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Nonstoichiometric Alkali Metal Titanium Sulfides with Channel Structure.

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Chem. 277, 156 (1954); A. Schieede, N . Wellmann, Z . Phys. Chem. B 18, I
In polar solvents ternary compounds A(solv),C, are ex(1932); M . A. M . Boersma. Catal. Rev. 10, 243 (1974): b) D. Biifaud, A. Hepectedly formed according to eq. (1); this also provides the
roid, Carbon 17. 183 (1979). and references cited therein.
first one-step entry to such compounds solvated with ar[2] a) W. Riidorff, E. Schulre. 0. Rubisch, Z. Anorg. Allg. Chem. 282,232 (1955);
enes@I. Thus, reaction of HOPG (highly oriented pyrolytic
b) I. B. Rashkou. I . M . Panayotou, Y C. Shishkoua. Carbon 17. 103 (1979); c)
graphite) with excess potassium (10% C O ( C ~ H ~ ) ( P M
in ~ ~ ) ~ J. 0.Besenhard, ibid. 14, 111 (1976).
[3] A. Herold. Bull. SOC.Chim. Fr. 22, 999 (1955).
benzene, 8 d, 25 " c ) gave the C6H6-solvatedcompounds of
[4] Manufacturer: Kropfmiihl, Passau (Germany), RFL 99.5
the 1st and 2nd stage, for which the compositions
15) Structure of the catalytically active species: H:F. Klein. J. Gross, J. M . BasK(C6H6)yC24
and K ( C ~ H ~ ) , Cand
~ Rbasal spacings of 930 and
sei, 0. Schuberf. Z . Naturforsch. B 35, 614 (1980).
161 a) C. Merie, I. Rashkou. C. Mar, J. CoIe, Mater. Sci. Eng. 31. 39 (1977); b) L.
1260 pm, respectively, are given[6b'. For the 2nd stage, howBonneiain, P. Touzain, A . Hamwi, ibid. 31, 45 (1977).
ever, we found a basal spacing of only 1245 pml'l. Although
[7] For samples prepared in presence of air we obtained basal spacings of 1260the composition and X-ray diffraction data of the nonsol1270 pm.
vated and the solvated alkali metal-graphite compounds cor[8] J. 0.Besenhard. H . - F Kiein. J. Gross, H. Mohwaid, J. J. Nickl, Synth. Metals, in press.
respond to those reported in the literature, some of the properties of the catalytically generated species are modified:
On rigorous exclusion of air, KC8 forms lustrous golden
flakes. They swell on contact with benzene, turning black.
Nonstoichiometric Alkali Metal Titanium Sulfides
"High-temperature" KC8 has been described as inert towith
Channel Structure
wards this arene[6"1.During the synthesis of KC24 we observed that a small portion of the graphite flakes adopts a
By Robert Schollhorn, Wolfgang Schramm, and Dieter
golden sheen immediately after dissolution of the potassium,
while the major part appears unchanged.
The reduction of binary transition metal chalcogenides
M,X, in alkali metal halide melts represents a suitable techCO(C~H~)(PM
in ~pentane,
5 d, 25°C) are all the flakes
nique for the preparation of ternary chalcogenides A,M,X,
uniformly dark blue and have the same basal spacing. Equa(A = alkali metal, M =transition metal, X = S, Se, Te)[']. In a
tion (2) describes the overall reaction. The cobalt complex
study on the Ti/S system we observed the formation of the
also catalyzes equilibration between phases of different deternary sulfide KO3Ti3S4,which crystallizes in a structure
grees of intercalation.
type not described so far for the alkali metal titanium sulfides. Reduction of TiS2 in a KCl melt at 1300 K with potassium metal (TiS2:K = 1 :1.7) leads to formation of a solid
K +
phase consisting of gray, needle-shaped crystals with a mepentane. 4 d, 2S°C
[cxl pentane, 1 d, 2SoC+
tallic luster; analytical data correspond to a ratio K/Ti/
S = 0.3/3/4. Direct reduction of TiSz with K in titanium vessels at 1300 K yields the same compound, which, however, is
The reaction mechanism was confirmed by X-ray powder
contaminated by additional phases. Guinier powder diadiagrams for nonsolvated K, Rb, and Cs compounds: After
grams and Weissenberg single crystal photographs showed
short reaction times only the compounds of the 1st stage
Ko3Ti3S4to be hexagonal (a=950.5, c=341.4 pm, 2=2).
(AC,) were generally observed along with unchanged graphThe structure was determined from automatic diffractometer
ite. On prolonged reaction times compounds of higher stages
data (MoK,, 590 symmetry independent reflections, space
could be prepared with appropriate quantities of potassium.
group P6,/m(CZh). There are two different sulfur positions
Thus, intercalation according to reaction (1) is kinetically
in the unit cell; Ti and S(2) atoms occupy the position 6 h,
controlled. Nucleation of the AC, phases appears to be the
whereas the S(l) atoms occupy the positions 2(c) (for posirate determining step. In contrast, electrochemical intercalational parameters see Table 1). With Ti and S parameters
tion is thermodynamically controlled, i. e. the reaction proonly the structure model gave an agreement factor of
ceeds starting from graphite via higher stages to the 1st stage
R = 0.081. In a subsequent difference Fourier synthesis maxias the final
ma could be detected on the positions 2a (0, 0, 1/4) and 2b
The unusual reactivity of catalytically generated KC8 is
(0, 0, 0). With the assumption of a statistical distribution of
probably attributable to disorder effects. In general, solid
K' on these positions R showed a minimum at 0.30(5) K/
state reactions performed at room temperature lead to less
Ti3S4;the agreement factor was R = 0.065.
ordered, and hence frequently more "active" products than
high temperature reactions.
Table 1. Positional parameters of Ti and S atoms in K,,,Ti,S,.
Catalytic intercalation in solution permits the first transformation of highly oriented carbon fibers into good electriX
cal conductors by conversion into KC,'*'.
Preliminary experiments have shown that solution interTI
1 /4
calation of alkali metals can also be accomplished with metal
chalcogenides having layer structures (MoS2,WS2). Catalytic
reductions with Li are also feasible. Thus gray antimony (1.7
(10 ml), 48 h,
g, 1% C O ( C ~ H , ) ( P M ~in~ )tetrahydrofuran
The structure can be described in terms of distorted TiS6
25 "C) quantitatively yields the cubic low-temperature phase
octahedra joining common faces and edges to form a threeP-Li,Sb. The potential of these highly reducing solutions is
dimensional framework which is characterized by wide
estimated at 2.5-3 V.
channels parallel to the hexagonal c axis which are incom-
Received: December 1 I . 1979 [Z 482 IE]
German version: Angew. Chem. 92,476 (1980)
CAS Registry numbers:
KC,. 12081-88-8; RbCx. 12193-29-2; CsC8, 12079-66-2 Co(CIH4)(PMeA
111 a) W. Rudorff, Adv. Inorg. Chem. Radiochem. 1. 224 (1959); G. R . Hennig,
Progr. Inorg. Chem. I, 125 (1959); W . Riidor/f, E. Schulze. Z . Anorg. Allg
0 Verlag Chemie, GmbH. 6940 Weinheim, 1980
pletely occupied by potassium atoms (Fig. 1). The Ti atoms
are displaced from the center of the TiSh octahedra so that
[*) Prof. Dr. R. Schollhorn, Dipl.-Chem. W. Schramm. Pnv.-Doz. Dr. D.
Anorganisch-chemisches lnstitut der Universitat
Gievenbecker Weg 9, D-4400 Munster (Germany)
0570-0833/80/0606-492 $ 02.50/0
Angew. Chem. I n i . Ed. Engl. 19 (1980) No. 6
Fig. 1 Scheme of &a
,Ti& structure (cross section perpendicular to channel
axis. circles indicate positions of K Q ions).
metal-metal zig-zag chains are formed; the Ti-Ti distance
of 315.2(3) pm is close to that in titanium metal. The S(1)
atoms are surrounded by six Ti atoms at the corners of a trigonal prism, while the S(2) atoms form the “channel wall”
and have strongly asymmetric environment. Similarly to
A,Nb3S4 and A,Nb3Se4f31the ternary sulfide
I?, 3Ti3S4can thus be considered as a partially filled up structural version of the Nb3Se4typer4I.
Chalcogenides with channel type structure (e.g. Nb3S4,
Mo6SX)have recently been shown by us to undergo reversible
topotactic redox reactions at ambient temperature by electron/ion tran~fer’~.~].
Like layered structures[6]they are of interest regarding their application as reversible electrodes in
high density batteries. We found that the ternary titanium
sulfide phase described here contains highly mobile K @ions
and is able to react in a similar way according to:
tion K,,3Ti3S4is obtained at the upper phase limit. The reduction of Ti3S4in organic Li@/propylenecarbonate electrolyte results in the reversible formation of LioxTi3S4;the steps
appearing in the potential/charge transfer curve (Fig. 2) indicate the existence of intermediate phases. As a consequence of the rigid host lattice matrix changes in the lattice
parameters with x are very small.
The ternary phases TlV5Sx and @-CuOSV2O5,
both of
which are characterized by channel type structures[7], revealed a topotactic redox behavior basically similar to that of
KxTi3S4.The lattice channels in these compounds are occupied by T1 and Cu atoms, respectively, which according to
our results are mobile at ambient temperature. Oxidation of
TlV& results in the formation of V5Sx(residual T1 content
corresponding to Tlo07V5S8)with the monoclinic lattice parameters u = 1139.9 pm, b=664.5 pm, c=1129.3 pm,
@=91.49”. On cathodic reduction in aqueous or organic
electrolytes VsSs may take up reversibly mono- and bivalent
cations with an ionic radius up to cu. 140 pm; for Li@/propylene carbonate a maximum degree of reduction corresponding to LilV5SRwas observed (Fig. 2).
On anodic oxidation of p-Cuo5V205a binary metastable
phase @-V205is obtained after a transfer of l.OeO/
CU,.,~V~O~;the upper phase limit on cathodic reduction of
V205in Cu2@/H20electrolyte is equivalent to Cuo65V205.
For Li,V205 phases, which can be prepared, e. g., from Lie/
propylene carbonate, the maximum guest ion content corresponds to Li, ,VZOs(Fig. 2). In contrast to A,M3X4 phases
the vanadium sulfide and oxide phases show clear changes in
lattice parameters with the guest cation content. This reflects
a higher flexibility of the host lattice matrix due to lower
symmetry and less dense lattice framework.
Anodic oxidation of polycrystalline K0.3Ti3S4electrodes in
K @ / H 2 0electrolyte yields Ti3S4, while on cathodic reduc-
Received: December 20, 1979 [Z 483 IE]
German version: Angew. Chem. 92. 477 (1980)
CAS Registry numbers:
KO>Ti&. 39306-7 1-3; Ti&, 12067-25-3; Nb3S4, 12266-24-9; V5Sx. 12067-28-6;
P-V,Os, 1314-62-1
M. Kiimpers, D.Plorin. J. Less-Common Metals 58, 55 (1978);
R. Schollhorn, A. Lerf, J. Less-Common Metals 42, 89 (1975).
[21 K. Klepp, H . Boiler, Abstracts o f the 6th Int. Conf on Solid Compounds of
the Transition Elements 66 (1979).
[3] R. Schollhorn, W. Schramm, 2.Naturforsch. 34146, 697 (1979).
[41 R. Huisman, F Kadijk, A. J . Wagner, F. Jellinek, Acta Cryst. B 24, 1614
( 1968); K. Selle, A. Kjekshus, Acta Cryst. 17. 1568 (1 964).
[5] R. Schollhorn, M. Kumpers, A. Le& E. Umlouf, W Schmidt, Mat. Res. Bull.
14, 1039 (1979); R. Schollhorn, M . Kiimpers, J. 0. Besenhard, Mat. Res. Bull.
12,781 (1977).
[61 M. S. Whirringham, Progr. Solid State Chem. 12. 41 (1978); J. 0. Besenhard,
R. Schbllhorn, J. Power Sources 1. 267 (1977).
171 L. Fournes. M. Vlasse, M. Saux, Mat. Res. Bull. 12, 1 (1977); J. Galy, D. Lauaud, A. Casalor, P. Hagenmuller, J. Solid State Chem. 2, 531 (1970).
[ l ] R. Schollhorn,
Fig 2 Potential/charge transfer curves for topotactic cathodic reduction of
Ti&,. Nb.& V& and p-V,Os in 1 M Li*/propylene carbonate at 298 K; charge
transfer x = e“/unit formula.
Angew. Chem. Int. Ed. Engl. 19 (1980) No. 6
0 Verlag Chemie, GmbH, 6940 Weinheim, 1980
0570-0833/80/0606-493 S 02.50/0
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channel, titanium, structure, sulfide, metali, nonstoichiometry, alkali
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