Homologous Heterointerfaces and Interfacial Chemical Bonding for Greatly Improved Initial Coulombic Efficiency in Sodium Storage

Abstract

Transition metal chalcogenide (TMC), an appealing anode alternative for high-energy-density sodium-ion batteries (SIBs), still encounters considerable challenges in practical applications, such as poor reaction reversibility, sluggish Na⁺ transport, the notorious shuttle effect, and inferior structural stability. Herein, we propose an ambidextrous approach of internal homologous heterointerface (Ni₃S₂/Ni₉S₈) engineering and exterior interfacial chemical bonding (Ni–S–C) modulation to settle the above bottlenecks. In this configuration, a built-in electric field inside the homologous heterostructure enhances charge transport, reduces the Na diffusion barrier, and facilitates mass transfer. Meanwhile, the interfacial chemical bonding between NiS_x and the outer graphene scaffold effectively stabilizes the soluble NaPS and improves the durability of the structure, resulting in high reaction reversibility and a desirable cycle lifespan. Consequently, the prepared electrode exhibits a remarkable ICE value (94%) with a high specific capacity (366.9 mAh g^–1 at 10 A g^–1 after 1200 cycles). Additionally, the working mechanism is comprehensively revealed by combining in situ analysis and theoretical calculations. This study provides a light way to prepare elaborate TMC materials for advanced SIBs.