JP4595931B2 - Negative electrode material for lithium secondary battery and negative electrode sheet produced therefrom - Google Patents
Negative electrode material for lithium secondary battery and negative electrode sheet produced therefrom Download PDFInfo
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Description
本発明は、リチウム二次電池用負極材料及びそれから製造された負極シートに関する。詳しくは本発明は、充電受入性が高く、かつ電極の膨れの少ないリチウム二次電池用負極材料及びそれから製造された負極シートに関する。 The present invention relates to a negative electrode material for a lithium secondary battery and a negative electrode sheet produced therefrom. Specifically, the present invention relates to a negative electrode material for a lithium secondary battery having high charge acceptability and less electrode swelling, and a negative electrode sheet produced therefrom.
近年、電子機器の小型化に伴い二次電池の高容量化が望まれている。そのためニッケル・カドミウム二次電池、ニッケル・水素二次電池に比べ、よりエネルギー密度の高いリチウム二次電池（又はリチウムイオン二次電池）が注目されている。 In recent years, with the miniaturization of electronic devices, it is desired to increase the capacity of secondary batteries. Therefore, lithium secondary batteries (or lithium ion secondary batteries) with higher energy density are attracting attention as compared to nickel / cadmium secondary batteries and nickel / hydrogen secondary batteries.
その負極材料としては、最初にリチウム金属を用いることが試みられたが、充放電を繰り返すうちにデンドライト状のリチウムが析出し、セパレータを貫通して正極にまで達し、短絡して発火事故を起こす可能性があることが判明した。そのため、現在では、充放電過程における非水溶媒の出入りを層間で行ない、リチウム金属の析出を防止することのできる炭素材料を負極材料として使用することが注目されている。 As the negative electrode material, it was first attempted to use lithium metal, but dendritic lithium precipitated during repeated charging and discharging, reached the positive electrode through the separator, and short-circuited, causing a fire accident. It turns out that there is a possibility. Therefore, at present, attention is focused on the use of a carbon material capable of preventing the precipitation of lithium metal by allowing the non-aqueous solvent to enter and exit the charge / discharge process between the layers.
この炭素材料としては、特開昭５７−２０８０７９号公報に、黒鉛材料を使用することが提案されている。特に、結晶性のよい黒鉛をリチウム二次電池用の炭素負極材料として用いると、黒鉛のリチウム吸蔵の理論容量である３７２ｍＡｈ／ｇに近い容量が得られ、材料として好ましいことは知られている。
一方、黒鉛材料よりも結晶性の低い、いわゆる非晶質炭素材料を用いると黒鉛材料よりも重量当たりで高容量を得られることが知られているが、これらの材料は、Ｌｉに対する電位が高く、正極との電位差が取りにくいという欠点がある。また、真密度が黒鉛より小さいので、体積当たりの容量が低くなるという欠点があった。更に、一般に粒子が堅いので、電極成形性に欠け、従って電極密度を向上させにくいという問題もあった。
As this carbon material, Japanese Patent Application Laid-Open No. 57-208079 proposes to use a graphite material. In particular, it is known that when graphite having good crystallinity is used as a carbon negative electrode material for a lithium secondary battery, a capacity close to 372 mAh / g, which is the theoretical capacity of graphite occlusion, can be obtained.
On the other hand, it is known that when a so-called amorphous carbon material having lower crystallinity than graphite material is used, a higher capacity per unit weight than graphite material can be obtained. However, these materials have a higher potential with respect to Li. There is a drawback that it is difficult to take a potential difference from the positive electrode. Further, since the true density is smaller than that of graphite, there is a disadvantage that the capacity per volume is lowered. Furthermore, since the particles are generally hard, there is a problem that the electrode moldability is lacking and it is difficult to improve the electrode density.
また、リチウム二次電池の一形態として、これが角型であるものは、充放電時に生じる電極の膨れなどにより、筐体が膨れるという現象が報告されている。最初からこの膨れを考慮して電池体積を設計すると、筐体の厚みを必然的に薄くせざるを得ず、電池容量の低下を招くことになる。 In addition, as one form of the lithium secondary battery, it has been reported that a case where this is a square type has a case in which the housing swells due to the swelling of the electrodes generated during charging and discharging. If the battery volume is designed in consideration of this swelling from the beginning, the thickness of the casing must be reduced, and the battery capacity is reduced.
本発明の課題は、非晶質炭素材料を用いた場合に比較して、リチウム充放電時の電位の変化がＬｉの電位に近く、かつ充放電による電位ヒステリシスを持たないので、正極電位との差を取りやすい負極材料でありながら、高容量で、Ｌｉの充電受入性が高く、かつ電極の膨れも少ないことで、角型電池用としても好適なリチウム二次電池用負極材料を提供することである。 The problem of the present invention is that, compared with the case of using an amorphous carbon material, the change in potential at the time of lithium charging / discharging is close to the potential of Li and has no potential hysteresis due to charging / discharging. To provide a negative electrode material for a lithium secondary battery that is suitable for a prismatic battery because it is a negative electrode material that can easily take a difference, has a high capacity, has a high charge acceptability for Li, and has little electrode swelling. It is.
本発明者らは、上記課題を解決するため鋭意検討を重ねた結果、特定の炭素質材料が上記課題を解決することを見出して本発明に到達した。
即ち本発明の要旨は、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体状の負極材料であって、該黒鉛系炭素質物の粒径と、該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体の粒径とが同じであり、かつ黒鉛系炭素質物より結晶性の劣る炭素質物の含有量が、粉体全体を１００質量％とした時、１．２質量％以上６．３質量％以下の範囲である負極材料であり、負極材料と結着剤とから下記の負極の作成及び評価条件で作製され、かつ評価された場合のリチウム二次電池用負極の抵抗（Ｒ）が、６．５ｏｈｍ以下、負極／電解液界面の二重層容量（Ｃｄｌ）が、７．０×１０-4Ｆ以上、１０×１０-4Ｆ未満の範囲にあることを特徴とするリチウム二次電池用負極材料に存する。
・負極の作製及び評価条件
（ａ）負極材料粉体１０ｇに対し、粉体結着剤としてカルボキシメチルセルロース１質量％、及びスチレン・ブタジエンゴム１質量％を加えたものをミキサーで３分間撹拌し、スラリーを得る。このスラリーを集電体である銅箔上に塗布し、１１０℃で予備乾燥を行う。塗布は、集電体上に負極材料粉体が１０±０．１ｍｇ／ｃｍ2付着するようにする。乾燥後、電極密度を１．５±０．０３ｇ／ｃｍ3に調整し、負極シートとし、更に１５０℃で真空減圧乾燥を施して負極とする。
（ｂ）溶質としてＬｉＰＦ6を１ｍｏｌ／Ｌになるように溶解させたエチレンカーボネート及びエチルメチルカーボネート（１：１）を含む電解液を用い、セパレータ（多孔性ポリエチレンフィルム製）を介してＬｉＣｏＯ2を対極とした２０３２コイン型セルを組む。
（ｃ）上記２０３２コイン型セルについて、２４時間測定前休止をおいた後、０．６ｍＡ／ｃｍ2の電流値で、極間電位差が４．２Ｖになるまで充電を行い、極間電位差が３．０Ｖになるまで放電する。この充放電を室温で６回行った後、７回目の４．２Ｖ充電時に１０-2〜１０5Ｈｚの周波数帯で複素インピーダンス測定を行い、負極部分の抵抗（Ｒ）と、負極／電解液界面の二重層容量（Ｃｄｌ）を測定する。この際、正極や低周波部分の因子の影響を避ける為に、負極の被膜抵抗成分として現れる円弧の一部を外挿し、上記数値を求める。各数値はコイン型セル３個の結果の平均値とする。
As a result of intensive studies to solve the above problems, the present inventors have found that a specific carbonaceous material can solve the above problems, and have reached the present invention.
That is, the gist of the present invention is a powdery negative electrode material having a structure in which a carbonaceous material that is less crystalline than the graphite-based carbonaceous material is deposited on the graphite-based carbonaceous material, the particle size of the graphite-based carbonaceous material When the particle diameter and the same der powder having a structure obtained by depositing a carbonaceous material inferior graphite-based carbonaceous material having crystallinity is, and the content of crystallinity less carbonaceous material from the graphite carbonaceous material , when the entire powder is 100 mass%, a negative electrode material Ru der range of 1.2 mass% or more 6.3 wt%, made from a negative electrode material and the binder of the negative electrode below and evaluation conditions When the resistance (R) of the negative electrode for a lithium secondary battery is 6.5 ohms or less and the double layer capacity (Cdl) at the negative electrode / electrolyte interface is 7.0 × 10 −4 F above, it exists on the negative electrode material for lithium secondary battery, characterized in that in the range of less than 10 × 10 -4 F That.
· To a negative electrode of Production and Evaluation conditions (a) an anode material powder 10 g, carboxymethyl cellulose 1 wt% as a powder binder, and which was added 1 wt% styrene-butadiene stirred for 3 minutes in a mixer, A slurry is obtained. This slurry is applied on a copper foil as a current collector, and pre-dried at 110 ° C. The application is performed so that the negative electrode material powder adheres to 10 ± 0.1 mg / cm 2 on the current collector. After drying, the electrode density is adjusted to 1.5 ± 0.03 g / cm 3 to form a negative electrode sheet, which is further vacuum dried at 150 ° C. to obtain a negative electrode.
(B) Using an electrolytic solution containing ethylene carbonate and ethyl methyl carbonate (1: 1) in which LiPF 6 is dissolved to 1 mol / L as a solute, LiCoO 2 is passed through a separator (made of a porous polyethylene film). A 2032 coin cell as a counter electrode is assembled.
(C) The 2032 coin cell was charged for 24 hours before measurement, and then charged at a current value of 0.6 mA / cm 2 until the potential difference between the electrodes reached 4.2 V. The potential difference between the electrodes was 3 Discharge until 0V. After this charge / discharge was performed 6 times at room temperature, complex impedance measurement was performed in the frequency band of 10 −2 to 10 5 Hz during the 7th 4.2 V charge, and the resistance (R) of the negative electrode portion and the negative electrode / electrolyte The double layer capacity (Cdl) at the interface is measured. At this time, in order to avoid the influence of the factors of the positive electrode and the low frequency portion, a part of the arc appearing as the film resistance component of the negative electrode is extrapolated to obtain the above numerical value. Each numerical value is an average value of the results of three coin-type cells.
また、本発明の他の要旨は、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体状の負極材料であって、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物となる有機物質を付着させた後、６５０〜８５０℃で焼成し、当該焼成物を解砕して得られ、該黒鉛系炭素質物の粒径と、該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体の粒径とが同じであり、かつ黒鉛系炭素質物より結晶性の劣る炭素質物の含有量が、粉体全体を１００質量％とした時、１．２質量％以上６．３質量％以下の範囲である負極材料であり、負極材料と結着剤とから上記の負極の作成及び評価条件で作製され、かつ評価された場合のリチウム二次電池用負極の抵抗（Ｒ）が、６．５ｏｈｍ以下、負極／電解液界面の二重層容量（Ｃｄｌ）が、７．０×１０-4Ｆ以上、１０×１０-4Ｆ未満の範囲にあることを特徴とするリチウム二次電池用負極材料に存する。
また、本発明の他の要旨は、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体状の負極材料に結着剤を加えてシート状に成形してなる負極シートであって、該負極材料が、該黒鉛系炭素質物の粒径と、該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体の粒径とが同じである負極材料であり、該負極材料と結着剤とから上記の負極の作成及び評価条件で作製され、かつ評価された場合のリチウム二次電池用負極の抵抗（Ｒ）が、６．５ｏｈｍ以下、負極／電解液界面の二重層容量（Ｃｄｌ）が、７．０×１０-4Ｆ以上、１０×１０-4Ｆ未満の範囲にあることを特徴とするリチウム二次電池用負極シートに存する。
また、本発明の他の要旨は、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体状の負極材料に結着剤を加えてシート状に成形してなる負極シートであって、該負極材料が、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物となる有機物質を付着させた後、６５０〜８５０℃で焼成し、当該焼成物を解砕して得られ、該黒鉛系炭素質物の粒径と、該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体の粒径とが同じであり、かつ黒鉛系炭素質物より結晶性の劣る炭素質物の含有量が、粉体全体を１００質量％とした時、１．２質量％以上６．３質量％以下の範囲である負極材料であり、該負極材料と結着剤とから下記の条件で作製され、かつ評価された場合のリチウム二次電池用負極の抵抗（Ｒ）が、６．５ｏｈｍ以下、負極／電解液界面の二重層容量（Ｃｄｌ）が、７．０×１０-4Ｆ以上、１０×１０-4Ｆ未満の範囲にあるものに、結着剤を加えてシート状に成形してなることを特徴とするリチウム二次電池用負極シートに存する。
また、本発明の他の要旨は、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体状の負極材料であって、該黒鉛系炭素質物の粒径と、該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体の粒径とが同じであり、かつ黒鉛系炭素質物より結晶性の劣る炭素質物の含有量が、粉体全体を１００質量％とした時、１．２質量％以上６．３質量％以下の範囲であることを特徴とするリチウム二次電池用負極材料の存する。
また、本発明の他の要旨は、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体状の負極材料であって、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物となる有機物質を付着させた後、６５０〜８５０℃で焼成し、当該焼成物を解砕して得られ、該黒鉛系炭素質物の粒径と、該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体の粒径とが同じであり、かつ黒鉛系炭素質物より結晶性の劣る炭素質物の含有量が、粉体全体を１００質量％とした時、１．２質量％以上６．３質量％以下の範囲であることを特徴とするリチウム二次電池用負極材料に存する。
Another aspect of the present invention is a negative-electrode material of powder form having deposited is not a structure of crystallinity less carbonaceous material from the graphite-based carbonaceous material to graphite carbonaceous material, a graphite-based carbonaceous material After adhering an organic substance that becomes a carbonaceous material that is less crystalline than the graphite-based carbonaceous material, firing is performed at 650-850 ° C., and the fired material is pulverized to obtain the particle size of the graphite-based carbonaceous material. , particle size and the same der powder having a structure obtained by depositing a carbonaceous material inferior graphite-based carbonaceous material having crystallinity is, and the content of crystallinity less carbonaceous material from the graphite carbonaceous material, when the entire powder is 100 mass%, a negative electrode material Ru der range of 1.2 mass% or more 6.3 wt%, and a negative electrode material and the binder of the above negative electrode creation and evaluation conditions When manufactured and evaluated, the resistance (R) of the negative electrode for a lithium secondary battery was 6.5 ohms. Lower, negative electrode / electrolyte double layer capacity of the interface (Cdl) is, 7.0 × 10 -4 F or more, the negative electrode material for lithium secondary battery, characterized in that in the range of less than 10 × 10 -4 F Exist.
Another aspect of the present invention is that a sheet is formed by adding a binder to a powdery negative electrode material having a structure in which a carbonaceous material that is less crystalline than the graphite-based carbonaceous material is deposited on the graphite-based carbonaceous material. A negative electrode sheet formed into a powder particle having a structure in which the negative electrode material has a structure in which a particle size of the graphite- based carbonaceous material and a carbonaceous material that is less crystalline than the graphite- based carbonaceous material are deposited. A negative electrode material having the same diameter, and the resistance (R) of the negative electrode for a lithium secondary battery when the negative electrode material and the binder are prepared and evaluated under the above-described negative electrode preparation and evaluation conditions. , 6.5 ohms or less, and the double layer capacity (Cdl) at the negative electrode / electrolyte interface is in the range of 7.0 × 10 −4 F or more and less than 10 × 10 −4 F, It exists in the negative electrode sheet.
Another aspect of the present invention is that a sheet is formed by adding a binder to a powdery negative electrode material having a structure in which a carbonaceous material that is less crystalline than the graphite-based carbonaceous material is deposited on the graphite-based carbonaceous material. The negative electrode sheet is formed into a negative electrode sheet , and the negative electrode material is baked at 650 to 850 ° C. after adhering an organic substance that becomes a carbonaceous material having lower crystallinity than the graphite-based carbonaceous material to the graphite-based carbonaceous material. The particle size of the graphite-based carbonaceous material obtained by crushing the fired product is the same as the particle size of the powder having a structure in which a carbonaceous material that is less crystalline than the graphite-based carbonaceous material is deposited. der is, and the content of crystallinity less carbonaceous material from the graphite carbonaceous material, when the entire powder is 100 mass%, 1.2 mass% or more 6.3 wt% or less der Ru anode This is a material manufactured from the negative electrode material and the binder under the following conditions and evaluated. Resistance of the arm secondary battery negative electrode (R) is, 6.5Ohm less, the negative electrode / electrolyte double layer capacity of the interface (Cdl) is, 7.0 × 10 -4 F or higher, 10 × 10 -4 less than F It exists in the negative electrode sheet for lithium secondary batteries characterized by adding a binder to what is in a range, and shape | molding in a sheet form.
Another gist of the present invention is a powdery negative electrode material having a structure in which a carbonaceous material having lower crystallinity than that of the graphite-based carbonaceous material is deposited on the graphite-based carbonaceous material, The particle size of the powder is the same as the particle size of the powder having a structure in which the carbonaceous material that is less crystalline than the graphite-based carbonaceous material is deposited, and the carbonaceous material that is less crystalline than the graphite-based carbonaceous material The negative electrode material for a lithium secondary battery is characterized in that the amount is in the range of 1.2% by mass to 6.3% by mass when the total powder is 100% by mass.
Another gist of the present invention is a powdery negative electrode material having a structure in which a carbonaceous material having lower crystallinity than that of the graphite-based carbonaceous material is deposited on the graphite-based carbonaceous material. After adhering an organic substance that becomes a carbonaceous material that is less crystalline than the graphite-based carbonaceous material, firing is performed at 650-850 ° C., and the fired material is pulverized to obtain the particle size of the graphite-based carbonaceous material. The particle size of the powder having the structure in which the carbonaceous material having lower crystallinity than that of the graphite-based carbonaceous material is deposited and the content of the carbonaceous material having lower crystallinity than the graphite-based carbonaceous material is The present invention resides in a negative electrode material for a lithium secondary battery, characterized by being in the range of 1.2 mass% or more and 6.3 mass% or less when the whole body is 100 mass%.
本発明によれば、充電受入性が高く、かつ電極の膨れの少ないリチウム二次電池用負極材料及び負極シートを得ることができる。 According to the present invention, it is possible to obtain a negative electrode material and a negative electrode sheet for a lithium secondary battery that have high charge acceptability and little electrode swelling.
以下、本発明の実施の形態につき詳細を述べる。
本発明のリチウム二次電池用負極材料は、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造を有する粉体状の負極材料であって、特定の物性を有するものである。
Details of the embodiments of the present invention will be described below.
The negative electrode material for a lithium secondary battery of the present invention is a powdery negative electrode material having a structure in which a carbonaceous material that is less crystalline than the graphite-based carbonaceous material is deposited on the graphite-based carbonaceous material, and has specific physical properties It is what has.
ここで「被着」とは、ある材料からなる核材の表面の少なくとも一部に他の材料からなる被覆相を形成させることを意味し、該被覆相の形成が該核材に対して外部から供給された材料の付着によるか、或いは該核材の表面部の材料の変質によるかは問わない。
［黒鉛系炭素質物］
本発明において核材として用いられる黒鉛系炭素質物とは、高結晶性の黒鉛系炭素質物を指し、好ましくはＸ線広角回折法による（００２）面の面間隔（ｄ００２）が３．３７Å未満の黒鉛系炭素質物を用いる。
Here, “deposition” means that a coating phase made of another material is formed on at least a part of the surface of the core material made of a certain material, and the formation of the coating phase is external to the core material. It does not matter whether it is due to the adhesion of the material supplied from or from the alteration of the material on the surface of the core material.
[Graphite-based carbonaceous material]
The graphite-based carbonaceous material used as a core material in the present invention refers to a highly crystalline graphite-based carbonaceous material, and preferably has a (002) plane spacing (d002) of less than 3.37 mm by X-ray wide angle diffraction. A graphite-based carbonaceous material is used.
黒鉛系炭素質物の具体例としては、天然黒鉛、人造黒鉛、又はこれらの機械的粉砕品、再熱処理品、膨張黒鉛の再熱処理品、或いはこれらの黒鉛の高純度精製品から選ばれる粉体が好ましい。
上記人造黒鉛の具体例としては、コールタールピッチ、石炭系重質油、常圧残油、石油系重質油、芳香族炭化水素、窒素含有環状化合物、硫黄含有環状化合物、ポリフェニレン、ポリ塩化ビニル、ポリビニルアルコール、ポリアクリロニトリル、ポリビニルブチラール、各種天然高分子、ポリフェニレンサルファイド、ポリフェニレンオキシド、フルフリルアルコール樹脂、フェノール−ホルムアルデヒド樹脂、イミド樹脂等から選ばれる１種以上の有機物質を、通常、２５００℃以上、３２００℃以下程度の焼成温度で黒鉛化したものを、適当な粉砕手段で粉化したものが好ましい。
Specific examples of the graphite-based carbonaceous material include natural graphite, artificial graphite, or a mechanically pulverized product thereof, a reheated product, a reheated product of expanded graphite, or a powder selected from high-purity purified products of these graphites. preferable.
Specific examples of the artificial graphite include coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride. One or more organic substances selected from polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, various natural polymers, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin, etc., usually at 2500 ° C. or higher What was graphitized at a firing temperature of about 3200 ° C. or less and pulverized by an appropriate pulverizing means is preferable.
［黒鉛系炭素質物より結晶性の劣る炭素質物］
上記の黒鉛系炭素質物からなる核材の表面に被覆相を形成させるための「黒鉛系炭素質物より結晶性の劣る炭素質物」としては、核材の黒鉛系炭素質物より結晶性の劣る種々の炭素質物を用いることができ、通常、Ｘ線広角回折法による（００２）面の面間隔（ｄ００２）が３．３７Å以上を示すような結晶性の低い各種炭素質物を用いる。
[Carbonaceous material with lower crystallinity than graphite-based carbonaceous material]
The “carbonaceous material having lower crystallinity than the graphite-based carbonaceous material” for forming a coating phase on the surface of the above-mentioned graphite-based carbonaceous material has various crystallinity inferior to that of the graphite-based carbonaceous material. A carbonaceous material can be used, and various carbonaceous materials having low crystallinity such that the (002) plane spacing (d002) by X-ray wide angle diffraction method is 3.37 mm or more are usually used.
上記「黒鉛系炭素質物より結晶性の劣る炭素質物」からなる被覆相の形成は、黒鉛系炭素質物からなる核材の表面部の変質、核材の外部から供給された結晶性の劣る炭素質物からなる材料の付着、或いは核材の外部から供給された各種材料の付着及び結晶性の劣る炭素質物への変質、等の種々の形態で達成される。その詳細は次項において詳述する。 The formation of the coating phase composed of the above-mentioned “carbonaceous material having lower crystallinity than graphite-based carbonaceous material” is caused by alteration of the surface portion of the core material made of graphite-based carbonaceous material, or carbonaceous material having inferior crystallinity supplied from the outside of the core material. It is achieved in various forms such as adhesion of a material made of or adhesion of various materials supplied from the outside of the core material and transformation to a carbonaceous material having poor crystallinity. Details will be described in the next section.
［リチウム二次電池用負極材料］
本発明のリチウム二次電池用負極材料は、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣る炭素質物を被着させた構造、即ち黒鉛系炭素質物からなる核材の表面の少なくとも一部に該黒鉛系炭素質物より結晶性の劣る炭素質物からなる被覆相を形成させた構造、を有する粉体状の負極材料である。
[Anode material for lithium secondary battery]
The negative electrode material for a lithium secondary battery of the present invention has a structure in which a carbonaceous material that is less crystalline than the graphite-based carbonaceous material is deposited on the graphite-based carbonaceous material, that is, at least one of the surfaces of the core material composed of the graphite-based carbonaceous material. This is a powdery negative electrode material having a structure in which a coating phase made of a carbonaceous material that is less crystalline than the graphite-based carbonaceous material is formed in the part.
上記リチウム二次電池用負極材料における、黒鉛系炭素質物と、該黒鉛系炭素質物より結晶性の劣る炭素質物との割合は、重量比で通常、９９／１〜５０／５０、好ましくは９
８／２〜９５／５、更に好ましくは９８／２〜９６／４である。結晶性の劣る炭素質物の量が少なすぎると被覆の効果が薄く、逆に多すぎると負極容量の低下を招く。
In the negative electrode material for a lithium secondary battery, the ratio of the graphite-based carbonaceous material to the carbonaceous material that is less crystalline than the graphite-based carbonaceous material is usually 99/1 to 50/50, preferably 9 in weight ratio.
It is 8/2 to 95/5, more preferably 98/2 to 96/4. If the amount of the carbonaceous material having inferior crystallinity is too small, the coating effect is thin, and conversely if too large, the negative electrode capacity is reduced.
前記の通り、黒鉛系炭素質物にこれより結晶性の劣る炭素質物を被着させる方法、即ち黒鉛系炭素質物の表面にこれより結晶性の劣る炭素質物からなる被覆相を形成させる方法、は多様であるが、代表的な方法は次の通りである。
1) 黒鉛系炭素質物を機械的又は化学的に処理して、その表面部の黒鉛系炭素質物をより結晶性の劣る炭素質物に変質させる方法。
As described above, there are various methods for depositing a carbonaceous material with poorer crystallinity on the graphite-based carbonaceous material, that is, methods for forming a coating phase composed of a carbonaceous material with less crystalline property on the surface of the graphite-based carbonaceous material. However, a typical method is as follows.
1) A method in which a graphite-based carbonaceous material is mechanically or chemically treated to change the surface of the graphite-based carbonaceous material into a carbonaceous material having poorer crystallinity.
2) Ｘ線広角回折法による（００２）面の面間隔（ｄ００２）が３．３７Å以上を示すような結晶性の低い土状黒鉛や鱗状黒鉛、これらの粉砕物、好ましくはレーザー回折法で得られる平均粒径ｄ５０が５μｍ以下、更に好ましくは１μｍ以下、最も好ましくは０．５μｍ以下となるように微粉砕した粉体、を黒鉛系炭素質物の表面に、必要により適当な粉体結着剤を用いて、結着させる方法。 2) Soil-like graphite and scale-like graphite with low crystallinity such that the (002) plane spacing (d002) is 3.37 mm or more by X-ray wide-angle diffraction method, these pulverized products, preferably obtained by laser diffraction method A powder powder finely pulverized so that the average particle diameter d50 is 5 μm or less, more preferably 1 μm or less, and most preferably 0.5 μm or less, and a suitable powder binder on the surface of the graphite-based carbonaceous material. A method of binding using
3) 焼成後にはリチウムイオンを吸蔵・放出可能な結晶性の劣る炭素質物に変質し得る性質を有する有機物質を、黒鉛系炭素質物の表面に付着させ、これを焼成して結晶性の劣る炭素質物に変質させる方法。
上記各方法の中では上記3)の方法（以下、焼成法という）が、簡便であり、かつ得られる効果としても優れた方法である。
3) After firing, an organic substance having the property of transforming into a carbonaceous material with poor crystallinity capable of inserting and extracting lithium ions is attached to the surface of the graphite-based carbonaceous material, and this is baked to produce carbon with poor crystallinity. A method of changing to a quality material.
Among the above-mentioned methods, the method 3) (hereinafter referred to as a firing method) is simple and has excellent effects.
上記焼成法において使用される有機物質の具体例としては、炭素化可能な有機物質として、液相で炭素化が進行する軟ピッチから硬ピッチまでのコールタールピッチや乾留液化油などの石炭系重質油や、常圧残油、減圧残油等の直留系重質油、原油、ナフサなどの熱分解時に副生するエチレンタール等分解系重質油等の石油系重質油、或いは以上のものを炭素化が進む以下の温度で蒸留、溶媒抽出等の手段を経て固化したものが挙げられる。更にアセナフチレン、デカシクレン、アントラセンなどの芳香族炭化水素、フェナジンやアクリジンなどの窒素含有環状化合物、チオフェンなどの硫黄含有環状化合物、３０ＭＰａ以上の加圧が必要となるがアダマンタンなどの多環脂環式化合物が挙げられる。また熱可塑性高分子である、炭素化に至る過程で液相を経るビフェニルやテルフェニルなどのポリフェニレン、ポリ塩化ビニル、ポリ酢酸ビニル、ポリビニルブチラールなどのポリビニルエステル類、ポリビニルアルコールが挙げられる。また、上記各種の有機物質に適量の燐酸、ホウ酸、塩酸などの酸類、水酸化ナトリウム等のアルカリ類を添加したものでもよい。更にこれらのものを３００〜６００℃、好ましくは３００〜４００℃で酸素、硫黄、窒素、又は硼素から選ばれる元素により適度に架橋処理したものでもよい。 Specific examples of the organic material used in the above-mentioned calcination method include, as carbonizable organic materials, coal-based heavy materials such as coal tar pitches from soft pitches to hard pitches where carbonization proceeds in a liquid phase to hard pitches and dry distillation liquefied oils. Petroleum heavy oil such as heavy oil, straight-run heavy oil such as atmospheric residual oil and vacuum residual oil, cracked heavy oil such as ethylene tar produced as a by-product during thermal cracking of crude oil, naphtha, etc. And solidified through means such as distillation and solvent extraction at the following temperatures at which carbonization proceeds. Furthermore, aromatic hydrocarbons such as acenaphthylene, decacyclene and anthracene, nitrogen-containing cyclic compounds such as phenazine and acridine, sulfur-containing cyclic compounds such as thiophene, and polycyclic alicyclic compounds such as adamantane which require pressurization of 30 MPa or more Is mentioned. Examples of the thermoplastic polymer include polyphenylenes such as biphenyl and terphenyl, which pass through a liquid phase in the process of carbonization, polyvinyl esters such as polyvinyl chloride, polyvinyl acetate, and polyvinyl butyral, and polyvinyl alcohol. In addition, an appropriate amount of acids such as phosphoric acid, boric acid and hydrochloric acid, and alkalis such as sodium hydroxide may be added to the above various organic substances. Further, these may be appropriately crosslinked at 300 to 600 ° C., preferably 300 to 400 ° C., with an element selected from oxygen, sulfur, nitrogen, or boron.
上記焼成法においては、上記黒鉛系炭素質物と上記有機物質とを混合し、焼成を行う。焼成温度は、通常、５００〜２２００℃、好ましくは６５０〜８５０℃、更に好ましくは７００〜８００℃とする。焼成温度が低すぎると導電性に劣り、充電受入性が悪化する。逆に高すぎると電極膨れが大きくなる。また、焼成時に容器へ詰め込む粉体厚みは、通常１〜５０ｃｍ、好ましくは５〜２０ｃｍとし、更に焼成時の圧力は、通常０．１００〜０．４００ＭＰａ、好ましくは０．１０１〜０．２００ＭＰａとする。 In the firing method, the graphite-based carbonaceous material and the organic material are mixed and fired. The firing temperature is usually 500 to 2200 ° C, preferably 650 to 850 ° C, more preferably 700 to 800 ° C. If the firing temperature is too low, the electrical conductivity is inferior and the charge acceptability deteriorates. On the other hand, if it is too high, the swelling of the electrode becomes large. Further, the thickness of the powder packed in the container at the time of firing is usually 1 to 50 cm, preferably 5 to 20 cm, and the pressure at the time of firing is usually 0.100 to 0.400 MPa, preferably 0.101 to 0.200 MPa. To do.
上記焼成の後、適当な解砕、または粉砕を行って、粒径を通常４〜４０μｍ、好ましくは１０〜３２μｍ、更に好ましくは１５〜３０μｍに調整することによって、本発明のリチウム二次電池用負極材料が得られる。
本発明のリチウム二次電池用負極材料は、後述の［電極材料の評価方法］に記載した方法に従って、これと結着剤とからリチウム二次電池用負極を作製して、２０３２コイン型セルを組み、複素インピーダンス測定を行うことによって得られる、負極部分の抵抗（Ｒ）が、６．５ｏｈｍ以下、また負極と電解液との界面の二重層容量（Ｃｄｌ）が、７．０ｘ１０-4Ｆ以上、１０ｘ１０-4Ｆ未満の範囲にある必要がある。上記のような好ましい性質の取得は、上記のような焼成温度の範囲内での焼成温度の調整によって達成することができる。
After the above firing, suitable pulverization or pulverization is performed to adjust the particle size to usually 4 to 40 μm, preferably 10 to 32 μm, more preferably 15 to 30 μm, so that the lithium secondary battery of the present invention is used. A negative electrode material is obtained.
A negative electrode material for a lithium secondary battery according to the present invention is prepared by preparing a negative electrode for a lithium secondary battery from this and a binder in accordance with the method described in [Method for evaluating electrode material] described later. The resistance (R) of the negative electrode portion obtained by combining and measuring complex impedance is 6.5 ohms or less, and the double layer capacity (Cdl) at the interface between the negative electrode and the electrolyte is 7.0 × 10 −4 F or more. It must be in the range of less than 10 × 10 −4 F. Acquisition of such preferable properties can be achieved by adjusting the firing temperature within the range of the firing temperature as described above.
また、上記リチウム二次電池用負極材料及び該負極材料と結着剤とから作製されたリチウム二次電池用負極について、Ｎ2ガスを用いたＢＥＴ表面積の測定を行い、得られた値
から下記式（１）で計算される、結着剤による活物質の表面被覆率Γ（％）が２０〜５５％の範囲にあるのが好ましい。
In addition, for the negative electrode material for lithium secondary batteries and the negative electrode for lithium secondary batteries prepared from the negative electrode material and a binder, the BET surface area was measured using N 2 gas. It is preferable that the surface coverage Γ (%) of the active material by the binder calculated by the formula (1) is in the range of 20 to 55%.
（数１）
表面被覆率Γ＝（粉体ＳＡ−負極ＳＡ）／粉体ＳＡｘ１００ （１）
粉体ＳＡ：リチウム二次電池用負極材料のＢＥＴ表面積
負極ＳＡ：リチウム二次電池用負極のＢＥＴ表面積
また、上記リチウム二次電池用負極材料のＮ2ガスによるＢＥＴ表面積が２．４〜４ｍ2／ｇであるのが好ましい。
(Equation 1)
Surface coverage Γ = (powder SA-negative electrode SA) / powder SAx100 (1)
Powder SA: BET surface area of negative electrode material for lithium secondary battery Negative electrode SA: BET surface area of negative electrode for lithium secondary battery The BET surface area of N 2 gas of the negative electrode material for lithium secondary battery is 2.4 to 4 m 2. / G is preferred.
また、上記リチウム二次電池用負極材料について、波長５１４５Åのアルゴンイオンレーザー光を用いたラマンスペクトル分析した結果で、１５７０〜１６２０ｃｍ-1の範囲に存在するピークの強度をＩA、１３５０〜１３７０ｃｍ-1の範囲に存在するピークの強度をＩBとしたとき、その比であるＲ値（＝ＩB／ＩA）が０．４を超えるものは、低抵抗な負極界面の被膜を形成しやすいので好ましい。 Moreover, the negative electrode material for the lithium secondary battery, the results obtained by Raman spectroscopy using an argon ion laser beam having a wavelength of 5145 Å, a peak of intensity I A existing in the range of 1570~1620cm -1, 1350~1370cm - When the intensity of the peak existing in the range of 1 is I B , the ratio R value (= I B / I A ) exceeding 0.4 tends to form a low-resistance negative electrode interface film. Therefore, it is preferable.
［リチウム二次電池用負極］
次に本発明のリチウム二次電池用負極材料を用いてリチウム二次電池用負極シート、或いはリチウム二次電池用負極を製造する方法について説明する。
負極の製造方法は、上記本発明のリチウム二次電池用負極材料を負極の成分として含む限り、特に限定されず、従来公知の種々の方法が採用可能である。例えば、リチウム二次電池用負極材料に結着剤及び溶媒等を加えてスラリー状とし、銅箔等の金属製の集電体基板に上記スラリーを塗布・乾燥して負極シートを形成させることで負極とする。銅箔の代わりにニッケル箔やステンレス箔を用いてもよい。また、上記負極材料をそのままロール成形、圧縮成形等の方法で負極シートの形状に成形することもできる。
[Negative electrode for lithium secondary battery]
Next, a method for producing a negative electrode sheet for a lithium secondary battery or a negative electrode for a lithium secondary battery using the negative electrode material for a lithium secondary battery of the present invention will be described.
The method for producing the negative electrode is not particularly limited as long as the negative electrode material for a lithium secondary battery of the present invention is included as a component of the negative electrode, and various conventionally known methods can be employed. For example, by adding a binder and a solvent to a negative electrode material for a lithium secondary battery to form a slurry, and applying the slurry to a metal current collector substrate such as a copper foil and drying to form a negative electrode sheet The negative electrode. Nickel foil or stainless steel foil may be used instead of copper foil. Further, the negative electrode material can be directly molded into the shape of a negative electrode sheet by a method such as roll molding or compression molding.
上記結着剤としては、溶媒に対して安定な、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート、芳香族ポリアミド、セルロース等の樹脂系高分子、スチレン・ブタジエンゴム、イソプレンゴム、ブタジエンゴム、エチレン・プロピレンゴム等のゴム状高分子、スチレン・ブタジエン・スチレンブロック共重合体、その水素添加物、スチレン・エチレン・ブタジエン・スチレン共重合体、スチレン・イソプレン・スチレンブロック共重合体、その水素添加物等の熱可塑性エラストマー状高分子、シンジオタクチック−１，２−ポリブタジエン、エチレン・酢酸ビニル共重合体、プロピレン・α−オレフィン（炭素数２〜１２）共重合体等の軟質樹脂状高分子、メチルセルロース、カルボキシメチルセルロース、ポリビニルアルコール、ポリビニルブチラール、これらのポリマーのホルマール化物、などを用いることができる。ここに、ポリフッ化ビニリデン、ポリテトラフルオロエチレンなどのフッ素系結着剤を更に適量添加してもよい。アルカリ金属イオン、特にリチウムイオンのイオン伝導性を有する有機高分子組成物を更に混合してもよいが、電極の賦形性を損なわないように注意が必要である。 Examples of the binder include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, and cellulose, styrene / butadiene rubber, isoprene rubber, butadiene rubber, and ethylene / propylene rubber, which are stable to solvents. Rubber-like polymers, styrene / butadiene / styrene block copolymers, hydrogenated products thereof, styrene / ethylene / butadiene / styrene block copolymers, styrene / isoprene / styrene block copolymers, thermoplastic elastomers such as hydrogenated products Polymer, syndiotactic-1,2-polybutadiene, ethylene / vinyl acetate copolymer, soft resin polymer such as propylene / α-olefin (carbon number 2 to 12) copolymer, methylcellulose, carboxymethylcellulose, Polyvinyl alcohol It can be used polyvinyl butyral, formal products of these polymers, and the like. An appropriate amount of a fluorine-based binder such as polyvinylidene fluoride or polytetrafluoroethylene may be further added thereto. An organic polymer composition having ion conductivity of alkali metal ions, particularly lithium ions, may be further mixed, but care must be taken so as not to impair the shapeability of the electrode.
リチウム二次電池用負極を製造する際のリチウム二次電池用負極材料と上記結着剤との混合形態は特に限定されず、各種の形態をとることができる。即ち、両者の粒子が混合した形態、繊維状の結着剤が炭素質物の粒子に絡み合う形で混合した形態、または結着剤の層が炭素質物の粒子表面に付着した形態などが挙げられる。炭素質物と結着剤との混合割合は、炭素質物に対して、通常０．１〜３０重量％、好ましくは、０．５〜１０重量％、より好ましくは０．５〜５重量％である。結着剤の量が多すぎると、電極の内部抵抗が大きくなり、逆に少なすぎると集電体と炭素質粉体との結着性に劣る。 The form of mixing the negative electrode material for a lithium secondary battery and the binder when producing the negative electrode for a lithium secondary battery is not particularly limited, and can take various forms. That is, a form in which both particles are mixed, a form in which a fibrous binder is entangled with carbonaceous particles, or a form in which a binder layer adheres to the surface of carbonaceous particles. The mixing ratio of the carbonaceous material and the binder is usually 0.1 to 30% by weight, preferably 0.5 to 10% by weight, more preferably 0.5 to 5% by weight with respect to the carbonaceous material. . When the amount of the binder is too large, the internal resistance of the electrode increases, and conversely, when the amount is too small, the binding property between the current collector and the carbonaceous powder is poor.
また、負極の作製時に、適当な導電剤を添加してもよい。導電剤の例としては、アセチレンブラック、ファーネスブラック、ケッチェンブラックなどのカーボンブラックや平均粒径が１μｍ以下のニッケル、銅などの金属パウダーが挙げられる。
上記のように、リチウム二次電池用負極材料と適当な粉体結着剤とを混合し、その量を調整することで、Ｌｉの挿入に好ましい表面積を持つ電極を作製することができる。更に低抵抗の負極界面の被膜形成が可能なため、Ｌｉの充電受入性に好ましい影響を与えることができる。また、被膜が均一にできるため、表面被膜由来の電極膨れが少ない。従って、本発明のリチウム二次電池用負極材料は、例えば、角型電池用負極材料として好適である。
Moreover, you may add an appropriate electrically conductive agent at the time of preparation of a negative electrode. Examples of the conductive agent include carbon black such as acetylene black, furnace black, and ketjen black, and metal powder such as nickel and copper having an average particle size of 1 μm or less.
As described above, an electrode having a surface area preferable for insertion of Li can be produced by mixing a negative electrode material for a lithium secondary battery and an appropriate powder binder and adjusting the amount thereof. Furthermore, since a film can be formed on the negative electrode interface having a low resistance, it is possible to favorably influence the charge acceptability of Li. In addition, since the coating can be made uniform, there is little swelling of the electrode derived from the surface coating. Therefore, the negative electrode material for lithium secondary batteries of the present invention is suitable as a negative electrode material for square batteries, for example.
更に、本発明のリチウム二次電池用負極材料は、その構成要素として黒鉛系炭素質物を用いるため、サイクル時の可逆容量も大きく、かつ非晶質炭素のようにＬｉに対し高電位をとることもなく、正極と共に電池に組んだときのセル電圧を確保しやすいため、高容量化にも役立つ。
［電解液］
本発明のリチウム二次電池用負極材料と結着剤とから作製されたリチウム二次電池用負極を電池として用いる場合の電解液は有機溶媒及び電解質から構成される。
Furthermore, since the negative electrode material for a lithium secondary battery of the present invention uses a graphite-based carbonaceous material as a constituent element, it has a large reversible capacity during cycling and takes a high potential with respect to Li like amorphous carbon. In addition, since it is easy to ensure the cell voltage when assembled in a battery together with the positive electrode, it is useful for increasing the capacity.
[Electrolyte]
When the negative electrode for a lithium secondary battery produced from the negative electrode material for a lithium secondary battery of the present invention and the binder is used as a battery, the electrolytic solution is composed of an organic solvent and an electrolyte.
上記有機溶媒としては、例えばエチレンカーボネート等の環状カーボネート、ジエチルカーボネート、ジメチルカーボネート、エチルメチルカーボネート等の鎖状カーボネート、１，２−ジメトキシエタン、テトラヒドロフラン、２−メチルテトラヒドロフラン、１，３−ジオキソラン等のエーテル類、スルホランなどが挙げられる。これら有機溶媒中にビニレンカーボネート、ビニルエチレンカーボネート、メチルフェニルカーボネート、エチレンサルファイド、プロピレンサルファイド、１，３−プロパンスルトン、１，４−ブタンスルトン、或いはマレイン酸無水物、コハク酸無水物等の酸無水物から選ばれるいわゆる皮膜形成剤を添加してもよい。皮膜形成剤の添加量は通常１０重量％以下、好ましくは８重量％以下、より好ましくは５重量％以下、さらに好ましくは２重量％以下である。皮膜形成剤の添加量が多すぎると初期不可逆容量の増加や低温特性、レート特性の低下等、他の電池特性に悪影響を及ぼす恐れがある。 Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and the like. Examples include ethers and sulfolane. In these organic solvents, vinylene carbonate, vinyl ethylene carbonate, methyl phenyl carbonate, ethylene sulfide, propylene sulfide, 1,3-propane sultone, 1,4-butane sultone, or acid anhydrides such as maleic anhydride and succinic anhydride You may add what is called a film formation agent chosen from these. The addition amount of the film forming agent is usually 10% by weight or less, preferably 8% by weight or less, more preferably 5% by weight or less, and further preferably 2% by weight or less. If the amount of the film-forming agent added is too large, other battery characteristics such as an increase in initial irreversible capacity, low temperature characteristics, and rate characteristics may be adversely affected.
上記電解質としては、例えばＬｉＣｌＯ4、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣＦ3ＳＯ3、
ＬｉＡｓＦ6、ＬｉＣｌ、ＬｉＢｒ、Ｌｉトリフルオロメタンスルホンイミド等の塩が挙
げられる。電解質の濃度は有機溶媒中、０．５〜２．０Ｍ程度とする。
これらの電解液を更に有機高分子化合物に含ませ、ゲル状またはゴム状或いは固体シート状としたものを用いてもよい。そのような場合には骨材となる有機高分子化合物の分量を除いた有機溶媒のみの組成で上記組成を議論する。上記有機高分子化合物の具体例としては、ポリエチレンオキシド、ポリプロピレンオキシド等のポリエーテル系高分子化合物、これらポリエーテル系高分子化合物の架橋体高分子、ポリビニルアルコール、ポリビニルブチラール、これらの不溶化物、ポリエピクロルヒドリン、ポリホスファゼン、ポリシロキサン、ポリビニルピロリドン、ポリビニリデンカーボネート、ポリアクリロニトリルが挙げられる。また、ポリ（ω−メトキシオリゴオキシエチレンメタクリレート）、ポリ（ω−メトキシオリゴオキシエチレンメタクリレート−ｃｏ−メチルメタクリレート）等のポリマー共重合体も使用可能である。
Examples of the electrolyte include LiClO 4 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 ,
Examples of the salt include LiAsF 6 , LiCl, LiBr, and Li trifluoromethanesulfonimide. The concentration of the electrolyte is about 0.5 to 2.0 M in the organic solvent.
These electrolytic solutions may be further included in an organic polymer compound to form a gel, rubber, or solid sheet. In such a case, the above composition will be discussed based on the composition of only the organic solvent excluding the amount of the organic polymer compound serving as the aggregate. Specific examples of the organic polymer compound include polyether polymer compounds such as polyethylene oxide and polypropylene oxide, crosslinked polymers of these polyether polymer compounds, polyvinyl alcohol, polyvinyl butyral, insolubilized materials thereof, and polyepichlorohydrin. , Polyphosphazene, polysiloxane, polyvinylpyrrolidone, polyvinylidene carbonate, and polyacrylonitrile. Polymer copolymers such as poly (ω-methoxyoligooxyethylene methacrylate) and poly (ω-methoxyoligooxyethylene methacrylate-co-methyl methacrylate) can also be used.
また、リチウムイオン等のアルカリ金属カチオンの導電体である高分子固体電解質を用いることもでき、その例としては、上記ポリエーテル系高分子化合物にＬｉ塩を溶解させたものや、ポリエーテル末端水酸基がアルコキシドに置換されているポリマーなどが挙げられる。
［リチウム二次電池用正極］
リチウム二次電池を構成するための正極体の材料は、特に限定されないが、上記リチウム二次電池用負極と組み合わせて使用するための標準的なものとしては、ＬｉＣｏＯ2を
アセチレンブラックなどの導電材及びポリフッ化ビニリデンなどと混合し、アルミニウム箔上に塗布、乾燥し、プレスを施したものが挙げられる。その他、一般にリチウムイオンなどのアルカリ金属カチオンを充放電時に吸蔵、放出することのできる金属カルコゲン化合物からなることが好ましい。そのような金属カルコゲン化合物としては、バナジウムの酸化物、バナジウムの硫化物、モリブデンの酸化物、モリブデンの硫化物、マンガンの酸化物、クロムの酸化物、チタンの酸化物、チタンの硫化物及びこれらの複合酸化物、複合硫化物等が挙げられる。好ましくは、Ｃｒ3Ｏ8、Ｖ2Ｏ5、Ｖ5Ｏ13、ＶＯ2、Ｃｒ2Ｏ5、ＭｎＯ2、ＴｉＯ2、ＭｏＶ2Ｏ8、ＴｉＳ2、Ｖ2Ｓ5、Ｃｒ0.25Ｖ0.75Ｓ2、Ｃｒ0.5Ｖ0.5Ｓ2等である。また、ＬｉＭＹ2（Ｍは、Ｃｏ、Ｎｉ等の遷移金属、ＹはＯ、Ｓ等のカルコゲン元素）、ＬｉＭ2Ｙ4（ＭはＭｎ、ＹはＯ）、ＷＯ3等の酸化物、ＣｕＳ、Ｆｅ0.25Ｖ0.75Ｓ2、Ｎａ0.1ＣｒＳ2等の硫化物、ＮｉＰＳ3、ＦｅＰＳ3等のリン・硫黄化合物、ＶＳｅ2、ＮｂＳｅ3等のセレン化合物等を用いることもできる。
Moreover, a polymer solid electrolyte which is a conductor of an alkali metal cation such as lithium ion can also be used. Examples thereof include those obtained by dissolving a Li salt in the polyether polymer compound, and polyether-terminated hydroxyl groups. Are polymers substituted with alkoxide.
[Positive electrode for lithium secondary battery]
The material of the positive electrode body for constituting the lithium secondary battery is not particularly limited. As a standard material for use in combination with the negative electrode for lithium secondary battery, a conductive material such as acetylene black is used as LiCoO 2. In addition, it may be mixed with polyvinylidene fluoride or the like, coated on an aluminum foil, dried, and pressed. In addition, it is generally preferable to use a metal chalcogen compound that can occlude and release alkali metal cations such as lithium ions during charging and discharging. Examples of such metal chalcogen compounds include vanadium oxide, vanadium sulfide, molybdenum oxide, molybdenum sulfide, manganese oxide, chromium oxide, titanium oxide, titanium sulfide, and the like. And composite oxides and sulfides. Preferably, Cr 3 O 8 , V 2 O 5 , V 5 O 13 , VO 2 , Cr 2 O 5 , MnO 2 , TiO 2 , MoV 2 O 8 , TiS 2 , V 2 S 5 , Cr 0.25 V 0.75 S 2 , Cr 0.5 V 0.5 S 2 or the like. In addition, LiMY 2 (M is a transition metal such as Co and Ni, Y is a chalcogen element such as O and S), LiM 2 Y 4 (M is Mn and Y is O), an oxide such as WO 3 , CuS, Fe 0.25 V 0.75 S 2, Na 0.1 CrS sulfides such as 2, NIPS 3, FEPS phosphorus-sulfur compounds such as 3, can also be used VSe 2, NbSe 3 selenium compounds such like.
上記の化合物を、前記の負極の製造法と同様の手法で、結着剤と混合し、集電体上に塗布、乾燥して正極板とする。
［リチウム二次電池］
上記のようにして作製した負極板、正極板及び電解液を、その他の電池構成要素であるセパレータ、ガスケット、集電体、封口板、セルケース等と組み合わせてリチウム二次電池を構成する。作製可能な電池は筒型、角型、コイン型等特に限定されるものではないが、基本的にはセル床板上に集電体と負極材料とを乗せ、その上に電解液とセパレータを、更に負極と正極を対向させ、ガスケット、封口板と共にかしめて二次電池とする。
The above compound is mixed with a binder in the same manner as in the method for producing the negative electrode, applied onto a current collector, and dried to obtain a positive electrode plate.
[Lithium secondary battery]
A lithium secondary battery is formed by combining the negative electrode plate, the positive electrode plate, and the electrolytic solution prepared as described above with other battery components such as a separator, a gasket, a current collector, a sealing plate, a cell case, and the like. The battery that can be produced is not particularly limited to a cylindrical shape, a rectangular shape, a coin shape, etc., but basically, a current collector and a negative electrode material are placed on a cell floor plate, and an electrolyte and a separator are placed thereon. Further, the negative electrode and the positive electrode are made to face each other and caulked together with a gasket and a sealing plate to obtain a secondary battery.
電解液を保持するセパレータは、一般的に保液性に優れた材料であり、例えば、ポリオレフィン系樹脂の不織布や多孔性フィルムなどを使用して、上記電解液を含浸させる。 The separator that holds the electrolytic solution is generally a material that has excellent liquid retaining properties. For example, a nonwoven fabric of polyolefin resin or a porous film is used to impregnate the electrolytic solution.
次に実施例により本発明の具体的態様を更に詳細に説明するが、本発明はこれらの例によって限定されるものではない。
［電極材料の評価方法］
負極材料中の結晶性の劣る炭素質物の含有量
焼成法においては、黒鉛系炭素質物の表面に有機物質を付着させ焼成することによって生成される炭素質物が結晶性の劣る炭素質物を構成するので、この焼成操作による重量の増加、即ち残炭率によって結晶性の劣る炭素質物の量を定量した。
EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
[Evaluation method of electrode material]
Content of carbonaceous material with poor crystallinity in negative electrode material In the firing method, the carbonaceous material produced by attaching and firing an organic substance on the surface of a graphite-based carbonaceous material constitutes a carbonaceous material with poor crystallinity. The amount of carbonaceous material having poor crystallinity was quantified by the increase in weight due to the firing operation, that is, the residual carbon ratio.
ラマンスペクトル測定
日本分光製、ＮＲ−１８００により行い、波長５１４５Åのアルゴンイオンレーザー光を、３０ｍＷの強度で照射した。ここでは１５７０〜１６２０ｃｍ-1の範囲に存在するピークの強度および、１３５０〜１３７０ｃｍ-1の範囲に存在するピークの強度を測定し、これらから得られるラマンＲ値を求めた。
Raman spectrum measurement was performed by JASCO Corporation, NR-1800, and an argon ion laser beam having a wavelength of 5145 mm was irradiated at an intensity of 30 mW. Wherein the intensity and peaks present in the range of 1570～1620Cm -1 measures the intensity of a peak existing in the range of 1350 -1, was determined Raman R value obtained from these.
結着剤による活物質の表面被覆率
負極材料及び負極について、Ｎ2ガスを用いたＢＥＴ１点法によりＢＥＴ表面積の測定
を行った。なお、電極の表面積は、電極密度を調整する前のものとした。得られたＢＥＴ表面積の値から下記式（１）で、結着剤による活物質の表面被覆率Γ（％）を算出した。
The surface coverage of the active material by the binder The BET surface area of the negative electrode material and the negative electrode was measured by the BET one-point method using N 2 gas. The surface area of the electrode was the one before adjusting the electrode density. From the value of the obtained BET surface area, the surface coverage Γ (%) of the active material by the binder was calculated by the following formula (1).
（数２）
表面被覆率Γ＝（粉体ＳＡ−負極ＳＡ）／粉体ＳＡｘ１００ （１）
粉体ＳＡ：リチウム二次電池用負極材料のＢＥＴ表面積
負極ＳＡ：リチウム二次電池用負極のＢＥＴ表面積
電気化学的評価のためのサンプルの作製
負極材料粉体１０ｇに対し、粉体結着剤としてカルボキシメチルセルロース１重量％、及びスチレン・ブタジエンゴム１重量％を加えたものをキーエンス製ハイブリッドミキサーで３分間撹拌し、スラリーを得た。このスラリーを銅箔上に塗布し、１１０℃で予備乾燥を行った。集電体上に負極材料粉体が１０±０．１ｍｇ／ｃｍ2付着するようにした。
乾燥後、電極密度を１．５±０．０３ｇ／ｃｍ3に調整し、負極シートとした。更に１５
０℃で真空減圧乾燥を施して負極とした。
(Equation 2)
Surface coverage Γ = (powder SA-negative electrode SA) / powder SAx100 (1)
Powder SA: BET surface area of negative electrode material for lithium secondary battery Negative electrode SA: BET surface area of negative electrode for lithium secondary battery
Preparation of Sample for Electrochemical Evaluation For 10 minutes of negative electrode material powder, 1% by weight of carboxymethyl cellulose and 1% by weight of styrene-butadiene rubber were added as a powder binder for 3 minutes using a KEYENCE hybrid mixer. Stir to obtain a slurry. This slurry was applied onto a copper foil and pre-dried at 110 ° C. The negative electrode material powder was allowed to adhere to 10 ± 0.1 mg / cm 2 on the current collector.
After drying, the electrode density was adjusted to 1.5 ± 0.03 g / cm 3 to obtain a negative electrode sheet. 15 more
Vacuum drying under reduced pressure was performed at 0 ° C. to obtain a negative electrode.
溶質としてＬｉＰＦ6を１ｍｏｌ／Ｌになるように溶解させたエチレンカーボネート及
びエチルメチルカーボネート（１：１）を含む電解液を用い、セパレータ（多孔性ポリエチレンフィルム製）を介してＬｉＣｏＯ2を対極とした２０３２コイン型セルを組んだ。
複素インピーダンス測定
上記２０３２コイン型セルについて、２４時間測定前休止をおいた後、０．６ｍＡ／ｃｍ2の電流値で、極間電位差が４．２Ｖになるまで充電を行い、極間電位差が３．０Ｖに
なるまで放電した。この充放電を室温で６回行った後、７回目の４．２Ｖ充電時に１０-2〜１０5Ｈｚの周波数帯で複素インピーダンス測定を行い、負極部分の抵抗（Ｒ）と、負
極／電解液界面の二重層容量（Ｃｄｌ）を測定した。この際、正極や低周波部分の因子の影響を避ける為に、負極の被膜抵抗成分として現れる円弧の一部を外挿し、上記パラメータの数値を求めた。各数値はコイン型セル３個の結果の平均値とした。
Using an electrolytic solution containing ethylene carbonate and ethyl methyl carbonate (1: 1) in which LiPF 6 was dissolved at 1 mol / L as a solute, LiCoO 2 was used as a counter electrode through a separator (made of a porous polyethylene film). A 2032 coin cell was assembled.
Complex impedance measurement The above 2032 coin cell was charged for 24 hours before measurement, and then charged at a current value of 0.6 mA / cm 2 until the potential difference between the electrodes became 4.2 V. The potential difference between the electrodes was 3 Discharge until 0V. After this charge / discharge was performed 6 times at room temperature, complex impedance measurement was performed in the frequency band of 10 −2 to 10 5 Hz during the 7th 4.2 V charge, and the resistance (R) of the negative electrode portion and the negative electrode / electrolyte The double layer capacity (Cdl) at the interface was measured. At this time, in order to avoid the influence of the factors of the positive electrode and the low frequency part, a part of the arc appearing as the film resistance component of the negative electrode was extrapolated to obtain the numerical values of the above parameters. Each numerical value is an average value of the results of three coin-type cells.
電極の膨れ
負極、電解液及びセパレータに上記と同じものを、対極にリチウム金属を用いて２０１６コイン型セルを組み、上記と同様の５回目の充放電の後に電池を解体し、負極を取り出し、マイクロメータ（ミツトヨ製）で電極厚みを測定した。充放電前と５回目放電後の電極厚みの差から、電極の膨張率を下記式（２）で算出し、電極膨れを求めた。なお、放電は電流密度０．３３ｍＡ／ｃｍ2で極間電位差が１．５Ｖになるまで行った。
Assembling the 2016 coin-type cell using the same as above for the swollen negative electrode, electrolyte and separator, and lithium metal as the counter electrode, disassembling the battery after the fifth charge / discharge similar to the above, taking out the negative electrode, The electrode thickness was measured with a micrometer (Mitutoyo). From the difference in electrode thickness before and after the fifth discharge, the expansion coefficient of the electrode was calculated by the following formula (2) to obtain the electrode swelling. The discharge was performed until the potential difference between the electrodes became 1.5 V at a current density of 0.33 mA / cm 2 .
（数３）
電極の膨張率（％）＝（５回目放電後電極厚み−充放電前電極厚み）
／充放電前電極厚み×１００ （２）
充電受入性
電極膨れの場合と同様にコイン型セルを組み立て、電流密度０．１６ｍＡ／ｃｍ2で極
間電位差が０Ｖになるまで充電を行い、電流密度０．３３ｍＡ／ｃｍ2で極間電位差が１
．５Ｖになるまで放電した。この充放電過程を２回繰り返した後、１．６ｍＡ／ｃｍ2で
０Ｖになるまで充電を行い、充電容量を測定した。結果はコイン型セル４個の結果の平均値で評価した。これから、高電流密度時のＬｉ充電受入性が推測可能である。本測定ではリチウムを対極とした半電池評価としたが、ＬｉＣｏＯ2の様な正極材料を用いた場合も
同様の効果が期待できる。
(Equation 3)
Electrode expansion rate (%) = (electrode thickness after the fifth discharge−electrode thickness before charge / discharge)
/ Electrode thickness before charge / discharge x 100 (2)
Assembled as in the case coin cell blister charge acceptance electrodes was charged at a current density of 0.16 mA / cm 2 until the interelectrode potential difference becomes to 0V, and the interelectrode electric potential difference at a current density of 0.33 mA / cm 2 1
. Discharge until 5V. After repeating this charging / discharging process twice, the battery was charged at 1.6 mA / cm 2 until it reached 0 V, and the charge capacity was measured. The result was evaluated by the average value of the results of four coin-type cells. From this, it is possible to estimate Li charge acceptability at high current density. In this measurement, the half-cell evaluation using lithium as a counter electrode was performed, but the same effect can be expected when a positive electrode material such as LiCoO 2 is used.
実施例１
機械粉砕により平均粒径２５μｍにした天然黒鉛粒子１５重量部と石油系ピッチ１重量部とを、大気中、７０℃でミキサーを使用して均一混合した。得られた混合物を上面が開放された容器に１０ｃｍの厚みで詰め、回分式加熱炉で不活性雰囲気下にて６００℃で１時間熱処理した。冷却後、得られた混合物焼成体を２０ｃｍ厚みに詰め直し、圧力０．１０３ＭＰａに調整した不活性雰囲気下にて更に８００℃で１時間熱処理した。冷却後、得られた焼成体を解砕、篩い分けし、中心粒径ｄ５０が２５μｍのサンプル粉体とした。残炭率から計算される黒鉛より結晶性の劣る炭素質物の含有量は、粉体全体を１００重量％とした時、１．２重量％であった。また、ラマン分光の結果から計算されたＲ値は０．３５であった。本粉体のＢＥＴ表面積は、３．７ｍ2／ｇであり、表面被覆率Γは３３％であった。電気化学的評価から得られた負極の抵抗は４．９ｏｈｍであり、負極／電解液界面の二重層容量は９．６×１０-4Ｆであった。また、充電受入性は１２５ｍＡｈ／ｇであり、電極膨れは１３％であった。
Example 1
15 parts by weight of natural graphite particles having an average particle diameter of 25 μm by mechanical pulverization and 1 part by weight of petroleum-based pitch were uniformly mixed using a mixer at 70 ° C. in the atmosphere. The obtained mixture was packed in a container having an open top with a thickness of 10 cm, and heat-treated at 600 ° C. for 1 hour in an inert atmosphere in a batch heating furnace. After cooling, the obtained fired mixture was repacked to a thickness of 20 cm and further heat-treated at 800 ° C. for 1 hour in an inert atmosphere adjusted to a pressure of 0.103 MPa. After cooling, the obtained fired body was crushed and sieved to obtain a sample powder having a center particle size d50 of 25 μm. The content of the carbonaceous material having lower crystallinity than graphite calculated from the residual carbon ratio was 1.2% by weight when the total powder was 100% by weight. The R value calculated from the result of Raman spectroscopy was 0.35. This powder had a BET surface area of 3.7 m 2 / g and a surface coverage Γ of 33%. The resistance of the negative electrode obtained from the electrochemical evaluation was 4.9 ohm, and the double layer capacity at the negative electrode / electrolyte interface was 9.6 × 10 −4 F. Moreover, charge acceptance was 125 mAh / g and the electrode swelling was 13%.
実施例２
原料の黒鉛と石油系ピッチの割合をそれぞれ３重量部、１重量部に変えたこと以外は実施例１と同様に混合し、６００℃で１時間熱処理した。冷却後、得られた混合物焼成体を２０ｃｍ厚みに詰め直し、圧力０．１５３ＭＰａに調整した不活性雰囲気下にて更に７００℃で１時間熱処理した。冷却後、得られた焼成体を解砕、篩い分けし、中心粒径ｄ５０が２５μｍのサンプル粉体とした。残炭率から計算される黒鉛より結晶性の劣る炭素質物の含有量は、粉体全体を１００重量％とした時、６．３重量％であった。また、ラマン分光の結果から計算されたＲ値は０．５７であった。本粉体のＢＥＴ表面積は、２．９ｍ2／ｇであり、表面被覆率Γは２１％であった。電気化学的評価から得られた負極の抵抗は５．９ｏｈｍであり、負極／電解液界面の二重層容量は８．２×１０-4Ｆであった。また、充電受入性は１１１ｍＡｈ／ｇであり、電極膨れは１５％であった。
Example 2
They were mixed in the same manner as in Example 1 except that the ratios of the raw material graphite and petroleum-based pitch were changed to 3 parts by weight and 1 part by weight, respectively, and heat-treated at 600 ° C. for 1 hour. After cooling, the obtained fired mixture was repacked to a thickness of 20 cm and further heat-treated at 700 ° C. for 1 hour in an inert atmosphere adjusted to a pressure of 0.153 MPa. After cooling, the obtained fired body was crushed and sieved to obtain a sample powder having a center particle size d50 of 25 μm. The content of the carbonaceous material having crystallinity inferior to that of graphite calculated from the residual carbon ratio was 6.3% by weight when the entire powder was 100% by weight. The R value calculated from the result of Raman spectroscopy was 0.57. The BET surface area of this powder was 2.9 m 2 / g, and the surface coverage Γ was 21%. The resistance of the negative electrode obtained from the electrochemical evaluation was 5.9 ohm, and the double layer capacity at the negative electrode / electrolyte interface was 8.2 × 10 −4 F. The charge acceptance was 111 mAh / g, and the electrode swelling was 15%.
実施例３
原料の黒鉛と石油系ピッチの割合をそれぞれ５重量部、１重量部に変えたこと以外は、実施例２と同様に混合し、熱処理した。冷却後、得られた焼成体を解砕、篩い分けし、中心粒径ｄ５０が２５μｍのサンプル粉体とした。残炭率から計算される黒鉛より結晶性の劣る炭素質物の含有量は、粉体全体を１００重量％とした時、４．４重量％であった。また、ラマン分光の結果から計算されたＲ値は０．５２であった。本粉体のＢＥＴ表面積は、２．９ｍ2／ｇであり、表面被覆率Γは３１％であった。電気化学的評価から得られた負極の抵抗は５．４ｏｈｍであり、負極／電解液界面の二重層容量は９．１×１０-4Ｆであった。また、充電受入性は１１５ｍＡｈ／ｇであり、電極膨れは１３％であった。
Example 3
The materials were mixed and heat-treated in the same manner as in Example 2 except that the proportions of the raw material graphite and petroleum-based pitch were changed to 5 parts by weight and 1 part by weight, respectively. After cooling, the obtained fired body was crushed and sieved to obtain a sample powder having a center particle size d50 of 25 μm. The content of the carbonaceous material having crystallinity inferior to that of graphite calculated from the residual carbon ratio was 4.4% by weight when the total powder was 100% by weight. The R value calculated from the result of Raman spectroscopy was 0.52. The BET surface area of this powder was 2.9 m 2 / g, and the surface coverage Γ was 31%. The resistance of the negative electrode obtained from the electrochemical evaluation was 5.4 ohm, and the double layer capacity at the negative electrode / electrolyte interface was 9.1 × 10 −4 F. The charge acceptance was 115 mAh / g, and the electrode swelling was 13%.
比較例１
原料の黒鉛と石油系ピッチの割合をそれぞれ３重量部、１重量部とし、大気中、７０℃でミキサーを使用して均一混合した。得られた混合物を上面が開放された容器に４０ｃｍの厚みで詰め、回分式加熱炉で不活性雰囲気下にて６００℃で１時間熱処理した。冷却後、得られた混合物焼成体を更に、圧力０．１０３ＭＰａに調整した不活性雰囲気下にて１３００℃で１時間熱処理した。冷却後、得られた焼成体を解砕、篩い分けし、中心粒径ｄ５０が２５μｍのサンプル粉体とした。残炭率から計算される黒鉛より結晶性の劣る炭素質物の含有量は、粉体全体を１００重量％とした時６．０重量％であった。また、ラマン分光の結果から計算されたＲ値は０．３５であった。本粉体のＢＥＴ表面積は、２．３ｍ2／ｇであり、表面被覆率Γは１８％であった。電気化学的評価から得られた負極の抵抗は６．８ｏｈｍであり、負極／電解液界面の二重層容量は７．１×１０- 4Ｆであった。また、充電受入性は８３ｍＡｈ／ｇであり、電極膨れは１９％であった。
Comparative Example 1
The ratios of the raw material graphite and petroleum-based pitch were 3 parts by weight and 1 part by weight, respectively, and they were uniformly mixed in the atmosphere at 70 ° C. using a mixer. The obtained mixture was packed in a container having an open top surface with a thickness of 40 cm and heat-treated at 600 ° C. for 1 hour in an inert atmosphere in a batch heating furnace. After cooling, the resulting fired mixture was further heat-treated at 1300 ° C. for 1 hour in an inert atmosphere adjusted to a pressure of 0.103 MPa. After cooling, the obtained fired body was crushed and sieved to obtain a sample powder having a center particle size d50 of 25 μm. The content of the carbonaceous material having crystallinity inferior to that of graphite calculated from the residual carbon ratio was 6.0% by weight when the total powder was 100% by weight. The R value calculated from the result of Raman spectroscopy was 0.35. The BET surface area of this powder was 2.3 m 2 / g, and the surface coverage Γ was 18%. Resistance of the negative electrode obtained from the electrochemical evaluation is 6.8Ohm, the double layer capacity of the anode / electrolyte interface 7.1 × 10 - was 4 F. The charge acceptance was 83 mAh / g, and the electrode swelling was 19%.
比較例２
原料の黒鉛と石油系ピッチの割合をそれぞれ１重量部、２．３重量部とし、大気中、８０℃でミキサーを使用して均一混合した。得られた混合物を上面が開放された容器に４０ｃｍの厚みで詰め、回分式加熱炉で不活性雰囲気下にて６００℃で１時間熱処理した。冷却後、得られた混合物を更に、圧力０．１０３ＭＰａに調整した不活性雰囲気下にて１２００℃で１時間熱処理した。Ｒ値は０．７１であった。本粉体のＢＥＴ表面積は、１．５ｍ2／ｇであり、表面被覆率Γは５７％であった。電気化学的評価から得られた被膜抵抗は５．０ｏｈｍであり、負極／電解液界面の二重層容量は１．１×１０-3Ｆであった。また、充電受入性は５５ｍＡｈ／ｇであり、電極膨れは２５％であった。
Comparative Example 2
The ratios of the raw material graphite and petroleum-based pitch were 1 part by weight and 2.3 parts by weight, respectively, and the mixture was uniformly mixed in the atmosphere at 80 ° C. using a mixer. The obtained mixture was packed in a container having an open top surface with a thickness of 40 cm and heat-treated at 600 ° C. for 1 hour in an inert atmosphere in a batch heating furnace. After cooling, the obtained mixture was further heat-treated at 1200 ° C. for 1 hour under an inert atmosphere adjusted to a pressure of 0.103 MPa. The R value was 0.71. This powder had a BET surface area of 1.5 m 2 / g and a surface coverage Γ of 57%. The film resistance obtained from the electrochemical evaluation was 5.0 ohms, and the double layer capacity at the negative electrode / electrolyte interface was 1.1 × 10 −3 F. Further, the charge acceptance was 55 mAh / g, and the electrode swelling was 25%.
Claims (14)
・負極の作製及び評価条件
（ａ）負極材料粉体１０ｇに対し、粉体結着剤としてカルボキシメチルセルロース１質量％、及びスチレン・ブタジエンゴム１質量％を加えたものをミキサーで３分間撹拌し、スラリーを得る。このスラリーを集電体である銅箔上に塗布し、１１０℃で予備乾燥を行う。塗布は、集電体上に負極材料粉体が１０±０．１ｍｇ／ｃｍ2付着するようにする。乾燥後、電極密度を１．５±０．０３ｇ／ｃｍ3に調整し、負極シートとし、更に１５０℃で真空減圧乾燥を施して負極とする。
（ｂ）溶質としてＬｉＰＦ6を１ｍｏｌ／Ｌになるように溶解させたエチレンカーボネート及びエチルメチルカーボネート（１：１）を含む電解液を用い、セパレータ（多孔性ポリエチレンフィルム製）を介してＬｉＣｏＯ2を対極とした２０３２コイン型セルを組む。
（ｃ）上記２０３２コイン型セルについて、２４時間測定前休止をおいた後、０．６ｍＡ／ｃｍ2の電流値で、極間電位差が４．２Ｖになるまで充電を行い、極間電位差が３．０Ｖになるまで放電する。この充放電を室温で６回行った後、７回目の４．２Ｖ充電時に１０-2〜１０5Ｈｚの周波数帯で複素インピーダンス測定を行い、負極部分の抵抗（Ｒ）と、負極／電解液界面の二重層容量（Ｃｄｌ）を測定する。この際、正極や低周波部分の因子の影響を避ける為に、負極の被膜抵抗成分として現れる円弧の一部を外挿し、上記数値を求める。各数値はコイン型セル３個の結果の平均値とする。 A powdery negative electrode material having a structure in which a carbonaceous material that is less crystalline than the graphite-based carbonaceous material is deposited on the graphite-based carbonaceous material, the particle size of the graphite-based carbonaceous material, and the graphite-based carbonaceous material more crystalline particle size and the same der powder having a structure obtained by depositing a carbonaceous material with poor is, and the content of crystallinity less carbonaceous material from the graphite carbonaceous material, 100 parts by mass the entire powder % and then when he is a negative electrode material Ru der range of 1.2 mass% or more 6.3 wt%, is produced from the anode material and the binder in the negative electrode of the creation and evaluation under the following conditions, and evaluated In this case, the resistance (R) of the negative electrode for a lithium secondary battery is 6.5 ohms or less, and the double layer capacity (Cdl) at the negative electrode / electrolyte interface is 7.0 × 10 −4 F or more, 10 × 10 −4 A negative electrode material for a lithium secondary battery, wherein the negative electrode material is in a range of less than F.
· To a negative electrode of Production and Evaluation conditions (a) an anode material powder 10 g, carboxymethyl cellulose 1 wt% as a powder binder, and which was added 1 wt% styrene-butadiene stirred for 3 minutes in a mixer, A slurry is obtained. This slurry is applied on a copper foil as a current collector, and pre-dried at 110 ° C. The application is performed so that the negative electrode material powder adheres to 10 ± 0.1 mg / cm 2 on the current collector. After drying, the electrode density is adjusted to 1.5 ± 0.03 g / cm 3 to form a negative electrode sheet, which is further vacuum dried at 150 ° C. to obtain a negative electrode.
(B) Using an electrolytic solution containing ethylene carbonate and ethyl methyl carbonate (1: 1) in which LiPF 6 is dissolved to 1 mol / L as a solute, LiCoO 2 is passed through a separator (made of a porous polyethylene film). A 2032 coin cell as a counter electrode is assembled.
(C) The 2032 coin cell was charged for 24 hours before measurement, and then charged at a current value of 0.6 mA / cm 2 until the potential difference between the electrodes reached 4.2 V. The potential difference between the electrodes was 3 Discharge until 0V. After this charge / discharge was performed 6 times at room temperature, complex impedance measurement was performed in the frequency band of 10 −2 to 10 5 Hz during the 7th 4.2 V charge, and the resistance (R) of the negative electrode portion and the negative electrode / electrolyte The double layer capacity (Cdl) at the interface is measured. At this time, in order to avoid the influence of the factors of the positive electrode and the low frequency portion, a part of the arc appearing as the film resistance component of the negative electrode is extrapolated to obtain the above numerical value. Each numerical value is an average value of the results of three coin-type cells.
表面被覆率Γ＝（粉体ＳＡ−負極ＳＡ）／粉体ＳＡ×１００ （１）
粉体ＳＡ：リチウム二次電池用負極材料のＢＥＴ表面積
負極ＳＡ：リチウム二次電池用負極のＢＥＴ表面積 The negative electrode material for lithium secondary battery and the negative electrode for lithium secondary battery prepared under the above-mentioned negative electrode preparation conditions from the negative electrode material and the binder were obtained by measuring the BET surface area using N 2 gas. 2. The negative electrode for a lithium secondary battery according to claim 1, wherein the surface coverage Γ (%) of the active material by the binder, which is calculated by the following formula (1) from the measured value, is in the range of 20 to 55%. material.
Surface coverage Γ = (powder SA−negative electrode SA) / powder SA × 100 (1)
Powder SA: BET surface area of negative electrode material for lithium secondary battery Negative electrode SA: BET surface area of negative electrode for lithium secondary battery
負極、電解液及びセパレータに上記（ａ）及び（ｂ）と同じものを、対極にリチウム金属を用いて２０１６コイン型セルを組み、上記（ｃ）と同様の５回目の充放電の後に電池を解体し、負極を取り出し、マイクロメータで電極厚みを測定する。充放電前と５回目放電後の電極厚みの差から、電極の膨張率を下記式（２）で算出し、電極膨れを求める。なお、放電は電流密度０．３３ｍＡ／ｃｍ2で極間電位差が１．５Ｖになるまで行う。
電極の膨張率（％）＝（５回目放電後電極厚み−充放電前電極厚み）
／充放電前電極厚み×１００ （２） The negative electrode material for a lithium secondary battery according to any one of claims 1 to 3, wherein an expansion coefficient of the electrode when evaluated by the following method is 15% or less.
The same thing as said (a) and (b) is used for a negative electrode, electrolyte solution, and a separator, and a 2016 coin type cell is assembled using lithium metal for a counter electrode, and a battery is charged after the fifth charge / discharge similar to (c) above. dismantled, removed negative electrode, for measuring the electrode thickness in the micrometer data. From the difference between charge and discharge before and 5 th post-discharge of the electrode thickness, to calculate the expansion ratio of the electrode by the following formula (2), Ru seek blister electrode. Incidentally, discharge intends line at a current density of 0.33 mA / cm 2 until the interelectrode potential difference becomes 1.5V.
Electrode expansion rate (%) = (electrode thickness after the fifth discharge−electrode thickness before charge / discharge)
/ Electrode thickness before charge / discharge x 100 (2)
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| JP5636149B2 (en) * | 2007-04-27 | 2014-12-03 | 日立化成株式会社 | A negative electrode material for a non-aqueous electrolyte secondary battery, a manufacturing method thereof, a negative electrode for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery. |
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| JP5729613B2 (en) * | 2012-10-09 | 2015-06-03 | トヨタ自動車株式会社 | Non-aqueous electrolyte secondary battery and method of manufacturing the battery |
| JP5637199B2 (en) * | 2012-10-12 | 2014-12-10 | 日産自動車株式会社 | Electrode for lithium ion secondary battery |
| JP6098885B2 (en) * | 2013-09-05 | 2017-03-22 | トヨタ自動車株式会社 | Nonaqueous electrolyte secondary battery |
| WO2017056448A1 (en) * | 2015-09-30 | 2017-04-06 | パナソニックＩｐマネジメント株式会社 | Non-aqueous electrolyte secondary battery |
| WO2023122855A1 (en) * | 2021-12-27 | 2023-07-06 | 宁德新能源科技有限公司 | Electrochemical device and electronic device |
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| JP2007103382A (en) | 2007-04-19 |
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