3D Electrode architecture of high surface area carbon-sulfur composite as high energy density cathode for lithium-sulfur battery

Abstract

High-performance lithium-sulfur (Li-S) battery is a potential candidate for next-generation energy storage systems to mitigate the ever-rising energy demand. The low cost of sulfur, eco-friendliness, and high energy density compared to the emerging LIBs (450 Wh kg−1 for Li-S batteries vs. 150–250 Wh kg−1 for LIBs) inspires the research on Li–S technology. In this work, carbon fiber-based free-standing electrodes are fabricated using a high surface area carbon-sulfur (HSAC-S) composite synthesized by the melt-diffusion method. The porous carbon host facilitates high sulfur loading in the void spaces and benefits the electrolyte infiltration and Li-ion diffusivity. Electrochemistry reveals that HSAC-S@CF exhibits an enhanced discharge capacity of 1000 mAh g−1 (750 mAh g−1 for HSAC-S@Al) in the 2nd cycle and maintains 620 mAh g−1 capacity till the 100th cycle. In comparison, HSAC-S@Al delivers 350 mAh g−1 capacity at the 80th cycle at a current density of 100 mA g−1. Besides, at 200 mA g−1, the free-standing electrode HSAC-S@CF delivers an initial capacity of 600 mAh g−1 (498 mAh g−1 HSAC-S@Al) and retains 497 mAh g−1 till the 100th cycle with 83 % capacity retention (60 % HSAC-S@Al). HSAC-S@CF displays good C-rate performance at a higher current density of 1 A g−1 (408 mAh g−1) and 1.5 A g−1 (346 mAh g−1). The conductive CF backbone provides mechanical stability, accommodates volume changes, and reduces particle agglomeration. The internal void spaces of the CF matrix act as a reservoir for polysulfides and minimize the shuttling effect. This work represents an effective cathode modification approach to understand the impact of high surface area carbon additives on free-standing 3D electrode architecture and its interaction with sulfur for improving the capacity and cycling stability in Li-S batteries.