Poly(thiourea triethylene glycol) as a multifunctional binder for enhanced performance in lithium-sulfur batteries

A mechanically strong binder with polar functional groups could overcome the dilemma of the large volume change during charge/discharge processes and poor cyclability of lithium-sulfur batteries (LSBs). In this work, for the first time, we report the use of poly(thiourea triethylene glycol) (PTTG) as a multifunctional binder for sulfur cathodes to enhance the performance of LSBs. As expected, the PTTG binder facilitates the high performance and stability delivered by the Sulfur-PTTG cathode, including a higher reversible capacity of 825 mAh g−1 at 0.2 C after 80 cycles, a lower capacity fading (0.123% per cycle) over 350 cycles at 0.5 C, a higher areal capacity of 2.5 mAh cm−2 at 0.25 mA cm−2, and better rate capability of 587 mAh g−1 at 2 C. Such superior electrochemical performances could be attributed to PTTG's strong chemical adsorption towards polysulfides which may avoid the lithium polysulfide shuttle effect and excellent mechanical characteristics which prevents electrode collapse during cycling and allows the Sulfur-PTTG electrode to maintain robust electron and ion migration pathways for accelerated redox reaction kinetics.