JPH0343749B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aqueous primary battery using modified fluorinated graphite as a positive electrode active material of the aqueous battery.
More specifically, the present invention provides a modified graphite fluoride (hereinafter often referred to as "GF") with improved battery characteristics obtained by irradiating electromagnetic waves to partially decompose the graphite fluoride. The present invention relates to an aqueous solution battery using modified graphite fluoride (hereinafter often referred to as "modified GF"). GF is a solid powder with unique lubricity, water and oil repellency, and excellent chemical resistance.
It is used as a solid lubricant, wet-proofing agent, antifouling agent, water and oil repellent, etc. On the other hand, it is well known that it is also useful as a battery active material and provides a primary battery with high energy density and good storage stability. As described above, GF is highly evaluated industrially in a wide range of fields, and is a compound that can be expected to be applied and developed in many more fields in the future. One of the GFs is polymonocarbon monofluoride represented by (CF) _o , which is well known to be useful as a battery active material as mentioned above (Japanese Patent Publication No. 48-25565). (see book).
(CF) _o is produced by reacting an amorphous carbon material such as petroleum coke with fluorine at about 200°C to about 450°C, or reacting a crystalline carbon material such as natural or artificial graphite with fluorine. It is obtained by reacting at about 500°C to about 630°C. Yet another GF is polydicarbon monofluoride, represented by (C ₂ F) _o , discovered by Watanabe et al. (C ₂ F) _o can be obtained in relatively high yield and at low cost. _This (C ₂ F)
As detailed in Re30667, graphite material is heated to 300 mmHg under a fluorine pressure of 100 to 760 mmHg.
Obtained by heating at ~500°C.
The graphite material used in the production of (C ₂ F) _o is
Natural graphite, artificial graphite, hardwood graphite, pyrolytic graphite or mixtures thereof can be used. (C ₂ F) _o , which has a crystal structure, has a laminated structure in which layers forming a lattice structure are stacked with an interlayer distance of approximately 90 Å, and the distance between the layers is approximately 6 Å.
It has an interlayer distance of (CF) which is different from the crystal structure of _o . Also, while each carbon in each layer is bonded to one fluorine atom in the case of (CF) _o ,
In the case of (C ₂ F) _o , every other carbon in each layer is bonded to one fluorine. But (CF) _o and (C ₂ F) _o
Both of these compounds have CF ₂ and CF ₃ groups as peripheral groups at the ends of the carbon hexagonal network layer of the compound.
Therefore, if graphite is completely fluorinated, (CF) _o
The F/C ratio of (C ₂ F) _o is 0.5 or more and 1.0 or more, respectively. The amount of excess fluorine attributable to surrounding CF ₂ and CF ₃ groups increases as the size of the crystal in the a- and b-axis directions of the GF crystal becomes smaller [Journal of American Chemical Society,
101 Volume 1, 3832 pages 1979 {J.Amer.Chem.Soc.,
101, 3832 (1979)}. As can be seen from the above, depending on the reaction conditions and the crystallinity or type of carbon material, (CF+) _o , (C ₂ F) _o or a mixture thereof can be obtained. Moreover, unreacted carbon material can also be left in these GFs. As is clear from the above, the composition of GF produced by fluorination of a carbon material depends on the reaction temperature and the type or crystallinity of the carbon material. (CF) _o is about amorphous carbon material such as petroleum coke and fluorine.
(CF) _o rich compositions obtained by reacting at 200°C to about 450°C and consisting of (CF) _o or (CF) _o and (C ₂ F) _o are crystalline carbons such as natural and artificial graphite. The material is approx.
The product is then reacted at 500°C to about 630°C. Performing the fluorination reaction at 630°C or lower means that the decomposition of (CF) _o is 630°C or lower.
This is because corrosion is accelerated when the temperature exceeds .degree. C., and there is no material for the reaction vessel that can withstand corrosion by fluorine even at such high temperatures. (CF) _o Compounds can be obtained with various degrees of crystallinity, but those with high crystallinity are fixed white. On the other hand, (C ₂ F) _o or a mixture of (C ₂ F _{) o} rich consisting of (C ₂ F) _o and (CF) o is a mixture of crystalline carbon materials such as natural and artificial graphite and about fluorine. It is obtained by reacting at 300°C to about 500°C. The color of (C ₂ F) _o is black under its formed conditions, but heat treatment up to 600°C changes the color from black to gray to white, and the degree of crystallinity also increases. When natural graphite is used as a starting material, if the fluorination reaction is carried out at a temperature exceeding about 500℃, the produced GF will be (CF) _o rich, whereas if the fluorination reaction is carried out at a temperature of up to about 500℃, the produced GF will be (CF) o rich. GF is (C ₂ F)
_o Become rich. That is, the higher the reaction temperature, the more the (CF) _o content of the product increases, and the lower the reaction temperature, the more the (C ₂ F) _o content of the product. The same is true when artificial graphite is used as a starting material. However, when artificial graphite is used, the boundary temperature at which it becomes (CF) _o rich or (C ₂ F) _o rich is not about 500℃ but about
The temperature is 470℃. The reaction time is not critical; if the carbon material is to be completely fluorinated, the fluorination reaction may be continued until no increase in the weight of the produced GF is observed. As mentioned above, solid powder GF is known to be represented by (CF) _o or (C ₂ F) _o .
In some reports, it is written as (CF _x ) _o . Also
As mentioned above, GF is useful in a wide range of fields, but the low surface energy characteristic of GF may be a disadvantage in some fields, as it may have too strong water and oil repellency. For example, when GF is used as a battery active material, it is generally necessary to add a binder or a conductive agent because GF itself does not have moldability or conductivity. Because it has poor solubility and GF itself is an insulator, a relatively large amount of binder and conductive agent must be added. The present inventors modified GF into a dispersion medium in order to reduce its water and oil repellency and make it conductive.
A part of GF, by dispersing it and irradiating it with electromagnetic waves,
For example, when we attempted to disperse the surface, we found that in addition to the expected effect of reducing water and oil repellency, GF treated in this way was found to be more effective in aqueous battery cells than untreated GF. They found that the characteristics were significantly improved and completed the present invention. In general, the characteristics required for batteries are:
Large discharge capacity, high discharge potential,
One example is that the flatness of the discharge potential is good. It has been found that in the aqueous primary battery using the modified fluorinated graphite of the present invention, an increase in discharge capacity and an improvement in discharge potential can be achieved in particular. Therefore, an object of the present invention is to provide a modified fluorinated graphite having suitable battery characteristics as a positive electrode active material for an aqueous battery. The above and other purposes, features and benefits are:
It will become clearer from the following detailed description with reference to the accompanying drawings. According to the present invention, in a primary battery consisting of a zinc negative electrode, a positive electrode made of graphite fluoride, and an electrolyte made of an alkaline aqueous solution, graphite fluoride is irradiated with electromagnetic waves to partially decompose the graphite fluoride. An aqueous solution primary battery using modified fluorinated graphite is provided, which is characterized in that modified fluorinated graphite is used as the positive electrode. The modified graphite fluoride of the present invention is obtained by dispersing GF in a dispersion medium by means of stirring or the like, and irradiating this with electromagnetic waves to disperse a portion of the graphite fluoride. The graphite fluoride (GF) referred to in the present invention applies to all the graphite fluorides that are generally called graphite fluoride, such as (CF) _o and (C ₂ F) _o mentioned above, and includes (CF) _o or ( C ₂ F) _o may be used alone or in a mixture thereof, or may further contain unreacted carbon material. There is no limit to the particle size of the GF used in the present invention, but 0.01μ to 100μ is generally used. The modified graphite fluoride of the present invention is preferably obtained by decomposing graphite fluoride by electromagnetic wave irradiation at a decomposition rate (described later) in the range of 0.01 to 50%. Decomposition rate is 0.01
If it is less than 50%, the effect of the present invention will be small, and if it exceeds 50%, it will take time to decompose the graphite fluoride, which is not efficient, and the battery characteristics will deteriorate, which is not preferable. A more preferable range of the decomposition rate of the modified graphite fluoride of the present invention is 0.1 to 10%. The electromagnetic waves used in the present invention may be of any wavelength as long as they are in the wavelength range generally called electromagnetic waves (approximately 10 ^-17 to ^{10 5} m), but from the viewpoint of effectiveness in decomposing GF, wavelengths shorter than 10 ^-4 cm are preferred. It is preferable that
In addition, from the viewpoint of adverse effects on the human body, electromagnetic waves with wavelengths longer than 10 ^-7 cm are preferable. In other words, as an electromagnetic wave
Visible light, ultraviolet rays, X-rays, etc. within the range of 10 ^-4 to ^{10 -7} cm are preferably used. The intensity and irradiation time of the electromagnetic waves are not critical, and may be any intensity and irradiation time that can provide the above-mentioned decomposition rate. Generally, the stronger the intensity of electromagnetic waves, the shorter the irradiation time, so the intensity of the electromagnetic waves and the irradiation time can be changed as necessary. The dispersion medium for dispersing GF may be any liquid as long as it can wet the GF, such as organic solvents such as ethanol and acetone, water added with a surfactant, and the like. or,
In order to accelerate the decomposition rate of GF, an alkaline aqueous solution in which an alkali such as potassium hydroxide or sodium hydroxide is dissolved in water can be used. The concentration of this alkaline aqueous solution is generally
It is 0.1wt% to 30wt%. For example, an alkaline gas such as ammonia gas can also be used as a dispersion medium for dispersing GF. When GF is dispersed in a dispersion medium and irradiated with electromagnetic waves, decomposition occurs first at the surface of GF, but if irradiation continues, the decomposition progresses to the inside of GF.
It can be efficiently decomposed up to a decomposition rate of about 50%. When the battery active material made of modified graphite fluoride of the present invention is used as a positive electrode active material of an aqueous solution battery, zinc metal or zinc alloy such as a zinc plate or a zinc sheet is used for the negative electrode. Zinc powder, gelled zinc, etc. can also be used. The electrolyte used in the battery of the present invention is any aqueous alkaline solution consisting of an aqueous solution of potassium hydroxide, sodium hydroxide and lithium hydroxide and mixtures thereof, the concentration of which is usually in the range of 5 to 15 molar. is used. A battery constructed using a battery active material made of modified graphite fluoride of the present invention as a positive electrode, a negative electrode and an aqueous electrolyte as described above has a discharge potential, a discharge capacity, a fluorine utilization rate in GF ( (described later) have a higher specific resistance than GF before being decomposed by irradiating electromagnetic waves, and the modified graphite fluoride of the present invention has a lower specific resistance than GF before being decomposed by irradiating electromagnetic waves.
Since the compatibility with the resin is improved, it is possible to provide a highly advantageous battery with high energy density, which has the advantage that less conductive agent and binder are required when used as a battery active material. In this way, the modified graphite fluoride of the present invention is
Through simple processing, it exhibits better battery characteristics than the already known GF, and it also makes it possible to develop new applications, which has great industrial significance. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the scope of the present invention is not limited to the Examples. The fluorine content in the raw GF and modified GF in the examples was determined by the following method. 100 mg of GF was accurately weighed in a platinum crucible and mixed uniformly with a fluxing agent (25 g each of calcium carbonate and sodium carbonate). This homogeneous mixture of GF and flux is
After melting at °C, the resulting melt was dissolved in a predetermined amount of water to form an aqueous solution. A certain amount of this aqueous solution was taken, the pH was adjusted to 3.4, and the fluorine content was determined by titration with a standard thorium nitrate solution using Alizarin Red S as an indicator. At this time, an automatic photometric titration device was used for the titration. The decomposition rate of GF by electromagnetic wave irradiation was determined by the following formula, where x ₁ is the fluorine content of GF before electromagnetic wave irradiation, and x ₂ is the fluorine content of GF after electromagnetic wave irradiation. GF decomposition rate (%) = x ₁ − x ₂ / x ₁ × 100 Example 1 As an electromagnetic wave irradiation device, a 400W high-pressure mercury lamp (irradiation wavelength: 3126 to 3132 Å, 3650 to 3663 Å,
A UVL-400HA photochemical reaction device manufactured by Riko Kagaku Sangyo Co., Ltd. equipped with 4047-4058 Å, 5461 Å, and 5770-591 Å) was used. In the above photochemical reaction device, 1 liter of cyclohexane was added as a dispersion medium, _{and GF} containing (CF) as the main component (fluorine content, 62.69wt%, F/C ratio
1.06, average particle size 14μ) was added, and the mixture was irradiated with light from the high-pressure mercury lamp for 3 hours while stirring and cooling with water. After irradiation with light, GF was overseparated and dried to obtain modified GF. The fluorine content of the modified GF was measured and was 62.23wt%, and the decomposition rate of GF was 0.73.
% and F/C ratio was 10.4. The discharge characteristics when the obtained modified GF was used in a battery were measured by the following method. 20 mg of the modified GF obtained above was mixed with 20 mg of expanded graphite manufactured by Toyo Tanso Co., Ltd. as a conductive agent and a binder.
The mixture was compressed for 1 minute at a pressure of about 8,800 kg/cm ² and formed into a pellet with a diameter of 10 mm, which was used as a positive electrode. The negative electrode was cut out from a zinc plate10
A mm x 50 mm plate washed with dilute nitric acid and acetone was used. 30% KOH saturated with ZnO as electrolyte
An aqueous solution was used. These battery components were placed in a Teflon container, and all experiments were conducted in a constant temperature bath at 30°C. In addition, experiments were conducted with a distance between electrodes of 10 mm. The discharge characteristics of this battery (sample No. A) under a constant resistance load of 1 kΩ are shown in curve A in Fig. 1. or,
OCV (open circuit voltage), measured discharge capacity (mA・hr) and GF when discharging the electrode at a final voltage of 0.6V
Table 1 shows the fluorine utilization rate (%). At this time, the fluorine utilization rate was determined according to the following formula. Fluorine utilization rate (%) in GF = measured discharge capacity (mA・hr
)/Theoretical discharge capacity (mA・hr)×100=yt/96500×X/
19×100 However, X is the amount of fluorine contained in the positive electrode (g),
y indicates the current (milliampere) that flows when the electrode is discharged, and t indicates the discharge time (hours). Comparative Example 1 A battery (sample no.
B) Discharge characteristics and discharge capacity (m
A.hr) and fluorine utilization rate (%) were measured. The obtained discharge characteristics are shown in curve B of FIG. or,
OCV (open circuit voltage), discharge capacity (mA・hr), and fluorine utilization rate (%) are shown in Table 1. As is clear from Figure 1 and Table 1, when the modified GF obtained in Example 1 was used (Sample No.
A), OCV, discharge potential, and fluorine utilization rate were all improved compared to the GF before modification in Comparative Example 1 (Sample No. B). Furthermore, as is clear from Table 1,
Compared to the unmodified GF of Comparative Example 1 (sample No. B), the modified GF obtained in Example 1 (sample No. A) has a high fluorine content even though it has a reduced fluorine content. It shows the discharge capacity. Example 2 Example 1 except that the electromagnetic wave irradiation time was 24 hours.
Modified GF was obtained in the same manner. Obtained modified GF
When the fluorine content was measured, it was 61.12 wt%, the GF decomposition rate was 2.5%, and the F/C ratio was 0.99. When the modified GF obtained above was used in a battery (sample No. C), the discharge characteristics were measured in the same manner as in Example 1. The obtained discharge characteristics are shown in curve C in FIG. Further, Table 1 shows the measured discharge capacity (mA·hr) and fluorine utilization rate (%) when the electrode was discharged with OCV and final voltage of 0.6V. As is clear from Figure 1 and Table 1, when the modified GF obtained in Example 2 was used (Sample No.
C), OCV, discharge potential, and fluorine utilization rate were all improved compared to the GF before modification in Comparative Example 1 (Sample No. B). Furthermore, as is clear from Table 1, the modified GF obtained in Example 2 (Sample No. C) has a lower fluorine content than the unmodified GF of Comparative Example 1 (Sample No. B). Despite the decrease, it showed a high discharge capacity. Example 3 Using 120 ml of water and 80 ml of ethanol as a dispersion medium, 10 g of GF used in Example 1 as a raw material was placed in the photochemical reaction device described in Example 1, and irradiated with a light source of a mercury lamp for 3 hours while stirring and cooling with water. . After irradiation, the GF was over-separated and dried to obtain modified GF. modification
When the fluorine content of GF was measured, it was 60.61 wt%, the decomposition rate of GF was 3.32%, and the F/C ratio was 0.97. A battery (sample No. D) was prepared in the same manner as in Example 1.
Discharge characteristics and discharge capacity (mA・
hr) and fluorine utilization rate (%) were measured. The obtained discharge characteristics are shown in curve D in FIG. Also, OCV
Table 1 shows the potential, discharge capacity (mA.hr), and fluorine utilization rate (%). As is clear from Figure 1 and Table 1, when the modified GF obtained in Example 3 was used (Sample No.
D), OCV, discharge potential, and fluorine utilization rate were all improved compared to the GF before modification in Comparative Example 1 (Sample No. B). Furthermore, as is clear from Table 1,
Compared to the unimproved GF of Comparative Example 1 (Sample No. B), the modified GF obtained in Example 3 (Sample No. D) had a high discharge despite the reduced fluorine content. Indicated capacity. Example 4 GF containing (C ₂ F) _as the main component (fluorine content 51.55 wt%, F/C ratio 0.67, average particle diameter
20μ) was used. Further, as a dispersion medium, a solution in which 5 wt % of caustic potassium was added to a 50 vol % ethanol aqueous solution was used. One liter of the above dispersion medium was placed in a glass flask, and 100 g of raw material GF was dispersed therein. This dispersion was stirred and exposed to sunlight through the flask for 3 hours outdoors on a sunny day. After irradiation with sunlight, GF was overseparated and dried to obtain modified GF. When the fluorine content of the obtained modified GF was measured, it was 51.33wt%, and the decomposition rate of GF was 0.43%.
The F/C ratio was 0.67. The discharge characteristics when the modified GF obtained above was used for electricity (sample No. E) were measured in the same manner as in Example 1. The obtained discharge characteristics are shown as curve E in Figure 2.
Shown below. Further, Table 1 shows the measured discharge capacity (mA·hr) and fluorine utilization rate (%) when the electrode was discharged with OCV and final voltage of 0.6V. Comparative Example 2 The raw material GF of Example 4 was used as a battery (sample) in the same manner as Example 1 without electromagnetic treatment.
The discharge characteristics and discharge capacity when used in No.F) were measured. The obtained discharge characteristics are shown in curve F in FIG. In addition, OCV, discharge capacity, and fluorine utilization rate (%) are shown in Table 1. As is clear from FIG. 2 and Table 1, when the modified GF obtained in Example 4 (sample No. E) was used, the OCV, discharge potential, and fluorine utilization rate (%) were also It was improved compared to the case where GF before modification (sample No. F) was used. Furthermore, as is clear from Table 1, compared to the unimproved GF of Comparative Example 2 (Sample No. F), the modified GF obtained in Example 4
(Sample No. E) had a high electrostatic capacity despite the reduced fluorine content. Example 5 Using 120 ml of water and 80 ml of ethanol as a dispersion medium, 10 g of the GF used in Example 1 as a raw material was placed in the photochemical reaction device described in Example 1, and the light source of the mercury lamp was turned on for 3 hours while stirring and cooling with water. Irradiated. After irradiation, GF is over-separated and then dried and modified.
Got GF. When the fluorine content of the modified GF was measured, it was 50.49wt%, and the decomposition rate of GF was 2.6%.
The F/C ratio was 0.64. A battery (sample No. G) was prepared in the same manner as in Example 1.
Discharge potential and discharge capacity (mA・
hr) and fluorine utilization rate (%) were measured. The obtained discharge characteristics are shown in curve G in FIG. Also, OCV
Table 1 shows the measured discharge capacity (mA·hr) and fluorine utilization rate (%) when the electrode was discharged at a potential and final voltage of 0.6V. [Table] As is clear from Figure 2 and Table 1, when the modified GF obtained in Example 5 (sample No. G) was used, both the discharge potential and the fluorine utilization rate (%) of Comparative Example 2
It was improved compared to the case where GF (sample No. F) before modification was used. Furthermore, as is clear from Table 1, the GF before modification of Comparative Example 2 (Sample No.
Compared to Sample No. F), the modified GF obtained in Example 5 (Sample No. G) exhibited a high discharge capacity despite the reduced fluorine content.

[Brief explanation of drawings]

FIGS. 1 and 2 show the relationship between discharge potential and discharge time for an aqueous solution battery using the modified graphite fluoride of the present invention and an aqueous solution battery using untreated graphite fluoride. A...Example 1 [modified (CF) _o ], B...Comparative example 1 [untreated (CF) _o ], C...Example 2 [modified (CF)]
_o ], D...Example 3 [Modified (CF) _o ], E...Example 4 [Modified (C ₂ F) _o ], F...Comparative Example 2 [Untreated (C ₂ F) _o] ], G...Example 5 [Reformed (C ₂ F) _o ].

Claims (1)

[Claims] 1. In a primary battery consisting of a zinc negative electrode, a positive electrode made of graphite fluoride, and an electrolyte made of aqueous alkaline solution, the graphite fluoride is dispersed in a dispersion medium, irradiated with electromagnetic waves, and one part of the graphite fluoride is dispersed in a dispersion medium. 1. An aqueous solution-based primary battery characterized by being made of modified fluorinated graphite obtained by decomposing carbon into carbon and fluorine.