JP4200326B2 - Non-aqueous electrolyte primary battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte battery, and more particularly to a non-aqueous electrolyte primary battery using graphite fluoride as a positive electrode active material.

  Non-aqueous electrolyte lithium primary batteries have high energy density, excellent storability, leakage resistance, and other reliability, and can be reduced in size and weight. As a memory backup power source, the demand is increasing year by year.

  In recent years, an increasing number of applications include in-vehicle applications. In particular, the use as a power source of a sensor for measuring the pressure inside the tire has recently attracted attention. In such applications, the lower limit of the operating temperature range is −40 ° C. and the upper limit is 100 ° C. or more, which is a very severe condition for the battery. Representative lithium primary batteries include a CR system using manganese dioxide as a positive electrode active material and a BR system using fluorinated graphite as a positive electrode active material. In general, the CR system has excellent load characteristics at low temperatures, but the resistance to high temperatures is low. When the temperature rises above 60 ° C, the electrolyte decomposes due to the catalytic action of manganese dioxide in the presence of a small amount of moisture in the battery. As a result, the internal resistance increases due to a decrease in tightness of the battery due to the swelling of the battery. The other BR system is low in reactivity between power generation materials such as fluorinated graphite and electrolyte even at a high temperature of 100 ° C. or higher, so that the characteristic deterioration is small and the high temperature resistance is excellent. Therefore, in the case where high reliability at 100 ° C. or higher is required for the above-mentioned applications, the BR system is predominant.

Since fluorinated graphite as a positive electrode active material of a BR-based battery is excellent in fluorinated graphite (CFx) n with x = 1 in terms of flatness of discharge voltage and energy density as described in Patent Document 1, Originally considered the most desirable. Actually, an appropriate value close to 1 is considered good in consideration of manufacturing conditions and cost. Therefore, graphite fluoride currently used as an active material of the battery satisfies 0.95 ≦ x ≦ 1.05, and is a battery having a high capacity and excellent high-temperature resistance.
Japanese Patent Publication No. 48-25565

  However, fluorinated graphite as described above has the disadvantage that the low-temperature load characteristic is particularly low because the bond between fluorine and carbon is stable and the reactivity is low. This low-temperature load characteristic is not a problem for weak currents such as memory backups because the voltage drop is small, but the main current application equipment that emits radio waves uses a large current, so the voltage drop is large. Thus, there is a problem that the device cannot be used.

The present invention solves such a conventional problem, and an object of the present invention is to provide a non-aqueous electrolyte primary battery excellent in load characteristics at a low temperature.

The non-aqueous electrolyte primary battery of the present invention uses fluorinated graphite as a positive electrode active material, and the fluorinated graphite is composed of fluorinated carbon and non-fluorinated carbon (CFx) n (0.30 ≦ x ≦ 0.90).

When a fluorine gas and a carbon material such as graphite or coke are reacted under predetermined conditions, fluorination occurs from the surface of the graphite, so that the surface is fluorinated, and the inside has left unreacted carbon x
Can produce (CFx) n of 1 or less (this fluorinated graphite is hereinafter referred to as low-fluorinated fluorinated graphite). The low fluorinated fluorinated graphite has a fluorinated portion and an unreacted portion as described above, and a portion between them has a low binding energy between fluorine and carbon in a transition state. Therefore, since the potential of the fluorinated graphite is higher than that of the fully fluorinated graphite, the discharge voltage is also improved. However, when the value of x is larger than 0.90, the portion with low binding energy is reduced, so that the discharge voltage cannot be improved. On the other hand, when the value of x is smaller than 0.30, the internal resistance increases, so that the voltage drop at the beginning of discharge increases. This is presumably because the transition state portion having a low binding energy exists at a position close to the surface. In the transition state portion, there is also fluorine eluted in the electrolytic solution, which is eluted in the electrolytic solution and reacts with the negative electrode lithium to form a resistance film, which seems to be a cause of an increase in internal resistance. This low fluorinated fluorinated graphite is characterized by being fluorinated from the surface to the inside. Even if the value of x is low, the surface is covered with a fluorinated graphite layer, so unstable fluorine is eluted. Although it is difficult, a large amount of elution is observed when x is 0.3 or less, which seems to affect the internal resistance.

  By using fluorinated graphite represented by (CFx) n (0.30 ≦ x ≦ 0.90) composed of fluorinated carbon and unfluorinated carbon in this way as a positive electrode active material, load characteristics at low temperature Can be improved.

In the present invention, as described above, the fluorinated graphite, which is the positive electrode active material of the non-aqueous electrolyte primary battery, comprises (CFx) n (0.30 ≦ x ≦ 0.90) composed of fluorinated carbon and non-fluorinated carbon. It has been found that an improvement in load characteristics at a low temperature can be obtained with the fluorinated graphite represented by (2).

  Further, in the preparation of fluorinated graphite, a more uniform fluorinated graphite (a uniform interface between the unfluorinated phase and the fluorinated phase) can be produced by heat treatment at a low temperature for a long time.

  Furthermore, the present invention is a method for producing a non-aqueous electrolyte battery comprising a negative electrode having a light metal as an active material and a positive electrode having a fluorinated graphite as an active material, comprising petroleum coke and fluorine at 300 ° C. to 400 ° C., 6 A step of obtaining a fluorinated graphite represented by (CFx) n (0.30 ≦ x ≦ 0.90) in which unfluorinated carbon is covered with fluorinated carbon by reacting under a condition of ˜12 hours; And a step of obtaining a positive electrode by kneading and drying the fluorinated graphite, a conductive agent and a binder.

  An embodiment of the present invention will be described with reference to the drawings, taking a flat lithium primary battery as an example.

  Here, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to the following Example.

(Example 1)
FIG. 1 is a cross-sectional view of a nonaqueous electrolyte battery according to an embodiment of the present invention after sealing a flat fluorinated graphite lithium battery BR2450. In FIG. 1, a battery case 1 is a metal cup also serving as a positive electrode terminal, a positive electrode pellet 2 is a pellet obtained by pressure-molding a mixed powder of graphite fluoride, a conductive agent, and a binder, a separator 3 is a non-woven fabric of polybutylene terephthalate, The negative electrode 4 is made of metallic lithium, the sealing plate 5 is made of a metal substantially serving as a negative electrode, and the insulating gasket 6 has a substantially L-shaped cross section.

The positive electrode is kneaded, dried, and pulverized in a mass ratio of 84: 8: 8 with graphite fluoride as a positive electrode active material, acetylene black as a conductive agent, and polytetrafluoroethylene as a binder, and this powder is pressed. Then, it was formed into a disk shape having a diameter of 16 mm and a thickness of 3 mm, and was prepared by removing moisture by high-temperature drying at 150 ° C. for 5 hours. The fluorinated graphite used was (CF _0.90 ) n prepared by reacting petroleum coke having an average particle diameter of about 20 μm with fluorine gas at 340 ° C. for 12 hours. When the cross section of this fluorinated graphite was confirmed by X-ray, the presence of non-fluorinated carbon could be confirmed in the vicinity of the central portion.

The negative electrode was made by punching a 1.3 mm lithium foil into a disk shape having a diameter of 18 mm, pressurizing the inner surface of the sealing plate so as to be concentric with each other, and press-bonding them.
The electrolytic solution used was a solution of 1 mol of LiBF ₄ as a solute in γ-butyrolactone as a solvent.

  Then, each of these component materials was constituted, and finally, a gasket was caulked so as to be compressed with a sealing plate and a case to produce a non-aqueous electrolyte battery. The battery dimensions are 24.5 mm in diameter and 5.0 mm in thickness.

(Example 2)
In Example 2, a non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that (CF _0.50 ) n produced with a reaction time of petroleum coke and fluorine of 8 hours was used as the positive electrode active material. Was designated as battery 2. In this case, the presence of unfluorinated carbon was also confirmed in the vicinity of the central portion of the fluorinated graphite.

(Example 3)
In Example 3, a lithium primary battery was produced in the same manner as in Example 1 except that (CF _0.30 ) n produced with a reaction time between petroleum coke and fluorine of 6 hours was used as the positive electrode active material. It was set to 3. Similarly, the presence of unfluorinated carbon was confirmed in the vicinity of the central portion of the fluorinated graphite in this case.

(Comparative Example 1)
A lithium primary battery was prepared in the same manner as in Example 1 except that (CF _1.05 ) n prepared with a reaction time between petroleum coke and fluorine being 18 hours was used as the positive electrode active material. did. In this fluorinated graphite, the presence of an unfluorinated carbon portion could not be confirmed.

(Comparative Example 2)
A lithium primary battery was prepared in the same manner as in Example 1 except that (CF _0.95 ) n prepared with a reaction time of petroleum coke and fluorine being 15 hours was used as the positive electrode active material. did. The presence of a clear unfluorinated carbon portion could not be confirmed at the center of the fluorinated graphite.

(Comparative Example 3)
A lithium primary battery was produced in the same manner as in Example 1 except that (CF _0.20 ) n produced as a positive electrode with a reaction time between petroleum coke and fluorine being 4 hours was used as the positive electrode active material. did. In this case, the presence of unfluorinated carbon could be confirmed from the vicinity of the surface.

  After measuring the internal resistance of the battery produced as described above, the load characteristics at low temperature were examined. The specific discharge conditions are as follows: a pattern in which discharge at 100 mA for 10 ms at −40 ° C. is repeated once per minute for 300 hours, and the minimum voltage in pulse discharge after 300 hours is defined as the pulse discharge voltage of the battery. did. Five discharges were performed for each, and the average values were compared. The results are shown in Table 1.

In the results of the low temperature pulse discharge test, the pulse voltage is improved in the batteries 1 to 3 as compared with the conventional batteries 4 and 5, and the battery using the low fluorinated fluorinated graphite has a low temperature load characteristic. Improved. This difference in pulse discharge voltage is not a difference in the amount of voltage change when the pulse current flows, but correlates with the battery voltage immediately before the pulse current flows. In the case of using low fluorinated fluorinated graphite, the voltage just before the pulse current flowed was high. This is because the low fluorinated fluorinated graphite has a fluorinated portion and an unreacted portion, and a portion between them has a low binding energy between fluorine and carbon in the transition state. This is probably because the potential has increased. When the fluorination is larger than 0.90 as in Comparative Example 4 and Battery 5, the portion with low binding energy decreases, so the voltage immediately before the pulse current flows and the voltage of the pulse discharge are reduced. Conceivable.

  Moreover, although the battery 6 uses low fluorinated fluorinated graphite, the pulse discharge voltage was not improved. This was because the voltage immediately before the pulse current flow was improved, but the internal resistance of the battery was high and the voltage drop during pulse discharge became large. Analysis of this battery revealed that a large amount of fluorine was present on the negative electrode lithium surface, and a fluorine-based resistance film was formed. This is because there is fluorine that elutes in the electrolyte at the boundary between the fluorinated part and the non-fluorinated part, that is, the transition state part. This is probably because the fluorine easily eluted and reacted with the negative electrode.

Example 4
Example 4 was prepared in the same manner as in Example 1 except that (CF _0.70 ) n prepared with a reaction temperature of petroleum coke and fluorine of 300 ° C. and a reaction time of 10 hours was used as the positive electrode active material. A battery was produced and designated as battery 7. Similarly, the presence of unfluorinated carbon was confirmed in the vicinity of the central portion of the fluorinated graphite in this case.

(Example 5)
Example 5 is a non-aqueous electrolyte similar to Example 1 except that (CF _0.50 ) n prepared with a reaction temperature of petroleum coke and fluorine of 400 ° C. and a reaction time of 7 hours was used as the positive electrode active material. A battery was produced and designated as battery 8. In this case, the presence of unfluorinated carbon was also confirmed in the vicinity of the central portion of the fluorinated graphite.

(Comparative Example 4)
Comparative Example 4 was a non-aqueous electrolyte similar to Example 1 except that (CF _0.30 ) n produced with a reaction temperature of petroleum coke and fluorine of 200 ° C. and a reaction time of 12 hours was used as the positive electrode active material. A battery was produced and designated as battery 9. In this case, the presence of unfluorinated carbon was also confirmed in the vicinity of the central portion of the fluorinated graphite.

(Comparative Example 5)
Comparative Example 5 was a non-aqueous electrolyte similar to Example 1 except that (CF _0.50 ) n prepared with a reaction temperature between petroleum coke and fluorine of 450 ° C. and a reaction time of 4 hours was used as the positive electrode active material. A battery was produced and designated as battery 10. In this case, the presence of unfluorinated carbon was also confirmed in the vicinity of the central portion of the fluorinated graphite.

  After measuring the internal resistance of the battery produced as described above, the load characteristics at low temperature were examined. The specific discharge conditions are as follows: a pattern in which discharge at 100 mA for 10 ms at −40 ° C. is repeated once per minute for 300 hours, and the minimum voltage in pulse discharge after 300 hours is defined as the pulse discharge voltage of the battery. did. Five discharges were performed for each, and the average values were compared. The results are shown in Table 2.

In the batteries 7 and 8 in which the production temperature of fluorinated graphite was 300 ° C. and 400 ° C., the pulse voltage increased. When the battery 7 and the battery 8 are compared, the degree of increase in the battery 7 is large. This is presumably because the fluorinated graphite produced at a low temperature is more uniformly fluorinated from the surface, so that less fluorine is eluted. In Battery 9, since the reaction temperature of fluorination was too low, there were many portions where the bond between fluorine and carbon was unstable, and a large amount of fluorine was eluted, so that the internal resistance increased and the pulse voltage did not improve. Battery 10 did not show an increase in the low temperature pulse. Although the voltage before the pulse current flowed increased, the internal resistance increased, so the voltage drop when the pulse current flowed became large. This is because the reaction temperature is high because the reaction temperature is high, fluorination on the surface is not uniformly performed, and the transition portion described above is partially present in the portion close to the surface, so that the fluorine is eluted. it is conceivable that.

  As described above, according to the present invention, in a non-aqueous electrolyte battery comprising a negative electrode with a light metal as an active material and a positive electrode with a fluorinated graphite as an active material, the fluorinated graphite contains fluorinated carbon and non-fluorinated carbon. Provided is a non-aqueous electrolyte battery having excellent load characteristics at low temperatures by using a fluorinated graphite (CFx) n (0.30 ≦ x ≦ 0.90) made of fluorinated carbon. be able to.

  Since the non-aqueous electrolyte battery of the present invention has excellent low-temperature load characteristics, for example, it is suitable for use as a vehicle-mounted application that requires reliability at low temperatures.

Sectional drawing of the flat type nonaqueous electrolyte battery in the Example of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode case 2 Positive electrode 3 Separator 4 Negative electrode 5 Sealing plate 6 Gasket

Claims (1)

A non-aqueous electrolyte primary battery comprising a negative electrode using a light metal as an active material and a positive electrode using a fluorinated graphite as an active material, wherein the fluorinated graphite is covered with fluorinated carbon from non-fluorinated carbon A nonaqueous electrolyte primary battery characterized by being fluorinated graphite represented by (CFx) n (0.30 ≦ x ≦ 0.90).