Highly efficient flexible Li–S full batteries with hollow Ru–RuO2−x nanofibers as robust polysulfide anchoring-catalysts and lithium dendrite inhibitors

Abstract

Lithium–sulfur (Li–S) batteries with high theoretical energy densities are a promising next-generation energy storage system. However, it is not easy to simultaneously obtain highly effective utilization of a sulfur cathode and dendrite-free lithium anode for commercial use. Herein, a free-standing conductive fabric is made up of N-doped hollow carbon nanofibers implanted with defective Ru–RuO_2−xin situ, which is employed as a dual-functional host for both the sulfur cathode and lithium anode. Oxygen vacancy-rich in-doped Ru–RuO_2−x heterostructures endow the surrounding nanofibers with abundant active sites and subtly tailor the density of state (DOS) distribution near the Fermi level, facilitating continuous reactivation and enhancing the conductivity. Furthermore, the composite interwoven by the hollow nanofibers has a large inner space and unique three-dimensional frame architecture. As the sulfur host, such synergetic merits effectively strengthen the sulfur immobilization, accommodate the volume expansion and catalyze the redox reactions. Meanwhile, the well-designed Li host is highly lithiophilic and can facilitate homogeneous nucleation and suppress Li dendrite growth, leading to outstanding stable cycling performance over 400 h with a high current density of 5 mA cm⁻² during Li plating/stripping. Considering these advantages, the Li–S full battery (denoted as S/Ru–RuO_2−x@NC‖Li/Ru–RuO_2−x@NC) delivers a high areal capacity of 5.8 mA h cm⁻² at 0.1C with a sulfur loading of 6.8 mg cm⁻². This work offers a significant defect engineering strategy for rational heterostructure modulation to realize flexible and durable Li–S full batteries, analysed using a series of experimental analyses and theoretical simulation.