Effect of carbon-sulphur bond in a sulphur/dehydrogenated polyacrylonitrile/reduced graphene oxide composite cathode for lithium-sulphur batteries

A S/DPAN (dehydrogenated polyacrylonitrile) composite shows promising electrode performances as a cathode material for Li-S batteries though its electric conductivity is insufficient for high rate tests. In an attempt to enhance the electric conductivity, the S/DPAN composite is attached on reduced graphene oxide (rGO) sheets via self-assembling modification. As a result, the conductivity improves to ∼10⁻⁴ S cm⁻¹, and the S/DPAN/rGO composite thereby delivers approximately 90% of the theoretical capacity of sulphur at a rate of 0.2C (0.34 A g⁻¹) over 700 mAh (g-S)⁻¹ even at 2C (3.4 A g⁻¹). We first report on the C[sbnd]S bond between sulphur and DPAN in a composite that maintains the bond even after an extensive cycling test, as confirmed by time-of-flight secondary-ion mass spectroscopy (ToF-SIMS). These synergistic effects enable facile electron transport such that the S/DPAN/rGO composite electrode is able to maintain superior electrode performances.