JPS5816468A - Cell active substance - Google Patents

Abstract

PURPOSE:To improve the discharge potential, specific capacity and the utilization of the cell and to reduce the cost, by employing the graphite fluoride shown by (C2F)n to be produced through the reaction between the artifitial graphite and the fluorine as the main component of the cell active substance. CONSTITUTION:The graphite fluoride shown by (C2F)n to be produced through the reaction between the artifitial graphite and the fluorine is employed as the main component of the cell active substance. Said cell active substance is employed as the positive pole of the cell while the alkali metal such as Li, alkali earth metal such as Mg, Ca or Al or Al alloy is employed for the cathode. Water system or non-water system electrolyte can be used. The cell thus composed has high specific volume and the utilization of the active substance per unit volume and the high discharge potential, while having the excellent flatness and the good storage life. While since the artifitial graphite is used, (C2F)n can be manufactured in short time with high yield resulting in the considerable reduction of cost.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a battery active material, and in particular, the present invention relates to a battery active material using artificial graphite as a graphite raw material.
The present invention relates to a battery active material whose main component is fluorinated graphite represented by C2F)n.

Conventionally, fluorinated graphite synthesized from carbon material and fluorine (
(hereinafter referred to as "GF") having a (CF)n structure is known, and such (CF)n-type GF is used as a battery active material and a lubricant due to its unique properties.

It is highly valued industrially in a wide range of fields as a wet-proofing agent, antifouling agent, water and oil repellent, etc. In particular, when used as an active material in batteries, it is well known that there is no voltage drop due to discharge over a long period of time, the battery has good storage stability, and it provides a primary battery with high energy density. There is (
For example, see Japanese Patent Publication No. 48-28867). However, the major drawback of the synthesis of (CF)n-type GF is that the yield is extremely low because the production temperature of the target product (CF)n and the decomposition temperature of the produced (CF)n are close to each other. was there.

Therefore, the present inventors first investigated (C2F), which can be obtained at a relatively low cost and in extremely high yield as a GF with a novel structure.
We succeeded in manufacturing n-type GF. Regarding this new (C2F) n-type GF and its manufacturing method, please refer to JP-A-53-1028.
As detailed in No. 93 and US Pat. No. 4,139,474, graphite is obtained by heating graphite at 300 to 500° C. under a fluorine pressure of 100 to 760 ++ nHg. As the graphite, natural graphite, artificial graphite, Quiche graphite, pyrolytic graphite, etc., or a mixture thereof is used.

Its structure consists of a layer of carbon atoms forming a lattice structure with a distance between the eyebrows of about 9
．． Unlike OX, it is unique in that every other fluorine is bonded to one fluorine. However, in both cases, CF2. C
The F5 group is present. Therefore, the F/C ratios of (02F)n and (CF)n, in which graphite is fully fluorinated, are each 0
．． 5 and 1.0 or more, and the amount of excess fluorine is GF
Crystallites in the ab-axis direction of the crystal become smaller 3832, 19
79). Furthermore, (C2F)n exhibits a unique infrared absorption at 940 cm-', which is not observed in (CF)n. However, the raw material graphite is completely fluorinated (
The time required to generate C2F)n is especially (02F)
Under mild conditions favorable for obtaining n with high selectivity, it is extremely long, for example 200 to 250 mta
Mada of h (Tyler) made 375 natural graphite from Skull.
When it is reacted with fluorine at a temperature of 200 mtHg and a fluorine pressure of 200 mtHg, its generation requires as long as 120 hours.

On the other hand, regarding the use as a battery active material,
Although detailed in the specification of No. 28246, (C2F)n
It is advantageous because it shows a higher discharge potential than (CF)n, and the amount of conductive agent mixed in is smaller than that for (CF)n, and the content of (CF)n in the electrode can be increased accordingly. be.

The present inventors produced (C
In the process of researching the battery characteristics of 2F)n, we found that the battery characteristics differ significantly depending on the conditions.

That is, when (C/)n, which is obtained by using artificial graphite as a raw material for (C2F)n-type QF and fluorinating it, is used as a battery active material, it has a high discharge potential and specific capacity.

We found that it shows the usage rate. Even more surprising,
It has also been found that in the case of artificial graphite, the time required for completely fluorinating graphite to generate (C2F)n is extremely short compared to when natural graphite or pyrolytic graphite is used as a raw material. For example, natural graphite has a fluorine pressure of 760 llHg.
r When reacted at 375°C for 120 hours (02F)
On the other hand, if artificial graphite (average particle size 300μ, Franklin P-value 0.07) was reacted under the same conditions as above, the same 100% yield could be obtained. It can be achieved in 18 hours.Based on the above findings, the present invention has been completed.

Therefore, one object of the present invention is to provide a formula (C
2F) To provide a GF represented by n.

Other objects, features, and advantages of the present invention will become apparent from the description that follows.

That is, basically, according to the present invention, the formula (C2F) obtained by using artificial graphite as a graphite raw material and reacting it with fluorine.
A battery active material containing fluorinated graphite represented by n as a main component is provided. The artificial graphite used in the present invention preferably has a Franklin P-value of 0 to 0.4. Further, in a more preferred embodiment of the battery active material of the present invention, artificial graphite and fluorine are mixed under a fluorine pressure of 100 to 760111 Hg to
The main component is fluorinated graphite expressed by the formula (02F)n obtained by reacting at a reaction temperature of 500°C until there is no increase in the weight of the product, and the ratio is 0.55 to 0.
．． It is characterized by being 8. A more preferable range of reaction temperature is 300 to 450°C.

In the present invention, "artificial graphite" refers to a carbon material obtained by carbonizing coke (petroleum coke, pitch coke, etc.), ph pitch, or an organic polymer compound.
By heating to 00 to 3,000°C, impurities are volatilized and graphitized, and amorphous carbon atoms are arranged in a regular graphite network plane.

Further, the Franklin P-value indicates the degree of crystallinity of graphite, that is, the degree of graphitization, and can be obtained by calculating from the following formula.

d(oo2) =3.440 0.086(]-P2)
(where d(..2) is the interplanar spacing measured by X@diffraction (
d(..2)), where P indicates the Franklin P-value). (R,E, Franklins A
cta Cryst, +4 +235
e (1951)).

Originally, compared to natural graphite and pyrolytic graphite, artificial graphite has smaller crystallites in the ab-axis direction of the crystal, and because the proportion of carbon present at the terminals to the total carbon is high, it combines with fluorine and produces a large amount of CF2. CF3 groups are generated, and the F content in GF increases. For this reason, there is concern about the influence of the CF2 + CF5 group on the discharge potential, and (C2F)n produced from artificial graphite has not been used as a battery active material. However, according to the research of the present inventors, if artificial graphite with a certain Franklin P-value is used as a raw material, these groups have almost no effect on the discharge potential of GF, and on the contrary, It has been found that the specific capacity can be increased. That is,
GF containing (02F)n as a main component produced using these artificial graphites provides far superior and stable battery characteristics compared to those produced from natural graphite.

(C2F)n used as a battery active material according to the present invention
The raw material is preferably artificial graphite having a Franklin P-value of 0 to 0.4. When the P value is 0.4 or more, '(
The content of CF)n increases and the discharge potential decreases.

Furthermore, when natural graphite is used, the discharge potential and specific capacity decrease.

It is not clear why (02F)n obtained by fluorinating artificial graphite has a higher discharge potential than that obtained by fluorinating ordinary natural graphite, but the ab
The crystallites in the axial direction are smaller than those of natural graphite and pyrolytic graphite, and therefore, it was obtained by fluorinating artificial graphite (C2
F) The crystallites of n are also small.

Therefore, the electrochemical surface area becomes large and Ll
This is thought to be because ions easily diffuse into the GF interlayer.

(C2F)n used as a battery active material according to the present invention
The F ratio is 0.55 to 0.8. If the lie ratio is less than 0.55, unreacted graphite remains and the specific capacity decreases significantly. Further, when the ratio is 0.8 or more, the content of (CF')n in GF becomes high, 9 and the discharge potential decreases.

The fluorinated graphite containing (C2F)n as a main component according to the present invention, which is crystallized at a temperature of 500 to 600 DEG C. in a fluorine atmosphere after completion of the reaction, has similar excellent properties.

In order to use GF represented by the formula (CF)n as a battery active material, a predetermined amount of carbon powder as a conductive agent and a fluororesin or expanded graphite as a binder, for example, are added to (C2F)n to give it a predetermined shape. It can be easily obtained by molding it into

When this battery active material made of (02F)n is used in a battery, it is used as a positive electrode, and an alkali metal such as lithium or magnesium is used as a negative electrode.

Alkaline earth metals such as calcium or aluminum alone or alloys containing these as main components can be advantageously used. As the electrolyte, depending on the type of negative electrode used, not only non-aqueous electrolytes but also aqueous electrolytes can be used.

A battery constructed using the battery active material made of (C2F)n according to the present invention as a positive electrode, and the above-described negative electrode and electrolyte has a high capacity and utilization rate per unit volume of the active material, In addition to its excellent characteristics of high discharge potential, excellent flatness, and long shelf life, the raw material (C2F)n can be produced in a short time due to the use of artificial graphite and at a high yield, making it extremely inexpensive. It is possible to provide a battery with a high energy density that can be obtained in a short period of time and is extremely advantageous from the point of view of economic efficiency, and its industrial value is extremely high.

The present invention will be explained in more detail below with reference to Examples, but the scope of the present invention is not limited to the Examples.

Note that since the GF ratio differs depending on the fluorine measurement method, the F ratio in the present invention was determined by the following fluorine measurement method.

Precisely weigh 100 Da of fluorinated graphite in platinum Ludde, mix uniformly with flux (potassium carbonate, sodium carbonate each 2.5.9 kg), melt at 700-750°C, and then dissolve the melt in water. do. A certain amount of this is collected, adjusted to pH 3.4, and titrated with a standard thorium nitrate solution using Alizoline Red S as an indicator. An automatic photometric titrator was used for titration. Leave the carbon as the remainder.

The utilization rate is determined by the following formula, assuming that the current flowing when the electrode is discharged is y amperes and the discharge time is t seconds.

[However, X is the amount of fluorine contained in the positive electrode] Example 1 Fluorinated graphite whose main component is (C2F)n has an average particle size of 3
00μ artificial graphite (Franklin P value -007) was reacted at 380° C. for 18 hours under a fluorine pressure of 760×tnHg.

The enrichment of the obtained fluorinated graphite was 0.73, but the X-ray diffraction diagram showed a slight diffraction peak at 2θ = 10.1 @, and an infrared absorption peak at 940 crn-'. (
It was proved to be C2F) type GF.

Further, Table 1 shows the specific capacity per unit volume calculated from the fluorine content and true specific gravity of this GF.

Using expanded graphite (manufactured by Toyo Tanso Co., Ltd.) as a conductive agent and a binder, it was mixed with (C2F)n at a weight ratio of 1:1, resulting in approximately 8,800
kl? The mixture was compressed for 1 minute at a pressure of /=2 and formed into a pellet shape with a diameter of 10 mm, which was separated as a positive electrode.

The negative electrode was cut out from a lithium block and used as it was. As an electrolyte, lithium perchlorate (LiClO
A propylene carbonate solution in which l mol/l of 4) was dissolved was used. These battery components were placed in a Teflon container, and all experiments were conducted in Drydex at 30° C. in an argon atmosphere. The distance between the electrodes was 10 mm.

The discharge characteristics of this battery under a constant resistance load of 20Ω are shown in FIG. 1 (4).

Example 2 Fluorinated graphite whose main component is (C2F)n has an average particle size of 1
The product obtained by reacting 0 μm artificial graphite (Franklin P-value = 0.35) at 360° C. for 18 hours under a vacuum pressure of 760 mmH% was used.

The F/C ratio of the obtained GF was 0.76, but the X-ray diffraction diagram had a -1 diffraction line at 2θ-10 and 4°, and there was an infrared absorption line at 940 ern-1'. and (C
2F) type GF. Measurement is in Example 1
It is similar to

The discharge characteristics of this battery under a constant resistance load of 20Ω are shown in FIG. 1(B). Further, the specific capacity of this GF is shown in Table 1.

Comparative Example 1 Fluorinated graphite is natural graphite with an average particle size of 10 μm (Franklin P-value = 1) under a fluorine process of 760 m1 + Hg.
The one obtained by reacting at ℃ for 300 hours was used.

The F/C ratio of the obtained CF was 0.63, but the X-ray diffraction diagram had a few diffraction lines with a peak at 2θ-10.0° and also showed infrared absorption at 940 cm-'. , (C2
F) type GF was proven. The measurements were the same as in Example 1. The discharge characteristics are shown in Figure 1 (Q).

Further, the specific capacity of this GF is shown in Table 1.

Comparative Example 2 Fluorinated graphite was obtained by reacting petroleum coke with an average particle size of 15 μm (Franklin P-value = 1.0.0) at 280° C. for 200 hours under a fluorine process of 760 mmHg.

The lie ratio of the obtained GF was 1.03, and the X-ray diffraction diagram had a diffraction line with a peak at 1,2θ=12.2°, and 9
There was no infrared absorption at 40 cm-,', proving that it was a (CF)n-type GF. The measurements were the same as in Example 1. The discharge characteristics are shown in FIG. 1(D). Further, the specific capacity of this GF is shown in Table 1.

Comparative Example 3 Fluorinated graphite was obtained by reacting artificial graphite (Franklin P-value = 0.51) with an average particle size of 40 μm at 360° C. for 300 hours under a fluorine pressure of 760 mm Hg.

The lie ratio of the obtained GF was 0.82, and the X-ray diffraction diagram had a diffraction line with a peak at 2θ = 124°, with a peak of 940c.
rn-1 shows small infrared absorption, and CF\ and (C2
F) is considered to be a mixture of n. The measurement is the same as on the actual flow side 1. The discharge characteristics are shown in Figure 2.

Comparative Example 4 Fluorinated graphite is artificial graphite (Franklin P-value = 0.14) with an average particle size of 40 μm under a fluorine pressure of 760 mmHg.
The product obtained by reacting at 60°C for 2 hours was used.

The obtained GF enrichment was o4. g, and the X-ray diffraction diagram has a diffraction line with a peak at 2θ = 11.2°, 940
cm-' shows infrared absorption, (C2F)n-type G
It was proven that F. However, unreacted graphite was also detected in the X-ray diffraction pattern. The measurements were the same as in Example 1. The discharge characteristics are shown in Figure 2.

Comparative Example 5 Fluorinated graphite is artificial graphite (Franklin P-value = 0.07) with an average particle size of 10 μm under a pressure of 760 Hg.
The product obtained by reacting at 0°C for 2 hours was used.

The F/C ratio of the obtained GF was 0.87, and the X-ray diffraction diagram had a diffraction line with a peak at 2θ-13,1'.
40crn-1 shows small infrared absorption, and the measurement is the same as in Example 1.

The discharge characteristics are shown in FIG. 2 (G).

As is clear from Table 1, when used as a battery active material, (CF)n has a special characteristic of having a higher discharge potential than (CF)n, but due to its small fluorine content, the specific capacity is )n is inferior. However, it was produced from artificial graphite (
The specific capacitance of A and B containing C2F)n as a main component is much improved compared to C produced from natural graphite, and is comparable to that of D of CF)n.

[Brief explanation of the drawing]

FIGS. 1 and 2 show relationship curves between utilization factor and discharge potential when various fluorinated graphites are used as battery active materials.

Claims (4)

[Claims] (1) A battery active material whose main component is fluorinated graphite expressed by the formula (02F)n obtained by reacting artificial graphite as a graphite raw material with fluorine. (2) The battery active material according to claim 1, wherein the artificial graphite has a Franklin pH of 0 to 0.4. (3) Artificial graphite and fluorine at 100 to 760 Hg
The main component is fluorinated graphite represented by the formula (CF)n, which is obtained by reacting at a reaction temperature of 300 to 500'C under a fluorine pressure of .55 to 0.8, the battery active material according to claim 1 or claim 2. (4) The battery active material according to claim 3, wherein the reaction temperature is 300 to 450°C.