Empowering Low-Temperature Lithium-Sulfur Batteries: Unlocking the Potential of Transition Metal Alloy-Based Cathode Materials.

ABSTRACT

At low temperatures, lithium-sulfur (Li-S) batteries have poor kinetics, resulting in extreme polarization and decreased capacity. In this study, we investigated the electrochemical performance of Li-S batteries utilizing transition metal alloy-based cathode materials. Specifically, binary transition metal alloys (FeNi, FeCo, and NiCo) are integrated into a porous carbon nanofiber (CNF) matrix as composite cathode material. Our findings reveal that alloying metallic Ni with Fe in the FeNi@CNFs composite enhances the catalytic conversion of sulfur species, mitigating the shuttle effect and improving battery performance even under low temperatures. Li-S batteries employing a Li2S6/FeNi@CNFs cathode exhibited a significantly high initial discharge capacity of 1655 mAh g-1 at 0.1 C. Even at the higher current density of 10 C, the Li2S6/FeNi@CNFs composite can still reach an ultrahigh specific capacity of 828 mAh g-1. In addition, Li2S6/FeNi@CNFs demonstrated exceptional initial discharge capacities of 890.5 and 382.7 mAh g-1 at 0.1 C under -20 and -40 °C, respectively. With an initial capacity of 392.02 mAh g-1 and a capacity retention rate of 88.86% (after 60 cycles) at 0.2 C, the conversion of LiPSs in Li2S6/FeNi@CNFs is significantly enhanced even at ultralow temperatures of -40 °C. The findings of this study hold significant implications for the advancement of extremely low-temperature Li-S batteries.