Architecting robust solid electrolyte interface for enhanced Na+ storage via single-atom ZnN4 sites decorating hard carbon

Abstract

The solid electrolyte interphase (SEI) with homogeneous and rich inorganic composition is crucial for enhancing the stability of hard carbon (HC) anodes. The atom-level decoration may offer the potential to engineer surface configurations for HC anodes, enabling effective modulation of SEI. However, it remains an open question underlying the precise mechanisms of this process. Herein, we proposed an atom-level modification strategy for HC anodes using single-atom ZnN₄ sites (Zn_SA-CNS), significantly enhancing Na⁺ storage kinetics and cycling stability. Enriched characterization verified the positive role of ZnN₄ sites in contributing to thinner and inorganic-rich component SEI and enhancing Na⁺ storage kinetics. Surprisingly, we have identified the dynamic behavior of single Zn atoms that partially spontaneously transform into Zn nanoclusters during the discharge process. The symbiotic system of single Zn atoms and nanoclusters provided sufficient active sites for Na⁺ adsorption and reduced the Na⁺ diffusion barrier. Consequently, Zn_SA-CNS exhibited an exceptionally high reversible capacity (321.4 mAh g⁻¹ at 0.05 A g⁻¹) and an extended cycling lifespan (the capacity maintained 92.1 % after 4000 cycles). Our single-atom modification approach offers a rational and effective solution to the challenges of sluggish storage kinetics and poor cycling stability in HC anodes for sodium-ion batteries.