JP2012028158A - Anode for nonaqueous electrolytic secondary battery and nonaqueous electrolytic secondary battery - Google Patents

Anode for nonaqueous electrolytic secondary battery and nonaqueous electrolytic secondary battery Download PDF

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JP2012028158A
JP2012028158A JP2010165465A JP2010165465A JP2012028158A JP 2012028158 A JP2012028158 A JP 2012028158A JP 2010165465 A JP2010165465 A JP 2010165465A JP 2010165465 A JP2010165465 A JP 2010165465A JP 2012028158 A JP2012028158 A JP 2012028158A
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positive electrode
secondary battery
mixture layer
electrolyte secondary
binder
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JP5639400B2 (en
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Hiroshi Hashimoto
裕志 橋本
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Hitachi Maxell Energy Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic secondary battery having a flat wound electrode body and offering a high reliability, a good productivity and an excellent load characteristic, and to provide an anode which allows the production of the nonaqueous electrolytic secondary battery.SOLUTION: The anode is used for a nonaqueous electrolytic secondary battery having a wound electrode body formed by putting an anode, a cathode and a separator together, and winding them together in a whirling pattern form, and shaping them in a flat form in cross section. The anode has anode mixture layers formed on either side of a current collector and including an anode active material, a conductive assistant and a binding agent. In the anode for a nonaqueous electrolytic secondary battery and the nonaqueous electrolytic secondary battery having the anode, if the tensile elasticity of the binding agent is represented by y(MPa), and the volume percentage of the binding agent in the anode mixture layer is represented by x(vol.%), x and y meet the conditional relation (y=-600x+z)[where 3.5≤x≤4.5, and 3300≤z≤4100], and the tensile strength of the current collector is 3.15 N/mm or larger.

Description

本発明は、扁平状の巻回電極体を有し、かつ信頼性が高く生産性が良好な非水電解質二次電池と、前記非水電解質二次電池を構成し得る正極に関するものである。   The present invention relates to a non-aqueous electrolyte secondary battery having a flat wound electrode body and having high reliability and good productivity, and a positive electrode capable of constituting the non-aqueous electrolyte secondary battery.

近年、携帯電話、ノート型パソコンなどのポータブル電子機器の発達や、電気自動車の実用化などに伴い、小型軽量で且つ高容量の非水電解質二次電池が必要とされるようになってきた。   In recent years, along with the development of portable electronic devices such as mobile phones and notebook computers, and the practical application of electric vehicles, small and light non-aqueous electrolyte secondary batteries have been required.

こうした小型化・軽量化を図った非水電解質二次電池としては、例えば、正極と負極とを、セパレータを介在させつつ重ね合わせて渦巻状に巻回し、更に横断面が扁平状になるように成形した扁平状巻回電極体を、角形（角筒形）の外装缶や金属ラミネートフィルムで構成されるラミネートフィルム外装体のような薄型の外装体内に収容した構造のものが挙げられる。   As such a non-aqueous electrolyte secondary battery that is reduced in size and weight, for example, a positive electrode and a negative electrode are overlapped with a separator interposed therebetween and wound into a spiral shape, and the cross section becomes flattened. The thing of the structure where the shape | molded flat wound electrode body was accommodated in the thin exterior body like the laminated film exterior body comprised with a square (square cylinder shape) exterior can and a metal laminate film is mentioned.

ところが、前記のような扁平状巻回電極体においては、その湾曲部（特に最内周の湾曲部）において、正極の合剤層（正極活物質を含む合剤層）に割れが生じやすく、これにより、製造した多数の電池の中に、前記の割れによって信頼性の低いものが含まれることで、電池の生産効率が低下するなどの虞がある。   However, in the flat wound electrode body as described above, in the curved portion (particularly the innermost curved portion), the positive electrode mixture layer (the mixture layer containing the positive electrode active material) is likely to crack, Thereby, there exists a possibility that the production efficiency of a battery may fall because a thing with low reliability is contained in many manufactured batteries by the said crack.

こうした事情を受けて、扁平状巻回電極体における正極の合剤層の割れによる短絡の発生を抑制する技術も開発されている（特許文献１）。特許文献１に開示の技術は、扁平状電極巻回体のうち、合剤層の割れが特に発生しやすい箇所を充放電反応に関与し得ないようにして、短絡の発生を抑制するものである。   Under such circumstances, a technique for suppressing the occurrence of a short circuit due to the crack of the positive electrode mixture layer in the flat wound electrode body has been developed (Patent Document 1). The technique disclosed in Patent Document 1 suppresses the occurrence of a short circuit by preventing a portion of the flat electrode wound body that is particularly susceptible to cracking of the mixture layer from being involved in the charge / discharge reaction. is there.

特開２００８−４１５８１号公報JP 2008-41581 A

特許文献１に記載の技術によれば、扁平状巻回電極体における正負極の合剤層の割れによる問題を回避可能であるが、前記の通り、その一部を充放電反応に関与し得ない構成としていることから、容量低下を回避し難い。   According to the technique described in Patent Document 1, it is possible to avoid the problem caused by the crack of the mixture layer of the positive and negative electrodes in the flat wound electrode body, but as described above, a part thereof can be involved in the charge / discharge reaction. It is difficult to avoid a decrease in capacity because it has no configuration.

特許文献１では、信頼性を高めつつ容量低下も極力抑える技術も提案しており、これにより良好な結果を得ているが、その一方で、電極体の一部に充放電反応に関与し得ない部分を積極的に形成する以外の方法によって、扁平状巻回電極体の抱える前記の問題を回避する技術の開発要請もある。   Patent Document 1 also proposes a technique for minimizing the decrease in capacity while increasing the reliability, and has obtained good results. On the other hand, a part of the electrode body can be involved in the charge / discharge reaction. There is also a request for development of a technique for avoiding the above-described problem of the flat wound electrode body by a method other than positively forming a non-existing portion.

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、扁平状の巻回電極体を有し、かつ信頼性が高く生産性が良好で、負荷特性にも優れた非水電解質二次電池と、前記非水電解質二次電池を構成し得る正極を提供することにある。   The present invention has been made in view of the above circumstances, and the object thereof is a nonaqueous electrolyte having a flat wound electrode body, having high reliability, good productivity, and excellent load characteristics. It is providing the positive electrode which can comprise a secondary battery and the said nonaqueous electrolyte secondary battery.

前記目的を達成し得た本発明の非水電解質二次電池用正極は、正極、負極およびセパレータを重ねて渦巻状に巻回し、横断面を扁平状にした巻回電極体を有する電池に使用されるものであって、金属製の集電体と、前記集電体の両面に形成された、正極活物質、導電助剤および結着剤を含有する正極合剤層とを有しており、前記結着剤の引張弾性率をｙ（ＭＰａ）、前記正極合剤層の構成成分の全体積中における前記結着剤の体積割合をｘ（体積％）としたとき、前記ｘと前記ｙとが、下記式（１）
ｙ＝−６００ｘ＋ｚ （１）
［ただし、前記式（１）中、３．５≦ｘ≦４．５であり、かつ３３００≦ｚ≦４１００である］
で表される関係を満たし、前記集電体の引張強度が、３．１５Ｎ／ｍｍ以上であることを特徴とするものである。 The positive electrode for a non-aqueous electrolyte secondary battery of the present invention that can achieve the above object is used for a battery having a wound electrode body in which a positive electrode, a negative electrode, and a separator are wound in a spiral shape and the cross section is flattened. A current collector made of metal and a positive electrode mixture layer formed on both surfaces of the current collector and containing a positive electrode active material, a conductive additive and a binder. X and y when the tensile modulus of the binder is y (MPa) and the volume ratio of the binder in the total volume of the constituents of the positive electrode mixture layer is x (volume%). And the following formula (1)
y = −600x + z (1)
[In the formula (1), 3.5 ≦ x ≦ 4.5 and 3300 ≦ z ≦ 4100]
And the current collector has a tensile strength of 3.15 N / mm or more.

また、本発明の非水電解質二次電池は、正極、負極およびセパレータを重ねて渦巻状に巻回し、横断面を扁平状にした巻回電極体を有するものであって、前記正極が、本発明の非水電解質二次電池用正極であることを特徴とするものである。   The non-aqueous electrolyte secondary battery of the present invention has a wound electrode body in which a positive electrode, a negative electrode, and a separator are overlapped and wound in a spiral shape, and the cross section is flattened. It is a positive electrode for non-aqueous electrolyte secondary batteries of the invention.

本発明によれば、扁平状の巻回電極体を有し、かつ信頼性が高く生産性が良好で、負荷特性にも優れた非水電解質二次電池と、前記非水電解質二次電池を構成し得る正極を提供することができる。   According to the present invention, a nonaqueous electrolyte secondary battery having a flat wound electrode body, having high reliability and good productivity, and excellent load characteristics, and the nonaqueous electrolyte secondary battery are provided. The positive electrode which can be comprised can be provided.

本発明の非水電解質二次電池の一例を模式的に示す図で、（ａ）はその平面図、（ｂ）はその部分縦断面図である。It is a figure which shows typically an example of the nonaqueous electrolyte secondary battery of this invention, (a) is the top view, (b) is the fragmentary longitudinal cross-sectional view. 図１に示す非水電解質二次電池の斜視図である。It is a perspective view of the nonaqueous electrolyte secondary battery shown in FIG. 実施例および比較例の非水電解質二次電池に用いた正極について、結着剤の引張弾性率と、正極合剤層の構成成分の全体積中における結着剤の体積割合との関係を表すグラフである。About the positive electrode used for the nonaqueous electrolyte secondary battery of an Example and a comparative example, the relationship between the tensile elasticity modulus of a binder and the volume ratio of the binder in the whole volume of the component of a positive mix layer is represented. It is a graph. 実施例および比較例の非水電解質二次電池に用いた正極における正極合剤層と集電体との剥離強度の測定方法の説明図である。It is explanatory drawing of the measuring method of the peeling strength of the positive mix layer and collector in the positive electrode used for the nonaqueous electrolyte secondary battery of an Example and a comparative example.

本発明の非水電解質二次電池用正極は、正極活物質、導電助剤および結着剤を含有する正極合剤層を、金属製の集電体の両面に形成した構造を有するものである。   The positive electrode for a non-aqueous electrolyte secondary battery of the present invention has a structure in which a positive electrode mixture layer containing a positive electrode active material, a conductive additive and a binder is formed on both surfaces of a metal current collector. .

本発明の正極に係る集電体は、引張強さが３．１５Ｎ／ｍｍ以上のものであり、これにより、本発明の正極が使用される扁平状巻回電極体内において、集電体の破れなどの発生を抑えることができる。前記集電体の引張強さは、３．１５Ｎ／ｍｍ以上であることが好ましく、また、４．５０Ｎ／ｍｍ以下であることが好ましい。   The current collector according to the positive electrode of the present invention has a tensile strength of 3.15 N / mm or more, whereby the current collector is broken in the flat wound electrode body in which the positive electrode of the present invention is used. Etc. can be suppressed. The current collector has a tensile strength of preferably 3.15 N / mm or more, and preferably 4.50 N / mm or less.

なお、本明細書でいう集電体の引張強さは、前処理として集電体を１５ｍｍ×２５０ｍｍの矩形に切り出して試験片とし、この試験片をチャック間距離１００ｍｍとして引張り試験機（今田製作所社製「ＳＤＴ−５２型」）を用いて、クロスヘッド速度１０ｍｍ／分で試験を行って得られた値である。   The tensile strength of the current collector referred to in this specification is a pre-treatment where the current collector is cut into a 15 mm × 250 mm rectangle to form a test piece, and this test piece has a distance between chucks of 100 mm. It is a value obtained by conducting a test at a crosshead speed of 10 mm / min using a “SDT-52 type” manufactured by the company.

前記のような引張強度を有する集電体としては、例えば、以下のものが挙げられる。   Examples of the current collector having the tensile strength as described above include the following.

正極に係る集電体の材質としては、主成分をアルミニウムとしたアルミニウム合金が望ましい。アルミニウム合金はアルミニウムの純度が９５．５５質量％以上あり、その他の添加物として、例えばＳｉ≦０．６質量％、Ｆｅ≦０．７質量％、Ｃｕ≦０．２５質量％、Ｍｎ≦１．５質量％、Ｍｇ≦１．３質量％、Ｚｎ≦０．２５質量％を含有することが望ましい。このような材質で構成された箔、フィルムを集電体として使用することができる。   The material of the current collector for the positive electrode is preferably an aluminum alloy whose main component is aluminum. The aluminum alloy has an aluminum purity of 95.55% by mass or more. As other additives, for example, Si ≦ 0.6% by mass, Fe ≦ 0.7% by mass, Cu ≦ 0.25% by mass, Mn ≦ 1. It is desirable to contain 5% by mass, Mg ≦ 1.3% by mass, and Zn ≦ 0.25% by mass. A foil or film made of such a material can be used as a current collector.

正極に係る集電体は、薄すぎると前記の引張強度を確保し難くなることから、その厚みは、８μｍ以上であることが好ましく、１２μｍ以上であることがより好ましい。ただし、正極に係る集電体が厚すぎると、これを用いた電池のエネルギー密度が低下する虞があることから、その厚みは、２０μｍ以下であることが好ましく、１５μｍ以下であることがより好ましい。   If the current collector according to the positive electrode is too thin, it is difficult to ensure the tensile strength. Therefore, the thickness is preferably 8 μm or more, and more preferably 12 μm or more. However, if the current collector associated with the positive electrode is too thick, the energy density of a battery using the current collector may be reduced. Therefore, the thickness is preferably 20 μm or less, and more preferably 15 μm or less. .

本発明の正極は、正極合剤層の含有する結着剤の引張弾性率ｙ（ＭＰａ）と、正極合剤層の構成成分の全体積中における結着剤の体積割合ｘ（体積％）とが、前記式（１）で表される関係を満たしている。これにより、前記の引張強度を有する集電体を備えつつ、扁平形巻回電極体内における正極合剤層の割れを抑制し得るだけの強度と、扁平形巻回電極体の形状を良好にし得るだけの柔軟性とを確保することができ、更に、扁平形巻回電極体内における正極合剤層からの正極活物質や導電助剤の脱落の抑制と、この扁平形巻回電極体が使用される電池（本発明の非水電解質二次電池）の負荷特性向上とを図ることができる。   The positive electrode of the present invention includes the tensile modulus y (MPa) of the binder contained in the positive electrode mixture layer, the volume ratio x (volume%) of the binder in the total volume of the constituent components of the positive electrode mixture layer, and Satisfies the relationship represented by the formula (1). As a result, while having the current collector having the tensile strength, the strength sufficient to suppress the cracking of the positive electrode mixture layer in the flat wound electrode body and the shape of the flat wound electrode body can be improved. In addition, it is possible to ensure the flexibility of the flat wound electrode body, and further, the positive electrode active material and the conductive auxiliary agent are prevented from dropping from the positive electrode mixture layer in the flat wound electrode body, and this flat wound electrode body is used. The load characteristics of the battery (nonaqueous electrolyte secondary battery of the present invention) can be improved.

本発明の正極では、前記式（１）におけるｙ切片ｚを、３３００以上、好ましくは３４００以上とする。これにより、正極合剤層の柔軟性を高めて、この正極が使用される扁平形巻回電極体の形状を良好にすることができる。すなわち、前記ｚの値が小さすぎると、正極合剤層の柔軟性が低下して、この正極が使用される扁平形巻回電極体の横断面（巻回軸方向に垂直な断面）の形状を良好な楕円形状にすることができず、例えば、横断面における長軸方向の両端が曲線とならずにコの字状のように角が生じやすくなる。このような形状の扁平形巻回電極体は、外装体（特に角筒形の外装缶）に挿入し難いため、電池の生産性を損なってしまう。   In the positive electrode of the present invention, the y-intercept z in the formula (1) is 3300 or more, preferably 3400 or more. Thereby, the softness | flexibility of a positive mix layer can be improved and the shape of the flat winding electrode body in which this positive electrode is used can be made favorable. That is, when the value of z is too small, the flexibility of the positive electrode mixture layer is lowered, and the shape of the cross section (cross section perpendicular to the winding axis direction) of the flat wound electrode body in which the positive electrode is used. Cannot be made into a good elliptical shape, for example, both ends in the long axis direction in the cross section are not curved and a corner is likely to be formed like a U-shape. Since the flat wound electrode body having such a shape is difficult to insert into an exterior body (particularly, a rectangular tube-shaped exterior can), the productivity of the battery is impaired.

また、本発明の正極では、前記式（１）におけるｙ切片ｚを、４１００以下、好ましくは４０００以下とする。これにより、正極合剤層の強度を高めて、この正極が使用される扁平形巻回電極体内における正極合剤層の割れなどの欠陥の発生を抑制できる。   In the positive electrode of the present invention, the y-intercept z in the formula (1) is 4100 or less, preferably 4000 or less. Thereby, the intensity | strength of a positive mix layer can be raised and generation | occurrence | production of defects, such as a crack of the positive mix layer, in the flat wound electrode body in which this positive electrode is used can be suppressed.

正極合剤層の構成成分の全体積（正極合剤層が空孔を有している場合には、その空孔部分の体積を除く体積）中における結着剤の体積割合ｘは、正極合剤層における正極活物質や導電助剤を良好に結着できるようにして、これらの正極合剤層からの脱離を防止し、この正極が用いられる電池の信頼性を高める観点から、３．５体積％以上、好ましくは３．６体積％以上である。なお、結着剤の体積割合ｘが大きすぎると、この正極が用いられる電池における負荷特性（特に低温での負荷特性）が低下する虞があることから、結着剤の体積割合ｘは、４．５体積％以下、好ましくは４．４体積％以下である。   The volume ratio x of the binder in the total volume of the components of the positive electrode mixture layer (the volume excluding the volume of the hole portion when the positive electrode mixture layer has holes) 2. From the viewpoint of improving the reliability of the battery in which the positive electrode is used by preventing the detachment from the positive electrode mixture layer by allowing the positive electrode active material and the conductive additive in the agent layer to be satisfactorily bound. It is 5 volume% or more, preferably 3.6 volume% or more. If the volume ratio x of the binder is too large, load characteristics (particularly load characteristics at a low temperature) in a battery in which the positive electrode is used may be lowered. Therefore, the volume ratio x of the binder is 4 .5% by volume or less, preferably 4.4% by volume or less.

なお、本明細書でいう結着剤の引張弾性率ｙは、前処理として結着剤をＮ−メチル−２−ピロリドン（ＮＭＰ）に溶解または分散させて１２質量％濃度の溶液または分散液を調製し、得られた液をステンレス鋼製の容器にキャストし、１２０℃で４０分間乾燥して厚さ３０μｍのフィルムを作製し、このフィルムを１００ｍｍ×５ｍｍの矩形に切り出して試験片とし、この試験片をチャック間距離５０ｍｍで引張り試験機（今田製作所社製「ＳＤＴ−５２型」）を用いて、クロスヘッド速度１００ｍｍ／分で試験を行って得られた値である。   The tensile modulus y of the binder referred to in the present specification is obtained by dissolving or dispersing the binder in N-methyl-2-pyrrolidone (NMP) as a pretreatment to obtain a 12% by mass solution or dispersion. The prepared liquid was cast into a stainless steel container and dried at 120 ° C. for 40 minutes to produce a 30 μm thick film. This film was cut into a 100 mm × 5 mm rectangle to form a test piece. It is a value obtained by testing a test piece at a crosshead speed of 100 mm / min using a tensile tester (“SDT-52 type” manufactured by Imada Seisakusho) with a distance between chucks of 50 mm.

正極に係る正極合剤層に使用する結着剤には、従来から知られている非水電解質二次電池の正極に係る正極合剤層に使用されている結着剤の中から、前記式（１）の関係を満足する引張弾性率を有するものを選択して使用することができる。なお、詳しくは後述するが、本発明の正極を製造するにあたっては、正極活物質、導電助剤および結着剤などを含有する正極合剤をＮＭＰなどの有機溶剤に分散（結着剤は溶解していてもよい）させて調製した正極合剤含有組成物を用いた製法が通常採用される。よって、本発明の正極に用いる結着剤としては、ＮＭＰなどの有機溶剤に溶解または分散可能なポリマー（ゴムを含む）が好ましい。   In the binder used for the positive electrode mixture layer related to the positive electrode, the above formula is selected from the binders used for the positive electrode mixture layer related to the positive electrode of the conventionally known non-aqueous electrolyte secondary battery. Those having a tensile elastic modulus satisfying the relationship (1) can be selected and used. As will be described in detail later, in the production of the positive electrode of the present invention, a positive electrode mixture containing a positive electrode active material, a conductive additive and a binder is dispersed in an organic solvent such as NMP (the binder is dissolved). A manufacturing method using a positive electrode mixture-containing composition prepared in a conventional manner is usually employed. Therefore, as the binder used in the positive electrode of the present invention, a polymer (including rubber) that can be dissolved or dispersed in an organic solvent such as NMP is preferable.

結着剤として好適な、ＮＭＰなどの有機溶剤に溶解または分散可能なゴムの具体例としては、ポリ１，３−ブタジエン、ポリイソプレン、イソプレン−イソブチレンコポリマー、天然ゴム、スチレン−１，３−ブタジエンコポリマー（ＳＢＲ）、スチレン−イソプレンコポリマー、１，３−ブタジエン−イソプレン−アクリロニトリルコポリマー、スチレン−１，３−ブタジエン−イソプレンコポリマー、１，３−ブタジエン−アクリロニトリルコポリマー、スチレン−アクリロニトリル−１，３−ブタジエン−メタクリル酸メチルコポリマー、スチレン−アクリロニトリル−１，３−ブタジエン−イタコン酸コポリマー、スチレン−アクリロニトリル−１，３−ブタジエン−メタクリル酸メチル−フマル酸コポリマー、スチレン−１，３−ブタジエン−イタコン酸−メタクリル酸メチル−アクリロニトリルコポリマー、アクリロニトリル−１，３−ブタジエン−メタクリル酸−メタクリル酸メチルコポリマー、１，３−ブタジエン−スチレン−メタクリル酸メチルコポリマー、スチレン−１，３−ブタジエン−イタコン酸−メタクリル酸メチル−アクリロニトリルコポリマー、スチレン−アクリロニトリル−１，３−ブタジエン−メタクリル酸メチル−フマル酸コポリマーなどのジエン系ゴム；エチレン−プロピレンコポリマー、エチレン−プロピレン−ジエンコポリマーなどのオレフィン系ゴム；スチレン−エチレン−ブタジエンコポリマー、スチレン−ブタジエン−プロピレンコポリマー、スチレン−アクリル酸ｎ−ブチル−イタコン酸−メタクリル酸メチル−アクリロニトリルコポリマー、スチレン−アクリル酸ｎ−ブチル−イタコン酸−メタクリル酸メチル−アクリロニトリルコポリマーなどのスチレン系ゴム；などが挙げられる。   Specific examples of rubbers that can be dissolved or dispersed in organic solvents such as NMP, which are suitable as binders, include poly 1,3-butadiene, polyisoprene, isoprene-isobutylene copolymers, natural rubber, styrene-1,3-butadiene. Copolymer (SBR), styrene-isoprene copolymer, 1,3-butadiene-isoprene-acrylonitrile copolymer, styrene-1,3-butadiene-isoprene copolymer, 1,3-butadiene-acrylonitrile copolymer, styrene-acrylonitrile-1,3-butadiene Methyl methacrylate copolymer, styrene-acrylonitrile-1,3-butadiene-itaconic acid copolymer, styrene-acrylonitrile-1,3-butadiene-methyl methacrylate-fumaric acid copolymer, styrene-1,3- Tadiene-itaconic acid-methyl methacrylate-acrylonitrile copolymer, acrylonitrile-1,3-butadiene-methacrylic acid-methyl methacrylate copolymer, 1,3-butadiene-styrene-methyl methacrylate copolymer, styrene-1,3-butadiene-itacon Diene rubber such as acid-methyl methacrylate-acrylonitrile copolymer, styrene-acrylonitrile-1,3-butadiene-methyl methacrylate-fumaric acid copolymer; Olefin rubber such as ethylene-propylene copolymer, ethylene-propylene-diene copolymer; styrene Ethylene-butadiene copolymer, styrene-butadiene-propylene copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonite And the like; Rukoporima, styrene - acrylate n- butyl - itaconic acid - - Methyl methacrylate styrene rubbers such as acrylonitrile copolymer.

また、正極合剤層の結着剤には、前記のゴム以外の結着剤を使用することもできる。ＮＭＰなどの有機溶剤に溶解または分散可能なゴム以外のポリマーとしては、例えば、ポリエチレン、ポリプロピレン、エチレン−ビニルアセテートコポリマー、エチレン系アイオノマー、ポリビニルアルコール、エチレン−ビニルアルコールコポリマー、塩素化ポリエチレン、クロロスルホン化ポリエチレンなどオレフィン系ポリマー；ポリメチルメタクリレート、ポリメチルアクリレート、ポリエチルアクリレート、ポリブチルアクリレート、アクリレート−アクリロニトリルコポリマー、アクリル酸２−エチルヘキシル−アクリル酸メチル−アクリル酸−メトキシポリエチレングリコールモノメタクリレート、ポリアクリル酸、ポリメタクリル酸、ポリアクリルアミド、ポリ−Ｎ−イソプロピルアクリルアミド、ポリ−Ｎ，Ｎ−ジメチルアクリルアミドなどの（メタ）アクリル系ポリマー；ポリアミド６、ポリアミド６６、ポリアミド１１、ポリアミド１２、芳香族ポリアミド、ポリイミドなどのポリアミド系およびポリイミド系ポリマー；ポリエチレンテレフタレート、ポリブチレンテレフタレートなどのエステル系ポリマー；ポリビニリデンフルオライド（ＰＶＤＦ）、ポリテトラフルオロエチレン、ポリヘキサフルオロプロピレン、ビニリデンフルオライド−ヘキサフルオロプロピレン（ＶＤＦ−ＨＦＰ）コポリマー、ビニリデンフルオライド−ヘキサフルオロプロピレン−テトラフルオロエチレン（ＶＤＦ−ＨＦＰ−ＴＦＥ）コポリマー、ビニリデンフルオライド−ペンタフルオロプロピレン（ＶＤＦ−ＰＦＰ）コポリマー、ビニリデンフルオライド−ペンタフルオロプロピレン−テトラフルオロエチレン（ＶＤＦ−ＰＦＰ−ＴＦＥ）コポリマー、ビニリデンフルオライド−パーフルオロメチルビニルエーテル−テトラフルオロエチレン（ＶＤＦ−ＰＦＭＶＥ−ＴＦＥ）コポリマー、ビニリデンフルオライド−クロロトリフルオロエチレン（ＶＤＦ−ＣＴＦＥ）コポリマーなどのフッ素系ポリマー；などが挙げられる。   In addition, a binder other than the rubber can be used as the binder of the positive electrode mixture layer. Examples of polymers other than rubber that can be dissolved or dispersed in an organic solvent such as NMP include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene ionomer, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, chlorinated polyethylene, and chlorosulfonated. Olefin polymers such as polyethylene; polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, acrylate-acrylonitrile copolymer, 2-ethylhexyl acrylate-methyl acrylate-acrylic acid-methoxy polyethylene glycol monomethacrylate, polyacrylic acid, Polymethacrylic acid, polyacrylamide, poly-N-isopropylacrylamide, poly-N, N-dimethyl (Meth) acrylic polymers such as acrylamide; polyamide-based and polyimide-based polymers such as polyamide 6, polyamide 66, polyamide 11, polyamide 12, aromatic polyamide, and polyimide; ester-based polymers such as polyethylene terephthalate and polybutylene terephthalate; polyvinylidene Fluoride (PVDF), polytetrafluoroethylene, polyhexafluoropropylene, vinylidene fluoride-hexafluoropropylene (VDF-HFP) copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene (VDF-HFP-TFE) copolymer, Vinylidene fluoride-pentafluoropropylene (VDF-PFP) copolymer, vinylidene fluoride-pentafluor Propylene-tetrafluoroethylene (VDF-PFP-TFE) copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene (VDF-PFMVE-TFE) copolymer, vinylidene fluoride-chlorotrifluoroethylene (VDF-CTFE) copolymer, etc. And the like.

また、ポリビニルピロリドン、ポリエチレンイミン、ポリオキシエチレン、ポリ（２−メトキシエトキシエチレン）、ポリ（３−モルフィニルエチレン）、ポリビニルスルホン酸なども、結着剤として用いることができる。更に、ポリスチレン−ポリブタジエンブロックコポリマー、スチレン−ブタジエン−スチレン・ブロックコポリマー、スチレン−エチレン−ブチレン−スチレン・ブロックコポリマー、スチレン−イソプレン・ブロックコポリマー、スチレン−エチレン−プロピレン−スチレン・ブロックコポリマーなどのブロックポリマーも結着剤として使用可能である。   In addition, polyvinylpyrrolidone, polyethyleneimine, polyoxyethylene, poly (2-methoxyethoxyethylene), poly (3-morphinylethylene), polyvinyl sulfonic acid, and the like can also be used as the binder. In addition, block polymers such as polystyrene-polybutadiene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-isoprene block copolymer, styrene-ethylene-propylene-styrene block copolymer are also available. It can be used as a binder.

なお、正極合剤層に係る結着剤は、その引張弾性率ｙが、２０００ＭＰａ以下であることが好ましく、また、６００ＭＰａ以上であることが好ましい。   In addition, it is preferable that the binder which concerns on a positive mix layer has the tensile elasticity modulus y 2000 MPa or less, and it is preferable that it is 600 MPa or more.

また、正極合剤層に係る結着剤には、その少なくとも一部にゴム（例えば、前記のゴム）を使用することが好ましい。ゴムは、それ以外のポリマーに比べて真密度や弾性率が小さいため、このゴムを結着剤の少なくとも一部に使用することで、正極合剤層における結着剤の体積割合ｘを前記の値の中でも比較的多くしつつ、前記式（１）を満たすようにできることから、正極合剤層での結着性をより高めて、正極活物質や導電助剤などの脱離をより良好に抑制できる正極とすることが可能となる。   Moreover, it is preferable to use rubber (for example, the above-mentioned rubber) for at least a part of the binder related to the positive electrode mixture layer. Since rubber has a smaller true density and elastic modulus than other polymers, by using this rubber as at least a part of the binder, the volume ratio x of the binder in the positive electrode mixture layer is set as described above. Since the above formula (1) can be satisfied while relatively increasing the value, the binding property in the positive electrode mixture layer can be further improved, and the desorption of the positive electrode active material and the conductive auxiliary agent can be improved. A positive electrode that can be suppressed can be obtained.

ただし、前記の通り、ゴムはその弾性率（引張弾性率）が小さいことから、正極合剤層の結着剤には、ゴムとポリフッ化ビニリデンとを併用することがより好ましく、これにより前記式（１）をより容易に満たすようにすることができる。   However, as described above, since rubber has a small elastic modulus (tensile elastic modulus), it is more preferable to use rubber and polyvinylidene fluoride in combination for the binder of the positive electrode mixture layer. It is possible to satisfy (1) more easily.

前記のゴムやその他のポリマーは、それぞれ先に例示したもののなかから、１種のみを使用してもよく、２種以上を併用してもよい。   Of the rubbers and other polymers described above, only one type may be used, or two or more types may be used in combination.

本発明の正極に係る正極活物質には、従来から知られている非水電解質二次電池用の正極活物質として使用されているもの、例えば、リチウムイオンを吸蔵・放出できる活物質が使用される。このような正極活物質の具体例としては、例えば、Ｌｉ１＋ｘＭＯ２（−０．１＜ｘ＜０．１、Ｍ：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、ＬｉＭＰＯ４（Ｍ：Ｃｏ、Ｎｉ、Ｍｎ、Ｆｅなど）で表されるオリビン型化合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−ｘＣｏｘ−ｙＡｌｙＯ２（０．１≦ｘ≦０．３、０．０１≦ｙ≦０．２）などの他、少なくともＣｏ、ＮｉおよびＭｎを含む酸化物（ＬｉＭｎ１／３Ｎｉ１／３Ｃｏ１／３Ｏ２、ＬｉＭｎ５／１２Ｎｉ５／１２Ｃｏ１／６Ｏ２、ＬｉＮｉ３／５Ｍｎ１／５Ｃｏ１／５Ｏ２など）などを例示することができる。 As the positive electrode active material according to the positive electrode of the present invention, a conventionally known positive electrode active material for a non-aqueous electrolyte secondary battery, for example, an active material capable of occluding and releasing lithium ions is used. The As a specific example of such a positive electrode active material, for example, a layered structure represented by Li 1 + x MO 2 (−0.1 <x <0.1, M: Co, Ni, Mn, Al, Mg, etc.) Lithium-containing transition metal oxide, LiMn 2 O 4 and spinel-structured lithium manganese oxide obtained by substituting some of its elements with other elements, LiMPO 4 (M: Co, Ni, Mn, Fe, etc.) Type compounds. Specific examples of the lithium-containing transition metal oxide having a layered structure include LiCoO 2 and LiNi 1-x Co xy Al y O 2 (0.1 ≦ x ≦ 0.3, 0.01 ≦ y ≦ 0. 2) and other oxides containing at least Co, Ni and Mn (LiMn 1/3 Ni 1/3 Co 1/3 O 2 , LiMn 5/12 Ni 5/12 Co 1/6 O 2 , LiNi 3 / 5 Mn 1/5 Co 1/5 O 2 etc.).

なお、正極活物質は、その比表面積が、０．２ｍ２／ｇ以上であることが好ましく、０．３ｍ２／ｇ以上であることがより好ましく、また、０．６ｍ２／ｇ以下であることが好ましく、０．４ｍ２／ｇ以下であることがより好ましい。このような形態の正極活物質を使用することで、正極が使用される電池の負荷特性などをより高めることが可能となる。 The positive electrode active material has a specific surface area of preferably 0.2 m 2 / g or more, more preferably 0.3 m 2 / g or more, and 0.6 m 2 / g or less. It is preferable that it is 0.4 m 2 / g or less. By using the positive electrode active material in such a form, it becomes possible to further improve the load characteristics of a battery in which the positive electrode is used.

本明細書でいう正極合剤層の比表面積は、Ｎ２ガス吸着を利用した１点式のＢＥＴ測定装置（マウンテック社製「Ｍａｃｓｏｒｂ ＨＭ−１２０１」）を用いて、前処理として、Ｎ２ガスフロー中、１５０℃の環境下で１時間保持した後に測定することにより得られる値である。 The specific surface area of the positive electrode mixture layer referred to herein, using N 2 1-point BET measurement apparatus using a gas adsorbing (Mountech Co. "Macsorb HM-1201"), as a pretreatment, N 2 gas It is a value obtained by measuring after holding for 1 hour in an environment of 150 ° C. during the flow.

本発明の正極に係る導電助剤には、例えば、天然黒鉛（鱗片状黒鉛など）、人造黒鉛などのグラファイト類；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−ボンブラック類；炭素繊維；などの炭素材料を用いることが好ましく、また、金属繊維などの導電性繊維類；フッ化カーボン；アルミニウムなどの金属粉末類；酸化亜鉛；チタン酸カリウムなどの導電性ウィスカー類；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などの有機導電性材料；などを用いることもできる。   Examples of the conductive additive according to the positive electrode of the present invention include graphites such as natural graphite (eg, flaky graphite) and artificial graphite; acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and the like. It is preferable to use carbon materials such as carbon blacks; carbon fibers; and conductive fibers such as metal fibers; carbon fluorides; metal powders such as aluminum; zinc oxide; Conductive whiskers; conductive metal oxides such as titanium oxide; organic conductive materials such as polyphenylene derivatives; and the like can also be used.

正極を作製するにあたっては、前記の正極活物質、導電助剤および結着剤などを含む正極合剤を、ＮＭＰなどの溶剤を用いて均一に分散させたペースト状やスラリー状の組成物を調製し（結着剤は溶剤に溶解していてもよい）、この組成物を正極集電体表面に塗布して乾燥し、必要に応じてプレス処理により正極合剤層の厚みや密度を調整する方法が採用できる。ただし、本発明の正極の作製方法は前記の方法に限られず、他の方法を採用しても構わない。   In producing the positive electrode, a paste-like or slurry-like composition is prepared by uniformly dispersing the positive electrode mixture containing the positive electrode active material, the conductive additive and the binder using a solvent such as NMP. (The binder may be dissolved in a solvent), this composition is applied to the surface of the positive electrode current collector and dried, and the thickness and density of the positive electrode mixture layer are adjusted by pressing as necessary. The method can be adopted. However, the method for producing the positive electrode of the present invention is not limited to the above method, and other methods may be adopted.

正極における正極合剤層の厚みは、片面あたり、３０〜８０μｍであることが好ましい。また、正極合剤層においては、より高容量とする観点から、充填率が７５％以上であることが好ましい。ただし、正極合剤層の充填率が高すぎると、正極合剤層中の空孔が少なくなりすぎて、正極合剤層中への非水電解質（非水電解液）の浸透性が低下する虞があることから、その充填率は、８３％以下であることが好ましい。なお、正極合剤層の充填率は、下記式により求められる。   The thickness of the positive electrode mixture layer in the positive electrode is preferably 30 to 80 μm per side. In the positive electrode mixture layer, the filling rate is preferably 75% or more from the viewpoint of higher capacity. However, when the filling rate of the positive electrode mixture layer is too high, the number of pores in the positive electrode mixture layer becomes too small, and the permeability of the nonaqueous electrolyte (nonaqueous electrolyte solution) into the positive electrode mixture layer decreases. Since there exists a possibility, it is preferable that the filling rate is 83% or less. In addition, the filling rate of a positive mix layer is calculated | required by a following formula.

充填率（％） ＝ １００×（正極合剤層の実密度／正極合剤層の理論密度）     Filling rate (%) = 100 × (actual density of positive electrode mixture layer / theoretical density of positive electrode mixture layer)

なお、正極合剤層の充填率を算出するための前記式における「正極合剤層の理論密度」とは、正極合剤層の各構成成分の密度と含有量とから算出される密度（正極合剤層中に空孔が存在しないものとして求めた密度）であり、「正極合剤層の実密度」とは、以下の方法により測定されるものである。まず、正極を１ｃｍ×１ｃｍの大きさに切り取り、マイクロメータで厚み（ｌ１）を、精密天秤で質量（ｍ１）を測定する。次に、正極合剤層を削り取り、集電体のみを取り出して、その集電体の厚み（ｌｃ）と質量（ｍｃ）を正極と同様に測定する。得られた厚みと質量から、以下の式によって正極合剤層の実密度（ｄｃａ）を求める（なお、前記の厚みの単位はｃｍ、質量の単位はｇである）。
ｄｃａ＝（ｍ１−ｍｃ）／（ｌ１−ｌｃ） The “theoretical density of the positive electrode mixture layer” in the above formula for calculating the filling rate of the positive electrode mixture layer is the density calculated from the density and content of each component of the positive electrode mixture layer (positive electrode The density obtained by assuming that there are no pores in the mixture layer), and the “actual density of the positive electrode mixture layer” is measured by the following method. First, it cuts a positive electrode to a size of 1 cm × 1 cm, a thickness micrometer (l 1), measuring the mass (m 1) a precision balance. Next, we scraped off the positive electrode mixture layer, and extract only the collector, measuring the thickness of the current collector (l c) mass (m c) in the same manner as the positive electrode. From the obtained thickness and mass, the actual density (d ca ) of the positive electrode mixture layer is determined by the following formula ( note that the unit of thickness is cm and the unit of mass is g).
d ca = (m 1 −m c ) / (l 1 −l c )

正極合剤層における結着剤以外の各成分の含有量は、正極活物質が９４〜９８質量％であることが好ましく、導電助剤が１〜４質量％であることが好ましい。   The content of each component other than the binder in the positive electrode mixture layer is preferably 94 to 98% by mass of the positive electrode active material, and preferably 1 to 4% by mass of the conductive assistant.

また、正極合剤層の比表面積は、０．９ｍ２／ｇ以上であることが好ましく、１．０ｍ２／ｇ以上であることがより好ましく、また、１．５ｍ２／ｇ以下であることが好ましく、１．２ｍ２／ｇ以下であることがより好ましい。正極合剤層の比表面積をこのような値とすることで、正極の折り曲げ強度（実施例において詳述する）を高めることができるため、扁平状巻回電極体内における正極合剤層の割れなどの発生を更に抑制することが可能となる。 The specific surface area of the positive electrode mixture layer is preferably 0.9 m 2 / g or more, more preferably 1.0 m 2 / g or more, and 1.5 m 2 / g or less. Is more preferable, and 1.2 m 2 / g or less is more preferable. By setting the specific surface area of the positive electrode mixture layer to such a value, the bending strength of the positive electrode (described in detail in the examples) can be increased, so that the positive electrode mixture layer cracks in the flat wound electrode body, etc. Can be further suppressed.

本明細書でいう正極合剤層の比表面積は、前処理として、正極から約５ｍｍ×３０ｍｍ×１３〜１６枚切り出し、その質量を秤量後、試料管に封入した後、高精度全自動ガス吸着装置（ＢＥＴ測定装置、日本ベル株式会社製「ＢＥＬＳＯＲＰ３６」）を用いて、室温で真空脱気後、液体窒素（７７Ｋ）におけるＮ２ガスの吸着等温線を測定し、得られた等温線をＢＥＴ多点法で解析することで得られる値である。 The specific surface area of the positive electrode mixture layer referred to in the present specification is about 5 mm × 30 mm × 13 to 16 pieces cut out from the positive electrode as a pretreatment, weighed its mass, sealed in a sample tube, and then highly accurate fully automatic gas adsorption. Using a device (BET measuring device, “BELSORP36” manufactured by Nippon Bell Co., Ltd.) after vacuum degassing at room temperature, the adsorption isotherm of N 2 gas in liquid nitrogen (77K) was measured, and the obtained isotherm was BET It is a value obtained by analyzing by the multipoint method.

本発明の非水電解質二次電池は、前記本発明の正極を有する扁平状巻回電極体を有していればよく、その他の構成および構造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に採用されている各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 only needs to have the flat wound electrode body having the positive electrode of the present invention, and there is no particular limitation on the other configuration and structure, and it has been conventionally known. Each structure and structure employed in the nonaqueous electrolyte secondary battery can be applied.

負極としては、例えば、負極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形成したものが挙げられる。負極合剤層は、負極活物質の他に、結着剤や、必要に応じて導電助剤を含有しており、例えば、負極活物質および結着剤（更には導電助剤）などを含む混合物（負極合剤）に、適当な溶剤を加えて十分に混練して得られる負極合剤含有組成物（スラリーなど）を、集電体表面に塗布し乾燥することで、所望の厚みとしつつ形成することができる。   As a negative electrode, what formed the negative mix layer containing a negative electrode active material in the single side | surface or both surfaces of a collector is mentioned, for example. The negative electrode mixture layer contains, in addition to the negative electrode active material, a binder and, if necessary, a conductive aid, and includes, for example, a negative electrode active material and a binder (further, a conductive aid). A negative electrode mixture-containing composition (slurry etc.) obtained by adding a suitable solvent to the mixture (negative electrode mixture) and kneading thoroughly is applied to the surface of the current collector and dried to obtain a desired thickness. Can be formed.

負極活物質としては、例えば、天然黒鉛（鱗片状黒鉛）、人造黒鉛、膨張黒鉛などの黒鉛材料；ピッチをか焼して得られるコークスなどの易黒鉛化性炭素質材料；フルフリルアルコール樹脂（ＰＦＡ）やポリパラフェニレン（ＰＰＰ）およびフェノール樹脂を低温焼成して得られる非晶質炭素などの難黒鉛化性炭素質材料；などの炭素材料が挙げられる。また、炭素材料の他に、リチウムやリチウム含有化合物も負極活物質として用いることができる。リチウム含有化合物としては、Ｌｉ−Ａｌなどのリチウム合金や、Ｓｉ、Ｓｎなどのリチウムとの合金化が可能な元素を含む合金が挙げられる。更にＳｎ酸化物やＳｉ酸化物などの酸化物系材料も用いることができる。負極合剤全量中における負極活物質量は、例えば、９７〜９９質量％であることが好ましい。   Examples of the negative electrode active material include graphite materials such as natural graphite (flaky graphite), artificial graphite, and expanded graphite; graphitizable carbonaceous materials such as coke obtained by calcining pitch; furfuryl alcohol resin ( Carbon materials such as non-graphitizable carbonaceous materials such as amorphous carbon obtained by low-temperature firing of PFA), polyparaphenylene (PPP), and phenol resins. In addition to the carbon material, lithium or a lithium-containing compound can also be used as the negative electrode active material. Examples of the lithium-containing compound include lithium alloys such as Li—Al, and alloys containing elements that can be alloyed with lithium such as Si and Sn. Furthermore, oxide-based materials such as Sn oxide and Si oxide can also be used. The amount of the negative electrode active material in the total amount of the negative electrode mixture is preferably 97 to 99% by mass, for example.

導電助剤は、電子伝導性材料であれば特に限定されないし、使用しなくても構わない。導電助剤の具体例としては、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ーボンブラック類；炭素繊維；などの炭素材料の他、金属繊維などの導電性繊維類；フッ化カーボン；銅、ニッケルなどの金属粉末類；ポリフェニレン誘導体などの有機導電性材料；などが挙げられ、これらを１種単独で用いてもよく、２種以上を併用しても構わない。これらの中でも、アセチレンブラック、ケッチェンブラックや炭素繊維が特に好ましい。ただし、負極に導電助剤を使用する場合には、高容量化のために、負極合剤全量中における導電助剤量を１０質量％以下とすることが望ましい。   The conductive aid is not particularly limited as long as it is an electron conductive material, and may not be used. Specific examples of conductive aids include acetylene black; ketjen black; carbon blacks such as channel black, furnace black, lamp black, and thermal black; carbon materials such as carbon fibers; and conductive fibers such as metal fibers. Carbon fluoride, metal powders such as copper and nickel, organic conductive materials such as polyphenylene derivatives, and the like. These may be used alone or in combination of two or more. . Among these, acetylene black, ketjen black and carbon fiber are particularly preferable. However, when a conductive additive is used for the negative electrode, it is desirable that the conductive additive amount in the total amount of the negative electrode mixture be 10% by mass or less in order to increase the capacity.

負極合剤層に係る結着剤としては、熱可塑性樹脂、熱硬化性樹脂のいずれであってもよい。具体的には、例えば、本発明の正極に係る結着剤と同じ材料や、エチレン−アクリル酸共重合体または該共重合体のＮａ＋イオン架橋体、エチレン−メタクリル酸共重合体または該共重合体のＮａ＋イオン架橋体、エチレン−アクリル酸メチル共重合体または該共重合体のＮａ＋イオン架橋体、エチレン−メタクリル酸メチル共重合体または該共重合体のＮａ＋イオン架橋体などが使用でき、それらの材料を１種単独で用いてもよく、２種以上を併用しても構わない。 As a binder concerning a negative mix layer, any of a thermoplastic resin and a thermosetting resin may be sufficient. Specifically, for example, the same material as the binder according to the positive electrode of the present invention, an ethylene-acrylic acid copolymer, a Na + ion crosslinked product of the copolymer, an ethylene-methacrylic acid copolymer, or the copolymer. A polymer Na + ion cross-linked product, an ethylene-methyl acrylate copolymer or a Na + ion cross-linked product of the copolymer, an ethylene-methyl methacrylate copolymer, or a Na + ion cross-linked product of the copolymer These materials may be used alone or in combination of two or more.

前記の中でも、ＰＶＤＦ、ＳＢＲ、エチレン−アクリル酸共重合体または該共重合体のＮａ＋イオン架橋体、エチレン−メタクリル酸共重合体または該共重合体のＮａ＋イオン架橋体、エチレン−アクリル酸メチル共重合体または該共重合体のＮａ＋イオン架橋体、エチレン−メタクリル酸メチル共重合体または該共重合体のＮａ＋イオン架橋体が特に好ましい。負極合剤全量中における結着剤量は、例えば、１〜５質量％であることが好ましい。 Among these, PVDF, SBR, ethylene-acrylic acid copolymer or Na + ion crosslinked product of the copolymer, ethylene-methacrylic acid copolymer or Na + ion crosslinked product of the copolymer, ethylene-acrylic acid A methyl copolymer or a Na + ion crosslinked product of the copolymer, an ethylene-methyl methacrylate copolymer or a Na + ion crosslinked product of the copolymer is particularly preferable. The amount of the binder in the total amount of the negative electrode mixture is preferably 1 to 5% by mass, for example.

負極合剤層の厚み（集電体の両面に負極合剤層が形成されている場合には、その片面あたりの厚み）は、３０〜８０μｍであることが好ましい。   The thickness of the negative electrode mixture layer (when the negative electrode mixture layer is formed on both sides of the current collector, the thickness per one surface thereof) is preferably 30 to 80 μm.

負極に用いる集電体としては、非水電解質二次電池内において、実質上、化学的に安定な電子伝導体であれば特に限定されない。かかる集電体を構成する材料としては、例えば、ステンレス鋼、ニッケルやその合金、銅やその合金、チタンやその合金、炭素、導電性樹脂などの他に、銅またはステンレス鋼の表面にカーボンまたはチタンを処理させたものなどが用いられる。これらの中でも、銅および銅合金が特に好ましい。これらの材料は表面を酸化して用いることもできる。また、表面処理により集電体表面に凹凸を付けることが好ましい。集電体の形状としては、フォイルの他、フィルム、シート、ネット、パンチングされたもの、ラス体、多孔質体、発泡体、繊維群の成形体などが挙げられる。集電体の厚みは特に限定されないが、例えば、５〜５０μｍであることが好ましい。   The current collector used for the negative electrode is not particularly limited as long as it is an electron conductor that is substantially chemically stable in the nonaqueous electrolyte secondary battery. Examples of the material constituting the current collector include stainless steel, nickel or an alloy thereof, copper or an alloy thereof, titanium or an alloy thereof, carbon, conductive resin, carbon, or the like on the surface of copper or stainless steel. A material obtained by treating titanium is used. Among these, copper and copper alloys are particularly preferable. These materials can also be used after oxidizing the surface. Moreover, it is preferable to give unevenness | corrugation to the collector surface by surface treatment. Examples of the shape of the current collector include films, sheets, nets, punched materials, lath bodies, porous bodies, foamed bodies, and molded bodies of fiber groups, in addition to foils. Although the thickness of a collector is not specifically limited, For example, it is preferable that it is 5-50 micrometers.

非水電解質としては、例えば、下記の非水系溶媒中に、リチウム塩を溶解させることで調製した溶液（非水電解液）が使用できる。   As the non-aqueous electrolyte, for example, a solution (non-aqueous electrolyte) prepared by dissolving a lithium salt in the following non-aqueous solvent can be used.

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）、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（γ-
ＢＬ）、１，２−ジメトキシエタン(ＤＭＥ)、テトラヒドロフラン(ＴＨＦ)、２−メチルテトラヒドロフラン、ジメチルスルフォキシド(ＤＭＳＯ)、１，３−ジオキソラン、ホルムアミド、ジメチルホルムアミド(ＤＭＦ)、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を１種単独で、または２種以上を混合した混合溶媒として用いることができる。 Examples of the solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone (γ-
BL), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, dimethyl sulfoxide (DMSO), 1,3-dioxolane, formamide, dimethylformamide (DMF), dioxolane, acetonitrile, nitromethane , Aprotic such as methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivative, sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, 1,3-propane sultone The organic solvent can be used alone or as a mixed solvent in which two or more are mixed.

非水電解液に係る無機イオン塩としては、例えば、ＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、Ｌｉ２Ｃ２Ｆ４（ＳＯ３）２、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＣｎＦ２ｎ＋１ＳＯ３（ｎ≧２）、ＬｉＮ（ＲｆＯＳＯ２）２［ここでＲｆはフルオロアルキル基］などのリチウム塩から選ばれる少なくとも１種が挙げられる。これらのリチウム塩の非水電解液中の濃度としては、０．６〜１．８ｍｏｌ／ｌとすることが好ましく、０．９〜１．６ｍｏｌ／ｌとすることがより好ましい。 The inorganic ion salt according to the non-aqueous electrolyte solution, for example, LiClO 4, LiPF 6, LiBF 4, LiAsF 6, LiSbF 6, 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 (n ≧ 2), LiN (RfOSO 2 ) 2 [where Rf is a fluoroalkyl group] There may be mentioned at least one selected. The concentration of these lithium salts in the non-aqueous electrolyte is preferably 0.6 to 1.8 mol / l, and more preferably 0.9 to 1.6 mol / l.

なお、本発明に係る非水電解質では、環外にＣ＝Ｃ二重結合を有するエステル、または環内にＣ＝Ｃ二重結合を有するエステルを用いることが好ましい。   In the non-aqueous electrolyte according to the present invention, it is preferable to use an ester having a C═C double bond outside the ring or an ester having a C═C double bond in the ring.

前記の環外にＣ＝Ｃ二重結合を有するエステルおよび環内にＣ＝Ｃ二重結合を有するエステル（以下、両者を纏めて「Ｃ＝Ｃ二重結合を有するエステル」と略す場合がある）は電池充電中（特に初期充電中）に正極活物質の表面に表面保護皮膜を形成する機能を有しており、かかる表面保護皮膜によって、正極と非水電解質と直接の接触が抑制される。また、Ｃ＝Ｃ二重結合を有するエステルは、充電状態の電池を例えば高温下で貯蔵している際に、徐々に電池の回路電圧を低下させる作用を有している。そのため、本発明の電池がＣ＝Ｃ二重結合を有するエステルを含有する非水電解質を有する場合、充電状態で、例えば１５０℃程度の高温下の貯蔵しても、前記表面保護皮膜による正極と非水電解質との直接の接触を抑制する作用と、電池電圧の低下によって、正極と非水電解質との反応が抑制されるため、かかる反応による電池の温度上昇を抑えることができ、更に安全性に優れたものとなる。   The ester having a C═C double bond outside the ring and the ester having a C═C double bond in the ring (hereinafter, both may be collectively referred to as “ester having a C═C double bond”) ) Has a function of forming a surface protective film on the surface of the positive electrode active material during battery charging (particularly during initial charging), and direct contact between the positive electrode and the nonaqueous electrolyte is suppressed by the surface protective film. . In addition, the ester having a C═C double bond has an action of gradually reducing the circuit voltage of the battery when the charged battery is stored at a high temperature, for example. Therefore, when the battery of the present invention has a non-aqueous electrolyte containing an ester having a C═C double bond, the positive electrode formed by the surface protective film can be stored in a charged state, for example, at a high temperature of about 150 ° C. Since the reaction between the positive electrode and the non-aqueous electrolyte is suppressed by the action of suppressing direct contact with the non-aqueous electrolyte and the decrease in battery voltage, the temperature rise of the battery due to such reaction can be suppressed, and further safety It will be excellent.

環外にＣ＝Ｃ二重結合を有するエステルとしては、例えば、ビニルエチレンカーボネート、４−メチル−４−ビニルエチレンカーボネート、４−エチル−４−ビニルエチレンカーボネート、４−ｎ−プロピル−４−ビニルエチレンカーボネート、５−メチル−４−ビニルエチレンカーボネート、４，４−ジビニルエチレンカーボネート、４，５−ジビニルエチレンカーボネートなどが挙げられる。   Examples of the ester having a C═C double bond outside the ring include vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate, 4-ethyl-4-vinylethylene carbonate, 4-n-propyl-4-vinyl. Examples include ethylene carbonate, 5-methyl-4-vinylethylene carbonate, 4,4-divinylethylene carbonate, 4,5-divinylethylene carbonate, and the like.

環内にＣ＝Ｃ二重結合を有するエステルとしては、例えば、ビニレンカーボネート、メチルビニレンカーボネート、エチルビニレンカーボネート、４，５−ジメチルビニレンカーボネート、４，５−ジエチルビニレンカーボネート、メチルエチルビニレンカーボネートなどが挙げられる。   Examples of the ester having a C═C double bond in the ring include vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4,5-dimethyl vinylene carbonate, 4,5-diethyl vinylene carbonate, methyl ethyl vinylene carbonate, and the like. Can be mentioned.

前記の環外にＣ＝Ｃ二重結合を有するエステルと、前記の環内にＣ＝Ｃ二重結合を有するエステルとは、両者を併用することが好ましい。   The ester having a C═C double bond outside the ring and the ester having a C═C double bond inside the ring are preferably used in combination.

前記の環内にＣ＝Ｃ二重結合を有するエステルの非水電解質中の添加量は、これらの化合物の添加による作用をより有効に発揮させる観点から、非水電解質全量中、０．５質量％以上であることが好ましく、０．９質量％以上であることがより好ましく、１．８質量％以上であることが更に好ましい。ただし、環内にＣ＝Ｃ二重結合を有するエステルの非水電解質中の添加量が多すぎると、電池の電圧低下が大きくなるため、環内にＣ＝Ｃ二重結合を有するエステルの添加量は、非水電解質全量中、５質量％以下であることが好ましく、３質量％以下であることがより好ましく、２．５質量％以下であることがさらに好ましい。前記の環外にＣ＝Ｃ二重結合を有するエステルの非水電解質中の添加量は、これらの化合物の添加による作用をより有効に発揮させる観点から、非水電解質全量中、０．２質量％以上であることが好ましく、０．５質量％以上であることがより好ましく、０．８質量％以上であることが更に好ましい。ただし、環外にＣ＝Ｃ二重結合を有するエステルの非水電解質中の添加量が多すぎると、電池の電圧低下が大きくなるため、環外にＣ＝Ｃ二重結合を有するエステルの添加量は、非水電解質全量中、３質量％以下であることが好ましく、２質量％以下であることがより好ましく、１．５質量％以下であることが更に好ましい。   The addition amount of the ester having a C═C double bond in the ring in the non-aqueous electrolyte is 0.5 mass in the total amount of the non-aqueous electrolyte from the viewpoint of more effectively exerting the action of the addition of these compounds. % Or more, preferably 0.9% by mass or more, and more preferably 1.8% by mass or more. However, if the amount of the ester having a C═C double bond in the ring is too large in the non-aqueous electrolyte, the voltage drop of the battery increases, so the addition of the ester having a C═C double bond in the ring The amount is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2.5% by mass or less in the total amount of the nonaqueous electrolyte. The addition amount of the ester having a C═C double bond outside the ring in the non-aqueous electrolyte is 0.2 mass in the total amount of the non-aqueous electrolyte from the viewpoint of more effectively exerting the effect of the addition of these compounds. % Or more, preferably 0.5% by mass or more, and more preferably 0.8% by mass or more. However, if the amount of the ester having a C═C double bond outside the ring is too large in the non-aqueous electrolyte, the voltage drop of the battery increases, so the addition of the ester having a C═C double bond outside the ring The amount is preferably 3% by mass or less, more preferably 2% by mass or less, and still more preferably 1.5% by mass or less in the total amount of the nonaqueous electrolyte.

本発明の非水電解質二次電池内では、前記正極と前記負極との間に、前記の非水電解質を含ませたセパレータが配される。セパレータとしては、大きなイオン透過度および所定の機械的強度を有する絶縁性の微多孔性薄膜が用いられる。また、一定温度以上（例えば１００〜１４０℃）で構成材料の溶融によって孔が閉塞し、抵抗を上げる機能を有するもの（すなわち、シャットダウン機能を有するもの）が好ましい。このようなセパレータの具体例としては、耐有機溶剤性および疎水性を有するポリエチレン、ポリプロピレンなどポリオレフィン系ポリマー、またはガラス繊維などの材料で構成されるシート（多孔質シート）、不織布若しくは織布；前記例示のポリオレフィン系ポリマーの微粒子を接着剤で固着した多孔質体；などが挙げられる。セパレータの孔径は、正負極より脱離した正負極の活物質、導電助剤および結着剤などが通過しない程度であることが好ましく、例えば、０．０１〜１μｍであることが望ましい。セパレータの厚みは、８〜３０μｍとすることが一般的であるが、本発明では、１０〜２０μｍとすることが好ましい。また、セパレータの空孔率は、構成材料や厚みに応じて決定されるが、３０〜８０％であることが一般的である。   In the non-aqueous electrolyte secondary battery of the present invention, a separator containing the non-aqueous electrolyte is disposed between the positive electrode and the negative electrode. As the separator, an insulating microporous thin film having a large ion permeability and a predetermined mechanical strength is used. Moreover, what has a function which a hole is obstruct | occluded by fusion | melting of a structural material above a fixed temperature (for example, 100-140 degreeC), and raises resistance (namely, what has a shutdown function) is preferable. Specific examples of such a separator include a sheet (porous sheet), a nonwoven fabric or a woven fabric composed of a material such as polyethylene solvent, hydrophobic polymer such as polyethylene, polypropylene, or glass fiber having organic solvent resistance and hydrophobicity; And a porous material in which fine particles of the exemplified polyolefin polymer are fixed with an adhesive. The pore diameter of the separator is preferably such that the active material of the positive and negative electrodes, the conductive auxiliary agent, the binder and the like detached from the positive and negative electrodes do not pass through, and is preferably 0.01 to 1 μm, for example. The thickness of the separator is generally 8-30 μm, but is preferably 10-20 μm in the present invention. Further, the porosity of the separator is determined according to the constituent material and thickness, but is generally 30 to 80%.

本発明の電池においては、前記の通り、本発明の正極と前記の負極とを、前記のセパレータを介して重ね合わせて渦巻状に巻回し、押しつぶすなどして横断面を扁平状にした扁平状巻回電極体を使用する。   In the battery of the present invention, as described above, the positive electrode of the present invention and the negative electrode are overlapped via the separator, wound into a spiral shape, and flattened in a cross-sectional shape by flattening. A wound electrode body is used.

そして、本発明の電池では、扁平状巻回電極体を使用することから、電池の薄型化を可能とし得る角形（角筒形）の外装缶を外装体に使用することができる。また、本発明の電池には、金属層の片面または両面に樹脂層を形成したラミネートフィルムからなる外装体を使用することもできる。   In the battery of the present invention, since a flat wound electrode body is used, a rectangular (rectangular cylindrical) outer can that can make the battery thinner can be used for the outer body. Moreover, the battery of this invention can also use the exterior body which consists of a laminate film which formed the resin layer in the single side | surface or both surfaces of a metal layer.

本発明の非水電解質二次電池は、従来から知られている非水電解質二次電池と同様の用途に適用することができる。   The non-aqueous electrolyte secondary battery of the present invention can be applied to the same applications as conventionally known non-aqueous electrolyte secondary batteries.

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
正極活物質であるＬｉＣｏＯ２（比表面積０．３ｍ２／ｇ）：９７．１５質量部、導電助剤であるアセチレンブラック：１．５質量部および結着剤であるＰＶＤＦ（クレハ社製「ＫＦ１１００（商品名）」、引張弾性率１５５０ＭＰａ）：１．３５質量部を混合して正極合剤とし、この正極合剤に、溶剤であるＮＭＰを加え、エム・テクニック社製の「クレアミックス ＣＬＭ０．８（商品名）」を用いて、回転数：１００００ｍｉｎ−１で３０分間処理を行い、ペースト状の混合物とした。この混合物に、溶剤であるＮＭＰを更に加えて、回転数：１００００ｍｉｎ−１で１５分間処理を行い、正極合剤含有組成物を調製した。 Example 1
LiCoO 2 as a positive electrode active material (specific surface area 0.3 m 2 / g): 97.15 parts by mass, acetylene black as a conductive auxiliary agent: 1.5 parts by mass and PVDF as a binder (“KF1100” manufactured by Kureha) (Trade name) ”, tensile elastic modulus 1550 MPa): 1.35 parts by mass were mixed to form a positive electrode mixture, and NMP as a solvent was added to this positive electrode mixture, and“ Claremix CLM0. 8 (trade name) "was processed at a rotational speed of 10,000 min -1 for 30 minutes to obtain a paste-like mixture. NMP which is a solvent was further added to this mixture, and the mixture was treated at a rotational speed of 10000 min −1 for 15 minutes to prepare a positive electrode mixture-containing composition.

前記の正極合剤含有組成物を、集電体であるアルニミウム合金箔（厚み：１２μｍ、引張強度３．１５Ｎ／ｍｍ）の両面に塗布し、１２０℃で１２時間真空乾燥を施し、更にプレス処理を施して、集電体の両面に、厚みが６１μｍの正極合剤層を有する正極を作製した。前記の方法によって求めたプレス処理後の正極合剤層の充填率は７６％であり、正極合剤層の比表面積は１．３ｍ２／ｇであった。 The positive electrode mixture-containing composition is applied to both surfaces of an aluminum alloy foil (thickness: 12 μm, tensile strength 3.15 N / mm) as a current collector, vacuum-dried at 120 ° C. for 12 hours, and further press-treated. As a result, a positive electrode having a positive electrode mixture layer with a thickness of 61 μm on both surfaces of the current collector was produced. The filling rate of the positive electrode mixture layer after the press treatment obtained by the above method was 76%, and the specific surface area of the positive electrode mixture layer was 1.3 m 2 / g.

＜負極の作製＞
天然黒鉛：９７．５質量％、ＳＢＲ：１．５質量％、およびカルボキシメチルセルロース（増粘剤）：１質量％を、水を用いて混合してスラリー状の負極合剤含有組成物を調製した。この負極合剤含有組成物を、集電体である銅箔（厚み：８μｍ）の両面に塗布し、１２０℃で１２時間真空乾燥を施し、更にプレス処理を施して、集電体の両面に、厚みが６３μｍの負極合剤層を有する負極を作製した。 <Production of negative electrode>
Natural graphite: 97.5% by mass, SBR: 1.5% by mass, and carboxymethylcellulose (thickener): 1% by mass were mixed with water to prepare a slurry-like negative electrode mixture-containing composition. . This negative electrode mixture-containing composition was applied to both sides of a copper foil (thickness: 8 μm) as a current collector, vacuum-dried at 120 ° C. for 12 hours, and further subjected to a press treatment to form both sides of the current collector. A negative electrode having a negative electrode mixture layer with a thickness of 63 μm was prepared.

＜電極体の作製＞
前記の正極と負極とをセパレータ（厚みが１４μｍで、透気度が３００秒／１００ｃｍ３のポリエチレン製多孔膜）を介して重ね合わせ、渦巻状に巻回した後、横断面が扁平状になるように押しつぶして扁平状巻回電極体を作製した。 <Production of electrode body>
The positive electrode and the negative electrode are overlapped via a separator (a polyethylene porous film having a thickness of 14 μm and an air permeability of 300 seconds / 100 cm 3 ), wound in a spiral shape, and then the cross section becomes flat. In this way, a flat wound electrode body was produced.

＜非水電解液の調製＞
メチルエチルカーボネートとジエチルカーボネートとエチレンカーボネートとの混合溶媒（体積比 ２：１：３）に、１.２ｍｏｌ／ｌの濃度でＬｉＰＦ６を溶解し、これにビニレンカーボネート（ＶＣ）２質量％、ビニルエチレンカーボネート（Ｖ−ＥＣ）１質量％を加えて非水電解液（非水電解質）を調製した。 <Preparation of non-aqueous electrolyte>
LiPF 6 was dissolved at a concentration of 1.2 mol / l in a mixed solvent of methyl ethyl carbonate, diethyl carbonate and ethylene carbonate (volume ratio 2: 1: 3), and vinylene carbonate (VC) 2% by mass, vinyl A non-aqueous electrolyte (non-aqueous electrolyte) was prepared by adding 1% by mass of ethylene carbonate (V-EC).

＜電池の組み立て＞
前記の電極体および非水電解液を用いて、角形非水電解質二次電池を組み立てた。まず、前記電極体の各端面に集電板を溶接により接合した。次に、集電板のリード部を蓋体に取り付けられている電極端子集電機構と接続した。その後、外装缶の内部に電極体を収容して、外装缶の開口部に蓋体を溶接固定した。最後に蓋体に設けられた注液孔から外装缶内に非水電解液を注入して、厚さ４ｍｍ、幅３４ｍｍ、高さ５０ｍｍで、図１に示す構造で、図２に示す外観の角形非水電解質二次電池を作製した。 <Battery assembly>
A prismatic nonaqueous electrolyte secondary battery was assembled using the electrode body and the nonaqueous electrolyte. First, a current collector plate was joined to each end face of the electrode body by welding. Next, the lead part of the current collecting plate was connected to an electrode terminal current collecting mechanism attached to the lid. Thereafter, the electrode body was accommodated inside the outer can, and the lid was welded and fixed to the opening of the outer can. Finally, a nonaqueous electrolytic solution is injected into the outer can through the injection hole provided in the lid, and the structure shown in FIG. 1 has a thickness of 4 mm, a width of 34 mm, and a height of 50 mm. A square nonaqueous electrolyte secondary battery was produced.

ここで図１および図２に示す電池について説明すると、図１の（ａ）は平面図、（ｂ）はその部分断面図であって、図１（ｂ）に示すように、正極１と負極２は前記のようにセパレータ３を介して渦巻状に巻回した後、扁平状になるように加圧して扁平状巻回電極体６として、角筒形の外装缶４に電解液と共に収容されている。ただし、図１では、煩雑化を避けるため、正極１や負極２の作製にあたって使用した集電体としての金属箔や非水電解液などは図示していない。   Here, the battery shown in FIGS. 1 and 2 will be described. FIG. 1A is a plan view, and FIG. 1B is a partial cross-sectional view thereof. As shown in FIG. 2 is spirally wound through the separator 3 as described above, and then pressurized so as to be flattened, and is accommodated in a rectangular tube-shaped outer can 4 together with the electrolyte as a flat wound electrode body 6. ing. However, in FIG. 1, in order to avoid complication, a metal foil, a non-aqueous electrolyte, or the like as a current collector used for manufacturing the positive electrode 1 and the negative electrode 2 is not illustrated.

外装缶４はアルミニウム合金製で電池の外装体を構成するものであり、この外装缶４は正極端子を兼ねている。そして、外装缶４の底部にはポリエチレンシートからなる絶縁体５が配置され、正極１、負極２およびセパレータ３からなる扁平状巻回電極体６からは、正極１および負極２のそれぞれ一端に接続された正極リード体７と負極リード体８が引き出されている。また、外装缶４の開口部を封口するアルミニウム合金製の封口用蓋板９にはポリプロピレン製の絶縁パッキング１０を介してステンレス鋼製の端子１１が取り付けられ、この端子１１には絶縁体１２を介してステンレス鋼製のリード板１３が取り付けられている。   The outer can 4 is made of an aluminum alloy and constitutes an outer casing of the battery. The outer can 4 also serves as a positive electrode terminal. And the insulator 5 which consists of a polyethylene sheet is arrange | positioned at the bottom part of the armored can 4, From the flat wound electrode body 6 which consists of the positive electrode 1, the negative electrode 2, and the separator 3, it connects to each one end of the positive electrode 1 and the negative electrode 2 The positive electrode lead body 7 and the negative electrode lead body 8 thus drawn are drawn out. Further, a stainless steel terminal 11 is attached to a sealing lid plate 9 made of aluminum alloy for sealing the opening of the outer can 4 through a polypropylene insulating packing 10, and an insulator 12 is attached to the terminal 11. A stainless steel lead plate 13 is attached.

そして、この蓋板９は外装缶４の開口部に挿入され、両者の接合部を溶接することによって、外装缶４の開口部が封口され、電池内部が密閉されている。また、図１の電池では、蓋板９に非水電解液注入口１４が設けられており、この非水電解液注入口１４には、封止部材が挿入された状態で、例えばレーザー溶接などにより溶接封止されて、電池の密閉性が確保されている（従って、図１および図２の電池では、実際には、非水電解液注入口１４は、非水電解液注入口と封止部材であるが、説明を容易にするために、非水電解液注入口１４として示している）。更に、蓋板９には、電池の温度が上昇した際に内部のガスを外部に排出する機構として、開裂ベント１５が設けられている。   And this cover plate 9 is inserted in the opening part of the armored can 4, and the opening part of the armored can 4 is sealed by welding the junction part of both, and the inside of a battery is sealed. Further, in the battery of FIG. 1, a non-aqueous electrolyte inlet 14 is provided in the cover plate 9, and a sealing member is inserted into the non-aqueous electrolyte inlet 14, for example, laser welding or the like. (See FIG. 1 and FIG. 2, in practice, the non-aqueous electrolyte inlet 14 is actually sealed with the non-aqueous electrolyte inlet.) Although it is a member, for ease of explanation, it is shown as a non-aqueous electrolyte inlet 14). Further, the lid plate 9 is provided with a cleavage vent 15 as a mechanism for discharging the internal gas to the outside when the temperature of the battery rises.

この実施例１の電池では、正極リード体７を蓋板９に直接溶接することによって外装缶４と蓋板９とが正極端子として機能し、負極リード体８をリード板１３に溶接し、そのリード板１３を介して負極リード体８と端子１１とを導通させることによって端子１１が負極端子として機能するようになっているが、外装缶４の材質などによっては、その正負が逆になる場合もある。   In the battery of Example 1, the outer can 4 and the lid plate 9 function as a positive electrode terminal by directly welding the positive electrode lead body 7 to the lid plate 9, and the negative electrode lead body 8 is welded to the lead plate 13. The terminal 11 functions as a negative electrode terminal by conducting the negative electrode lead body 8 and the terminal 11 through the lead plate 13, but depending on the material of the outer can 4, the sign may be reversed. There is also.

図２は前記図１に示す電池の外観を模式的に示す斜視図であり、この図２は前記電池が角形電池であることを示すことを目的として図示されたものであって、この図２では電池を概略的に示しており、電池の構成部材のうち特定のものしか図示していない。また、図１においても、扁平状巻回電極体の内周側の部分は断面にしていない。   FIG. 2 is a perspective view schematically showing the external appearance of the battery shown in FIG. 1. FIG. 2 is shown for the purpose of showing that the battery is a square battery. FIG. 1 schematically shows a battery, and only specific members of the battery are shown. Also in FIG. 1, the inner peripheral side portion of the flat wound electrode body is not cross-sectional.

実施例２
正極合剤の調製時において、正極活物質の量を９７質量部に、ＰＶＤＦの量を１．５質量部に、それぞれ変更した以外は、実施例１と同様にして正極を作製した。プレス処理後の正極合剤層の充填率は７６％であり、正極合剤層の比表面積は１．３ｍ２／ｇであった。
この正極を用いた以外は、実施例１と同様にして角形非水電解質二次電池を作製した。 Example 2
A positive electrode was produced in the same manner as in Example 1 except that the amount of the positive electrode active material was changed to 97 parts by mass and the amount of PVDF was changed to 1.5 parts by mass when preparing the positive electrode mixture. The filling rate of the positive electrode mixture layer after the press treatment was 76%, and the specific surface area of the positive electrode mixture layer was 1.3 m 2 / g.
A square nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

実施例３
正極活物質であるＬｉＣｏＯ２（比表面積０．３ｍ２／ｇ）：９７．１５質量部、導電助剤であるアセチレンブラック：１．５質量部、並びに結着剤であるＰＶＤＦ（クレハ社製「ＫＦ１１００（商品名）」、引張弾性率１５５０ＭＰａ）：１質量部およびアクリル酸ブチル−メタクリル酸ブチル−アクリロニトリルコポリマー（ゴム結着剤、引張弾性率４００ＭＰａ）：０．３５質量部を混合して調製した正極合剤を用いた以外は、実施例１と同様にして正極を作製した。プレス処理後の正極合剤層の充填率は７６％であり、正極合剤層の比表面積は１．０ｍ２／ｇであった。この正極を用いた以外は、実施例１と同様にして角形非水電解質二次電池を作製した。 Example 3
LiCoO 2 as a positive electrode active material (specific surface area 0.3 m 2 / g): 97.15 parts by mass, acetylene black as a conductive auxiliary agent: 1.5 parts by mass, and PVDF as a binder (manufactured by Kureha “ KF1100 (trade name) ", tensile elastic modulus 1550 MPa): 1 part by mass and butyl acrylate-butyl methacrylate-acrylonitrile copolymer (rubber binder, tensile elastic modulus 400 MPa): 0.35 parts by mass were prepared. A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture was used. The filling rate of the positive electrode mixture layer after the press treatment was 76%, and the specific surface area of the positive electrode mixture layer was 1.0 m 2 / g. A square nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

実施例４
正極合剤の調製時において、正極活物質の量を９７．３５質量部に、ＰＶＤＦの量を０．８質量部に、それぞれ変更した以外は、実施例３と同様にして正極を作製した。プレス処理後の正極合剤層の充填率は７６％であり、正極合剤層の比表面積は１．０ｍ２／ｇであった。この正極を用いた以外は、実施例１と同様にして角形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 3, except that the amount of the positive electrode active material was changed to 97.35 parts by mass and the amount of PVDF was changed to 0.8 parts by mass when preparing the positive electrode mixture. The filling rate of the positive electrode mixture layer after the press treatment was 76%, and the specific surface area of the positive electrode mixture layer was 1.0 m 2 / g. A square nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

実施例５
正極活物質であるＬｉＣｏＯ２（比表面積０．３ｍ２／ｇ）：９７．３質量部、導電助剤であるアセチレンブラック：１．５質量部、並びに結着剤であるＰＶＤＦ（クレハ社製「ＫＦ１１００（商品名）」、引張弾性率１５００ＭＰａ）：０．７質量部およびアクリル酸ブチル−メタクリル酸ブチル−アクリロニトリルコポリマー（ゴム結着剤、引張弾性率４００ＭＰａ）：０．５質量部を混合して調製した正極合剤を用いた以外は、実施例１と同様にして正極を作製した。プレス処理後の正極合剤層の充填率は７６％であり、正極合剤層の比表面積は０．９ｍ２／ｇであった。この正極を用いた以外は、実施例１と同様にして角形非水電解質二次電池を作製した。 Example 5
LiCoO 2 as a positive electrode active material (specific surface area 0.3 m 2 / g): 97.3 parts by mass, acetylene black as a conductive auxiliary agent: 1.5 parts by mass, and PVDF as a binder (manufactured by Kureha “ KF1100 (trade name), tensile elastic modulus 1500 MPa): 0.7 parts by mass and butyl acrylate-butyl methacrylate-acrylonitrile copolymer (rubber binder, tensile elastic modulus 400 MPa): 0.5 parts by mass A positive electrode was produced in the same manner as in Example 1 except that the prepared positive electrode mixture was used. The filling rate of the positive electrode mixture layer after the press treatment was 76%, and the specific surface area of the positive electrode mixture layer was 0.9 m 2 / g. A square 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
正極活物質であるＬｉＣｏＯ２（比表面積０．３ｍ２／ｇ）：９７．１５質量部、導電助剤であるアセチレンブラック：１．５質量部、並びに結着剤であるＰＶＤＦ（クレハ社製「ＫＦ１３００（商品名）」、引張弾性率２０１６ＭＰａ）：１．３５質量部を混合して調製した正極合剤を用いた以外は、実施例１と同様にして正極を作製した。プレス処理後の正極合剤層の充填率は７６％であり、正極合剤層の比表面積は１．３ｍ２／ｇであった。この正極を用いた以外は、実施例１と同様にして角形非水電解質二次電池を作製した。 Comparative Example 1
LiCoO 2 as a positive electrode active material (specific surface area 0.3 m 2 / g): 97.15 parts by mass, acetylene black as a conductive auxiliary agent: 1.5 parts by mass, and PVDF as a binder (manufactured by Kureha “ KF1300 (trade name), tensile modulus 2016 MPa): A positive electrode was produced in the same manner as in Example 1 except that a positive electrode mixture prepared by mixing 1.35 parts by mass was used. The filling rate of the positive electrode mixture layer after the press treatment was 76%, and the specific surface area of the positive electrode mixture layer was 1.3 m 2 / g. A square nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

比較例２
正極合剤の調製時において、正極活物質の量を９６．８５質量部に、ＰＶＤＦの量を１．６５質量部に、それぞれ変更した以外は、実施例１と同様にして正極を作製した。プレス処理後の正極合剤層の充填率は７６％であり、正極合剤層の比表面積は１．３ｍ２／ｇであった。この正極を用いた以外は、実施例１と同様にして角形非水電解質二次電池を作製した。 Comparative Example 2
A positive electrode was produced in the same manner as in Example 1 except that the amount of the positive electrode active material was changed to 96.85 parts by mass and the amount of PVDF was changed to 1.65 parts by mass at the time of preparing the positive electrode mixture. The filling rate of the positive electrode mixture layer after the press treatment was 76%, and the specific surface area of the positive electrode mixture layer was 1.3 m 2 / g. A square nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

比較例３
正極合剤の調製時において、正極活物質の量を９７質量部に、ＰＶＤＦの量を０．５０質量部に、ゴム結着剤の量を０．７０質量部に、それぞれ変更した以外は、実施例３と同様にして正極を作製した。プレス処理後の正極合剤層の充填率は７６％であり、正極合剤層の比表面積は０．８ｍ２／ｇであった。この正極を用いた以外は、実施例１と同様にして角形非水電解質二次電池を作製した。 Comparative Example 3
Except for changing the amount of the positive electrode active material to 97 parts by mass, the amount of PVDF to 0.50 parts by mass, and the amount of the rubber binder to 0.70 parts by mass at the time of preparing the positive electrode mixture, A positive electrode was produced in the same manner as in Example 3. The filling rate of the positive electrode mixture layer after the press treatment was 76%, and the specific surface area of the positive electrode mixture layer was 0.8 m 2 / g. A square nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

比較例４
正極合剤の調製時において、正極活物質の量を９７．４５質量部に、ＰＶＤＦの量を０．７質量部に、それぞれ変更した以外は、実施例３と同様にして正極を作製した。プレス処理後の正極合剤層の充填率は７６％であり、正極合剤層の比表面積は１．０ｍ２／ｇであった。この正極を用いた以外は、実施例１と同様にして角形非水電解質二次電池を作製した。 Comparative Example 4
A positive electrode was produced in the same manner as in Example 3 except that the amount of the positive electrode active material was changed to 97.45 parts by mass and the amount of PVDF was changed to 0.7 parts by mass when preparing the positive electrode mixture. The filling rate of the positive electrode mixture layer after the press treatment was 76%, and the specific surface area of the positive electrode mixture layer was 1.0 m 2 / g. A square nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

比較例５
正極合剤の調製時において、正極活物質の量を９７．５５質量部に、ＰＶＤＦの量を０．６質量部に、それぞれ変更した以外は、実施例３と同様にして正極を作製した。プレス処理後の正極合剤層の充填率は７５％であり、正極合剤層の比表面積は１．０ｍ２／ｇであった。この正極を用いた以外は、実施例１と同様にして角形非水電解質二次電池を作製した。 Comparative Example 5
A positive electrode was produced in the same manner as in Example 3 except that the amount of the positive electrode active material was changed to 97.55 parts by mass and the amount of PVDF was changed to 0.6 parts by mass when preparing the positive electrode mixture. The filling rate of the positive electrode mixture layer after the press treatment was 75%, and the specific surface area of the positive electrode mixture layer was 1.0 m 2 / g. A square nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

比較例６
正極合剤の調製時において、正極活物質の量を９７．４５質量部に、ＰＶＤＦの量を０．６質量部に、ゴム結着剤の量を０．４５質量部に、それぞれ変更した以外は、実施例３と同様にして正極を作製した。プレス処理後の正極合剤層の充填率は７６％であり、正極合剤層の比表面積は１．０ｍ２／ｇであった。この正極を用いた以外は、実施例１と同様にして角形非水電解質二次電池を作製した。 Comparative Example 6
When preparing the positive electrode mixture, the amount of the positive electrode active material was changed to 97.45 parts by mass, the amount of PVDF was changed to 0.6 parts by mass, and the amount of the rubber binder was changed to 0.45 parts by mass. Produced a positive electrode in the same manner as in Example 3. The filling rate of the positive electrode mixture layer after the press treatment was 76%, and the specific surface area of the positive electrode mixture layer was 1.0 m 2 / g. A square nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

実施例１〜５および比較例１〜６の非水電解質二次電池に用いた正極における結着剤の引張弾性率［前記式（１）におけるｙ］、正極合剤層の構成成分の全体積中における結着剤の体積割合［前記式（１）におけるｘ］、および前記式（１）におけるｙ切片ｚを、表１に示す。   Tensile elastic modulus of the binder in the positive electrode used in the non-aqueous electrolyte secondary batteries of Examples 1 to 5 and Comparative Examples 1 to 6 [y in the above formula (1)], the total volume of the constituent components of the positive electrode mixture layer Table 1 shows the volume ratio [x in the above formula (1)] and the y intercept z in the above formula (1).

また、実施例１〜５および比較例１〜６の非水電解質二次電池に用いた正極について、結着剤の引張弾性率ｙを縦軸に、結着剤の体積割合ｘを横軸にとったグラフを図３に示す。なお、図３では、前記式（１）においてｚが３３００の場合を直線Ａで、ｚが４１００の場合を直線Ｂで示し、更に、結着剤の体積割合ｘが３．５体積％の場合および４．５体積％の場合を、それぞれ直線Ｃ、Ｄで示しており、これら直線Ａ〜Ｄで囲まれる領域が、前記式（１）を満たすものに該当する。すなわち、図３のグラフでは、前記の直線Ａ〜Ｄで囲まれる領域に５つの点が示されているが、これらは、実施例１〜５の非水電解質二次電池で用いた正極に該当する。   Moreover, about the positive electrode used for the nonaqueous electrolyte secondary battery of Examples 1-5 and Comparative Examples 1-6, the tensile elasticity modulus y of a binder is on a vertical axis | shaft, and the volume ratio x of a binder is on a horizontal axis. The obtained graph is shown in FIG. In FIG. 3, the straight line A represents the case where z is 3300 in the above formula (1), the straight line B represents the case where z is 4100, and the volume ratio x of the binder is 3.5% by volume. And 4.5% by volume are indicated by straight lines C and D, respectively, and regions surrounded by these straight lines A to D correspond to those satisfying the formula (1). That is, in the graph of FIG. 3, although five points are shown in the area | region enclosed by said straight line AD, these correspond to the positive electrode used with the nonaqueous electrolyte secondary battery of Examples 1-5. To do.

Figure 2012028158
Figure 2012028158

また、実施例１〜５および比較例１〜６の非水電解質二次電池、並びに、それに用いた正極および扁平状巻回電極体について、下記の各評価を行った。   Moreover, each of the following evaluation was performed about the nonaqueous electrolyte secondary battery of Examples 1-5 and Comparative Examples 1-6, the positive electrode used for it, and a flat winding electrode body.

＜正極の折り曲げ強度＞
扁平状巻回電極体を分解し、正極の最内周部分の折り曲がった部分を中心にして電極の長尺方向に５ｃｍ×幅４ｃｍに切り出し、折り曲がった部分を再度折り曲げて切り出した正極を半分に畳み、畳んだ状態の面に均一に１０Ｎで３秒間加重後、畳んだ正極を開き、折り曲げ部の観察を行った。観察では、折り曲げ線の凸部を観察し、正極の切断、クラックの発生の有無を確認した。折り曲げ試験は、各実施例・比較例の正極のそれぞれから切り出した３サンプルについて行い、３回の試験で観察した視野全てにおいて、切断、クラックが全く確認されない場合の折り曲げ強度を○、切断、クラックが確認された場合の折り曲げ強度を×として、各正極の折り曲げ強度を評価した。 <Bending strength of positive electrode>
Disassemble the flat wound electrode body, cut out 5cm × width 4cm in the longitudinal direction of the electrode around the bent part of the innermost peripheral part of the positive electrode, and fold the bent part again and cut out the positive electrode The folded surface was folded in half and uniformly weighted with 10 N for 3 seconds on the folded surface, the folded positive electrode was opened, and the bent portion was observed. In the observation, the convex portion of the fold line was observed to confirm whether the positive electrode was cut or cracked. The bending test was performed on three samples cut out from each of the positive electrodes of the examples and comparative examples, and the bending strength when no cuts or cracks were confirmed in all the fields of view observed in the three tests was shown as ◯, cut, cracks The bending strength when each of the positive electrodes was confirmed as x was evaluated for the bending strength of each positive electrode.

＜正極における正極合剤層と集電体との剥離強度＞
正極の両面塗布部分を長尺方向に１０ｃｍ、幅方向に１ｃｍに切り出して得た試料を、両面テープ（ニチバン社製「ナイスタックＮＷ−１５」）の一方の面に接着し、両面テープの他方の面を、図４に示すように、９０°剥離試験機（テスター産業社製「ＴＥ−３００１」）の試料設置面１００に接着させた。前記の試料(正極１）の試料設置面１００に接着させた側とは反対側の端部を９０°剥離試験機の治具１０１で挟み、試料設置面１００に対して９０°の角度で剥離速度５０ｍｍ／ｍｉｎにて長尺方向（図中矢印の方向）に試料１を引っ張って正極合剤層と集電体とを剥がし、その際の強度を測定した。この剥離強度が大きいほど、正極合剤層からの正極活物質や導電助剤の脱落を良好に抑制し得ると評価できる。 <Peel strength between positive electrode mixture layer and current collector in positive electrode>
A sample obtained by cutting the double-sided coated part of the positive electrode into 10 cm in the longitudinal direction and 1 cm in the width direction was adhered to one side of a double-sided tape (“Nystack NW-15” manufactured by Nichiban Co., Ltd.), and the other side of the double-sided tape As shown in FIG. 4, this surface was adhered to the sample mounting surface 100 of a 90 ° peel tester (“TE-3001” manufactured by Tester Sangyo Co., Ltd.). The end of the sample (positive electrode 1) opposite to the side adhered to the sample setting surface 100 is sandwiched between the jigs 101 of a 90 ° peeling tester and peeled at an angle of 90 ° with respect to the sample setting surface 100. The sample 1 was pulled in the longitudinal direction (the direction of the arrow in the figure) at a speed of 50 mm / min to peel off the positive electrode mixture layer and the current collector, and the strength at that time was measured. It can be evaluated that the larger the peel strength, the better the suppression of the positive electrode active material and the conductive additive from the positive electrode mixture layer can be suppressed.

＜正極巻回体の形状評価＞
扁平状巻回電極体を分解して正極を取り出し、その正極のみ再度巻回して正極巻回体を作製し、その形状を観察した。観察では、正極巻回体の横断面の形状が楕円状である場合を○、長軸方向の両端が尖状やコの字状となった場合を×として、各正極の形状を評価した。 <Evaluation of the shape of the positive electrode winding body>
The flat wound electrode body was disassembled, the positive electrode was taken out, only the positive electrode was wound again to produce a positive electrode wound body, and the shape was observed. In the observation, the shape of each positive electrode was evaluated with a case where the shape of the cross section of the positive electrode wound body was elliptical and a case where both ends in the major axis direction were pointed or U-shaped, and x.

＜非水電解質二次電池の負荷特性＞
４．２Ｖまで０．２Ｃの定電流で充電後、総充電時間が８時間となるまで定電圧充電し、続いて室温で０．２Ｃで電池電圧が３．３Ｖまで定電流放電を行って、そのときの放電容量を求めた。（なお、前記定電流充電時のリチウム基準の電池電圧は４．３Ｖを意味する。）その後、前記条件で再び充電を行った後、２．０Ｃで電池電圧が３．３Ｖになるまで放電を行って、そのときの放電容量を求めた。表では、各電池について得られた充放電サイクル後の放電容量を、実施例１の放電容量を１００としたときの相対値で示す。 <Load characteristics of non-aqueous electrolyte secondary battery>
After charging at a constant current of 0.2 C to 4.2 V, charge at a constant voltage until the total charging time is 8 hours, and then perform a constant current discharge at room temperature to 3.3 V at 0.2 C at room temperature, The discharge capacity at that time was determined. (Note that the lithium-based battery voltage at the time of constant current charging is 4.3 V.) After that, after charging again under the above conditions, the battery is discharged until the battery voltage becomes 3.3 V at 2.0 C. The discharge capacity at that time was determined. In the table, the discharge capacity after the charge / discharge cycle obtained for each battery is shown as a relative value when the discharge capacity of Example 1 is taken as 100.

前記の各評価結果を表２に示す。   The evaluation results are shown in Table 2.

Figure 2012028158
Figure 2012028158

実施例１〜５の非水電解質二次電池に用いた正極は、前記式（１）で表される関係を満たしており、扁平状巻回電極体内での正極合剤層の割れなどの欠陥の発生を抑制可能な程度に折り曲げ強度が大きい。実際に、これらの正極を用いて作製した扁平状巻回電極体（実施例１〜５の電池で用いた扁平状巻回電極体と同じもの）では、正極合剤層の割れなどの欠陥が認められなかった。また、実施例１〜５の非水電解質二次電池に用いた扁平状巻回電極体に係る正極では、正極巻回体としたときの横断面の長軸方向の両端が良好な形状であり、これらの扁平状巻回電極体に用いた正極に係る正極合剤層において、優れた柔軟性を確保し得ていることが確認できる。なお、実施例１〜５の非水電解質二次電池の組み立て時においては、扁平状巻回電極体を外装缶に挿入する際に、挿入が困難になるようなトラブルは発生しなかった。   The positive electrodes used in the nonaqueous electrolyte secondary batteries of Examples 1 to 5 satisfy the relationship represented by the above formula (1), and have defects such as cracks in the positive electrode mixture layer in the flat wound electrode body. The bending strength is high enough to suppress the occurrence of Actually, in the flat wound electrode body produced using these positive electrodes (same as the flat wound electrode body used in the batteries of Examples 1 to 5), defects such as cracks in the positive electrode mixture layer were observed. I was not able to admit. Moreover, in the positive electrode which concerns on the flat winding electrode body used for the nonaqueous electrolyte secondary battery of Examples 1-5, the both ends of the major axis direction of a cross section when it is set as a positive electrode winding body are favorable shapes. In the positive electrode mixture layer according to the positive electrode used in these flat wound electrode bodies, it can be confirmed that excellent flexibility can be secured. In addition, when assembling the nonaqueous electrolyte secondary batteries of Examples 1 to 5, there was no trouble that would make it difficult to insert the flat wound electrode body into the outer can.

更に、実施例１〜５の非水電解質二次電池に用いた正極では、正極合剤層と集電体との剥離強度が大きく、正極合剤層からの正極活物質や導電助剤の脱落を良好に抑制できると考えられる。   Furthermore, in the positive electrode used for the nonaqueous electrolyte secondary batteries of Examples 1 to 5, the peel strength between the positive electrode mixture layer and the current collector was large, and the positive electrode active material and the conductive auxiliary agent dropped off from the positive electrode mixture layer. It is considered that can be suppressed satisfactorily.

このように、実施例１〜５の非水電解質二次電池は、高い信頼性と生産性を有しており、更に表２から明らかなように高い負荷特性も有している。   Thus, the nonaqueous electrolyte secondary batteries of Examples 1 to 5 have high reliability and productivity, and also have high load characteristics as apparent from Table 2.

これに対し、比較例１〜６の非水電解質二次電池は、いずれも、前記式（１）で表される関係を満たしていない正極を使用しているが、このうち、前記式（１）におけるｚが大きすぎる（図３のグラフにおける直線Ｂよりも上に位置する）比較例１、２の電池に使用した正極は、扁平状巻回電極体内での正極合剤層の割れなどの欠陥の発生を抑制可能な程度の折り曲げ強度を確保できておらず、実際に、これらの正極を用いて作製した扁平状巻回電極体（比較例１、２の電池で用いた扁平状巻回電極体と同じもの）では、正極合剤層の割れが生じていた。   On the other hand, all of the nonaqueous electrolyte secondary batteries of Comparative Examples 1 to 6 use the positive electrode that does not satisfy the relationship represented by the formula (1). Z) is too large (positioned above the straight line B in the graph of FIG. 3), the positive electrode used in the batteries of Comparative Examples 1 and 2 was such as a crack in the positive electrode mixture layer in the flat wound electrode body. The bending strength to the extent that the occurrence of defects can be suppressed has not been secured, and the flat wound electrode body fabricated using these positive electrodes (the flat winding used in the batteries of Comparative Examples 1 and 2) In the same case as the electrode body), the positive electrode mixture layer was cracked.

また、比較例３の電池は、使用した正極の正極合剤層における結着剤の体積割合ｘが大きすぎるため、負荷特性が劣っている。   Further, the battery of Comparative Example 3 has inferior load characteristics because the volume ratio x of the binder in the positive electrode mixture layer of the positive electrode used is too large.

更に、前記式（１）におけるｚが小さすぎる（図３のグラフにおける直線Ａよりも下に位置する）比較例４〜６の電池に使用した扁平状巻回電極体に係る正極では、正極巻回体としたときの横断面の長軸方向の両端がコの字状になっており、これらの扁平状巻回電極体に用いた正極に係る正極合剤層において、柔軟性が不足していることが確認できる。なお、比較例４〜６の電池の組み立て時においては、扁平状巻回電極体を外装缶に挿入する際に、外装缶の開口端に扁平状巻回電極体の端部が引っ掛かるトラブルが発生したものがあった。また、比較例５の電池に用いた正極は、正極合剤層における結着剤の体積割合ｘも小さすぎ（図３のグラフにおける直線Ｃよりも左に位置する）、正極合剤層と集電体との剥離強度が小さく、正極合剤層からの正極活物質や導電助剤の脱落が生じやすいと考えられる。   Furthermore, in the positive electrode according to the flat wound electrode body used in the batteries of Comparative Examples 4 to 6 in which z in the formula (1) is too small (located below the straight line A in the graph of FIG. 3) Both ends in the major axis direction of the cross section when it is formed into a circular body are U-shaped, and in the positive electrode mixture layer according to the positive electrode used for these flat wound electrode bodies, the flexibility is insufficient. It can be confirmed. In addition, when assembling the batteries of Comparative Examples 4 to 6, when the flat wound electrode body was inserted into the outer can, there was a problem that the end of the flat wound electrode body was caught at the opening end of the outer can. There was something to do. In the positive electrode used in the battery of Comparative Example 5, the volume ratio x of the binder in the positive electrode mixture layer was too small (positioned to the left of the straight line C in the graph of FIG. 3). It is considered that the peel strength with respect to the electric body is small, and the positive electrode active material and the conductive additive are likely to fall off from the positive electrode mixture layer.

このように、比較例１、２、４〜６の各電池は、実施例１〜５の電池に比べて、信頼性および生産性が劣っている。   Thus, each battery of Comparative Examples 1, 2, 4-6 is inferior in reliability and productivity as compared with the batteries of Examples 1-5.

また、正極合剤層における結着剤の体積割合ｘが大きすぎる（図３のグラフにおける直線Ｄよりも右に位置する）正極を用いた比較例３の電池は、実施例１〜５の電池に比べて負荷特性が劣っている。   Further, the battery of Comparative Example 3 using the positive electrode in which the volume ratio x of the binder in the positive electrode mixture layer is too large (located to the right of the straight line D in the graph of FIG. 3) is the battery of Examples 1-5. Load characteristics are inferior to.

１ 正極
２ 負極
３ セパレータ
４ 外装缶
６ 扁平状巻回電極体 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Exterior can 6 Flat wound electrode body

Claims (6)

正極、負極およびセパレータを重ねて渦巻状に巻回し、横断面を扁平状にした巻回電極体を有する非水電解質二次電池に使用される正極であって、
金属製の集電体と、前記集電体の両面に形成された、正極活物質、導電助剤および結着剤を含有する正極合剤層とを有しており、
前記結着剤の引張弾性率をｙ（ＭＰａ）、前記正極合剤層の構成成分の全体積中における前記結着剤の体積割合をｘ（体積％）としたとき、前記ｘと前記ｙとが、下記式（１）
ｙ＝−６００ｘ＋ｚ （１）
［ただし、前記式（１）中、３．５≦ｘ≦４．５であり、かつ３３００≦ｚ≦４１００である］
で表される関係を満たし、
前記集電体の引張強度が、３．１５Ｎ／ｍｍ以上であることを特徴とする非水電解質二次電池用正極。 A positive electrode used for a non-aqueous electrolyte secondary battery having a spirally wound electrode body in which a positive electrode, a negative electrode, and a separator are overlapped and wound in a spiral shape,
A metal current collector, and a positive electrode mixture layer formed on both surfaces of the current collector, containing a positive electrode active material, a conductive additive, and a binder;
When the tensile modulus of the binder is y (MPa) and the volume ratio of the binder in the total volume of the constituent components of the positive electrode mixture layer is x (volume%), the x and the y Is the following formula (1)
y = −600x + z (1)
[In the formula (1), 3.5 ≦ x ≦ 4.5 and 3300 ≦ z ≦ 4100]
Satisfy the relationship represented by
A positive electrode for a non-aqueous electrolyte secondary battery, wherein the current collector has a tensile strength of 3.15 N / mm or more. 正極合剤層の充填率が７５％以上である請求項１に記載の非水電解質二次電池用正極。   The positive electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein a filling rate of the positive electrode mixture layer is 75% or more. 結着剤の少なくとも一部がゴムである請求項１または２に記載の非水電解質二次電池用正極。   The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein at least a part of the binder is rubber. 正極合剤層において、結着剤であるゴムの量が、正極活物質１００質量部に対して０．１〜０．５質量部である請求項３に記載の非水電解質二次電池用正極。   The positive electrode for a nonaqueous electrolyte secondary battery according to claim 3, wherein the amount of rubber as a binder in the positive electrode mixture layer is 0.1 to 0.5 parts by mass with respect to 100 parts by mass of the positive electrode active material. . 正極、負極およびセパレータを重ねて渦巻状に巻回し、横断面を扁平状にした巻回電極体を有する非水電解質二次電池であって、
前記正極が、請求項１〜４のいずれかに記載の非水電解質二次電池用正極であることを特徴とする非水電解質二次電池。 A non-aqueous electrolyte secondary battery having a wound electrode body in which a positive electrode, a negative electrode, and a separator are overlapped and wound in a spiral shape, and the cross section is flattened,
The said positive electrode is a positive electrode for nonaqueous electrolyte secondary batteries in any one of Claims 1-4, The nonaqueous electrolyte secondary battery characterized by the above-mentioned. 角筒形の外装缶を有している請求項５に記載の非水電解質二次電池。   The nonaqueous electrolyte secondary battery according to claim 5, comprising a rectangular tube-shaped outer can.
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