TY - JOUR
T1 - Probing the lithium-sulfur redox reactions
T2 - A rotating-ring disk electrode study
AU - Lu, Yi Chun
AU - He, Qi
AU - Gasteiger, Hubert A.
PY - 2014/3/20
Y1 - 2014/3/20
N2 - Detailed mechanistic understanding of sulfur redox reactions is critical for developing efficient and stable lithium-sulfur batteries. Here, we employ the rotating-ring disk electrode technique to probe the reaction kinetics and reaction mechanism of lithium-sulfur redox reactions in dimethyl sulfoxide and 1,3-dioxolane:1,2-dimethoxyethane. We quantitatively determine the number of electrons involved in the reduction reactions and the specific activity of sulfur reduction reactions. We show that the electrochemical steps of sulfur reduction exhibit fast reaction kinetics and only account for approximately one-quarter of the total capacity (i.e., ≈4 e-/S8) within the short reaction time in RRDE experiments (seconds). The complete conversion of sulfur to Li2S can only be accomplished via chemical (i.e., potential-independent) polysulfide recombination/dissociation reactions that generate electrochemically reducible polysulfides with long reaction time (hours) in a closed battery cell. The influence of the solvent's solvation power on the rate capability of the sulfur reduction/oxidation processes and the implications for lithium-sulfur batteries will be discussed.
AB - Detailed mechanistic understanding of sulfur redox reactions is critical for developing efficient and stable lithium-sulfur batteries. Here, we employ the rotating-ring disk electrode technique to probe the reaction kinetics and reaction mechanism of lithium-sulfur redox reactions in dimethyl sulfoxide and 1,3-dioxolane:1,2-dimethoxyethane. We quantitatively determine the number of electrons involved in the reduction reactions and the specific activity of sulfur reduction reactions. We show that the electrochemical steps of sulfur reduction exhibit fast reaction kinetics and only account for approximately one-quarter of the total capacity (i.e., ≈4 e-/S8) within the short reaction time in RRDE experiments (seconds). The complete conversion of sulfur to Li2S can only be accomplished via chemical (i.e., potential-independent) polysulfide recombination/dissociation reactions that generate electrochemically reducible polysulfides with long reaction time (hours) in a closed battery cell. The influence of the solvent's solvation power on the rate capability of the sulfur reduction/oxidation processes and the implications for lithium-sulfur batteries will be discussed.
UR - http://www.scopus.com/inward/record.url?scp=84897858628&partnerID=8YFLogxK
U2 - 10.1021/jp500382s
DO - 10.1021/jp500382s
M3 - Article
AN - SCOPUS:84897858628
SN - 1932-7447
VL - 118
SP - 5733
EP - 5741
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 11
ER -