<p>Leveraging the favorable physicochemical properties of expanded graphite (EG), including its high electrical conductivity and structural robustness, a solvothermal strategy was adopted to systematically investigate the regulatory effect of EG content on an FeS/EG composite system. Through this optimization, an FeS/EG composite with a more rational phase composition (FeS: troilite) and improved microstructural compatibility was successfully constructed, denoted as FeS/25%EG. The highly symmetric crystal framework is expected to provide more isotropic Na⁺ transport pathways and lower the Na⁺ diffusion energy barrier, thereby facilitating homogeneous ion migration, alleviating stress concentration, mitigating the adverse effects of volume expansion during cycling, and enhancing both Na⁺ transport efficiency and crystallographic stability. Half-cell electrochemical measurements demonstrated that FeS/25%EG exhibits stable cycling performance and excellent rate tolerance, delivering a reversible capacity of 594.5 mAh g⁻¹ at 0.5 A g⁻¹ and retaining 373.5 mAh g⁻¹ even at 5 A g⁻¹. The capacities under cycling at 0.2 A g⁻¹ and 1 A g⁻¹ were 562.3 mAh g⁻¹ (96.7% retention, 0.033% per cycle) and 522.5 mAh g⁻¹ (92.7% retention, 0.049% per cycle), respectively. Combined with reaction-kinetics evaluation and analysis of the dominant charge-storage mechanism, the origin of its remarkable rate capability is further clarified. These findings provide a practical performance benchmark for the solvothermal construction of iron sulfide electrodes and offer useful guidance for phase and microstructure regulation of transition-metal sulfides to enhance sodium storage performance.</p>