JP3953502B1 - Power storage system - Google Patents
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- JP3953502B1 JP3953502B1 JP2006129399A JP2006129399A JP3953502B1 JP 3953502 B1 JP3953502 B1 JP 3953502B1 JP 2006129399 A JP2006129399 A JP 2006129399A JP 2006129399 A JP2006129399 A JP 2006129399A JP 3953502 B1 JP3953502 B1 JP 3953502B1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Abstract
【課題】耐電圧が高い蓄電システムを提供すること。
【解決手段】有機電解液中に正電極および負電極が浸されてなる蓄電システムにおいて、該有機電解液がリチウム塩を溶質の少なくとも一部として含有し、該正電極が電極活物質として黒鉛質材料を有し、該負電極が電極活物質としてリチウムの吸蔵あるいはインターカレーション／脱インターカレーションが可能な炭素質材料を有する、蓄電システム。
【選択図】なしA power storage system with high withstand voltage is provided.
In a power storage system in which a positive electrode and a negative electrode are immersed in an organic electrolyte, the organic electrolyte contains a lithium salt as at least a part of a solute, and the positive electrode is graphitic as an electrode active material. A power storage system comprising a material, wherein the negative electrode comprises a carbonaceous material capable of occlusion or intercalation / deintercalation of lithium as an electrode active material.
[Selection figure] None
Description
本発明は有機電解液中に炭素質電極が浸されてなる蓄電システムに関する。 The present invention relates to a power storage system in which a carbonaceous electrode is immersed in an organic electrolyte.
キャパシタは蓄電システムの一種であり、大電流で充電放電を繰り返すことができるため、充放電頻度の高い用途に有用である。 A capacitor is a kind of power storage system, and can be repeatedly charged and discharged with a large current. Therefore, the capacitor is useful for applications with a high charge / discharge frequency.
有機電解液中に炭素質電極を浸すと電気二重層キャパシタが得られることは知られている。非特許文献１第３４〜３７頁には、セパレータで２区画に仕切られた槽、槽に満たされた有機電解液、及びそれぞれの区画に浸漬された２つの炭素質電極を有する電気二重層キャパシタが記載されている。炭素質電極には活性炭が使用されている。有機電解液は有機溶媒中に溶質を溶解した溶液である。 It is known that an electric double layer capacitor can be obtained by immersing a carbonaceous electrode in an organic electrolyte. Non-Patent Document 1, pages 34 to 37, an electric double layer capacitor having a tank partitioned into two sections by a separator, an organic electrolyte filled in the tank, and two carbonaceous electrodes immersed in each section Is described. Activated carbon is used for the carbonaceous electrode. An organic electrolytic solution is a solution in which a solute is dissolved in an organic solvent.
電極部材として使用する際には、活性炭は、金属シートや金属箔で裏打ちすることによって層状に成形されている。電気はこの金属シートや金属箔を通じて槽に導入され、槽から引き出される。通電すると、活性炭の層は槽内で分極することによって静電容量を発現する。活性炭のように、分極して静電容量を示す材料を電極活物質という。電極活物質を層状に成形したものを分極性電極という。また、電極活物質を支持する導電材を集電極という。 When used as an electrode member, activated carbon is formed into a layer by lining it with a metal sheet or metal foil. Electricity is introduced into the tank through the metal sheet or metal foil and drawn out of the tank. When energized, the activated carbon layer develops capacitance by being polarized in the bath. A material such as activated carbon that polarizes and exhibits capacitance is called an electrode active material. The electrode active material formed into a layer is called a polarizable electrode. A conductive material that supports the electrode active material is called a collector electrode.
ここで、活性炭とは、無数の微細な孔を有するために非常に大きな比表面積を有する無定形炭素をいう。本明細書では、アルカリ賦活や水蒸気賦活など各種合成法により合成された、BET表面積が約５００ｍ２／ｇ以上の比表面積を有する無定形炭素を活性炭と呼ぶ。 Here, the activated carbon refers to amorphous carbon having a very large specific surface area because it has countless fine pores. In the present specification, amorphous carbon having a specific surface area with a BET surface area of about 500 m 2 / g or more synthesized by various synthesis methods such as alkali activation and water vapor activation is referred to as activated carbon.
特許文献１および２には、電気二重層キャパシタに用いる電極活物質として、非多孔性炭素質材料が記載されている。この炭素質材料は黒鉛類似の微結晶炭素を有し、比表面積は活性炭と比較して小さい。非多孔性炭素質材料は、電圧を印加すると、黒鉛類似の微結晶炭素にイオンが特殊な吸着をすることで、電気二重層を形成すると考えられている。
特許文献３には、蓄電要素に用いる電極活物質として黒鉛が記載されている。ここでは、特に本発明者らの研究によって、黒鉛を用いた電極は耐電圧性が高く、電気二重層キャパシタのエネルギー密度が顕著に向上することが示されている。しかしながら、分極性電極の耐電圧性が高いとはいっても、出現容量が低いので、その効果は限定的となっている。 Patent Document 3 describes graphite as an electrode active material used for a power storage element. Here, in particular, studies by the present inventors have shown that an electrode using graphite has high voltage resistance, and the energy density of the electric double layer capacitor is remarkably improved. However, even though the voltage resistance of the polarizable electrode is high, the effect is limited because the appearance capacity is low.
電気自動車、電池、発電装置等の補助電源として実用に供するためには、電気二重層キャパシタのエネルギー密度をさらに向上させることが好ましく、そのためには特に耐電圧を高めることが有効である。 In order to be put into practical use as an auxiliary power source for electric vehicles, batteries, power generators, etc., it is preferable to further improve the energy density of the electric double layer capacitor, and for that purpose, it is particularly effective to increase the withstand voltage.
特許文献４には、耐電圧の高い電気二重層キャパシタが記載されている。この電気二重層キャパシタは、有機電解液中に正電極および負電極が浸された構成を有し、有機電解液がリチウム塩を溶質として含有し、負電極がリチウムのインターカレーション／脱インターカレーションが可能な炭素材料を有している。しかしながら、この蓄電システムは耐電圧がせいぜい２．７Ｖであり、実用的に要求される耐電圧のレベルには達していない。 Patent Document 4 describes an electric double layer capacitor having a high withstand voltage. This electric double layer capacitor has a configuration in which a positive electrode and a negative electrode are immersed in an organic electrolyte, the organic electrolyte contains a lithium salt as a solute, and the negative electrode is an intercalation / deintercalation of lithium. Carbon material that can be used. However, this power storage system has a withstand voltage of 2.7 V at most, and has not reached the practically required withstand voltage level.
特許文献５には、ホウ素又はホウ素化合物を含有する炭素材料を黒鉛化して得られるホウ素含有黒鉛粒子を含有する正電極、及び活性炭粒子を含有する負電極を有機電解液中に浸してなる電気化学素子が記載されている。この有機電解液はリチウム塩を溶質として含有してもよい。
しかしながら、ここでは、ホウ素を含有しない合成黒鉛材料もしくは天然黒鉛材料について、結晶子内部に存在する格子欠陥の量が僅かであり、正電極に用いると充放電での劣化が大きく、電気化学素子の容量が維持されない、と説明されている。 However, here, for synthetic graphite materials or natural graphite materials that do not contain boron, the amount of lattice defects present inside the crystallite is small, and when used for the positive electrode, the deterioration due to charge / discharge is large, and the electrochemical device It is explained that capacity is not maintained.
本発明は上記従来の問題を解決するものであり、その目的とするところは、耐電圧が高い蓄電システムを提供することにある。 The present invention solves the above-described conventional problems, and an object of the present invention is to provide a power storage system having a high withstand voltage.
本発明は、
有機溶媒中に溶質を溶解させた有機電解液中に正電極および負電極が浸されてなる蓄電システムにおいて、
該有機電解液がリチウム塩を溶質の少なくとも一部として含有し、
該正電極が、電極活物質として、炭素の結晶構造中に存在する六方晶系構造に対する菱面体晶系構造の割合が３０％以上である炭素質材料を有し、
該負電極が電極活物質としてリチウムの吸蔵あるいはインターカレーション／脱インターカレーションが可能な炭素質材料を有する、蓄電システムを提供するものであり、そのことにより上記目的が達成される。
The present invention
In a power storage system in which a positive electrode and a negative electrode are immersed in an organic electrolytic solution in which a solute is dissolved in an organic solvent ,
The organic electrolyte contains a lithium salt as at least part of a solute;
The positive electrode has , as an electrode active material , a carbonaceous material in which the ratio of rhombohedral structure to hexagonal structure existing in the crystal structure of carbon is 30% or more ;
The negative electrode has a carbonaceous material capable of occluding or intercalating / deintercalating lithium as an electrode active material, and the object is achieved thereby.
本発明の蓄電システムは非常に高い耐電圧を示す。その結果、エネルギー密度も向上している。更に、本発明の蓄電システムは作動電圧が高く、充放電過程における電圧の安定性にも優れている。 The power storage system of the present invention exhibits a very high withstand voltage. As a result, the energy density is also improved. Furthermore, the power storage system of the present invention has a high operating voltage and is excellent in voltage stability during the charge / discharge process.
本発明の蓄電システムでは、正電極の電極活物質として、その炭素質材料の組織に電解質等がインターカレーションあるいは負イオンを吸着可能で、そのため蓄電容量が発現する炭素質材料の粒子を用いる。かかる炭素質材料には、例えば黒鉛及び黒鉛類似の微結晶炭素を有する非多孔性炭素が含まれる。本明細書では、黒鉛及び黒鉛類似の微結晶炭素を有する非多孔性炭素を総称して黒鉛類材料と呼ぶ。 The power storage system of the present invention, as an electrode active material of the positive electrode, can be adsorbed electrolyte and the like to tissue of the carbonaceous material is intercalated or negative ions, therefore use particles of carbonaceous material storage capacity is expressed. Such carbonaceous materials include, for example, non-porous carbon having graphite and graphite-like microcrystalline carbon . In this specification, graphite and non-porous carbon having graphite-like microcrystalline carbon are collectively referred to as graphite materials.
黒鉛類材料の結晶構造には、主として六方晶構造と菱面体晶系構造とがある。六方晶系の結晶構造では、炭素網面はＡ層に対して近接するＢ層がずれたＡＢＡＢ型積層構造をとっている。これに対し、菱面体晶系はＡＢＣＡＢＣ型積層構造をとる結晶構造である。 The crystal structure of the graphite material mainly includes a hexagonal structure and a rhombohedral structure. In the hexagonal crystal structure, the carbon network surface has an ABAB type laminated structure in which the B layer adjacent to the A layer is shifted. On the other hand, the rhombohedral system is a crystal structure having an ABCABC type laminated structure.
本発明の蓄電システムの正電極活物質用黒鉛類材料として、黒鉛類材料中の菱面体晶系構造の量は多ければ多いほどよい。例えば、結晶構造中に存在する六方晶系構造に対する菱面体晶系構造の割合が２０％以上、例えば２５〜５００％、３０％以上、３０〜３００％、３５〜２５０％、５０％以上、５０〜２００％、５０〜１８０％、５０〜１７５％、７０〜２００％、７０〜１８０％、７０〜１７５％、８０〜１８０％、８０〜１７５％、９０〜１８０％、９０〜１７５％、１００〜１８０％、１００〜１７５％、１２０〜１８０％、１２０〜１７５％である。 As the graphite material for the positive electrode active material of the electricity storage system of the present invention, the larger the amount of rhombohedral structure in the graphite material, the better. For example, the ratio of the rhombohedral structure to the hexagonal structure existing in the crystal structure is 20% or more, such as 25 to 500%, 30% or more, 30 to 300%, 35 to 250%, 50% or more, 50 -200%, 50-180%, 50-175%, 70-200%, 70-180%, 70-175%, 80-180%, 80-175%, 90-180%, 90-175%, 100 -180%, 100-175%, 120-180%, 120-175%.
好ましい非多孔性炭素は、例えば、特許文献１及び２に記載されているものである。特に好ましい非多孔性炭素は、以下のようにして製造することができる。
Preferred non-porous carbons are those described in
ニードルコークスグリーンパウダーの粉末を不活性雰囲気下、例えば窒素やアルゴンの雰囲気下で、５００〜９００℃、好ましくは６００〜８００℃、より好ましくは６５０〜７５０℃で、２〜４時間焼成する。この焼成工程において炭素組織の菱面結晶構造が形成されると考えられている。 The powder of needle coke green powder is baked at 500 to 900 ° C., preferably 600 to 800 ° C., more preferably 650 to 750 ° C. for 2 to 4 hours in an inert atmosphere, for example, an atmosphere of nitrogen or argon. It is believed that a rhombohedral crystal structure of carbon structure is formed in this firing step.
焼成した炭素粉末は、重量比で、１.８〜２.２倍、好ましくは２倍程度の水酸化アルカリと混合する。そして粉末混合物を不活性雰囲気下６５０〜８５０℃、好ましくは７００℃から７５０℃で２〜４時間焼成する。この工程はアルカリ賦活と呼ばれ、アルカリ金属原子の蒸気が炭素組織に浸透して炭素の菱面結晶構造を緩める効果があると考えられている。 The calcined carbon powder is mixed with an alkali hydroxide having a weight ratio of 1.8 to 2.2 times, preferably about 2 times. The powder mixture is calcined at 650 to 850 ° C., preferably 700 to 750 ° C. for 2 to 4 hours under an inert atmosphere. This process is called alkali activation and is considered to have an effect of loosening the rhombohedral crystal structure of carbon by the vapor of alkali metal atoms penetrating into the carbon structure.
次いで、得られた粉末混合物を洗浄して水酸化アルカリを除去する。洗浄は、例えば上記アルカリ処理後の炭素から粒子を回収し、ステンレス製のカラムに充填し、１２０℃〜１５０℃、１０〜１００ｋｇｆ、好ましくは１０〜５０ｋｇｆの加圧水蒸気をカラムに導入し、排水のｐＨが〜７となるまで加圧水蒸気を導入し続けることにより行うことができる（通常６〜１０時間）。アルカリ除去工程の終了後、アルゴンや窒素のような不活性ガスをカラムに流し、乾燥して炭素の粉末を得る。 The resulting powder mixture is then washed to remove the alkali hydroxide. In the washing, for example, particles are collected from the carbon after the alkali treatment, filled in a stainless steel column, 120 to 150 ° C., 10 to 100 kgf, preferably 10 to 50 kgf of pressurized water vapor is introduced into the column, This can be done by continuing to introduce pressurized steam until the pH is ˜7 (usually 6-10 hours). After completion of the alkali removal step, an inert gas such as argon or nitrogen is passed through the column and dried to obtain carbon powder.
得られる炭素の粉末は、ＢＥＴ法により測定された比表面積が約５００ｍ2/ｇ以下、好ましくは３０〜３００ｍ２／ｇ、より好ましくは５０〜２００ｍ２／ｇのものであり、各種電解質イオン、溶媒、ＣＯ2ガスなどを取り込める程度の細孔が少ない、いわゆる「非多孔性炭素」に分類される。しかしながら、ニードルコークスグリーンパウダーを原料として、このように調製された炭素粉末は単なる「非多孔性炭素」ではなく、ある程度細孔を有している。すなわち、本発明で用いる炭素粉末は、細孔径０．８ｎｍ以下の細孔容積が０．０１〜０．１ｍｌ/ｇであり、好ましくは０．０２〜０．０６ｍｌ/ｇである。 Powder of the resulting carbon measured specific surface area of about 500 meters 2 / g or less by the BET method, is preferably intended 30~300m 2 / g, more preferably 50 to 200 m 2 / g, various electrolyte ions, It is classified as so-called “non-porous carbon” that has few pores that can take in solvent, CO 2 gas, and the like. However, the carbon powder thus prepared using needle coke green powder as a raw material is not merely “non-porous carbon” but has some pores. That is, the carbon powder used in the present invention has a pore volume with a pore diameter of 0.8 nm or less of 0.01 to 0.1 ml / g, preferably 0.02 to 0.06 ml / g.
本発明で用いるのに好ましい黒鉛は、００２面の結晶格子定数Ｃ0(002)が０．６７０〜０．６８８ｎｍであればよい。平均面間隔ｄ002は０．３４４ｎｍ以下であればよい。 Graphite preferable for use in the present invention may have a 002-plane crystal lattice constant C 0 (002) of 0.670 to 0.688 nm. The average spacing d 002 may be 0.344 nm or less.
黒鉛は一般に六方晶系の結晶構造を有しているといわれているが、多かれ少なかれ菱面体晶との混合物である。また、粉砕や摩砕することにより六方晶系構造から菱面体晶系構造への構造変化が生じることが良く知られている（非特許文献２）。 Graphite is generally said to have a hexagonal crystal structure, but is more or less a mixture with rhombohedral crystals. In addition, it is well known that structural change from a hexagonal structure to a rhombohedral structure occurs by grinding or grinding (Non-patent Document 2).
例えば、黒鉛粒子を剪断力をかけながら粉砕すれば、六方晶系構造から菱面体晶系構造への構造変化が効果的に生じる。好ましい粉砕方法の例は、ボールミルである。粉砕時間は結晶構造の変化が好ましい状態になるまで行なえばよい。一方、菱面体晶は樹脂、コークスなど炭素含有の物質を窒素気流中などで焼成する過程でも生成する。 For example, if graphite particles are pulverized while applying a shearing force, a structural change from a hexagonal structure to a rhombohedral structure is effectively produced. An example of a preferable grinding method is a ball mill . The pulverization time may be performed until the change of the crystal structure becomes a preferable state. On the other hand, rhombohedral crystals are also generated in the process of firing a carbon-containing substance such as resin or coke in a nitrogen stream.
本明細書において、炭素質材料の結晶構造中に存在する六方晶系構造に対する菱面体晶系構造の割合とは、炭素質材料の結晶構造中に存在する菱面体晶系構造の量の、六方晶構造の量に対する割合をいう。つまり、炭素質材料の結晶構造中に存在する六方晶系構造に対する菱面体晶系構造の割合Ｒ（％）は、以下の式にしたがって決定した。 In the present specification, the ratio of the rhombohedral structure to the hexagonal structure present in the crystal structure of the carbonaceous material is the hexagonal amount of the rhombohedral structure present in the crystal structure of the carbonaceous material. The ratio to the amount of crystal structure. That is, the ratio R (%) of the rhombohedral structure to the hexagonal structure existing in the crystal structure of the carbonaceous material was determined according to the following formula.
［数１］
Ｒ（％）＝（Ｉ（１０１−Ｒ）／Ｉ（１０１−Ｈ））×１００ （１）
［式中、Ｉ（１０１−Ｒ）はＸ線結晶回折スペクトルにおける菱面体晶（１０１）面に帰属するピークの積分強度であり、Ｉ（１０１−Ｈ）はＸ線結晶回折スペクトルにおける六方晶（１０１）面に帰属するピークの積分強度である。］
[Equation 1]
R (%) = (I (101−R) / I (101−H)) × 100 (1)
[Wherein, I (101-R) is the integrated intensity of the peak attributed to the rhombohedral crystal (101) plane in the X-ray crystal diffraction spectrum, and I (101-H) is the hexagonal crystal ( 101) The integrated intensity of the peak attributed to the plane. ]
黒鉛はグラファイト層に適度な乱れを生じ、ベーサル面とエッジ面の比がある一定の範囲に入るものが好ましい。グラファイト層の乱れは、例えば、ラマン分光分析の結果に現れる。好ましい黒鉛は、ラマン分光スペクトルにおける１３６０ｃｍ−１のピーク強度（以下「Ｉ（１３６０）」という。）と１５８０ｃｍ−１のピーク強度（以下「Ｉ（１５８０）」という。）との比（以下「Ｉ（１３６０）／Ｉ（１５８０）」という。）が０．０２〜０．５、好ましくは０．０５〜０．３、より好ましくは０．１〜０．２、更に好ましくは約０．１５（例えば、０．１３〜０．１７）となるものである。 It is preferable that the graphite is moderately disturbed in the graphite layer, and the ratio of the basal surface to the edge surface falls within a certain range. The disorder of the graphite layer appears in the result of Raman spectroscopic analysis, for example. Preferable graphite has a ratio (hereinafter referred to as “I”) of a peak intensity of 1360 cm −1 (hereinafter referred to as “I (1360)”) and a peak intensity of 1580 cm −1 (hereinafter referred to as “I (1580)”) in a Raman spectrum. (1360) / I (1580) ”) is 0.02 to 0.5, preferably 0.05 to 0.3, more preferably 0.1 to 0.2, and still more preferably about 0.15 ( For example, 0.13 to 0.17).
黒鉛粒子の形状や寸法は、分極性電極に成形できる範囲であれば、特に限定されない。例えば、薄片状黒鉛粒子、圧密化黒鉛粒子及び球状化黒鉛粒子、針状黒鉛等を使用できる。これら黒鉛粒子の性状及び製造方法は公知である。 The shape and dimensions of the graphite particles are not particularly limited as long as they can be formed into a polarizable electrode. For example, flaky graphite particles, consolidated graphite particles and spheroidized graphite particles, acicular graphite and the like can be used. The properties and production methods of these graphite particles are known.
薄片状黒鉛粒子は一般に厚みが１μｍ以下、好ましくは０．１μｍ以下であり、かつ最大粒子長は１００μｍ以下、好ましくは５０μｍ以下である。該薄片状黒鉛粒子は、天然黒鉛や人造黒鉛を特殊な方法で粉砕したり、薄片化及び粒子化することにより得られる。 The flaky graphite particles generally have a thickness of 1 μm or less, preferably 0.1 μm or less, and the maximum particle length is 100 μm or less, preferably 50 μm or less. The flaky graphite particles can be obtained by pulverizing natural graphite or artificial graphite by a special method, flaking and granulating.
圧密化黒鉛粒子は嵩密度が高い黒鉛粒子であり、一般にタップ密度が０．７〜１．３ｇ／ｃｍ3である。圧密化黒鉛粒子はアスペクト比が１〜５の紡錘状をなす黒鉛粒子を１０体積％以上含むか、若しくはアスペクト比が１〜１０の円盤状をなす黒鉛粒子を５０体積％以上含むものと、ここでは定義する。 The consolidated graphite particles are graphite particles having a high bulk density, and generally have a tap density of 0.7 to 1.3 g / cm 3 . Consolidated graphite particles include 10% by volume or more of spindle-shaped graphite particles having an aspect ratio of 1 to 5, or 50% or more of disk-shaped graphite particles having an aspect ratio of 1 to 10, Let's define it.
圧密化黒鉛粒子は、原料黒鉛粒子を圧密化することによって製造することができる。原料黒鉛粒子としては、天然黒鉛、人造黒鉛のいずれを用いても良いが、結晶性の高さと、入手の容易さとから、天然黒鉛が好ましい。黒鉛はそのまま粉砕して原料黒鉛粒子にすることができるが、上述の薄片状黒鉛粒子を原料黒鉛粒子としてもよい。 The consolidated graphite particles can be produced by consolidating the raw graphite particles. As raw material graphite particles, either natural graphite or artificial graphite may be used, but natural graphite is preferred because of its high crystallinity and availability. Graphite can be pulverized as it is to obtain raw graphite particles, but the above-mentioned flaky graphite particles may be used as raw graphite particles.
圧密化処理は、原料黒鉛粒子に衝撃を加えることにより行う。振動ミルを用いる圧密化処理は、特に圧密化を高くでき、より好ましいものである。振動ミルの例としては、振動ボールミル、振動ディスクミル、振動ロッドミル等が挙げられる。 The consolidation process is performed by applying an impact to the raw graphite particles. Consolidation treatment using a vibration mill is particularly preferable because it can increase the consolidation. Examples of the vibration mill include a vibration ball mill, a vibration disk mill, and a vibration rod mill.
アスペクト比の大きな鱗片状の原料黒鉛粒子を圧密化処理すると、原料黒鉛粒子は主に黒鉛のベーサルプレーン（基礎面）で積層しながら二次粒子化し、同時に積層した二次粒子の端部は丸く削られて厚みのある円盤状、或は紡錘状に変化し、アスペクト比の小さな黒鉛粒子に変換される。 When scale-like raw graphite particles with a large aspect ratio are consolidated, the raw graphite particles become secondary particles while being laminated mainly on the basal plane (base surface) of graphite, and the edges of the simultaneously laminated secondary particles are rounded. It is cut into a thick disk shape or a spindle shape and converted into graphite particles with a small aspect ratio.
このようにして黒鉛粒子をアスペクト比の小さなものに変換した結果、黒鉛粒子は高結晶性であるにもかかわらず、等方性に優れ、タップ密度が高い黒鉛粒子が得られる。そのため、これを分極性電極に成型する場合、黒鉛スラリー中の黒鉛濃度を高くすることができ、成型後の電極は、黒鉛の密度が高くなる。 As a result of converting the graphite particles into those having a small aspect ratio in this way, graphite particles having excellent isotropic properties and high tap density can be obtained despite the high crystallinity of the graphite particles. Therefore, when this is molded into a polarizable electrode, the graphite concentration in the graphite slurry can be increased, and the molded electrode has a higher density of graphite.
正電極活物質用黒鉛類材料は、黒鉛類複合粒子であってもよい。黒鉛類複合粒子とは、コア黒鉛粒子と、該コア黒鉛粒子を被覆する炭素層とを有する複合体粒子をいう。コア黒鉛粒子は上述の黒鉛類材料の粒子を用いればよい。黒鉛類複合粒子を電極の活物質として用いると、蓄電システムのサイクル特性が安定化し、特に高温環境下における耐久性が著しく向上する。 The graphite material for the positive electrode active material may be graphite composite particles. The graphite composite particles mean composite particles having core graphite particles and a carbon layer covering the core graphite particles. The core graphite particles may be the above-mentioned graphite material particles. When graphite composite particles are used as the active material of the electrode, the cycle characteristics of the power storage system are stabilized, and the durability under a high temperature environment is remarkably improved.
コア黒鉛粒子の表面に被覆される炭素は非結晶性、低結晶性、結晶性のいずれでもよい。尚、黒鉛粒子の表面に非結晶性炭素又は低結晶性炭素を被覆した材料は公知である。例えば、化学蒸着法を用いてグラファイトを非晶質炭素で被覆した複合材料（特許文献６）、黒鉛を平均面間隔ｄ002が０．３３７ｎｍ以上の炭素で被覆した複合材料（特許文献７）、及び化学蒸着法を用いて黒鉛化炭素繊維をアモルファス炭素で被覆した複合材料（特許文献８）等が挙げられる。 The carbon coated on the surface of the core graphite particles may be non-crystalline, low crystalline, or crystalline. A material in which the surface of graphite particles is coated with amorphous carbon or low crystalline carbon is known. For example, a composite material in which graphite is coated with amorphous carbon using a chemical vapor deposition method (Patent Document 6), a composite material in which graphite is coated with carbon having an average interplanar spacing d002 of 0.337 nm or more (Patent Document 7), And a composite material (Patent Document 8) in which graphitized carbon fibers are coated with amorphous carbon using a chemical vapor deposition method.
しかしながら、コア黒鉛粒子の表面に被覆される炭素は結晶性であると、イオンの吸脱着速度が向上するという利点が得られる。 However, if the carbon coated on the surface of the core graphite particles is crystalline, there is an advantage that the ion adsorption / desorption rate is improved.
コア黒鉛粒子の表面に結晶性炭素を被覆する方法としては、流動床式の反応炉を用いる化学蒸着処理が優れている。化学蒸着処理の炭素源として使用する有機物としては、ベンゼン、トルエン、キシレン、スチレン等の芳香族炭化水素や、メタン、エタン、プロパン等の脂肪族炭化水素を挙げることができる。 As a method for coating the surface of the core graphite particles with crystalline carbon, chemical vapor deposition using a fluidized bed reactor is excellent. Examples of the organic substance used as the carbon source for the chemical vapor deposition treatment include aromatic hydrocarbons such as benzene, toluene, xylene, and styrene, and aliphatic hydrocarbons such as methane, ethane, and propane.
流動床式反応炉には、これらの有機物を窒素等の不活性ガスと混合して導入する。混合ガス中の有機物の濃度としては、２〜５０モル％が好ましく、５〜３３モル％がより好ましい。化学蒸着処理温度としては、８５０〜１２００℃が好ましく、９５０〜１１５０℃がより好ましい。このような条件で化学蒸着処理を行うことにより、コア黒鉛粒子の表面を均一、かつ完全に被覆することができる。 These organic substances are introduced into the fluidized bed reactor mixed with an inert gas such as nitrogen. As a density | concentration of the organic substance in mixed gas, 2-50 mol% is preferable and 5-33 mol% is more preferable. As chemical vapor deposition processing temperature, 850-1200 degreeC is preferable and 950-1150 degreeC is more preferable. By performing chemical vapor deposition under such conditions, the surface of the core graphite particles can be uniformly and completely covered.
被覆層の形成に必要な炭素の量は、コア黒鉛粒子の粒子径及び形状によって異なるが、複合材料中における被覆炭素量として、１〜３０質量％、好ましくは２〜２０質量％、より好ましくは５〜１５質量％である。被覆量が１質量％以下では被覆の効果が得られず、逆に被覆炭素量が多すぎると、コア黒鉛粒子の割合が低下するので、充放電量が低下する等の不都合を生じる。また、製造コストも高くなる。 The amount of carbon necessary for forming the coating layer varies depending on the particle diameter and shape of the core graphite particles, but the coating carbon amount in the composite material is 1 to 30% by mass, preferably 2 to 20% by mass, more preferably 5 to 15% by mass. If the coating amount is 1% by mass or less, the effect of coating cannot be obtained. Conversely, if the coating carbon amount is too large, the ratio of the core graphite particles is reduced, so that the charge / discharge amount is reduced. In addition, the manufacturing cost increases.
黒鉛類複合粒子は、黒鉛類粒子をコアとして用いて樹脂を被覆し、その後被覆された樹脂を炭化することにより、形成してもよい。被覆するのに好ましい樹脂は炭化収率が高い樹脂であり、例えばレゾルシノール樹脂、フルフリルアルコール樹脂などが挙げられる。 The graphite composite particles may be formed by coating a resin using the graphite particles as a core and then carbonizing the coated resin. Preferred resins for coating are resins having a high carbonization yield, such as resorcinol resin and furfuryl alcohol resin.
樹脂の被覆は、樹脂を適当な溶媒に溶解させて溶液とし、その中にコア黒鉛粒子を浸漬し、乾燥させることにより行なえばよい。また、コア黒鉛粒子に被覆された樹脂の炭化は、被覆された粒子を焼成することにより行なえばよい。焼成条件は、一般に不活性雰囲気下で３００℃から２０００℃、好ましくは５００℃からにて１０００℃、０．５〜１０時間、好ましくは１．０〜２．０時間である。 The resin coating may be performed by dissolving the resin in a suitable solvent to form a solution, immersing the core graphite particles in the solution, and drying. Carbonization of the resin coated on the core graphite particles may be performed by firing the coated particles. Firing conditions are generally 300 ° C. to 2000 ° C., preferably 500 ° C. to 1000 ° C., 0.5 to 10 hours, preferably 1.0 to 2.0 hours under an inert atmosphere.
本発明の蓄電システムでは、負電極の電極活物質として、リチウムのインターカレーション／脱インターカレーションや吸蔵が可能な炭素質材料を使用する。かかる炭素質材料は、一般に００２面の結晶格子定数Ｃ0(002)が０．６８８以上であり、グラファイト系材料と非グラファイト系材料とに分類され得る。グラファイト系材料の例には、フレーク形天然又は合成黒鉛、メソフェーズカーボンファイバー（ＭＣＦ）、メソフェーズカーボンピッチ（ＭＣＭＢ）などのようなメソフェーズピッチを基礎とした黒鉛が含まれる。非グラファイト系化合物の例には石油炭素、軟質炭素、硬質炭素、ポリプロピレン又はポリアセニック化合物、石炭、フェノール樹脂などを基礎とした材料のような８００〜１８００℃で熱処理した、ハードカーボンやソフトカーボンが含まれる。 In the electricity storage system of the present invention, a carbonaceous material capable of lithium intercalation / deintercalation and occlusion is used as the electrode active material of the negative electrode. Such a carbonaceous material generally has a crystal lattice constant C 0 (002) of 002 plane of 0.688 or more, and can be classified into a graphite-based material and a non-graphite-based material. Examples of graphite-based materials include graphite based on mesophase pitch such as flake-shaped natural or synthetic graphite, mesophase carbon fiber (MCF), mesophase carbon pitch (MCMB) and the like. Examples of non-graphite compounds include hard carbon and soft carbon heat treated at 800-1800 ° C. such as materials based on petroleum carbon, soft carbon, hard carbon, polypropylene or polyacenic compounds, coal, phenol resin, etc. included.
負電極の電極活物質として、第４級アンモニウム塩などのカチオンが吸着可能な活性炭を用いてもよい。例えば、非特許文献１第４９〜６１頁には、好ましい活性炭の製法や構造が説明されている。一般には、ＢＥＴ法により測定された比表面積が５００〜４０００ｍ２／ｇ、好ましくは８００〜３０００ｍ２／ｇ、より好ましくは１０００〜２５００ｍ２／ｇ、平均粒径が１〜１００μｍ、好ましくは３〜５０μｍ、より好ましくは５〜２０μｍの活性炭粒子を用いる。 As the electrode active material of the negative electrode, activated carbon capable of adsorbing cations such as quaternary ammonium salts may be used. For example, Non-Patent Document 1, pages 49-61, describes a preferred method for producing activated carbon and its structure. In general, the specific surface area measured by the BET method is 500 to 4000 m 2 / g, preferably 800 to 3000 m 2 / g, more preferably 1000 to 2500 m 2 / g, and the average particle size is 1 to 100 μm, preferably 3 to 3 μm. Activated carbon particles of 50 μm, more preferably 5 to 20 μm are used.
活性炭粒子は市販品を用いてもよい。好ましい市販の活性炭粒子は、武田薬品工業製「白鷺」、クラレケミカル株式会社製「BP２０」である。 As the activated carbon particles, commercially available products may be used. Preferred commercially available activated carbon particles are “Shirakaba” manufactured by Takeda Pharmaceutical Co., Ltd. and “BP20” manufactured by Kuraray Chemical Co., Ltd.
負電極活物質用炭素質材料は、上記のような炭素質粒子と、該炭素質粒子を被覆する炭素層とを有する複合体粒子であってもよい。かかる炭素質複合粒子は、黒鉛類複合粒子と同様にして製造することができる。炭素質複合粒子を蓄電システムの負電極に用いると、高温環境下における耐久性が著しく向上する。 The carbonaceous material for the negative electrode active material may be a composite particle having the carbonaceous particles as described above and a carbon layer covering the carbonaceous particles. Such carbonaceous composite particles can be produced in the same manner as the graphite composite particles. When the carbon composite particles are used for the negative electrode of the electricity storage system, the durability under a high temperature environment is remarkably improved.
正電極および負電極は従来と同様の方法により作製することができる。例えば、シート状の分極性電極を作製するには、上述の黒鉛類材料及び炭素質材料のような電極活物質を５〜１００μｍ程度に粉砕し粒度を整えた後、炭素粉末に導電性を付与するための導電性補助剤として例えばカーボン・ブラックと、結着剤として例えばポリテトラフルオロエチレン（ＰＴＦＥ）とを添加して混練りし、圧延伸によりシート状に成形することにより行う。導電性補助剤としては、カーボン・ブラックの他、粉末グラファイトなどを用いることができ、また、結着剤としては、ＰＴＦＥの他、ＰＶＤＦ、ＰＥ、ＰＰなどを使用することができる。この際、非多孔性炭素と導電性補助剤（カーボン・ブラック）と結着剤（ＰＴＦＥ）との配合比は、一般に、１０〜１：０.５〜１０：０.５〜０.２５程度である。 The positive electrode and the negative electrode can be produced by a method similar to the conventional method. For example, in order to produce a sheet-like polarizable electrode, an electrode active material such as the above-mentioned graphite material and carbonaceous material is pulverized to about 5 to 100 μm to adjust the particle size, and then conductivity is imparted to the carbon powder. For example, carbon black as a conductive auxiliary agent and, for example, polytetrafluoroethylene (PTFE) as a binder are added and kneaded, and formed into a sheet by pressure drawing. In addition to carbon black, powder graphite and the like can be used as the conductive auxiliary agent, and as the binder, PVDF, PE, PP and the like can be used in addition to PTFE. At this time, the blending ratio of non-porous carbon, conductive auxiliary agent (carbon black), and binder (PTFE) is generally about 10 to 1: 0.5 to 10: 0.5 to 0.25. It is.
得られたシート状の分極性電極を集電極と結合させて、電極部材を得る。集電極としては蓄電システム用として通常用いられる形態を有する材料を使用する。集電極の形態はシート状、角柱状、および円柱状等であればよい。特に好ましい形態は、シート状又は箔状である。 The obtained sheet-like polarizable electrode is combined with a collecting electrode to obtain an electrode member. As the collector electrode, a material having a form normally used for a power storage system is used. The form of the collecting electrode may be a sheet shape, a prismatic shape, a cylindrical shape, or the like. A particularly preferable form is a sheet shape or a foil shape.
電解液に対する酸化還元電位がそれぞれ異なることから、集電極の材料はアルミニウム、銅、銀、ニッケル、チタンなどであればよい。正電極についてはアルミニウム、負電極については銅又はニッケルとすることが好ましい。 Since the oxidation-reduction potential with respect to the electrolytic solution is different, the material of the collector electrode may be aluminum, copper, silver, nickel, titanium, or the like. The positive electrode is preferably aluminum, and the negative electrode is preferably copper or nickel.
作製した炭素質電極又は電極部材は、従来から知られている構造の蓄電システムに使用することができる。蓄電システムの構造は、例えば、特許文献１の図５及び図６、特許文献２の図６、特許文献９の図１〜図４等に示されている。一般に、このような蓄電システムは、電極部材をセパレータを介して重ね合わせることにより正電極と負電極とを構成した後、電解液を含浸させて組み立てることができる。
The produced carbonaceous electrode or electrode member can be used for a power storage system having a conventionally known structure. The structure of the power storage system is shown, for example, in FIGS. 5 and 6 of Patent Document 1, FIG. 6 of
電解液は、例えば、電解質を溶質として用いて有機溶媒に溶解して得られる、有機電解液を使用することができる。電解質としては、リチウム塩あるいはリチウム塩と第４級アンモニウム塩など電気２重層キャパシタ用電解液の混合液を用いる。リチウム塩の対アニオンは従来から有機電解液の電解質イオンとして使用されているものであればよい。例えば、４フッ化ホウ酸アニオン、フッ化ホウ酸アニオン、フッ化リン酸アニオン、６フッ化リン酸アニオン、過塩素酸アニオン、ボロジサリチル酸アニオン、ボロジシュウ酸アニオン、が挙げられる。好ましい対アニオンは４フッ化ホウ酸アニオン及び６フッ化リン酸アニオンである。また混合液として用いられる、電気２重層キャパシタ用電解液は、テトラエチルアンモニウム、スピロビオイロリジニウム、エチルメチルイミダゾリニウムなどの第４級アンモニウムイオンからなる電解液である。 As the electrolytic solution, for example, an organic electrolytic solution obtained by dissolving in an organic solvent using an electrolyte as a solute can be used. As the electrolyte, a lithium salt or a mixed solution of an electrolytic solution for an electric double layer capacitor such as a lithium salt and a quaternary ammonium salt is used. The counter anion of the lithium salt may be any one that has been conventionally used as an electrolyte ion of an organic electrolyte. For example, a tetrafluoroborate anion, a fluoroborate anion, a fluorophosphate anion, a hexafluorophosphate anion, a perchlorate anion, a borodisalicylate anion, and a borodisoxalate anion. Preferred counter anions are tetrafluoroborate anion and hexafluorophosphate anion. Moreover, the electrolytic solution for electric double layer capacitors used as a mixed solution is an electrolytic solution composed of quaternary ammonium ions such as tetraethylammonium, spirobioiridinium, and ethylmethylimidazolinium.
有機溶媒は従来から有機系の蓄電システムに使用されてきたものを使用してよい。例えば、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、γ−ブチルラクトン（ＧＢＬ）及びスルホラン（ＳＬ）等はピロリジニウム化合物塩の溶解能に優れ、安全性も高いため好ましい。また、これらを主溶媒とし、ジメチルカーボネート（ＤＭＣ）、エチルメチルカーボネート（ＥＭＣ）、ジエチルカーボネート（ＤＥＣ）の少なくとも１種を副溶媒としたものも有用である。蓄電システムの低温特性が改善されるためである。また、有機溶媒としてアセトニトリル（ＡＣ）を使用すると電解液の導電率が高まるため特性上好ましいが、使用用途が限定される場合がある。 As the organic solvent, those conventionally used for organic power storage systems may be used. For example, ethylene carbonate (EC), propylene carbonate (PC), γ-butyl lactone (GBL), sulfolane (SL) and the like are preferable because of their excellent solubility in pyrrolidinium compound salts and high safety. Also useful are those containing these as a main solvent and at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) as a sub-solvent. This is because the low temperature characteristics of the power storage system are improved. In addition, when acetonitrile (AC) is used as the organic solvent, the conductivity of the electrolytic solution is increased, which is preferable in terms of characteristics. However, the use application may be limited.
電解液中のリチウム塩の濃度は、電解液による内部抵抗を小さくするため、少なくとも０．１ｍｏｌ／ｌ以上とすることが望ましく、通常０．２〜１．５ｍｏｌ／ｌとすることが好ましい。 The concentration of the lithium salt in the electrolytic solution is preferably at least 0.1 mol / l or more, and preferably 0.2 to 1.5 mol / l in order to reduce the internal resistance due to the electrolytic solution.
以下の実施例により本発明を更に具体的に説明するが、本発明はこれらに限定されない。尚、実施例中「部」又は「％」で表される量は特にことわりなき限り重量基準である。 The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “part” or “%” is based on weight unless otherwise specified.
正電極用電極活物質（黒鉛類粒子）の製造
黒鉛粒子１〜４は、中国産の天然黒鉛をメディアを用いて摩砕することにより平均粒子径が５ミクロン程度となるように調整し、得られた薄片化黒鉛粒子を更に磨砕することで、菱面体晶の割合を表１のように調整したものである。
Manufacture of electrode active material (graphite particles) for positive electrode Graphite particles 1 to 4 are obtained by adjusting the average particle size to about 5 microns by grinding Chinese natural graphite using media. The exfoliated graphite particles thus obtained were further ground to adjust the ratio of rhombohedral crystals as shown in Table 1 .
非多孔性炭素粒子１および２は、ニードルコークスを窒素気流中で９００℃にて焼成し、次に等量のＫＯＨと混練後、６５０℃で再焼成し、これを摩砕することにより平均粒子径が５ミクロン程度となるようにしたものである。
黒鉛類粒子の分析
（１）Ｘ線結晶解析
Ｘ線回折装置（株式会社リガク製「RINT-UltimaIII」）を用い、黒鉛類粒子を測定した。得られたX線回折スペクトルを分析して、（００２）面の結晶格子定数（C0（００２））、平均面間隔ｄ００２、及び（００２）ピーク（２θ＝２６．５°付近にあるピーク）の半値幅を決定した。ターゲットをCuKαとし、40kV、200mAにて測定を行った。
Analysis of Graphite Particles (1) X-ray Crystal Analysis Graphite particles were measured using an X-ray diffractometer (“RINT-UltimaIII” manufactured by Rigaku Corporation). The obtained X-ray diffraction spectrum was analyzed, and the (002) plane crystal lattice constant (C 0 (002) ), the average plane spacing d 002 , and the (002) peak (2θ = 26.5 ° vicinity) ) Was determined. The target was CuKα, and measurement was performed at 40 kV and 200 mA.
また、菱面体晶（１０１-R）のピーク位置は２θ＝４３．３°付近にあり、その積分強度をＩ(１０１-R)とした。六方晶（１０１-H）のピーク位置は２θ＝44.5°付近にあり、その積分強度をＩ(１０１-H)とした。そして、式（１）に従って、結晶構造中に存在する六方晶系構造に対する菱面体晶系構造の割合Ｒ（％）を求めた。 The rhombohedral crystal (101-R) peak position is in the vicinity of 2θ = 43.3 °, and its integrated intensity is I (101-R). The peak position of hexagonal crystal (101-H) is in the vicinity of 2θ = 44.5 °, and its integrated intensity is I (101-H). And according to Formula (1), the ratio R (%) of the rhombohedral structure to the hexagonal structure existing in the crystal structure was determined.
［表１］
ラマン分光装置（日本分光株式会社製「レーザラマン分光光度計ＮＲＳ−３１００」）を用い、黒鉛類粒子を下記条件にて測定した。 Graphite particles were measured under the following conditions using a Raman spectrometer (“Laser Raman spectrophotometer NRS-3100” manufactured by JASCO Corporation).
［表２］
［表３］
負電極用電極活物質の調製
負電極用炭素質材料として、メソフェーズカーボンピッチ（ＭＣＭＢ）系黒鉛粒子（大阪ガス社製）、メソフェーズカーボンファイバー（ＭＣＦ）系黒鉛粒子（ペトカ社製）、天然黒鉛粒子（日本黒鉛製、ハードカーボン（呉羽化学社製）、及びＢＥＴ法による表面積が１７００ｍ２の活性炭粒子（武田薬品工業製）を準備した。
Preparation of electrode active material for negative electrode As carbonaceous material for negative electrode, mesophase carbon pitch (MCMB) graphite particles (Osaka Gas Co., Ltd.), mesophase carbon fiber (MCF) graphite particles (Petka Co., Ltd.), natural graphite particles (Nippon graphite, hard carbon (manufactured by Kureha Chemical), and activated carbon particles (manufactured by Takeda Pharmaceutical Co., Ltd.) having a surface area of 1700 m 2 by the BET method were prepared.
複合粒子の製造
Ａ）ＣＶＤによる処理：９００から１１００℃に昇温された炉内の石英製キュベットに電極活物質粒子を静置し、これにアルゴンガスをキャリアとしてベンゼン蒸気を導入し、キシレンを黒鉛上に析出炭化させる。析出炭素量を種々変更し実施した。
Ｂ）樹脂被覆処理：ベークライト樹脂の溶液（群栄化学：レジトップ）を種々の濃度に調整した。次に電極活物質粒子をこれら溶液に浸し、乾燥した。窒素気流中にて６００℃で焼成し、樹脂を炭化した。
Manufacture of composite particles A) Treatment by CVD: Electrode active material particles are allowed to stand in a quartz cuvette in a furnace heated to 900 to 1100 ° C., benzene vapor is introduced using argon gas as a carrier, and xylene is introduced. Precipitate and carbonize on graphite. Various changes were made in the amount of precipitated carbon.
B) Resin coating treatment: Bakelite resin solution (Gunei Chemical: Resitop) was adjusted to various concentrations. Next, the electrode active material particles were immersed in these solutions and dried. The resin was carbonized by firing at 600 ° C. in a nitrogen stream.
実施例１
（１）電極の製造
正電極：
電極活物質３ｇ、アセチレンブラック０．３ｇ、及びポリビニリデンフロリド（ＰＶＤＦ）溶液（呉羽化学社製）１．０ｇを混合し、小型ニーダーを用いて混練した。成形装置を用いて、混練物を０．４ｍｍから０．５ｍｍの均一な厚みのシート状に成形して正電極を得た。
負電極：
電極活物質３ｇ、アセチレンブラック０．３ｇ、及びポリビニリデンフロリド（ＰＶＤＦ）溶液（呉羽化学社製）１．０ｇを混合し、小型ニーダーを用いて混練した。成形装置を用いて、混練物を０．４ｍｍから０．５ｍｍの均一な厚みのシート状に成形して負電極を得た。
電極の目付け重量は、正負極がほぼ同等となるように調整した。
Example 1
(1) Production of electrode Positive electrode:
3 g of electrode active material, 0.3 g of acetylene black, and 1.0 g of polyvinylidene fluoride (PVDF) solution (manufactured by Kureha Chemical Co., Ltd.) were mixed and kneaded using a small kneader. Using a molding apparatus, the kneaded product was molded into a sheet having a uniform thickness of 0.4 mm to 0.5 mm to obtain a positive electrode.
Negative electrode:
3 g of electrode active material, 0.3 g of acetylene black, and 1.0 g of polyvinylidene fluoride (PVDF) solution (manufactured by Kureha Chemical Co., Ltd.) were mixed and kneaded using a small kneader. Using a molding apparatus, the kneaded material was molded into a sheet having a uniform thickness of 0.4 mm to 0.5 mm to obtain a negative electrode.
The basis weight of the electrode was adjusted so that the positive and negative electrodes were almost equal.
（２）蓄電システムの製造
得られた各炭素シートを２０ｍｍΦのディスクに打ち抜き、図１に示すような、３電極セルに組み立てた。その際、集電極として正電極にはアルミニウム箔を用い、負電極には銅を用いた。セパレーターとしてガラスフィルタを用いた。参照電極は＃１７１１活性炭を上記と同様の方法にてシート化したものを用いた。このセルを真空中１４０℃で２４時間乾燥し冷却した。六フッ化燐酸リチウムをエチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）の混合溶媒に１．０モル％となるように溶解させて電解液を調製した。そして、得られた電解液をセルに注入して試験セルを作製した。
(2) Production of power storage system Each obtained carbon sheet was punched into a 20 mmφ disk and assembled into a three-electrode cell as shown in FIG. At that time, an aluminum foil was used for the positive electrode as a collecting electrode, and copper was used for the negative electrode. A glass filter was used as a separator. The reference electrode used was a sheet of # 1711 activated carbon formed by the same method as above. The cell was dried in a vacuum at 140 ° C. for 24 hours and cooled. An electrolyte solution was prepared by dissolving lithium hexafluorophosphate in a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) so as to be 1.0 mol%. And the obtained electrolyte solution was inject | poured into the cell and the test cell was produced.
（３）性能試験
組み立てた蓄電システムにパワーシステム製充放電試験装置「ＣＤＴ−ＲＤ２０」を接続し、５ｍＡにて７２００秒間の定電流充電を行い、設定電圧に到達した後、５ｍＡにての定電流放電を行った。最大電圧は５．０Ｖとし、３．０Ｖまでの充放電を３サイクル実施し３サイクル目のデータを採用した。
放電電力より容量（ｍＡｈ／ｇ）を算出した。
ついで、周囲の温度を６０℃に上昇させ、上記条件の充放電を１００サイクル行った。容量維持率（％）を測定した。
これら試験結果を表４に示す。
(3) Performance test A power system charge / discharge test device “CDT-RD20” is connected to the assembled power storage system, constant current charging is performed at 5 mA for 7200 seconds, and after reaching a set voltage, a constant current at 5 mA is set. A current discharge was performed. The maximum voltage was 5.0 V, and charge / discharge up to 3.0 V was performed for 3 cycles, and the data for the 3rd cycle was adopted.
The capacity (mAh / g) was calculated from the discharge power.
Next, the ambient temperature was raised to 60 ° C., and charging and discharging under the above conditions were performed 100 cycles. The capacity retention rate (%) was measured.
These test results are shown in Table 4.
［表４］
樹脂被覆：複合粒子中における樹脂被覆炭素量（質量％）
[Table 4]
Resin coating: Resin-coated carbon content in composite particles (% by mass)
実施例の結果によれば、本発明の蓄電システムは、エネルギー密度等の基本的特性に優れ、この炭素をCVD法などにより被覆したものについては、安定したサイクル特性が得られた。 According to the results of the examples, the power storage system of the present invention was excellent in basic characteristics such as energy density, and stable cycle characteristics were obtained for the carbon coated with the CVD method or the like.
１、１１…絶縁ワッシャ、
２…トップカバー、
３…スプリング、
４、８…集電極、
５、７…炭素質電極、
６…セパレータ、
９…ガイド、
１０、１３…Ｏリング、
１２…本体、
１４…押え板、
１５…参照電極、
１６…ボトムカバー。
1, 11 ... Insulating washer,
2 ... Top cover,
3 ... Spring,
4, 8 ... collector electrode,
5, 7 ... carbonaceous electrode,
6 ... separator,
9 ... Guide,
10, 13 ... O-ring,
12 ... the body,
14 ... Presser plate,
15 ... Reference electrode,
16 ... Bottom cover.
Claims (7)
該有機電解液がリチウム塩を溶質の少なくとも一部として含有し、
該正電極が、電極活物質として、炭素の結晶構造中に存在する六方晶系構造に対する菱面体晶系構造の割合が３０％以上である炭素質材料を有し、
該負電極が電極活物質としてリチウムの吸蔵あるいはインターカレーション／脱インターカレーションが可能な炭素質材料を有する、蓄電システム。 A power storage system in which a positive electrode and a negative electrode are immersed in an organic electrolyte obtained by dissolving a solute in an organic solvent ,
The organic electrolyte contains a lithium salt as at least part of a solute;
The positive electrode has , as an electrode active material , a carbonaceous material in which the ratio of rhombohedral structure to hexagonal structure existing in the crystal structure of carbon is 30% or more ;
A power storage system in which the negative electrode has a carbonaceous material capable of occluding or intercalating / deintercalating lithium as an electrode active material.
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