JP4496366B2 - Negative electrode material for polymer solid electrolyte lithium secondary battery and method for producing the same - Google Patents

Negative electrode material for polymer solid electrolyte lithium secondary battery and method for producing the same Download PDF

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JP4496366B2
JP4496366B2 JP2005110759A JP2005110759A JP4496366B2 JP 4496366 B2 JP4496366 B2 JP 4496366B2 JP 2005110759 A JP2005110759 A JP 2005110759A JP 2005110759 A JP2005110759 A JP 2005110759A JP 4496366 B2 JP4496366 B2 JP 4496366B2
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保雄 武田
宇 劉
誠之 今西
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Description

本発明は、ポリエチレンオキサイド(PEO)を電解質材料とする高分子固体電解質リチウムイオン2次電池のインターカレーション負極としての黒鉛系材料に関わる。 The present invention relates to a graphite-based material as an intercalation negative electrode of a polymer solid electrolyte lithium ion secondary battery using polyethylene oxide (PEO) as an electrolyte material.

1991年にリチウムイオン電池が発売されて以来、その高作動電圧と高いエネルギー密度のために多大な注目が払われてきた。
そして、このリチウムイオン電池は、携帯電話、ノート型パソコン、ビデオカメラ、その他デジタル製品の電源として広く使われている。市販のリチウムイオン電池は、低い作動電位と優れたサイクル性を持つ黒鉛系材料を負極とし、又、リチウムを含む遷移金属酸化物を正極とし、さらに、カーボネート系の有機化合物を主体とする溶媒にLiPF等のリチウム塩を溶解させたものを電解質として使用している。
Since the introduction of lithium ion batteries in 1991, much attention has been paid to their high operating voltage and high energy density.
The lithium ion battery is widely used as a power source for mobile phones, notebook computers, video cameras, and other digital products. Commercially available lithium ion batteries use a graphite-based material having a low operating potential and excellent cycleability as a negative electrode, a transition metal oxide containing lithium as a positive electrode, and a solvent mainly composed of a carbonate-based organic compound. A lithium salt such as LiPF 6 dissolved therein is used as the electrolyte.

しかしながら、有機液体を電解質とするリチウムイオン電池は電解液の漏洩や熱的安定性から来る安全性の問題が常に存在する。この問題は、電気自動車あるいはハイブリッド車(EV/HEV)などへの大きなスケールのリチウムイオン電池の適用の障害となっている。
そして、ここ20年間の研究で、ポリエチレンオキサイド(PEO)にリチウム塩を溶解させた固体PEO電解質が室温より高い温度であるが、10−3Scm−1の導電性を示すようになってきた。このPEO電解質を使用した高分子固体電解質リチウム二次電池は、前述の有機液体電解質に発生する問題を解決できる可能性がある。
However, a lithium ion battery using an organic liquid as an electrolyte always has a safety problem due to leakage of the electrolyte and thermal stability. This problem is an obstacle to the application of large scale lithium ion batteries to electric vehicles or hybrid vehicles (EV / HEV).
In the last 20 years of research, a solid PEO electrolyte in which a lithium salt is dissolved in polyethylene oxide (PEO) has a temperature higher than room temperature, but has an electrical conductivity of 10 −3 Scm −1 . The polymer solid electrolyte lithium secondary battery using this PEO electrolyte may be able to solve the problems that occur in the organic liquid electrolyte.

ところで、これまでに開発されたリチウムポリマー電池はリチウム(Li)金属が負極として使われており、リチウムデンドライト形成に起因する安全性上の問題点があった。この、問題点を解決するにはいわゆるインターカレーション化合物の採用が効果的である。
たとえば、スピネル構造のLi1.33Ti1.67のように充放電でひずみを生ぜず、優れたサイクル性を示すLi−M−O物質を採用することが望ましいが、それらは容量が小さく電圧が高いという欠点がある。一方、もっと大きな容量を持つLi合金を採用する方法が考えられるが、これらは充放電サイクルによって大きな体積変化が生じ電極劣化が解決できず採用は難しい。
結局、平坦で低い電位を示し有機電解液系で優れたサイクル特性を示す、黒鉛性材料が最適な負極と考えられている。
By the way, the lithium polymer battery developed so far uses lithium (Li) metal as a negative electrode, and has a safety problem due to the formation of lithium dendrite. In order to solve this problem, it is effective to employ a so-called intercalation compound.
For example, it is desirable to employ a Li—M—O material that does not generate strain due to charge / discharge, such as spinel-structured Li 1.33 Ti 1.67 O 4 , and exhibits excellent cycle characteristics. There is a drawback that the voltage is small and high. On the other hand, a method using a Li alloy having a larger capacity is conceivable, but these are difficult to employ because a large volume change occurs due to a charge / discharge cycle and electrode deterioration cannot be solved.
After all, a graphitic material that is flat and exhibits a low potential and exhibits excellent cycle characteristics in an organic electrolyte system is considered to be the optimum negative electrode.

ところが、市販のリチウムイオン電池で優れた性能を示す層状の黒鉛材料は、PEO電解質では電解質/電極界面の相性が悪く、低い初期効率と劣ったサイクル特性を示し、適用できないのが現状である。上記の点から、PEO電解質としての黒鉛負極の電気化学的性能向上のため、PEOと炭素負極の界面の最適な設計に重点が置かれている(例えば、特許文献1)が、必ずしも良好な結果を示していない。 However, a layered graphite material that exhibits excellent performance in a commercially available lithium ion battery has a poor compatibility with the electrolyte / electrode interface in a PEO electrolyte, exhibits low initial efficiency and inferior cycle characteristics, and cannot be applied at present. From the above points, in order to improve the electrochemical performance of the graphite negative electrode as the PEO electrolyte, an emphasis is placed on the optimum design of the interface between the PEO and the carbon negative electrode (for example, Patent Document 1), but the results are not always satisfactory. Not shown.

特願平6−292744号Japanese Patent Application No.6-292744

又、津村らは天然黒鉛をカーボンでコートしPEOと接触させる方法をとっている(非特許文献1)。
こうして得られた黒鉛負極は60℃のPEO電解質で約300mAhg−1の容量を4サイクル目まで示している 。しかしながら、初期不可逆容量が大きく残るのが欠点であった。
In addition, Tsumura et al. Have used a method in which natural graphite is coated with carbon and brought into contact with PEO (Non-patent Document 1).
The graphite negative electrode thus obtained is a PEO electrolyte at 60 ° C. and has a capacity of about 300 mAhg −1 up to the fourth cycle. However, a large initial irreversible capacity remains.

T.Tsumura, Solid State Ionics, 135 (2000) 209-212T. Tsumura, Solid State Ionics, 135 (2000) 209-212

PEOとリチウム塩を組合せて電解質とする高分子固体電解質リチウム2次電池用の負極としてのグラファイトの電気化学的性能を向上させることが、本発明の第一の課題である。 It is a first object of the present invention to improve the electrochemical performance of graphite as a negative electrode for a polymer solid electrolyte lithium secondary battery using a combination of PEO and a lithium salt as an electrolyte.

本発明は、PEO電解質と黒鉛性炭素の接触界面を適正化すること、より詳細には黒鉛性炭素の表面構造を改善することにより、特性を大幅に向上させることに成功した。具体的には、黒鉛の表面部にリチウムと炭素からなる化合物膜を形成した高分子固体電解質リチウム2次電池用負極材を提供することにより課題が達成される。ここで、リチウムと炭素からなる化合物膜とは、LiCの化学式で示される化合物で構成される膜を言う。そして、黒鉛表面部に形成されたリチウムと炭素からなる化合物膜の表層部は、少なくとも非晶質状態であることが望ましい。図1に黒鉛及びその表面部に形成されたリチウムと炭素からなる化合物膜の構造概要図を示す。ここで、リチウムと炭素からなる化合物膜の表層部は非晶質状態になっていると考えられる。
The present invention has succeeded in greatly improving the characteristics by optimizing the contact interface between the PEO electrolyte and the graphitic carbon, more specifically by improving the surface structure of the graphitic carbon. Specifically, the problem is achieved by providing a negative electrode material for a polymer solid electrolyte lithium secondary battery in which a compound film composed of lithium and carbon is formed on the surface of graphite. Here, the compound film composed of lithium and carbon refers to a film composed of a compound represented by the chemical formula of LiC x . And it is desirable that the surface layer portion of the compound film made of lithium and carbon formed on the graphite surface portion is at least in an amorphous state. FIG. 1 shows a schematic structure of a compound film made of graphite and lithium and carbon formed on the surface of graphite. Here, it is considered that the surface layer portion of the compound film made of lithium and carbon is in an amorphous state.

又、高分子固体電解質はポリエチレンオキサイドにリチウム塩が溶解されたものであり、更に、ポリエチレンオキサイドがセラミックスフィラーを含有している方が望ましい。セラミックフィラーを含有することにより、PEOの強度が増加する上に電気化学的特性も向上するからである。   Further, the solid polymer electrolyte is obtained by dissolving a lithium salt in polyethylene oxide, and it is more preferable that the polyethylene oxide contains a ceramic filler. This is because the inclusion of the ceramic filler increases the strength of PEO and improves the electrochemical characteristics.

そして、本発明は、黒鉛、金属リチウム及び沸点が190℃〜260℃の有機溶剤で構成される混合物に、ボールミリング処理を施し、黒鉛表面部にリチウムと炭素からなる化合物膜を形成する製造方法に関わる。有機溶剤の沸点が190℃より低いと有機溶剤が常温で気体状であり、逆に260℃より高いと10℃前後で有機溶剤が凝固し、有機溶剤としての特性が充分に発揮できなくなるからである。従って、ドデカン(CH(CH10CH)(沸点216℃、凝固点−10℃)が有機溶剤として適切である。
又、上述の混合物において、黒鉛/リチウムの重量混合比がリチウム1に対し黒鉛0.01−0.8であり、有機溶剤/リチウムの容積混合比がリチウム1gに対し有機溶剤1−40mlであることを特徴としている。上述の比率から外れると、黒鉛表面へのリチウムと炭素からなる化合物膜の形成が効率的でなくなるからである。
And this invention is the manufacturing method which performs a ball milling process to the mixture comprised with graphite, metallic lithium, and the organic solvent whose boiling point is 190 to 260 degreeC, and forms the compound film which consists of lithium and carbon in a graphite surface part Involved. If the boiling point of the organic solvent is lower than 190 ° C., the organic solvent is in a gaseous state at room temperature. Conversely, if the boiling point is higher than 260 ° C., the organic solvent is solidified around 10 ° C., and the characteristics as the organic solvent cannot be fully exhibited. is there. Accordingly, dodecane (CH 3 (CH 2 ) 10 CH 3 ) (boiling point 216 ° C., freezing point −10 ° C.) is suitable as the organic solvent.
Further, in the above-mentioned mixture, the graphite / lithium weight mixing ratio is 0.01 to 0.8 graphite with respect to lithium 1, and the organic solvent / lithium volume mixing ratio is 1 to 40 ml organic solvent with respect to 1 g lithium. It is characterized by that. If the ratio is outside the above ratio, the formation of a compound film composed of lithium and carbon on the graphite surface becomes inefficient.

本発明により、高い初期充放電効率とサイクル安定性を有するポリマー電解質リチウム2次電池の提供が可能になり、安全性を重視する用途への展開が可能となった。   According to the present invention, it has become possible to provide a polymer electrolyte lithium secondary battery having high initial charge / discharge efficiency and cycle stability, and it has become possible to develop applications for which safety is important.

本発明においては、リチウム金属と黒鉛系炭素を適した有機溶媒中で高エネルギー機械的ミリング( high energy mechanical milling (HEMM)) を行うが、その基本的な方法は以下の通りである。 先ず、指定量の黒鉛性材料を高温真空中で一定時間乾燥した後、この黒鉛性材料と金属リチウム及び特定の有機溶剤とを不活性ガス中でさらに混合する。ここで、有機溶媒を使用するのは、金属リチウムと黒鉛性炭素の分散を良くして成分材料同士の集合密着を防ぎ、表面に均一で安定な膜を形成するのに有効であるためである。 In the present invention, high energy mechanical milling (HEMM) is performed in a suitable organic solvent for lithium metal and graphite-based carbon. The basic method is as follows. First, after a specified amount of graphitic material is dried for a certain period of time in a high-temperature vacuum, the graphitic material, metallic lithium and a specific organic solvent are further mixed in an inert gas. Here, the organic solvent is used because it is effective for improving the dispersion of metallic lithium and graphitic carbon to prevent the collective adhesion between the component materials and to form a uniform and stable film on the surface. .

次に、上記混合物に一定時間、高エネルギーメカニカルミリング処理(HEMM)を行う。これにより黒鉛性炭素のエッジ部分に非晶質構造が形成され、その非晶質構造により、例えばO2−の様なある種の陰イオンや電解質成分が黒鉛層にLiと同時挿入されることが防止される。更に、黒鉛性材料粒子表面に高いLiイオン導電性を持ったリチウムと炭素の安定な化合物(LiC)を形成させることが可能となる。このような化合物は、PEO電解質と黒鉛性材料が直接接触することを防止するからである。 HEMM処理された混合物はさらに残存の有機溶剤を取り除くため高温で乾燥される。このように処理されて得られる黒鉛性炭素材料は、PEO電解質に対して高い初期充放電効率、高い可逆性容量、安定なサイクル特性で示される優れた電気化学特性を示す。 Next, the mixture is subjected to high energy mechanical milling (HEMM) for a certain period of time. As a result, an amorphous structure is formed at the edge portion of the graphitic carbon, and certain anions such as O 2− and electrolyte components are simultaneously inserted into the graphite layer together with Li + due to the amorphous structure. It is prevented. Furthermore, it becomes possible to form a stable lithium and carbon compound (LiC x ) having high Li ion conductivity on the surface of the graphitic material particles. This is because such a compound prevents direct contact between the PEO electrolyte and the graphitic material. The HEMM-treated mixture is further dried at an elevated temperature to remove residual organic solvent. The graphitic carbon material obtained by processing in this way exhibits excellent electrochemical characteristics exhibited by high initial charge / discharge efficiency, high reversible capacity, and stable cycle characteristics with respect to the PEO electrolyte.

本発明の実施例について下記に説明するが、本発明の技術的範囲は本実施例によって限定されるものではなく、その要旨を変更することなく様々に改変して実施することができる。又、本発明の技術的範囲は、均等の範囲にまで及ぶものである。 Examples of the present invention will be described below, but the technical scope of the present invention is not limited by the examples, and various modifications can be made without changing the gist thereof. Further, the technical scope of the present invention extends to an equivalent range.

粒径20−25μmのマイクロビーズメソカーボン(MCMB)を真空中20時間、80℃で乾燥する。このように処理した一定量のMCMBを金属リチウムとドデカン{CH(CH10CH)とを混合する。黒鉛材料と金属リチウム比は20.3:1(重量比)であった。また黒鉛材料とドデカンの比は、ドデカン1mlに対し黒鉛1gとした。混合物はボールミルのポット(40cc)に、適量のボール(直径1cm)と共に入れる。ここで、1gの混合物に対し、ボールは12個とした。次に、ポットにアルゴンガスを充填し、混合物を回転数600rpmで15時間のHEMM処理を施した後、混合物を真空中で、90℃、10時間の乾燥処理を行った。 Microbead mesocarbon (MCMB) having a particle size of 20-25 μm is dried at 80 ° C. in vacuum for 20 hours. A certain amount of MCMB treated in this way is mixed with lithium metal and dodecane {CH 3 (CH 2 ) 10 CH 3 ). The ratio of graphite material to metallic lithium was 20.3: 1 (weight ratio). The ratio of the graphite material to dodecane was 1 g of graphite per 1 ml of dodecane. The mixture is placed in a ball mill pot (40 cc) with an appropriate amount of balls (1 cm in diameter). Here, 12 balls were used for 1 g of the mixture. Next, the pot was filled with argon gas, the mixture was subjected to HEMM treatment for 15 hours at a rotation speed of 600 rpm, and then the mixture was dried in vacuum at 90 ° C. for 10 hours.

PEO系固体電解質の作成は以下の通りである。一定量のLiN(CFSOとポリエチレンオキサイド(MW=6×10)(O/Li=18)を無水アセトニトリル溶媒に溶かす。無機フィラーとしてBaTiO(約0.1μ)を均一に分散させる。得られた粘性の複合溶液をフッ素樹脂プレート上にキャストする。次に、窒素気流中でアセトニトリル溶媒をゆっくり蒸発させ、その後真空中で90℃×10時間乾燥させる。得られた膜の厚さは300μであった。この複合ポリマー電解質の導電率は、80℃で1.7×10−3Scm−1、65℃で0,82×10−3Scm−1であった。
The production of the PEO solid electrolyte is as follows. A certain amount of LiN (CF 3 SO 2 ) 2 and polyethylene oxide (MW = 6 × 10 5 ) (O / Li = 18) are dissolved in anhydrous acetonitrile solvent. BaTiO 3 (about 0.1 μ) is uniformly dispersed as an inorganic filler. The obtained viscous composite solution is cast on a fluororesin plate. Next, the acetonitrile solvent is slowly evaporated in a nitrogen stream, and then dried in a vacuum at 90 ° C. for 10 hours. The thickness of the obtained film was 300 μm. The conductivity of the composite polymer electrolyte was 1.7 × 10 −3 Scm −1 at 80 ° C. and 0.82 × 10 −3 Scm −1 at 65 ° C.

複合電極はグローブボックスの中で作成した。電極の構成物質は、PEO、LiN(CFSO、アセチレンブラック、黒鉛性材料粒子とし、ヘキサン存在下、乳鉢中で混合し、300メッシュのステンレスの網に押しつけて作成した。ステンレスは集電体の働きをし、電極面積は0.55cm、厚さは100〜160μであった。
電極の電気化学的特性を調査するために、リチウム金属を対極に用いPEOフィルムを電解質兼セパレータとして使用し、3層に積み重ねて2025コイン型電池セル内に入れた。充放電は0.05mAcm−2の電流密度、電圧範囲を2.0/0V vs・Li/Li+とし、温度は70℃で行った。測定前に、セルを2時間70℃で保持した。電極の容量は活物質の重量あたりで計算した。
以上により得られた、リチウムと炭素からなる化合物膜の電子顕微鏡写真を図2に示す。本発明の処理法により、黒鉛結晶の表面部にLiC結晶層が、更にその表層部にLiCアモルファス層が形成されていることが、図2から判る。
The composite electrode was made in a glove box. The constituent materials of the electrode were PEO, LiN (CF 3 SO 2 ) 2 , acetylene black, and graphitic material particles, which were mixed in a mortar in the presence of hexane and pressed against a 300 mesh stainless steel net. Stainless steel acted as a current collector, and the electrode area was 0.55 cm 2 and the thickness was 100 to 160 μm.
In order to investigate the electrochemical characteristics of the electrode, lithium metal was used as a counter electrode, a PEO film was used as an electrolyte and separator, and the layers were stacked in a 2025 coin-type battery cell. Charging / discharging was performed at a current density of 0.05 mAcm −2 , a voltage range of 2.0 / 0 V vs. Li / Li +, and a temperature of 70 ° C. Prior to measurement, the cell was held at 70 ° C. for 2 hours. The capacity of the electrode was calculated per active material weight.
An electron micrograph of the compound film composed of lithium and carbon obtained as described above is shown in FIG. It can be seen from FIG. 2 that the LiC x crystal layer is formed on the surface portion of the graphite crystal and the LiC x amorphous layer is formed on the surface layer portion by the treatment method of the present invention.

図3は、粒径20−25μmの黒鉛について、本発明による処理を施した場合と処理を施していない場合のPEO電解質系における充放電特性を比較したものであるが、処理を施した黒鉛は初期充放電効率が37.6%から63.7%へと増加し、又、可逆容量が120mAhg−1から 260mAhg−1へと増加し、顕著な向上を見せた。又、処理した黒鉛のサイクルによる容量保持性能も優れていた。 FIG. 3 is a graph comparing the charge / discharge characteristics of the PEO electrolyte system when the treatment according to the present invention is performed with respect to graphite having a particle size of 20-25 μm. The initial charge / discharge efficiency increased from 37.6% to 63.7%, and the reversible capacity increased from 120 mAhg −1 to 260 mAhg −1 , showing a marked improvement. Moreover, the capacity retention performance by the cycle of the treated graphite was also excellent.

粒子径1μm の天然黒鉛を真空中で80℃×20時間乾燥し、乾燥した黒鉛と金属リチウム、ドデカンを一定量混合した。黒鉛対リチウム比は重量比で10.3:1に、黒鉛対ドデカン比は黒鉛1gに対しドデカン2mlとした。混合物をボールミルのポット(40cc)に、適量のボール(直径1cm)と共に入れるが、このとき混合物1gに対し、ボールを16個とした。ポットにアルゴンガスを充填し、混合物を、回転数600rpmで20時間のHEMM処理を施した。この時、1.5時間毎に5分の休止時間をとった。その後、混合物を90℃で10時間、真空中で乾燥させた。以降の作成条件は実施例と同一とした。その結果を図4および表1に示す。   Natural graphite having a particle diameter of 1 μm was dried in a vacuum at 80 ° C. for 20 hours, and a certain amount of dried graphite, metallic lithium and dodecane were mixed. The graphite to lithium ratio was 10.3: 1 by weight, and the graphite to dodecane ratio was 2 ml of dodecane per 1 g of graphite. The mixture was put into a ball mill pot (40 cc) together with an appropriate amount of balls (1 cm in diameter). At this time, 16 balls were added to 1 g of the mixture. The pot was filled with argon gas, and the mixture was subjected to HEMM treatment for 20 hours at 600 rpm. At this time, a pause of 5 minutes was taken every 1.5 hours. The mixture was then dried in vacuo at 90 ° C. for 10 hours. The subsequent creation conditions were the same as in the example. The results are shown in FIG.

ここで、図4は、粒径1μmの黒鉛について、本発明による処理を施した場合と処理を施していない場合のPEO電解質系における特性を比較したものであるが、処理を施した黒鉛は初期充放電効率が28.1%から75.4%に増加し、可逆容量は110mAhg−1から220mAhg−1に増加し、顕著な向上を示した。処理した黒鉛のサイクルによる容量保持性能も同様に優れていた。 Here, FIG. 4 compares the characteristics in the PEO electrolyte system when the treatment according to the present invention is applied to the graphite having a particle diameter of 1 μm and when the treatment is not performed. The charge / discharge efficiency increased from 28.1% to 75.4%, and the reversible capacity increased from 110 mAhg −1 to 220 mAhg −1 , indicating a marked improvement. The capacity retention performance by the cycle of the treated graphite was also excellent.

又、図5は粒径20−25μmの黒鉛について、本発明による処理を施した場合と処理を施していない場合のPEO電解質系におけるサイクリックボルタモグラムを示す(70℃)。通常の黒鉛に一回目にLiを挿入する際、PEOと電極間にある不可逆な反応が起こることで現れる0.2、0.9、1.35、2.3Vのピークが、処理した黒鉛では完全に消えていた。 FIG. 5 shows a cyclic voltammogram (70 ° C.) in a PEO electrolyte system with and without the treatment of graphite having a particle diameter of 20-25 μm. When Li is inserted into normal graphite for the first time, peaks of 0.2, 0.9, 1.35, and 2.3 V appearing due to an irreversible reaction between the PEO and the electrode occur in the treated graphite. It disappeared completely.

表1は異なった電解質における本発明による処理を施した黒鉛と処理を施していない黒鉛の初期充放電効率と可逆容量を比較したものである。処理をしていない黒鉛材料は液体電解質との組み合わせとは異なり、PEO電解質とは明らかに劣った特性しか示さなかった。しかし、本発明による処理を施した黒鉛材料は初期効率においても可逆容量においても飛躍的な性能向上を示した。 Table 1 compares the initial charge and discharge efficiency and the reversible capacity of the graphite treated with the present invention and the untreated graphite in different electrolytes. The untreated graphite material, unlike the combination with the liquid electrolyte, showed clearly inferior properties to the PEO electrolyte. However, the graphite material treated according to the present invention showed a dramatic improvement in both initial efficiency and reversible capacity.

Figure 0004496366
Figure 0004496366

HEMM処理により、黒鉛表面にLiCを形成させた場合の模式図である。It is a schematic diagram at the time of forming LiC x on the graphite surface by HEMM treatment. 黒鉛表面に形成されたLiCを示す透過型電子顕微鏡写真を示す図である。ここで、写真[1]は、本発明の処理無しの場合を、写真[2]は、処理を施した場合を示す図である。It shows a transmission electron micrograph showing a LiC x formed on the graphite surface. Here, Photo [1] is a diagram showing a case where the processing of the present invention is not performed, and Photo [2] is a diagram showing a case where processing is performed. 粒径20−25μmの黒鉛を負極材料に用いた場合の、充放電性能を示す図である。本発明の処理(modification)を施した場合は、処理無し(without modification)に比べ特性がかなり改善されている。It is a figure which shows charging / discharging performance at the time of using graphite with a particle size of 20-25 micrometers for negative electrode material. When the modification according to the present invention is applied, the characteristics are considerably improved as compared to without modification. 粒径1μmの黒鉛を負極材料に用いた場合の、充放電性能を示す図である。本発明の処理(modification)を施した場合は、処理無し(without modification)に比べ特性がかなり改善されている。It is a figure which shows charging / discharging performance at the time of using graphite with a particle size of 1 micrometer for negative electrode material. When the modification according to the present invention is applied, the characteristics are considerably improved as compared to without modification. 粒径20−25μmの黒鉛を負極材料に用いた場合の、サイクリックボルタモグラムを示す図である。It is a figure which shows the cyclic voltammogram at the time of using graphite with a particle size of 20-25 micrometers for negative electrode material.

Claims (7)

黒鉛の表面部にリチウムと炭素からなる化合物膜が形成されていることを特徴とする高分子固体電解質リチウム2次電池用負極材。   A negative electrode material for a polymer solid electrolyte lithium secondary battery, wherein a compound film comprising lithium and carbon is formed on a surface portion of graphite. 前記において、黒鉛表面部に形成されたリチウムと炭素からなる化合物膜の表層部が少なくとも非晶質状態であることを特徴とする請求項1に記載の高分子固体電解質リチウム2次電池用負極材。
2. The negative electrode material for a solid polymer electrolyte lithium secondary battery according to claim 1, wherein the surface layer portion of the compound film composed of lithium and carbon formed on the graphite surface portion is at least in an amorphous state. .
前記の高分子固体電解質がポリエチレンオキサイドにリチウム塩を溶解したものであることを特徴とする請求項1または2の何れかに記載の高分子固体電解質リチウム2次電池用負極材。   3. The negative electrode material for a solid polymer electrolyte lithium secondary battery according to claim 1, wherein the solid polymer electrolyte is obtained by dissolving a lithium salt in polyethylene oxide. 前記ポリエチレンオキサイドがセラミックスフィラーを含有することを特徴とする請求項3に記載の高分子固体電解質リチウム2次電池用負極材。   The negative electrode material for a polymer solid electrolyte lithium secondary battery according to claim 3, wherein the polyethylene oxide contains a ceramic filler. 黒鉛、金属リチウム及び沸点が190℃〜260℃の有機溶剤で構成される混合物に、ボールミリング処理を施し、黒鉛表面部にリチウムと炭素からなる化合物膜を形成することを特徴とする高分子固体電解質リチウム2次電池用負極材の製造方法。   A polymer solid characterized by subjecting a mixture composed of graphite, metallic lithium and an organic solvent having a boiling point of 190 ° C. to 260 ° C. to ball milling to form a compound film composed of lithium and carbon on the surface of the graphite A method for producing a negative electrode material for an electrolyte lithium secondary battery. 前記の混合物において、黒鉛/リチウムの重量混合比がリチウム1に対し黒鉛0.01−0.8であり、有機溶剤/リチウムの容積混合比がリチウム1gに対し有機溶剤1−40mlであることを特徴とする請求項5に記載の高分子固体電解質リチウム2次電池用負極材の製造方法。
In the above mixture, the weight mixing ratio of graphite / lithium is 0.01-0.8 of graphite with respect to lithium 1, and the volume mixing ratio of organic solvent / lithium is 1-40 ml of organic solvent with respect to 1 g of lithium. The manufacturing method of the negative electrode material for polymer solid electrolyte lithium secondary batteries of Claim 5 characterized by the above-mentioned .
前記有機溶剤がドデカン(CH(CH10CH)であることを特徴とする請求項5または6の何れかに記載の高分子固体電解質リチウム2次電池用負極材の製造方法。













Manufacturing method of the organic solvent dodecane (CH 3 (CH 2) 10 CH 3) negative electrode material for solid polymer electrolyte lithium secondary battery according to claim 5 or 6, characterized in that a.













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