Electrolytic cell of high voltage

An electrolytic cell comprising a negative electrode having as the active material a light metal and a positive electrode as the main active material a poly-dicarbon monofluoride represented by the formula (C.sub.2 F).sub.n has been found to exhibit a high discharge voltage as compared with the conventional electrolytic cell of the type using as the active material of the positive electrode a polycarbon monofluoride represented by the formula (CF).sub.n and also been found to be excellent in flatness of discharge voltage and shelf-life. The electrolytic cell of the present invention can be produced at low cost due to high yield of (C.sub.2 F).sub.n in production, and is useful as the energy source of such devices as watch, clock, desk type computer, small type radio, etc.

This invention relates to an electrolytic cell. More specifically, the 
invention is concerned with an electrolytic cell of the type having as the 
negative electrode a light metal, such as an alkali metal or aluminum, and 
an electrolyte in which the negative electrode is not dissolved. The 
electrolytic cell of this invention is characterized in that the positive 
electrode has as an active material thereof poly-dicarbon monofluoride 
represented by the formula (C.sub.2 F).sub.n. 
It is known that polycarbon monofluoride represented by the formula 
(CF).sub.n in which the ratio of carbon to fluorine is 1 and n is an 
integer is obtained by reacting carbon material or graphite with fluorine 
at a temperature of about 410.degree. C. to about 630.degree. C. in an 
atmosphere of fluorine, a halogen fluoride or a mixture thereof or their 
mixture with an inert gas or air. It is also known that the structure of 
the above-mentioned polycarbon monofluoride is such that fluorine atoms 
introduced into interlayer spacings between lattice layers which are 
characteristic of graphite or carbon are covalently bonded to the carbon 
atoms by forming a pair of electrons from a valence electron of the 
fluorine atom and an excess valence electron of the carbon atoms. 
Polycarbon monofluoride (CF).sub.n as described above is highly 
appreciated due to its peculiar properties in a wide variety of industrial 
fields for usages thereof as active materials in electrolytic cells, 
lubricants, anti-wetting, stain resistant and water and/or oil-repellent 
materials, etc. Especially, in the field of electrolytic cells, polycarbon 
monofluoride is known to be an active material which provides a primary 
cell of high energy density and long shelf life in which voltage drop due 
to discharge is scarcely observed for a long period of time. In this 
connection, however, it is to be noted that the electrolytic cell using as 
the active material a compound (CE).sub.n has such a disadvantage that it 
exhibits a relatively low voltage. 
The conventionally known polycarbon monofluoride (CF).sub.n has further 
fatal drawbacks in the production thereof. Illustratively stated, the 
thermal decomposition temperature of (CF).sub.n is extremely close to the 
temperature employed for the formation of the (CF).sub.n. For example, 
when petroleum coke (not graphitized by heat treatment) is employed as a 
carbon material and reacted with fluorine, the desired (CF).sub.n is 
obtained by the reaction of at 400.degree. C. for several hours but the so 
obtained (CF).sub.n easily decomposes at 450.degree. C. Whereas, when 
natural graphite is employed as a carbon material and reacted with 
fluorine, the desired (CF).sub.n is obtained by the reaction of at 
600.degree. C. for 48 hours but the so obtained (CF).sub.n easily 
decomposes at 610.degree. C. Generally, the temperature difference between 
the formation temperature of (CF).sub.n and the decomposition temperature 
is only about 10 to about 50.degree. C. It should be further noted that 
both the formation reaction of (CF).sub.n and the decomposition reaction 
thereof are exothermic. Hence, with the progress of formation of 
(CF).sub.n, the temperature of the reaction system is liable to rise and, 
at the same time, the low crystallinity (CF).sub.n moiety partially formed 
is caused to decompose, whereby heat is further generated by such 
decomposition reaction to further elevate the temperature of the reaction 
system. As a result of this, the decomposition of the formed (CF).sub.n is 
accelerated, and occasionally the temperature of the whole reaction system 
is caused to rise to above the decomposition temperature of the formed 
(CF).sub.n, whereby all of the formed (CF).sub.n is caused to completely 
decompose to amorphous carbon and gaseous fluorocarbons such as CF.sub.4. 
Consequently, the yield of (CF).sub.n is extremely low. For this reason, 
in order to obtain (CF).sub.n in an improved yield, there have been made 
such attempts that the temperature of the reaction system is always 
adjusted to the temperature of formation of (CF).sub.n and that the 
reaction is effected in multiple steps. However, the former encounters 
difficulty in controlling the temperature of the reaction system, and the 
latter leads to complicatedness of the process. Neither of them is 
practical. Accordingly, at present, (CF).sub.n is produced in a yield as 
low as only several percent in relation to the fluorine employed and 
several ten percent in relation to the carbon material employed. 
As described above, the production of (CF).sub.n is inevitably and 
disadvantageously accompanied by its liability to decomposition. 
Therefore, when the reaction of a carbon material with fluorine is 
effected in a closed system, the fluorine partial pressure in the reaction 
interface regions is reduced due to presence of gaseous fluorocarbons 
formed by the decomposition of the formed (CF).sub.n, leading to extreme 
reduction of the rate of formation of (CF).sub.n whereby there is hardly 
produced a compound (CF).sub.n. For this reason, there is usually employed 
a so-called fluorine flow method for the production of (CF).sub.n. 
However, even with the flow method, the yield of (CF).sub.n in relation to 
the fluorine employed is extremely low and, in addition, the unreacted 
fluorine is flowed out and usually burnt, leading to large loss of 
expensive fluorine. Further, since the reaction for the production of 
(CF).sub.n is generally conducted at relatively high temperatures, for 
example, about 550.degree. to about 630.degree. C. for shortening the 
reaction time, corrosion of the reaction vessel by a high temperature 
fluorine gas is large and cannot be neglected from the viewpoint of 
chemical engineering. 
As fully understood from the above, also due to the difficulties in the 
production thereof, the practical use of polycarbon monofluoride 
(CF).sub.n as the cathode material in electrolytic cells is extremely 
limited. 
We have previously proposed a completely novel compound poly-dicarbon 
monofluoride (C.sub.2 F).sub.n having properties comparable to those of 
polycarbon monofluoride (CF).sub.n. In this connection, it should be noted 
that a novel poly-dicarbon monofluoride (C.sub.2 F).sub.n can surprisingly 
be obtained in a yield as high as 100% as opposed to the polycarbon 
monofluoride which can be obtained in extremely low yield. 
The novel compound poly-dicarbon monofluoride represented by the formula 
(C.sub.2 F).sub.n is as low as about 44.2% by weight with respect to 
theoretical fluorine content as compared with the conventional polycarbon 
monofluoride (CF).sub.n having a theoretical fluorine content of about 
61.3% by weight. Notwithstanding, poly-dicarbon monofluoride (C.sub.2 
F).sub.n unexpectedly exhibits high discharge voltage in use thereof as 
the active material in electrolytic cells as compared with polycarbon 
monofluoride (CF).sub.n. The present invention has been made, based on 
this novel finding. 
Accordingly, it is one object of the present invention to provide an 
electrolytic cell of the type using a fluorinated carbon material as the 
positive electrode, which exhibits high voltage and good discharge 
characteristics with respect to, for example, flatness of discharge 
voltage, high density energy and freedom of leakage. 
It is another object of the present invention to provide an electrolytic 
cell of the kind described above, which can be manufactured at low cost.

According to the present invention, there is provided an electrolytic cell 
comprising a negative electrode having as the active material a light 
metal, an electrolyte and a positive electrode having as the main active 
material a poly-dicarbon monofluoride represented by the formula (C.sub.2 
F).sub.n wherein n is an integer and having a crystalline structure in 
which a layer structure is stacked with an interlayer spacing of about 9.0 
A to form a packing structure, said crystalline structure exhibiting a 
peak at about 10.degree. in terms of an angle of 2.theta. in the X-ray 
diffraction powder pattern. 
Referring now to FIGS. 1 to 3, explanation will be given on novel 
poly-dicarbon monofluoride (C.sub.2 F).sub.n and process for the 
preparation thereof. 
In FIG. 1, there is illustrated a graph obtained by plotting F/C ratios of 
the products prepared by reacting natural graphite (produced in Madagascar 
and having a purity of more than 99%) having a sieve size of 200 to 250 
mesh (Tyler) with fluorine under an F.sub.2 pressure of 200 mmHg against 
the reaction temperatures employed. The following Table 1 corresponds to 
FIG. 1. 
TABLE 1 
______________________________________ 
Relationships between the reaction temperatures 
and F/C ratios of the products (empirical formulae) 
(Natural graphite, 200 to 250 mesh; F.sub.2, 200 mmHg) 
Temperature, Reaction Empirical 
.degree.C. Time Formula 
______________________________________ 
375 120 hrs. CF.sub.0.58 
400 50 hrs. CF.sub.0.61 
450 10 hrs. CF.sub.0.67 
450 70 hrs. CF.sub.0.67 
475 5 hrs. CF.sub.0.71 
475 50 hrs. CF.sub.0.72 
500 150 min. CF.sub.0.82 
525 100 min. CF.sub.0.88 
550 50 min. CF.sub.0.90 
570 40 min. CF.sub.0.93 
570 120 hrs. CF.sub.0.93 
600 20 min. CF.sub.0.96 
600 140 hrs. CF.sub.0.97 
640 5 hrs. CF.sub.1.00 
______________________________________ 
As apparent from Table 1 and FIG. 1, the ratio of F/C gets closer to 1 
according to elevation of the reaction temperature. The product obtained 
at a relatively low temperature, for example, of 375.degree. C. has an F/C 
ratio of 0.58 (namely, CF.sub.0.58) and a black color. In this connection, 
it should be noted that once the product having such an F/C ratio of 0.58 
is formed, the F/C ratio unexpectedly no longer changes even if the 
product is further heat-treated at 600.degree. C. for a period of time as 
long as 120 hrs. in a fluorine atmosphere. Only the color of the product 
changes from black to white. 
In FIG. 2, there are shown X-ray diffraction powder patterns of the 
products obtained by the experiments for making Table 1 and FIG. 1. In 
FIG. 3, based on the X-ray diffraction powder patterns of FIG. 2, 
interlayer spacings (d.sub.001) and half width (.beta..sub.001) are 
plotted against the reaction temperatures. As clear from FIGS. 2 and 3, 
the position of the peak due to the diffraction (001) is shifted to the 
side of small angle of diffraction and the half width also changes 
according to lowering of the reaction temperature. The interlayer spacing 
of the product obtained by the reaction at 640.degree. C. is 5.85 A and 
corresponds to that of (CF).sub.n ', while the interlayer spacing of the 
product obtained by the reaction at 375.degree. C. is 9.0 A. The products 
obtained by the reactions at the intermediate temperatures have varied 
interlayer spacings intermediate the range of 5.85 to 9.0 A. The half 
width of the diffraction (001) increases with elevation of the reaction 
temperature, shows maximum at a reaction temperature of about 480.degree. 
C. and then decreases with further elevation of the reaction temperature. 
In the regions intermediate the reaction temperature range of 375.degree. 
C. to 640.degree. C., the formed products consist essentially of C.sub.2 F 
stoichiometry and CF stoichiometry. When the (001) diffraction lines of 
the products obtained by the reactions at temperatures intermediate the 
range of 375.degree. C. to 640.degree. C. are corrected using a Lorentz's 
deviation factor, it becomes apparent that the respective diffraction 
lines consist of the diffraction line of (C.sub.2 F).sub.n having a peak 
at about 10.degree.(2.theta.) and that of (CF).sub.n having a peak at 
13.5.degree.(2.theta.). 
The data of FIGS. 1 to 3 clearly substantiates the formation a novel 
chemical compound poly-dicarbon monofluoride represented by the formula 
(C.sub.2 F).sub.n and having a crystalline structure in which a layer 
structure is stacked with an interlayer spacing of about 9.0 A to form a 
packing structure, said crystalline structure exhibiting a peak at about 
10.degree. in terms of an angle of 2.theta. in the X-ray diffraction 
powder pattern. The specific gravity of (C.sub.2 F).sub.n is about 2.8, 
whereas that of (CF).sub.n is about 2.7. 
A poly-dicarbon monofluoride (C.sub.2 F).sub.n may be prepared by reacting 
a particulate carbon material having Franklin's P-value of about 0 to 
about 0.6 with fluorine at a temperature of 300.degree. to 500.degree. C. 
until complete fluorination of the particulate carbon material is 
accomplished (reference may be made to reissue application of U.S. Pat. 
No. 4,139,474). 
In the fluorination reaction of a particulate carbon material, the reaction 
temperature range of from 300.degree. to 500.degree. C. is most important 
and critical for obtaining polydicarbon monofluoride, namely (C.sub.2 
F).sub.n. When the reaction temperature is lower than 300.degree. C., the 
reaction does not proceed. On the other hand, if the reaction temperature 
is higher than 500.degree. C., formation of (CF).sub.n preferentially 
proceeds, so that the amount of (C.sub.2 F).sub.n formed is small. In 
addition, with a reaction temperature of higher than 500.degree. C., the 
formed product is liable to easily decompose, leading to considerable 
decrease in yield. 
The crystallinity of a particulate carbon material to be employed as a raw 
material also is critical for obtaining (C.sub.2 F).sub.n. The 
crystallinity of a carbon material can be expressed in terms of Franklin's 
P-value. The Franklin's P-value is defined by the formula 
EQU d.sub.(002) =3.440-0.086(1-P.sup.2) 
wherein d.sub.(002) is an interlayer spacing of (002) [R. E. Franklin: 
Proc. Roy. Soc. A 209, 196 (1951)]. For obtaining (C.sub.2 F).sub.n, the 
Franklin's P-value of the carbon material should be in the range of from 0 
to 0.6. The carbon material having a Franklin's P-value of 0 is completely 
crystalline, and the representative example is natural graphite from 
Madagascar ores. When the carbon material having a Franklin's P-value of 
more than 0.6, the formation reaction of (CF).sub.n rapidly proceeds and 
there is formed no (C.sub.2 F).sub.n. As stated above, the natural 
graphite may most preferably be employed for obtaining (C.sub.2 F).sub.n. 
Besides, there may also preferably be employed graphitized carbon 
materials having a Franklin's P-value of 0.6 or less, for example, 
petroleum cokes which have been heat-treated at about 2,000.degree. to 
about 3,000.degree. C., for about 10 to about 120 minutes in a 
graphitizing furnace. In this connection, it is noted that when such 
graphitized carbon materials as heat-treated petroleum cokes are used, the 
products tend to have a relatively much amount of peripheral CF.sub.2 
groups and CF.sub.3 groups since the particle size of petroleum coke is 
relatively small. 
The reaction period of time is not critical. For obtaining (C.sub.2 
F).sub.n to be employed in the present invention, it is essential that the 
reaction of a particulate carbon material with fluorine is conducted until 
complete fluorination of the particulate carbon material is accomplished, 
that is, until further heating of the product in an atmosphere of fluorine 
gas does not cause increase in the fluorine content of the product any 
more. The time required for the complete fluorination of a particulate 
carbon material varies depending on the reaction temperature, 
crystallinity of a carbon material, particle size of a carbon material and 
pressure of a fluorine atmosphere, but, generally, may be 10 minutes to 
150 hours. If fluorination of the particulate carbon material is not 
complete, the products naturally contain unreacted carbon material. In 
this connection, it is noted that in view of the reaction temperatures and 
reaction periods of time employed in U.S. Pat. No. 3,536,532, the products 
(CF.sub.x).sub.n wherein x&lt;1.0 disclosed therein are not stoichiometrical 
but only empirical and contain unreacted carbon material. 
The particle size of a particulate carbon material also is not critical. 
However, if the particle size is too large, extremely long reaction time 
is needed for complete fluorination of the particulate carbon material. 
While, if the particle size is too small, the (CF).sub.n formation 
reaction tends to preferentially proceed, resulting in decrease of the 
(C.sub.2 F).sub.n content of the product. In general, the article size of 
particulate carbon material may preferably be in the range of from 1 to 
1503/4, more preferably in the range of 20 to 100.mu. and most preferably 
in the range of 30 to 80.mu.. 
The pressure of fluorine gas also is not critical. Generally, it can be 
said that although the higher the fluorine pressure, the larger the 
(C.sub.2 F).sub.n content of the product is, a reaction vessel resistible 
to a very high pressure fluorine atmosphere at temperatures employed is 
not available. Usually, as a material for a reaction vessel, nickel or 
such a nickel alloy as Monel metal is most suitably used. For this reason, 
the range of fluorine gas pressure is advantageously 50 mmHg to 1.5 atm. 
The optimum temperature conditions for obtaining (C.sub.2 F).sub.n to be 
employed in the present invention slighly varies according to 
crystallinity of the carbon material to be employed. When the Franklin's 
P-value is 0 to about 0.10, the optimum reaction temperature is 
350.degree. to 500.degree. C. When the Franklin's P-value is about 0.11 to 
0.45, the optimum reaction temperature is 320.degree. to 450.degree. C. 
When the Franklin's P-value is about 0.46 to 0.60, the optimum reaction 
temperature is 300.degree. to 420.degree. C. As aforementioned, the 
reaction time varies depending on the reaction temperature etc. Generally, 
for example, when the reaction temperature is about 350.degree. C., the 
reaction time may preferably be in the range of from 50 to 150 hrs. When 
the reaction is conducted at about 500.degree. C., the reaction time may 
suitably be 10 to 100 minutes. 
In order to selectively obtain a poly-dicarbon monofluoride of the formula 
(C.sub.2 F).sub.n only, the reaction temperature is further limited and 
varies according to the Franklin's P-value of the carbon material to be 
employed. When the Franklin's P-value is 0 to about 0.10, the reaction 
temperature may preferably be 350.degree. to 400.degree. C. When the 
Franklin's P-value is about 0.11 to about 0.45, the reaction temperature 
may preferably be 320.degree. to 360.degree. C. When the Franklin's 
P-value is about 0.46 to about 0.6, the reaction temperature may 
preferably be 300.degree. to 340.degree. C. 
According to the present invention, as the active material of the positive 
electrode, there may also be employed a (C.sub.2 F)-rich polycarbon 
fluoride composition consisting essentially of C.sub.2 F stoichiometry and 
CF stoichiometry, the content of C.sub.2 F stoichiometry being more than 
50 mole %, based on the composition. Previously, we have unexpectedly 
found that the yield of the CF stoichiometry moiety of the (C.sub.2 
F).sub.n -rich polycarbon fluoride composition obtained by the reaction of 
at a temperature of 500.degree. C. or less is also 100% with respect to 
not only the carbon material but also the fluoride. The decomposition of 
the product does not occur at all. 
In the electrolytic cell according to the present invention, as stated 
before, there is employed a positive electrode having as the main active 
material a poly-dicarbon monofluoride represented by the formula (C.sub.2 
F).sub.n. Preparation of such a positive electrode may be prepared as 
follows. For example, the powder of poly-dicarbon monofluoride (C.sub.2 
F).sub.n obtained by reacting natural graphite with fluorine at 
375.degree. C. under a fluorine pressure of 760 mmHg for 120 hours was 
mixed with an electrically conductive agent such as a carbon powder, 
acetylene black or the like and a binder such as a powder of polyethylene 
or a fluoropolymer, e.g., polytetrafluoroethylene, or an expanded graphite 
to prepare an active material mixture for a positive electrode. This 
mixture can be easily molded into a predetermined shape to form a positive 
electrode. The amount of a carbon black or acetylene black as the 
electrically conductive agent may be employed in an amount of about 3 to 
20% by weight, preferably about 8 to 15% by weight based on the active 
material mixture. The amount of the binder may be employed in an amount of 
about 1 to 10% by weight based on the active material mixture. An expanded 
graphite can serve not only as a binder but also as an electrically 
conductive agent, and a suitable amount of an expanded graphite to be used 
for attaining both the functions is about 25 to 75% by weight based on the 
active material mixture. Needless to say, the larger the (C.sub.2 F).sub.n 
content of the active material mixture, the better the electrochemical 
performance of a positive electrode produced from said mixture. However, 
it is possible to use a mixture containing about 25% by weight of (C.sub.2 
F).sub.n for providing a positive electrode which sufficiently performs in 
the intended use of an electrolytic cell of the present invention. In this 
connection, it is to be noted that, since poly-dicarbon monofluoride 
(C.sub.2 F).sub.n is more electrically conductive than polycarbon 
monofluoride (CF).sub.n, the amount of the electrically conductive agent 
incorporated into the mixture may be smaller in the case of use of the 
(C.sub.2 F).sub.n than that in the case of use of the (CF).sub.n, thus 
enabling the (C.sub.2 F).sub.n content of the mixture for a positive 
electrode to be advantageously increased. The positive electrode is 
produced simply by molding the mixture, preferably about a metallic 
reinforcing member comprising a central screen of nickel. Said reinforcing 
member may alternatively be any metal screen or grid, a perforated plate 
or lath plate or fibrous carbon. 
A negative electrode to be used in combination with the above-mentioned 
positive electrode having as the main active material a poly-dicarbon 
monofluoride (C.sub.2 F).sub.n may be made of a light metal or light metal 
alloy, examples of which include alkali metals such as lithium and sodium; 
alkaline earth metals such as magnesium and calcium; aluminum; and alloys 
containing as the main component any of the above-mentioned metals. 
An electrolyte to be used in the electrolytic cell of this invention 
depends on the kind of negative electrode metal and is usually of a 
non-aqueous system. The concentration of an electrolyte is not critical 
and may be chosen so that it gives a high electrical conductivity. As the 
solute of the electrolyte, there may be used various compounds, for 
example, LiClO.sub.4, KPF.sub.6, LiAlCl.sub.4 and the like. As the 
non-aqueous solvent of the electrolyte, there may be used various 
compounds, for example, propylene carbonate, ethylene carbonate, 
dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, dimethyl sulfite, 
1,2-dimethyoxyethane, methyl formate, acetonitrile and the like. 
The electrolytic cell of the present invention comprising a negative 
electrode having as the active material a light metal, an electrolyte and 
a positive electrode having as the main active material a poly-dicarbon 
monofluoride represented by the formula (C.sub.2 F).sub.n is excellent in 
energy density, utilization of active material, flatness of discharge 
voltage and shelf life. 
Further, it is particularly to be noted that the electrolytic cell using 
(C.sub.2 F).sub.n as the active material of the positive electrode 
according to the present invention exhibits a voltage higher than that of 
the electric cell using (CF).sub.n as the active material of the positive 
electrode. The electrolytic cell of this type is advantageously used in 
such devices as needs a higher voltage rather than a higher electric 
power. Such devices include, for example, a watch, a clock, a desk type 
computer, a small type radio and the like which generally operate at a 
current density of only not more than about 0.1 mA/cm.sup.2. The cell of 
the present invention surprisingly provides high discharge voltage in 
spite of the lower fluorine content of the (C.sub.2 F).sub.n than the 
fluorine content of the (CF).sub.n. 
Furthermore, the electrolytic cell of the present invention has an 
advantage that it can be produced at very low cost because, due to the 
production yield thereof surprisingly as high as 100%, a poly-dicarbon 
monofluoride (C.sub.2 F).sub.n is very cheap as compared with the 
conventional polycarbon monofluoride (CF).sub.n whose production yield is 
as low as only a few percent. Thus, the electrolytic cell of the present 
invention can provide a very high industrial value. 
Illustrative features and advantages of the invention will appear from the 
following description of embodiments of the invention, given only by way 
of example. 
An electrolytic cell was produced as follows. 
Propylene carbonate (hereinafter often referred to "PC") to be used for the 
preparation of an electrolytic solution was prepared by subjecting a 
commercially available PC to dehydration and purification by vacuum 
distillation at a temperature below 100.degree. C. under a pressure of 10 
mmHg, and stored in a desiccator where the propylene carbonate was dried 
on a 4 A molecular sieve (a sieve having a sieve size of 4 A and 
manufactured by Du Pont Co., U.S.A.). Lithium perchlorate (LiClO.sub.4) to 
be used as the solute of an electrolytic solution was prepared by a method 
in which a commercially available LiClO.sub.4 was kept over phosphorus 
pentoxide and vacuum-dried for about one week. A solution of 1 M lithium 
perchlorate (LiClO.sub.4) in one liter of propylene carbonate (PC) was 
prepared, and placed in a desiccator where the solution was dried on a 4A 
molecular sieve and stored in a dry box. A poly-dicarbon monofluoride 
(C.sub.2 F).sub.n as the active material was produced by reacting 
particulate natural graphite (200 mesh, Tyler) from Madagascar ore with 
fluorine at 375.degree. C. under a fluorine pressure of 760 mmHg for 144 
hours. 75 times expanded graphite (manufactured by Chuo Kasei K.K., Japan) 
produced by subjecting natural graphite to oxidation with fuming nitric 
acid, washing with water, separation by centrifugation and rapid heating 
at about 1,000.degree. C. was used as a material serving as both an 
electrically conductive agent and a binder for making it easy to analyze 
the performance of the (C.sub.2 F).sub.n active material. The (C.sub.2 
F).sub.n was mixed with the expanded graphite in a weight ratio of 1:1, 
and the mixture was compression-molded under a pressure of about 4,600 
Kg/cm.sup.2 for 1 minute to obtain a pellet of 9 mm and 1 mm in diameter 
and thickness, respectively. Around the (C.sub.2 F).sub.n pellet was wound 
Carboron (trade name of carbon fiber manufactured by Nihon Carbon K.K., 
Japan) in a thickness of about 1 mm. The terminal portion of carbon fiber 
was inserted through a polyethylene tube to give an electrical connection. 
The above-prepared (C.sub.2 F).sub.n electrode element was coated with 
polyethylene using on electric iron, leaving one-side surface thereof 
exposed, thereby to provide a (C.sub.2 F).sub.n positive electrode. 
Lithium pellets cut off from a lithium block were used as the negative 
electrode and the reference electrode. The cell body was made of Polyflon 
(trade mark of a polyfluoroethylene type resin manufactured and sold by 
Daikin Kogyo K.K., Japan). The negative electrode and the positive 
electrode were disposed at a distance of 10 mm therebetween. The (C.sub.2 
F).sub.n positive electrode was securely inserted in a first concaved 
portion on the inner wall of the cell body to hold the same therein. The 
lithium negative electrode (100 mm.times.35 mm) was given electrical 
connection by means of a nickel net and securely inserted in a second 
concaved portion formed opposite to the first concaved portion to hold the 
same therein. The lithium reference electrode was given electrical 
connection by means of a platinum wire. The respective lead fiber and wire 
were insulated with polyethylene as mentioned above. 
For comparison, another electrolytic cell was produced by using (CF).sub.n 
as the active material in the same manner as described above, except that 
(CF).sub.n was employed in place of (C.sub.2 F).sub.n. The (CF).sub.n 
active material was produced by reacting natural graphite (200 mesh, 
Tyler) from Madagascar ore with fluorine at 600.degree. C. under a 
fluorine pressure of 100 mmHg for 8 hours. 
Potentiostatic and Galvanostatic polarizations were recorded on a recorder 
Model 3056 (manufactured and sold by Yokogawa Denki K.K., Japan) by using 
a potentiostat Model NP-G1000E (manufactured and sold by Nichia Keiki 
K.K., Japan). In measuring voltage, an OP amplifier (operational 
amplifier) of having an internal impedance of 10.sup.14 .OMEGA. was used 
for enabling the iR drop to be neglected. Potential scanning was carried 
out at a scanning rate of 120 sec/volt by using an automatic potential 
scanning apparatus Model PTC-5A (manufactured and sold by Hokuto Denko 
K.K., Japan) which was connected to a potentiostat, to record a 
potential-current relationship on an X-Y recorder Model F-3E (manufactured 
and sold by Riken Denshi K.K., Japan). All the measurements were carried 
out by keeping the electrolytic cell system in a dry box filled with a 
30.degree. C. argon gas. 
1. Open Circuit Voltage 
Referring to FIG. 4, there is shown a graph showing the respective 
relationships, with respect to (CF).sub.n and (C.sub.2 F).sub.n 
electrodes, between open circuit voltage and discharge percent. 
Measurements were done using electrolytic cells respectively having 
(CF).sub.n and (C.sub.2 F).sub.n electrodes in 1 M LiClO.sub.4 -PC at 
30.degree. C. In the graph, the data of (CF).sub.n and (C.sub.2 F).sub.n 
electrodes are shown by open circles and filled circles, respectively. 
With respect to the (CF).sub.n positive electrode, the average initial 
open circuit voltage was 3.20 volts. With respect to the (C.sub.2 F).sub.n 
positive electrode, the initial open circuit voltage was 3.22 volts. With 
respect to the (CF).sub.n positive electrode, the discharge was carried 
out at a constant-current of 2 milliamperes, while, with respect to the 
(C.sub.2 F).sub.n positive electrode, the discharge was carried out at a 
constant-current of 1 milliampere. Dey et al. reported in J. Electrochem. 
Soc., 117, 222 (1970) that the electrochemical reduction, on a graphite 
electrode, of propylene carbonate in a 1 M lithium perchlorate-propylene 
carbonate system into propylene and carbonate ions starts to occur at 
below 1 volt vs. Li and proceeds stably at about 0.6 volt, and therefore 
the discharge, in this experiment, was regarded as being completed when 
the discharge voltage reached 1 volt vs. Li. The respective open circuit 
voltages were values measured every 2 hours after termination of the 
polarization. With respect to the (CF).sub.n positive electrode and the 
(C.sub.2 F).sub.n positive electrode, the respective open circuit voltages 
decreased rapidly by the initial discharge and, thereafter, became 
substantially constant at certain values, which were around 2.8 volts vs. 
Li for the (CF).sub.n positive electrode and around 3 volts vs. Li for the 
(C.sub.2 F).sub.n positive electrode. The open circuit voltage after 
completion of the discharge was 2.4 volts vs. Li for both of the 
(CF).sub.n positive electrode and the (C.sub.2 F).sub.n positive 
electrode. 
2. Potential Scanning Curve 
Referring to FIG. 5, there is shown potential scanning curves respectively 
with respect to (CF).sub.n and (C.sub.2 F).sub.n electrodes in 1 M 
LiClO.sub.4 -PC. The potential scanning was conducted at a rate of 120 
sec/volt. In the graph, the data of (CF).sub.n and (C.sub.2 F).sub.n 
electrodes are shown by circles and triangles, respectively. The electrode 
reaction of fluorinated graphite was different in behavior between the low 
current region and the high current region. A marked difference in 
behavior was observed between both sides of about 2.2 volts vs. Li 
(overvoltage: about 1.2 volts) as the boundary for the (CF).sub.n positive 
electrode and between both sides of about 2.5 volts vs. Li (overvoltage: 
about 0.9 volts) as the boundary for the (C.sub.2 F).sub.n positive 
electrode. The current was substantially constant in the low current 
region because the discharge products produced by the diffusion of 
Li.sup.+ ions into the positive electrode forms a resistant layer. The 
overvoltage increased in the high current region because the Li.sup.+ ions 
moved across the resistant layer. The (C.sub.2 F).sub.n positive electrode 
gave a low overvoltage as compared with the (CF).sub.n positive electrode. 
Particularly in the high current region, with the (C.sub.2 F).sub.n 
positive electrode, the current was observed to be 1.5 times as high as 
that with the (CF).sub.n positive electrode. 
3. Potential-Time Characteristics 
Referring to FIGS. 6 and 7, there are shown galvanostatic discharge curves 
of a (CF).sub.n electrode at varied current densities and galvanostatic 
discharge curves of a (C.sub.2 F).sub.n electrode at varied current 
densities, respectively. In FIG. 6, the curves A, B and C were obtained by 
the discharges at 1 milliampere (1.57 mA/cm.sup.2), 2 milliamperes (3.14 
mA/cm.sup.2) and 4 milliamperes (6.29 mA/cm.sup.2), respectively. In FIG. 
7, the curves A, B and C were obtained by the discharges at 0.5 
milliampere (0.78 mA/cm.sup.2), 1 milliampere (1.57 mA/cm.sup.2) and 2 
milliamperes (3.14 mA/cm.sup.2), respectively. Measurements were done 
using electric cells having the respective (CF).sub.n and (C.sub.2 
F).sub.n electrodes in 1 M LiClO.sub.4 -PC at 30.degree. C. 
With respect to the (CF).sub.n positive electrode, the discharge voltage 
became substantially constant at about 2 volts vs. Li. As can be seen in 
FIG. 6, however, the increase in current density led to the large decrease 
in capacity. This is believed to be attributed to the lagging diffusion of 
Li.sup.+ ions into the interlayer spacings of the (CF).sub.n because of 
the increase in resistance caused by the discharge products produced in 
the course of discharge. This is so because the voltage stayed 
substantially constant at about 1.5 volts after the voltage drop from 2 
volts and, thereafter, decreased gradually as the discharge was further 
continued. 
As can be seen in FIG. 7, the (C.sub.2 F).sub.n positive electrode gave a 
behavior somewhat similar to that given by the (CF).sub.n positive 
electrode. However, the discharge voltage with the (C.sub.2 F).sub.n 
positive electrode stayed substantially constant at a higher level than 
the level given by the (CF).sub.n positive electrode when the polarization 
of the (C.sub.2 F).sub.n positive electrode proceeded to substantially the 
same extent as that of the (CF).sub.n positive electrode polarization. For 
example, in the case of the constant-current discharge at 1 milliampere, 
the (C.sub.2 F).sub.n positive electrode gave a discharge voltage of 2.4 
volts vs. Li which was higher than that given by the (CF).sub.n positive 
electrode, and gave an overvoltage about 0.4 volt lower than that given by 
the (CF).sub.n positive electrode. 
In some experiments or embodiments as given above, the different discharge 
conditions were employed between (CF).sub.n and (C.sub.2 F).sub.n in view 
of the fluorine content of (C.sub.2 F).sub.n which is a half, in mole, 
that of (CF).sub.n. However, as will be well understood from the results 
shown in FIGS. 4 to 7, the actual use conditions in which the discharge 
current is only less than 0.1 mA, sometimes only 0.01-0.03 mA, importance 
of voltage rather than electric power, etc., it is apparent that an 
electrolytic cell using (C.sub.2 F).sub.n as the active material has 
superior in many points to the conventional electrolytic cell using 
(CF).sub.n as the active material. Further, it is noted that, due to a 
relatively high electric conductivity and a lost cost of material, the 
(C.sub.2 F).sub.n content of the positive electrode can be easily 
increased so that the desired level of performance of electrolytic cell 
may be obtained with respect to capacity also.