Influence of synthesis parameters on g-C 3 N 4 polysulfides trapping: A systematic study

DANIELE VERSACI; MELINA COZZARIN; JULIA AMICI; CARLOTTA FRANCIA; EZEQUIEL P.M. LEIVA; VISINTIN A.; SILVIA BODOARDO

MATERIALS TODAY

ELSEVIER SCI LTD

Año: 2021 vol. 25 p. 101169 - 101182

1369-7021

Beyond Li-ion batteries, one of the most promising technology is the Lithium-Sulphur (Li-S) not only for its higher theoretical energy density (about 2600 Wh kg −1 ) but because sulfur is relatively inexpensive and non-toxic. However, the Li-S battery suffers from ?shuttle effect?of polysulfides. Thus, restricting shuttling means increasing cell performance and durability. DFT calculations showed that graphitic car- bon nitride (g-C 3 N 4 ) exhibits strong interactions with Li 2 S ( e.g. superior to graphene-like carbon) and acts as polysulfides trapping agent. In this work, the role of g-C 3 N 4 , synthetized from different pre- cursor and at different polycondensation temperatures was systematically studied, using a double layer approach for the electrode preparation, which ensures direct interaction between g-C 3 N 4 and soluble lithium-polysulfides. This systematic study confirms the importance of the morphological and superficial properties of the material. In particular, carbon nitride from urea precursor remarkably improves the performance of the sulphur cathode, increasing the specific capacity of the cell by 25% and improving its useful life over 500 cycles. According to the morphological characterization and the XPS analysis, benefits are achieved from polycondensation of urea at 550 °C. The obtained g-C 3 N 4 shows the highest proportion of -NH 2 species on the surface, which favours the interaction with polysulfides.