Synergy between Interconnected Porous Carbon-Sulfur Cathode and Metallic MgB2 Interlayer as a Lithium Polysulfide Immobilizer for High-Performance Lithium-Sulfur Batteries

摘要

Lithium-sulfur (Li-S) batteries are the potential candidates for developing high-energy-density electric vehicles. However, poor electrical conductivity of sulfur/discharged products, low active material utilization, shuttle mechanism, and poor cycle life remain the major challenges for the development of Li-S batteries. Herein, we report the nitrogen-doped highly porous carbon (NC) with interconnected pores as the sulfur host (NC-S), which is synthesized by a facile one-step process without using any template and activation agents. The highly interconnected porous structure of NC can accommodate a high amount of sulfur loading and provide space for sulfur volume expansion during redox reactions. Besides, to mitigate the lithium polysulfide dissolution and shuttle mechanism, metallic and polar magnesium diboride (MgB_(2)) is used as an interlayer. Consequently, the NC-S/MgB_(2) cathode delivers higher specific capacity, rate capability, and excellent cyclic stability than the NC-S cathode and bulk sulfur cathode with MgB_(2) interlayer. The lithium polysulfide (LPS) adsorption test shows that MgB_(2) has strong chemisorption toward lithium polysulfides, which can inhibit the dissolution of LPS into the electrolyte and minimizes the shuttle effect. The dynamic electrochemical impedance spectroscopy analysis investigates the electrochemical reaction kinetics of the NC-S/MgB_(2) cathode during the charging and discharging processes. Overall, this work demonstrates that the synergy between the nitrogen-doped porous carbon-sulfur host and polar metallic MgB_(2) improves the performance of the Li-S battery, which is beneficial for the development of high-energy-density batteries for the future.