The graphite intercalation compounds: Their uses in industry and chemistry

Synthetic Metals, 23 (1988) 467-473

467

THE GRAPHITE INTERCALATION COMPOUNDS : THEIR USES IN INDUSTRY AND CHEMISTRY ~

R. SETTON Centre de Recherche sur les Solides ~ Organisation Cristalline Imparfaite, C.N.R.S.

IB, rue de la F6rollerie, 450710rl~ans

Cddex 02, France.

ABSTRACT About 300 patents featuring graphite intercalation compounds have been granted in the period 1977-1985, in which graphite fluoride is used in the majority of cases and in a wide range of applications, followed by the Lewis acid GIC's. However,

the alkali metal GIC's form the majority of Compounds used for pre-

parative chemistry in over IO0 monographs published during the same period.

INTRODUCTION In this paper, a critical assessment of the uses of graphite intercalation compounds (GIC's) is presented, as seen through the uses found for them in industry and in the synthetic chemistry laboratory. Leaving aside the papers dealing with the synthesis of the various GIC's, those reporting results of measurements of physical properties and '~theoretical" monographs, we are left, for the years 1977 to 1986, with over 400 patents and papers in which GIC's are used as such, or in the preparation of other compounds, or for the manufacture of a large variety of devices. This excludes references to graphite, except when GIC's are used to obtain forms of carbon with improved characteristics. We shall first examine the patents, their distribution in time and among the various subjects, firms and countries, then the research papers. The literature search covered Volumes 86 to 104 of Chemical Abstracts, i.e. 19 semesters starting with 1977, the year of the La Napoule Conference. A reasonable effort was made at having as complete a coverage as possible, although no claim is made of it being absolute.

I n v i t e d paper. 0379-6779/88/$3.50

© Elsevier Sequoia/Printed in The Netherlands

468

THE PATENT LITERATURE Of the 30] patents which were found,3 the most recent patents

the end of the bibliographical represented

were taken before

1977; a~ain, some of

(say dated after 1984) may have been abstracted after

. Nevertheless,

search so that |985 and 1986 may not be fully

the data obtained seems sufficiently

to enable a number of conclusions

significant

to be drawn [1].

|O

40

TI

,

,

,

;,

,

,

,;

Fig. 1. Total number of patents involving graphite intercalation compounds taken each year between 1976 and 1985 (upper curve, full line). The lower curve (dashed line) is the Japanese contribution to the total.

In Figure

I, the full line gives the distribution,

in time, of the yearly

totals, which are broken down in Table I to show the total contributions from the different countries. Japanese

contribution

Also shown in FiFure

1 (dashed line) is the

to the total : the parallelism between the two curves is

striking and an examination of the values in Figure the number of Japanese patents all the other contributions The graph in Figure trend follows

combined.

l has two maxima,

the Japanese

I shows that, as from 1979,

(JP) is at least equal to or even greater than

contribution,

for 1978 and 1983. Since the general if we are to find an explanation

for

the large number of natents taken in 1983, it must be amon~ the JP : examining the data reveals

that

this

maximum

to 19 patents on the use of graphite linings,

this having apparently

is due, among other similar causes, fluoride

(hereafter G/F) in exhaust-tube

fully covered the matter since no other patents

on this subject were taken at later dates. Once these contributions removed,

the rest falls to more reasonable values

with a trend in the range of 30 - 40 patents/year.

have been

(points A and A' in Figure From the numbers given in

I),

469

the last column of Table I, 95% of the patents originate wing seven sources

from one of the follo-

: JP (193), US (28), DE (18), EP (16), SU (14), FR (9),

CS (6).

TABLE

1

Country of origin and number of patents per country Austria (AT) Belgium (BE) Czechoslovakia (CS) German D.R. (DD) German F.R.(DE)

Only 40 patents remainder,141

| 1 6 1 18

European patent (EP) 16 France (FR) 9 United Kingdom (GB) 6 Japan (JP) 193 Netherlands (NL) 3

(13.6%) were attributed

to inventors

(46.8%) bear only the name of industrial

tions, while the rest (119 patents,

Poland (PL) Romania (RO) U.S.S.~.(SU) U.S.A. (US)

3 2 14 28

in their own name; of the firms or public organiza-

39,5%) bear the name of the inventors

and of

the firm to which the rights seem to have been ceded. That over 85% of the patent are directly

connected with Industry

mere laboratory

is an indication that the GIC's are not

curiosities.

TABLE 2 The distribution

of patents or licenses among the firms and organizations

Matsushita Electric Industrial Co., Ltd. Central Glass Co., Ltd. Mitsubishi Electric Corp. Asahi Chemical Industry Co., Ltd. Hitachi Ltd. Canon K.K. Toshiba Corp. Hitachi Chemical Co., Ltd. Agence Ntle. Valorisation de la Recherche Daikin Kogyo Co., Ltd. Suwa Seikosha Co., Ltd. Toray Industries Inc. Others

34 27 27 9 9 8 8 7 5 5 5 5

: 2 firms hold 4 patents or licenses 8 " " 3 " " 17 " " 2 " " 52 " " l " "

Table 2 gives the distribution examined)

of patents or licenses

(for the total period

among the firms. Three firms stand out, with 34 , 27 and 27 patents

or licenses

respectively, while the next firms drop to 9 or less. The first

firms in the list total over 50% of the entries. holds 5 patents or licenses.

The first non-Japanese

firm

12

470 TABLE 3 The uses of graphite intercalation compounds in industry The number of patents related to each item is in brackets. I. Preparation of GIC's Manufacture of graphite fluoride (21) ; Manufacture of graphite sulfate (5) ; Manufacture of graphite-Lewis acid compounds (10) ; Manufacture of graphitemetal combinations (4). II. GIS's in graphite and diamond manufacture Improvement of the characteristics of graphite (4) ; Manufacture of expanded graphite (4) ; Manufacture of diamond (|). III. GIC's as catalyst ~ydrocarhons synthesis and isomerization (14) ; Plastics polymerization (7) ; Ammonia synthesis (3) ; Others (IO). IV. GIC's in power sources Electrodes and batteries (80) ; Fuel cells and fuel cell electrodes (19) ; Concentration cells (2) ; Thermal energy storage (I). V. GIS's in lubricants and low-friction coating (52). VI. GIC's is recording materials, inks and colored leads (16). VII. GIC's in combustion engine technology (20). VIII. GIC's as or in electric conductors (II). IX. Miscellaneous uses of GIC's Extinction of metal fires (7) ; Permionic membranes and electrolysis cells (5) ; Moisture sensing devices (4); Others (12).

The patents in Table 3 have been classified in 9 main groups. The first (40 entries) is directly concerned with the preparation of GIC's

while the other

groups, totaling 275 entries, deal with their uses. (The number of entries is larger than the number of patents since some of the latter appear more than once in the list of uses.). The division is arbitrary and a number of applications represented by very few or a single patent have been grouped under "Others". The largest group contains 102 entries claiming the use of GIC's in power sources, usually with G/F as cathode in high-voltage batteries. The next group has 52 entries on GIC's as lubricants, or in protective wear-resisting coatings. G/F is, again, quite dominant : it is used for instance in precision self-lubricating bearings for watches, or electro-deposited with a noble metal to form wear-resistant coatings. Although it seldom appears in the group (34 entries) claiming the use of GIC's as catalysts, in which it is mainly a support for Lewis acid intercalates, G/F forms the basis of all the entries of the next two groups (20 and 16 entries) as sound-absorbing and tar-depositlon preventing material in exhaust tubes, as additive in combustion engine oil, in colored pencil leads, in toner inks for photo-copying process, or in the preparation of photosensitive imaging materials. Even in the last group (28 entries), there is a small number of cases in which G/F is used, mainly in the preparation of moistu -~ re-sensitive devices.

It is however totally absent in the group of 13 patents

dealing with electric conductors, but even this may change in the near future since some of the graphite fluorides have a fairly high electric conductivity.

471

In vlew of th~ relatively large number Of entries (138) in which G/F is involved under one form or another,

it is not surprising that 21 entries describe

the preparation of CxF , in which x is very often 2 but may vary between ] and 4, depending on the uses to which the compound is put. Next in line are the graphite-Lewis acid compounds, with 36 entries, the three most important uses being as catalysts (]3), in power sources (12), and as electric conductors (IO). This is reflected in the first group of patents in which I0 entries deal with the preparation of these compounds. In spite of this, there is therefore an extremely large drop between the number of applications found for G/F and those found for the next "most useful" group of GIC's. A somewhat lesser drop is seen on going to the next most populated type of GIC, namely the acid derivatives, in which 6 out of the 25 entries deal with the preparation of graphite (with improved chemical or mechanical characteristics) or of expanded graphite, while 6 describe the electrolytic deposition of alloys with microparticles of graphite for improved gliding and wear-resistance proper ties. TABLE 4 Graphite intercalation compounds in preparative chemistry I. The preparation of active forms of metals (Mg, Zn, Fe, Co, Pd, Ti, Sn)(IO) II. Halogen chemistry Fluorination (5); Chlorination and bromination (2); Dehalo~enation (7). III. C-C bond chemistry Coupling reactions (7); Isomerizations (]4); Alkylations (12); Cracking and cleavage (4). IV. C-H bond chemistry Reduction of double bonds (4); Dehydrogenation reactions (]); Fischer-Tropsch process (6). V. C-O bond chemistry Oxidation and hydroxylation (ll); Esterification (2); C-O bond cleavage (2). VI. Graphite as a graft support Chiral synthesis (I); Imobilization enzyme electrodes (3). VII. Heteroatom-bond chemistry (7) VIII. Isotope effect (5) IX. Synthesis of ammonia (4) X. Polymerization catalysts (16).

THE RESEARCH MONOGRAPHS Table

4 indicates the uses to which the GIC's have been put in preparative

chemistry. It is based on papers published after 1976 [2] and does not include references to papers discussing reaction mechanisms or the actual status of the intercalate. Again, and somewhat arbit~aril~,

the entries have been divided

into ten broad categories, the most important numerically being "C-C bond che~ mistry" (with 37 entries), followed by "Polymerization catalysts" (16), "C-O bond chemistry" (15) and "Halogen chemistry" (14). Although "The preparation of active forms of metals" only comes 5th in number of entries, this use is, in

472

fatt,among

the most important since the metals thus prepared

Pd, Ti, Sn, formed by reduction of the corresponding solvent by an alkali metal-GIC),

(Mg, Zn, Fe, Co,

halide in an appropriate

have all been used in a large number of reac-

tions which appear in other divisions of the Table. This shows up quite well in Table 5, which gives the frequency of occurrence of the various GIC's among the research monographs

types of

: the alkali metal GIC's are, by far, the

compounds which have been found to be most useful and/or investigated tries),

followed by the Lewis acid compounds

superacid"

(23 entries)

(45 en-

and by the "solid

SbF 5 GIC (II entries).

TABLE 5 Frequency

of use of the different

types of graphite compounds

in preparative

chemistry. G/alkali metals : 45 ; G/ Lewis acids : 23 ; G/SbF~ : II ; Graphitic G/ Bronsted acids: 4; G/ mixed metals : 4; G/xenOn fluorides : 4.

oxide :5;

Referring once more to Table 4, one should note that the GIC's have been used either as "finite quantity" sources of reagent species

is consumed as the reaction progresses)

(i.e. when the intercalated

or as catalysts.

The first usa-

ge is, by far, the one most commonly met, especially where the alkali metal GIC's are concerned.

However,

taining a transition metal

the appearance

excess of alkali metal is particularly in the characteristics

of "mixed metal" catalysts

(from an intercalated

interesting

of these catalysts

con-

halide reduced in situ) and an in view of the improvement

for the low-pressure

synthesis

of

ammonia or of its derivatives. CONCLUSION The comparison of the GIC's found to be most useful in industry and in the laboratory

immediately brings to light the following

- air-stability

facts

:

and ease of handling seem to be the qualities most prized by

industry, whereas high reactivity

is the prime criterion soughtin preparative

usage; - industrially,

the GIC's do not seem so far to have found a place among the

important catalysts,

probably because of a limited thermal stability and a

fairly low rate of turnover in the applications most interesting possibilities, - in preparative

chemistry,

the preparation

of activated

(isomerizations,

which all, initially, transalkylations,

offer

etc);

the GIC's offer a wide scope of possibilities

for

reagents yet, once again, only a small number of

research teams seem to be aware of this. The extreme difference between the results obtained in industry and those reported by the academic research laboratories

could be attributed

to a

473

number of causes; approach, cases

the main one, however,

on the part of industry;

(isotope separation,

dustrial

research

interesting

seems to be a much more pragmatic

this same approach was used in a number of

preparation

of active forms of metals) by non-in-

teams : it seems to have led, each time, to most useful and

results.

REFERENCES I The list of Patents is given in these Proceedings 2 The list of Papers is given in these Proceedings

on pp. 511-517. on pp. 519-524.