JP5440488B2 - Carbon material for secondary battery - Google Patents
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Description
本発明は、二次電池用炭素材、二次電池用導電剤、二次電池用組成物、二次電池用電極合剤、二次電池用電極、及び二次電池に関し、特には、リチウムイオン二次電池用炭素材、リチウムイオン二次電池用導電剤、リチウムイオン二次電池用組成物、リチウムイオン二次電池用電極合剤、リチウムイオン二次電池用電極、及びリチウムイオン二次電池に関する。 The present invention relates to a carbon material for a secondary battery, a conductive agent for a secondary battery, a composition for a secondary battery, an electrode mixture for a secondary battery, an electrode for a secondary battery, and a secondary battery. Carbon material for secondary battery, conductive agent for lithium ion secondary battery, composition for lithium ion secondary battery, electrode mixture for lithium ion secondary battery, electrode for lithium ion secondary battery, and lithium ion secondary battery .
電子機器類のポータブル化、コードレス化が進むにつれ、二次電池の高容量化、高サイクル特性（長寿命化）等が求められている。特に、携帯電話やビデオカメラ等の小型携帯機器用二次電池として、近年、リチウムイオン二次電池が脚光を浴びており、リチウムイオン二次電池の小型軽量化及び高エネルギー密度化が、より一層求められている。 As electronic devices become more portable and cordless, there is a demand for higher secondary battery capacity, higher cycle characteristics (longer life), and the like. In particular, as secondary batteries for small portable devices such as mobile phones and video cameras, in recent years, lithium ion secondary batteries have attracted attention, and lithium ion secondary batteries have become smaller and lighter and have higher energy density. It has been demanded.
例えば、特許文献１には、リチウムを吸蔵・放出できる負極活物質、導電性炭素材料、及びバインダーを含むリチウム二次電池用負極であり、負極活物質が、粉末Ｘ線回折による黒鉛構造の（００２）面の面間隔ｄ（００２）が０．３３５〜０．３３７ｎｍの天然黒鉛または人造黒鉛を用いた黒鉛質材料であり、導電性炭素材料が、平均繊維径１〜２００ｎｍで、内部に中空構造を有し、繊維の長さ方向に対して垂直方向にグラフェンシートが積層した構造を持ち、粉末Ｘ線回折による黒鉛構造の（００２）面の面間隔ｄ（００２）が０．３３６〜０．３４５ｎｍの範囲にある気相法炭素繊維であり、前記気相法炭素繊維が１０μｍ以上の大きさの凝集体を形成することなく負極全体の０．１〜１０質量％含まれているリチウム二次電池用負極が提案され、長サイクル寿命、大電流特性に優れたリチウム二次電池を提供することができると記載されている。 For example, Patent Document 1 discloses a negative electrode for a lithium secondary battery that includes a negative electrode active material capable of inserting and extracting lithium, a conductive carbon material, and a binder, and the negative electrode active material has a graphite structure by powder X-ray diffraction ( 002) is a graphite material using natural graphite or artificial graphite having an interplanar spacing d (002) of 0.335 to 0.337 nm, and the conductive carbon material has an average fiber diameter of 1 to 200 nm and is hollow inside. The structure has a structure in which graphene sheets are laminated in a direction perpendicular to the length direction of the fiber, and the plane spacing d (002) of the (002) plane of the graphite structure by powder X-ray diffraction is 0.336-0. A vapor grown carbon fiber in the range of 345 nm, wherein the vapor grown carbon fiber is contained in an amount of 0.1 to 10% by mass of the whole negative electrode without forming an aggregate having a size of 10 μm or more. Negative for secondary battery There are proposed, it is described that it is possible to provide an excellent lithium secondary battery long cycle life, the large current characteristics.
また、例えば、特許文献２には、リチウムイオンの挿入・脱離が可能なケイ素原子または／及び錫原子を含む化合物を含有する粒子と、気相法炭素繊維との混合物を含むことを特徴とする負極材料が提案され、充放電容量が大きく、充放電サイクル特性に優れ、不可逆容量の小さいリチウムイオン二次電池を作製することができ、また、内部抵抗、特に低温における内部抵抗の値が小さなリチウムイオン二次電池を作成することができると記載されている。 In addition, for example, Patent Document 2 includes a mixture of particles containing a compound containing a silicon atom and / or a tin atom capable of inserting / extracting lithium ions, and vapor grown carbon fiber. A negative electrode material has been proposed, a lithium ion secondary battery having a large charge / discharge capacity, excellent charge / discharge cycle characteristics, a small irreversible capacity, and a low internal resistance, particularly at a low temperature. It is described that a lithium ion secondary battery can be produced.
しかしながら、電子機器類のポータブル化、コードレス化、そしてコンパクト化が更に進む状況においては、二次電池、特にはリチウムイオン二次電池の更なる高容量化、高サイクル特性（長寿命化）等が求められているのが現状である。 However, in situations where electronic devices are becoming more portable, cordless, and more compact, secondary batteries, especially lithium-ion secondary batteries, have higher capacities and higher cycle characteristics (longer life). The current situation is what is required.
上記のニーズを踏まえて、本発明者らが検討した結果、特許文献１及び２に記載の発明のように、炭素繊維を、Ｓｉ、Ｓｎ化合物又は黒鉛にただ単に混合又は含有させただけでは、炭素繊維の量が増えると炭素繊維と活物質とが増粘して分散性が悪化し、一方、炭素繊維の量が少なくなると、活物質、特にはナノサイズの活物質の滑落が生じ、二次電池の更なる高容量化、及び充放電サイクル特性の更なる改良が困難であるという問題が浮き彫りになった。 Based on the above needs, as a result of the study by the present inventors, as in the inventions described in Patent Documents 1 and 2, the carbon fiber is simply mixed or contained in Si, Sn compound or graphite. As the amount of carbon fiber increases, the carbon fiber and the active material thicken and the dispersibility deteriorates. On the other hand, when the amount of carbon fiber decreases, the active material, in particular, the nano-sized active material slips. The problem that it was difficult to further increase the capacity of the secondary battery and to further improve the charge / discharge cycle characteristics became apparent.
それゆえ、上記問題点を鑑みて、本発明は、二次電池、特にはリチウムイオン二次電池の高容量、高充放電サイクル特性を達成することができる、二次電池用炭素材、二次電池用導電剤、二次電池用組成物、二次電池用電極合剤、二次電池用電極、及び二次電池、並びに、リチウムイオン二次電池用炭素材、リチウム二次電池用導電剤、リチウム二次電池用組成物、リチウム二次電池用電極合剤、リチウム二次電池用電極、及びリチウムイオン二次電池を提供することを目的とする。 Therefore, in view of the above problems, the present invention is able to achieve the high capacity and high charge / discharge cycle characteristics of a secondary battery, particularly a lithium ion secondary battery. Battery conductive agent, composition for secondary battery, electrode mixture for secondary battery, electrode for secondary battery, and secondary battery, carbon material for lithium ion secondary battery, conductive agent for lithium secondary battery, It aims at providing the composition for lithium secondary batteries, the electrode mixture for lithium secondary batteries, the electrode for lithium secondary batteries, and a lithium ion secondary battery.
本発明者らは、上記目的を達成するために、鋭意研究を重ねた結果、二次電池用炭素材に、炭素核とその炭素核を始点として少なくとも３方向に延在する繊維状炭素とを含ませることによって、驚くべきことに、二次電池、特にはリチウムイオン二次電池の高容量、高充放電サイクル特性を達成することができることを見出し、本発明を完成するに至った。 As a result of intensive studies to achieve the above object, the present inventors have obtained a carbon material for a secondary battery with a carbon nucleus and fibrous carbon extending in at least three directions starting from the carbon nucleus. Surprisingly, it has been found that the high capacity and high charge / discharge cycle characteristics of a secondary battery, particularly a lithium ion secondary battery can be achieved, and the present invention has been completed.
すなわち、上記目的を達成するための手段は、以下の第（１）項〜第（１０）項である。
（１）炭素核と、その炭素核を始点として少なくとも３方向に延在する繊維状炭素とを含むことを特徴とする、二次電池用炭素材。
（２）その炭素核が中空であることを特徴とする、第（１）項に記載の二次電池用炭素材。
（３）その炭素核が球状粒子であることを特徴とする、第（１）項又は第（２）項に記載の二次電池用炭素材。
（４）その炭素核が板状粒子であることを特徴とする、第（１）項又は第（２）項に記載の二次電池用炭素材。
（５）第（１）項〜第（４）項のいずれか１項に記載の二次電池用炭素材を少なくとも含むことを特徴とする、二次電池用導電剤。
（６）第（５）項に記載の二次電池用導電剤と、活物質とを少なくとも含むことを特徴とする、二次電池用組成物。
（７）第（６）項に記載の二次電池用組成物を少なくとも含むことを特徴とする、二次電池用電極合剤。
（８）第（７）項に記載の二次電池用電極合剤を少なくとも含むことを特徴とする、二次電池用電極。
（９）第（８）項に記載の二次電池用電極を少なくとも含むことを特徴とする、二次電池。
（１０）リチウムイオン二次電池であることを特徴とする、第（９）項に記載の二次電池。
That is, means for achieving the above object are the following items (1) to (10).
(1) A carbon material for a secondary battery comprising a carbon nucleus and fibrous carbon extending in at least three directions starting from the carbon nucleus.
(2) The carbon material for a secondary battery as described in the item (1), wherein the carbon nucleus is hollow.
(3) The carbon material for a secondary battery according to (1) or (2), wherein the carbon nucleus is a spherical particle.
(4) The carbon material for a secondary battery according to (1) or (2), wherein the carbon nucleus is a plate-like particle.
(5) A conductive agent for a secondary battery, comprising at least the carbon material for a secondary battery according to any one of (1) to (4).
(6) A composition for a secondary battery, comprising at least the conductive agent for a secondary battery according to item (5) and an active material.
(7) A secondary battery electrode mixture comprising at least the secondary battery composition according to item (6).
(8) An electrode for a secondary battery comprising at least the electrode mixture for a secondary battery as described in item (7).
(9) A secondary battery comprising at least the secondary battery electrode according to item (8).
(10) The secondary battery according to item (9), which is a lithium ion secondary battery.
本発明によれば、二次電池、特にはリチウムイオン二次電池の電池容量を高め、充放電サイクル特性を一層向上させる、二次電池用炭素材、二次電池用導電剤、二次電池用組成物、二次電池用電極合剤、二次電池用電極、及び二次電池、並びに、リチウムイオン二次電池用炭素材、リチウム二次電池用導電剤、リチウム二次電池用組成物、リチウム二次電池用電極合剤、リチウム二次電池用電極、及びリチウムイオン二次電池が提供される。 According to the present invention, the secondary battery, particularly the lithium ion secondary battery, increases the battery capacity, and further improves the charge / discharge cycle characteristics, the secondary battery carbon material, the secondary battery conductive agent, and the secondary battery use. Composition, electrode mixture for secondary battery, electrode for secondary battery, and secondary battery, and carbon material for lithium ion secondary battery, conductive agent for lithium secondary battery, composition for lithium secondary battery, lithium An electrode mixture for a secondary battery, an electrode for a lithium secondary battery, and a lithium ion secondary battery are provided.
以下、本発明について更に詳細に説明をする。 Hereinafter, the present invention will be described in more detail.
（１）二次電池用炭素材
本発明による二次電池用炭素材は、炭素核と、炭素核を始点として少なくとも３方向に延在する繊維状炭素とを含むことを特徴とする。本発明による二次電池用炭素材は、高容量活物質と容易に混合して分散する効果を奏する。また、本発明による二次電池用炭素材は、正極層中又は負極層中で強固なカーボンネットワークを形成して高容量活物質を滑落させないで高容量活物質の大きな膨張によってもカーボンネットワークが壊れない効果を奏する。ここで、カーボンネットワークとは高容量活物質と集電体との間で電気をやりとりするために必要な導電性を有する炭素の連結体を意味する。高容量活物質は、充放電により大きい体積の膨張収縮を繰り返すものが多い。この膨張収縮により、カーボンネットワークが切断されると、高容量活物質と集電体との電気のやりとりがなされなくなり、その高容量活物質は充放電をしなくなる。これにより、二次電池の充放電サイクル特性が悪化するという問題が生じる。
(1) Carbon Material for Secondary Battery The carbon material for a secondary battery according to the present invention includes a carbon nucleus and fibrous carbon extending in at least three directions starting from the carbon nucleus. The carbon material for a secondary battery according to the present invention has an effect of being easily mixed and dispersed with a high capacity active material. In addition, the carbon material for a secondary battery according to the present invention forms a strong carbon network in the positive electrode layer or the negative electrode layer, and the carbon network is broken by large expansion of the high capacity active material without causing the high capacity active material to slide down. Has no effect. Here, the carbon network means a connected carbon body having conductivity necessary for exchanging electricity between the high-capacity active material and the current collector. Many high-capacity active materials repeatedly expand and contract a larger volume during charge and discharge. When the carbon network is cut by this expansion and contraction, the high-capacity active material and the current collector are not exchanged electricity, and the high-capacity active material is not charged or discharged. Thereby, the problem that the charging / discharging cycle characteristic of a secondary battery deteriorates arises.
本発明による二次電池用炭素材に含まれる炭素核の形状は、特に限定されることはないが、例えば、炭素核内部が実質的に満たされている球状粒子、板状粒子等が挙げられ、板状粒子の概念には鱗片状のものも含まれ、また、炭素核内部の一部でも空洞が存在する中空粒子も例示として挙げられ、その具体的態様として、中空球状粒子、中空板状粒子等が挙げられるが、高容量活物質の滑落を防止し、良好なカーボンネットワークを形成する観点からは、板状粒子、中空粒子、特には中空球状粒子、中空板状粒子であることが好ましく、板状粒子がより好ましい。なお、球状については真球状である必要はなく、変形していてもよい。板状については、波打っていたり、中空粒子が壊れて、曲面を有する薄片となったものでもよい。また、本発明においては、例えば中空粒子を作製後、粉砕して板状にしたものや、二次電池用電極の製造プロセスで、何らかの外力を加えたことにより、当初の形状が破壊され、または変形されて、板状になった場合など、本発明の炭素核の形状は、本発明の炭素材製造プロセス以降〜電池を製造するプロセスのいずれかで生じるものであってもよい。 The shape of the carbon nuclei contained in the carbon material for a secondary battery according to the present invention is not particularly limited, and examples thereof include spherical particles and plate-like particles that are substantially filled with the inside of the carbon nuclei. In addition, the concept of plate-like particles includes scaly ones, and hollow particles in which cavities exist even in part of carbon nuclei are given as examples, and specific embodiments thereof include hollow spherical particles, hollow plate-like particles From the viewpoint of preventing slipping of the high-capacity active material and forming a good carbon network, it is preferably a plate-like particle, a hollow particle, particularly a hollow spherical particle, or a hollow plate-like particle. More preferred are plate-like particles. The spherical shape does not need to be a true spherical shape, and may be deformed. As for the plate shape, it may be wavy or a hollow particle may be broken to form a flake having a curved surface. Further, in the present invention, for example, after making hollow particles, pulverized into a plate shape, or by applying some external force in the manufacturing process of the secondary battery electrode, the initial shape is destroyed, or The shape of the carbon core of the present invention, such as when deformed into a plate shape, may occur in any of the processes after the carbon material manufacturing process of the present invention to the process of manufacturing a battery.
本発明による二次電池用炭素材に含まれる炭素核の平均粒子径は、特に限定されることがないが、初期不可逆容量低下を防止し、電極合剤にした場合の増粘を抑える観点から、０．１μｍ〜１００μｍであることが好ましく、０．５μｍ〜５０μｍであることがより好ましく、１μｍ〜１０μｍであることが更に好ましい。本発明による炭素核の平均粒子径の定義としては、粒子形状とＭｉｅ理論を用いて測定量を粒子径に算出した値とし、有効径と称されるものである。本発明による炭素核の平均粒子径は、レーザー回折式粒度分布測定法による測定される体積換算で頻度が５０％となる粒子径を平均粒子径Ｄ５０％として定めたものである。板状粒子のように、レーザー回折式粒度分布測定法での測定が難しい場合は、ＳＥＭ観察により得られた板状粒子の長径を測定し、その平均値を算出することにより、平均粒子径とすることができる。なお、ＳＥＭ観察画像中に見える粒子３０個をランダムに観察し粒子径を求め、それらの平均値を平均粒径と定義した。板状粒子の場合の平均厚みは、高容量活物質の含有率を高め、かつ屈曲性を有し良好な導電ネットワークを形成維持する観点から、０．００１μｍ〜１μｍであることが好ましく、０．０１μｍ〜０．５μであることがより好ましく、０．０１μｍ〜０．１μｍであることが更に好ましい。中空粒子の場合の平均厚みも同様、高容量活物質の含有率を高め、かつ、屈曲性を有し良好な導電ネットワークを形成維持する観点から、０．００１μｍ〜１μｍであることが好ましく、０．０１μｍ〜０．５μｍであることがより好ましく、０．０１μｍ〜０．１μｍであることが更に好ましい。なお、ＳＥＭ観察画像中に見える粒子３０個をランダムに観察して厚みを求め、それらの平均値を平均厚みと定義する。 The average particle size of the carbon nuclei contained in the carbon material for secondary batteries according to the present invention is not particularly limited, but from the viewpoint of preventing the initial irreversible capacity reduction and suppressing the thickening when used as an electrode mixture. The thickness is preferably 0.1 μm to 100 μm, more preferably 0.5 μm to 50 μm, and still more preferably 1 μm to 10 μm. The definition of the average particle diameter of the carbon nuclei according to the present invention is a value obtained by calculating the measured amount into the particle diameter using the particle shape and Mie theory, and is referred to as an effective diameter. The average particle diameter of the carbon nuclei according to the present invention is determined by setting the particle diameter having a frequency of 50% in terms of volume measured by a laser diffraction particle size distribution measurement method as an average particle diameter D50%. When measurement by the laser diffraction particle size distribution measurement method is difficult, as in the case of plate-like particles, the average particle diameter is calculated by measuring the major axis of the plate-like particles obtained by SEM observation and calculating the average value. can do. In addition, 30 particles visible in the SEM observation image were randomly observed to determine the particle diameter, and the average value thereof was defined as the average particle diameter. The average thickness in the case of plate-like particles is preferably 0.001 μm to 1 μm from the viewpoint of increasing the content of the high-capacity active material and maintaining the formation of a good conductive network having flexibility. The thickness is more preferably 01 μm to 0.5 μm, and further preferably 0.01 μm to 0.1 μm. Similarly, the average thickness in the case of hollow particles is preferably 0.001 μm to 1 μm from the viewpoint of increasing the content of the high-capacity active material and maintaining the formation of a good conductive network having flexibility. The thickness is more preferably 0.01 μm to 0.5 μm, and still more preferably 0.01 μm to 0.1 μm. In addition, 30 particles visible in the SEM observation image are randomly observed to obtain a thickness, and an average value thereof is defined as an average thickness.
本発明による二次電池用炭素材に含まれる炭素核は、例えば、液相合成、噴霧乾燥、発泡フェノール樹脂の粉砕等の手法により得られた炭素核前駆体を炭化することによって得られる。ここで、本発明で用いられる炭素前駆体は、乾燥した樹脂、樹脂硬化物又は未炭化部分が残るものを意味する。例えば、水溶性フェノール樹脂水溶液に、必要に応じて炭酸リチウムを添加して、超音波霧化により微小液滴として、窒素などの不活性ガス気流下、２００℃以上５００℃以下の炉に搬送して３分以上３００分以下熱処理した後、静電捕集器により炭素核前駆体を回収し、さらに窒素などの不活性ガス気流下、５００℃以上１１００℃以下で５分以上１０時間以下、次いで１１００℃以上２０００℃以下で５分以上２４時間以下、にて炭化することにより、球状炭素核や中空炭素核などの本発明の炭素核が得られる。また、異なる態様としては、前記２００℃以上５００℃以下の工程の後、一気に１１００℃以上２０００℃以下での温度に昇温し、１０分以上２４時間以下加熱炭化する方法でもよい。前記態様のうち、炭素核の比表面積を低下し、初期不可逆容量の発生を抑制する観点で、２００℃以上４００℃以下で１秒以上３００分以下熱処理した後、５００℃以上７００℃以下の温度で５分以上１０時間以下、１１００℃以上２０００℃以下で１０分以上２４時間以下、炭化処理を行い、炭化を完了させ炭素核を得ることが好ましい。前記炭素核前駆体は、完全に炭化処理が完了しておらず、その段階では、未炭化物や表面活性点が残っているため、炭素核前駆体表面に繊維状炭素を生成させたり、結合させたりするのに好適なものとなる。炭素核を中空にするには、水溶性フェノール樹脂水溶液の濃度を０．１〜１％程度に低減したり、水溶性フェノール樹脂水溶液中に、中空形成剤（テンプレート）として、ポリスチレンラテックス等の炭化時に分解し消失する球状粒子を含有させるなどの手法を用いることができる。炭素核の板状化は、上記のように作製した中空でない炭素核又は中空である炭素核を、加圧、真空引き、機械的破砕等を施す方法、発泡フェノール樹脂を前記方法などを使用して炭化した後、粉砕、分級することによる方法、塗工装置やスピンコーター等の薄膜作製装置により、樹脂薄膜を作製した後、前記工程を経る方法などで板状炭素核を作製することができる。また噴霧乾燥より、長径の大きな板状粒子を作製することができる。 The carbon nucleus contained in the carbon material for a secondary battery according to the present invention can be obtained by carbonizing a carbon nucleus precursor obtained by a technique such as liquid phase synthesis, spray drying, and pulverization of a foamed phenol resin. Here, the carbon precursor used in the present invention means a dried resin, a cured resin, or an uncarbonized portion. For example, lithium carbonate is added to a water-soluble phenol resin aqueous solution as necessary, and is transported to a furnace at 200 ° C. or higher and 500 ° C. or lower as a fine droplet by ultrasonic atomization under an inert gas stream such as nitrogen. Then, after the heat treatment for 3 minutes to 300 minutes, the carbon nucleus precursor is recovered by an electrostatic collector, and further under an inert gas stream such as nitrogen at 500 ° C. to 1100 ° C. for 5 minutes to 10 hours, By carbonizing at 1100 ° C. or more and 2000 ° C. or less for 5 minutes or more and 24 hours or less, the carbon nuclei of the present invention such as spherical carbon nuclei and hollow carbon nuclei can be obtained. Moreover, as a different aspect, after the step of 200 ° C. or more and 500 ° C. or less, the temperature may be raised to a temperature of 1100 ° C. or more and 2000 ° C. or less at once and heated and carbonized for 10 minutes to 24 hours. Among the above embodiments, from the viewpoint of reducing the specific surface area of the carbon nuclei and suppressing the generation of the initial irreversible capacity, after the heat treatment at 200 ° C. to 400 ° C. for 1 second to 300 minutes, the temperature of 500 ° C. to 700 ° C. It is preferable to perform carbonization treatment at 1100 ° C. to 2000 ° C. for 10 minutes to 24 hours to complete carbonization to obtain carbon nuclei. The carbon nucleus precursor has not been completely carbonized, and at that stage, uncarburized materials and surface active sites remain. Therefore, fibrous carbon is generated or bonded to the surface of the carbon nucleus precursor. It becomes a suitable thing. In order to hollow out the carbon core, the concentration of the water-soluble phenol resin aqueous solution is reduced to about 0.1 to 1%, or carbonization of polystyrene latex or the like as a hollow forming agent (template) in the water-soluble phenol resin aqueous solution. Techniques such as containing spherical particles that sometimes decompose and disappear can be used. The plate formation of carbon nuclei uses a method of applying pressure, evacuation, mechanical crushing, etc. to a non-hollow carbon core or a hollow carbon nuclei prepared as described above, and using a foamed phenol resin as described above. After carbonizing, a plate-like carbon nucleus can be produced by a method by pulverization and classification, a thin film production device such as a coating device or a spin coater, and then a method passing through the above-described steps. . Further, plate-like particles having a large long diameter can be produced by spray drying.
本発明による二次電池用炭素材に含まれる繊維状炭素は、本発明による二次電池用炭素材に含まれる炭素核を始点として少なくとも３方向に延在する。繊維状炭素は、少なくとも炭素原子から構成されて繊維状のものであれば特に限定されることはないが、例えば、繊維径が１００ｎｍ〜１０μｍである炭素繊維（カーボンファイバー）、短径が１０ｎｍ〜１０００ｎｍである繊維状炭素（カーボンナノファイバー、ヘリカルカーボンナノファイバー、カーボンナノホーン）、繊維径が１〜１００ｎｍであるカーボンナノチューブ（単層カーボンナノチューブ、多層カーボンナノチューブ）等が挙げられる。また、上記繊維状炭素、カーボンマイクロバルーン、カーボンナノバルーン、破砕板状体、球状カーボンなどが連結して繊維状形態をなすもの等が挙げられる。高容量活物質の滑落を防止し、良好なカーボンネットワークを形成する観点から、繊維径又は短径が中心核の平均粒径又は長径の１／５〜１／１０００であることが好ましく、繊維径又は短径が中心核の平均粒径又は長径の１／１０〜１／１００であることがより好ましい。 The fibrous carbon contained in the carbon material for a secondary battery according to the present invention extends in at least three directions starting from the carbon nucleus contained in the carbon material for a secondary battery according to the present invention. Fibrous carbon is not particularly limited as long as it is composed of at least carbon atoms and is fibrous, for example, carbon fiber (carbon fiber) having a fiber diameter of 100 nm to 10 μm, and a short diameter of 10 nm to 10 nm. Examples thereof include fibrous carbon (carbon nanofibers, helical carbon nanofibers, carbon nanohorns) having a thickness of 1000 nm, carbon nanotubes having a fiber diameter of 1 to 100 nm (single-walled carbon nanotubes, multi-walled carbon nanotubes), and the like. Moreover, the thing etc. which the said fibrous carbon, a carbon microballoon, a carbon nanoballoon, a crushing plate-like body, spherical carbon, etc. connect and make a fibrous form are mentioned. From the viewpoint of preventing slipping of the high-capacity active material and forming a good carbon network, the fiber diameter or short diameter is preferably 1/5 to 1/1000 of the average particle diameter or long diameter of the central core, the fiber diameter Alternatively, the minor axis is more preferably 1/10 to 1/100 of the average particle diameter or major axis of the central core.
本発明による二次電池用炭素材に含まれる繊維状炭素は、本発明による二次電池用炭素材に含まれる炭素核を始点として延在するが、繊維状炭素が炭素核の表面部を始点として延在してもよいし、炭素核の内部を始点として延在してもよい。また、繊維状炭素が炭素核の表面部全体又は内部全体を始点として延在してもよいし、炭素核の表面部の少なくとも１部分又は内部の少なくとも１部分を始点として延在してもよい。 The fibrous carbon contained in the carbon material for the secondary battery according to the present invention extends from the carbon nucleus contained in the carbon material for the secondary battery according to the present invention, but the fibrous carbon starts from the surface portion of the carbon nucleus. Or may extend from the inside of the carbon nucleus. Further, the fibrous carbon may extend from the entire surface portion or inside of the carbon nucleus as a starting point, or may extend from at least one portion of the surface portion of the carbon nucleus or at least one portion inside. .
本発明による二次電池用炭素材に含まれる繊維状炭素は、本発明による二次電池用炭素材に含まれる炭素核を始点として少なくとも３方向に延在するが、１つの始点から繊維状炭素が延在して、延在した繊維状炭素のある地点から少なくとも３方向に繊維状炭素が枝分かれしてもよいし、２つの始点から繊維状炭素が延在して、少なくともどちらか１方の始点から延在した繊維状炭素のある地点から少なくとも２つの方向に繊維状炭素が枝分かれしてもよいし、さらには、少なくも３つの始点から繊維状炭素が延在して、少なくも３つの始点から延在した繊維状炭素がそれぞれ枝分かれしなくてもよいし、枝分かれしてもよい。 The fibrous carbon contained in the carbon material for a secondary battery according to the present invention extends in at least three directions starting from the carbon nucleus contained in the carbon material for a secondary battery according to the present invention, but the fibrous carbon from one starting point. May extend, and the fibrous carbon may branch in at least three directions from a certain point of the extended fibrous carbon, or at least one of the fibrous carbons may extend from two starting points. The fibrous carbon may branch in at least two directions from a certain point of the fibrous carbon extending from the starting point, and further, the fibrous carbon extends from at least three starting points, The fibrous carbon extending from the starting point may or may not be branched.
本発明による二次電池用炭素材に含まれる繊維状炭素は、例えば、上記のように生産した炭素核前駆体を５質量％の硝酸鉄水溶液で処理することによって、鉄触媒担持型の炭素核前駆体粒子が得られる。 The fibrous carbon contained in the carbon material for a secondary battery according to the present invention is obtained by, for example, treating the carbon nucleus precursor produced as described above with a 5% by mass iron nitrate aqueous solution to thereby provide an iron catalyst-supporting carbon nucleus. Precursor particles are obtained.
そして、上記のように生産した鉄触媒担持型の炭素核前駆体粒子を、炭素核の炭化処理をする段階で繊維状炭素を有する本発明による二次電池用炭素材が得られる。また、本発明の二次電池用炭素材事例の他の態様である、繊維状炭素、カーボンマイクロバルーン、カーボンナノバルーン、破砕板状体、球状カーボンなどが連結して繊維状形態をなす二次電池用炭素材は、前記炭素核前駆体と別途準備した繊維状炭素、カーボンマイクロバルーン、カーボンナノバルーン、破砕板状体、球状カーボンを、ヘンシェルミキサーなどを用いて、混合、撹拌し、加熱、マイクロ波照射等の高エネルギーを照射することによっても作製できる。ただし、前記炭素核前駆体に別途準備した繊維状炭素、カーボンマイクロバルーン、カーボンナノバルーン、破砕板状体、球状カーボン等がただ単に付着したものは炭素核と、繊維状炭素、カーボンマイクロバルーン、カーボンナノバルーン、破砕板状体及び球状カーボンから選ばれる少なくとも１つとを混合して得ることもできるが、単に混合するだけでは、繊維状炭素と炭素核前駆体との接合が不十分となり、高容量及び高充放電サイクル特性を達成することができない。したがって、前記炭素核前駆体と、別途準備した繊維状炭素、カーボンマイクロバルーン、カーボンナノバルーン、破砕板状体、球状カーボンなどを水やアルコールなどの溶媒中低濃度で十分に混合、撹拌するなどの方法で高分散をしたのち、加熱、マイクロ波照射、プラズマ照射、液中プラズマ（ソリューションプラズマ）処理、高圧プレス等の高エネルギーを与えることで繊維状炭素が炭素核と強固に接合している本発明の二次電池用炭素材を作製できるものである。 And the carbon material for secondary batteries by this invention which has a fibrous carbon in the stage which carbonizes the carbon nucleus precursor particle | grains of the iron catalyst carrying | support type produced as mentioned above is obtained. In addition, the secondary material in which the carbon material for the secondary battery of the present invention is another embodiment, in which fibrous carbon, carbon microballoon, carbon nanoballoon, crushed plate, spherical carbon, etc. are connected to form a fibrous form. The carbon material for a battery is prepared by mixing, stirring, heating, using a Henschel mixer or the like, the carbon nuclear precursor and fibrous carbon, carbon microballoon, carbon nanoballoon, crushed plate-like body, and spherical carbon prepared separately. It can also be produced by irradiation with high energy such as microwave irradiation. However, fibrous carbon, carbon microballoon, carbon nanoballoon, crushed plate, spherical carbon, etc. prepared separately to the carbon nucleus precursor are simply attached to the carbon nucleus, fibrous carbon, carbon microballoon, It can also be obtained by mixing at least one selected from carbon nanoballoons, crushed plate-like bodies, and spherical carbon, but simply mixing them results in insufficient bonding between the fibrous carbon and the carbon nucleus precursor. The capacity and high charge / discharge cycle characteristics cannot be achieved. Therefore, the carbon nucleus precursor and separately prepared fibrous carbon, carbon microballoon, carbon nanoballoon, crushed plate, spherical carbon, etc. are sufficiently mixed and stirred at a low concentration in a solvent such as water or alcohol. After high dispersion by this method, fibrous carbon is firmly bonded to the carbon core by applying high energy such as heating, microwave irradiation, plasma irradiation, in-liquid plasma (solution plasma) treatment, high pressure press, etc. The carbon material for a secondary battery of the present invention can be produced.
本発明による二次電池用炭素材は、リチウムイオン二次電池用炭素材であることが好ましい。本発明による二次電池用炭素材は、二次電池、特にはリチウムイオン二次電池の正極に用いられてもよいし、負極に用いられてもよい。本発明による二次電池用炭素材は、電極用材料として用いられれば特に制限されることはないが、二次電池用導電剤として用いられることが好ましい。 The carbon material for a secondary battery according to the present invention is preferably a carbon material for a lithium ion secondary battery. The carbon material for a secondary battery according to the present invention may be used for a positive electrode or a negative electrode of a secondary battery, particularly a lithium ion secondary battery. The carbon material for a secondary battery according to the present invention is not particularly limited as long as it is used as an electrode material, but is preferably used as a conductive agent for a secondary battery.
（２）二次電池用導電剤
本発明による二次電池用導電剤は、本発明による二次電池用炭素材を少なくとも含むことを特徴とし、導電補助剤を含んでもよい。
(2) Secondary Battery Conductive Agent The secondary battery conductive agent according to the present invention includes at least the secondary battery carbon material according to the present invention, and may include a conductive auxiliary agent.
導電補助剤としては、例えば、特に限定されることはないが、黒鉛、アセチレンブラック、ケッチェンブラック、導電性樹脂、導電性繊維等が挙げられる。 Examples of the conductive auxiliary agent include, but are not particularly limited to, graphite, acetylene black, ketjen black, conductive resin, conductive fiber, and the like.
本発明による二次電池用導電剤は、リチウムイオン二次電池用導電剤であることが好ましい。本発明による二次電池用導電剤は、二次電池、特にはリチウムイオン二次電池の正極に用いられてもよいし、負極に用いられてもよい。 The conductive agent for a secondary battery according to the present invention is preferably a conductive agent for a lithium ion secondary battery. The conductive agent for a secondary battery according to the present invention may be used for a positive electrode of a secondary battery, particularly a lithium ion secondary battery, or may be used for a negative electrode.
（３）二次電池用組成物
本発明による二次電池用組成物は、本発明による二次電池用導電剤と、活物質とを少なくとも含むことを特徴とし、例えば、後述する電極合剤を製造する前に、本発明の二次電池用炭素材及び／又は前記二次電池用導電剤と活物質を予備的に混合、分散した状態で保持したものである。粉末状で混合したものでも、水やアルコールなどの溶媒中に分散したものでもよい。
(3) Composition for secondary battery The composition for secondary battery according to the present invention comprises at least a conductive agent for secondary battery according to the present invention and an active material. Prior to production, the carbon material for secondary battery of the present invention and / or the conductive material for secondary battery and the active material are preliminarily mixed and dispersed. It may be mixed in powder form or dispersed in a solvent such as water or alcohol.
本発明による二次電池用組成物に含まれる活物質は正極用活物質でもよく、負極用活物質でもよい。 The active material contained in the composition for a secondary battery according to the present invention may be a positive electrode active material or a negative electrode active material.
本発明による二次電池用組成物に含まれる活物質の一次粒子の平均粒径は、リチウム拡散反応、体積膨張の影響緩和等の観点から、１μｍ以下であることが好ましく、ナノサイズの活物質が好ましい。ナノサイズの活物質の平均粒子サイズは１００ｎｍ以下であることが好ましい。 The average particle diameter of the primary particles of the active material contained in the composition for a secondary battery according to the present invention is preferably 1 μm or less from the viewpoint of reducing the influence of lithium diffusion reaction, volume expansion, and the like. Is preferred. The average particle size of the nano-sized active material is preferably 100 nm or less.
本発明による二次電池用組成物に含まれる負極用活物質は、特に限定されることはないが、例えば、リチウムイオンの吸蔵・放出が可能な金属もしくは半金属またはこれらの合金、酸化物、窒化物もしくは炭化物が挙げられる。具体的には、ケイ素（Ｓｉ）、スズ（Ｓｎ）、ゲルマニウム（Ｇｅ）、アルミニウム（Ａｌ）等を挙げることができる。さらにこれら金属または半金属の合金、酸化物、窒化物または炭化物の例として、酸化ケイ素（ＳｉＯｘ）、一酸化スズ（ＳｎＯ）、二酸化スズ（ＳｎＯ2）、窒化スズ（ＳｎＮ）、炭化スズ（ＳｎＣ）、一酸化ゲルマニウム（ＧｅＯ）、窒化ゲルマニウム（Ｇｅ3Ｎ4）、炭化ゲルマニウム（ＧｅＣ）、酸化アルミニウム（Ａｌ2Ｏ3）、窒化アルミニウム（ＡｌＮ）、炭化アルミニウム（Ａｌ4Ｃ3）、アルミニウムリチウム合金（Ａｌ−Ｌｉ系）等が挙げられる。できるだけ容量を高めるという観点で、Ｓｉ、ＳｉＯX（Ｘ＝０．１以上２未満）、Ｆｅ2Ｏ3等が好ましい。これらは、混合して用いてもよい。本発明による二次電池用組成物に含まれる正極用活物質は、特に限定されることではないが、例えば、リチウムイオンの吸蔵・放出が可能な材料であれば良く、ＬｉＣｏＯ2等のコバルト複合酸化物、ＬｉＭｎ2Ｏ4、Ｌｉ2ＭｎＯ3等のマンガン複合酸化物、ＬｉＮｉＯ2、等のニッケル複合酸化物、ＬｉＦｅＰＯ4、ＬｉＦｅＶＯ4、等の鉄複合酸化物、Ｌｉ（Ｎｉ，Ｃｏ）Ｏ2、Ｌｉ（Ｎｉ，Ｍｎ）Ｏ2、Ｌｉ（Ｃｏ，Ｍｇ）Ｏ2、Ｌｉ（Ｎｉ，Ｃｏ，Ｍｎ）Ｏ2、Ｌｉ（Ｎｉ，Ｃｏ，Ａｌ）Ｏ2、Ｌｉ（Ｃｏ，Ｍｇ，Ａｌ）Ｏ2、Ｌｉ（Ｎｉ，Ｃｏ，Ｍｎ，Ａｌ）Ｏ2等の複合酸化物等が挙げられる。これらは、混合して用いてもよい。 The negative electrode active material contained in the composition for a secondary battery according to the present invention is not particularly limited. For example, a metal or a semimetal capable of occluding and releasing lithium ions, an alloy thereof, an oxide, Nitride or carbide may be mentioned. Specifically, silicon (Si), tin (Sn), germanium (Ge), aluminum (Al), and the like can be given. Further, examples of these metal or metalloid alloys, oxides, nitrides or carbides include silicon oxide (SiOx), tin monoxide (SnO), tin dioxide (SnO 2 ), tin nitride (SnN), tin carbide (SnC). ), Germanium monoxide (GeO), germanium nitride (Ge 3 N 4 ), germanium carbide (GeC), aluminum oxide (Al 2 O 3 ), aluminum nitride (AlN), aluminum carbide (Al 4 C 3 ), aluminum lithium An alloy (Al-Li system) etc. are mentioned. From the viewpoint of increasing the capacity as much as possible, Si, SiO x (X = 0.1 to less than 2), Fe 2 O 3 and the like are preferable. You may mix and use these. The positive electrode active material contained in the composition for a secondary battery according to the present invention is not particularly limited, and may be any material capable of occluding and releasing lithium ions, for example, a cobalt composite such as LiCoO 2. Oxides, manganese composite oxides such as LiMn 2 O 4 and Li 2 MnO 3 , nickel composite oxides such as LiNiO 2 , iron composite oxides such as LiFePO 4 and LiFeVO 4 , Li (Ni, Co) O 2 Li (Ni, Mn) O 2 , Li (Co, Mg) O 2 , Li (Ni, Co, Mn) O 2 , Li (Ni, Co, Al) O 2 , Li (Co, Mg, Al) O 2 and complex oxides such as Li (Ni, Co, Mn, Al) O 2 . You may mix and use these.
本発明による二次電池用組成物は、リチウムイオン二次電池用組成物であることが好ましい。本発明による二次電池用組成物は、二次電池、特にはリチウムイオン二次電池の正極に用いられてもよいし、負極に用いられてもよい。 The composition for a secondary battery according to the present invention is preferably a composition for a lithium ion secondary battery. The composition for a secondary battery according to the present invention may be used for a positive electrode or a negative electrode of a secondary battery, particularly a lithium ion secondary battery.
（４）二次電池用電極合剤
本発明による二次電池用電極合剤は本発明による二次電池用組成物を少なくとも含むことを特徴とし、結着剤や粘度調整剤等を含んでもよい。本発明による二次電池用電極合剤の調製は、従来公知の方法を用いればよく、本発明による二次電池用組成物に、結着剤、水、溶媒を添加したり、乾燥することにより、粘度調整剤を添加することにより粘度を調整し、適当な溶媒又は分散媒で所定粘度としたスラリーとして調製することができる。
(4) Secondary battery electrode mixture The secondary battery electrode mixture according to the present invention includes at least the secondary battery composition according to the present invention, and may include a binder, a viscosity modifier, and the like. . The secondary battery electrode mixture according to the present invention may be prepared by using a conventionally known method. By adding a binder, water, or a solvent to the secondary battery composition according to the present invention or drying the composition. The viscosity can be adjusted by adding a viscosity modifier, and the slurry can be prepared to have a predetermined viscosity with an appropriate solvent or dispersion medium.
結着剤としては、特に限定されることはないが、カルボキシシメチルセルロース、ポリフッ化ビニリデン樹脂、ポリテトラフルオロエチレン、スチレン・ブタジエン共重合体、ポリイミド樹脂、ポリアミド樹脂、ポリビニルアルコール、ポリビニルブチラール、ポリアクリル酸又はそのアルカリ塩、ポリアミック酸等が挙げられる。これらは、表面修飾などにより改質されたものであってもよい。 The binder is not particularly limited, but carboxymethyl cellulose, polyvinylidene fluoride resin, polytetrafluoroethylene, styrene / butadiene copolymer, polyimide resin, polyamide resin, polyvinyl alcohol, polyvinyl butyral, polyacrylic. An acid or its alkali salt, a polyamic acid, etc. are mentioned. These may be modified by surface modification or the like.
溶媒又は分散媒としては、均一に混合できる材料であれば特に限定されることはなく、例えば、水、メタノール、エタノール等のアルコール類、Ｎ−メチル−２−ピロリドン、アセトニトリル等が挙げられる。これらは、表面修飾などにより改質されたものであってもよい。 The solvent or dispersion medium is not particularly limited as long as it is a material that can be uniformly mixed, and examples thereof include water, alcohols such as methanol and ethanol, N-methyl-2-pyrrolidone, and acetonitrile. These may be modified by surface modification or the like.
本発明による二次電池用電極合剤は、リチウムイオン二次電池用電極合剤であることが好ましい。本発明による二次電池用電極合剤は、二次電池、特にはリチウムイオン二次電池の正極に用いられてもよいし、負極に用いられてもよい。 The electrode mixture for secondary batteries according to the present invention is preferably an electrode mixture for lithium ion secondary batteries. The electrode mixture for secondary batteries according to the present invention may be used for a positive electrode or a negative electrode of a secondary battery, particularly a lithium ion secondary battery.
（５）二次電池用電極
本発明による二次電池用電極は、本発明による二次電池用電極合剤を少なくとも含み、上述のようにして得られた本発明による二次電池用電極合剤を用いることにより、本発明による二次電池用電極を作製することができる。具体的には、本発明による二次電池用電極は、本発明による二次電池用電極合剤を銅箔等の金属箔などの集電体に塗工し、厚さ数μｍ〜数百μｍのコーティングを形成させ、そのコーティングを５０〜２００℃程度で熱処理することにより溶媒又は分散媒を除去することにより作製することができる。
(5) Secondary Battery Electrode The secondary battery electrode according to the present invention includes at least the secondary battery electrode mixture according to the present invention, and the secondary battery electrode mixture according to the present invention obtained as described above. By using the secondary battery electrode according to the present invention can be produced. Specifically, the electrode for a secondary battery according to the present invention is applied to a current collector such as a metal foil such as a copper foil with the electrode mixture for a secondary battery according to the present invention, and has a thickness of several μm to several hundred μm. This coating can be formed by removing the solvent or the dispersion medium by heat-treating the coating at about 50 to 200 ° C.
本発明による二次電池用電極は、リチウムイオン二次電池用電極であることが好ましい。本発明による二次電池用電極は、二次電池、特にはリチウムイオン二次電池の正極として用いられてもよいし、負極として用いられてもよい。 The secondary battery electrode according to the present invention is preferably a lithium ion secondary battery electrode. The secondary battery electrode according to the present invention may be used as a positive electrode or a negative electrode of a secondary battery, particularly a lithium ion secondary battery.
（６）二次電池
本発明による二次電池は二次電池用電極を少なくとも含むことを特徴とする。本発明による二次電池は、本発明による導電剤を含み、該導電剤が電子の授受の少なくとも一部を担うことで電池として使用でき、繰り返し使用できる化学電池であれば特に限定されることはなく、例えば、リチウムイオン二次電池、鉛蓄電池、ニカド電池等が挙げられ、リチウムイオン二次電池が好ましい。
(6) Secondary Battery The secondary battery according to the present invention includes at least a secondary battery electrode. The secondary battery according to the present invention includes the conductive agent according to the present invention, and the conductive agent can be used as a battery by taking charge of at least part of electron transfer. For example, a lithium ion secondary battery, a lead storage battery, a nickel-cadmium battery, etc. are mentioned, A lithium ion secondary battery is preferable.
本発明による二次電池用電極を用いることにより、本発明による二次電池を作製することができる。本発明による二次電池は、従来公知の方法で作製することができ、一般に、本発明による二次電池用電極（正極用及び負極用）と、電解質とを含み、さらにこれらの負極と正極が短絡しないようにするセパレータを含む。電解質がポリマーと複合化された固体電解質であってセパレータの機能を併せ持つものである場合には、独立したセパレータは不要である。本発明の二次電池の作製方法（製造方法）は、公知な方法を適用することができるが、例えば、まず、上記で得た正極および負極を、所定の形、大きさに切断して用意し、次いで、正極と負極を直接接触しないように、セパレータを介して貼りあわせ、それを単層セルとする。次いで、この単層セルの電極間に、注液などの方法により、電解質を注入する。このようにして得られたセルを、例えば、ポリエステルフィルム／アルミニウムフィルム／変性ポリオレフィンフィルムの三層構造のラミネートフィルムからなる外装体に挿入し封止することにより、二次電池が得られる。得られた二次電池は、用途により、単セルとして用いても、複数のセルを繋いだモジュールとして用いてもよい。 By using the secondary battery electrode according to the present invention, the secondary battery according to the present invention can be manufactured. The secondary battery according to the present invention can be produced by a conventionally known method, and generally includes the secondary battery electrode (for positive electrode and negative electrode) according to the present invention and an electrolyte, and further, these negative electrode and positive electrode are Includes separator to prevent short circuit. When the electrolyte is a solid electrolyte combined with a polymer and has the function of a separator, an independent separator is not necessary. As a manufacturing method (manufacturing method) of the secondary battery of the present invention, a known method can be applied. For example, first, the positive electrode and the negative electrode obtained above are first cut into a predetermined shape and size. Then, the positive electrode and the negative electrode are bonded through a separator so as not to be in direct contact with each other, thereby forming a single-layer cell. Next, an electrolyte is injected between the electrodes of the single-layer cell by a method such as injection. A secondary battery is obtained by inserting and sealing the thus obtained cell into an exterior body made of a laminate film having a three-layer structure of polyester film / aluminum film / modified polyolefin film, for example. The obtained secondary battery may be used as a single cell or a module in which a plurality of cells are connected depending on the application.
本発明による二次電池用電極を好適にリチウムイオン二次電池用途にすることにより、本発明によるリチウムイオン二次電池を作製することができる。本発明によるリチウムイオン二次電池は、従来公知の方法で作製することができ、一般に、本発明によるリチウムイオン二次電池用電極（正極用及び負極用）と、電解質とを含み、さらにこれらの負極と正極が短絡しないようにするセパレータを含む。電解質がポリマーと複合化された固体電解質であってセパレータの機能を併せ持つものである場合には、独立したセパレータは不要である。本発明のリチウムイオン二次電池の作製方法（製造方法）は、公知な方法を適用することができるが、例えば、まず、上記で得たリチウムイオン二次電池用の正極及び負極を、所定の形、大きさに切断して用意し、次いで、正極と負極を直接接触しないように、セパレータを介して貼りあわせ、それを単層セルとする。次いで、この単層セルの電極間に、注液などの方法により、電解質を注入する。このようにして得られたセルを、例えば、ポリエステルフィルム／アルミニウムフィルム／変性ポリオレフィンフィルムの三層構造のラミネートフィルムからなる外装体に挿入し封止することにより、リチウムイオン二次電池が得られる。得られたリチウムイオン二次電池は、用途により、単セルとして用いても、複数のセルを繋いだモジュールとして用いてもよい。 The lithium ion secondary battery according to the present invention can be produced by suitably using the secondary battery electrode according to the present invention for a lithium ion secondary battery. The lithium ion secondary battery according to the present invention can be produced by a conventionally known method, and generally includes a lithium ion secondary battery electrode (for positive electrode and negative electrode) according to the present invention, and an electrolyte. A separator that prevents the negative electrode and the positive electrode from being short-circuited is included. When the electrolyte is a solid electrolyte combined with a polymer and has the function of a separator, an independent separator is not necessary. As a manufacturing method (manufacturing method) of the lithium ion secondary battery of the present invention, a known method can be applied. For example, first, the positive electrode and the negative electrode for the lithium ion secondary battery obtained above are used in a predetermined manner. Prepared by cutting into a shape and size, and then bonded together through a separator so that the positive electrode and the negative electrode are not in direct contact with each other to form a single-layer cell. Next, an electrolyte is injected between the electrodes of the single-layer cell by a method such as injection. A lithium ion secondary battery can be obtained by inserting and sealing the thus obtained cell into an outer package made of, for example, a laminate film having a three-layer structure of polyester film / aluminum film / modified polyolefin film. The obtained lithium ion secondary battery may be used as a single cell or a module in which a plurality of cells are connected depending on the application.
本発明による二次電池用電極がリチウムイオン二次電池用の負極として用いられる場合、本発明によるリチウムイオン二次電池の作製に用いられる正極は、従来公知の方法で作製することができる。例えば、正極活物質に、結着剤、導電剤等を加えて適当な溶媒又は分散媒で所定粘度としたスラリーを調製し、これを金属箔等の集電体に塗工し、厚さ数μｍ〜数百μｍのコーティングを形成させ、そのコーティングを５０〜２００℃程度で熱処理することにより溶媒又は分散媒を除去すればよい。正極活物質は、従来公知の材料であればよく、例えば、ＬｉＣｏＯ2等のコバルト複合酸化物、ＬｉＭｎ2Ｏ4等のマンガン複合酸化物、ＬｉＮｉＯ2等のニッケル複合酸化物、これら酸化物の混合物、ＬｉＮｉＯ2のニッケルの一部をコバルトやマンガンに置換したもの、ＬｉＦｅＶＯ4、ＬｉＦｅＰＯ4等の鉄複合酸化物、等を使用することができる。 When the secondary battery electrode according to the present invention is used as a negative electrode for a lithium ion secondary battery, the positive electrode used for preparing the lithium ion secondary battery according to the present invention can be manufactured by a conventionally known method. For example, a slurry having a predetermined viscosity is prepared with a suitable solvent or dispersion medium by adding a binder, a conductive agent, etc. to the positive electrode active material, and this is applied to a current collector such as a metal foil, What is necessary is just to remove a solvent or a dispersion medium by forming a coating of micrometer-several hundred micrometer, and heat-processing the coating at about 50-200 degreeC. The positive electrode active material may be a conventionally known material, for example, a cobalt composite oxide such as LiCoO 2 , a manganese composite oxide such as LiMn 2 O 4 , a nickel composite oxide such as LiNiO 2 , and a mixture of these oxides. , LiNiO 2 in which a part of nickel is replaced with cobalt or manganese, iron composite oxides such as LiFeVO 4 and LiFePO 4 , and the like can be used.
本発明によるリチウムイオン二次電池の作製に用いられる正極に用いられる導電剤は本発明による二次電池用導電剤が好ましく、本発明によるリチウムイオン二次電池の作製に用いられる正極と負極とに本発明による二次電池用導電剤が同時に用いられることにより、本発明によるリチウムイオン二次電池は、容量が更に高くなり、かつ、充放電サイクル特性がより優れたものとなる。 The conductive agent used for the positive electrode used in the production of the lithium ion secondary battery according to the present invention is preferably the conductive agent for the secondary battery according to the present invention. For the positive electrode and the negative electrode used for the production of the lithium ion secondary battery according to the present invention. By simultaneously using the conductive agent for a secondary battery according to the present invention, the lithium ion secondary battery according to the present invention has a higher capacity and more excellent charge / discharge cycle characteristics.
電解質としては、公知の電解液、常温溶融塩（イオン液体）、及び有機系若しくは無機系の固体電解質などを用いることができる。公知の電解液としては、例えば、エチレンカーボネートおよびプロピレンカーボネートなどの環状炭酸エステル、エチルメチルカーボネートおよびジエチルカーボネートなどの鎖状炭酸エステルなどが挙げられる。また、常温溶融塩（イオン液体）としては、例えば、イミダゾリウム系塩、ピロリジニウム系塩、ピリジニウム系塩、アンモニウム系塩、ホスホニウム系塩、スルホニウム系塩などが挙げられる。前記固体電解質としては、例えば、ポリエーテル系ポリマー、ポリエステル系ポリマー、ポリイミン系ポリマー、ポリビニルアセタール系ポリマー、ポリアクリロニトリル系ポリマー、ポリフッ化アルケン系ポリマー、ポリ塩化ビニル系ポリマー、ポリ（塩化ビニル−フッ化ビニリデン）系ポリマー、ポリ（スチレン−アクリロニトリル）系ポリマー、及びニトリルゴムなどの直鎖型ポリマーなどに代表される有機系ポリマーゲル；ジルコニアなどの無機セラミックス；ヨウ化銀、ヨウ化銀硫黄化合物、ヨウ化銀ルビジウム化合物などの無機系電解質；などが挙げられる。また、前記電解質にリチウム塩を溶解したものを二次電池用の電解質として用いることができる。また、電解質に難燃性を付与するために難燃性電解質溶解剤を加えることもできる。同様に、電解質の粘度を低下させるために可塑剤を加えることもできる。 As the electrolyte, a known electrolytic solution, a room temperature molten salt (ionic liquid), an organic or inorganic solid electrolyte, and the like can be used. Examples of the known electrolyte include cyclic carbonates such as ethylene carbonate and propylene carbonate, and chain carbonates such as ethyl methyl carbonate and diethyl carbonate. Examples of the room temperature molten salt (ionic liquid) include imidazolium salts, pyrrolidinium salts, pyridinium salts, ammonium salts, phosphonium salts, sulfonium salts, and the like. Examples of the solid electrolyte include polyether polymers, polyester polymers, polyimine polymers, polyvinyl acetal polymers, polyacrylonitrile polymers, polyfluorinated alkene polymers, polyvinyl chloride polymers, poly (vinyl chloride-fluoride). Vinylidene) -based polymers, poly (styrene-acrylonitrile) -based polymers, and organic polymer gels represented by linear polymers such as nitrile rubber; inorganic ceramics such as zirconia; silver iodide, silver iodide sulfur compounds, iodine And inorganic electrolytes such as silver rubidium compounds. Moreover, what melt | dissolved lithium salt in the said electrolyte can be used as an electrolyte for secondary batteries. A flame retardant electrolyte solubilizer can also be added to impart flame retardancy to the electrolyte. Similarly, a plasticizer can be added to reduce the viscosity of the electrolyte.
電解質に溶解させるリチウム塩としては、例えば、ＬｉＰＦ6、ＬｉＣｌＯ4、ＬｉＣＦ3ＳＯ3、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＮ（Ｃ2Ｆ5ＳＯ2）2およびＬｉＣ（ＣＦ3ＳＯ2）3などが挙げられる。上記リチウム塩は、単独で用いても、また２種以上を組み合わせて用いてもよい。上記リチウム塩は、電解質全体に対して、一般に０．１質量％〜８９．９質量％、好ましくは１．０質量％〜７９．０質量％の含有量で用いられる。電解質のリチウム塩以外の成分は、リチウム塩の含有量が上記範囲内にあることを条件に、適当な量で添加することができる。 Examples of the lithium salt dissolved in the electrolyte include LiPF 6 , LiClO 4 , LiCF 3 SO 3 , LiBF 4 , LiAsF 6 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 and LiC ( CF 3 SO 2 ) 3 and the like. The lithium salts may be used alone or in combination of two or more. The lithium salt is generally used in a content of 0.1% by mass to 89.9% by mass, preferably 1.0% by mass to 79.0% by mass, based on the entire electrolyte. Components other than the lithium salt of the electrolyte can be added in an appropriate amount on condition that the content of the lithium salt is within the above range.
上記電解質に用いられるポリマーとしては、電気化学的に安定であり、イオン伝導度が高いものであれば特に制限はなく、例えば、アクリレート系ポリマー、ポリフッ化ビニリデン等を使用することができる。また、重合性官能基を有するオニウムカチオンと重合性官能基を有する有機アニオンとから構成される塩モノマーを含むものから合成されたポリマーは、特にイオン伝導度が高く、充放電特性のさらなる向上に寄与し得る点で、より好ましい。電解質中のポリマー含有量は、好ましくは０．１質量％〜５０質量％、より好ましくは１質量％〜４０質量％の範囲内である。 The polymer used for the electrolyte is not particularly limited as long as it is electrochemically stable and has high ionic conductivity. For example, an acrylate polymer, polyvinylidene fluoride, or the like can be used. In addition, polymers synthesized from those containing a salt monomer composed of an onium cation having a polymerizable functional group and an organic anion having a polymerizable functional group have particularly high ionic conductivity, which further improves charge / discharge characteristics. It is more preferable at the point which can contribute. The polymer content in the electrolyte is preferably in the range of 0.1 mass% to 50 mass%, more preferably 1 mass% to 40 mass%.
上記難燃性電解質溶解剤としては、自己消火性を示し、かつ、電解質塩が共存した状態で電解質塩を溶解させることができる化合物であれば特に制限はなく、例えば、リン酸エステル、ハロゲン化合物、フォスファゼン等を使用することができる。 The flame retardant electrolyte solubilizer is not particularly limited as long as it is a compound that exhibits self-extinguishing properties and can dissolve the electrolyte salt in the presence of the electrolyte salt. For example, phosphate ester, halogen compound Phosphazene etc. can be used.
上記可塑剤の例としては、エチレンカーボネート、プロピレンカーボネート等の環状炭酸エステル、エチルメチルカーボネート、ジエチルカーボネート等の鎖状炭酸エステル、等が挙げられる。上記可塑剤は、単独で用いても、また２種以上を組み合わせて用いてもよい。 Examples of the plasticizer include cyclic carbonates such as ethylene carbonate and propylene carbonate, and chain carbonates such as ethyl methyl carbonate and diethyl carbonate. The above plasticizers may be used alone or in combination of two or more.
本発明によるリチウムイオン二次電池にセパレータを用いる場合、正極と負極の間の短絡を防止することができ、電気化学的に安定である従来公知の材料を使用すればよい。セパレータの例としては、ポリエチレン製セパレータ、ポリプロピレン製セパレータ、セルロース製セパレータ、不織布、無機系セパレータ、グラスフィルター等が挙げられる。電解質にポリマーを含める場合には、その電解質がセパレータの機能を兼ね備える場合もあり、その場合、独立したセパレータは不要である。 When a separator is used in the lithium ion secondary battery according to the present invention, a conventionally known material that can prevent a short circuit between the positive electrode and the negative electrode and is electrochemically stable may be used. Examples of the separator include a polyethylene separator, a polypropylene separator, a cellulose separator, a nonwoven fabric, an inorganic separator, a glass filter, and the like. When a polymer is included in the electrolyte, the electrolyte may also have a separator function, and in that case, an independent separator is unnecessary.
以下、本発明をより具体的に説明するための実施例を提供する。なお、本発明は、その目的及び主旨を逸脱しない範囲で以下の実施例に限定されるものではない。 Hereinafter, an example for explaining the present invention more concretely is provided. In addition, this invention is not limited to a following example in the range which does not deviate from the objective and the main point.
＜実施例１＞
１）中空球状炭素核前駆体粒子の作製
炭酸リチウム濃度が１ｗｔ％（質量％）、水溶性フェノール樹脂（住友ベークライト株式会社製 ＰＲ−５５７４３）濃度が０．２ｗｔ％（質量％）の水溶液を調製し、超音波霧化装置（超音波霧化ユニット：本多電子株式会社製 ＨＭ−２４１２を用いて自作）を用いて微小液滴を発生させ、窒素気流下、３００℃の炉に微小液滴を搬送し、微小液滴を乾燥させ、１５０℃、−１０ｋＶに調整した静電捕集器（高圧電源：松定プレシジョン株式会社製 ＨＡＲｂ−１５Ｎ２を用いて作製したもの）により、乾燥粉末樹脂を捕集した。得られた粉末樹脂を、アルミナ管に入れ、窒素雰囲気下、６００℃、１時間炭化処理を実施し、炭素粉末を得た。走査型電子顕微鏡（ＳＥＭ）（日本電子株式会社製 ＪＳＭ-７４０１Ｆ）により、得られた炭素粉末を観察した結果、概球形で、平均粒径は約１μｍであることを確認した。なお、平均粒径の測定方法は、作製した炭素粉末の母体をよく混合した後、約０．３ｇずつ５か所ランダムにサンプリングして再度混合し、両面テープを貼り付けた板にサンプルを０．５ｇ広げてＳＥＭ観察を行い、ＳＥＭ画像中に見える粒子３０個をランダムに観察し粒子径を求め、それらの平均値を平均粒径とした。また、得られた炭素粉末を銅箔にはさみロールプレスしたものを走査型電子顕微鏡（ＳＥＭ）により観察した結果、中空球状炭素核前駆体粒子であることを確認した。ＳＥＭ観察より求めた平均厚みは０．０１μｍであった。なお前記平均厚みは、前記よく混合した炭素粉末の母体から１ｇをサンプリングし、ステンレス板に挟んでロールプレスで圧力を加えて破砕した後、破砕サンプルを集めて再度混合し、両面テープを貼り付けた板にサンプルを０．５ｇ広げてＳＥＭ観察を行い、ＳＥＭ画像中に見える粒子３０個をランダムに観察し厚みを求め、それらの平均値を平均厚みと定義した。
<Example 1>
1) Preparation of hollow spherical carbon core precursor particles An aqueous solution having a lithium carbonate concentration of 1 wt% (mass%) and a water-soluble phenolic resin (PR-55743 manufactured by Sumitomo Bakelite Co., Ltd.) having a concentration of 0.2 wt% (mass%) was prepared. Then, micro droplets are generated using an ultrasonic atomizer (ultrasonic atomization unit: self-made using HM-2412 manufactured by Honda Electronics Co., Ltd.), and the micro droplet is placed in a furnace at 300 ° C. under a nitrogen stream. The dry powder resin was dried with an electrostatic collector (high-voltage power source: manufactured using Matsubari Precision Co., Ltd. HARb-15N2) adjusted to 150 ° C. and −10 kV. I collected it. The obtained powder resin was put into an alumina tube and carbonized at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain carbon powder. As a result of observing the obtained carbon powder with a scanning electron microscope (SEM) (JSM-7401F, manufactured by JEOL Ltd.), it was confirmed that it was approximately spherical and the average particle diameter was about 1 μm. The average particle size was measured by mixing the matrix of the produced carbon powder well, sampling at about 0.3 g at 5 locations at random, mixing again, and placing the sample on the plate with double-sided tape attached. SEM observation was performed with a spread of 5 g, 30 particles visible in the SEM image were randomly observed to determine the particle size, and the average value thereof was taken as the average particle size. Moreover, as a result of observing with a scanning electron microscope (SEM) what carried out the roll pressing of the obtained carbon powder between copper foil, it confirmed that it was a hollow spherical carbon nucleus precursor particle. The average thickness determined from SEM observation was 0.01 μm. The average thickness is sampled from 1 g of the well-mixed carbon powder matrix, crushed by applying pressure with a roll press between stainless steel plates, collected crushed samples, mixed again, and a double-sided tape attached. A sample was spread by 0.5 g on a flat plate and subjected to SEM observation, 30 particles visible in the SEM image were randomly observed to determine the thickness, and the average value was defined as the average thickness.
２）中空球状炭素核粒子を始点として少なくとも３方向に延在する繊維状炭素の作製
２ｗｔ％（質量％）の硝酸鉄水溶液５０ｇに、上記１）における中空球状炭素核前駆体１９ｇを混合し、オーブン中で加熱乾燥した炭素粉末をアルミナ管に入れ、窒素雰囲気下、１２００℃、４時間加熱した。走査型電子顕微鏡（ＳＥＭ）により、得られた炭素粉末を観察した結果、中空球状炭素核粒子を始点として３方向以上の多数が前記炭素核粒子からほぼ全周囲方向に延在する繊維状炭素の存在を確認した。繊維状炭素の繊維径は、ＳＥＭ観察結果から、中空球状炭素核の平均粒径の１／１０〜１／１００の範囲であることを確認した。
2) Preparation of fibrous carbon extending in at least three directions starting from hollow spherical carbon core particles 50 g of iron nitrate aqueous solution of 2 wt% (mass%) is mixed with 19 g of hollow spherical carbon core precursor in 1) above, The carbon powder heated and dried in an oven was placed in an alumina tube and heated at 1200 ° C. for 4 hours in a nitrogen atmosphere. As a result of observing the obtained carbon powder with a scanning electron microscope (SEM), a large number of three or more directions starting from the hollow spherical carbon core particles, the fibrous carbon extending from the carbon core particles almost in the entire circumferential direction. Confirmed existence. From the SEM observation results, it was confirmed that the fiber diameter of the fibrous carbon was in the range of 1/10 to 1/100 of the average particle diameter of the hollow spherical carbon nuclei.
３）リチウムイオン二次電池用電極合剤の作製
２）で得た繊維状炭素が延在して含んでなる中空球状炭素核粒子、市販のナノ活物質である酸化鉄粉末（Ｆｅ2Ｏ3、平均一次粒子径：＜１００ｎｍ、キシダ化学株式会社 製品コード ＮＧＫ０００００６）、市販の結着剤であるカルボキシメチルセルロース（ＣＭＣ）（ダイセルファインケム株式会社製、ＣＭＣダイセル２２００）を質量比９：９０：１で、水中で混合し、必要に応じ濃縮し粘度を調整し、リチウムイオン二次電池用電極合剤を得た。
3) Preparation of electrode mixture for lithium ion secondary battery 2) Hollow spherical carbon core particles obtained by extending the fibrous carbon obtained in 2), iron oxide powder (Fe 2 O 3) as a commercially available nano-active material , Average primary particle size: <100 nm, Kishida Chemical Co., Ltd. product code NGK000006), commercially available binder carboxymethylcellulose (CMC) (manufactured by Daicel Finechem Co., Ltd., CMC Daicel 2200) at a mass ratio of 9: 90: 1 The mixture was mixed in water, concentrated as necessary to adjust the viscosity, and an electrode mixture for a lithium ion secondary battery was obtained.
４）リチウムイオン二次電池用電極（負極）の作製
上記のリチウムイオン二次電池用電極合剤を２０μｍ厚の銅箔に塗布し、その後、１１０℃で１時間真空乾燥した。真空乾燥後、ロールプレスによって加圧成形し、φ１３ｍｍの径で打ち抜き、リチウムイオン二次電池用電極を得た。
4) Preparation of Lithium Ion Secondary Battery Electrode (Negative Electrode) The above lithium ion secondary battery electrode mixture was applied to a 20 μm thick copper foil, and then vacuum dried at 110 ° C. for 1 hour. After vacuum drying, it was pressure-formed by a roll press and punched out with a diameter of 13 mm to obtain an electrode for a lithium ion secondary battery.
５）リチウムイオン二次電池の作製
上記で作製したリチウムイオン二次電池用電極（負極）、セパレータ（ポリプロピレン製多孔質フィルム：直径φ１６、厚さ２５μｍ）、作用極としてリチウム金属（直径φ１２、厚さ１ｍｍ）の順で、宝泉製２０３２型コインセル内の所定の位置に配置した。さらに、電解液としてエチレンカーボネートとジエチレンカーボネートの混合液（体積比が１：１）に、過塩素酸リチウムを１［モル／リットル］の濃度で溶解させたものを注液し、リチウムイオン二次電池を作製した。
5) Production of lithium ion secondary battery Lithium ion secondary battery electrode (negative electrode) produced above, separator (polypropylene porous film: diameter φ16, thickness 25 μm), lithium metal (diameter φ12, thickness as working electrode) 1 mm) in the order of 20 mm type coin cell made by Hosen. Further, an electrolytic solution in which lithium perchlorate is dissolved at a concentration of 1 [mol / liter] in a mixed solution of ethylene carbonate and diethylene carbonate (volume ratio is 1: 1) is injected into a lithium ion secondary solution. A battery was produced.
６）初期充放電特性評価
充電容量については、充電時の電流密度を２５ｍＡ／ｇとして定電流充電を行い、電位が０Ｖに達した時点から、０Ｖで定電圧充電を行い、電流密度が１．２５ｍＡ／ｇになるまでに充電した電気量を充電容量とした。一方、放電容量については、放電時の電流密度も２５ｍＡ／ｇとして定電流放電を行い、電位が２．５Ｖに達した時点から、２．５Ｖで定電圧放電を行い、電流密度が１．２５ｍＡ／ｇになるまでに放電した電気量を放電容量とした。なお、充放電特性の評価は、充放電特性評価装置（北斗電工（株）製：ＨＪＲ−１０１０ｍＳＭ８）を用いて行った。
6) Evaluation of initial charge / discharge characteristics Regarding the charge capacity, constant current charge was performed at a current density of 25 mA / g during charge, and constant voltage charge was performed at 0 V from the time when the potential reached 0 V. The amount of electricity charged up to 25 mA / g was taken as the charge capacity. On the other hand, with respect to the discharge capacity, constant current discharge was performed with a current density at the time of discharge of 25 mA / g, and constant voltage discharge was performed at 2.5 V from the time when the potential reached 2.5 V, and the current density was 1.25 mA. The amount of electricity discharged up to / g was taken as the discharge capacity. In addition, evaluation of the charging / discharging characteristic was performed using the charging / discharging characteristic evaluation apparatus (Hokuto Denko Co., Ltd. product: HJR-1010mSM8).
また、以下の式により初回の充放電効率を定義した。
初回充放電効率（％）＝初回放電容量（ｍＡｈ／ｇ）／初回充電容量（ｍＡｈ／ｇ）×１００
The initial charge / discharge efficiency was defined by the following equation.
Initial charge / discharge efficiency (%) = initial discharge capacity (mAh / g) / initial charge capacity (mAh / g) × 100
以上の評価方法を用いて、５）で作製したリチウムイオン二次電池を評価した結果、初期放電容量は８９１ｍＡｈ／ｇ、初回充放電効率（％）は８０％であった。 As a result of evaluating the lithium ion secondary battery produced in 5) using the above evaluation method, the initial discharge capacity was 891 mAh / g, and the initial charge / discharge efficiency (%) was 80%.
７）サイクル性評価
初期充放電特性評価条件を５０回繰り返し測定した後に得られた放電容量を５０サイクル目の放電容量とした。また、以下の式によりサイクル性（５０サイクル容量維持率）を定義した。
7) Evaluation of cycle performance The discharge capacity obtained after repeatedly measuring the initial charge / discharge characteristics evaluation conditions 50 times was taken as the discharge capacity of the 50th cycle. Moreover, the cycle property (50 cycle capacity maintenance rate) was defined by the following formula.
サイクル性（％、５０サイクル容量維持率）＝５０サイクル目の放電容量（ｍＡｈ／ｇ）／初回放電容量（ｍＡｈ／ｇ）×１００ Cycle performance (%, 50 cycle capacity retention rate) = 50th cycle discharge capacity (mAh / g) / initial discharge capacity (mAh / g) × 100
以上の評価方法を用いて、５）で作製したリチウムイオン二次電池を評価した結果、サイクル性（％、５０サイクル容量維持率）が９０％以上であることを確認した。 As a result of evaluating the lithium ion secondary battery produced in 5) using the above evaluation method, it was confirmed that the cycle performance (%, 50 cycle capacity retention rate) was 90% or more.
＜実施例２＞
１）板状炭素核前駆体粒子の作製
発泡フェノール樹脂粉末（住友ベークライト株式会社製）を、オーブン中で、１５５℃で発泡させ約３０分加熱することにより、内部に空孔を有する発泡フェノール樹脂硬化物を得た。これを粉砕し、アルミナ管に入れ、窒素雰囲気下、６００℃、１時間炭化処理を実施し、分級して大きな粒子を取り除き、炭素粉末を得た。走査型電子顕微鏡（ＳＥＭ）により、得られた炭素粉末を観察した結果、厚み数１０〜数１００ｎｍ、一辺の大きさが数μｍ〜数１０μｍの板状炭素核粒子が含有されていることを確認した。ＳＥＭ観察より求めた平均粒子径は５８μｍで平均厚みは０．０７７μｍであった。
<Example 2>
1) Preparation of plate-like carbon nucleus precursor particles Foamed phenol resin powder (manufactured by Sumitomo Bakelite Co., Ltd.) is foamed at 155 ° C. in an oven and heated for about 30 minutes, whereby a foamed phenol resin having pores therein. A cured product was obtained. This was pulverized, put into an alumina tube, subjected to carbonization treatment at 600 ° C. for 1 hour in a nitrogen atmosphere, classified to remove large particles, and carbon powder was obtained. As a result of observing the obtained carbon powder with a scanning electron microscope (SEM), it was confirmed that plate-like carbon core particles having a thickness of several tens to several hundreds of nanometers and a side of several μm to several tens of μm were contained. did. The average particle diameter determined by SEM observation was 58 μm and the average thickness was 0.077 μm.
２）板状炭素核粒子を始点として少なくとも３方向に延在する繊維状炭素の作製
２ｗｔ％（質量％）の硝酸鉄水溶液５０ｇに、１）で得た板状炭素核前駆体粒子１９ｇを混合し、オーブン中で加熱乾燥した炭素粉末をアルミナ管に入れ、窒素雰囲気下、１２００℃、４時間加熱した。走査型電子顕微鏡（ＳＥＭ）により、得られた炭素粉末を観察した結果、板状炭素粒子核を始点として３方向以上の多数の繊維状炭素が前記炭素核粒子から延在する繊維状炭素の存在を確認した。
2) Preparation of fibrous carbon extending in at least three directions starting from plate-like carbon core particles 50 g of iron nitrate aqueous solution of 2 wt% (mass%) is mixed with 19 g of plate-like carbon nucleus precursor particles obtained in 1). The carbon powder heated and dried in an oven was placed in an alumina tube and heated at 1200 ° C. for 4 hours in a nitrogen atmosphere. As a result of observing the obtained carbon powder with a scanning electron microscope (SEM), the presence of fibrous carbon in which a large number of fibrous carbons extending in three directions or more starting from the plate-like carbon particle nuclei extend from the carbon nuclei particles. It was confirmed.
３）リチウムイオン二次電池用電極合剤の作製
２）で得た繊維状炭素が延在して含んでなる板状炭素核粒子、市販のナノ活物質であるケイ素粉末（Ｓｉ、平均一次粒子径：５０ｎｍ、Ｎａｎｏｓｔｒｕｃｔｕｒｅｄ & ａｍｏｒｐｈｏｕｓ ｍａｔｅｒｉａｌｓ製）、市販の結着剤であるカルボキシメチルセルロース（ＣＭＣ）（ダイセルファインケム株式会社製 ＣＭＣダイセル２２００）を重量比１８：８０：２で混合し、必要に応じ濃縮し粘度を調整し、リチウムイオン二次電池用電極合剤を得た。
3) Preparation of electrode mixture for lithium ion secondary battery 2) Plate-like carbon core particles obtained by extending the fibrous carbon obtained in 2), silicon powder (Si, average primary particles) as a commercially available nano-active material Diameter: 50 nm, manufactured by Nanostructured & amorphous materials), carboxymethyl cellulose (CMC) (CMC Daicel 2200 manufactured by Daicel Finechem Co., Ltd.), a commercially available binder, is mixed at a weight ratio of 18: 80: 2, and concentrated as necessary. The viscosity was adjusted to obtain an electrode mixture for a lithium ion secondary battery.
４）リチウムイオン二次電池用電極（負極）の作製
上記リチウムイオン二次電池用電極合剤を２０μｍ厚の銅箔に塗布し、その後、１１０℃で１時間真空乾燥した。真空乾燥後、ロールプレスによって加圧成形し、φ１３ｍｍの径で打ち抜き、リチウムイオン二次電池用電極（負極）を得た。
4) Preparation of Lithium Ion Secondary Battery Electrode (Negative Electrode) The lithium ion secondary battery electrode mixture was applied to a 20 μm thick copper foil, and then vacuum dried at 110 ° C. for 1 hour. After vacuum drying, it was pressure-formed by a roll press and punched out with a diameter of 13 mm to obtain an electrode (negative electrode) for a lithium ion secondary battery.
５）リチウムイオン二次電池の作製
上記で作製したリチウムイオン二次電池用電極（負極）、セパレータ（ポリプロピレン製多孔質フィルム：直径φ１６、厚さ２５μｍ）、作用極としてリチウム金属（直径φ１２、厚さ１ｍｍ）の順で、宝泉製２０３２型コインセル内の所定の位置に配置した。さらに、電解液としてエチレンカーボネートとジエチレンカーボネートの混合液（体積比が１：１）に、過塩素酸リチウムを１［モル／リットル］の濃度で溶解させたものを注液し、リチウムイオン二次電池を作製した。
5) Production of lithium ion secondary battery Lithium ion secondary battery electrode (negative electrode) produced above, separator (polypropylene porous film: diameter φ16, thickness 25 μm), lithium metal (diameter φ12, thickness as working electrode) 1 mm) in the order of 20 mm type coin cell made by Hosen. Further, an electrolytic solution in which lithium perchlorate is dissolved at a concentration of 1 [mol / liter] in a mixed solution of ethylene carbonate and diethylene carbonate (volume ratio is 1: 1) is injected into a lithium ion secondary solution. A battery was produced.
６）初期充放電特性評価
充電容量については、充電時の電流密度を２５ｍＡ／ｇとして定電流充電を行い、電位が０Ｖに達した時点から、０Ｖで定電圧充電を行い、電流密度が１．２５ｍＡ／ｇになるまでに充電した電気量を充電容量とした。一方、放電容量については、放電時の電流密度も２５ｍＡ／ｇとして定電流放電を行い、電位が２．５Ｖに達した時点から、２．５Ｖで定電圧放電を行い、電流密度が１．２５ｍＡ／ｇになるまでに放電した電気量を放電容量とした。なお、充放電特性の評価は、充放電特性評価装置を用いて行った。
6) Evaluation of initial charge / discharge characteristics Regarding the charge capacity, constant current charge was performed at a current density of 25 mA / g during charge, and constant voltage charge was performed at 0 V from the time when the potential reached 0 V. The amount of electricity charged up to 25 mA / g was taken as the charge capacity. On the other hand, with respect to the discharge capacity, constant current discharge was performed with a current density at the time of discharge of 25 mA / g, and constant voltage discharge was performed at 2.5 V from the time when the potential reached 2.5 V, and the current density was 1.25 mA. The amount of electricity discharged up to / g was taken as the discharge capacity. In addition, evaluation of the charge / discharge characteristic was performed using the charge / discharge characteristic evaluation apparatus.
また、以下の式により初回の充放電効率を定義した。
初回充放電効率（％）＝初回放電容量（ｍＡｈ／ｇ）／初回充電容量（ｍＡｈ／ｇ）×１００
The initial charge / discharge efficiency was defined by the following equation.
Initial charge / discharge efficiency (%) = initial discharge capacity (mAh / g) / initial charge capacity (mAh / g) × 100
以上の評価方法を用いて、５）で作製したリチウムイオン２次電池を評価した結果、初期放電容量は１９９２ｍＡｈ／ｇ、初回充放電効率（％）は８２％であった。 As a result of evaluating the lithium ion secondary battery produced in 5) using the above evaluation method, the initial discharge capacity was 1992 mAh / g, and the initial charge / discharge efficiency (%) was 82%.
７）サイクル性評価
初期充放電特性評価条件を５０回繰り返し測定した後に得られた放電容量を５０サイクル目の放電容量とした。また、以下の式によりサイクル性（５０サイクル容量維持率）を定義した。
7) Evaluation of cycle performance The discharge capacity obtained after the initial charge / discharge characteristics evaluation conditions were measured 50 times repeatedly was defined as the discharge capacity of the 50th cycle. Moreover, the cycle property (50 cycle capacity maintenance rate) was defined by the following formula.
サイクル性（％、５０サイクル容量維持率）＝５０サイクル目の放電容量（ｍＡｈ／ｇ）／初回放電容量（ｍＡｈ／ｇ）×１００ Cycle performance (%, 50 cycle capacity retention rate) = 50th cycle discharge capacity (mAh / g) / initial discharge capacity (mAh / g) × 100
以上の評価方法を用いて、５）で作製したリチウムイオン二次電池を評価した結果、サイクル性（％、５０サイクル容量維持率）が８５％以上であることを確認した。 As a result of evaluating the lithium ion secondary battery produced in 5) using the above evaluation method, it was confirmed that the cycle performance (%, 50 cycle capacity retention rate) was 85% or more.
＜実施例３＞
１）板状炭素核前駆体粒子の作製
実施例２と全く同じ方法を用いて板状炭素核粒子を得た。
<Example 3>
1) Preparation of plate-like carbon nucleus precursor particles Plate-like carbon nucleus particles were obtained using the same method as in Example 2.
２）板状炭素核粒子を始点として少なくとも３方向に延在する繊維状炭素の作製
水とメタノールの混合溶媒（水：メタノール１：１）５００ｍｌに。１）で得た板状炭素核前駆体粒子１２ｇ、市販の導電性炭素繊維（繊維径約１５０ｎｍ）（昭和電工株式会社製 ＶＧＣＦ）を６ｇ混合し、約１時間撹拌し後、エバポレーターを用いて、溶媒を除去し、アルミナ管に入れ、１２００℃、４時間加熱した。走査型電子顕微鏡（ＳＥＭ）により、得られた炭素粉末を観察した結果、板状炭素核粒子を始点として３方向以上の多数の繊維状炭素が前記炭素核粒子から延在する繊維状炭素の存在を確認した。
2) Preparation of fibrous carbon extending in at least three directions starting from plate-like carbon core particles into 500 ml of a mixed solvent of water and methanol (water: methanol 1: 1). 6 g of the plate-like carbon nucleus precursor particles obtained in 1) and 6 g of commercially available conductive carbon fiber (fiber diameter of about 150 nm) (VGCF manufactured by Showa Denko KK) are mixed and stirred for about 1 hour, and then using an evaporator. The solvent was removed, placed in an alumina tube, and heated at 1200 ° C. for 4 hours. As a result of observing the obtained carbon powder with a scanning electron microscope (SEM), the presence of fibrous carbon in which a large number of fibrous carbons in three or more directions start from the plate-like carbon core particles and extend from the carbon core particles. It was confirmed.
３）リチウムイオン二次電池用電極合剤の作製
水とエタノールの混合溶液中に、２）で得た繊維状炭素が延在して含んでなる板状炭素核粒子、市販の酸化ケイ素粉末を粉砕したもの（ＳｉＯｘ、ｘ＝１〜１．２、平均一次粒子径：約０．５μｍ）、市販の結着剤であるカルボキシメチルセルロース（ＣＭＣ）（ダイセルファインケム株式会社製 ＣＭＣダイセル２２００）を重量比１８：８０：２で混合し、必要に応じ濃縮し粘度を調整し、２次電池用電極合剤を得た。粉砕後の酸化ケイ素粉末の粒径は、レーザ回折／散乱式粒度分布測定装置（（株）堀場製作所製ＬＡ−９２０）を用いて測定した。平均粒子径は体積換算とし、頻度が累積で５０％になったところを平均粒子径と定義した。
3) Preparation of electrode mixture for lithium ion secondary battery Plate-like carbon core particles obtained by extending the fibrous carbon obtained in 2) into a mixed solution of water and ethanol, commercially available silicon oxide powder Weight ratio of pulverized product (SiOx, x = 1 to 1.2, average primary particle size: about 0.5 μm), carboxymethyl cellulose (CMC) (CMC Daicel 2200, manufactured by Daicel Finechem Co., Ltd.) It mixed by 18: 80: 2, was concentrated as needed, the viscosity was adjusted, and the electrode mixture for secondary batteries was obtained. The particle size of the pulverized silicon oxide powder was measured using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.). The average particle diameter was converted to volume, and the place where the frequency reached 50% cumulatively was defined as the average particle diameter.
４）リチウムイオン二次電池用電極（負極）の作製
実施例２と全く同じ方法を用いてリチウムイオン二次電池用電極を作製して得た。
4) Preparation of Lithium Ion Secondary Battery Electrode (Negative Electrode) A lithium ion secondary battery electrode was produced in the same manner as in Example 2.
５）リチウムイオン二次電池の作製
実施例２と全く同じ方法を用いてリチウムイオン二次電池を作製して得た。
5) Production of Lithium Ion Secondary Battery A lithium ion secondary battery was produced using exactly the same method as in Example 2.
６）初期充放電特性評価
実施例２と全く同じ方法を用いて、５）で作製したリチウムイオン二次電池を評価した結果、初期放電容量は１３７１ｍＡｈ／ｇ、初回充放電効率（％）は８３％であった。
6) Evaluation of initial charge / discharge characteristics Using the same method as in Example 2, the lithium ion secondary battery produced in 5) was evaluated. As a result, the initial discharge capacity was 1371 mAh / g, and the initial charge / discharge efficiency (%) was 83. %Met.
７）サイクル性評価
実施例２と全く同じ方法を用いて、５）で作製したリチウムイオン二次電池を評価した結果、サイクル性（％、５０サイクル容量維持率）が９０％以上であることを確認した。
7) Evaluation of cycle performance Using the same method as in Example 2, the lithium ion secondary battery produced in 5) was evaluated. As a result, the cycle performance (%, 50 cycle capacity retention rate) was 90% or more. confirmed.
＜比較例１＞
実施例１の３）で作製した繊維状炭素が延在して含んでなる中空炭素核粒子の代わりに、市販のアセチレンブラック（電気化学工業株式会社製）を用いる以外は、実施例１と全く同じ方法を用いてリチウムイオン二次電池を作製して、実施例１と全く同じ評価方法を用いてリチウムイオン二次電池を評価した結果、初期放電容量は７８９ｍＡｈ／ｇ、初回充放電効率（％）は７１％、サイクル性（％、５０サイクル容量維持率）は１８％であった。
<Comparative Example 1>
Example 1 is exactly the same as Example 1 except that commercially available acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) is used in place of the hollow carbon core particles formed by extending the fibrous carbon prepared in 3) of Example 1. A lithium ion secondary battery was produced using the same method, and the lithium ion secondary battery was evaluated using the same evaluation method as in Example 1. As a result, the initial discharge capacity was 789 mAh / g, and the initial charge / discharge efficiency (% ) Was 71%, and the cycle performance (%, 50 cycle capacity retention rate) was 18%.
＜比較例２＞
実施例２の３）で作製した繊維状炭素が延在して含んでなる板状炭素核粒子の代わりに、市販のアセチレンブラック（電気化学工業株式会社製）を用いる以外は、実施例２と全く同じ方法を用いてリチウムイオン二次電池を作製して、実施例２と全く同じ評価方法を用いてリチウムイオン二次電池を評価した結果、初期放電容量は１８２５ｍＡｈ／ｇ、初回充放電効率（％）は７３％、サイクル性（％、５０サイクル容量維持率）は１３％であった。
<Comparative example 2>
Example 2 and Example 2 were used except that commercially available acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) was used instead of the plate-like carbon core particles formed by extending the fibrous carbon prepared in 3) of Example 2. A lithium ion secondary battery was produced using the same method and the lithium ion secondary battery was evaluated using the same evaluation method as in Example 2. As a result, the initial discharge capacity was 1825 mAh / g, and the initial charge / discharge efficiency ( %) Was 73%, and the cycle performance (%, 50 cycle capacity retention rate) was 13%.
＜比較例３＞
実施例３の３）で作製した繊維状炭素を含む板状炭素核粒子の代わりに、市販の導電性炭素繊維（繊維径約１５０ｎｍ）（昭和電工株式会社製 ＶＧＣＦ）を用いる以外は、実施例３と全く同じ方法を用いてリチウムイオン二次電池を作製して、実施例３と全く同じ評価方法を用いてリチウムイオン二次電池を評価した結果、初期放電容量は１３１５ｍＡｈ／ｇ、初回充放電効率（％）は８２％、サイクル性（％、５０サイクル容量維持率）は１７％であった。
<Comparative Example 3>
Example of Example 3 except that commercially available conductive carbon fiber (fiber diameter: about 150 nm) (VGCF manufactured by Showa Denko KK) was used instead of the plate-like carbon core particles containing fibrous carbon prepared in 3) of Example 3. As a result of producing a lithium ion secondary battery using the same method as in Example 3 and evaluating the lithium ion secondary battery using the same evaluation method as in Example 3, the initial discharge capacity was 1315 mAh / g, and the initial charge / discharge The efficiency (%) was 82%, and the cycle performance (%, 50 cycle capacity retention rate) was 17%.
Claims (8)
活物質と
を少なくとも含むことを特徴とする、二次電池用組成物。 A conductive agent including at least a carbon material including a carbon nucleus and fibrous carbon extending in at least three directions starting from the carbon nucleus ;
With active material
The composition for secondary batteries characterized by including at least .
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