The use of a ternary metal sulfide loading on carbon fibers as the sulfur host for high performance low-temperature lithium sulfur batteries

Abstract

The use of lithium-sulfur (Li-S) batteries is limited by sulfur redox reactions involving multi-phase transformations, especially at low-temperatures. To address this issue, we report a material (FCNS@NCFs) consisting of nitrogen-doped carbon fibers loaded with a ternary metal sulfide ((Fe, Co, Ni)₉S₈) for use as the sulfur host in Li-S batteries. This material was prepared using transfer blot filter paper as the carbon precursor, thiourea as the source of nitrogen and sulfur, and FeCl₃·6H₂O, CoCl₂·6H₂O and NiCl₂·6H₂O as the metal ion sources. It was synthesized by an impregnation method followed by calcination. The nitrogen doping significantly increased the conductivity of the host, and the metal sulfides have excellent catalytic activities. Theoretical calculations, and adsorption and deposition experiments show that active sites on the surface of FCNS@NCFs selectively adsorb polysulfides, facilitate rapid adsorption and conversion, prevent cathode passivation and inhibit the polysulfide shuttling. The FCNS@NCFs used as the sulfur host has excellent electrochemical properties. Its initial discharge capacity is 1639.0 mAh g⁻¹ at 0.2 C and room temperature, and it remains a capacity of 1255.1 mAh g⁻¹ after 100 cycles. At −20 ~C, it has an initial discharge capacity of 1578.5 mAh g⁻¹ at 0.2 C, with a capacity of 867.5 mAh g⁻¹ after 100 cycles. Its excellent performance at both ambient and low temperatures suggests a new way to produce high-performance low-temperature Li-S batteries.

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