JP2019029307A - Nonaqueous electrolyte secondary battery - Google Patents

Nonaqueous electrolyte secondary battery Download PDF

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JP2019029307A
JP2019029307A JP2017150747A JP2017150747A JP2019029307A JP 2019029307 A JP2019029307 A JP 2019029307A JP 2017150747 A JP2017150747 A JP 2017150747A JP 2017150747 A JP2017150747 A JP 2017150747A JP 2019029307 A JP2019029307 A JP 2019029307A
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negative electrode
secondary battery
lithium
flat
aqueous electrolyte
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JP6864851B2 (en
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祐介 小野田
Yusuke Onoda
祐介 小野田
永明 小岩
Nagaaki Koiwa
永明 小岩
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Toyota Motor 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
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Abstract

To provide a technique for surely preventing lithium from depositing on a negative electrode surface in a nonaqueous electrolyte secondary battery in which LiBOB is added to a nonaqueous electrolyte solution.SOLUTION: A nonaqueous electrolyte secondary battery herein disclosed comprises: a wound electrode body; and a nonaqueous electrolyte solution containing LiBOB. The wound electrode body of the nonaqueous electrolyte secondary battery is a flat shaped wound electrode body having two flat parts of which the surface makes a flat face and two R parts of which the surface is a curved face. When the length of the flat parts is denoted by A, and the radius of the surface of the R parts is denoted by D, they satisfy the relation given by A>2D. In the nonaqueous electrolyte secondary battery herein disclosed, a lithium fluorosulfonate is added to the nonaqueous electrolyte solution. Supposing that the whole solid content of a negative electrode mixture layer is 100 wt.%, a binder content is 1.07 wt.% or more and 1.30 wt.% or less. A foil-shaped negative electrode current collector has a thickness of 9 μm or less.SELECTED DRAWING: None

Description

本発明は、捲回電極体と非水電解液とを備えた非水電解液二次電池に関する。   The present invention relates to a non-aqueous electrolyte secondary battery including a wound electrode body and a non-aqueous electrolyte.

リチウムイオン二次電池、ニッケル水素電池等の非水電解液二次電池は、近年、パソコンや携帯端末等のいわゆるポータブル電源や車両駆動用電源として好ましく用いられている。特に、軽量で高エネルギー密度が得られるリチウムイオン二次電池は、電気自動車、ハイブリッド自動車等の車両に搭載して用いられる高出力電源（例えば、車両の駆動輪に連結されたモータを駆動させる電源）として重要性が高まっている。   In recent years, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries and nickel metal hydride batteries are preferably used as so-called portable power sources for vehicles and personal computers and power sources for driving vehicles. In particular, a lithium-ion secondary battery that is lightweight and obtains a high energy density is a high-output power source (for example, a power source that drives a motor connected to a driving wheel of the vehicle) used in a vehicle such as an electric vehicle or a hybrid vehicle. ) Is becoming increasingly important.

かかる非水電解液二次電池の分野では、非水電解液にリチウムビス（オキサレート）ボレート（Ｌｉｔｈｉｕｍ ｂｉｓ（ｏｘａｌａｔｅ）ｂｏｒａｔｅ：ＬｉＢＯＢ）を添加する技術が提案されている。かかるＬｉＢＯＢが添加された非水電解液二次電池では、初期の充放電においてＬｉＢＯＢ由来の被膜が負極表面に形成され、非水電解液の分解が抑制されるため、充放電サイクルに伴う内部抵抗の増加を防止することができる。   In the field of such non-aqueous electrolyte secondary batteries, a technique for adding lithium bis (oxalate) borate (LiBOB) to the non-aqueous electrolyte has been proposed. In such a non-aqueous electrolyte secondary battery to which LiBOB is added, a LiBOB-derived film is formed on the surface of the negative electrode during the initial charge and discharge, and the decomposition of the non-aqueous electrolyte is suppressed. Can be prevented from increasing.

一方で、上記のように、非水電解液にＬｉＢＯＢを添加すると、負極の表面にリチウムが析出してしまうことがある。特許文献１には、かかるリチウムの析出を抑制する技術の一例として、高さに対する幅の割合が２以上の捲回電極体を有した非水電解液二次電池において、ＬｉＢＯＢとフルオロスルホン酸リチウム（ＦＳＯ３Ｌｉ）を含有した非水電解質を用いる技術が開示されている。 On the other hand, as described above, when LiBOB is added to the non-aqueous electrolyte, lithium may be deposited on the surface of the negative electrode. In Patent Document 1, as an example of a technique for suppressing the precipitation of lithium, LiBOB and lithium fluorosulfonate in a nonaqueous electrolyte secondary battery having a wound electrode body having a width to height ratio of 2 or more. A technique using a nonaqueous electrolyte containing (FSO 3 Li) is disclosed.

特開２０１６−１４３４５４号公報JP 2006-143454 A

しかしながら、上述した特許文献１に記載の技術では、リチウムの析出を十分に抑制できているとは言えず、依然として負極の表面にリチウムが析出することがあった。
本発明は、かかる問題を鑑みてなされたものであり、その主な目的は、非水電解液にＬｉＢＯＢが添加された非水電解液二次電池において、負極の表面にリチウムが析出することを確実に防止することができる技術を提供することである。 However, in the technique described in Patent Document 1 described above, it cannot be said that lithium deposition is sufficiently suppressed, and lithium may still be deposited on the surface of the negative electrode.
The present invention has been made in view of such problems, and its main purpose is that lithium is deposited on the surface of the negative electrode in a non-aqueous electrolyte secondary battery in which LiBOB is added to the non-aqueous electrolyte. It is to provide a technique that can be surely prevented.

上記目的を実現するべく、本発明によって以下の構成の非水電解液二次電池が提供される。   In order to achieve the above object, the present invention provides a non-aqueous electrolyte secondary battery having the following configuration.

ここで開示される非水電解液二次電池は、正極と負極とがセパレータを介して捲回された捲回電極体と、リチウムビス（オキサレート）ボレートを含有する非水電解液とを備えている。
かかる非水電解液二次電池の正極は箔状の正極集電体の表面に正極合材層が付与されることによって形成され、かつ、負極は箔状の負極集電体の表面に負極合材層が付与ることによって形成されている。
また、捲回電極体は、捲回軸を挟んで両側に形成された表面が平面である２つの平坦部と、該２つの平坦部間に形成された表面が曲面である２つのＲ部とを有する扁平形状の捲回電極体であって、捲回軸に垂直な断面における平坦部の長さをＡとし、Ｒ部の表面の半径をＤとした場合にＡ＞２Ｄの関係を満たしている。
そして、ここで開示される非水電解液二次電池では、非水電解液にフルオロスルホン酸リチウムが添加されており、負極合材層の固形分全体を１００ｗｔ％としたときのバインダ含有量が１．０７ｗｔ％以上１．３０ｗｔ％以下であり、かつ、箔状の負極集電体の厚みが９μｍ以下である。 A non-aqueous electrolyte secondary battery disclosed herein includes a wound electrode body in which a positive electrode and a negative electrode are wound via a separator, and a non-aqueous electrolyte containing lithium bis (oxalate) borate. Yes.
The positive electrode of such a non-aqueous electrolyte secondary battery is formed by applying a positive electrode mixture layer on the surface of a foil-shaped positive electrode current collector, and the negative electrode is formed on the surface of the foil-shaped negative electrode current collector. It is formed by providing a material layer.
Further, the wound electrode body includes two flat portions whose surfaces formed on both sides of the winding axis are flat surfaces, and two R portions whose surface formed between the two flat portions is a curved surface. A flat-shaped wound electrode body having a relationship of A> 2D, where A is the length of the flat portion in the cross section perpendicular to the winding axis, and D is the radius of the surface of the R portion. Yes.
And in the non-aqueous electrolyte secondary battery disclosed here, lithium fluorosulfonate is added to the non-aqueous electrolyte, and the binder content when the total solid content of the negative electrode mixture layer is 100 wt% is The thickness is 1.07 wt% or more and 1.30 wt% or less, and the thickness of the foil-shaped negative electrode current collector is 9 μm or less.

本発明者は、種々の実験と検討を行った結果、ＬｉＢＯＢを添加した非水電解液二次電池では、捲回電極体のＲ部にリチウムの析出が発生し易いことを発見し、特許文献１のように非水電解液にフルオロスルホン酸リチウム（ＦＳＯ３Ｌｉ）を添加しただけでは、かかるＲ部におけるリチウムの析出を抑制することが難しいことを見出した。
そして、Ｒ部においてリチウムが析出し易い原因について本発明者が検討した結果、Ｒ部を有する扁平形状の捲回電極体では、当該Ｒ部の形状を維持することができずに正極と負極との極間が広くなることがあり、このような場合に正極から溶出した金属が負極の表面に堆積してリチウム析出耐性が低下することを見出した。 As a result of various experiments and studies, the present inventor found that in a non-aqueous electrolyte secondary battery to which LiBOB was added, lithium precipitation was likely to occur in the R part of the wound electrode body. It was found that just adding lithium fluorosulfonate (FSO 3 Li) to the non-aqueous electrolyte solution as in No. 1 makes it difficult to suppress the precipitation of lithium in the R portion.
And as a result of the present inventors examining the reason why lithium is likely to precipitate in the R portion, the flat wound electrode body having the R portion cannot maintain the shape of the R portion, and the positive electrode, the negative electrode, In such a case, it has been found that the metal eluted from the positive electrode is deposited on the surface of the negative electrode and the lithium deposition resistance is lowered.

ここで開示される非水電解液二次電池は、上記知見に基づいて種々の実験を行うことによってなされたものである。
この非水電解液二次電池では、先ず、非水電解液にＦＳＯ３Ｌｉが添加されているため、従来の非水電解液二次電池と同様に、リチウムの析出を抑制できる。
さらに、ここで開示される非水電解液二次電池では、上記のＡ＞２Ｄの関係を満たす扁平形状の捲回電極体において、負極合材層の固形分全体を１００ｗｔ％としたときのバインダ含有量を１．０７ｗｔ％以上にすると共に、負極集電体の厚みを９μｍ以下にしている。これによって、扁平形状の捲回電極体のＲ部の形状を好適に維持することができるため、正負極の極間が広くなることによるリチウム析出耐性の低下を好適に防止できる。 The non-aqueous electrolyte secondary battery disclosed here has been made by conducting various experiments based on the above findings.
In this non-aqueous electrolyte secondary battery, first, since FSO 3 Li is added to the non-aqueous electrolyte, the precipitation of lithium can be suppressed as in the conventional non-aqueous electrolyte secondary battery.
Furthermore, in the non-aqueous electrolyte secondary battery disclosed herein, in the flat wound electrode body that satisfies the relationship of A> 2D, the binder when the total solid content of the negative electrode mixture layer is 100 wt% The content is set to 1.07 wt% or more, and the thickness of the negative electrode current collector is set to 9 μm or less. Thereby, since the shape of the R portion of the flat wound electrode body can be suitably maintained, it is possible to suitably prevent a decrease in resistance to lithium deposition due to an increase in the distance between the positive and negative electrodes.

なお、本発明者は、上記した技術に至る実験において、負極合材層のバインダ含有量を多くし過ぎると、負極活物質の反応面積が少なくなって抵抗が増加するため、却ってリチウムが析出し易くなることを発見した。ここで開示される非水電解液二次電池では、かかる点を考慮して、バインダ含有量の上限が１．３０ｗｔ％に定められている。   In addition, in the experiment leading to the above-described technique, the present inventor, when the binder content of the negative electrode mixture layer is excessively increased, the reaction area of the negative electrode active material is decreased and the resistance is increased. I found it easier. In the non-aqueous electrolyte secondary battery disclosed here, the upper limit of the binder content is set to 1.30 wt% in consideration of this point.

本発明の一実施形態に係るリチウムイオン二次電池を模式的に示す斜視図である。1 is a perspective view schematically showing a lithium ion secondary battery according to an embodiment of the present invention. 本発明の一実施形態に係るリチウムイオン二次電池の捲回電極体を模式的に示す斜視図である。It is a perspective view which shows typically the winding electrode body of the lithium ion secondary battery which concerns on one Embodiment of this invention. 図２に示す捲回電極体の捲回軸に垂直な断面図である。It is sectional drawing perpendicular | vertical to the winding axis | shaft of the wound electrode body shown in FIG. 試験例におけるサンプル１〜６およびサンプル１０〜１３の容量維持率とバインダ含有率との関係を示すグラフであり、縦軸は容量維持率、横軸はバインダ含有量を示している。It is a graph which shows the relationship between the capacity | capacitance maintenance factor and binder content rate of the samples 1-6 and samples 10-13 in a test example, a vertical axis | shaft has shown the capacity | capacitance maintenance factor and the horizontal axis has shown binder content. 試験例におけるサンプル７〜１１の容量維持率と負極集電体の厚みとの関係を示すグラフであり、縦軸は容量維持率、横軸は負極集電体の厚みを示している。It is a graph which shows the relationship between the capacity | capacitance maintenance factor of the samples 7-11 in a test example, and the thickness of a negative electrode collector, and the vertical axis | shaft has shown the capacity | capacitance maintenance factor and the horizontal axis has shown the thickness of the negative electrode collector.

以下、本発明の好適な実施形態を説明する。なお、本発明において特に言及している事項以外の事柄であって本発明の実施に必要な事項は、当該分野における従来技術に基づく当業者の設計事項として把握され得る。本発明は、本明細書に開示されている内容と当該分野における技術常識とに基づいて実施することができる。   Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters specifically mentioned in the present invention and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

１．リチウムイオン二次電池の構造
以下、ここで開示される非水電解液二次電池の一実施形態としてリチウムイオン二次電池を説明する。なお、ここで開示される非水電解液二次電池は、リチウムイオン二次電池に限定されない。
図１は本実施形態に係るリチウムイオン二次電池を模式的に示す斜視図である。なお、図１〜図３の各図における符号Ｘはリチウムイオン二次電池の長さ方向を示し、符号Ｙは厚み方向を示し、符号Ｚは高さ方向を示している。 1. Structure of Lithium Ion Secondary Battery Hereinafter, a lithium ion secondary battery will be described as an embodiment of the nonaqueous electrolyte secondary battery disclosed herein. Note that the nonaqueous electrolyte secondary battery disclosed herein is not limited to a lithium ion secondary battery.
FIG. 1 is a perspective view schematically showing a lithium ion secondary battery according to this embodiment. In addition, the code | symbol X in each figure of FIGS. 1-3 shows the length direction of a lithium ion secondary battery, the code | symbol Y shows the thickness direction, and the code | symbol Z has shown the height direction.

（１）電池ケース
図１に示すように、このリチウムイオン二次電池１００は、扁平な角形の電池ケース５０を備えている。この電池ケース５０は、上面が開放された扁平なケース本体５２と、当該上面の開口部を塞ぐ蓋体５４とから構成されている。また、電池ケース５０の蓋体５４には、正極端子７０と負極端子７２とが設けられている。 (1) Battery Case As shown in FIG. 1, the lithium ion secondary battery 100 includes a flat rectangular battery case 50. The battery case 50 includes a flat case main body 52 having an open upper surface and a lid 54 that closes the opening of the upper surface. The lid 54 of the battery case 50 is provided with a positive terminal 70 and a negative terminal 72.

（２）捲回電極体
本実施形態に係るリチウムイオン二次電池１００では、図１に示す電池ケース５０の内部に、図２および図３に示す捲回電極体８０が収容されている。図２は本実施形態に係るリチウムイオン二次電池の捲回電極体を模式的に示す斜視図であり、図３は図２に示す捲回電極体の捲回軸に垂直な断面図である。 (2) Winding electrode body In the lithium ion secondary battery 100 according to the present embodiment, the winding electrode body 80 shown in FIGS. 2 and 3 is accommodated in the battery case 50 shown in FIG. 1. 2 is a perspective view schematically showing a wound electrode body of the lithium ion secondary battery according to the present embodiment, and FIG. 3 is a cross-sectional view perpendicular to the winding axis of the wound electrode body shown in FIG. .

図２に示すように、本実施形態における捲回電極体８０は、セパレータ４０を介して正極１０と負極２０とを積層させ、当該積層体を捲回することによって形成されている。また、この捲回電極体８０は、捲回後に所定の圧力でプレスすることによって扁平形状に成形されている。図３に示すように、この扁平形状の捲回電極体８０では、捲回軸ＷＬを挟んだ両側に表面が平面である平坦部８２が２つ形成されている。そして、この２つの平坦部８２間には、表面が曲面であるＲ部８４が２つ形成されている。
また、本明細書においては、図３のような捲回軸ＷＬに垂直な断面図における平坦部８２の長さ（高さ方向Ｚの平坦部８２の長さ）をＡとし、Ｒ部８４の表面の半径をＤとしている。そして、本実施形態に係るリチウムイオン二次電池１００では、平坦部８２の長さＡとＲ部８４の表面の半径Ｄとの関係がＡ＞２Ｄを満たすように扁平形状の捲回電極体８０が成形されている。 As shown in FIG. 2, the wound electrode body 80 in the present embodiment is formed by laminating the positive electrode 10 and the negative electrode 20 via the separator 40 and winding the laminated body. The wound electrode body 80 is formed into a flat shape by pressing with a predetermined pressure after winding. As shown in FIG. 3, in this flat wound electrode body 80, two flat portions 82 having a flat surface are formed on both sides of the winding axis WL. Two R portions 84 having a curved surface are formed between the two flat portions 82.
In this specification, the length of the flat portion 82 (the length of the flat portion 82 in the height direction Z) in the cross-sectional view perpendicular to the winding axis WL as shown in FIG. The radius of the surface is D. In the lithium ion secondary battery 100 according to this embodiment, the flat wound electrode body 80 is flat so that the relationship between the length A of the flat portion 82 and the radius D of the surface of the R portion 84 satisfies A> 2D. Is molded.

（ａ）正極
次に、捲回電極体８０を構成する各部材について説明する。
図２に示すように、正極１０は、正極集電体１２の両面に正極合材層１４を付与することによって形成される。なお、正極１０の一方の側縁部には、正極合材層１４が付与されておらず、集電体露出部１６が形成されている。そして、この集電体露出部１６が捲回された正極接続部８０ａには、上述した正極端子７０（図１参照）が接続される。 (A) Positive electrode Next, each member which comprises the wound electrode body 80 is demonstrated.
As shown in FIG. 2, the positive electrode 10 is formed by applying a positive electrode mixture layer 14 to both surfaces of a positive electrode current collector 12. Note that the positive electrode mixture layer 14 is not provided on one side edge of the positive electrode 10, and a current collector exposed portion 16 is formed. And the positive electrode terminal 70 (refer FIG. 1) mentioned above is connected to the positive electrode connection part 80a by which this collector exposed part 16 was wound.

正極集電体１２は、長尺な箔状の導電性部材である。かかる正極集電体１２には、例えば、アルミニウムなどを用いることができる。正極集電体１２の厚みは、捲回電極体８０のＲ部８４の形状を好適に維持するという観点と、十分な強度を維持するという観点に基づいて設定されると好ましい。かかる正極集電体１２の厚みとしては、例えば４０μｍ〜６０μｍの範囲内に設定すると好ましい。   The positive electrode current collector 12 is a long foil-like conductive member. For the positive electrode current collector 12, for example, aluminum or the like can be used. The thickness of the positive electrode current collector 12 is preferably set based on the viewpoint of suitably maintaining the shape of the R portion 84 of the wound electrode body 80 and the viewpoint of maintaining sufficient strength. The thickness of the positive electrode current collector 12 is preferably set within a range of 40 μm to 60 μm, for example.

正極合材層１４には、正極活物質が含まれている。この正極活物質には、リチウムイオンを吸蔵・放出し得るリチウム複合酸化物が用いられる。かかる正極活物質に使用されるリチウム複合酸化物の一例として、リチウムニッケルコバルトマンガン複合酸化物（例、ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ2）のような三元系リチウム含有複合酸化物が挙げられる。
また、正極合材層１４には、上述の正極活物質以外に種々の添加物が含まれていてもよい。かかる添加物としては、導電材やバインダ等が挙げられる。導電材としては、例えば、アセチレンブラック（ＡＢ）等のカーボンブラックやグラファイト等の炭素材料を好適に使用し得る。バインダとしては、例えばポリフッ化ビニリデン（ＰＶＤＦ）等を使用し得る。 The positive electrode mixture layer 14 contains a positive electrode active material. As this positive electrode active material, a lithium composite oxide capable of occluding and releasing lithium ions is used. As an example of the lithium composite oxide used for such a positive electrode active material, a ternary lithium-containing composite such as lithium nickel cobalt manganese composite oxide (eg, LiNi 1/3 Co 1/3 Mn 1/3 O 2 ) is used. An oxide is mentioned.
The positive electrode mixture layer 14 may contain various additives in addition to the positive electrode active material described above. Examples of such additives include conductive materials and binders. As the conductive material, for example, carbon black such as acetylene black (AB) or carbon material such as graphite can be suitably used. As the binder, for example, polyvinylidene fluoride (PVDF) can be used.

（ｂ）負極
負極２０は、負極集電体２２の両面に負極合材層２４を付与することによって形成される。上述した正極１０と同様に、負極２０の一方の側縁部には、負極合材層２４が付与されておらず、集電体露出部２６が形成されている。そして、この集電体露出部２６が捲回された負極接続部８０ｂに、上述した負極端子７２（図１参照）が接続される。 (B) Negative Electrode The negative electrode 20 is formed by applying the negative electrode mixture layer 24 to both surfaces of the negative electrode current collector 22. Similar to the positive electrode 10 described above, the negative electrode mixture layer 24 is not provided on one side edge of the negative electrode 20, and a current collector exposed portion 26 is formed. And the negative electrode terminal 72 (refer FIG. 1) mentioned above is connected to the negative electrode connection part 80b by which this collector exposed part 26 was wound.

負極集電体２２は、長尺な箔状の導電性部材である。かかる負極集電体２２には、例えば、銅などを用いることができる。
また、本実施形態における負極合材層２４には、少なくとも、負極活物質とバインダとが含まれている。負極活物質としては、例えば黒鉛、ハードカーボン、ソフトカーボン等の炭素材料を使用することができる。また、バインダとしては、例えばスチレンブタジエンラバー（ＳＢＲ）やカルボキシメチルセルロース（ＣＭＣ）などを使用することができる。なお、捲回電極体８０のＲ部８４の形状を好適に維持するためには、負極合材層２４にはＳＢＲとＣＭＣの２種類のバインダが含まれていると好ましい。
また、負極合材層２４には、上述した負極活物質とバインダ以外に、増粘剤等が含まれていてもよい。 The negative electrode current collector 22 is a long foil-like conductive member. For the negative electrode current collector 22, for example, copper or the like can be used.
Further, the negative electrode mixture layer 24 in the present embodiment contains at least a negative electrode active material and a binder. As the negative electrode active material, for example, carbon materials such as graphite, hard carbon, and soft carbon can be used. As the binder, for example, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), or the like can be used. In order to suitably maintain the shape of the R portion 84 of the wound electrode body 80, the negative electrode mixture layer 24 preferably contains two types of binders, SBR and CMC.
The negative electrode mixture layer 24 may contain a thickener in addition to the negative electrode active material and the binder described above.

（ｃ）セパレータ
セパレータ４０には、例えば、リチウムイオンを通過させる微細な孔を有した多孔質の絶縁シートが用いられる。かかるセパレータ４０には、例えば、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）、ポリエステル、ポリアミド等の絶縁性樹脂を用いることができる。また、これらの樹脂を二層以上積層させた積層シートであってもよい。セパレータ４０の厚みは、例えば５μｍ〜４０μｍ、典型的には１０μｍ〜３０μｍ、好ましくは１５μｍ〜２５μｍである。 (C) Separator For the separator 40, for example, a porous insulating sheet having fine holes through which lithium ions pass is used. For the separator 40, for example, an insulating resin such as polyethylene (PE), polypropylene (PP), polyester, and polyamide can be used. Moreover, the lamination sheet which laminated | stacked two or more of these resin may be sufficient. The thickness of the separator 40 is, for example, 5 μm to 40 μm, typically 10 μm to 30 μm, and preferably 15 μm to 25 μm.

（３）非水電解液
図示は省略するが、本実施形態に係るリチウムイオン二次電池１００では、電池ケース５０の内部に非水電解液が収容されている。この非水電解液には、有機溶媒（非水溶媒）に支持塩を含有させたものが用いられる。
非水溶媒としては、例えば、一般的なリチウムイオン二次電池の電解液に用いられる各種の有機溶媒（例えば、カーボネート類、エーテル類、エステル類、ニトリル類、スルホン類、ラクトン類）を特に限定なく用いることができる。かかる非水電解液の非水溶媒の具体例としては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ジエチルカーボネート（ＤＥＣ）、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）、モノフルオロエチレンカーボネート（ＭＦＥＣ）、ジフルオロエチレンカーボネート（ＤＦＥＣ）、モノフルオロメチルジフルオロメチルカーボネート（Ｆ−ＤＭＣ）、トリフルオロジメチルカーボネート（ＴＦＤＭＣ）等が挙げられる。
また、支持塩としては、例えば、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４等のリチウム塩を好適に用いることができる。なお、非水電解液に含まれる支持塩の濃度は、０．７ｍｏｌ／Ｌ以上１．３ｍｏｌ／Ｌ以下が好ましい。 (3) Nonaqueous Electrolytic Solution Although not shown, in the lithium ion secondary battery 100 according to the present embodiment, the nonaqueous electrolytic solution is accommodated in the battery case 50. As this non-aqueous electrolyte, an organic solvent (non-aqueous solvent) containing a supporting salt is used.
Examples of the nonaqueous solvent include, for example, various organic solvents (for example, carbonates, ethers, esters, nitriles, sulfones, lactones) used in an electrolyte solution of a general lithium ion secondary battery. Can be used. Specific examples of the nonaqueous solvent of the nonaqueous electrolyte include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate. (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyldifluoromethyl carbonate (F-DMC), trifluorodimethyl carbonate (TFDMC) and the like.
Further, as the supporting salt, for example, a lithium salt such as LiPF 6 , LiBF 4 , or LiClO 4 can be suitably used. The concentration of the supporting salt contained in the nonaqueous electrolytic solution is preferably 0.7 mol / L or more and 1.3 mol / L or less.

そして、本実施形態に係るリチウムイオン二次電池１００では、非水電解液にリチウムビス（オキサラト）ボレート（Ｌｉ［Ｂ（Ｃ２Ｏ４）２］；ＬｉＢＯＢ）が添加されている。かかるＬｉＢＯＢは、中心元素であるホウ素（Ｂ）に、少なくとも一つのシュウ酸イオン（Ｃ２Ｏ４ ２−）が配位結合することで形成される錯体化合物である。このＬｉＢＯＢを非水電解液に添加することによって、充放電の初期に負極２０の表面にＬｉＢＯＢ由来のＳＥＩ被膜を形成することができるため、充放電サイクルに伴う内部抵抗の増加を防止することができる。なお、ＬｉＢＯＢの添加量は、負極合材層２４に対して０．０２５Ｍ〜０．０４５Ｍ（好ましくは０．０２５Ｍ〜０．０４Ｍ）の割合で含まれるように調整されていると好ましい。 In the lithium ion secondary battery 100 according to the present embodiment, lithium bis (oxalato) borate (Li [B (C 2 O 4 ) 2 ]; LiBOB) is added to the nonaqueous electrolytic solution. Such LiBOB is a complex compound formed by coordinate bonding of at least one oxalate ion (C 2 O 4 2− ) to boron (B) which is a central element. By adding this LiBOB to the non-aqueous electrolyte, a LiBOB-derived SEI film can be formed on the surface of the negative electrode 20 at the initial stage of charge / discharge, and therefore, it is possible to prevent an increase in internal resistance accompanying the charge / discharge cycle. it can. The amount of LiBOB added is preferably adjusted so as to be included at a ratio of 0.025 M to 0.045 M (preferably 0.025 M to 0.04 M) with respect to the negative electrode mixture layer 24.

２．リチウム析出の防止
本実施形態に係るリチウムイオン二次電池１００では、上記したように、非水電解液にＬｉＢＯＢが添加されているが、これによって負極２０の表面にリチウムが析出することがないように、以下の要件を備えている。 2. Prevention of Lithium Precipitation In the lithium ion secondary battery 100 according to the present embodiment, LiBOB is added to the non-aqueous electrolyte as described above, so that lithium does not precipitate on the surface of the negative electrode 20. Has the following requirements.

（１）フルオロスルホン酸リチウムの添加
先ず、本実施形態に係るリチウムイオン二次電池１００では、非水電解液にフルオロスルホン酸リチウム（ＦＳＯ３Ｌｉ）が添加されている。このＦＳＯ３Ｌｉを非水電解液に添加することによって、ＳＥＩ被膜の形成にむらが生じることを抑制し、ＬｉＢＯＢ由来の被膜を略均一に形成できるため、リチウムの析出を抑制することができる。なお、ＦＳＯ３Ｌｉの添加量は、非水電解液の総量に対して０．１〜４．０ｗｔ％とすることが好ましく、０．３〜１．５ｗｔ％とすることがより好ましい。 (1) Addition of lithium fluorosulfonate First, in the lithium ion secondary battery 100 according to the present embodiment, lithium fluorosulfonate (FSO 3 Li) is added to the non-aqueous electrolyte. By adding this FSO 3 Li to the non-aqueous electrolyte, it is possible to suppress unevenness in the formation of the SEI coating and to form a LiBOB-derived coating substantially uniformly, thereby suppressing lithium precipitation. The addition amount of the FSO 3 Li is preferably to 0.1～4.0Wt% based on the total amount of the nonaqueous electrolyte solution, and more preferably to 0.3 to 1.5%.

（２）バインダ含有量
さらに、本実施形態に係るリチウムイオン二次電池１００では、捲回電極体８０のＲ部８４の形状を好適に維持してリチウムの析出を適切に防止するために、負極合材層２４におけるバインダ含有量が調整されている。具体的には、本実施形態では、固形分全体を１００ｗｔ％としたときのバインダ含有量が１．０７ｗｔ％以上に設定されている。このように負極合材層２４に十分な量のバインダを添加することによって、捲回電極体８０のＲ部８４の形状を適切に維持し、正極１０と負極２０との極間が広くなることによるリチウムの析出を好適に防止することができる。
また、本実施形態に係るリチウムイオン二次電池１００では、バインダ含有量の上限が１．３０ｗｔ％以下に設定されている。これは、バインダ含有量を多くし過ぎると、負極活物質の反応面積が少なくなって抵抗が増加し、逆にリチウムの析出が生じ易くなるためである。 (2) Binder Content Furthermore, in the lithium ion secondary battery 100 according to this embodiment, in order to appropriately maintain the shape of the R portion 84 of the wound electrode body 80 and appropriately prevent lithium deposition, the negative electrode The binder content in the composite material layer 24 is adjusted. Specifically, in the present embodiment, the binder content when the total solid content is 100 wt% is set to 1.07 wt% or more. In this way, by adding a sufficient amount of binder to the negative electrode mixture layer 24, the shape of the R portion 84 of the wound electrode body 80 is appropriately maintained, and the gap between the positive electrode 10 and the negative electrode 20 is widened. It is possible to suitably prevent the precipitation of lithium due to.
In the lithium ion secondary battery 100 according to this embodiment, the upper limit of the binder content is set to 1.30 wt% or less. This is because if the binder content is excessively increased, the reaction area of the negative electrode active material is decreased, the resistance is increased, and conversely, lithium is liable to be precipitated.

（３）負極集電体の厚み
加えて、本実施形態に係るリチウムイオン二次電池１００では、捲回電極体８０のＲ部８４の形状を好適に維持するために、負極集電体２２の厚みを９μｍ以下に設定している。すなわち、負極集電体２２の厚みが厚すぎると、Ｒ部８４において負極２０を好適に湾曲させることができずに、正極１０と負極２０との極間が大きくなる恐れがある。本実施形態では、上記のように、厚さ９μｍ以下という薄い負極集電体２２を用いることによって、Ｒ部８４において正極１０と負極２０との極間が大きくなることを防止している。なお、負極集電体２２の強度を十分に確保するという観点から、負極集電体２２の厚みは６μｍ以上であると好ましい。 (3) Thickness of the negative electrode current collector In addition, in the lithium ion secondary battery 100 according to the present embodiment, in order to suitably maintain the shape of the R portion 84 of the wound electrode body 80, The thickness is set to 9 μm or less. That is, if the thickness of the negative electrode current collector 22 is too thick, the negative electrode 20 cannot be curved appropriately in the R portion 84, and the gap between the positive electrode 10 and the negative electrode 20 may be increased. In the present embodiment, as described above, the use of the thin negative electrode current collector 22 having a thickness of 9 μm or less prevents an increase in the distance between the positive electrode 10 and the negative electrode 20 in the R portion 84. In addition, from the viewpoint of ensuring sufficient strength of the negative electrode current collector 22, the thickness of the negative electrode current collector 22 is preferably 6 μm or more.

以上のように、本実施形態に係るリチウムイオン二次電池１００では、非水電解液にＦＳＯ３Ｌｉを添加した上で、負極合材層２４におけるバインダ含有量と、負極集電体２２の厚みとが適切に調整されている。これによって、捲回電極体８０のＲ部８４の形状を好適に維持し、負極２０の表面にリチウムが析出することを確実に防止することができる。 As described above, in the lithium ion secondary battery 100 according to this embodiment, after adding FSO 3 Li to the non-aqueous electrolyte, the binder content in the negative electrode mixture layer 24 and the thickness of the negative electrode current collector 22 are added. And are adjusted appropriately. Thereby, the shape of the R portion 84 of the wound electrode body 80 can be suitably maintained, and lithium can be reliably prevented from being deposited on the surface of the negative electrode 20.

［試験例］
以下、本発明に関する試験例を説明するが、かかる試験例の説明は本発明を限定することを意図したものではない。 [Test example]
Hereinafter, although the test example regarding this invention is demonstrated, description of this test example is not intended to limit this invention.

１．各試験例
本試験例では、下記の１３種類のリチウムイオン二次電池（サンプル１〜１３）を作製した。 1. Each test example In this test example, the following 13 types of lithium ion secondary batteries (samples 1 to 13) were produced.

（１）サンプル１
サンプル１では、負極合材層におけるバインダ含有量を１．０７ｗｔ％とし、負極集電体の厚みを８μｍとし、かつ、非水電解液にフルオロスルホン酸リチウムを添加したリチウムイオン二次電池を作製した。 (1) Sample 1
In Sample 1, a lithium ion secondary battery in which the binder content in the negative electrode mixture layer is 1.07 wt%, the thickness of the negative electrode current collector is 8 μm, and lithium fluorosulfonate is added to the non-aqueous electrolyte is manufactured. did.

具体的には、先ず、正極活物質（ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ2）の粉末と、分散媒（ＮＭＰ：Ｎメチルピロリドン）と、バインダ（ＰＶＤＦ：ポリフッ化ビニリデン）とを混合して正極合材を調製した。そして、シート状の正極集電体（アルミニウム箔）の一方の側縁部に露出部が形成されるように、正極合材を正極集電体の両面に塗布し、当該正極合材を乾燥させて長尺シート状の正極を作製した。 Specifically, first, a positive electrode active material (LiNi 1/3 Co 1/3 Mn 1/3 O 2 ) powder, a dispersion medium (NMP: N-methylpyrrolidone), a binder (PVDF: polyvinylidene fluoride), Were mixed to prepare a positive electrode mixture. Then, the positive electrode mixture is applied to both surfaces of the positive electrode collector so that an exposed portion is formed on one side edge of the sheet-like positive electrode collector (aluminum foil), and the positive electrode mixture is dried. Thus, a long sheet-like positive electrode was produced.

次に、天然黒鉛（グラファイト）を核とした負極活物質の粉末と、水と、バインダとを混合して負極合材ペーストを調製した。このとき、サンプル１では、バインダとして、スチレンブタジエンラバー（ＳＢＲ）とカルボキシメチルセルロース（ＣＭＣ）を使用し、固形分全体に対するＳＢＲとＣＭＣの総量（バインダ含有量）を１．０７ｗｔ％に設定した。
そして、負極集電体として厚みが８μｍの長尺シート状の銅箔を使用し、当該銅箔の一方の側縁部に露出部が形成されるように、負極合材ペーストを両面に塗布した後、塗布されたペーストを乾燥させることによって長尺シート状の負極を作製した。 Next, a negative electrode active material powder having natural graphite (graphite) as a core, water, and a binder were mixed to prepare a negative electrode mixture paste. At this time, in Sample 1, styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were used as binders, and the total amount of SBR and CMC (binder content) with respect to the entire solid content was set to 1.07 wt%.
Then, a long sheet-like copper foil having a thickness of 8 μm was used as the negative electrode current collector, and the negative electrode mixture paste was applied to both sides so that an exposed portion was formed on one side edge of the copper foil. Thereafter, the applied paste was dried to prepare a long sheet-like negative electrode.

次に、シート状のセパレータを介して上述の正極と負極を積層させた後、積層体を捲回させて扁平状の捲回電極体を作製した。このとき、平坦部の長さＡが５．７ｍｍ、Ｒ部の表面の半径Ｄが３８．０ｍｍとなるように正極と負極とを捲回し、Ａ＞２Ｄの関係を満たす捲回電極体を作製した。   Next, after laminating the above-described positive electrode and negative electrode through a sheet-like separator, the laminate was wound to produce a flat wound electrode body. At this time, the positive electrode and the negative electrode are wound so that the length A of the flat portion is 5.7 mm and the radius D of the surface of the R portion is 38.0 mm, thereby producing a wound electrode body that satisfies the relationship of A> 2D. did.

そして、作製した捲回電極体をケースの外部端子と接続した後、非水電解液とともにケース内に収容して密閉することによりサンプル１のリチウムイオン二次電池を構築した。
なお、サンプル１では、電解液として、ＥＣとＤＭＣとＥＭＣとを３：４：３の体積比で含む混合溶媒に支持塩としてのＬｉＰＦ６を約１ｍｏｌ／リットルの濃度で含有させた非水電解液を使用しており、当該非水電解液に０．４０％のＬｉＢＯＢと、１．０％のフルオロスルホン酸リチウムとを添加した。 And after connecting the produced winding electrode body with the external terminal of a case, the lithium ion secondary battery of the sample 1 was constructed | assembled by accommodating in a case and sealing with a non-aqueous electrolyte.
In Sample 1, a nonaqueous electrolytic solution in which LiPF6 as a supporting salt was contained in a mixed solvent containing EC, DMC, and EMC at a volume ratio of 3: 4: 3 at a concentration of about 1 mol / liter as an electrolytic solution. And 0.40% LiBOB and 1.0% lithium fluorosulfonate were added to the non-aqueous electrolyte.

（２）サンプル２〜６
サンプル２〜６では、負極合材中のバインダ含有量をそれぞれ異ならせたことを除いて、サンプル１と同じ条件で試験用のリチウムイオン二次電池を作製した。具体的には、後述の表１に示すように、サンプル２ではバインダ含有量を１．１０ｗｔ％に設定し、サンプル３では１．２０ｗｔ％に設定し、サンプル４では１．３０ｗｔ％に設定した。また、サンプル５では１．４０に設定し、サンプル６では１．００ｗｔ％に設定した。 (2) Samples 2-6
In Samples 2 to 6, test lithium ion secondary batteries were produced under the same conditions as Sample 1 except that the binder contents in the negative electrode mixture were varied. Specifically, as shown in Table 1 described later, the binder content in sample 2 was set to 1.10 wt%, sample 3 was set to 1.20 wt%, and sample 4 was set to 1.30 wt%. . In sample 5, it was set to 1.40, and in sample 6, it was set to 1.00 wt%.

（３）サンプル７〜１１
サンプル７〜１０では、負極集電体の厚みをそれぞれ異ならせたことを除いて、サンプル２と同じ条件で試験用のリチウムイオン二次電池を作製した。具体的には、後述の表１に示すように、サンプル７では負極集電体の厚みを６μｍに設定し、サンプル８では７μｍに設定し、サンプル９では８μｍに設定した。また、サンプル１０では９μｍに設定した。また、サンプル１１では、負極集電体の厚みを１０μｍに設定したことを除いて、サンプル１と同じ条件で試験用のリチウムイオン二次電池を作製した。なお、サンプル１１は、負極の極板の面積がサンプル７〜１０と同じになるように作製した。 (3) Samples 7 to 11
In Samples 7 to 10, a test lithium ion secondary battery was fabricated under the same conditions as Sample 2 except that the thickness of the negative electrode current collector was varied. Specifically, as shown in Table 1 described later, the thickness of the negative electrode current collector was set to 6 μm in sample 7, 7 μm in sample 8, and 8 μm in sample 9. In sample 10, the thickness was set to 9 μm. In Sample 11, a test lithium ion secondary battery was fabricated under the same conditions as Sample 1, except that the thickness of the negative electrode current collector was set to 10 μm. Sample 11 was prepared such that the area of the negative electrode plate was the same as that of samples 7-10.

（４）サンプル１２、１３
サンプル１２、１３では、フルオロスルホン酸リチウムが添加されていない非水電解液を用いて試験用のリチウムイオン二次電池を作製した。具体的には、サンプル１２では、フルオロスルホン酸リチウムが添加されていない点を除いて、サンプル１１と同じ条件で試験用のリチウムイオン二次電池を作製した。また、サンプル１３では、フルオロスルホン酸リチウムが添加されていない点を除いて、サンプル１と同じ条件で試験用のリチウムイオン二次電池を作製した。 (4) Samples 12 and 13
In Samples 12 and 13, a test lithium ion secondary battery was manufactured using a non-aqueous electrolyte solution to which lithium fluorosulfonate was not added. Specifically, in Sample 12, a test lithium ion secondary battery was manufactured under the same conditions as Sample 11 except that lithium fluorosulfonate was not added. In Sample 13, a test lithium ion secondary battery was fabricated under the same conditions as Sample 1, except that lithium fluorosulfonate was not added.

２．評価試験
上記した各サンプルのリチウムイオン二次電池に対して充放電耐久試験を実施し、当該試験の結果に基づいて各サンプルのリチウム析出耐性を評価した。なお、本試験例では、リチウム析出耐性の指標として容量維持率を測定した。
具体的には、先ず、各サンプルのリチウムイオン二次電池をＳＯＣ８０％まで充電した。このとき、電流値は２００Ａに設定し、温度環境は−１０℃に設定し、充電時間は１０分間に設定した。次に、上記した充電条件と同じ条件で、各サンプルのリチウムイオン二次電池をＳＯＣ０％まで放電した。そして、上記した充放電サイクルを５００サイクル繰り返し実施した。そして、充放電耐久試験の前後の電池容量とＩＶ抵抗を測定し、測定結果に基づいて容量維持率を算出した。 2. Evaluation test The lithium ion secondary battery of each sample described above was subjected to a charge / discharge durability test, and the lithium deposition resistance of each sample was evaluated based on the result of the test. In this test example, the capacity retention rate was measured as an index of lithium deposition resistance.
Specifically, first, the lithium ion secondary battery of each sample was charged to SOC 80%. At this time, the current value was set to 200 A, the temperature environment was set to −10 ° C., and the charging time was set to 10 minutes. Next, the lithium ion secondary battery of each sample was discharged to SOC 0% under the same conditions as the above-described charging conditions. The above charge / discharge cycle was repeated 500 cycles. And the battery capacity and IV resistance before and after a charging / discharging endurance test were measured, and the capacity | capacitance maintenance factor was computed based on the measurement result.

本試験の測定結果を表１、図４、図５に示す。図４は本試験例におけるサンプル１〜６およびサンプル１０〜１３の容量維持率とバインダ含有率との関係を示すグラフであり、図５はサンプル７〜１１の容量維持率と負極集電体の厚みとの関係を示すグラフである。
なお、本試験では、容量維持率の算出結果が９９％を下回った場合、負極表面にリチウムが析出し、捲回電極体が劣化していると評価した。 The measurement results of this test are shown in Table 1, FIG. 4 and FIG. FIG. 4 is a graph showing the relationship between the capacity retention rate and the binder content of Samples 1 to 6 and Samples 10 to 13 in this test example, and FIG. It is a graph which shows the relationship with thickness.
In addition, in this test, when the calculation result of the capacity retention rate was less than 99%, it was evaluated that lithium was deposited on the negative electrode surface and the wound electrode body was deteriorated.

Figure 2019029307
Figure 2019029307

３．評価結果
表１および図４に示すように、サンプル１〜１３のうち、サンプル１〜４、サンプル７〜１０では、９９％を超える容量維持率が得られ、リチウムの析出が確実に抑制されていることが分かった。一方、バインダ含有量が１．３０ｗｔ％を上回ったサンプル５や、１．０７ｗｔを下回ったサンプル６では、容量維持率の若干の低下が確認された。このことから、リチウムの析出を確実に抑制するためには、バインダ含有量を１．０７ｗｔ以上１．３０ｗｔ％以下の範囲に設定する必要があることが分かった。 3. Evaluation results As shown in Table 1 and FIG. 4, among samples 1 to 13, in samples 1 to 4 and samples 7 to 10, a capacity retention rate exceeding 99% was obtained, and lithium deposition was reliably suppressed. I found out. On the other hand, in sample 5 in which the binder content was higher than 1.30 wt% and sample 6 in which the binder content was lower than 1.07 wt, a slight decrease in the capacity retention rate was confirmed. From this, it was found that the binder content needs to be set in the range of 1.07 wt% or more and 1.30 wt% or less in order to reliably suppress lithium deposition.

また、図５に示すように、厚みが９μｍを超えた負極集電体を使用したサンプル１１では、Ｒ部にリチウムが析出して容量維持率が低下することが確認された。このことから、リチウムの析出を確実に抑制するためには、負極集電体の厚みを９μｍ以下に設定する必要があることが分かった。   Further, as shown in FIG. 5, in Sample 11 using the negative electrode current collector having a thickness exceeding 9 μm, it was confirmed that lithium was deposited in the R portion and the capacity retention rate was lowered. From this, it was found that the thickness of the negative electrode current collector needs to be set to 9 μm or less in order to reliably suppress the precipitation of lithium.

さらに、サンプル１２、１３で容量維持率の大幅な低下が確認されたことから、リチウムの析出を確実に防止するためには、従来の技術と同様に、非水電解液にフルオロスルホン酸リチウムを添加する必要があることが確認できた。   Furthermore, since a significant decrease in the capacity retention rate was confirmed in Samples 12 and 13, in order to reliably prevent lithium deposition, lithium fluorosulfonate was added to the non-aqueous electrolyte as in the prior art. It was confirmed that it was necessary to add.

以上の試験結果より、非水電解液にＬｉＢＯＢが添加されたリチウムイオン二次電池において、リチウムの析出を確実に防止するためには、本試験例におけるサンプル１〜４およびサンプル７〜１０のように、負極合材層のバインダ含有量を１．０７ｗｔ以上１．３０ｗｔ％以下にし、負極集電体の厚みを９μｍ以下にした上で、非水電解液にオロスルホン酸リチウムを添加する必要があることが分かった。   From the above test results, in the lithium ion secondary battery in which LiBOB is added to the nonaqueous electrolytic solution, in order to reliably prevent lithium deposition, Samples 1 to 4 and Samples 7 to 10 in this test example In addition, it is necessary to add lithium orosulfonate to the non-aqueous electrolyte after the binder content of the negative electrode mixture layer is 1.07 wt% or more and 1.30 wt% or less and the thickness of the negative electrode current collector is 9 μm or less. I understood that.

以上、本発明の具体例を詳細に説明したが、これらは例示にすぎず、請求の範囲を限定するものではない。請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。   As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

１０ 正極
１２ 正極集電体
１４ 正極合材層
２０ 負極
２２ 負極集電体
２４ 負極合材層
４０ セパレータ
５０ 電池ケース
５２ ケース本体
５４ 蓋体
７０ 正極端子
７２ 負極端子
８０ 捲回電極体
８２ 平坦部
８４ Ｒ部
１００ リチウムイオン二次電池
Ａ 平坦部の長さ
Ｄ Ｒ部の表面の半径
ＷＬ 捲回軸
Ｘ 長さ方向
Ｙ 幅方向
Ｚ 高さ方向
DESCRIPTION OF SYMBOLS 10 Positive electrode 12 Positive electrode collector 14 Positive electrode mixture layer 20 Negative electrode 22 Negative electrode collector 24 Negative electrode mixture layer 40 Separator 50 Battery case 52 Case main body 54 Lid body 70 Positive electrode terminal 72 Negative electrode terminal 80 Winding electrode body 82 Flat part 84 R portion 100 Lithium ion secondary battery A Flat portion length D Radius surface R radius Winding axis X Length direction Y Width direction Z Height direction

Claims (1)

正極と負極とがセパレータを介して捲回された捲回電極体と、リチウムビス（オキサレート）ボレートを含有する非水電解液とを備えた非水電解液二次電池であって、
前記正極は箔状の正極集電体の表面に正極合材層が付与されることによって形成され、かつ、前記負極は箔状の負極集電体の表面に負極合材層が付与ることによって形成されており、
前記捲回電極体は、捲回軸を挟んで両側に形成された表面が平面である２つの平坦部と、該２つの平坦部間に形成された表面が曲面である２つのＲ部とを有する扁平形状の捲回電極体であって、前記捲回軸に垂直な断面における前記平坦部の長さをＡとし、前記Ｒ部の表面の半径をＤとした場合にＡ＞２Ｄの関係を満たしており、
ここで、前記非水電解液にフルオロスルホン酸リチウムが添加されており、
前記負極合材層の固形分全体を１００ｗｔ％としたときのバインダ含有量が１．０７ｗｔ％以上１．３０ｗｔ％以下であり、かつ、
前記箔状の負極集電体の厚みが９μｍ以下である、非水電解液二次電池。



A non-aqueous electrolyte secondary battery comprising a wound electrode body in which a positive electrode and a negative electrode are wound through a separator, and a non-aqueous electrolyte containing lithium bis (oxalate) borate,
The positive electrode is formed by providing a positive electrode mixture layer on the surface of a foil-shaped positive electrode current collector, and the negative electrode is formed by applying a negative electrode mixture layer on the surface of a foil-shaped negative electrode current collector. Formed,
The wound electrode body includes two flat portions having a flat surface formed on both sides of the winding axis, and two R portions having a curved surface formed between the two flat portions. A flat-shaped wound electrode body having a relationship of A> 2D where A is the length of the flat portion in the cross section perpendicular to the winding axis, and D is the radius of the surface of the R portion. Meets
Here, lithium fluorosulfonate is added to the non-aqueous electrolyte,
The binder content when the total solid content of the negative electrode mixture layer is 100 wt% is 1.07 wt% or more and 1.30 wt% or less, and
A non-aqueous electrolyte secondary battery in which the thickness of the foil-shaped negative electrode current collector is 9 μm or less.



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