Dual-strategy of carbon-coating and nanoengineering enables reversible and durable Na storage in an iron-based pyrophosphate cathode

In situ carbon-coated Na 3.12 Fe 2.44 (P 2 O 7 ) 2 /C nanoflakes successfully synthesized in a molten surfactant–paraffin medium, demonstrating exceptional electrochemical reversibility and ultra-long lifespan as cathodes for sodium-ion batteries.