Si. Tobishima et al., STUDY ON THE REDUCTION SPECIES OF SULFUR BY ALKALI-METALS IN NONAQUEOUS SOLVENTS, Electrochimica acta, 42(6), 1997, pp. 1019-1029
Rechargeable cells with a sulfur cathode, a lithium anode and a nonaqu
eous electrolyte operating at ambient temperature have been extensivel
y studied as a possible application of sulfur combined with nonaqueous
solvent. However, the behavior of the chemical species formed by the
reduction of sulfur with alkali metals in nonaqueous solvent has not y
et been clarified. In this report, sulfur is reduced in tetrahydrofura
n (THF) by alkali metals (M: Na, K, Li and Cs), by anthracene radical
anions or by diphenylethylene dimer dianions with alkali metal counter
cations mainly under the experimental condition of [S-s]/[M] > 0.25.
The system produced by the reduction is the yellow solution consisting
of polysulfide dianions (S-m(2-), m > 1) and radical anions (S-n(radi
cal anion), n > 1) which changes into a blue solution by the addition
of hexamethylphosphoric triamide with a much higher polarity than THF.
The influence of the kind of alkali metal, the temperature and the ad
dition of solvents such as crown ether on the behavior of the chemical
species formed are examined by ultraviolet (uv)-visual electronic spe
ctra, electron spin resonance (ESR) spectra and Raman spectra measurem
ents. In addition, gamma-irradiation with Co-60 was carried out to red
uce sulfur in glassy solid 2-methyl-THF at -196 degrees C. Furthermore
, the reaction between the yellow solution and aliphatic bromide is in
vestigated. As a result, it is revealed that the yellow species is S-4
(2-), the blue species is S-3(radical anion) and several polysulfide d
ianions and radial anions are in a state of equilibrium. Copyright (C)
1997 Elsevier Science Ltd.