JPS59228362A - battery active material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] This invention relates to a battery active material with improved characteristics.

So far, graphite fluoride obtained by converting graphite into a fluoride has been confirmed to be represented by the formula <CF)n and that represented by the formula (CzF)n. It is also known to exist in However, there are still many aspects of its reality that are unclear. It is well known that this fluorinated graphite has excellent properties as a battery active material, as described below.

For example, Japanese Patent Publication No. 48-25565 describes solid fluorinated graphite (CFx) as a positive electrode active material for batteries (where 0.5≦X≦1), especially when x is 1.
It is also described that by using fluorinated graphite close to 1, a primary battery with high energy density, high utilization as an active material, excellent voltage flatness, and good shelf life can be obtained.

Furthermore, in Japanese Patent Application Laid-open No. 53-102893, the formula (C
A new fluorinated graphite represented by zF)n (hereinafter simply (C
zF)n) and its manufacturing method are described, and this (C2F)n shows no increase in fluorine content even after heat treatment in a fluorine atmosphere at 600°C. It has also been suggested that it can be used as a battery active material.
In the publication, fluorinated graphite in which (CzF>n is represented by the above formula (CF)n) (hereinafter simply referred to as (CF>n)
It is stated that the discharge potential is higher than that of the

Sarani JP-A No. 57-84570 discloses that by mixing (CF)n and (02F)n and using it as a positive electrode active material of a battery, the problem of (CF)n, which is the temporary voltage change in the early stage of discharge, can be improved. In addition, Japanese Patent Application Laid-Open No. 16468/1983 relates to a battery active material whose main component is (CzF)n, which is obtained by reacting artificial graphite with fluorine. describes a preferred embodiment of a battery active material containing (C2F)n as a main component, which is obtained by reacting artificial graphite as a raw material with fluorine until there is no increase in the weight of the product, and which exhibits a high discharge potential. It has been made clear that

The present inventors conducted various studies on the production process of fluorinated graphite, and found that there was no reaction product in the fluorination reaction of graphite with fluorine.

In the first reaction stage where reactive graphite remains, the fluorination reaction proceeds despite the absence of unreacted graphite in the reaction product, resulting in an increase in the weight or fluorine content of the reaction product. There are three reaction stages: the second reaction stage, and the third reaction stage, in which no increase in weight or fluorine content is observed in the reaction product even if the fluorination reaction is proceeded, and the crystallinity is mainly considered to be increased. However, it was found that all of the fluorinated graphites described in the above-mentioned publications were almost at the third reaction stage.

The inventors further researched the properties of fluorinated graphite obtained at each reaction stage as a battery active material, and found that
The fact that the fluorinated graphite obtained in the second reaction step has a discharge potential 100 to 200@V higher than the fluorinated graphite obtained in the third reaction step, especially in the above-mentioned JP-A-58-1646.
In Japanese Patent No. 8, we discovered the unexpected fact that there is a region exhibiting a higher discharge potential in a range that deviates from the preferred embodiment, and we have completed the present invention.

That is, the present invention provides fluorinated graphite obtained by fluorinating graphite, which (1) contains substantially no unreacted graphite, and (2) when it is refluorinated with fluorine, the product has a weight The present invention relates to a battery active material that satisfies the condition that an increase in fluorine content or an increase in fluorine content is observed.

It was discovered for the first time by the present inventors that the graphite fluorination reaction product has a unique fluorinated graphite region such as the second reaction stage that satisfies such conditions. It differs from the fluorinated graphite obtained in the conventional first and third reaction stages in the above points (1) and (2).

That is, the battery active material of the present invention is powder XI! When analyzed by diffraction method, no peak of unreacted graphite (diffraction angle 2θ of (002) plane is around 26.5 degrees) is observed. Fluorine 1 in the first reaction stage in which unreacted graphite remains
Free fluorine is occluded in graphite, and although its discharge potential is high, the free fluorine impairs battery performance, so there are cases where practical problems remain as a battery active material.

Furthermore, when the battery active material of the present invention is subjected to a fluorination reaction with fluorine, an increase in weight or an increase in fluorine content is observed in the product.

Note that in this specification, weight increase is approximately 1% (weight%,
(The same applies hereinafter) Above, it is preferably an increase in weight of 3% or more, and an increase in fluorine content means an increase in fluorine content of about 0.5% or more, preferably 1.5% or more.

The conditions for the fluorination reaction using fluorine to observe the weight increase or increase in fluorine content are the same reaction temperature, pressure, and fluorine concentration as those used in the production of fluorinated graphite used in the present invention. be done.

One possible reason why an increase in weight or fluorine content is observed when the battery active material of the present invention is refluorinated is that, unlike the previously known (02F)n, which is in the so-called stabilized state, , (02F)n to (CF)n
It is presumed that this is because (02F)n, which is a so-called transition state that can change to , is mixed. Further, the improvement in the discharge potential in the present invention is considered to be due to the presence of (CzF)n in the transition state, and this may be the reason why the discharge potential of conventional fluorinated graphite is lower than that of the present invention. This is considered to be because (02F)n is in a stable state.

The battery active material of the present invention is preferably the above-mentioned fluorinated graphite having a fluorine content of 48 to 58% and a fluorine content of 50 to 56%. Although the lower limit of the fluorine content of 48% is not an important limit in relation to the discharge voltage, anything less than 48% is generally undesirable due to the presence of free fluorine occluded in unreacted graphite. When it exceeds 58%, the desired effect of improving the discharge voltage cannot be obtained.

The battery active material of the present invention is a powder X based on a fluorinated graphite moiety.
The diffraction angle (2θ) of the (001) plane in line diffraction is 9.
A peak appears at 9 to 14.5 degrees, and depending on the case, 1
A peak or shoulder indicating (CzF)n may appear near 0 degrees.

Examples of the raw material graphite used in the present invention include natural graphite,
Examples include artificial graphite and artificial scaly graphite (for example, XS series and T series manufactured by Rozan).

The battery active material of the present invention is usually used by mixing raw material graphite with fluorine gas (if necessary, fluorine gas is mixed with diluent gas).
(but not limited to).

Fluorine gas or a mixed gas of fluorine gas and diluent gas is introduced into the reactor at room temperature so that the partial pressure of fluorine gas is 0.1 to 1 atl. The temperature is gradually raised from room temperature to the desired reaction temperature, that is, 300 to 500'C1.
Preferably it is stored at 300-450°C.

The fluorination reaction for producing the battery active material of the present invention is
For example, perform a fluorination reaction under the same conditions in advance and check the reaction time from the start of the reaction until no unreacted graphite exists, and the reaction time until no increase in the fluorine content or weight of the product occurs. Then, either stop the reaction during the re-reaction time, or sample the product at regular intervals, separately examine the sample for the presence of unreacted graphite by powder X-ray diffraction, and then perform the reaction under the same conditions. The reaction may be stopped after carrying out a fluorination reaction and checking for an increase in weight and fluorine content.

The reaction time varies depending on the crystallinity of the raw graphite, particle size, fluorine gas pressure, reaction temperature, etc., but usually the reaction temperature is 38.
At 0°C, the time is 15 to 100 hours.

This reaction time is 1/2 to 1/1 of the reaction time of 100 to 200 hours at the same temperature when producing conventional fluorinated graphite.
0, and production efficiency can be greatly improved.

The raw material graphite is preferably degassed at the normal reaction temperature to remove moisture.

As the diluent gas to be mixed with the fluorine gas, a gas that does not react with fluorine and graphite is used. Specific examples include nitrogen gas, perfluorocarbon, rare gas, and the like.

An electrode material can be obtained by blending a binder and a conductive material with the battery active material of the present invention. Their compounding ratio is 10 parts of fluorinated graphite (by weight, the same applies hereinafter), 1 to 4 parts of binder, and 0.5 parts of conductive material.
Preferably it is 5 to 2 parts.

Examples of the binder include polytetrafluoroethylene (PTFE), and examples of the conductive material include highly electrically conductive carbon black such as acetylene black and Ketjen black, or natural graphite.

When the battery active material of the present invention is used in a battery, it is preferable to use the battery active material of the present invention as a positive electrode and to use, for example, lithium, magnesium, calcium, aluminum alone or an alloy containing these as main components for the negative electrode. Although it depends on the type of negative electrode used as the electrolyte, a non-aqueous electrolyte is usually used.

Next, the battery active material of the present invention will be explained with reference to Examples, but the present invention is not limited to these Examples.

Example 1 and Comparative Example 1 Artificial graphite (average particle size 15 μm) 10.017 was placed in a reactor and aerated at 380° C. for 30 minutes to remove moisture, and then cooled to room temperature.

Then, fluorine gas (90%) was introduced into the reactor using IATM, the temperature was raised to 380°C, and the reaction was carried out for 16 hours.

The product is a dark brown powder with a fluorine content of 5.
2.8%, weight was 21.1 (l).

When this material was analyzed by powder xi diffraction method, no graphite-based diffraction lines were observed, and the diffraction angle of the (001) plane was 2.
A peak appeared at 10.54 degrees at θ (hereinafter simply referred to as 2θ).

Furthermore, when this product was taken as 10.00++ and the fluorination reaction was carried out again under the same conditions, the weight was 10.33 (1 (weight increase 3.3%) 114 hours after the start of the refluorination reaction. A product with a fluorine content of 54.5% (fluorine content increase of 1.7%) and a peak at 10.90 degrees 2θ was obtained.Even if the fluorination reaction was performed thereafter, the weight did not increase. No increase in fluorine content was observed either.

Note that the product obtained after the 114 hours is referred to as fluorinated graphite of Comparative Example 1.

Then, 10 parts of these products, 1 part of PTFEa, and 1 part of acetylene black were thoroughly mixed and pressed onto a nickel mesh to prepare a positive electrode with a surface area of 1.57. The negative electrode was cut out from a block and held in a nickel net, and the electrolyte was 1 mol/l of γ of lithium fluoroborate.
- A butyrolactone solution was used. Measurement of discharge voltage is 25
The test was carried out with constant resistance discharge at 10 KO at .degree. Figure 1 shows the change in terminal voltage obtained over time.

Example 2 and Comparative Example 2 Artificial graphite (average particle size 2oμ) 10, OQ as raw material graphite
The fluorination reaction was carried out under the same conditions as in Example 1 except that 16 hours later, the reaction was stopped to obtain a battery active material of the present invention. This product is a blackish brown powder, with no unreacted graphite observed, a fluorine content of 51.8%, and a weight of 20,747. When this product was analyzed by powder X-ray diffraction, no graphite-based diffraction lines were observed, and a peak appeared at 11.41 degrees in 2θ.

Furthermore, add this to 10. When OOo was taken and the fluorination reaction was carried out again under the same conditions, 1 from the start of the refluorination reaction.
After 13 hours, the weight is 10.30g (3.0% weight increase)
The fluorine content is 54.0% (Fluorine content increase is 2.2%)
%) and having a peak at 11.59 degrees 2θ was obtained. No increase in weight or fluorine content was observed even after subsequent fluorination reactions. Said 1
The product obtained after 13 hours was designated as fluorinated graphite of Comparative Example 2.

Batteries were produced in the same manner as in Example 1 using the products obtained in Example 2 and Comparative Example 2, and changes in terminal voltage over time were measured.

The results are shown in Figure 2.

Example 3 and Comparative Example 3 Natural graphite (average particle size 10μ) 1o, og as raw material graphite
The fluorination reaction was carried out under the same conditions as in Example 1, except that 11 hours later, the reaction was stopped to obtain a battery active material of the present invention. This material was in the form of a blackish brown powder, with no detectable presence of unreacted graphite, its fluorine content was 49.5%, and its weight was 19.8 (J). Upon analysis, no graphite-based diffraction lines were observed, and a peak appeared at 10.41 degrees in 2θ.

Further, 1o, oog was taken and the fluorination reaction was carried out again under the same conditions. After 110 hours from the start of the reaction, the weight was io, 361) (weight increase: 3.6%) and the fluorine content was 51.5% ( A product with a fluorine content increase of 2.0%) and a peak at 10.10 degrees 2θ was obtained. No increase in weight or fluorine content was observed even after subsequent fluorination reactions. The product obtained after the 110 hours is referred to as fluorinated graphite of Comparative Example 3.

Batteries were produced in the same manner as in Example 1 using the products obtained in Example 3 and Comparative Example 3, and changes in their terminal voltages over time were measured.

The results are shown in Figure 3.

As is clear from Figures 1-3, the battery active material of the present invention exhibits a higher group N potential than that obtained in the third reaction stage.

[Brief Description of the Drawings] Figures 1 to 3 show batteries using battery active materials obtained in Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3, respectively. It is a graph showing a change in terminal voltage over time. Procedural amendment (voluntary) 1980 12 Do 2B Commissioner of the Japan Patent Office Kazuo Wakasugi 1 Display of the case 1988 Patent Application No. 103667 2 Name of the invention Battery active material 3 Relationship with the amended person case Patent application Address: New Hankyu Building, 1-12-69 Umeda, Kita-ku, Osaka (1) Contents of amendment to column 6 of “Detailed Description of the Invention” of the specification (1) “Block” on page 12 of the specification, line 8 to line 9 "Cut it out from a block of lithium with a surface area of 1Cm2,
Cut it out to a thickness of iBm and correct it. Written amendment to the above procedure (voluntary) Commissioner of the Japan Patent Office Kazuo Wakasugi 1 Description of the case 1982 Patent Application No. 103667 2 Name of the invention Battery active material 3 Relationship with the person making the amendment Patent applicant)) 2 1. Subject of 5 amendments (1) Contents of amendment in column 6 of “Detailed description of the invention” of the specification (1) Amend [(02F base code) to “new (02F)n” on page 7, line 3 of the specification (2) “Unreacted graphite” on page 7, line 14 is “reaction product”.
and correct it. that's all

Claims (1)

[Scope of Claims] 1 Fluorinated graphite obtained by fluorinating graphite with fluorine, which (1) contains substantially no unreacted graphite and (a) when it is refluorinated with fluorine, the product A battery active material characterized by satisfying the condition that an increase in weight or an increase in fluorine content is observed.