Electrochemical evaluation of different graphene/sulfur composite synthesis routes in all-solid-state lithium-sulfur batteries

The preparation of different cathode composites with intimate contact between the components is of great importance to obtain batteries with better electrochemical performance. Among different cathode systems, graphene-sulfur composites are widely utilized in lithium-sulfur batteries and their electrochemical performances are directly linked to syntheses methods. In this study, graphene-sulfur composite cathodes were prepared by three distinct routes and their performances were evaluated in all-solid-state lithium-sulfur batteries where the lithium and Li7P3S11 were utilized as anode and solid electrolyte, respectively. Our results indicate that cathodes prepared by solution-based techniques were found to impart higher capacity and cycling stability compared with cathode prepared by the melt-diffusion method. Better performance was attributed to fine and homogeneously distributed particles obtained in cathodes prepared by solution-based techniques. Besides, higher capacity was acquired in the cathodes where the sulfur was obtained through reduction from Na2S2O3 instead of utilizing sulfur in elemental powder form. Among three different cathodes synthesized by different routes, the best performance was gained in the cathode prepared by sulfur-amine chemistry method where the sulfur was obtained by reduction from Na2S2O3 with 970 mAh g-1 and 795 mAh g-1 initial and after 200 cycles discharge capacity respectively. Our results indicate the significance of particle size and intimate contact between components on the electrochemical performance of the sulfur-based cathodes and the synthesis route to follow for high-performance all-solid-state lithium-sulfur batteries.