Enhancing Ion Adsorption Capability through the Strong Interaction in Co9S8-Carbon Hybrids Achieves Superior Sodium Ion Storage

Abstract

Metal sulfides materials are promising anode candidates for Na⁺ storage due to their low cost and high theoretical capacity, while the complex phase transition and inevitable volume expansion during cycling restrain their practical applications. Herein, a simple one-pot manipulation strategy was designed to construct Co₉S₈ nanoparticles strongly encapsulated in carbon nanotubes (Co₉S₈@C/NTs) composite structure with enhanced structural stability and reaction kinetics, resulting in greatly improved Na⁺ storage performance. Specifically, the obtained Co₉S₈@C/NTs could exhibit a remarkable capacity of 500 mAh g⁻¹ at 0.5 A g⁻¹ after 100 cycles and exceptional cycling stability over 600 cycles with 88 % capacity retention at 1 A g⁻¹. Furthermore, the theoretical calculations combined with systematic characterizations confirm that the strong interaction between Co₉S₈ and the carbon matrix could greatly enhance the Na⁺ adsorption ability and facilitate the electron transfer dynamics for superior Na⁺ storage capability. More importantly, the full cell device can deliver an outstanding energy density of 144.32 Wh kg⁻¹ and a decent cycling life with 82 % capacity retention of almost 100 cycles at 0.1 A g⁻¹. This work could provide more valuable insights for designing advanced metal sulfide nanocomposites and demonstrate fascinating prospects for commercial application.