JP5021979B2 - Mesocarbon microsphere graphitized material for lithium ion secondary battery negative electrode material and method for producing the same, lithium ion secondary battery negative electrode material, lithium ion secondary battery negative electrode and lithium ion secondary battery - Google Patents
Mesocarbon microsphere graphitized material for lithium ion secondary battery negative electrode material and method for producing the same, lithium ion secondary battery negative electrode material, lithium ion secondary battery negative electrode and lithium ion secondary battery Download PDFInfo
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- JP5021979B2 JP5021979B2 JP2006222218A JP2006222218A JP5021979B2 JP 5021979 B2 JP5021979 B2 JP 5021979B2 JP 2006222218 A JP2006222218 A JP 2006222218A JP 2006222218 A JP2006222218 A JP 2006222218A JP 5021979 B2 JP5021979 B2 JP 5021979B2
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- negative electrode
- lithium ion
- ion secondary
- secondary battery
- mesocarbon
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- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000003232 water-soluble binding agent Substances 0.000 description 1
- 239000002759 woven fabric Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
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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
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- Carbon And Carbon Compounds (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、メソカーボン小球体黒鉛化物とその製造方法、および、該メソカーボン小球体黒鉛化物からなるリチウムイオン二次電池用負極材料、負極、電池に関する。 The present invention relates to a mesocarbon small sphere graphitized material, a method for producing the mesocarbon small sphere graphitized material, and a negative electrode material for a lithium ion secondary battery, the negative electrode, and the battery comprising the mesocarbon small sphere graphitized material.
近年、電子機器の小型化あるいは高性能化に伴い、電池のエネルギー密度を高める要望がますます高まっている。特に、リチウムイオン二次電池は、他の二次電池に比べて高電圧化が可能なので、高いエネルギー密度が達成されるため注目されている。リチウムイオン二次電池は、負極、正極および電解液（非水電解質）を主たる構成要素とする。 In recent years, with the miniaturization or high performance of electronic devices, there is an increasing demand for increasing the energy density of batteries. In particular, lithium ion secondary batteries are attracting attention because they can achieve higher voltages than other secondary batteries, and thus achieve high energy density. A lithium ion secondary battery includes a negative electrode, a positive electrode, and an electrolytic solution (nonaqueous electrolyte) as main components.
負極は、一般に、銅箔からなる集電材とバインダーによって結着された負極材料（活物質）から構成される。通常、負極材料には炭素材料が使用される。このような炭素材料として、例えば特公昭６２−２３４３３号公報の記載にあるように、充放電特性に優れ、高い放電容量と電位平坦性とを示す黒鉛が汎用的に用いられている。 The negative electrode is generally composed of a current collector made of copper foil and a negative electrode material (active material) bound by a binder. Usually, a carbon material is used for the negative electrode material. As such a carbon material, for example, as described in Japanese Patent Publication No. 62-23433, graphite having excellent charge / discharge characteristics and high discharge capacity and potential flatness is generally used.
これまで、リチウムイオン二次電池の容量は、特に負極用炭素材料の質量当たりの放電容量に大きく依存していた。しかし、炭素材料として高純度の天然黒鉛を用いた場合でも、理論容量の372mAh/gが限界である。そのため、リチウムイオン二次電池の容量を高めるには、負極の集電体の上に、炭素材料からなる活物質を高密度で充填し、体積当たりの放電容量を向上させることが重要となる。 Until now, the capacity of the lithium ion secondary battery has been largely dependent on the discharge capacity per mass of the carbon material for the negative electrode. However, even when high-purity natural graphite is used as the carbon material, the theoretical capacity of 372 mAh / g is the limit. Therefore, in order to increase the capacity of the lithium ion secondary battery, it is important to fill the negative electrode current collector with an active material made of a carbon material at a high density to improve the discharge capacity per volume.
高圧プレスによって集電体上の活物質の充填密度を高めた場合、従来の炭素材料ではサイクル特性などの電池特性が悪化するという問題を生じていた。例えば、天然黒鉛を用いた場合には、粒子形状が鱗片状であるために、黒鉛の六角網面（ベーサル面）側が負極の表面を向くように一方向に積層（配向）されてしまう。このため、充放電に伴う黒鉛の膨張、収縮が負極の厚み方向に偏り、繰り返して充放電することによって、黒鉛粒子間の接触が保てずにサイクル特性が低下することがある。また、負極の表面が、扁平な黒鉛粒子によって閉塞してしまうため、電解液の注入に時間を要し、電池の生産性の低下を引き起こす。さらに、黒鉛粒子の周囲に含浸される電解液の量が不足するため、リチウムイオンの拡散性が低くなり、急速放電特性が低下することもある。 When the packing density of the active material on the current collector is increased by a high-pressure press, the conventional carbon material has a problem that battery characteristics such as cycle characteristics deteriorate. For example, when natural graphite is used, since the particle shape is scaly, it is laminated (oriented) in one direction so that the hexagonal mesh surface (basal surface) side of the graphite faces the surface of the negative electrode. For this reason, the expansion and contraction of graphite accompanying charging / discharging is biased in the thickness direction of the negative electrode, and repeated charging / discharging may not maintain the contact between graphite particles and may deteriorate cycle characteristics. Further, since the surface of the negative electrode is clogged with flat graphite particles, it takes time to inject the electrolytic solution, resulting in a decrease in battery productivity. Furthermore, since the amount of the electrolyte impregnated around the graphite particles is insufficient, the diffusibility of lithium ions is lowered, and the rapid discharge characteristics may be deteriorated.
そこで、高圧プレスによって活物質の充填密度を高くした場合においても、黒鉛のベーサル面の向きをランダムにし、配向を抑えるには、炭素材料の形状を鱗片状から球状に変更することが有効である。 Therefore, even when the packing density of the active material is increased by a high-pressure press, it is effective to change the shape of the carbon material from flaky to spherical in order to randomize the orientation of the basal plane of graphite and suppress the orientation. .
球状のメソカーボン小球体はピッチ類等を加熱して、ピッチマトリックス中にメソカーボン小球体を発生させるが、加熱の際に、原料ピッチ類に含まれるフリーカーボン（微粒子）の作用によって、メソフェーズの合体が阻止され表面張力によって球状を保持するものと考えられる。このようにして得られた従来のメソカーボン小球体の平均アスペクト比は１．０から１．１程度である。メソカーボン小球体を黒鉛化したメソカーボン小球体黒鉛化物の平均アスペクト比も１．０〜１．１程度である。 Spherical mesocarbon microspheres heat pitches and generate mesocarbon microspheres in the pitch matrix. During heating, the action of free carbon (fine particles) contained in the raw material pitches causes mesophase It is considered that the coalescence is prevented and the spherical shape is retained by the surface tension. The average aspect ratio of the conventional mesocarbon microspheres thus obtained is about 1.0 to 1.1. The average aspect ratio of the mesocarbon microsphere graphitized product obtained by graphitizing mesocarbon microspheres is also about 1.0 to 1.1.
特許文献１には、メソカーボン小球体の黒鉛化物をリチウムイオン二次電池の負極材料の活物質として用いる例が記載されている。このメソカーボン小球体黒鉛化物は、直径方向に垂直な方向に黒鉛のベーサル面が層状に配列したブルックス・テーラー型の単結晶であるが、粒子が球状であるために、活物質層の中ではベーサル面の向きがランダムとなり、天然黒鉛のような配向の問題が軽減されている。 Patent Document 1 describes an example in which graphitized mesocarbon spherules are used as an active material for a negative electrode material of a lithium ion secondary battery. This mesocarbon microsphere graphitized material is a Brooks-Taylor type single crystal in which the basal planes of graphite are arranged in layers in a direction perpendicular to the diameter direction, but because the particles are spherical, in the active material layer The orientation of the basal plane is random, and orientation problems like natural graphite are reduced.
また、特許文献２には、同じくメソカーボン小球体黒鉛化物をリチウムイオン二次電池の負極材料の活物質として用いる例が記載されているが、このメソカーボン小球体黒鉛化物は、粒子内の結晶がランダムに配置した多結晶体であり、特許文献１よりも、活物質層を形成したときにベーサル面の向きがランダムとなり、サイクル特性などの電池特性が改善されている。 Patent Document 2 also describes an example in which mesocarbon microsphere graphitized material is used as an active material for a negative electrode material of a lithium ion secondary battery. Are randomly arranged polycrystals, and the orientation of the basal plane is random when the active material layer is formed, and battery characteristics such as cycle characteristics are improved as compared with Patent Document 1.
しかしながら、これらのメソカーボン小球体黒鉛化物は、球状で（平均アスペクト比が１．０〜１．１程度）、かつ緻密な黒鉛粒子であるため、集電材に積層してプレスした際に、充填密度を高めることが難しい。具体的には充填密度を1.75g/cm3以上に高めようとした場合、プレス圧力を極めて高くする必要がある。プレス圧力が高いと、集電材である銅箔が延びてシワを生じたり、破断してしまうことがある。リチウムイオン二次電池の容量を高めるには、集電材をできるだけ薄くして、電池内の活物質の割合を増やすことが有効だが、集電材を薄くするほど、プレスした際に集電材の変形や破断を生じやすくなる。このように、負極の活物質層の充填密度を高めることが従来の負極材料では実現困難であった。
本発明の目的は、リチウムイオン二次電池の負極材料として用いた場合に、低いプレス圧力で高い充填密度に到達し、体積当たりの放電容量が高く、かつ、高い充填密度でありながら、配向を抑え、電解液の浸透性や保持性を損なうことのない新たな黒鉛化物とその製造方法、その黒鉛化物を用いた負極材料を提供することにある。 The purpose of the present invention is to achieve a high packing density at a low pressing pressure, a high discharge capacity per volume and a high packing density when used as a negative electrode material for a lithium ion secondary battery. An object of the present invention is to provide a new graphitized material, a method for producing the same, and a negative electrode material using the graphitized material that are suppressed and do not impair the permeability and retention of the electrolyte.
本発明の要旨は、以下のとおりである。
（１）第一の発明は、平均アスペクト比が２．８〜１０の楕円球状であることを特徴と
するリチウムイオン二次電池負極材料用メソカーボン小球体黒鉛化物である。
（２）第二の発明は、第一の発明に記載のメソカーボン小球体黒鉛化物を含むことを特
徴とするリチウムイオン二次電池負極材料である。
（３）第三の発明は、第二の発明に記載のリチウムイオン二次電池用負極材料を用いた
ことを特徴とするリチウムイオン二次電池用負極である。
（４）第四の発明は、第三の発明に記載のリチウムイオン二次電池用負極を用いたこと
を特徴とするリチウムイオン二次電池である。
（５）第五の発明は、石炭系および／または石油系の重質油、タール類ならびにピッチ
類から選ばれる１種または２種以上の原料に、液晶ポリマーを０．５〜２０質量％添加し、該液晶ポリマーの溶融温度以上、５００℃以下の温度範囲で加熱して、メソカーボン小球体を生成させるメソカーボン小球体生成工程と、該メソカーボン小球体を加熱して、黒鉛化する黒鉛化工程とを有することを特徴とするリチウムイオン二次電池負極材料用メソカーボン小球体黒鉛化物の製造方法である。
（６）第六の発明は、前記液晶ポリマーが、炭素と反応する性質および炭素を溶解する
性質のうちの少なくとも一方の性質を有する金属および／または金属化合物を含有することを特徴とする第五の発明に記載のリチウムイオン二次電池負極材料用メソカーボン小球体黒鉛化物の製造方法である。
The gist of the present invention is as follows.
(1) A first invention is a mesocarbon microsphere graphitized material for a negative electrode material for a lithium ion secondary battery , characterized in that the average aspect ratio is an elliptical sphere having a 2.8 to 10 average aspect ratio.
(2) A second invention is a lithium ion secondary battery negative electrode material comprising the mesocarbon microsphere graphitized product according to the first invention.
(3) A third invention is a negative electrode for a lithium ion secondary battery using the negative electrode material for a lithium ion secondary battery described in the second invention.
(4) A fourth invention is a lithium ion secondary battery using the negative electrode for a lithium ion secondary battery described in the third invention.
(5) 5th invention adds 0.5-20 mass% of liquid crystal polymers to 1 type, or 2 or more types of raw materials chosen from coal type and / or petroleum type heavy oil, tars, and pitches And a mesocarbon microsphere production step for producing mesocarbon microspheres by heating in a temperature range of not lower than the melting temperature of the liquid crystal polymer and not higher than 500 ° C., and graphite that is graphitized by heating the mesocarbon microspheres A mesocarbon microsphere graphitized material for a negative electrode material for a lithium ion secondary battery , characterized in that it comprises a crystallization step.
(6) A sixth invention is characterized in that the liquid crystal polymer contains a metal and / or a metal compound having at least one of a property of reacting with carbon and a property of dissolving carbon. It is a manufacturing method of the mesocarbon microsphere graphitized material for lithium ion secondary battery negative electrode materials as described in this invention.
本発明のメソカーボン小球体黒鉛化物を負極材料としたリチウムイオン二次電池用負極は、活物質の充填密度を高くした場合においても、集電体の変形や破断を生じることがなく、また、電解液の浸透性や保持性にも優れる。このため、本発明のメソカーボン小球体黒鉛化物を負極材料としたリチウムイオン二次電池は、体積当たり容量が高く、サイクル特性、急速放電特性などの電池特性が良好である。 The negative electrode for a lithium ion secondary battery using the mesocarbon microsphere graphitized material of the present invention as a negative electrode material does not cause deformation or breakage of the current collector even when the packing density of the active material is increased. Excellent permeability and retention of electrolyte. For this reason, the lithium ion secondary battery using the mesocarbon microsphere graphitized material of the present invention as a negative electrode material has a high capacity per volume and good battery characteristics such as cycle characteristics and rapid discharge characteristics.
以下、本発明をより具体的に説明する。
リチウムイオン二次電池は、通常、電解液（非水電解質）、負極および正極を主たる電池構成要素とし、これら要素が、例えば、電池缶内に封入されている。負極および正極はそれぞれリチウムイオンの担持体として作用する。充電時にはリチウムイオンが負極中に吸蔵され、放電時には負極からリチウムイオンが離脱する電池機構によっている。
Hereinafter, the present invention will be described more specifically.
A lithium ion secondary battery usually has an electrolyte solution (non-aqueous electrolyte), a negative electrode, and a positive electrode as main battery components, and these elements are enclosed in, for example, a battery can. The negative electrode and the positive electrode each act as a lithium ion carrier. The battery mechanism is such that lithium ions are occluded in the negative electrode during charging, and lithium ions are released from the negative electrode during discharging.
１．メソカーボン小球体黒鉛化物について
本発明のメソカーボン小球体黒鉛化物は、非造粒、非破砕型の黒鉛粒子であり、楕円球状からなることを特徴とする。楕円球状とは球状を押しつぶした形状を指す。
1. Mesocarbon small sphere graphitized material The mesocarbon small sphere graphitized material of the present invention is non-granulated, non-crushed graphite particles, and is characterized by comprising an oval sphere. An elliptical sphere refers to a shape obtained by crushing a sphere.
楕円球状は平均アスペクト比で定義することができ、黒鉛粒子の短軸方向の長さに対する、これと直交する長軸方向の長さの比の平均値から算出する。走査型電子顕微鏡などを用い、黒鉛粒子の形状が確認できる倍率で撮影して、黒鉛粒子のアスペクト比を個別に算出し、５０個以上の平均値を求める。平均アスペクト比は２．８〜１０の範囲である。
２．８未満の場合は、充填密度を高める効果が小さいものとなり、１０を超える場合には、黒鉛粒子内のベーサル面の配列が強くなって、サイクル特性や急速充放電特性の改善効果が低下することがある。
The elliptical sphere can be defined by an average aspect ratio, and is calculated from the average value of the ratio of the length in the major axis direction perpendicular to the length in the minor axis direction of the graphite particles. Using a scanning electron microscope or the like, the photograph is taken at a magnification at which the shape of the graphite particles can be confirmed, the aspect ratio of the graphite particles is individually calculated, and an average value of 50 or more is obtained. The average aspect ratio is in the range of 2.8 to 10.
If it is less than 2.8, the effect of increasing the packing density is small, and if it exceeds 10, the arrangement of the basal surfaces in the graphite particles becomes strong, and the effect of improving cycle characteristics and rapid charge / discharge characteristics is reduced. There are things to do.
本発明のメソカーボン小球体黒鉛化物は高い結晶性を有する。結晶性が高いがゆえに軟質であり、負極の充填密度を高くすることに寄与する。結晶性の指標として、Ｘ線広角回折における（002）面の平均格子面間隔ｄ002が0.3370nm以下、特に0.3365nm以下であることが好ましい。ここで、Ｘ線広角回折における（002）面の平均格子面間隔ｄ002とは、X線としてCuKα線を用い、高純度シリコンを標準物質に使用して黒鉛粒子の（002）面の回折ピークを測定し、そのピーク位置から算出する。算出方法は、学振法（日本学術振興会第17委員会が定めた測定法）に従うものであり、具体的には、「炭素繊維」[大谷杉郎、733−742頁（1986年3月）、近代編集社]に記載された方法によって測定された値である。 The mesocarbon microsphere graphitized product of the present invention has high crystallinity. Because of its high crystallinity, it is soft and contributes to increasing the packing density of the negative electrode. As an index of crystallinity, the X-ray wide angle diffraction (002) an average lattice spacing d 002 of face 0.3370nm or less, more preferably 0.3365nm or less. Here, the average lattice spacing d 002 of (002) plane in X-ray wide angle diffraction is a diffraction peak of (002) plane of graphite particles using CuKα ray as X-ray and using high purity silicon as a standard substance. Is calculated from the peak position. The calculation method follows the Japan Science and Technology Act (measurement method established by the 17th Committee of the Japan Society for the Promotion of Science). ), Measured by the method described in Modern Editorial Company].
本発明のメソカーボン小球体黒鉛化物の平均粒子径は、体積換算の平均粒子径で3〜100μｍ、特に5〜50μｍであることが好ましい。3μｍ以上であれば、負極の充填密度を高められ、体積当たりの放電容量が向上するし、100μｍ以下の方が、サイクル特性や急速充放電特性が向上するからである。体積換算の平均粒子径とは、レーザー回折式粒度分布計により粒度分布の累積度数が体積百分率で50％となる粒子径である。 The average particle size of the mesocarbon microsphere graphitized material of the present invention is preferably 3 to 100 μm, particularly preferably 5 to 50 μm in terms of volume average particle size. This is because if it is 3 μm or more, the packing density of the negative electrode can be increased, and the discharge capacity per volume is improved, and if it is 100 μm or less, cycle characteristics and rapid charge / discharge characteristics are improved. The average particle diameter in terms of volume is a particle diameter at which the cumulative frequency of particle size distribution is 50% by volume by a laser diffraction particle size distribution meter.
本発明のメソカーボン小球体黒鉛化物は、表面および／または内部に空孔を有することが好ましい。黒鉛粒子の表面に窪み、亀裂、細孔などの空孔を有し、黒鉛粒子の表面から内部へ空孔が連続的に存在することが好ましい。空孔の大きさや容積には特に規定はないが、空孔の最大径は、10nm〜5μｍ、空孔が占める体積は、黒鉛１ｇあたり0.01〜0.4cm3/gが好ましい。空孔のサイズと体積が好適範囲にあれば、電解液の浸透性が良好であり、かつ、負極をプレスする際の黒鉛粒子の変形を助長することができるからである。なお空孔の大きさや容積は水銀圧入法で測定することができる。 The mesocarbon microsphere graphitized product of the present invention preferably has pores on the surface and / or inside. It is preferable that the surface of the graphite particle has pits such as depressions, cracks, and pores, and the pores continuously exist from the surface of the graphite particle to the inside. There are no particular restrictions on the size and volume of the pores, but the maximum pore diameter is preferably 10 nm to 5 μm, and the volume occupied by the pores is preferably 0.01 to 0.4 cm 3 / g per gram of graphite. This is because, if the size and volume of the pores are in the preferred range, the permeability of the electrolytic solution is good and the deformation of the graphite particles when pressing the negative electrode can be promoted. The size and volume of the pores can be measured by mercury porosimetry.
２．リチウムイオン二次電池負極材料について
本発明の負極材料は、上記のメソカーボン小球体黒鉛化物を含むものであって、メソカーボン小球体黒鉛化物を単独で用いてもよいし、炭素材料、黒鉛材料、金属材料などの公知の各種負極材料との混合物、複合物であってもよい。
2. Regarding negative electrode material of lithium ion secondary battery The negative electrode material of the present invention contains the above mesocarbon microsphere graphitized material, and the mesocarbon microsphere graphitized material may be used alone, or the carbon material, the graphite material Further, it may be a mixture or composite with various known negative electrode materials such as metal materials.
混合する場合の負極材料とは、天然黒鉛などの黒鉛粒子、あるいは易黒鉛化性炭素質材料、例えば、球状のメソフェーズ小球体（従来品）やメソフェーズ焼成体（バルクメソフェーズ）、メソフェーズ繊維などのメソフェーズ系炭素質材料、石油コークス、ニードルコークス、生コークス、グリーンコークス、ピッチコークスなどのコークス系炭素質材料を1500℃以上、好ましくは2800℃以上で黒鉛化してなる黒鉛質粒子などが例示される。また、非晶質ハードカーボンなどの炭素質材料、有機物、金属、金属化合物などを含有する黒鉛質材料であってもよい。 The negative electrode material in the case of mixing is graphite particles such as natural graphite, or easily graphitizable carbonaceous materials such as spherical mesophase spherules (conventional product), mesophase fired bodies (bulk mesophase), and mesophase fibers. Examples thereof include graphitic particles obtained by graphitizing coke carbonaceous materials such as carbonaceous materials, petroleum coke, needle coke, green coke, green coke and pitch coke at 1500 ° C. or higher, preferably 2800 ° C. or higher. Further, it may be a carbonaceous material such as amorphous hard carbon, or a graphite material containing an organic substance, a metal, a metal compound, or the like.
３．メソカーボン小球体黒鉛化物の製造方法について
メソカーボン小球体は、石炭系および／または石油系の重質油、タール類ならびにピッチ類から選ばれる1種または2種以上を300〜500℃で加熱処理することにより生成する光学的的異方性の球状の重合物であるが、本発明の製造方法では、前記の石炭系、石油系の重質油、タール類、ピッチ類から選ばれる原料に、さらに液晶ポリマーを加えることを特徴とする。
3. Method for producing mesocarbon microsphere graphitized material Mesocarbon microspheres are heat-treated at 300 to 500 ° C, at least one selected from coal-based and / or petroleum-based heavy oils, tars and pitches. In the production method of the present invention, a raw material selected from the above coal-based, petroleum-based heavy oil, tars, pitches, Further, a liquid crystal polymer is added.
液晶ポリマーとは、溶融状態で液晶性を示すサーモトロピック液晶であり、パラヒドロキシ安息香酸、６−ヒドロキシ−2−ナフタレンカルボン酸、ビフェノールなどを原料とするポリエステルが例示される。ポリエチレンテレフタレートなどのポリエステルとの共重合体であってもよい。本発明では、融点が150℃以上、好ましくは300℃以上の液晶ポリマーを用い、液晶ポリマーが溶融状態を示す温度でメソカーボン小球体を生成させる。 The liquid crystal polymer is a thermotropic liquid crystal that exhibits liquid crystallinity in a molten state, and examples thereof include polyesters made from parahydroxybenzoic acid, 6-hydroxy-2-naphthalenecarboxylic acid, biphenol, and the like. It may be a copolymer with polyester such as polyethylene terephthalate. In the present invention, a liquid crystal polymer having a melting point of 150 ° C. or higher, preferably 300 ° C. or higher is used, and mesocarbon microspheres are generated at a temperature at which the liquid crystal polymer shows a molten state.
石炭系または石油系の重質油、タール類、ピッチ類から選ばれる原料に対し、液晶ポリマーを0.5〜20質量％添加する。添加量が0.5〜20質量％の範囲であると、好ましい楕円球状の形状に制御することができる。
液晶ポリマーはあらかじめ粉砕したものを用いることが好ましい。粉砕物の平均粒子径は、20μｍ以下とすることが好ましい。
0.5 to 20% by mass of a liquid crystal polymer is added to a raw material selected from coal-based or petroleum-based heavy oil, tars, and pitches. When the addition amount is in the range of 0.5 to 20% by mass, it can be controlled to have a preferable oval shape.
The liquid crystal polymer is preferably used in advance. The average particle size of the pulverized product is preferably 20 μm or less.
また、液晶ポリマーにあらかじめ金属および／または金属化合物を含有させておくことが好ましい。金属、金属化合物は、後記する黒鉛化の工程で、分解、蒸発して、最終的に得られる黒鉛化物の中に実質的に残存しないものが好ましい。金属および金属化合物を構成する金属は、炭素と反応する性質および炭素を溶解する性質のうちの少なくとも一方の性質を有するものが好ましく、Ｎａ，Ｋなどのアルカリ金属、Ｍｇ，Ｃａなどのアルカリ土類金属、Ｔｉ，Ｖ，Ｃｒ，Ｍｎ，Ｆｅ，Ｃｏ，Ｎｉ，Ｚｒ，Ｎｂ，Ｍｏ，Ｔｃ，Ｒｕ，Ｒｈ，Ｐｄ，Ｈｆ，Ｔａ，Ｗ，Ｒｅ，Ｏｓ，Ｉｒ，Ｐｔなどの遷移金属、Ａｌ，Ｇｅなどの金属、Ｂ，Ｓｉなどの半金属が例示される。これらの金属は化合物であってもよい。化合物としては、水酸化物、酸化物、窒化物、塩化物、硫化物などが例示される。このような金属、金属化合物は単独で用いてもよいし、２以上を混合して用いてもよいし、２以上の合金として用いてもよい。 Moreover, it is preferable that the liquid crystal polymer contains a metal and / or a metal compound in advance. It is preferable that the metal and the metal compound are decomposed and evaporated in the graphitization step described later and do not substantially remain in the finally obtained graphitized product. The metal and the metal composing the metal compound preferably have at least one of the property of reacting with carbon and the property of dissolving carbon, alkali metals such as Na and K, and alkaline earths such as Mg and Ca Transition metals such as metals, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, Pt, Al, Examples include metals such as Ge and semi-metals such as B and Si. These metals may be compounds. Examples of the compound include hydroxide, oxide, nitride, chloride, sulfide and the like. Such metals and metal compounds may be used alone, in combination of two or more, or may be used as two or more alloys.
これらの金属および／または金属化合物は、あらかじめ微粒子状に加工して、液晶ポリエステルに混合、分散、付着させることが好ましい。その場合の微粒子の平均粒子径は、５μｍ以下であることが好ましい。 These metals and / or metal compounds are preferably processed into fine particles in advance and mixed, dispersed and adhered to the liquid crystal polyester. In this case, the average particle diameter of the fine particles is preferably 5 μm or less.
金属および／または金属化合物の配合量は、金属および／または金属化合物と液晶ポリマーの総量に対して、5〜80質量％添加することが好ましい。 The compounding amount of the metal and / or metal compound is preferably 5 to 80% by mass based on the total amount of the metal and / or metal compound and the liquid crystal polymer.
石炭系、石油系の重質油、タール類、ピッチ類等から選ばれる原料に、所定量の液晶ポリマー、あるいは、金属／金属化合物を含有する液晶ポリマーの粉砕物を加え、液晶ポリマーの融点以上、500℃以下、好ましくは液晶ポリマーの融点以上、480℃以下で、10〜120分間熱処理する。原料にコールタールピッチを用いる場合には、コールタールピッチ中のフリーカーボン量を調整することによって、生成するメソカーボン小球体の含有量、粒子径を制御することができる。ピッチマトリックス中に占めるメソカーボン小球体の含有率は、１０〜５０質量％に制御することが好ましい。 Add a predetermined amount of liquid crystal polymer or pulverized liquid crystal polymer containing metal / metal compound to raw materials selected from coal-based, petroleum-based heavy oil, tars, pitches, etc. And heat treatment for 10 to 120 minutes at 500 ° C. or lower, preferably above the melting point of liquid crystal polymer and 480 ° C. or lower. When coal tar pitch is used as the raw material, the content and particle size of the mesocarbon microspheres to be produced can be controlled by adjusting the amount of free carbon in the coal tar pitch. The content of mesocarbon microspheres in the pitch matrix is preferably controlled to 10 to 50% by mass.
生成した楕円球状のメソカーボン小球体の分離方法、熱処理方法について例示すると、まず、ピッチマトリックス中に生成したメソカーボン小球体を抽出油で抽出し、ろ過や遠心分離などの方法によってメソカーボン小球体を分離し乾燥する。抽出油としては、ベンゼン、トルエン、キノリン、タール中油、タール重油などが例示される。抽出条件の操作によって、メソフェーズ小球体にピッチを少量残留させてもよい。 To illustrate the separation method and heat treatment method of the generated oval spherical mesocarbon spherules, first, the mesocarbon spherules generated in the pitch matrix are extracted with extraction oil, and then mesocarbon spherules are obtained by a method such as filtration or centrifugation. Isolate and dry. Examples of the extracted oil include benzene, toluene, quinoline, tar oil, and tar heavy oil. A small amount of pitch may remain in the mesophase spherules by operating the extraction conditions.
分離したメソカーボン小球体を、直接、または、350〜1300℃で予備焼成したのち、非酸化性雰囲気中1500〜3300℃で熱処理して黒鉛化する。黒鉛化方法としては、アチェソン炉などの公知の高温炉を用いることができる。 The separated mesocarbon spherules are pre-fired directly or at 350 to 1300 ° C., and then heat-treated at 1500 to 3300 ° C. in a non-oxidizing atmosphere to graphitize. As the graphitization method, a known high-temperature furnace such as an Acheson furnace can be used.
金属および／または金属化合物を配合した場合には、金属が蒸発または分解して実質的に除去される温度で黒鉛化することが好ましい。1500℃未満では黒鉛化できないほか、金属化合物が残存して、負極に用いた場合に放電容量が不足することがある。3300℃超の場合は、黒鉛粒子の一部が昇華することがあり、収率が低下するので好ましくない。黒鉛化に要する時間は一概には言えないが、１〜50時間程度である。 When a metal and / or a metal compound is blended, graphitization is preferably performed at a temperature at which the metal is substantially removed by evaporation or decomposition. If it is less than 1500 ° C., it cannot be graphitized, and the metal compound may remain and the discharge capacity may be insufficient when used for a negative electrode. When the temperature exceeds 3300 ° C., some of the graphite particles may sublime, which is not preferable because the yield decreases. Although the time required for graphitization cannot be generally stated, it is about 1 to 50 hours.
４．リチウムイオン二次電池用負極について
リチウムイオン二次電池の負極の作製は、通常の負極の成形方法に準じて行うことができるが、化学的、電気化学的に安定な負極を得ることができる成形方法であれば何ら制限されない。
4). About the negative electrode for lithium ion secondary batteries Although the production of the negative electrode of a lithium ion secondary battery can be carried out according to a normal method of forming a negative electrode, it is possible to obtain a chemically and electrochemically stable negative electrode. The method is not limited at all.
また、負極の作製時には、前記負極材料に結合剤を加えた負極合剤を用いることができる。結合剤としては、電解質に対して化学的安定性、電気化学的安定性を有するものを用いることが好ましく、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、ポリエチレン、ポリビニルアルコール、スチレンブタジエンゴム、さらにはカルボキシメチルセルロースなどが用いられる。また、これらを併用することもできる。結合剤は、通常、負極合剤の全量中１〜２０質量％程度の量で用いるのが好ましい。 Moreover, the negative electrode mixture which added the binder to the said negative electrode material can be used at the time of preparation of a negative electrode. As the binder, those having chemical stability and electrochemical stability with respect to the electrolyte are preferably used. For example, fluorine-based resins such as polyvinylidene fluoride and polytetrafluoroethylene, polyethylene, polyvinyl alcohol, and styrene Butadiene rubber, carboxymethyl cellulose and the like are used. Moreover, these can also be used together. In general, the binder is preferably used in an amount of about 1 to 20% by mass in the total amount of the negative electrode mixture.
負極の作製の具体例として、前記負極材料の粒子を結合剤と混合することによって負極合剤を調製し、この負極合剤を、通常、集電体の片面または両面に塗布することで負極合剤層を形成する方法が挙げられる。 As a specific example of the preparation of the negative electrode, a negative electrode mixture is prepared by mixing the particles of the negative electrode material with a binder, and this negative electrode mixture is usually applied to one or both sides of a current collector to form a negative electrode mixture. The method of forming an agent layer is mentioned.
負極の作製には、負極作製用の通常の溶媒を用いることができる。負極合剤を溶媒中に分散させ、ペースト状にした後、集電体に塗布、乾燥すれば、負極合剤層が均一かつ強固に集電体に接着される。より具体的には、例えば、前記負極材料の粒子とポリフッ化ビニリデンなどのフッ素系樹脂粉末またはスチレンブタジエンゴムなどの水分散粘結剤、カルボキシメチルセルロースなどの水溶性粘結剤とを、Ｎ−メチルピロリドン、ジメチルホルムアルデヒドまたは水、アルコールなどの溶媒と混合してスラリーとした後、ニーダーなどで混練し、ペーストを調製する。このペーストを集電材の片面または両面に塗布し、乾燥すれば、負極合剤層が均一かつ強固に接着した負極が得られる。前記負極合剤層の膜厚は１０〜２００μｍ、好ましくは３０〜１００μｍである。 A normal solvent for preparing a negative electrode can be used for preparing the negative electrode. When the negative electrode mixture is dispersed in a solvent and made into a paste, and then applied to the current collector and dried, the negative electrode mixture layer is uniformly and firmly adhered to the current collector. More specifically, for example, the negative electrode material particles and a fluorine-based resin powder such as polyvinylidene fluoride or a water-dispersible binder such as styrene butadiene rubber, or a water-soluble binder such as carboxymethyl cellulose are used. A paste is prepared by mixing with pyrrolidone, dimethylformaldehyde or a solvent such as water or alcohol to form a slurry, and then kneading with a kneader. If this paste is applied to one or both sides of the current collector and dried, a negative electrode in which the negative electrode mixture layer is uniformly and firmly bonded can be obtained. The film thickness of the negative electrode mixture layer is 10 to 200 μm, preferably 30 to 100 μm.
また、前記負極材料の粒子と、結合剤としてのポリエチレン、ポリビニルアルコールなどの樹脂粉末とを乾式混合し、金型内でホットプレス成形して負極を作製することもできる。ただし、乾式混合では、十分な負極の強度を得るために多くの結合剤を必要とし、結合剤が過多の場合は、リチウムイオン二次電池の放電容量や急速充放電効率が低下することがある。 Alternatively, the negative electrode material particles can be dry-mixed with resin powders such as polyethylene and polyvinyl alcohol as a binder, and hot-press molded in a mold to produce a negative electrode. However, dry mixing requires a large amount of binder to obtain sufficient strength of the negative electrode, and if the binder is excessive, the discharge capacity and rapid charge / discharge efficiency of the lithium ion secondary battery may be reduced. .
前記負極合剤層を形成した後、プレス加圧などの圧着を行うと、負極合剤層と集電体との接着強度をさらに高めることができる。 When the negative electrode mixture layer is formed and then pressure bonding such as pressurization is performed, the adhesive strength between the negative electrode mixture layer and the current collector can be further increased.
前記負極に用いる集電体の形状は特に限定されないが、箔状またはメッシュ、エキスパンドメタルなどの網状等のものが好ましい。また、前記集電体の材質としては、銅、ステンレス、ニッケルなどが好ましい。また、集電体の厚みは、箔状の場合、５〜２０μｍ程度とすることが好ましい。 The shape of the current collector used for the negative electrode is not particularly limited, but is preferably a foil shape or a net shape such as a mesh or expanded metal. Moreover, as a material of the said electrical power collector, copper, stainless steel, nickel, etc. are preferable. Moreover, it is preferable that the thickness of an electrical power collector shall be about 5-20 micrometers in the case of foil shape.
５．リチウムイオン二次電池について
また、本発明は、前記リチウムイオン二次電池用負極を用いて形成されるリチウムイオン二次電池でもある。
本発明のリチウムイオン二次電池は、前記負極を用いること以外は特に限定されず、他の電池構成要素については、一般的なリチウムイオン二次電池の要素に準じる。
5. About lithium ion secondary battery Moreover, this invention is also a lithium ion secondary battery formed using the said negative electrode for lithium ion secondary batteries.
The lithium ion secondary battery of the present invention is not particularly limited except that the negative electrode is used, and other battery components are in accordance with elements of a general lithium ion secondary battery.
５．１．正極材について
本発明のリチウムイオン二次電池に使用される正極材（正極活物質）としては、リチウム化合物が用いられるが、充分な量のリチウムを吸蔵／脱離し得るものを選択することが好ましい。例えば、リチウム含有遷移金属酸化物、遷移金属カルコゲン化物、バナジウム酸化物、その他のリチウム含有化合物、一般式ＭｘＭｏ６Ｓ８−Ｙ（式中Ｘは０≦Ｘ≦４、Ｙは０≦Ｙ≦１の範囲の数値であり、Ｍは少なくとも一種の遷移金属を表す）で表されるシュブレル相化合物、活性炭、活性炭素繊維などを用いることができる。前記バナジウム酸化物としては、Ｖ２Ｏ５、Ｖ６Ｏ１３、Ｖ２Ｏ４、Ｖ３Ｏ８で示されるものなどを用いることができる。
5.1. As the positive electrode material (positive electrode active material) used in the lithium ion secondary battery of the present invention, a lithium compound is used, but it is preferable to select a material that can occlude / desorb a sufficient amount of lithium. . For example, lithium-containing transition metal oxide, transition metal chalcogenide, vanadium oxide, other lithium-containing compounds, general formula M x Mo 6 S 8-Y (where X is 0 ≦ X ≦ 4, Y is 0 ≦ Y) A numerical value in the range of ≦ 1, and M represents at least one kind of transition metal) can be used. Examples of the vanadium oxide, or the like can be used those represented by V 2 O 5, V 6 O 13, V 2 O 4, V 3 O 8.
前記リチウム含有遷移金属酸化物は、リチウムと遷移金属との複合酸化物であり、リチウムと２種類以上の遷移金属を固溶したものであってもよい。複合酸化物は単独で使用しても、２種類以上を組み合わせて使用してもよい。リチウム含有遷移金属酸化物は、具体的には、ＬｉＭ1 1-XＭ2 ｘＯ2（式中Ｘは０≦Ｘ≦１の範囲の数値であり、Ｍ1、Ｍ2は少なくとも一種の遷移金属元素である）またはＬｉＭ1 1-YＭ2 YＯ4（式中Ｙは０≦Ｙ≦１の範囲の数値であり、Ｍ1、Ｍ2は少なくとも一種の遷移金属元素である）で示される。式中Ｍ1、Ｍ2で示される遷移金属はＣｏ、Ｎｉ、Ｍｎ、Ｃｒ、Ｔｉ、Ｖ、Ｆｅ、Ｚｎ、Ａｌ、Ｉｎ、Ｓｎなどである。好ましくはＣｏ、Ｍｎ、Ｃｒ、Ｔｉ、Ｖ、Ｆｅ、Ａｌなどである。具体例としては、ＬｉＣｏＯ2、ＬｉＮｉＯ2、ＬｉＭｎＯ2、ＬｉＮｉ0.9Ｃｏ0.1Ｏ2、ＬｉＮｉ0.5Ｃｏ0.5Ｏ2などを挙げることができる。 The lithium-containing transition metal oxide is a composite oxide of lithium and a transition metal, and may be a solid solution of lithium and two or more transition metals. The composite oxide may be used alone or in combination of two or more. Specifically, the lithium-containing transition metal oxide is LiM 1 1-X M 2 x O 2 (where X is a numerical value in the range of 0 ≦ X ≦ 1, and M 1 and M 2 are at least one kind of transition. A metal element) or LiM 1 1-Y M 2 Y O 4 (where Y is a numerical value in the range of 0 ≦ Y ≦ 1, and M 1 and M 2 are at least one transition metal element) It is. In the formula, transition metals represented by M 1 and M 2 are Co, Ni, Mn, Cr, Ti, V, Fe, Zn, Al, In, Sn, and the like. Preferably, Co, Mn, Cr, Ti, V, Fe, Al and the like are used. Specific examples include LiCoO 2 , LiNiO 2 , LiMnO 2 , LiNi 0.9 Co 0.1 O 2 , LiNi 0.5 Co 0.5 O 2 and the like.
また、前記リチウム含有遷移金属酸化物は、例えば、リチウム、遷移金属の酸化物、塩類などを出発原料とし、これら出発原料を所望の金属酸化物の組成に応じて混合し、酸素雰囲気下６００〜１０００℃の温度で焼成することにより得ることができる。なお、出発原料は酸化物および塩類に限定されず、水酸化物などであってもよい。 Further, the lithium-containing transition metal oxide is, for example, lithium, transition metal oxide, salts and the like as a starting material, these starting materials are mixed according to the composition of the desired metal oxide, and 600 ~ It can be obtained by firing at a temperature of 1000 ° C. The starting materials are not limited to oxides and salts, and may be hydroxides.
本発明のリチウムイオン二次電池においては、正極活物質は前記のリチウム化合物を単独で使用しても、２種類以上併用して使用してもよい。また、正極中に炭酸リチウムなどの炭酸アルカリ塩を添加することもできる。 In the lithium ion secondary battery of the present invention, the positive electrode active material may be used alone or in combination of two or more of the above lithium compounds. Further, an alkali carbonate such as lithium carbonate can be added to the positive electrode.
正極は、例えば、前記リチウム化合物と結合剤、および正極に導電性を付与するための導電剤よりなる正極合剤を、集電体の片面または両面に塗布して正極合剤層を形成して作製される。結合剤としては、負極の作製に使用されるものと同じものが使用可能である。導電剤としては、黒鉛やカーボンブラックなどの炭素材料が使用される。 The positive electrode is formed by, for example, applying a positive electrode mixture composed of the lithium compound, a binder, and a conductive agent for imparting conductivity to the positive electrode on one or both sides of the current collector to form a positive electrode mixture layer. Produced. As the binder, the same one as that used for producing the negative electrode can be used. As the conductive agent, a carbon material such as graphite or carbon black is used.
正極も負極と同様に、正極合剤を溶剤中に分散させペースト状にし、このペースト状の正極合剤を集電体に塗布、乾燥して正極合剤層を形成してもよく、正極合剤層を形成した後、さらにプレス加圧等の圧着を行ってもよい。これにより正極合剤層が均一且つ強固に集電体に接着される。 Similarly to the negative electrode, the positive electrode mixture may be formed in a paste by dispersing the positive electrode mixture in a solvent, and the paste-like positive electrode mixture may be applied to a current collector and dried to form a positive electrode mixture layer. After forming the agent layer, pressure bonding such as press pressing may be further performed. As a result, the positive electrode mixture layer is uniformly and firmly bonded to the current collector.
集電体の形状は特に限定されないが、箔状またはメッシュ、エキスパンドメタルなどの網状等のものが好ましい。また、前記集電体の材質としては、アルミニウム、ステンレス、ニッケルなどが好ましい。また、集電体の厚みは、箔状の場合、１０〜４０μｍ程度とすることが好ましい。 The shape of the current collector is not particularly limited, but is preferably a foil shape or a mesh shape such as a mesh or expanded metal. Moreover, as a material of the said electrical power collector, aluminum, stainless steel, nickel, etc. are preferable. The thickness of the current collector is preferably about 10 to 40 μm in the case of a foil shape.
５．２．非水電解質について
本発明のリチウムイオン二次電池に用いられる非水電解質としては、通常の非水電解液に使用される電解質塩である、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＣｌＯ4、ＬｉＢ（Ｃ6Ｈ5）、ＬｉＣｌ、ＬｉＢｒ、ＬｉＣＦ3ＳＯ3、ＬｉＣＨ3ＳＯ3、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＣ（ＣＦ3ＳＯ２）3、ＬｉＮ（ＣＦ3ＣＨ2ＯＳＯ2）2、ＬｉＮ（ＣＦ3ＣＦ2ＯＳＯ2）2、ＬｉＮ（ＨＣＦ2ＣＦ2ＣＨ2ＯＳＯ2）2、ＬｉＮ（（ＣＦ3）2ＣＨＯＳＯ2）2、ＬｉＢ［｛Ｃ6Ｈ3（ＣＦ3）2｝］4、ＬｉＡｌＣｌ4 、ＬｉＳｉＦ6などのリチウム塩を用いることができる。酸化安定性の点からは、特に、ＬｉＰＦ6、ＬｉＢＦ4が好ましい。
5.2. The non-aqueous electrolyte used in the lithium ion secondary battery of the present invention for non-aqueous electrolyte, an electrolyte salt used in the conventional non-aqueous 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 2 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 Lithium salts such as LiAlCl 4 and LiSiF 6 can be used. From the viewpoint of oxidation stability, LiPF 6 and LiBF 4 are particularly preferable.
電解液中の電解質塩濃度は０．１〜５ｍｏｌ／ｌが好ましく、０．５〜３．０ｍｏｌ／ｌがより好ましい。 The electrolyte salt concentration in the electrolytic solution is preferably 0.1 to 5 mol / l, and more preferably 0.5 to 3.0 mol / l.
前記非水電解質は液状の非水電解質としてもよく、固体電解質またはゲル電解質などの高分子電解質としてもよい。前者の場合、非水電解質電池は、いわゆるリチウムイオン二次電池として構成され、後者の場合は、非水電解質電池は高分子固体電解質、高分子ゲル電解質電池などの高分子電解質電池として構成される。 The non-aqueous electrolyte may be a liquid non-aqueous electrolyte or a polymer electrolyte such as a solid electrolyte or a gel electrolyte. In the former case, the non-aqueous electrolyte battery is configured as a so-called lithium ion secondary battery, and in the latter case, the non-aqueous electrolyte battery is configured as a polymer electrolyte battery such as a polymer solid electrolyte or a polymer gel electrolyte battery. .
非水電解質液を調製するための溶媒としては、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−オキサゾリドン、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などを用いることができる。 As a solvent for preparing the nonaqueous electrolyte solution, carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate, 1,1- or 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, ethers such as 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-oxazolidone, ethylene glycol, aprotic organic solvents such as dimethyl sulfite may be used.
前記非水電解質を高分子固体電解質または高分子ゲル電解質などの高分子電解質とする場合には、マトリックスとして可塑剤（非水電解液）でゲル化された高分子を用いることが好ましい。前記マトリックスを構成する高分子としては、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系高分子化合物、ポリ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などを用いることが特に好ましい。 When the non-aqueous electrolyte is a polymer electrolyte such as a polymer solid electrolyte or a polymer gel electrolyte, it is preferable to use a polymer gelled with a plasticizer (non-aqueous electrolyte) as a matrix. Examples of the polymer constituting the matrix include ether-based polymer compounds such as polyethylene oxide and cross-linked products thereof, polymethacrylate-based polymer compounds, polyacrylate-based polymer compounds, polyvinylidene fluoride, and vinylidene fluoride-hexafluoropropylene. It is particularly preferable to use a fluorine-based polymer compound such as a copolymer.
前記高分子固体電解質または高分子ゲル電解質には、可塑剤が配合されるが、この可塑剤としては、前記の電解質塩や非水溶媒が使用可能である。高分子ゲル電解質の場合、可塑剤である非水電解液中の電解質塩濃度は０．１〜５ｍｏｌ／ｌが好ましく、０．５〜２．０ｍｏｌ／ｌがより好ましい。 A plasticizer is blended in the polymer solid electrolyte or polymer gel electrolyte, and the electrolyte salt or non-aqueous solvent can be used as the plasticizer. In the case of a polymer gel electrolyte, the electrolyte salt concentration in the non-aqueous electrolyte solution that is a plasticizer is preferably 0.1 to 5 mol / l, and more preferably 0.5 to 2.0 mol / l.
前記高分子固体電解質の作製方法は特に限定されないが、例えば、マトリックスを構成する高分子化合物、リチウム塩および非水溶媒（可塑剤）を混合し、加熱して高分子化合物を溶融する方法、有機溶剤に高分子化合物、リチウム塩、および非水溶媒（可塑剤）を溶解させた後、混合用有機溶剤を蒸発させる方法、重合性モノマー、リチウム塩および非水溶媒（可塑剤）を混合し、混合物に紫外線、電子線または分子線などを照射して、重合性モノマーを重合させ、ポリマーを得る方法などを挙げることができる。 The method for producing the polymer solid electrolyte is not particularly limited. For example, a method in which a polymer compound constituting a matrix, a lithium salt, and a nonaqueous solvent (plasticizer) are mixed and heated to melt the polymer compound, organic After dissolving a polymer compound, a lithium salt, and a non-aqueous solvent (plasticizer) in a solvent, a method of evaporating an organic solvent for mixing, a polymerizable monomer, a lithium salt, and a non-aqueous solvent (plasticizer) are mixed, Examples include a method of obtaining a polymer by irradiating the mixture with ultraviolet rays, an electron beam, a molecular beam or the like to polymerize a polymerizable monomer.
ここで、前記固体電解質中の非水溶媒（可塑剤）の割合は１０〜９０質量％が好ましく、３０〜８０質量％がより好ましい。１０質量％未満であると導電率が低くなり、９０質量％を超えると機械的強度が弱くなり、成膜しにくくなる。 Here, the ratio of the non-aqueous solvent (plasticizer) in the solid electrolyte is preferably 10 to 90% by mass, and more preferably 30 to 80% by mass. If it is less than 10% by mass, the electrical conductivity will be low, and if it exceeds 90% by mass, the mechanical strength will be weak and film formation will be difficult.
５．３．セパレータについて
本発明のリチウムイオン二次電池においては、セパレータを使用することもできる。
セパレータの材質は特に限定されるものではないが、例えば、織布、不織布、合成樹脂製微多孔膜などを用いることができる。前記セパレータの材質としては、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、厚さ、膜強度、膜抵抗の面で好適である。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等が好適である。
5.3. About the separator In the lithium ion secondary battery of this invention, a separator can also be used.
Although the material of a separator is not specifically limited, For example, a woven fabric, a nonwoven fabric, a synthetic resin microporous film, etc. can be used. As a material for the separator, a microporous membrane made of synthetic resin is suitable. Among them, a polyolefin microporous membrane is suitable in terms of thickness, membrane strength, and membrane resistance. Specifically, polyethylene and polypropylene microporous membranes, or microporous membranes composed of these are suitable.
本発明のリチウムイオン二次電池は、上述した構成の、黒鉛質物を含有する負極、正極および非水電解質を、例えば、負極、非水電解質、正極の順で積層し、電池の外装材内に収容することで構成される。さらに、負極と正極の外側に非水電解質を配するようにしてもよい。 The lithium ion secondary battery of the present invention comprises a negative electrode, a positive electrode, and a non-aqueous electrolyte containing a graphite material, which are configured as described above, in the order of, for example, a negative electrode, a non-aqueous electrolyte, and a positive electrode. Consists of housing. Further, a non-aqueous electrolyte may be disposed outside the negative electrode and the positive electrode.
また、本発明のリチウムイオン二次電池の構造は特に限定されず、その形状、形態についても特に限定されるものではなく、用途、搭載機器、要求される充放電容量などに応じて、円筒型、角型、コイン型、ボタン型などの中から任意に選択することができる。より安全性の高い密閉型非水電解液電池を得るためには、過充電などの異常時に電池内圧上昇を感知して電流を遮断させる手段を備えたものを用いることが好ましい。 In addition, the structure of the lithium ion secondary battery of the present invention is not particularly limited, and the shape and form thereof are not particularly limited, and are cylindrical, depending on the application, mounted equipment, required charge / discharge capacity, and the like. , Square shape, coin shape, button shape, and the like. In order to obtain a sealed nonaqueous electrolyte battery with higher safety, it is preferable to use a battery equipped with means for detecting an increase in the internal pressure of the battery and shutting off the current when an abnormality such as overcharging occurs.
リチウムイオン二次電池が高分子固体電解質電池や高分子ゲル電解質電池の場合には、ラミネートフィルムに封入した構造とすることもできる。 In the case where the lithium ion secondary battery is a polymer solid electrolyte battery or a polymer gel electrolyte battery, a structure in which the lithium ion secondary battery is enclosed in a laminate film may be used.
次に本発明を実施例により具体的に説明するが、本発明はこれらの実施例に限定されるものではない。以下の実施例および比較例では、図１に示すような構成の評価用のボタン型二次電池を作製して評価した。該電池は、本発明の目的に基づき、公知の方法に準拠して作製することができる。 EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In the following Examples and Comparative Examples, button-type secondary batteries for evaluation having a configuration as shown in FIG. 1 were produced and evaluated. The battery can be produced according to a known method based on the object of the present invention.
［本発明例１］
１（ａ）液晶ポリマーの調製
ｐ−アセトキシ安息香酸、4,4’−ジアセトキシビフェニル、テレフタル酸を反応器に入れ、加熱下で攪拌しながら徐々に減圧し、酢酸を回収しながら重縮合反応を行い、融点410℃のサーモトロピック液晶ポリエステルを合成した。
[Invention Example 1]
1 (a) Preparation of liquid crystal polymer p-acetoxybenzoic acid, 4,4'-diacetoxybiphenyl, and terephthalic acid are put into a reactor and gradually reduced in pressure while stirring under heating, and polycondensation reaction is performed while acetic acid is recovered. Then, a thermotropic liquid crystal polyester having a melting point of 410 ° C. was synthesized.
１（ｂ）液晶ポリマーと金属化合物の混合
得られた液晶ポリマー50質量部と、平均粒子径２μｍの二酸化ケイ素50質量部を、二軸押出機を用いて溶融混練した。混練物を冷却したのち、平均粒子径５μｍに粉砕した。
1 (b) Mixing of liquid crystal polymer and metal compound 50 parts by mass of the obtained liquid crystal polymer and 50 parts by mass of silicon dioxide having an average particle diameter of 2 μm were melt-kneaded using a twin screw extruder. After cooling the kneaded product, it was pulverized to an average particle size of 5 μm.
１（ｃ）楕円球状のメソカーボン小球体の調製
フリーカーボンを１質量％含有するコールタールピッチ92質量部に、前記の金属化合物を含有する液晶ポリマーの粉砕物を8質量部混合し、不活性雰囲気中450℃で30分加熱処理し、メソカーボン小球体をピッチマトリックス中に35質量％生成させた。その後、タール中油を用いて、コールタールピッチからピッチマトリックスを溶解抽出し、メソカーボン小球体をろ過によって分離し、窒素雰囲気中120℃で乾燥した。これを窒素雰囲気中600℃で３時間加熱処理して、メソカーボン小球体の焼成物を調製した。該メソカーボン小球体の焼成物の断面を偏光顕微鏡で観察した結果を図２（ａ）に示す。断面は、楕円球状であり、光学的異方性を示していた。
1 (c) Preparation of ellipsoidal spherical mesocarbon spherules 92 parts by mass of coal tar pitch containing 1% by mass of free carbon is mixed with 8 parts by mass of the pulverized liquid crystal polymer containing the above metal compound. Heat treatment was performed in an atmosphere at 450 ° C. for 30 minutes to produce 35% by mass of mesocarbon microspheres in the pitch matrix. Thereafter, the pitch matrix was dissolved and extracted from the coal tar pitch using tar oil, and the mesocarbon spherules were separated by filtration and dried at 120 ° C. in a nitrogen atmosphere. This was heat-treated at 600 ° C. for 3 hours in a nitrogen atmosphere to prepare a fired product of mesocarbon microspheres. The result of observing the cross section of the fired product of the mesocarbon microspheres with a polarizing microscope is shown in FIG. The cross section was elliptical and spherical and showed optical anisotropy.
１（ｄ）メソカーボン小球体黒鉛化物の調製
得られたメソカーボン小球体の焼成物を黒鉛るつぼに充填し、非酸化性雰囲気下3150℃で5時間かけて黒鉛化処理を行い、メソカーボン小球体黒鉛化物を調製した。該メソカーボン小球体黒鉛化物の外観を走査型電子顕微鏡で観察した結果を図３（ａ）に示す。
1 (d) Preparation of mesocarbon microsphere graphitized material The obtained mesocarbon microsphere calcined product was filled in a graphite crucible and graphitized at 3150 ° C. for 5 hours in a non-oxidizing atmosphere. Spherical graphitized material was prepared. The result of observing the appearance of the mesocarbon microsphere graphitized material with a scanning electron microscope is shown in FIG.
外観は、楕円球状を呈しており、50個について粒子外観から平均アスペクト比を算出すると3.5であった。また、平均粒子径は34μｍ、Ｘ線広角回折における（００２）面の平均格子面間隔ｄ002は0.3359nmであった。 The appearance was oval and the average aspect ratio calculated from the particle appearance for 50 particles was 3.5. The average particle diameter of 34 .mu.m, the average lattice spacing d 002 of (002) plane in the X-ray wide angle diffraction was 0.3359Nm.
１（ｅ）負極合剤ペーストの調製
前記メソカーボン小球体黒鉛化物９８質量部、結合剤としてのカルボキシメチルセルロース１質量部およびスチレンーブタジエンゴム１質量部を水に入れ、攪拌して負極合剤ペーストを調製した。
1 (e) Preparation of Negative Electrode Mixture Paste 98 parts by mass of the mesocarbon microsphere graphitized material, 1 part by mass of carboxymethyl cellulose as a binder and 1 part by mass of styrene-butadiene rubber were put in water and stirred to mix the negative electrode mixture paste. Was prepared.
１（ｆ）作用電極の作製
前記負極合剤ペーストを厚み16μｍの銅箔上に均一な厚さで塗布し、さらに真空中90℃で分散媒の水を蒸発させて乾燥した。次に、この銅箔上に塗布された負極合剤をハンドプレスによって200MPaの圧力で加圧し、さらに直径15.5ｍｍの円形状に打抜くことで、銅箔からなる集電材に密着した負極合剤層（厚み60μｍ）からなる作用電極（負極）を作成した。なお、充填密度は1.78g/cm3に到達した。充填密度の測定は次のように行った。
1 (f) Production of Working Electrode The negative electrode mixture paste was applied on a copper foil having a thickness of 16 μm in a uniform thickness, and further, water in a dispersion medium was evaporated at 90 ° C. in a vacuum and dried. Next, the negative electrode mixture applied on the copper foil is pressed with a pressure of 200 MPa by a hand press, and further punched into a circular shape with a diameter of 15.5 mm, thereby adhering to the current collector made of copper foil. A working electrode (negative electrode) composed of a layer (thickness 60 μm) was prepared. The packing density reached 1.78 g / cm 3 . The packing density was measured as follows.
作用電極の端部、中央部の計5箇所について、接触部が直径５ｍｍの鏡面であるマイクロメーターを用いて平均厚みを計測し、銅箔の厚みを減じて負極合剤の厚みを求めた。次に、作用電極の質量から同一サイズの銅箔の質量を減じて負極合剤の質量を求めた。次式（１）から充填密度を算出した。
充填密度（g/cm3）＝負極合剤層の質量／（負極合剤層の厚み×作用電極の面積） （１）
The average thickness was measured using a micrometer whose contact portion was a mirror surface having a diameter of 5 mm at the end portion and the central portion of the working electrode, and the thickness of the copper foil was reduced to determine the thickness of the negative electrode mixture. Next, the mass of the negative electrode mixture was determined by subtracting the mass of the copper foil of the same size from the mass of the working electrode. The packing density was calculated from the following equation (1).
Packing density (g / cm 3 ) = mass of negative electrode mixture layer / (thickness of negative electrode mixture layer × area of working electrode) (1)
１（ｇ）対極の作製
リチウム金属箔をニッケルネットに押付け、直径１５．５ｍｍの円形状に打抜いて、ニッケルネットからなる集電体と、該集電体に密着したリチウム金属箔（厚み０．５ｍｍ）からなる対極（正極）を作製した。
1 (g) Fabrication of counter electrode A lithium metal foil was pressed against a nickel net, punched into a circular shape with a diameter of 15.5 mm, and a current collector made of nickel net, and a lithium metal foil closely attached to the current collector (thickness 0) 0.5 mm) was prepared.
１（ｈ）電解液、セパレータの作成
エチレンカーボネート３３vol%−メチルエチルカーボネート６７vol%の混合溶剤に、ＬｉＰＦ６を１ｍｏｌ／ｌとなる濃度で溶解させ、非水電解液を調製した。得られた非水電解液をポリプロピレン多孔質体（厚み２０μｍ）に含浸させ、電解液が含浸したセパレータを作製した。
1 (h) Preparation of Electrolytic Solution and Separator LiPF 6 was dissolved at a concentration of 1 mol / l in a mixed solvent of ethylene carbonate 33vol% -methylethyl carbonate 67vol% to prepare a nonaqueous electrolytic solution. The obtained nonaqueous electrolytic solution was impregnated into a polypropylene porous body (thickness 20 μm) to produce a separator impregnated with the electrolytic solution.
１（ｉ）評価電池の作製
評価電池として図１に示すボタン型二次電池を作製した。
1 (i) Production of Evaluation Battery A button type secondary battery shown in FIG. 1 was produced as an evaluation battery.
外装カップ１と外装缶３は、その周縁部において絶縁ガスケット６を介在させ、両周縁部をかしめて密閉した。その内部に外装缶３の内面から順に、ニッケルネットからなる集電体７ａ、リチウム箔よりなる円筒状の対極（正極）４、電解液が含浸されたセパレータ５、負極合剤からなる円盤状の作用電極（負極）２および銅箔からなる集電体７ｂが積層された電池系である。 The exterior cup 1 and the exterior can 3 were sealed by interposing an insulating gasket 6 at the peripheral portion thereof and caulking both peripheral portions. Inside, in order from the inner surface of the outer can 3, a current collector 7 a made of nickel net, a cylindrical counter electrode (positive electrode) 4 made of lithium foil, a separator 5 impregnated with an electrolyte, and a disk-like made of a negative electrode mixture A battery system in which a working electrode (negative electrode) 2 and a current collector 7b made of copper foil are laminated.
前記評価電池は電解液を含浸させたセパレータ５を集電体７ｂに密着した作用電極（負極）２と、集電体７ａに密着した対極（正極）４との間に挟んで積層した後、作用電極（負極）２を外装カップ１内に、対極（正極）４を外装缶３内に収容して、外装カップ１と外装缶３とを合わせ、さらに、外装カップ１と外装缶３との周縁部に絶縁ガスケット６を介在させ、両周縁部をかしめて密閉して作製した。 The evaluation battery was laminated by sandwiching the separator 5 impregnated with the electrolyte between the working electrode (negative electrode) 2 in close contact with the current collector 7b and the counter electrode (positive electrode) 4 in close contact with the current collector 7a. The working electrode (negative electrode) 2 is accommodated in the exterior cup 1, the counter electrode (positive electrode) 4 is accommodated in the exterior can 3, and the exterior cup 1 and the exterior can 3 are combined. The insulating gasket 6 was interposed at the peripheral edge, and both peripheral edges were caulked and sealed.
評価電池は実電池において負極用活物質として使用可能な黒鉛質物粒子を含有する作用電極（負極）２と、リチウム金属箔とからなる対極（正極）４とから構成される電池である。
前記のように作製した評価電池について、25℃の温度下で以下に示すような充放電試験を行い、質量当たり放電容量、体積当たり放電容量、初期充放電効率、急速放電率およびサイクル特性を評価した。評価結果を表１に示した。
The evaluation battery is a battery including a working electrode (negative electrode) 2 containing graphite particles that can be used as a negative electrode active material in a real battery, and a counter electrode (positive electrode) 4 made of a lithium metal foil.
The evaluation battery produced as described above was subjected to a charge / discharge test as shown below at a temperature of 25 ° C. to evaluate discharge capacity per mass, discharge capacity per volume, initial charge / discharge efficiency, rapid discharge rate, and cycle characteristics. did. The evaluation results are shown in Table 1.
１（ｊ）質量当たり放電容量、初期充放電効率、体積当たり放電容量の評価
回路電圧が０ｍVに達するまで０．９ｍAの定電流充電を行った後、定電圧充電に切り替え、電流値が２０μAになるまで充電を続けた。その間の通電量から質量当たり充電容量を求めた。その後、120分間休止した。次に０．９ｍAの電流値で、回路電圧が１．５Vに達するまで定電流放電を行い、この間の通電量から質量当たり放電容量を求めた。これを第１サイクルとした。次式（２）から初期充放電効率を計算した。
初期充放電効率（％）＝（第１サイクルの質量当たり放電容量
／第１サイクルの質量当たり充電容量）×１００ （２）
また、次式（３）から体積当たり放電容量を計算した。
体積当たり放電容量（mAh/cm3）＝第１サイクルの質量当たり放電容量×負極合剤層の充填密度×0.98 （３）
なお、（３）式で０．９８を掛けたのは、電池容量に寄与しないバインダー（２質量％）が含まれているからである。
1 (j) Evaluation of discharge capacity per mass, initial charge / discharge efficiency, discharge capacity per volume After constant current charging of 0.9 mA until the circuit voltage reaches 0 mV, switching to constant voltage charging, the current value becomes 20 μA I continued charging until. The charge capacity per mass was determined from the energization amount during that time. Then, it rested for 120 minutes. Next, constant current discharge was performed at a current value of 0.9 mA until the circuit voltage reached 1.5 V, and the discharge capacity per mass was determined from the amount of electricity supplied during this period. This was the first cycle. The initial charge / discharge efficiency was calculated from the following equation (2).
Initial charge / discharge efficiency (%) = (discharge capacity per mass of first cycle
/ Charging capacity per mass of the first cycle) × 100 (2)
Further, the discharge capacity per volume was calculated from the following equation (3).
Discharge capacity per volume (mAh / cm 3 ) = Discharge capacity per mass of first cycle x Filling density of negative electrode mixture layer x 0.98 (3)
The reason why 0.98 is multiplied by the expression (3) is because a binder (2% by mass) that does not contribute to the battery capacity is included.
１（ｋ）急速放電率の評価
引き続き、第２サイクルにおいて急速放電を行った。第１サイクルと同様にして定電圧充電に切り替え、満充電した後、電流値を第１サイクルの１６倍の１４．４ｍAとして、回路電圧が１．５Vに達するまで、定電流放電を行った。得られた放電容量から、次式（４）により急速放電率を計算した。
急速放電率＝（第２サイクルにおける質量当たり放電容量／第１サイクルにおける質量当たり放電容量）×１００ （４）
1 (k) Evaluation of rapid discharge rate Subsequently, rapid discharge was performed in the second cycle. After switching to constant voltage charging in the same manner as in the first cycle and fully charging, constant current discharge was performed until the circuit voltage reached 1.5 V with the current value set to 14.4 mA, 16 times that of the first cycle. From the obtained discharge capacity, the rapid discharge rate was calculated by the following equation (4).
Rapid discharge rate = (discharge capacity per mass in the second cycle / discharge capacity per mass in the first cycle) × 100 (4)
１（ｌ）サイクル特性の評価
質量当たり放電容量、初期充放電効率、急速放電率を評価した評価電池とは別の評価電池を作製し、以下のような評価を行った。
Evaluation of 1 (l) cycle characteristics An evaluation battery different from the evaluation battery evaluated in terms of discharge capacity per mass, initial charge / discharge efficiency, and rapid discharge rate was prepared and evaluated as follows.
回路電圧が０ｍVに達するまで４．０ｍAの定電流充電を行った後、定電圧充電に切り替え、電流値が２０μAになるまで充電を続けた後、120分間休止した。次に４．０ｍAの電流値で、回路電圧が１．５Vに達するまで定電流放電を行った。２０回充放電を繰り返し、得られた質量当たり放電容量から、次式（５）を用いてサイクル特性を計算した。
サイクル特性（％）＝（第２０サイクルの質量当たり放電容量
／第１サイクルの質量当たり放電容量）×１００ （５）
After 4.0 mA constant current charging was performed until the circuit voltage reached 0 mV, switching to constant voltage charging was continued until the current value reached 20 μA, and then rested for 120 minutes. Next, constant current discharge was performed at a current value of 4.0 mA until the circuit voltage reached 1.5V. The charge / discharge was repeated 20 times, and the cycle characteristics were calculated from the obtained discharge capacity per mass using the following equation (5).
Cycle characteristics (%) = (Discharge capacity per mass of 20th cycle)
/ Discharge capacity per mass of first cycle) × 100 (5)
表１に示すように、作用電極に実施例１の負極材料を用いて得られた評価電池は、充填密度を高くすることができ、かつ高い質量当たり放電容量を有する。このため、体積当たりの放電容量を大幅に向上することができる。その高い充填密度においても、初期充放電効率、急速放電特性、サイクル特性は優れた値を維持している。 As shown in Table 1, the evaluation battery obtained using the negative electrode material of Example 1 as the working electrode can have a high packing density and has a high discharge capacity per mass. For this reason, the discharge capacity per volume can be improved significantly. Even at the high packing density, the initial charge / discharge efficiency, rapid discharge characteristics, and cycle characteristics maintain excellent values.
［比較例１］
本発明例１において、液晶ポリマーおよび金属化合物を配合しない以外は本発明例１と同様にしてメソカーボン小球体を調製した。得られたメソカーボン小球体の焼成物の断面を偏光顕微鏡で観察した結果を図２（ｂ）に示す。断面は、真球状であり、光学的異方性を示していた。
[Comparative Example 1]
In Example 1 of the present invention, mesocarbon spherules were prepared in the same manner as Example 1 except that the liquid crystal polymer and the metal compound were not blended. The result of observing the cross section of the fired product of the obtained mesocarbon microspheres with a polarizing microscope is shown in FIG. The cross section was spherical and exhibited optical anisotropy.
最終的に得られたメソカーボン小球体黒鉛化物は、平均粒子径が32μｍ、Ｘ線広角回折における（００２）面の平均格子面間隔ｄ002が0.3363nmであった。走査型電子顕微鏡で撮影した該黒鉛化物の外観を図３（ｂ）に示す。走査型電子顕微鏡で観察すると、黒鉛化物はほぼ真球状を呈しており、50個について粒子外観から平均アスペクト比を算出すると1.1であった。 Finally mesocarbon spherules graphitized product obtained had an average particle diameter of 32 [mu] m, average lattice spacing d 002 of (002) plane in the X-ray wide angle diffraction was 0.3363 nm. The appearance of the graphitized material taken with a scanning electron microscope is shown in FIG. When observed with a scanning electron microscope, the graphitized product was almost spherical, and the average aspect ratio calculated from the particle appearance of 50 particles was 1.1.
この黒鉛化物を用いて、実施例１と同様な方法と条件で、作用電極および評価電池を作製して、充放電試験を行った。電池特性の評価結果を表１に示した。
なお、充填密度は1.67g/cm3にまでしか到達しなかった。
表１に示されるように、作用電極に、従来技術からなるメソカーボン小球体黒鉛化物を負極材料として用いた場合には、充填密度を高めることができず、体積当たり放電容量が不十分なものとなる。
Using this graphitized product, a working electrode and an evaluation battery were produced under the same method and conditions as in Example 1, and a charge / discharge test was performed. The evaluation results of the battery characteristics are shown in Table 1.
The packing density only reached 1.67 g / cm 3 .
As shown in Table 1, when the mesocarbon microsphere graphitized material of the prior art is used as the negative electrode material for the working electrode, the packing density cannot be increased and the discharge capacity per volume is insufficient. It becomes.
［比較例２］
比較例１で作製したメソカーボン小球体黒鉛化物を用いて、本発明例１と同様な方法と条件で、作用電極および評価電池を作製したが、銅箔上に塗布された負極合剤をハンドプレスする際に、本発明例１と同じ充填密度（1.78g/cm3）に到達するまでプレス圧力を高めた。
[Comparative Example 2]
Using the mesocarbon microsphere graphitized material produced in Comparative Example 1, a working electrode and an evaluation battery were produced in the same manner and under the same conditions as in Invention Example 1, but the negative electrode mixture coated on the copper foil was hand-held. During pressing, the pressing pressure was increased until the same packing density as in Example 1 of the present invention (1.78 g / cm 3) was reached.
その結果、320MPaの圧力で加圧することで充填密度1.78g/cm3に到達したが、銅箔にシワを生じた。得られた作用電極について、本発明例１と同様の充放電試験を行った。電池特性の評価結果を表１に示した。 As a result, the packing density reached 1.78 g / cm3 by pressurization at a pressure of 320 MPa, but wrinkles were formed on the copper foil. The obtained working electrode was subjected to the same charge / discharge test as Example 1 of the present invention. The evaluation results of the battery characteristics are shown in Table 1.
表１に示されるように、作用電極に、従来技術からなるメソカーボン小球体黒鉛化物を負極材料として用い、プレス圧力を高めて充填密度を高くした場合には、集電材である銅箔の変形を生じるほか、初期充放電効率、急速放電率、サイクル特性が大きく低下する。 As shown in Table 1, when the mesocarbon microsphere graphitized material of the prior art is used as the negative electrode material for the working electrode and the press pressure is increased to increase the packing density, the deformation of the copper foil as the current collector is changed. In addition, the initial charge / discharge efficiency, rapid discharge rate, and cycle characteristics are greatly reduced.
［本発明例２〜５］
実施例１において、液晶ポリマーの配合量や金属化合物の種類や配合量を変えたほかは実施例１と同様にしてメソカーボン小球体黒鉛化物を調製した。
この黒鉛化物を用いて、実施例１と同様な方法と条件で、作用電極および評価電池を作製して、充放電試験を行った。電池特性の評価結果を表１に示した。
[Invention Examples 2 to 5]
A mesocarbon microsphere graphitized material was prepared in the same manner as in Example 1 except that the blending amount of the liquid crystal polymer and the type and blending amount of the metal compound were changed.
Using this graphitized product, a working electrode and an evaluation battery were produced under the same method and conditions as in Example 1, and a charge / discharge test was performed. The evaluation results of the battery characteristics are shown in Table 1.
表１に示されるように、作用電極に、本発明のメソカーボン小球体黒鉛化物からなる負極材料を用いた場合には、体積当たり放電容量が高く、初期充放電効率、急速放電率、サイクル特性も良好なリチウムイオン二次電池が得られる。 As shown in Table 1, when the negative electrode material made of the mesocarbon microsphere graphitized product of the present invention was used for the working electrode, the discharge capacity per volume was high, the initial charge / discharge efficiency, the rapid discharge rate, the cycle characteristics. A good lithium ion secondary battery can be obtained.
［比較例３］
負極材料として平均粒径10μｍの天然黒鉛を用いた。Ｘ線広角回折における（００２）面の平均格子面間隔ｄ002が0.3357nmであった。走査型電子顕微鏡で観察すると、鱗片状を呈しており、50個について粒子外観から平均アスペクト比を算出すると15であった。
[Comparative Example 3]
Natural graphite having an average particle size of 10 μm was used as the negative electrode material. Average lattice spacing d 002 of the X-ray wide angle diffraction (002) plane was 0.3357Nm. When observed with a scanning electron microscope, it showed a scale-like shape, and the average aspect ratio calculated from the particle appearance of 50 particles was 15.
この天然黒鉛を用いて、本発明例１と同様な方法と条件で、作用電極および評価電池を作製して、充放電試験を行った。電池特性の評価結果を表１に示した。
なお、110MPaでプレスした際に充填密度が1.78g/cm3に到達した。充填密度1.78g/cm3で作用電極を作製した。
Using this natural graphite, a working electrode and an evaluation battery were produced under the same method and conditions as in Inventive Example 1, and a charge / discharge test was performed. The evaluation results of the battery characteristics are shown in Table 1.
The packing density reached 1.78 g / cm 3 when pressed at 110 MPa. A working electrode was prepared at a packing density of 1.78 g / cm 3 .
表１に示されるように、作用電極に、従来技術である天然黒鉛を負極材料として用いた場合には、体積当たり放電容量は高いものの、初期充放電効率、急速放電率およびサイクル特性が極めて低いものとなる。 As shown in Table 1, when natural graphite, which is the prior art, is used as the negative electrode material for the working electrode, although the discharge capacity per volume is high, the initial charge / discharge efficiency, the rapid discharge rate, and the cycle characteristics are extremely low. It will be a thing.
本発明の負極材料は、搭載する機器の小型化および高性能化に有効に寄与するリチウムイオン二次電池の負極材料に用いることができる。 The negative electrode material of the present invention can be used as a negative electrode material for a lithium ion secondary battery that contributes effectively to downsizing and high performance of equipment to be mounted.
１ 外装カップ
２ 作用電極（負極）
３ 外装缶
４ 対極（正極）
５ セパレータ
６ 絶縁ガスケット
７ａ，７ｂ 集電体
1 exterior cup 2 working electrode (negative electrode)
3 Exterior can 4 Counter electrode (positive electrode)
5 Separator 6 Insulating gasket 7a, 7b Current collector
Claims (6)
二次電池負極材料。 A lithium ion secondary battery negative electrode material comprising the mesocarbon microsphere graphitized product according to claim 1.
ウムイオン二次電池用負極。 A negative electrode for a lithium ion secondary battery, wherein the negative electrode material for a lithium ion secondary battery according to claim 2 is used.
オン二次電池。 A lithium ion secondary battery using the negative electrode for a lithium ion secondary battery according to claim 3.
たは２種以上の原料に、液晶ポリマーを０．５〜２０質量％添加し、該液晶ポリマーの溶
融温度以上、５００℃以下の温度範囲で加熱して、メソカーボン小球体を生成させるメソ
カーボン小球体生成工程と、該メソカーボン小球体を加熱して、黒鉛化する黒鉛化工程と
を有することを特徴とするリチウムイオン二次電池負極材料用メソカーボン小球体黒鉛化物の製造方法。 0.5 to 20% by mass of a liquid crystal polymer is added to one or more raw materials selected from coal-based and / or petroleum-based heavy oil, tars, and pitches, and the melting temperature of the liquid crystal polymer is exceeded. And a mesocarbon microsphere production step for producing mesocarbon microspheres by heating in a temperature range of 500 ° C. or less, and a graphitization step for heating the mesocarbon microspheres to graphitize. Of producing mesocarbon microsphere graphitized material for negative electrode material of lithium ion secondary battery .
も一方の性質を有する金属および／または金属化合物を含有することを特徴とする請求項
５に記載のリチウムイオン二次電池負極材料用メソカーボン小球体黒鉛化物の製造方法。 6. The lithium ion secondary battery according to claim 5, wherein the liquid crystal polymer contains a metal and / or metal compound having at least one of a property of reacting with carbon and a property of dissolving carbon. Method for producing mesocarbon microsphere graphitized material for negative electrode material .
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