Design and synthesis of an interfacial layer of the polysulfide immobilizer for lithium-sulfur batteries by the one-pot hydrothermal method

Abstract

To overcome the low electrical conductivity and large volume expansion of a sulfur cathode during electrochemical reactions, a composite of SnO2 nanoparticles with 5-10 nm size dispersed on reduced graphene oxide (rGO) sheets and sulfur (rGO/SnO2/S) was prepared by a one-pot hydrothermal process. This cathode shows 1.2-fold higher interfacial Li ion diffusivity (1.8x10(-12) cm(2) s(-1)) than that of an rGO/S cathode (1.5x10(-12) cm(2) s(-1)). This improvement is attributed to the synergistic effect of the hybrid matrix comprising rGO sheets and SnO2. The rGO sheets provide a fast electron pathway and accommodate a large amount of sulfur. Moreover, the dispersed SnO2 nanoparticle acts as an immobilizer to prevent the dissolution of polysulfide during the electrochemical reaction. The synthesized rGO/SnO2/S cathode also exhibits an electrical resistivity of 4.4x10(-1) Omega cm due to interfacial modification. Further, it exhibits improved electrochemical performance with an initial discharge capacity of 1591.57 mA h g(-1) at 0.1 C, which stabilizes to 606.98 mA h g(-1) at 0.2 C after 100 cycles. In addition, it shows a discharge capacity of 575.45 mA h g(-1) even at a high current density of 5 C.