Lakhasly

at least keep up with the consumption by electrochemical reduction.This increase is fueled by both the dissolution of solid sulfur and the subsequent reduction of S2-x species producing shorter, but also more numerous molecules.Once no more sulfur dissolves into the electrolyte (or only at comparatively low rates, see above), the total concentration of polysulfides levels off.The continuous precipitation of Li2S from the electrolyte is balanced by the progressive reduction of longer S2-x species down to S2-4 .Later during the discharge, when less longer species are available, most reduction products precipitate immediately, reducing the total amount of dissolved polysulfides.5.23 contains the most relevant information about the liquid electrolyte system, which is also confirmed by various experimental characterization techniques, see e.g. Ref.Hence, there is a constant flow of sulfur in its highest oxidation state into the electrolyte, stabilizing a steady-state equilibrium, which in turn results in a constant cell voltage.In that situation, the voltage decreases continuously as does the average oxidation state of the dissolved S2-x polysulfide species.Therefore, each electron extracted from the system directly lowers all concentrations simultaneously, in the end precipitating 1/16 molecule of S8 per electron.The shorter polysulfides are very short lived; they are fully reduced to S2- and rapidly precipitate as solid Li2S.Depending on the discharge cutoff voltage, the total concentration may either become as low as that of a fully charged cell or remain close to the plateau level.As indicated by the solid lines in Fig.[P4].

at least keep up with the consumption by electrochemical reduction. Hence, there is
a constant flow of sulfur in its highest oxidation state into the electrolyte, stabilizing a
steady-state equilibrium, which in turn results in a constant cell voltage. If the reduction is much faster than the dissolution, the steady-state value for the concentration
of S8(ds) is close to zero. More sulfur may still enter the system, but it will be reduced
almost immediately. In that situation, the voltage decreases continuously as does the
average oxidation state of the dissolved S2−x polysulfide species. As indicated by the
solid lines in Fig. 5.23, their concentration increases more than fourfold during the first
half of the discharge. This increase is fueled by both the dissolution of solid sulfur and
the subsequent reduction of S2−x
species producing shorter, but also more numerous
molecules. Once no more sulfur dissolves into the electrolyte (or only at comparatively
low rates, see above), the total concentration of polysulfides levels off. The continuous
precipitation of Li2S from the electrolyte is balanced by the progressive reduction of
longer S2−x
species down to S2−4
. The shorter polysulfides are very short lived; they
are fully reduced to S2− and rapidly precipitate as solid Li2S. Later during the discharge, when less longer species are available, most reduction products precipitate
immediately, reducing the total amount of dissolved polysulfides. Depending on the
discharge cutoff voltage, the total concentration may either become as low as that of a
fully charged cell or remain close to the plateau level. Only for the quasistatically slow
discharge the plateau does not exist, since the ratio of each pair of S2−x
species is always
equilibrated, i.e. constant. Therefore, each electron extracted from the system directly
lowers all concentrations simultaneously, in the end precipitating 1/16 molecule of S8
per electron. As outlined by the above discussion, Fig. 5.23 contains the most relevant
information about the liquid electrolyte system, which is also confirmed by various
experimental characterization techniques, see e.g. Ref. [P4].