JP2006107912A - Nonaqueous electrolyte secondary battery - Google Patents

Nonaqueous electrolyte secondary battery Download PDF

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JP2006107912A
JP2006107912A JP2004292541A JP2004292541A JP2006107912A JP 2006107912 A JP2006107912 A JP 2006107912A JP 2004292541 A JP2004292541 A JP 2004292541A JP 2004292541 A JP2004292541 A JP 2004292541A JP 2006107912 A JP2006107912 A JP 2006107912A
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negative electrode
active material
material layer
siox
secondary battery
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JP4815777B2 (en
JP2006107912A5 (en
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Shigeki Yamate
山手　　茂樹
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GS Yuasa 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
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    • 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

<P>PROBLEM TO BE SOLVED: To prevent deformation of anode collectors of nonaqueous electrolyte secondary batteries using silicon or silicon oxide as an anode active material to reduce fraction defective. <P>SOLUTION: The nonaqueous secondary battery comprises a cathode, an anode, and a nonaqueous electrolyte. The anode is an active material layer supported on a collector, and the active material layer contains silicon oxide expressed by the formula SiOx, where 0<x<2. Provided that the average composition of SiOx in all of the active material layer is x=x<SB>av</SB>and composition of SiOx of the active material layer near the collector is x=x<SB>B</SB>, it is characterized by satisfying the relationship x<SB>B</SB>>x<SB>av</SB>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、非水電解質二次電池に関する。   The present invention relates to a non-aqueous electrolyte secondary battery.

非水電解質二次電池には、集電体上に黒鉛等の炭素材料を含有した合剤層を形成した負極が広く用いられているが、この非水電解質二次電池のエネルギー密度は必ずしも十分とは言えず、さらなるエネルギー密度の向上が切望されていた。
そこで、負極活物質として、炭素材料に比べて非常に大きな容量を有するケイ素又はその酸化物を用いた非水電解質二次電池が提案されている。
特開２００２−３１３３１９公報 For nonaqueous electrolyte secondary batteries, negative electrodes in which a mixture layer containing a carbon material such as graphite is formed on a current collector are widely used. However, the energy density of this nonaqueous electrolyte secondary battery is not always sufficient. However, further improvement in energy density has been desired.
Therefore, a non-aqueous electrolyte secondary battery using silicon or an oxide thereof having a very large capacity as compared with a carbon material as a negative electrode active material has been proposed.
JP 2002-313319 A

しかしながら、このものでは、充放電に伴うケイ素又はその酸化物の膨張収縮が炭素材料よりも著しく大きい。そのため、負極が変形して電池内部で短絡が生じて、電池の不良率が高いという問題点があった。
本発明は上記のような事情に基づいて完成されたものであって、負極活物質としてケイ素又はその酸化物を用いた非水電解質二次電池において負極の変形を抑制し、不良率を低減することを目的とする。 However, in this material, the expansion and contraction of silicon or its oxide accompanying charge / discharge is significantly larger than that of the carbon material. As a result, the negative electrode is deformed, causing a short circuit inside the battery, resulting in a high battery defect rate.
The present invention has been completed based on the above circumstances, and suppresses deformation of the negative electrode in a nonaqueous electrolyte secondary battery using silicon or an oxide thereof as a negative electrode active material, thereby reducing the defect rate. For the purpose.

本発明者らは、負極活物質としてケイ素又はその酸化物を用いた非水電解質二次電池の負極の変形を抑制するため鋭意研究を重ね、負極活物質として酸素含有率の異なる種々の酸化ケイ素を用いた場合の負極の変形を詳細に調べたところ、酸化ケイ素の酸素含有率が低くなる程、つまり単体ケイ素に近づく程、充放電に伴う膨縮・収縮が大きくなる傾向にあり、逆に酸化ケイ素の酸素含有率が高くなる程、つまり二酸化ケイ素に近づく程、充放電に伴う膨縮が小さくなる傾向にあるという特異的な性質を見出した。
このため、集電体近傍に酸素含有率の高い酸化ケイ素を配した時に、ケイ素化合物を用いた非水電解質二次電池の特徴である高い放電量を維持しつつ、負極の変形を抑制できるという事実が判明した。 The present inventors have intensively studied to suppress deformation of the negative electrode of a non-aqueous electrolyte secondary battery using silicon or an oxide thereof as a negative electrode active material, and various silicon oxides having different oxygen contents as the negative electrode active material. When the deformation of the negative electrode was investigated in detail, the lower the oxygen content of silicon oxide, that is, the closer it was to single silicon, the greater the expansion / contraction associated with charge / discharge, and conversely The inventors have found a unique property that the higher the oxygen content of silicon oxide, that is, the closer to silicon dioxide, the smaller the expansion and contraction associated with charge and discharge.
Therefore, when silicon oxide with a high oxygen content is arranged near the current collector, it is possible to suppress deformation of the negative electrode while maintaining a high discharge amount, which is a feature of a nonaqueous electrolyte secondary battery using a silicon compound. The facts turned out.

本発明は、この知見に基づいてなされたものである。
すなわち、請求項１の発明は、正極、負極、および非水電解質を備えた非水電解質二次電池であって、前記負極が活物質層を集電体上に担持したものであり、前記活物質層が一般式ＳｉＯｘ（但し、０＜ｘ＜２）で表されるケイ素酸化物を含有し、前記活物質層全体に含まれるＳｉＯｘの平均組成をｘ＝ｘａｖとし、前記活物質層の集電体近傍におけるＳｉＯｘの組成をｘ＝ｘＢとした時、ｘＢ＞ｘａｖの関係を満たすことを特徴とする非水電解質二次電池である。 The present invention has been made based on this finding.
That is, the invention of claim 1 is a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte, wherein the negative electrode carries an active material layer on a current collector, and The material layer contains a silicon oxide represented by the general formula SiOx (where 0 <x <2), the average composition of SiOx contained in the entire active material layer is x = x av , and the active material layer when the composition of SiOx in the vicinity collector was x = x B, a non-aqueous electrolyte secondary battery, characterized by satisfying the relation of x B> x av.

請求項２の発明は、請求項１に記載のものにおいて、１．０≦ｘＢであることを特徴とする。 The invention of claim 2 is the one described in claim 1, characterized in that it is a 1.0 ≦ x B.

本発明の非水電解質二次電池によれば、集電体近傍の活物質層には酸素含有率の高い酸化ケイ素が配されているから、負極の変形が抑制され、電池の不良率を低減することができる。   According to the non-aqueous electrolyte secondary battery of the present invention, since the active material layer near the current collector is provided with silicon oxide having a high oxygen content, deformation of the negative electrode is suppressed and the defective rate of the battery is reduced. can do.

本発明の非水電解質二次電池は、正極、集電体を備えた負極、及び非水電解質を備えてなる。
図６に示すように、負極１は、活物質層３を集電体５上に担持してなる（なお、集電体の両面に活物質層を担持していてもよい）。集電体５としては、高い導電性を有し、Ｌｉと合金化しない材料、例えば、銅箔等の金属箔が用いられる。
活物質層３は、一般式ＳｉＯｘ（但し、０＜ｘ＜２）であらわされるケイ素酸化物を含有する。さらに、活物質層全体でみたときのｘ値の平均値をｘａｖとし、集電体近傍の活物質層３Ａでみたときのｘ値をｘＢとすると、ｘＢ＞ｘａｖの関係が満たされている。 The nonaqueous electrolyte secondary battery of the present invention comprises a positive electrode, a negative electrode equipped with a current collector, and a nonaqueous electrolyte.
As shown in FIG. 6, the negative electrode 1 has an active material layer 3 supported on a current collector 5 (the active material layer may be supported on both sides of the current collector). As the current collector 5, a material having high conductivity and not alloyed with Li, for example, a metal foil such as a copper foil is used.
The active material layer 3 contains a silicon oxide represented by a general formula SiOx (where 0 <x <2). Further, when the average value of x values when viewed in the entire active material layer is x av and the x value when viewed in the active material layer 3A in the vicinity of the current collector is x B , the relationship x B > x av is satisfied. Has been.

この活物質層３は、集電体５上に気相からケイ素酸化物を堆積させることで形成できる。具体的には、スパッタリング法、ＣＶＤ法、及び蒸着法などの気相からの薄膜形成法により形成することができ、ｘＢ＞ｘａｖの関係を満たすようにするには、例えばスパッタリング法では、雰囲気ガスの酸素濃度を変化させることでｘＢ＞ｘａｖとすることができる。すなわち、雰囲気ガス中の酸素濃度が時間の経過とともに減少するようにしたり、活物質層の形成開始から所定時間までは酸素濃度を所定濃度Ｃ１としそれ以降はＣ１よりも低い濃度Ｃ２とするようにしたりすることで形成することができる。 The active material layer 3 can be formed by depositing silicon oxide from the gas phase on the current collector 5. Specifically, it can be formed by a thin film forming method from a gas phase such as a sputtering method, a CVD method, and an evaporation method, and in order to satisfy the relationship of x B > x av , for example, in the sputtering method, By changing the oxygen concentration of the atmospheric gas, x B > x av can be established. That is, the oxygen concentration in the atmospheric gas is decreased with time, or the oxygen concentration is set to the predetermined concentration C1 from the start of the formation of the active material layer to the predetermined time, and thereafter the concentration C2 is lower than C1. Can be formed.

なお、ｘＢは、２．０＞ｘＢ≧１．０であることが好ましく、さらに２．０＞ｘＢ＞１．３であることが好ましく、特に２．０＞ｘＢ＞１．５であることが好ましい。この範囲で、負極集電体の変形が著しく抑制されるからである。 X B is preferably 2.0> x B ≧ 1.0, more preferably 2.0> x B > 1.3, and particularly 2.0> x B > 1.5. It is preferable that This is because the deformation of the negative electrode current collector is remarkably suppressed within this range.

正極は、アルミニウム、ニッケル、又はステンレス製の集電体の両面又は片面にリチウムイオンを吸蔵・放出する正極活物質を含有する正極活物質層を設けた構造となっている。正極活物質としては、特に限定されず、公知のリチウム含有複合金属酸化物、すなわち、リチウムを含むコバルト酸化物、リチウムを含むマンガン酸化物、リチウムを含むニッケル酸化物あるいはこれらの複合酸化物、混合物であれば特に限定されず、例えば、ＬｉＭＯ２（ただし、Ｍは一種以上の遷移金属）で表される基本構造を有するリチウム遷移金属複合酸化物を主体とする化合物として、ＬｉＣｏＯ２、ＬｉＮｉＯ２が挙げられ、また、ＬｉＭｎＯ２、ＬｉＭｎ２Ｏ４、ＬｉＭｙＭｎ２−ｙＯ４（Ｍ＝Ｃｒ，Ｃｏ，Ｎｉ、ただし０≦ｙ≦０．５）等、あるいはこれらの複合酸化物、混合物を用いることも可能である。ＬｉＭＯ２（ただし、Ｍは一種以上の遷移金属）で表される基本構造を有するリチウム遷移金属複合酸化物を主体とする化合物を用いる場合は、特に放電電圧を高くする観点から遷移金属ＭとしてＣｏ，Ｎｉ，Ｍｎからなる群から選択してなる少なくとも１つ以上の元素を使用することが望ましい。 The positive electrode has a structure in which a positive electrode active material layer containing a positive electrode active material that occludes and releases lithium ions is provided on both surfaces or one surface of a current collector made of aluminum, nickel, or stainless steel. The positive electrode active material is not particularly limited, and is a known lithium-containing composite metal oxide, that is, cobalt oxide containing lithium, manganese oxide containing lithium, nickel oxide containing lithium, or a composite oxide thereof, or a mixture thereof. is not particularly limited as long as, for example, LiMO 2 (however, M is one or more transition metals) as a compound consisting mainly of lithium transition metal composite oxide having a basic structure represented by, LiCoO 2, LiNiO 2 is LiMnO 2 , LiMn 2 O 4 , LiM y Mn 2−y O 4 (M = Cr, Co, Ni, where 0 ≦ y ≦ 0.5), etc., or complex oxides and mixtures thereof. It is also possible to use it. When a compound mainly composed of a lithium transition metal composite oxide having a basic structure represented by LiMO 2 (where M is one or more transition metals) is used, Co as the transition metal M particularly from the viewpoint of increasing the discharge voltage. It is desirable to use at least one element selected from the group consisting of Ni, Mn.

非水電解質としては、非水電解液又は固体電解質のいずれも使用することができる。非水電解液を用いる場合には特に限定されず、例えばエチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、エチルメチルカーボネート、ジエチルカーボネート、γ−ブチロラクトン、スルホラン、ジメチルスルホキシド、アセトニトリル、ジメチルホルムアミド、ジメチルアセトアミド、１，２−ジメトキシエタン、１，２−ジエトキシエタン、テトラヒドロフラン、２−メチルテトラヒドロフラン、ジオキソラン、ブチレンカーボネート、トリフルオロプロピレンカーボネート、２−メチル−γ−ブチルラクトン、アセチル−γ−ブチロラクトン、γ−バレロラクトン、３−メチル−１，３−ジオキソラン、酢酸メチル、酢酸エチル、プロピオン酸メチル、プロピオン酸エチル、ジプロピルカーボネート、メチルプロピルカーボネート、エチルイソプロピルカーボネート、ジブチルカーボネート等を単独でまたは二種以上混合して使用することができる。   As the non-aqueous electrolyte, either a non-aqueous electrolyte or a solid electrolyte can be used. When using a non-aqueous electrolyte, it is not particularly limited. For example, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1, 2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, butylene carbonate, trifluoropropylene carbonate, 2-methyl-γ-butyllactone, acetyl-γ-butyrolactone, γ-valerolactone, 3-methyl-1,3-dioxolane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, dipropyl carbonate, methyl propionate Carbonate, ethyl isopropyl carbonate, it can be mixed and used dibutyl carbonate, alone or.

非水電解液の溶質としての電解質塩は、特に限定されず例えば、ＬｉＰＦ6、ＬｉＣｌＯ4、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＣＦ３ＣＯ２、 ＬｉＰＦ３（ＣＦ３）３、ＬｉＰＦ３（Ｃ２Ｆ５）３、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＳＯ２ＣＦ３）２、ＬｉＮ（ＳＯ２ＣＦ２ＣＦ３）２、ＬｉＮ（ＣＯＣＦ３）２およびＬｉＮ（ＣＯＣＦ２ＣＦ３）２、ＬｉＰＦ３（ＣＦ２ＣＦ３）３、ＬｉＢ（Ｃ２Ｏ４）２、ＬｉＢＦ２Ｃ２Ｏ４等を単独でまたは二種以上を混合して使用することができる。 The electrolyte salt as the solute of the nonaqueous electrolytic solution is not particularly limited. For example, LiPF 6 , LiClO 4 , LiBF 4 , LiAsF 6 , LiCF 3 CO 2 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3 , LiCF 3 SO 3 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 CF 2 CF 3 ) 2 , LiN (COCF 3 ) 2 and LiN (COCF 2 CF 3 ) 2 , LiPF 3 (CF 2 CF 3 ) 3 , LiB (C 2 O 4 ) 2 , LiBF 2 C 2 O 4 and the like can be used alone or in admixture of two or more.

電解質塩の非水電解液に対する溶解量は、特に限定されないが、０．２〜２．５ｍｏｌ／ｌが好ましい。特に、０．８〜２．０ｍｏｌ／ｌとすることがより好ましい。   The amount of electrolyte salt dissolved in the non-aqueous electrolyte is not particularly limited, but is preferably 0.2 to 2.5 mol / l. In particular, it is more preferable to set it as 0.8-2.0 mol / l.

固体電解質としては、公知の固体電解質を用いることができ、例えば無機固体電解質、ポリマー固体電解質を用いることができる。   As the solid electrolyte, a known solid electrolyte can be used. For example, an inorganic solid electrolyte or a polymer solid electrolyte can be used.

以下、実施例によって本発明を更に詳しく説明するが、本発明は実施例に限定されるものではない。
＜負極Ａの作製＞
Ｃｕ箔（Cu foil)の片面上に、次の条件でＳｉＯｘをスパッタリングで析出させて、負極Ａを作製した。ターゲットにはＳｉＯを用い、基板間距離（ターゲットとＣｕ箔との距離）を３ｃｍ、印加電力を３００Ｗ、基板温度（Ｃｕ箔の温度）を１００℃として５時間スパッタリングした。なお、スパッタリング装置にはＳＲＶ４３１０型（神港精機社製）を使用した。
雰囲気中のＡｒ流量を図１に示すように
０時間〜２時間；１５ｓｃｃｍ
２時間〜５時間；２０ｓｃｃｍ
とし、
雰囲気中のＯ２流量を図１に示すように
０時間〜２時間；５ｓｃｃｍ
２時間〜５時間；０ｓｃｃｍ
とした。 EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to an Example.
<Preparation of negative electrode A>
On one surface of Cu foil (Cu foil), SiOx was deposited by sputtering under the following conditions to produce negative electrode A. SiO was used as a target, and sputtering was performed for 5 hours with a distance between substrates (distance between the target and Cu foil) of 3 cm, an applied power of 300 W, and a substrate temperature (Cu foil temperature) of 100 ° C. In addition, SRV4310 type (made by Shinko Seiki Co., Ltd.) was used for the sputtering apparatus.
Ar flow rate in the atmosphere is 0 to 2 hours as shown in FIG. 1; 15 sccm
2 to 5 hours; 20 sccm
age,
As shown in FIG. 1, the O 2 flow rate in the atmosphere is 0 to 2 hours; 5 sccm
2 hours to 5 hours; 0 sccm
It was.

＜負極Ｂの作製＞
雰囲気中のＡｒ流量を、図２に示すようにスパッタリングの開始時には１０ｓｃｃｍで、この流量から２ｓｃｃｍ・ｈ−１で連続的に増加させる一方、雰囲気中のＯ２流量を、スパッタリングの開始時には１０ｓｃｃｍで、この流量から２ｓｃｃｍ・ｈ−１で連続的に減少させたこと以外は、負極Ａと同様にして負極Ｂを作製した。 <Preparation of negative electrode B>
The Ar flow rate in the atmosphere is 10 sccm at the start of sputtering as shown in FIG. 2 and is continuously increased from this flow rate by 2 sccm · h −1 , while the O 2 flow rate in the atmosphere is 10 sccm at the start of sputtering. A negative electrode B was produced in the same manner as the negative electrode A, except that the flow rate was continuously decreased at 2 sccm · h −1 from this flow rate.

＜負極Ｃの作製＞
雰囲気中のＡｒ流量を図３に示すように
０時間〜２時間；１０ｓｃｃｍ
２時間〜３時間；１５ｓｃｃｍ
３時間〜５時間；２０ｓｃｃｍ
とし、
雰囲気中のＯ２流量を図３に示すように
０時間〜２時間；１０ｓｃｃｍ
２時間〜３時間； ５ｓｃｃｍ
３時間〜５時間； ０ｓｃｃｍ
としたこと以外は、負極Ａと同様にして負極Ｃを作製した。 <Preparation of negative electrode C>
Ar flow rate in the atmosphere is 0 to 2 hours as shown in FIG. 3; 10 sccm
2 to 3 hours; 15 sccm
3 hours to 5 hours; 20 sccm
age,
As shown in FIG. 3, the O 2 flow rate in the atmosphere is 0 to 2 hours; 10 sccm
2 to 3 hours; 5 sccm
3 to 5 hours; 0 sccm
A negative electrode C was produced in the same manner as the negative electrode A, except that.

＜負極Ｄの作製＞
雰囲気中のＡｒ流量を図４に示すように
０時間〜５時間；２０ｓｃｃｍ
とし、
雰囲気中のＯ２流量を図４に示すように
０時間〜５時間；０ｓｃｃｍ
としたこと以外は、負極Ａと同様にして負極Ｄを作製した。 <Preparation of negative electrode D>
Ar flow rate in the atmosphere is 0 to 5 hours as shown in FIG. 4; 20 sccm
age,
As shown in FIG. 4, the O 2 flow rate in the atmosphere is 0 to 5 hours; 0 sccm
A negative electrode D was produced in the same manner as the negative electrode A, except that.

＜負極Ｅの作製＞
雰囲気中のＡｒ流量を図５に示すように
０時間〜２時間；２０ｓｃｃｍ
２時間〜５時間；１５ｓｃｃｍ
とし、
雰囲気中のＯ２流量を図５に示すように
０時間〜２時間；０ｓｃｃｍ
２時間〜５時間；５ｓｃｃｍ
としたこと以外は、負極Ａと同様にして負極Ｅを作製した。 <Preparation of negative electrode E>
Ar flow rate in the atmosphere is 0 to 2 hours as shown in FIG. 5; 20 sccm
2-5 hours; 15 sccm
age,
As shown in FIG. 5, the O 2 flow rate in the atmosphere is 0 to 2 hours; 0 sccm
2 to 5 hours; 5 sccm
A negative electrode E was produced in the same manner as the negative electrode A, except that.

＜負極Ａ〜Ｅの分析＞
まず、ＥＳＣＡ(Electron Spectroscopy for Chemical Analysis,Ｘ線光電子分光装置）によって、各負極表面近傍（図６の３Ｂ）におけるＳｉに対するＯの元素比（一般式ＳｉＯｘのｘの値）を算出した。
具体的には、各負極をそれぞれ３分間Ａｒ＋イオンエッチング（電流値；１５ｍＡ）した後に、ＥＳＣＡ装置（島津／ＫＲＡＴＯＳ製 ＡＸＩＳ−ＨＳ）を用いて、Ｓｉ（５３２．３ｅＶ，及び５３４．１ｅＶ付近）のピーク面積と、Ｏ１ｓ（１０４．２ｅＶ付近）のピーク面積との面積比から表面近傍におけるＳｉに対するＯの元素比を算出した。 <Analysis of Negative Electrodes A to E>
First, the element ratio of O to Si (the value of x in the general formula SiOx) in the vicinity of each negative electrode surface (3B in FIG. 6) was calculated by ESCA (Electron Spectroscopy for Chemical Analysis, X-ray photoelectron spectrometer).
Specifically, each negative electrode was subjected to Ar + ion etching (current value: 15 mA) for 3 minutes, and then Si (532.3 eV and 534.1 eV vicinity) using an ESCA apparatus (AXIS-HS manufactured by Shimadzu / KRATOS). ) And the area ratio of the peak area of O 1s (near 104.2 eV), the element ratio of O to Si in the vicinity of the surface was calculated.

次に、負極の厚み方向のＳｉに対するＯの元素比を以下のようにして求めた。すなわち、負極を樹脂に包埋し、その後、厚み方向に切断して断面を露出させた。この断面をバフ研磨した後、さらにアルコールで洗浄・乾燥させた。そして、この断面をＥＰＭＡ法(Electron Probe MicroAnalysis,電子線マイクロアナリシス）により線分析することにより、負極の表面近傍から集電体近傍までのＳｉのピーク強度とＯのピーク強度との強度比を求めた。なお、この測定には、島津製作所製ＥＰＭＡ−Ｃ１を用いた。
そして、このようにして求められた厚み方向のＥＰＭＡ法による強度比のうち表面近傍の強度比をＥＳＣＡによって求められた元素比に対応させて、ＥＰＭＡ法による厚み方向における強度比を規格化して、表面近傍から集電体近傍までのＳｉに対するＯの元素比（一般式ＳｉＯｘのｘの値）を得た。
なお、本発明において、「集電体近傍」とは、負極活物質層の厚みをａμｍとした時、負極活物質層の、集電体表面からの距離が０〜０．１６ａμｍ（ａμｍの０倍から０.１６倍）の部分をさすものとする。 Next, the element ratio of O to Si in the thickness direction of the negative electrode was determined as follows. That is, the negative electrode was embedded in resin, and then cut in the thickness direction to expose the cross section. After this section was buffed, it was further washed with alcohol and dried. This cross section is subjected to line analysis by the EPMA method (Electron Probe MicroAnalysis) to obtain the intensity ratio between the peak intensity of Si and the peak intensity of O from the vicinity of the negative electrode surface to the vicinity of the current collector. It was. For this measurement, EPMA-C1 manufactured by Shimadzu Corporation was used.
Then, the strength ratio in the thickness direction by the EPMA method is normalized by making the strength ratio in the vicinity of the surface of the strength ratio by the EPMA method in the thickness direction thus determined correspond to the element ratio determined by the ESCA, The element ratio of O to Si (the value of x in the general formula SiOx) from the vicinity of the surface to the vicinity of the current collector was obtained.
In the present invention, “in the vicinity of the current collector” means that when the thickness of the negative electrode active material layer is a μm, the distance of the negative electrode active material layer from the current collector surface is 0 to 0.16 a μm (0 μm of a μm). It is assumed to indicate the portion from double to 0.16 times.

結果を図７〜１１に示す。図７は負極Ａのｘ値を、図８は負極Ｂのｘ値を、図９は負極Ｃのｘ値を、図１０は負極Ｄのｘ値を、図１１は負極Ｅのｘ値を示している。
負極Ａでは、図７に示されるように、Ｃｕ箔近傍のＳｉＯｘのｘの値は１．５であり、Ｃｕ箔近傍から表面までの平均値１．２よりも大きくなっていることが分かる。
また、負極Ｂでは、図８に示されるように、Ｃｕ箔近傍のＳｉＯｘのｘの値は１．８であり、Ｃｕ箔近傍から表面までの平均値１．３よりも大きくなっていることが分かる。
また、負極Ｃでは、図９に示されるように、Ｃｕ箔近傍のＳｉＯｘのｘの値は１．８であり、Ｃｕ箔近傍から表面までの平均値１．３よりも大きくなっていることが分かる。
一方、負極Ｄでは、図１０に示されるように、Ｃｕ箔近傍のＳｉＯｘのｘの値は１．０であり、Ｃｕ箔近傍から表面までの平均値１．０と同じであることが分かる。
また、負極Ｅでは、図１１に示されるように、Ｃｕ箔近傍のＳｉＯｘのｘの値は１．０であり、Ｃｕ箔近傍から表面までの平均値１．２よりも小さくなっていることが分かる。 The results are shown in FIGS. 7 shows the x value of the negative electrode A, FIG. 8 shows the x value of the negative electrode B, FIG. 9 shows the x value of the negative electrode C, FIG. 10 shows the x value of the negative electrode D, and FIG. ing.
In the negative electrode A, as shown in FIG. 7, the value of x of SiOx in the vicinity of the Cu foil is 1.5, which is larger than the average value 1.2 from the vicinity of the Cu foil to the surface.
Further, in the negative electrode B, as shown in FIG. 8, the value of x of SiOx in the vicinity of the Cu foil is 1.8, which is larger than the average value 1.3 from the vicinity of the Cu foil to the surface. I understand.
Further, in the negative electrode C, as shown in FIG. 9, the value of x of SiOx in the vicinity of the Cu foil is 1.8, which is larger than the average value 1.3 from the vicinity of the Cu foil to the surface. I understand.
On the other hand, in the negative electrode D, as shown in FIG. 10, the value x of SiOx in the vicinity of the Cu foil is 1.0, which is the same as the average value 1.0 from the vicinity of the Cu foil to the surface.
Further, in the negative electrode E, as shown in FIG. 11, the value of x of SiOx in the vicinity of the Cu foil is 1.0, which is smaller than the average value 1.2 from the vicinity of the Cu foil to the surface. I understand.

＜負極Ａ〜Ｅの充放電に伴う変形の測定＞
各負極を、ＳｉＯｘが形成された部分が２ｃｍ×２ｃｍとなるように切り出した。そして、ＳｉＯｘが形成されていない部分にリード部を取り付けて試験極を作製した。これを用いて、３端子式のビーカー形セルで０〜２Ｖｖｓ．Ｌｉ／Ｌｉ＋の範囲で充放電サイクルを３回行った。なお、対極及び参照極には金属Ｌｉを、電解液にはエチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）の体積比１：１の混合溶媒に、１ｍｏｌ・ｄｍ−３のＬｉＣｌＯ４を溶解したものをそれぞれ用いた。 <Measurement of deformation accompanying charging / discharging of negative electrodes A to E>
Each negative electrode was cut out so that the portion where SiO x was formed was 2 cm × 2 cm. And the lead part was attached to the part in which SiOx is not formed, and the test electrode was produced. Using this, it is 0 to 2 Vvs. The charge / discharge cycle was performed three times in the range of Li / Li + . The counter electrode and the reference electrode are made of metal Li, and the electrolyte is a solution of 1 mol · dm −3 LiClO 4 in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1: 1. Were used respectively.

このようにして充放電を各負極に対して行ったが、負極の変形は、膨張率によって評価した。この膨張率は、負極のＣｕ箔面側の表面積を、充放電サイクル試験前後で求め、試験後の表面積を試験前の表面積で除して求めた。なお、Ｃｕ箔面側の表面積は、レーザー顕微鏡（キーエンス社製、型番ＶＫ−８５００）で１０倍の対物レンズを使用して表面プロファイルを計測し、これをレーザー顕微鏡に付属の解析ソフトウェアで解析して得た。
結果を表１に示す。なお、Ｃｕ箔の膨張率は百分率で示してある。 Thus, although charging / discharging was performed with respect to each negative electrode, the deformation | transformation of the negative electrode was evaluated by the expansion coefficient. This expansion coefficient was obtained by determining the surface area of the negative electrode Cu foil surface before and after the charge / discharge cycle test and dividing the surface area after the test by the surface area before the test. The surface area of the Cu foil surface was measured with a laser microscope (Keyence Co., model number VK-8500) using a 10x objective lens and analyzed with the analysis software attached to the laser microscope. I got it.
The results are shown in Table 1. In addition, the expansion coefficient of Cu foil is shown in percentage.

Figure 2006107912
Figure 2006107912

表１の結果から、負極Ａ〜Ｃでは、負極Ｄ、Ｅに比べてＣｕ箔の膨張率が抑制されていることが分かった。従って、Ｃｕ箔近傍のＳｉＯｘのｘの値が、Ｃｕ箔近傍から表面までのｘの平均値よりも大きい場合には、Ｃｕ箔の変形が抑制され、ひいては、電池の短絡等の不良率を低減することができることが確認された。 特に、負極Ｂ、Ｃでは、Ｃｕ箔の膨張率が小さいことからＣｕ箔近傍のＳｉＯｘのｘの値は、２．０＞ｘ＞１．５であることが好ましいことが確認された。   From the results of Table 1, it was found that the expansion rates of the Cu foil were suppressed in the negative electrodes A to C as compared with the negative electrodes D and E. Therefore, when the value of x of SiOx in the vicinity of the Cu foil is larger than the average value of x from the vicinity of the Cu foil to the surface, the deformation of the Cu foil is suppressed, and consequently the defect rate such as a short circuit of the battery is reduced. Confirmed that you can. In particular, in the negative electrodes B and C, it was confirmed that the x value of SiOx in the vicinity of the Cu foil preferably satisfies 2.0> x> 1.5 because the expansion coefficient of the Cu foil is small.

負極Ａを作製したときのＡｒ及びＯ２流量Ar and O 2 flow rates when the negative electrode A was produced 負極Ｂを作製したときのＡｒ及びＯ２流量Ar and O 2 flow rates when producing negative electrode B 負極Ｃを作製したときのＡｒ及びＯ２流量Ar and O 2 flow rates when producing negative electrode C 負極Ｄを作製したときのＡｒ及びＯ２流量Ar and O 2 flow rates when producing negative electrode D 負極Ｅを作製したときのＡｒ及びＯ２流量Ar and O 2 flow rates when producing negative electrode E 負極の断面図Cross section of negative electrode 負極Ａのｘ値X value of negative electrode A 負極Ｂのｘ値X value of negative electrode B 負極Ｃのｘ値X value of negative electrode C 負極Ｄのｘ値X value of negative electrode D 負極Ｅのｘ値X value of negative electrode E

符号の説明Explanation of symbols

１…負極
３…活物質層
３Ａ…集電体近傍の活物質層
５…集電体 DESCRIPTION OF SYMBOLS 1 ... Negative electrode 3 ... Active material layer 3A ... Active material layer near current collector 5 ... Current collector

Claims (2)

正極、負極、および非水電解質を備えた非水電解質二次電池であって、前記負極が活物質層を集電体上に担持したものであり、前記活物質層が一般式ＳｉＯｘ（但し、０＜ｘ＜２）で表されるケイ素酸化物を含有し、前記活物質層全体に含まれるＳｉＯｘの平均組成をｘ＝ｘａｖとし、前記活物質層の集電体近傍におけるＳｉＯｘの組成をｘ＝ｘＢとした時、ｘＢ＞ｘａｖの関係を満たすことを特徴とする非水電解質二次電池。 A nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte, wherein the negative electrode carries an active material layer on a current collector, and the active material layer has a general formula SiOx (provided that 0 <x <2) is contained, the average composition of SiOx contained in the entire active material layer is x = x av, and the composition of SiOx in the vicinity of the current collector of the active material layer is x = when the x B, x B> x nonaqueous electrolyte secondary battery, characterized by satisfying the relation of av. １．０≦ｘＢであることを特徴とする請求項１に記載の非水電解質二次電池。 The non-aqueous electrolyte secondary battery according to claim 1, characterized in that a 1.0 ≦ x B.
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