JP2013218817A - Negative electrode active material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery - Google Patents
Negative electrode active material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery Download PDFInfo
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Abstract
Description
本発明は、非水電解質二次電池用の負極活物質、及びこれを用いた非水電解質二次電池に関するものである。 The present invention relates to a negative electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery using the same.
リチウムイオン二次電池等の非水電解質二次電池において、負極活物質としては従来、粒子状黒鉛が広く用いられている。電界質との反応性を抑制するために、粒子状黒鉛の表面に非晶質炭素被膜を設けることがなされている。 In non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, particulate graphite has been widely used as the negative electrode active material. In order to suppress the reactivity with the electrolyte, an amorphous carbon film is provided on the surface of the particulate graphite.
例えば、特許文献１には、負極の密着性及び負荷特性に優れた非水電解質二次電池を提供することを目的として、粒子状黒鉛の表面に、単体で焼成した場合の比表面積が２００〜５００ｍ２／ｇ、分子量が３００〜５００の非晶質炭素となる物質が被覆され、且つ被覆量が前記黒鉛に対して０．１〜１０質量％である非水電解質二次電池用の負極活物質が開示されている（請求項１）。
For example,
本発明の関連技術としては特許文献２がある。
特許文献２には、前方微小角散乱法による粒子径及び粒子形状の同時計測・判定方法及び装置が開示されている（請求項１、２）。
There exists
非水電解質二次電池においては、容量維持率、例えば６０℃保存における容量維持率が高いことが好ましい。従来、粒子状黒鉛と非黒鉛炭素被膜とを備えた負極活物質において、容量維持率に関与する因子が不明である。炭素被膜量が少ないため、その状態を評価すること自体が難しい。
例えば特許文献２に記載のように、光散乱法を用いて粒子形状を測定することが可能である。しかしながら、本発明者が検討したところ、特許文献２に記載の方法を粒子状黒鉛と非黒鉛炭素被膜とを備えた負極活物質にそのまま適用しても、容量維持率との関与を見出すことができなかった。
In the non-aqueous electrolyte secondary battery, it is preferable that the capacity maintenance rate, for example, the capacity maintenance rate at 60 ° C. storage is high. Conventionally, in a negative electrode active material provided with particulate graphite and a non-graphite carbon coating, the factors involved in the capacity retention rate are unknown. Since the amount of carbon coating is small, it is difficult to evaluate the state itself.
For example, as described in
本発明は上記事情に鑑みてなされたものであり、粒子状黒鉛と非黒鉛炭素被膜とを備えた負極活物質において容量維持率に関与する因子を明らかとし、粒子状黒鉛の表面に非黒鉛炭素被膜が形成されており、非水電解質二次電池の容量維持率を向上することが可能な非水電解質二次電池用の負極活物質を提供することを目的とするものである。 The present invention has been made in view of the above circumstances, and has clarified factors relating to capacity retention in a negative electrode active material having a particulate graphite and a non-graphitic carbon coating, and the surface of the particulate graphite is non-graphitic carbon. An object of the present invention is to provide a negative electrode active material for a non-aqueous electrolyte secondary battery that has a coating film and can improve the capacity retention rate of the non-aqueous electrolyte secondary battery.
本発明の非水電解質二次電池用の負極活物質は、
粒子状黒鉛と、当該粒子状黒鉛の表面に形成された非黒鉛炭素被膜とを有する非水電解質二次電池用の負極活物質であって、
前記非黒鉛炭素被膜は、走査型透過電子顕微鏡（ＳＴＥＭ）観察にて格子縞が確認されるものであり、
前記負極活物質の平均粒径ｄ５０が９〜２４μｍであり、
前記負極活物質の光散乱光学測定を実施したとき、Ｑ＝４πｓｉｎθ／λ＝０．００１７〜０．００４８ｎｍ−１の範囲において、得られたデータの近似式ｙ＝ａ・Ｑ−ｂを求め（ここで、ｙは散乱強度、θは散乱角の１／２、λはＸ線の波長、ａ及びｂは定数をそれぞれ示す。）、パラメータｂが０．１〜２．１の範囲にある非水電解質二次電池用の負極活物質である。
The negative electrode active material for the non-aqueous electrolyte secondary battery of the present invention is
A negative electrode active material for a non-aqueous electrolyte secondary battery having a particulate graphite and a non-graphite carbon coating formed on the surface of the particulate graphite,
The non-graphitic carbon coating is one in which lattice fringes are confirmed by scanning transmission electron microscope (STEM) observation,
The negative electrode active material has an average particle diameter d50 of 9 to 24 μm,
When light scattering optical measurement of the negative electrode active material was performed, an approximate expression y = a · Q −b of the obtained data was obtained in the range of Q = 4π sin θ / λ = 0.001 to 0.0048 nm −1 ( Here, y is the scattering intensity, θ is 1/2 of the scattering angle, λ is the X-ray wavelength, a and b are constants, respectively), and the parameter b is in the range of 0.1 to 2.1. It is a negative electrode active material for water electrolyte secondary batteries.
本発明の非水電解質二次電池は、正極と、上記の非水電解質二次電池用の負極活物質を含む負極と、非水電解質とを備えたものである。 The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode including the negative electrode active material for the non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte.
本発明によれば、粒子状黒鉛と非黒鉛炭素被膜とを備えた負極活物質において容量維持率に関与する因子が明らかとされ、粒子状黒鉛の表面に非黒鉛炭素被膜が形成されており、非水電解質二次電池の容量維持率を向上することが可能な非水電解質二次電池用の負極活物質を提供することができる。 According to the present invention, the factor relating to the capacity retention rate in the negative electrode active material provided with the particulate graphite and the non-graphitic carbon coating is clarified, and the non-graphitic carbon coating is formed on the surface of the particulate graphite. A negative electrode active material for a non-aqueous electrolyte secondary battery that can improve the capacity retention rate of the non-aqueous electrolyte secondary battery can be provided.
以下、本発明について詳述する。
本発明は、非水電解質二次電池用の負極活物質、及びこれを用いた非水電解質二次電池に関するものである。
Hereinafter, the present invention will be described in detail.
The present invention relates to a negative electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery using the same.
「負極活物質」
本発明の非水電解質二次電池用の負極活物質は、
粒子状黒鉛と、当該粒子状黒鉛の表面に形成された非黒鉛炭素被膜とを有する非水電解質二次電池用の負極活物質であって、
前記非黒鉛炭素被膜は、走査型透過電子顕微鏡（ＳＴＥＭ）観察にて格子縞が確認されるものであり、
前記負極活物質の平均粒径ｄ５０が９〜２４μｍであり、
前記負極活物質の光散乱光学測定を実施したとき、Ｑ＝０．００１７〜０．００４８ｎｍ−１の範囲において、得られたデータの近似式ｙ＝ａ・Ｑ−ｂを求め（ここで、ｙは散乱強度、θは散乱角の１／２、λはＸ線の波長、ａ及びｂは定数をそれぞれ示す。）、パラメータｂが０．１〜２．１の範囲にある非水電解質二次電池用の負極活物質である。
"Negative electrode active material"
The negative electrode active material for the non-aqueous electrolyte secondary battery of the present invention is
A negative electrode active material for a non-aqueous electrolyte secondary battery having a particulate graphite and a non-graphite carbon coating formed on the surface of the particulate graphite,
The non-graphitic carbon coating is one in which lattice fringes are confirmed by scanning transmission electron microscope (STEM) observation,
The negative electrode active material has an average particle diameter d50 of 9 to 24 μm,
When light scattering optical measurement of the negative electrode active material was performed, an approximate expression y = a · Q −b of the obtained data was obtained in the range of Q = 0.007 to 0.0048 nm −1 (where y Is the scattering intensity, θ is 1/2 of the scattering angle, λ is the X-ray wavelength, a and b are constants, respectively), and the non-aqueous electrolyte secondary whose parameter b is in the range of 0.1 to 2.1 It is a negative electrode active material for batteries.
リチウムイオン二次電池等の非水電解質二次電池において、負極活物質には、リチウムイオン等の吸蔵及び放出が可能な炭素材料が広く使用されている。特に高結晶性を有する黒鉛は、放電電位が平坦であり、真密度が高く、かつ充填性が良いなどの特性を有していることから、市販のリチウムイオン二次電池の多くの負極活物質として使用されている。 In nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries, carbon materials capable of inserting and extracting lithium ions and the like are widely used as negative electrode active materials. In particular, graphite having high crystallinity has characteristics such as a flat discharge potential, high true density, and good filling properties. Therefore, many negative electrode active materials for commercially available lithium ion secondary batteries are used. It is used as
本発明の負極活物質においては、電界質との反応性を抑制するために、粒子状黒鉛の表面に非黒鉛炭素被膜が形成されている。
「背景技術」の項で述べたように、従来、粒子状黒鉛の表面に形成される非黒鉛炭素被膜は、「非晶質」であることが一般的である。
本発明では、粒子状黒鉛の表面に形成される非黒鉛炭素被膜は、「非晶質」ではなく、黒鉛よりも低い「低結晶性」を有する。かかる低結晶性を有する非黒鉛炭素被膜を有する負極活物質自体、新規である。
In the negative electrode active material of the present invention, a non-graphitic carbon film is formed on the surface of particulate graphite in order to suppress reactivity with the electrolyte.
As described in the “Background Art” section, conventionally, the non-graphite carbon coating formed on the surface of particulate graphite is generally “amorphous”.
In the present invention, the non-graphite carbon film formed on the surface of the particulate graphite is not “amorphous” but has “low crystallinity” lower than that of graphite. The negative electrode active material itself having such a non-graphite carbon film having low crystallinity is novel.
「炭素材料の結晶性」は、ＳＴＥＭ観察にて評価できる。炭素材料のＳＴＥＭ像に格子縞が確認された場合、その材料は結晶性を有していると特定できる。
本発明において、粒子状黒鉛の表面に形成される低結晶性の非黒鉛炭素被膜は、ＳＴＥＭ像にて格子縞が観察され、かつ、ａ軸方向の結晶子サイズが小さく、あるいは、格子縞がウェーブするなど、黒鉛よりも格子縞の秩序が低く観察される。
The “crystallinity of the carbon material” can be evaluated by STEM observation. When lattice fringes are confirmed in the STEM image of the carbon material, it can be specified that the material has crystallinity.
In the present invention, the low crystalline non-graphite carbon film formed on the surface of particulate graphite has lattice fringes observed in the STEM image, and the crystallite size in the a-axis direction is small, or the lattice fringes are waved. For example, the order of lattice fringes is lower than that of graphite.
本発明者は、低結晶性を有する非黒鉛炭素被膜を備えた負極活物質を用いることにより、非晶質の非黒鉛炭素被膜を備えた従来の負極活物質を用いるよりも、初期抵抗の低い非水電解質二次電池が得られることを見出している。
非黒鉛炭素被膜が低結晶性を有することで、被膜の導電性等の特性が向上して、初期抵抗が低減されると考えられる。
なお、非黒鉛炭素被膜の結晶性が高くなりすぎて、黒鉛と同等あるいはそれに極めて近いレベルになると、粒子状黒鉛単独の場合との差がなくなり、表面凹凸が過小になって、電解質との反応性の抑制効果が低減されたり、リチウムイオン等の電気伝導を担うイオンの入るサイトが低減されてしまうと考えられる。
したがって、非黒鉛炭素被膜は、黒鉛よりも低い「低結晶性」を有することが重要である。
By using a negative electrode active material having a non-graphite carbon coating having low crystallinity, the present inventor has a lower initial resistance than using a conventional negative electrode active material having an amorphous non-graphite carbon coating. It has been found that a non-aqueous electrolyte secondary battery can be obtained.
It is considered that the non-graphite carbon coating has low crystallinity, thereby improving the properties such as the conductivity of the coating and reducing the initial resistance.
Note that if the non-graphite carbon coating becomes too high in crystallinity and is equivalent to or very close to that of graphite, there will be no difference from the case of particulate graphite alone, surface irregularities will be too small, and reaction with the electrolyte will occur. It is considered that the site where ions that bear electric conduction such as lithium ions enter is reduced.
Therefore, it is important that the non-graphitic carbon coating has a “low crystallinity” lower than that of graphite.
非水電解質二次電池においては、容量維持率、例えば６０℃保存における容量維持率が高いことが好ましい。
従来は、粒子状黒鉛と低結晶性を有する非黒鉛炭素被膜とを備えた負極活物質において、容量維持率に関与する因子が不明であった。
本発明者は、粒子状黒鉛と低結晶性を有する非黒鉛炭素被膜とを備えた負極活物質の粒子形状に着目した。
活物質粒子が真球状又はそれに近い形状であると、リチウムイオン等の電気伝導を担うイオンの脱挿入に伴う膨張収縮によって活物質粒子同士の接触面積が小さくなり、非水電解質二次電池の容量維持率が低下する傾向があると考えられる。活物質粒子の形状は真球状よりも、真球状から外れた形状が好ましいと考えられる。
In the non-aqueous electrolyte secondary battery, it is preferable that the capacity maintenance rate, for example, the capacity maintenance rate at 60 ° C. storage is high.
Conventionally, in a negative electrode active material provided with particulate graphite and a non-graphite carbon film having low crystallinity, a factor related to the capacity retention rate has been unknown.
The inventor paid attention to the particle shape of a negative electrode active material provided with particulate graphite and a non-graphite carbon film having low crystallinity.
If the active material particles have a spherical shape or a shape close thereto, the contact area between the active material particles is reduced due to expansion / contraction caused by the desorption / insertion of ions responsible for electrical conduction such as lithium ions, and the capacity of the non-aqueous electrolyte secondary battery It is thought that the maintenance rate tends to decrease. It is considered that the shape of the active material particles is preferably a shape deviating from the true sphere rather than the true sphere.
一般的に光散乱測定においては、粒子の形状あるいは粒子の界面状態等の情報が取得可能である。一般的な光散乱測定において、粒子サイズの逆数、散乱強度、及び得られる粒子情報については、図１左図のグラフに示す関係がある（非特許文献１より引用）。このグラフにおける横軸のｋ値は、粒子サイズＲ、Ｌ、又はεの逆数に対応する。粒子サイズＲ、Ｌ、εについては、図１右図を参照されたい。
図１には、一般的な光散乱測定において、ステージ（II）の範囲において粒子形状の情報が得られることが示されている。
光散乱光学測定におけるＱ値は、上記のｋ値である。
In general, in light scattering measurement, information such as particle shape or particle interface state can be acquired. In general light scattering measurement, the reciprocal of the particle size, the scattering intensity, and the obtained particle information have the relationship shown in the left graph of FIG. 1 (cited from Non-Patent Document 1). The k value on the horizontal axis in this graph corresponds to the inverse of the particle size R, L, or ε. For the particle sizes R, L, and ε, see the right figure in FIG.
FIG. 1 shows that particle shape information can be obtained in the range of stage (II) in a general light scattering measurement.
The Q value in the light scattering optical measurement is the k value described above.
本発明者は、Ｑ値を上記範囲（０．００１７〜０．００４８ｎｍ−１）としてパラメータｂを求めることで、非黒鉛炭素被膜の粒子形状の情報が良好に得られることを見出している。 The present inventor has found that the particle shape information of the non-graphite carbon coating can be obtained satisfactorily by obtaining the parameter b with the Q value in the above range (0.0017 to 0.0048 nm −1 ).
本発明者は、負極活物質の製造条件を変えて光散乱光学測定を行い、種々の条件で評価を実施した結果、
負極活物質の平均粒径ｄ５０が９〜２４μｍのとき、
負極活物質の光散乱光学測定を実施し、Ｑ＝０．００１７〜０．００４８ｎｍ−１の範囲において、得られたデータの近似式ｙ＝ａ・Ｑ−ｂを求め（ここで、ｙは散乱強度、θは散乱角の１／２、λはＸ線の波長、ａ及びｂは定数をそれぞれ示す。）、形状の指標値であるパラメータｂが非水電解質二次電池の容量維持率と関与すること、
さらにそのパラメータｂが０．１〜２．１の範囲にあるとき、非水電解質二次電池の容量維持率、例えば６０℃保存の容量維持率を向上できることを見出している（後記[実施例]の項、図３、表１−表２を参照）。
The present inventor performed light scattering optical measurement while changing the production conditions of the negative electrode active material, and as a result of performing the evaluation under various conditions,
When the average particle diameter d50 of the negative electrode active material is 9 to 24 μm,
The light scattering optical measurement of the negative electrode active material is performed, and an approximate expression y = a · Q− b of the obtained data is obtained in the range of Q = 0.007 to 0.0048 nm −1 (where y is scattering) Intensity, θ is 1/2 of the scattering angle, λ is the X-ray wavelength, a and b are constants, respectively), and the parameter b which is an index value of the shape is related to the capacity retention rate of the nonaqueous electrolyte secondary battery To do,
Furthermore, it has been found that when the parameter b is in the range of 0.1 to 2.1, the capacity retention rate of the nonaqueous electrolyte secondary battery, for example, the capacity retention rate of 60 ° C. storage can be improved (see below [Example] Section, FIG. 3, Table 1 to Table 2).
本発明において、負極活物質の平均粒径ｄ５０は、レーザ回折・散乱法により求めるものとする。
リチウムイオン二次電池等の非水電解質二次電池において、負極活物質の平均粒径ｄ５０は通常、９〜２４μｍの範囲内である。
本発明者は、負極活物質の平均粒径ｄ５０が９〜２４μｍのとき、Ｑ＝０．００１７〜０．００４８ｎｍ−１の範囲において、図１におけるステージ（II）の粒子形状の情報が良好に得られることを見出している。
In the present invention, the average particle diameter d50 of the negative electrode active material is determined by a laser diffraction / scattering method.
In a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery, the average particle diameter d50 of the negative electrode active material is usually in the range of 9 to 24 μm.
When the average particle diameter d50 of the negative electrode active material is 9 to 24 μm, the inventor has good information on the particle shape of the stage (II) in FIG. 1 in the range of Q = 0.417 to 0.0048 nm −1 . It has been found that it can be obtained.
パラメータｂが大きくなる程、負極活物質の形状が真球状に近づき、容量維持率が低下すると考えられる。
パラメータｂが小さくなる程、負極活物質の形状が真球状から外れ、容量維持率が向上すると考えられる。
容量維持率の向上の観点から、パラメータｂは２．１以下であり、１．９以下が特に好ましい。
製造容易性から、パラメータｂは０．１以上であり、０．４以上が特に好ましい。
It is considered that as the parameter b increases, the shape of the negative electrode active material approaches a perfect sphere and the capacity retention rate decreases.
It is considered that as the parameter b becomes smaller, the shape of the negative electrode active material deviates from a true sphere, and the capacity retention rate improves.
From the viewpoint of improving the capacity retention rate, the parameter b is 2.1 or less, and particularly preferably 1.9 or less.
In view of ease of manufacture, the parameter b is 0.1 or more, and 0.4 or more is particularly preferable.
なお、形状の指標値であるパラメータｂには、単に負極活物質の全体的な粒子形状だけでなく、粒子状黒鉛の形状とそれを被覆する被膜の状態の情報も含まれていると考えられる。
負極活物質の粒子形態には例えば、
（１）粒子状黒鉛が略真球状で、その周りをほぼ均一な厚みで非黒鉛炭素被膜が覆ったもの、
（２）粒子状黒鉛が略真球状で、その周りを凹凸を有して非黒鉛炭素被膜が覆ったもの、
（３）粒子状黒鉛は表面凹凸を有する略球状で、その周りを非黒鉛炭素被膜が覆って全体として真球状となったもの、
（４）粒子状黒鉛は表面凹凸を有する略球状で、その周りに沿ってほぼ均一な厚みで非黒鉛炭素被膜が覆ったものなどが考えられる。
パラメータｂには、上記のような負極活物質の粒子形態の情報が含まれると考えられる。
The parameter b, which is an index value of the shape, is considered to include not only the overall particle shape of the negative electrode active material but also information on the shape of the particulate graphite and the state of the coating film covering it. .
Examples of the particle form of the negative electrode active material include:
(1) Particulate graphite is substantially spherical, and is surrounded by a non-graphite carbon coating with a substantially uniform thickness.
(2) The particulate graphite is substantially spherical and has a concavo-convex surrounding and covered with a non-graphitic carbon coating,
(3) The particulate graphite is a substantially spherical shape with surface irregularities, and a non-graphitic carbon coating is covered around it to form a true sphere as a whole.
(4) Particulate graphite is a substantially spherical shape having surface irregularities, and a non-graphitic carbon coating covered with a substantially uniform thickness along the periphery thereof may be considered.
The parameter b is considered to include information on the particle form of the negative electrode active material as described above.
本発明の負極活物質は、粒子状黒鉛の表面に対して、重質油等の油、ポリビニルアルコール（ＰＶＡ）等のポリマー、石炭あるいは石油等を原料として製造されたピッチ等の炭素材料、及び必要に応じて溶媒等の添加剤を含む被膜材料を、気相法又は液相法により被覆し、不活性雰囲気下で焼成することにより、製造できる。
気相法としては例えば、ＣＶＤ（Chemical Vapor Deposition）法等が挙げられる。
焼成時の不活性雰囲気としては、Ｎ２雰囲気、Ａｒ等の希ガス雰囲気、及びこれらの組合わせ等が挙げられる。
The negative electrode active material of the present invention is a carbon material such as pitch produced using oil such as heavy oil, polymer such as polyvinyl alcohol (PVA), coal, petroleum, etc. as a raw material with respect to the surface of particulate graphite. A coating material containing an additive such as a solvent can be coated by a vapor phase method or a liquid phase method, if necessary, and fired in an inert atmosphere.
Examples of the vapor phase method include a CVD (Chemical Vapor Deposition) method.
Examples of the inert atmosphere at the time of firing include an N 2 atmosphere, a rare gas atmosphere such as Ar, and combinations thereof.
用いる黒鉛の粒子形状、非黒鉛炭素被膜の被覆量・被覆方法・焼成プロファイル等の製造条件を調整することで、パラメータｂを調整することができる。
具体的な製造条件の例については、後記［実施例］の項を参照されたい。
The parameter b can be adjusted by adjusting manufacturing conditions such as the shape of the graphite particles used, the coating amount of the non-graphite carbon coating, the coating method, and the firing profile.
For specific examples of production conditions, see the section “Examples” below.
略球状、あるいは非球状の粒子状黒鉛を用いることができる。
後記［実施例］の項において、本発明者は、いずれの形状の粒子状黒鉛を用いても、パラメータｂが０．１〜２．１の範囲にあり、容量維持率が向上された負極活物質を実現している（実施例１、２）。
実施例１では、略球状の粒子状黒鉛を用い、非黒鉛炭素被膜の被覆量・被覆方法・焼成プロファイルを工夫することにより、パラメータｂの値を０．１〜２．１の範囲内とし、容量維持率を向上することに成功している。
特に、非球状の粒子状黒鉛を用いた実施例２では、略球状の粒子状黒鉛を用いた実施例１よりもパラメータｂの値が小さく、より高い容量維持率が実現されている。
したがって、非球状の粒子状黒鉛を用いることが特に好ましい。
非球状としては例えば、略紡錘状等が挙げられる。紡錘状は紡錘に糸を巻いたときの形であり、横断面が円形であり、中央部の横断面積が最も大きく、上下両端に向けて横断面積が次第に小さくなる形状である。
Substantially spherical or non-spherical particulate graphite can be used.
In the section of [Example] described later, the present inventor has found that the negative electrode active in which the parameter b is in the range of 0.1 to 2.1 and the capacity retention rate is improved regardless of the shape of the particulate graphite. The substance is realized (Examples 1 and 2).
In Example 1, using a substantially spherical particulate graphite, the value of the parameter b is set within the range of 0.1 to 2.1 by devising the coating amount / coating method / firing profile of the non-graphitic carbon coating, It has succeeded in improving the capacity maintenance rate.
In particular, in Example 2 using non-spherical particulate graphite, the value of parameter b is smaller than in Example 1 using substantially spherical particulate graphite, and a higher capacity retention rate is realized.
Therefore, it is particularly preferable to use non-spherical particulate graphite.
Examples of the non-spherical shape include a substantially spindle shape. The spindle shape is a shape when a yarn is wound around the spindle, the cross section is circular, the cross-sectional area at the center is the largest, and the cross-sectional area gradually decreases toward the upper and lower ends.
粒子状黒鉛に対する非黒鉛炭素被膜の量（被覆量）は特に制限されない。被覆量が過小では、電解質との反応性の抑制効果が充分に発現しなくなる。被覆量が過大では、黒鉛を被覆せずに非黒鉛炭素のみで塊が形成されるなど、マクロなレベルでの不均一性が増して所望の電池特性が得られなくなる恐れ、あるいは、被膜が厚くなりすぎて初期抵抗が増大するなどの恐れがある。
粒子状黒鉛１００質量部に対する非黒鉛炭素被膜の量（被覆量）は例えば、２〜７質量部が好ましい。
The amount of non-graphite carbon coating (particulate amount) with respect to particulate graphite is not particularly limited. If the coating amount is too small, the effect of suppressing the reactivity with the electrolyte is not sufficiently exhibited. If the coating amount is too large, a non-graphite carbon layer may be formed only with non-graphite carbon, which may increase the non-uniformity at the macro level, resulting in failure to obtain desired battery characteristics, or a thick coating. There is a risk that the initial resistance will increase due to too much.
The amount of the non-graphitic carbon coating (covering amount) with respect to 100 parts by mass of particulate graphite is preferably 2 to 7 parts by mass, for example.
黒鉛を被覆せずに非黒鉛炭素のみで塊が形成されることなく、粒子状黒鉛に対して非黒鉛炭素を良好に均一に被覆できることから、被覆法としては気相法が特に好ましい。 A gas phase method is particularly preferable as the coating method because the non-graphitic carbon can be coated uniformly and uniformly on the particulate graphite without forming a lump with only the non-graphitic carbon without coating the graphite.
焼成プロファイルとしては例えば、仮焼成と本焼成の２段階焼成が好ましい。
低結晶性を有する被膜を形成するには、９００℃以上の本焼成が必要である。本焼成温度が高くなりすぎると、炭素材料の消失が多くなる傾向がある。本焼成温度は、９００〜１０００℃が好ましい。
９００℃以上の本焼成の前に、本焼成よりは低いが、炭素化かつある程度の結晶化が進む温度、具体的には６００〜７００℃の仮焼成を行うことが好ましい。かかる温度で仮焼成を行うことで、本焼成前に、溶媒等の添加物あるいは不純物等の不要物が良好に除去され、かつ、比較的秩序の高い炭素骨格構造が得られ、その状態で本焼成を行うことで、より秩序の高い良質な低結晶構造が得られると考えられる。
したがって、６００〜７００℃で仮焼成した後、９００℃以上で本焼成する焼成プロファイルが好ましい。
仮焼成時間は温度にもよるが、３〜１０時間が好ましい。
本焼成時間は温度にもよるが、３〜１０時間が好ましい。
As the firing profile, for example, two-stage firing of temporary firing and main firing is preferable.
In order to form a film having low crystallinity, main baking at 900 ° C. or higher is necessary. If the main firing temperature is too high, the carbon material tends to disappear. The firing temperature is preferably 900 to 1000 ° C.
Prior to the main baking at 900 ° C. or higher, it is preferable to perform a preliminary baking at a temperature that is lower than the main baking but at which carbonization and a certain degree of crystallization progress, specifically 600 to 700 ° C. By performing preliminary firing at such a temperature, additives such as a solvent or unnecessary substances such as impurities are removed well before the main firing, and a relatively ordered carbon skeleton structure is obtained. By firing, it is considered that a high-quality low-crystal structure with higher order can be obtained.
Therefore, a firing profile is preferable in which calcining is performed at a temperature of 900 ° C. or higher after preliminary firing at 600 to 700 ° C.
Although the pre-baking time depends on the temperature, it is preferably 3 to 10 hours.
The main baking time depends on the temperature, but 3 to 10 hours are preferable.
負極活物質のＮ２吸着法によるＢＥＴ比表面積は特に制限されない。
ＢＥＴ比表面積が大きい程、活性点が多くなり、初期抵抗が低減する傾向があるが、電池容量が低減する傾向がある。
負極活物質のＮ２吸着法によるＢＥＴ比表面積は例えば、２〜５ｍ２／ｇが好ましい。
The BET specific surface area of the negative electrode active material by the N 2 adsorption method is not particularly limited.
The larger the BET specific surface area, the more active points and the initial resistance tends to decrease, but the battery capacity tends to decrease.
The BET specific surface area by the N 2 adsorption method of the negative electrode active material is preferably 2 to 5 m 2 / g, for example.
「非水電解質二次電池」
本発明の非水電解質二次電池は、正極と、上記の本発明の非水電解質二次電池用の負極活物質を含む負極と、非水電解質とを備えたものである。
"Nonaqueous electrolyte secondary battery"
The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode containing the negative electrode active material for the non-aqueous electrolyte secondary battery of the present invention, and a non-aqueous electrolyte.
非水電解質二次電池としては、リチウムイオン二次電池等が挙げられる。以下、リチウムイオン二次電池を例として、主な構成要素について説明する。 Examples of the non-aqueous electrolyte secondary battery include a lithium ion secondary battery. Hereinafter, main components will be described by taking a lithium ion secondary battery as an example.
＜正極＞
正極は、公知の方法により、アルミニウム箔などの正極集電体に正極活物質を塗布して、製造することができる。
公知の正極活物質としては特に制限なく、例えば、ＬｉＣｏＯ２、ＬｉＭｎＯ２、ＬｉＭｎ２Ｏ４、ＬｉＮｉＯ２、ＬｉＮｉｘＣｏ（１−ｘ）Ｏ２、及びＬｉＮｉｘＣｏｙＭｎ（１−ｘ−ｙ）Ｏ２等のリチウム含有複合酸化物等が挙げられる。
例えば、Ｎ−メチル−２−ピロリドン等の分散剤を用い、上記の正極活物質と、炭素粉末等の導電剤と、ポリフッ化ビニリデン（ＰＶＤＦ）等の結着剤とを混合して、スラリーを得、このスラリーをアルミニウム箔等の正極集電体上に塗布し、乾燥し、プレス加工して、正極を得ることができる。
<Positive electrode>
The positive electrode can be manufactured by applying a positive electrode active material to a positive electrode current collector such as an aluminum foil by a known method.
Known no particular limitation on the positive electrode active material, for example, LiCoO 2, LiMnO 2, LiMn 2
For example, using a dispersant such as N-methyl-2-pyrrolidone, the above positive electrode active material, a conductive agent such as carbon powder, and a binder such as polyvinylidene fluoride (PVDF) are mixed to form a slurry. This slurry can be applied onto a positive electrode current collector such as an aluminum foil, dried, and pressed to obtain a positive electrode.
＜負極＞
上記の本発明の非水電解質二次電池用の負極活物質を含む負極を用いる。
必要に応じて、上記の本発明の非水電解質二次電池用の負極活物質以外の公知の負極活物質を併用しても構わない。
併用可能な負極活物質としては特に制限なく、Ｌｉ／Ｌｉ＋基準で２．０Ｖ以下にリチウム吸蔵能力を持つものが好ましく用いられる。併用可能な負極活物質としては、金属リチウム、リチウム合金、リチウムイオンのド−プ・脱ド−プが可能な遷移金属酸化物／遷移金属窒化物／遷移金属硫化物、及び、これらの組合わせ等が挙げられる。
<Negative electrode>
The negative electrode containing the negative electrode active material for the nonaqueous electrolyte secondary battery of the present invention is used.
As needed, you may use together well-known negative electrode active materials other than the negative electrode active material for said nonaqueous electrolyte secondary batteries of this invention.
The negative electrode active material that can be used in combination is not particularly limited, and those having a lithium storage capacity of 2.0 V or less on the basis of Li / Li + are preferably used. Negative electrode active materials that can be used in combination include lithium metal, lithium alloys, transition metal oxides / transition metal nitrides / transition metal sulfides capable of doping / dedoping lithium ions, and combinations thereof. Etc.
負極は、公知の方法により、銅箔などの負極集電体に負極活物質を塗布して、製造することができる。
例えば、水等の分散剤を用い、上記の負極活物質と、変性スチレン−ブタジエン共重合体ラテックス等の結着剤と、必要に応じてカルボキシメチルセルロースＮａ塩（ＣＭＣ）等の増粘剤とを混合して、スラリーを得、このスラリーを銅箔等の負極集電体上に塗布し、乾燥し、プレス加工して、負極を得ることができる。
The negative electrode can be produced by applying a negative electrode active material to a negative electrode current collector such as a copper foil by a known method.
For example, using a dispersant such as water, the negative electrode active material described above, a binder such as a modified styrene-butadiene copolymer latex, and a thickener such as carboxymethyl cellulose Na salt (CMC) as necessary. Mixing is performed to obtain a slurry, and this slurry is applied onto a negative electrode current collector such as a copper foil, dried, and pressed to obtain a negative electrode.
＜非水電解質＞
非水電解質としては公知のものが使用でき、液状、ゲル状もしくは固体状の非水電解質が使用できる。
例えば、プロピレンカーボネ−トあるいはエチレンカーボネ−ト等の高誘電率カーボネート溶媒と、ジエチルカーボネート、メチルエチルカーボネート、ジメチルカーボネート等の低粘度カーボネート溶媒との混合溶媒に、リチウム含有電解質を溶解した非水電界液が好ましく用いられる。
混合溶媒としては例えば、エチレンカーボネート（ＥＣ）／ジメチルカーボネート（ＤＭＣ）／エチルメチルカーボネート（ＥＭＣ）の混合溶媒が好ましく用いられる。
リチウム含有電解質としては例えば、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４、ＬｉＡｓＦ６、Ｌｉ２ＳｉＦ６、ＬｉＯＳＯ２ＣｋＦ（２ｋ＋１）（ｋ＝１〜８の整数）、ＬｉＰＦｎ｛ＣｋＦ（２ｋ＋１）｝（６−ｎ）（ｎ＝１〜５の整数、ｋ＝１〜８の整数）等のリチウム塩、及びこれらの組合わせが挙げられる。
<Nonaqueous electrolyte>
As the non-aqueous electrolyte, known ones can be used, and liquid, gel-like or solid non-aqueous electrolytes can be used.
For example, a lithium-containing electrolyte is dissolved in a mixed solvent of a high dielectric constant carbonate solvent such as propylene carbonate or ethylene carbonate and a low viscosity carbonate solvent such as diethyl carbonate, methyl ethyl carbonate, or dimethyl carbonate. A water electrolysis solution is preferably used.
As the mixed solvent, for example, a mixed solvent of ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) is preferably used.
Examples of the lithium-containing electrolyte include LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , Li 2 SiF 6 , LiOSO 2 C k F (2k + 1) (k = 1 to 8), LiPF n {C k F (2k + 1) )} (6-n) ( n = 1~5 integer, k = 1 to 8 integer) lithium salts such as, and combinations thereof.
＜セパレータ＞
セパレータは、正極と負極とを電気的に絶縁し、かつリチウムイオンが透過可能な膜であればよく、多孔質高分子フィルムが好ましく使用される。
セパレータとしては例えば、ＰＰ（ポリプロピレン）製多孔質フィルム、ＰＥ（ポリエチレン）製多孔質フィルム、あるいは、ＰＰ（ポリプロピレン）−ＰＥ（ポリエチレン）の積層型多孔質フィルム等のポリオレフィン製多孔質フィルムが好ましく用いられる。
<Separator>
The separator may be a film that electrically insulates the positive electrode and the negative electrode and is permeable to lithium ions, and a porous polymer film is preferably used.
As the separator, for example, a porous film made of polyolefin such as a porous film made of PP (polypropylene), a porous film made of PE (polyethylene), or a laminated porous film of PP (polypropylene) -PE (polyethylene) is preferably used. It is done.
＜ケース＞
ケースとしては公知のものが使用できる。
二次電池の型としては、円筒型、コイン型、角型、あるいはフィルム型等があり、所望の型に合わせてケースを選定することができる。
<Case>
A well-known case can be used.
The secondary battery type includes a cylindrical type, a coin type, a square type, a film type, and the like, and a case can be selected according to a desired type.
以上説明したように、本発明によれば、粒子状黒鉛と非黒鉛炭素被膜とを備えた負極活物質において容量維持率に関与する因子が明らかとされ、粒子状黒鉛の表面に非黒鉛炭素被膜が形成されており、非水電解質二次電池の容量維持率を向上することが可能な非水電解質二次電池用の負極活物質を提供することができる。 As described above, according to the present invention, the factor relating to the capacity retention rate in the negative electrode active material provided with the particulate graphite and the non-graphitic carbon coating is clarified, and the non-graphitic carbon coating is formed on the surface of the particulate graphite. Thus, a negative electrode active material for a non-aqueous electrolyte secondary battery that can improve the capacity retention rate of the non-aqueous electrolyte secondary battery can be provided.
本発明に係る実施例及び比較例について説明する。 Examples and comparative examples according to the present invention will be described.
[実施例１、２、比較例１〜３]
実施例１、２及び比較例１〜３では、負極活物質の製造条件を変更する以外は、同一条件として、リチウムイオン二次電池を製造した。
[Examples 1 and 2 and Comparative Examples 1 to 3]
In Examples 1 and 2 and Comparative Examples 1 to 3, lithium ion secondary batteries were manufactured under the same conditions except that the manufacturing conditions of the negative electrode active material were changed.
＜正極＞
正極活物質として、ＬｉＮｉ１／３Ｃｏ１／３Ｍｎ１／３Ｏ２を用いた。
分散剤としてＮ−メチル−２−ピロリドンを用い、上記の正極活物質と、導電剤であるアセチレンブラックと、結着剤であるＰＶＤＦとを９３／４／３（質量比）で混合して、電極層形成用ペーストを得た。
上記電極層形成用ペーストを集電体であるアルミニウム箔の両面にドクターブレード法で塗布し、１５０℃で３０分間乾燥し、プレス機械を用いてプレス加工して、電極層を形成した。
以上のようにして、正極を得た。正極電極層は、片面当たり、目付３０ｍｇ／ｃｍ２、密度２．８ｇ／ｃｍ３とした。
<Positive electrode>
LiNi 1/3 Co 1/3 Mn 1/3 O 2 was used as the positive electrode active material.
Using N-methyl-2-pyrrolidone as a dispersant, mixing the above positive electrode active material, acetylene black as a conductive agent, and PVDF as a binder at 93/4/3 (mass ratio), An electrode layer forming paste was obtained.
The electrode layer forming paste was applied to both surfaces of an aluminum foil as a current collector by a doctor blade method, dried at 150 ° C. for 30 minutes, and pressed using a press machine to form an electrode layer.
As described above, a positive electrode was obtained. The positive electrode layer had a basis weight of 30 mg / cm 2 and a density of 2.8 g / cm 3 per side.
＜負極＞
実施例１及び比較例１〜３では、粒子状黒鉛として略球状の天然黒鉛を用い、実施例２では、粒子状黒鉛として略紡錘状の天然黒鉛を用いた。
なお、黒鉛の粒子形状は、走査型電子顕微鏡（ＳＥＭ）観察にて確認した。
<Negative electrode>
In Example 1 and Comparative Examples 1 to 3, substantially spherical natural graphite was used as the particulate graphite, and in Example 2, substantially spindle-shaped natural graphite was used as the particulate graphite.
The particle shape of graphite was confirmed by observation with a scanning electron microscope (SEM).
実施例１（試料Ａ）では、略球状の上記粒子状黒鉛の表面に対して、ピッチを被覆材料としてＣＶＤ法により被覆し、Ｎ２雰囲気下で焼成することにより、負極活物質を製造した。粒子状黒鉛に対する非黒鉛炭素の被覆量は２質量％とした。
実施例１（試料Ａ）では、６００℃で３時間焼成し、昇温速度１０℃／ｍｉｎで９００℃に昇温し、この温度で１０時間保持するプロファイルとした。
In Example 1 (Sample A), a negative electrode active material was manufactured by coating a substantially spherical surface of the particulate graphite with a pitch as a coating material by a CVD method and firing in a N 2 atmosphere. The coating amount of non-graphite carbon on the particulate graphite was 2% by mass.
In Example 1 (Sample A), the profile was calcined at 600 ° C. for 3 hours, heated to 900 ° C. at a heating rate of 10 ° C./min, and held at this temperature for 10 hours.
比較例１（試料Ｂ）では、略球状の上記粒子状黒鉛の表面に対して、ピッチを被覆材料としてＣＶＤ法により被覆し、Ｎ２雰囲気下で焼成することにより、負極活物質を製造した。粒子状黒鉛に対する非黒鉛炭素の被覆量は１０質量％とした。
比較例１（試料Ｂ）では、６００℃で３時間焼成し、昇温速度１０℃／ｍｉｎで９００℃に昇温し、この温度で１０時間保持するプロファイルとした。
In Comparative Example 1 (Sample B), a negative electrode active material was manufactured by coating the substantially spherical surface of the particulate graphite with a pitch as a coating material by a CVD method and firing it in an N 2 atmosphere. The coating amount of non-graphitic carbon on the particulate graphite was 10% by mass.
In Comparative Example 1 (Sample B), the profile was calcined at 600 ° C. for 3 hours, heated to 900 ° C. at a heating rate of 10 ° C./min, and held at this temperature for 10 hours.
実施例２（試料Ｃ）では、略紡錘状の上記粒子状黒鉛の表面に対して、ピッチを被覆材料としてＣＶＤ法により被覆し、Ｎ２雰囲気下で焼成することにより、負極活物質を製造した。粒子状黒鉛に対する非黒鉛炭素の被覆量は２質量％とした。
実施例２（試料Ｃ）では、６００℃で３時間焼成し、昇温速度１０℃／ｍｉｎで９００℃に昇温し、この温度で１０時間保持するプロファイルとした。
In Example 2 (Sample C), the surface of the substantially spindle-shaped particulate graphite was coated with a pitch as a coating material by a CVD method, and fired in an N 2 atmosphere to produce a negative electrode active material. . The coating amount of non-graphite carbon on the particulate graphite was 2% by mass.
In Example 2 (Sample C), the profile was calcined at 600 ° C. for 3 hours, heated to 900 ° C. at a temperature increase rate of 10 ° C./min, and held at this temperature for 10 hours.
比較例２（試料Ｄ）では、略球状の上記粒子状黒鉛の表面に対して、ピッチを被覆材料としてＣＶＤ法により被覆し、Ｎ２雰囲気下で焼成することにより、負極活物質を製造した。粒子状黒鉛に対する非黒鉛炭素の被覆量は２質量％とした。
比較例２（試料Ｄ）では、６００℃で３時間焼成し、昇温速度１０℃／ｍｉｎで９００℃に昇温し、この温度で１０時間保持するプロファイルとした。
In Comparative Example 2 (Sample D), a negative electrode active material was manufactured by coating the substantially spherical surface of the particulate graphite with a pitch as a coating material by a CVD method and firing in a N 2 atmosphere. The coating amount of non-graphite carbon on the particulate graphite was 2% by mass.
In Comparative Example 2 (Sample D), the profile was calcined at 600 ° C. for 3 hours, heated to 900 ° C. at a heating rate of 10 ° C./min, and held at this temperature for 10 hours.
比較例３（試料Ｅ）では、略球状の上記粒子状黒鉛の表面に対して、ピッチを被覆材料として液相法により被覆し、Ｎ２雰囲気下で焼成することにより、負極活物質を製造した。粒子状黒鉛に対する非黒鉛炭素の被覆量は２質量％とした。
比較例３（試料Ｅ）では、６００℃で３時間焼成し、昇温速度１０℃／ｍｉｎで９００℃に昇温し、この温度で１０時間保持するプロファイルとした。
In Comparative Example 3 (Sample E), a negative electrode active material was manufactured by coating a substantially spherical surface of the particulate graphite with a pitch as a coating material by a liquid phase method and firing in a N 2 atmosphere. . The coating amount of non-graphite carbon on the particulate graphite was 2% by mass.
In Comparative Example 3 (Sample E), the profile was calcined at 600 ° C. for 3 hours, heated to 900 ° C. at a heating rate of 10 ° C./min, and held at this temperature for 10 hours.
いずれの例においても、分散剤として水を用い、上記の負極活物質と、結着剤である変性スチレン−ブタジエン共重合体ラテックス（ＳＢＲ）と、増粘剤であるカルボキシメチルセルロースＮａ塩（ＣＭＣ）とを９８／１／１（質量比）で混合して、スラリーを得た。
上記電極層形成用ペーストを集電体であるアルミニウム箔の両面にドクターブレード法で塗布し、１５０℃で３０分間乾燥し、プレス機械を用いてプレス加工して、電極層を形成した。
以上のようにして、負極を得た。負極電極層は、片面当たり、目付１８ｍｇ／ｃｍ２、密度１．４ｇ／ｃｍ３とした。
In any of these examples, water is used as a dispersant, the negative electrode active material, a modified styrene-butadiene copolymer latex (SBR) as a binder, and a carboxymethyl cellulose Na salt (CMC) as a thickener. Were mixed at 98/1/1 (mass ratio) to obtain a slurry.
The electrode layer forming paste was applied to both surfaces of an aluminum foil as a current collector by a doctor blade method, dried at 150 ° C. for 30 minutes, and pressed using a press machine to form an electrode layer.
A negative electrode was obtained as described above. The negative electrode layer had a basis weight of 18 mg / cm 2 and a density of 1.4 g / cm 3 per side.
＜セパレータ＞
ＰＥ（ポリエチレン）製多孔質フィルムからなる市販のセパレータを用意した。
<Separator>
A commercially available separator made of a PE (polyethylene) porous film was prepared.
＜非水電解質＞
エチレンカーボネート（ＥＣ）／ジメチルカーボネート（ＤＭＣ）／エチルメチルカーボネート（ＥＭＣ）＝３／４／３（体積比）の混合溶液を溶媒とし、電解質としてリチウム塩であるＬｉＰＦ６を１．１ｍｏｌ／Ｌの濃度で溶解して、非水電界液を調製した。
<Nonaqueous electrolyte>
A mixed solution of ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) = 3/4/3 (volume ratio) was used as a solvent, and LiPF 6 which is a lithium salt as an electrolyte was 1.1 mol / L. A non-aqueous electrolysis solution was prepared by dissolving at a concentration.
＜リチウムイオン二次電池の製造＞
上記の正極と負極とセパレータと非水電解液と円筒型の缶ケースを用い、公知方法により、リチウムイオン二次電池を製造した。
各例の主な製造条件を表１に示す。
<Manufacture of lithium ion secondary batteries>
Using the above positive electrode, negative electrode, separator, non-aqueous electrolyte, and cylindrical can case, a lithium ion secondary battery was manufactured by a known method.
Table 1 shows the main production conditions for each example.
＜負極活物質のＢＥＴ比表面積＞
各例において得られた負極活物質について、窒素吸着法によりＢＥＴ比表面積を求めた。
装置としては、ＭＯＵＮＴＥＣＨ社製Ｍａｃｓｏｒｂ（ＨＭ ｍｏｄｅｌ−１２０８）を用いた。
結果を表２に示す。
<BET specific surface area of negative electrode active material>
About the negative electrode active material obtained in each example, the BET specific surface area was calculated | required by the nitrogen adsorption method.
As the apparatus, Macsorb (HM model-1208) manufactured by MOUNTECH was used.
The results are shown in Table 2.
＜負極活物質の平均粒径ｄ５０＞
各例において得られた負極活物質について、負極活物質の平均粒径ｄ５０を求めた。
装置としては、レーザ回折式粒子径分布測定装置SALD-2300を用いた。
結果を表２に示す。
<Average particle diameter d50 of negative electrode active material>
About the negative electrode active material obtained in each example, the average particle diameter d50 of the negative electrode active material was calculated | required.
As a device, a laser diffraction particle size distribution measuring device SALD-2300 was used.
The results are shown in Table 2.
＜ＳＴＥＭ観察＞
各例において得られた負極活物質について、走査型透過電子顕微鏡（ＳＴＥＭ）観察を実施した。
負極活物質をエポキシ系樹脂に包埋させ、ＦＩＢ（集束イオンビーム）により活物質粒子の断面を得、これをサンプルとした。負極活物質の微小な空隙に樹脂を充填することで、ＳＴＥＭ観察が容易となる。
装置としては、株式会社日立ハイテクノロジーズ社製の走査透過電子顕微鏡ＨＤ−２７００を用いた。加速電圧は２００ｋＶとした。
<STEM observation>
The negative electrode active material obtained in each example was observed with a scanning transmission electron microscope (STEM).
The negative electrode active material was embedded in an epoxy resin, and a cross section of the active material particles was obtained by FIB (focused ion beam). This was used as a sample. STEM observation is facilitated by filling the resin in the minute voids of the negative electrode active material.
As the apparatus, a scanning transmission electron microscope HD-2700 manufactured by Hitachi High-Technologies Corporation was used. The acceleration voltage was 200 kV.
各例において、幅１５０ｎｍ×深さ５０ｎｍの範囲で負極活物質の断面観察を実施し、非黒鉛炭素被膜の格子縞の有無とそのパターンを観察した。
いずれの例においても、被膜のＳＴＥＭ像に格子縞が観察された。また、これらの格子縞は、ａ軸方向の結晶子サイズが小さく、あるいは、格子縞がウェーブするなど、黒鉛よりも格子縞の秩序が低く観察された。
In each example, the cross-section of the negative electrode active material was observed in a range of 150 nm width × 50 nm depth, and the presence and absence of lattice fringes of the non-graphitic carbon coating and its pattern were observed.
In any of the examples, lattice fringes were observed in the STEM image of the coating. In addition, these lattice fringes were observed to have a lower order of lattice fringes than graphite, such as the crystallite size in the a-axis direction being small, or the lattice fringes waved.
＜光散乱測定＞
各例において得られた負極活物質について、光散乱測定を実施した。
装置としては、大塚電子株式会社社製のダイナミックス光散乱光度計を用いた。測定条件は以下の通りとした。
使用レーザと波長：Ｈｅ−Ｎｅレーザ ６３２．８ｎｍ、
測定角度θ：１０〜１６０℃（Ｑ＝０．００１７３１〜０．０１９５５７ｎｍ−１に相当）。
Ｑ＝４πｓｉｎθ／λ＝０．００１７〜０．００４８ｎｍ−１の範囲において、得られたデータの近似式ｙ＝ａ・Ｑ−ｂを求め（ここで、ｙは散乱強度、θは散乱角の１／２、λはＸ線の波長、ａ及びｂは定数をそれぞれ示す。）、形状の指標値であるパラメータｂを求めた。
光散乱の測定データ、近似直線、及び近似式の例を図２に示す。この図は、比較例２のものである。
結果を表２に示す。
<Light scattering measurement>
Light scattering measurement was performed on the negative electrode active material obtained in each example.
As the apparatus, a dynamics light scattering photometer manufactured by Otsuka Electronics Co., Ltd. was used. The measurement conditions were as follows.
Laser used and wavelength: He-Ne laser 632.8 nm,
Measurement angle θ: 10 to 160 ° C. (corresponding to Q = 0.001731 to 0.019557 nm −1 ).
In the range of Q = 4πsin θ / λ = 0.0017 to 0.0048 nm −1 , an approximate expression y = a · Q −b of the obtained data is obtained (where y is the scattering intensity, θ is 1 of the scattering angle). / 2, λ is the wavelength of X-ray, a and b are constants, respectively), and a parameter b which is an index value of the shape was obtained.
Examples of light scattering measurement data, approximate straight lines, and approximate expressions are shown in FIG. This figure is that of Comparative Example 2.
The results are shown in Table 2.
＜６０℃保存の容量維持率＞
６０℃にて６０日保存後に、２ＡのＣＣ充電で３〜４．１Ｖの容量を測定し、容量維持率を求めた。
結果を表２に示す。
<Capacity maintenance rate of 60 ° C storage>
After storage at 60 ° C. for 60 days, a capacity of 3 to 4.1 V was measured by CC charging at 2 A, and a capacity maintenance rate was obtained.
The results are shown in Table 2.
＜結果のまとめ＞
実施例１、２及び比較例１〜３の結果をまとめ、光散乱測定における形状の指標値であるパラメータｂと容量維持率との関係を図３に示す。
図３に示すように、光散乱測定における形状の指標値であるパラメータｂと容量維持率との間には良好な相関関係が見られ、
パラメータｂが２．４以上の比較例１〜３では容量維持率が低かったのに対して、パラメータｂが１．９以下の実施例１、２では高い容量維持率が実現された。
特に、略紡錘状の粒子状黒鉛を用いた実施例２では、より高い容量維持率が実現された。
実施例１、２及び比較例１〜３のデータをなめらかに結ぶと、概ね、パラメータ２．１以下で容量維持率８０％以上が実現されている。
したがって、本発明において、形状の指標値であるパラメータｂは０．１〜２．１に規定し、パラメータｂは０．４〜１．９が特に好ましい。
<Summary of results>
The results of Examples 1 and 2 and Comparative Examples 1 to 3 are summarized, and the relationship between the parameter b, which is an index value of the shape in the light scattering measurement, and the capacity retention rate is shown in FIG.
As shown in FIG. 3, there is a good correlation between the parameter b, which is an index value of the shape in the light scattering measurement, and the capacity retention rate,
In Comparative Examples 1 to 3 in which the parameter b is 2.4 or higher, the capacity retention rate was low, whereas in Examples 1 and 2 in which the parameter b was 1.9 or less, a high capacity retention rate was realized.
In particular, in Example 2 using substantially spindle-shaped particulate graphite, a higher capacity retention rate was realized.
When the data of Examples 1 and 2 and Comparative Examples 1 to 3 are smoothly connected, a capacity retention rate of 80% or more is generally achieved with a parameter of 2.1 or less.
Therefore, in the present invention, the parameter b which is an index value of the shape is defined as 0.1 to 2.1, and the parameter b is particularly preferably 0.4 to 1.9.
実施例１（試料Ａ）と比較例１（試料Ｂ）との比較から、負極活物質の製造において、非黒鉛炭素の被覆量には好適な範囲があることが分かる。
実施例１（試料Ａ）と比較例２（試料Ｄ）との比較から、負極活物質の製造において、好適なＢＥＴ比表面積・平均粒径ｄ５０があることが分かる。
実施例１（試料Ａ）と比較例３（試料Ｅ）との比較から、負極活物質の製造において、気相法による被覆がより好ましいことが分かる。
From the comparison between Example 1 (Sample A) and Comparative Example 1 (Sample B), it can be seen that there is a suitable range for the coating amount of non-graphite carbon in the production of the negative electrode active material.
From the comparison between Example 1 (Sample A) and Comparative Example 2 (Sample D), it can be seen that there is a suitable BET specific surface area / average particle size d50 in the production of the negative electrode active material.
From comparison between Example 1 (Sample A) and Comparative Example 3 (Sample E), it can be seen that in the production of the negative electrode active material, coating by a gas phase method is more preferable.
本発明の負極活物質は、プラグインハイブリッド車（ＰＨＶ）あるいは電気自動車（ＥＶ）に搭載されるリチウムイオン二次電池等の非水電解質二次電池に好ましく適用できる。 The negative electrode active material of the present invention can be preferably applied to a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery mounted on a plug-in hybrid vehicle (PHV) or an electric vehicle (EV).
Claims (5)
前記非黒鉛炭素被膜は、走査型透過電子顕微鏡（ＳＴＥＭ）観察にて格子縞が確認されるものであり、
前記負極活物質の平均粒径ｄ５０が９〜２４μｍであり、
前記負極活物質の光散乱光学測定を実施したとき、Ｑ＝４πｓｉｎθ／λ＝０．００１７〜０．００４８ｎｍ−１の範囲において、得られたデータの近似式ｙ＝ａ・Ｑ−ｂを求め（ここで、ｙは散乱強度、θは散乱角の１／２、λはＸ線の波長、ａ及びｂは定数をそれぞれ示す。）、パラメータｂが０．１〜２．１の範囲にある非水電解質二次電池用の負極活物質。 A negative electrode active material for a non-aqueous electrolyte secondary battery having a particulate graphite and a non-graphite carbon coating formed on the surface of the particulate graphite,
The non-graphitic carbon coating is one in which lattice fringes are confirmed by scanning transmission electron microscope (STEM) observation,
The negative electrode active material has an average particle diameter d50 of 9 to 24 μm,
When light scattering optical measurement of the negative electrode active material was performed, an approximate expression y = a · Q −b of the obtained data was obtained in the range of Q = 4π sin θ / λ = 0.001 to 0.0048 nm −1 ( Here, y is the scattering intensity, θ is 1/2 of the scattering angle, λ is the X-ray wavelength, a and b are constants, respectively), and the parameter b is in the range of 0.1 to 2.1. Negative electrode active material for water electrolyte secondary battery.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106898740A (en) * | 2017-02-22 | 2017-06-27 | 深圳市金润能源材料有限公司 | Graphite cathode material and lithium ion battery |
Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH09237638A (en) * | 1995-12-25 | 1997-09-09 | Sharp Corp | Nonaqueous secondary battery |
| JPH11335106A (en) * | 1998-03-25 | 1999-12-07 | Shimadzu Corp | Production of carbon |
| JP2001126726A (en) * | 1999-10-25 | 2001-05-11 | Mitsui Chemicals Inc | Nonaqueous electrolytic secondary cell |
| JP2004059386A (en) * | 2002-07-30 | 2004-02-26 | Hitachi Chem Co Ltd | Production method for carbon-coated graphite particle, carbon-coated graphite particle, cathode for lithium-ion secondary battery, and lithium-ion secondary battery |
| JP2004253379A (en) * | 2003-01-29 | 2004-09-09 | Jfe Chemical Corp | Negative electrode material and negative electrode for lithium-ion secondary battery, and lithium-ion secondary battery |
| JP2005004974A (en) * | 2003-06-09 | 2005-01-06 | Matsushita Electric Ind Co Ltd | Lithium-ion secondary battery |
| JP2008069015A (en) * | 2003-04-04 | 2008-03-27 | Canon Inc | Flaky carbonaceous particle and production method thereof |
| JP2008157968A (en) * | 2005-08-29 | 2008-07-10 | Rigaku Corp | Method of measuring small angle x-ray scattering |
| WO2008093724A1 (en) * | 2007-01-31 | 2008-08-07 | Sumitomo Metal Industries, Ltd. | Carbon material and process for producing the carbon material |
| JP2013134938A (en) * | 2011-12-27 | 2013-07-08 | Panasonic Corp | Negative electrode for nonaqueous electrolyte secondary battery, method for manufacturing the same, and nonaqueous electrolyte secondary battery including the same |
-
2012
- 2012-04-05 JP JP2012086292A patent/JP2013218817A/en active Pending
Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH09237638A (en) * | 1995-12-25 | 1997-09-09 | Sharp Corp | Nonaqueous secondary battery |
| JPH11335106A (en) * | 1998-03-25 | 1999-12-07 | Shimadzu Corp | Production of carbon |
| JP2001126726A (en) * | 1999-10-25 | 2001-05-11 | Mitsui Chemicals Inc | Nonaqueous electrolytic secondary cell |
| JP2004059386A (en) * | 2002-07-30 | 2004-02-26 | Hitachi Chem Co Ltd | Production method for carbon-coated graphite particle, carbon-coated graphite particle, cathode for lithium-ion secondary battery, and lithium-ion secondary battery |
| JP2004253379A (en) * | 2003-01-29 | 2004-09-09 | Jfe Chemical Corp | Negative electrode material and negative electrode for lithium-ion secondary battery, and lithium-ion secondary battery |
| JP2008069015A (en) * | 2003-04-04 | 2008-03-27 | Canon Inc | Flaky carbonaceous particle and production method thereof |
| JP2005004974A (en) * | 2003-06-09 | 2005-01-06 | Matsushita Electric Ind Co Ltd | Lithium-ion secondary battery |
| JP2008157968A (en) * | 2005-08-29 | 2008-07-10 | Rigaku Corp | Method of measuring small angle x-ray scattering |
| WO2008093724A1 (en) * | 2007-01-31 | 2008-08-07 | Sumitomo Metal Industries, Ltd. | Carbon material and process for producing the carbon material |
| JP2013134938A (en) * | 2011-12-27 | 2013-07-08 | Panasonic Corp | Negative electrode for nonaqueous electrolyte secondary battery, method for manufacturing the same, and nonaqueous electrolyte secondary battery including the same |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106898740A (en) * | 2017-02-22 | 2017-06-27 | 深圳市金润能源材料有限公司 | Graphite cathode material and lithium ion battery |
| CN106898740B (en) * | 2017-02-22 | 2020-09-01 | 深圳市金润能源材料有限公司 | Graphite negative electrode material and lithium ion battery |
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