Rational Design of Surface S‐Doped Fe ₂ O ₃ Micro‐Hollow Structure on Graphdiyne for High‐Performance Sodium‐Ion Batteries

Abstract The practical implementation of Fe‐based anodes is constrained by the sluggish ion diffusion kinetics and low conductivity. Herein, the surface S‐doped Fe ₂ O ₃ micro‐hollow particles dispersed on few‐layered graphdiyne (S‐Fe ₂ O ₃ ‐GDY) are synthesized based on the strong interaction between the Fe ³⁺ and the triangle poles of GDY with the most negative electrostatic potential (ESP) during the hydrothermal process following the sulfuration process. The homogeneous distribution of nanoparticles enables direct contact with the electrolyte to increase the electrode‐electrolyte interfacial area, combining with the unique micro‐hollow structure to shorten the Na ⁺ diffusion path and relieve the volume expansion. Additionally, the surface doping with sulphur (S) can provide excess capacity due to the unique reversible electrochemical behavior, enhance the structural stability, and promote electron transfer, combining with the excellent conductivity of GDY to construct a conductive framework. As a result, the S ₁ ‐Fe ₂ O ₃ ‐GDY delivers a high capacity of 617.5 mAh g ⁻¹ at a current density of 0.1 A g ⁻¹ . Notably, a high specific capacity of 397.8 mAh g ⁻¹ (92.8% of the initial capacities) at 1.0 A g ⁻¹ is achieved after 765 cycles. This strategy provides a valuable insight into the design of Fe‐based anodes with enhanced rate capability and long‐term cycling stability.