JP2019029205A - Positive electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery - Google Patents

Positive electrode for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery Download PDF

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JP2019029205A
JP2019029205A JP2017147683A JP2017147683A JP2019029205A JP 2019029205 A JP2019029205 A JP 2019029205A JP 2017147683 A JP2017147683 A JP 2017147683A JP 2017147683 A JP2017147683 A JP 2017147683A JP 2019029205 A JP2019029205 A JP 2019029205A
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positive electrode
active material
electrode active
mixture layer
current collector
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JP6957257B2 (en
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直之 和田
Naoyuki Wada
直之 和田
福本　友祐
Yusuke Fukumoto
友祐 福本
朝樹 塩崎
Tomoki Shiozaki
朝樹 塩崎
行広 岡田
Yukihiro Okada
行広 岡田
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Panasonic Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

To provide a positive electrode for a nonaqueous electrolyte secondary battery capable of restraining heat evolution of the battery at the time of an internal short circuit.SOLUTION: A positive electrode 11 for a nonaqueous electrolyte secondary battery has a positive electrode collector 30, and a positive electrode material layer 32 being provided on the positive electrode collector 30, and containing first and second positive electrode active materials. The first positive electrode active material is Ni-containing lithium composite oxide, where a ratio of Ni to the total mol number of metal elements excepting Li is 70-100 mole %, the second positive electrode active material is Ni-containing lithium composite oxide, where a ratio of Ni to the total mol number of metal elements excepting Li is 10-60 mole %, and in a thickness direction of the positive electrode material layer 32, an abundance ratio of the second positive electrode active material existing in the positive electrode material layer (hatching region A) from a positive electrode collector side surface 32a to a portion having a thickness of 4 μm is 55% or more.SELECTED DRAWING: Figure 2

Description

本開示は、非水電解質二次電池用正極、及び非水電解質二次電池に関する。   The present disclosure relates to a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.

近年、高出力、高エネルギー密度の二次電池として、正極と、負極と、非水電解質とを備え、正極と負極との間でリチウムイオンを移動させて充放電を行う非水電解質二次電池が広く利用されている。   In recent years, as a secondary battery with high output and high energy density, a nonaqueous electrolyte secondary battery that includes a positive electrode, a negative electrode, and a nonaqueous electrolyte, and performs charge / discharge by moving lithium ions between the positive electrode and the negative electrode Is widely used.

特許文献１には、大粒径活物質と小粒径活物質を含み、大粒径活物質と小粒径活物質の平均粒径の比が６：１〜１００：１であり、大粒径活物質と小粒径活物質との混合比率が６０：４０〜９０：１０である正極活物質を含む正極が開示されている。特許文献１によれば、上記構成を備えることにより、正極活物質の充填密度、熱的安定性を向上させることができると記載されている。   Patent Document 1 includes a large particle size active material and a small particle size active material, and the ratio of the average particle size of the large particle size active material and the small particle size active material is 6: 1 to 100: 1. A positive electrode including a positive electrode active material in which the mixing ratio of the diameter active material and the small particle size active material is 60:40 to 90:10 is disclosed. According to Patent Document 1, it is described that the packing density and thermal stability of the positive electrode active material can be improved by providing the above configuration.

特開２００６−２２８７３３号公報JP 2006-228733 A

ところで、正極集電体と、正極集電体上に配置され、正極活物質を含む正極合材層とを有する正極と、負極とを備える非水電解質二次電池において、例えば、導電性異物等が突き刺さり、負極電位を帯びた導電性異物等が正極集電体に達して内部短絡が発生すると、正極集電体と負極との間で短絡電流が流れて、電池が発熱する場合がある。ここで、リチウムを除く金属元素の総モル数に対するＮｉの割合が７０モル％以上１００モル％以下のＮｉ含有リチウム複合酸化物は、非水電解質二次電池の高容量化を図ることができる正極活物質として期待されているが、電子抵抗が低いため、当該Ｎｉ含有リチウム複合酸化物を正極活物質として用いた非水電解質二次電池において内部短絡が発生した場合には、正極集電体と負極との間に流れる短絡電流が増大し、電池の発熱がより大きくなる場合がある。   By the way, in a non-aqueous electrolyte secondary battery including a positive electrode current collector, a positive electrode having a positive electrode mixture layer that is disposed on the positive electrode current collector and includes a positive electrode active material, and a negative electrode, for example, conductive foreign matters, etc. When a conductive foreign material or the like having a negative electrode potential reaches the positive electrode current collector and an internal short circuit occurs, a short-circuit current flows between the positive electrode current collector and the negative electrode, and the battery may generate heat. Here, the Ni-containing lithium composite oxide in which the ratio of Ni to the total number of moles of metal elements excluding lithium is 70 mol% or more and 100 mol% or less is a positive electrode capable of increasing the capacity of the nonaqueous electrolyte secondary battery. Although expected as an active material, since the electronic resistance is low, when an internal short circuit occurs in a nonaqueous electrolyte secondary battery using the Ni-containing lithium composite oxide as a positive electrode active material, a positive electrode current collector and In some cases, the short-circuit current flowing between the negative electrode and the battery increases, and the heat generation of the battery increases.

そこで、本開示の目的は、正極活物質としてリチウムを除く金属元素の総モル数に対するＮｉの割合が７０モル％以上１００モル％以下のＮｉ含有リチウム複合酸化物を用いた場合においても、内部短絡時の電池の発熱を抑制することが可能な非水電解質二次電池用正極及び非水電解質二次電池を提供することである。   Therefore, an object of the present disclosure is to provide an internal short circuit even when a Ni-containing lithium composite oxide in which the ratio of Ni to the total number of moles of metal elements excluding lithium is 70 mol% or more and 100 mol% or less is used as the positive electrode active material. It is to provide a positive electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery that can suppress heat generation of the battery at the time.

本開示の一態様である非水電解質二次電池用正極は、正極集電体と、前記正極集電体上に設けられ、第１正極活物質と第２正極活物質を含む正極合材層と、を有し、前記第１正極活物質は、Ｎｉ含有リチウム複合酸化物であって、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が７０モル％以上１００モル％以下であり、前記第２正極活物質は、Ｎｉ含有リチウム複合酸化物であって、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が１０モル％以上６０モル％以下であり、前記正極合材層の厚み方向において、正極集電体側表面から４μｍの厚さまでの正極合材層内に存在する前記第２正極活物質の存在率は、５５％以上である。   A positive electrode for a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure includes a positive electrode current collector and a positive electrode mixture layer provided on the positive electrode current collector and including a first positive electrode active material and a second positive electrode active material And the first positive electrode active material is a Ni-containing lithium composite oxide, wherein the ratio of Ni to the total number of moles of metal elements excluding Li is 70 mol% or more and 100 mol% or less, The second positive electrode active material is a Ni-containing lithium composite oxide, wherein the ratio of Ni to the total number of moles of metal elements excluding Li is 10 mol% or more and 60 mol% or less, and the thickness direction of the positive electrode mixture layer , The abundance ratio of the second positive electrode active material present in the positive electrode mixture layer from the positive electrode current collector side surface to a thickness of 4 μm is 55% or more.

本開示の一態様である非水電解質二次電池は、正極と、負極と、非水電解質とを備え、前記正極が上記非水電解質二次電池用正極である。   A nonaqueous electrolyte secondary battery which is one embodiment of the present disclosure includes a positive electrode, a negative electrode, and a nonaqueous electrolyte, and the positive electrode is the positive electrode for a nonaqueous electrolyte secondary battery.

本開示の一態様によれば、正極活物質としてリチウムを除く金属元素の総モル数に対するＮｉの割合が７０モル％以上１００モル％以下のＮｉ含有リチウム複合酸化物を用いた場合においても、内部短絡時の電池の発熱を抑制することが可能となる。   According to one aspect of the present disclosure, even when a Ni-containing lithium composite oxide in which the ratio of Ni to the total number of moles of metal elements excluding lithium is 70 mol% or more and 100 mol% or less is used as the positive electrode active material, It becomes possible to suppress the heat generation of the battery at the time of a short circuit.

実施形態の一例である非水電解質二次電池の断面図である。It is sectional drawing of the nonaqueous electrolyte secondary battery which is an example of embodiment. 実施形態の一例である正極の断面図である。It is sectional drawing of the positive electrode which is an example of embodiment.

本開示の一態様である非水電解質二次電池用正極は、正極集電体と、前記正極集電体上に設けられ、第１正極活物質と第２正極活物質を含む正極合材層と、を有し、前記第１正極活物質は、Ｎｉ含有リチウム複合酸化物であって、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が７０モル％以上１００モル％以下であり、前記第２正極活物質は、Ｎｉ含有リチウム複合酸化物であって、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が１０モル％以上６０モル％以下であり、前記正極合材層の厚み方向において、正極集電体側表面から４μｍの厚さまでの正極合材層内に存在する前記第２正極活物質の存在率は、５５％以上である。ここで、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が１０モル％以上６０モル％以下であるＮｉ含有リチウム複合酸化物（第２正極活物質）は、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が７０モル％以上１００モル％以下のＮｉ含有リチウム複合酸化物（第１正極活物質）と比較して、電子抵抗が高い物質である。そして、このような電子抵抗の高い第２正極活物質を用いて、正極集電体側表面から４μｍの厚さまでの間の正極合材層内に存在する第２正極活物質の存在率を５５％以上とすることで、負極電位を帯びた導電性異物等が正極集電体に達して内部短絡が発生した場合でも、正極集電体側表面から４μｍの厚さまでの間の正極合材層が、当該導電性異物の周囲に存在する抵抗成分となるため、第１正極活物質のみを用いた場合と比較して、内部短絡時における正極集電体と負極との間の短絡電流が抑制され、電池の発熱も抑制される。   A positive electrode for a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure includes a positive electrode current collector and a positive electrode mixture layer provided on the positive electrode current collector and including a first positive electrode active material and a second positive electrode active material And the first positive electrode active material is a Ni-containing lithium composite oxide, wherein the ratio of Ni to the total number of moles of metal elements excluding Li is 70 mol% or more and 100 mol% or less, The second positive electrode active material is a Ni-containing lithium composite oxide, wherein the ratio of Ni to the total number of moles of metal elements excluding Li is 10 mol% or more and 60 mol% or less, and the thickness direction of the positive electrode mixture layer , The abundance ratio of the second positive electrode active material present in the positive electrode mixture layer from the positive electrode current collector side surface to a thickness of 4 μm is 55% or more. Here, the Ni-containing lithium composite oxide (second positive electrode active material) in which the ratio of Ni to the total number of moles of metal elements excluding Li is 10 mol% or more and 60 mol% or less is the total number of metal elements excluding Li. Compared with the Ni-containing lithium composite oxide (first positive electrode active material) in which the ratio of Ni to the number is 70 mol% or more and 100 mol% or less, the electron resistance is high. Then, using such a second positive electrode active material having a high electron resistance, the abundance ratio of the second positive electrode active material existing in the positive electrode mixture layer from the positive electrode current collector side surface to a thickness of 4 μm is 55%. With the above, even when a conductive foreign material or the like having a negative electrode potential reaches the positive electrode current collector and an internal short circuit occurs, the positive electrode mixture layer between the positive electrode current collector side surface and a thickness of 4 μm is Since it becomes a resistance component that exists around the conductive foreign matter, compared with the case where only the first positive electrode active material is used, the short circuit current between the positive electrode current collector and the negative electrode at the time of internal short circuit is suppressed, Battery heat generation is also suppressed.

以下、実施形態の一例について詳細に説明する。実施形態の説明で参照する図面は、模式的に記載されたものであり、図面に描画された構成要素の寸法比率などは、現物と異なる場合がある。   Hereinafter, an example of the embodiment will be described in detail. The drawings referred to in the description of the embodiments are schematically described, and the dimensional ratios of the components drawn in the drawings may be different from the actual products.

図１は、実施形態の一例である非水電解質二次電池の断面図である。図１に示す非水電解質二次電池１０は、正極１１及び負極１２がセパレータ１３を介して巻回されてなる巻回型の電極体１４と、非水電解質と、電極体１４の上下にそれぞれ配置された絶縁板１７，１８と、上記部材を収容する電池ケースと、を備える。電池ケースは、有底円筒形状のケース本体１５と封口体１６とにより構成される。なお、巻回型の電極体１４の代わりに、正極及び負極がセパレータを介して交互に積層されてなる積層型の電極体など、他の形態の電極体が適用されてもよい。また、電池ケースとしては、円筒形、角形、コイン形、ボタン形等の金属製ケース、樹脂シートをラミネートして形成された樹脂製ケース（ラミネート型電池）などが例示できる。   FIG. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery which is an example of an embodiment. A non-aqueous electrolyte secondary battery 10 shown in FIG. 1 includes a wound electrode body 14 in which a positive electrode 11 and a negative electrode 12 are wound via a separator 13, a non-aqueous electrolyte, and an electrode body 14 above and below, respectively. Insulating plates 17 and 18 disposed, and a battery case that accommodates the members are provided. The battery case includes a bottomed cylindrical case body 15 and a sealing body 16. Instead of the wound electrode body 14, other forms of electrode bodies such as a stacked electrode body in which positive and negative electrodes are alternately stacked via separators may be applied. Examples of battery cases include metal cases such as cylinders, squares, coins, and buttons, and resin cases (laminated batteries) formed by laminating resin sheets.

ケース本体１５は、例えば有底円筒形状の金属製容器である。ケース本体１５と封口体１６との間にはガスケット２７が設けられ、電池ケース内部の密閉性が確保される。ケース本体１５は、例えば側面部を外側からプレスして形成された、封口体１６を支持する張り出し部２１を有することが好適である。張り出し部２１は、ケース本体１５の周方向に沿って環状に形成されることが好ましく、その上面で封口体１６を支持する。   The case body 15 is, for example, a bottomed cylindrical metal container. A gasket 27 is provided between the case main body 15 and the sealing body 16 to ensure the airtightness inside the battery case. The case main body 15 preferably has an overhanging portion 21 that supports the sealing body 16 formed by pressing a side surface portion from the outside, for example. The overhang portion 21 is preferably formed in an annular shape along the circumferential direction of the case body 15, and supports the sealing body 16 on the upper surface thereof.

封口体１６は、フィルタ開口部２２ａが形成されたフィルタ２２と、フィルタ２２上に配置された弁体とを有する。弁体は、フィルタ２２のフィルタ開口部２２ａを塞いでおり、内部短絡等による発熱で電池の内圧が上昇した場合に破断する。本実施形態では、弁体として下弁体２３及び上弁体２５が設けられており、下弁体２３と上弁体２５の間に配置される絶縁部材２４、及びキャップ開口部２６ａを有するキャップ２６がさらに設けられている。封口体１６を構成する各部材は、例えば円板形状又はリング形状を有し、絶縁部材２４を除く各部材は互いに電気的に接続されている。具体的には、フィルタ２２と下弁体２３が各々の周縁部で互いに接合され、上弁体２５とキャップ２６も各々の周縁部で互いに接合されている。下弁体２３と上弁体２５は、各々の中央部で互いに接続され、各周縁部の間には絶縁部材２４が介在している。なお、内部短絡等による発熱で内圧が上昇すると、例えば下弁体２３が薄肉部で破断し、これにより上弁体２５がキャップ２６側に膨れて下弁体２３から離れることにより両者の電気的接続が遮断される。   The sealing body 16 includes a filter 22 in which a filter opening 22 a is formed and a valve body disposed on the filter 22. The valve element closes the filter opening 22a of the filter 22, and breaks when the internal pressure of the battery rises due to heat generated by an internal short circuit or the like. In the present embodiment, a lower valve body 23 and an upper valve body 25 are provided as valve bodies, and an insulating member 24 disposed between the lower valve body 23 and the upper valve body 25, and a cap having a cap opening 26a. 26 is further provided. The members constituting the sealing body 16 have, for example, a disk shape or a ring shape, and the members other than the insulating member 24 are electrically connected to each other. Specifically, the filter 22 and the lower valve body 23 are joined to each other at the peripheral portion, and the upper valve body 25 and the cap 26 are also joined to each other at the peripheral portion. The lower valve body 23 and the upper valve body 25 are connected to each other at the center, and an insulating member 24 is interposed between the peripheral edges. When the internal pressure rises due to heat generation due to an internal short circuit or the like, for example, the lower valve body 23 is broken at the thin wall portion, whereby the upper valve body 25 swells to the cap 26 side and separates from the lower valve body 23, thereby The connection is interrupted.

図１に示す非水電解質二次電池１０では、正極１１に取り付けられた正極リード１９が絶縁板１７の貫通孔を通って封口体１６側に延び、負極１２に取り付けられた負極リード２０が絶縁板１８の外側を通ってケース本体１５の底部側に延びている。例えば、正極リード１９は封口体１６の底板であるフィルタ２２の下面に溶接等で接続され、フィルタ２２と電気的に接続された封口体１６の天板であるキャップ２６が正極端子となる。負極リード２０はケース本体１５の底部内面に溶接等で接続され、ケース本体１５が負極端子となる。   In the nonaqueous electrolyte secondary battery 10 shown in FIG. 1, the positive electrode lead 19 attached to the positive electrode 11 extends to the sealing body 16 side through the through hole of the insulating plate 17, and the negative electrode lead 20 attached to the negative electrode 12 is insulated. It extends to the bottom side of the case body 15 through the outside of the plate 18. For example, the positive electrode lead 19 is connected to the lower surface of the filter 22 that is the bottom plate of the sealing body 16 by welding or the like, and the cap 26 that is the top plate of the sealing body 16 electrically connected to the filter 22 serves as the positive electrode terminal. The negative electrode lead 20 is connected to the bottom inner surface of the case main body 15 by welding or the like, and the case main body 15 serves as a negative electrode terminal.

［正極］
図２は、実施形態の一例である正極の断面図である。正極１１は、正極集電体３０と、正極集電体３０上に配置される正極合材層３２とを備える。なお、正極合材層３２は正極集電体３０の両面に配置されることが望ましい。 [Positive electrode]
FIG. 2 is a cross-sectional view of a positive electrode that is an example of the embodiment. The positive electrode 11 includes a positive electrode current collector 30 and a positive electrode mixture layer 32 disposed on the positive electrode current collector 30. The positive electrode mixture layer 32 is desirably disposed on both surfaces of the positive electrode current collector 30.

正極集電体３０には、アルミニウムやアルミニウム合金などの正極の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等を用いることができる。正極集電体３０は、例えば、１０μｍ〜１００μｍ程度の厚みを有する。   As the positive electrode current collector 30, a metal foil that is stable in the potential range of the positive electrode, such as aluminum or an aluminum alloy, a film in which the metal is disposed on the surface layer, or the like can be used. The positive electrode current collector 30 has a thickness of about 10 μm to 100 μm, for example.

正極合材層３２は、第１正極活物質及び第２正極活物質を含む。正極合材層３２は、正極活物質同士を結着して正極合材層３２の機械的強度を確保する等の点で、結着材を含むことが好適である。また、正極合材層３２は、当該層の導電性を向上させることができる等の点で、導電材を含むことが好適である。   The positive electrode mixture layer 32 includes a first positive electrode active material and a second positive electrode active material. The positive electrode mixture layer 32 preferably includes a binder in that the positive electrode active materials are bonded together to ensure the mechanical strength of the positive electrode mixture layer 32. In addition, the positive electrode mixture layer 32 preferably contains a conductive material in that the conductivity of the layer can be improved.

第１正極活物質は、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が７０モル％以上１００モル％以下であるＮｉ含有リチウム複合酸化物であれば特に制限されるものではないが、例えば、非水電解質二次電池の充放電サイクル特性の低下を抑制することができる等の点から、以下の一般式（１）で表されるＮｉ含有リチウム複合酸化物であることが好ましい。
Ｌｉａ１Ｎｉｂ１Ｃｏｃ１Ｍｄ１Ｏ２ （１）
式中、ａ１、ｂ１、ｃ１、及びｄ１はそれぞれ、０．９≦ａ１≦１．２、０．７≦ｂ１≦０．９５、０≦ｃ１≦０．３、０≦ｄ１≦０．３を満たすことが好ましく、０．９≦ａ１≦１．２、０．７≦ｂ１≦０．９、０．０５≦ｃ１≦０．１５、０．０５≦ｄ１≦０．１５を満たすことがより好ましい。また、式中Ｍは、Ｌｉ、Ｎｉ、Ｃｏ以外の少なくとも１種の元素であれば特に制限されるものではないが、例えば、Ｍｎ、Ａｌ、Ｚｒ、Ｗ、Ｆｅ、Ｍｇ、Ｔｉ、Ｃｒ、Ｃｕ、Ｚｅ、Ｓｎ、Ｎｂ、Ｍｏ、Ｔａ、Ｎａ、Ｋ、Ｂａ、Ｓｒ、Ｂｉ、Ｂｅ及びＢから選ばれる少なくとも１種の元素であることが好ましく、Ｍｎ、Ａｌ、Ｚｒ、及びＷから選ばれる少なくとも１種の元素であることがより好ましい。 The first positive electrode active material is not particularly limited as long as it is a Ni-containing lithium composite oxide in which the ratio of Ni to the total number of moles of metal elements excluding Li is 70 mol% or more and 100 mol% or less. In view of the ability to suppress a decrease in charge / discharge cycle characteristics of the nonaqueous electrolyte secondary battery, a Ni-containing lithium composite oxide represented by the following general formula (1) is preferable.
Li a1 Ni b1 Co c1 M d1 O 2 (1)
In the formula, a1, b1, c1, and d1 are 0.9 ≦ a1 ≦ 1.2, 0.7 ≦ b1 ≦ 0.95, 0 ≦ c1 ≦ 0.3, and 0 ≦ d1 ≦ 0.3, respectively. Preferably, it satisfies 0.9 ≦ a1 ≦ 1.2, 0.7 ≦ b1 ≦ 0.9, 0.05 ≦ c1 ≦ 0.15, and more preferably 0.05 ≦ d1 ≦ 0.15. . In the formula, M is not particularly limited as long as it is at least one element other than Li, Ni, and Co. For example, Mn, Al, Zr, W, Fe, Mg, Ti, Cr, Cu , Ze, Sn, Nb, Mo, Ta, Na, K, Ba, Sr, Bi, Be and B are preferable, and at least one selected from Mn, Al, Zr and W is preferable. More preferably, it is one kind of element.

第２正極活物質は、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が１０モル％以上６０モル％以下であるＮｉ含有リチウム複合酸化物であれば特に制限されるものではないが、例えば、内部短絡時の電池の発熱をより抑制することができる等の点から、以下の一般式（２）で表されるＮｉ含有リチウム複合酸化物であることが好ましい。
Ｌｉａ２Ｎｉｂ２Ｃｏｃ２Ｍｄ２Ｏ２ （２）
式中、ａ２、ｂ２、ｃ２、及びｄ２はそれぞれ、０．９≦ａ２≦１．２、０．１≦ｂ２≦０．６、０．１≦ｃ２≦０．６、０．１≦ｄ２≦０．５５を満たすことが好ましく、０．９≦ａ２≦１．２、０．２≦ｂ２≦０．５、０．２≦ｃ２≦０．４、０．２≦ｄ２≦０．５５を満たすことがより好ましい。また、式中Ｍは、Ｌｉ、Ｎｉ、Ｃｏ以外の少なくとも１種の元素であれば特に制限されるものではないが、例えば、Ｍｎ、Ａｌ、Ｚｒ、Ｗ、Ｆｅ、Ｍｇ、Ｔｉ、Ｃｒ、Ｃｕ、Ｚｅ、Ｓｎ、Ｎｂ、Ｍｏ、Ｔａ、Ｎａ、Ｋ、Ｂａ、Ｓｒ、Ｂｉ、Ｂｅ及びＢから選ばれる少なくとも１種の元素であることが好ましく、Ｍｎ、Ａｌ、Ｚｒ、及びＷから選ばれる少なくとも１種の元素であることがより好ましい。 The second positive electrode active material is not particularly limited as long as it is a Ni-containing lithium composite oxide in which the ratio of Ni to the total number of moles of metal elements excluding Li is 10 mol% or more and 60 mol% or less. From the point that the heat generation of the battery at the time of an internal short circuit can be further suppressed, it is preferable that the Ni-containing lithium composite oxide represented by the following general formula (2).
Li a2 Ni b2 Co c2 M d2 O 2 (2)
In the formula, a2, b2, c2, and d2 are 0.9 ≦ a2 ≦ 1.2, 0.1 ≦ b2 ≦ 0.6, 0.1 ≦ c2 ≦ 0.6, and 0.1 ≦ d2 ≦, respectively. 0.55 is preferably satisfied, and 0.9 ≦ a2 ≦ 1.2, 0.2 ≦ b2 ≦ 0.5, 0.2 ≦ c2 ≦ 0.4, and 0.2 ≦ d2 ≦ 0.55 are satisfied. It is more preferable. In the formula, M is not particularly limited as long as it is at least one element other than Li, Ni, and Co. For example, Mn, Al, Zr, W, Fe, Mg, Ti, Cr, Cu , Ze, Sn, Nb, Mo, Ta, Na, K, Ba, Sr, Bi, Be and B are preferable, and at least one selected from Mn, Al, Zr and W is preferable. More preferably, it is one kind of element.

正極合材層３２の厚み方向において、正極集電体側表面３２ａから４μｍの厚さまでの正極合材層（図２に示すハッチング領域Ａ）内に存在する第２正極活物質の存在率は５５％以上である。既述したように、第２正極活物質の存在率を５５％以上とした正極集電体側表面３２ａから４μｍの厚さまでの間の正極合材層は、内部短絡時の導電性異物の周囲に存在する抵抗成分となるため、正極集電体と負極との間の短絡電流が抑制され、電池の発熱も抑制される。正極集電体側表面３２ａから４μｍの厚さまでの正極合材層内に存在する第２正極活物質の存在率は、内部短絡時における電池の発熱を抑制する点、非水電解質二次電池の高容量化を図る点等で、６０％以上８５％以下であることが好ましい。   In the thickness direction of the positive electrode mixture layer 32, the abundance of the second positive electrode active material existing in the positive electrode mixture layer (hatched area A shown in FIG. 2) from the positive electrode current collector side surface 32a to a thickness of 4 μm is 55%. That's it. As described above, the positive electrode mixture layer between the positive electrode current collector-side surface 32a and the thickness of 4 μm having the abundance ratio of the second positive electrode active material of 55% or more is around the conductive foreign matter at the time of internal short circuit. Since the resistance component is present, a short-circuit current between the positive electrode current collector and the negative electrode is suppressed, and heat generation of the battery is also suppressed. The abundance ratio of the second positive electrode active material present in the positive electrode mixture layer from the positive electrode current collector side surface 32a to a thickness of 4 μm suppresses the heat generation of the battery at the time of an internal short circuit, and is high in the nonaqueous electrolyte secondary battery. From the viewpoint of increasing the capacity, etc., it is preferably 60% or more and 85% or less.

第２正極活物質の存在率は、電子線マイクロアナライザ（ＥＰＭＡ）の元素マッピングを行える装置を利用することで検出することができる。例えば、ＥＰＭＡのＮｉ元素マッピングにより、Ｎｉ含有量の高い第１正極活物質とＮｉ含有量の低い第２正極活物質とを判別することができる。第１正極活物質と第２正極活物質で含まれている元素が異なる場合は、その元素でマッピングしてもよい。より具体的には、クロスセクションポリッシャー等により、正極の厚み方向における断面を作製し、その断面を、電子線マイクロアナライザ（日本電子社製）を用いて、３００倍の画像観察を行い、この画像において、正極集電体側表面３２ａから４μｍの厚さまでの正極合材層中に存在する第２正極活物質の総面積を求める。そして、画像観察の行われた正極集電体側表面３２ａから４μｍの厚さまでの正極合材層の面積に対する上記算出した第２正極活物質の総面積の割合を求める。この測定を１０回繰り返した結果の平均を、正極合材層３２の厚み方向において、正極集電体側表面３２ａから４μｍの厚さまでの正極合材層に存在する第２正極活物質の存在率とする。   The abundance of the second positive electrode active material can be detected by using a device capable of element mapping by an electron beam microanalyzer (EPMA). For example, the first positive electrode active material having a high Ni content and the second positive electrode active material having a low Ni content can be discriminated by Ni element mapping of EPMA. When the elements contained in the first positive electrode active material and the second positive electrode active material are different, mapping may be performed using the element. More specifically, a cross section in the thickness direction of the positive electrode is produced by a cross section polisher or the like, and the cross section is subjected to 300-fold image observation using an electron beam microanalyzer (manufactured by JEOL Ltd.). The total area of the second positive electrode active material present in the positive electrode mixture layer from the positive electrode current collector side surface 32a to a thickness of 4 μm is determined. Then, the ratio of the calculated total area of the second positive electrode active material to the area of the positive electrode mixture layer from the positive electrode current collector side surface 32a where the image is observed to the thickness of 4 μm is obtained. The average of the results of repeating this measurement 10 times is the abundance ratio of the second positive electrode active material existing in the positive electrode mixture layer from the positive electrode current collector side surface 32a to a thickness of 4 μm in the thickness direction of the positive electrode mixture layer 32. To do.

第１正極活物質と第２正極活物質の質量比、第１正極活物質及び第２正極活物質の平均粒径及び粒径比は、正極合材層３２の厚み方向において、正極集電体側表面３２ａから４μｍの厚さまでの正極合材層内に存在する第２正極活物質の存在率を５５％以上に調整することが容易となる点で、以下の範囲を満たすことが好ましい。また、以下の範囲を満たすことで、非水電解質二次電池の電池容量が増加したり、非水電解質二次電池の電池抵抗が低減したり、或いは非水電解質二次電池の充放電サイクル特性の低下が抑制されたりする場合がある。   The mass ratio of the first positive electrode active material and the second positive electrode active material, the average particle size and the particle size ratio of the first positive electrode active material and the second positive electrode active material are the positive electrode current collector side in the thickness direction of the positive electrode mixture layer 32. The following range is preferably satisfied in that it is easy to adjust the abundance ratio of the second positive electrode active material existing in the positive electrode mixture layer from the surface 32a to a thickness of 4 μm to 55% or more. In addition, by satisfying the following ranges, the battery capacity of the nonaqueous electrolyte secondary battery increases, the battery resistance of the nonaqueous electrolyte secondary battery decreases, or the charge / discharge cycle characteristics of the nonaqueous electrolyte secondary battery May be suppressed.

正極合材層３２に含まれる第１正極活物質の質量（Ｗ１）と第２正極活物質の質量（Ｗ２）の比（Ｗ１／Ｗ２）は、例えば、１以上９以下であることが好ましく、４以上９以下であることがより好ましい。なお、正極合材層３２中の第１正極活物質の含有量は、５０質量％以上９０質量％以下であることが好ましく、正極合材層３２中の第２正極活物質の含有量は、１０質量％以上５０質量％以下であることが好ましい。   The ratio (W1 / W2) of the mass (W1) of the first positive electrode active material and the mass (W2) of the second positive electrode active material contained in the positive electrode mixture layer 32 is preferably 1 or more and 9 or less, More preferably, it is 4 or more and 9 or less. The content of the first positive electrode active material in the positive electrode mixture layer 32 is preferably 50% by mass or more and 90% by mass or less, and the content of the second positive electrode active material in the positive electrode mixture layer 32 is It is preferable that they are 10 mass% or more and 50 mass% or less.

第１正極活物質の平均粒径（Ｄ１）は、８μｍ以上２０μｍ以下であることが好ましく、８μｍ以上１２μｍ以下であることがより好ましい。また、第２正極活物質の平均粒径（Ｄ２）は、２μｍ以上６μｍ以下であることが好ましく、２μｍ以上４μｍ以下であることがより好ましい。また、第１正極活物質の平均粒径（Ｄ１）と第２正極活物質の平均粒径（Ｄ２）との比（Ｄ１／Ｄ２）は２以上１０以下であることが好ましく、３以上５以下であることがより好ましい。   The average particle diameter (D1) of the first positive electrode active material is preferably 8 μm or more and 20 μm or less, and more preferably 8 μm or more and 12 μm or less. The average particle diameter (D2) of the second positive electrode active material is preferably 2 μm or more and 6 μm or less, and more preferably 2 μm or more and 4 μm or less. The ratio (D1 / D2) of the average particle diameter (D1) of the first positive electrode active material to the average particle diameter (D2) of the second positive electrode active material is preferably 2 or more and 10 or less, and preferably 3 or more and 5 or less. It is more preferable that

ここで、平均粒径とは、レーザ回折法によって測定される体積平均粒径であって、粒子径分布において体積積算値が５０％となるメジアン径を意味する。第１正極活物質及び第２正極活物質の平均粒径は、例えば、レーザ回折散乱式粒度分布測定装置（株式会社堀場製作所製）を用いて測定できる。   Here, the average particle diameter is a volume average particle diameter measured by a laser diffraction method, and means a median diameter at which the volume integrated value is 50% in the particle diameter distribution. The average particle diameter of the first positive electrode active material and the second positive electrode active material can be measured using, for example, a laser diffraction / scattering particle size distribution analyzer (manufactured by Horiba, Ltd.).

正極合材層３２に含まれる導電材としては、カーボンブラック、アセチレンブラック、ケッチェンブラック、黒鉛等の炭素材料が例示できる。これらは、単独で用いてもよく、２種類以上を組み合わせて用いてもよい。   Examples of the conductive material included in the positive electrode mixture layer 32 include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. These may be used alone or in combination of two or more.

正極合材層３２に含まれる導電材の含有量は、例えば、非水電解質二次電池の高容量化を図りながら、内部短絡時の電池の発熱を抑制することができる点等で、０．５質量％以上４質量％以下であることが好ましく、０．５質量％以上１．５質量％以下であることがより好ましい。   The content of the conductive material contained in the positive electrode mixture layer 32 is, for example, 0. 0 in that the heat generation of the battery at the time of an internal short circuit can be suppressed while increasing the capacity of the nonaqueous electrolyte secondary battery. It is preferably 5% by mass or more and 4% by mass or less, and more preferably 0.5% by mass or more and 1.5% by mass or less.

正極合材層３２に含まれる結着材としては、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶｄＦ）等のフッ素樹脂、ポリアクリロニトリル（ＰＡＮ）、ポリイミド、アクリル樹脂、ポリオレフィン等が例示できる。また、これらの樹脂と、カルボキシメチルセルロース（ＣＭＣ）又はその塩、ポリエチレンオキシド（ＰＥＯ）等が併用されてもよい。これらは、単独で用いてもよく、２種類以上を組み合わせて用いてもよい。   Examples of the binder contained in the positive electrode mixture layer 32 include fluorine resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide, acrylic resin, and polyolefin. These resins may be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), and the like. These may be used alone or in combination of two or more.

正極合材層３２には、第１正極活物質及び第２正極活物質以外の正極活物質が含有されていてもよい。第１正極活物質及び第２正極活物質以外の正極活物質としては、可逆的にリチウムを挿入・脱離可能な化合物であれば特に限定されず、例えば、ＬｉＭｎ２Ｏ４、ＬｉＣｏＯ２等のＮｉ非含有のＬｉ複合酸化物、第２正極活物質よりＮｉ含有量の少ないＮｉ含有リチウム複合酸化物等が挙げられる。 The positive electrode mixture layer 32 may contain a positive electrode active material other than the first positive electrode active material and the second positive electrode active material. The positive electrode active material other than the first positive electrode active material and the second positive electrode active material is not particularly limited as long as it is a compound that can reversibly insert and desorb lithium. For example, LiMn 2 O 4 , LiCoO 2, etc. Examples include Ni-free Li composite oxides, Ni-containing lithium composite oxides having a lower Ni content than the second positive electrode active material, and the like.

正極合材層３２の目付量は、例えば、非水電解質二次電池の高容量化、高出力化を図りながら、内部短絡時の電池の発熱を抑制することができる点等で、３０ｍｇ／ｃｍ２以上８０ｍｇ／ｃｍ２以下であることが好ましく、３５ｍｇ／ｃｍ２以上６０ｍｇ／ｃｍ２以下であることがより好ましい。 The basis weight of the positive electrode mixture layer 32 is, for example, 30 mg / cm in terms of suppressing the heat generation of the battery at the time of an internal short circuit while increasing the capacity and output of the nonaqueous electrolyte secondary battery. preferably 2 or more and 80 mg / cm 2 or less, more preferably 35 mg / cm 2 or more 60 mg / cm 2 or less.

以下に、本実施形態に係る正極の製造方法の一例について説明する。   Below, an example of the manufacturing method of the positive electrode which concerns on this embodiment is demonstrated.

まず、第１正極活物質、第２正極活物質、導電材及び結着材を混合した後、Ｎ−メチル−２−ピロリドン（ＮＭＰ）等の分散媒を添加することによって正極合材スラリーを調製する。次いで、正極集電体上に正極合材スラリーを塗布し、塗膜を乾燥させた後、圧延することにより、本実施形態に係る正極が作製される。但し、正極の製造に使用する第１正極活物質及び第２正極活物質の質量比や、第１正極活物質及び第２正極活物質の平均粒径及び粒径比が、上記説明した範囲を満たしていない場合、上記製造方法では、正極活物質層の厚み方向において、正極集電体側表面から４μｍの厚さまでの間の正極活物質層内に存在する第２正極活物質の存在率を５５％以上とすることが困難となる場合がある。その場合には、以下の製造方法が好ましい。   First, after mixing the first positive electrode active material, the second positive electrode active material, the conductive material and the binder, a dispersion medium such as N-methyl-2-pyrrolidone (NMP) is added to prepare a positive electrode mixture slurry. To do. Next, the positive electrode mixture slurry is applied on the positive electrode current collector, the coating film is dried, and then rolled to produce the positive electrode according to the present embodiment. However, the mass ratio of the first positive electrode active material and the second positive electrode active material used in the manufacture of the positive electrode, and the average particle size and particle size ratio of the first positive electrode active material and the second positive electrode active material are within the ranges described above. When not satisfying, in the manufacturing method described above, in the thickness direction of the positive electrode active material layer, the abundance ratio of the second positive electrode active material existing in the positive electrode active material layer between the positive electrode current collector side surface and the thickness of 4 μm is 55. % Or more may be difficult. In that case, the following manufacturing method is preferable.

例えば、（１）第１正極活物質、導電材及び結着材を含む第１正極合材スラリーと、第２正極活物質、導電材及び結着材を含む第２正極合材スラリーとを調製するスラリー調製工程、（２）第２正極合材スラリーを正極集電体の表面に塗布し、塗膜を乾燥させ、正極集電体上に、第２正極活物質を含む第１層を形成する第１層形成工程、（３）第１正極合材スラリーを第１層の表面に塗布し、塗膜を乾燥させ、第１層上に、第１正極活物質を含む第２層を形成する第２層形成工程、及び（４）第１層及び第２層を圧延する圧延工程、を有する正極の製造方法である。ダブルスロットのダイで一度に二層塗布したのち、乾燥して電極を作製してもよい。第１正極合材スラリーには、第２正極活物質を含んでいてもよいが、第２正極活物質の割合が増えると、例えば、非水電解質二次電池の電池容量が低下する場合があるため、第１正極合材スラリー中の第２正極活物質の含有量は、例えば、０質量％以上２０質量％以下であることが好ましい。また、第２正極合材スラリーには、第１正極活物質を含んでいてもよいが、第１正極活物質の割合が増えると、例えば、内部短絡時の電池温度が高くなる場合があるため、第２正極合材スラリー中の第１正極活物質の含有量は、例えば、０質量％以上５０質量％以下であることが好ましい。   For example, (1) a first positive electrode mixture slurry containing a first positive electrode active material, a conductive material and a binder, and a second positive electrode mixture slurry containing a second positive electrode active material, a conductive material and a binder are prepared. (2) Applying the second positive electrode mixture slurry to the surface of the positive electrode current collector, drying the coating film, and forming the first layer containing the second positive electrode active material on the positive electrode current collector (3) applying the first positive electrode mixture slurry to the surface of the first layer, drying the coating film, and forming the second layer containing the first positive electrode active material on the first layer A second layer forming step, and (4) a rolling step of rolling the first layer and the second layer. An electrode may be produced by applying two layers at once with a double slot die and then drying. The first positive electrode mixture slurry may contain the second positive electrode active material, but when the proportion of the second positive electrode active material increases, for example, the battery capacity of the nonaqueous electrolyte secondary battery may decrease. Therefore, the content of the second positive electrode active material in the first positive electrode mixture slurry is preferably, for example, 0% by mass or more and 20% by mass or less. In addition, the second positive electrode mixture slurry may contain the first positive electrode active material, but when the proportion of the first positive electrode active material increases, for example, the battery temperature at the time of internal short circuit may increase. The content of the first positive electrode active material in the second positive electrode mixture slurry is preferably 0% by mass or more and 50% by mass or less, for example.

当該製造方法は、正極合材スラリーを２回塗布する必要があるため、正極合材スラリーを１回塗布する製造方法より、工程が煩雑になる、しかし、第１正極活物質及び第２正極活物質の質量比や、第１正極活物質及び第２正極活物質の平均粒径及び粒径比に関わらず、正極活物質層の厚み方向において、正極集電体側表面から４μｍの厚さまでの間の正極活物質層内に存在する第２正極活物質の存在率を５５％以上とすることが可能となる。   In this manufacturing method, since the positive electrode mixture slurry needs to be applied twice, the process becomes more complicated than the manufacturing method in which the positive electrode mixture slurry is applied once. However, the first positive electrode active material and the second positive electrode active material Regardless of the mass ratio of the materials, the average particle size and the particle size ratio of the first positive electrode active material and the second positive electrode active material, in the thickness direction of the positive electrode active material layer, from the surface of the positive electrode current collector to the thickness of 4 μm The abundance ratio of the second positive electrode active material present in the positive electrode active material layer can be 55% or more.

［負極］
負極１２は、例えば、負極集電体と、当該集電体上に形成された負極合材層とで構成される。負極集電体には、銅などの負極の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等を用いることができる。負極合材層は、例えば、負極活物質及び結着材等を含む。負極は、例えば、負極活物質、増粘剤、結着材等を含む負極合材スラリーを調整し、この負極合材スラリーを負極集電体上に塗布し、塗膜を乾燥させた後、この塗膜を圧延することにより作製できる。 [Negative electrode]
The negative electrode 12 includes, for example, a negative electrode current collector and a negative electrode mixture layer formed on the current collector. As the negative electrode current collector, a metal foil that is stable in the potential range of a negative electrode such as copper, a film in which the metal is disposed on the surface layer, or the like can be used. The negative electrode mixture layer includes, for example, a negative electrode active material and a binder. The negative electrode is prepared, for example, by preparing a negative electrode mixture slurry containing a negative electrode active material, a thickener, a binder, etc., applying this negative electrode mixture slurry on the negative electrode current collector, and drying the coating film. It can produce by rolling this coating film.

負極活物質は、リチウムイオンを吸蔵・放出することが可能な材料であれば特に制限されるものではなく、例えば、金属リチウム、リチウム−アルミニウム合金、リチウム−鉛合金、リチウム−シリコン合金、リチウム−スズ合金等のリチウム合金、黒鉛、コークス、有機物焼成体等の炭素材料、ＳｎＯ２、ＳｎＯ、ＴｉＯ２等の金属酸化物等が挙げられる。これらは、１種単独でもよいし、２種以上を組み合わせて使用してもよい。 The negative electrode active material is not particularly limited as long as it is a material capable of inserting and extracting lithium ions. For example, metallic lithium, lithium-aluminum alloy, lithium-lead alloy, lithium-silicon alloy, lithium- Examples thereof include lithium alloys such as tin alloys, carbon materials such as graphite, coke, and organic fired bodies, and metal oxides such as SnO 2 , SnO, and TiO 2 . These may be used alone or in combination of two or more.

負極合材層に含まれる結着材としては、正極の場合と同様にフッ素系樹脂、ＰＡＮ、ポリイミド系樹脂、アクリル系樹脂、ポリオレフィン系樹脂等を用いることができる。水系溶媒を用いて負極合材スラリーを調製する場合は、スチレン−ブタジエンゴム（ＳＢＲ）、ＣＭＣ又はその塩、ポリアクリル酸（ＰＡＡ）又はその塩（ＰＡＡ−Ｎａ、ＰＡＡ−Ｋ等、また部分中和型の塩であってもよい）、ポリビニルアルコール（ＰＶＡ）等を用いることが好ましい。   As the binder contained in the negative electrode mixture layer, a fluorine resin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like can be used as in the case of the positive electrode. When preparing a negative electrode mixture slurry using an aqueous solvent, styrene-butadiene rubber (SBR), CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof (PAA-Na, PAA-K, etc.) It is preferable to use polyvinyl alcohol (PVA) or the like.

［セパレータ］
セパレータ１３には、例えば、イオン透過性及び絶縁性を有する多孔性シート等が用いられる。多孔性シートの具体例としては、微多孔薄膜、織布、不織布等が挙げられる。セパレータ１３は、例えばポリエチレン、ポリプロピレン等のポリオレフィン、セルロースなどで構成される。セパレータ１３は、セルロース繊維層及びポリオレフィン等の熱可塑性樹脂繊維層を有する積層体であってもよい。また、セパレータ１３は、ポリエチレン層及びポリプロピレン層を含む多層セパレータであってもよく、アラミド樹脂で構成される表面層又は無機物フィラーを含有する表面層を有していてもよい。 [Separator]
For the separator 13, for example, a porous sheet having ion permeability and insulating properties is used. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. The separator 13 is made of, for example, polyolefin such as polyethylene or polypropylene, cellulose, or the like. The separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as polyolefin. Moreover, the separator 13 may be a multilayer separator including a polyethylene layer and a polypropylene layer, and may have a surface layer made of an aramid resin or a surface layer containing an inorganic filler.

［非水電解質］
非水電解質は、非水溶媒と、非水溶媒に溶解した電解質塩とを含む。非水電解質は、液体電解質（非水電解液）に限定されず、ゲル状ポリマー等を用いた固体電解質であってもよい。非水溶媒には、例えばエステル類、エーテル類、アセトニトリル等のニトリル類、ジメチルホルムアミド等のアミド類、及びこれらの２種以上の混合溶媒等を用いることができる。非水溶媒は、これら溶媒の水素の少なくとも一部をフッ素等のハロゲン原子で置換したハロゲン置換体を含有していてもよい。 [Nonaqueous electrolyte]
The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The nonaqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolyte solution), and may be a solid electrolyte using a gel polymer or the like. As the non-aqueous solvent, for example, esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, and a mixed solvent of two or more of these can be used. The non-aqueous solvent may contain a halogen-substituted product in which at least a part of hydrogen in these solvents is substituted with a halogen atom such as fluorine.

上記エステル類の例としては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート等の環状炭酸エステル、ジメチルカーボネート（ＤＭＣ）、メチルエチルカーボネート（ＥＭＣ）、ジエチルカーボネート（ＤＥＣ）、メチルプロピルカーボネート、エチルプロピルカーボネート、メチルイソプロピルカーボネート等の鎖状炭酸エステル、γ−ブチロラクトン、γ−バレロラクトン等の環状カルボン酸エステル、酢酸メチル、酢酸エチル、酢酸プロピル、プロピオン酸メチル（ＭＰ）、プロピオン酸エチル等の鎖状カルボン酸エステルなどが挙げられる。   Examples of the esters include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate, dimethyl carbonate (DMC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), and methyl propyl carbonate. Chain carbonates such as ethyl propyl carbonate and methyl isopropyl carbonate, cyclic carboxylic acid esters such as γ-butyrolactone and γ-valerolactone, methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), ethyl propionate, etc. And a chain carboxylic acid ester.

上記エーテル類の例としては、１，３−ジオキソラン、４−メチル−１，３−ジオキソラン、テトラヒドロフラン、２−メチルテトラヒドロフラン、プロピレンオキシド、１，２−ブチレンオキシド、１，３−ジオキサン、１，４−ジオキサン、１，３，５−トリオキサン、フラン、２−メチルフラン、１，８−シネオール、クラウンエーテル等の環状エーテル、１，２−ジメトキシエタン、ジエチルエーテル、ジプロピルエーテル、ジイソプロピルエーテル、ジブチルエーテル、ジヘキシルエーテル、エチルビニルエーテル、ブチルビニルエーテル、メチルフェニルエーテル、エチルフェニルエーテル、ブチルフェニルエーテル、ペンチルフェニルエーテル、メトキシトルエン、ベンジルエチルエーテル、ジフェニルエーテル、ジベンジルエーテル、o−ジメトキシベンゼン、１，２−ジエトキシエタン、１，２−ジブトキシエタン、ジエチレングリコールジメチルエーテル、ジエチレングリコールジエチルエーテル、ジエチレングリコールジブチルエーテル、１，１−ジメトキシメタン、１，１−ジエトキシエタン、トリエチレングリコールジメチルエーテル、テトラエチレングリコールジメチル等の鎖状エーテル類などが挙げられる。   Examples of the ethers include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-butylene oxide, 1,3-dioxane, 1,4 -Cyclic ethers such as dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineol, crown ether, 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether , Dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl ether, methoxy toluene, benzyl ethyl ether, diphenyl ether, dibenzyl Ether, o-dimethoxybenzene, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,1-dimethoxymethane, 1,1-diethoxyethane, tri Examples thereof include chain ethers such as ethylene glycol dimethyl ether and tetraethylene glycol dimethyl.

上記ニトリル類の例としては、アセトニトリル、プロピオニトリル、ブチロニトリル、バレロニトリル、ｎ−ヘプタニトリル、スクシノニトリル、グルタロニトリル、アジボニトリル、ピメロニトリル、１，２，３−プロパントリカルボニトリル、１，３，５−ペンタントリカルボニトリル等が挙げられる。   Examples of the nitriles include acetonitrile, propionitrile, butyronitrile, valeronitrile, n-heptanitrile, succinonitrile, glutaronitrile, adionitrile, pimeonitrile, 1,2,3-propanetricarbonitrile, 1,3. , 5-pentanetricarbonitrile and the like.

上記ハロゲン置換体の例としては、フルオロエチレンカーボネート（ＦＥＣ）等のフッ素化環状炭酸エステル、フッ素化鎖状炭酸エステル、フルオロプロピオン酸メチル（ＦＭＰ）等のフッ素化鎖状カルボン酸エステルなどが挙げられる。   Examples of the halogen-substituted product include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, and fluorinated chain carboxylates such as methyl fluoropropionate (FMP). .

電解質塩の例としては、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＡｌＣｌ４、ＬｉＳＣＮ、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、Ｌｉ（Ｐ(Ｃ２Ｏ４)Ｆ４）、ＬｉＰＦ６−ｘ（ＣｎＦ２ｎ＋１）ｘ（１＜ｘ＜６，ｎは１又は２）、ＬｉＢ１０Ｃｌ１０、ＬｉＣｌ、ＬｉＢｒ、ＬｉＩ、クロロボランリチウム、低級脂肪族カルボン酸リチウム、Ｌｉ２Ｂ４Ｏ７、Ｌｉ（Ｂ(Ｃ２Ｏ４)Ｆ２）等のホウ酸塩類、ＬｉＮ（ＳＯ２ＣＦ３）２、ＬｉＮ（ＣｌＦ２ｌ＋１ＳＯ２）（ＣｍＦ２ｍ＋１ＳＯ２）｛ｌ，ｍは１以上の整数｝等のイミド塩類などが挙げられる。電解質塩は、これらを１種単独で用いてもよいし、複数種を混合して用いてもよい。電解質塩の濃度は、例えば非水溶媒１Ｌ当り０．８〜１．８モルである。 Examples of the electrolyte salt, LiBF 4, LiClO 4, LiPF 6, LiAsF 6, LiSbF 6, LiAlCl 4, LiSCN, LiCF 3 SO 3, LiCF 3 CO 2, Li (P (C 2 O 4) F 4), LiPF 6-x (C n F 2n + 1 ) x (1 <x <6, n is 1 or 2), LiB 10 Cl 10 , LiCl, LiBr, LiI, lithium chloroborane, lithium lower aliphatic carboxylate, Li 2 B 4 O 7, Li (B ( C 2 O 4) F 2) boric acid salts such as, LiN (SO 2 CF 3) 2, LiN (C l F 2l + 1 SO 2) (C m F 2m + 1 SO 2) {l , M is an integer greater than or equal to 1} and the like. These electrolyte salts may be used alone or in combination of two or more. The concentration of the electrolyte salt is, for example, 0.8 to 1.8 mol per liter of the nonaqueous solvent.

本実施形態の非水電解質二次電池の電池容量は、５０Ａｈ以上であることが好ましい。電池容量が大きくなるほど、内部短絡時の電池の発熱も大きくなるが、本実施形態の非水電解質二次電池用正極を用いることで、５０Ａｈ以上の高い電池容量を有する非水電解質二次電池においても、内部短絡時の電池の発熱を抑制することができる。   The battery capacity of the nonaqueous electrolyte secondary battery of this embodiment is preferably 50 Ah or more. As the battery capacity increases, the heat generation of the battery at the time of an internal short circuit also increases. However, in the nonaqueous electrolyte secondary battery having a high battery capacity of 50 Ah or more by using the positive electrode for a nonaqueous electrolyte secondary battery of this embodiment, Moreover, the heat generation of the battery at the time of an internal short circuit can be suppressed.

以下、実施例により本開示をさらに説明するが、本開示はこれらの実施例に限定されるものではない。   Hereinafter, although this indication is further explained by an example, this indication is not limited to these examples.

＜実施例１＞
［正極の作製］
第１正極活物質としてＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２（平均粒径：１２μｍ）と第２正極活物質としてＬｉＮｉ０．３Ｃｏ０．３Ｍｎ０．４Ｏ２（平均粒径：４μｍ）を７０：３０の質量比で混合した。この混合した正極活物質１００質量％に対し、導電材としてのアセチレンブラック１質量％、結着材としてのＰＶＤＦ１質量％を混合し、さらにＮ−メチル−２−ピロリドン（ＮＭＰ）を適量加えて、正極合材スラリーを調製した。このスラリーを厚さ１２μｍのアルミニウム箔からなる正極集電体の両面に塗布し、塗膜を乾燥し、正極集電体の両面に正極合材層を形成した。正極合材層の目付量は５３．０ｍｇ／ｃｍ２であった。その後、正極合材層の密度が３．７ｇ／ｃｍ３となるように、正極合材層を圧延した。これを実施例１の正極とした。 <Example 1>
[Production of positive electrode]
LiNi 0.8 Co 0.1 Mn 0.1 O 2 (average particle diameter: 12 μm) as the first positive electrode active material and LiNi 0.3 Co 0.3 Mn 0.4 O 2 (average) as the second positive electrode active material Particle size: 4 μm) was mixed at a mass ratio of 70:30. To 100% by mass of the mixed positive electrode active material, 1% by mass of acetylene black as a conductive material and 1% by mass of PVDF as a binder are mixed, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) is added. A positive electrode mixture slurry was prepared. This slurry was applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 12 μm, the coating film was dried, and a positive electrode mixture layer was formed on both surfaces of the positive electrode current collector. The basis weight of the positive electrode mixture layer was 53.0 mg / cm 2 . Thereafter, the positive electrode mixture layer was rolled so that the density of the positive electrode mixture layer was 3.7 g / cm 3 . This was used as the positive electrode of Example 1.

前述した電子線マイクロアナライザの元素マッピングにより、正極集電体側表面から４μｍの厚さまでの正極合材層に存在する第２正極活物質の存在率を算出した結果、７０％であった。以下、正極集電体側表面から４μｍの厚さまでの正極合材層に存在する第２正極活物質の存在率を正極集電体付近の第２正極活物質の存在率と称する。   As a result of calculating the abundance ratio of the second positive electrode active material present in the positive electrode mixture layer from the positive electrode current collector side surface to a thickness of 4 μm by element mapping of the electron beam microanalyzer described above, it was 70%. Hereinafter, the abundance ratio of the second cathode active material present in the cathode mixture layer from the cathode current collector side surface to a thickness of 4 μm is referred to as the abundance ratio of the second cathode active material in the vicinity of the cathode current collector.

［負極の作製］
黒鉛９４質量部、ＳｉＯ６質量部、ＣＭＣ１質量部、ＳＢＲ１質量部を混合し、これを水と混合して負極合材スラリーを調製した。このスラリーを厚さ８μｍの銅箔からなる負極集電体の両面に塗布し、塗膜を乾燥し、負極集電体の両面に負極合材層を形成した。負極合材層の目付量は、両面で２５ｍｇ／ｃｍ２であった。その後、負極合材層の密度が１．７ｇ／ｃｍ３となるように、負極合材層を圧延した。これを実施例１の負極とした。 [Production of negative electrode]
94 parts by mass of graphite, 6 parts by mass of SiO, 1 part by mass of CMC and 1 part by mass of SBR were mixed and mixed with water to prepare a negative electrode mixture slurry. This slurry was applied to both sides of a negative electrode current collector made of a copper foil having a thickness of 8 μm, the coating film was dried, and a negative electrode mixture layer was formed on both sides of the negative electrode current collector. The basis weight of the negative electrode mixture layer was 25 mg / cm 2 on both sides. Thereafter, the negative electrode mixture layer was rolled so that the density of the negative electrode mixture layer was 1.7 g / cm 3 . This was used as the negative electrode of Example 1.

［非水電解液の作製］
エチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）とエチルメチルカーボネート（ＥＭＣ）との等体積混合非水溶媒に、ＬｉＰＦ６を１．０モル／Ｌの濃度で溶解させて非水電解液を得た。 [Preparation of non-aqueous electrolyte]
LiPF 6 was dissolved at a concentration of 1.0 mol / L in an equal volume mixed non-aqueous solvent of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) to obtain a non-aqueous electrolyte. .

［非水電解質二次電池の作製］
正極と負極とを厚さ１６μｍのポリエチレン製セパレータを介して積層し（正極及び負極の積層数６９）、積層型の電極体を作製した。正極及び負極それぞれに集電端子を取り付け、幅２６ｍｍ、長さ１４８ｍｍ、高さ９１ｍｍのアルミニウム製外装缶に電極体を収容すると共に非水電解液を注入した後、封口体によって外装缶を密閉した。これを実施例１の電池とした。 [Production of non-aqueous electrolyte secondary battery]
A positive electrode and a negative electrode were laminated via a polyethylene separator having a thickness of 16 μm (the number of laminated positive electrodes and negative electrodes was 69) to produce a laminated electrode body. A current collecting terminal is attached to each of the positive electrode and the negative electrode, and the electrode body is accommodated in an aluminum outer can having a width of 26 mm, a length of 148 mm, and a height of 91 mm, and a nonaqueous electrolyte is injected, and then the outer can is sealed with a sealing body. . This was designated as the battery of Example 1.

＜実施例２＞
第１正極活物質としてＬｉＮｉ０．８２Ｃｏ０．１５Ａｌ０．０３Ｏ２（平均粒径：１２μｍ）を用いたこと、正極合材層の目付量が５４．８ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例２の正極では、正極集電体付近の第２正極活物質の存在率は６９％であった。また、実施例２の正極を用いたこと、正極及び負極の積層数を６８としたこと以外は、実施例１と同様に電池を作製した。 <Example 2>
LiNi 0.82 Co 0.15 Al 0.03 O 2 (average particle size: 12 μm) was used as the first positive electrode active material, and the basis weight of the positive electrode mixture layer was 54.8 mg / cm 2. A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer was applied. In the positive electrode of Example 2, the abundance ratio of the second positive electrode active material in the vicinity of the positive electrode current collector was 69%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 2 was used and the number of stacked positive electrodes and negative electrodes was 68.

＜実施例３＞
第１正極活物質としてＬｉ０．９Ｎｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２（平均粒径：１２μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例３の正極では、正極集電体付近の第２正極活物質の存在率が７２％であった。また、実施例３の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 3>
A positive electrode was produced in the same manner as in Example 1 except that Li 0.9 Ni 0.8 Co 0.1 Mn 0.1 O 2 (average particle size: 12 μm) was used as the first positive electrode active material. In the positive electrode of Example 3, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 72%. A battery was fabricated in the same manner as in Example 1 except that the positive electrode of Example 3 was used.

＜実施例４＞
第１正極活物質としてＬｉ１．２Ｎｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２（平均粒径：１２μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例４の正極では、正極集電体付近の第２正極活物質の存在率が７１％であった。また、実施例４の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 4>
A positive electrode was produced in the same manner as in Example 1 except that Li 1.2 Ni 0.8 Co 0.1 Mn 0.1 O 2 (average particle size: 12 μm) was used as the first positive electrode active material. In the positive electrode of Example 4, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 71%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 4 was used.

＜実施例５＞
第１正極活物質としてＬｉＮｉ０．９５Ｃｏ０．０３Ｍｎ０．０２Ｏ２（平均粒径：１２μｍ）を用いたこと、正極合材層の目付量が５１．８ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例５の正極では、正極集電体付近の第２正極活物質の存在率が７０％であった。また、実施例５の正極を用いたこと、正極及び負極の積層数を７０としたこと以外は、実施例１と同様に電池を作製した。 <Example 5>
LiNi 0.95 Co 0.03 Mn 0.02 O 2 (average particle size: 12 μm) was used as the first positive electrode active material, and the basis weight of the positive electrode mixture layer was 51.8 mg / cm 2. A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer was applied. In the positive electrode of Example 5, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 70%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 5 was used and the number of stacked positive and negative electrodes was 70.

＜実施例６＞
第１正極活物質としてＬｉＮｉ０．７Ｃｏ０．１５Ｍｎ０．１５Ｏ２（平均粒径：１２μｍ）を用いたこと、正極合材層の目付量が５６．２ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例６の正極では、正極集電体付近の第２正極活物質の存在率が６９％であった。また、実施例６の正極を用いたこと、正極及び負極の積層数を６８としたこと以外は、実施例１と同様に電池を作製した。 <Example 6>
LiNi 0.7 Co 0.15 Mn 0.15 O 2 (average particle size: 12 μm) was used as the first positive electrode active material, and the basis weight of the positive electrode mixture layer was 56.2 mg / cm 2. A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer was applied. In the positive electrode of Example 6, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 69%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 6 was used and the number of stacked positive electrodes and negative electrodes was 68.

＜実施例７＞
第１正極活物質としてＬｉＮｉ０．７Ｃｏ０．３Ｏ２（平均粒径：１２μｍ）を用いたこと、正極合材層の目付量が５５．７ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例７の正極では、正極集電体付近の第２正極活物質の存在率が７２％であった。また、実施例７の正極を用いたこと、正極及び負極の積層数を６８としたこと以外は、実施例１と同様に電池を作製した。 <Example 7>
LiNi 0.7 Co 0.3 O 2 (average particle size: 12 μm) was used as the first positive electrode active material, and the positive electrode mixture layer so that the basis weight of the positive electrode mixture layer was 55.7 mg / cm 2. A positive electrode was produced in the same manner as in Example 1 except that was applied. In the positive electrode of Example 7, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 72%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 7 was used and the number of stacked positive electrodes and negative electrodes was 68.

＜実施例８＞
第１正極活物質としてＬｉＮｉ０．７Ｍｎ０．３Ｏ２（平均粒径：１２μｍ）を用いたこと、正極合材層の目付量が５６．８ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例８の正極では、正極集電体付近の第２正極活物質の存在率が７０％であった。また、実施例８の正極を用いたこと、正極及び負極の積層数を６８としたこと以外は、実施例１と同様に電池を作製した。 <Example 8>
LiNi 0.7 Mn 0.3 O 2 (average particle size: 12 μm) was used as the first positive electrode active material, and the positive electrode mixture layer so that the basis weight of the positive electrode mixture layer was 56.8 mg / cm 2. A positive electrode was produced in the same manner as in Example 1 except that was applied. In the positive electrode of Example 8, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 70%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 8 was used and the number of stacked positive electrodes and negative electrodes was 68.

＜実施例９＞
第２正極活物質としてＬｉ０．９Ｎｉ０．３Ｃｏ０．３Ｍｎ０．４Ｏ２（平均粒径：４μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例９の正極では、正極集電体付近の第２正極活物質の存在率が７２％であった。また、実施例９の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 9>
A positive electrode was produced in the same manner as in Example 1 except that Li 0.9 Ni 0.3 Co 0.3 Mn 0.4 O 2 (average particle size: 4 μm) was used as the second positive electrode active material. In the positive electrode of Example 9, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 72%. A battery was fabricated in the same manner as in Example 1 except that the positive electrode of Example 9 was used.

＜実施例１０＞
第２正極活物質としてＬｉ１．２Ｎｉ０．３Ｃｏ０．３Ｍｎ０．４Ｏ２（平均粒径：４μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例１０の正極では、正極集電体付近の第２正極活物質の存在率が７０％であった。また、実施例１０の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 10>
A positive electrode was produced in the same manner as in Example 1 except that Li 1.2 Ni 0.3 Co 0.3 Mn 0.4 O 2 (average particle size: 4 μm) was used as the second positive electrode active material. In the positive electrode of Example 10, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 70%. A battery was fabricated in the same manner as in Example 1 except that the positive electrode of Example 10 was used.

＜実施例１１＞
第２正極活物質としてＬｉＮｉ０．６Ｃｏ０．２Ｍｎ０．２Ｏ２（平均粒径：４μｍ）を用いたこと、正極合材層の目付量が５１．５ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例１１の正極では、正極集電体付近の第２正極活物質の存在率が６９％であった。また、実施例１１の正極を用いたこと、正極及び負極の積層数を７０としたこと以外は、実施例１と同様に電池を作製した。 <Example 11>
LiNi 0.6 Co 0.2 Mn 0.2 O 2 (average particle size: 4 μm) was used as the second positive electrode active material, and the basis weight of the positive electrode mixture layer was 51.5 mg / cm 2. A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer was applied. In the positive electrode of Example 11, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 69%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 11 was used and the number of stacked positive and negative electrodes was 70.

＜実施例１２＞
第２正極活物質としてＬｉＮｉ０．１Ｃｏ０．６Ｍｎ０．３Ｏ２（平均粒径：４μｍ）を用いたこと、正極合材層の目付量が５４．３ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例１２の正極では、正極集電体付近の第２正極活物質の存在率が６９％であった。また、実施例１２の正極を用いたこと、正極及び負極の積層数を６８としたこと以外は、実施例１と同様に電池を作製した。 <Example 12>
LiNi 0.1 Co 0.6 Mn 0.3 O 2 (average particle size: 4 μm) was used as the second positive electrode active material, and the basis weight of the positive electrode mixture layer was 54.3 mg / cm 2. A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer was applied. In the positive electrode of Example 12, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 69%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 12 was used and the number of stacked positive electrodes and negative electrodes was 68.

＜実施例１３＞
第２正極活物質としてＬｉＮｉ０．４５Ｃｏ０．１Ｍｎ０．４５Ｏ２（平均粒径：４μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例１３の正極では、正極集電体付近の第２正極活物質の存在率が７０％であった。また、実施例１３の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 13>
A positive electrode was produced in the same manner as in Example 1 except that LiNi 0.45 Co 0.1 Mn 0.45 O 2 (average particle size: 4 μm) was used as the second positive electrode active material. In the positive electrode of Example 13, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 70%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 13 was used.

＜実施例１４＞
第２正極活物質としてＬｉＮｉ０．２Ｃｏ０．２５Ｍｎ０．５５Ｏ２（平均粒径：４μｍ）を用いたこと、正極合材層の目付量が５３．３ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例１４の正極では、正極集電体付近の第２正極活物質の存在率が６９％であった。また、実施例１４の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 14>
LiNi 0.2 Co 0.25 Mn 0.55 O 2 (average particle size: 4 μm) was used as the second positive electrode active material, and the basis weight of the positive electrode mixture layer was 53.3 mg / cm 2. A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer was applied. In the positive electrode of Example 14, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 69%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 14 was used.

＜実施例１５＞
第２正極活物質としてＬｉＮｉ０．４Ｃｏ０．５Ｍｎ０．１Ｏ２（平均粒径：４μｍ）を用いたこと、正極合材層の目付量が５１．３ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例１５の正極では、正極集電体付近の第２正極活物質の存在率が７１％であった。また、実施例１５の正極を用いたこと、正極及び負極の積層数を７０としたこと以外は、実施例１と同様に電池を作製した。 <Example 15>
LiNi 0.4 Co 0.5 Mn 0.1 O 2 (average particle size: 4 μm) was used as the second positive electrode active material, and the basis weight of the positive electrode mixture layer was 51.3 mg / cm 2. A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer was applied. In the positive electrode of Example 15, the abundance ratio of the second positive electrode active material in the vicinity of the positive electrode current collector was 71%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 15 was used, and the number of stacked positive and negative electrodes was 70.

＜実施例１６＞
第１正極活物質と第２正極活物質を８０：２０の質量比で混合したこと、正極合材層の目付量が５１．５ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例１６の正極では、正極集電体付近の第２正極活物質の存在率が６３％であった。また、実施例１６の正極を用いたこと、正極及び負極の積層数を７０としたこと以外は、実施例１と同様に電池を作製した。 <Example 16>
Other than mixing the first positive electrode active material and the second positive electrode active material at a mass ratio of 80:20, and applying the positive electrode mixture layer so that the basis weight of the positive electrode mixture layer is 51.5 mg / cm 2. Produced a positive electrode in the same manner as in Example 1. In the positive electrode of Example 16, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 63%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 16 was used and the number of stacked positive electrodes and negative electrodes was 70.

＜実施例１７＞
第１正極活物質と第２正極活物質を９０：１０の質量比で混合したこと、正極合材層の目付量が５０．４ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例１７の正極では、正極集電体付近の第２正極活物質の存在率が５５％であった。また、実施例１７の正極を用いたこと、正極及び負極の積層数を７０としたこと以外は、実施例１と同様に電池を作製した。 <Example 17>
Other than mixing the first positive electrode active material and the second positive electrode active material at a mass ratio of 90:10, and applying the positive electrode mixture layer so that the basis weight of the positive electrode mixture layer is 50.4 mg / cm 2. Produced a positive electrode in the same manner as in Example 1. In the positive electrode of Example 17, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 55%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 17 was used and the number of stacked positive and negative electrodes was 70.

＜実施例１８＞
第１正極活物質と第２正極活物質を５０：５０の質量比で混合したこと、正極合材層の目付量が５５．７ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例１８の正極では、正極集電体付近の第２正極活物質の存在率が８０％であった。また、実施例１８の正極を用いたこと、正極及び負極の積層数を６８としたこと以外は、実施例１と同様に電池を作製した。 <Example 18>
Other than mixing the first positive electrode active material and the second positive electrode active material in a mass ratio of 50:50 and applying the positive electrode mixture layer so that the basis weight of the positive electrode mixture layer is 55.7 mg / cm 2. Produced a positive electrode in the same manner as in Example 1. In the positive electrode of Example 18, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 80%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 18 was used and the number of stacked positive and negative electrodes was 68.

＜実施例１９＞
第１正極活物質としてＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２（平均粒径：２０μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例１９の正極では、正極集電体付近の第２正極活物質の存在率が７２％であった。また、実施例１９の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 19>
A positive electrode was produced in the same manner as in Example 1 except that LiNi 0.8 Co 0.1 Mn 0.1 O 2 (average particle size: 20 μm) was used as the first positive electrode active material. In the positive electrode of Example 19, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 72%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 19 was used.

＜実施例２０＞
第１正極活物質としてＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２（平均粒径：８μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例２０の正極では、正極集電体付近の第２正極活物質の存在率が６９％であった。また、実施例２０の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 20>
A positive electrode was produced in the same manner as in Example 1 except that LiNi 0.8 Co 0.1 Mn 0.1 O 2 (average particle size: 8 μm) was used as the first positive electrode active material. In the positive electrode of Example 20, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 69%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 20 was used.

＜実施例２１＞
第２正極活物質としてＬｉＮｉ０．３Ｃｏ０．３Ｍｎ０．４Ｏ２（平均粒径：６μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例２１の正極では、正極集電体付近の第２正極活物質の存在率が６８％であった。また、実施例２の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 21>
A positive electrode was produced in the same manner as in Example 1 except that LiNi 0.3 Co 0.3 Mn 0.4 O 2 (average particle size: 6 μm) was used as the second positive electrode active material. In the positive electrode of Example 21, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 68%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 2 was used.

＜実施例２２＞
第１正極活物質としてＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２（平均粒径：２０μｍ）を用いたこと、第２正極活物質としてＬｉＮｉ０．３Ｃｏ０．３Ｍｎ０．４Ｏ２（平均粒径：２μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例２２の正極では、正極集電体付近の第２正極活物質の存在率が７３％であった。また、実施例２２の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 22>
LiNi 0.8 Co 0.1 Mn 0.1 O 2 (average particle size: 20 μm) was used as the first positive electrode active material, and LiNi 0.3 Co 0.3 Mn 0.4 was used as the second positive electrode active material. A positive electrode was produced in the same manner as in Example 1 except that O 2 (average particle diameter: 2 μm) was used. In the positive electrode of Example 22, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 73%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 22 was used.

＜実施例２３＞
正極合材層の目付量が３０．０ｍｇ／ｃｍ２となるように正極合材層を塗布し、負極合材層の目付量が１４．２ｍｇ／ｃｍ２となるように負極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例２３の正極では、正極集電体付近の第２正極活物質の存在率が７０％であった。また、実施例２３の正極を用いたこと、正極及び負極の積層数を１１０としたこと以外は、実施例１と同様に電池を作製した。 <Example 23>
The positive electrode mixture layer is applied so that the basis weight of the positive electrode mixture layer is 30.0 mg / cm 2, and the negative electrode mixture layer is applied so that the basis weight of the negative electrode mixture layer is 14.2 mg / cm 2 A positive electrode was produced in the same manner as in Example 1 except that. In the positive electrode of Example 23, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 70%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 23 was used and the number of stacked positive and negative electrodes was 110.

＜実施例２４＞
正極合材層の目付量が８０．０ｍｇ／ｃｍ２となるように正極合材層を塗布し、負極合材層の目付量が３７．７ｍｇ／ｃｍ２となるように負極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例２４の正極では、正極集電体付近の第２正極活物質の存在率が７０％であった。また、実施例２４の正極を用いたこと、正極及び負極の積層数を４９としたこと以外は、実施例１と同様に電池を作製した。 <Example 24>
The positive electrode composite material layer was coated with a basis weight of the positive electrode material layer is 80.0 mg / cm 2, coated with a negative-electrode mixture layer as basis weight of the negative electrode material layer is 37.7 mg / cm 2 A positive electrode was produced in the same manner as in Example 1 except that. In the positive electrode of Example 24, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 70%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 24 was used and the number of stacked positive and negative electrodes was 49.

＜実施例２５＞
導電材を０．５質量％としたこと、正極合材層の目付量が５２．７ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例２５の正極では、正極集電体付近の第２正極活物質の存在率が７２％であった。また、実施例２５の正極を用いたこと、正極及び負極の積層数を７０としたこと以外は、実施例１と同様に電池を作製した。 <Example 25>
A positive electrode was produced in the same manner as in Example 1 except that the conductive material was 0.5% by mass and the positive electrode mixture layer was applied so that the basis weight of the positive electrode mixture layer was 52.7 mg / cm 2. did. In the positive electrode of Example 25, the existence ratio of the second positive electrode active material in the vicinity of the positive electrode current collector was 72%. A battery was fabricated in the same manner as in Example 1 except that the positive electrode of Example 25 was used and the number of stacked positive and negative electrodes was 70.

＜実施例２６＞
導電材を４質量％としたこと、正極合材層の目付量が５４．１ｍｇ／ｃｍ２となるように正極合材層を塗布したこと、正極合材層の密度が３．５ｇ／ｃｍ３となるように正極合材層を圧延したこと以外は、実施例１と同様に正極を作製した。実施例２６の正極では、正極集電体付近の第２正極活物質の存在率が７０％であった。また、実施例２６の正極を用いたこと、正極及び負極の積層数を６７としたこと以外は、実施例１と同様に電池を作製した。 <Example 26>
The conductive material was set to 4% by mass, the positive electrode mixture layer was applied so that the basis weight of the positive electrode mixture layer was 54.1 mg / cm 2, and the density of the positive electrode mixture layer was 3.5 g / cm 3. A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer was rolled so that In the positive electrode of Example 26, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 70%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 26 was used and the number of stacked positive and negative electrodes was 67.

＜実施例２７＞
第１正極活物質としてのＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２（平均粒径：１２μｍ）１００質量％に対し、導電材としてのアセチレンブラック１質量％、結着材としてのＰＶＤＦ１質量％を混合し、さらにＮ−メチル−２−ピロリドン（ＮＭＰ）を適量加えて、第１正極合材スラリーを調製した。また、第２正極活物質としてのＬｉＮｉ０．３Ｃｏ０．３Ｍｎ０．４Ｏ２（平均粒径：４μｍ）１００質量％に対し、導電材としてのアセチレンブラック１質量％、結着材としてのＰＶＤＦ１質量％を混合し、さらにＮ−メチル−２−ピロリドン（ＮＭＰ）を適量加えて、第２正極合材スラリーを調製した。第２正極合材スラリーを厚さ１２μｍのアルミニウム箔からなる正極集電体の両面に塗布し、塗膜を乾燥し、正極集電体の両面に第１層を形成した。次に、第１正極合材スラリーを第１層上に塗布し、塗膜を乾燥し、第１層上に第２層を形成した。第１層の目付量は１５．９ｍｇ／ｃｍ２、第２層の目付量は３７．１ｍｇ／ｃｍ２、第１層及び第２層からなる正極合材層の目付量は５３．０ｍｇ／ｃｍ２であった。その後、第１層及び第２層からなる正極合材層の密度が３．７ｇ／ｃｍ３となるように、正極合材層を圧延した。これを実施例２７の正極とした。実施例２７の正極では、正極集電体付近の第２正極活物質の存在率が８５％であった。また、実施例２７の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 27>
With respect to 100% by mass of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (average particle size: 12 μm) as the first positive electrode active material, 1% by mass of acetylene black as a conductive material, PVDF1 as a binder A first positive electrode mixture slurry was prepared by mixing mass% and further adding an appropriate amount of N-methyl-2-pyrrolidone (NMP). Further, for 100% by mass of LiNi 0.3 Co 0.3 Mn 0.4 O 2 (average particle size: 4 μm) as the second positive electrode active material, 1% by mass of acetylene black as a conductive material and as a binder 1% by mass of PVDF was mixed, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added to prepare a second positive electrode mixture slurry. The second positive electrode mixture slurry was applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 12 μm, the coating film was dried, and a first layer was formed on both surfaces of the positive electrode current collector. Next, the first positive electrode mixture slurry was applied on the first layer, the coating film was dried, and a second layer was formed on the first layer. The basis weight of the first layer is 15.9 mg / cm 2 , the basis weight of the second layer is 37.1 mg / cm 2 , and the basis weight of the positive electrode mixture layer composed of the first layer and the second layer is 53.0 mg / cm 2 . Thereafter, the positive electrode mixture layer was rolled so that the density of the positive electrode mixture layer composed of the first layer and the second layer was 3.7 g / cm 3 . This was designated as the positive electrode of Example 27. In the positive electrode of Example 27, the existence ratio of the second positive electrode active material in the vicinity of the positive electrode current collector was 85%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 27 was used.

＜実施例２８＞
第１層の目付量を５．０ｍｇ／ｃｍ２、第２層の目付量を４５．４ｍｇ／ｃｍ２、第１層及び第２層からなる正極合材層の目付量を５０．４ｍｇ／ｃｍ２としたこと以外は実施例２７と同様に正極を作製した。実施例２８の正極では、正極集電体付近の第２正極活物質の存在率が８５％であった。また、実施例２８の正極を用いたこと、正極及び負極の積層数を７０としたこと以外は、実施例１と同様に電池を作製した。 <Example 28>
5.0 mg / cm 2 the basis weight of the first layer, 45.4 mg / cm 2 the basis weight of the second layer, the first layer and the basis weight of 50.4 mg / cm of the positive-electrode mixture layer made of the second layer A positive electrode was produced in the same manner as in Example 27 except that it was set to 2 . In the positive electrode of Example 28, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 85%. A battery was fabricated in the same manner as in Example 1 except that the positive electrode of Example 28 was used and the number of stacked positive and negative electrodes was 70.

＜実施例２９＞
第１層の目付量を２．５ｍｇ／ｃｍ２、第２層の目付量を４７．４ｍｇ／ｃｍ２、第１層及び第２層からなる正極合材層の目付量を４９．９ｍｇ／ｃｍ２としたこと以外は実施例２７と同様に正極を作製した。実施例２９の正極では、正極集電体付近の第２正極活物質の存在率が７２％であった。また、実施例２９の正極を用いたこと、正極及び負極の積層数を７１としたこと以外は、実施例１と同様に電池を作製した。 <Example 29>
Basis weight of 2.5 mg / cm 2 of the first layer, 47.4 mg / cm 2 the basis weight of the second layer, the first layer and the basis weight of 49.9 mg / cm of the positive-electrode mixture layer made of the second layer A positive electrode was produced in the same manner as in Example 27 except that it was set to 2 . In the positive electrode of Example 29, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 72%. A battery was fabricated in the same manner as in Example 1 except that the positive electrode of Example 29 was used and the number of stacked positive and negative electrodes was 71.

＜実施例３０＞
第１正極活物質と第２正極活物質を４０：６０の質量比で混合したこと、正極合材層の目付量が５７．４ｍｇ／ｃｍ２となるように正極合材層を塗布したこと、正極合材層の密度が３．５ｇ／ｃｍ３となるように正極合材層を圧延したこと以外は、実施例１と同様に正極を作製した。実施例３０の正極では、正極集電体付近の第２正極活物質の存在率が８３％であった。また、実施例３０の正極を用いたこと、正極及び負極の積層数を６５としたこと以外は、実施例１と同様に電池を作製した。 <Example 30>
The first positive electrode active material and the second positive electrode active material were mixed at a mass ratio of 40:60, and the positive electrode mixture layer was applied so that the basis weight of the positive electrode mixture layer was 57.4 mg / cm 2 ; A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer was rolled so that the density of the positive electrode mixture layer was 3.5 g / cm 3 . In the positive electrode of Example 30, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 83%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 30 was used and the number of stacked positive and negative electrodes was 65.

＜実施例３１＞
第１正極活物質としてＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２（平均粒径：３０μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例３１の正極では、正極集電体付近の第２正極活物質の存在率が７２％であった。また、実施例３１の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 31>
A positive electrode was produced in the same manner as in Example 1 except that LiNi 0.8 Co 0.1 Mn 0.1 O 2 (average particle size: 30 μm) was used as the first positive electrode active material. In the positive electrode of Example 31, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 72%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 31 was used.

＜実施例３２＞
第１正極活物質としてＬｉＮｉ０．８Ｃｏ０．１Ｍｎ０．１Ｏ２（平均粒径：６μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例３２の正極では、正極集電体付近の第２正極活物質の存在率が６９％であった。また、実施例３２の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 32>
A positive electrode was produced in the same manner as in Example 1 except that LiNi 0.8 Co 0.1 Mn 0.1 O 2 (average particle size: 6 μm) was used as the first positive electrode active material. In the positive electrode of Example 32, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 69%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 32 was used.

＜実施例３３＞
第２正極活物質としてＬｉＮｉ０．３Ｃｏ０．３Ｍｎ０．４Ｏ２（平均粒径：１μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。実施例３３の正極では、正極集電体付近の第２正極活物質の存在率が７３％であった。また、実施例３３の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Example 33>
A positive electrode was produced in the same manner as in Example 1 except that LiNi 0.3 Co 0.3 Mn 0.4 O 2 (average particle size: 1 μm) was used as the second positive electrode active material. In the positive electrode of Example 33, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 73%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Example 33 was used.

＜実施例３４＞
第１正極活物質としてＬｉＮｉＯ２（平均粒径：２０μｍ）を用いたこと、正極合材層の目付量が５１．１ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。実施例３４の正極では、正極集電体付近の第２正極活物質の存在率が７０％であった。また、実施例３４の正極を用いたこと、正極及び負極の積層数を７０としたこと以外は、実施例１と同様に電池を作製した。 <Example 34>
Implemented except that LiNiO 2 (average particle size: 20 μm) was used as the first positive electrode active material, and that the positive electrode mixture layer was applied so that the basis weight of the positive electrode mixture layer was 51.1 mg / cm 2. A positive electrode was produced in the same manner as in Example 1. In the positive electrode of Example 34, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 70%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Example 34 was used and the number of stacked positive and negative electrodes was 70.

＜比較例１＞
第２正極活物質としてＬｉＮｉ０．７Ｃｏ０．１５Ｍｎ０．１５Ｏ２（平均粒径：４μｍ）を用いたこと、正極合材層の目付量が５０．６ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。比較例１の正極では、正極集電体付近の第２正極活物質の存在率が７１％であった。また、比較例１の正極を用いたこと、正極及び負極の積層数を７１としたこと以外は、実施例１と同様に電池を作製した。 <Comparative Example 1>
LiNi 0.7 Co 0.15 Mn 0.15 O 2 (average particle size: 4 μm) was used as the second positive electrode active material, and the basis weight of the positive electrode mixture layer was 50.6 mg / cm 2. A positive electrode was produced in the same manner as in Example 1 except that the positive electrode mixture layer was applied. In the positive electrode of Comparative Example 1, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 71%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Comparative Example 1 was used and the number of stacked positive and negative electrodes was 71.

＜比較例２＞
第１正極活物質と第２正極活物質を９５：５の質量比で混合したこと、正極合材層の目付量が４９．９ｍｇ／ｃｍ２となるように正極合材層を塗布したこと以外は、実施例１と同様に正極を作製した。比較例２の正極では、正極集電体付近の第２正極活物質の存在率が４０％であった。また、比較例２の正極を用いたこと、正極及び負極の積層数を７１としたこと以外は、実施例１と同様に電池を作製した。 <Comparative example 2>
Other than mixing the first positive electrode active material and the second positive electrode active material at a mass ratio of 95: 5, and applying the positive electrode mixture layer so that the basis weight of the positive electrode mixture layer is 49.9 mg / cm 2. Produced a positive electrode in the same manner as in Example 1. In the positive electrode of Comparative Example 2, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 40%. A battery was fabricated in the same manner as in Example 1, except that the positive electrode of Comparative Example 2 was used and the number of stacked positive and negative electrodes was 71.

＜比較例３＞
第２正極活物質としてＬｉＮｉ０．３Ｃｏ０．３Ｍｎ０．４Ｏ２（平均粒径：１２μｍ）を用いたこと以外は、実施例１と同様に正極を作製した。比較例３の正極では、正極集電体付近の第２正極活物質の存在率が３４％であった。また、比較例３の正極を用いたこと以外は、実施例１と同様に電池を作製した。 <Comparative Example 3>
A positive electrode was produced in the same manner as in Example 1 except that LiNi 0.3 Co 0.3 Mn 0.4 O 2 (average particle size: 12 μm) was used as the second positive electrode active material. In the positive electrode of Comparative Example 3, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector was 34%. A battery was produced in the same manner as in Example 1 except that the positive electrode of Comparative Example 3 was used.

[電池抵抗の測定]
２５℃の恒温槽で、各実施例及び各比較例の電池を２０Ａで、電圧が３．７Ｖになるまで定電流充電を行った後、３．７Ｖで３０分間定電圧充電を行った。このときのＯＣＶをＶ１（Ｖ）とした。次に、６０Ａで１０秒間定電流放電を行い、１０秒後の電圧をＶ２（Ｖ）とした。そして、以下の式から電池抵抗を求めた。
電池抵抗（Ω）＝（Ｖ１−Ｖ２）／６０ [Measurement of battery resistance]
Each battery of each example and each comparative example was charged with constant current at 20A in a thermostat at 25 ° C. until the voltage reached 3.7V, and then charged at 3.7V for 30 minutes. The OCV at this time was defined as V 1 (V). Next, constant current discharge was performed at 60 A for 10 seconds, and the voltage after 10 seconds was defined as V 2 (V). And battery resistance was calculated | required from the following formula | equation.
Battery resistance (Ω) = (V 1 −V 2 ) / 60

[初期容量の測定及び充放電サイクル特性の評価]
２５℃の恒温槽で、各実施例及び各比較例の電池を２０Ａで、電圧が４．２Ｖになるまで定電流充電を行った後、４．２Ｖで３０分間定電圧充電を行い、２０Ａで、電圧が２．５Ｖになるまで定電流放電を行った。この時の放電容量を初期容量とした。 [Measurement of initial capacity and evaluation of charge / discharge cycle characteristics]
In a constant temperature bath at 25 ° C., the batteries of each Example and each Comparative Example were charged at 20 A until the voltage reached 4.2 V, then charged at 4.2 V for 30 minutes, and then charged at 20 A. The constant current discharge was performed until the voltage reached 2.5V. The discharge capacity at this time was defined as the initial capacity.

初期容量測定後、２５℃の恒温槽で、各実施例及び各比較例の電池を２０Ａで、電圧が４．２Ｖまで定電流充電を行った後、４．２Ｖで３０分間定電圧充電を行い、２０Ａで、電圧が２．５Ｖまで定電流放電を行った。この充放電サイクルを１０００サイクル行った。次に、２５℃の恒温槽で、１０００サイクル後の各実施例及び各比較例の電池を２０Ａで、電圧が４．２Ｖまで定電流充電を行った後、４．２Ｖで３０分間定電圧充電を行い、２０Ａで、電圧が２．５Ｖまで定電流放電を行った。この時の放電容量を１０００サイクル後の容量とし、下式により容量維持率を算出した。容量維持率が高いほど、充放電サイクル特性の低下が抑制されたことを示している。
容量維持率（％）＝１０００サイクル後の容量／初期容量×１００ After the initial capacity measurement, the battery of each example and each comparative example was charged at a constant current of 20A and a voltage of 4.2V in a constant temperature bath at 25 ° C, and then charged at a constant voltage of 4.2V for 30 minutes. , 20 A, and a constant current discharge was performed until the voltage was 2.5V. This charge / discharge cycle was repeated 1000 cycles. Next, the battery of each example and each comparative example after 1000 cycles was charged at a constant current of 20 A in a 25 ° C. thermostatic chamber at a voltage of 4.2 V, and then charged at a constant voltage of 4.2 V for 30 minutes. A constant current discharge was performed at 20 A until the voltage was 2.5 V. The discharge capacity at this time was taken as the capacity after 1000 cycles, and the capacity retention rate was calculated by the following formula. The higher the capacity retention rate, the lower the charge / discharge cycle characteristics are suppressed.
Capacity retention rate (%) = capacity after 1000 cycles / initial capacity × 100

［釘刺し試験］
各実施例及び比較例の電池について、下記手順で釘刺し試験を行った。
（１）２５℃の環境下にて、２０Ａで電圧が４．２Ｖになるまで定電流充電を行った後、４．２Ｖで３０分間定電圧充電を行った。
（２）２５℃の環境下にて、（１）で充電した電池の側面中央部に１ｍｍφの太さの丸釘の先端を接触させ、１ｍｍ／秒の速度で、電池における電極体の積層方向に丸釘を突き刺し、内部短絡による電池電圧降下を検出した直後、丸釘の突き刺しを停止した。
（３）丸釘によって電池が短絡を開始して１分後の電池表面温度を測定した。 [Nail penetration test]
The batteries of each Example and Comparative Example were subjected to a nail penetration test according to the following procedure.
(1) Under an environment of 25 ° C., constant current charging was performed until the voltage became 4.2 V at 20 A, and then constant voltage charging was performed at 4.2 V for 30 minutes.
(2) In the environment of 25 ° C., the tip of a round nail having a thickness of 1 mmφ is brought into contact with the central portion of the side surface of the battery charged in (1), and the electrode body is laminated in the battery at a speed of 1 mm / second. Immediately after detecting a battery voltage drop due to an internal short circuit, the round nail was stopped.
(3) The battery surface temperature 1 minute after the battery started short-circuiting with the round nail was measured.

表１及び表２に、各実施例及び各比較例における第１正極活物質及び第２正極活物質の組成、質量比、平均粒径、粒径比、導電材含有量をまとめた。また、表３及び表４に、各実施例及び各比較例における正極集電体付近の第２正極活物質の存在率、正極合材層の目付量、正極合材層の密度、正極及び負極の積層数、電池の初期容量、電池抵抗、容量維持率、釘刺し試験の電池温度をまとめた。   Tables 1 and 2 summarize the composition, mass ratio, average particle size, particle size ratio, and conductive material content of the first positive electrode active material and the second positive electrode active material in each Example and each Comparative Example. In Tables 3 and 4, the abundance of the second positive electrode active material in the vicinity of the positive electrode current collector in each example and each comparative example, the basis weight of the positive electrode mixture layer, the density of the positive electrode mixture layer, the positive electrode and the negative electrode The number of layers, the initial capacity of the battery, the battery resistance, the capacity retention rate, and the battery temperature of the nail penetration test were summarized.

各実施例及び各比較例はいずれも、リチウムを除く金属元素の総モル数に対するＮｉの割合が７０モル％以上１００モル％以下のＮｉ含有リチウム複合酸化物（第１正極活物質）を正極合材層中に含むものである。ここで、各実施例のように、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が１０モル％以上６０モル％以下のＮｉ含有リチウム複合酸化物（第２正極活物質）を正極合材層中に含み、正極合材層の厚み方向において、正極集電体側表面から４μｍの厚さまでの正極合材層内に存在する第２正極活物質の存在率を５５％以上とすることで、各比較例のように、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が１０モル％以上６０モル％以下のＮｉ含有リチウム複合酸化物（第２正極活物質）を含まない、或いは含んでいても、正極合材層の厚み方向において、正極集電体側表面から４μｍの厚さまでの正極合材層内に存在する第２正極活物質の存在率を５５％未満とした場合と比べて、釘刺し試験による電池温度は低く抑えられ、内部短絡時の電池の発熱が抑制された。   In each of the examples and comparative examples, a Ni-containing lithium composite oxide (first positive electrode active material) in which the ratio of Ni to the total number of moles of metal elements excluding lithium is 70 mol% to 100 mol% is mixed with the positive electrode. It is included in the material layer. Here, as in each example, a Ni-containing lithium composite oxide (second positive electrode active material) in which the ratio of Ni to the total number of moles of metal elements excluding Li is 10 mol% or more and 60 mol% or less is used as the positive electrode mixture. In the thickness direction of the positive electrode mixture layer included in the layer, the abundance ratio of the second positive electrode active material existing in the positive electrode mixture layer from the positive electrode current collector side surface to a thickness of 4 μm is 55% or more, As in each comparative example, the Ni-containing lithium composite oxide (second positive electrode active material) in which the ratio of Ni to the total number of moles of metal elements excluding Li is 10 mol% or more and 60 mol% or less is not included or is included. However, in the thickness direction of the positive electrode mixture layer, compared to the case where the abundance ratio of the second positive electrode active material existing in the positive electrode mixture layer from the positive electrode current collector side surface to a thickness of 4 μm is less than 55%, The battery temperature by the nail penetration test is kept low, and the inside Heat generation of the battery at the time of short circuit was suppressed.

実施例１〜３４の中では、正極合材層の厚み方向において、正極集電体側表面から４μｍの厚さまでの正極合材層内に存在する第２正極活物質の存在率を６０％以上８５％以下とした実施例１〜１６、１８〜３４は、上記範囲を満たさない実施例１７と比較して、釘刺し試験による電池温度はより低く抑えられ、内部短絡時の電池の発熱はより抑制された。   In Examples 1-34, in the thickness direction of the positive electrode mixture layer, the abundance ratio of the second positive electrode active material existing in the positive electrode mixture layer from the positive electrode current collector side surface to a thickness of 4 μm is 60% or more and 85. % In Examples 1 to 16 and 18 to 34, compared with Example 17 that does not satisfy the above range, the battery temperature by the nail penetration test is suppressed lower, and the heat generation of the battery at the time of internal short circuit is further suppressed. It was done.

また、実施例１〜３４の中では、第１正極活物質／第２正極活物質の質量比が１以上１９以下である実施例１〜２９、３１〜３４は、第１正極活物質／第２正極活物質の質量比が１未満である実施例３０と比較して、電池の初期容量が高く、電池抵抗が低い結果となった。   Moreover, in Examples 1-34, Examples 1-29 and 31-34 whose mass ratio of 1st positive electrode active material / 2nd positive electrode active material is 1-19 is 1st positive electrode active material / first Compared to Example 30 in which the mass ratio of the two positive electrode active materials was less than 1, the battery had a high initial capacity and a low battery resistance.

また、実施例１〜３４の中では、第１正極活物質の平均粒径（Ｄ１）が、８μｍ以上２０μｍ以下であり、第２正極活物質の平均粒径（Ｄ２）が、２μｍ以上６μｍ以下であり、また、第１正極活物質の平均粒径（Ｄ１）と第２正極活物質の平均粒径（Ｄ２）との比（Ｄ１／Ｄ２）が２以上１０以下である実施例１〜３１、３４は、平均粒径や粒径比のいずれかが上記範囲を満たさない実施例３２及び３３と比較して、容量維持率が高く、充放電サイクル特性の低下が抑制された。さらに、実施例１〜３１、３４の中では、第１正極活物質として、リチウムを除く金属元素の総モル数に対するＮｉの割合が７０モル％以上９５モル％以下のＮｉ含有リチウム複合酸化物を用いた実施例１〜３１は、Ｎｉの割合が１００モル％である実施例３４と比較して、容量維持率が高く、充放電サイクル特性の低下がより抑制された。   In Examples 1 to 34, the average particle diameter (D1) of the first positive electrode active material is 8 μm or more and 20 μm or less, and the average particle diameter (D2) of the second positive electrode active material is 2 μm or more and 6 μm or less. Moreover, Examples 1-31 whose ratio (D1 / D2) of the average particle diameter (D1) of a 1st positive electrode active material and the average particle diameter (D2) of a 2nd positive electrode active material is 2-10 , 34 had a higher capacity retention rate than those of Examples 32 and 33 in which either the average particle size or the particle size ratio did not satisfy the above range, and the deterioration of the charge / discharge cycle characteristics was suppressed. Furthermore, in Examples 1-31, 34, as the first positive electrode active material, a Ni-containing lithium composite oxide in which the ratio of Ni with respect to the total number of moles of metal elements excluding lithium is 70 mol% or more and 95 mol% or less is used. The used Examples 1-31 had a high capacity | capacitance maintenance factor compared with Example 34 whose ratio of Ni is 100 mol%, and the fall of charging / discharging cycling characteristics was suppressed more.

１０ 非水電解質二次電池、１１ 正極、１２ 負極、１３ セパレータ、１４ 電極体、１５ ケース本体、１６ 封口体、１７，１８ 絶縁板、１９ 正極リード、２０ 負極リード、２１ 張り出し部、２２ フィルタ、２２ａ フィルタ開口部、２３ 下弁体、２４ 絶縁部材、２５ 上弁体、２６ キャップ、２６ａ キャップ開口部、２７ ガスケット、３０ 正極集電体、３２ 正極合材層、３２ａ 正極集電体側表面。

DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Case main body, 16 Sealing body, 17, 18 Insulation board, 19 Positive electrode lead, 20 Negative electrode lead, 21 Overhang | projection part, 22 Filter, 22a Filter opening, 23 Lower valve body, 24 Insulating member, 25 Upper valve body, 26 Cap, 26a Cap opening, 27 Gasket, 30 Positive electrode current collector, 32 Positive electrode mixture layer, 32a Positive electrode current collector side surface.

Claims (8)

正極集電体と、前記正極集電体上に設けられ、第１正極活物質と第２正極活物質を含む正極合材層と、を有し、
前記第１正極活物質は、Ｎｉ含有リチウム複合酸化物であって、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が７０モル％以上１００モル％以下であり、
前記第２正極活物質は、Ｎｉ含有リチウム複合酸化物であって、Ｌｉを除く金属元素の総モル数に対するＮｉの割合が１０モル％以上６０モル％以下であり、
前記正極合材層の厚み方向において、正極集電体側表面から４μｍの厚さまでの正極合材層内に存在する前記第２正極活物質の存在率は、５５％以上である、非水電解質二次電池用正極。 A positive electrode current collector, and a positive electrode mixture layer provided on the positive electrode current collector and including a first positive electrode active material and a second positive electrode active material,
The first positive electrode active material is a Ni-containing lithium composite oxide, and the ratio of Ni to the total number of moles of metal elements excluding Li is 70 mol% or more and 100 mol% or less,
The second positive electrode active material is a Ni-containing lithium composite oxide, and the ratio of Ni to the total number of moles of metal elements excluding Li is 10 mol% or more and 60 mol% or less,
In the thickness direction of the positive electrode mixture layer, the abundance ratio of the second positive electrode active material present in the positive electrode mixture layer from the positive electrode current collector side surface to a thickness of 4 μm is 55% or more. Positive electrode for secondary battery. 前記第１正極活物質は、一般式Ｌｉａ１Ｎｉｂ１Ｃｏｃ１Ｍｄ１Ｏ２（０．９≦ａ１≦１．２、０．７≦ｂ１≦０．９５、０≦ｃ１≦０．３、０≦ｄ１≦０．３、Ｍは、Ｍｎ、Ａｌ、Ｚｒ及びＷからなる群から選択される少なくとも１種）で表され、
前記第２正極活物質は、一般式Ｌｉａ２Ｎｉｂ２Ｃｏｃ２Ｍｄ２Ｏ２（０．９≦ａ１≦１．２、０．１≦ｂ１≦０．６、０．１≦ｃ１≦０．６、０．１≦ｄ１≦０．５５、Ｍは、Ｍｎ、Ａｌ、Ｚｒ及びＷからなる群から選択される少なくとも１種）で表される、請求項１に記載の非水電解質二次電池用正極。 The first positive electrode active material has a general formula Li a1 Ni b1 Co c1 M d1 O 2 (0.9 ≦ a1 ≦ 1.2, 0.7 ≦ b1 ≦ 0.95, 0 ≦ c1 ≦ 0.3, 0 ≦ d1 ≦ 0.3, M is represented by at least one selected from the group consisting of Mn, Al, Zr and W),
The second positive electrode active material has a general formula Li a2 Ni b2 Co c2 M d2 O 2 (0.9 ≦ a1 ≦ 1.2, 0.1 ≦ b1 ≦ 0.6, 0.1 ≦ c1 ≦ 0.6). 0.1 ≦ d1 ≦ 0.55, and M is at least one selected from the group consisting of Mn, Al, Zr and W). Positive electrode. 前記正極合材層における前記第１正極活物質の質量（Ｗ１）と前記第２正極活物質の質量（Ｗ２）の比（Ｗ１／Ｗ２）は１以上９以下であり、
前記第１正極活物質の平均粒径（Ｄ１）は、８μｍ以上２０μｍ以下であり、前記第２正極活物質の平均粒径（Ｄ２）は、２μｍ以上６μｍ以下であり、
前記第１正極活物質の平均粒径（Ｄ１）と前記第２正極活物質の平均粒径（Ｄ２）との比（Ｄ１／Ｄ２）が２以上１０以下である、請求項１又は２に記載の非水電解質二次電池用正極。 The ratio (W1 / W2) of the mass (W1) of the first positive electrode active material and the mass (W2) of the second positive electrode active material in the positive electrode mixture layer is 1 or more and 9 or less,
The average particle diameter (D1) of the first positive electrode active material is 8 μm or more and 20 μm or less, and the average particle diameter (D2) of the second positive electrode active material is 2 μm or more and 6 μm or less,
The ratio (D1 / D2) between the average particle diameter (D1) of the first positive electrode active material and the average particle diameter (D2) of the second positive electrode active material is 2 or more and 10 or less. Positive electrode for non-aqueous electrolyte secondary battery. 前記正極合材層の厚み方向において、正極集電体側表面から４μｍの厚さまでの正極合材層内に存在する前記第２正極活物質の存在率は、６０％以上８５％以下である請求項１〜３のいずれか１項に記載の非水電解質二次電池用正極。   The abundance ratio of the second positive electrode active material existing in the positive electrode mixture layer from the positive electrode current collector side surface to a thickness of 4 μm in the thickness direction of the positive electrode mixture layer is 60% or more and 85% or less. The positive electrode for nonaqueous electrolyte secondary batteries of any one of 1-3. 前記正極合材層の目付量は、３０ｍｇ／ｃｍ２以上８０ｍｇ／ｃｍ２以下である、請求項１〜４のいずれか１項に記載の非水電解質二次電池用正極。 5. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein a basis weight of the positive electrode mixture layer is 30 mg / cm 2 or more and 80 mg / cm 2 or less. 正極合材層は導電材を含み、
前記正極合材層中の前記導電材の含有量は、０．５質量％以上４質量％以下である、請求項１〜５のいずれか１項に記載の非水電解質二次電池用正極。 The positive electrode mixture layer includes a conductive material,
6. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the content of the conductive material in the positive electrode mixture layer is 0.5% by mass or more and 4% by mass or less. 正極、負極、及び非水電解質を含み、
前記正極は請求項１〜６のいずれか１項に記載の非水電解質二次電池用正極である、非水電解質二次電池。 Including a positive electrode, a negative electrode, and a non-aqueous electrolyte;
The said positive electrode is a nonaqueous electrolyte secondary battery which is a positive electrode for nonaqueous electrolyte secondary batteries of any one of Claims 1-6. 電池容量が５０Ａｈ以上である、請求項７に記載の非水電解質二次電池。
The nonaqueous electrolyte secondary battery according to claim 7, wherein the battery capacity is 50 Ah or more.
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