JP5836254B2 - Conductive composite particles, positive electrode active material, and secondary battery using the same - Google Patents
Conductive composite particles, positive electrode active material, and secondary battery using the same Download PDFInfo
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Description
本発明は、オリビン型シリケート化合物を含む導電性複合粒子、二次電池用正極活物質及びそれを用いた二次電池に関する。 The present invention relates to conductive composite particles containing an olivine-type silicate compound, a positive electrode active material for a secondary battery, and a secondary battery using the same.
リチウムイオン電池等の二次電池は、非水電解質電池の１種であり、携帯電話、デジタルカメラ、ノートＰＣ、ハイブリッド自動車、電気自動車等広い分野に利用されている。リチウムイオン電池は、正極材料としてリチウム金属酸化物を用い、負極材料としてグラファイトなどの炭素材を用いるものが主流となっている。 A secondary battery such as a lithium ion battery is a kind of non-aqueous electrolyte battery, and is used in a wide range of fields such as a mobile phone, a digital camera, a notebook PC, a hybrid vehicle, and an electric vehicle. Lithium ion batteries mainly use lithium metal oxide as a positive electrode material and a carbon material such as graphite as a negative electrode material.
この正極材料としては、コバルト酸リチウム（ＬｉＣｏＯ2）、マンガン酸リチウム（ＬｉＭｎＯ2）、リン酸鉄リチウム（ＬｉＦｅＰＯ4）、ケイ酸鉄リチウム（Ｌｉ2ＦｅＳｉＯ4）等が知られている。このうち、ＬｉＦｅＰＯ4やＬｉ2ＦｅＳｉＯ4等は、オリビン構造を有し、高容量のリチウムイオン電池用正極材料として有用である。 As this positive electrode material, lithium cobaltate (LiCoO 2 ), lithium manganate (LiMnO 2 ), lithium iron phosphate (LiFePO 4 ), lithium iron silicate (Li 2 FeSiO 4 ) and the like are known. Among these, LiFePO 4 and Li 2 FeSiO 4 have an olivine structure and are useful as a positive electrode material for a high capacity lithium ion battery.
二次電池の放電容量は、正極材料の種類によって大きく変化するので、種々のオリビン型化合物が報告され（特許文献１及び２）、さらに前記オリビン型ケイ酸鉄リチウムにＭｎなどをドープすることにより放電容量の向上が検討されている（非特許文献１〜３）。 Since the discharge capacity of the secondary battery varies greatly depending on the type of positive electrode material, various olivine-type compounds have been reported (Patent Documents 1 and 2), and further by doping Mn and the like into the olivine-type lithium iron silicate. Improvement of discharge capacity has been studied (Non-Patent Documents 1 to 3).
一方、オリビン型シリケート化合物のような放電容量の高い正極材料であっても、それ自体の比導電率は低いので、これらの正極材料にアセチレンブラック、ケッチェンブラック等の炭素材料を担持させて導電性を付与させている（特許文献３〜５）。 On the other hand, even a positive electrode material having a high discharge capacity, such as an olivine type silicate compound, has a low specific conductivity, so that a carbon material such as acetylene black or ketjen black is supported on the positive electrode material to conduct electricity. (Patent Documents 3 to 5).
しかしながら、オリビン型シリケート化合物は特に導電性が低く、従来の手段によるカーボンブラック等の担持では十分な導電性が得られず、導電性を高くするためにはカーボンブラック等を過剰に担持させる必要があった。
従って、本発明の課題は、オリビン型シリケート化合物を含有する導電性の高い正極活物質及びそれを用いた二次電池を提供することにある。
However, olivine-type silicate compounds are particularly low in conductivity, and sufficient conductivity cannot be obtained by loading carbon black or the like by conventional means. To increase conductivity, it is necessary to load carbon black or the like excessively. there were.
Therefore, the subject of this invention is providing the positive electrode active material with high electroconductivity containing an olivine type silicate compound, and a secondary battery using the same.
そこで本発明者は、オリビン型シリケート化合物の特性を十分に活かす正極活物質を開発すべく種々検討した結果、オリビン型シリケート化合物と少量のグラフェンとを複合化して微細な粒子とすれば、優れた導電性を有する正極活物質が得られ、これを用いた二次電池は高い充放電容量を示すことを見出し、本発明を完成した。 Therefore, as a result of various studies to develop a positive electrode active material that makes full use of the characteristics of the olivine-type silicate compound, the present inventor is excellent if the olivine-type silicate compound and a small amount of graphene are combined into fine particles. A positive electrode active material having conductivity was obtained, and a secondary battery using the positive electrode active material was found to exhibit a high charge / discharge capacity, thereby completing the present invention.
すなわち、本発明は、（Ａ）オリビン型シリケート化合物と（Ｂ）グラフェンとを質量比（Ａ：Ｂ）で９９：１〜９３：７の割合で含有し、粒子径５〜３０μｍである導電性複合粒子を提供するものである。
また、本発明は、上記の導電性複合粒子からなる正極活物質を提供するものである。
さらに本発明は、上記の正極活物質を含有する二次電池を提供するものである。
That is, the present invention contains (A) an olivine-type silicate compound and (B) graphene in a mass ratio (A: B) in a ratio of 99: 1 to 93: 7 and has a particle size of 5 to 30 μm. A composite particle is provided.
Moreover, this invention provides the positive electrode active material which consists of said electroconductive composite particle.
Furthermore, this invention provides the secondary battery containing said positive electrode active material.
本発明の導電性複合粒子は、オリビン型シリケート化合物の特性を有しつつ、グラフェンにより粒子表面が効率良く被覆されているため優れた導電性を示し、これを用いた二次電池は高い充放電容量を有する。 The conductive composite particle of the present invention has excellent conductivity because the surface of the particle is efficiently coated with graphene while having the characteristics of an olivine type silicate compound, and a secondary battery using this has high charge and discharge. Have capacity.
本発明の導電性複合粒子は、（Ａ）オリビン型シリケート化合物と（Ｂ）グラフェンとを質量比（Ａ：Ｂ）で９９：１〜９３：７の割合で含有し、粒子径５〜３０μｍである。 The conductive composite particles of the present invention contain (A) an olivine-type silicate compound and (B) graphene at a mass ratio (A: B) of 99: 1 to 93: 7, and a particle diameter of 5 to 30 μm. is there.
（Ａ）オリビン型シリケート化合物としては、リチウムイオン、遷移金属イオン及びケイ酸イオン（ＳｉＯ4 4-）を含むオリビン型シリケート化合物が挙げられ、特にリチウムイオン及び遷移金属Ｍ（ＭはＦｅ、Ｎｉ、Ｃｏ、Ａｌ、Ｚｎ、Ｍｎ、Ｖ及びＺｒから選ばれる１種又は２種以上）イオンを含み、かつケイ酸イオン（ＳｉＯ4 4-）を含むオリビン型シリケート化合物が好ましい。 (A) Examples of the olivine-type silicate compound include olivine-type silicate compounds containing lithium ions, transition metal ions and silicate ions (SiO 4 4− ), and in particular lithium ions and transition metals M (M is Fe, Ni, An olivine silicate compound containing one or more selected from Co, Al, Zn, Mn, V and Zr) and containing a silicate ion (SiO 4 4− ) is preferred.
オリビン型シリケート化合物の具体例としては、例えば、以下のものが挙げられる。
Ｌｉ2ＦｅxＭｎyＣｏzＳｉＯ4 ・・・（１）
（式中、ｘ、ｙ及びｚは、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ＜１、ｘ＋ｙ＋ｚ＝１、及びｘ＋ｙ≠０を満たす数を示す。）
Ｌｉa1ＦｅxＭｎyＡｌzＳｉＯ4 ・・・（２）
（式中、ａ1、ｘ、ｙ及びｚは、１＜ａ1≦２、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ＜１、ａ1＋２ｘ＋２ｙ＋３ｚ＝４、及びｘ＋ｙ≠０を満たす数を示す。）
Ｌｉ2Ｍ1ＳｉＯ4-x1Ｆ2x1 ・・・（３）
（式中、Ｍ1はＦｅ、Ｍｎ、Ｃｏ及びＮｉから選ばれる１種又は２種以上を示し、ｘ1は０＜ｘ1≦８を満たす数を示す。）
Ｌｉa2ＦｅxＭｎyＶzＳｉＯ4 ・・・（４）
（式中、ａ2、ｘ、ｙ及びｚは、１＜ａ2≦２、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ＜１、ａ2＋２ｘ＋２ｙ＋（２〜５）ｚ＝４、及びｘ＋ｙ≠０を満たす数を示す。）
Ｌｉ2ＦｅxＭｎyＺｎzＳｉＯ4 ・・・（５）
（式中、ｘ、ｙ及びｚは、０≦ｘ＜１、０≦ｙ＜１、０＜ｚ＜１、ｘ＋ｙ＋ｚ＝１、及びｘ＋ｙ≠０を満たす数を示す。）
Ｌｉ2Ｆｅa3ＮｉbＣｏcＭｎdＺｒx2ＳｉＯ4・・・（６）
（式中、ａ、ｂ、ｃ及びｄは、ａ＋ｂ＋ｃ＋ｄ＝１−２ｘを満たし、ｘ2は、０＜ｘ2＜０．５を満たす数を示す）
Specific examples of the olivine type silicate compound include the following.
Li 2 Fe x Mn y Co z SiO 4 (1)
(In the formula, x, y, and z represent numbers satisfying 0 ≦ x <1, 0 ≦ y <1, 0 <z <1, x + y + z = 1, and x + y ≠ 0.)
Li a1 Fe x Mn y Al z SiO 4 ··· (2)
(Wherein a 1 , x, y and z are 1 <a 1 ≦ 2, 0 ≦ x <1, 0 ≦ y <1, 0 <z <1, a 1 + 2x + 2y + 3z = 4 and x + y ≠ 0. Indicates the number to satisfy.)
Li 2 M 1 SiO 4-x1 F 2x1 (3)
(In the formula, M 1 represents one or more selected from Fe, Mn, Co and Ni, and x 1 represents a number satisfying 0 <x 1 ≦ 8.)
Li a2 Fe x Mn y V z SiO 4 ··· (4)
(Wherein a 2 , x, y and z are 1 <a 2 ≦ 2, 0 ≦ x <1, 0 ≦ y <1, 0 <z <1, a 2 + 2x + 2y + (2-5) z = 4 , And a number satisfying x + y ≠ 0.)
Li 2 Fe x Mn y Zn z SiO 4 (5)
(In the formula, x, y, and z represent numbers satisfying 0 ≦ x <1, 0 ≦ y <1, 0 <z <1, x + y + z = 1, and x + y ≠ 0.)
Li 2 Fe a3 Ni b Co c Mn d Zr x2 SiO 4 (6)
(Wherein, a, b, c and d satisfy a + b + c + d = 1−2x, and x 2 represents a number satisfying 0 <x 2 <0.5)
また、上記オリビン型シリケート化合物は、ドープすることによりＦ等を含有していてもよい。 The olivine type silicate compound may contain F or the like by doping.
（Ａ）オリビン型シリケート化合物のうち、粒子径が小さく、均質なものは、例えば、リチウム含有化合物、遷移金属化合物及びケイ酸化合物を含む混合物を水熱反応させることにより製造できる。 (A) Among olivine-type silicate compounds, those having a small particle size and being homogeneous can be produced by, for example, hydrothermal reaction of a mixture containing a lithium-containing compound, a transition metal compound and a silicate compound.
原料であるリチウム含有化合物としては、水酸化リチウム（例えばＬｉＯＨ・Ｈ2Ｏ）、炭酸リチウム（Ｌｉ2ＣＯ3）、硫酸リチウム、酢酸リチウムが挙げられるが、水酸化リチウム、炭酸リチウムが特に好ましい。水分散液中のリチウム含有化合物の濃度は、０．３０〜３．００ｍｏｌ／ｌが好ましく、さらに１．００〜１．５０ｍｏｌ／ｌが好ましい。 Examples of the lithium-containing compound as a raw material include lithium hydroxide (for example, LiOH.H 2 O), lithium carbonate (Li 2 CO 3 ), lithium sulfate, and lithium acetate, and lithium hydroxide and lithium carbonate are particularly preferable. The concentration of the lithium-containing compound in the aqueous dispersion is preferably 0.30 to 3.00 mol / l, more preferably 1.00 to 1.50 mol / l.
遷移金属化合物としては、鉄化合物、マンガン化合物、コバルト化合物、ニッケル化合物、アルミニウム化合物、亜鉛化合物、パラジウム化合物又はジルコニウム化合物を用いればよい。 As the transition metal compound, an iron compound, a manganese compound, a cobalt compound, a nickel compound, an aluminum compound, a zinc compound, a palladium compound, or a zirconium compound may be used.
鉄化合物、マンガン化合物、コバルト化合物、ニッケル化合物、亜鉛化合物としては、２価の鉄化合物、２価のマンガン化合物、２価のコバルト化合物、２価のニッケル化合物、２価の亜鉛化合物であればよく、例えば、ハロゲン化鉄、ハロゲン化マンガン、ハロゲン化コバルト、ハロゲン化ニッケル、ハロゲン化亜鉛等のハロゲン化物、硫酸鉄、硫酸マンガン、硫酸コバルト、硫酸ニッケル、硫酸亜鉛等の硫酸塩、シュウ酸鉄、酢酸鉄、酢酸マンガン、酢酸コバルト、酢酸ニッケル、酢酸亜鉛等の有機酸塩が挙げられる。 The iron compound, manganese compound, cobalt compound, nickel compound, and zinc compound may be any bivalent iron compound, divalent manganese compound, divalent cobalt compound, divalent nickel compound, or divalent zinc compound. , For example, halides such as iron halide, manganese halide, cobalt halide, nickel halide and zinc halide, sulfates such as iron sulfate, manganese sulfate, cobalt sulfate, nickel sulfate and zinc sulfate, iron oxalate, Examples thereof include organic acid salts such as iron acetate, manganese acetate, cobalt acetate, nickel acetate, and zinc acetate.
アルミニウム化合物としては、３価の化合物であればよく、例えば、ハロゲン化アルミニウム等のハロゲン化物、硫酸アルミニウム等の金属硫酸塩、酢酸アルミニウム、乳酸アルミニウム等の金属有機酸塩が挙げられる。バナジウム化合物としては、ハロゲン化バナジウム等が挙げられる。 The aluminum compound may be a trivalent compound, and examples thereof include halides such as aluminum halide, metal sulfates such as aluminum sulfate, and metal organic acid salts such as aluminum acetate and aluminum lactate. Examples of vanadium compounds include vanadium halides.
ジルコニウム化合物としては、４価の化合物であればよく、例えば、ハロゲン化ジルコニウム、硫酸ジルコニウム、二酢酸酸化ジルコニウム、オクタン酸ジルコニウム、ラウリン酸酸化ジルコニウム等の有機酸塩が挙げられる。 The zirconium compound may be a tetravalent compound, and examples thereof include organic acid salts such as zirconium halide, zirconium sulfate, zirconium diacetate oxide, zirconium octoate, and zirconium laurate oxide.
反応混合液中の遷移金属化合物の濃度は、０．１５〜１.５０ｍｏｌ／ｌが好ましく、さらに０．５０〜０．７５ｍｏｌ／ｌが好ましい。 The concentration of the transition metal compound in the reaction mixture is preferably 0.15 to 1.50 mol / l, more preferably 0.50 to 0.75 mol / l.
ケイ酸化合物としては、反応性のあるシリカ化合物であれば特に限定されず、非晶質シリカ、Ｎａ4ＳｉＯ4やＮａ4ＳｉＯ4・ｎＨ2Ｏ（例えばＮａ4ＳｉＯ4・Ｈ2Ｏ）が好ましい。このうちＮａ4ＳｉＯ4を用いた場合、反応混合液が塩基性になるので、より好ましい。
ケイ酸化合物の濃度は、０．１５〜１.５０ｍｏｌ／ｌが好ましく、さらに０．５０〜０．７５ｍｏｌ／ｌが好ましい。
The silicic acid compound is not particularly limited as long as it is a reactive silica compound, and amorphous silica, Na 4 SiO 4 and Na 4 SiO 4 .nH 2 O (for example, Na 4 SiO 4 .H 2 O) can be used. preferable. Of these, the use of Na 4 SiO 4 is more preferable because the reaction mixture becomes basic.
The concentration of the silicate compound is preferably 0.15 to 1.50 mol / l, more preferably 0.50 to 0.75 mol / l.
上記リチウム含有化合物、遷移金属化合物及びケイ酸化合物を含有する混合物は、副反応を防止し、ケイ酸化合物の溶解性の点から、水を用い、塩基性の水分散液とするのがよい。具体的には、該水分散液のｐＨは、１２．０〜１４．５であるのが好ましい。該水分散液のｐＨの調整は、塩基、例えば、水酸化ナトリウムを添加することにより行ってもよいが、ケイ酸化合物としてＮａ4ＳｉＯ4を用いるのが好ましい。 The mixture containing the lithium-containing compound, the transition metal compound and the silicate compound is preferably a basic aqueous dispersion using water from the viewpoint of solubility of the silicate compound, preventing side reactions. Specifically, the pH of the aqueous dispersion is preferably 12.0 to 14.5. The pH of the aqueous dispersion may be adjusted by adding a base such as sodium hydroxide, but it is preferable to use Na 4 SiO 4 as the silicate compound.
水分散液を作製するにあたり、遷移金属化合物として、例えば、金属硫酸塩を用いる場合、副反応を抑制する点から、かかる金属硫酸塩とは別に、リチウム化合物、ケイ酸化合物及び界面活性剤と、酸化防止剤とを含有する塩基性水分散液を予め調製しておくのが好ましい。この場合、該水分散液と金属硫酸塩とを混合し、水熱反応に付す。リチウム化合物、ケイ酸化合物、界面活性剤及び酸化防止剤の添加順序は特に限定されず、これらの４成分を水に添加してもよい。 In producing an aqueous dispersion, as a transition metal compound, for example, when a metal sulfate is used, a lithium compound, a silicate compound, and a surfactant, in addition to the metal sulfate, from the viewpoint of suppressing side reactions, It is preferable to prepare in advance a basic aqueous dispersion containing an antioxidant. In this case, the aqueous dispersion and the metal sulfate are mixed and subjected to a hydrothermal reaction. The order of addition of the lithium compound, the silicate compound, the surfactant and the antioxidant is not particularly limited, and these four components may be added to water.
また、遷移金属化合物として、例えば、有機酸塩を用いる場合、リチウム化合物、ケイ酸化合物及び界面活性剤と、酸化防止剤とを含有し、さらに有機酸塩を含有する塩基性水分散液を調製するのが好ましい。通常、有機酸塩は固相法に用いられる原料であるが、水熱反応に用いることにより副反応を抑制することができる。 In addition, for example, when an organic acid salt is used as the transition metal compound, a basic aqueous dispersion containing a lithium compound, a silicate compound, a surfactant, and an antioxidant and further containing an organic acid salt is prepared. It is preferable to do this. Usually, an organic acid salt is a raw material used in a solid phase method, but side reactions can be suppressed by using it in a hydrothermal reaction.
酸化防止剤としては、ハイドロサルファイトナトリウム（Ｎａ2Ｓ2Ｏ4）、アンモニア水、亜硫酸ナトリウム等が挙げられる。水分散液中の酸化防止剤の含有量は、多量に添加するとオリビン型シリケート化合物の生成を抑制してしまうため、遷移金属（Ｍ）に対して等モル量以下が好ましく、遷移金属に対してモル比で０．５以下がさらに好ましい。 Examples of the antioxidant include sodium hydrosulfite (Na 2 S 2 O 4 ), aqueous ammonia, sodium sulfite and the like. The content of the antioxidant in the aqueous dispersion is preferably equal to or less than the transition metal (M) because the formation of the olivine-type silicate compound is suppressed when added in a large amount. The molar ratio is more preferably 0.5 or less.
水熱反応に付す際の温度は、１３０〜２５０℃が好ましく、さらに１５０〜２００℃が好ましい。水熱反応は耐圧容器中で行うのが好ましく、１３０〜２５０℃で反応を行う場合この時の圧力は０．３〜４．０ＭＰａとなり、１５０〜２００℃で反応を行う場合の圧力は０．５〜１．６ＭＰａとなる。水熱反応時間は０．５〜２４時間が好ましく、さらに３〜１２時間が好ましい。 130-250 degreeC is preferable and the temperature at the time of attaching | subjecting to a hydrothermal reaction has more preferable 150-200 degreeC. The hydrothermal reaction is preferably performed in a pressure vessel. When the reaction is performed at 130 to 250 ° C, the pressure at this time is 0.3 to 4.0 MPa, and the pressure when the reaction is performed at 150 to 200 ° C is 0. 5 to 1.6 MPa. The hydrothermal reaction time is preferably 0.5 to 24 hours, and more preferably 3 to 12 hours.
なお、前記混合液の作製及び水熱反応は、いずれも非酸素条件下、例えば窒素雰囲気下に行うのが好ましい。 The preparation of the mixed solution and the hydrothermal reaction are preferably performed under non-oxygen conditions, for example, in a nitrogen atmosphere.
当該水熱反応により、粒子径の小さいオリビン型シリケート化合物が高収率で得られ、その結晶度も高い。
水熱反応後、生成したオリビン型シリケート化合物をろ過により採取し、洗浄することによって一次粒子を得る。洗浄は、ケーキ洗浄機能を有した濾過装置を用いて水で行うのが好ましい。
ここで、得られる一次粒子の粒径は、小さい程好ましく、２０〜２００ｎｍが好ましく、さらに２０〜１００ｎｍが好ましい。
By the hydrothermal reaction, an olivine-type silicate compound having a small particle size is obtained in a high yield, and its crystallinity is also high.
After the hydrothermal reaction, the produced olivine-type silicate compound is collected by filtration and washed to obtain primary particles. Washing is preferably carried out with water using a filtration device having a cake washing function.
Here, the particle size of the obtained primary particles is preferably as small as possible, preferably 20 to 200 nm, and more preferably 20 to 100 nm.
次いで乾燥を行う。乾燥手段としては、箱型乾燥機、凍結乾燥、真空乾燥、流動床乾燥機、あるいは、噴霧型乾燥機（スプレードライヤー）を用いることができる。
得られる乾燥物については、乳鉢、ピンミル、ロールミル、クラッシャー等を用いて解砕してもよい。
Then, drying is performed. As the drying means, a box-type dryer, freeze-drying, vacuum drying, fluidized bed dryer, or spray-type dryer (spray dryer) can be used.
About the obtained dried material, you may crush using a mortar, a pin mill, a roll mill, a crusher, etc.
かくして得られる（Ａ）オリビン型シリケート化合物の複合化に用いる（Ｂ）グラフェンは、炭素原子が六角形格子構造をとった単層のシート、すなわち単層のグラファイトである。グラファイトとしては、厚さ１〜３ｎｍであり、大きさが０．０１〜１０μｍのものを用いるのが好ましい。 The (B) graphene used for the composite of the (A) olivine type silicate compound thus obtained is a single layer sheet in which carbon atoms have a hexagonal lattice structure, that is, a single layer graphite. It is preferable to use graphite having a thickness of 1 to 3 nm and a size of 0.01 to 10 μm.
本発明導電性複合粒子中の（Ａ）オリビン型シリケート化合物と（Ｂ）グラフェンとの含有質量比（Ａ：Ｂ）は９９：１〜９３：７であり、９９：１〜９４：６がより好ましく９９：１〜９５：５がさらに好ましい。グラフェンの含有量が１質量部よりも少ないと十分な導電性が得られず、７質量部よりも多いと導電性は得られるが、経済的でなく、さらに充放電の際、リチウムイオンの移動速度を低下させるため好ましくない。 The content mass ratio (A: B) of (A) olivine type silicate compound and (B) graphene in the conductive composite particles of the present invention is 99: 1 to 93: 7, and 99: 1 to 94: 6 is more. 99: 1 to 95: 5 is more preferable. When the content of graphene is less than 1 part by mass, sufficient conductivity cannot be obtained, and when it is more than 7 parts by mass, conductivity is obtained, but it is not economical, and the movement of lithium ions during charging / discharging. This is not preferable because it reduces the speed.
本発明の導電性複合粒子の粒子径は５〜３０μｍであり、７〜２５μｍがより好ましく、１０〜２０μｍがさらに好ましい。粒子径が５μｍ未満の場合は、電極作製の際、塗工性が悪化することがあり、３０μｍを超えると複合粒子の内部に欠陥が生じやすくなる。 The particle diameter of the conductive composite particles of the present invention is 5 to 30 μm, more preferably 7 to 25 μm, still more preferably 10 to 20 μm. When the particle diameter is less than 5 μm, the coatability may be deteriorated during electrode production, and when it exceeds 30 μm, defects are likely to occur inside the composite particles.
本発明の導電性複合粒子においては、（Ａ）オリビン型シリケート化合物粒子の表面に（Ｂ）グラフェンが均一に被覆した状態であるのが好ましく、より具体的には（Ａ）オリビン型シリケート化合物粒子の表面を（Ｂ）グラフェンが網目状に被覆しているのが好ましい。このように、（Ａ）オリビン型シリケート化合物粒子の表面を（Ｂ）グラフェンが均一に被覆していることにより、複合粒子全体の導電性が向上するものと考えられる。 In the conductive composite particles of the present invention, it is preferable that (B) graphene is uniformly coated on the surface of (A) olivine-type silicate compound particles, and more specifically, (A) olivine-type silicate compound particles. It is preferable that the surface of (B) is coated with (B) graphene. Thus, it is considered that the conductivity of the composite particles as a whole is improved by uniformly coating the surface of the (A) olivine-type silicate compound particles with (B) graphene.
また、（Ｂ）グラフェンの被覆厚みは、導電性の点から５〜１００ｎｍが好ましく、５〜５０ｎｍがより好ましい。 In addition, the coating thickness of (B) graphene is preferably 5 to 100 nm, more preferably 5 to 50 nm from the viewpoint of conductivity.
また、本発明の導電性複合粒子の形状は、球状、多角状、立方体状、金平糖状、紡錘状等の形態でよいが、塗工性および導電性の点から、そのアスペクト比は１〜２．５が好ましく、１〜２がより好ましく、１〜１．５がさらに好ましい。またタップ密度は０．８〜２．５ｇ／ｍｌが好ましく、１．２〜２．５ｇ／ｍｌがさらに好ましい。 Further, the shape of the conductive composite particles of the present invention may be spherical, polygonal, cubic, confetti shape, spindle shape, etc., but from the viewpoint of coating property and conductivity, the aspect ratio is 1-2. 0.5 is preferable, 1-2 is more preferable, and 1-1.5 is more preferable. The tap density is preferably 0.8 to 2.5 g / ml, and more preferably 1.2 to 2.5 g / ml.
本発明の導電性複合粒子は、（Ａ）オリビン型シリケート化合物と（Ｂ）グラフェンとをせん断力条件下、さらに圧縮せん断力条件下に混合複合化することにより製造するのが、オリビン型シリケート化合物粒子表面上にグラフェンを均一に被覆する点で好ましい。
せん断力条件、特に圧縮せん断力条件としては、材料の軸に直角方向に一対の力を与える条件であり、例えばシータコンポーザー（徳寿製作所）、メカノハイブリット、コンポジ（日本コークス工業）、ノビルタ、メカノフュージョン（ホソカワミクロン）などの装置を用いて与えることができる。
The conductive composite particles of the present invention are produced by mixing and compounding (A) an olivine type silicate compound and (B) graphene under shear force conditions and further under compressive shear force conditions. This is preferable in that the graphene is uniformly coated on the particle surface.
The shearing force condition, particularly the compressive shearing force condition, is a condition that applies a pair of forces in the direction perpendicular to the axis of the material. (Hosokawamicron) can be used.
これらの装置の運転条件は、水平円筒状、または直立円筒状の混合容器内において、特殊形状のローターが周速２５ｍ／ｓ以上で回転し、混合容器内の内壁とローター先端で、オリビン型シリケート化合物粒子とグラフェンの混合粉体に、均一に圧縮せん断力を加えながら、粒子複合化を行う。処理時間は５〜６０分が好ましく、より好ましくは１０〜３０分である。また、複合化処理においては、容器内の処理物の温度が１００℃以上にならないように、冷却することが好ましい。冷却手段は特に限定されないが、容器を冷却ジャケットなどで覆い、冷却することができる。処理物の温度が１００℃以上になる場合、処理物が酸化し性能低下を引き起こすため、好ましくない。 The operating conditions of these devices are that a specially shaped rotor rotates at a peripheral speed of 25 m / s or more in a horizontal cylindrical or upright cylindrical mixing vessel, and an olivine type silicate at the inner wall of the mixing vessel and the tip of the rotor. Particle compounding is performed while uniformly applying compressive shearing force to the mixed powder of compound particles and graphene. The treatment time is preferably 5 to 60 minutes, more preferably 10 to 30 minutes. Further, in the complexing treatment, it is preferable to cool so that the temperature of the processed material in the container does not become 100 ° C. or higher. The cooling means is not particularly limited, but the container can be covered with a cooling jacket or the like for cooling. When the temperature of the processed product is 100 ° C. or higher, the processed product is oxidized and causes a decrease in performance, which is not preferable.
なお、電池特性をより高める観点から、得られた複合体を焼成してもよい。焼成条件は、不活性ガス雰囲気下又は還元雰囲気下に２２０℃以上、好ましくは２５０℃〜７００℃で１０分〜３時間、好ましくは０．５〜１．５時間行うのが好ましい。 In addition, you may bake the obtained composite body from a viewpoint of improving a battery characteristic more. The baking conditions are 220 ° C. or higher, preferably 250 ° C. to 700 ° C., for 10 minutes to 3 hours, preferably 0.5 to 1.5 hours in an inert gas atmosphere or a reducing atmosphere.
本発明の導電性複合粒子は、導電性に優れており、二次電池用正極活物質として有用である。また、当該導電性複合粒子は、カーボン担持し、次いで焼成することにより、二次電池用正極活物質とすることもできる。カーボン担持は、複合粒子に常法により、グルコース、フルクトース、ポリエチレングリコール、ポリビニルアルコール、カルボキシメチルセルロース、サッカロース、デンプン、デキストリン、クエン酸等の炭素源及び水を添加し、次いで焼成すればよい。なかでも、コストの面から、炭素源としてグルコースを用いるのが好ましい。焼成条件は、不活性ガス雰囲気下又は還元条件下に４００℃以上、好ましくは４００〜８００℃で１０分〜３時間、好ましくは０．５〜１．５時間行うのが好ましい。かかる処理により複合粒子表面にカーボンが担持された正極活物質とすることができる。炭素源の使用量は、複合粒子１００質量部に対し、炭素源に含まれる炭素として３〜１５質量部が好ましく、炭素源に含まれる炭素として５〜１０質量部がさらに好ましい。 The conductive composite particles of the present invention are excellent in conductivity and are useful as a positive electrode active material for a secondary battery. In addition, the conductive composite particles can be used as a positive electrode active material for a secondary battery by carrying carbon and then firing. Carbon support may be obtained by adding a carbon source such as glucose, fructose, polyethylene glycol, polyvinyl alcohol, carboxymethyl cellulose, saccharose, starch, dextrin, citric acid and water to the composite particles and then baking. Especially, it is preferable to use glucose as a carbon source from the surface of cost. The firing conditions are 400 ° C. or higher, preferably 400 to 800 ° C. for 10 minutes to 3 hours, preferably 0.5 to 1.5 hours under an inert gas atmosphere or reducing conditions. By this treatment, a positive electrode active material in which carbon is supported on the composite particle surface can be obtained. The amount of the carbon source used is preferably 3 to 15 parts by mass as carbon contained in the carbon source and more preferably 5 to 10 parts by mass as carbon contained in the carbon source with respect to 100 parts by mass of the composite particles.
得られた二次電池用正極活物質は、充放電容量の点で優れており、非常に有用な二次電池を得ることができる。本発明の二次電池正極活物質を適用できる二次電池としては、リチウムイオン二次電池であればよく、正極と負極と電解液とセパレータを必須構成とするものであれば特に限定されない。 The obtained positive electrode active material for a secondary battery is excellent in terms of charge / discharge capacity, and a very useful secondary battery can be obtained. The secondary battery to which the secondary battery positive electrode active material of the present invention can be applied may be a lithium ion secondary battery, and is not particularly limited as long as it has a positive electrode, a negative electrode, an electrolytic solution, and a separator as essential components.
ここで、負極については、リチウムイオンを充電時には吸蔵し、かつ放電時には放出することができれば、その材料構成で特に限定されるものではなく、公知の材料構成のものを用いることができる。たとえば、リチウム金属、グラファイト又は非晶質炭素等の炭素材料等である。そしてリチウムを電気化学的に吸蔵・放出し得るインターカレート材料で形成された電極、特に炭素材料を用いることが好ましい。 Here, as long as lithium ions can be occluded at the time of charging and released at the time of discharging, the material structure is not particularly limited, and a known material structure can be used. For example, a carbon material such as lithium metal, graphite, or amorphous carbon. It is preferable to use an electrode formed of an intercalating material capable of electrochemically inserting and extracting lithium, particularly a carbon material.
電解液は、有機溶媒に支持塩を溶解させたものである。有機溶媒は、通常リチウムイオン二次電池の電解液の用いられる有機溶媒であれば特に限定されるものではなく、例えば、カーボネート類、ハロゲン化炭化水素、エーテル類、ケトン類、ニトリル類、ラクトン類、オキソラン化合物等を用いることができる。 The electrolytic solution is obtained by dissolving a supporting salt in an organic solvent. The organic solvent is not particularly limited as long as it is an organic solvent that is usually used for an electrolyte solution of a lithium ion secondary battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones An oxolane compound or the like can be used.
支持塩は、その種類が特に限定されるものではないが、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4及びＬｉＡｓＦ6から選ばれる無機塩、該無機塩の誘導体、ＬｉＳＯ3ＣＦ3、ＬｉＣ（ＳＯ3ＣＦ3）2及びＬｉＮ（ＳＯ3ＣＦ3）2、ＬｉＮ（ＳＯ2Ｃ2Ｆ5）2及びＬｉＮ（ＳＯ2ＣＦ3）（ＳＯ2Ｃ4Ｆ9）から選ばれる有機塩、並びに該有機塩の誘導体の少なくとも１種であることが好ましい。 The type of the supporting salt is not particularly limited, but an inorganic salt selected from LiPF 6 , LiBF 4 , LiClO 4 and LiAsF 6 , a derivative of the inorganic salt, LiSO 3 CF 3 , LiC (SO 3 CF 3 ) 2 and LiN (SO 3 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 and LiN (SO 2 CF 3 ) (SO 2 C 4 F 9 ), and organic salt derivatives It is preferable that it is at least 1 sort of.
セパレータは、正極及び負極を電気的に絶縁し、電解液を保持する役割を果たすものである。たとえば、多孔性合成樹脂膜、特にポリオレフィン系高分子（ポリエチレン、ポリプロピレン）の多孔膜を用いればよい。 The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. For example, a porous synthetic resin film, particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used.
以下、本発明について、実施例に基づき具体的に説明するが、本発明はこれら実施例に限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.
［参考例１］
ＬｉＯＨ・Ｈ2Ｏ ４２．０ｇ（１．０ｍｏｌ）、Ｎａ4ＳｉＯ4・ｎＨ2Ｏ １４０．０ｇ（０．５ｍｏｌ）、Ｎａ2Ｓ2Ｏ4 ８．７ｇ（０．０５ｍｏｌ）に超純水４００ｃｍ3を加えて混合した（この時のｐＨは約１３）。この水分散液にＦｅＳＯ4・７Ｈ2Ｏ６２．６ｇ（０．２２５ｍｏｌ）、ＭｎＳＯ4・５Ｈ2Ｏ ５４．２ｇ（０．２２５ｍｏｌ）及びＺｒ（ＳＯ4）2・４Ｈ2Ｏ７．１ｇ（０．０２５ｍｏｌ）を添加し、混合した。得られた混合液をオートクレーブに投入し、１５０℃で１６ｈｒ水熱反応を行った。反応液をろ過後、凍結乾燥し（約１２時間）、粉末を得た。得られた粉末の平均粒径は、５６ｎｍであった。
[Reference Example 1]
LiOH.H 2 O 42.0 g (1.0 mol), Na 4 SiO 4 .nH 2 O 140.0 g (0.5 mol), Na 2 S 2 O 4 8.7 g (0.05 mol) and ultrapure water 400 cm 3 was added and mixed (the pH at this time was about 13). In this aqueous dispersion, 62.6 g (0.225 mol) of FeSO 4 .7H 2 O, 54.2 g (0.225 mol) of MnSO 4 .5H 2 O and 7.1 g (0.025 mol) of Zr (SO 4 ) 2 .4H 2 O were added. ) Was added and mixed. The obtained mixed liquid was put into an autoclave and subjected to a hydrothermal reaction at 150 ° C. for 16 hours. The reaction solution was filtered and freeze-dried (about 12 hours) to obtain a powder. The average particle size of the obtained powder was 56 nm.
［参考例２］
ＬｉＯＨ・Ｈ2Ｏ ４２．０ｇ（１．０ｍｏｌ）、Ｎａ4ＳｉＯ4・ｎＨ2Ｏ １４０．０ｇ（０．５ｍｏｌ）、Ｎａ2Ｓ2Ｏ4 ８．７ｇ（０．０５ｍｏｌ）に超純水４００ｃｍ3を加えて混合した（この時のｐＨは約１３）。この水分散液にＦｅＳＯ4・７Ｈ2Ｏ ８９．４ｇ（０．３２２ｍｏｌ）、ＭｎＳＯ4・５Ｈ2Ｏ ３８．２ｇ（０．１５８ｍｏｌ）及びＺｒ（ＳＯ4）2・４Ｈ2Ｏ ２．８ｇ（０．０１０ｍｏｌ）を添加し、混合した。得られた混合液をオートクレーブに投入し、１５０℃で１６ｈｒ水熱反応を行った。反応液をろ過後、凍結乾燥し（約１２時間）、粉末を得た。得られた粉末の平均粒径は、６３ｎｍであった。
[Reference Example 2]
LiOH.H 2 O 42.0 g (1.0 mol), Na 4 SiO 4 .nH 2 O 140.0 g (0.5 mol), Na 2 S 2 O 4 8.7 g (0.05 mol) and ultrapure water 400 cm 3 was added and mixed (the pH at this time was about 13). In this aqueous dispersion, 89.4 g (0.322 mol) of FeSO 4 .7H 2 O, 38.2 g (0.158 mol) of MnSO 4 .5H 2 O and 2.8 g (0) of Zr (SO 4 ) 2 .4H 2 O were added. .010 mol) was added and mixed. The obtained mixed liquid was put into an autoclave and subjected to a hydrothermal reaction at 150 ° C. for 16 hours. The reaction solution was filtered and freeze-dried (about 12 hours) to obtain a powder. The average particle size of the obtained powder was 63 nm.
［参考例３］
ＬｉＯＨ・Ｈ2Ｏ ４２．０ｇ（１．０ｍｏｌ）、Ｎａ4ＳｉＯ4・ｎＨ2Ｏ １４０．０ｇ（０．５ｍｏｌ）、Ｎａ2Ｓ2Ｏ4 ８．７ｇ（０．０５ｍｏｌ）に超純水４００ｃｍ3を加えて混合した（この時のｐＨは約１３）。この水分散液にＭｎＳＯ4・５Ｈ2Ｏ １０８．５ｇ（０．４５ｍｏｌ）及びＺｒ（ＳＯ4）2・４Ｈ2Ｏ７．１ｇ（０．０２５ｍｏｌ）を添加し、混合した。得られた混合液をオートクレーブに投入し、１５０℃で１６ｈｒ水熱反応を行った。反応液をろ過後、凍結乾燥し（約１２時間）、粉末を得た。得られた粉末の平均粒径は、５８ｎｍであった。
[Reference Example 3]
LiOH.H 2 O 42.0 g (1.0 mol), Na 4 SiO 4 .nH 2 O 140.0 g (0.5 mol), Na 2 S 2 O 4 8.7 g (0.05 mol) and ultrapure water 400 cm 3 was added and mixed (the pH at this time was about 13). To this aqueous dispersion, 108.5 g (0.45 mol) of MnSO 4 .5H 2 O and 7.1 g (0.025 mol) of Zr (SO 4 ) 2 .4H 2 O were added and mixed. The obtained mixed liquid was put into an autoclave and subjected to a hydrothermal reaction at 150 ° C. for 16 hours. The reaction solution was filtered and freeze-dried (about 12 hours) to obtain a powder. The average particle size of the obtained powder was 58 nm.
［実施例１］
参考例１で得られた粉末１９６ｇと市販グラフェン粉末（ＸＧ Ｓｃｉｅｎｃｅｓ社製、平均粒径０．２μｍ）４ｇとを予め混合して混合物を得て、得られた混合物を微粒子複合化装置ノビルタ（ホソカワミクロン社製）に投入し、３５〜４５℃で３０分間混合して、複合体Ａを得た。得られた複合体Ａの平均粒径は、１７μｍであり、タップ密度は１．６１ｇ／ｃｍ3であった。得られた複合体ＡのＳＥＭ像を図１に示す。
[Example 1]
196 g of the powder obtained in Reference Example 1 and 4 g of commercially available graphene powder (manufactured by XG Sciences, average particle size: 0.2 μm) were mixed in advance to obtain a mixture, and the resulting mixture was mixed with a fine particle composite apparatus Nobilta (Hosokawa Micron). And mixed at 35 to 45 ° C. for 30 minutes to obtain a composite A. The composite A thus obtained had an average particle diameter of 17 μm and a tap density of 1.61 g / cm 3 . The SEM image of the obtained composite A is shown in FIG.
［実施例２］
参考例２で得られた粉末１９２ｇと市販グラフェン粉末（ＸＧ Ｓｃｉｅｎｃｅｓ社製、平均粒径０．２μｍ）８ｇとを予め混合して混合物を得て、得られた混合物を微粒子複合化装置ノビルタ（ホソカワミクロン社製）に投入し、３５〜４５℃で３０分間混合して、複合体Ｂを得た。得られた複合体Ｂの平均粒径は、１８μｍであり、タップ密度は１．５２ｇ／ｃｍ3であった。得られた複合体ＢのＳＥＭ像を図２に示す。
[Example 2]
192 g of the powder obtained in Reference Example 2 and 8 g of commercially available graphene powder (manufactured by XG Sciences, average particle size: 0.2 μm) were mixed in advance to obtain a mixture, and the resulting mixture was mixed with a fine particle composite apparatus Nobilta (Hosokawa Micron). And mixed for 30 minutes at 35 to 45 ° C. to obtain a composite B. The average particle diameter of the obtained composite B was 18 μm, and the tap density was 1.52 g / cm 3 . The SEM image of the obtained composite B is shown in FIG.
［実施例３］
参考例３で得られた粉末１９２ｇと市販グラフェン粉末（ＸＧ Ｓｃｉｅｎｃｅｓ社製、平均粒径０．２μｍ）８ｇとを予め混合して混合物を得て、得られた混合物を微粒子複合化装置ノビルタ（ホソカワミクロン社製）に投入し、３５〜４５℃で３０分間混合して、複合体Ｃを得た。得られた複合体Ｃの平均粒径は、１６μｍであり、タップ密度は１．４９ｇ／ｃｍ3であった。得られた複合体ＣのＳＥＭ像を図３に示す。
[Example 3]
192 g of the powder obtained in Reference Example 3 and 8 g of commercially available graphene powder (manufactured by XG Sciences, average particle size 0.2 μm) were mixed in advance to obtain a mixture, and the resulting mixture was mixed with a fine particle composite apparatus Nobilta (Hosokawa Micron). And mixed for 30 minutes at 35 to 45 ° C. to obtain a composite C. The obtained composite C had an average particle size of 16 μm and a tap density of 1.49 g / cm 3 . The SEM image of the obtained composite C is shown in FIG.
［比較例１］
参考例１で得られた粉末１９６ｇと４ｇとケッチェンブラック（ライオン社製、平均粒径３０ｎｍ）を予め混合して混合物を得て、得られた混合物を微粒子複合化装置ノビルタ（ホソカワミクロン社製）に投入し、３５〜４５℃で３０分間混合して、複合体Ｄを得た。得られた複合体Ｄの平均粒径は、２３μｍであり、タップ密度は１．４５ｇ／ｃｍ3であった。得られた複合体ＤのＳＥＭ像を図４に示す。
[Comparative Example 1]
196 g and 4 g of the powder obtained in Reference Example 1 and Ketjen black (made by Lion, average particle size 30 nm) were mixed in advance to obtain a mixture, and the resulting mixture was mixed with a fine particle composite apparatus Nobilta (made by Hosokawa Micron). And mixed at 35 to 45 ° C. for 30 minutes to obtain a complex D. The average particle diameter of the obtained composite D was 23 μm, and the tap density was 1.45 g / cm 3 . The SEM image of the obtained composite D is shown in FIG.
［比較例２］
参考例１で得られた粉末１９６ｇと４ｇとアセチレンブラック（電気化学工業社製、平均粒径３５ｎｍ）を予め混合して混合物を得て、得られた混合物を微粒子複合化装置ノビルタ（ホソカワミクロン社製）に投入し、３５〜４５℃で３０分間混合して、複合体Ｅを得た。得られた複合体Ｅの平均粒径は、１０μｍであり、タップ密度は１．３２ｇ／ｃｍ3であった。得られた複合体ＥのＳＥＭ像を図５に示す。
[Comparative Example 2]
196 g and 4 g of the powder obtained in Reference Example 1 and acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., average particle size 35 nm) were mixed in advance to obtain a mixture, and the resulting mixture was mixed with a fine particle composite apparatus Nobilta (manufactured by Hosokawa Micron Co., Ltd.). ) And mixed at 35 to 45 ° C. for 30 minutes to obtain a complex E. The average particle size of the obtained composite E was 10 μm, and the tap density was 1.32 g / cm 3 . The SEM image of the obtained composite E is shown in FIG.
実施例１で得られた複合体Ａと比較例１で得られた複合体ＤのＳＥＭ像の表面拡大像（１万倍）を、図６及び図７に示す。図６と図７の対比から、実施例１の複合体Ａは、（Ａ）オリビン型シリケート化合物の表面をグラフェンが均一に被覆していることがわかる。 The surface enlarged images (10,000 times) of the SEM images of the composite A obtained in Example 1 and the composite D obtained in Comparative Example 1 are shown in FIGS. 6 and 7. From the comparison between FIG. 6 and FIG. 7, it can be seen that in the complex A of Example 1, the surface of the (A) olivine silicate compound is uniformly coated with graphene.
［試験例１］
実施例１〜３、および比較例１〜２で得られた複合体を用い、リチウムイオン二次電池の正極を作製した。実施例１〜３、および比較例１〜２で得られた複合体、ケッチェンブラック（導電剤）、ポリフッ化ビニリデン（粘結剤）を重量比７５：１５：１０の配合割合で混合し、これにＮ−メチル−２−ピロリドンを加えて充分混練し、正極スラリーを調製した。正極スラリーを厚さ２０μｍのアルミニウム箔からなる集電体に塗工機を用いて塗布し、８０℃で１２時間の真空乾燥を行った。その後、φ１４ｍｍの円盤状に打ち抜いてハンドプレスを用いて１６ＭＰａで２分間プレスし、正極とした。
[Test Example 1]
Using the composites obtained in Examples 1 to 3 and Comparative Examples 1 to 2, positive electrodes of lithium ion secondary batteries were produced. The composites obtained in Examples 1 to 3 and Comparative Examples 1 to 2, Ketjen Black (conductive agent), polyvinylidene fluoride (binding agent) were mixed at a weight ratio of 75:15:10, N-methyl-2-pyrrolidone was added to this and kneaded sufficiently to prepare a positive electrode slurry. The positive electrode slurry was applied to a current collector made of an aluminum foil having a thickness of 20 μm using a coating machine, and vacuum dried at 80 ° C. for 12 hours. Thereafter, it was punched into a disk shape of φ14 mm and pressed at 16 MPa for 2 minutes using a hand press to obtain a positive electrode.
次いで、上記の正極を用いてコイン型リチウムイオン二次電池を構築した。負極には、φ１５ｍｍに打ち抜いたリチウム箔を用いた。電解液には、エチレンカーボネート及びエチルメチルカーボネートを体積比１：１の割合で混合した混合溶媒に、ＬＩＰＦ6を１ｍｏｌ／ｌの濃度で溶解したものを用いた。セパレータには、ポリプロピレンなどの高分子多孔フィルムなど、公知のものを用いた。これらの電池部品を露点が−５０℃以下の雰囲気で常法により組み込み収容し、コイン型リチウム二次電池（ＣＲ−２０３２）を製造した。 Next, a coin-type lithium ion secondary battery was constructed using the positive electrode. A lithium foil punched to φ15 mm was used for the negative electrode. As the electrolytic solution, a solution obtained by dissolving LIPF 6 at a concentration of 1 mol / l in a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 1 was used. As the separator, a known one such as a polymer porous film such as polypropylene was used. These battery components were assembled and housed in a conventional manner in an atmosphere with a dew point of −50 ° C. or lower to produce a coin-type lithium secondary battery (CR-2032).
製造したリチウムイオン二次電池を用いて定電流密度での充放電を１サイクル行った。このときの充電条件は電流０．１ＣＡ（３３ｍＡ／ｇ）、電圧４．５Ｖの定電流定電圧充電とし、放電条件は電流０．１ＣＡ、終止電圧１．５Ｖの定電流放電とした。温度は全て３０℃とした。
実施例１〜３、および比較例１〜２の正極材で構築した電池の充放電曲線を図８〜図１２に示す。図８〜図１０より、本発明の複合粒子を用いた二次電池は、優れた放電容量を示すことがわかる。
One cycle of charge and discharge at a constant current density was performed using the manufactured lithium ion secondary battery. The charging conditions at this time were constant current and constant voltage charging with a current of 0.1 CA (33 mA / g) and a voltage of 4.5 V, and the discharging conditions were constant current discharging with a current of 0.1 CA and a final voltage of 1.5 V. All temperatures were 30 ° C.
The charge / discharge curves of the batteries constructed with the positive electrode materials of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in FIGS. 8 to 10, it can be seen that the secondary battery using the composite particles of the present invention exhibits an excellent discharge capacity.
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