JP2018029049A - Composite active material for silicon based lithium secondary battery and method for manufacturing the same - Google Patents
Composite active material for silicon based lithium secondary battery and method for manufacturing the same Download PDFInfo
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- JP2018029049A JP2018029049A JP2017017707A JP2017017707A JP2018029049A JP 2018029049 A JP2018029049 A JP 2018029049A JP 2017017707 A JP2017017707 A JP 2017017707A JP 2017017707 A JP2017017707 A JP 2017017707A JP 2018029049 A JP2018029049 A JP 2018029049A
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- Prior art keywords
- lithium secondary
- active material
- silicon
- carbon
- composite active
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
Description
本発明は、シリコン系のリチウム二次電池用複合活物質およびその製造方法に関するものである。 The present invention relates to a silicon-based composite active material for a lithium secondary battery and a method for producing the same.
電子材料の小型軽量化、および、ＨＥＶまたはＥＶの開発の進展に伴い、大容量、高速充放電特性、良好なサイクル特性、かつ安全性に優れた電池の開発の要望は益々増大している。なかでも、リチウムイオン二次電池（リチウム二次電池）が最も有望な電池として注目されている。 As electronic materials become smaller and lighter and HEV or EV development progresses, the demand for development of batteries with high capacity, high-speed charge / discharge characteristics, good cycle characteristics, and excellent safety is increasing. Among these, a lithium ion secondary battery (lithium secondary battery) has attracted attention as the most promising battery.
しかしながら、優れた性能を示すリチウム二次電池が開発される前提として、各種性能に優れた負極材料、正極材料、電解液、セパレータ、または集電体などが開発され、且つ、それらの特性を十分に生した電池設計がなされなくてはならない。 However, as a premise for the development of lithium secondary batteries that exhibit excellent performance, negative electrode materials, positive electrode materials, electrolytes, separators, or current collectors that are excellent in various performances have been developed, and their characteristics are sufficient. The battery design must be made.
なかでも、負極材料は基本的な電池特性を決定するものであるため、充放電容量などの特性がより優れる材料の開発が活発に行われている。例えば、特許文献１では、大充放電容量、高速充放電特性、および良好なサイクル特性を併せ持ったリチウム二次電池の作製が可能なリチウム二次電池用複合活物質、並びに、その製造方法が開示されている。同様に金属元素を添加することで、高い充放電容量を有しながら、タールピッチ由来の炭素質を含ませたリチウム二次電池用複合活物質が開示されている（例えば特許文献２参照）。 Among these, since the negative electrode material determines basic battery characteristics, materials having more excellent characteristics such as charge / discharge capacity are being actively developed. For example, Patent Document 1 discloses a composite active material for a lithium secondary battery capable of producing a lithium secondary battery having both large charge / discharge capacity, high-speed charge / discharge characteristics, and good cycle characteristics, and a manufacturing method thereof. Has been. Similarly, a composite active material for a lithium secondary battery containing a carbonaceous material derived from tar pitch while having a high charge / discharge capacity by adding a metal element is disclosed (for example, see Patent Document 2).
しかし、金属元素を添加したリチウム二次電池用複合活物質は、初回の充放電容量などの特性が優れるが、充放電を繰り返すことによりサイクル寿命が低下し易い問題があった。 However, the composite active material for a lithium secondary battery to which a metal element is added is excellent in characteristics such as the initial charge / discharge capacity, but has a problem that the cycle life tends to be reduced by repeated charge / discharge.
近年、電池材料に対する要求特性が非常に高まってきており、サイクル特性に対する要求水準もより一層高まっている。本発明者らは、上述した特許文献１に記載の製造方法に従って、リチウムイオンと化合可能な電池活物質としてシリコンを含むリチウム二次電池用複合活物質を製造して、得られたリチウム二次電池用複合活物質を含む電極材料（例えば、負極材料）のサイクル特性について評価を行ったところ、従来の要求レベルは満たすものの、昨今のより高い要求レベルを満たしておらず、更なる改良が必要であった。 In recent years, the required characteristics for battery materials have increased greatly, and the required level for cycle characteristics has further increased. The inventors of the present invention manufactured a lithium secondary battery composite active material containing silicon as a battery active material that can be combined with lithium ions in accordance with the manufacturing method described in Patent Document 1 described above. When the cycle characteristics of electrode materials (for example, negative electrode materials) containing composite active materials for batteries were evaluated, the previous required level was satisfied, but the current higher level was not satisfied, and further improvements were required. Met.
そのため、ソフトカーボンを含ませた複合活物質により、充放電サイクル寿命を改善した複合活物質も開示されている（例えば特許文献３参照）。電池特性の１つとして、「ｎ回目放電容量÷ｎ回目充電容量」と定義されるクーロン効率がある。このクーロン効率を改善する事で高いレベルのサイクル寿命を維持できると考えられることから、クーロン効率の向上が求められているが、上述した特許文献３にはクーロン効率が記載されていない。 Therefore, a composite active material whose charge / discharge cycle life is improved by a composite active material containing soft carbon is also disclosed (for example, see Patent Document 3). One of the battery characteristics is coulomb efficiency defined as “nth discharge capacity ÷ nth charge capacity”. Since it is considered that a high level of cycle life can be maintained by improving the coulomb efficiency, there is a demand for improvement in coulomb efficiency. However, the above-mentioned Patent Document 3 does not describe the coulomb efficiency.
本発明は、上記実情に鑑みて、高いクーロン効率を持つ電極材料の作製が可能で、かつ、優れたサイクル特性を示すリチウム二次電池の作製が可能なシリコン系リチウム二次電池用複合活物質およびその製造方法を提供することを課題とする。 In view of the above circumstances, the present invention is a composite active material for silicon-based lithium secondary batteries capable of producing an electrode material having high Coulomb efficiency and capable of producing a lithium secondary battery exhibiting excellent cycle characteristics. It is another object of the present invention to provide a manufacturing method thereof.
本発明者らは、従来技術について鋭意検討を行った結果、以下の構成によって上記課題を解決できることを見出した。
（１）ＳｉまたはＳｉ合金と、炭素質物または炭素質物と黒鉛成分とを、含んでなるシリコン系リチウム二次電池用複合活物質において、ＢＥＴ法によるＢＥＴ比表面積が０．１〜１０ｍ２／ｇ、平均粒径（Ｄ５０）が３〜４０μｍ、開気孔体積が０．０６ｃｍ３／ｇ以下、Ｘ線回折装置による回折において１０〜２０°にブロードピークを有しないシリコン系リチウム二次電池用複合活物質。
（２）Ｓｉ又はＳｉ合金の平均粒径（Ｄ５０）が０．０１〜０．６μｍ、Ｄ９０が０．０１〜１．０μｍであり、ＢＥＴ法によるＢＥＴ比表面積が４０〜３００ｍ２／ｇである（１）に記載のシリコン系リチウム二次電池用複合活物質。
（３）前記ＳｉまたはＳｉ合金の含有量が１０〜８０質量部、前記炭素質物の含有量が９０〜１０質量部である（１）又は（２）に記載のシリコン系リチウム二次電池用複合活物質。
（４）前記ＳｉまたはＳｉ合金の含有量が１０〜６０質量部、前記炭素質物の含有量が５〜６０質量部、前記黒鉛成分の含有量が２０〜８０質量部である（１）又は（２）に記載のシリコン系リチウム二次電池用複合活物質。
（５）前記ＳｉまたはＳｉ合金が、炭素質物と共に０．２μｍ以下の厚みの黒鉛薄層の間に挟まった構造であり、その構造が積層および／または網目状に広がっており、該黒鉛薄層がシリコン系リチウム二次電池用複合活物質粒子の表面付近で湾曲してシリコン系リチウム二次電池用複合活物質粒子を覆っており、最外層の表面を炭素質物が覆っている（１）〜（４）のいずれかに記載のシリコン系リチウム二次電池用複合活物質。
（６）該黒鉛成分は、ＩＣＰ発光分光分析法による２６元素（Ａｌ、Ｃａ、Ｃｒ、Ｆｅ、Ｋ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｖ、Ｚｎ、Ｚｒ、Ａｇ、Ａｓ、Ｂａ、Ｂｅ、Ｃｄ、Ｃｏ、Ｃｕ、Ｍｏ、Ｐｂ、Ｓｂ、Ｓｅ、Ｔｈ、Ｔｌ、Ｕ）の不純物半定量値より求めた純度が９９．９重量％以上（１０００ｐｐｍ以下）で酸素フラスコ燃焼法によるイオンクロマトグラフィー（ＩＣ）測定法によるＳ量が０．３重量％以下、及び／又はＢＥＴ比表面積４０ｍ２／ｇ以下である（１）〜（５）のいずれかに記載のシリコン系リチウム二次電池用複合活物質。
（７）ＳｉまたはＳｉ合金、炭素前駆体、必要に応じて黒鉛成分を混合する工程と、造粒・圧密化する工程と、混合物を粉砕および球形化処理して略球状の複合粒子を形成する工程と、該複合粒子を不活性雰囲気中で焼成する工程と、炭素前駆体と該複合粒子もしくは焼成粉とを混合する工程とその混合物を不活性雰囲気中で加熱する事で炭素被覆した焼成粉もしくは炭素被覆した複合粒子を得る工程を含む（１）〜（６）のいずれかに記載のシリコン系リチウム二次電池用複合活物質の製造方法。
（８）（７）で得られた炭素被覆した複合粒子、球形化した複合粒子もしくは焼成粉と炭化水素ガスとを不活性雰囲気中で均一混合可能な焼成炉にて焼成しＣＶＤ炭素膜を複合粒子もしくは焼成粉の内外に被覆する工程を行う（７）に記載のシリコン系リチウム二次電池用複合活物質の製造方法。
（９）（８）の均一混合可能な焼成炉がロータリーキルンであることを特徴とする（７）又は（８）に記載のシリコン系リチウム二次電池用複合活物質の製造方法。
（１０）気相で被覆する工程の後、粉砕および球形処理した粉体もしくは焼成粉もしくは炭素被覆した粉体若しくはＣＶＤ炭素被覆した紛体を風力分級する工程を行う（７）〜（９）のいずれかに記載のシリコン系リチウム二次電池用複合活物質の製造方法。
（１１）複合粒子及び焼成粉を炭素前駆体と共に不活性雰囲気中で焼成する工程及び炭化水素ガスを不活性雰囲気中で加熱する事で炭素被覆した焼成粉もしくは炭素被覆した複合粒子もしくは炭素被覆した焼成粉の内外にＣＶＤ炭素被覆する工程の温度が、それぞれ３００〜１２００℃である（７）〜（１０）のいずれかに記載のシリコン系リチウム二次電池用複合活物質の製造方法。
As a result of intensive studies on the prior art, the present inventors have found that the above problem can be solved by the following configuration.
(1) In a composite active material for a silicon-based lithium secondary battery comprising Si or a Si alloy and a carbonaceous material or a carbonaceous material and a graphite component, the BET specific surface area by the BET method is 0.1 to 10 m 2 / g. And a composite active for a silicon-based lithium secondary battery having an average particle size (D50) of 3 to 40 μm, an open pore volume of 0.06 cm 3 / g or less, and having no broad peak at 10 to 20 ° in diffraction by an X-ray diffractometer. material.
(2) The average particle diameter (D50) of Si or Si alloy is 0.01 to 0.6 μm, D90 is 0.01 to 1.0 μm, and the BET specific surface area by the BET method is 40 to 300 m 2 / g. The composite active material for silicon-type lithium secondary batteries as described in (1).
(3) The silicon-based lithium secondary battery composite according to (1) or (2), wherein the Si or Si alloy content is 10 to 80 parts by mass and the carbonaceous material content is 90 to 10 parts by mass. Active material.
(4) The content of the Si or Si alloy is 10 to 60 parts by mass, the content of the carbonaceous material is 5 to 60 parts by mass, and the content of the graphite component is 20 to 80 parts by mass (1) or ( The composite active material for silicon-type lithium secondary batteries as described in 2).
(5) The Si or Si alloy has a structure sandwiched between carbonaceous materials and a graphite thin layer having a thickness of 0.2 μm or less, and the structure spreads in a laminated and / or network shape. Is curved near the surface of the composite active material particles for the silicon-based lithium secondary battery to cover the composite active material particles for the silicon-based lithium secondary battery, and the carbonaceous material covers the surface of the outermost layer (1) to (4) The composite active material for silicon-type lithium secondary batteries in any one of.
(6) The graphite component contains 26 elements (Al, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, V, Zn, Zr, Ag, As, Ba, Be, Cd by ICP emission spectroscopy. , Co, Cu, Mo, Pb, Sb, Se, Th, Tl, U) The purity determined from the semi-quantitative value of impurities is 99.9% by weight (1000 ppm or less), and ion chromatography (IC ) The composite active material for a silicon-based lithium secondary battery according to any one of (1) to (5), wherein the S amount by the measurement method is 0.3 wt% or less and / or the BET specific surface area is 40 m 2 / g or less. .
(7) Step of mixing Si or Si alloy, carbon precursor and, if necessary, graphite component, step of granulating and compacting, and grinding and spheronizing the mixture to form substantially spherical composite particles A step of firing the composite particles in an inert atmosphere, a step of mixing the carbon precursor and the composite particles or the fired powder, and a powder coated with carbon by heating the mixture in an inert atmosphere. Or the manufacturing method of the composite active material for silicon-type lithium secondary batteries in any one of (1)-(6) including the process of obtaining the carbon-coated composite particle.
(8) The carbon-coated composite particles obtained in (7), the spheroidized composite particles, or the baked powder and the hydrocarbon gas are baked in a baking furnace capable of uniform mixing in an inert atmosphere, and the CVD carbon film is combined. (7) The manufacturing method of the composite active material for silicon-type lithium secondary batteries as described in (7) which performs the process of coat | covering the inside of particle | grains or baking powder.
(9) The method for producing a composite active material for a silicon-based lithium secondary battery according to (7) or (8), wherein the uniformly kiln that can be uniformly mixed is a rotary kiln.
(10) After the step of coating in the gas phase, any step of (7) to (9) is performed in which the pulverized and spherically processed powder or baked powder, carbon-coated powder, or CVD carbon-coated powder is subjected to air classification A method for producing a composite active material for a silicon-based lithium secondary battery according to claim 1.
(11) A step of calcining the composite particles and the calcined powder together with the carbon precursor in an inert atmosphere and a carbon-coated calcined powder or carbon-coated composite particles or carbon-coated by heating a hydrocarbon gas in an inert atmosphere The manufacturing method of the composite active material for silicon-type lithium secondary batteries in any one of (7)-(10) whose temperature of the process which coat | covers CVD carbon inside and outside of baking powder is 300-1200 degreeC, respectively.
本発明によれば、充放電を繰り返した後でも高いクーロン効率を持つ電極材料の作製が可能で、かつ、優れたサイクル特性を示すリチウム二次電池の作製が可能なシリコン系リチウム二次電池用複合活物質およびその製造方法を提供することができる。 According to the present invention, an electrode material having high Coulomb efficiency can be produced even after repeated charge and discharge, and a lithium secondary battery exhibiting excellent cycle characteristics can be produced. A composite active material and a method for producing the same can be provided.
以下に、本発明のシリコン系リチウム二次電池用複合活物質およびその製造方法について詳述する。 Below, the composite active material for silicon-type lithium secondary batteries of this invention and its manufacturing method are explained in full detail.
本発明のシリコン系リチウム二次電池用複合活物質は、ＳｉまたはＳｉ合金（以下、Ｓｉ化合物）と、炭素質物または炭素質物と黒鉛成分とを含んでなるシリコン系リチウム二次電池用複合活物質において、該活物質のＢＥＴ法によるＢＥＴ比表面積が０．１〜１０ｍ２／ｇ、平均粒径（Ｄ５０）が３〜４０μｍ、開気孔体積が０．０６ｃｍ３／ｇ以下、Ｘ線回折装置による回折において１０〜２０°にブロードピークを有しないシリコン系リチウム二次電池用複合活物質である。 The composite active material for a silicon-based lithium secondary battery of the present invention is a composite active material for a silicon-based lithium secondary battery comprising Si or a Si alloy (hereinafter referred to as Si compound) and a carbonaceous material or a carbonaceous material and a graphite component. The active material has a BET specific surface area of 0.1 to 10 m 2 / g, an average particle diameter (D50) of 3 to 40 μm, an open pore volume of 0.06 cm 3 / g or less, and an X-ray diffractometer It is a composite active material for silicon-based lithium secondary batteries that does not have a broad peak at 10 to 20 ° in diffraction.
Ｓｉとは、純度が９８重量％程度の汎用グレードの金属シリコン、純度が２〜４Ｎのケミカルグレードの金属シリコン、塩素化して蒸留精製した４Ｎより高純度のポリシリコン、単結晶成長法による析出工程を経た超高純度の単結晶シリコン、もしくはそれらに周期表１３族もしくは１５族元素をドーピングして、ｐ型またはｎ型としたもの、半導体製造プロセスで発生したウエハの研磨や切断の屑、プロセスで不良となった廃棄ウエハなど、汎用グレードの金属シリコン以上の純度のものであれば特に限定されない。
Si is a general grade metal silicon having a purity of about 98% by weight, a chemical grade metal silicon having a purity of 2 to 4N, a polysilicon of higher purity than 4N purified by chlorination and distillation, and a precipitation process by a single crystal growth method. High-purity single crystal silicon that has undergone the above, or those that have been doped with
Ｓｉ合金とは、Ｓｉが主成分の合金である。前記Ｓｉ合金において、Ｓｉ以外に含まれる元素としては、周期表２〜１５族の元素の一つ以上が好ましく、合金に含まれる相の融点が９００℃以上となる元素の選択および／または添加量が好ましい。 Si alloy is an alloy containing Si as a main component. In the Si alloy, the element contained other than Si is preferably one or more elements of Groups 2 to 15 of the periodic table, and the selection and / or addition amount of the element having a melting point of the phase contained in the alloy of 900 ° C. or more Is preferred.
シリコン系リチウム二次電池用複合活物質において、Ｓｉ化合物の平均粒径（Ｄ５０）は０．０１〜０．６μｍが好ましく、さらに好ましくは０．０５〜０．５μｍであり、特に好ましくは０．１〜０．４μｍである。０．０１μｍより小さいと、表面酸化による容量や初期効率の低下が激しく、０．６μｍより大きいと、リチウム挿入による膨張で割れが激しく生じ、サイクル劣化が激しくなりやすい。 In the composite active material for a silicon-based lithium secondary battery, the average particle diameter (D50) of the Si compound is preferably 0.01 to 0.6 μm, more preferably 0.05 to 0.5 μm, and particularly preferably 0.8. 1 to 0.4 μm. If it is smaller than 0.01 μm, the capacity and initial efficiency due to surface oxidation are drastically decreased, and if it is larger than 0.6 μm, cracks are severely caused by expansion due to lithium insertion, and cycle deterioration tends to be severe.
Ｓｉ化合物の平均粒径（Ｄ９０）は０．０１〜１．０μｍが好ましく、さらに好ましくは０．０５〜０．６μｍであり、特に好ましくは０．１〜０．５μｍである。 The average particle size (D90) of the Si compound is preferably 0.01 to 1.0 μm, more preferably 0.05 to 0.6 μm, and particularly preferably 0.1 to 0.5 μm.
なお、平均粒径（Ｄ５０）、平均粒径（Ｄ９０）はレーザー粒度分布計で測定した体積平均の粒子径である。 The average particle diameter (D50) and the average particle diameter (D90) are volume average particle diameters measured with a laser particle size distribution meter.
Ｓｉ化合物のＢＥＴ法によるＢＥＴ比表面積が４０〜３００ｍ２／ｇが好ましく、さらに好ましくは６０〜３００ｍ２／ｇであり、特に好ましくは６０〜２００ｍ２／ｇである。 The BET specific surface area of the Si compound by the BET method is preferably 40 to 300 m 2 / g, more preferably 60 to 300 m 2 / g, and particularly preferably 60 to 200 m 2 / g.
炭素質物とは、非晶質もしくは微結晶の炭素物質であり、２０００℃を超える熱処理で黒鉛化する易黒鉛化炭素（ソフトカーボン）と、黒鉛化しにくい難黒鉛化炭素（ハードカーボン）が挙げられる。 The carbonaceous material is an amorphous or microcrystalline carbon material, and includes easily graphitizable carbon (soft carbon) that is graphitized by a heat treatment exceeding 2000 ° C. and non-graphitizable carbon (hard carbon) that is difficult to graphitize. .
ハードカーボンは、樹脂または樹脂組成物などの前駆体を炭化処理して得ることが好ましい。炭化処理することで、樹脂または樹脂組成物が炭化処理され、リチウムイオン二次電池用炭素材として用いることができる。ハードカーボンの原材料（前駆体）となる、樹脂又は樹脂組成物としては、高分子化合物など（例えば、熱硬化性樹脂、熱可塑性樹脂）が挙げられる。熱硬化性樹脂としては特に限定されず、例えば、ノボラック型フェノール樹脂、レゾール型フェノール樹脂などのフェノール樹脂；ビスフェノール型エポキシ樹脂、ノボラック型エポキシ樹脂などのエポキシ樹脂；メラミン樹脂；尿素樹脂；アニリン樹脂；シアネート樹脂；フラン樹脂；ケトン樹脂；不飽和ポリエステル樹脂；ウレタン樹脂などが挙げられる。また、これらが種々の成分で変性された変性物を用いることもできる。 The hard carbon is preferably obtained by carbonizing a precursor such as a resin or a resin composition. By carbonizing, the resin or resin composition is carbonized and can be used as a carbon material for a lithium ion secondary battery. Examples of the resin or resin composition that is the raw material (precursor) of the hard carbon include polymer compounds (for example, thermosetting resins and thermoplastic resins). The thermosetting resin is not particularly limited. For example, a phenol resin such as a novolac type phenol resin or a resol type phenol resin; an epoxy resin such as a bisphenol type epoxy resin or a novolac type epoxy resin; a melamine resin; a urea resin; Examples include cyanate resins; furan resins; ketone resins; unsaturated polyester resins; urethane resins. In addition, modified products obtained by modifying these with various components can also be used.
また、熱可塑性樹脂としては、特に限定されず、例えば、ポリエチレン、ポリスチレン、アクリロニトリル−スチレン（ＡＳ）樹脂、アクリロニトリル−ブタジエン−スチレン（ＡＢＳ）樹脂、ポリプロピレン、ポリエチレンテレフタレート、ポリカーボネート、ポリアセタール、ポリフェニレンエーテル、ポリブチレンテレフタレート、ポリフェニレンサルファイド、ポリサルホン、ポリエーテルサルホン、ポリエーテルエーテルケトンなどが挙げられる。 The thermoplastic resin is not particularly limited. For example, polyethylene, polystyrene, acrylonitrile-styrene (AS) resin, acrylonitrile-butadiene-styrene (ABS) resin, polypropylene, polyethylene terephthalate, polycarbonate, polyacetal, polyphenylene ether, poly Examples include butylene terephthalate, polyphenylene sulfide, polysulfone, polyethersulfone, and polyetheretherketone.
これらのうち１種または２種以上を組み合わせて用いることができる。 Among these, one kind or a combination of two or more kinds can be used.
これらの中でも特に好ましいハードカーボンの原材料（前駆体）は、ノボラック型フェノール樹脂、レゾール型フェノール樹脂などのフェノール樹脂等が挙げられる。 Among these, particularly preferred hard carbon raw materials (precursors) include phenolic resins such as novolac type phenolic resins and resol type phenolic resins.
ハードカーボンの前駆体の形状は特に制限されず、粉状、板状、粒状、繊維状、塊状、球状など、あらゆる形状のものが使用可能である。これらの前駆体は、各種成分を混合する際に使用する溶剤に溶解することが好ましい。 The shape of the hard carbon precursor is not particularly limited, and any shape such as powder, plate, granule, fiber, lump, and sphere can be used. These precursors are preferably dissolved in a solvent used when various components are mixed.
使用されるハードカーボンの前駆体の重量平均分子量としては、シリコン系リチウム二次電池用複合活物質の効果がより優れる点で１０００以上が好ましく、１，０００，０００以上がより好ましい。 The weight average molecular weight of the hard carbon precursor to be used is preferably 1000 or more, more preferably 1,000,000 or more, from the viewpoint that the effect of the composite active material for a silicon-based lithium secondary battery is more excellent.
ソフトカーボンは、樹脂または樹脂組成物などの前駆体を炭化処理して得ることが好ましい。炭化処理することで、樹脂または樹脂組成物が炭化され、シリコン系リチウムイオン二次電池用炭素材として用いることができる。ソフトカーボンの原材料（前駆体）となる、樹脂又は樹脂組成物としては、特に限定されず、石炭系ピッチ（例えば、コールタールピッチ）、石油系ピッチ、メソフェーズピッチ、コークス、低分子重質油、またはそれらの誘導体などが挙げられ、石炭系ピッチ（例えば、コールタールピッチ）、石油系ピッチ、メソフェーズピッチ、コークス、低分子重質油、またはそれらの誘導体など固体又は液体が好ましい。なかでも、シリコン系リチウム二次電池用複合活物質の効果がより優れる点で、石炭系ピッチなどの前駆体から得られるソフトカーボンが好ましい。 The soft carbon is preferably obtained by carbonizing a precursor such as a resin or a resin composition. By performing the carbonization treatment, the resin or the resin composition is carbonized and can be used as a carbon material for a silicon-based lithium ion secondary battery. The resin or resin composition that is the raw material (precursor) of the soft carbon is not particularly limited, and coal-based pitch (for example, coal tar pitch), petroleum-based pitch, mesophase pitch, coke, low molecular weight heavy oil, Or a derivative thereof and the like, and a solid or liquid such as coal-based pitch (for example, coal tar pitch), petroleum-based pitch, mesophase pitch, coke, low molecular weight heavy oil, or a derivative thereof is preferable. Especially, the soft carbon obtained from precursors, such as coal pitch, is more preferable at the point which the effect of the composite active material for silicon-type lithium secondary batteries is more excellent.
ソフトカーボンの前駆体の形状は特に制限されず、粉状、板状、粒状、繊維状、塊状、球状など、あらゆる形状のものが使用可能である。これらの前駆体は、各種成分を混合する際に使用する溶剤に溶解することもできる。 The shape of the soft carbon precursor is not particularly limited, and any shape such as powder, plate, granule, fiber, lump, and sphere can be used. These precursors can also be dissolved in a solvent used when mixing various components.
使用されるソフトカーボンの前駆体の重量平均分子量としては、シリコン系リチウム二次電池用複合活物質の効果がより優れる点で１０００以上が好ましく、１，０００，０００以上がより好ましい。 The weight average molecular weight of the soft carbon precursor used is preferably 1000 or more, and more preferably 1,000,000 or more, from the viewpoint that the effect of the composite active material for silicon-based lithium secondary battery is more excellent.
黒鉛成分としては、天然黒鉛材、人造黒鉛等が挙げられ、その中でも通常グラファイトと呼ばれる天然黒鉛を薄片化した薄片化黒鉛が好ましい。 Examples of the graphite component include natural graphite materials and artificial graphite. Among them, exfoliated graphite obtained by exfoliating natural graphite usually called graphite is preferable.
本明細書においては、薄片化黒鉛とは、グラフェンシートの積層数が４００層以下の黒鉛を意図する。なお、グラフェンシートは主にファンデルワールス力によって互いに結合している。 In the present specification, exfoliated graphite means graphite having 400 or less graphene sheets stacked. The graphene sheets are bonded to each other mainly by van der Waals force.
薄片化黒鉛におけるグラフェンシートの積層数は、Ｓｉ化合物と薄片化黒鉛とがより均一に分散し、シリコン系リチウム二次電池用複合活物質を用いた電池材料の膨張がより抑制される、および／または、リチウム二次電池のサイクル特性がより優れる点で、３００層以下が好ましく、２００層以下がより好ましく、１５０層以下がさらに好ましい。取り扱い性の点からは、５層以上が好ましい。 The number of graphene sheets laminated in exfoliated graphite is such that the Si compound and exfoliated graphite are more uniformly dispersed, and the expansion of the battery material using the composite active material for silicon-based lithium secondary batteries is further suppressed, and / or Or 300 layers or less are preferable at the point which the cycling characteristics of a lithium secondary battery are more excellent, 200 layers or less are more preferable, 150 layers or less are more preferable. From the viewpoint of handleability, 5 or more layers are preferable.
なお、薄片化黒鉛におけるグラフェンシートの積層数は透過型電子顕微鏡（ＴＥＭ）を用いて測定することができる。 The number of graphene sheets stacked in exfoliated graphite can be measured using a transmission electron microscope (TEM).
薄片化黒鉛の平均厚みは、シリコン系リチウム二次電池用複合活物質の効果がより優れる点で、４０ｎｍ以下が好ましく、２２ｎｍ以下がより好ましい。下限は特に制限されないが、製造手順が煩雑になることから、通常、４ｎｍ以上である場合が多い。 The average thickness of exfoliated graphite is preferably 40 nm or less, and more preferably 22 nm or less, in that the effect of the composite active material for a silicon-based lithium secondary battery is more excellent. The lower limit is not particularly limited, but is usually 4 nm or more because the production procedure becomes complicated.
なお、上記平均厚みの測定方法としては、電子顕微鏡（ＴＥＭ）によって薄片化黒鉛を観察し、薄片化黒鉛中の積層したグラフェンシートの層の厚みを１０個以上測定して、その値を算術平均することによって、平均厚みが得られる。 The average thickness is measured by observing exfoliated graphite with an electron microscope (TEM), measuring the thickness of 10 or more layers of the graphene sheets laminated in exfoliated graphite, and calculating the average of the values. By doing so, an average thickness is obtained.
薄片化黒鉛は、黒鉛化合物をその層面間において剥離し薄片化して得られる。 The exfoliated graphite is obtained by exfoliating a graphite compound between its layer surfaces.
薄片化黒鉛としては、例えば、いわゆる膨張黒鉛が挙げられる。 Examples of exfoliated graphite include so-called expanded graphite.
膨張黒鉛中には、黒鉛が含まれており、例えば、鱗片状黒鉛を濃硫酸や硝酸や過酸化水素水等で処理し、グラフェンシートの隙間にこれら薬液をインターカレートさせ、さらに加熱してインターカレートされた薬液が気化する際にグラフェンシートの隙間を広げることによって得られる。なお、後述するように、膨張黒鉛を出発原料として所定のシリコン系リチウム二次電池用複合活物質を製造することができる。つまり、シリコン系リチウム二次電池用複合活物質中の黒鉛成分として、膨張黒鉛を使用することもできる。 The expanded graphite contains graphite, for example, scaly graphite is treated with concentrated sulfuric acid, nitric acid, hydrogen peroxide, etc., and these chemicals are intercalated into the gaps in the graphene sheet, and further heated. It is obtained by widening the gap between the graphene sheets when the intercalated chemical solution is vaporized. As will be described later, a predetermined composite active material for a silicon-based lithium secondary battery can be produced using expanded graphite as a starting material. That is, expanded graphite can also be used as the graphite component in the composite active material for silicon-based lithium secondary batteries.
また、黒鉛成分として、球形化処理が施された膨張黒鉛も挙げられる。球形化処理の手順は後段で詳述する。なお、後述するように、膨張黒鉛に球形化処理を実施する際には、他の成分（例えば、ハードカーボン及びソフトカーボンの前駆体、Ｓｉ化合物など）と共に、球形化処理が実施されてもよい。 Examples of the graphite component include expanded graphite that has been spheroidized. The procedure of the spheronization process will be described in detail later. As will be described later, when the spheroidizing treatment is performed on the expanded graphite, the spheroidizing treatment may be performed together with other components (for example, hard carbon and soft carbon precursors, Si compounds, etc.). .
なお、黒鉛成分の比表面積は特に制限されないが、シリコン系リチウム二次電池用複合活物質の効果がより優れる点で、１０ｍ２／ｇ以上が好ましく、２０ｍ２／ｇ以上がより好ましい。上限は特に制限されないが、製造の手順が煩雑となり、合成が困難な点で、比表面積は２００ｍ２／ｇ以下が好ましい。 The specific surface area of the graphite component is not particularly limited, but is preferably 10 m 2 / g or more, and more preferably 20 m 2 / g or more in that the effect of the composite active material for silicon-based lithium secondary battery is more excellent. The upper limit is not particularly limited, but the specific surface area is preferably 200 m 2 / g or less in that the production procedure is complicated and the synthesis is difficult.
なお、黒鉛成分の比表面積は、窒素吸着によるＢＥＴ法（ＪＩＳ Ｚ ８８３０、一点
法）を用いて測定したものである。
In addition, the specific surface area of a graphite component is measured using the BET method (JIS Z 8830, one point method) by nitrogen adsorption.
黒鉛成分は、純度９９．９重量％以上、若しくは不純物量１０００ｐｐｍ以下であり、Ｓ量が０．３重量％以下及び／又はＢＥＴ比表面積が４０ｍ２／ｇ以下であることが好ましい。純度が９９．９重量％よりも少なく、若しくは不純物量が１０００ｐｐｍよりも多いと、不純物由来のＳＥＩ形成による不可逆容量が多くなるため、初回の充電容量に対する放電容量である初回充放電効率が低くなる傾向がある。また、Ｓ量が０．３重量％よりも高くなると同様に不可逆容量が高くなるため、初回充放電効率が低くなる。さらに好ましくは、Ｓ量が０．１重量％以下が好ましい。黒鉛成分のＢＥＴ比表面積が４０ｍ２／ｇよりも高いと、電解液との反応する面積が多くなるため、初回充放電効率が低くなる。 The graphite component preferably has a purity of 99.9% by weight or more, or an impurity amount of 1000 ppm or less, an S amount of 0.3% by weight or less, and / or a BET specific surface area of 40 m 2 / g or less. If the purity is less than 99.9% by weight or the amount of impurities is more than 1000 ppm, the irreversible capacity due to the formation of SEI derived from impurities increases, so the initial charge / discharge efficiency, which is the discharge capacity with respect to the initial charge capacity, decreases. Tend. Moreover, since the irreversible capacity | capacitance similarly becomes high when S amount becomes higher than 0.3 weight%, initial charge / discharge efficiency becomes low. More preferably, the amount of S is preferably 0.1% by weight or less. When the BET specific surface area of the graphite component is higher than 40 m 2 / g, the area where the graphite component reacts increases, and the initial charge / discharge efficiency decreases.
不純物の測定は、ＩＣＰ発光分光分析法により、以下の２６元素（Ａｌ、Ｃａ、Ｃｒ、Ｆｅ、Ｋ、Ｍｇ、Ｍｎ、Ｎａ、Ｎｉ、Ｖ、Ｚｎ、Ｚｒ、Ａｇ、Ａｓ、Ｂａ、Ｂｅ、Ｃｄ、Ｃｏ、Ｃｕ、Ｍｏ、Ｐｂ、Ｓｂ、Ｓｅ、Ｔｈ、Ｔｌ、Ｕ）の不純物半定量値により測定する。また、Ｓ量は、酸素フラスコ燃焼法で燃焼吸収処理した後、フィルター濾過してイオンクロマトグラフィー（ＩＣ）測定により行う。 Impurity is measured by ICP emission spectroscopic analysis using the following 26 elements (Al, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, V, Zn, Zr, Ag, As, Ba, Be, Cd. , Co, Cu, Mo, Pb, Sb, Se, Th, Tl, U). Further, the amount of S is measured by ion chromatography (IC) measurement after filtering and filtering by an oxygen flask combustion method.
本発明のシリコン系リチウム二次電池用複合活物質において、Ｓｉ化合物、炭素質物を含有する際のＳｉ化合物の含有量は１０〜８０質量部が好ましく、１５〜５０質量部が特に好ましい。Ｓｉ化合物の含有量が１０質量部未満の場合、従来の黒鉛に比べて十分に大きい容量が得られず、８０質量部より大きい場合、サイクル劣化が激しくなりやすい。炭素質物の含有量は９０〜１０質量部が好ましく、６０〜１０質量部が特に好ましい。炭素質物の含有量が１０質量部未満の場合、炭素質物がＳｉ化合物を覆うことができず、導電パスが不十分となって容量劣化が激しく起こりやすく、９０質量部より大きい場合、容量が十分に得られない。 In the composite active material for a silicon-based lithium secondary battery of the present invention, the content of the Si compound when the Si compound and the carbonaceous material are contained is preferably 10 to 80 parts by mass, and particularly preferably 15 to 50 parts by mass. When the content of the Si compound is less than 10 parts by mass, a sufficiently large capacity cannot be obtained as compared with the conventional graphite, and when it is greater than 80 parts by mass, cycle deterioration tends to become severe. 90-10 mass parts is preferable and, as for content of a carbonaceous material, 60-10 mass parts is especially preferable. When the content of the carbonaceous material is less than 10 parts by mass, the carbonaceous material cannot cover the Si compound, the conductive path becomes insufficient, and the capacity deterioration easily occurs. When the content is larger than 90 parts by mass, the capacity is sufficient. I can't get it.
Ｓｉ化合物、炭素質物、黒鉛成分を含有する際のＳｉ化合物の含有量は、１０〜６０質量部が好ましく、炭素質物の含有量は５〜６０質量部が好ましく、１０〜５５質量部が特に好ましい。炭素質物の含有量が１０質量部未満の場合、炭素質物がＳｉ化合物および黒鉛を覆うことができず、Ｓｉ化合物と黒鉛との接着が不十分となり、シリコン系リチウム二次電池用複合活物質粒子の形成が困難となりやすい。また、６０質量部より大きい場合、導電性が炭素質物より高い黒鉛の効果が十分に引き出されない。黒鉛成分の含有量は２０〜８０質量部が好ましく、３０〜７０質量部が特に好ましい。黒鉛成分の含有量が２０質量部未満の場合、炭素質物より高い導電性を有する黒鉛の効果が十分でなく、８０質量部より大きい場合、従来の黒鉛に比べて十分に大きい容量が得られない。 The content of the Si compound when containing the Si compound, the carbonaceous material, and the graphite component is preferably 10 to 60 parts by mass, the content of the carbonaceous material is preferably 5 to 60 parts by mass, and particularly preferably 10 to 55 parts by mass. . When the content of the carbonaceous material is less than 10 parts by mass, the carbonaceous material cannot cover the Si compound and graphite, adhesion between the Si compound and graphite becomes insufficient, and the composite active material particles for silicon-based lithium secondary battery The formation of is likely to be difficult. Moreover, when larger than 60 mass parts, the effect of the graphite whose electroconductivity is higher than a carbonaceous material is not fully drawn out. The content of the graphite component is preferably 20 to 80 parts by mass, particularly preferably 30 to 70 parts by mass. When the content of the graphite component is less than 20 parts by mass, the effect of graphite having higher conductivity than the carbonaceous material is not sufficient, and when it is greater than 80 parts by mass, a sufficiently large capacity cannot be obtained compared to conventional graphite. .
本発明のシリコン系リチウム二次電池用複合活物質の粒径（Ｄ５０：５０％体積粒径）は、シリコン系リチウム二次電池用複合活物質の効果がより優れる点で、３〜４０μｍであり、５〜３５μｍが好ましく、５〜３０μｍがさらに好ましい。 The particle size (D50: 50% volume particle size) of the composite active material for silicon-based lithium secondary battery of the present invention is 3 to 40 μm in that the effect of the composite active material for silicon-based lithium secondary battery is more excellent. 5 to 35 μm is preferable, and 5 to 30 μm is more preferable.
なお、粒径（Ｄ９０：９０％体積粒径）は特に制限されないが、シリコン系リチウム二次電池用複合活物質の効果がより優れる点で、１０〜７５μｍが好ましく、１０〜６０μｍがより好ましく、２０〜４５μｍがさらに好ましい。 The particle size (D90: 90% volume particle size) is not particularly limited, but is preferably 10 to 75 μm, more preferably 10 to 60 μm, in terms of more excellent effects of the composite active material for silicon-based lithium secondary batteries. More preferably, the thickness is 20 to 45 μm.
さらに、粒径（Ｄ１０：１０％体積粒径）は特に制限されないが、シリコン系リチウム二次電池用複合活物質の効果がより優れる点で、１〜２０μｍが好ましく、２〜１０μｍがより好ましい。 Further, the particle size (D10: 10% volume particle size) is not particularly limited, but is preferably 1 to 20 μm, and more preferably 2 to 10 μm in that the effect of the composite active material for a silicon-based lithium secondary battery is more excellent.
Ｄ１０、Ｄ５０およびＤ９０は、レーザー回折散乱法により測定した累積粒度分布の微粒側から累積１０％、累積５０％、累積９０％の粒径にそれぞれ該当する。 D10, D50 and D90 correspond to the particle sizes of 10%, 50% and 90% from the fine particle side of the cumulative particle size distribution measured by the laser diffraction scattering method, respectively.
なお、測定に際しては、シリコン系リチウム二次電池用複合活物質を液体に加えて超音波などを利用しながら激しく混合し、作製した分散液を装置にサンプルとして導入し、測定を行う。液体としては作業上、水やアルコール、低揮発性の有機溶媒を用いることが好ましい。この時、得られる粒度分布図は正規分布を示すことが好ましい。 In the measurement, the composite active material for silicon-based lithium secondary battery is added to the liquid and mixed vigorously using ultrasonic waves, and the prepared dispersion is introduced as a sample into the apparatus for measurement. As the liquid, it is preferable to use water, alcohol, or a low-volatile organic solvent for work. At this time, the obtained particle size distribution diagram preferably shows a normal distribution.
シリコン系リチウム二次電池用複合活物質は、ＢＥＴ法によるＢＥＴ比表面積が０．１〜１０ｍ２／ｇであり、好ましくは０．５〜９ｍ２／ｇである。この範囲とすることにより電解液との接触及び充放電によりシリコン系リチウム二次電池用複合活物質表面に形成される固体電解質層（ＳＥＩ）を抑制し、初回クーロン効率と容量維持率を改善できる。 The composite active material for a silicon-based lithium secondary battery has a BET specific surface area by the BET method of 0.1 to 10 m 2 / g, preferably 0.5 to 9 m 2 / g. By setting it within this range, the solid electrolyte layer (SEI) formed on the surface of the composite active material for silicon-based lithium secondary battery by contact with the electrolytic solution and charge / discharge can be suppressed, and the initial coulomb efficiency and capacity retention rate can be improved. .
また、平均細孔径は１０〜４０ｎｍが好ましく、さらに好ましくは１０〜３０ｎｍ、特に好ましくは１０〜２０ｎｍである。開気孔体積が０．０６ｃｍ３／ｇ以下であり、好ましくは０．０４ｃｍ３／ｇ以下、特に好ましくは０．０１ｃｍ３／ｇ以下である。平均細孔径及び開気孔体積をこの範囲とすることによりシリコン系リチウム二次電池用複合活物質内部への電解液侵入を抑制し、容量維持率、過膨張率を改善できる。 The average pore diameter is preferably 10 to 40 nm, more preferably 10 to 30 nm, and particularly preferably 10 to 20 nm. Open pore volume is at most 0.06 cm 3 / g, preferably 0.04 cm 3 / g, particularly preferably at most 0.01 cm 3 / g. By setting the average pore diameter and the open pore volume within these ranges, the electrolyte solution can be prevented from penetrating into the composite active material for the silicon-based lithium secondary battery, and the capacity retention rate and the overexpansion rate can be improved.
シリコン系リチウム二次電池用複合活物質の比表面積（ＢＥＴ比表面積）、平均細孔径、開気孔体積の測定方法は、試料を３００℃で３０分真空乾燥後、窒素吸着多点法で測定する。 The measurement method of the specific surface area (BET specific surface area), average pore diameter, and open pore volume of the composite active material for silicon-based lithium secondary battery is measured by the nitrogen adsorption multipoint method after vacuum drying the sample at 300 ° C. for 30 minutes. .
シリコン系リチウム二次電池用複合活物質は、Ｘ線回折において１０°〜２０°にブロードピークを有しない。１０°〜２０°ブロードピークは細孔由来の長周期構造を示すと考えられ、このピークを有しないことで電解液の浸漬を抑制し、容量維持率、クーロン効率を改善できる。 The composite active material for silicon-based lithium secondary batteries does not have a broad peak at 10 ° to 20 ° in X-ray diffraction. The 10 ° to 20 ° broad peak is considered to exhibit a long-period structure derived from pores, and by not having this peak, immersion of the electrolyte can be suppressed, and the capacity retention rate and Coulomb efficiency can be improved.
Ｘ線回析の測定方法は、シリコン系リチウム二次電池用複合活物質に対して粉末Ｘ線回折法にて行う。測定条件としては、特性Ｘ線として銅のＫα線を使用し、４０ｋＶ、４０ｍＡ、スキャンスピード２°／分とし、この条件下で１０°〜２０°にブロードピークを有しないことである。 X-ray diffraction is measured by a powder X-ray diffraction method for a composite active material for a silicon-based lithium secondary battery. As the measurement conditions, copper Kα rays are used as characteristic X-rays, 40 kV, 40 mA, a scan speed of 2 ° / min, and there is no broad peak at 10 ° to 20 ° under these conditions.
シリコン系リチウム二次電池用複合活物質においては、Ｓｉ化合物が０．２μｍ以下の厚みの黒鉛薄層の間に挟まった構造であり、その構造が積層および／または網目状に広がっており、黒鉛薄層がシリコン系リチウム二次電池用複合活物質粒子の表面付近で湾曲してシリコン系リチウム二次電池用複合活物質粒子を覆っていることが好ましい。 The composite active material for a silicon-based lithium secondary battery has a structure in which an Si compound is sandwiched between thin graphite layers having a thickness of 0.2 μm or less, and the structure spreads in a laminated and / or network shape. It is preferable that the thin layer bends in the vicinity of the surface of the composite active material particles for silicon-based lithium secondary battery and covers the composite active material particles for silicon-based lithium secondary battery.
厚みが０．２μｍを超えると黒鉛薄層の電子伝達効果が薄まる。黒鉛薄層を断面で見て線状の場合、その長さはシリコン系リチウム二次電池用複合活物質粒子のサイズの半分以上あることが電子伝達に好ましく、シリコン系リチウム二次電池用複合活物質粒子のサイズと同等程度であることがさらに好ましい。黒鉛薄層が網目状の場合、黒鉛薄層の網がシリコン系リチウム二次電池用複合活物質粒子のサイズの半分以上に渡って繋がっていることが電子伝達に好ましく、シリコン系リチウム二次電池用複合活物質粒子のサイズと同等程度であることがさらに好ましい。 When the thickness exceeds 0.2 μm, the electron transfer effect of the graphite thin layer is reduced. When the graphite thin layer is linear when viewed in cross section, its length is preferably at least half the size of the composite active material particles for silicon-based lithium secondary batteries for electron transfer. More preferably, it is approximately the same as the size of the substance particles. When the graphite thin layer is network-like, it is preferable for electron transfer that the graphite thin layer network is connected to more than half the size of the composite active material particles for the silicon-based lithium secondary battery, and the silicon-based lithium secondary battery More preferably, it is approximately the same size as the composite active material particles.
シリコン系リチウム二次電池用複合活物質においては、黒鉛薄層がシリコン系リチウム二次電池用複合活物質粒子の表面付近で湾曲してシリコン系リチウム二次電池用複合活物質粒子を覆うことが好ましい。そのような形状にすることで、黒鉛薄層端面から電解液が侵入して、Ｓｉ化合物や黒鉛薄層端面と電解液が直接接して、充放電時に反応物が形成され、効率が下がるというリスクが低減する。 In the composite active material for silicon-based lithium secondary batteries, the graphite thin layer may be curved near the surface of the composite active material particles for silicon-based lithium secondary batteries to cover the composite active material particles for silicon-based lithium secondary batteries. preferable. By adopting such a shape, there is a risk that the electrolyte enters from the end face of the graphite thin layer, the Si compound or the end face of the graphite thin layer is in direct contact with the electrolyte, and a reaction product is formed during charge and discharge, resulting in reduced efficiency. Is reduced.
シリコン系リチウム二次電池用複合活物質は、同一ロット内のＣＶＤ炭素被覆量のばらつきが標準偏差５以下であることが好ましい。標準偏差５以下であることで、ＣＶＤ炭素被覆のばらつきが少なく、均一な炭素被覆がされている。炭素被覆量は、例えばＣＶＤ炭素被覆前後の重量増加量やシリコン系リチウム二次電池用複合活物質内Ｓｉ化合物濃度の減少量から算出することで得られる。化学気相蒸着法（ＣＶＤ）炭素被膜とは、メタン、エチレン、アセチレン、プロピレン等の炭化水素ガスを窒素、アルゴンなどの不活性雰囲気中で加熱して得ることが好ましい。 The composite active material for a silicon-based lithium secondary battery preferably has a standard deviation of 5 or less in variation in the CVD carbon coating amount in the same lot. When the standard deviation is 5 or less, there is little variation in CVD carbon coating, and uniform carbon coating is achieved. The carbon coating amount can be obtained, for example, by calculating from the weight increase amount before and after CVD carbon coating and the decrease amount of the Si compound concentration in the composite active material for silicon-based lithium secondary battery. The chemical vapor deposition (CVD) carbon coating is preferably obtained by heating a hydrocarbon gas such as methane, ethylene, acetylene or propylene in an inert atmosphere such as nitrogen or argon.
次に、本発明のシリコン系リチウム二次電池用複合活物質の製造方法について説明する。 Next, the manufacturing method of the composite active material for silicon-type lithium secondary batteries of this invention is demonstrated.
シリコン系リチウム二次電池用複合活物質の製造方法は、ＳｉまたはＳｉ合金、炭素前駆体、必要に応じて黒鉛成分を混合する工程と、造粒・圧密化する工程と、混合物を粉砕および球形化処理して略球状の複合粒子を形成する工程と、該複合粒子を不活性雰囲気中で焼成する工程と、炭素前駆体と該複合粒子もしくは焼成粉とを混合する工程とその混合物を不活性雰囲気中で加熱する事で炭素被覆した焼成粉もしくは炭素被覆した複合粒子を得る工程を含むものである。 A method for producing a composite active material for a silicon-based lithium secondary battery includes a step of mixing Si or a Si alloy, a carbon precursor, and a graphite component as necessary, a step of granulating and compacting, and a mixture pulverized and spherical A step of forming a substantially spherical composite particle by performing a chemical treatment, a step of firing the composite particle in an inert atmosphere, a step of mixing a carbon precursor and the composite particle or the fired powder, and a mixture thereof. The method includes a step of obtaining carbon-coated fired powder or carbon-coated composite particles by heating in an atmosphere.
原料であるＳｉ化合物は、平均粒径（Ｄ５０）が０．０１〜５μｍの粉末を使用することが好ましい。所定の粒子径のＳｉ化合物を得るためには、上述のＳｉ化合物の原料（インゴット、ウエハ、粉末などの状態）を粉砕機で粉砕し、場合によっては分級機を用いる。インゴット、ウエハなどの塊の場合、最初はジョークラッシャー等の粗粉砕機を用いて粉末化することができる。その後、例えば、ボール、ビーズなどの粉砕媒体を運動させ、その運動エネルギーによる衝撃力や摩擦力、圧縮力を利用して被砕物を粉砕するボールミル、媒体撹拌ミルや、ローラによる圧縮力を利用して粉砕を行うローラミルや、被砕物を高速で内張材に衝突もしくは粒子相互に衝突させ、その衝撃による衝撃力によって粉砕を行うジェットミルや、ハンマー、ブレード、ピンなどを固設したローターの回転による衝撃力を利用して被砕物を粉砕するハンマーミル、ピンミル、ディスクミルや、剪断力を利用するコロイドミルや高圧湿式対向衝突式分散機「アルティマイザー」などを用いて微粉砕することができる。 As the Si compound as a raw material, it is preferable to use a powder having an average particle diameter (D50) of 0.01 to 5 μm. In order to obtain a Si compound having a predetermined particle diameter, the above-described Si compound raw material (ingot, wafer, powder, etc.) is pulverized by a pulverizer, and in some cases, a classifier is used. In the case of a lump such as an ingot or a wafer, it can be first pulverized using a coarse pulverizer such as a jaw crusher. After that, for example, a ball or bead is used to move the grinding medium, and the impact force, frictional force, or compression force of the kinetic energy is used to grind the material to be crushed, the media agitation mill, or the compression force of the roller. Rotation of a roller mill that pulverizes, a jet mill that collides crushed objects with the lining material or collides with each other at high speed, and pulverizes by the impact force of the impact, and a rotor with a fixed hammer, blade, pin, etc. It can be finely pulverized by using a hammer mill, pin mill, disk mill that pulverizes the material to be crushed using the impact force of the colloid, a colloid mill that uses shear force, or a high-pressure wet-on-front collision disperser "Ultimizer" .
粉砕は、湿式、乾式共に用いることができる。さらに微粉砕するには、例えば、湿式のビーズミルを用い、ビーズの径を段階的に小さくすること等により非常に細かい粒子を得ることができる。また、粉砕後に粒度分布を整えるため、乾式分級や湿式分級もしくはふるい分け分級を用いることができる。乾式分級は、主として気流を用い、分散、分離（細粒子と粗粒子の分離）、捕集（固体と気体の分離）、排出のプロセスが逐次もしくは同時に行われ、粒子相互間の干渉、粒子の形状、気流の乱れ、速度分布、静電気の影響などで分級効率を低下させないように、分級をする前に前処理（水分、分散性、湿度などの調整）を行うか、使用される気流の水分や酸素濃度を調整して行う。乾式で分級機が一体となっているタイプでは、一度に粉砕、分級が行われ、所望の粒度分布とすることが可能となる。 The pulverization can be used for both wet and dry processes. For further fine pulverization, very fine particles can be obtained, for example, by using a wet bead mill and gradually reducing the diameter of the beads. In order to adjust the particle size distribution after pulverization, dry classification, wet classification, or sieving classification can be used. In the dry classification, the process of dispersion, separation (separation of fine particles and coarse particles), collection (separation of solid and gas), and discharge are performed sequentially or simultaneously, mainly using air flow. Pre-classification (adjustment of moisture, dispersibility, humidity, etc.) before classification, or the moisture in the airflow used so that the classification efficiency is not lowered due to the influence of shape, air flow disturbance, velocity distribution, static electricity, etc. Adjust the oxygen concentration. In a dry type in which a classifier is integrated, pulverization and classification are performed at a time, and a desired particle size distribution can be obtained.
別の所定の粒子径のＳｉ化合物を得る方法としては、プラズマやレーザー等でＳｉ化合物を加熱して蒸発させ、不活性雰囲気中で凝固させて得る方法、ガス原料を用いてＣＶＤやプラズマＣＶＤ等で得る方法があり、これらの方法は０．１μｍ以下の超微粒子を得るのに適している。 As another method for obtaining a Si compound having a predetermined particle size, a method in which the Si compound is heated and evaporated by plasma, laser, or the like, and solidified in an inert atmosphere, or CVD or plasma CVD using a gas raw material is used. These methods are suitable for obtaining ultrafine particles of 0.1 μm or less.
原料の炭素前駆体としては、炭素を主体とする炭素系化合物で、不活性雰囲気中での熱処理により炭素質物になるものであれば特に限定はなく、前記易黒鉛化炭素（ソフトカーボン）、黒鉛化しにくい前記難黒鉛化炭素（ハードカーボン）等が挙げられる。 The carbon precursor as a raw material is not particularly limited as long as it is a carbon-based compound mainly composed of carbon and becomes a carbonaceous material by heat treatment in an inert atmosphere. The graphitizable carbon (soft carbon), graphite Examples thereof include non-graphitizable carbon (hard carbon) that is difficult to be converted.
原料である黒鉛成分は、天然黒鉛、石油や石炭のピッチを黒鉛化した人造黒鉛等が利用でき、鱗片状、小判状もしくは球状、円柱状もしくはファイバー状等が用いられる。また、それらの黒鉛成分を酸処理、酸化処理した後、熱処理することにより膨張させて黒鉛層間の一部が剥離してアコーディオン状となった膨張黒鉛もしくは膨張黒鉛の粉砕物、または超音波等により層間剥離させたグラフェン等も用いることができる。膨張黒鉛もしくは膨張黒鉛の粉砕物はその他の黒鉛に比べて可とう性に優れており、後述する複合粒子を形成する工程において、粉砕された粒子が再結着して略球状の複合粒子を容易に形成することができる。上記の点で、膨張黒鉛もしくは膨張黒鉛の粉砕物を用いることが好ましい。原料の黒鉛成分は予め混合工程で使用可能な大きさに整えて使用し、混合前の粒子サイズとしては天然黒鉛や人造黒鉛では１〜１００μｍ、膨張黒鉛もしくは膨張黒鉛の粉砕物、グラフェンでは５μｍ〜５ｍｍ程度である。 As the raw material graphite component, natural graphite, artificial graphite obtained by graphitizing the pitch of petroleum or coal, and the like can be used, and scale-like, oval or spherical, cylindrical, fiber-like, and the like are used. In addition, these graphite components are subjected to acid treatment, oxidation treatment, and then expanded by heat treatment, and part of the graphite layer is peeled off to form an accordion, or by pulverized expanded graphite or ultrasonic waves, etc. Graphene or the like exfoliated can also be used. Expanded graphite or a pulverized product of expanded graphite is superior in flexibility to other graphites, and in the process of forming composite particles, which will be described later, the pulverized particles can be rebound to easily form substantially spherical composite particles. Can be formed. In view of the above, it is preferable to use expanded graphite or a pulverized product of expanded graphite. The raw material graphite component is preliminarily adjusted to a size that can be used in the mixing step, and the particle size before mixing is 1 to 100 μm for natural graphite or artificial graphite, or 5 μm to crushed expanded graphite or expanded graphite, or graphene. It is about 5 mm.
これらのＳｉ化合物、炭素前駆体、さらに必要に応じて黒鉛成分との混合は、炭素前駆体が加熱により軟化、液状化するものである場合は、加熱下でＳｉ化合物、炭素前駆体、さらに必要に応じて黒鉛成分を混練することによって行うことができる。また、炭素前駆体が溶媒に溶解するものである場合には、溶媒にＳｉ化合物、炭素前駆体、さらに必要に応じて黒鉛成分を投入し、炭素前駆体が溶解した溶液中でＳｉ化合物、炭素前駆体、さらに必要に応じて黒鉛成分を分散、混合し、次いで溶媒を除去することで行うことができる。用いる溶媒は、炭素前駆体を溶解できるものであれば特に制限なく使用できる。例えば、炭素前駆体としてピッチ、タール類を用いる場合には、キノリン、ピリジン、トルエン、ベンゼン、テトラヒドロフラン、クレオソート油等が使用でき、ポリ塩化ビニルを用いる場合には、テトラヒドロフラン、シクロヘキサノン、ニトロベンゼン等が使用でき、フェノール樹脂、フラン樹脂を用いる場合には、エタノール、メタノール等が使用できる。 Mixing with these Si compounds, carbon precursors, and, if necessary, graphite components, when the carbon precursors are softened or liquefied by heating, Si compounds, carbon precursors, and further necessary under heating Depending on the process, the graphite component can be kneaded. When the carbon precursor is dissolved in a solvent, an Si compound, a carbon precursor, and, if necessary, a graphite component are added to the solvent, and the Si compound and carbon are dissolved in the solution in which the carbon precursor is dissolved. It can be carried out by dispersing and mixing the precursor and, if necessary, the graphite component, and then removing the solvent. The solvent to be used can be used without particular limitation as long as it can dissolve the carbon precursor. For example, when pitch or tar is used as the carbon precursor, quinoline, pyridine, toluene, benzene, tetrahydrofuran, creosote oil or the like can be used. When polyvinyl chloride is used, tetrahydrofuran, cyclohexanone, nitrobenzene or the like can be used. When phenol resin or furan resin is used, ethanol, methanol or the like can be used.
混合方法としては、炭素前駆体を加熱軟化させる場合は、混練機（ニーダー）を用いることができる。溶媒を用いる場合は、上述の混練機の他、ナウターミキサー、レーディゲミキサー、ヘンシェルミキサ、ハイスピードミキサー、ホモミキサー等を用いることができる。また、これらの装置でジャケット加熱したり、その後、振動乾燥機、パドルドライヤーなどで溶媒を除去する。 As a mixing method, when the carbon precursor is heat-softened, a kneader (kneader) can be used. In the case of using a solvent, in addition to the above-described kneader, a Nauter mixer, a Roedige mixer, a Henschel mixer, a high speed mixer, a homomixer, or the like can be used. Further, the jacket is heated with these apparatuses, and then the solvent is removed with a vibration dryer, a paddle dryer or the like.
これらの装置で、炭素前駆体を固化、または、溶媒除去の過程における撹拌をある程度の時間続けることで、Ｓｉ化合物、炭素前駆体、さらに必要に応じて黒鉛成分との混合物は造粒・圧密化される。また、炭素前駆体を固化、または溶媒除去後の混合物をローラーコンパクタ等の圧縮機によって圧縮し、解砕機で粗粉砕することにより、造粒・圧密化することができる。これらの造粒・圧密化物の大きさは、その後の粉砕工程での取り扱いの容易さから０．１〜５ｍｍが好ましい。 With these devices, the carbon precursor is solidified, or stirring in the process of solvent removal is continued for a certain amount of time, so that the mixture of Si compound, carbon precursor, and, if necessary, the graphite component is granulated and consolidated. Is done. Further, the carbon precursor is solidified or the mixture after removing the solvent is compressed by a compressor such as a roller compactor and coarsely pulverized by a crusher, whereby granulation and consolidation can be achieved. The size of the granulated / consolidated product is preferably 0.1 to 5 mm in view of ease of handling in the subsequent pulverization step.
造粒・圧密化の方法は、圧縮力を利用して被砕物を粉砕するボールミル、媒体撹拌ミルや、ローラによる圧縮力を利用して粉砕を行うローラミルや、被砕物を高速で内張材に衝突もしくは粒子相互に衝突させ、その衝撃による衝撃力によって粉砕を行うジェットミルや、ハンマー、ブレード、ピンなどを固設したローターの回転による衝撃力を利用して被砕物を粉砕するハンマーミル、ピンミル、ディスクミル等の乾式の粉砕方法が好ましい。また、粉砕後に粒度分布を整えるため、風力分級、ふるい分け等の乾式分級が用いられる。粉砕機と分級機が一体となっているタイプでは、一度に粉砕、分級が行われ、所望の粒度分布とすることが可能となる。 The granulation / consolidation methods include ball mills that pulverize the material to be crushed using compressive force, media agitation mills, roller mills that pulverize using the compressive force of rollers, and crushed material to lining material at high speed. A jet mill that collides or collides with particles and pulverizes by the impact force of the impact, and a hammer mill and pin mill that crushes the material to be crushed using the impact force of the rotation of a rotor with a fixed hammer, blade, pin, etc. A dry pulverization method such as a disk mill is preferred. In order to adjust the particle size distribution after pulverization, dry classification such as air classification and sieving is used. In the type in which the pulverizer and the classifier are integrated, pulverization and classification are performed at a time, and a desired particle size distribution can be obtained.
造粒・圧密化した混合物を粉砕及び球形化処理を施す方法としては、上述の粉砕方法により粉砕して粒度を整えた後、専用の球形化装置を通す方法と、上述のジェットミルやローターの回転による衝撃力を利用して被砕物を粉砕する方法を繰り返す、もしくは処理時間を延長することで球形化する方法がある。専用の球形化装置としては、ホソカワミクロン社のファカルティ（登録商標）、ノビルタ（登録商標）、メカノフュージョン（登録商標）、日本コークス工業社のＣＯＭＰＯＳＩ、奈良機械製作所社のハイブリダイゼーションシステム、アーステクニカ社のクリプトロンオーブ、クリプトロンエディ等が挙げられる。 The granulated and consolidated mixture is pulverized and spheroidized by the above-mentioned pulverization method to adjust the particle size, and then passed through a special spheronizing device, and the above-mentioned jet mill and rotor There is a method of spheroidizing by repeating a method of pulverizing an object to be crushed using an impact force caused by rotation or extending a processing time. Specialized spheroidizing devices include Hosokawa Micron's Faculty (registered trademark), Nobilta (registered trademark), Mechano-Fusion (registered trademark), Nippon Coke Industries' COMPOSI, Nara Machinery Co., Ltd. hybridization system, Earth Technica's Examples include kryptron orb and kryptron eddy.
上記粉砕および球形化処理を行うことにより、略球状の複合粒子を得ることができる。 By performing the pulverization and spheronization treatment, substantially spherical composite particles can be obtained.
得られた複合粒子は、アルゴンガスや窒素ガス気流中、もしくは真空などで焼成する。焼成温度は３００〜１２００℃とすることが好ましく、特に好ましくは６００〜１２００℃である。焼成温度が３００℃未満であると、炭素前駆体の未熱分解成分の残存により、複合粒子内部の黒鉛層とＳｉ、及び、複合粒子間の電気抵抗が増大するため、放電容量が低下する傾向にある。一方、焼成温度が１２００℃を超える場合、Ｓｉ化合物と炭素前駆体由来の非晶質炭素や黒鉛成分との反応が起こる可能性が強くなり、放電容量の低下が発生する傾向にある。 The obtained composite particles are fired in an argon gas or nitrogen gas stream or in a vacuum. The firing temperature is preferably 300 to 1200 ° C, particularly preferably 600 to 1200 ° C. When the firing temperature is less than 300 ° C., the electric resistance between the graphite layer and Si inside the composite particles and the composite particles increases due to the remaining unheated components of the carbon precursor, and the discharge capacity tends to decrease. It is in. On the other hand, when the firing temperature exceeds 1200 ° C., there is a strong possibility that a reaction between the Si compound and the amorphous carbon derived from the carbon precursor or the graphite component occurs, and the discharge capacity tends to decrease.
また、本発明のシリコン系リチウム二次電池用複合活物質は、前工程で得られた炭素被覆した複合粒子、球形化した複合粒子もしくは焼成粉と炭化水素ガスとを不活性雰囲気中で均一混合可能な焼成炉にて焼成しＣＶＤ炭素膜を複合粒子もしくは焼成粉の内外に被覆する工程を行い、製造することが好ましい。 In addition, the composite active material for silicon-based lithium secondary battery of the present invention is a uniform mixture of carbon-coated composite particles, spheroidized composite particles or calcined powder obtained in the previous step and hydrocarbon gas in an inert atmosphere. It is preferable to manufacture by performing a step of baking in a possible baking furnace and coating a CVD carbon film on the inside and outside of the composite particles or the baking powder.
炭素被覆した複合粒子、球形化した複合粒子もしくは焼成粉と炭素前駆体と炭化水素ガスとを不活性雰囲気中で均一混合可能な焼成炉にて焼成しＣＶＤ炭素膜を複合粒子もしくは焼成粉の内外に被覆する際には、不活性雰囲気中にメタン、エタン、エチレン、アセチレン、プロピレン等の炭化水素ガスを添加し、加熱する事により、炭素被覆した焼成粉もしくは炭素被覆した複合粒子もしくは炭素被覆した焼成粉の内外に気相でＣＶＤ炭素被覆することが好ましい。炭化水素ガスについては、緻密な炭素被覆を行う観点からエチレン、プロピレンが特に好ましい。特に複合粒子もしくは焼成粉に均一に炭素被覆を行うため、焼成中に回転による撹拌が可能なバッチ式や連続式のロータリーキルンで加熱する事が好ましい。ロータリーキルンによる炭化水素ガスを使用した炭素被覆を行う条件としては、温度３００〜１２００℃とすることが好ましい。温度が３００℃未満であると炭素被覆膜の膜質が悪くＢＥＴ比表面積が高くなることで電解液の浸漬が発生し、サイクル維持率が低下する傾向にある。 Carbon coated composite particles, spheroidized composite particles or calcined powder, carbon precursor and hydrocarbon gas are baked in a firing furnace that can be uniformly mixed in an inert atmosphere, and a CVD carbon film is inside and outside of the composite particles or calcined powder. When coating with, by adding a hydrocarbon gas such as methane, ethane, ethylene, acetylene, propylene, etc. in an inert atmosphere and heating, carbon-coated calcined powder or carbon-coated composite particles or carbon-coated It is preferable to coat CVD carbon on the inside and outside of the fired powder in the gas phase. As for the hydrocarbon gas, ethylene and propylene are particularly preferable from the viewpoint of dense carbon coating. In particular, in order to uniformly coat the composite particles or fired powder with carbon, it is preferable to heat with a batch-type or continuous rotary kiln that can be stirred by rotation during firing. As conditions for performing carbon coating using hydrocarbon gas by a rotary kiln, it is preferable to set the temperature to 300 to 1200 ° C. When the temperature is less than 300 ° C., the quality of the carbon coating film is poor, and the BET specific surface area is increased, so that the electrolytic solution is immersed, and the cycle retention rate tends to decrease.
また、１分間当たりの炭化水素ガスの流量は、加熱部の容積に対して０．３〜３ｖｏｌ％が好ましい。０．３ｖｏｌ％よりも少ないと炭素被膜の堆積効率が悪く、３ｖｏｌ％よりも高いと炭素被膜の膜質が悪い。 Further, the flow rate of the hydrocarbon gas per minute is preferably 0.3 to 3 vol% with respect to the volume of the heating unit. If it is less than 0.3 vol%, the deposition efficiency of the carbon coating is poor, and if it is higher than 3 vol%, the film quality of the carbon coating is poor.
さらに、本発明のシリコン系リチウム二次電池用複合活物質は、気相で炭素膜を被覆する工程の後、粉砕および球形処理した粉体もしくは焼成粉もしくは炭素被覆した粉体若しくはＣＶＤ炭素被覆をした粉体を風力分級する工程を行い、製造することが好ましい。 Furthermore, the composite active material for a silicon-based lithium secondary battery of the present invention comprises a step of coating a carbon film in the gas phase, followed by pulverized and spherically processed powder, calcined powder, carbon-coated powder, or CVD carbon coating. It is preferable to carry out a step of air classification of the powder thus produced.
風力分級の方法としては、ホソカワミクロン製ＡＴＰ−５０のような風力分級装置に粉体を投入し、ローター回転数、や差圧等の運転条件を調整することで、分級される粉体の粒径を制御することが可能である。 As a method of air classification, the particle size of the powder to be classified is adjusted by adjusting the operating conditions such as the rotational speed of the rotor and the differential pressure by introducing the powder into an air classifier such as ATP-50 manufactured by Hosokawa Micron. Can be controlled.
本発明のシリコン系リチウム二次電池用複合活物質は、リチウム二次電池で使用される電池材料（電極材料）に使用されるシリコン系リチウム二次電池用複合活物質として有用である。 The composite active material for silicon-based lithium secondary batteries of the present invention is useful as a composite active material for silicon-based lithium secondary batteries used for battery materials (electrode materials) used in lithium secondary batteries.
シリコン系リチウム二次電池用複合活物質を使用してリチウム二次電池用負極を製造する方法は特に制限されず、公知の方法を使用することができる。 A method for producing a negative electrode for a lithium secondary battery using the composite active material for a silicon-based lithium secondary battery is not particularly limited, and a known method can be used.
例えば、シリコン系リチウム二次電池用複合活物質と結着剤とを混合し、溶剤を用いてペースト化し、銅箔上に塗布してリチウム二次電池用負極とすることができる。 For example, a composite active material for a silicon-based lithium secondary battery and a binder can be mixed, pasted using a solvent, and applied onto a copper foil to form a negative electrode for a lithium secondary battery.
なお、集電体としては銅箔以外に、電池のサイクルがより優れる点で、三次元構造を有する集電体が好ましい。三次元構造を有する集電体の材料としては、例えば、炭素繊維、スポンジ状カーボン（スポンジ状樹脂にカーボンを塗工したもの）、金属などが挙げられる。 In addition to the copper foil, the current collector is preferably a current collector having a three-dimensional structure in that the battery cycle is more excellent. Examples of the current collector material having a three-dimensional structure include carbon fiber, sponge-like carbon (a sponge-like resin coated with carbon), metal, and the like.
三次元構造を有する集電体（多孔質集電体）としては、金属や炭素の導電体の多孔質体として、平織り金網、エキスパンドメタル、ラス網、金属発泡体、金属織布、金属不織布、炭素繊維織布、または炭素繊維不織布などが挙げられる。 As a current collector (porous current collector) having a three-dimensional structure, a metal or carbon conductor porous body, a plain weave wire mesh, expanded metal, lath net, metal foam, metal woven fabric, metal nonwoven fabric, A carbon fiber woven fabric or a carbon fiber non-woven fabric may be used.
使用される結着剤としては、公知の材料を使用でき、例えば、ポリフッ化ビニリデン、ポリテトラフルオロエチレンなどのフッ素系樹脂、ＳＢＲ、ポリエチレン、ポリビニルアルコール、カルボキシメチルセルロース、ポリアクリル酸、膠などが用いられる。 As the binder to be used, known materials can be used, for example, fluorine-based resins such as polyvinylidene fluoride and polytetrafluoroethylene, SBR, polyethylene, polyvinyl alcohol, carboxymethyl cellulose, polyacrylic acid, glue and the like are used. It is done.
また、溶剤としては、例えば、水、イソプロピルアルコール、Ｎ−メチルピロリドン、ジメチルホルムアミドなどが挙げられる。 Examples of the solvent include water, isopropyl alcohol, N-methylpyrrolidone, dimethylformamide and the like.
なお、ペースト化する際には、上記のように必要に応じて、公知の攪拌機、混合機、混練機、ニーダーなどを用いて攪拌混合してもよい。 In addition, when making into a paste, you may stir and mix using a well-known stirrer, a mixer, a kneader, a kneader, etc. as needed as mentioned above.
シリコン系リチウム二次電池用複合活物質を用いて塗工用スラリーを調製する場合、導電材として導電性カーボンブラック、カーボンナノチューブまたはその混合物を添加することが好ましい。上記工程により得られたシリコン系リチウム二次電池用複合活物質の形状は、比較的、粒状化（特に、略球形化）している場合が多く、粒子間の接触は点接触となりやすい。この弊害を避けるために、スラリーにカーボンブラック、カーボンナノチューブまたはその混合物を配合する方法が挙げられる。カーボンブラック、カーボンナノチューブまたはその混合物はスラリー溶剤の乾燥時に該シリコン系リチウム二次電池用複合活物質が接触して形成する毛細管部分に集中的に凝集することが出来るので、サイクルに伴う接点切れ（抵抗増大）を防止することが出来る。 When preparing a slurry for coating using a composite active material for a silicon-based lithium secondary battery, it is preferable to add conductive carbon black, carbon nanotube, or a mixture thereof as a conductive material. The shape of the composite active material for a silicon-based lithium secondary battery obtained by the above process is often relatively granulated (particularly substantially spherical), and the contact between the particles tends to be point contact. In order to avoid this adverse effect, a method of blending carbon black, carbon nanotubes or a mixture thereof into the slurry can be mentioned. Since carbon black, carbon nanotubes, or a mixture thereof can be intensively aggregated in the capillary part formed by contact with the composite active material for silicon-based lithium secondary battery when the slurry solvent is dried, the contact breakage associated with the cycle ( Resistance increase) can be prevented.
カーボンブラック、カーボンナノチューブまたはその混合物の配合量は特に制限されないが、シリコン系リチウム二次電池用複合活物質１００質量部に対して、０．２〜４質量部であることが好ましく、０．５〜２質量部であることがより好ましい。カーボンナノチューブの例としては、シングルウォールカーボンナノチューブ、マルチウォールカーボンナノチューブがある。
（正極）
上記シリコン系リチウム二次電池用複合活物質を使用して得られる負極を有するリチウム二次電池に使用される正極としては、公知の正極材料を使用した正極を使用することができる。
The blending amount of carbon black, carbon nanotube or a mixture thereof is not particularly limited, but is preferably 0.2 to 4 parts by mass with respect to 100 parts by mass of the composite active material for silicon-based lithium secondary battery, More preferably, it is ˜2 parts by mass. Examples of the carbon nanotube include a single wall carbon nanotube and a multi-wall carbon nanotube.
(Positive electrode)
As a positive electrode used for a lithium secondary battery having a negative electrode obtained by using the composite active material for silicon-based lithium secondary battery, a positive electrode using a known positive electrode material can be used.
正極の製造方法としては公知の方法が挙げられ、正極材料と結合剤および導電剤よりなる正極合剤を集電体の表面に塗布する方法などが挙げられる。正極材料（正極活物質）としては、酸化クロム、酸化チタン、酸化コバルト、五酸化バナジウムなどの金属酸化物や、ＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＮｉ１−ｙＣｏｙＯ２、ＬｉＮｉ１−ｘ−ｙＣｏｘＡｌｙＯ２、ＬｉＭｎＯ２、ＬｉＭｎ２Ｏ４、ＬｉＦｅＯ２などのリチウム金属酸化物、硫化チタン、硫化モリブデンなどの遷移金属のカルコゲン化合物、または、ポリアセチレン、ポリパラフェニレン、ポリピロールなどの導電性を有する共役系高分子物質などが挙げられる。
（電解液）
上記シリコン系リチウム二次電池用複合活物質を使用して得られる負極を有するリチウム二次電池に使用される電解液としては、公知の電解液を使用することができる。
As a manufacturing method of a positive electrode, a well-known method is mentioned, The method etc. which apply | coat the positive electrode mixture which consists of positive electrode material, a binder, and a electrically conductive agent to the surface of an electrical power collector are mentioned. Examples of the positive electrode material (positive electrode active material) include metal oxides such as chromium oxide, titanium oxide, cobalt oxide, and vanadium pentoxide, LiCoO 2 , LiNiO 2 , LiNi 1-y Co y O 2 , and LiNi 1-xy. Co x Al y O 2, LiMnO 2, LiMn 2 O 4, LiFeO 2 lithium metal oxides such as titanium sulfide, chalcogen compounds of transition metals such as molybdenum sulfide, or polyacetylene, polyparaphenylene, conductive polypyrrole Conjugated polymer substances having
(Electrolyte)
As an electrolytic solution used for a lithium secondary battery having a negative electrode obtained by using the composite active material for a silicon-based lithium secondary battery, a known electrolytic solution can be used.
例えば、電解液中に含まれる電解質塩として、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＣｌＯ４、ＬｉＢ（Ｃ６Ｈ５）、ＬｉＣｌ、ＬｉＢｒ、ＬｉＣＦ３ＳＯ３、ＬｉＣＨ３ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＮ（ＣＦ３ＣＨ２ＯＳＯ２）２、ＬｉＮ（ＣＦ３ＣＦ３ＯＳＯ２）２、ＬｉＮ（ＨＣＦ２ＣＦ２ＣＨ２ＯＳＯ２）２、ＬｉＮ｛（ＣＦ３）２ＣＨＯＳＯ２｝２、ＬｉＢ｛Ｃ６Ｈ３（ＣＦ３）２｝４、ＬｉＮ（ＳＯ２ＣＦ３）２、ＬｉＣ（ＳＯ２ＣＦ３）３、ＬｉＡｌＣｌ４、ＬｉＳｉＦ６などのリチウム塩を用いることができる。特にＬｉＰＦ６およびＬｉＢＦ４が酸化安定性の点から好ましい。 For example, as an electrolyte salt contained in the electrolyte, LiPF 6, LiBF 4, LiAsF 6, LiClO 4, LiB (C 6 H 5), LiCl, LiBr, LiCF 3 SO 3, LiCH 3 SO 3, LiN (CF 3 SO 2) 2, LiC (CF 3 SO 2) 3, LiN (CF 3 CH 2 OSO 2) 2, LiN (CF 3 CF 3 OSO 2) 2, LiN (HCF 2 CF 2 CH 2 OSO 2) 2, LiN {(CF 3 ) 2 CHOSO 2 } 2 , LiB {C 6 H 3 (CF 3 ) 2 } 4 , LiN (SO 2 CF 3 ) 2 , LiC (SO 2 CF 3 ) 3 , LiAlCl 4 , LiSiF 6 Lithium salts can be used. In particular, LiPF 6 and LiBF 4 are preferable from the viewpoint of oxidation stability.
電解質溶液中の電解質塩濃度は０．１〜５モル／リットルが好ましく、０．５〜３モル／リットルがより好ましい。 The electrolyte salt concentration in the electrolyte solution is preferably 0.1 to 5 mol / liter, and more preferably 0.5 to 3 mol / liter.
電解液で使用される溶媒としては、例えば、エチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、ジエチルカーボネートなどのカーボネート、１，１−または１，２−ジメトキシエタン、１，２−ジエトキシエタン、テトラヒドロフラン、２−メチルテトラヒドロフラン、γ−ブチロラクトン、１，３−ジオキソフラン、４−メチル−１，３−ジオキソラン、アニソール、ジエチルエーテルなどのエーテル、スルホラン、メチルスルホランなどのチオエーテル、アセトニトリル、クロロニトリル、プロピオニトリルなどのニトリル、ホウ酸トリメチル、ケイ酸テトラメチル、ニトロメタン、ジメチルホルムアミド、Ｎ−メチルピロリドン、酢酸エチル、トリメチルオルトホルメート、ニトロベンゼン、塩化ベンゾイル、臭化ベンゾイル、テトラヒドロチオフェン、ジメチルスルホキシド、３−メチル−２−オキサゾリン、エチレングリコール、ジメチルサルファイトなどの非プロトン性有機溶媒を用いることができる。 Examples of the solvent used in the electrolytic solution include carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate, 1,1- or 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2 -Ethers such as methyltetrahydrofuran, γ-butyrolactone, 1,3-dioxofuran, 4-methyl-1,3-dioxolane, anisole and diethyl ether, thioethers such as sulfolane and methylsulfolane, acetonitrile, chloronitrile, propionitrile, etc. Nitrile, trimethyl borate, tetramethyl silicate, nitromethane, dimethylformamide, N-methylpyrrolidone, ethyl acetate, trimethyl orthoformate, nitrobenzene, benzoyl chloride, Benzoyl, tetrahydrothiophene, dimethyl sulfoxide, 3-methyl-2-oxazoline, ethylene glycol, may be used an aprotic organic solvent such as dimethyl sulfite.
なお、電解液の代わりに、高分子固体電解質、高分子ゲル電解質などの高分子電解質を使用してもよい。高分子固体電解質または高分子ゲル電解質のマトリクスを構成する高分子化合物としては、ポリエチレンオキサイドやその架橋体などのエーテル系高分子化合物、ポリメタクリレートなどのメタクリレート系高分子化合物、ポリアクリレートなどのアクリレート系高分子化合物、ポリビニリデンフルオライド（ＰＶＤＦ）やビニリデンフルオライド−ヘキサフルオロプロピレン共重合体などのフッ素系高分子化合物が好ましい。これらを混合して使用することもできる。酸化還元安定性などの観点から、ＰＶＤＦやビニリデンフルオライド−ヘキサフルオロプロピレン共重合体などのフッ素系高分子化合物が特に好ましい。
（セパレータ）
上記シリコン系リチウム二次電池用複合活物質を使用して得られる負極を有するリチウム二次電池に使用されるセパレータとしては、公知の材料を使用できる。例えば、織布、不織布、合成樹脂製微多孔膜などが例示される。合成樹脂製微多孔膜が好適であるが、なかでもポリオレフィン系微多孔膜が、膜厚、膜強度、膜抵抗などの点から好適である。具体的には、ポリエチレンおよびポリプロピレン製微多孔膜、またはこれらを複合した微多孔膜などである。
In place of the electrolytic solution, a polymer electrolyte such as a polymer solid electrolyte or a polymer gel electrolyte may be used. Examples of the polymer compound constituting the matrix of the polymer solid electrolyte or polymer gel electrolyte include ether polymer compounds such as polyethylene oxide and cross-linked products thereof, methacrylate polymer compounds such as polymethacrylate, and acrylate compounds such as polyacrylate. Fluorine polymer compounds such as polymer compounds, polyvinylidene fluoride (PVDF) and vinylidene fluoride-hexafluoropropylene copolymers are preferred. These can also be mixed and used. From the viewpoint of oxidation-reduction stability, a fluorine-based polymer compound such as PVDF or vinylidene fluoride-hexafluoropropylene copolymer is particularly preferable.
(Separator)
A well-known material can be used as a separator used for the lithium secondary battery which has a negative electrode obtained using the said composite active material for silicon-type lithium secondary batteries. For example, a woven fabric, a nonwoven fabric, a synthetic resin microporous film, etc. are illustrated. A synthetic resin microporous membrane is preferred, and among them, a polyolefin microporous membrane is preferred from the viewpoint of film thickness, membrane strength, membrane resistance, and the like. Specifically, it is a microporous film made of polyethylene and polypropylene, or a microporous film in which these are combined.
リチウム二次電池は、上述した負極、正極、セパレータ、電解液、その他電池構成要素（例えば、集電体、ガスケット、封口板、ケースなど）を用いて、常法にしたがって円筒型、角型あるいはボタン型などの形態を有することができる。 The lithium secondary battery uses the negative electrode, the positive electrode, the separator, the electrolyte, and other battery components (for example, a current collector, a gasket, a sealing plate, a case, etc.), and is cylindrical, square, or It can have a form such as a button type.
本発明のシリコン系リチウム二次電池用複合活物質を用いたリチウム二次電池は、充放電を２０回繰り返した際のクーロン効率が、他のシリコン系リチウム二次電池用複合活物質を用いたリチウム二次電池より高いものである。より具体的には市販の人造黒鉛と比較して９９％以上である。クーロン効率は充放電サイクルを繰り返すことで徐々に増加し２０回程度から一定になる傾向があり、長期のサイクル維持率を反映するために２０回目でのクーロン効率を確認する。 The lithium secondary battery using the composite active material for silicon-based lithium secondary battery according to the present invention uses a composite active material for other silicon-based lithium secondary battery having a Coulomb efficiency when charging / discharging is repeated 20 times. It is higher than the lithium secondary battery. More specifically, it is 99% or more compared to commercially available artificial graphite. The coulomb efficiency gradually increases by repeating the charge / discharge cycle and tends to be constant from about 20 times. The coulomb efficiency at the 20th time is confirmed to reflect the long-term cycle maintenance rate.
本発明のリチウム二次電池は、各種携帯電子機器に用いられ、特にノート型パソコン、ノート型ワープロ、パームトップ（ポケット）パソコン、携帯電話、携帯ファックス、携帯プリンター、ヘッドフォンステレオ、ビデオカメラ、携帯テレビ、ポータブルＣＤ、ポータブルＭＤ、電動髭剃り機、電子手帳、トランシーバー、電動工具、ラジオ、テープレコーダー、デジタルカメラ、携帯コピー機、携帯ゲーム機などに用いることができる。また、さらに、電気自動車、ハイブリッド自動車、自動販売機、電動カート、ロードレベリング用蓄電システム、家庭用蓄電器、分散型電力貯蔵機システム（据置型電化製品に内蔵）、非常時電力供給システムなどの二次電池として用いることもできる。 The lithium secondary battery of the present invention is used in various portable electronic devices, particularly notebook computers, notebook word processors, palmtop (pocket) computers, mobile phones, mobile faxes, mobile printers, headphone stereos, video cameras, and mobile TVs. , Portable CDs, portable MDs, electric shaving machines, electronic notebooks, transceivers, power tools, radios, tape recorders, digital cameras, portable copying machines, portable game machines, and the like. In addition, electric vehicles, hybrid vehicles, vending machines, electric carts, load leveling power storage systems, household power storage devices, distributed power storage systems (built into stationary appliances), emergency power supply systems, etc. It can also be used as a secondary battery.
以下、実施例により、本発明についてさらに詳細に説明するが、本発明はこれらに限定されるものではない。
＜実施例１＞
（膨張黒鉛の調製）
平均粒子径１ｍｍの鱗片状天然黒鉛を硫酸９質量部、硝酸１質量部の混酸に室温で１時間浸漬後、Ｎｏ３ガラスフィルターで混酸を除去して酸処理黒鉛を得た。さらに酸処理黒鉛を水洗後、乾燥した。乾燥した酸処理黒鉛５ｇを蒸留水１００ｇ中で攪拌し、１時間後にｐＨを測定したところ、ｐＨは６．７であった。乾燥した酸処理黒鉛を８５０℃に設定した窒素雰囲気下の縦型電気炉に投入し、膨張黒鉛を得た。膨張黒鉛の嵩密度は０．００２ｇ／ｃｍ３、比表面積は４５ｍ２／ｇであった。
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.
<Example 1>
(Preparation of expanded graphite)
After immersing scaly natural graphite having an average particle diameter of 1 mm in a mixed acid of 9 parts by mass of sulfuric acid and 1 part by mass of nitric acid at room temperature for 1 hour, the mixed acid was removed with a No 3 glass filter to obtain acid-treated graphite. Further, the acid-treated graphite was washed with water and dried. When 5 g of dried acid-treated graphite was stirred in 100 g of distilled water and the pH was measured after 1 hour, the pH was 6.7. The dried acid-treated graphite was put into a vertical electric furnace under a nitrogen atmosphere set at 850 ° C. to obtain expanded graphite. The expanded graphite had a bulk density of 0.002 g / cm 3 and a specific surface area of 45 m 2 / g.
（混合工程）
平均粒径（Ｄ５０）が７μｍのケミカルグレードの金属Ｓｉ（純度３Ｎ）をエタノールに２１重量％混合し、直径０．３ｍｍのジルコニアビーズを用いた微粉砕を６時間行い、平均粒径（Ｄ５０）０．２μｍ、乾燥時のＢＥＴ比表面積が１００ｍ２／ｇの超微粒子Ｓｉスラリーを得た。
(Mixing process)
21% by weight of chemical grade metal Si (purity 3N) with an average particle size (D50) of 7 μm was mixed with ethanol and pulverized with zirconia beads having a diameter of 0.3 mm for 6 hours. The average particle size (D50) 0.2 [mu] m, BET specific surface area after drying to obtain ultrafine particles Si slurry 100 m 2 / g.
粒子径０．３ｍｍ（（２００）面方向の幅）、厚み１０μｍの酸処理した天然黒鉛を振動粉末供給器に入れ、１２Ｌ／分の流量の窒素ガスに乗せて電気ヒーターで８５０℃に加熱した長さ１ｍ、内径２０ｍｍのムライト管に通し、端面から大気に放出し、亜硫酸等のガスを上部に排気、下部に膨張黒鉛をステンレス容器で捕集した。膨張黒鉛の（２００）面方向の幅は０．３ｍｍで元の黒鉛の値を保っていたが、厚みは２．４ｍｍと２４０倍に膨張し、外観はコイル状であり、ＳＥＭ観察で黒鉛層が剥離し、アコーディオン状であることが確認された。 Acid-treated natural graphite having a particle diameter of 0.3 mm (width in the (200) plane direction) and a thickness of 10 μm was placed in a vibrating powder feeder, placed on nitrogen gas at a flow rate of 12 L / min, and heated to 850 ° C. with an electric heater. It was passed through a mullite tube having a length of 1 m and an inner diameter of 20 mm, discharged from the end face to the atmosphere, and a gas such as sulfurous acid was exhausted at the top and expanded graphite was collected at the bottom in a stainless steel container. The expanded graphite had a (200) plane width of 0.3 mm and maintained the original graphite value, but the thickness expanded 2.4 times to 2.4 mm, the appearance was coiled, and the graphite layer was observed by SEM observation. Was peeled off and confirmed to be in the form of an accordion.
上記超微粒子Ｓｉスラリーを１０４９ｇ、上記膨張黒鉛を３００ｇ、レゾール型のフェノール樹脂（重量平均分子量（Ｍｗ）＝３７０）を１２５ｇ、エタノール５Ｌを撹拌容器に入れ、インラインミキサーで２２分混合撹拌した。その後、混合液をロータリーエバポレーターに移し、回転しながら温浴で４０℃に加熱し、アスピレータで真空に引き、溶媒を除去した。その後、ドラフト中でバットに広げて排気しながら２時間乾燥し、目開き２ｍｍのメッシュを通し、さらに１日間乾燥して、混合乾燥物（軽装かさ密度２６６ｇ／Ｌ）を得た。 1049 g of the ultrafine Si slurry, 300 g of the expanded graphite, 125 g of a resol type phenol resin (weight average molecular weight (Mw) = 370) and 5 L of ethanol were placed in a stirring vessel, and mixed and stirred for 22 minutes by an in-line mixer. Thereafter, the mixed solution was transferred to a rotary evaporator, heated to 40 ° C. with a warm bath while rotating, and evacuated with an aspirator to remove the solvent. Thereafter, it was spread on a bat in a fume hood and dried for 2 hours while evacuating, passed through a mesh with a mesh opening of 2 mm, and further dried for 1 day to obtain a mixed dried product (light bulk density 266 g / L).
（プレス工程）
この混合乾燥物を３本ロールミルに２回通し、目開き１ｍｍの篩を通し、軽装かさ密度４５７ｇ／Ｌに造粒・圧密化した。
(Pressing process)
This mixed dried product was passed through a three-roll mill twice, passed through a sieve having an opening of 1 mm, and granulated and consolidated to a light bulk density of 457 g / L.
（球形化工程）
次に、この造粒・圧密化物をニューパワーミルに入れて水冷しながら、２１０００ｒｐｍで３００秒粉砕し、同時に球形化し、軽装かさ密度５０９ｇ／Ｌの略球状複合粉末を得た。
(Spheronization process)
Next, the granulated / consolidated product was placed in a new power mill and pulverized at 21000 rpm for 300 seconds while cooling with water, and at the same time, spheroidized to obtain a substantially spherical composite powder having a light bulk density of 509 g / L.
（焼成工程）
得られた粉末を石英ボートに入れて、管状炉で窒素ガスを流しながら、最高温度９００℃で１時間焼成する事でフェノール樹脂の炭化を同時に行った。これにより、黒鉛成分の含有量６０質量部、Ｓｉ含有量３０質量部、炭素質物１０質量部（フェノール樹脂由来のハードカーボン含有量）からなる略球状焼成粉を得た。
(Baking process)
The obtained powder was put into a quartz boat, and the phenol resin was carbonized at the same time by firing at a maximum temperature of 900 ° C. for 1 hour while flowing nitrogen gas in a tubular furnace. As a result, a substantially spherical calcined powder having a graphite component content of 60 parts by mass, a Si content of 30 parts by mass, and a carbonaceous material of 10 parts by mass (phenolic resin-derived hard carbon content) was obtained.
その後、目開き４５μｍのメッシュを通し、軽装かさ密度６３５ｇ／Ｌ、平均粒径（Ｄ５０）が２２．０μｍ、ＢＥＴ比表面積：６３．３ｍ２／ｇの略球状焼成粉を得た。 Thereafter, a substantially spherical calcined powder having a light bulk density of 635 g / L, an average particle diameter (D50) of 22.0 μm, and a BET specific surface area of 63.3 m 2 / g was obtained through a mesh having an opening of 45 μm.
（コールタールピッチによる炭素被覆）
得られた略球状焼成粉１５０ｇとコールタールピッチ１１８ｇをボールミルにより混合した後、キノリン１５０ｇを加え、１０分間撹拌した後、以下の方法を用い焼成を行い、被覆を行った。
(Carbon coating with coal tar pitch)
After 150 g of the obtained substantially spherical fired powder and 118 g of coal tar pitch were mixed by a ball mill, 150 g of quinoline was added and stirred for 10 minutes, followed by firing using the following method for coating.
（焼成）
窒素を流しながら（４Ｌ／ｍｉｎ）、昇温速度を５℃／ｍｉｎとし、混合物を６００℃で２時間加熱することで、コールタールピッチをソフトカーボンへ変性させた。これにより、黒鉛成分の含有量６０質量部、Ｓｉ含有量３０質量部、炭素質物４０質量部（フェノール樹脂由来のハードカーボンの含有量１０質量部、コールタールピッチ由来のソフトカーボンの含有量３０質量部）からなるシリコン系リチウム二次電池用複合活物質を得た。
(Baking)
While flowing nitrogen (4 L / min), the heating rate was set to 5 ° C./min, and the mixture was heated at 600 ° C. for 2 hours to modify the coal tar pitch to soft carbon. Thereby, the content of graphite component is 60 parts by mass, the Si content is 30 parts by mass, the carbonaceous material is 40 parts by mass (the content of hard carbon derived from phenol resin is 10 parts by mass, the content of soft carbon derived from coal tar pitch is 30 parts by mass. A composite active material for silicon-based lithium secondary batteries.
（解砕・篩）
得られたシリコン系リチウム二次電池用複合活物質をスタンプミルにて解砕した後にボールミルによって粉砕し、目開き４５μｍのメッシュを通し、軽装かさ密度４０５ｇ／Ｌ、平均粒径（Ｄ５０）が１５．９μｍの粉砕粉を得た。
(Crushing / Sieving)
The obtained composite active material for a silicon-based lithium secondary battery was pulverized by a stamp mill and then pulverized by a ball mill, passed through a mesh having a mesh size of 45 μm, a light bulk density of 405 g / L, and an average particle size (D50) of 15 A pulverized powder of 9 μm was obtained.
（気相コートによる炭素被覆）
コールタールピッチによる炭素被覆された粉砕粉１００ｇを高砂工業製バッチ式ロータリーキルンＴＲＢ−０−１Ｅ（容量１００Ｌ）に投入し、昇温速度は２００℃／ｈｒ、エチレン２Ｌ／ｍｉｎ、窒素８Ｌ／ｍｉｎを流しながら９００℃１時間の加熱によるＣＶＤ炭素被覆を行った。ＣＶＤ炭素被覆による重量増加量は同一バッチ内３か所測定して平均１７％、標準偏差４．０であった。これにより、黒鉛成分の含有量６０質量部、Ｓｉ含有量３０質量部、炭素質物５９質量部（フェノール樹脂由来のハードカーボンの含有量１０質量部、コールタールピッチ由来のソフトカーボンの含有量３２質量部、ＣＶＤ炭素被膜１７質量部）からなるシリコン系リチウム二次電池用複合活物質を得た。
(Carbon coating by vapor phase coating)
100 g of pulverized powder coated with carbon by coal tar pitch is put into a batch rotary kiln TRB-0-1E (capacity 100 L) manufactured by Takasago Industry, and the heating rate is 200 ° C./hr, ethylene 2 L / min, nitrogen 8 L / min. CVD carbon coating was performed by heating at 900 ° C. for 1 hour while flowing. The weight gain due to CVD carbon coating was measured at 3 locations in the same batch with an average of 17% and a standard deviation of 4.0. Thereby, the content of graphite component is 60 parts by mass, the Si content is 30 parts by mass, the carbonaceous material is 59 parts by mass (the content of hard carbon derived from phenol resin is 10 parts by mass, the content of soft carbon derived from coal tar pitch is 32 parts by mass. A composite active material for a silicon-based lithium secondary battery was obtained.
その物性は以下の通りである。粒度分布Ｄ５０：３２μｍ、Ｄ９０：５２μｍ、ＢＥＴ比表面積：１．５ｍ２／ｇ、開気孔体積：０．００３ｃｍ３／ｇ、形状：略球状。 The physical properties are as follows. Particle size distribution D50: 32 μm, D90: 52 μm, BET specific surface area: 1.5 m 2 / g, open pore volume: 0.003 cm 3 / g, shape: substantially spherical.
ＳＥＭ（走査型電子顕微鏡）による、シリコン系リチウム二次電池用複合活物質の二次電子像を図１に、またシリコン系リチウム二次電池用複合活物質の粒子断面の二次電子像を図２に示す。 FIG. 1 shows a secondary electron image of a composite active material for a silicon-based lithium secondary battery, and FIG. 1 shows a secondary electron image of a particle cross section of the composite active material for a silicon-based lithium secondary battery, using an SEM (scanning electron microscope). It is shown in 2.
これによりシリコン系リチウム二次電池用複合活物質においては、黒鉛成分およびＳｉ化合物がソフトカーボンで覆われた構造であることが分かる。 Accordingly, it can be seen that the composite active material for a silicon-based lithium secondary battery has a structure in which the graphite component and the Si compound are covered with soft carbon.
また、上記（コールタールピッチによる被覆）を実施する前の略球形の混合物のＢＥＴ比表面積が６３．３ｍ２／ｇであり、得られた略球形のシリコン系リチウム二次電池用複合活物質のＢＥＴ比表面積が１．５ｍ２／ｇであり、ＢＥＴ比表面積が大きく低下している点からも、黒鉛成分およびＳｉが炭素質物であるソフトカーボン、ＣＶＤ炭素被膜で覆われた構造をとっていることが分かる。 Moreover, the BET specific surface area of the substantially spherical mixture before carrying out the above (coating with coal tar pitch) is 63.3 m 2 / g, and the obtained substantially spherical composite active material for a silicon-based lithium secondary battery From the point that the BET specific surface area is 1.5 m 2 / g and the BET specific surface area is greatly reduced, it has a structure in which the graphite component and Si are covered with soft carbon, which is a carbonaceous material, and a CVD carbon film. I understand that.
得られたシリコン系リチウム二次電池用複合活物質は、Ｘ線回析において１０〜２０°にピークを有しない（図３）。 The obtained composite active material for a silicon-based lithium secondary battery does not have a peak at 10 to 20 ° in X-ray diffraction (FIG. 3).
（リチウム二次電池用負極の作製）
得られたシリコン系リチウム二次電池用複合活物質９５．５重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてＴｉｍｃａｌ製スーパーＣ６５を０．５重量％と、バインダとして和光純薬工業製ＣＬＰを４重量％、水とを混合して負極合剤含有スラリーを調製した。
(Preparation of negative electrode for lithium secondary battery)
With respect to the obtained composite active material for silicon-based lithium secondary battery 95.5% by weight (content in the total amount of solids, the same applies hereinafter), Supercal C65 manufactured by Timcal as a conductive auxiliary agent was 0.5% by weight. Then, 4% by weight of CLP manufactured by Wako Pure Chemical Industries, Ltd. as a binder and water were mixed to prepare a negative electrode mixture-containing slurry.
得られたスラリーを、アプリケータを用いて固形分塗布量が４．９ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて２時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力３ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で２時間熱処理して、厚みが２４μｍの負極合剤層を形成したリチウムイオン二次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 4.9 mg / cm 2, and dried at 110 ° C. in a vacuum dryer for 2 hours. After drying, the battery is punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 3 t / cm 2 , and further heat-treated at 110 ° C. for 2 hours under vacuum to form a negative electrode mixture layer having a thickness of 24 μm. A negative electrode was obtained.
「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１８ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒とし、添加剤はＦＥＣ（フルオロエチレンカーボネイト）とし、ＬｉＰＦ６を１．２ｖｏｌ／Ｌの濃度になるように溶解させたものを使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置に接続した。
"Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, a 18 mmφ 0.2 mm thick metal lithium and a stainless steel foil of the base material into the electrolyte solution in the glove box. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolyte used was a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1, the additive was FEC (fluoroethylene carbonate), and LiPF 6 was dissolved to a concentration of 1.2 vol / L. did. The evaluation cell was further placed in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to the charge / discharge device.
評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、２．２ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、２．２ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。また、サイクル特性は、前記充放電条件にて２０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。
＜実施例２＞
（分級工程）
実施例１で作成したＣＶＤ炭素被覆粉３０ｇを準備した。
The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V at a constant current of 2.2 mA until the current value reached 0.2 mA at a constant voltage of 0.01 V. The discharge was performed at a constant current of 2.2 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test. In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 20 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.
<Example 2>
(Classification process)
30 g of CVD carbon-coated powder prepared in Example 1 was prepared.
このシリコン系リチウム二次電池用複合活物質を風力分級装置（ホソカワミクロン製 ＡＴＰ−５０）に投入し、分級機回転速度１５，０００ｒｐｍにて分級し、平均粒径（Ｄ５０）が８μｍ、Ｄ９０が１６μｍ、ＢＥＴ比表面積が４．９ｍ２／ｇ、開気孔体積：０．０２ｃｍ３／ｇ、軽装かさ密度が２２０ｇ／Ｌのシリコン系リチウム二次電池用複合活物質を得た。 This composite active material for silicon-based lithium secondary battery is put into an air classifier (ATP-50 manufactured by Hosokawa Micron), and classified at a classifier rotating speed of 15,000 rpm, with an average particle diameter (D50) of 8 μm and D90 of 16 μm. A composite active material for a silicon-based lithium secondary battery having a BET specific surface area of 4.9 m 2 / g, an open pore volume of 0.02 cm 3 / g, and a light bulk density of 220 g / L was obtained.
また、上記（炭素質物であるコールタールピッチによる被覆）を実施する前の略球形の混合物のＢＥＴ比表面積が６３．３ｍ２／ｇであり、得られた略球形のシリコン系リチウム二次電池用複合活物質のＢＥＴ比表面積が４．９ｍ２／ｇであり、ＢＥＴ比表面積が大きく低下している点からも、黒鉛成分およびＳｉが炭素質物であるソフトカーボン、ＣＶＤ炭素被膜で覆われた構造をとっていることが分かる。 Moreover, the BET specific surface area of the substantially spherical mixture before the above (coating with coal tar pitch, which is a carbonaceous material) is 63.3 m 2 / g, and the obtained substantially spherical silicon-based lithium secondary battery Since the BET specific surface area of the composite active material is 4.9 m 2 / g and the BET specific surface area is greatly reduced, the structure in which the graphite component and soft carbon in which Si is a carbonaceous material and a CVD carbon film are covered. You can see that
（リチウムイオン２次電池用負極の作製）
得られたシリコン系リチウム二次電池用複合活物質９５．５重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてＴｉｍｃａｌ製スーパーＣ６５を０．５重量％と、バインダとして和光純薬工業製ＣＬＰＡを４重量％、水とを混合して負極合剤含有スラリーを調製した。
(Preparation of negative electrode for lithium ion secondary battery)
With respect to the obtained composite active material for silicon-based lithium secondary battery 95.5% by weight (content in the total amount of solids, the same applies hereinafter), Supercal C65 manufactured by Timcal as a conductive auxiliary agent was 0.5% by weight. Then, 4% by weight of CLPA manufactured by Wako Pure Chemical Industries, Ltd. as a binder and water were mixed to prepare a negative electrode mixture-containing slurry.
得られたスラリーを、アプリケータを用いて固形分塗布量が４．２ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて２時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力３ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で２時間熱処理して、厚みが２０μｍの負極合剤層を形成したリチウムイオン二次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 4.2 mg / cm 2 and dried at 110 ° C. for 2 hours in a vacuum dryer. After drying, the battery is punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 3 t / cm 2 , and further heat-treated at 110 ° C. for 2 hours under vacuum to form a negative electrode mixture layer having a thickness of 20 μm. A negative electrode was obtained.
「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１８ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒とし、添加剤はＦＥＣ（フルオロエチレンカーボネイト）とし、ＬｉＰＦ６を１．２ｖｏｌ／Ｌの濃度になるように溶解させたものを使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置に接続した。
"Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, a 18 mmφ 0.2 mm thick metal lithium and a stainless steel foil of the base material into the electrolyte solution in the glove box. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolyte used was a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1, the additive was FEC (fluoroethylene carbonate), and LiPF 6 was dissolved to a concentration of 1.2 vol / L. did. The evaluation cell was further placed in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to the charge / discharge device.
評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、２．２ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、２．２ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。また、サイクル特性は、前記充放電条件にて１０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。 The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V at a constant current of 2.2 mA until the current value reached 0.2 mA at a constant voltage of 0.01 V. The discharge was performed at a constant current of 2.2 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test. In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 10 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.
また、得られたシリコン系リチウム二次電池用複合活物質に電解液（エチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒とし、ＬＩＰＦ６を１．２ｍｏｌ／Ｌの濃度になるように溶解させ、これにフルオロエチレンカーボネートを２体積％添加したものを使用した）をアルゴン雰囲気中に１２時間浸漬し、乾燥後、断面をＥＤＳにて電解液成分であるＦ元素の測定を行い、浸漬の有無を確認した結果、浸漬は認められなかった。
＜実施例３＞
実施例１と同様の方法で膨張黒鉛の調整から解砕・篩を行った。
（気相コートによる炭素被覆）
コールタールピッチによる炭素被覆された粉砕粉１００ｇをロータリーキルンに投入し、昇温速度は２００℃／ｈｒ、プロピレン１Ｌ／ｍｉｎ、窒素９Ｌ／ｍｉｎを流しながら９５０℃１時間の加熱によるＣＶＤ炭素被覆を行った。ＣＶＤ炭素被覆による重量増加量は１９％であった。これにより、黒鉛成分の含有量６０質量部、Ｓｉ含有量３０質量部、炭素質物６１質量部（フェノール樹脂由来のハードカーボンの含有量１０質量部、コールタールピッチ由来のソフトカーボンの含有量３２質量部、ＣＶＤ炭素被膜１９質量部）からなるシリコン系リチウム二次電池用複合活物質を得た。 その物性は以下の通りである。粒度分布Ｄ５０：３０μｍ、Ｄ９０：５０μｍ、ＢＥＴ比表面積：０．９ｍ２／ｇ、開気孔体積：０．００３ｃｍ３／ｇ、形状：略球状。
In addition, an electrolytic solution (ethylene carbonate and diethyl carbonate as a mixed solvent having a volume ratio of 1: 1) and LIPF 6 dissolved to a concentration of 1.2 mol / L in the obtained composite active material for a silicon-based lithium secondary battery And 2% by volume of fluoroethylene carbonate was used) was immersed in an argon atmosphere for 12 hours, and after drying, the cross-section of the element F was measured with an EDS, and the immersion was measured. As a result of confirming the presence or absence, immersion was not recognized.
<Example 3>
Crushing and sieving were performed from the adjustment of expanded graphite in the same manner as in Example 1.
(Carbon coating by vapor phase coating)
100 g of pulverized powder coated with carbon by coal tar pitch is put into a rotary kiln and CVD carbon coating is performed by heating at 950 ° C. for 1 hour while flowing a heating rate of 200 ° C./hr, propylene 1 L / min, and nitrogen 9 L / min. It was. Weight gain due to CVD carbon coating was 19%. Thereby, the content of graphite component is 60 parts by mass, the Si content is 30 parts by mass, the carbonaceous material is 61 parts by mass (the content of hard carbon derived from phenol resin is 10 parts by mass, the content of soft carbon derived from coal tar pitch is 32 parts by mass. A composite active material for a silicon-based lithium secondary battery was obtained. The physical properties are as follows. Particle size distribution D50: 30 μm, D90: 50 μm, BET specific surface area: 0.9 m 2 / g, open pore volume: 0.003 cm 3 / g, shape: substantially spherical.
また、上記（コールタールピッチによる被覆）を実施する前の略球形の混合物のＢＥＴ比表面積が６３．３ｍ２／ｇであり、得られた略球形のシリコン系リチウム二次電池用複合活物質のＢＥＴ比表面積が０．９ｍ２／ｇであり、ＢＥＴ比表面積が大きく低下している点からも、黒鉛成分およびＳｉが炭素質物であるソフトカーボン、ＣＶＤ炭素被膜で覆われた構造をとっていることが分かる。 Moreover, the BET specific surface area of the substantially spherical mixture before carrying out the above (coating with coal tar pitch) is 63.3 m 2 / g, and the obtained substantially spherical composite active material for a silicon-based lithium secondary battery From the point that the BET specific surface area is 0.9 m 2 / g and the BET specific surface area is greatly reduced, the graphite component and Si are covered with soft carbon, a carbonaceous material, and a CVD carbon film. I understand that.
（リチウムイオン２次電池用負極の作製）
得られたシリコン系リチウム二次電池用複合活物質に対して、実施例２と同様の方法でリチウムイオン二次電池用負極を得て、評価用セルの作製と評価を行った。
＜実施例４＞
実施例３で作成したＣＶＤ炭素被覆粉３０ｇを準備した。
(Preparation of negative electrode for lithium ion secondary battery)
With respect to the obtained composite active material for a silicon-based lithium secondary battery, a negative electrode for a lithium ion secondary battery was obtained in the same manner as in Example 2, and an evaluation cell was prepared and evaluated.
<Example 4>
30 g of CVD carbon-coated powder prepared in Example 3 was prepared.
このシリコン系リチウム二次電池用複合活物質を実施例２と同様の方法で分級し、平均粒径（Ｄ５０）が７μｍ、Ｄ９０が１２μｍ、ＢＥＴ比表面積が４．２ｍ２／ｇ、開気孔体積：０．０２ｃｍ３／ｇ、軽装かさ密度が２２０ｇ／Ｌのシリコン系リチウム二次電池用複合活物質を得た。
（リチウムイオン２次電池用負極の作製）
得られたシリコン系リチウム二次電池用複合活物質に対して、実施例２と同様の方法でリチウムイオン二次電池用負極を得て、評価用セルの作製と評価を行った。
＜実施例５＞
実施例１と同様の方法で膨張黒鉛の調整から解砕・篩を行った。
（気相コートによる炭素被覆）
コールタールピッチによる炭素被覆された粉砕粉１００ｇをロータリーキルンに投入し、昇温速度は２００℃／ｈｒ、エチレン０．５Ｌ／ｍｉｎ、窒素１Ｌ／ｍｉｎを流しながら９５０℃１．７時間の加熱によるＣＶＤ炭素被覆を行った。ＣＶＤ炭素被覆による重量増加量は２７％であった。これにより、黒鉛成分の含有量６０質量部、Ｓｉ含有量３０質量部、炭素質物６９質量部（フェノール樹脂由来のハードカーボンの含有量１０質量部、コールタールピッチ由来のソフトカーボンの含有量３２質量部、ＣＶＤ炭素被膜２７質量部）からなるシリコン系リチウム二次電池用複合活物質を得た。このシリコン系リチウム二次電池用複合活物質を実施例２と同様の装置、条件にて分級し、平均粒径（Ｄ５０）が９μｍ、Ｄ９０が１９μｍ、ＢＥＴ比表面積が７．１ｍ２／ｇ、開気孔体積：０．０２ｃｍ３／ｇのシリコン系リチウム二次電池用複合活物質を得た。
This composite active material for a silicon-based lithium secondary battery was classified in the same manner as in Example 2. The average particle size (D50) was 7 μm, D90 was 12 μm, the BET specific surface area was 4.2 m 2 / g, and the open pore volume. : A composite active material for a silicon-based lithium secondary battery having 0.02 cm 3 / g and a light bulk density of 220 g / L was obtained.
(Preparation of negative electrode for lithium ion secondary battery)
With respect to the obtained composite active material for a silicon-based lithium secondary battery, a negative electrode for a lithium ion secondary battery was obtained in the same manner as in Example 2, and an evaluation cell was prepared and evaluated.
<Example 5>
Crushing and sieving were performed from the adjustment of expanded graphite in the same manner as in Example 1.
(Carbon coating by vapor phase coating)
100 g of pulverized powder coated with carbon by coal tar pitch is put into a rotary kiln, and the heating rate is 200 ° C./hr, ethylene 0.5 L / min, nitrogen 1 L / min, and heating by 950 ° C. for 1.7 hours. Carbon coating was performed. Weight gain due to CVD carbon coating was 27%. Thereby, content of graphite component 60 parts by mass,
また、上記（コールタールピッチによる被覆）を実施する前の略球形の混合物のＢＥＴ比表面積が６３．３ｍ２／ｇであり、得られた略球形のシリコン系リチウム二次電池用複合活物質のＢＥＴ比表面積が７．１ｍ２／ｇであり、ＢＥＴ比表面積が大きく低下している点からも、黒鉛成分およびＳｉが炭素質物であるソフトカーボン、ＣＶＤ炭素被膜で覆われた構造をとっていることが分かる。 Moreover, the BET specific surface area of the substantially spherical mixture before carrying out the above (coating with coal tar pitch) is 63.3 m 2 / g, and the obtained substantially spherical composite active material for a silicon-based lithium secondary battery The BET specific surface area is 7.1 m 2 / g, and from the point that the BET specific surface area is greatly reduced, the graphite component and Si are covered with soft carbon, which is a carbonaceous material, and a CVD carbon film. I understand that.
（リチウムイオン２次電池用負極の作製）
得られたシリコン系リチウム二次電池用複合活物質に対して、実施例２と同様の方法でリチウムイオン二次電池用負極を得て、評価用セルの作製と評価を行った。
＜参考例１＞
実施例１で得られた略球状焼成粉を参考例１のシリコン系リチウム二次電池用複合活物質とし、得られたシリコン系リチウム二次電池用複合活物質９５．５重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてＴｉｍｃａｌ製スーパーＣ６５を０．５重量％と、バインダとして和光純薬工業製ＣＬＰＡを４重量％、水とを混合して負極合剤含有スラリーを調製した。
(Preparation of negative electrode for lithium ion secondary battery)
With respect to the obtained composite active material for a silicon-based lithium secondary battery, a negative electrode for a lithium ion secondary battery was obtained in the same manner as in Example 2, and an evaluation cell was prepared and evaluated.
<Reference Example 1>
The substantially spherical calcined powder obtained in Example 1 was used as the composite active material for silicon-based lithium secondary battery of Reference Example 1, and the resulting composite active material for silicon-based lithium secondary battery was 95.5% by weight (total amount of solids) The same is applied to the negative electrode), and 0.5% by weight of Timcal Super C65 as a conductive additive, 4% by weight of CLPA manufactured by Wako Pure Chemical Industries as a binder, and water are mixed. An agent-containing slurry was prepared.
得られたスラリーを、アプリケータを用いて固形分塗布量が３．９ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて２時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力３ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で２時間熱処理して、厚みが１９μｍの負極合剤層を形成したリチウムイオン二次電池用負極を得た。 The obtained slurry was applied to a copper foil with a thickness of 18 μm using an applicator so that the solid content was 3.9 mg / cm 2 and dried at 110 ° C. for 2 hours in a vacuum dryer. After drying, a lithium ion secondary battery in which a negative electrode mixture layer having a thickness of 19 μm is formed by punching into a circle of 14 mmφ, uniaxial pressing under conditions of a pressure of 3 t / cm 2 , and further heat-treating at 110 ° C. for 2 hours under vacuum. A negative electrode was obtained.
「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１８ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒とし、添加剤はＦＥＣ（フルオロエチレンカーボネイト）とし、ＬｉＰＦ６を１．２ｖｏｌ／Ｌの濃度になるように溶解させたものを使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置に接続した。
"Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, a 18 mmφ 0.2 mm thick metal lithium and a stainless steel foil of the base material into the electrolyte solution in the glove box. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolyte used was a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1, the additive was FEC (fluoroethylene carbonate), and LiPF 6 was dissolved to a concentration of 1.2 vol / L. did. The evaluation cell was further placed in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to the charge / discharge device.
評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、２．２ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、２．２ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。また、サイクル特性は、前記充放電条件にて２０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。
＜比較例１＞
市販の人造黒鉛９５．５重量％（固形分全量中の含有量。以下同じ。）に対して、導電助剤としてＴｉｍｃａｌ製スーパーＣ６５を０．５重量％と、バインダとして和光純薬工業製ＣＬＰＡを４重量％、水とを混合して負極合剤含有スラリーを調製した。
The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V at a constant current of 2.2 mA until the current value reached 0.2 mA at a constant voltage of 0.01 V. The discharge was performed at a constant current of 2.2 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test. In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 20 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.
<Comparative Example 1>
With respect to 95.5% by weight of commercially available artificial graphite (content in the total solid content; the same applies hereinafter), 0.5% by weight of Timcal Super C65 as a conductive auxiliary and CLPA manufactured by Wako Pure Chemical Industries as a binder Was mixed with 4% by weight of water to prepare a negative electrode mixture-containing slurry.
得られたスラリーを、アプリケータを用いて固形分塗布量が４．７ｍｇ／ｃｍ２になるように厚みが１８μｍの銅箔に塗布し、１１０℃で真空乾燥機にて２時間乾燥した。乾燥後、１４ｍｍφの円形に打ち抜き、圧力０．６ｔ／ｃｍ２の条件で一軸プレスし、さらに真空下、１１０℃で２時間熱処理して、厚みが２２μｍの負極合剤層を形成したリチウムイオン二次電池用負極を得た。 The obtained slurry was applied to a copper foil having a thickness of 18 μm using an applicator so that the solid content was 4.7 mg / cm 2 and dried at 110 ° C. for 2 hours in a vacuum dryer. After drying, it was punched into a circle of 14 mmφ, uniaxially pressed under conditions of a pressure of 0.6 t / cm 2 , and further heat-treated at 110 ° C. for 2 hours under vacuum to form a negative electrode mixture layer having a thickness of 22 μm. A negative electrode for a secondary battery was obtained.
「評価用セルの作製」
評価用セルは、グローブボックス中でスクリューセルに上記負極、２４ｍｍφのポリプロピレン製セパレータ、２１ｍｍφのガラスフィルター、１８ｍｍφで厚み０．２ｍｍの金属リチウムおよびその基材のステンレス箔を、各々、電解液にディップしたのち、この順に積層し、最後に蓋をねじ込み作製した。電解液はエチレンカーボネートとジエチルカーボネートを体積比１対１の混合溶媒とし、添加剤はＦＥＣ（フルオロエチレンカーボネイト）とし、ＬｉＰＦ６を１．２ｖｏｌ／Ｌの濃度になるように溶解させたものを使用した。評価用セルは、さらにシリカゲルを入れた密閉ガラス容器に入れて、シリコンゴムの蓋を通した電極を充放電装置に接続した。
"Production of evaluation cells"
In the glove box, the evaluation cell was prepared by dipping the negative electrode, a 24 mmφ polypropylene separator, a 21 mmφ glass filter, a 18 mmφ 0.2 mm thick metal lithium and a stainless steel foil of the base material into the electrolyte solution in the glove box. After that, the layers were laminated in this order, and finally the lid was screwed in. The electrolyte used was a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1, the additive was FEC (fluoroethylene carbonate), and LiPF 6 was dissolved to a concentration of 1.2 vol / L. did. The evaluation cell was further placed in a sealed glass container containing silica gel, and an electrode through a silicon rubber lid was connected to the charge / discharge device.
評価用セルは２５℃の恒温室にて、サイクル試験した。充電は、２．２ｍＡの定電流で０．０１Ｖまで充電後、０．０１Ｖの定電圧で電流値が０．２ｍＡになるまで行った。また放電は、２．２ｍＡの定電流で１．５Ｖの電圧値まで行った。初回放電容量と初期充放電効率は、初回充放電試験の結果とした。また、サイクル特性は、前記充放電条件にて２０回充放電試験した後の放電容量を初回の放電容量と比較し、その容量維持率として評価した。 The evaluation cell was cycle tested in a constant temperature room at 25 ° C. Charging was performed after charging to 0.01 V at a constant current of 2.2 mA until the current value reached 0.2 mA at a constant voltage of 0.01 V. The discharge was performed at a constant current of 2.2 mA up to a voltage value of 1.5V. The initial discharge capacity and initial charge / discharge efficiency were the results of the initial charge / discharge test. In addition, the cycle characteristics were evaluated as the capacity retention rate by comparing the discharge capacity after 20 charge / discharge tests under the charge / discharge conditions with the initial discharge capacity.
上記表１に示すように、実施例１で示される、本発明のシリコン系リチウム二次電池用複合活物質を用いたハーフセルは、９００ｍＡｈ／ｇ以上の高い容量を示すにもかかわらず９９．０％以上の高い２０回目クーロン効率を示すことが確認された。実施例３〜５で示される本発明のシリコン系リチウム二次電池用複合活物質を用いたハーフセルは、８５０ｍＡｈ／ｇ以上の高い容量を示すにもかかわらず９８．０％以上の高い２０回目クーロン効率を示すことが確認された。参考例１では２０回目クーロン効率に劣り、比較例１では充放電容量に劣った。 As shown in Table 1 above, the half cell using the composite active material for a silicon-based lithium secondary battery of the present invention shown in Example 1 is 99.0 despite showing a high capacity of 900 mAh / g or more. It was confirmed that the 20th Coulomb efficiency was as high as% or more. Although the half cell using the composite active material for silicon-based lithium secondary batteries of the present invention shown in Examples 3 to 5 shows a high capacity of 850 mAh / g or more, it is a high 20th coulomb of 98.0% or more. It was confirmed to show efficiency. In Reference Example 1, the 20th Coulomb efficiency was inferior, and in Comparative Example 1, the charge / discharge capacity was inferior.
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| CN115332523B (en) * | 2022-10-11 | 2022-12-27 | 无锡威孚环保催化剂有限公司 | Silicon-carbon negative electrode material derived by using polymer gel as matrix and preparation method thereof |
| CN117080420A (en) * | 2023-10-16 | 2023-11-17 | 瑞浦兰钧能源股份有限公司 | Negative plate and battery |
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