電サイクル特性評価＞
実施例および比較例の各非水電解液二次電池を、１０ｍＡの定電流で４．２Ｖまで充電し、続いて４．２Ｖの定電圧で充電した。定電流充電と定電圧充電との総充電時間は５時間とした。そして、充電後の各電池を、１０ｍＡの定電流で２．５Ｖになるまで放電させた。前記の定電流−定電圧充電と、その後の定電流放電とを行う一連の操作を１サイクルとして、これらを５００サイクル行った。そして、各電池について、２０サイクル目、１００目および５００サイクル目の各放電容量を、初回放電容量で除した値を百分率で表して、容量維持率を求めた。
<Charge / discharge cycle characteristics evaluation>
Each of the nonaqueous electrolyte secondary batteries of Examples and Comparative Examples was charged to 4.2 V with a constant current of 10 mA, and subsequently charged with a constant voltage of 4.2 V. The total charging time for constant current charging and constant voltage charging was 5 hours. And each battery after charge was discharged until it became 2.5V with a constant current of 10 mA. A series of operations for performing the constant current-constant voltage charging and the subsequent constant current discharging was regarded as one cycle, and these were performed for 500 cycles. And about each battery, the value which remove | divided each discharge capacity of 20th cycle, 100th cycle, and 500th cycle by initial discharge capacity was represented by percentage, and the capacity | capacitance maintenance factor was calculated | required.
＜負極合剤層と集電体との間の接着強度評価＞
実施例および比較例の各非水電解液二次電池に使用した負極と同じ負極を用意し、それぞれの負極合剤層に、１マスが２ｍｍ×２ｍｍの碁盤目状にカッターで切れ目を入れ、その部分に粘着テープを押し付けて剥がすことにより、負極合剤層が集電体から剥離する程度を調べて、負極合剤層と集電体との間の剥離強度を判断した。
<Adhesion strength evaluation between negative electrode mixture layer and current collector>
Prepare the same negative electrode as the negative electrode used for each of the nonaqueous electrolyte secondary batteries of Examples and Comparative Examples, and cut each of the negative electrode mixture layers with a cutter into a grid of 2 mm × 2 mm, The extent to which the negative electrode mixture layer was peeled from the current collector was examined by pressing and peeling the adhesive tape on that portion, and the peel strength between the negative electrode mixture layer and the current collector was judged.
負極合剤層と集電体との間の剥離強度が大きいものは、粘着テープを剥がしたときの集電体の露出部分が小さくなる。よって、本評価では、碁盤目状のマス目での集電体の剥離面積が３０％未満の場合を◎、同剥離面積が３０％以上５０％未満の場合を○、同剥離面積が５０％以上の場合を×として分類した。 In the case where the peel strength between the negative electrode mixture layer and the current collector is large, the exposed portion of the current collector becomes smaller when the adhesive tape is peeled off. Therefore, in this evaluation, the case where the peeled area of the current collector in the grid pattern is less than 30% is ◎, the case where the peeled area is 30% or more and less than 50% is ○, and the peeled area is 50%. The above cases were classified as x.
＜非水電解液二次電池の充放電による負極の厚み変化量の測定＞
実施例および比較例の各非水電解液二次電池について、前記の充放電サイクル特性評価時と同じ条件で３サイクルの充放電を行った。その後、各電池を分解して負極を取り出し、表面に付着している非水電解液を除去してから、ノギスを用いて負極の厚み（充放電後の負極の厚み）を測定した。そして、非水電解液二次電池の組み立て前に予めノギスを用いて測定しておいた負極の厚みと、充放電後の負極の厚みとの差から、電池の充放電による負極の厚み変化量を求めた。
<Measurement of change in thickness of negative electrode due to charging / discharging of non-aqueous electrolyte secondary battery>
About each nonaqueous electrolyte secondary battery of an Example and a comparative example, 3 cycles charge / discharge was performed on the same conditions as the time of the above-mentioned charge / discharge cycle characteristic evaluation. Thereafter, each battery was disassembled, the negative electrode was taken out, the non-aqueous electrolyte adhering to the surface was removed, and the thickness of the negative electrode (the thickness of the negative electrode after charge / discharge) was measured using calipers. Then, the amount of change in the thickness of the negative electrode due to charging / discharging of the battery is determined from the difference between the thickness of the negative electrode measured using a caliper in advance before assembling the non-aqueous electrolyte secondary battery and the thickness of the negative electrode after charging / discharging. Asked.
実施例および比較例の非水電解液二次電池に係る負極の構成を表１に示し、前記の各評価結果を表２および表３に示す。 The structure of the negative electrode concerning the nonaqueous electrolyte secondary battery of an Example and a comparative example is shown in Table 1, and each said evaluation result is shown in Table 2 and Table 3.
なお、表１の「ポリアクリル酸のアルカリ塩」の欄では塩の種類を示している。また、表１における「ＣＭＣおよびＰＶＡの比率」は、ポリアクリル酸のアルカリ塩を１００質量部としたときの比率（質量部）を意味している。更に、表１におけるバインダの「その他」の欄には、ポリアクリル酸のアルカリ塩、ＣＭＣおよびＰＶＡ以外のバインダを使用した場合の、その種類を示している。また、表３における「接着強度」は、負極合剤層と集電体との間の接着強度を意味しており、「充放電による負極の厚みの変化量」は、非水電解液二次電池の充放電による負極の厚み変化量を意味している。 In the column of “Alkali salt of polyacrylic acid” in Table 1, the type of salt is shown. Further, “the ratio of CMC and PVA” in Table 1 means the ratio (parts by mass) when the alkali salt of polyacrylic acid is 100 parts by mass. Furthermore, the “others” column of the binder in Table 1 shows the types of binders other than the alkali salt of polyacrylic acid, CMC, and PVA. “Adhesive strength” in Table 3 means the adhesive strength between the negative electrode mixture layer and the current collector, and “the amount of change in the thickness of the negative electrode due to charge and discharge” is the non-aqueous electrolyte secondary It means the amount of change in the thickness of the negative electrode due to charging / discharging of the battery.
表１および表２に示すように、負極合剤層のバインダにポリアクリル酸のアルカリ塩とＣＭＣまたはＰＶＡとを、適正な比率で使用した各実施例の非水電解液二次電池では、充放電サイクルの初期（２０サイクル目）および中期（１００サイクル目）において、容量の急激な低下が認められず、結果的に、５００サイクル経過時には、比較例４以外の比較例の電池に比べて１０％以上容量維持率が高くなり、優れた充放電サイクル特性を有していた。この結果は、負極活物質に黒鉛とＳｉＯとを使用したケースと、黒鉛とＳｉとを使用したケースでも同様であり、また、負極合剤層のバインダに、ポリアクリル酸のアルカリ塩、ＣＭＣおよびＰＶＡ以外のもの（負極合剤層の柔軟性を高め得るバインダ）を更に使用したケースでも同様であった。 As shown in Tables 1 and 2, in the non-aqueous electrolyte secondary battery of each example in which an alkali salt of polyacrylic acid and CMC or PVA were used in an appropriate ratio for the binder of the negative electrode mixture layer, In the initial stage (20th cycle) and middle stage (100th cycle) of the discharge cycle, no sudden decrease in capacity was observed. As a result, when 500 cycles had elapsed, the capacity was 10 times higher than that of comparative batteries other than Comparative Example 4. %, The capacity retention rate was high, and the battery had excellent charge / discharge cycle characteristics. This result is the same in the case where graphite and SiO are used as the negative electrode active material, and the case where graphite and Si are used. In addition, an alkali salt of polyacrylic acid, CMC and The same was true for cases in which a material other than PVA (a binder capable of enhancing the flexibility of the negative electrode mixture layer) was further used.
これに対し、負極合剤層のバインダにＣＭＣやＰＶＡを使用しなかった比較例１、５の電池、負極合剤層のバインダにポリアクリル酸のアルカリ塩を使用しなかった比較例２の電池、およびポリアクリル酸のアルカリ塩の使用量に対するＣＭＣの使用量が不適であった比較例３、４の電池では、前記の通り、実施例の電池よりも５００サイクル目の容量維持率が低く、充放電サイクル特性が劣っていた。 In contrast, the batteries of Comparative Examples 1 and 5 that did not use CMC or PVA as the binder of the negative electrode mixture layer, and the batteries of Comparative Example 2 that did not use polyacrylic acid alkali salt as the binder of the negative electrode mixture layer In the batteries of Comparative Examples 3 and 4 in which the amount of CMC used was inappropriate with respect to the amount of alkali salt of polyacrylic acid, as described above, the capacity maintenance rate at the 500th cycle was lower than that of the battery of Example, The charge / discharge cycle characteristics were inferior.
表３に示す通り、各実施例の非水電解液二次電池に使用した負極は、負極合剤層と集電体との間の接着強度が大きく、また、電池の充放電による厚みの変化量が比較的小さく、これらによって、非水電解液二次電池の充放電サイクル特性が良好に高められたと考えられる。 As shown in Table 3, the negative electrode used in the non-aqueous electrolyte secondary battery of each example has a large adhesive strength between the negative electrode mixture layer and the current collector, and changes in thickness due to charging / discharging of the battery. It is considered that the charge / discharge cycle characteristics of the non-aqueous electrolyte secondary battery were improved satisfactorily.
１ 非水電解液二次電池
２ 外装体
５ 正極
６ 負極
７ セパレータ
DESCRIPTION OF
Claims (3)
前記負極は、前記活物質およびバインダを含有する負極合剤層を、集電体の片面または両面に有しており、
前記負極合剤層は、前記バインダとして、ポリアクリル酸のナトリウム塩と、カルボキシメチルセルロースおよびポリビニルアルコールより選ばれる少なくとも１種とを含有しており、
ポリアクリル酸のナトリウム塩１００質量部に対し、カルボキシメチルセルロースおよびポリビニルアルコールより選ばれる少なくとも１種の比率が２０質量部以上８０質量部以下であり、
前記負極合剤層は、前記活物質として、黒鉛と、組成式ＳｉＯｘで表される材料（ただし、Ｓｉに対するＯの原子比ｘは０．５≦ｘ≦１．５である）、ＳｉまたはＳｉ合金とを含有していることを特徴とする非水電解液二次電池。 A non-aqueous electrolyte secondary comprising a positive electrode containing a transition metal composite oxide containing lithium as an active material, a negative electrode containing an active material capable of inserting and extracting lithium ions, a separator, and a non-aqueous electrolyte A battery,
The negative electrode has a negative electrode mixture layer containing the active material and a binder on one side or both sides of a current collector,
The negative electrode mixture layer contains, as the binder, a sodium salt of polyacrylic acid and at least one selected from carboxymethyl cellulose and polyvinyl alcohol,
The ratio of at least one selected from carboxymethyl cellulose and polyvinyl alcohol is 20 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the sodium salt of polyacrylic acid,
The negative electrode mixture layer includes, as the active material, graphite and a material represented by a composition formula SiO x (provided that the atomic ratio x of O to Si is 0.5 ≦ x ≦ 1.5), Si or A non-aqueous electrolyte secondary battery comprising a Si alloy.
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