JP6128481B2 - Nonaqueous electrolyte secondary battery - Google Patents
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Description
本発明は非水電解質二次電池に関し、詳しくは非水電解質二次電池の安全性の向上に関する。 The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to improving the safety of a non-aqueous electrolyte secondary battery.
携帯電話、ノートパソコン、タブレット型コンピュータ等の移動情報端末の高機能化、小型軽量化が急速に進展している。これらの端末の駆動電源として、高いエネルギー密度を有し、高容量である非水電解質二次電池が広く利用されている。 Mobile information terminals such as mobile phones, notebook computers, and tablet computers are rapidly becoming more functional, smaller, and lighter. As a driving power source for these terminals, non-aqueous electrolyte secondary batteries having high energy density and high capacity are widely used.
非水電解質二次電池の負極活物質としては、炭素材料が広く用いられているが、非水電解質二次電池に対するさらなる高容量化の要望が高まっており、炭素材料よりも放電容量の大きいケイ素材料に対する注目が高まっている。 Carbon materials are widely used as negative electrode active materials for non-aqueous electrolyte secondary batteries, but there is an increasing demand for higher capacity for non-aqueous electrolyte secondary batteries, and silicon having a higher discharge capacity than carbon materials. There is a growing interest in materials.
ケイ素材料を用いた非水電解質二次電池に関する技術としては、下記特許文献１がある。 As a technique related to a non-aqueous electrolyte secondary battery using a silicon material, there is Patent Document 1 below.
特許文献１は、ＳｉまたはＳｎとＯとを構成元素に含む化合物（ただし、ＳｉとＳｎの総量に対するＯの原子比ｘは、０．５≦ｘ≦１．５である）を含むコアとその表面を被覆する炭素の被覆層とで構成された負極活物質を含有する負極と、ハロゲン置換された環状カーボネートを含有する非水電解質とを用い、正極活物質の重量Ｐと負極活物質の重量Ｎとの比Ｐ／Ｎを、３．７〜６．８とする技術を開示している。この技術によると、高容量でサイクル特性等の特性が優れ、かつ重負荷放電特性にも優れた非水電解質二次電池を実現できるとされる。 Patent Document 1 discloses a core containing Si or a compound containing Sn and O as constituent elements (however, the atomic ratio x of O with respect to the total amount of Si and Sn is 0.5 ≦ x ≦ 1.5) and the core Using a negative electrode containing a negative electrode active material composed of a carbon coating layer covering the surface and a non-aqueous electrolyte containing a halogen-substituted cyclic carbonate, the weight P of the positive electrode active material and the weight of the negative electrode active material The technique which makes ratio P / N with N 3.7-6.8 is disclosed. According to this technology, it is said that a non-aqueous electrolyte secondary battery having a high capacity, excellent cycle characteristics and the like and excellent heavy load discharge characteristics can be realized.
ところで、ケイ素材料は炭素材料よりも充放電に伴う体積変動が大きく、充放電によってケイ素材料が芯体から脱離してサイクル特性を低下させるという問題がある。しかしながら、上記特許文献１は、このような問題について何ら考慮していない。 By the way, the volume fluctuation accompanying charging / discharging is larger in the silicon material than in the carbon material, and there is a problem that the silicon material is detached from the core body by charging / discharging to deteriorate the cycle characteristics. However, Patent Document 1 does not consider such a problem at all.
本発明は、上記に鑑みなされたものであり、ケイ素材料と芯体との密着性が高く、サイクル特性に優れた高容量な非水電解質二次電池を提供することを目的とする。 The present invention has been made in view of the above, and an object of the present invention is to provide a high-capacity non-aqueous electrolyte secondary battery having high adhesion between a silicon material and a core and excellent cycle characteristics.
上記課題を解決するための本発明は、負極芯体上に、負極活物質と結着剤とを有する負極活物質層が形成された負極板を備える非水電解質二次電池において、前記負極活物質は、ケイ素酸化物と、炭素質物と、を有し、前記ケイ素酸化物と前記炭素質物との質量の和に対する前記ケイ素酸化物の質量が、１〜２０質量％であり、前記ケイ素酸化物の酸素原子とケイ素原子との比Ｏ／Ｓｉが０．５〜１．５であり、前記結着剤は、二重結合を有する化合物からなる結着剤Ａと、水溶性高分子化合物からなる結着剤Ｂと、を有し、前記結着剤Ａは、前記負極活物質層の表面側よりも負極芯体側に多く存在する分布であり、前記結着剤Ｂは、少なくとも前記ケイ素酸化物の周囲に存在することを特徴とする。 In order to solve the above problems, the present invention provides a nonaqueous electrolyte secondary battery comprising a negative electrode plate in which a negative electrode active material layer having a negative electrode active material and a binder is formed on a negative electrode core. The substance has a silicon oxide and a carbonaceous material, and a mass of the silicon oxide with respect to a sum of masses of the silicon oxide and the carbonaceous material is 1 to 20% by mass, and the silicon oxide The oxygen atom to silicon atom ratio O / Si is 0.5 to 1.5, and the binder comprises a binder A composed of a compound having a double bond and a water-soluble polymer compound. A binder B, wherein the binder A is distributed more on the negative electrode core side than on the surface side of the negative electrode active material layer, and the binder B includes at least the silicon oxide. It exists in the circumference of.
上記構成では、負極活物質が、ケイ素酸化物を１質量％以上有しているので、負極活物質が炭素質物のみからなる場合よりも放電容量を高めることができる。また、負極芯体との密着性に優れた、二重結合を有する化合物からなる結着剤Ａが、負極活物質層内において負極芯体側に多く分布しているので、結着剤Ａの量を過剰とすることなくケイ素酸化物と負極芯体との密着性を高める事ができ、充放電サイクルによる活物質の脱離を抑制することができる。また、水溶性高分子化合物からなり、ケイ素酸化物の周囲に存在する結着剤Ｂが、ケイ素酸化物と導電性の高い炭素質物とを良好に結着する。これにより、炭素質物による良好な導電パスが形成されるので、導電性の低いケイ素酸化物が十分に充放電に使用されるようになる。これらの効果が相乗的に作用して、サイクル特性や放電容量を高めることができる。 In the said structure, since a negative electrode active material has 1 mass% or more of silicon oxides, discharge capacity can be raised rather than the case where a negative electrode active material consists only of a carbonaceous material. In addition, since the binder A composed of a compound having a double bond and excellent adhesion to the negative electrode core is distributed on the negative electrode core side in the negative electrode active material layer, the amount of the binder A The adhesion between the silicon oxide and the negative electrode core can be improved without making the amount excessive, and the desorption of the active material due to the charge / discharge cycle can be suppressed. Further, the binder B made of a water-soluble polymer compound and present around the silicon oxide favorably binds the silicon oxide and the highly conductive carbonaceous material. Thereby, since a favorable conductive path is formed by the carbonaceous material, silicon oxide having low conductivity is sufficiently used for charging and discharging. These effects can act synergistically to improve cycle characteristics and discharge capacity.
ここで、ケイ素酸化物の含有量が過大であると、上記のような結着剤を用いていても芯体からの脱離を抑制しきれず、サイクル特性が不十分となる。一方、ケイ素酸化物の含有量が過少であると、放電容量を十分に高めることができない。よって、ケイ素酸化物の含有量は上記範囲内に規制する。また、良好な充放電特性を得るために、ケイ素酸化物の酸素原子とケイ素原子との比Ｏ／Ｓｉを、上記範囲内に規制する。 Here, when the content of silicon oxide is excessive, even if the binder as described above is used, desorption from the core cannot be suppressed, and the cycle characteristics become insufficient. On the other hand, when the content of silicon oxide is too small, the discharge capacity cannot be sufficiently increased. Therefore, the content of silicon oxide is regulated within the above range. Further, in order to obtain good charge / discharge characteristics, the ratio O / Si of oxygen atoms to silicon atoms in the silicon oxide is regulated within the above range.
上記構成において、前記負極活物質層の厚みを１とするとき、前記負極活物質層の芯体がわ面を基点として厚み０〜０．３の領域に存在する前記結着剤Ａの量が、前記結着剤Ａの総量の５０％以上である構成とすることができる。 In the above configuration, when the thickness of the negative electrode active material layer is 1, the amount of the binder A present in the region having a thickness of 0 to 0.3 with the core of the negative electrode active material layer as a base point , 50% or more of the total amount of the binder A.
上記のように結着剤Ａを芯体側により偏在させることにより、結着剤Ａによる負極芯体とケイ素酸化物との密着性向上効果がより高まる。 By making the binder A unevenly distributed on the core side as described above, the effect of improving the adhesion between the negative electrode core body and the silicon oxide by the binder A is further increased.
上記構成において、前記負極活物質層の厚みを１とするとき、前記負極活物質層の芯体がわ面を基点として厚み０〜０．５の領域に存在する前記ケイ素酸化物の量が、前記ケイ素酸化物の総量の５０％未満である構成とすることができる。 In the above configuration, when the thickness of the negative electrode active material layer is 1, the amount of the silicon oxide present in the region of the thickness of 0 to 0.5 with the core of the negative electrode active material layer as a base point is It can be set as the structure which is less than 50% of the total amount of the said silicon oxide.
ケイ素酸化物は、炭素質物よりも充電時にリチウムが析出してその後の放電容量が低下し易いが、これはケイ素酸化物が負極活物質層の芯体側に存在する場合により起こり易くなる。このため、ケイ素酸化物の分布は、上記の如く、負極活物質層の表面側に多く分布する構成とすることが好ましい。 The silicon oxide is more liable to deposit lithium during charging than the carbonaceous material and lower the discharge capacity thereafter, but this is more likely to occur when the silicon oxide is present on the core side of the negative electrode active material layer. For this reason, it is preferable that the distribution of the silicon oxide is a large distribution on the surface side of the negative electrode active material layer as described above.
この構成においては、ケイ素酸化物と炭素質物との導電接点を確保するために、前記負極活物質層の芯体がわ面を基点として厚み０〜０．５の領域に存在する前記結着剤Ｂの量が、前記結着剤Ｂの総量の５０％未満である構成（ケイ素酸化物と同様に、負極活物質層の表面側に多く分布する構成）とすることが好ましい。 In this configuration, in order to secure a conductive contact between the silicon oxide and the carbonaceous material, the binder in which the core of the negative electrode active material layer is present in a region having a thickness of 0 to 0.5 starting from the back surface It is preferable to adopt a configuration in which the amount of B is less than 50% of the total amount of the binder B (a configuration in which a large amount is distributed on the surface side of the negative electrode active material layer as in the case of silicon oxide).
ここで、二重結合を有する化合物からなる結着剤Ａとしては、スチレンブタジエンゴム、ハイスチレンゴム、エチレンプロピレンゴム、ブチルゴム、クロロプレンゴム、ブタジエンゴム、イソプレンゴム、アクリロニトリルブタジエンゴム、アクリロニトリルゴム、フッ素ゴム、アクリルゴム、シリコーンゴム等のゴムバインダを１種単独で、または２種以上を混合して使用できる。また、負極活物質層質量に占める結着剤Ａの質量割合は、０．５〜２質量％であることが好ましい。 Here, as the binder A composed of a compound having a double bond, styrene butadiene rubber, high styrene rubber, ethylene propylene rubber, butyl rubber, chloroprene rubber, butadiene rubber, isoprene rubber, acrylonitrile butadiene rubber, acrylonitrile rubber, fluorine rubber A rubber binder such as acrylic rubber or silicone rubber can be used alone or in combination of two or more. Moreover, it is preferable that the mass ratio of the binder A to the negative electrode active material layer mass is 0.5 to 2 mass%.
また、水溶性高分子化合物からなる結着剤Ｂとしては、ポリマー系水溶性高分子化合物（以下「ポリマー系化合物」とする）、多糖系水溶性高分子化合物（以下「多糖系化合物」とする）の１種単独で、または２種以上を混合して使用できる。ポリマー系化合物としては、ポリビニルアルコール、ポリビニルピロリドン、ポリエチレンオキシド、これらの誘導体等を使用でき、多糖系化合物としては、セルロース、カルボキシメチルセルロース等を使用できる。中でも、カルボキシメチルセルロースが好適である。また、負極活物質層質量に占める結着剤Ｂの質量割合は、０．６〜２質量％であることが好ましい。 In addition, as the binder B made of a water-soluble polymer compound, a polymer water-soluble polymer compound (hereinafter referred to as “polymer compound”) and a polysaccharide water-soluble polymer compound (hereinafter referred to as “polysaccharide compound”). ) Alone or in admixture of two or more. As the polymer compound, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, derivatives thereof and the like can be used, and as the polysaccharide compound, cellulose, carboxymethyl cellulose and the like can be used. Of these, carboxymethylcellulose is preferred. Moreover, it is preferable that the mass ratio of the binder B to the negative electrode active material layer mass is 0.6-2 mass%.
また、ケイ素酸化物としては、ケイ素と酸素とからなる、ＳｉＯｘ（０．５≦ｘ≦１．５）で示される化合物のほか、ＳｉｙＭ１−ｙＯｘ（０．５≦ｘ≦１．５、０≦ｙ≦０．５、ＭはＢ、Ｍｇ、Ｎｉ、Ｔｉ、Ｍｏ、Ｃｏ、Ｃａ、Ｃｒ、Ｃｕ、Ｆｅ、Ｍｎ、Ｎｂ、Ｔａ、Ｖ、Ｗ、Ｚｎ、Ｃ、ＮおよびＳｎの少なくとも一種、）で示される、Ｓｉの一部が他の元素で置換された化合物を用いることができる。これらは１種単独で、または２種以上を混合して使用できる。 In addition to silicon oxide and a compound represented by SiO x (0.5 ≦ x ≦ 1.5), the silicon oxide includes Si y M 1-y O x (0.5 ≦ x ≦ 1.5, 0 ≦ y ≦ 0.5, M is B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Nb, Ta, V, W, Zn, C, N and A compound in which a part of Si, which is represented by at least one kind of Sn), is substituted with another element can be used. These can be used individually by 1 type or in mixture of 2 or more types.
また、炭素質物としては、例えば天然黒鉛、人造黒鉛等の黒鉛質炭素質物や、コークス、黒鉛化途上炭素、炭素繊維、球状炭素、非晶質炭素等の非晶質炭素質物を、１種単独で、または２種以上を混合して使用できる。 Examples of the carbonaceous material include graphite carbonaceous materials such as natural graphite and artificial graphite, and amorphous carbonaceous materials such as coke, graphitized carbon, carbon fiber, spherical carbon, and amorphous carbon. Or a mixture of two or more.
また、負極活物質は、ケイ素酸化物及び炭素質物以外に、ケイ素酸化物よりも充電時の膨張率（満充電時体積／放電時体積）の低い第三の活物質材料が混合されていてもよい。第三の活物質材料としては、例えばＳｎＯｘ（０＜ｘ＜２）、ＳｎＯ２、ＳｎＳｉＯ３等のスズ酸化物を１種単独で、または２種以上を混合して使用できる。第三の活物質材料は、負極活物質の合計質量の２０質量％以下であることが好ましい。 The negative electrode active material may be mixed with a third active material other than silicon oxide and carbonaceous material, which has a lower expansion coefficient during charging (volume during full charge / volume during discharge) than silicon oxide. Good. As the third active material, for example, tin oxides such as SnO x (0 <x <2), SnO 2 , and SnSiO 3 can be used singly or in combination of two or more. The third active material is preferably 20% by mass or less of the total mass of the negative electrode active material.
以上に説明したように、本発明によれば、高容量で且つサイクル特性に優れた非水電解質二次電池を提供することができる。 As described above, according to the present invention, a non-aqueous electrolyte secondary battery having a high capacity and excellent cycle characteristics can be provided.
以下、実施例を用いて、本発明を説明する。 Hereinafter, the present invention will be described using examples.
（実施例１）
＜正極板の作製＞
正極活物質としての、リチウムニッケルコバルト複合酸化物（ＬｉＮｉ０．８２Ｃｏ０．１５Ａｌ０．０３Ｏ２）粒子と、導電剤としてのアセチレンブラックと、結着剤であるポリフッ化ビニリデン（ＰＶｄＦ）とを、質量比１００：１．２５：１．７で、Ｎ−メチル−２−ピロリドン（ＮＭＰ）に投入、混練して、正極スラリーを調製した。
Example 1
<Preparation of positive electrode plate>
Lithium nickel cobalt composite oxide (LiNi 0.82 Co 0.15 Al 0.03 O 2 ) particles as a positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder Were put into N-methyl-2-pyrrolidone (NMP) at a mass ratio of 100: 1.25: 1.7 and kneaded to prepare a positive electrode slurry.
上記正極スラリーを、厚さ１５μｍのアルミニウム箔製の芯体の両面に、ドクターブレード法により塗布した。この後、乾燥し、スラリー調整に用いた溶媒（ＮＭＰ）を除去した。この後、ロールプレス機で厚みが０．１７７ｍｍとなるように圧延し、５８．５×６５６ｍｍのサイズに裁断して、正極板を得た。 The positive electrode slurry was applied to both surfaces of a 15 μm thick aluminum foil core by the doctor blade method. Then, it dried and removed the solvent (NMP) used for slurry adjustment. Then, it rolled so that thickness might be set to 0.177 mm with the roll-press machine, and it cut | judged to the size of 58.5x656mm, and obtained the positive electrode plate.
＜負極板の作製＞
黒鉛粉末（日立化成製）とＳｉＯｘ（ｘ＝１）で表されるケイ素酸化物粒子（信越化学製ＫＳＣ１０６５）とを質量比９６：４で混合した負極活物質１００質量部と、結着剤Ｂであるカルボキシメチルセルロース（ＣＭＣ）１質量部と、水と、を混合して、固形分濃度が６０％の混練物とした。この混練物に結着剤Ａであるスチレンブタジエンゴム（ＳＢＲ）２質量部と、水と、を混合して、固形分濃度が５０％の負極スラリー１を調製した。
また、黒鉛粉末（日立化成製）とＳｉＯｘ（ｘ＝１）で表されるケイ素酸化物粒子（信越化学製ＫＳＣ１０６５）とを質量比９６：４で混合した負極活物質１００質量部と、結着剤Ｂであるカルボキシメチルセルロース（ＣＭＣ）１質量部と、水と、を混合して、固形分濃度が６０％の混練物とした。この混練物にさらに水を混合して、固形分濃度が５０％の負極スラリー２を調製した。
<Preparation of negative electrode plate>
100 parts by mass of a negative electrode active material in which graphite powder (manufactured by Hitachi Chemical) and silicon oxide particles represented by SiO x (x = 1) (KSC 1065 manufactured by Shin-Etsu Chemical Co., Ltd.) are mixed at a mass ratio of 96: 4, and a binder 1 part by mass of carboxymethyl cellulose (CMC) as B and water were mixed to obtain a kneaded product having a solid content concentration of 60%. 2 parts by mass of styrene butadiene rubber (SBR), which is binder A, and water were mixed with this kneaded product to prepare negative electrode slurry 1 having a solid content concentration of 50%.
Further, 100 parts by mass of a negative electrode active material obtained by mixing graphite powder (manufactured by Hitachi Chemical) and silicon oxide particles represented by SiO x (x = 1) (KSC 1065 manufactured by Shin-Etsu Chemical Co., Ltd.) at a mass ratio of 96: 4, 1 part by mass of carboxymethyl cellulose (CMC) as the adhering agent B and water were mixed to obtain a kneaded product having a solid content concentration of 60%. Water was further mixed into the kneaded product to prepare a negative electrode slurry 2 having a solid content concentration of 50%.
負極スラリー１を、厚みが８μｍの銅箔製の芯体の両面に、ドクターブレード法により塗布した。この後、乾燥し、スラリー調整に用いた溶媒（水）を除去した。この後、負極スラリー１による層の上に、負極スラリー２を、厚みが１２μｍの銅箔製の芯体の両面に、ドクターブレード法により塗布した。この後、乾燥し、スラリー調整に用いた溶媒（水）を除去した。 The negative electrode slurry 1 was applied to both surfaces of a copper foil core having a thickness of 8 μm by a doctor blade method. Then, it dried and removed the solvent (water) used for slurry adjustment. Then, the negative electrode slurry 2 was apply | coated on both surfaces of the core body made from a copper foil with a thickness of 12 micrometers on the layer by the negative electrode slurry 1 by the doctor blade method. Then, it dried and removed the solvent (water) used for slurry adjustment.
この時、負極スラリー１による層に含まれる負極活物質質量と、負極スラリー２による層に含まれる負極活物質質量と、を同じとした。この後、ロールプレス機で活物質充填密度が１．６５ｇ／ｍｌとなるように圧延し、５９．５×５９０ｍｍのサイズに裁断して、負極板を得た。 At this time, the mass of the negative electrode active material contained in the layer made of the negative electrode slurry 1 and the mass of the negative electrode active material contained in the layer made of the negative electrode slurry 2 were the same. Then, it rolled with the roll press machine so that the active material filling density might be 1.65 g / ml, and it cut | judged to the size of 59.5 * 590 mm, and obtained the negative electrode plate.
＜電解質の調製＞
エチレンカーボネート（ＥＣ）と、ジメチルカーボネート（ＤＭＣ）と、を体積比２５：７５（２５℃、１気圧条件）で混合した混合溶媒に、５質量％となるようにビニレンカーボネートを混合し、これにＬｉＰＦ６を１．４モル／リットルの濃度で溶解して、非水電解質を得た。
<Preparation of electrolyte>
Vinylene carbonate was mixed in a mixed solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 25:75 (25 ° C., 1 atm condition) so as to be 5% by mass. LiPF 6 was dissolved at a concentration of 1.4 mol / liter to obtain a non-aqueous electrolyte.
＜電池の組み立て＞
正極板にアルミニウム製の正極タブを溶接し、負極板にニッケル製の負極タブを溶接した。こののち、正極板及び負極板を、ポリエチレン製微多孔膜からなるセパレータを介して重ね合わせた後に捲回して、電極体を得た。
<Battery assembly>
A positive electrode tab made of aluminum was welded to the positive electrode plate, and a negative electrode tab made of nickel was welded to the negative electrode plate. Thereafter, the positive electrode plate and the negative electrode plate were overlapped via a separator made of a polyethylene microporous film and then wound to obtain an electrode body.
得られた捲回型電極体の上下面にそれぞれ絶縁板を配置し、負極タブを有底円筒形の外装缶底面に溶接し、正極タブを電池内圧上昇時に作動する安全機構が組み込まれた封口体に溶接した後、有底円筒形の外装缶内に上記電極体を挿入した。 Insulation plates are arranged on the upper and lower surfaces of the wound electrode body, the negative electrode tab is welded to the bottom of the bottomed cylindrical outer can, and the positive tab is sealed with a safety mechanism that operates when the internal pressure of the battery rises. After welding to the body, the electrode body was inserted into a bottomed cylindrical outer can.
次いで、上記非水電解質を外装缶内に注液した。この後、封口体を、絶縁ガスケットを用いてカシメ固定して、直径１８ｍｍ、高さ６５ｍｍ、設計容量が３５９０ｍＡｈの非水電解質二次電池を作製した。 Next, the non-aqueous electrolyte was injected into the outer can. Thereafter, the sealing body was fixed by caulking using an insulating gasket to produce a nonaqueous electrolyte secondary battery having a diameter of 18 mm, a height of 65 mm, and a design capacity of 3590 mAh.
（実施例２）
黒鉛９９質量部とＳｉＯｘ（ｘ＝１）１質量部とを混合した負極活物質を用いた負極スラリー１、２を用い、且つ、負極の単位面積当たりの容量を、実施例１と同じとなるように負極スラリー１、２の塗布量を変化させたこと以外は、実施例１と同様にして、実施例２に係る非水電解質二次電池を作製した。
(Example 2)
The negative electrode slurries 1 and 2 using a negative electrode active material in which 99 parts by mass of graphite and 1 part by mass of SiO x (x = 1) were mixed, and the capacity per unit area of the negative electrode was the same as in Example 1. A nonaqueous electrolyte secondary battery according to Example 2 was produced in the same manner as in Example 1 except that the coating amounts of the negative electrode slurries 1 and 2 were changed.
（実施例３）
黒鉛８０質量部とＳｉＯｘ（ｘ＝１）２０質量部とを混合した負極活物質を用いた負極スラリー１、２を用い、且つ、負極の単位面積当たりの容量を、実施例１と同じとなるように負極スラリー１、２の塗布量を変化させたこと以外は、実施例１と同様にして、実施例３に係る非水電解質二次電池を作製した。
(Example 3)
The negative electrode slurries 1 and 2 using a negative electrode active material in which 80 parts by mass of graphite and 20 parts by mass of SiO x (x = 1) were mixed, and the capacity per unit area of the negative electrode was the same as in Example 1. A nonaqueous electrolyte secondary battery according to Example 3 was produced in the same manner as in Example 1 except that the coating amounts of the negative electrode slurries 1 and 2 were changed.
（実施例４）
負極スラリー１のスチレンブタジエンゴムを負極活物質１００質量部に対して１．０５質量部とし、負極スラリー２のスチレンブタジエンゴムを負極活物質１００質量部に対して０．９５質量部としたこと以外は、実施例１と同様にして、実施例４に係る非水電解質二次電池を作製した。
Example 4
Except that the styrene butadiene rubber of the negative electrode slurry 1 is 1.05 parts by mass with respect to 100 parts by mass of the negative electrode active material, and the styrene butadiene rubber of the negative electrode slurry 2 is 0.95 parts by mass with respect to 100 parts by mass of the negative electrode active material. Produced a nonaqueous electrolyte secondary battery according to Example 4 in the same manner as in Example 1.
（実施例５）
負極活物質１００質量部に対してスチレンブタジエンゴムを３質量部、カルボキシメチルセルロースを１質量部混合した負極スラリー１を用い、負極スラリー２のスチレンブタジエンゴムを負極活物質１００質量部に対して１質量部とし、負極スラリー１による層に含まれる負極活物質質量と、負極スラリー２による層に含まれる負極活物質質量と、の比を３：７としたこと以外は、実施例１と同様にして、実施例５に係る非水電解質二次電池を作製した。
(Example 5)
A negative electrode slurry 1 in which 3 parts by mass of styrene butadiene rubber and 1 part by mass of carboxymethylcellulose were mixed with 100 parts by mass of the negative electrode active material, and 1 mass of styrene butadiene rubber in negative electrode slurry 2 was 100 parts by mass with respect to 100 parts by mass of the negative electrode active material. The negative electrode active material mass contained in the layer made of the negative electrode slurry 1 and the negative electrode active material mass contained in the layer made of the negative electrode slurry 2 were set to 3: 7 in the same manner as in Example 1. A nonaqueous electrolyte secondary battery according to Example 5 was produced.
（実施例６）
黒鉛１００質量部からなる負極活物質を用いた負極スラリー１を用い、黒鉛９２質量部とＳｉＯｘ（ｘ＝１）８質量部とを混合した負極活物質を用いた負極スラリー２を用いたこと以外は、実施例１と同様にして、実施例６に係る非水電解質二次電池を作製した。
(Example 6)
Using negative electrode slurry 1 using negative electrode active material composed of 100 parts by mass of graphite, and using negative electrode slurry 2 using negative electrode active material in which 92 parts by mass of graphite and 8 parts by mass of SiO x (x = 1) were mixed. A nonaqueous electrolyte secondary battery according to Example 6 was made in the same manner as Example 1 except for the above.
（実施例７）
黒鉛９８質量部とＳｉＯｘ（ｘ＝１）２質量部とを混合した負極活物質を用いた負極スラリー１を用い、黒鉛９４質量部とＳｉＯｘ（ｘ＝１）６質量部とを混合した負極活物質を用いた負極スラリー２を用いたこと以外は、実施例１と同様にして、実施例７に係る非水電解質二次電池を作製した。
(Example 7)
Using negative electrode slurry 1 using a negative electrode active material in which 98 parts by mass of graphite and 2 parts by mass of SiO x (x = 1) were mixed, 94 parts by mass of graphite and 6 parts by mass of SiO x (x = 1) were mixed. A nonaqueous electrolyte secondary battery according to Example 7 was fabricated in the same manner as Example 1 except that the negative electrode slurry 2 using the negative electrode active material was used.
（実施例８）
黒鉛１００質量部からなる負極活物質を用い、且つ、カルボキシメチルセルロースを含まない負極スラリー１を用い、黒鉛９２質量部とＳｉＯｘ（ｘ＝１）８質量部とを混合した負極活物質を用い、且つ、負極活物質１００質量部に対してカルボキシメチルセルロースを２質量部含む負極スラリー２を用いたこと以外は、実施例１と同様にして、実施例８に係る非水電解質二次電池を作製した。
(Example 8)
Using a negative electrode active material composed of 100 parts by mass of graphite, using a negative electrode slurry 1 that does not contain carboxymethylcellulose, and using a negative electrode active material obtained by mixing 92 parts by mass of graphite and 8 parts by mass of SiO x (x = 1), And the nonaqueous electrolyte secondary battery which concerns on Example 8 was produced like Example 1 except having used the negative electrode slurry 2 which contains 2 mass parts of carboxymethylcellulose with respect to 100 mass parts of negative electrode active materials. .
（実施例９）
負極スラリー１，２を次のように調整したこと以外は、実施例１と同様にして、実施例９に係る非水電解質二次電池を作製した。
黒鉛粉末（日立化成製）とＳｉＯｘ（ｘ＝１）で表されるケイ素酸化物粒子（信越化学製ＫＳＣ１０６５）とを質量比９８：２で混合した負極活物質１００質量部と、結着剤Ｂであるカルボキシメチルセルロース（ＣＭＣ）０．５質量部と、水と、を混合して、固形分濃度が５０％の混練物とした。この混練物に結着剤Ａであるスチレンブタジエンゴム（ＳＢＲ）２質量部と、水と、を混合して、固形分濃度が４９．５％の負極スラリー１を調製した。
また、黒鉛粉末（日立化成製）とＳｉＯｘ（ｘ＝１）で表されるケイ素酸化物粒子（信越化学製ＫＳＣ１０６５）とを質量比９４：６で混合した負極活物質１００質量部と、結着剤Ｂであるカルボキシメチルセルロース（ＣＭＣ）１．５質量部と、水と、を混合して、固形分濃度が５０％の混練物とした。この混練物にさらに水を混合して、固形分濃度が４９．５％の負極スラリー２を調製した。
Example 9
A nonaqueous electrolyte secondary battery according to Example 9 was produced in the same manner as Example 1 except that the negative electrode slurries 1 and 2 were adjusted as follows.
100 parts by mass of a negative electrode active material obtained by mixing graphite powder (manufactured by Hitachi Chemical) and silicon oxide particles represented by SiO x (x = 1) (KSC 1065 manufactured by Shin-Etsu Chemical Co., Ltd.) at a mass ratio of 98: 2, and a binder. 0.5 parts by mass of carboxymethylcellulose (CMC) as B and water were mixed to obtain a kneaded product having a solid concentration of 50%. 2 parts by mass of styrene butadiene rubber (SBR) as the binder A and water were mixed with this kneaded product to prepare a negative electrode slurry 1 having a solid content concentration of 49.5%.
Further, 100 parts by mass of a negative electrode active material obtained by mixing graphite powder (manufactured by Hitachi Chemical) and silicon oxide particles represented by SiO x (x = 1) (KSC 1065 manufactured by Shin-Etsu Chemical Co., Ltd.) at a mass ratio of 94: 6, 1.5 parts by mass of carboxymethyl cellulose (CMC) as the adhering agent B and water were mixed to obtain a kneaded product having a solid content concentration of 50%. Water was further mixed into the kneaded product to prepare a negative electrode slurry 2 having a solid content concentration of 49.5%.
（実施例１０）
黒鉛９５質量部とＳｉＯｘ（ｘ＝１）５質量部とを混合した負極活物質を用い、且つ、カルボキシメチルセルロースを１．２５質量部含む負極スラリー１を用い、黒鉛９７質量部とＳｉＯｘ３質量部とを混合した負極活物質を用い、且つ、カルボキシメチルセルロースを０．７５質量部含む負極スラリー２を用いたこと以外は、実施例１と同様にして、実施例１０に係る非水電解質二次電池を作製した。
(Example 10)
Using a negative electrode active material obtained by mixing 95 parts by mass of graphite and 5 parts by mass of SiO x (x = 1), and using negative electrode slurry 1 containing 1.25 parts by mass of carboxymethyl cellulose, 97 parts by mass of graphite and SiO x 3 The nonaqueous electrolyte 2 according to Example 10 is the same as Example 1, except that the negative electrode active material mixed with parts by mass and the negative electrode slurry 2 containing 0.75 parts by mass of carboxymethylcellulose are used. A secondary battery was produced.
（実施例１１）
負極スラリー１のカルボキシメチルセルロースを負極活物質１００質量部に対して１．５質量部とし、負極スラリー２のカルボキシメチルセルロースを負極活物質１００質量部に対して０．５質量部含む負極スラリー２としたこと以外は、実施例１と同様にして、実施例１１に係る非水電解質二次電池を作製した。
(Example 11)
The negative electrode slurry 1 contains 1.5 parts by mass of carboxymethylcellulose with respect to 100 parts by mass of the negative electrode active material, and the negative electrode slurry 2 contains 0.5 parts by mass of carboxymethylcellulose of the negative electrode slurry 2 with respect to 100 parts by mass of the negative electrode active material. A nonaqueous electrolyte secondary battery according to Example 11 was made in the same manner as Example 1 except for the above.
（実施例１２）
負極スラリー１、２調整時の混練物の固形分濃度を、それぞれ５０％としたこと以外は、実施例１と同様にして、実施例１２に係る非水電解質二次電池を作製した。
(Example 12)
A nonaqueous electrolyte secondary battery according to Example 12 was produced in the same manner as in Example 1 except that the solid content concentration of the kneaded material at the time of preparing the negative electrode slurries 1 and 2 was 50%.
（比較例１）
スチレンブタジエンゴムを１質量部含む負極スラリー１のみを用いて負極活物質層を形成したこと以外は、実施例１と同様にして、比較例１に係る非水電解質二次電池を作製した。なお、負極活物質層の結着剤分布を調べたところ、負極活物質層の芯体側５０％の領域にスチレンブタジエンゴム総量の３０％、カルボキシメチルセルロース総量の４０％が存在していた。これは、乾燥時に水の揮発とともにこれらの結着剤が表面側に移動したためと考えられる。
(Comparative Example 1)
A nonaqueous electrolyte secondary battery according to Comparative Example 1 was produced in the same manner as in Example 1 except that the negative electrode active material layer was formed using only the negative electrode slurry 1 containing 1 part by mass of styrene butadiene rubber. When the binder distribution of the negative electrode active material layer was examined, 30% of the total amount of styrene butadiene rubber and 40% of the total amount of carboxymethyl cellulose were present in the region of 50% on the core side of the negative electrode active material layer. This is considered because these binders moved to the surface side with the volatilization of water at the time of drying.
（比較例２）
黒鉛のみからなる負極活物質を用い、且つ、スチレンブタジエンゴムを１質量部含む負極スラリー１のみを用いて負極活物質層を形成したこと以外は、実施例１と同様にして、比較例２に係る非水電解質二次電池を作製した。
(Comparative Example 2)
Comparative Example 2 was made in the same manner as in Example 1 except that the negative electrode active material composed of only graphite and only the negative electrode slurry 1 containing 1 part by mass of styrene butadiene rubber was used to form the negative electrode active material layer. Such a non-aqueous electrolyte secondary battery was produced.
（比較例３）
黒鉛７５質量部とＳｉＯｘ（ｘ＝１）２５質量部とを混合した負極活物質を用いた負極スラリー１、２を用い、且つ、負極の単位面積当たりの容量を、実施例１と同じとなるように負極スラリー１、２の塗布量を変化させたこと以外は、実施例１と同様にして、比較例３に係る非水電解質二次電池を作製した。
(Comparative Example 3)
The negative electrode slurries 1 and 2 using negative electrode active materials in which 75 parts by mass of graphite and 25 parts by mass of SiO x (x = 1) were mixed, and the capacity per unit area of the negative electrode was the same as in Example 1. A nonaqueous electrolyte secondary battery according to Comparative Example 3 was produced in the same manner as in Example 1 except that the coating amounts of the negative electrode slurries 1 and 2 were changed.
（比較例４）
負極スラリー１のスチレンブタジエンゴムを負極活物質１００質量部に対して０．９質量部とし、負極スラリー２のスチレンブタジエンゴムを負極活物質１００質量部に対して１．１質量部としたこと以外は、実施例１と同様にして、比較例４に係る非水電解質二次電池を作製した。
(Comparative Example 4)
Except that the styrene butadiene rubber of the negative electrode slurry 1 is 0.9 parts by mass with respect to 100 parts by mass of the negative electrode active material, and the styrene butadiene rubber of the negative electrode slurry 2 is 1.1 parts by mass with respect to 100 parts by mass of the negative electrode active material. In the same manner as in Example 1, a nonaqueous electrolyte secondary battery according to Comparative Example 4 was produced.
（比較例５）
負極スラリー１のスチレンブタジエンゴムを負極活物質１００質量部に対して０質量部とし、負極スラリー２のスチレンブタジエンゴムを負極活物質１００質量部に対して２質量部としたこと以外は、実施例１と同様にして、比較例５に係る非水電解質二次電池を作製した。
(Comparative Example 5)
Except that the styrene butadiene rubber of the negative electrode slurry 1 was 0 part by mass with respect to 100 parts by mass of the negative electrode active material, and the styrene butadiene rubber of the negative electrode slurry 2 was 2 parts by mass with respect to 100 parts by mass of the negative electrode active material. In the same manner as in Example 1, a nonaqueous electrolyte secondary battery according to Comparative Example 5 was produced.
（比較例６）
スチレンブタジエンゴムを２質量部含む負極スラリー１のみを用いて負極活物質層を形成したこと以外は、実施例１と同様にして、比較例６に係る非水電解質二次電池を作製した。
(Comparative Example 6)
A nonaqueous electrolyte secondary battery according to Comparative Example 6 was produced in the same manner as in Example 1 except that the negative electrode active material layer was formed using only the negative electrode slurry 1 containing 2 parts by mass of styrene-butadiene rubber.
なお、上記実施例１〜１２及び比較例１〜６においては、正極充電容量と、負極充電容量との比を１：１．０５〜１：１．１とし、且つ、正極板と負極板との合計厚みが所定の値となるように、負極活物質層及び正極活物質層の厚みを調整した。 In Examples 1 to 12 and Comparative Examples 1 to 6, the ratio between the positive electrode charge capacity and the negative electrode charge capacity was 1: 1.05 to 1: 1.1, and the positive electrode plate and the negative electrode plate The thicknesses of the negative electrode active material layer and the positive electrode active material layer were adjusted so that the total thickness of each would be a predetermined value.
《サイクル試験》
実施例１〜１２及び比較例１〜６と同じ条件で電池をそれぞれ作製し、以下に示す条件で充放電を行い、初期容量（１サイクル目放電容量）を測定し、容量維持率を算出した。なお、充放電はすべて２５℃条件で行った。この結果を下記表１〜４に示す。なお、１Ｉｔとは、１時間で電池の初期容量を放電させる電流値を意味する。
《Cycle test》
Batteries were respectively produced under the same conditions as in Examples 1 to 12 and Comparative Examples 1 to 6, charged and discharged under the conditions shown below, initial capacity (first cycle discharge capacity) was measured, and capacity retention rate was calculated. . In addition, all charging / discharging was performed on 25 degreeC conditions. The results are shown in Tables 1 to 4 below. 1 It means a current value for discharging the initial capacity of the battery in one hour.
充電：定電流０．５Ｉｔで電圧が４．２Ｖとなるまで、その後定電圧４．２Ｖで電流が０．０１Ｉｔとなるまで
休止：１０分
放電：定電流１．０Ｉｔで電圧が２．５Ｖとなるまで
休止：１０分
容量維持率（％）＝５００サイクル目放電容量÷１サイクル目放電容量×１００
Charging: Until the voltage reaches 4.2 V at a constant current of 0.5 It, then pause until the current reaches 0.01 It at a constant voltage of 4.2 V: Discharge: 10 volts at a constant current of 1.0 It Pause until: 10 minute capacity retention rate (%) = 500th cycle discharge capacity / first cycle discharge capacity × 100
《剥離強度の測定》
実施例１〜１２及び比較例１〜６と同じ条件で負極をそれぞれ作製した。また、図１に示すように、水平方向にスライドが可能で、試験片（負極板）の一方の面を接着剤もしくは両面テープを用いて固定する事のできる基台と、該試験素材の他方の面とを剥離するために、応力を測定しながら一定速度で基台に対して垂直方向に引き上げる事が可能なチャックを具備する引き上げ部とを備えた剥離試験装置を用意した。そして、３００ｍｍ×１５ｍｍに切り出した試験片の一方面を基台に固定し、他方面の一端を引き上げ部のチャックを用いて固定した後、引き上げ部を２０ｍｍ／ｓｅｃの速度で引き上げ、引き上げ部を基材に対して垂直引き上げる距離と同時に、同じ距離を基台が水平方向にスライドさせて、この際の層間から剥離する際の応力（９０°剥離強度）を測定した。この結果を、下記表１〜４に示す。
<Measurement of peel strength>
Negative electrodes were produced under the same conditions as in Examples 1 to 12 and Comparative Examples 1 to 6, respectively. Moreover, as shown in FIG. 1, the base which can be slid horizontally and can fix one surface of a test piece (negative electrode plate) using an adhesive or a double-sided tape, and the other of the test material In order to peel off the surface, a peeling test apparatus provided with a pulling unit having a chuck capable of pulling up in a direction perpendicular to the base at a constant speed while measuring stress was prepared. And after fixing one side of the test piece cut out to 300 mm × 15 mm to the base and fixing one end of the other side using the chuck of the lifting part, the lifting part is pulled up at a speed of 20 mm / sec. The stress (90 ° peel strength) when the base was slid horizontally from the same distance at the same time as the vertical pull-up with respect to the substrate and peeled from the interlayer was measured. The results are shown in Tables 1 to 4 below.
上記表１から、ＳｉＯｘ（ｘ＝１）の含有比率が１〜２０質量％である実施例１〜３は、初期容量が３３００〜３４００ｍＡｈ、剥離強度が２０〜２５Ｎ、容量維持率が５５〜６０％であった。これに対し、ＳｉＯｘの含有比率が０％である比較例１は、初期容量が３２００ｍＡｈと劣っており、ＳｉＯｘの含有比率が２５％である比較例３は、容量維持率が０％と、実施例１よりも劣っていることが分かる。 From Table 1 above, in Examples 1 to 3, in which the content ratio of SiO x (x = 1) is 1 to 20% by mass, the initial capacity is 3300 to 3400 mAh, the peel strength is 20 to 25 N, and the capacity maintenance ratio is 55 to 55%. 60%. On the other hand, Comparative Example 1 in which the content ratio of SiO x is 0% is inferior to the initial capacity of 3200 mAh, and Comparative Example 3 in which the content ratio of SiO x is 25% is 0% in capacity retention rate. It turns out that it is inferior to Example 1.
このことは、次のように考えられる。ケイ素酸化物（ＳｉＯｘ）は、黒鉛よりも放電容量が高いので、これを含まない場合、同一の電極サイズでは放電容量が小さくなってしまう。また、ケイ素酸化物は、黒鉛よりも充放電に伴う体積変動が大きく、これを多量に含ませると、体積変動によって芯体から活物質が脱離して、サイクル劣化が大きくなる。よって、ケイ素酸化物の含有量は、負極活物質全体の１〜２０質量％とすることが好ましい。 This is considered as follows. Since silicon oxide (SiO x ) has a higher discharge capacity than graphite, if it is not included, the discharge capacity will be reduced with the same electrode size. Further, silicon oxide has a larger volume fluctuation due to charging / discharging than graphite, and when this is included in a large amount, the active material is detached from the core body due to the volume fluctuation, and the cycle deterioration is increased. Therefore, the content of silicon oxide is preferably 1 to 20% by mass of the whole negative electrode active material.
また、上記表１から、また、スチレンブタジエンゴム（ＳＢＲ）の含有比率が、芯体側、表面側ともに１質量％である比較例１は剥離強度が５Ｎ、芯体側、表面側ともに２質量％である比較例６では剥離強度が１２．５Ｎであり、含有量を増加させることにより強度が高まるが、いずれも容量維持率が０％であり、スチレンブタジエンゴムの含有比率が、芯体側で２質量％、表面側で０質量％である実施例１の６０％よりも劣っていることが分かる。また、ケイ素酸化物を含まない比較例２では、比較例１と同じスチレンブタジエンゴムの分布であっても、容量維持率が６０％と高いことが分かる。 Moreover, from the said Table 1, the comparative example 1 whose content rate of a styrene butadiene rubber (SBR) is 1 mass% on both the core body side and the surface side is 5 N, and the peel strength is 2 mass% on both the core body side and the surface side. In Comparative Example 6, the peel strength is 12.5 N, and the strength is increased by increasing the content. However, in all cases, the capacity retention rate is 0%, and the content ratio of the styrene butadiene rubber is 2 mass on the core side. %, Which is inferior to 60% of Example 1 which is 0% by mass on the surface side. Further, it can be seen that, in Comparative Example 2 that does not contain silicon oxide, the capacity retention rate is as high as 60% even with the same styrene butadiene rubber distribution as in Comparative Example 1.
このことは、次のように考えられる。上述したように、単層構造の負極では、溶媒の揮発に伴って結着剤が表面側に移動するので、同量の結着剤を含ませていても、負極活物質層の芯体側に含まれる結着剤量は少なくなる。このため、剥離強度が低下するとともに、充放電によって活物質粒子が剥がれやすくなり、サイクル後の容量維持率が低下してしまう。また、黒鉛は、充放電に伴う体積変動がケイ素酸化物よりも小さいため、活物質のはがれが起こり難い。しかしながら、ケイ素酸化物を含まない負極は、初期容量が小さくなってしまうという問題がある。 This is considered as follows. As described above, in the negative electrode having a single layer structure, the binder moves to the surface side as the solvent evaporates, so even if the same amount of the binder is included, the negative electrode active material layer has a core side. The amount of binder contained is reduced. For this reason, while peeling strength falls, it becomes easy to peel active material particle by charging / discharging, and the capacity | capacitance maintenance factor after a cycle will fall. In addition, graphite has less volume fluctuations associated with charge / discharge than silicon oxide, so that the active material is unlikely to peel off. However, the negative electrode not containing silicon oxide has a problem that the initial capacity is reduced.
また、表２から、スチレンブタジエンゴム（ＳＢＲ）の含有比率が、芯体側＞表面側である実施例１、４、５は、剥離強度が１２〜３０Ｎ、容量維持率が５０〜６５％と、スチレンブタジエンゴムの含有比率が、芯体側＜表面側である比較例４、５の剥離強度１０Ｎ、１．６Ｎ、容量維持率３０％、０％よりも優れていることが分かる。 Also, from Table 2, Examples 1, 4 and 5 in which the content ratio of styrene butadiene rubber (SBR) is core side> surface side have a peel strength of 12 to 30 N and a capacity maintenance rate of 50 to 65%. It can be seen that the content ratio of the styrene butadiene rubber is superior to the peel strengths 10N and 1.6N, the capacity retention rate 30%, and 0% of Comparative Examples 4 and 5 in which the core side is smaller than the surface side.
このことは、次のように考えられる。結着剤は、負極活物質粒子相互、及び負極活物質粒子と負極芯体とを結着するが、結着剤のうち、スチレンブタジエンゴム（二重結合を有する化合物からなる結着剤）は、負極活物質粒子と負極芯体との結着力を高める作用がある。負極活物質層の芯体側に含まれるスチレンブタジエンゴム量が過小であると、剥離強度が低下するとともに、充放電によって活物質粒子が剥がれやすくなり、サイクル後の容量維持率が低下してしまう。 This is considered as follows. The binder binds the negative electrode active material particles to each other, and the negative electrode active material particles and the negative electrode core. Among the binders, styrene butadiene rubber (binder composed of a compound having a double bond) is used. There is an effect of increasing the binding force between the negative electrode active material particles and the negative electrode core. When the amount of the styrene butadiene rubber contained in the core side of the negative electrode active material layer is too small, the peel strength is lowered, and active material particles are easily peeled off due to charge / discharge, and the capacity retention rate after the cycle is lowered.
また、表３から、ケイ素酸化物（ＳｉＯｘ）の分布が、芯体側＜表面側である実施例６〜９は、容量維持率が６５〜７０％であり、ケイ素酸化物の分布が、芯体側＝表面側である実施例１、１１は、容量維持率がともに６０％であり、ケイ素酸化物の分布が、芯体側＞表面側である実施例１０は、容量維持率が５５％であり、表面側のＳｉＯｘ量が増加するに伴い、容量維持率が高まる傾向にあることが分かる。 Moreover, from Table 3, Examples 6 to 9 in which the distribution of silicon oxide (SiO x ) is core side <surface side have a capacity retention of 65 to 70%, and the distribution of silicon oxide is the core In Examples 1 and 11 where the body side = surface side, the capacity retention rate is both 60%, and in Example 10 where the distribution of silicon oxide is on the core side> surface side, the capacity retention rate is 55%. It can be seen that the capacity retention rate tends to increase as the amount of SiO x on the surface side increases.
このことは、次のように考えられる。ケイ素酸化物は、黒鉛よりも充電時にリチウムが析出してその後の放電容量が低下し易いが、これはケイ素酸化物が芯体側に存在する場合により起こり易くなる。このため、ケイ素酸化物の分布は、芯体側≦表面側であることが好ましく、芯体側＜表面側であることがより好ましい。 This is considered as follows. Silicon oxide is more liable to deposit lithium during charging and lower discharge capacity than graphite than graphite, but this is more likely to occur when silicon oxide is present on the core side. For this reason, the distribution of the silicon oxide is preferably core side ≦ surface side, and more preferably core side <surface side.
また、表３から、カルボキシメチルセルロース（ＣＭＣ）とケイ素酸化物（ＳｉＯｘ）との質量比が、ケイ素酸化物が存在する部分で常に１／４である実施例１、８〜１０は、初期容量がいずれも３４００ｍＡｈであり、カルボキシメチルセルロースとケイ素酸化物との質量比が、芯体側と表面側とで異なっている実施例１１は、初期容量が３３５０ｍＡｈであり、実施例１、８〜１０が優れていることが分かる。このため、ケイ素酸化物の存在する部分では、カルボキシメチルセルロース（水溶性高分子化合物からなる結着剤）とケイ素酸化物との比を一定に保つ（カルボキシメチルセルロースがケイ素酸化物の周囲に均一に分散している）ことが好ましい。 Also, from Table 3, Examples 1, 8 to 10 in which the mass ratio of carboxymethyl cellulose (CMC) to silicon oxide (SiO x ) is always 1/4 in the portion where silicon oxide is present are the initial capacities. Is 11400 mAh, and Example 11 in which the mass ratio of carboxymethylcellulose and silicon oxide is different between the core side and the surface side has an initial capacity of 3350 mAh, and Examples 1 and 8 to 10 are excellent. I understand that For this reason, in the part where silicon oxide exists, the ratio of carboxymethylcellulose (a binder made of a water-soluble polymer compound) and silicon oxide is kept constant (carboxymethylcellulose is uniformly dispersed around the silicon oxide) Preferably).
また、表４から、混練物の固形分濃度が６０％である実施例１は、初期容量が３４００ｍＡｈと、混練物の固形分濃度が５０％である実施例１２の初期容量３３５０ｍＡｈよりも優れていることが分かる。 Moreover, from Table 4, Example 1 in which the solid content concentration of the kneaded product is 60% is superior to the initial capacity of 3400 mAh and the initial capacity of 3350 mAh in Example 12 in which the solid content concentration of the kneaded product is 50%. I understand that.
このことは、次のように考えられる。混練物の固形分濃度が高く、混練の抵抗が高いほうがは、負極活物質層成分（固形分）の混合分散状態が良好となって、初期容量が高まる。 This is considered as follows. The higher the solid content concentration of the kneaded product and the higher the kneading resistance, the better the mixed and dispersed state of the negative electrode active material layer component (solid content) and the higher the initial capacity.
（追加事項）
上記実施例では、結着剤Ａの量が不連続に変化する構成としたが、連続的に変化する構成であってもよい。このような負極活物質層は、負極スラリー１による層が完全に乾燥しきる前に負極スラリー２による層を形成することにより作製できる。
(Additions)
In the said Example, although it was set as the structure which the quantity of the binder A changes discontinuously, the structure which changes continuously may be sufficient. Such a negative electrode active material layer can be produced by forming a layer made of the negative electrode slurry 2 before the layer made of the negative electrode slurry 1 is completely dried.
また、非水溶媒としては、カーボネート類、ラクトン類、ケトン類、エーテル類、エステル類等を用いることができる。具体的には、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ジエチルカーボネート、エチルメチルカーボネート、ジメチルカーボネート、γ−ブチロラクトン、γ−バレロラクトン、γ−ジメトキシエタン、テトロヒドロフラン、１，４−ジオキサン等を用いることができる。 Further, as the non-aqueous solvent, carbonates, lactones, ketones, ethers, esters and the like can be used. Specifically, ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, γ-butyrolactone, γ-valerolactone, γ-dimethoxyethane, tetrohydrofuran, 1,4-dioxane, etc. are used. be able to.
また、電解質塩としては、ＬｉＰＦ６、ＬｉＢＦ６、ＬｉＣｌＯ４等の一種または複数種の混合物が使用できる。また、非水溶媒に対する溶解量は、０．８〜１．８モル／リットルとすることが好ましい。 As the electrolyte salt, one kind or a mixture of plural kinds such as LiPF 6 , LiBF 6 , LiClO 4 can be used. Moreover, it is preferable that the dissolution amount with respect to a non-aqueous solvent shall be 0.8-1.8 mol / liter.
また、正極活物質としては、リチウム含有コバルトニッケルマンガン複合酸化物（ＬｉｘＮｉａＭｎｂＣｏｃＯ２、０．９＜ｘ≦１．２、ａ＋ｂ＋ｃ＝１）、スピネル型マンガン酸リチウム（ＬｉｘＭｎ２Ｏ４）、これらの遷移金属元素を他の元素に置換した化合物等を単独で、又は二種以上混合して用いることができる。 As the positive electrode active material, lithium-containing cobalt-nickel-manganese composite oxide (Li x Ni a Mn b Co c O 2, 0.9 <x ≦ 1.2, a + b + c = 1), spinel-type lithium manganate (Li x Mn 2 O 4 ), compounds obtained by substituting these transition metal elements with other elements, or the like can be used alone or in admixture of two or more.
また、上記実施例では、ケイ素酸化物として、ＳｉＯｘ（ｘ＝１）を用いたが、本発明はこれに限定されるものではなく、０．５≦ｘ≦１．５の範囲のものや異種元素によってＳｉの一部が置換されたものを好適に用いることができる。また、ケイ素酸化物は、ｘの値や異種元素の組成が異なる複数種が混合されていてもよい。 In the above embodiment, SiO x (x = 1) is used as the silicon oxide. However, the present invention is not limited to this, and the silicon oxide has a range of 0.5 ≦ x ≦ 1.5. A material in which a part of Si is replaced by a different element can be preferably used. Moreover, the silicon oxide may be mixed with a plurality of types having different values of x and different elements.
以上説明したように、本発明によれば、高容量でサイクル特性に優れた非水電解質二次電池を実現できる。よって、産業上の利用可能性は大きい。 As described above, according to the present invention, a nonaqueous electrolyte secondary battery having a high capacity and excellent cycle characteristics can be realized. Therefore, industrial applicability is great.
Claims (5)
前記負極活物質は、ケイ素酸化物と、炭素質物と、を有し、
前記ケイ素酸化物と前記炭素質物との質量の和に対する前記ケイ素酸化物の質量が、１〜２０質量％であり、
前記ケイ素酸化物の酸素原子とケイ素原子との比Ｏ／Ｓｉが０．５〜１．５であり、
前記結着剤は、二重結合を有するゴムバインダからなる結着剤Ａと、水溶性高分子化合物からなる結着剤Ｂと、を有し、
前記結着剤Ａは、前記負極活物質層の表面側よりも負極芯体側に多く存在する分布であり、
前記結着剤Ｂは、少なくとも前記ケイ素酸化物の周囲に存在する、
ことを特徴とする非水電解質二次電池。 In a non-aqueous electrolyte secondary battery comprising a negative electrode plate on which a negative electrode active material layer having a negative electrode active material and a binder is formed on a negative electrode core,
The negative electrode active material has a silicon oxide and a carbonaceous material,
The mass of the silicon oxide with respect to the sum of the mass of the silicon oxide and the carbonaceous material is 1 to 20% by mass,
The ratio O / Si of oxygen atoms to silicon atoms in the silicon oxide is 0.5 to 1.5,
The binder has a binder A made of a rubber binder having a double bond, and a binder B made of a water-soluble polymer compound,
The binder A is a distribution that exists more on the negative electrode core side than on the surface side of the negative electrode active material layer,
The binder B is present at least around the silicon oxide.
A non-aqueous electrolyte secondary battery.
前記負極活物質層の厚みを１とするとき、前記負極活物質層の芯体がわ面を基点として厚み０〜０．３の領域に存在する前記結着剤Ａの量が、前記結着剤Ａの総量の５０％以上である、
ことを特徴とする非水電解質二次電池。 The nonaqueous electrolyte secondary battery according to claim 1,
When the thickness of the negative electrode active material layer is 1, the amount of the binding agent A present in the region having a thickness of 0 to 0.3 with the core of the negative electrode active material layer as a base point is the binding amount. 50% or more of the total amount of agent A,
A non-aqueous electrolyte secondary battery.
前記負極活物質層の厚みを１とするとき、前記負極活物質層の芯体がわ面を基点として厚み０〜０．５の領域に存在する前記ケイ素酸化物の量が、前記ケイ素酸化物の総量の５０％未満である、
ことを特徴とする非水電解質二次電池。 The nonaqueous electrolyte secondary battery according to claim 1 or 2,
When the thickness of the negative electrode active material layer is 1, the amount of the silicon oxide present in the region of the thickness of 0 to 0.5 with the core of the negative electrode active material layer as the base point is the silicon oxide. Less than 50% of the total amount of
A non-aqueous electrolyte secondary battery.
前記負極活物質層の芯体がわ面を基点として厚み０〜０．５の領域に存在する前記結着剤Ｂの量が、前記結着剤Ｂの総量の５０％未満である、
ことを特徴とする非水電解質二次電池。 The nonaqueous electrolyte secondary battery according to claim 3,
The amount of the binding agent B present in the region of the thickness of 0 to 0.5 with the core of the negative electrode active material layer as a starting point is less than 50% of the total amount of the binding agent B,
A non-aqueous electrolyte secondary battery.
前記結着剤Ｂは、カルボキシメチルセルロースである、
ことを特徴とする非水電解質二次電池。 The nonaqueous electrolyte secondary battery according to any one of claims 1 to 4,
The binder B is carboxymethyl cellulose.
A non-aqueous electrolyte secondary battery.
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