JP5932688B2 - Method for producing electrode material - Google Patents
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- JP5932688B2 JP5932688B2 JP2013051624A JP2013051624A JP5932688B2 JP 5932688 B2 JP5932688 B2 JP 5932688B2 JP 2013051624 A JP2013051624 A JP 2013051624A JP 2013051624 A JP2013051624 A JP 2013051624A JP 5932688 B2 JP5932688 B2 JP 5932688B2
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Description
本発明は、リチウムイオン二次電池等に使用可能な電極材料の製造方法に関する。 The present invention relates to a method for producing a conductive electrode material can be used for a lithium ion secondary battery or the like.
従来から、リチウムイオン二次電池等の電極として、オリビン型結晶構造（空間群Ｐｎｍａ）を有するＬｉＦｅＰＯ４等のリン酸金属リチウムが使用されている。リン酸金属リチウムは、コスト、安全性、耐久性などの観点において優れている一方、電子伝導性及びＬｉイオン伝導性に乏しい。リン酸金属リチウムを電極材料として使用する場合、電子伝導性を補うために該電極活物質の表面に炭素コート処理をしなければならない場合がある。
例えば、特許文献１には、一般式ＬｉＭｎＰＯ４で表される電極活物質においてＬｉＦｅＰＯ４からなる被膜層及び炭素を含む被膜層で被膜した電極活物質が開示されている。
Conventionally, lithium metal phosphates such as LiFePO 4 having an olivine crystal structure (space group Pnma) have been used as electrodes for lithium ion secondary batteries and the like. Lithium metal phosphate is excellent in terms of cost, safety, durability, and the like, but is poor in electronic conductivity and Li ion conductivity. When lithium metal phosphate is used as an electrode material, the surface of the electrode active material may need to be subjected to carbon coating treatment in order to supplement electron conductivity.
For example, Patent Document 1 discloses an electrode active material coated with a coating layer made of LiFePO 4 and a coating layer containing carbon in the electrode active material represented by the general formula LiMnPO 4 .
リン酸金属リチウムを使用した電極活物質基体に炭素コート処理を行うと、二次電池の電極として使用したときの充放電特性（特にレート特性）は向上する。しかしながら、この充放電特性がより高いものが求められている。特に、導電性炭素を含む層でなるべく均一に薄く且つ高い被覆率で電極活物質基体の粉体表面を覆い、電子伝導性の高いものが求められている。導電性炭素による被覆率が低いと電子伝導性は低くなる場合があり、導電性炭素が不均一に多く付きすぎると電子伝導性は向上するが、リチウムイオン伝導性は低下する場合があるためである。 When carbon coating treatment is performed on an electrode active material substrate using lithium metal phosphate, charge / discharge characteristics (particularly rate characteristics) are improved when used as an electrode of a secondary battery. However, there is a demand for higher charge / discharge characteristics. In particular, there is a demand for a layer containing conductive carbon that is as thin as possible and covers the powder surface of the electrode active material substrate with a high coverage, and has high electron conductivity. If the coverage with conductive carbon is low, the electronic conductivity may be low, and if too much conductive carbon is attached unevenly, the electronic conductivity will improve, but the lithium ion conductivity may decrease. is there.
そこで、本発明の目的は、リン酸金属リチウムを使用した電極活物質基体の一次粒子の表面を、導電性炭素を含む層をなるべく均一に薄く且つ高い被覆率で覆うことにより、優れた電極特性の電極材料を提供することである。 Accordingly, an object of the present invention is to provide excellent electrode characteristics by covering the surface of primary particles of an electrode active material substrate using lithium metal phosphate with a layer containing conductive carbon as thinly as possible and with a high coverage. It is providing the electrode material of this.
上記課題を解決するための本発明の第１の態様に係る電極材料は、一般式ＬｉＭＰＯ４（ただし、Ｍ＝［ＦｅｔＭｎ１−ｔ］であり、ｔは０以上１以下の数である）で表される電極活物質基体の一次粒子の表面に、導電性炭素を含む層を備え、前記導電性炭素を１．０質量％以上２．５質量％以下含有し、圧縮導電率が１０−２Ｓ／ｃｍ以上であることを特徴とする。 The electrode material according to the first aspect of the present invention for solving the above-mentioned problem is a general formula LiMPO 4 (where M = [Fe t Mn 1-t ], and t is a number of 0 or more and 1 or less. ) On the surface of the primary particles of the electrode active material substrate represented by the following formula: a layer containing conductive carbon, containing 1.0% by mass to 2.5% by mass of the conductive carbon, and having a compressive conductivity of 10 -2 S / cm or more.
本明細書では、一般式ＬｉＭＰＯ４とは、Ｌｉ：Ｍ：Ｐ：Ｏが大凡１：１：１：４となる数の割合で各成分を含有していることを意味する。すなわち、厳密に１：１：１：４の割合で各成分を含有していることや不純物を全く含まないことまでは要求していない。 In this specification, the general formula LiMPO 4 means that Li: M: P: O contains each component at a ratio of approximately 1: 1: 1: 4. That is, it does not require that each component is contained at a ratio of 1: 1: 1: 4 strictly or that no impurities are contained.
圧縮導電率は粉体表面の電子伝導性を反映するので、一般的に電極活物質基体の一次粒子の表面に多く導電性炭素を被覆させると圧縮導電率は高くなる。しかしながら、導電性炭素を多く付けすぎるとリチウムイオン伝導性は低下する場合がある。
本態様の電極材料は、前記電極活物質基体の一次粒子の表面に導電性炭素を含む層を備え、前記導電性炭素を１．０質量％以上２．５質量％以下含有し、圧縮導電率が１０−２Ｓ／ｃｍ以上となる従来にない電極材料である。すなわち、導電性炭素の量が適当でありながら高い圧縮導電率となるように、導電性炭素を含む層により、均一に薄く且つ高い被覆率で、前記電極活物質基体の一次粒子の表面が覆われている。このため、本態様によれば、従来にない優れた電極特性の電極材料を提供することができる。
Since the compressive conductivity reflects the electronic conductivity of the powder surface, generally, when the surface of the primary particles of the electrode active material substrate is coated with a large amount of conductive carbon, the compressive conductivity increases. However, if too much conductive carbon is added, the lithium ion conductivity may decrease.
The electrode material of this aspect includes a layer containing conductive carbon on the surface of the primary particles of the electrode active material substrate, contains 1.0% by mass to 2.5% by mass of the conductive carbon, and has a compressive conductivity. Is an unprecedented electrode material of 10 −2 S / cm or more. That is, the surface of the primary particles of the electrode active material substrate is uniformly and thinly covered with the layer containing the conductive carbon so that the compressive conductivity is high while the amount of the conductive carbon is appropriate. It has been broken. For this reason, according to this aspect, it is possible to provide an electrode material having superior electrode characteristics that has not been obtained conventionally.
上記課題を解決するための本発明の第２の態様に係る電極材料の製造方法は、一般式ＬｉＭＰＯ４（ただし、Ｍ＝［ＦｅｔＭｎ１−ｔ］であり、ｔは０以上１以下の数である）で表される粒状の電極活物質基体と、合成樹脂材料と、有機溶媒とを混合する混合工程と、前記一般式ＬｉＭＰＯ４で表される電極活物質基体の一次粒子の表面に前記合成樹脂材料に由来する導電性炭素を含む層が生成するように、前記混合工程で得られる混合物を焼成する焼成工程と、を有することを特徴とする。 The manufacturing method of the electrode material according to the second aspect of the present invention for solving the above-mentioned problem is a general formula LiMPO 4 (where M = [Fe t Mn 1-t ], and t is 0 or more and 1 or less. A mixing step of mixing a granular electrode active material substrate represented by the formula), a synthetic resin material, and an organic solvent; and a surface of primary particles of the electrode active material substrate represented by the general formula LiMPO 4 A firing step of firing the mixture obtained in the mixing step so that a layer containing conductive carbon derived from the synthetic resin material is generated.
本発明者らは、鋭意検討した結果、粒状の前記電極活物質基体と、合成樹脂材料と、有機溶媒とを混合し、この混合物を焼成することで、電極材料として好適な電極材料を製造することができることを見出した。
本態様によれば、優れた電極特性の電極材料を提供することができる。
As a result of intensive studies, the inventors of the present invention produce a suitable electrode material as an electrode material by mixing the granular electrode active material substrate, a synthetic resin material, and an organic solvent, and firing the mixture. I found that I can do it.
According to this aspect, an electrode material having excellent electrode characteristics can be provided.
本発明の第３の態様に係る電極材料の製造方法は、前記第２の態様において、前記有機溶媒は、リモネンであることを特徴とする。 The method for producing an electrode material according to a third aspect of the present invention is characterized in that, in the second aspect, the organic solvent is limonene.
本発明者らは、鋭意検討した結果、前記有機溶媒としてリモネンを使用することで、特に、電極材料として好適な電極材料を製造することができることを見出した。
本態様によれば、特に優れた電極特性の電極材料を提供することができる。
As a result of intensive studies, the present inventors have found that an electrode material particularly suitable as an electrode material can be produced by using limonene as the organic solvent.
According to this aspect, an electrode material having particularly excellent electrode characteristics can be provided.
本発明の第４の態様に係る電極材料の製造方法は、前記第２又は第３の態様において、前記合成樹脂材料は、ポリスチレンであることを特徴とする。 The electrode material manufacturing method according to a fourth aspect of the present invention is characterized in that, in the second or third aspect, the synthetic resin material is polystyrene.
本発明者らは、鋭意検討した結果、前記合成樹脂材料としてポリスチレンを使用することで、特に、電極材料として好適な電極材料を製造することができることを見出した。
本態様によれば、特に優れた電極特性の電極材料を提供することができる。
As a result of intensive studies, the present inventors have found that an electrode material particularly suitable as an electrode material can be produced by using polystyrene as the synthetic resin material.
According to this aspect, an electrode material having particularly excellent electrode characteristics can be provided.
本発明の第５の態様に係る電極材料の製造方法は、前記第２から第４のいずれか１つの態様において、前記電極材料は、前記導電性炭素を１．０質量％以上２．５質量％以下含有し、圧縮導電率が１０−２Ｓ／ｃｍ以上であることを特徴とする。 The electrode material manufacturing method according to a fifth aspect of the present invention is the electrode material according to any one of the second to fourth aspects, wherein the electrode material contains 1.0% by mass or more and 2.5% by mass of the conductive carbon. % Or less, and the compression conductivity is 10 −2 S / cm or more.
本態様によれば、前記電極活物質基体の一次粒子の表面に導電性炭素を含む層を備え、前記導電性炭素を１．０質量％以上２．５質量％以下含有し、圧縮導電率が１０−２Ｓ／ｃｍ以上となる従来にない電極材料を製造することができる。このため、従来にない優れた電極特性の電極材料を提供することができる。 According to this aspect, a layer containing conductive carbon is provided on the surface of the primary particles of the electrode active material substrate, the conductive carbon is contained in an amount of 1.0% by mass to 2.5% by mass, and the compression conductivity is An unprecedented electrode material of 10 −2 S / cm or more can be produced. For this reason, the electrode material of the outstanding electrode characteristic which is not in the past can be provided.
本発明の第６の態様係る電極材料は、前記第２から第５のいずれか１つの態様において、前記混合工程における前記合成樹脂材料の含有量は、５質量％以上２５質量％以下であることを特徴とする。 In the electrode material according to a sixth aspect of the present invention, in any one of the second to fifth aspects, the content of the synthetic resin material in the mixing step is 5% by mass or more and 25% by mass or less. It is characterized by.
本態様によれば、前記電極活物質基体の一次粒子の表面を、特に好ましい状態で、導電性炭素を含む層を均一に薄く且つ高い被覆率で覆うことができる。このため、特に優れた電極特性の電極材料を提供することができる。なお、前記合成樹脂材料の特に好ましい含有量は１０質量％以上１５質量％以下である。 According to this aspect, the surface of the primary particles of the electrode active material substrate can be uniformly and thinly covered with a high covering rate in a particularly preferable state. For this reason, an electrode material having particularly excellent electrode characteristics can be provided. The particularly preferable content of the synthetic resin material is 10% by mass or more and 15% by mass or less.
以下に、本発明を実施するための好ましい形態について説明する。
＜電極活物質＞
本実施例の電極材料における電極活物質は、一般式ＬｉＭＰＯ４（ただし、Ｍ＝［ＦｅｔＭｎ１−ｔ］であり、ｔは０以上１以下の数である）で表され、電気化学的酸化又は還元に伴ってＬｉイオンを放出又は吸蔵する。そして、前記酸化又は還元の過程で、結晶格子内部で一次元の許容移動方向のみを前記カチオンが移動し得る結晶構造を有する。なお、電極活物質の好ましい一次粒子径は５０ｎｍ以上２００ｎｍ以下である。
Below, the preferable form for implementing this invention is demonstrated.
<Electrode active material>
The electrode active material in the electrode material of this example is represented by the general formula LiMPO 4 (where M = [Fe t Mn 1-t ], t is a number of 0 or more and 1 or less), and is electrochemical. Li ions are released or occluded along with oxidation or reduction. And, in the process of oxidation or reduction, it has a crystal structure in which the cation can move only in the one-dimensional allowable movement direction inside the crystal lattice. In addition, the preferable primary particle diameter of an electrode active material is 50 nm or more and 200 nm or less.
このような電極活物質としては、例えば、ＬｉＭＰＯ４で表わされるオリビン型の結晶構造（斜方晶系、空間群Ｐｎｍａ）を持つものが挙げられる。本明細書では、一般式ＬｉＭＰＯ４とは、Ｌｉ：Ｍ：Ｐ：Ｏが大凡１：１：１：４となる数の割合で各成分を含有していることを意味する。すなわち、厳密に１：１：１：４の割合で各成分を含有していることや不純物を全く含まないことまでは要求していない。 Examples of such an electrode active material include those having an olivine type crystal structure (orthorhombic system, space group Pnma) represented by LiMPO 4 . In this specification, the general formula LiMPO 4 means that Li: M: P: O contains each component at a ratio of approximately 1: 1: 1: 4. That is, it does not require that each component is contained at a ratio of 1: 1: 1: 4 strictly or that no impurities are contained.
また、ＭはＦｅ及びＭｎのうちの少なくともいずれか一つである。このため、これらを複数含む場合、これらの合計数をＭの数としてＬｉ：Ｍ：Ｐ：Ｏが大凡１：１：１：４となるように各成分を含有していれば本発明に含まれる。 M is at least one of Fe and Mn. Therefore, in the case where a plurality of these are included, the total number of these is included in the present invention as long as each component is contained such that Li: M: P: O is approximately 1: 1: 1: 4, where M is the number. It is.
前記電極活物質は、公知の湿式製法、固相焼成製法、あるいは湿式合成による反応中間体の固相焼成製法（例えば所謂ゾル−ゲル製法）等の方法に基づき合成することができ、その製法は特に限定されない。例を挙げると、オリビン型結晶構造を持つＬｉＭＰＯ４に相当する電極活物質乃至それを含む電極材料の製法は、特開２００２−１５１０８２号（湿式製法）、特開２００４−０９５３８５号（湿式製法）、特開２００７−１１９３０４号（湿式製法）、特開平９−１３４７２４号（固相焼成製法）、特開２００４−６３３８６号（固相焼成製法）及び特開２００３−１５７８４５号（ゾル−ゲル製法）等の公報に記載されている。 The electrode active material can be synthesized based on a known wet manufacturing method, solid phase baking manufacturing method, or solid phase baking manufacturing method of a reaction intermediate by wet synthesis (for example, so-called sol-gel manufacturing method). There is no particular limitation. For example, an electrode active material corresponding to LiMPO 4 having an olivine type crystal structure or a method for producing an electrode material containing the same is disclosed in JP-A No. 2002-151082 (wet process) and JP-A No. 2004-095385 (wet process). JP-A No. 2007-119304 (wet manufacturing method), JP-A No. 9-134724 (solid phase baking method), JP-A No. 2004-63386 (solid phase baking method) and JP-A No. 2003-157845 (sol-gel manufacturing method). Are described in such publications.
＜導電性炭素＞
本実施例の電極材料は、電極活物質基体の一次粒子の表面に導電性炭素を含む層を備えるが、該導電性炭素を１．０質量％以上２．５質量％以下含有することが好ましい。導電性炭素を１．０質量％以上２．５質量％以下含有することで、電子伝導性とリチウムイオン伝導性とを共に高く保つことができるためである。
<Conductive carbon>
The electrode material of this example includes a layer containing conductive carbon on the surface of the primary particles of the electrode active material substrate, and preferably contains 1.0% by mass to 2.5% by mass of the conductive carbon. . This is because by containing conductive carbon in an amount of 1.0% by mass or more and 2.5% by mass or less, both electron conductivity and lithium ion conductivity can be kept high.
導電性炭素源となる原料としては、糖類及びビチューメン類のほか、ポリスチレン及びポリビニルアルコール等の合成樹脂材料を用いることができるが、不純物が少なく安価なポリスチレンが特に好ましく用いられる。また、ポリスチレンと、該ポリスチレンの溶媒としての有機溶媒と、前記電極活物質とを混合して前記電極活物質に該ポリスチレンを均一に被覆させ、これを焼成して前記電極活物質基体の一次粒子の表面に導電性炭素を含む層を備えさせるのが好ましい。また、有機溶媒としてはリモネンが特に好ましく用いられる。 As a raw material to be a conductive carbon source, in addition to sugars and bitumen, synthetic resin materials such as polystyrene and polyvinyl alcohol can be used, but inexpensive polystyrene with few impurities is particularly preferably used. Also, polystyrene, an organic solvent as a solvent for the polystyrene, and the electrode active material are mixed to uniformly coat the polystyrene on the electrode active material, and this is fired to produce primary particles of the electrode active material substrate. It is preferable to provide a layer containing conductive carbon on the surface. As the organic solvent, limonene is particularly preferably used.
導電性炭素源となる原料としてポリスチレンを用いると、タール及び石炭ピッチ等を用いた場合と比較して不純物の混入を抑制することができる。また、該ポリスチレンの溶媒としてリモネンを用いると、ポリスチレンとリモネンとの相性が特に良いため、夫々を個別に用いた場合と比較して、相乗効果として、導電性炭素を特に均一に薄く前記電極活物質に被覆させることが可能になる。 When polystyrene is used as a raw material to be a conductive carbon source, it is possible to suppress contamination of impurities as compared with the case where tar, coal pitch, or the like is used. In addition, when limonene is used as the solvent for the polystyrene, the compatibility between polystyrene and limonene is particularly good. Therefore, compared with the case where each is used individually, as a synergistic effect, the conductive carbon is made particularly thin and thin. The substance can be coated.
＜電極活物質一次粒子の表面層＞
本実施例の電極材料は、電極活物質基体の一次粒子の表面に導電性炭素を含む層を備えており、１０−２Ｓ／ｃｍ以上であることが好ましい。
圧縮導電率は電極活物質の粉体表面の電子伝導性を反映するため、この数値が高いほど該電極活物質を電極材料として用いた電池の抵抗を減らすことができる。一般的に一般式ＬｉＭＰＯ４（ただしＭ＝［ＦｅｔＭｎ１−ｔ］であり、ここでｔは０以上１以下の数）で表される電極活物質の電子伝導性は、ＬｉＭｎ２Ｏ４やＬｉＣｏＯ２よりも低い。このため、ＬｉＭＰＯ４は電子伝導性を付与しない状態で電極材料として使用できない。このため、電極活物質基体の一次粒子の表面に導電性炭素をコートする。
<Surface layer of primary particles of electrode active material>
The electrode material of this example includes a layer containing conductive carbon on the surface of primary particles of the electrode active material substrate, and is preferably 10 −2 S / cm or more.
Since the compressive conductivity reflects the electronic conductivity of the powder surface of the electrode active material, the higher this value, the lower the resistance of a battery using the electrode active material as an electrode material. Generally, the electronic conductivity of the electrode active material represented by the general formula LiMPO 4 (where M = [Fe t Mn 1-t ], where t is 0 or more and 1 or less) is LiMn 2 O 4. And lower than LiCoO 2 . For this reason, LiMPO 4 cannot be used as an electrode material without imparting electronic conductivity. For this reason, the surface of the primary particles of the electrode active material substrate is coated with conductive carbon.
また、本実施例の電極材料は、一般式ＬｉＭＰＯ４（ただしＭ＝［ＦｅｔＭｎ１−ｔ］であり、ここでｔは０以上１以下の数）で表される電極活物質の一次粒子の表面に、導電性炭素を含む層を備える。なお、該表面層の好ましい厚みは１ｎｍ以上３ｎｍ以下である。 The electrode material of this example is a primary particle of an electrode active material represented by the general formula LiMPO 4 (where M = [Fe t Mn 1-t ], where t is a number of 0 or more and 1 or less). A layer containing conductive carbon is provided on the surface. The preferred thickness of the surface layer is 1 nm or more and 3 nm or less.
以下に、本発明について実施例に基づき詳細に説明する。ただし、本発明はこれらの実施例に制約されない。
［実施例１］
電極活物質としての粒状のＬｉＦｅＰＯ４（ＬＦＰ）と、リモネンと、ポリスチレン（ＰＳ）とを、ＬＦＰ：リモネン：ＰＳが１００：４０：１０となるように混合し、この混合物を窒素気流下で約７００℃にて焼成し、導電性炭素を含む層を被覆した実施例１の電極材料を得た。
Hereinafter, the present invention will be described in detail based on examples. However, the present invention is not limited to these examples.
[Example 1]
Particulate LiFePO 4 (LFP) as an electrode active material, limonene, and polystyrene (PS) are mixed so that LFP: limonene: PS is 100: 40: 10, and this mixture is mixed under nitrogen flow. The electrode material of Example 1 which baked at 700 degreeC and coat | covered the layer containing electroconductive carbon was obtained.
［実施例２］
電極活物質としての粒状のＬｉＦｅＰＯ４（ＬＦＰ）と、リモネンと、ポリスチレン（ＰＳ）とを、ＬＦＰ：リモネン：ＰＳが１００：４０：１５となるように混合し、この混合物を窒素気流下で約７００℃にて焼成し、導電性炭素を含む層を被覆した実施例２の電極材料を得た。
[Example 2]
Granular LiFePO 4 (LFP) as an electrode active material, limonene, and polystyrene (PS) are mixed so that LFP: limonene: PS is 100: 40: 15, and this mixture is mixed under a nitrogen stream. The electrode material of Example 2 which baked at 700 degreeC and coat | covered the layer containing electroconductive carbon was obtained.
［実施例３］
電極活物質としての粒状のＬｉＦｅｔＭｎ１−ｔＰＯ４（ＬＭＦＰ）と、リモネンと、ポリスチレン（ＰＳ）とを、ＬＭＦＰ：リモネン：ＰＳが１００：４０：１０となるように混合し、この混合物を窒素気流下で約７００℃にて焼成し、導電性炭素を含む層を被覆した実施例３の電極材料を得た。なお、本実施例における上記ｔは約０．２である。
[Example 3]
Granular LiFe t Mn 1-t PO 4 (LMFP) as an electrode active material, limonene and polystyrene (PS) are mixed so that LMFP: limonene: PS is 100: 40: 10, and this mixture Was fired at about 700 ° C. under a nitrogen stream to obtain the electrode material of Example 3 in which the layer containing conductive carbon was coated. In the present embodiment, the above t is about 0.2.
［実施例４］
電極活物質としての粒状のＬｉＦｅｔＭｎ１−ｔＰＯ４（ＬＭＦＰ）と、リモネンと、ポリスチレン（ＰＳ）とを、ＬＭＦＰ：リモネン：ＰＳが１００：４０：１５となるように混合し、この混合物を窒素気流下で約７００℃にて焼成し、導電性炭素を含む層を被覆した実施例４の電極材料を得た。なお、本実施例における上記ｔは約０．２である。
[Example 4]
Granular LiFe t Mn 1-t PO 4 (LMFP) as electrode active material, limonene and polystyrene (PS) are mixed so that LMFP: limonene: PS is 100: 40: 15, and this mixture Was fired at about 700 ° C. under a nitrogen stream to obtain the electrode material of Example 4 in which the layer containing conductive carbon was coated. In the present embodiment, the above t is about 0.2.
［比較例１］
電極活物質としての粒状のＬｉＦｅＰＯ４（ＬＦＰ）と、ポリスチレン（ＰＳ）とを、ＬＦＰ：ＰＳが１００：１０となるように混合し、この混合物を窒素気流下で約７００℃にて焼成し、導電性炭素を含む層を被覆した比較例１の電極材料を得た。
[Comparative Example 1]
Granular LiFePO 4 (LFP) as an electrode active material and polystyrene (PS) are mixed so that LFP: PS is 100: 10, and this mixture is fired at about 700 ° C. under a nitrogen stream. An electrode material of Comparative Example 1 was obtained in which a layer containing conductive carbon was coated.
［比較例２］
電極活物質としての粒状のＬｉＦｅＰＯ４（ＬＦＰ）と、ポリアクリロニトリル（ＰＡＮ）とを、ＬＦＰ：ＰＡＮが１００：１０となるように混合し、この混合物を窒素気流下で約７００℃にて焼成し、導電性炭素を含む層を被覆した比較例２の電極材料を得た。
[Comparative Example 2]
Granular LiFePO 4 (LFP) as an electrode active material and polyacrylonitrile (PAN) are mixed so that LFP: PAN is 100: 10, and this mixture is fired at about 700 ° C. under a nitrogen stream. Then, an electrode material of Comparative Example 2 in which a layer containing conductive carbon was coated was obtained.
［比較例３］
電極活物質としての粒状のＬｉＦｅＰＯ４（ＬＦＰ）と、リグニンとを、ＬＦＰ：リグニンが１００：１０となるように混合し、この混合物を窒素気流下で約７００℃にて焼成し、導電性炭素を含む層を被覆した比較例３の電極材料を得た。
[Comparative Example 3]
Particulate LiFePO 4 (LFP) as an electrode active material and lignin are mixed so that LFP: lignin is 100: 10, and this mixture is baked at about 700 ° C. in a nitrogen stream to form conductive carbon. As a result, an electrode material of Comparative Example 3 coated with a layer containing was obtained.
上記実施例１〜４及び比較例１〜３の電極材料の炭素量と圧縮導電率とを測定した。
なお、圧縮導電率の測定は、ケミカルインピーダンスメーター３５３２−８０（日置電機株式会社製）を用い、四端子法を用いて、１００ＭＰａの圧力条件下で測定した。
また、炭素量の測定は、炭素・硫黄分析装置ＥＭＩＡ−２２１Ｖ（株式会社堀場製作所製）を用い、酸素気流中燃焼−赤外線吸収法で測定した。
下記表１は、上記実施例１〜４及び比較例１〜３の電極材料の炭素量と圧縮導電率とをまとめたものであり、これらをグラフにしたものを図１に表す。
The carbon content and compression conductivity of the electrode materials of Examples 1 to 4 and Comparative Examples 1 to 3 were measured.
The compression conductivity was measured using a chemical impedance meter 3532-80 (manufactured by Hioki Electric Co., Ltd.) and using a four-terminal method under a pressure condition of 100 MPa.
The amount of carbon was measured by a carbon / sulfur analyzer EMIA-221V (manufactured by Horiba, Ltd.) by combustion in an oxygen stream-infrared absorption method.
Table 1 below summarizes the carbon content and compression conductivity of the electrode materials of Examples 1 to 4 and Comparative Examples 1 to 3, and a graph of these is shown in FIG.
図１は、実施例１〜４及び比較例１〜３の電極材料の炭素量と圧縮導電率とを表すグラフである。
図１において、横軸は炭素量（質量％）であり、縦軸は圧縮導電率（Ｓ／ｃｍ）である。図中の矢印Ａは、単純に炭素量を増やした場合の圧縮導電率の推移を示している。また、図中の斜線で表された領域Ｒは、電極材料として特に好ましい炭素量と圧縮導電率との領域を示している。具体的には、導電性炭素を１．０質量％以上２．５質量％以下含有し、圧縮導電率が１０−２Ｓ／ｃｍ以上である領域である。
FIG. 1 is a graph showing the carbon content and compression conductivity of the electrode materials of Examples 1 to 4 and Comparative Examples 1 to 3.
In FIG. 1, the horizontal axis represents the amount of carbon (% by mass), and the vertical axis represents the compression conductivity (S / cm). The arrow A in the figure shows the transition of the compressive conductivity when the amount of carbon is simply increased. In addition, a region R indicated by diagonal lines in the drawing indicates a region having a particularly preferable carbon amount and compression conductivity as an electrode material. Specifically, it is an area | region which contains electroconductive carbon 1.0 mass% or more and 2.5 mass% or less, and a compressive conductivity is 10 <-2 > S / cm or more.
図１で表されるように、比較例１〜３で表される電極材料について単純に炭素量を増減しても、図中の領域Ｒには含まれない。同様に、電極活物質基体の一次粒子の表面に導電性炭素を含む層を備える従来の電極材料において、単純に炭素量を増減しても、図中の領域Ｒには含まれない。 As shown in FIG. 1, even if the amount of carbon is simply increased or decreased for the electrode materials represented by Comparative Examples 1 to 3, they are not included in the region R in the figure. Similarly, in the conventional electrode material having a layer containing conductive carbon on the surface of the primary particles of the electrode active material substrate, even if the amount of carbon is simply increased or decreased, it is not included in the region R in the figure.
このように、実施例１〜４で表される電極材料は、従来の電極材料と比較して好ましい炭素量と圧縮導電率との範囲になっている。すなわち、特に好ましい状態で、導電性炭素を含む層を均一に薄く且つ高い被覆率で覆うことができており、特に優れた電極特性の電極材料であると言える。 As described above, the electrode materials represented by Examples 1 to 4 have a preferable carbon amount and compression conductivity range as compared with conventional electrode materials. That is, in a particularly preferable state, the layer containing conductive carbon can be uniformly and thinly covered with a high coverage, and can be said to be an electrode material having particularly excellent electrode characteristics.
Ａ 単純に炭素量を増やした場合の圧縮導電率の推移、
Ｒ 電極材料として好ましい炭素量と圧縮導電率との領域
A Changes in compression conductivity when simply increasing the carbon content,
Region of preferred carbon content and compression conductivity as R electrode material
Claims (2)
前記一般式ＬｉＭＰＯ４で表される電極活物質基体の粒子の表面に前記合成樹脂材料に由来する導電性炭素を含む層が生成するように、前記混合工程で得られる混合物を焼成する焼成工程と、を有する電極材料の製造方法であって、
前記有機溶媒は、リモネンであり、
前記合成樹脂材料は、ポリスチレンであり、
前記電極材料は、
前記導電性炭素を１．０質量％以上２．５質量％以下含有し、
圧縮導電率が１０ −２ Ｓ／ｃｍ以上である
ことを特徴とする電極材料の製造方法。 A granular electrode active material substrate represented by the general formula LiMPO4 (where M = [Fe t Mn 1-t ], t is a number of 0 or more and 1 or less), a synthetic resin material, an organic solvent, Mixing step of mixing,
A firing step of firing the mixture obtained in the mixing step so that a layer containing conductive carbon derived from the synthetic resin material is formed on the surfaces of the particles of the electrode active material substrate represented by the general formula LiMPO4; A method for producing an electrode material comprising:
The organic solvent is limonene;
The synthetic resin material is polystyrene,
The electrode material is
Containing 1.0% by mass to 2.5% by mass of the conductive carbon,
The method for producing an electrode material, wherein the compressive conductivity is 10-2 S / cm or more .
前記混合工程における前記合成樹脂材料の含有量は、５質量％以上２５質量％以下であることを特徴とする電極材料の製造方法。 In the manufacturing method of the electrode material of Claim 1 ,
Content of the said synthetic resin material in the said mixing process is 5 mass% or more and 25 mass% or less, The manufacturing method of the electrode material characterized by the above-mentioned.
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