1 research outputs found
Structural Transformation in a Sulfurized Polymer Cathode to Enable Long-Life Rechargeable Lithium–Sulfur Batteries
Sulfurized polyacrylonitrile (SPAN) represents a class
of sulfur-bonded
polymers, which have shown thousands of stable cycles as a cathode
in lithium–sulfur batteries. However, the exact molecular structure
and its electrochemical reaction mechanism remain unclear. Most significantly,
SPAN shows an over 25% 1st cycle irreversible capacity loss before
exhibiting perfect reversibility for subsequent cycles. Here, with
a SPAN thin-film platform and an array of analytical tools, we show
that the SPAN capacity loss is associated with intramolecular dehydrogenation
along with the loss of sulfur. This results in an increase in the
aromaticity of the structure, which is corroborated by a >100×
increase in electronic conductivity. We also discovered that the conductive
carbon additive in the cathode is instrumental in driving the reaction
to completion. Based on the proposed mechanism, we have developed
a synthesis procedure to eliminate more than 50% of the irreversible
capacity loss. Our insights into the reaction mechanism provide a
blueprint for the design of high-performance sulfurized polymer cathode
materials