JP3643108B2

JP3643108B2 - Anode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery

Info

Publication number: JP3643108B2
Application number: JP2003278615A
Authority: JP
Inventors: 善樹坂口; 清隆安田; 信一武者; 暁宏茂出木; 智善松島; 仁彦本田
Original assignee: Mitsui Mining and Smelting Co Ltd
Current assignee: Mitsui Mining and Smelting Co Ltd
Priority date: 2003-07-23
Filing date: 2003-07-23
Publication date: 2005-04-27
Anticipated expiration: 2023-07-23
Also published as: JP2005044672A

Description

本発明は、非水電解液二次電池用負極に関し、更に詳しくはエネルギー密度が高く、リチウムを多量に吸蔵、脱蔵することができ、またサイクル寿命の向上した非水電解液二次電池を得ることができる負極に関する。また本発明は、該負極を備えた非水電解液二次電池に関する。 The present invention relates to a negative electrode for a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a non-aqueous electrolyte secondary battery that has a high energy density, can absorb and desorb a large amount of lithium, and has an improved cycle life. The present invention relates to a negative electrode that can be obtained. The present invention also relates to a non-aqueous electrolyte secondary battery including the negative electrode.

リチウムイオン二次電池用の負極が種々提案されている。例えばリチウムと合金を作らない金属元素からなる集電部の一面に、リチウムと合金を作る金属元素を含有する層を形成し、この層の上に、リチウムと合金を作らない金属元素の層を形成してなる負極が提案されている（特許文献１参照）。この文献によれば、電池の充放電に起因して、リチウムと合金を作る金属元素を含有する層が微粉化することを、この構成の負極によって抑えることができるとされている。しかし前記文献の実施例の記載によれば、最表面に形成されているリチウムと合金を作らない金属元素の層はその厚みが５０ｎｍと極めて薄いので、該層が、リチウムと合金を作る金属元素を含有する層の表面を十分に被覆していない可能性がある。その場合、リチウムと合金を作る金属元素を含有する層が電池の充放電に起因して微粉化すると、その脱落を十分に抑えることができない。逆にリチウムと合金を作らない金属元素の層が、リチウムと合金を作る金属元素を含有する層の表面を完全に被覆している場合、該層が、リチウムと合金を作る金属元素を含有する層へ電解液が流通することを妨げてしまい十分な電極反応が起こりづらくなってしまう。このような相反する機能を両立させる技術は未だ提案されていない。 Various negative electrodes for lithium ion secondary batteries have been proposed. For example, a layer containing a metal element that forms an alloy with lithium is formed on one surface of a current collector made of a metal element that does not form an alloy with lithium, and a layer of a metal element that does not form an alloy with lithium is formed on this layer. A formed negative electrode has been proposed (see Patent Document 1). According to this document, it can be said that the negative electrode having this configuration can prevent the layer containing a metal element that forms an alloy with lithium from being pulverized due to charge / discharge of the battery. However, according to the description of the example in the above document, the thickness of the metal element layer that does not form an alloy with lithium formed on the outermost surface is as thin as 50 nm. There is a possibility that the surface of the layer containing is not sufficiently covered. In that case, if the layer containing the metal element that forms an alloy with lithium is pulverized due to charge / discharge of the battery, the drop-off cannot be sufficiently suppressed. Conversely, when a layer of a metal element that does not form an alloy with lithium completely covers the surface of the layer that contains a metal element that forms an alloy with lithium, the layer contains a metal element that forms an alloy with lithium. The electrolyte solution is prevented from flowing through the layer, and sufficient electrode reaction is difficult to occur. No technology has yet been proposed to achieve such conflicting functions.

特開平８−５０９２２号公報JP-A-8-50922

従って本発明は、前述した種々の欠点を解消し得る非水電解液二次電池用負極及びこれを備えた非水電解液二次電池を提供することを目的とする。 Accordingly, an object of the present invention is to provide a negative electrode for a non-aqueous electrolyte secondary battery that can eliminate the various disadvantages described above and a non-aqueous electrolyte secondary battery including the same.

本発明者らは鋭意検討した結果、活物質の粒子を含む層を、電解液の流通の可能な微細空隙を有し且つリチウム化合物の形成能の低い導電性材料からなる層で被覆することによって、前記目的が達成されることを知見した。 As a result of intensive studies, the inventors of the present invention have covered a layer containing active material particles with a layer made of a conductive material having fine voids through which an electrolyte can flow and having a low ability to form a lithium compound. The inventors have found that the above-mentioned purpose is achieved.

本発明は前記知見に基づきなされたもので、集電体の片面又は両面上に、シリコン系又はスズ系材料からなる活物質の粒子を含む層と、該層上に位置する表面被覆層とを具備する活物質構造体が形成されている非水電解液二次電池用負極であって、
前記表面被覆層は、その厚みが０．３〜５０μｍであり、
前記表面被覆層に、該表面被覆層の厚さ方向へ延び且つ非水電解液の浸透が可能な微細空隙が多数形成されており、
前記表面被覆層が、リチウム化合物の形成能の低い導電性材料からなることを特徴とする非水電解液二次電池用負極を提供することにより前記目的を達成したものである。
また本発明は、集電体の片面又は両面上に、シリコン系又はスズ系材料からなる活物質の粒子を含む層と、該層上に位置する表面被覆層とを具備する活物質構造体が形成されている非水電解液二次電池用負極であって、
前記表面被覆層に、該表面被覆層の厚さ方向へ延び且つ非水電解液の浸透が可能な微細空隙が多数形成されており、
前記表面被覆層が、リチウム化合物の形成能の低い導電性材料からなり、
前記表面被覆層の構成材料が、前記活物質の粒子を含む層全体に浸透していることを特徴とする非水電解液二次電池用負極を提供するものである。
また本発明は、集電体の片面又は両面上に、シリコン系又はスズ系材料からなる活物質の粒子を含む層と、該層上に位置する表面被覆層とを具備する活物質構造体が形成されている非水電解液二次電池用負極であって、
前記表面被覆層に、該表面被覆層の厚さ方向へ延び且つ非水電解液の浸透が可能な微細空隙が多数形成されており、
前記表面被覆層が、リチウム化合物の形成能の低い導電性材料からなり、
前記活物質の粒子が、シリコン又はスズと金属との混合粒子であり、該混合粒子が、３０〜９９．９重量％のシリコン又はスズ並びに０．１〜７０重量％のＣｕ、Ａｇ、Ｌｉ、Ｎｉ、Ｃｏ、Ｆｅ、Ｃｒ、Ｚｎ、Ｂ、Ａｌ、Ｇｅ、Ｓｎ（但し、前記粒子がスズを含む場合を除く）、Ｓｉ（但し、前記粒子がシリコンを含む場合を除く）、Ｉｎ、Ｖ、Ｔｉ、Ｙ、Ｚｒ、Ｎｂ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｒ、Ｐｄ及びＮｄからなる群から選択される１種類以上の元素を含むことを特徴とする非水電解液二次電池用負極を提供するものである。
更に本発明は、集電体の片面又は両面上に、シリコン系又はスズ系材料からなる活物質の粒子を含む層と、該層上に位置する表面被覆層とを具備する活物質構造体が形成されている非水電解液二次電池用負極であって、
前記表面被覆層に、該表面被覆層の厚さ方向へ延び且つ非水電解液の浸透が可能な微細空隙が多数形成されており、
前記表面被覆層が、リチウム化合物の形成能の低い導電性材料からなり、
前記活物質の粒子が、シリコン単体又はスズ単体の粒子の表面に金属が被覆されてなる粒子であり、該金属がＣｕ、Ａｇ、Ｎｉ、Ｃｏ、Ｆｅ、Ｃｒ、Ｚｎ、Ｂ、Ａｌ、Ｇｅ、Ｓｎ（但し、前記粒子がスズを含む場合を除く）、Ｓｉ（但し、前記粒子がシリコンを含む場合を除く）、Ｉｎ、Ｖ、Ｔｉ、Ｙ、Ｚｒ、Ｎｂ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｒ、Ｐｄ及びＮｄからなる群から選択される１種類以上の元素であり、該粒子が３０〜９９．９重量％のシリコン又はスズ及び０．１〜７０重量％の該金属を含むことを特徴とする非水電解液二次電池用負極を提供するものである。 The present invention has been made on the basis of the above knowledge, and on one side or both sides of a current collector, a layer containing particles of an active material made of a silicon-based or tin-based material, and a surface coating layer positioned on the layer A negative electrode for a non-aqueous electrolyte secondary battery in which an active material structure is provided,
The surface coating layer has a thickness of 0.3 to 50 μm,
In the surface coating layer, a number of fine voids extending in the thickness direction of the surface coating layer and capable of penetrating the non-aqueous electrolyte are formed,
The object is achieved by providing a negative electrode for a non-aqueous electrolyte secondary battery, wherein the surface coating layer is made of a conductive material having a low ability to form a lithium compound.
Further, the present invention provides an active material structure comprising a layer containing active material particles made of a silicon-based or tin-based material on one or both sides of a current collector, and a surface coating layer positioned on the layer. A formed negative electrode for a non-aqueous electrolyte secondary battery,
In the surface coating layer, a number of fine voids extending in the thickness direction of the surface coating layer and capable of penetrating the non-aqueous electrolyte are formed,
The surface coating layer is made of a conductive material having a low lithium compound forming ability,
The constituent material of the surface coating layer penetrates the entire layer including the particles of the active material, and provides a negative electrode for a non-aqueous electrolyte secondary battery.
Further, the present invention provides an active material structure comprising a layer containing active material particles made of a silicon-based or tin-based material on one or both sides of a current collector, and a surface coating layer positioned on the layer. A formed negative electrode for a non-aqueous electrolyte secondary battery,
In the surface coating layer, a number of fine voids extending in the thickness direction of the surface coating layer and capable of penetrating the non-aqueous electrolyte are formed,
The surface coating layer is made of a conductive material having a low ability to form a lithium compound,
The particles of the active material are mixed particles of silicon or tin and metal, and the mixed particles include 30 to 99.9% by weight of silicon or tin and 0.1 to 70% by weight of Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except when the particles contain tin), Si (except when the particles contain silicon), In, V, A negative electrode for a nonaqueous electrolyte secondary battery comprising one or more elements selected from the group consisting of Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd and Nd It is to provide.
Furthermore, the present invention provides an active material structure comprising a layer containing active material particles made of a silicon-based or tin-based material on one or both sides of a current collector, and a surface coating layer positioned on the layer. A formed negative electrode for a non-aqueous electrolyte secondary battery,
In the surface coating layer, a number of fine voids extending in the thickness direction of the surface coating layer and capable of penetrating the non-aqueous electrolyte are formed,
The surface coating layer is made of a conductive material having a low ability to form a lithium compound,
The particles of the active material are particles formed by coating a metal on the surface of particles of silicon alone or tin alone, and the metals are Cu, Ag, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except when the particles contain tin), Si (except when the particles contain silicon), In, V, Ti, Y, Zr, Nb, Ta, W, La, Ce, One or more elements selected from the group consisting of Pr, Pd and Nd, wherein the particles comprise 30-99.9 wt% silicon or tin and 0.1-70 wt% metal. A negative electrode for a non-aqueous electrolyte secondary battery is provided.

また本発明は、前記負極を備えてなることを特徴とする非水電解液二次電池を提供するものである。 The present invention also provides a non-aqueous electrolyte secondary battery comprising the negative electrode.

本発明の非水電解液二次電池用負極によれば、従来の負極よりもエネルギー密度の高い二次電池を得ることができる。また本発明の非水電解液二次電池用負極によれば、活物質の集電体からの剥離が防止され、充放電を繰り返しても活物質の集電性が確保される。またこの負極を用いた二次電池は充放電を繰り返しても劣化率が低く寿命が大幅に長くなり、充放電効率も高くなる。 According to the negative electrode for a non-aqueous electrolyte secondary battery of the present invention, a secondary battery having a higher energy density than a conventional negative electrode can be obtained. In addition, according to the negative electrode for a non-aqueous electrolyte secondary battery of the present invention, the active material is prevented from being peeled off from the current collector, and the current collector is secured even after repeated charge and discharge. Moreover, the secondary battery using this negative electrode has a low deterioration rate and a long life even when charging and discharging are repeated, and the charging and discharging efficiency is also increased.

以下、本発明をその好ましい実施形態に基づき図面を参照しながら説明する。図１には、本発明の負極の一実施形態の表面の電子顕微鏡写真像が示されている。図２には、本発明の負極の一実施形態の断面の電子顕微鏡写真像が示されている。負極１は、集電体２の片面又は両面上に、活物質の粒子の層（以下、活物質層という）３、及び該層３上に位置する表面被覆層４を具備する活物質構造体５が形成されてなるものである。 Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. FIG. 1 shows an electron micrograph image of the surface of one embodiment of the negative electrode of the present invention. FIG. 2 shows an electron micrograph image of a cross section of one embodiment of the negative electrode of the present invention. The negative electrode 1 includes an active material structure including a layer 3 of active material particles (hereinafter referred to as an active material layer) 3 and a surface coating layer 4 positioned on the layer 3 on one side or both sides of a current collector 2. 5 is formed.

集電体２は、非水電解液二次電池の集電体となり得る金属から構成されている。特にリチウム二次電池の集電体となり得る金属から構成されていることが好ましい。そのような金属としては例えば銅、鉄、コバルト、ニッケル、亜鉛若しくは銀又はこれらの金属の合金などが挙げられる。これらの金属のうち銅若しくは銅合金又はニッケル若しくはニッケル合金を用いることが特に好適である。銅を用いる場合、集電体は銅箔の状態で用いられる。この銅箔は例えば銅含有溶液を用いた電解析出により得られ、その厚みは２〜１００μｍ、特に１０〜３０μｍが望ましい。特に特開２０００−９０９３７号公報に記載の方法より得られた銅箔は、厚みが１２μｍ以下と極めて薄いことから好ましく用いられる。集電体２として電解金属箔を用いると、集電体２と活物質層３との密着性が向上するので好ましい。この理由は、電解金属箔の表面が適度な粗さを有するからである。 The current collector 2 is made of a metal that can be a current collector of a non-aqueous electrolyte secondary battery. In particular, it is preferably made of a metal that can be a current collector of a lithium secondary battery. Examples of such a metal include copper, iron, cobalt, nickel, zinc, silver, and alloys of these metals. Of these metals, it is particularly preferable to use copper or a copper alloy or nickel or a nickel alloy. When copper is used, the current collector is used in the form of a copper foil. This copper foil is obtained, for example, by electrolytic deposition using a copper-containing solution, and the thickness is preferably 2 to 100 μm, particularly 10 to 30 μm. In particular, the copper foil obtained by the method described in Japanese Patent Application Laid-Open No. 2000-90937 is preferably used because it has an extremely thin thickness of 12 μm or less. It is preferable to use an electrolytic metal foil as the current collector 2 because adhesion between the current collector 2 and the active material layer 3 is improved. This is because the surface of the electrolytic metal foil has an appropriate roughness.

活物質層３は、シリコン系又はスズ系材料からなる活物質の粒子７を含む層である。活物質粒子７は、粒径が最大粒径で表して好ましくは５０μｍ以下、更に好ましくは２０μｍ以下である。また活物質粒子７の粒径をＤ₅₀値で表すと０．１〜８μｍ、特に０．３〜１μｍであることが好ましい。最大粒径が５０μｍ超であると、活物質粒子７の脱落が起こりやすくなり、電極の寿命が短くなる場合がある。粒径の下限値に特に制限はなく小さいほど好ましい。活物質粒子７の製造方法（その製造例については後述する）に鑑みると、下限値は０．０１μｍ程度である。活物質粒子７の粒径は、マイクロトラック、電子顕微鏡観察（ＳＥＭ観察）によって測定される。 The active material layer 3 is a layer including active material particles 7 made of a silicon-based or tin-based material. The active material particles 7 are preferably 50 μm or less, more preferably 20 μm or less in terms of the maximum particle size. Moreover, when the particle diameter of the active material particle 7 is expressed by a D ₅₀ value, it is preferably 0.1 to 8 μm, particularly preferably 0.3 to 1 μm. If the maximum particle size is more than 50 μm, the active material particles 7 are likely to fall off, and the life of the electrode may be shortened. There is no particular limitation on the lower limit of the particle size, and the smaller the better. In view of the method for producing the active material particles 7 (the production example will be described later), the lower limit is about 0.01 μm. The particle diameter of the active material particles 7 is measured by microtrack observation or electron microscope observation (SEM observation).

活物質層４には空隙が存在していることが好ましい。この空隙の存在によって、活物質粒子７がリチウムを吸脱蔵して膨張収縮することに起因する応力が緩和される。この観点から、活物質層４における空隙の割合は５〜３０体積％程度、特に５〜９体積％程度であることが好ましい。空隙の割合は、電子顕微鏡マッピングによって求めることができる。空隙の割合をこのような範囲にするためには、例えば後述する方法で活物質層を形成した後、適切な条件下でプレス加工すればよい。 It is preferable that voids exist in the active material layer 4. The presence of the voids relieves stress caused by the active material particles 7 absorbing and desorbing lithium and expanding and contracting. From this viewpoint, the ratio of the voids in the active material layer 4 is preferably about 5 to 30% by volume, particularly about 5 to 9% by volume. The void ratio can be determined by electron microscope mapping. In order to set the ratio of the voids in such a range, for example, an active material layer may be formed by a method described later and then pressed under suitable conditions.

活物質層３中には活物質粒子７に加えて導電性炭素材料が含まれていることが好ましい。これによって活物質構造体５に電子伝導性が一層付与される。この観点から活物質層３中に含まれる導電性炭素材料の量は０．１〜２０重量％、特に１〜１０重量％であることが好ましい。導電性炭素材料は粒子の形態であることが好ましく、その粒径は４０μｍ以下、特に２０μｍ以下であることが、電子伝導性の一層付与の点から好ましい。該粒子の粒径の下限値に特に制限はなく小さいほど好ましい。該粒子の製造方法に鑑みると、その下限値は０．０１μｍ程度となる。導電性炭素材料としては、例えばアセチレンブラック、グラファイトなどが挙げられる。 The active material layer 3 preferably contains a conductive carbon material in addition to the active material particles 7. This further imparts electronic conductivity to the active material structure 5. From this viewpoint, the amount of the conductive carbon material contained in the active material layer 3 is preferably 0.1 to 20% by weight, particularly 1 to 10% by weight. The conductive carbon material is preferably in the form of particles, and the particle size is preferably 40 μm or less, and particularly preferably 20 μm or less from the viewpoint of further imparting electronic conductivity. The lower limit of the particle size of the particles is not particularly limited and is preferably as small as possible. In view of the method for producing the particles, the lower limit is about 0.01 μm. Examples of the conductive carbon material include acetylene black and graphite.

表面被覆層４は活物質層３の表面を連続的に厚く被覆しており、活物質粒子７は負極表面に実質的に露出していない。表面被覆層４は活物質層３の表面をほぼ同じ厚さで被覆しているが、その一部４ａが活物質層３に入り込んでいる部分もある。また表面被覆層４が、活物質層３に入り込み更に集電体２にまで達している部分もある。更に表面被覆層４の構成材料が集電体２まで達し活物質層３の厚さ方向全体に浸透している部分もある。表面被覆層４の構成材料が活物質層３に入り込めば入り込むほど、負極全体の導電性が高まるので好ましい。また表面被覆層４の構成材料によって形成されたネットワーク構造が、活物質粒子７の膨張収縮に伴う脱落を防止するので好ましい。表面被覆層４は、該被覆層４の酸化及び脱落の防止の点から、リチウム化合物の形成能の低い導電性材料からなる。そのような導電性材料としては例えば銅、銀、ニッケル、コバルト、クロム、鉄、インジウム及びこれらの金属の合金（例えば銅とスズとの合金）などが挙げられる。これらの金属のうち、リチウム化合物の形成能が特に低い金属である銅、銀、ニッケル、クロム、コバルト及びこれらの金属を含む合金を用いることが好ましい。また前記導電性材料として、導電性プラスチックや導電性ペーストなどを用いることもできる。「リチウム化合物の形成能が低い」とは、リチウムと金属間化合物若しくは固溶体を形成しないか、又は形成したとしてもリチウムが微量であるか若しくは非常に不安定であることを意味する。 The surface coating layer 4 continuously covers the surface of the active material layer 3 so that the active material particles 7 are not substantially exposed on the negative electrode surface. The surface coating layer 4 covers the surface of the active material layer 3 with substantially the same thickness, but there is also a portion in which a part 4 a enters the active material layer 3. In addition, there is a portion where the surface coating layer 4 enters the active material layer 3 and further reaches the current collector 2. Further, there is a portion where the constituent material of the surface coating layer 4 reaches the current collector 2 and penetrates the entire thickness direction of the active material layer 3. The more the constituent material of the surface coating layer 4 enters the active material layer 3, the better the conductivity of the whole negative electrode increases. Further, the network structure formed by the constituent material of the surface coating layer 4 is preferable because it prevents the active material particles 7 from falling off due to expansion and contraction. The surface coating layer 4 is made of a conductive material having a low ability to form a lithium compound from the viewpoint of preventing the coating layer 4 from being oxidized and falling off. Examples of such a conductive material include copper, silver, nickel, cobalt, chromium, iron, indium, and alloys of these metals (for example, alloys of copper and tin). Among these metals, it is preferable to use copper, silver, nickel, chromium, cobalt, and alloys containing these metals, which are metals with particularly low ability to form lithium compounds. In addition, as the conductive material, a conductive plastic, a conductive paste, or the like can be used. “Lithium compound forming ability is low” means that lithium does not form an intermetallic compound or solid solution, or even if formed, lithium is in a very small amount or very unstable.

表面被覆層４にはその表面に、該被覆層４の厚さ方向へ延びる微細空隙６が多数形成されている。微細空隙６は曲折しながら延びている。多数の微細空隙６のうちの一部は、表面被覆層４の厚さ方向へ延び活物質層３にまで達している。微細空隙６は、表面被覆層４を断面観察した場合にその幅が約０．１μｍから約３０μｍ程度の微細なものである。微細であるものの、微細空隙６は非水電解液の浸透が可能な程度の幅を有していることが必要である。尤も非水電解液は水系の電解液に比べて表面張力が小さいことから、微細空隙６の幅が小さくても十分に浸透が可能である。 A large number of fine voids 6 extending in the thickness direction of the coating layer 4 are formed on the surface coating layer 4. The fine gap 6 extends while being bent. A part of the numerous fine voids 6 extends in the thickness direction of the surface coating layer 4 and reaches the active material layer 3. The fine gap 6 is a fine one having a width of about 0.1 μm to about 30 μm when the cross section of the surface coating layer 4 is observed. Although fine, the fine gap 6 needs to have a width that allows the non-aqueous electrolyte to penetrate. However, since the nonaqueous electrolytic solution has a smaller surface tension than the aqueous electrolytic solution, it can sufficiently penetrate even if the width of the fine gap 6 is small.

表面被覆層４を電子顕微鏡観察により平面視したときの微細空隙６の開孔面積は、平均して０．１〜１００μｍ²、特に１〜３０μｍ²程度であることが、非水電解液の十分な浸透を確保しつつ、活物質層３の脱落を効果的に防止し得る点から好ましい。また同様の理由により、表面被覆層４を電子顕微鏡観察により平面視したときに、どのような観察視野をとっても、１００μｍ×１００μｍの正方形の視野範囲内に１〜３０個、特に３〜１０個の微細空隙６が存在していることが好ましい（この値を分布率という）。更に同様の理由により、表面被覆層４を電子顕微鏡観察により平面視したときに、観察視野の面積に対する微細空隙６の開孔面積の総和の割合（この割合を開孔率という）が０．１〜１０％、特に１〜５％であることが好ましい。 Open area of the micropores 6 when the surface coating layer 4 was viewed by electron microscopy, 0.1 to 100 [mu] m ² on average, to be particularly 1 to 30 [mu] m ² or so, enough of the non-aqueous electrolyte It is preferable from the viewpoint that the active material layer 3 can be effectively prevented from falling off while ensuring proper penetration. For the same reason, when the surface coating layer 4 is viewed in plan by electron microscope observation, no matter what observation field of view is taken, 1 to 30, particularly 3 to 10, within a 100 μm × 100 μm square field range. It is preferable that fine voids 6 exist (this value is referred to as distribution rate). Furthermore, for the same reason, when the surface coating layer 4 is viewed in plan by electron microscope observation, the ratio of the total opening area of the fine voids 6 to the area of the observation field (this ratio is referred to as the opening ratio) is 0.1. -10%, particularly 1-5%.

図１に示す通り電子顕微鏡観察によって微細空隙６の有無は確認できるが、微細空隙６はその幅が極めて小さいことから、場合によっては電子顕微鏡観察でも明確にその存在の有無が判定できないことがある。そのような場合に微細空隙６の有無を判定する方法として、本発明では次の方法を採用している。微細空隙６の有無の判定対象となる負極を用いて電池を構成し充放電を一回行う。その後に負極断面を電子顕微鏡観察して、充放電前と断面構造が変化している場合には、充放電前の負極には微細空隙６が形成されていると判断する。充放電前と断面構造が変化している原因は、充放電前の負極に存在している微細空隙６を通じて非水電解液が活物質層３に到達し、非水電解液中のリチウムイオンと活物質粒子７との反応が起こった結果によるものだからである。 As shown in FIG. 1, the presence or absence of the fine void 6 can be confirmed by observation with an electron microscope, but the width of the fine void 6 is extremely small. . In such a case, the following method is adopted in the present invention as a method for determining the presence or absence of the fine gap 6. A battery is configured using a negative electrode that is a target for determination of the presence or absence of the fine gap 6 and is charged and discharged once. Thereafter, the cross section of the negative electrode is observed with an electron microscope, and when the cross-sectional structure is changed from that before charge / discharge, it is determined that the fine gap 6 is formed in the negative electrode before charge / discharge. The cause of the change in the cross-sectional structure before and after charge / discharge is that the non-aqueous electrolyte reaches the active material layer 3 through the fine voids 6 existing in the negative electrode before charge / discharge, and the lithium ions in the non-aqueous electrolyte and This is because the reaction with the active material particles 7 results.

微細空隙６が形成されていることで、非水電解液が活物質層３へ十分に浸透することができ、活物質粒子７との反応が十分に起こる。また充放電によって活物質粒子７が微粉化することに起因する脱落は、活物質層３の表面を厚く被覆する表面被覆層４によって防止される。つまり活物質粒子７が表面被覆層４によって閉じこめられているので、リチウムの吸脱蔵に起因する活物質粒子７の脱落が効果的に防止される。また電気的に孤立した活物質粒子７が生成することが効果的に防止され、集電機能が保たれる。その結果、負極としての機能低下が抑えられる。更に負極の長寿命化も図られる。特に、表面被覆層４の一部４ａが活物質層３に入り込んでいると、集電機能が一層効果的に保たれる。シリコンやスズ等の活物質をそのままの状態で集電体上に形成すると、リチウムの吸脱蔵に起因してこれらが微粉化して集電体から電気的に孤立化してしまう。その結果、負極としての機能が低下し、不可逆容量の増大、充放電効率の低下、短寿命化などの問題が生じてしまう。このように、本発明の負極を用いた二次電池はその単位体積当たり及び単位重量当たりのエネルギー密度が従来のものに比べて非常に大きくなり、しかも長寿命となる。 By forming the fine voids 6, the non-aqueous electrolyte can sufficiently penetrate into the active material layer 3, and the reaction with the active material particles 7 occurs sufficiently. Further, the falling off due to the active material particles 7 being pulverized by charging / discharging is prevented by the surface coating layer 4 that covers the surface of the active material layer 3 thickly. That is, since the active material particles 7 are confined by the surface coating layer 4, the falling off of the active material particles 7 due to the absorption and desorption of lithium is effectively prevented. Further, the generation of electrically isolated active material particles 7 is effectively prevented, and the current collecting function is maintained. As a result, functional degradation as a negative electrode is suppressed. In addition, the life of the negative electrode can be extended. In particular, when a part 4 a of the surface coating layer 4 enters the active material layer 3, the current collecting function is more effectively maintained. When an active material such as silicon or tin is formed on the current collector as it is, they are finely powdered due to the absorption and desorption of lithium and are electrically isolated from the current collector. As a result, the function as the negative electrode is lowered, and problems such as an increase in irreversible capacity, a decrease in charge / discharge efficiency, and a shortened life are caused. As described above, the secondary battery using the negative electrode of the present invention has an energy density per unit volume and unit weight which is much higher than that of the conventional battery and has a long life.

微細空隙６は、種々の方法で形成することが可能である。例えば、表面被覆層４を適切な条件下でプレス加工することによって形成することができる。特に好ましい方法は、後述するように表面被覆層４を電解めっきによって形成し、この形成と同時に微細空隙を形成する方法である。更に詳しくは、活物質層３は先に述べた通り活物質粒子７を含む層であることから、該活物質層３の表面はミクロの凹凸形状となっている。つまりめっきが成長しやすい活性サイトとそうでないサイトとが混在した状態となっている。このような状態の活物質層３上に電解めっきを行うと、めっきの成長にムラが生じ、表面被覆層４の構成材料の粒子が多結晶状に成長していく。結晶の成長が進み、隣り合う結晶がぶつかるとその部分に空隙が形成される。このようにして形成された空隙が多数連なることによって微細空隙６が形成される。この方法によれば微細空隙６はその構造が極めて微細になる。また、表面被覆層４の厚さ方向へ延びる微細空隙６を容易に形成することができる。更に、この方法によれば表面被覆層４にプレス加工などの外力が加わらないので、表面被覆層４、ひいては負極１が損傷を受けることがない。 The fine gap 6 can be formed by various methods. For example, the surface coating layer 4 can be formed by pressing under appropriate conditions. A particularly preferable method is a method in which the surface coating layer 4 is formed by electrolytic plating as described later, and fine voids are formed simultaneously with this formation. More specifically, since the active material layer 3 is a layer containing the active material particles 7 as described above, the surface of the active material layer 3 has a micro uneven shape. That is, the active site where plating is likely to grow and the site that is not so are mixed. When electrolytic plating is performed on the active material layer 3 in such a state, the growth of the plating is uneven, and the particles of the constituent material of the surface coating layer 4 grow in a polycrystalline form. When crystal growth proceeds and adjacent crystals collide with each other, a void is formed in that portion. The fine voids 6 are formed by a large number of voids formed in this way. According to this method, the structure of the fine gap 6 becomes extremely fine. Moreover, the fine space | gap 6 extended in the thickness direction of the surface coating layer 4 can be formed easily. Further, according to this method, no external force such as pressing is applied to the surface coating layer 4, so that the surface coating layer 4 and thus the negative electrode 1 is not damaged.

活物質粒子７の脱落を効果的に防止し且つ集電機能を十分に維持する観点から、表面被覆層４はその厚みが０．３〜５０μｍ、特に０．３〜１０μｍ、とりわけ１〜１０μｍと厚いことが好ましい。表面被覆層４を厚く形成しても微細空隙６が形成されていることで、非水電解液の浸透は確実に確保される。活物質層３の厚みは１〜１００μｍ、特に３〜４０μｍであることが、負極容量の十分な確保の点から好ましい。表面被覆層４及び活物質層３を含む活物質構造体５の厚みは２〜５０μｍ程度であることが好ましい。更に負極全体の厚みは２０〜１００μｍであることが、電池の小型化及び高エネルギー密度化の点から好ましい。 From the viewpoint of effectively preventing the active material particles 7 from falling off and sufficiently maintaining the current collecting function, the surface coating layer 4 has a thickness of 0.3 to 50 μm, particularly 0.3 to 10 μm, especially 1 to 10 μm. Thickness is preferred. Even if the surface coating layer 4 is formed thick, the fine voids 6 are formed, so that the penetration of the non-aqueous electrolyte is reliably ensured. The thickness of the active material layer 3 is preferably 1 to 100 μm, particularly 3 to 40 μm, from the viewpoint of sufficiently securing the negative electrode capacity. The thickness of the active material structure 5 including the surface coating layer 4 and the active material layer 3 is preferably about 2 to 50 μm. Furthermore, it is preferable that the thickness of the whole negative electrode is 20-100 micrometers from the point of size reduction and high energy density of a battery.

活物質層３及び表面被覆層４を含む活物質構造体５中における活物質粒子７の量は好ましくは５〜８０重量％であり、更に好ましくは１０〜５０重量％、一層好ましくは２０〜５０重量％である。この範囲内であれば活物質粒子７の脱落を効果的に防止でき、不可逆容量の増大、充放電効率の低下、短寿命化などの問題を防止でき、電池のエネルギー密度を十分に向上させることが容易である。 The amount of the active material particles 7 in the active material structure 5 including the active material layer 3 and the surface coating layer 4 is preferably 5 to 80% by weight, more preferably 10 to 50% by weight, and still more preferably 20 to 50%. % By weight. Within this range, it is possible to effectively prevent the active material particles 7 from falling off, prevent problems such as an increase in irreversible capacity, a decrease in charge / discharge efficiency, and a shortened life, and sufficiently improve the energy density of the battery. Is easy.

活物質粒子７としては、例えばイ）シリコン単体又はスズ単体の粒子、ロ）少なくともシリコン又はスズの粒子と炭素の粒子との混合粒子、ハ）シリコン又はスズの粒子と金属の粒子との混合粒子、ニ）シリコン又はスズと金属との化合物粒子、ホ）シリコン又はスズと金属との化合物粒子と、金属の粒子との混合粒子、ヘ）シリコン単体又はスズ単体の粒子の表面に金属が被覆されてなる粒子などが挙げられる。これら各粒子はそれぞれ単独で或いはイ）〜ヘ）の２種類以上を適宜組み合わせて用いることができる。ロ）、ハ）、ニ）、ホ）及びヘ）の粒子を用いると、イ）のシリコン単体又はスズ単体の粒子を用いる場合に比べて、リチウムの吸脱蔵に起因する活物質粒子７の微粉化が一層抑制されるという利点がある。この利点は特にホ）の粒子を用いた場合に顕著である。またシリコンを用いる場合には、半導体であり電気導電性の乏しいシリコンに電子導電性を付与できるという利点がある。 Examples of the active material particles 7 include: a) particles of silicon or tin alone, b) mixed particles of at least silicon or tin particles and carbon particles, and c) mixed particles of silicon or tin particles and metal particles. D) Compound particles of silicon or tin and metal, e) Mixed particles of silicon or tin and metal compound particles and metal particles, f) The surface of silicon or tin particles is coated with metal. And the like. Each of these particles can be used alone or in appropriate combination of two or more of a) to f). When the particles b), c), d), e), and f) are used, the active material particles 7 resulting from the absorption and desorption of lithium are compared with the case of using the particles of silicon or tin as in i). There is an advantage that pulverization is further suppressed. This advantage is particularly remarkable when particles (e) are used. When silicon is used, there is an advantage that electronic conductivity can be imparted to silicon which is a semiconductor and has poor electrical conductivity.

特に、活物質粒子７がロ）の少なくともシリコンと炭素との混合粒子からなる場合には、サイクル寿命が向上すると共に負極容量が増加する。この理由は次の通りである。炭素、特に非水電解液二次電池用負極に用いられているグラファイトは、リチウムの吸脱蔵に寄与し、３００ｍＡｈ／ｇ程度の負極容量を有し、しかもリチウム吸蔵時の体積膨張が非常に小さいという特徴を持つ。一方、シリコンは、グラファイトの１０倍以上である４２００ｍＡｈ／ｇ程度の負極容量を有するという特徴を持つ。反面シリコンは、リチウム吸蔵時の体積膨張がグラファイトの約４倍に達する。そこで、シリコンとグラファイトのような炭素とを所定の比率でメカニカルミリング法などを用い混合・粉砕して、粒径が約０．１〜１μｍの均質に混合された粉末とすると、リチウム吸蔵時のシリコンの体積膨張がグラファイトによって緩和されて、サイクル寿命が向上し、また１０００〜３０００ｍＡｈ／ｇ程度の負極容量が得られる。シリコンと炭素との混合比率は、
シリコンの量が１０〜９０重量％、特に３０〜７０重量％、とりわけ３０〜５０重量％であることが好ましい。一方、炭素の量は９０〜１０重量％、特に７０〜３０重量％、とりわけ７０〜５０重量％であることが好ましい。組成がこの範囲内であれば、電池の高容量化及び負極の長寿命化を図ることができる。なお、この混合粒子においては、シリコンカーバイドなどの化合物は形成されていない。 In particular, when the active material particles 7 are composed of mixed particles of at least silicon and carbon (b), the cycle life is improved and the negative electrode capacity is increased. The reason is as follows. Carbon, particularly graphite used in negative electrodes for non-aqueous electrolyte secondary batteries, contributes to the absorption and desorption of lithium, has a negative electrode capacity of about 300 mAh / g, and has a very large volume expansion during occlusion of lithium. It is small. On the other hand, silicon is characterized by having a negative electrode capacity of about 4200 mAh / g, which is 10 times or more that of graphite. On the other hand, the volume expansion of silicon during lithium occlusion reaches about 4 times that of graphite. Therefore, silicon and carbon such as graphite are mixed and pulverized at a predetermined ratio using a mechanical milling method or the like to obtain a homogeneously mixed powder having a particle size of about 0.1 to 1 μm. The volume expansion of silicon is relaxed by graphite, the cycle life is improved, and a negative electrode capacity of about 1000 to 3000 mAh / g is obtained. The mixing ratio of silicon and carbon is
It is preferred that the amount of silicon is 10 to 90% by weight, in particular 30 to 70% by weight, in particular 30 to 50% by weight. On the other hand, the amount of carbon is preferably 90 to 10% by weight, particularly 70 to 30% by weight, and particularly preferably 70 to 50% by weight. If the composition is within this range, the capacity of the battery and the life of the negative electrode can be increased. In this mixed particle, a compound such as silicon carbide is not formed.

活物質粒子７がロ）の粒子からなる場合、該粒子は、シリコン又はスズ及び炭素に加えて他の金属元素を含む、３種以上の元素の混合粒子であってもよい。金属元素としてはＣｕ、Ａｇ、Ｌｉ、Ｎｉ、Ｃｏ、Ｆｅ、Ｃｒ、Ｚｎ、Ｂ、Ａｌ、Ｇｅ、Ｉｎ、Ｖ、Ｔｉ、Ｙ、Ｚｒ、Ｎｂ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｒ、Ｐｄ及びＮｄからなる群から選択される１種類以上の元素が挙げられる。 In the case where the active material particles 7 are composed of particles (b), the particles may be mixed particles of three or more elements including other metal elements in addition to silicon or tin and carbon. Metal elements include Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge, In, V, Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd and One or more kinds of elements selected from the group consisting of Nd can be mentioned.

活物質粒子７がハ）のシリコン又はスズと金属との混合粒子である場合、該混合粒子に含まれる金属としては、Ｃｕ、Ａｇ、Ｌｉ、Ｎｉ、Ｃｏ、Ｆｅ、Ｃｒ、Ｚｎ、Ｂ、Ａｌ、Ｇｅ、Ｓｎ（但し、粒子７がスズを含む場合を除く）、Ｓｉ（但し、粒子７がシリコンを含む場合を除く）、Ｉｎ、Ｖ、Ｔｉ、Ｙ、Ｚｒ、Ｎｂ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｒ、Ｐｄ及びＮｄからなる群から選択される１種類以上の元素が挙げられる。これらの金属のうち、Ｃｕ、Ａｇ、Ｎｉ、Ｃｏ、Ｃｅが好ましく、特に電子伝導性に優れ且つリチウム化合物の形成能の低さの点から、Ｃｕ、Ａｇ、Ｎｉを用いることが望ましい。また前記金属としてＬｉを用いると、負極活物質に予め金属リチウムが含まれることになり、不可逆容量の低減、充放電効率の向上、及び体積変化率の低減によるサイクル寿命向上等の利点が生ずるので好ましい。ハ）の混合粒子においては、シリコン又はスズの量が３０〜９９．９重量％、特に５０〜９５重量％、とりわけ７５〜９５重量％であることが好ましい。一方、銅を始めとする金属の量は０．１〜７０重量％、特に５〜５０重量％、とりわけ５〜３０重量％であることが好ましい。組成がこの範囲内であれば、電池の高容量化及び負極の長寿命化を図ることができる。 In the case where the active material particles 7 are mixed particles of silicon or tin and metal of c), the metals contained in the mixed particles include Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al , Ge, Sn (except when the particle 7 contains tin), Si (except when the particle 7 contains silicon), In, V, Ti, Y, Zr, Nb, Ta, W, La And one or more elements selected from the group consisting of Ce, Pr, Pd, and Nd. Among these metals, Cu, Ag, Ni, Co, and Ce are preferable, and Cu, Ag, and Ni are preferably used from the viewpoint of excellent electronic conductivity and low ability to form a lithium compound. Further, when Li is used as the metal, metallic lithium is included in the negative electrode active material in advance, and there are advantages such as reduction in irreversible capacity, improvement in charge / discharge efficiency, and improvement in cycle life due to reduction in volume change rate. preferable. In the mixed particles (c), the amount of silicon or tin is preferably 30 to 99.9% by weight, more preferably 50 to 95% by weight, and particularly preferably 75 to 95% by weight. On the other hand, the amount of metal such as copper is preferably 0.1 to 70% by weight, particularly 5 to 50% by weight, particularly 5 to 30% by weight. If the composition is within this range, the capacity of the battery and the life of the negative electrode can be increased.

ハ）の混合粒子は例えば次に述べる方法で製造することができる。先ず、シリコン粒子又はスズ粒子及び銅を始めとする金属の金属粒子を混合し、粉砕機によってこれらの粒子の混合及び粉砕を同時に行う。粉砕機としてはアトライター、ジェットミル、サイクロンミル、ペイントシェイカ、ファインミルなどを用いることができる。これらの粉砕機を用いた粉砕は乾式及び湿式のどちらでもよいが、小粒径化の観点からは湿式粉砕であることが好ましい。粉砕前のこれらの粒子の粒径は２０〜５００μｍ程度であることが好ましい。粉砕機による混合及び粉砕によってシリコン又はスズと前記金属とが均一に混ざり合った粒子が得られる。粉砕機の運転条件を適切にコントロールすることで得られる粒子の粒径を例えば４０μｍ以下となす。これによってハ）の混合粒子が得られる。 The mixed particles (c) can be produced, for example, by the method described below. First, metal particles such as silicon particles or tin particles and copper are mixed, and these particles are mixed and pulverized simultaneously by a pulverizer. As a pulverizer, an attritor, a jet mill, a cyclone mill, a paint shaker, a fine mill, or the like can be used. The pulverization using these pulverizers may be either dry or wet, but wet pulverization is preferable from the viewpoint of reducing the particle size. The particle size of these particles before pulverization is preferably about 20 to 500 μm. By mixing and pulverizing by a pulverizer, particles in which silicon or tin and the metal are uniformly mixed are obtained. The particle size of the particles obtained by appropriately controlling the operating conditions of the pulverizer is, for example, 40 μm or less. Thereby, mixed particles of c) are obtained.

活物質粒子７が、ニ）のシリコン又はスズと金属との化合物粒子である場合、該化合物は、シリコン又はスズと金属との合金を含み、１）シリコン又はスズと金属との固溶体、２）シリコン又はスズと金属との金属間化合物、或いは３）シリコン又はスズ単相、金属単相、シリコン又はスズと金属との固溶体、シリコン又はスズと金属との金属間化合物のうちの二相以上の相からなる複合体の何れかである。前記金属としては、ハ）の混合粒子に含まれる金属と同様のものを用いることができる。ニ）の化合物粒子におけるシリコン又はスズと金属との組成は、ハ）の混合粒子と同様にシリコン又はスズの量が３０〜９９．９重量％で、金属の量が０．１〜７０重量％であることが好ましい。更に好ましい組成は、化合物粒子の製造方法に応じて適切な範囲が選択される。例えば該化合物が、シリコン又はスズと金属との二元系合金であり、該合金を後述する急冷法を用いて製造する場合、シリコン又はスズの量は４０〜９０重量％であることが望ましい。一方、銅を始めとする金属の量は１０〜６０重量％であることが好ましい。 When the active material particle 7 is a compound particle of silicon or tin and metal of d), the compound includes silicon or an alloy of tin and metal, 1) a solid solution of silicon or tin and metal, 2) Silicon or an intermetallic compound of tin and metal, or 3) two or more phases of silicon or tin single phase, metal single phase, solid solution of silicon or tin and metal, or intermetallic compound of silicon or tin and metal It is one of a complex composed of phases. As the metal, the same metals as those contained in the mixed particles of c) can be used. The composition of silicon or tin and metal in the compound particles of d) is 30 to 99.9% by weight of silicon or tin and 0.1 to 70% by weight of metal as with the mixed particles of c). It is preferable that A more preferable composition is selected in an appropriate range depending on the method for producing compound particles. For example, when the compound is a binary alloy of silicon or tin and metal, and the alloy is manufactured using a rapid cooling method described later, the amount of silicon or tin is preferably 40 to 90% by weight. On the other hand, the amount of metal including copper is preferably 10 to 60% by weight.

前記化合物がシリコン又はスズと金属との三元系以上の合金である場合には、先に述べた二元系合金に更にＢ、Ａｌ、Ｎｉ、Ｃｏ、Ｆｅ、Ｃｒ、Ｚｎ、Ｉｎ、Ｖ、Ｙ、Ｚｒ、Ｎｂ、Ｔａ、Ｗ、Ｌａ、Ｃｅ、Ｐｒ、Ｐｄ及びＮｄからなる群から選択される元素が少量含まれていてもよい。これによって、微粉化が抑制されるという付加的な効果が奏される。この効果を一層高めるため、これらの元素はシリコン又はスズと金属との合金中に０．０１〜１０重量％、特に０．０５〜１．０重量％含まれていることが好ましい。 In the case where the compound is a ternary or higher alloy of silicon or tin and a metal, B, Al, Ni, Co, Fe, Cr, Zn, In, V, A small amount of an element selected from the group consisting of Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd and Nd may be contained. Thereby, the additional effect that pulverization is suppressed is produced. In order to further enhance this effect, these elements are preferably contained in an alloy of silicon or tin and metal in an amount of 0.01 to 10% by weight, particularly 0.05 to 1.0% by weight.

ニ）の化合物粒子が合金粒子である場合、該合金粒子は、例えば以下に説明する急冷法によって製造されることが、合金の結晶子が微細なサイズとなり且つ均質分散されることにより、微粉化が抑制され、電子伝導性が保持される点から好ましい。この急冷法においては、先ずシリコン又はスズと、銅を始めとする金属とを含む原料の溶湯を準備する。原料は高周波溶解によって溶湯となす。溶湯におけるシリコン又はスズと他の金属との割合は前述した範囲とする。溶湯の温度は１２００〜１５００℃、特に１３００〜１４５０℃とすることが急冷条件との関係で好ましい。鋳型鋳造法を用いてこの溶湯から合金を得る。即ち、該溶湯を銅製又は鉄製の鋳型に流し込んで、急冷された合金のインゴットを得る。このインゴットを粉砕し篩い分けして、例えば粒径４０μｍ以下のものを本発明に供する。この鋳型鋳造法に代えてロール鋳造法を用いることもできる。即ち、溶湯を高速回転する銅製のロールにおける周面に対して射出する。ロールの回転速度は、溶湯を急冷させる観点から回転数５００〜４０００ｒｐｍ、特に１０００〜２０００ｒｐｍとすることが好ましい。ロールの回転速度を周速で表す場合には、８〜７０ｍ／ｓｅｃ、特に１５〜３０ｍ／ｓｅｃであることが好ましい。前述の範囲の温度の溶湯を、前述範囲の速度で回転するロールを用いて急冷することで、冷却速度は１０²Ｋ／ｓｅｃ以上、特に１０³Ｋ／ｓｅｃ以上という高速になる。射出された溶湯はロールにおいて急冷されて薄体となる。この薄体を粉砕、篩い分けして例えば粒径４０μｍ以下のものを本発明に供する。この急冷法に代えて、ガスアトマイズ法を用い、１２００〜１５００℃の溶湯に、アルゴンなどの不活性ガスを５〜１００ａｔｍの圧力で吹き付けて微粒化及び急冷して所望の粒子を得ることもできる。更に別法として、アーク溶解法やメカニカルミリングを用いることもできる。 In the case where the compound particles of d) are alloy particles, the alloy particles are produced by, for example, a rapid cooling method described below, so that the crystallites of the alloy have a fine size and are uniformly dispersed. Is preferable from the viewpoint of suppressing the electron conductivity. In this rapid cooling method, first, a raw material melt containing silicon or tin and copper and other metals is prepared. The raw material is made into molten metal by high frequency melting. The ratio of silicon or tin to the other metal in the molten metal is in the range described above. The temperature of the molten metal is preferably 1200 to 1500 ° C., particularly 1300 to 1450 ° C., in relation to the rapid cooling conditions. An alloy is obtained from this molten metal using a mold casting method. That is, the molten metal is poured into a copper or iron mold to obtain a quenched alloy ingot. The ingot is pulverized and sieved, and a particle having a particle size of 40 μm or less is provided for the present invention. Instead of this mold casting method, a roll casting method can also be used. That is, the molten metal is injected onto the peripheral surface of a copper roll that rotates at high speed. The rotational speed of the roll is preferably 500 to 4000 rpm, particularly 1000 to 2000 rpm from the viewpoint of quenching the molten metal. When the rotational speed of the roll is expressed as a peripheral speed, it is preferably 8 to 70 m / sec, particularly 15 to 30 m / sec. By rapidly cooling the molten metal having a temperature in the above-described range using a roll rotating at a speed in the above-described range, the cooling rate becomes 10 ² K / sec or higher, particularly 10 ³ K / sec or higher. The injected molten metal is rapidly cooled in a roll to become a thin body. The thin body is pulverized and sieved and, for example, one having a particle size of 40 μm or less is provided for the present invention. Instead of this rapid cooling method, a desired atomization method can be obtained by spraying an inert gas such as argon at a pressure of 5 to 100 atm on a molten metal at 1200 to 1500 ° C. and atomizing and rapidly cooling. Further, as another method, an arc melting method or mechanical milling can be used.

活物質粒子が、ホ）のシリコン又はスズと金属との化合物粒子と、金属の粒子との混合粒子である場合、該化合物粒子としては、先に述べたニ）の化合物粒子と同様の粒子を用いることができる。一方、金属の粒子としては、先に述べたハ）の混合粒子に用いられる金属の粒子と同様のものを用いることができる。化合物粒子に含まれる金属元素と、金属の粒子を構成する金属元素とは同種でも異種でもよい。特に、化合物粒子に含まれる金属元素がニッケル、銅、銀又は鉄であり、金属の粒子を構成する金属元素がニッケル、銅、銀又は鉄であると、活物質層３中にこれらの金属のネットワーク構造が形成されやすくなる。その結果、電子伝導性の向上、活物質粒子７の膨張収縮による脱落の防止等という有利な効果が奏されるので好ましい。この観点から、化合物粒子に含まれる金属元素と金属の粒子を構成する金属元素とは同種であることが好ましい。ホ）の活物質粒子は、先に述べたニ）の化合物粒子の製造方法と同様の方法によって先ず化合物粒子を得て、この化合物粒子と金属の粒子とを、先に述べたハ）の混合粒子の製造方法に従い混合することで得られる。化合物粒子中におけるシリコン又はスズと金属との割合は、先に述べたニ）の化合物粒子中における両者の割合と同様とすることができる。また化合物粒子と金属の粒子との割合は、先に述べたハ）の混合粒子におけるシリコン又はスズの粒子と金属の粒子との割合と同様とすることができる。これら以外でホ）の活物質粒子に関して特に説明しない点については、先に述べたハ）の混合粒子又はニ）の化合物粒子に関して詳述した説明が適宜適用される。 In the case where the active material particles are mixed particles of silicon or tin / metal compound particles of e) and metal particles, the compound particles are the same particles as the compound particles of d) described above. Can be used. On the other hand, as the metal particles, the same metal particles as those used for the mixed particles of c) described above can be used. The metal element contained in the compound particle and the metal element constituting the metal particle may be the same or different. In particular, when the metal element contained in the compound particle is nickel, copper, silver or iron and the metal element constituting the metal particle is nickel, copper, silver or iron, A network structure is easily formed. As a result, advantageous effects such as improvement of electron conductivity and prevention of falling off due to expansion and contraction of the active material particles 7 are exhibited, which is preferable. From this viewpoint, it is preferable that the metal element contained in the compound particle and the metal element constituting the metal particle are the same type. The active material particles of e) are first obtained by the same method as the production method of the compound particles of d) described above, and the compound particles and the metal particles are mixed with c) described above. It is obtained by mixing according to the method for producing particles. The ratio of silicon or tin and metal in the compound particles can be the same as the ratio of both in the compound particles of d) described above. Further, the ratio of the compound particles to the metal particles can be the same as the ratio of the silicon or tin particles to the metal particles in the mixed particles in (c) described above. Except for these points, the explanation in detail regarding the mixed particles of c) or the compound particles of d) is applied as appropriate to the points not particularly explained regarding the active material particles of e).

活物質粒子７が、ヘ）のシリコン単体又はスズ単体の粒子の表面に金属が被覆されてなる粒子（この粒子を金属被覆粒子という）である場合、被覆金属としては、先に述べたハ）やニ）の粒子に含まれる金属、例えば銅などと同様のものが用いられる（但しＬｉを除く）。金属被覆粒子におけるシリコン又はスズの量は７０〜９９．９重量％、特に８０〜９９重量％、とりわけ８５〜９５であることが好ましい。一方、銅を始めとする被覆金属の量は０．１〜３０重量％、特に１〜２０重量％、とりわけ５〜１５重量％であることが好ましい。金属被覆粒子は例えば無電解めっき法を用いて製造される。この無電解めっき法においては、先ずシリコン粒子又はスズ又はが懸濁されており且つ銅を始めとする被覆金属とを含むめっき浴を用意する。このめっき浴中において、シリコン粒子又はスズ粒子を無電解めっきして該粒子の表面に前記被覆金属を被覆させる。めっき浴中におけるシリコン粒子又はスズ粒子の濃度は４００〜６００ｇ／ｌ程度とすることが好ましい。前記被覆金属として銅を無電解めっきする場合には、めっき浴中に硫酸銅、ロシェル塩等を含有させておくことが好ましい。この場合硫酸銅の濃度は６〜９ｇ／ｌ、ロシェル塩の濃度は７０〜９０ｇ／ｌであることが、めっき速度のコントロールの点から好ましい。同様の理由からめっき浴のｐＨは１２〜１３、浴温は２０〜３０℃であることが好ましい。めっき浴中に含まれる還元剤としては、例えばホルムアルデヒド等が用いられ、その濃度は１５〜３０ｃｃ／ｌ程度とすることができる。 In the case where the active material particles 7 are particles in which metal is coated on the surface of the particles of silicon or tin as described in (i) above (this particle is referred to as metal-coated particles), Or the metal contained in the particles of (ii), such as copper, is used (except for Li). The amount of silicon or tin in the metal-coated particles is preferably 70 to 99.9% by weight, particularly 80 to 99% by weight, especially 85 to 95. On the other hand, the amount of the coating metal including copper is preferably 0.1 to 30% by weight, particularly 1 to 20% by weight, particularly 5 to 15% by weight. The metal-coated particles are produced using, for example, an electroless plating method. In this electroless plating method, first, a plating bath in which silicon particles or tin or suspension is suspended and containing a coating metal such as copper is prepared. In this plating bath, silicon particles or tin particles are electrolessly plated to coat the surface of the particles with the coating metal. The concentration of silicon particles or tin particles in the plating bath is preferably about 400 to 600 g / l. When electrolessly plating copper as the coating metal, it is preferable to contain copper sulfate, Rochelle salt or the like in the plating bath. In this case, the concentration of copper sulfate is preferably 6 to 9 g / l, and the concentration of Rochelle salt is preferably 70 to 90 g / l from the viewpoint of controlling the plating rate. For the same reason, the pH of the plating bath is preferably 12 to 13, and the bath temperature is preferably 20 to 30 ° C. As the reducing agent contained in the plating bath, for example, formaldehyde or the like is used, and the concentration thereof can be about 15 to 30 cc / l.

活物質粒子７が前記イ）〜ヘ）のうちのどのような形態である場合においても、活物質粒子７は、含有している酸素の濃度が３重量％以下、特に２重量％以下であることが好ましい。これによって活物質粒子７が酸化されることに起因する劣化が効果的に防止され、負極１の長寿命化を図ることができる。この理由から明らかなように、酸素の濃度は低ければ低いほど好ましい。同様の理由により、活物質粒子７は、その最表面におけるシリコン又はスズの濃度が、最表面における酸素の濃度の１／２以上である、とりわけ４／５以上であることが好ましい（但し、前記ヘ）の粒子である場合を除く）。酸素の濃度は、測定対象試料の燃焼を伴うガス分析法によって測定される。酸素濃度の分布はＸ線光電子分光分析装置（ＥＳＣＡ）やオージェ電子分光分析装置（ＡＥＳ）などを始めとする各種表面状態分析装置によって測定される。 The active material particles 7 have an oxygen concentration of 3 wt% or less, particularly 2 wt% or less, in any case of the active material particles 7 in any form of the above-mentioned a) to f). It is preferable. As a result, deterioration due to oxidation of the active material particles 7 is effectively prevented, and the life of the negative electrode 1 can be extended. As is apparent from this reason, the lower the oxygen concentration, the better. For the same reason, it is preferable that the active material particles 7 have a silicon or tin concentration on the outermost surface that is 1/2 or more of the oxygen concentration on the outermost surface, particularly 4/5 or more (however, F) except for particles). The concentration of oxygen is measured by a gas analysis method that involves combustion of the sample to be measured. The oxygen concentration distribution is measured by various surface state analyzers such as an X-ray photoelectron spectrometer (ESCA) and an Auger electron spectrometer (AES).

次に、本発明の負極の好ましい製造方法について説明する。本製造方法においては先ず集電体の表面に塗工するスラリーを準備する。スラリーは、例えば活物質粒子、導電性炭素材料の粒子、結着剤及び希釈溶媒を含んでいる。これらの成分のうち、活物質粒子及び導電性炭素材料の粒子については先に説明した通りである。結着剤としてはポリビニリデンフルオライド（ＰＶＤＦ）、ポリエチレン（ＰＥ）、エチレンプロピレンジエンモノマー（ＥＰＤＭ）などが用いられる。希釈溶媒としてはＮ−メチルピロリドン、シクロヘキサンなどが用いられる。 Next, the preferable manufacturing method of the negative electrode of this invention is demonstrated. In this production method, first, a slurry to be applied to the surface of the current collector is prepared. The slurry contains, for example, active material particles, conductive carbon material particles, a binder, and a diluent solvent. Among these components, the active material particles and the conductive carbon material particles are as described above. As the binder, polyvinylidene fluoride (PVDF), polyethylene (PE), ethylene propylene diene monomer (EPDM) or the like is used. As a diluting solvent, N-methylpyrrolidone, cyclohexane or the like is used.

スラリー中における活物質粒子の量は１４〜４０重量％程度とすることが好ましい。導電性炭素材料の粒子の量は０．４〜４重量％程度とすることが好ましい。結着剤の量は０．４〜４重量％程度とすることが好ましい。また希釈溶媒の量は６０〜８５重量％程度とすることが好ましい。 The amount of active material particles in the slurry is preferably about 14 to 40% by weight. The amount of the conductive carbon material particles is preferably about 0.4 to 4% by weight. The amount of the binder is preferably about 0.4 to 4% by weight. Moreover, it is preferable that the quantity of a dilution solvent shall be about 60 to 85 weight%.

このスラリーを集電体の表面に塗工して活物質層を形成する。集電体は予め製造しておいてもよく、或いは本発明の負極の製造工程における一工程としてインラインで製造されてもよい。集電体がインラインで製造される場合、電解析出によって製造されることが好ましい。集電体へのスラリーの塗工量は、乾燥後の活物質層の膜厚が、最終的に得られる活物質構造体の厚みの１〜３倍程度となるような量とすることが好ましい。スラリーの塗膜が乾燥して活物質層が形成された後、該活物質層が形成された集電体を、リチウム化合物の形成能の低い導電性材料を含むめっき浴中に浸漬し、その状態下に活物質層上に該導電性材料による電解めっきを行い表面被覆層を形成する。この方法を用いることで、表面被覆層に多数の微細空隙を容易に形成することができる。詳細には先に述べた通り活物質層３の表面はミクロの凹凸形状となっていて、めっきが成長しやすい活性サイトとそうでないサイトとが混在した状態となっている。このような状態の活物質層３上に電解めっきを行うと、めっきの成長にムラが生じ、表面被覆層４の構成材料の粒子が多結晶状に成長していく。結晶の成長が進み、隣り合う結晶がぶつかるとその部分に空隙が形成される。電解めっきの条件としては、例えば導電性材料として金属である銅を用いる場合、硫酸銅系溶液を用いるときには、銅の濃度を３０〜１００ｇ／ｌ、硫酸の濃度を５０〜２００ｇ／ｌ、塩素の濃度を３０ｐｐｍ以下とし、液温を３０〜８０℃、電流密度を１〜１００Ａ／ｄｍ²とすればよい。この電解条件を用いると、その一部が活物質層に入り込んだ表面被覆層、或いは集電体にまで達する表面被覆層ないしは活物質層全体に浸透した表面被覆層を容易に形成することができる。別の電解条件としてピロ燐酸銅系溶液を用いることもできる。この場合には、銅の濃度２〜５０ｇ／ｌ、ピロ燐酸カリウムの濃度１００〜７００ｇ／ｌとし、液温を３０〜６０℃、ｐＨを８〜１２、電流密度を１〜１０Ａ／ｄｍ²とすればよい。 This slurry is applied to the surface of the current collector to form an active material layer. The current collector may be manufactured in advance, or may be manufactured in-line as one step in the manufacturing process of the negative electrode of the present invention. When the current collector is manufactured in-line, it is preferably manufactured by electrolytic deposition. The amount of slurry applied to the current collector is preferably such that the thickness of the active material layer after drying is about 1 to 3 times the thickness of the finally obtained active material structure. . After the slurry coating is dried and an active material layer is formed, the current collector on which the active material layer is formed is immersed in a plating bath containing a conductive material having a low ability to form a lithium compound. Under the state, electrolytic plating with the conductive material is performed on the active material layer to form a surface coating layer. By using this method, a large number of fine voids can be easily formed in the surface coating layer. Specifically, as described above, the surface of the active material layer 3 has a micro uneven shape, and an active site on which plating is likely to grow and a site on which the plating is not likely are mixed. When electrolytic plating is performed on the active material layer 3 in such a state, the growth of the plating is uneven, and the particles of the constituent material of the surface coating layer 4 grow in a polycrystalline form. When crystal growth proceeds and adjacent crystals collide with each other, a void is formed in that portion. As the conditions for electrolytic plating, for example, when copper, which is a metal, is used as a conductive material, when using a copper sulfate solution, the concentration of copper is 30 to 100 g / l, the concentration of sulfuric acid is 50 to 200 g / l, The concentration may be 30 ppm or less, the liquid temperature may be 30 to 80 ° C., and the current density may be 1 to 100 A / dm ² . When this electrolysis condition is used, a surface coating layer partially entering the active material layer, or a surface coating layer reaching the current collector or a surface coating layer penetrating the entire active material layer can be easily formed. . As another electrolytic condition, a copper pyrophosphate-based solution can also be used. In this case, the concentration of copper is 2 to 50 g / l, the concentration of potassium pyrophosphate is 100 to 700 g / l, the liquid temperature is 30 to 60 ° C., the pH is 8 to 12, and the current density is 1 to 10 A / dm ² . do it.

このようにして活物質層上に表面被覆層が形成された後、活物質層を表面被覆層ごとプレス加工する。これによって活物質層を圧密化する。圧密化によって、活物質粒子及び導電性炭素材料の粒子の間の空隙を、表面被覆層を構成する導電性材料が埋め、活物質粒子及び導電性炭素材料の粒子が分散された状態となる。またこれらの粒子と表面被覆層とが密着して、電子伝導性が付与される。更に、活物質層に存在する空隙の程度が適度に調整され、活物質粒子リチウムを吸脱蔵して膨張収縮することに起因する応力が緩和される。十分な電子伝導性を得る観点から、プレス加工による圧密化は、プレス加工後の活物質層と表面被覆層との厚みの総和が、プレス加工前の９０％以下、好ましくは８０％以下となるように行うことが好ましい。プレス加工には、例えばロールプレス機を用いることができる。 After the surface coating layer is formed on the active material layer in this way, the active material layer is pressed together with the surface coating layer. As a result, the active material layer is consolidated. Due to the consolidation, the gap between the active material particles and the conductive carbon material particles is filled with the conductive material constituting the surface coating layer, and the active material particles and the conductive carbon material particles are dispersed. In addition, these particles and the surface coating layer are in close contact with each other to impart electron conductivity. Furthermore, the degree of voids existing in the active material layer is appropriately adjusted, and the stress due to the active material particle lithium being absorbed and desorbed and expanded and contracted is relieved. From the viewpoint of obtaining sufficient electron conductivity, the consolidation by press working is such that the total thickness of the active material layer and the surface coating layer after the press work is 90% or less, preferably 80% or less before the press work. It is preferable to do so. For the press working, for example, a roll press machine can be used.

本製造方法においては、活物質層上に電解めっきを行うに先立ち、該活物質層をプレス加工することが好ましい（このプレス加工を、先に述べたプレス加工と区別する意味で前プレス加工と呼ぶ）。前プレス加工を行うことで、活物質層と集電体との剥離が防止され、また活物質粒子が表面被覆層の表面に露出することが防止される。その結果、活物質粒子の脱落に起因する電池のサイクル寿命の劣化を防ぐことができる。前プレス加工の条件としては、前プレス加工後の活物質層の厚みが、前プレス加工前の活物質層の厚みの９５％以下、特に９０％以下となるような条件であることが好ましい。 In this production method, it is preferable to press the active material layer prior to electrolytic plating on the active material layer (this press processing is different from the pre-press processing in the sense of distinguishing from the press processing described above). Call). By performing the pre-press processing, peeling between the active material layer and the current collector is prevented, and the active material particles are prevented from being exposed on the surface of the surface coating layer. As a result, it is possible to prevent the deterioration of the cycle life of the battery due to the falling off of the active material particles. The conditions for the pre-pressing are preferably such that the thickness of the active material layer after the pre-pressing is 95% or less, particularly 90% or less of the thickness of the active material layer before the pre-pressing.

なお本製造方法においては、表面被覆層の形成に電解めっきを用いたが、これに代えてスパッター法、化学気相蒸着法、又は物理気相蒸着法を用いることもできる。また表面被覆層が金属箔の圧延やメッシュ金属箔の圧延、或いは導電性プラスチックの圧延によって形成されていてもよい。これらの方法を用いる場合には、先に述べたプレス加工の条件をコントロールして表面被覆層に微細空隙を形成する。 In this manufacturing method, electrolytic plating is used to form the surface coating layer, but instead, sputtering, chemical vapor deposition, or physical vapor deposition may be used. The surface coating layer may be formed by rolling metal foil, rolling metal mesh foil, or rolling conductive plastic. When these methods are used, fine voids are formed in the surface coating layer by controlling the press working conditions described above.

このようにして得られた本発明の負極は、公知の正極、セパレータ、非水系電解液と共に用いられて非水電解液二次電池となされる。正極は、正極活物質並びに必要により導電剤及び結着剤を適当な溶媒に懸濁し、正極合剤を作製し、これを集電体に塗布、乾燥した後、ロール圧延、プレスし、さらに裁断、打ち抜きすることにより得られる。正極活物質としては、リチウムニッケル複合酸化物、リチウムマンガン複合酸化物、リチウムコバルト複合酸化物等の従来公知の正極活物質が用いられる。セパレーターとしては、合成樹脂製不織布、ポリエチレン又はポリプロピレン多孔質フイルム等が好ましく用いられる。非水電解液は、リチウム二次電池の場合、支持電解質であるリチウム塩を有機溶媒に溶解した溶液からなる。リチウム塩としては、例えば、ＬｉＣ１Ｏ₄、ＬｉＡ１Ｃｌ₄、ＬｉＰＦ₆、ＬｉＡｓＦ₆、ＬｉＳｂＦ₆、ＬｉＳＣＮ、ＬｉＣ１、ＬｉＢｒ、ＬｉＩ、ＬｉＣＦ₃ＳＯ₃、ＬｉＣ₄Ｆ₉ＳＯ₃等が例示される。 The negative electrode of the present invention thus obtained is used with a known positive electrode, separator, and non-aqueous electrolyte solution to form a non-aqueous electrolyte secondary battery. The positive electrode is prepared by suspending a positive electrode active material and, if necessary, a conductive agent and a binder in an appropriate solvent to prepare a positive electrode mixture, applying this to a current collector, drying it, then rolling and pressing, and further cutting. It is obtained by punching. As the positive electrode active material, conventionally known positive electrode active materials such as lithium nickel composite oxide, lithium manganese composite oxide, and lithium cobalt composite oxide are used. As the separator, a synthetic resin nonwoven fabric, polyethylene, polypropylene porous film, or the like is preferably used. In the case of a lithium secondary battery, the nonaqueous electrolytic solution is a solution in which a lithium salt that is a supporting electrolyte is dissolved in an organic solvent. The lithium salt, for _{_{example, LiC1O 4, LiA1Cl 4, LiPF}} 6, LiAsF 6, LiSbF 6, LiSCN, LiC1, LiBr, LiI, etc. _{_{_{LiCF 3 SO 3, LiC 4 F}}} 9 SO 3 are exemplified.

本発明は前記実施形態に制限されない。例えば集電体としては、多数の開孔を有するパンチングメタル若しくはエキスパンドメタル又は発泡ニッケルなどの金属発泡体を用いることができる。パンチングメタルやエキスパンドメタルを用いる場合には、開孔の面積は０．０００１〜４ｍｍ²、特に０．００２〜１ｍｍ²程度であることが好ましい。パンチングメタルやエキスパンドメタルを用いる場合には、開孔の部分に活物質層が優先的に形成され、形成された活物質層の表面及びパンチングメタルやエキスパンドメタルの表面に、表面被覆層が形成される。一方、金属発泡体を用いる場合には、発泡体のセル内が活物質層で満たされ、該活物質層の表面及び金属発泡体の表面に、表面被覆層が形成される。 The present invention is not limited to the embodiment. For example, as the current collector, a metal foam such as punched metal or expanded metal having a large number of openings or foamed nickel can be used. When using a punching metal or an expanded metal, the area of the opening is preferably about 0.0001 to ⁴ mm ² , particularly about 0.002 to ¹ mm ² . When punching metal or expanded metal is used, an active material layer is preferentially formed in the opening portion, and a surface coating layer is formed on the surface of the formed active material layer and the surface of the punching metal or expanded metal. The On the other hand, when a metal foam is used, the inside of the cell of the foam is filled with the active material layer, and a surface coating layer is formed on the surface of the active material layer and the surface of the metal foam.

また図２に示す断面写真像では、集電体２の一面にのみ活物質構造体５が形成された状態が示されているが、活物質構造体は集電体の両面に形成されていてもよい。 2 shows a state in which the active material structure 5 is formed only on one surface of the current collector 2, but the active material structure is formed on both surfaces of the current collector. Also good.

以下、実施例により本発明を更に詳細に説明する。しかしながら本発明の範囲はかかる実施例に制限されるものではない。以下の例中、特に断らない限り「％」は「重量％」を意味する。 Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. In the following examples, “%” means “% by weight” unless otherwise specified.

〔実施例１〕
（１）活物質粒子の製造
シリコン９０％、ニッケル１０％を含む１４００℃の溶湯を、銅製の鋳型に流し込んで、急冷されたシリコン−ニッケル合金のインゴットを得た。このインゴットを粉砕し篩い分けして、粒径０．１〜１０μｍのシリコン−ニッケル合金粒子を得た。このシリコン−ニッケル合金粒子８０％及びニッケル粒子（粒径３０μｍ）２０％を混合し、アトライターによってこれらの粒子の混合及び粉砕を同時に行った。これによってシリコン−ニッケル合金とニッケルとが均一に混ざり合った混合粒子を得た。この混合粒子の最大粒径は１μｍであり、Ｄ₅₀値は０．８μｍであった。 [Example 1]
(1) Production of Active Material Particles A 1400 ° C. molten metal containing 90% silicon and 10% nickel was poured into a copper mold to obtain a rapidly cooled silicon-nickel alloy ingot. The ingot was pulverized and sieved to obtain silicon-nickel alloy particles having a particle size of 0.1 to 10 μm. The silicon-nickel alloy particles 80% and the nickel particles (particle size 30 μm) 20% were mixed, and these particles were mixed and pulverized at the same time by an attritor. As a result, mixed particles in which the silicon-nickel alloy and nickel were uniformly mixed were obtained. The maximum particle size of the mixed particles was 1 μm, and the D ₅₀ value was 0.8 μm.

（２）スラリーの調製
以下の組成のスラリーを調製した。
・前記（１）で得られた混合粒子１６％
・アセチレンブラック（粒径０．１μｍ）２％
・結着剤（ポリビニリデンフルオライド）２％
・希釈溶媒（Ｎ−メチルピロリドン）８０％ (2) Preparation of slurry A slurry having the following composition was prepared.
-16% of mixed particles obtained in (1) above
-Acetylene black (particle size 0.1 μm) 2%
・ Binder (polyvinylidene fluoride) 2%
・ Dilution solvent (N-methylpyrrolidone) 80%

（３）活物質層の形成
調製されたスラリーを、厚さ３５μｍの銅箔上に塗工し乾燥させた。乾燥後の活物質層の厚みは６０μｍであった。乾燥後の活物質層を前プレス加工した。 (3) Formation of active material layer The prepared slurry was coated on a 35 μm thick copper foil and dried. The thickness of the active material layer after drying was 60 μm. The active material layer after drying was pre-pressed.

（４）表面被覆層の形成
活物質層が形成された銅箔を、以下の組成を有するめっき浴中に浸漬し、活物質層上に電解めっきを行った。
・ニッケル５０ｇ／ｌ
・硫酸６０ｇ／ｌ
・浴温４０℃
表面被覆層の形成後、銅箔をめっき浴から引き上げ、次いで活物質層を表面被覆層ごとロールプレス加工し圧密化した。このようにして得られた活物質構造体の厚みは、電子顕微鏡観察の結果２３μｍであった。また化学分析の結果、活物質構造体における活物質粒子の量は４０％、アセチレンブラックの量は５％であった。このようにして得られた負極について、電子顕微鏡観察で微細空隙の存在の有無を判定したところ、その存在が確認された。 (4) Formation of surface coating layer The copper foil in which the active material layer was formed was immersed in the plating bath which has the following compositions, and the electroplating was performed on the active material layer.
・ Nickel 50g / l
・ Sulfuric acid 60g / l
・ Bath temperature 40 ℃
After forming the surface coating layer, the copper foil was pulled up from the plating bath, and then the active material layer was roll-pressed together with the surface coating layer to be consolidated. The thickness of the active material structure thus obtained was 23 μm as a result of observation with an electron microscope. As a result of chemical analysis, the amount of active material particles in the active material structure was 40%, and the amount of acetylene black was 5%. About the negative electrode obtained in this way, when the presence or absence of the fine space | gap was determined by electron microscope observation, the presence was confirmed.

〔実施例２〜４〕
活物質粒子として表１に示す組成のものを用いる以外は実施例１と同様にして負極を得た。得られた負極について、実施例１と同様の方法で微細空隙の存在の有無を判定したところ、その存在が確認された。 [Examples 2 to 4]
A negative electrode was obtained in the same manner as in Example 1 except that the active material particles having the composition shown in Table 1 were used. About the obtained negative electrode, when the presence or absence of the fine space | gap was determined by the method similar to Example 1, the presence was confirmed.

〔実施例５〕
集電体として厚さ３５μｍの銅箔上に２μｍのニッケルめっきを施した。このニッケルめっき上に実施例１と同様にして活物質層及び表面被覆層を形成した。但し活物質層に含まれる活物質粒子として表１に示す組成のものを用いた。このようにして負極を得た。得られた負極について、実施例１と同様の方法で微細空隙の存在の有無を判定したところ、その存在が確認された。 Example 5
As a current collector, 2 μm nickel plating was applied on a 35 μm thick copper foil. An active material layer and a surface coating layer were formed on the nickel plating in the same manner as in Example 1. However, the active material particles contained in the active material layer had the compositions shown in Table 1. In this way, a negative electrode was obtained. About the obtained negative electrode, when the presence or absence of the fine space | gap was determined by the method similar to Example 1, the presence was confirmed.

〔実施例６〕
集電体として厚さ４００μｍのニッケル発泡体を用いた。この発泡体における気泡の平均径は２０μｍであった。表１に示す組成の活物質粒子を含む以外は実施例１と同様のスラリーを調製し、該スラリーを発泡体に染み込ませた。この発泡体を、実施例１で用いためっき浴と同様の組成を有するめっき浴中に浸漬し、電解めっきを行い負極を得た。得られた負極について、実施例１と同様の方法で微細空隙の存在の有無を判定したところ、その存在が確認された。 Example 6
A nickel foam having a thickness of 400 μm was used as a current collector. The average diameter of the bubbles in this foam was 20 μm. A slurry similar to that of Example 1 was prepared except that the active material particles having the composition shown in Table 1 were included, and the slurry was impregnated into the foam. This foam was immersed in a plating bath having the same composition as the plating bath used in Example 1, and electroplated to obtain a negative electrode. About the obtained negative electrode, when the presence or absence of the fine space | gap was determined by the method similar to Example 1, the presence was confirmed.

〔実施例７〕
集電体として厚さ４０μｍの銅製エキスパンドメタルを用いた。このエキスパンドメタルの各開孔の面積は０．０１ｍｍ²であった。表１に示す組成の活物質粒子を含む以外は実施例１と同様のスラリーを調製し、該スラリーをエキスパンドメタルに染み込ませた。このエキスパンドメタルを、実施例１で用いためっき浴と同様の組成を有するめっき浴中に浸漬し、電解めっきを行い負極を得た。得られた負極について、実施例１と同様の方法で微細空隙の存在の有無を判定したところ、その存在が確認された。 Example 7
A copper expanded metal having a thickness of 40 μm was used as a current collector. The area of each opening of this expanded metal was 0.01 mm ² . A slurry similar to that of Example 1 was prepared except that the active material particles having the composition shown in Table 1 were included, and the slurry was impregnated into the expanded metal. This expanded metal was immersed in a plating bath having the same composition as the plating bath used in Example 1, and electroplated to obtain a negative electrode. About the obtained negative electrode, when the presence or absence of the fine space | gap was determined by the method similar to Example 1, the presence was confirmed.

〔比較例１〕
粒径１０μｍのグラファイト粉末、結着剤（ＰＶＤＦ）及び希釈溶媒（Ｎ−メチルピロリドン）を混練してスラリーとなし、厚さ３０μｍの銅箔上に塗工し乾燥させた後プレス加工し負極を得た。プレス加工後のグラファイト塗膜の厚みは２０μｍであった。 [Comparative Example 1]
A graphite powder having a particle size of 10 μm, a binder (PVDF) and a diluting solvent (N-methylpyrrolidone) are kneaded to form a slurry, which is coated on a 30 μm thick copper foil, dried and then pressed to form a negative electrode. Obtained. The thickness of the graphite coating after pressing was 20 μm.

〔比較例２〕
グラファイト粉末に代えて粒径５μｍのシリコン粒子を用いる以外は比較例１と同様にして負極を得た。 [Comparative Example 2]
A negative electrode was obtained in the same manner as in Comparative Example 1 except that silicon particles having a particle size of 5 μm were used in place of the graphite powder.

〔性能評価〕
実施例及び比較例で得られた負極を用いて以下の通り非水電解液二次電池を作製した。以下の方法で不可逆容量、充電時体積容量密度、１０サイクル時の充放電効率及び５０サイクル容量維持率を測定した。これらの結果を以下の表１に示す。 [Performance evaluation]
Using the negative electrodes obtained in Examples and Comparative Examples, non-aqueous electrolyte secondary batteries were produced as follows. The following methods were used to measure irreversible capacity, volumetric capacity density during charging, charge / discharge efficiency during 10 cycles, and 50 cycle capacity retention. These results are shown in Table 1 below.

〔非水電解液二次電池の作製〕
対極として金属リチウムを用い、また作用極として前記で得られた負極を用い、両極をセパレーターを介して対向させた。更に非水電解液としてＬｉＰＦ₆／エチレンカーボネートとジエチルカーボネートの混合溶液（１：１容量比）を用いて通常の方法によって非水電解液二次電池を作製した。 [Production of non-aqueous electrolyte secondary battery]
Metal lithium was used as the counter electrode, and the negative electrode obtained above was used as the working electrode, and both electrodes were opposed to each other through a separator. Further, a nonaqueous electrolyte secondary battery was produced by a conventional method using a mixed solution (1: 1 volume ratio) of LiPF ₆ / ethylene carbonate and diethyl carbonate as the nonaqueous electrolyte.

〔不可逆容量〕
不可逆容量（％）＝（１−初回放電容量／初回充電容量）×１００
すなわち、充電したが放電できず、活物質に残存した容量を示す。 [Irreversible capacity]
Irreversible capacity (%) = (1−initial discharge capacity / initial charge capacity) × 100
That is, it indicates the capacity remaining in the active material after being charged but not discharged.

〔容量密度〕
初回の放電容量を示す。単位はｍＡｈ／ｇである。 [Capacity density]
Indicates the initial discharge capacity. The unit is mAh / g.

〔１０サイクル時の充放電効率〕
１０サイクル時の充放電効率（％）＝１０サイクル目の放電容量／１０サイクル目の充電容量×１００ [Charging / discharging efficiency during 10 cycles]
Charging / discharging efficiency at 10th cycle (%) = 10th cycle discharge capacity / 10th cycle charge capacity × 100

〔５０サイクル容量維持率〕
５０サイクル容量維持率（％）＝５０サイクル目の放電容量／最大放電容量×１００ [50 cycle capacity maintenance rate]
50 cycle capacity retention rate (%) = 50th cycle discharge capacity / maximum discharge capacity × 100

表１に示す結果から明らかなように、各実施例で得られた負極を用いた二次電池は、比較例の負極を用いた二次電池に比べて不可逆容量が低く、容量密度が高く、充放電効率及び容量維持率も高いことが判る。なお表には示していないが、実施例１〜７で得られた負極の断面を電子顕微鏡観察したところ、図２に示す構造を有していた。 As is clear from the results shown in Table 1, the secondary battery using the negative electrode obtained in each example has a lower irreversible capacity and a higher capacity density than the secondary battery using the negative electrode of the comparative example, It can be seen that the charge / discharge efficiency and the capacity maintenance rate are also high. Although not shown in the table, when the cross sections of the negative electrodes obtained in Examples 1 to 7 were observed with an electron microscope, they had the structure shown in FIG.

本発明の負極の一実施形態の表面を示す電子顕微鏡写真像である。It is an electron micrograph image which shows the surface of one embodiment of the negative electrode of the present invention. 本発明の負極の一実施形態の断面を示す電子顕微鏡写真像である。It is an electron micrograph image which shows the cross section of one Embodiment of the negative electrode of this invention.

Explanation of symbols

１負極
２集電体
３活物質層
４表面被覆層
５活物質構造体
６微細空隙
７活物質粒子 DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Current collector 3 Active material layer 4 Surface coating layer 5 Active material structure 6 Fine void 7 Active material particle

Claims

An active material structure comprising a layer containing active material particles made of a silicon-based or tin-based material and a surface coating layer positioned on the layer is formed on one or both surfaces of the current collector. A negative electrode for a water electrolyte secondary battery,
The surface coating layer has a thickness of 0.3 to 50 μm,
In the surface coating layer, a number of fine voids extending in the thickness direction of the surface coating layer and capable of penetrating the non-aqueous electrolyte are formed,
The negative electrode for a non-aqueous electrolyte secondary battery, wherein the surface coating layer is made of a conductive material having a low lithium compound forming ability.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the constituent material of the surface coating layer enters a layer containing particles of the active material, or the introduced material reaches the current collector. Negative electrode.

The negative electrode for a non-aqueous electrolyte secondary battery according to claim 2, wherein the constituent material of the surface coating layer penetrates the entire layer including the particles of the active material.

The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the particles of the active material have a maximum particle size of 50 μm or less.

The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the particles of the active material are particles of silicon or tin alone.

The particles of the active material are at least mixed particles of silicon or tin and carbon, and the mixed particles contain 10 to 90% by weight of silicon or tin and 90 to 10% by weight of carbon. The negative electrode for nonaqueous electrolyte secondary batteries in any one.

The particles of the active material are mixed particles of silicon or tin and metal, and the mixed particles include 30 to 99.9% by weight of silicon or tin and 0.1 to 70% by weight of Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except when the particles contain tin), Si (except when the particles contain silicon), In, V, The nonaqueous electrolytic solution according to claim 1, comprising at least one element selected from the group consisting of Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd, and Nd. Negative electrode for secondary battery.

The particles of the active material are silicon compound or tin compound particles, and the silicon compound or tin compound particles are 30 to 99.9% by weight of silicon or tin and 0.1 to 70% by weight of Cu, Ag. , Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except when the particles include tin), Si (except when the particles include silicon), In The non-element according to claim 1, comprising one or more elements selected from the group consisting of V, Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd, and Nd. Negative electrode for water electrolyte secondary battery.

The particles of the active material are mixed particles of silicon compound or tin compound particles and metal particles,
The mixed particles include 30-99.9 wt% silicon compound or tin compound particles and 0.1-70 wt% Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge. , Sn (except when the compound particles contain tin), Si (except when the compound particles contain silicon), In, V, Ti, Y, Zr, Nb, Ta, W Including particles of one or more elements selected from the group consisting of La, Ce, Pr, Pd and Nd,
The compound particles comprise 30-99.9 wt% silicon or tin and 0.1-70 wt% Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn ( However, except that the compound particles include tin), Si (except where the compound particles include silicon), In, V, Ti, Y, Zr, Nb, Ta, W, La, The negative electrode for a nonaqueous electrolyte secondary battery according to claim 1, comprising one or more elements selected from the group consisting of Ce, Pr, Pd, and Nd.

The particles of the active material are particles formed by coating a metal on the surface of particles of silicon alone or tin alone, and the metals are Cu, Ag, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except when the particles contain tin), Si (except when the particles contain silicon), In, V, Ti, Y, Zr, Nb, Ta, W, La, Ce, 2. One or more elements selected from the group consisting of Pr, Pd and Nd, wherein the particles comprise 30-99.9% by weight silicon or tin and 0.1-70% by weight of the metal. The negative electrode for nonaqueous electrolyte secondary batteries in any one of -5.

The layer containing the active material particles is formed by applying a slurry containing the active material particles to the surface of the current collector. Negative electrode for secondary battery.

Non-aqueous electrolyte secondary battery negative electrode according to any one of claims 1 to 11 electrodes overall thickness of 20 to 100 [mu] m.

Non-aqueous electrolyte secondary battery negative electrode according to any of the claims 1 to 11 the thickness of the active material structure is a. 2 to 50 [mu] m comprising a layer and the surface coating layer comprising particles of pre Kikatsu substance .

The non-aqueous electrolyte secondary solution according to claim 1, wherein the surface coating layer contains one or more elements selected from the group consisting of Cu, Ag, Ni, Co, Cr, Fe, and In. Battery negative electrode.

The negative electrode for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 14, wherein the surface coating layer is formed by electrolytic plating.

The non-aqueous electrolyte 2 according to any one of claims 1 to 15, wherein the current collector is made of a punching metal or an expanded metal having a large number of openings of 0.0001 to ⁴ mm2, or a metal foam. Negative electrode for secondary battery.

The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the current collector is made of an electrolytic metal foil.

An active material structure comprising a layer containing active material particles made of a silicon-based or tin-based material and a surface coating layer positioned on the layer is formed on one or both surfaces of the current collector. A negative electrode for a water electrolyte secondary battery,
In the surface coating layer, a number of fine voids extending in the thickness direction of the surface coating layer and capable of penetrating the non-aqueous electrolyte are formed,
The surface coating layer is made of a conductive material having a low ability to form a lithium compound,
The negative electrode for a non-aqueous electrolyte secondary battery, wherein the constituent material of the surface coating layer penetrates the entire layer including the particles of the active material.

An active material structure comprising a layer containing active material particles made of a silicon-based or tin-based material and a surface coating layer positioned on the layer is formed on one or both surfaces of the current collector. A negative electrode for a water electrolyte secondary battery,
In the surface coating layer, a number of fine voids extending in the thickness direction of the surface coating layer and capable of penetrating the non-aqueous electrolyte are formed,
The surface coating layer is made of a conductive material having a low ability to form a lithium compound,
The particles of the active material are mixed particles of silicon or tin and metal, and the mixed particles include 30 to 99.9% by weight of silicon or tin and 0.1 to 70% by weight of Cu, Ag, Li, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except when the particles contain tin), Si (except when the particles contain silicon), In, V, A negative electrode for a nonaqueous electrolyte secondary battery comprising one or more elements selected from the group consisting of Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd, and Nd.

An active material structure comprising a layer containing active material particles made of a silicon-based or tin-based material and a surface coating layer positioned on the layer is formed on one or both surfaces of the current collector. A negative electrode for a water electrolyte secondary battery,
In the surface coating layer, a number of fine voids extending in the thickness direction of the surface coating layer and capable of penetrating the non-aqueous electrolyte are formed,
The surface coating layer is made of a conductive material having a low ability to form a lithium compound,
The particles of the active material are particles formed by coating a metal on the surface of particles of silicon alone or tin alone, and the metals are Cu, Ag, Ni, Co, Fe, Cr, Zn, B, Al, Ge, Sn (except when the particles contain tin), Si (except when the particles contain silicon), In, V, Ti, Y, Zr, Nb, Ta, W, La, Ce, One or more elements selected from the group consisting of Pr, Pd and Nd, wherein the particles comprise 30-99.9 wt% silicon or tin and 0.1-70 wt% metal. A negative electrode for a non-aqueous electrolyte secondary battery.

A nonaqueous electrolyte secondary battery comprising the negative electrode for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 20 .