Fabrication and Characterization of High Capacity and Long Cycle Life Lithium-Sulfur Battery Using Porous Material As a Polysulfide Adsorbent

The need for large-scale energy storage, improved safety, and sustainable transport are driving research into alternative battery technologies with higher specific energies. Rechargeable Li-S batteries have high capacities (1675 mAh g-1) and theoretical energy densities as high as 2600 Wh kg-1 making them promising candidates for the next-generation of energy storage systems. However, due to its insulating nature, polysulfide dissolution and poor cycle life, it has been challenging to achieve the existing technology requirement. Herein we choose porous carbon as conducting agent and TiO2 nanotube as polysulfide adsorbent and forming hybrid nanostructured materials to overcome active material utilization and polysulfide dissolution problems. The porous host materials for sulfur was produced by a low cost, hydrothermal and annealing process with one step green synthesis approach. The process is facile, cheap, scalable and environmental friendly. The material was characterized and examined by XRD, BET, XPS, SEM, TEM, Raman, TGA, CV, EIS and galvanostatic charge-discharge tastes. It is found that the materials are highly porous and show both the characteristics of microporous and mesoporous behavior and contain large pore volume to impregnate large amount of sulfur. Moreover, the microporous carbon can effectively adsorb smaller sulfur (S2-4) molecules in their narrow pores with increasing the electrical conductivity of the cathode by decreasing the resistance of sulfur and enhance active material utilization. Meanwhile, mesoporous carbon doped TiO2 nanotube were placed on the surface to prevent the overflow of sulfur as well as the dissolution of polysulfides in the electrolyte effectively and improve the strength of the entire electrode thereby enhancing the electrochemical performance. As a result, using the porous host-sulfur nanocomposite as a cathode material, we demonstrate excellent cycle stability with initial discharge capacity of 916 mAh g-1 with coulombic efficiency of over 98.6% at a current density of 0.2 C after 140 cycles. This improved performance is due to the unique design of the porous host materials and the good dispersion of sulfur in the narrow pores of microporous host with TiO2 support. Thus, our approach is a promising strategy to control the dissolution of polysulfides and cycle life problems of the battery. Key words: porous materials, lithium-sulfur battery, polysulfide adsorbent, cycle stability