JP4880016B2 - Anode material for lithium ion secondary battery - Google Patents

Anode material for lithium ion secondary battery Download PDF

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JP4880016B2
JP4880016B2 JP2009217106A JP2009217106A JP4880016B2 JP 4880016 B2 JP4880016 B2 JP 4880016B2 JP 2009217106 A JP2009217106 A JP 2009217106A JP 2009217106 A JP2009217106 A JP 2009217106A JP 4880016 B2 JP4880016 B2 JP 4880016B2
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silicon oxide
lithium ion
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ion secondary
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信吾 木崎
英明 菅野
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Osaka Titanium Technologies Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Description

本発明は、優れた初期効率およびサイクル特性を有するリチウムイオン二次電池の負極活物質として用いることのできる珪素酸化物を含有するリチウムイオン二次電池用負極材に関する。
The present invention relates to a negative electrode material for a lithium ion secondary battery containing silicon oxide that can be used as a negative electrode active material of a lithium ion secondary battery having excellent initial efficiency and cycle characteristics.

近年、携帯型の電子機器、通信機器等の著しい発展に伴い、経済性と機器の小型化および軽量化の観点から、高エネルギー密度の二次電池の開発が強く要望されている。現在、高エネルギー密度の二次電池として、ニッケルカドミウム電池、ニッケル水素電池、リチウムイオン二次電池およびポリマー電池などがある。このうち、リチウムイオン二次電池は、ニッケルカドミウム電池やニッケル水素電池に比べて格段に高寿命かつ高容量であることから、その需要は電源市場において高い伸びを示している。   In recent years, with the remarkable development of portable electronic devices, communication devices, and the like, there is a strong demand for the development of secondary batteries with high energy density from the viewpoints of economy and downsizing and weight reduction of devices. Currently, high energy density secondary batteries include nickel cadmium batteries, nickel metal hydride batteries, lithium ion secondary batteries, and polymer batteries. Among these, lithium ion secondary batteries have a much longer lifespan and higher capacity than nickel cadmium batteries and nickel metal hydride batteries, and thus the demand thereof has shown high growth in the power supply market.

図１は、リチウムイオン二次電池の構成例を示す図である。リチウムイオン二次電池は、図１に示すように、正極１、負極２および電解液を含浸させたセパレータ３、ならびに正極１と負極２の電気的絶縁性を保つとともに電池内容物を封止するガスケット４から構成されており、充放電によってリチウムイオンが電解液を介して正極１と負極２の間を往復する。   FIG. 1 is a diagram illustrating a configuration example of a lithium ion secondary battery. As shown in FIG. 1, the lithium ion secondary battery maintains the electrical insulation between the positive electrode 1, the negative electrode 2, the separator 3 impregnated with the electrolyte, and the positive electrode 1 and the negative electrode 2 and seals the battery contents. It is comprised from the gasket 4, and lithium ion reciprocates between the positive electrode 1 and the negative electrode 2 through electrolyte solution by charging / discharging.

正極１は、対極ケース１ａと対極集電体１ｂと対極１ｃとで構成され、対極１ｃにはコバルト酸リチウム（ＬｉＣｏＯ3）やマンガンスピネル（ＬｉＭｎ2Ｏ4）が主に使用される。負極２は、作用極ケース２ａと作用極集電体２ｂと作用極２ｃとで構成され、作用極２ｃに用いる負極材は、一般に、リチウムイオンの吸蔵放出が可能な活物質（負極活物質）と導電助剤およびバインダーとで構成される。 The positive electrode 1 includes a counter electrode case 1a, a counter electrode current collector 1b, and a counter electrode 1c. Lithium cobaltate (LiCoO 3 ) and manganese spinel (LiMn 2 O 4 ) are mainly used for the counter electrode 1c. The negative electrode 2 is composed of a working electrode case 2a, a working electrode current collector 2b, and a working electrode 2c, and the negative electrode material used for the working electrode 2c is generally an active material capable of occluding and releasing lithium ions (negative electrode active material). And a conductive assistant and a binder.

従来、リチウムイオン二次電池の負極活物質としては、リチウムとホウ素の複合酸化物、リチウムと遷移金属（Ｖ、Ｆｅ、Ｃｒ、Ｍｏ、Ｎｉなど）との複合酸化物、Ｓｉ、ＧｅまたはＳｎと窒素（Ｎ）および酸素（Ｏ）を含む化合物、化学蒸着により表面を炭素層で被覆したＳｉ粒子などが提案されている。   Conventionally, as a negative electrode active material of a lithium ion secondary battery, a composite oxide of lithium and boron, a composite oxide of lithium and a transition metal (V, Fe, Cr, Mo, Ni, etc.), Si, Ge, or Sn Compounds including nitrogen (N) and oxygen (O), Si particles whose surfaces are covered with a carbon layer by chemical vapor deposition, and the like have been proposed.

しかし、これらの負極活物質はいずれも、充放電容量を向上させ、エネルギー密度を高めることができるものの、充放電に伴って電極上にデンドライトや不働体化合物が生成するため劣化が顕著であり、またはリチウムイオンの吸蔵放出時の膨張や収縮が大きくなる。そのため、これらの負極活物質を用いたリチウムイオン二次電池は、充放電の繰り返しによる放電容量の維持性（以下、「サイクル特性」という）が不十分である。また、製造直後の放電容量と充電容量の比（放電容量／充電容量；以下、「初期効率」という）も十分ではない。   However, all of these negative electrode active materials can improve the charge / discharge capacity and increase the energy density, but due to the formation of dendrites and passive compounds on the electrodes along with charge / discharge, the deterioration is significant, Or the expansion and contraction at the time of occlusion and release of lithium ions increase. Therefore, lithium ion secondary batteries using these negative electrode active materials are insufficient in sustainability of discharge capacity (hereinafter referred to as “cycle characteristics”) due to repeated charge and discharge. Further, the ratio of the discharge capacity to the charge capacity immediately after manufacture (discharge capacity / charge capacity; hereinafter referred to as “initial efficiency”) is not sufficient.

これに対し、負極活物質としてＳｉＯなどの珪素酸化物を用いることが、従来から試みられている。珪素酸化物は、リチウムに対する電極電位が低く（卑であり）、充放電時のリチウムイオンの吸蔵、放出による結晶構造の崩壊や不可逆物質の生成等の劣化がなく、かつ可逆的にリチウムイオンを吸蔵、放出できることから、有効な充放電容量がより大きな負極活物質となり得る。そのため、珪素酸化物を負極活物質として用いることにより、高電圧、高エネルギー密度で、かつ充放電特性およびサイクル特性に優れた二次電池を得ることが期待できる。   On the other hand, it has been attempted to use silicon oxide such as SiO as the negative electrode active material. Silicon oxide has a low electrode potential with respect to lithium (base), and there is no deterioration such as collapse of crystal structure or generation of irreversible substances due to occlusion and release of lithium ions during charge and discharge, and reversible lithium ions. Since it can occlude and release, it can be a negative electrode active material having a larger effective charge / discharge capacity. Therefore, by using silicon oxide as the negative electrode active material, it can be expected to obtain a secondary battery having high voltage, high energy density, and excellent charge / discharge characteristics and cycle characteristics.

上述の負極活物質に関する試みとして、例えば、特許文献１では、リチウムイオンを収蔵放出可能とする珪素酸化物を負極活物質として用いた非水電解質二次電池を提案している。この提案された珪素酸化物は、その結晶構造中または非晶質構造内にリチウムを含有し、非水電解質中で電気化学反応によりリチウムイオンを収蔵および放出可能となるようにリチウムと珪素との複合酸化物を構成する。   As an attempt regarding the above-described negative electrode active material, for example, Patent Document 1 proposes a non-aqueous electrolyte secondary battery using, as a negative electrode active material, silicon oxide capable of storing and releasing lithium ions. This proposed silicon oxide contains lithium in its crystal structure or in an amorphous structure, so that lithium ions can be stored and released by an electrochemical reaction in a non-aqueous electrolyte. A composite oxide is formed.

特許文献１で提案された二次電池では、高容量の負極活物質を得ることができる。しかし、本発明者らの検討によれば、初回の充放電時における不可逆容量が大きく（すなわち、初期効率が十分ではなく）、また、サイクル特性が実用レベルに十分達していないことから、実用化には改良すべき余地がある。   In the secondary battery proposed in Patent Document 1, a high-capacity negative electrode active material can be obtained. However, according to the study by the present inventors, the irreversible capacity at the time of the first charge / discharge is large (that is, the initial efficiency is not sufficient), and the cycle characteristics have not sufficiently reached the practical level. There is room for improvement.

特許第２９９７７４１号公報Japanese Patent No. 2999741

上述のように、これまでに提案されている珪素酸化物を用いた負極活物質では、リチウムイオン二次電池の初期効率およびサイクル特性について、実用レベルに達していない問題があった。   As described above, the negative electrode active materials using silicon oxides proposed so far have a problem that the initial efficiency and cycle characteristics of the lithium ion secondary battery have not reached the practical level.

本発明は、これらの問題に鑑みてなされたものであり、優れた初期効率およびサイクル特性を有するリチウムイオン二次電池の負極活物質を用いたリチウムイオン二次電池用負極材を提供することを目的としている。
The present invention has been made in view of these problems, to provide a negative active material quality of the negative electrode material for a lithium ion secondary battery using the lithium ion secondary battery having excellent initial efficiency and cycle characteristics It is an object.

通常、リチウムイオン二次電池の負極活物質に用いられる粉末状の珪素酸化物を製造する場合は、一定の大きさを有する珪素酸化物原料を粉砕することにより、粉末状の珪素酸化物にする。   Usually, when producing a powdered silicon oxide used for a negative electrode active material of a lithium ion secondary battery, a silicon oxide raw material having a certain size is pulverized to obtain a powdered silicon oxide. .

ここで、粉末状の珪素酸化物の表面には、ＳｉＯ2膜が形成されており、珪素酸化物をリチウムイオン二次電池の負極活物質として用いた場合に、ＳｉＯ2膜は絶縁体となり抵抗を生じさせるばかりか、電解質を分解する。このため、珪素酸化物の微粉表面に形成されるＳｉＯ2膜は、リチウムイオン二次電池の初期効率およびサイクル特性を低下させる要因となる。 Here, a SiO 2 film is formed on the surface of the powdered silicon oxide, and when the silicon oxide is used as a negative electrode active material of a lithium ion secondary battery, the SiO 2 film becomes an insulator and has a resistance. Not only does this cause the electrolyte to decompose. For this reason, the SiO 2 film formed on the surface of the fine powder of silicon oxide becomes a factor that deteriorates the initial efficiency and cycle characteristics of the lithium ion secondary battery.

粉砕により粉末状とした珪素酸化物は、その際に発生する粒径１μｍ以下の微粉を多く含有する。珪素酸化物に微粉が多く含まれると、単位質量あたりの表面積が増加、すなわち、表面に形成されるＳｉＯ2膜を多く含むこととなる。したがって、珪素酸化物を製造する場合は、リチウムイオン二次電池の負極活物質として用いた場合に初期効率およびサイクル特性が低下するのを防ぐために、珪素酸化物から微粉を除去する必要がある。 The silicon oxide powdered by pulverization contains a large amount of fine powder having a particle diameter of 1 μm or less generated at that time. When silicon oxide contains a lot of fine powder, the surface area per unit mass increases, that is, it contains a lot of SiO 2 film formed on the surface. Therefore, when manufacturing silicon oxide, it is necessary to remove fine powder from silicon oxide in order to prevent deterioration in initial efficiency and cycle characteristics when used as a negative electrode active material of a lithium ion secondary battery.

珪素酸化物から微粉を除去するために、篩による乾式分級を用いると、粉末状の珪素酸化物は流動性が低いので、時間を要し、効率が悪い。また、乾式分級時に粒子同士が接触した際の衝撃により、珪素酸化物が粉砕され、さらに微粉が発生する。   When dry classification using a sieve is used to remove fine powder from silicon oxide, powdered silicon oxide has low fluidity, and thus requires time and is inefficient. Further, the silicon oxide is pulverized and fine powder is generated by the impact when the particles come into contact with each other during dry classification.

微粉の珪素酸化物を除去するために、アルコール等の有機溶剤に分散させた後、湿式分級を行うこともできる。この場合、湿式分級後に有機溶剤を取り除くために、珪素酸化物に熱処理を施す必要がある。熱処理を施すと珪素酸化物が変質し、粒径が１μｍを超える珪素酸化物の表面に形成されたＳｉＯ2膜が成長するので、リチウムイオン二次電池の負極活物質に用いた場合に、初期効率およびサイクル特性が低下する。 In order to remove fine silicon oxide, wet classification may be performed after dispersion in an organic solvent such as alcohol. In this case, it is necessary to heat-treat silicon oxide in order to remove the organic solvent after wet classification. When heat treatment is performed, the silicon oxide changes in quality, and a SiO 2 film formed on the surface of the silicon oxide having a particle size exceeding 1 μm grows. Therefore, when used as a negative electrode active material for a lithium ion secondary battery, Efficiency and cycle characteristics are reduced.

そこで、本発明者らは、粉末状の珪素酸化物を水に分散させた後、湿式分級により微粉を除去し、その後、雰囲気温度が１２０℃以下で乾燥させることにより、粒径が１μｍを超える珪素酸化物の表面に形成されたＳｉＯ2膜が成長することなく、１μｍ以下の微粉を効率的に除去できることを知見した。この場合、粉末状の珪素酸化物を分散させる水として、上水や工業用水を用いると、上水や工業用水に含まれる金属不純物が珪素酸化物に付着し、リチウムイオン二次電池の負極活物質に用いた場合に、電解質と反応または電解質を分解し、初期効率またはサイクル特性を低下させるおそれがある。 Therefore, the present inventors disperse the powdered silicon oxide in water, then remove the fine powder by wet classification, and then dry it at an atmospheric temperature of 120 ° C. or less, whereby the particle size exceeds 1 μm. It has been found that fine powders of 1 μm or less can be efficiently removed without the growth of the SiO 2 film formed on the surface of the silicon oxide. In this case, when water or industrial water is used as water for dispersing the powdered silicon oxide, metal impurities contained in the water or industrial water adhere to the silicon oxide, and the negative electrode active of the lithium ion secondary battery. When used as a substance, there is a risk of degrading the initial reaction or cycle characteristics by decomposing the electrolyte and reaction or electrolyte.

さらに、本発明者らは、湿式分級を行う際に、粉末状の珪素酸化物を分散させる水として、抵抗率が３ＭΩ・ｃｍ以上である水を用いることにより、粒径が１μｍを超える珪素酸化物の表面に形成されたＳｉＯ2膜が成長することなく、１μｍ以下の微粉を効率的に除去でき、珪素酸化物に金属不純物が付着することがないことを知見した。
Furthermore, the present inventors use silicon water having a resistivity of 3 MΩ · cm or more as water to disperse the powdered silicon oxide when performing wet classification, whereby silicon oxide having a particle size exceeding 1 μm. It has been found that fine powders of 1 μm or less can be efficiently removed without the growth of the SiO 2 film formed on the surface of the object, and metal impurities do not adhere to silicon oxide.

本発明は、上記の知見に基づいて完成したものであり、下記のリチウムイオン二次電池用負極材を要旨としている。
The present invention has been completed based on the above findings, and the gist of the negative electrode material for a lithium ion secondary battery under SL.

化学式ＳｉＯx （０．７＜ｘ＜１．３）で表される粉末状の珪素酸化物を負極活物質として２０質量％以上含有するリチウムイオン二次電池用負極材であって、前記珪素酸化物が、粒度の積算分布曲線における累積頻度９０％の粒径Ｄ90が３１μｍ以下であり、かつ粒径１μｍ以下である微粉の含有率を抵抗率が３ＭΩ・ｃｍ以上である水に分散させて行う湿式分級により５質量％以下とし、さらに前記珪素酸化物が、粒度の積算分布曲線における累積頻度９０％の粒径Ｄ 90 と、粒度の積算分布曲線における累積頻度１０％の粒径Ｄ 10 との比であるＤ 90 ／Ｄ 10 が２．４以下で、かつ、粒表面の酸素と珪素とのモル比であるＯ／Ｓｉが０．６〜１．８であることを特徴とするリチウムイオン二次電池用負極材である。
A chemical formula SiO x (0.7 <x <1.3 ) the negative electrode material for a lithium ion secondary battery containing more than 20 wt% of powdery silicon oxide represented by a negative electrode active material, the silicon oxide, and a cumulative frequency of 90% particle size D 90 in the cumulative distribution curve of the particle size is 31μm or less, and dispersed the content ratio of fine powder is a particle size 1μm or less in water resistivity is 3 milliohms · cm or more And 5 wt% or less by wet classification , and the silicon oxide has a particle size D 90 with a cumulative frequency of 90% in the cumulative particle size distribution curve and a particle size D with a cumulative frequency of 10% in the cumulative particle size distribution curve. in D 90 / D 10 which is the ratio of the 10 2.4 or less, and a molar ratio of oxygen to silicon particle surface O / Si is characterized in that it is a 0.6 to 1.8 It is a negative electrode material for lithium ion secondary batteries .

本発明において、「リチウムイオン二次電池用負極材が、珪素酸化物をｘ質量％以上含有する」とは、リチウムイオン二次電池用負極材の構成材料のうち、バインダーを除いた構成材料の合計質量に対する珪素酸化物の質量の比率がｘ％以上であることを意味する。   In the present invention, “the negative electrode material for a lithium ion secondary battery contains x mass% or more of silicon oxide” means that the constituent material of the negative electrode material for a lithium ion secondary battery excluding the binder. It means that the ratio of the mass of silicon oxide to the total mass is x% or more.

本発明のリチウムイオン二次電池用負極材に用いる珪素酸化物は、粒度の積算分布曲線における累積頻度９０％の粒径Ｄ90が３１μｍ以下で、かつ粒径１μｍ以下である微粉の含有率が５質量％以下であり、さらに粒度の積算分布曲線における累積頻度９０％の粒径Ｄ 90 と、粒度の積算分布曲線における累積頻度１０％の粒径Ｄ 10 との比であるＤ 90 ／Ｄ 10 が２．４以下であることにより、粉末状の珪素酸化物の単位質量あたりの表面積を減少させて、珪素酸化物の表面に形成されるＳｉＯ2膜の含有量を低減できるとともに、珪素酸化物を粒径が揃った状態にできる。
Silicon oxide used in the negative electrode material for a lithium ion secondary battery of the present invention is a cumulative frequency of 90% particle size D 90 in the cumulative distribution curve of the particle size is 31μm or less, and the content of fine powder is a particle size 1μm or less D 90 / D 10, which is a ratio of the particle size D 90 having a cumulative frequency of 90% in the cumulative distribution curve of particle size to 5% by mass or less and the particle size D 10 having a cumulative frequency of 10% in the cumulative distribution curve of particle size. Is 2.4 or less, the surface area per unit mass of the powdered silicon oxide can be reduced, and the content of the SiO 2 film formed on the surface of the silicon oxide can be reduced . Can be made to have a uniform particle size .

本発明のリチウムイオン二次電池用負極材は、上述のＳｉＯ2の含有率が低減されるとともに、粒径が揃った状態の珪素酸化物を負極活物質として用いることにより、リチウムイオン二次電池に適用すれば、抵抗を低減できるとともに、電解質の分解を低減でき、さらに負極材が均質となるので、優れた初期効率およびサイクル特性を有するリチウムイオン二次電池を得ることができる。
The negative electrode material for a lithium ion secondary battery of the present invention, by using SiO 2 content above is reduced Rutotomoni, a silicon oxide in a state where the particle diameter is uniform as a negative electrode active material, a lithium ion secondary battery When applied to, the resistance can be reduced, the decomposition of the electrolyte can be reduced , and the negative electrode material becomes homogeneous, so that a lithium ion secondary battery having excellent initial efficiency and cycle characteristics can be obtained.

リチウムイオン二次電池の構成例を示す図である。It is a figure which shows the structural example of a lithium ion secondary battery. 珪素酸化物の製造装置の構成例を示す図である。It is a figure which shows the structural example of the manufacturing apparatus of a silicon oxide.

以下に、本発明のリチウムイオン二次電池用負極材に用いる珪素酸化物および本発明のリチウムイオン二次電池用負極材を図面に基づいて説明する。
Below, the silicon oxide used for the negative electrode material for lithium ion secondary batteries of this invention and the negative electrode material for lithium ion secondary batteries of this invention are demonstrated based on drawing.

［珪素酸化物について］
本発明のリチウムイオン二次電池用負極材に用いる珪素酸化物は、化学式ＳｉＯxで表される粉末状の珪素酸化物であって、粒度の積算分布曲線における累積頻度９０％の粒径Ｄ90が３１μｍ以下で、かつ粒径１μｍ以下である微粉の含有率が５質量％以下であることを特徴とする珪素酸化物である。
[About silicon oxide]
The silicon oxide used for the negative electrode material for a lithium ion secondary battery of the present invention is a powdered silicon oxide represented by the chemical formula SiO x and has a particle size D 90 with a cumulative frequency of 90% in the cumulative distribution curve of particle size. Is 31 μm or less and the content of fine powder having a particle size of 1 μm or less is 5% by mass or less.

微粉の含有率が５質量％を超えると、単位質量あたりの表面積が増加、すなわち、表面に形成されるＳｉＯ2膜の含有量が増加するので、リチウムイオン二次電池の負極活物質に用いた場合に、初期効率およびサイクル特性が低下する。このため、本発明のリチウムイオン二次電池用負極材に用いる珪素酸化物は、粒径１μｍ以下である微粉の含有率が５質量％以下とする。
When the content of fine powder exceeds 5% by mass, the surface area per unit mass increases, that is, the content of the SiO 2 film formed on the surface increases, so it was used as the negative electrode active material of the lithium ion secondary battery. In some cases, the initial efficiency and cycle characteristics are degraded. For this reason, the silicon oxide used for the negative electrode material for lithium ion secondary batteries of the present invention has a content of fine powder having a particle size of 1 μm or less of 5 mass% or less.

粒度の積算分布曲線における累積頻度９０％の粒径Ｄ90が３１μｍを超えると、巨大な粒径の珪素酸化物を多数含有することになる。この場合、珪素酸化物、導電助材およびバインダーを混合してリチウムイオン二次電池用の負極材として用いると、リチウムイオンが巨大な粒径の珪素酸化物の内部まで入り込めず、酸化珪素が性能を十分に発揮できないので、初期効率が低下する。このため、本発明のリチウムイオン二次電池用負極材に用いる珪素酸化物は、粒度の積算分布曲線における累積頻度９０％の粒径Ｄ90を３１μｍ以下とする。
When the particle size D 90 having a cumulative frequency of 90% in the cumulative particle size distribution curve exceeds 31 μm, a large number of silicon oxides having a large particle size are contained. In this case, when silicon oxide, a conductive additive and a binder are mixed and used as a negative electrode material for a lithium ion secondary battery, lithium ions cannot enter the silicon oxide having a large particle size, Since the performance cannot be fully exhibited, the initial efficiency is lowered. For this reason, the silicon oxide used for the negative electrode material for lithium ion secondary batteries of the present invention has a particle size D 90 with a cumulative frequency of 90% in the integrated distribution curve of particle size of 31 μm or less.

なお、粒径１μｍ以下である微粉の含有率（質量％）、粒度の積算分布曲線における累積頻度９０％の粒径Ｄ90（μｍ）、および後述する粒度の積算分布曲線における累積頻度１０％の粒径Ｄ10（μｍ）は、レーザー回折散乱法による粒度分布の測定結果に基づき算出できる。この際、測定機としてＨＯＲＩＢＡ ＬＡ９２０を用いることができる。 In addition, the content (mass%) of fine powder having a particle size of 1 μm or less, the particle size D 90 (μm) of the cumulative frequency 90% in the cumulative distribution curve of particle size, and the cumulative frequency of 10% in the cumulative distribution curve of particle size described later The particle size D 10 (μm) can be calculated based on the measurement result of the particle size distribution by the laser diffraction scattering method. At this time, HORIBA LA920 can be used as a measuring instrument.

本発明のリチウムイオン二次電池用負極材に用いる珪素酸化物（ＳｉＯx）は、ｘ値を０．７＜ｘ＜１．３とし、粒表面の酸素と珪素とのモル比であるＯ／Ｓｉを０．６〜１．８にするのが好ましい。ｘ値が１．３を超えると、リチウムイオン二次電池の負極活物質として用いた場合に、初期効率が低下する。一方、ｘ値が０．７未満であると、リチウムイオン二次電池の負極活物質として用いた場合に、サイクル特性が低下するからである。
The silicon oxide (SiO x ) used for the negative electrode material for a lithium ion secondary battery of the present invention has an x value of 0.7 <x <1.3, and O / is the molar ratio of oxygen on the grain surface to silicon. Si is preferably 0.6 to 1.8. When the x value exceeds 1.3, the initial efficiency decreases when used as a negative electrode active material of a lithium ion secondary battery. On the other hand, when the x value is less than 0.7, the cycle characteristics deteriorate when used as a negative electrode active material of a lithium ion secondary battery.

珪素酸化物の粒表面における酸素と珪素とのモル比であるＯ／Ｓｉが１．８を超えると、珪素酸化物の表面に形成されるＳｉＯ2膜が厚くなり、珪素酸化物の導電率が低下する。このため、リチウムイオン二次電池の負極活物質として用いた場合に、十分な電流を流すことができなくなり、負極の抵抗による電池内部抵抗の上昇につながり、得られるリチウムイオン二次電池の能力が著しく低下する。一方、Ｏ／Ｓｉが０．６未満であると、リチウムイオン二次電池の負極活物質として用いた場合に、Ｓｉクラスターが形成され、充電時に膨張することにより、サイクル特性が劣化する。 When the O / Si molar ratio of oxygen to silicon on the surface of the silicon oxide exceeds 1.8, the SiO 2 film formed on the surface of the silicon oxide becomes thick, and the conductivity of the silicon oxide is increased. descend. For this reason, when used as a negative electrode active material of a lithium ion secondary battery, it becomes impossible to pass a sufficient current, leading to an increase in the internal resistance of the battery due to the negative electrode resistance, and the ability of the resulting lithium ion secondary battery It drops significantly. On the other hand, when O / Si is less than 0.6, when used as a negative electrode active material of a lithium ion secondary battery, Si clusters are formed and the cycle characteristics deteriorate due to expansion during charging.

珪素酸化物（ＳｉＯx）のｘ値は、Ｏ（酸素）をセラミック中酸素分析装置（不活性気流下溶融法）によって定量し、ＳｉはＳｉＯxを溶液化した後にＩＣＰ発光分光分析により定量することによって算出できる。また、粒表面におけるモル比であるＯ／Ｓｉは、Ｘ線光電子分光分析法により、珪素酸化物の表面から深さ２０〜８０ｎｍの部分のＯ（酸素）およびＳｉを定量することによって算出できる。 The x value of silicon oxide (SiO x ) is quantified by O (oxygen) by means of an oxygen analyzer in ceramics (melting method under an inert gas stream), and Si is quantified by ICP emission spectroscopic analysis after SiO x is made into a solution. Can be calculated. O / Si, which is the molar ratio on the grain surface, can be calculated by quantifying O (oxygen) and Si at a depth of 20 to 80 nm from the surface of the silicon oxide by X-ray photoelectron spectroscopy.

本発明のリチウムイオン二次電池用負極材に用いる珪素酸化物は、粒度の積算分布曲線における累積頻度９０％の粒径Ｄ90と、粒度の積算分布曲線における累積頻度１０％の粒径Ｄ10との比であるＤ90／Ｄ10が６以下であることが好ましい。Ｄ90／Ｄ10を６以下とすると、珪素酸化物の積算分布曲線はシャープな形状に、すなわち、珪素酸化物は粒径が揃った状態となる。この場合、珪素酸化物、導電助材およびバインダーとを混合してリチウムイオン二次電池の負極材に用いれば、負極材が均質となるので、リチウムイオン二次電池の初期効率およびサイクル特性がより向上する。
The silicon oxide used for the negative electrode material for a lithium ion secondary battery of the present invention has a particle size D 90 with a cumulative frequency of 90% in the cumulative particle size distribution curve and a particle size D 10 with a cumulative frequency of 10% in the cumulative particle size distribution curve. it is preferred D 90 / D 10 is the ratio of is 6 or less. When D 90 / D 10 is 6 or less, the integrated distribution curve of silicon oxide has a sharp shape, that is, the silicon oxide has a uniform particle size. In this case, if silicon oxide, a conductive additive and a binder are mixed and used as a negative electrode material for a lithium ion secondary battery, the negative electrode material becomes homogeneous, so that the initial efficiency and cycle characteristics of the lithium ion secondary battery are further improved. improves.

本発明のリチウムイオン二次電池用負極材に用いる珪素酸化物は、抵抗率が３ＭΩ・ｃｍ以上である水に分散させて行う湿式分級により、微粉の含有率を５質量％以下にするのが好ましい。前述の通り、抵抗率が３ＭΩ・ｃｍ以上である水に珪素酸化物を分散させて湿式分級を行うことにより、粒径が１μｍを超える珪素酸化物の表面に形成されたＳｉＯ2膜が成長すること、および珪素酸化物に金属不純物が付着することがなく、珪素酸化物から微粉を効率的に除去できるからである。
The silicon oxide used in the negative electrode material for a lithium ion secondary battery of the present invention has a fine powder content of 5% by mass or less by wet classification by dispersing in water having a resistivity of 3 MΩ · cm or more. preferable. As described above, by performing wet classification by dispersing silicon oxide in water having a resistivity of 3 MΩ · cm or more , a SiO 2 film formed on the surface of the silicon oxide having a particle size exceeding 1 μm grows. This is because metal impurities do not adhere to the silicon oxide and fine powder can be efficiently removed from the silicon oxide.

［珪素酸化物の製造方法について］
通常、リチウムイオン二次電池の負極活物質に用いられる粉末状の珪素酸化物を製造する場合は、一定の大きさを有する珪素酸化物原料を粉砕することにより粉末状にした後、分級により含有する微粉を除去して製造する。 [Production method of silicon oxide]
Usually, when producing a powdered silicon oxide used for the negative electrode active material of a lithium ion secondary battery, the silicon oxide raw material having a certain size is pulverized to form a powder and then contained by classification It is manufactured by removing fine powder.

一定の大きさを有する珪素酸化物原料は、例えば、以下に述べる構成を備えた装置により製造される珪素酸化物を使用できる。   As the silicon oxide raw material having a certain size, for example, a silicon oxide manufactured by an apparatus having a configuration described below can be used.

図２は、珪素酸化物の製造装置の構成例を示す図である。この装置は、真空室５と、真空室５内に配置された原料室６と、原料室６の上部に配置された析出室７とから構成される。   FIG. 2 is a diagram illustrating a configuration example of a silicon oxide manufacturing apparatus. This apparatus includes a vacuum chamber 5, a raw material chamber 6 disposed in the vacuum chamber 5, and a deposition chamber 7 disposed on the upper portion of the raw material chamber 6.

原料室６は円筒体で構成され、その中心部には、円筒状の原料容器８と、原料容器８を囲繞する加熱源９が配置される。加熱源９としては、例えば電熱ヒータを用いることができる。   The raw material chamber 6 is formed of a cylindrical body, and a cylindrical raw material container 8 and a heating source 9 surrounding the raw material container 8 are disposed at the center thereof. As the heating source 9, for example, an electric heater can be used.

析出室７は、原料容器８と軸が一致するように配置された円筒体で構成される。析出室７の内周面には、原料室６で昇華して発生した気体状の珪素酸化物を蒸着させるためのステンレス鋼からなる析出基体１１が設けられる。   The deposition chamber 7 is configured by a cylindrical body arranged so that its axis coincides with the raw material container 8. A deposition base 11 made of stainless steel is provided on the inner peripheral surface of the deposition chamber 7 for vapor deposition of gaseous silicon oxide generated by sublimation in the raw material chamber 6.

原料室６と析出室７とを収容する真空室５には、雰囲気ガスを排出するための真空装置（図示せず）が接続されており、矢印Ａ方向にガスが排出される。   A vacuum device (not shown) for discharging atmospheric gas is connected to the vacuum chamber 5 that accommodates the raw material chamber 6 and the deposition chamber 7, and the gas is discharged in the direction of arrow A.

上記図２に示す製造装置を用いて珪素酸化物原料を製造する場合、珪素粉末と二酸化珪素粉末とを配合し、混合、造粒および乾燥した混合造粒原料９を用いる。この混合造粒原料９を原料容器８に充填し、不活性ガス雰囲気または真空中で加熱してＳｉＯを生成（昇華）させる。昇華により発生した気体状のＳｉＯは、原料室６から上昇して析出室７に入り、周囲の析出基体１１上に蒸着し、珪素酸化物１２として析出する。その後、析出基体１１から析出珪素酸化物１２を取り外すことにより、珪素酸化物が得られる。   When a silicon oxide raw material is manufactured using the manufacturing apparatus shown in FIG. 2, a mixed granulated raw material 9 obtained by mixing, granulating and drying silicon powder and silicon dioxide powder is used. This mixed granulated raw material 9 is filled in the raw material container 8 and heated in an inert gas atmosphere or vacuum to generate (sublimate) SiO. Gaseous SiO generated by the sublimation rises from the raw material chamber 6 and enters the deposition chamber 7, is vapor-deposited on the surrounding deposition base 11, and is deposited as silicon oxide 12. Then, the silicon oxide is obtained by removing the deposited silicon oxide 12 from the deposited substrate 11.

析出した珪素酸化物を粉砕して粉末状の珪素酸化物にする方法については、一般的に用いられている粉砕方法を採用することができ、例えば、ボールミルを用いて粉砕することにより粉末状の珪素酸化物を得ることができる。   As a method for pulverizing the deposited silicon oxide to form a powdered silicon oxide, a commonly used pulverization method can be employed, for example, by pulverizing using a ball mill. Silicon oxide can be obtained.

分級により珪素酸化物に含有する微粉を除去する際には、抵抗率が３ＭΩ・ｃｍ以上である水に珪素酸化物を分散させた状態で湿式分級により行い、その後、温度が１２０℃以下の雰囲気で乾燥処理を珪素酸化物に施すのが好ましい。前述の通り、粒径が１μｍを超える珪素酸化物の表面に形成されたＳｉＯ2膜が成長すること、および珪素酸化物に金属不純物が付着することがなく、珪素酸化物から微粉を効率的に除去できるからである。
When removing fine powder contained in silicon oxide by classification, it is performed by wet classification in a state where silicon oxide is dispersed in water having a resistivity of 3 MΩ · cm or more , and then an atmosphere having a temperature of 120 ° C. or less. It is preferable to apply a drying treatment to the silicon oxide. As described above, the SiO 2 film formed on the surface of the silicon oxide having a particle size exceeding 1 μm grows, and metal impurities do not adhere to the silicon oxide, so that fine powder can be efficiently removed from the silicon oxide. This is because it can be removed.

湿式分級は、ろ過フィルタを用いた篩に珪素酸化物を分散させた水を投入した後、篩上に水を供給することにより珪素酸化物を分散させつつ、篩を振動させて微粉を除去する方式を用いるのが好ましい。ろ過フィルタを用いた分級機は、簡便であり、経済性も優れているからである。この場合、湿式分級による微粉の除去率は、篩を振動させる時間（処理時間）により調整することができる。処理時間を長くすれば、水に分散した珪素酸化物の微粉がろ過フィルタを通過する割合が増加するので、微粉の除去率が向上する。   In wet classification, after adding water in which silicon oxide is dispersed to a sieve using a filtration filter, water is supplied onto the sieve to disperse the silicon oxide, and the sieve is vibrated to remove fine powder. It is preferable to use the method. This is because a classifier using a filtration filter is simple and economical. In this case, the removal rate of fine powder by wet classification can be adjusted by the time (processing time) during which the sieve is vibrated. If the treatment time is lengthened, the rate at which silicon oxide fine powder dispersed in water passes through the filtration filter increases, so that the fine powder removal rate is improved.

［リチウムイオン二次電池ついて］
本発明のリチウムイオン二次電池用負極材を用いたコイン形状のリチウムイオン二次電池の構成例を前記図１を参照しながら説明する。同図に示すリチウムイオン二次電池は、正極１、負極２および電解液を含浸させたセパレータ３、ならびに正極１と負極２の電気的絶縁性を保つとともに電池内容物を封止するガスケット４から構成されており、充放電によってリチウムイオンが電解液を介して正極１と負極２の間を往復する。
[Lithium ion secondary battery]
An example of a configuration of a lithium ion secondary battery of coin-shaped with the lithium ion secondary negative electrode material for a battery of the present invention will be described with reference to FIG 1. The lithium ion secondary battery shown in FIG. 1 includes a positive electrode 1, a negative electrode 2, a separator 3 impregnated with an electrolyte, and a gasket 4 that maintains the electrical insulation between the positive electrode 1 and the negative electrode 2 and seals the battery contents. It is comprised, and lithium ion reciprocates between the positive electrode 1 and the negative electrode 2 through electrolyte solution by charging / discharging.

正極１は、対極ケース１ａと対極集電体１ｂと対極１ｃとで構成され、対極１ｃにはコバルト酸リチウム（ＬｉＣｏＯ3）やマンガンスピネル（ＬｉＭｎ2Ｏ4）を使用することができる。 The positive electrode 1 includes a counter electrode case 1a, a counter electrode current collector 1b, and a counter electrode 1c, and lithium cobaltate (LiCoO 3 ) or manganese spinel (LiMn 2 O 4 ) can be used for the counter electrode 1c.

負極２は、作用極ケース２ａと作用極集電体２ｂと作用極２ｃとで構成される。作用極２ｃに用いる負極材は、本発明の珪素酸化物（活物質）とその他の活物質と導電助材とバインダーとで構成することができる。その他の活物質は必ずしも添加しなくてもよい。導電助材としては、例えばアセチレンブラックを使用することができ、バインダーとしては例えばポリフッ化ビニリデンを使用することができる。   The negative electrode 2 includes a working electrode case 2a, a working electrode current collector 2b, and a working electrode 2c. The negative electrode material used for the working electrode 2c can be comprised by the silicon oxide (active material) of this invention, another active material, a conductive support material, and a binder. Other active materials are not necessarily added. As the conductive additive, for example, acetylene black can be used, and as the binder, for example, polyvinylidene fluoride can be used.

本発明のリチウムイオン二次電池用負極材は、本発明の珪素酸化物を２０質量％以上含有するものであり、その配合比の一例は、珪素酸化物：アセチレンブラック：ポリフッ化ビニリデン＝７０：１０：２０である。本発明のリチウムイオン二次電池用負極材を用いることにより、優れた初期効率およびサイクル特性を有するリチウムイオン二次電池を得ることができる。   The negative electrode material for a lithium ion secondary battery of the present invention contains 20% by mass or more of the silicon oxide of the present invention. An example of the blending ratio is silicon oxide: acetylene black: polyvinylidene fluoride = 70: 10:20. By using the negative electrode material for a lithium ion secondary battery of the present invention, a lithium ion secondary battery having excellent initial efficiency and cycle characteristics can be obtained.

本発明のリチウムイオン二次電池用負極材の効果を確認するため、下記の試験を行った。
To confirm the effect of the negative electrode material for lithium ion secondary battery of the present invention, the following test was conducted.

１．試験条件
Ｓｉ粉末とＳｉＯ2粉末とを等量配合し、混合、造粒した混合造粒原料を用い、前記図２に示した構成を有する装置を使用して減圧下で昇華反応させ、発生した気体状のＳｉＯを冷却した析出基体上に珪素酸化物として析出させた。析出した珪素酸化物を析出基体から取り外し、ボール径１０ｍ／ｍのボールミルを用いて粉砕し、粉砕処理の時間により粒度を調整した。粉砕処理の時間は、参考例２では４８時間、参考例３では２４時間、参考例４では１８時間、本発明例５では１２時間とした。参考例１では、粉砕処理を４８時間行った珪素酸化物と、１８時間行ったものとを質量比１：１で配合した。
1. Test conditions: An amount of Si powder and SiO 2 powder blended in equal amounts, mixed and granulated, was used for the sublimation reaction under reduced pressure using the apparatus having the configuration shown in FIG. Gaseous SiO was deposited as silicon oxide on a cooled deposition substrate. The precipitated silicon oxide was removed from the precipitation substrate, pulverized using a ball mill having a ball diameter of 10 m / m, and the particle size was adjusted according to the time of the pulverization treatment. Time of crushing treatment, 48 hours in Reference Example 2, 24 hours in Reference Example 3, 18 hours in Reference Example 4, was as Working Example 5 In 12 hours. In Reference Example 1, a silicon oxide that had been pulverized for 48 hours and a material that had been pulverized for 18 hours were blended at a mass ratio of 1: 1.

参考例２〜４では、粉砕した珪素酸化物を、旋回気流式分級機を用いた乾式分級により、分級して粗粒を除去した。旋回気流式分級機には、日清エンジニアリングのＡｅｒｏｆｉｎｅ Ｃｌａｓｓｉｆｉｅｒ ＡＣ−２０を用い、分級点を参考例２では１６μｍ、参考例３では２１μｍ、参考例４および本発明例５では３３μｍに設定した。
 In Reference Examples 2 to 4, the pulverized silicon oxide was classified by dry classification using a swirling airflow classifier to remove coarse particles. The swirling air classifier is used Aerofine Classifier AC-20 of Nisshin Engineering, in Reference Example 2 classification points 16 [mu] m, in Reference Example 3 21 [mu] m, was set in Reference Example 4 and Inventive Examples 5, 33 .mu.m.

粉砕または乾式分級した珪素酸化物を抵抗率が３．２ＭΩ・ｃｍである水に分散させた後、珪素酸化物を分散させた水をろ過フィルタを用いた篩に投入し、その後、篩上に水を供給することにより珪素酸化物を分散させつつ、篩を振動させて微粉を除去した。篩を振動させる時間（処理時間）を変化させることにより、珪素酸化物に含まれる微粉の除去率（含有率）を調整した。湿式分級を行った後、珪素酸化物を１２０℃に保持した雰囲気下で乾燥させ、粉末状の珪素酸化物を得た。
After pulverized or dry-classified silicon oxide is dispersed in water having a resistivity of 3.2 MΩ · cm , the silicon oxide-dispersed water is put into a sieve using a filtration filter, and then on the sieve The fine powder was removed by vibrating the sieve while dispersing silicon oxide by supplying water. The removal rate (content rate) of fine powder contained in the silicon oxide was adjusted by changing the time (treatment time) for vibrating the sieve. After wet classification, the silicon oxide was dried in an atmosphere maintained at 120 ° C. to obtain a powdered silicon oxide.

得られた粉末状の珪素酸化物について、粒径１μｍ以下である微粉の含有率（質量％）、粒度の積算分布曲線における累積頻度Ｘ％の粒径Ｄ10、Ｄ50およびＤ90、珪素酸化物（ＳｉＯx）のｘ値、並びに粒表面におけるモル比であるＯ／Ｓｉを測定または算出した。 About the obtained powdery silicon oxide, the content (mass%) of fine powder having a particle size of 1 μm or less, the particle size D 10 , D 50 and D 90 of the cumulative frequency X% in the cumulative distribution curve of the particle size, silicon oxidation The x value of the product (SiO x ) and O / Si which is the molar ratio on the grain surface were measured or calculated.

粒径１μｍ以下である微粉の含有率（質量％）、並びに粒度の積算分布曲線における累積頻度Ｘ％の粒径Ｄ10（μｍ）、Ｄ50（μｍ）およびＤ90（μｍ）は、レーザー回折散乱法による粒度分布の測定結果に基づき算出した。この際、測定機としてＨＯＲＩＢＡ ＬＡ９２０を用いた。 The content (% by mass) of fine powder having a particle size of 1 μm or less, and the particle sizes D 10 (μm), D 50 (μm) and D 90 (μm) of cumulative frequency X% in the cumulative distribution curve of particle size are determined by laser diffraction. It calculated based on the measurement result of the particle size distribution by the scattering method. At this time, HORIBA LA920 was used as a measuring machine.

珪素酸化物（ＳｉＯx）のｘ値は、Ｏ（酸素）をセラミック中酸素分析装置（不活性気流下溶融法）によって定量し、ＳｉはＳｉＯxを溶液化した後にＩＣＰ発光分光分析により定量することによって算出した。 The x value of silicon oxide (SiO x ) is quantified by O (oxygen) by means of an oxygen analyzer in ceramics (melting method under an inert gas stream), and Si is quantified by ICP emission spectroscopic analysis after SiO x is made into a solution. Calculated by.

粒表面におけるモル比であるＯ／Ｓｉは、Ｘ線光電子分光分析法により、珪素酸化物の表面から深さ２０〜８０ｎｍの部分のＯ（酸素）およびＳｉを定量することによって算出した。   O / Si, which is the molar ratio on the grain surface, was calculated by quantifying O (oxygen) and Si in a portion having a depth of 20 to 80 nm from the surface of the silicon oxide by X-ray photoelectron spectroscopy.

得られた粉末状の珪素酸化物を負極活物質として使用し、これに導電助剤としてのアセチレンブラックとバインダーを加えて、珪素酸化物を２０質量％含有するリチウムイオン二次電池用の負極材とした。この負極材を用いて前記図１に示す構成のコイン状のリチウムイオン二次電池を作製して、初期効率およびサイクル特性を調査した。なお、この場合のサイクル特性は、充放電を１００回繰り返した後の放電容量の初期放電容量（製造直後の放電容量）に対する維持率である。   The obtained powdered silicon oxide is used as a negative electrode active material, acetylene black and a binder as a conductive auxiliary agent are added thereto, and a negative electrode material for a lithium ion secondary battery containing 20% by mass of silicon oxide. It was. Using this negative electrode material, a coin-shaped lithium ion secondary battery having the configuration shown in FIG. 1 was fabricated, and the initial efficiency and cycle characteristics were investigated. In addition, the cycle characteristic in this case is a maintenance ratio with respect to the initial discharge capacity (discharge capacity immediately after manufacture) of the discharge capacity after repeating charging and discharging 100 times.

比較例１では、析出した珪素酸化物にボール径１０ｍ／ｍのボールミルを用いた粉砕を２４時間行い、その後、粉砕した珪素酸化物を旋回気流式分級機によりＤ90を２０μｍ狙いで乾式分級し、粉末状の珪素酸化物を得た。比較例２では、析出した珪素酸化物にボール径１０ｍ／ｍのボールミルを用いた粉砕を４８時間行った後、ボール径５ｍ／ｍのボールミルを用いた粉砕を４８時間行い、その後、粉砕した珪素酸化物を旋回気流式分級機によりＤ90を１０μｍ狙いで乾式分級し、粉末状の珪素酸化物を得た。 In Comparative Example 1, the deposited silicon oxide was pulverized using a ball mill having a ball diameter of 10 m / m for 24 hours, and then the pulverized silicon oxide was dry-classified with a swirling air flow classifier targeting D 90 of 20 μm. A powdered silicon oxide was obtained. In Comparative Example 2, the deposited silicon oxide was pulverized using a ball mill with a ball diameter of 10 m / m for 48 hours, then pulverized using a ball mill with a ball diameter of 5 m / m for 48 hours, and then crushed silicon The oxide was dry-classified with a swirling airflow classifier aiming at D 90 of 10 μm to obtain powdered silicon oxide.

表１に、実施条件、得られた粉末状の珪素酸化物の特性、およびリチウムイオン二次電池の特性を示す。   Table 1 shows the working conditions, the characteristics of the obtained powdered silicon oxide, and the characteristics of the lithium ion secondary battery.

Figure 0004880016
Figure 0004880016

表１に示す結果より、Ｄ90が３１μｍ以下で、かつ微粉の含有率が５質量％以下である粉末状の珪素酸化物を用いてリチウムイオン二次電池を作製した参考例１〜参考例４および本発明例５は、初期効率が８５．３％〜９７．８％となり、サイクル特性は９１．５％〜９７．２％であった。
一方、珪素酸化物の微粉の含有率が５質量％を超えた比較例１および比較例２は、初期効率が４５．５％〜５０．２％となり、サイクル特性は６４．１％〜８８．５％であった。
From the results shown in Table 1, Reference Examples 1 to 4 in which lithium ion secondary batteries were prepared using powdered silicon oxide having a D 90 of 31 μm or less and a fine powder content of 5% by mass or less. And, Example 5 of the present invention had an initial efficiency of 85.3% to 97.8% and a cycle characteristic of 91.5% to 97.2%.
On the other hand, Comparative Example 1 and Comparative Example 2 in which the content of silicon oxide fine powder exceeded 5% by mass had an initial efficiency of 45.5% to 50.2% and a cycle characteristic of 64.1% to 88.88. It was 5%.

したがって、粉末状の珪素酸化物のＤ90を３１μｍ以下にし、かつ微粉の含有率を５質量％以下にすることにより、その珪素酸化物をリチウムイオン二次電池の負極活物質に用いた場合に、リチウムイオン二次電池の初期効率およびサイクル特性を改善できることが確認できた。 Therefore, when the D 90 of the powdered silicon oxide is 31 μm or less and the fine powder content is 5 mass% or less, the silicon oxide is used as the negative electrode active material of the lithium ion secondary battery. It was confirmed that the initial efficiency and cycle characteristics of the lithium ion secondary battery can be improved.

参考例１では、Ｄ90／Ｄ10が６を超えた粉末状の珪素酸化物を用いてリチウムイオン二次電池を作製し、初期効率が８５．３％となり、サイクル特性は９１．５％であった。
一方、参考例２〜参考例４および本発明例５では、Ｄ90／Ｄ10が６以下である粉末状の珪素酸化物を用いてリチウムイオン二次電池を作製し、それぞれ初期効率が９０．３％〜９７．８％となり、サイクル特性は９６．６％〜９７．２％であった。

 In Reference Example 1, a lithium ion secondary battery was manufactured using a powdered silicon oxide having a D 90 / D 10 exceeding 6, the initial efficiency was 85.3%, and the cycle characteristics were 91.5%. there were.
On the other hand, in Reference Example 2 to Reference Example 4 and Invention Example 5, lithium ion secondary batteries were prepared using powdered silicon oxide having D 90 / D 10 of 6 or less, and the initial efficiency was 90. The cycle characteristics were 96.6% to 97.2%.

したがって、Ｄ90を３１μｍ以下にし、かつ微粉の含有率を５質量％以下である粉末状の珪素酸化物において、さらに、Ｄ90／Ｄ10を６以下にすることにより、その珪素酸化物をリチウムイオン二次電池の負極活物質に用いた場合に、リチウムイオン二次電池の初期効率およびサイクル特性をさらに改善できることが確認できた。 Accordingly, in a powdered silicon oxide having a D 90 of 31 μm or less and a fine powder content of 5% by mass or less, by further reducing the D 90 / D 10 to 6 or less, the silicon oxide is reduced to lithium. When used as the negative electrode active material of an ion secondary battery, it was confirmed that the initial efficiency and cycle characteristics of the lithium ion secondary battery could be further improved.

本発明のリチウムイオン二次電池用負極材に用いる珪素酸化物は、粒度の積算分布曲線における累積頻度９０％の粒径Ｄ90が３１μｍ以下で、かつ粒径１μｍ以下である微粉の含有率が５質量％以下であり、さらに粒度の積算分布曲線における累積頻度９０％の粒径Ｄ 90 と、粒度の積算分布曲線における累積頻度１０％の粒径Ｄ 10 との比であるＤ 90 ／Ｄ 10 が２．４以下であることにより、粉末状の珪素酸化物の単位質量あたりの表面積を減少させて、珪素酸化物の表面に形成されるＳｉＯ2膜の含有量を低減できるとともに、珪素酸化物を粒径が揃った状態にできる。
Silicon oxide used in the negative electrode material for a lithium ion secondary battery of the present invention is a cumulative frequency of 90% particle size D 90 in the cumulative distribution curve of the particle size is 31μm or less, and the content of fine powder is a particle size 1μm or less D 90 / D 10, which is a ratio of the particle size D 90 having a cumulative frequency of 90% in the cumulative distribution curve of particle size to 5% by mass or less and the particle size D 10 having a cumulative frequency of 10% in the cumulative distribution curve of particle size. Is 2.4 or less, the surface area per unit mass of the powdered silicon oxide can be reduced, and the content of the SiO 2 film formed on the surface of the silicon oxide can be reduced . Can be made to have a uniform particle size .

上述の珪素酸化物を負極活物質として含有する本発明の負極材をリチウムイオン二次電池に用いれば、抵抗を低減できるとともに、電解質の分解を低減でき、さらに負極材が均質となる。このため、優れた初期効率およびサイクル特性を有するリチウムイオン二次電池を得ることができる。したがって、本発明は、二次電池の分野において有用な技術である。
 If the negative electrode material of the present invention containing the above-described silicon oxide as a negative electrode active material is used for a lithium ion secondary battery, resistance can be reduced, decomposition of the electrolyte can be reduced , and the negative electrode material becomes homogeneous . For this reason, a lithium ion secondary battery having excellent initial efficiency and cycle characteristics can be obtained. Therefore, the present invention is a useful technique in the field of secondary batteries.

１：正極、 １ａ：対極ケース、 １ｂ：対極集電体、 １ｃ：対極、
２：負極、 ２ａ：作用極ケース、 ２ｂ：作用曲集電体、 ２ｃ：作用極、
３：セパレータ、 ４：ガスケット、 ５：真空室、 ６：原料室、
７：析出室、 ８：原料容器、 ９：混合造粒原料、 １０：加熱源、
１１：析出基体、 １２：析出珪素酸化物 1: positive electrode, 1a: counter electrode case, 1b: counter electrode current collector, 1c: counter electrode,
2: negative electrode, 2a: working electrode case, 2b: working music collector, 2c: working electrode,
3: separator, 4: gasket, 5: vacuum chamber, 6: raw material chamber,
7: precipitation chamber, 8: raw material container, 9: mixed granulated raw material, 10: heating source,
11: Precipitated substrate, 12: Precipitated silicon oxide

Claims (1)

化学式ＳｉＯ x （０．７＜ｘ＜１．３）で表される粉末状の珪素酸化物を負極活物質として２０質量％以上含有するリチウムイオン二次電池用負極材であって、
前記珪素酸化物が、粒度の積算分布曲線における累積頻度９０％の粒径Ｄ 90 が３１μｍ以下であり、かつ粒径１μｍ以下である微粉の含有率を抵抗率が３ＭΩ・ｃｍ以上である水に分散させて行う湿式分級により５質量％以下とし、
さらに前記珪素酸化物が、粒度の積算分布曲線における累積頻度９０％の粒径Ｄ 90 と、粒度の積算分布曲線における累積頻度１０％の粒径Ｄ 10 との比であるＤ 90 ／Ｄ 10 が２．４以下で、かつ、粒表面の酸素と珪素とのモル比であるＯ／Ｓｉが０．６〜１．８であることを特徴とするリチウムイオン二次電池用負極材。 A negative electrode material for a lithium ion secondary battery containing 20% by mass or more of a powdered silicon oxide represented by the chemical formula SiO x (0.7 <x <1.3) as a negative electrode active material ,
When the silicon oxide has a particle size D 90 with a cumulative frequency of 90% in a cumulative distribution curve of particle size of 31 μm or less and a content of fine powder with a particle size of 1 μm or less in water having a resistivity of 3 MΩ · cm or more. It is made 5 mass% or less by wet classification performed by dispersing,
Further, the silicon oxide, the cumulative frequency 90% particle size D 90 in the cumulative distribution curve of the particle size, the D 90 / D 10 which is the ratio of the particle diameter D 10 of the cumulative frequency of 10% in the cumulative distribution curve of the particle size A negative electrode material for a lithium ion secondary battery , having an O / Si ratio of 2.4 or less and a molar ratio of oxygen to silicon on the grain surface of 0.6 to 1.8 .
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