【発明の詳細な説明】[Detailed description of the invention]
本発明は陰極活物質にアルカリ金属，アルカリ
土類金属などの軽金属を、電解質に有機電解質
を、陽極活物質に式（C2F）ｎで表わされるフツ
化炭素を用いる有機電解質電池の製造法に関する
もので、式（C2F）ｎで表わされる活物質をその
生成温度よりも高温で熱処理することにより放電
特性，保存特性の良好な電池を提供することを目
的としている。
炭素をフツ素化することにより生成されるフツ
化炭素には、
(1) poly carbon monofluoride（CF）ｎ
(2) poly tetra carbon monofluoride（C4F）ｎ
の２種のものが知られていたが、最近、新たに式
（C2F）ｎで表わされるpoly dicarbon
monofluorideが提案されている（特開昭53−
102893）。このフツ化炭素（C2F）ｎは他の
（CF）ｎ，（C4F）ｎと同様に、有機電解質系の
陽極活物質として有用であることが知られている
（特開昭55−28246）。
この（C2F）ｎは（CF）ｎと比較して、種々
の特性を有しており、例えば（C2F）ｎは第２次
ステージ化合物であり、かつｃ軸方向の炭素平面
間に共有結合に相当する強い結合力の存在が考え
られている点や層間距離が（CF）ｎの約６Åに
対して、約９Åと大きい点などがあり、このため
電気化学的な特性も異なり、（C2F）ｎは（CF）
ｎよりも放電圧が高いという特徴をもつ。
しかしながら、（C2F）ｎは放電電圧は高いが、
平担性が悪く、放電の進行に伴い電圧が徐々に低
下してくること、また、電池を高温保存した際に
容量劣化が大であることなどの欠点を有する。高
温保存による劣化は、フツ化炭素陽極と陽極集電
体との間に、主にフツ化物による抵抗皮膜層が形
成されるためと考えられる。上記フツ化物は、主
にフツ化炭素中に含まれる化学吸着などによる弱
い結合をしているフツ素が有機電解質中で遊離し
（遊離フツ素）、恐らくはフツ素イオンとなつて陽
極集電体界面へ移動し、反応するためと考えられ
る。因に、この遊離フツ素をヨードメトリー法で
測定すると、（C2F）ｎは、（CF）ｎの数十倍以
上の値を示す。
本発明者らは、フツ化炭素（C2F）ｎをその生
成温度よりも高い400〜460℃の温度で熱処理を行
なうことにより、化学吸着などと考えられる弱い
結合のフツ素を、強固な共有結合に変えることが
でき、放電特性・保存特性が改良されることを見
い出した。
以下本発明をその実施例により説明する。
フツ化炭素（C2F）ｎには、人造黒鉛を400℃
でフツ素化したものを用いた。この（C2F）ｎの
空気中での熱分解開始温度は約500℃で、ピーク
温度は590℃であつたが、550℃付近より分解が急
激に進行することが分つた。このため、熱処理は
熱分解が始まる500℃より低い460℃以下で行つ
た。実験的には500℃および550℃の温度でも行つ
たが、これは熱分解を防ぐため、フツ素と窒素の
混合雰囲気中で行つたもので、分解反応とフツ素
化反応との競合反応下における熱処理であり実用
的ではない。460℃以下の熱処理は常圧・空気中
で、500℃と550℃の熱処理はフツ素：窒素の体積
比が１：９の雰囲気で行つた。次表に各処理条件
を示し、また処理後の固定フツ素量，遊離フツ素
量を示した。固定フツ素量は試料を十分な量の炭
酸カリと混合後、溶融，分解させたものを水溶液
として、フツ素イオン選択性電極により測定し、
遊離フツ素量は試料をエタノールと0.1Nの沃化
カリとの混合液で抽出し、下式により遊離した沃
素を0.01Nのチオ硫酸ナトリウムで滴定して求め
た。
２（Ｃ…Ｆ）＋2KI→Ｃ＋2KF＋I2
The present invention provides a method for producing an organic electrolyte battery using light metals such as alkali metals and alkaline earth metals as the cathode active material, an organic electrolyte as the electrolyte, and carbon fluoride represented by the formula (C 2 F) n as the anode active material. The purpose is to provide a battery with good discharge characteristics and storage characteristics by heat-treating an active material represented by the formula (C 2 F)n at a higher temperature than its formation temperature. There are two known types of fluorinated carbon produced by fluorinating carbon: (1) poly carbon monofluoride (CF) (2) poly tetra carbon monofluoride (C 4 F) However, recently, poly dicarbon expressed by the formula (C 2 F) n has been newly discovered.
Monofluoride has been proposed (Japanese Patent Application Laid-open No. 1983-
102893). This carbon fluoride (C 2 F) n, like other (CF) n and (C 4 F) n, is known to be useful as an anode active material for organic electrolyte systems (Japanese Patent Laid-Open No. 55 −28246). This (C 2 F) n has various properties compared to (CF) n. For example, (C 2 F) n is a second stage compound, and there is a difference between the carbon planes in the c-axis direction. It is thought that there is a strong bonding force equivalent to a covalent bond, and the interlayer distance is larger at about 9 Å compared to about 6 Å for (CF)n, so the electrochemical properties are also different. , (C 2 F)n is (CF)
It is characterized by a higher discharge voltage than n. However, although (C 2 F)n has a high discharge voltage,
It has disadvantages such as poor flatness, voltage gradually decreasing as discharge progresses, and large capacity deterioration when the battery is stored at high temperatures. The deterioration due to high-temperature storage is thought to be due to the formation of a resistive film layer mainly made of fluoride between the fluoride carbon anode and the anode current collector. The above-mentioned fluorides are mainly caused by weakly bonded fluorine contained in carbon fluoride, which is liberated in the organic electrolyte (free fluorine), and is probably converted into fluorine ions to form an anode current collector. This is thought to be because it moves to the interface and reacts. Incidentally, when this free fluorine is measured by iodometry, (C 2 F)n shows a value several tens of times or more than (CF)n. By heat-treating fluorocarbon (C 2 F)n at a temperature of 400 to 460°C, which is higher than its formation temperature, the present inventors succeeded in converting the weakly bonded fluorine, which is thought to be due to chemisorption, into a strong bond. It has been found that it can be converted into a covalent bond, improving discharge and storage characteristics. The present invention will be explained below with reference to Examples. For carbon fluoride (C 2 F), artificial graphite was heated at 400℃.
A fluorinated product was used. The starting temperature of thermal decomposition of this (C 2 F)n in air was about 500°C, and the peak temperature was 590°C, but it was found that the decomposition rapidly progressed from around 550°C. For this reason, the heat treatment was carried out at 460°C or lower, which is lower than the 500°C at which thermal decomposition begins. Experiments were carried out at temperatures of 500°C and 550°C, but this was done in a mixed atmosphere of fluorine and nitrogen to prevent thermal decomposition, and this was done under a competitive reaction between the decomposition reaction and the fluorination reaction. This is a heat treatment that is not practical. The heat treatment at temperatures below 460°C was performed in air at normal pressure, and the heat treatments at 500°C and 550°C were performed in an atmosphere with a fluorine:nitrogen volume ratio of 1:9. The following table shows each treatment condition, as well as the amount of fixed fluorine and amount of free fluorine after treatment. The amount of fixed fluorine is measured by mixing the sample with a sufficient amount of potassium carbonate, melting and decomposing it as an aqueous solution, and using a fluorine ion selective electrode.
The amount of free fluorine was determined by extracting the sample with a mixture of ethanol and 0.1N potassium iodide, and titrating the liberated iodine with 0.01N sodium thiosulfate using the following formula. 2(C...F)+2KI→C+2KF+I 2
【表】【table】
【表】
この表より明らかなように、熱処理及び再フツ
素化により、固定フツ素量は余り変化しないが、
遊離フツ素量は処理前の大体1/10ぐらいに減少す
る。
熱処理・再フツ素化したフツ化炭素（C2F）ｎ
を用いた電池特性比較のため、第１図に示す構造
の扁平型電池を構成した。
図中、１は封口板、２は金属リチウムからなる
陰極、３はセパレータ、４は樹脂ガスケツト、５
は陽極であり、これは活物質のフツ化炭素
（C2F）ｎと導電材のアセチレンブラツクおよび
フツ素樹脂結着材とを重量比で100：10：５の割
合で混合したものをペレツトに成型した。６は陽
極集電体、７は電池ケースである。電解液にはホ
ウフツ化リチウムをプロピレンカーボネイトとジ
メトキシエタンとの１：１の混合溶媒に１モル／
の割合で溶解させたものを用いた。
上記扁平型電池を組立直後に20℃において、
5KΩの抵抗を負荷として放電した放電曲線を第
２図に示した。図中Ａ〜Ｆは、前表に示したフツ
化炭素（C2F）ｎをそれぞれ陽極活物質とした電
池の放電曲線である。第２図より明らかなように
空気中で熱処理をしたフツ化炭素（C2F）nA，
Ｂ，Ｃの放電特性は、初期電圧では、未処理のＦ
に較べて低下しているが、電圧の変動は小さく、
また容量も大きくなり、利用率が良くなつている
ことが分る。また、再フツ素化した（C2F）nD，
Ｅの放電特性も、放電電圧は低下するが、電圧の
平担性が良くなり、容量も大となることが分る。
Ｄ，Ｅの放電特性はフツ化炭素（CF）ｎの特性
と似ているが、放電平担部の電圧は（CF）ｎの
場合約2.65Vであるのに対して、Ｄ，Ｅの電圧は
2.72Vと優位にある。一方、陽極活物質の利用率
は、未処理の（C2F）nFの場合約74％であるのに
対して、Ｃ及びＤ，Ｅでは約84％と大幅に改良さ
れ、Ａ，Ｂの場合でも76〜80％と改良されてい
る。しかしＤおよびＥは前述したようにフツ素と
窒素の混合雰囲気中での熱処理であり、空気中で
の熱処理であるＡ，Ｂ，Ｃと比べて工程が複雑で
あり実用的でない。
第３図は、上記扁平型電池を60℃３ケ月間保存
後の20℃，5KΩの定抵抗放電の放電曲線である。
図より明らかなように、未処理の（C2F）nFは、
放電初期の電圧降下が大きく、また放電容量も保
存前に較べて大きく低下している。一方、本発明
による処理を行なつた（C2F）ｎでは、放電電
圧・容量ともに、ほとんど劣化がみられない。高
温保存による劣化、特に放電初期の電圧降下は主
に陽極合剤ペレツト５と陽極集電体６の接触界面
に、陽極活物質の（C2F）ｎから遊離してきたフ
ツ素イオンがフツ化物層を形成し、これが絶縁抵
抗皮膜となるためと考えられる。本発明の処理に
より、前表に示したように、（C2F）ｎのヨード
メトリー法によつて検出された遊離フツ素量は1/
１０程度に減少していることと、上記の保存による
劣化の度合とはよく一致している。さらに、この
ヨードメトリー法によつて検出されるフツ素量
は、（C2F）ｎ全体に含まれているカーボン，フ
ツ素の弱い結合（Ｃ…Ｆ）の存在比を表わすもの
と考えられ、電池の高温保存により、正極中から
遊離してくるフツ素量、或いは放電に関与しない
フツ素量は、前表の結果より、未処理の（C2F）
ｎでは、本発明の処理を行なつた（C2F）ｎ、或
いはフツ化炭素（CF）ｎに対して、かなり大き
いと推測される。従つて、第３図のように未処理
の（C2F）nFでは、高温保存により放電容量も大
きく減少するものと考えられる。
本発明は、（C2F）ｎ中に存在する弱い結合の
Ｃ…Ｆを熱処理により安定化させることにより、
電池特性が改良されたと考えられるが、そのため
の下限処理温度は400℃とする必要がある。なぜ
なら、（C2F）ｎが単独で生成する温度は400℃以
下とされているが、前表Ｆのように、400℃では
弱い結合（Ｃ…Ｆ）が多量に存在していると考え
られるからである。
一方、上限温度は空気中で分解を抑え収率を上
げるためには、約460℃となる。 以上のように、
本発明のフツ化炭素（C2F）ｎを陽極活物質に用
いることにより、既に実用化されているLi／
（CF）ｎ系電池と同様に、放電特性・保存特性の
良好な電池を提供することができ、さらに、放電
電圧がLi／（CF）ｎ系よりも優位にあるという
特徴を発揮させることができる。[Table] As is clear from this table, the amount of fixed fluorine does not change much due to heat treatment and refluorination, but
The amount of free fluorine is reduced to approximately 1/10 of the amount before treatment. Heat-treated and re-fluorinated carbon fluoride (C 2 F) n
In order to compare the characteristics of a battery using a battery, a flat battery having the structure shown in FIG. 1 was constructed. In the figure, 1 is a sealing plate, 2 is a cathode made of metallic lithium, 3 is a separator, 4 is a resin gasket, and 5
is an anode, which is made of pellets made of a mixture of carbon fluoride (C 2 F) as an active material, acetylene black as a conductive material, and a fluororesin binder in a weight ratio of 100:10:5. It was molded into. 6 is an anode current collector, and 7 is a battery case. For the electrolyte, lithium borofluoride was mixed with 1 mole of propylene carbonate and dimethoxyethane in a 1:1 mixed solvent.
A solution dissolved at the following ratio was used. Immediately after assembling the above flat battery, place it at 20°C.
Figure 2 shows the discharge curve when a 5KΩ resistor was used as the load. A to F in the figure are discharge curves of batteries using carbon fluoride (C 2 F)n shown in the previous table as the positive electrode active material, respectively. As is clear from Figure 2, carbon fluoride (C 2 F) nA heat-treated in air,
The discharge characteristics of B and C are that at the initial voltage, the untreated F
Although the voltage fluctuation is small compared to
It can also be seen that the capacity has increased and the utilization rate has improved. In addition, refluorinated (C 2 F) nD,
As for the discharge characteristics of E, it can be seen that although the discharge voltage decreases, the voltage flatness improves and the capacity also increases.
The discharge characteristics of D and E are similar to those of fluorocarbon (CF)n, but the voltage at the discharge plateau is approximately 2.65V for (CF)n, whereas the voltage of D and E is teeth
It has an advantage of 2.72V. On the other hand, the utilization rate of the anode active material is approximately 74% for untreated (C 2 F) nF, whereas it is significantly improved to approximately 84% for C, D, and E, and In most cases, it has improved by 76-80%. However, as mentioned above, D and E are heat treatments in a mixed atmosphere of fluorine and nitrogen, and are more complicated than A, B, and C, which are heat treatments in air, and are not practical. FIG. 3 is a discharge curve of constant resistance discharge of 5KΩ at 20°C after the flat battery was stored at 60°C for 3 months.
As is clear from the figure, untreated (C 2 F) nF is
The voltage drop at the beginning of discharge was large, and the discharge capacity was also significantly reduced compared to before storage. On the other hand, with (C 2 F)n treated according to the present invention, almost no deterioration is observed in both discharge voltage and capacity. Deterioration due to high-temperature storage, especially the voltage drop at the beginning of discharge, is caused mainly by fluorine ions liberated from (C 2 F)n of the anode active material at the contact interface between the anode mixture pellet 5 and the anode current collector 6. This is thought to be because a layer is formed and this becomes an insulation resistance film. By the treatment of the present invention, as shown in the previous table, the amount of free fluorine detected by the iodometry method of (C 2 F)n is reduced by 1/
The decrease to about 10 is in good agreement with the degree of deterioration due to storage as described above. Furthermore, the amount of fluorine detected by this iodometry method is considered to represent the abundance ratio of carbon and fluorine weak bonds (C...F) contained in the entire (C 2 F)n. , the amount of fluorine liberated from the positive electrode due to high-temperature storage of the battery, or the amount of fluorine that does not participate in discharge, is determined from the results in the previous table by untreated (C 2 F).
It is presumed that n is considerably larger than (C 2 F) n or fluorocarbon (CF) n treated according to the present invention. Therefore, it is considered that in untreated (C 2 F) nF as shown in FIG. 3, the discharge capacity also decreases greatly due to high temperature storage. In the present invention, by stabilizing the weak bonds C...F existing in (C 2 F)n by heat treatment,
It is thought that the battery characteristics have been improved, but the lower limit treatment temperature for this purpose needs to be 400°C. This is because the temperature at which (C 2 F)n forms alone is said to be below 400℃, but as shown in Table F above, it is thought that a large amount of weak bonds (C...F) exist at 400℃. This is because it will be done. On the other hand, the upper limit temperature is approximately 460°C in order to suppress decomposition in air and increase yield. As mentioned above,
By using carbon fluoride (C 2 F)n of the present invention as an anode active material, Li/
As with (CF)n-based batteries, it is possible to provide a battery with good discharge and storage characteristics, and furthermore, it is possible to provide a battery with superior discharge voltage than Li/(CF)n-based batteries. can.
【図面の簡単な説明】[Brief explanation of the drawing]
第１図は本発明の実施例の電池の断面図、第２
図は各種（C2F）ｎを用いた電池の組立直後の放
電特性、第３図は電池の保存後の放電特性を示
す。
１…封口板、２…陰極、３…セパレータ、５…
陽極、７…電池ケース。
FIG. 1 is a cross-sectional view of a battery according to an embodiment of the present invention, and FIG.
The figure shows the discharge characteristics of batteries using various types of (C 2 F)n immediately after assembly, and FIG. 3 shows the discharge characteristics of the batteries after storage. 1... Sealing plate, 2... Cathode, 3... Separator, 5...
Anode, 7...Battery case.