Rational design of core–shell nanofibers structure integrated with cobalt sulfide catalyst for high-performance lithium-sulfur batteries

Abstract

The advancement of lithium-sulfur (Li-S) batteries were severely limited by the notorious “shuttle effect” and low electrochemical conversion of lithium polysulfides (LiPSs). Designing efficient electrocatalysts with core–shell structure for accelerating LiPSs conversion and manipulating redox kinetics is important. We designed an integrated sulfur cathode composed of titanium oxide-modified carbon nanofibers coated with a hollow carbon layer and integrated with cobalt sulfide nanosheets (TCF@C-CoS). TCF@C-CoS composite was fabricated through the template method and the hydrothermal method. Not only hollow structure establishes optimized channels for electron/ion conduction but also the CoS nanosheets create abundant electrochemically active sites, significantly enhancing LiPSs adsorption. Notably, the structure synergistically combining three key functionalities: physical confinement via the hollow carbon framework, polar adsorption enabled by TiO₂, and catalytic conversion driven by CoS nanosheets. Therefore, the optimized Li-S batteries achieve an outstanding initial specific capacity of 1036.56 mAh g⁻¹, maintain the capacity decay rate of 0.04 % per cycle. Additionally, even under the conditions including a sulfur loading of 7.30 mg cm⁻² and lean electrolyte (E/S ratio = 6.23 μL mg⁻¹) result in the areal capacity of 6.15 mAh cm⁻² after 80 cycles. This work provides innovative perspectives on the practical application of Li-S batteries.