Abstract
The lithium-sulfur battery is a compelling energy storage system because its high theoretical energy density exceeds Li-ion batteries at much lower cost, but applications are thwarted by capacity decay caused by the polysulfide shuttle. Here, proof of concept and the critical metrics of a strategy to entrap polysulfides within the sulfur cathode by their reaction to form a surface-bound active redox mediator are demonstrated. It is shown through a combination of surface spectroscopy and cyclic voltammetry studies that only materials with redox potentials in a targeted window react with polysulfides to form active surface-bound polythionate species. These species are directly correlated to superior Li-S cell performance by electrochemical studies of high surface area oxide cathodes with redox potentials below, above, and within this window. Optimized Li-S cells yield a very low fade rate of 0.048% per cycle. The insight gained into the fundamental surface mechanism and its correlation to the stability of the electrochemical cell provides a bridge between mechanistic understanding and battery performance essential for the design of high performance Li-S cells.
Original language | English |
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Article number | 1501636 |
Journal | Advanced Energy Materials |
Volume | 6 |
Issue number | 6 |
DOIs | |
State | Published - Mar 23 2016 |
Externally published | Yes |
Funding
This research was supported by the BASF International Scientific Network for Electrochemistry and Batteries. L.F.N. also thanks NSERC for generous support via a Canada Research Chair. L.F.N. thanks Ralf Steudel (TU Berlin) for helpful discussions. The spelling of author name Quan Pang was updated on April 4, 2016.
Keywords
- Li-S batteries
- polythionate
- redox potential
- sulfur hosts
- transition metal oxides