Hierarchically porous Zn0.76Co0.24S/CoS heterostructures confined in N,S-co-doped carbon as high-performance anodes for sodium-ion batteries

Abstract

Owing to the favorable merits of substantial capacity, low price, and eco-friendliness, metal sulfides have been widely desired as prospective anodes for sodium-ion batteries. However, the huge volumetric variation, inferior electrical conductivity, and sluggish Na⁺-storage kinetics seriously impede their large-scale practical applications. Herein, hierarchically porous Zn_0.76Co_0.24S/CoS heterostructures confined in N,S-co-doped carbon architectures (ZCS@NSC) have been rationally designed and engineered through a MOF-engaged sulfurization approach. In this delicate architecture, hierarchically porous nanostructures effectively alleviate the huge volumetric variation and also provide a mass of fast diffusion paths for Na⁺ ions in the Na⁺-storage reactions. The Zn_0.76Co_0.24S/CoS heterostructures contribute plentiful active Na⁺-storage sites and accelerate the Na⁺ ion diffusion kinetics. The NSC layer effectively mitigates the volumetric variation by the confinement effect and also establishes a highly conductive framework for rapid charge transfer during the cycling process. Profiting from the favorable synergistic effects, the resulting ZCS@NSC anode yields high capacity (568.2 mA h g⁻¹ at 0.1 A g⁻¹) and good rate properties (224.1 mA h g⁻¹ at 10.0 A g⁻¹) together with satisfied cyclic performance (68.3% capacity retention at 1.0 A g⁻¹ after 300 cycles).