JP2020136171A - Positive electrode material, positive electrode, lithium-ion secondary battery, manufacturing method of positive electrode material - Google Patents
Positive electrode material, positive electrode, lithium-ion secondary battery, manufacturing method of positive electrode material Download PDFInfo
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Abstract
Description
本発明は、正極材料、正極、リチウムイオン二次電池、正極材料の製造方法に関する。 The present invention relates to a positive electrode material, a positive electrode, a lithium ion secondary battery, and a method for manufacturing a positive electrode material.
リチウムイオン二次電池が知られている（例えば、特許文献１）。リチウムイオン二次電池には、電気容量が高いこと、高電流下での充電性能及び放電性能が高いことが求められる。リチウムイオン二次電池の電気容量を高くするために、下記の（１）及び（２）が提案されている。
（１）正極活物質の粒子の比表面積を大きくすること。
（２）正極活物質の粒子の粒子径を小さくすること。
Lithium ion secondary batteries are known (for example, Patent Document 1). Lithium-ion secondary batteries are required to have high electric capacity and high charge performance and discharge performance under high current. The following (1) and (2) have been proposed in order to increase the electric capacity of the lithium ion secondary battery.
(1) To increase the specific surface area of the particles of the positive electrode active material.
(2) To reduce the particle size of the particles of the positive electrode active material.
しかし、前記（１）又は前記（２）の提案においては、正極に正極活物質を固着するためのバインダー樹脂の使用量が増加するという問題があった。バインダー樹脂の使用量が増加すると、正極の電気抵抗が増加するため、電気容量を高くすることが困難である。 However, in the above (1) or (2) proposal, there is a problem that the amount of the binder resin used for fixing the positive electrode active material to the positive electrode increases. When the amount of the binder resin used increases, the electric resistance of the positive electrode increases, so that it is difficult to increase the electric capacity.
そこで、正極活物質の表面に繊維状の炭素材料を複合化した正極材料が提案されている（例えば、特許文献２〜４）。
特許文献２には、リチウム電池正極用複合材料が記載されている。特許文献２に記載のリチウム電池正極用複合材料は、正極活物質粒子が繊維状炭素により保持されている形態を有する複合粒子から構成される。
特許文献３には、ニッケル酸リチウム−炭素複合体正極活物質粒子粉末の製造方法が記載されている。
特許文献４には、リチウム含有リン酸塩粒子が炭素膜で被覆されている複合粒子が記載されている。
Therefore, a positive electrode material in which a fibrous carbon material is composited on the surface of the positive electrode active material has been proposed (for example, Patent Documents 2 to 4).
Patent Document 2 describes a composite material for a positive electrode of a lithium battery. The composite material for a positive electrode of a lithium battery described in Patent Document 2 is composed of composite particles having a form in which positive electrode active material particles are held by fibrous carbon.
Patent Document 3 describes a method for producing a positive electrode active material particle powder of a lithium nickelate-carbon composite positive electrode.
Patent Document 4 describes composite particles in which lithium-containing phosphate particles are coated with a carbon film.
しかしながら、特許文献２に記載の実施例１〜４の複合粒子は、繊維状炭素が正極活物質粒子を網目状に包み込んだ形態を有する。そのため、正極とした際に複数の複合粒子間にバインダー樹脂が介在すると複合粒子間の導電性が低下するおそれがある。
特許文献３に記載のニッケル酸リチウム−炭素複合体正極活物質粒子粉末の製造方法では、メカノケミカル処理によってニッケル酸リチウム表面に炭素を被覆させる。そのため、炭素が凝集した状態でニッケル酸リチウムに複合化される傾向があり、正極とした際の導電性が充分ではない。
特許文献４に記載の複合粒子においては、リチウム含有リン酸塩粒子の表面が炭素膜で被覆されている。そのため、正極とした際に複数の複合粒子間にバインダー樹脂が介在すると、複合粒子間の導電性が低下するおそれがある。
However, the composite particles of Examples 1 to 4 described in Patent Document 2 have a form in which fibrous carbon wraps the positive electrode active material particles in a network shape. Therefore, if the binder resin intervenes between the plurality of composite particles when the positive electrode is used, the conductivity between the composite particles may decrease.
In the method for producing lithium nickelate-carbon composite positive electrode active material particle powder described in Patent Document 3, the surface of lithium nickelate is coated with carbon by mechanochemical treatment. Therefore, the carbon tends to be composited with lithium nickelate in an agglomerated state, and the conductivity when used as a positive electrode is not sufficient.
In the composite particles described in Patent Document 4, the surface of the lithium-containing phosphate particles is coated with a carbon film. Therefore, if the binder resin intervenes between the plurality of composite particles when the positive electrode is used, the conductivity between the composite particles may decrease.
本発明は、正極とした際の導電性に優れる正極材料を提供する。 The present invention provides a positive electrode material having excellent conductivity when used as a positive electrode.
本発明は下記の態様を有する。
［１］ 正極活物質と、前記正極活物質に保持された繊維状の複数の炭素材料とを有する複合粒子を含む、正極材料であって、前記炭素材料の平均繊維長が５０μｍ超であり、前記複数の炭素材料のうち、一部の前記炭素材料の端部の少なくとも一方が、前記正極活物質に固定されていない、正極材料。
［２］ 前記炭素材料がカーボンナノチューブである、［１］の正極材料。
［３］ 下式（１）で算出されるαが０．３以上である、［１］又は［２］の正極材料。
α＝Ｓ／Ｄ ・・・式（１）
式（１）中、Ｓは前記正極活物質の比表面積であり、Ｄは前記正極活物質の平均粒子径である。
［４］ ［１］〜［３］のいずれかの正極材料を含む、正極。
［５］ ［４］の正極と、負極と、電解質とを有する、リチウムイオン二次電池。
［６］ 繊維状の炭素材料と液状媒体とを含む分散液を調製し、前記分散液と正極活物質とを混合した後に、前記液状媒体を除去する、正極材料の製造方法であり、前記炭素材料の平均繊維長が５０μｍ超であり、下式（１）で算出されるαが０．３以上である、正極材料の製造方法。
α＝Ｓ／Ｄ ・・・式（１）
式（１）中、Ｓは前記正極活物質の比表面積であり、Ｄは前記正極活物質の平均粒子径である。
The present invention has the following aspects.
[1] A positive electrode material containing composite particles having a positive electrode active material and a plurality of fibrous carbon materials held in the positive electrode active material, wherein the average fiber length of the carbon material is more than 50 μm. A positive electrode material in which at least one of the ends of a part of the carbon materials is not fixed to the positive electrode active material.
[2] The positive electrode material of [1], wherein the carbon material is a carbon nanotube.
[3] The positive electrode material of [1] or [2], wherein α calculated by the following formula (1) is 0.3 or more.
α = S / D ・ ・ ・ Equation (1)
In the formula (1), S is the specific surface area of the positive electrode active material, and D is the average particle size of the positive electrode active material.
[4] A positive electrode comprising any of the positive electrode materials of [1] to [3].
[5] A lithium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte of [4].
[6] A method for producing a positive electrode material, wherein a dispersion liquid containing a fibrous carbon material and a liquid medium is prepared, the dispersion liquid and the positive electrode active material are mixed, and then the liquid medium is removed. A method for producing a positive electrode material, wherein the average fiber length of the material is more than 50 μm, and α calculated by the following formula (1) is 0.3 or more.
α = S / D ・ ・ ・ Equation (1)
In the formula (1), S is the specific surface area of the positive electrode active material, and D is the average particle size of the positive electrode active material.
本発明によれば、正極とした際の導電性に優れる正極材料が得られる。 According to the present invention, a positive electrode material having excellent conductivity when used as a positive electrode can be obtained.
本明細書において数値範囲を示す「〜」は、その前後に記載された数値を下限値及び上限値として含むことを意味する。 In the present specification, "~" indicating a numerical range means that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.
＜正極材料＞
本発明の正極材料は、正極活物質と繊維状の複数の炭素材料とを有する複合粒子を含む。繊維状の複数の炭素材料は、正極活物質に保持されている。
複合粒子は、正極活物質と複数の炭素材料との複合体であるともいえる。複合粒子は、正極活物質からなる粒子と繊維状の複数の炭素材料とを有するともいえる。複合粒子は、繊維状の炭素材料以外の炭素材料をさらに有してもよい。
<Positive material>
The positive electrode material of the present invention contains composite particles having a positive electrode active material and a plurality of fibrous carbon materials. A plurality of fibrous carbon materials are held in the positive electrode active material.
It can be said that the composite particle is a composite of the positive electrode active material and a plurality of carbon materials. It can be said that the composite particles have particles made of a positive electrode active material and a plurality of fibrous carbon materials. The composite particles may further have a carbon material other than the fibrous carbon material.
正極活物質としては、マンガン酸リチウム（ＬｉＭｎ２Ｏ４）、コバルト酸リチウム（ＬｉＣｏＯ２）、ニッケル酸リチウム（ＬｉＮｉＯ２）、リン酸鉄リチウム（ＬｉＦｅＰＯ４等が挙げられる。これらの中でもマンガン酸リチウムが好ましい。 Examples of the positive electrode active material include lithium manganate (LiMn 2 O 4 ), lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), lithium iron phosphate (LiFePO 4 ), and the like. Is preferable.
正極活物質がマンガン酸リチウムを含む場合、マンガン酸リチウムの粒子の表面にはカルボキシル基が吸着していることが好ましい。マンガン酸リチウムの表面のカルボキシル基の吸着は、フーリエ変換赤外分光光度計（ＦＴ−ＩＲ）で測定して得られるピークによって検出できる。
この場合正極活物質の炭素濃度は、０．０４〜０．３質量％が好ましく、０．１０〜０．２質量％がより好ましい。ここで、炭素濃度が前記下限値以上であると、正極活物質の粒子の表面におけるカルボキシル基の量が充分であり、正極材表面での電子伝達の速度が高くなり、リチウムイオン二次電池とした際に、高電流下での充電性能及び放電性能がさらに高くなる。炭素濃度が前記上限値以下であると、リチウムイオン二次電池とした際の電気容量がさらに高くなる傾向がある。
正極活物質の炭素濃度は、炭素・硫黄分析装置（例えば、株式会社堀場製作所製「ＥＭＩＡ−９２０Ｖ」」）によって測定できる。
When the positive electrode active material contains lithium manganate, it is preferable that a carboxyl group is adsorbed on the surface of the lithium manganate particles. The adsorption of carboxyl groups on the surface of lithium manganate can be detected by the peak obtained by measuring with a Fourier transform infrared spectrophotometer (FT-IR).
In this case, the carbon concentration of the positive electrode active material is preferably 0.04 to 0.3% by mass, more preferably 0.10 to 0.2% by mass. Here, when the carbon concentration is at least the above lower limit value, the amount of carboxyl groups on the surface of the particles of the positive electrode active material is sufficient, the speed of electron transfer on the surface of the positive electrode material becomes high, and the lithium ion secondary battery and the battery At that time, the charging performance and the discharging performance under a high current are further improved. When the carbon concentration is not more than the above upper limit value, the electric capacity of the lithium ion secondary battery tends to be further increased.
The carbon concentration of the positive electrode active material can be measured by a carbon / sulfur analyzer (for example, "EMIA-920V" manufactured by HORIBA, Ltd.).
正極活物質がマンガン酸リチウムを含む場合、電子スピン共鳴を測定した際に得られるスピン濃度は、１．５×１０１７ｓｐｉｎｓ／ｇ以上が好ましく、２．０×１０１７ｓｐｉｎｓ／ｇ以上がより好ましく、２．５×１０１７ｓｐｉｎｓ／ｇ以上がさらに好ましい。
スピン濃度が１．５×１０１７ｓｐｉｎｓ／ｇ以上であると、リチウムイオン二次電池とした際の電気容量がさらに高くなり、高電流下での充電性能及び放電性能がさらに高くなる。
When the positive electrode active material contains lithium manganate, the spin concentration obtained when electron spin resonance is measured is preferably 1.5 × 10 17 spins / g or more, more preferably 2.0 × 10 17 spins / g or more. Preferably, 2.5 × 10 17 spins / g or more is more preferable.
When the spin concentration is 1.5 × 10 17 spins / g or more, the electric capacity of the lithium ion secondary battery becomes higher, and the charging performance and the discharging performance under a high current become higher.
正極活物質は、一次粒子の凝集物である二次粒子でもよい。一次粒子は、平均粒子径が５０〜１５０ｎｍである正極活物質からなる粒子である。正極活物質が二次粒子である場合、互いに凝集している一次粒子同士の間の隙間に繊維状の炭素材料の端部を固定できる。その結果、複合粒子から繊維状の炭素材料が脱落しにくくなり、リチウムイオン二次電池とした際の短絡等の不具合が起きにくくなる。 The positive electrode active material may be secondary particles which are aggregates of primary particles. The primary particles are particles made of a positive electrode active material having an average particle diameter of 50 to 150 nm. When the positive electrode active material is secondary particles, the ends of the fibrous carbon material can be fixed in the gaps between the primary particles that are agglomerated with each other. As a result, the fibrous carbon material is less likely to fall off from the composite particles, and problems such as a short circuit when the lithium ion secondary battery is used are less likely to occur.
正極活物質の下式（１）で算出されるαは、正極活物質の表面の凹凸の大きさを示す指標である。αが大きな値であるほど、正極活物質の表面の凹凸が大きいことを意味する。αは０．３以上が好ましく、０．４以上がより好ましく、０．７以上がさらに好ましい。αが前記下限値以上であると、正極活物質の表面に繊維状の炭素材料が固定化されやすくなる。その結果、正極とした際の導電性に優れる正極材料が得られやすくなる。
α＝Ｓ／Ｄ ・・・式（１）
式（１）中、Ｓは正極活物質の比表面積であり、Ｄは正極活物質の平均粒子径である。
Α calculated by the following formula (1) of the positive electrode active material is an index indicating the size of the unevenness on the surface of the positive electrode active material. The larger the value of α, the larger the unevenness of the surface of the positive electrode active material. α is preferably 0.3 or more, more preferably 0.4 or more, and even more preferably 0.7 or more. When α is at least the above lower limit value, the fibrous carbon material is likely to be immobilized on the surface of the positive electrode active material. As a result, it becomes easy to obtain a positive electrode material having excellent conductivity when used as a positive electrode.
α = S / D ・ ・ ・ Equation (1)
In the formula (1), S is the specific surface area of the positive electrode active material, and D is the average particle size of the positive electrode active material.
正極活物質の比表面積Ｓは、１．４〜１０ｍ２／ｇが好ましく、２．０〜８．０ｍ２／ｇがより好ましく、３．５〜８．０ｍ２／ｇがさらに好ましい。正極活物質の比表面積Ｓが前記下限値以上であると、繊維状の炭素材料が正極活物質に固定されやすく、炭素材料の固定性がよくなる。正極活物質の比表面積Ｓが前記上限値以下であると、繊維状の炭素材料が正極活物質の凹凸の間に保持されやすい。
正極活物質の比表面積Ｓは、全自動比表面積測定装置（例えば、株式会社マウンテック製「Ｍａｃｓｏｒｂ ＨＭ−１２０１」）によって測定できる。
The specific surface area S of the cathode active material is preferably 1.4~10m 2 / g, more preferably 2.0~8.0m 2 / g, more preferably 3.5~8.0m 2 / g. When the specific surface area S of the positive electrode active material is at least the above lower limit value, the fibrous carbon material is easily fixed to the positive electrode active material, and the fixability of the carbon material is improved. When the specific surface area S of the positive electrode active material is not more than the upper limit value, the fibrous carbon material is likely to be held between the irregularities of the positive electrode active material.
The specific surface area S of the positive electrode active material can be measured by a fully automatic specific surface area measuring device (for example, "Macsorb HM-1201" manufactured by Mountech Co., Ltd.).
正極活物質の平均粒子径Ｄは、０．５〜１０μｍが好ましく、１〜５μｍがより好ましい。正極活物質の平均粒子径Ｄが前記下限値以上であると、正極材料の表面の活性が抑えられ、正極とした際の耐久性がよくなる。正極活物質の平均粒子径Ｄが前記上限値以下であると、粒子表面から正極材料の内部までの距離が相対的に短く、正極材料の内部まで電子、リチウムイオンの移動反応速度が高くなる。その結果、リチウムイオン二次電池とした際の高電流下での充電性能及び放電性能がさらに高くなる。
正極活物質の平均粒子径Ｄは、レーザー回折式粒度分布測定装置（例えば、株式会社島津製作所製「ＳＡＬＤ−７１００」）によって、レーザー散乱法で測定されるＤ５０である。
The average particle size D of the positive electrode active material is preferably 0.5 to 10 μm, more preferably 1 to 5 μm. When the average particle size D of the positive electrode active material is at least the above lower limit value, the activity of the surface of the positive electrode material is suppressed, and the durability when the positive electrode is used is improved. When the average particle diameter D of the positive electrode active material is not more than the upper limit value, the distance from the particle surface to the inside of the positive electrode material is relatively short, and the transfer reaction rate of electrons and lithium ions to the inside of the positive electrode material is high. As a result, the charging performance and the discharging performance under a high current when the lithium ion secondary battery is used are further improved.
The average particle size D of the positive electrode active material is D50 measured by a laser scattering method using a laser diffraction type particle size distribution measuring device (for example, “SALD-7100” manufactured by Shimadzu Corporation).
正極活物質は、例えば、特開２０１６−１８６４５号公報に記載の方法で製造できる。すなわち、炭化水素系燃料を燃焼させて高温雰囲気を形成し、高温雰囲気中にマンガンとリチウムとを含む液体原料を噴霧し、加熱して、マンガン酸リチウムを合成することで製造できる。 The positive electrode active material can be produced, for example, by the method described in JP-A-2016-18645. That is, it can be produced by burning a hydrocarbon fuel to form a high temperature atmosphere, spraying a liquid raw material containing manganese and lithium in the high temperature atmosphere, and heating the mixture to synthesize lithium manganate.
複合粒子は繊維状の炭素材料を有する。繊維状の炭素材料としては、カーボンナノチューブが好ましい。
繊維状の炭素材料の平均繊維長は５０μｍ超であり、７５μｍ以上が好ましく、１００μｍ以上がより好ましい。繊維状の炭素材料の平均繊維長の上限値は特に限定されない。繊維状の炭素材料の平均繊維長は、例えば、６００μｍ以下でもよい。
炭素材料の平均繊維長が前記下限値以上であると、正極とした際の導電性がよくなる。
The composite particles have a fibrous carbon material. As the fibrous carbon material, carbon nanotubes are preferable.
The average fiber length of the fibrous carbon material is more than 50 μm, preferably 75 μm or more, and more preferably 100 μm or more. The upper limit of the average fiber length of the fibrous carbon material is not particularly limited. The average fiber length of the fibrous carbon material may be, for example, 600 μm or less.
When the average fiber length of the carbon material is at least the above lower limit value, the conductivity when used as a positive electrode is improved.
複合粒子は、複数の炭素材料を有する。本発明の正極材料においては、複数の炭素材料のうち、一部の炭素材料の端部の少なくとも一方が、正極活物質に固定されていない。一部の炭素材料の端部の少なくとも一方が正極活物質に固定されていないため、複合粒子の周囲の空間において、繊維状の炭素材料が放射状に伸びたような形態が実現される。その結果、複合粒子の周囲で繊維状の炭素材料が互いに絡み合うことができ、複合粒子の周囲で、繊維状の炭素材料同士の接点が形成され、複数の繊維状の炭素材料の間に導電経路が形成される。 The composite particle has a plurality of carbon materials. In the positive electrode material of the present invention, of the plurality of carbon materials, at least one of the ends of some carbon materials is not fixed to the positive electrode active material. Since at least one of the ends of some carbon materials is not fixed to the positive electrode active material, a form in which the fibrous carbon material is radially extended is realized in the space around the composite particles. As a result, the fibrous carbon materials can be entangled with each other around the composite particles, and contacts between the fibrous carbon materials are formed around the composite particles, and a conductive path is formed between the plurality of fibrous carbon materials. Is formed.
繊維状の複数の炭素材料のそれぞれは、第１の端部と第２の端部とを有してもよい。本発明の第１の態様においては、複数の炭素材料のうち、一部の炭素材料Ｃ１の第１の端部が、正極活物質に固定されている。そして、正極活物質に固定された第１の端部を有する炭素材料Ｃ１の第２の端部は、正極活物質に固定されていない。
かかる第１の態様においては、正極活物質に固定されていない第２の端部が、複合粒子の表面から複合粒子の周囲の空間に向かって伸びたような形態が実現される。そして正極活物質に固定された第１の端部を起点として、第２の端部が複合粒子の周囲の空間において、自由に動くことができる。その結果、炭素材料Ｃ１と他の複合粒子が有する繊維状の炭素材料とが互いに絡み合い、炭素材料Ｃ１の第１の端部に炭素材料同士の接点が形成され、導電経路が形成されやすくなる。
Each of the fibrous carbon materials may have a first end and a second end. In the first aspect of the present invention, among the plurality of carbon materials, the first end portion of a part of the carbon material C1 is fixed to the positive electrode active material. The second end of the carbon material C1 having the first end fixed to the positive electrode active material is not fixed to the positive electrode active material.
In such a first aspect, a form is realized in which the second end portion not fixed to the positive electrode active material extends from the surface of the composite particle toward the space around the composite particle. Then, starting from the first end portion fixed to the positive electrode active material, the second end portion can move freely in the space around the composite particle. As a result, the carbon material C1 and the fibrous carbon material contained in the other composite particles are entangled with each other, a contact point between the carbon materials is formed at the first end portion of the carbon material C1, and a conductive path is easily formed.
繊維状の複数の炭素材料のそれぞれは第１の端部と第２の端部とを有してもよい。本発明の第２の態様においては、複数の炭素材料のうち、一部の炭素材料Ｃ２の第１の端部及び第２の端部のいずれもが、正極活物質に固定されていない。そして、当該炭素材料Ｃ２の第１の端部及び第２の端部の間の部分が、正極活物質に固定されて保持されている。
かかる第２の態様においては、正極活物質に固定されていない第１の端部及び第２の端部が、複合粒子の表面から複合粒子の周囲の空間に向かって伸びたような形態が実現される。そして正極活物質に固定された第１の端部及び第２の端部の間の部分の固定点を起点として、第１の端部及び第２の端部が複合粒子の周囲の空間において、自由に動くことができる。その結果、炭素材料Ｃ２と他の複合粒子が有する繊維状の炭素材料とが互いに絡み合い、炭素材料Ｃ２の第１の端部及び第２の端部に炭素材料同士の接点が形成され、導電経路がさらに形成されやすくなる。
Each of the fibrous carbon materials may have a first end and a second end. In the second aspect of the present invention, none of the first end portion and the second end portion of a part of the carbon material C2 is fixed to the positive electrode active material among the plurality of carbon materials. Then, the portion between the first end portion and the second end portion of the carbon material C2 is fixed and held by the positive electrode active material.
In such a second aspect, a form in which the first end portion and the second end portion not fixed to the positive electrode active material extend from the surface of the composite particle toward the space around the composite particle is realized. Will be done. Then, starting from the fixed point of the portion between the first end and the second end fixed to the positive electrode active material, the first end and the second end are in the space around the composite particle. You can move freely. As a result, the carbon material C2 and the fibrous carbon material contained in the other composite particles are entangled with each other, and contacts between the carbon materials are formed at the first end and the second end of the carbon material C2, and the conductive path is formed. Is more likely to be formed.
本発明の正極材料においては、炭素材料は、上述の炭素材料Ｃ１、炭素材料Ｃ２を一種単独で含んでもよく、両方を含んでもよい。
加えて、上述の第１の態様及び第２の態様のいずれにおいても、複数の炭素材料のうち、第１の端部及び第２の端部のいずれもが、正極活物質に固定されている炭素材料Ｃ３が存在してもよい。
当該炭素材料Ｃ３にあっては、第１の端部及び第２の端部の間の部分が、正極活物質に固定されていないことが好ましい。第１の端部及び第２の端部の間の部分が、正極活物質に固定されていない場合、炭素材料Ｃ３の第１の端部及び第２の端部の間の部分が、正極活物質に固定された第１の端部及び第２の端部を起点として、複合粒子の周囲の空間において、自由に動くことができる。その結果、炭素材料Ｃ３と他の複合粒子が有する繊維状の炭素材料とが互いに絡み合い、炭素材料Ｃ３の第１の端部及び第２の端部の間の部分に炭素材料同士の接点が形成され、導電経路がさらに形成されやすくなる。
In the positive electrode material of the present invention, the carbon material may contain the above-mentioned carbon material C1 and carbon material C2 alone or both.
In addition, in both the first aspect and the second aspect described above, among the plurality of carbon materials, both the first end portion and the second end portion are fixed to the positive electrode active material. The carbon material C3 may be present.
In the carbon material C3, it is preferable that the portion between the first end portion and the second end portion is not fixed to the positive electrode active material. When the portion between the first end and the second end is not fixed to the positive electrode active material, the portion between the first end and the second end of the carbon material C3 is the positive electrode active. Starting from the first end and the second end fixed to the substance, it can move freely in the space around the composite particle. As a result, the carbon material C3 and the fibrous carbon material of the other composite particles are entangled with each other, and a contact point between the carbon materials is formed in the portion between the first end and the second end of the carbon material C3. This makes it easier for conductive paths to be formed.
繊維状の炭素材料以外の炭素材料としては、カーボンブラック、黒鉛、活性炭、グラフェン、フラーレン等が挙げられる。ただし、繊維状の炭素材料以外の炭素材料は、これらの例示に限定されない。 Examples of the carbon material other than the fibrous carbon material include carbon black, graphite, activated carbon, graphene, fullerene and the like. However, carbon materials other than fibrous carbon materials are not limited to these examples.
正極活物質の含有量は、正極材料１００質量％に対して９９．００〜９９．９５質量％が好ましく、９９．５〜９９．９質量％がより好ましく、９９．７〜９９．８質量％がさらに好ましい。正極活物質の含有量が前記下限値以上であると、リチウムイオン二次電池とした際の電気容量がさらに高くなり、高電流下での充電性能及び放電性能がさらに高くなる。正極活物質の含有量が前記上限値以下であると、活物質同士の結着性がよくなる。 The content of the positive electrode active material is preferably 99.0 to 99.95% by mass, more preferably 99.5 to 99.9% by mass, and 99.7 to 99.8% by mass with respect to 100% by mass of the positive electrode material. Is even more preferable. When the content of the positive electrode active material is at least the above lower limit value, the electric capacity of the lithium ion secondary battery is further increased, and the charging performance and the discharging performance under a high current are further improved. When the content of the positive electrode active material is not more than the above upper limit value, the binding property between the active materials is improved.
繊維状の炭素材料の含有量は、正極材料１００質量％に対して０．０５〜１質量％が好ましく、０．１〜０．５質量％がより好ましく、０．２〜０．３質量％がさらに好ましい。繊維状の炭素材料の含有量が前記下限値以上であると、正極とした際の導電性がさらによくなる。繊維状の炭素材料の含有量が前記上限値以下であると、正極とした際に炭素材料の剥離量、炭素材料の脱落量が少なくなり、リチウムイオン二次電池とした際の短絡等の不具合が起きにくくなる。 The content of the fibrous carbon material is preferably 0.05 to 1% by mass, more preferably 0.1 to 0.5% by mass, and 0.2 to 0.3% by mass with respect to 100% by mass of the positive electrode material. Is even more preferable. When the content of the fibrous carbon material is at least the above lower limit value, the conductivity when used as a positive electrode is further improved. When the content of the fibrous carbon material is not more than the above upper limit value, the amount of peeling of the carbon material and the amount of falling off of the carbon material are reduced when the positive electrode is used, and problems such as short circuit when the lithium ion secondary battery is used are reduced. Is less likely to occur.
（作用効果）
以上説明した本発明の正極材料にあっては、炭素材料の平均繊維長が５０μｍ超であり、一部の炭素材料の端部の少なくとも一方が、正極活物質に固定されていない。そのため、端部が正極活物質に固定されていない繊維状の炭素材料が、複合粒子の表面から複合粒子の周囲に向かって略放射状に伸びたような形態をとることができる。この略放射状に伸びた部分の繊維状の炭素材料が互いに絡み合うことで、複合粒子同士が電気的に接続されるため、正極とした際の導電性がよくなる。
(Action effect)
In the positive electrode material of the present invention described above, the average fiber length of the carbon material is more than 50 μm, and at least one of the ends of some carbon materials is not fixed to the positive electrode active material. Therefore, the fibrous carbon material whose ends are not fixed to the positive electrode active material can take a form in which the fibrous carbon material extends substantially radially from the surface of the composite particles toward the periphery of the composite particles. Since the fibrous carbon materials of the substantially radially extending portions are entangled with each other, the composite particles are electrically connected to each other, so that the conductivity when the positive electrode is used is improved.
＜正極材料の製造方法＞
本発明の正極材料の製造方法では、繊維状の炭素材料と液状媒体とを含む分散液を調製し、分散液と正極活物質とを混合した後に、液状媒体を除去する。
<Manufacturing method of positive electrode material>
In the method for producing a positive electrode material of the present invention, a dispersion liquid containing a fibrous carbon material and a liquid medium is prepared, the dispersion liquid and the positive electrode active material are mixed, and then the liquid medium is removed.
繊維状の炭素材料の詳細及び好ましい態様は、＜正極材料＞の項で述べた内容と同内容である。
正極活物質の詳細及び好ましい態様は、＜正極材料＞の項で述べた内容と基本的に同内容である。ただし、本発明の正極材料の製造方法においては、正極活物質の下式（１）で算出されるαが０．３以上であることを必須の要件とする。これにより、正極活物質の表面に繊維状の炭素材料が固定化され、正極とした際の導電性に優れる正極材料が得られる。
α＝Ｓ／Ｄ ・・・式（１）
式（１）中、Ｓは正極活物質の比表面積であり、Ｄは正極活物質の平均粒子径である。
The details and preferred embodiments of the fibrous carbon material are the same as those described in the section <Positive electrode material>.
The details and preferred embodiments of the positive electrode active material are basically the same as those described in the section <Positive electrode material>. However, in the method for producing a positive electrode material of the present invention, it is an essential requirement that α calculated by the following formula (1) of the positive electrode active material is 0.3 or more. As a result, the fibrous carbon material is immobilized on the surface of the positive electrode active material, and a positive electrode material having excellent conductivity when used as a positive electrode can be obtained.
α = S / D ・ ・ ・ Equation (1)
In the formula (1), S is the specific surface area of the positive electrode active material, and D is the average particle size of the positive electrode active material.
分散液としては、液状媒体中に繊維状の炭素材料が単一分散していることが好ましい。
液状媒体としては、繊維状の炭素材料が単一分散可能な液体であれば特に限定されない。液状媒体の具体例としては、水；メタノール、エタノール、１−プロパノール、２−プロパノール等のアルコール；アセトン、メチルエチルケトン、メチルイソブチルケトン等のケトン；エチレングリコール、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ−メチル−２−ピロリドン等の極性溶媒が挙げられる。
これらは一種を単独で使用してもよく、二種以上を併用してもよい。
As the dispersion liquid, it is preferable that the fibrous carbon material is singly dispersed in the liquid medium.
The liquid medium is not particularly limited as long as the fibrous carbon material is a single dispersible liquid. Specific examples of the liquid medium include water; alcohols such as methanol, ethanol, 1-propanol and 2-propanol; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ethylene glycol, N, N-dimethylformamide and N-methyl-. Examples include polar solvents such as 2-pyrrolidone.
These may be used alone or in combination of two or more.
分散液を調製する際には、繊維状の炭素材料の分散性をよくするために、分散剤を使用することが好ましい。分散剤としては、カルボキシルセルロース、エチルセルロース、セルロースエーテル、カルボキシルエチルセルロース、アミノエチルセルロース、オキシエチルセルロース、ヒドロキシメチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、メチルセルロース、ベンジルセルロース、トリメチルセルロース等のセルロース誘導体；メチル（メタ）アクリレート、エチル（メタ）アクリレート、ブチル（メタ）アクリレート、ベンジル（メタ）アクリレート、ヒドロキシエチル（メタ）アクリレート、ジメチルアミノエチルアクリレート、アクリルモノマー（アクリル酸、メタクリル酸等）の共重合体等のアクリルポリマーが挙げられる。
分散液の調製の際には、界面活性剤を使用してもよい。界面活性剤の具体例としては、ドデシル硫酸ナトリウム（ＳＤＳ）等のアニオン系界面活性剤；臭化ヘキサデシルトリメチルアンモニウム（Ｃ１６ＴＡＢ）等のカチオン系界面活性剤；３−［（３−コラミドプロピル）ジメチルアンモニオ］−１−プロパンスルホナート（ＣＨＡＰＳ）、３−［（３−コラミドプロピル）ジメチルアンモニオ］−２−ヒドロキシ−１−プロパンスルホナート（ＣＨＡＰＳＯ）等の両性界面活性剤；ポリビニルアルコール、ポリビニルピロリドン等の非イオン系界面活性剤等が挙げられる。
When preparing the dispersion, it is preferable to use a dispersant in order to improve the dispersibility of the fibrous carbon material. Dispersants include cellulose derivatives such as carboxyl cellulose, ethyl cellulose, cellulose ether, carboxyl ethyl cellulose, amino ethyl cellulose, oxyethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, benzyl cellulose, trimethyl cellulose; methyl (meth) acrylate, Acrylic polymers such as ethyl (meth) acrylate, butyl (meth) acrylate, benzyl (meth) acrylate, hydroxyethyl (meth) acrylate, dimethylaminoethyl acrylate, and copolymers of acrylic monomers (acrylic acid, methacrylic acid, etc.) are mentioned. Be done.
Surfactants may be used in the preparation of the dispersion. Specific examples of the surfactant include an anionic surfactant such as sodium dodecyl sulfate (SDS); a cationic surfactant such as hexadecyltrimethylammonium bromide (C16TAB); 3-[(3-colamidpropyl). Amphoteric surfactants such as dimethylammonio] -1-propanesulfonate (CHAPS), 3-[(3-colamidpropyl) dimethylammonio] -2-hydroxy-1-propanesulfonate (CHAPSO); polyvinyl alcohol , Nonionic surfactants such as polyvinylpyrrolidone and the like.
繊維状の炭素材料の含有量は、分散液１００質量％に対して、０．０１〜１質量％が好ましく、０．０２５〜０．５質量％がより好ましく、０．０５〜０．２質量％がさらに好ましい。繊維状の炭素材料の含有量が前記下限値以上であると、正極とした際の導電性がさらによくなる。繊維状の炭素材料の含有量が前記上限値以下であると、正極とした際に炭素材料の剥離量、炭素材料の脱落量が少なくなり、リチウムイオン二次電池とした際の短絡等の不具合が起きにくくなる。 The content of the fibrous carbon material is preferably 0.01 to 1% by mass, more preferably 0.025 to 0.5% by mass, and 0.05 to 0.2% by mass with respect to 100% by mass of the dispersion. % Is more preferable. When the content of the fibrous carbon material is at least the above lower limit value, the conductivity when used as a positive electrode is further improved. When the content of the fibrous carbon material is not more than the above upper limit value, the amount of peeling of the carbon material and the amount of falling off of the carbon material are reduced when the positive electrode is used, and problems such as short circuit when the lithium ion secondary battery is used are reduced. Is less likely to occur.
分散剤の使用量は、本発明の効果を損なわない範囲で適宜選択可能である。例えば、分散剤の使用量は、分散液中に含まれるカーボンナノチューブ１００質量部に対して５０〜３０００質量部が好ましく、７５〜２０００質量部がより好ましく、１００〜１０００質量部がさらに好ましい。
分散剤の使用量が前記下限値以上であると、液状媒体に繊維状の炭素材料が単一分散しやすくなる。分散剤の使用量が前記上限値以下であると、正極とした際の導電性がさらによくなる。
The amount of the dispersant used can be appropriately selected as long as the effect of the present invention is not impaired. For example, the amount of the dispersant used is preferably 50 to 3000 parts by mass, more preferably 75 to 2000 parts by mass, and even more preferably 100 to 1000 parts by mass with respect to 100 parts by mass of the carbon nanotubes contained in the dispersion liquid.
When the amount of the dispersant used is at least the above lower limit value, the fibrous carbon material is likely to be singlely dispersed in the liquid medium. When the amount of the dispersant used is not more than the above upper limit value, the conductivity when the positive electrode is used is further improved.
分散液の調製方法は特に限定されない。例えばカーボンナノチューブと必要に応じて分散剤とを液状媒体に投入し、超音波照射、ビーズミル等の手法で均一に混合することで、分散液を調製してもよい。
分散液は、本発明の効果を損なわない範囲内であれば、繊維状の炭素材料以外の炭素材料をさらに含んでもよい。
The method for preparing the dispersion is not particularly limited. For example, a dispersion liquid may be prepared by charging carbon nanotubes and, if necessary, a dispersant into a liquid medium and uniformly mixing them by a method such as ultrasonic irradiation or a bead mill.
The dispersion liquid may further contain a carbon material other than the fibrous carbon material as long as the effect of the present invention is not impaired.
分散液中の繊維状の炭素材料の平均繊維長は、１〜１００μｍが好ましく、５〜５０μｍがより好ましく、１０〜３０μｍがさらに好ましい。分散液中の繊維状の炭素材料の平均繊維長が前記下限値以上であると、正極とした際の導電性がさらによくなる。 The average fiber length of the fibrous carbon material in the dispersion is preferably 1 to 100 μm, more preferably 5 to 50 μm, and even more preferably 10 to 30 μm. When the average fiber length of the fibrous carbon material in the dispersion liquid is at least the above lower limit value, the conductivity when used as a positive electrode is further improved.
分散液と正極活物質とを混合する際には、スターラー攪拌、プロペラ攪拌、自公転式ミキサー等の方法が好ましい。分散液と正極活物質とを混合することで、正極活物質の表面に繊維状の炭素材料が固定され、複合粒子が生成する。
正極活物質の表面に複合化させる繊維状の炭素材料の量に応じて、分散液における繊維状の炭素材料の濃度を調整してもよい。例えば、繊維状の炭素材料の含有量が多い分散液をあらかじめ調製しておき、次いで、液状媒体で希釈して、繊維状の炭素材料の含有量を調整してもよい。
When mixing the dispersion liquid and the positive electrode active material, methods such as stirrer stirring, propeller stirring, and a self-revolving mixer are preferable. By mixing the dispersion liquid and the positive electrode active material, the fibrous carbon material is fixed on the surface of the positive electrode active material, and composite particles are generated.
The concentration of the fibrous carbon material in the dispersion may be adjusted according to the amount of the fibrous carbon material to be composited on the surface of the positive electrode active material. For example, a dispersion having a high content of the fibrous carbon material may be prepared in advance and then diluted with a liquid medium to adjust the content of the fibrous carbon material.
本発明の正極材料の製造方法においては、分散液と正極活物質とを混合した後に、液状媒体を除去する。ここで、遠心分離、ろ過等の固液分離によって、液状媒体の大半を除去した後、熱処理、真空乾燥によって溶媒をさらに除去してもよい。熱処理の加熱温度、乾燥温度は液状媒体の種類に応じて適宜選択する。 In the method for producing a positive electrode material of the present invention, the liquid medium is removed after mixing the dispersion liquid and the positive electrode active material. Here, after removing most of the liquid medium by solid-liquid separation such as centrifugation or filtration, the solvent may be further removed by heat treatment or vacuum drying. The heating temperature and drying temperature of the heat treatment are appropriately selected according to the type of the liquid medium.
（作用効果）
以上説明した本発明の正極材料の製造方法にあっては、繊維状の炭素材料の平均繊維長が５０μｍ超であり、上式（１）で算出されるαが０．３以上である。すなわち、正極活物質の表面の凹凸が相対的に大きく、平均繊維長が相対的に長い。よって、一部の繊維状の炭素材料の端部が正極活物質の表面に固定化され、かつ、複合粒子の表面から複合粒子の周囲に向かって略放射状に伸びたような形態をとることができる。この略放射状に伸びた部分の繊維状の炭素材料が互いに絡み合うことで、複合粒子同士が電気的に接続されるため、正極とした際の導電性がよくなる。
(Action effect)
In the method for producing a positive electrode material of the present invention described above, the average fiber length of the fibrous carbon material is more than 50 μm, and α calculated by the above formula (1) is 0.3 or more. That is, the surface irregularities of the positive electrode active material are relatively large, and the average fiber length is relatively long. Therefore, it is possible that the end portion of a part of the fibrous carbon material is fixed to the surface of the positive electrode active material and extends substantially radially from the surface of the composite particle toward the periphery of the composite particle. it can. Since the fibrous carbon materials of the substantially radially extending portions are entangled with each other, the composite particles are electrically connected to each other, so that the conductivity when the positive electrode is used is improved.
（用途）
本発明の正極材料は、リチウムイオン二次電池の正極に適用できる。すなわち、本発明の正極材料を含む電極は、リチウムイオン二次電池の正極に適用できる。この場合における正極は、本発明の正極材料以外の成分をさらに含んでもよい。本発明の正極材料を含む正極は、導電性に優れる。よって、リチウムイオン二次電池とした際の電気容量が高く、高電流下での充電性能及び放電性能が高くなる。
(Use)
The positive electrode material of the present invention can be applied to the positive electrode of a lithium ion secondary battery. That is, the electrode containing the positive electrode material of the present invention can be applied to the positive electrode of the lithium ion secondary battery. The positive electrode in this case may further contain components other than the positive electrode material of the present invention. The positive electrode containing the positive electrode material of the present invention has excellent conductivity. Therefore, the electric capacity of the lithium ion secondary battery is high, and the charging performance and the discharging performance under a high current are high.
リチウムイオン二次電池は、例えば、正極と、負極と、電解質とを有する。リチウムイオン二次電池は、正極、負極及び電解質以外にその他の構成をさらに有してもよい。 The lithium ion secondary battery has, for example, a positive electrode, a negative electrode, and an electrolyte. The lithium ion secondary battery may have other configurations besides the positive electrode, the negative electrode and the electrolyte.
リチウムイオン二次電池は、本発明の正極材料を含む正極を有するため、電気容量が高く、高電流下での充電性能及び放電性能が高い。 Since the lithium ion secondary battery has a positive electrode containing the positive electrode material of the present invention, it has a high electric capacity and high charging performance and discharging performance under a high current.
＜実施例＞
以下、実施例によって本発明を具体的に説明するが、本発明は以下の記載によって限定されない。
<Example>
Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited by the following description.
［測定方法］
（マンガン酸リチウムの比表面積Ｓ）
マンガン酸リチウムの比表面積Ｓは、全自動比表面積測定装置（株式会社マウンテック製「Ｍａｃｓｏｒｂ ＨＭ−１２０１」）を使用して測定した。
[Measuring method]
(Specific surface area S of lithium manganate)
The specific surface area S of lithium manganate was measured using a fully automatic specific surface area measuring device (“Macsorb HM-1201” manufactured by Mountech Co., Ltd.).
（マンガン酸リチウムの平均粒子径Ｄ）
マンガン酸リチウムの平均粒子径Ｄは、レーザー回折式粒度分布測定装置（株式会社島津製作所製「ＳＡＬＤ−７１００」）を使用して測定した。
(Average particle size D of lithium manganate)
The average particle size D of lithium manganate was measured using a laser diffraction type particle size distribution measuring device (“SALD-7100” manufactured by Shimadzu Corporation).
（マンガン酸リチウムの炭素濃度）
マンガン酸リチウムの炭素濃度は、炭素硫黄分析装置（株式会社堀場製作所製「ＥＭＩＡ−９２０Ｖ」）を使用して測定した。
(Carbon concentration of lithium manganate)
The carbon concentration of lithium manganate was measured using a carbon sulfur analyzer (“EMIA-920V” manufactured by HORIBA, Ltd.).
（分散液中の繊維状の炭素材料の平均繊維長）
分散液中の繊維状の炭素材料の平均繊維長は、粒度分布装置（大塚電子株式会社製「ＥＬＳＺ−２０００」）を使用して測定した。具体的には、カーボンナノチューブの形状を円筒形とみなし、カーボンナノチューブが単一分散していると仮定して、球の体積として計算される粒度分布の測定値に基づき、円筒の高さを繊維長として算出した。
(Average fiber length of fibrous carbon material in dispersion)
The average fiber length of the fibrous carbon material in the dispersion was measured using a particle size distribution device (“ELSZ-2000” manufactured by Otsuka Electronics Co., Ltd.). Specifically, assuming that the shape of the carbon nanotubes is cylindrical and the carbon nanotubes are singly dispersed, the height of the cylinder is set to the fiber based on the measured value of the particle size distribution calculated as the volume of the sphere. Calculated as length.
［評価方法］
（固定化）
各例の正極材料：１０gを液状媒体（Ｎ−メチル−２−ピロリドン）：２０ｇに添加し、超音波ホモジナイザーにて５分処理し、静置後の液相成分（上澄み溶液）を分取し、乾燥した乾燥物を走査型電子顕微鏡（ＳＥＭ）（ＪＥＯＬ社製「ＪＳＭ−６７００Ｆ」）で倍率を１０，０００倍として観察した。走査型電子顕微鏡による観察において、複合粒子のマンガン酸リチウムの表層にカーボンナノチューブが固定されているか否かを下記の評価基準で判定した。
〇：走査型電子顕微鏡による観察写真を２０視野取得し、取得した観察写真のすべてにおいて、マンガン酸リチウムから遊離したカーボンナノチューブが観察されない。
×：走査型電子顕微鏡による観察写真を２０視野取得し、取得した観察写真の１視野以上において、マンガン酸リチウムから遊離したカーボンナノチューブが観察される。
[Evaluation method]
(Fixed)
The positive electrode material of each example: 10 g was added to a liquid medium (N-methyl-2-pyrrolidone): 20 g, treated with an ultrasonic homogenizer for 5 minutes, and the liquid phase component (supernatant solution) after standing was separated. The dried dried product was observed with a scanning electron microscope (SEM) (“JSM-6700F” manufactured by JEOL Ltd.) at a magnification of 10,000 times. In the observation with a scanning electron microscope, it was judged by the following evaluation criteria whether or not the carbon nanotubes were fixed on the surface layer of the lithium manganate of the composite particles.
〇: 20 visual fields of observation photographs taken with a scanning electron microscope were acquired, and carbon nanotubes liberated from lithium manganate were not observed in all of the acquired observation photographs.
X: 20 visual fields of observation photographs taken by a scanning electron microscope are acquired, and carbon nanotubes liberated from lithium manganate are observed in one or more visual fields of the acquired observation photographs.
（固定されていない端部の有無）
各例で得られた正極材料を走査型電子顕微鏡（ＳＥＭ）（ＪＥＯＬ社製「ＪＳＭ−６７００Ｆ」）で倍率を７０，０００倍として観察した。観察写真において、マンガン酸リチウムの表層からカーボンナノチューブが露出しているか否かを下記の評価基準で判定した。
〇：複数のカーボンナノチューブのうち、端部の少なくとも一方がマンガン酸リチウムに固定されていないカーボンナノチューブが一部存在する。
×：複数のカーボンナノチューブの全てにおいて、端部のいずれもがマンガン酸リチウムに固定されている。
(Presence or absence of unfixed ends)
The positive electrode material obtained in each example was observed with a scanning electron microscope (SEM) (“JSM-6700F” manufactured by JEOL Ltd.) at a magnification of 70,000 times. In the observation photograph, whether or not the carbon nanotubes were exposed from the surface layer of lithium manganate was judged by the following evaluation criteria.
〇: Among the plurality of carbon nanotubes, there are some carbon nanotubes in which at least one of the ends is not fixed to lithium manganate.
X: In all of the plurality of carbon nanotubes, all of the ends are fixed to lithium manganate.
［原料］
（マンガン酸リチウム）
特開２０１６−１８６４５号公報の実施例に記載の方法にしたがって、表１に示す生成条件の下で、正極活物質としてマンガン酸リチウム（ＬＭＯ１，３〜５）を製造した。
ＬＭＯ１，３〜５について、比表面積、平均粒子径、炭素濃度をそれぞれ測定した。測定結果を表１に示す。
[material]
(Lithium manganate)
Lithium manganate (LMO1, 3-5) was produced as a positive electrode active material under the production conditions shown in Table 1 according to the method described in Examples of JP-A-2016-18645.
The specific surface area, average particle size, and carbon concentration of LMOs 1 and 3 to 5 were measured, respectively. The measurement results are shown in Table 1.
市販の正極活物質として、下記のＬＭＯ２、ＬＭＯ６を使用した。
ＬＭＯ２：大研化学工業株式会社製のマンガン酸リチウム。
ＬＭＯ６：イーエムジャパン株式会社製のマンガン酸リチウム（ＮＬ−Ａ−ＬＭＯ−５００Ｇ）。
The following LMO2 and LMO6 were used as commercially available positive electrode active materials.
LMO2: Lithium manganate manufactured by Daiken Kagaku Kogyo Co., Ltd.
LMO6: Lithium manganate (NL-A-LMO-500G) manufactured by EM Japan Co., Ltd.
（カーボンナノチューブ）
ＣＮＴ１：直径：１０ｎｍ、平均繊維長：４５０μｍであるカーボンナノチューブ（大陽日酸株式会社製「ＥＬグレード」）。
ＣＮＴ２：直径：１０ｎｍ、平均繊維長：１．５μｍであるカーボンナノチューブ（Ｎａｎｏｃｙｌ社製「ＮＣ７０００」）。
(carbon nanotube)
CNT1: Carbon nanotubes having a diameter of 10 nm and an average fiber length of 450 μm (“EL grade” manufactured by Taiyo Nippon Sanso Co., Ltd.).
CNT2: A carbon nanotube having a diameter of 10 nm and an average fiber length of 1.5 μm (“NC7000” manufactured by Nanocycl).
［実施例１］
液状媒体としてＮ−メチル−２−ピロリドン：１００質量部に、ＣＮＴ１：１０．０５質量部、分散剤としてアクリルポリマー：０．１５質量部をそれぞれ加え、超音波ホモジナイザーで１時間処理してＣＮＴ分散液１００ｇを得た。
次いで、Ｎ−メチル−２−ピロリドン２０ｇに、ＬＭＯ１の粒子を１０ｇ、ＣＮＴ１分散液を４０ｇ加え、スターラーにて３００ｒｐｍの回転数で、２５℃で９０分混合した。得られた混合スラリーを７０００ｒｐｍにて３０分遠心分離処理し、上澄み液を除去し、沈殿物を恒温乾燥器にて８０℃にて２４時間熱処理して溶媒を除去し、ＣＮＴ１とＬＭＯ１粒子との複合粒子を正極材料として回収した。
[Example 1]
To 100 parts by mass of N-methyl-2-pyrrolidone as a liquid medium, 1: 10.05 parts by mass of CNT and 0.15 parts by mass of acrylic polymer as a dispersant were added, and treated with an ultrasonic homogenizer for 1 hour to disperse CNT. 100 g of the liquid was obtained.
Next, 10 g of LMO1 particles and 40 g of CNT1 dispersion were added to 20 g of N-methyl-2-pyrrolidone, and the mixture was mixed with a stirrer at a rotation speed of 300 rpm for 90 minutes at 25 ° C. The obtained mixed slurry was centrifuged at 7000 rpm for 30 minutes to remove the supernatant, and the precipitate was heat-treated at 80 ° C. for 24 hours in a constant temperature dryer to remove the solvent, and the CNT1 and LMO1 particles were combined. The composite particles were recovered as a positive electrode material.
［実施例２〜６、比較例１〜３］
使用したマンガン酸リチウム、カーボンナノチューブを表２に示すように変更した以外は、実施例１と同様にしてマンガン酸リチウムとカーボンナノチューブとを複合化し、複合粒子を正極材料として回収した。
[Examples 2 to 6, Comparative Examples 1 to 3]
Lithium manganate and carbon nanotubes were composited in the same manner as in Example 1 except that the lithium manganate and carbon nanotubes used were changed as shown in Table 2, and the composite particles were recovered as the positive electrode material.
得られた各例の正極材料について、走査型電子顕微鏡による観察を行い、上述の記載にしたがって表面の状態を評価した。結果を表２に示す。 The positive electrode materials of each of the obtained examples were observed with a scanning electron microscope, and the surface condition was evaluated according to the above description. The results are shown in Table 2.
図１は、実施例１の正極材料の走査型電子顕微鏡による観察写真である。図２は、比較例１の正極材料の走査型電子顕微鏡による観察写真である。図１、２の観察写真の倍率は、いずれも７０，０００倍である。
図１に示すように、カーボンナノチューブの平均繊維長及びマンガン酸リチウムの比αが本発明で規定する範囲内である実施例１の複合粒子においては、複数のカーボンナノチューブのうち、端部の少なくとも一方が、マンガン酸リチウムに固定されていないカーボンナノチューブが一部存在し、マンガン酸リチウムの表層からカーボンナノチューブが露出していることを確認した。
図１に示すマンガン酸リチウムの表層から露出したカーボンナノチューブのように、一方の端部がマンガン酸リチウムに固定され、もう一方の端部がマンガン酸リチウムに固定されていないカーボンナノチューブが、複合粒子の表面から複合粒子の周囲に向かって伸びていることが確認できた。このように表面に露出したカーボンナノチューブは、複合粒子の周囲に向かって略放射状に伸びたような形態をとることができる。
よって、本実施例の結果から、この略放射状に伸びた部分のカーボンナノチューブが互いに絡み合うことで、複合粒子同士が電気的に接続され、正極とした際の導電性がよくなることが期待された。
FIG. 1 is an observation photograph of the positive electrode material of Example 1 with a scanning electron microscope. FIG. 2 is an observation photograph of the positive electrode material of Comparative Example 1 with a scanning electron microscope. The magnification of the observation photographs in FIGS. 1 and 2 is 70,000 times.
As shown in FIG. 1, in the composite particles of Example 1 in which the average fiber length of carbon nanotubes and the ratio α of lithium manganate are within the range specified in the present invention, at least the end portion of the plurality of carbon nanotubes is used. On the other hand, it was confirmed that some carbon nanotubes were not fixed to lithium manganate, and the carbon nanotubes were exposed from the surface layer of lithium manganate.
Like the carbon nanotubes exposed from the surface layer of lithium manganate shown in FIG. 1, carbon nanotubes having one end fixed to lithium manganate and the other end not fixed to lithium manganate are composite particles. It was confirmed that it extended from the surface of the composite particles toward the periphery of the composite particles. The carbon nanotubes exposed on the surface in this way can take the form of extending substantially radially toward the periphery of the composite particles.
Therefore, from the results of this example, it was expected that the carbon nanotubes in the substantially radially extending portions would be entangled with each other, so that the composite particles would be electrically connected to each other and the conductivity when the positive electrode was used would be improved.
比較例１ではカーボンナノチューブの平均繊維長が５０μｍ以下である。
図２に示すように比較例１の複合粒子では、複合粒子の表面から複合粒子の周囲に向かって伸びているカーボンナノチューブの存在が確認できず、カーボンナノチューブがマンガン酸リチウムの表面に固定化されなかった。そのため、比較例１の正極材料にあっては、カーボンナノチューブが複合粒子の周囲に向かって略放射状に伸びたような形態をとることができず、正極とした際の導電性が不充分であると考えられた。
In Comparative Example 1, the average fiber length of the carbon nanotubes is 50 μm or less.
As shown in FIG. 2, in the composite particles of Comparative Example 1, the presence of carbon nanotubes extending from the surface of the composite particles toward the periphery of the composite particles could not be confirmed, and the carbon nanotubes were immobilized on the surface of lithium manganate. There wasn't. Therefore, in the positive electrode material of Comparative Example 1, the carbon nanotubes cannot take a form in which the carbon nanotubes extend substantially radially toward the periphery of the composite particles, and the conductivity when the positive electrode is used is insufficient. It was considered.
本発明の正極材料は、高容量であり、高速での充電及び放電が可能なリチウムイオン二次電池の正極材料に適用できる。 The positive electrode material of the present invention can be applied to the positive electrode material of a lithium ion secondary battery having a high capacity and capable of charging and discharging at high speed.
Claims (6)
前記炭素材料の平均繊維長が５０μｍ超であり、
前記複数の炭素材料のうち、一部の前記炭素材料の端部の少なくとも一方が、前記正極活物質に固定されていない、正極材料。 A positive electrode material comprising composite particles having a positive electrode active material and a plurality of fibrous carbon materials held by the positive electrode active material.
The average fiber length of the carbon material is more than 50 μm.
A positive electrode material in which at least one of the ends of a portion of the plurality of carbon materials is not fixed to the positive electrode active material.
α＝Ｓ／Ｄ ・・・式（１）
式（１）中、Ｓは前記正極活物質の比表面積であり、Ｄは前記正極活物質の平均粒子径である。 The positive electrode material according to claim 1 or 2, wherein α calculated by the following formula (1) is 0.3 or more.
α = S / D ・ ・ ・ Equation (1)
In the formula (1), S is the specific surface area of the positive electrode active material, and D is the average particle size of the positive electrode active material.
前記分散液と正極活物質とを混合した後に、前記液状媒体を除去する、正極材料の製造方法であり、
前記炭素材料の平均繊維長が５０μｍ超であり、
下式（１）で算出されるαが０．３以上である、正極材料の製造方法。
α＝Ｓ／Ｄ ・・・式（１）
式（１）中、Ｓは前記正極活物質の比表面積であり、Ｄは前記正極活物質の平均粒子径である。 Prepare a dispersion containing a fibrous carbon material and a liquid medium,
A method for producing a positive electrode material, wherein the liquid medium is removed after mixing the dispersion liquid and the positive electrode active material.
The average fiber length of the carbon material is more than 50 μm.
A method for producing a positive electrode material, wherein α calculated by the following formula (1) is 0.3 or more.
α = S / D ・ ・ ・ Equation (1)
In the formula (1), S is the specific surface area of the positive electrode active material, and D is the average particle size of the positive electrode active material.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007048692A (en) * | 2005-08-12 | 2007-02-22 | Hitachi Vehicle Energy Ltd | Lithium secondary battery cathode material, cathode plate for lithium secondary battery, and lithium secondary battery using this |
| JP2009176721A (en) * | 2007-12-25 | 2009-08-06 | Kao Corp | Composite material for positive electrode of lithium battery |
| JP2013093288A (en) * | 2011-10-27 | 2013-05-16 | Showa Denko Kk | Production method of composite material for lithium secondary battery positive electrode |
| WO2013168785A1 (en) * | 2012-05-10 | 2013-11-14 | 東洋インキＳｃホールディングス株式会社 | Granulated particle for lithium secondary battery positive electrode and method for producing same, mixed ink, and lithium secondary battery |
| JP2014029863A (en) * | 2010-12-22 | 2014-02-13 | Hanwha Chemical Corp | Complex containing transition metal compound being electrode active material and fibrous carbon material, and method for producing the same |
-
2019
- 2019-02-22 JP JP2019030627A patent/JP2020136171A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007048692A (en) * | 2005-08-12 | 2007-02-22 | Hitachi Vehicle Energy Ltd | Lithium secondary battery cathode material, cathode plate for lithium secondary battery, and lithium secondary battery using this |
| JP2009176721A (en) * | 2007-12-25 | 2009-08-06 | Kao Corp | Composite material for positive electrode of lithium battery |
| JP2014029863A (en) * | 2010-12-22 | 2014-02-13 | Hanwha Chemical Corp | Complex containing transition metal compound being electrode active material and fibrous carbon material, and method for producing the same |
| JP2013093288A (en) * | 2011-10-27 | 2013-05-16 | Showa Denko Kk | Production method of composite material for lithium secondary battery positive electrode |
| WO2013168785A1 (en) * | 2012-05-10 | 2013-11-14 | 東洋インキＳｃホールディングス株式会社 | Granulated particle for lithium secondary battery positive electrode and method for producing same, mixed ink, and lithium secondary battery |
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