TY - JOUR
T1 - Cation-Directed Selective Polysulfide Stabilization in Alkali Metal-Sulfur Batteries
AU - Zou, Qingli
AU - Liang, Zhuojian
AU - Du, Guan Ying
AU - Liu, Chi You
AU - Li, Elise Y.
AU - Lu, Yi Chun
PY - 2018/8/29
Y1 - 2018/8/29
N2 -
Alkali metal sulfur redox chemistry offers promising potential for high-energy-density energy storage. Fundamental understanding of alkali metal sulfur redox reactions is the prerequisite for rational designs of electrode and electrolyte. Here, we revealed a strong impact of alkali metal cation (Li
+
, Na
+
, K
+
, and Rb
+
) on polysulfide (PS) stability, redox reversibility, and solid product passivation. We employed operando UV-vis spectroscopy to show that strongly negatively charged short-chain PS (e.g., S
4
2-
/S
3
2-
) is more stabilized in the electrolyte with larger cation (e.g., Rb
+
) than that with the smaller cation (e.g., Li
+
), which is attributed to a stronger cation-anion electrostatic interaction between Rb
+
and S
4
2-
/S
3
2-
owing to its weaker solvation energy. In contrast, Li
+
is much more strongly solvated by solvent and thus exhibits a weaker electrostatic interaction with S
4
2-
/S
3
2-
. The stabilization of short-chain PS in K
+
-, Rb
+
-sulfur cells promotes the reduction of long-chain PS to short-chain PS, leading to high discharge potential. However, it discourages the oxidation of short-chain PS to long-chain PS, leading to poor charge reversibility. Our work directly probes alkali metal-sulfur redox chemistry in operando and provides critical insights into alkali metal sulfur reaction mechanism.
AB -
Alkali metal sulfur redox chemistry offers promising potential for high-energy-density energy storage. Fundamental understanding of alkali metal sulfur redox reactions is the prerequisite for rational designs of electrode and electrolyte. Here, we revealed a strong impact of alkali metal cation (Li
+
, Na
+
, K
+
, and Rb
+
) on polysulfide (PS) stability, redox reversibility, and solid product passivation. We employed operando UV-vis spectroscopy to show that strongly negatively charged short-chain PS (e.g., S
4
2-
/S
3
2-
) is more stabilized in the electrolyte with larger cation (e.g., Rb
+
) than that with the smaller cation (e.g., Li
+
), which is attributed to a stronger cation-anion electrostatic interaction between Rb
+
and S
4
2-
/S
3
2-
owing to its weaker solvation energy. In contrast, Li
+
is much more strongly solvated by solvent and thus exhibits a weaker electrostatic interaction with S
4
2-
/S
3
2-
. The stabilization of short-chain PS in K
+
-, Rb
+
-sulfur cells promotes the reduction of long-chain PS to short-chain PS, leading to high discharge potential. However, it discourages the oxidation of short-chain PS to long-chain PS, leading to poor charge reversibility. Our work directly probes alkali metal-sulfur redox chemistry in operando and provides critical insights into alkali metal sulfur reaction mechanism.
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U2 - 10.1021/jacs.8b04536
DO - 10.1021/jacs.8b04536
M3 - Article
C2 - 30064216
AN - SCOPUS:85052338652
VL - 140
SP - 10740
EP - 10748
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 34
ER -