JP2015029028A - Electrochemical device - Google Patents

Electrochemical device Download PDF

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JP2015029028A
JP2015029028A JP2013158500A JP2013158500A JP2015029028A JP 2015029028 A JP2015029028 A JP 2015029028A JP 2013158500 A JP2013158500 A JP 2013158500A JP 2013158500 A JP2013158500 A JP 2013158500A JP 2015029028 A JP2015029028 A JP 2015029028A
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electrode active
active material
positive electrode
graphene
negative electrode
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清太郎 伊藤
Seitaro Ito
清太郎 伊藤
相原　雄一
Yuichi Aihara
雄一 相原
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Samsung Electronics Co Ltd
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Samsung Electronics Co Ltd
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Priority to KR1020140011740A priority patent/KR20150016072A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/36—Nanostructures, e.g. nanofibres, nanotubes or fullerenes
    • 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
    • Y02E60/10—Energy storage using batteries
    • 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
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Abstract

PROBLEM TO BE SOLVED: To provide an electrochemical device having a high energy density.SOLUTION: An electrochemical device comprises: a positive electrode active material layer containing graphene serving as a positive electrode active material; a negative electrode active material layer containing a negative electrode active material; and a nonaqueous electrolyte. The positive electrode active material layer includes at least 50 mass% of the graphene. The negative electrode active material is preferably a metal-ion-predoped carbon material, graphite or metal and more preferably, a lithium-ion-predoped carbon material or lithium metal.

Description

本発明は、イオン吸着と酸化還元反応とによりエネルギー密度を向上させる電気化学デバイスに関する。   The present invention relates to an electrochemical device that improves energy density by ion adsorption and redox reaction.

従来、電気二重層キャパシタ（以下「ＥＤＬＣ」という。）は、バス・コピー機等の電源、ハイブリッド電気自動車（ＨＥＶ）等の回生エネルギー蓄電、無停電電源装置（ＵＰＳ）等に利用されている。ＥＤＬＣは、正極材料および負極材料として活性炭を用い、活性炭への物理的なイオン吸着により静電容量を形成するため、高出力密度である。しかし、エネルギー密度は大きくない。ＥＤＬＣの充電電圧は最大２．５Ｖ程度である。   Conventionally, an electric double layer capacitor (hereinafter referred to as “EDLC”) is used for a power source of a bus / copier, a regenerative energy storage of a hybrid electric vehicle (HEV), an uninterruptible power supply (UPS), and the like. Since EDLC uses activated carbon as a positive electrode material and a negative electrode material, and forms a capacitance by physical ion adsorption on the activated carbon, it has a high output density. However, the energy density is not large. The charging voltage of EDLC is about 2.5V at maximum.

上記のＥＤＬＣの構造中、負極材料を活性炭から、リチウムイオンを吸蔵、放出可能な材料に代えたリチウムイオンキャパシタの商品化が進んでいる。リチウムイオンキャパシタは、ＥＤＬＣとリチウムイオン電池とのハイブリッド構造である。負極材料としては、通常リチウムイオンをプレドープさせた黒鉛が用いられる。   In the structure of the EDLC described above, commercialization of a lithium ion capacitor in which the negative electrode material is changed from activated carbon to a material capable of occluding and releasing lithium ions is in progress. The lithium ion capacitor has a hybrid structure of EDLC and a lithium ion battery. As the negative electrode material, graphite pre-doped with lithium ions is usually used.

上記の構造により、リチウムイオンキャパシタの充電電圧は、４Ｖまで印加可能となり、両電極に活性炭を用いるＥＤＬＣと比較してエネルギー密度を向上させている。リチウムイオンキャパシタのエネルギー密度は10Ｗｈ／Ｌ程度であり、上記ＥＤＬＣの約４倍である。しかしリチウムイオン電池のエネルギー密度が100−600Ｗｈ／Ｌであることと比較すると、リチウムイオンキャパシタのエネルギー密度は小さい。   With the above structure, the charging voltage of the lithium ion capacitor can be applied up to 4 V, and the energy density is improved as compared with EDLC using activated carbon for both electrodes. The energy density of the lithium ion capacitor is about 10 Wh / L, which is about four times that of the EDLC. However, compared with the energy density of the lithium ion battery being 100-600 Wh / L, the energy density of the lithium ion capacitor is small.

上記のリチウムイオンキャパシタは正極に活性炭を用いるため、正極におけるリチウムイオン吸着量が、黒鉛電極における吸着量と比較して少ない。したがって容量の大きな正極材料を利用することで、リチウムイオンキャパシタのエネルギー密度を著しく改善できる可能性がある。従来の正極容量を改善させた技術として、活性炭に変えてカップスタックカーボンナノチューブを利用した電気二重層キャパシタがある（特許文献１）。   Since the above lithium ion capacitor uses activated carbon for the positive electrode, the lithium ion adsorption amount at the positive electrode is smaller than the adsorption amount at the graphite electrode. Therefore, there is a possibility that the energy density of the lithium ion capacitor can be remarkably improved by using a positive electrode material having a large capacity. As a conventional technique for improving the positive electrode capacity, there is an electric double layer capacitor using cup-stacked carbon nanotubes instead of activated carbon (Patent Document 1).

グラフェンは高い電子伝導性などから近年注目を集める材料で、ＥＤＬＣでは主に導電助剤として用いられる。グラフェンは、黒鉛シート１層から数層で形成される２次元の炭素材料である。発見当初は黒鉛表面からテープで剥がして得る単純な手法が用いられ、応用に耐えうる高品質・大量合成法が存在しなかった。しかし近年、酸化還元法や超臨界流体を用いてグラファイトから剥離させる方法など様々な手法が開発され、高品質のグラフェンを安価に得ることが可能となっている。   Graphene is a material that has attracted attention in recent years because of its high electron conductivity, and is mainly used as a conductive aid in EDLC. Graphene is a two-dimensional carbon material formed from one layer of graphite sheet to several layers. At the time of discovery, a simple method was used that was obtained by peeling off the graphite surface with tape, and there was no high-quality, high-volume synthesis method that could withstand the application. However, in recent years, various methods such as a redox method and a method of exfoliating from graphite using a supercritical fluid have been developed, and high-quality graphene can be obtained at low cost.

グラフェンの利用例としては、特許文献２に、リン酸鉄リチウム等の正極活物質からなる主材料をグラフェンで被覆させた蓄電装置用正極活物質が開示される。特許文献３や特許文献４には、活性炭や金属酸化物とグラフェンを複合化させた電極を備えるキャパシタ等が開示される。特許文献５には、グラフェンに正孔を形成させて導電材として利用した蓄電装置が開示される。上記に例示されるように、グラフェンは良好な電子伝導性が着目され、従来導電助剤として利用される。しかしグラフェンを正極活物質として用いた電気化学デバイスは報告されていない。   As an example of the use of graphene, Patent Document 2 discloses a positive electrode active material for a power storage device in which a main material made of a positive electrode active material such as lithium iron phosphate is coated with graphene. Patent Documents 3 and 4 disclose capacitors and the like that include electrodes in which activated carbon, metal oxide, and graphene are combined. Patent Document 5 discloses a power storage device in which holes are formed in graphene and used as a conductive material. As exemplified above, graphene has attracted attention for its good electronic conductivity and has been conventionally used as a conductive additive. However, no electrochemical device using graphene as a positive electrode active material has been reported.

特開2012-059838号公報JP 2012-059838 A 特開2012-099467号公報JP 2012-099467 A 特開2012-114396号公報JP 2012-114396 A 特開2012-219010号公報JP 2012-219010 JP 特開2013-030472号公報JP 2013-030472 A

リチウムイオンキャパシタやリチウム二次電池等の電気化学デバイスにおいては更なるエネルギー密度の向上が求められる。本発明の課題は、エネルギー密度が高い電気化学デバイスを提供することにある。   In electrochemical devices such as lithium ion capacitors and lithium secondary batteries, further improvement in energy density is required. An object of the present invention is to provide an electrochemical device having a high energy density.

本発明は、正極活物質がグラフェンであり、グラフェンを含有する正極活物質層と、負極活物質を含有する負極活物質層と、非水系電解液とを備える電気化学デバイスである。本発明の正極活物質層は、グラフェンを少なくとも50質量％含有する。負極活物質は、金属イオンをプレドープさせた炭素材料、黒鉛、金属が好ましい。より好ましい負極活物質は、リチウムイオンをプレドープさせた炭素材料やリチウム金属である。   The present invention is an electrochemical device comprising a positive electrode active material comprising graphene, a positive electrode active material layer containing graphene, a negative electrode active material layer containing a negative electrode active material, and a non-aqueous electrolyte solution. The positive electrode active material layer of the present invention contains at least 50% by mass of graphene. The negative electrode active material is preferably a carbon material pre-doped with metal ions, graphite, or metal. A more preferable negative electrode active material is a carbon material or lithium metal pre-doped with lithium ions.

本発明の電気化学デバイスは、正極側で正極活物質であるグラフェンと非水系電解質中のアニオンとの酸化還元反応により、クーロン型静電容量を形成する。また該正極活物質は、グラフェンのイオン吸着能によりファラデー型静電容量を形成する。すなわち本発明は、正極活物質としてグラフェンを用いることにより、正極でクーロン型静電容量とファラデー型静電容量とを形成できる。そのため本発明は、リチウムイオンキャパシタより高エネルギー密度で、かつリチウムイオン二次電池より高放出密度の電気化学デバイスである。   The electrochemical device of the present invention forms a Coulomb-type capacitance by an oxidation-reduction reaction between graphene, which is a positive electrode active material, and an anion in a non-aqueous electrolyte on the positive electrode side. The positive electrode active material forms a Faraday-type capacitance due to the ion adsorption ability of graphene. That is, in the present invention, by using graphene as the positive electrode active material, a Coulomb capacitance and a Faraday capacitance can be formed on the positive electrode. Therefore, the present invention is an electrochemical device having a higher energy density than a lithium ion capacitor and a higher emission density than a lithium ion secondary battery.

本発明の電気化学デバイスの一例を示す概略図である。It is the schematic which shows an example of the electrochemical device of this invention.

本発明の電気化学デバイスは、少なくともグラフェンを含有する正極活物質層と負極活物質を含有する負極活物質層と、非水系電解液とを備える。正極活物質層と負極活物質層とはそれぞれ集電体表面に積層される。図１は、本発明の電気化学デバイスの一例を示す概略図である。図１において、１００は電気化学デバイス、１０１は正極活物質層、１０２は非水系電解液、１０３はセパレータ、１０４は負極活物質層、１０５、１０６は集電体である。電圧を印加することにより、非水系電解液中のアニオンは正極に引き付けられ、カチオンは負極に引き付けられる。   The electrochemical device of the present invention includes a positive electrode active material layer containing at least graphene, a negative electrode active material layer containing a negative electrode active material, and a non-aqueous electrolyte solution. The positive electrode active material layer and the negative electrode active material layer are respectively laminated on the current collector surface. FIG. 1 is a schematic view showing an example of the electrochemical device of the present invention. In FIG. 1, 100 is an electrochemical device, 101 is a positive electrode active material layer, 102 is a non-aqueous electrolyte, 103 is a separator, 104 is a negative electrode active material layer, and 105 and 106 are current collectors. By applying a voltage, anions in the non-aqueous electrolyte are attracted to the positive electrode and cations are attracted to the negative electrode.

［正極活物質層］
本発明の正極活物質層の主成分は、グラフェンである。グラフェンは炭素原子がｓｐ２結合により六角形格子構造を形成するシートであり、高導電性や大きな比表面積等を特徴とする。近年グラフェンの定義には、単層のシートだけでなく2〜10層程度のシートも包含される。黒鉛は、上記の六角形格子構造のシートを層間結合させた構造である。本発明においてグラフェンは、平坦な状態で集電体表面に積層させて正極活物質層としてもよいし、褶曲したグラフェンを集電体上に載置させてもよい。いずれの場合も本発明の作用効果を得ることができる。 [Positive electrode active material layer]
The main component of the positive electrode active material layer of the present invention is graphene. Graphene is a sheet in which carbon atoms form a hexagonal lattice structure by sp 2 bonds, and is characterized by high conductivity and a large specific surface area. In recent years, the definition of graphene includes not only single-layer sheets but also sheets of about 2 to 10 layers. Graphite has a structure in which sheets of the above hexagonal lattice structure are bonded together. In the present invention, graphene may be laminated on the surface of the current collector in a flat state to form a positive electrode active material layer, or curved graphene may be placed on the current collector. In either case, the effects of the present invention can be obtained.

非水系電解液中のアニオンは、正極活物質層に引き付けられる。引き付けられたアニオンの一部は、グラフェンのシート表面に吸着する。用いられるグラフェンの比表面積が大きいほど良好なアニオン吸着能を発揮する。グラフェンは黒鉛と基本構造が同じであるため、シート片面におけるアニオン吸着能は、黒鉛と同等である。また複数層からなるグラフェンの層間や褶曲させたシートでは、シートの両面にアニオンを吸着させることができるため、黒鉛より高いアニオン吸着能を発揮する。本発明の正極活物質層は優れたアニオン吸着能を発揮し、高いファラデー型静電容量を形成する。上記の放出密度は、主にアニオン吸脱着機構に由来する。   Anions in the non-aqueous electrolyte are attracted to the positive electrode active material layer. Some of the attracted anions are adsorbed on the surface of the graphene sheet. The larger the specific surface area of the graphene used, the better the anion adsorption ability. Since graphene has the same basic structure as graphite, the anion adsorption capacity on one side of the sheet is equivalent to that of graphite. In addition, a graphene layer composed of a plurality of layers or a curved sheet can adsorb anions on both sides of the sheet, and thus exhibits higher anion adsorption ability than graphite. The positive electrode active material layer of the present invention exhibits excellent anion adsorption ability and forms a high Faraday type capacitance. The release density is mainly derived from the anion adsorption / desorption mechanism.

本発明の正極活物質層においては、グラフェンの端部にアニオンが接触することにより酸化還元反応が起こる。該酸化還元反応の電子の授受によりクーロン型静電容量が形成される。したがって本発明は、グラフェンを正極活物質とすることにより、正極でファラデー静電容量とクーロン型静電容量とからなる高い静電容量を形成でき、エネルギー密度を向上させることができる。本発明のエネルギー密度は、正極重量に対して少なくとも60 Ｗｈ／ｋｇであり、好ましくは80 Ｗｈ／ｋｇ以上である。   In the positive electrode active material layer of the present invention, an oxidation-reduction reaction occurs when an anion contacts the end portion of graphene. Coulomb-type capacitance is formed by the exchange of electrons in the oxidation-reduction reaction. Therefore, according to the present invention, by using graphene as the positive electrode active material, a high capacitance composed of a Faraday capacitance and a Coulomb capacitance can be formed on the positive electrode, and the energy density can be improved. The energy density of the present invention is at least 60 Wh / kg, preferably 80 Wh / kg or more based on the weight of the positive electrode.

グラフェンの端部は、ジグザグ型とアームチェア型とに大別される。ジグザグ型とアームチェア型とでは電子の移動速度が異なる。ジグザグ型の端部では電子の移動速度が極めて速いが、アームチェア型の端部では極めて遅い。したがって、アニオンが、ジグザグ型とアームチェア型とのいずれの端部と接触するかにより酸化還元反応による電子の授受効率が異なり、静電容量の向上にも影響を与えると考えられる。また、反応性が高い型の端部にアニオンを接触させたり、端部のサイズを最適化したりすることによっても、クーロン静電容量をさらに向上させることができると推察される。   The ends of graphene are roughly classified into zigzag types and armchair types. The movement speed of electrons differs between the zigzag type and the armchair type. At the end of the zigzag type, the moving speed of electrons is extremely fast, but at the end of the armchair type, it is extremely slow. Therefore, it is considered that the electron transfer efficiency by the oxidation-reduction reaction differs depending on whether the anion comes in contact with either the zigzag type or the armchair type, and this also affects the improvement of the capacitance. Further, it is presumed that the Coulomb capacitance can be further improved by bringing an anion into contact with the end of a highly reactive mold or by optimizing the size of the end.

本発明の正極活物質層は、上記のグラフェンと結着剤とを含有する。該グラフェンは正極活物質100質量部に対し少なくとも50質量部含有されていればよく、より好ましくは80質量部以上含有され、さらに好ましくは95質量部以上含有されることが好ましい。グラフェンの骨格構造を保持するため、グラフェンには結着剤が添加される。結着剤の例としては、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリイミド（ＰＩ）、ポリアミドイミド（ＰＡＩ）、キトサン、スチレン・ブタジエンゴム（ＳＢＲ）等を挙げることができる。   The positive electrode active material layer of the present invention contains the above graphene and a binder. The graphene may be contained at least 50 parts by mass with respect to 100 parts by mass of the positive electrode active material, more preferably 80 parts by mass or more, and still more preferably 95 parts by mass or more. In order to maintain the skeleton structure of graphene, a binder is added to graphene. Examples of the binder include polyvinylidene fluoride (PVDF), polyimide (PI), polyamideimide (PAI), chitosan, styrene-butadiene rubber (SBR), and the like.

本発明の正極活物質層は導電助剤の添加を排除しないが、グラフェンが高導電性を備えるため、本発明は、導電助剤を添加しなくても十分な電気伝導性を有する。該正極活物質層は、本発明の作用効果を阻害しない限りにおいて、他の成分を含有させることができる。   Although the positive electrode active material layer of the present invention does not exclude the addition of a conductive additive, graphene has high conductivity, and therefore the present invention has sufficient electrical conductivity even without adding a conductive additive. The positive electrode active material layer can contain other components as long as the effects of the present invention are not impaired.

［負極活物質層］
本発明の負極活物質層は、金属イオンを可逆的に吸蔵、放出する材料により形成される。本発明は、上記の機能を備える公知の材料を負極活物質として用いることができる。具体的には、金属イオンをプレドープさせた炭素材料、特にリチウムイオンをプレドープさせた炭素材料が挙げられる。炭素材料としては、リチウムイオンと共に層間化合物を形成することができるものであればよく、黒鉛が好ましく用いられる。なお、プレドープは常法に従って行うことができる。例えば、黒鉛等の炭素材料に後に説明する非水系電解質を常温以上で所定時間含浸させることにより行われる。他の材料としてはリチウム金属、In-Li等の金属や、黒鉛が挙げられる。 [Negative electrode active material layer]
The negative electrode active material layer of the present invention is formed of a material that reversibly occludes and releases metal ions. In the present invention, a known material having the above function can be used as the negative electrode active material. Specifically, a carbon material pre-doped with metal ions, particularly a carbon material pre-doped with lithium ions may be mentioned. Any carbon material may be used as long as it can form an intercalation compound with lithium ions, and graphite is preferably used. The pre-doping can be performed according to a conventional method. For example, it is carried out by impregnating a carbon material such as graphite with a non-aqueous electrolyte described later at room temperature or higher for a predetermined time. Examples of other materials include metals such as lithium metal and In-Li, and graphite.

［非水系電解液］
本発明に用いられる非水系電解液としては、非水系溶媒に電解質塩を溶解させたものが好ましく用いられる。該非水系溶媒としては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート，ブチレンカーボネート，ビニレンカーボネートなどの環状カーボネート、ジエチルカーボネート（ＤＥＣ），ジメチルカーボネート（ＤＭＣ），エチルメチルカーボネートなどの鎖状カーボネートなどの公知の有機溶媒を用いることができる。 [Non-aqueous electrolyte]
As the non-aqueous electrolyte used in the present invention, a solution obtained by dissolving an electrolyte salt in a non-aqueous solvent is preferably used. Examples of the non-aqueous solvent include known organic compounds such as cyclic carbonates such as ethylene carbonate (EC), propylene carbonate, butylene carbonate, and vinylene carbonate, and chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate. A solvent can be used.

また、Ｎ，Ｎ−ジエチル−Ｎ−エチル−Ｎ−（２−メトキシエチル）アンモニウムビス（トリフルオロスルホニル）イミド、Ｎ−メチル−Ｎ−プロピルピペリジウムビス（トリフルオロスルホニル）イミド、１−メチル−３−プロピルイミダゾリウムビス（トリフルオロスルホニル）イミド、１−エチル−３−ブチルイミダゾリウムテトラフルオロボレートなどのイオン液体を用いてもよい。
上記の溶媒は、単独で用いてもよく、２種以上を併用してもよい。 N, N-diethyl-N-ethyl-N- (2-methoxyethyl) ammonium bis (trifluorosulfonyl) imide, N-methyl-N-propylpiperidinium bis (trifluorosulfonyl) imide, 1-methyl- Ionic liquids such as 3-propylimidazolium bis (trifluorosulfonyl) imide and 1-ethyl-3-butylimidazolium tetrafluoroborate may be used.
Said solvent may be used independently and may use 2 or more types together.

電解質塩としては、塩化リチウム（ＬｉＣｌ）、フッ化リチウム（ＦＣｌ）、過塩素酸リチウム（ＬｉＣlＯ４）、硼フッ化リチウム（ＬｉＢＦ４）、ＬｉＡｓＦ６、ＬｉＰＦ６、Ｌｉ（ＣＦ３ＳＯ２）２Ｎを挙げることができる。電解質塩の含有量は、溶媒に対し0.1〜3.0ｍｏｌ％が好ましく、0.7〜1.3ｍｏｌ％がより好ましい。 Examples of the electrolyte salt include lithium chloride (LiCl), lithium fluoride (FCl), lithium perchlorate (LiClO 4 ), lithium borofluoride (LiBF 4 ), LiAsF 6 , LiPF 6 , and Li (CF 3 SO 2 ) 2. N. The content of the electrolyte salt is preferably 0.1 to 3.0 mol% and more preferably 0.7 to 1.3 mol% with respect to the solvent.

［電気化学デバイス］
上記の正極活物質層と負極活物質層とは、それぞれ集電体表面に積層させて正極材および負極材とする。本発明の電気化学デバイスは、該正極材と負極材とをセパレータを介して配置させた積層体を非水系電解液中に浸漬させてなる。
本発明は、正極活物質層にグラフェンを用いることにより、クーロン型とファラデー型との静電容量を形成し、エネルギー密度の高い電気化学デバイスを提供する。また本発明は、放出密度においてもリチウムイオン二次電池と比較して良好である。 [Electrochemical devices]
The positive electrode active material layer and the negative electrode active material layer are laminated on the surface of the current collector to form a positive electrode material and a negative electrode material. The electrochemical device of the present invention is formed by immersing a laminate in which the positive electrode material and the negative electrode material are disposed via a separator in a non-aqueous electrolyte solution.
The present invention provides an electrochemical device having a high energy density by forming a Coulomb type and a Faraday type capacitance by using graphene for a positive electrode active material layer. In addition, the present invention is good in emission density as compared with a lithium ion secondary battery.

セパレータには、ポリエチレン、ポリプロピレン等の公知の多孔膜が用いられる。集電体材料としては、公知の導電材を用いることができる。具体的には、アルミニウム、銅、ニッケル、チタン等からなるシートやフィルムを用いることができる。上記の導電材は金属単体として用いてもよく、合金としてもよい。   For the separator, a known porous film such as polyethylene or polypropylene is used. A known conductive material can be used as the current collector material. Specifically, a sheet or film made of aluminum, copper, nickel, titanium, or the like can be used. The conductive material may be used as a simple metal or an alloy.

［電気化学デバイスの製造方法］
本発明の電気化学デバイスの製造方法を、図１に示される積層構造を例として説明する。以下の説明では、負極活物質としてリチウム金属を用いる。 [Method of manufacturing electrochemical device]
The method for producing an electrochemical device of the present invention will be described with reference to the laminated structure shown in FIG. In the following description, lithium metal is used as the negative electrode active material.

上記の正極活物質層は、上記のグラフェンと結着剤とを溶媒中で混合させたスラリーを集電体表面に膜厚10〜500μｍ程度になるまで塗布し、乾燥させることにより形成することができる。
スラリーの溶媒は、Ｎ−メチル−２−ピロリドン（ＮＭＰ）、Ｎ, Ｎ-ジメチルアセトアミド、Ｎ, Ｎ-ジメチルホルムアミド等を用いることが好ましい。該溶媒にグラフェンと結着剤とを、スラリー100質量部に対しグラフェン50〜95質量部と、結着剤5〜50質量部になるように添加し、原料成分が均質に分散するまで撹拌させてスラリーを調製する。スラリー中には、分散剤や増粘剤等を適宜添加してもよい。また、溶媒を用いてスラリーとせず、グラフェンと結着剤のみを上記の組成で混合し、ペレットに成型してもよい。 The positive electrode active material layer may be formed by applying a slurry obtained by mixing the graphene and the binder in a solvent to the surface of the current collector until the film thickness is about 10 to 500 μm and drying the slurry. it can.
As the solvent for the slurry, N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide, N, N-dimethylformamide, or the like is preferably used. Graphene and a binder are added to the solvent so that the graphene is 50 to 95 parts by mass and the binder is 5 to 50 parts by mass with respect to 100 parts by mass of the slurry, and stirred until the raw material components are uniformly dispersed. To prepare a slurry. A dispersant, a thickener, and the like may be appropriately added to the slurry. In addition, without using a solvent as a slurry, only graphene and a binder may be mixed with the above composition and molded into a pellet.

上記の負極活物質層は、金属イオンを可逆的に吸蔵、放出できる材料を集電体表面に積層させることにより形成される。リチウム金属を用いる場合は、リチウム金属箔を集電体上に圧着させる。   The negative electrode active material layer is formed by laminating a material capable of reversibly occluding and releasing metal ions on the current collector surface. When lithium metal is used, a lithium metal foil is pressed onto the current collector.

黒鉛を用いる場合は、黒鉛を溶媒に均質に分散させたスラリーを調製する。得られた黒鉛スラリーを集電体に塗布し、乾燥させて負極活物質層を形成する。負極活物質層の膜厚は1〜500μｍ程度が好ましい。炭素材料を用いる場合は、さらに公知の方法を用いてリチウムイオンを吸蔵させ、プレドープを行う。   When graphite is used, a slurry in which graphite is homogeneously dispersed in a solvent is prepared. The obtained graphite slurry is applied to a current collector and dried to form a negative electrode active material layer. The thickness of the negative electrode active material layer is preferably about 1 to 500 μm. When a carbon material is used, lithium ions are further occluded using a known method and pre-doping is performed.

上記に例示する方法で集電体表面に正極活物質層を形成させた正極材と、集電体表面に負極活物質層を形成させた負極材との間にセパレータを挟んだ積層体を筐体内に配置し、非水系電解液を筐体内に注入する。非水系電解液を注入後は、大気中の水分との反応を回避するため筐体を封止する。筐体の形状は、コイン型、捲回型、角型等を選択することができる。   A laminate in which a separator is sandwiched between a positive electrode material in which a positive electrode active material layer is formed on the current collector surface and a negative electrode material in which a negative electrode active material layer is formed on the current collector surface by the method exemplified above is provided. Place in the body and inject non-aqueous electrolyte into the housing. After injecting the non-aqueous electrolyte, the casing is sealed to avoid reaction with moisture in the atmosphere. As the shape of the housing, a coin type, a wound type, a square type, or the like can be selected.

以下に実施例を挙げて本発明をさらに説明する。ただし本発明は下記の実施例に限定されない。
［実施例］
イソプロピルアルコールを加えながら、グラフェン4.75 gとPVDF 0.25 gとを乳鉢を用いて混合し、ロールプレスを用いて膜厚100μmのシート状に圧延した。直径16ｍｍのペレット状にシートを打ち抜き、真空乾燥させ正極材を得た。
リチウム金属箔を集電体上に圧着させて負極材を得た。正極材と負極材との間にポリエチレン薄膜を配置させた積層体を組み立てた。
エチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）との混合溶液に、ＬｉＰＦ４を１Ｍになるまで溶解させ、非水系電解液を調製した。
コインセル型筐体の内部に上記積層体を載置し、電解液を注入して封止し、実施例の電気化学デバイスとした。 The following examples further illustrate the present invention. However, the present invention is not limited to the following examples.
[Example]
While adding isopropyl alcohol, 4.75 g of graphene and 0.25 g of PVDF were mixed using a mortar and rolled into a sheet having a thickness of 100 μm using a roll press. A sheet was punched into a pellet having a diameter of 16 mm and vacuum-dried to obtain a positive electrode material.
Lithium metal foil was pressed on the current collector to obtain a negative electrode material. A laminate in which a polyethylene thin film was disposed between the positive electrode material and the negative electrode material was assembled.
LiPF 4 was dissolved in a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) until the concentration became 1M to prepare a nonaqueous electrolytic solution.
The laminated body was placed inside a coin cell type casing, and an electrolytic solution was injected and sealed to obtain an electrochemical device of an example.

［比較例］
表面積1500ｍ２/ｇの活性炭4.75gとPVDF0.25gとを乳鉢を用いて混合し、ロールプレスを用いて膜厚100μmのシート状に圧延した。直径16ｍｍのペレット状にシートを打ち抜き、真空乾燥させ正極材を得た。上記の活性炭を正極活物質とする正極材を用いた他は、上記の実施例と同様にして作成し、比較例の電気化学デバイスを得た。 [Comparative example]
4.75 g of activated carbon having a surface area of 1500 m 2 / g and 0.25 g of PVDF were mixed using a mortar and rolled into a sheet having a thickness of 100 μm using a roll press. A sheet was punched into a pellet having a diameter of 16 mm and vacuum-dried to obtain a positive electrode material. An electrochemical device of a comparative example was obtained in the same manner as in the above example except that the positive electrode material using the activated carbon as a positive electrode active material was used.

実施例および比較例の各電気化学デバイスを室温25℃、電流密度0.2ｍＡ／ｃｍ２で充放電を行った。得られた放電曲線から電極材質量当たりのエネルギー密度を計算した。得られたエネルギー密度を表１に記載する。 Each electrochemical device of the examples and comparative examples was charged and discharged at room temperature of 25 ° C. and a current density of 0.2 mA / cm 2 . The energy density per mass of the electrode material was calculated from the obtained discharge curve. The obtained energy density is shown in Table 1.

１００ 電気化学デバイス
１０１ 正極活物質層
１０２ 非水系電解質
１０３ セパレータ
１０４ 負極活物質層
１０５ 集電体
１０６ 集電体
DESCRIPTION OF SYMBOLS 100 Electrochemical device 101 Positive electrode active material layer 102 Non-aqueous electrolyte 103 Separator 104 Negative electrode active material layer 105 Current collector 106 Current collector

Claims (5)

正極活物質としてグラフェンを含有する正極活物質層と、負極活物質を含有する負極活物質層と、非水系電解液とを備える電気化学デバイス。   An electrochemical device comprising a positive electrode active material layer containing graphene as a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a non-aqueous electrolyte solution. グラフェンを少なくとも50質量％含有する前記正極活物質層を備える請求項１に記載される電気化学デバイス。   The electrochemical device according to claim 1, comprising the positive electrode active material layer containing at least 50% by mass of graphene. 前記負極活物質が金属イオンをプレドープさせた炭素材料、もしくは黒鉛である請求項１または請求項２に記載される電気化学デバイス。   The electrochemical device according to claim 1 or 2, wherein the negative electrode active material is a carbon material pre-doped with metal ions or graphite. 前記負極活物質が金属である請求項１または請求項２に記載される電気化学デバイス。   The electrochemical device according to claim 1, wherein the negative electrode active material is a metal. 前記負極活物質がリチウムイオンをプレドープさせた炭素材料、もしくはリチウム金属である請求項１または請求項２に記載される電気化学デバイス。   The electrochemical device according to claim 1 or 2, wherein the negative electrode active material is a carbon material pre-doped with lithium ions or lithium metal.
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