Dual-Defects Engineering and Fe–S–Ga Bridging Synergy in Secondary Battery Anode Enable Fast-Charging and Durable Performances

Abstract Defect-engineering commonly enables improved energy-storage performance; however, how it synergizes with interfacial bond bridging to boost fast-charging capacity remains a challenge. Here, we develop a FeS2@Ga2S3 heterostructure as sodium-ion battery anode that integrates dual-phase vacancies with Fe–S–Ga bonds. Peak-force atomic force microscopy and insitu characterizations reveal that Fe–S–Ga bonds enable structural stability. Density functional theory (DFT) calculations and kinetic analyses demonstrate the tailored heterointerface exhibits moderate Na+ adsorption energy and reduced diffusion barrier. The FeS2@Ga2S3 anode delivers a capacity of 468.5 mAh g–1 after 1000 cycles at 10.0 A g–1 with nearly 100% Coulombic efficiency, an exceptional rate-performance keeping 416.8 mAh g–1 at 20.0 A g–1, and stable performance over wide temperatures from −15 to 50 °C. FeS2@Ga2S3||Na3V2(PO4)3 full cell retains 442.4 mAh g–1 after 500 cycles at 1.0 A g–1, exhibiting a good potential for applications. This dual-defects and chemical bond-bridging design could be applied for developing a broad set of battery systems.