Prussian blue analogues-derived highly stable and conductive CoSe2/FeSe2@C composite anode for sodium-ion batteries

This study centers on the synthesis and sodium-storage properties of CoSe 2 /FeSe 2 and its carbon-coated composite (CoSe 2 /FeSe 2 @C) derived from CoFe-based Prussian blue analogues (PBAs). The material offers high theoretical capacity for sodium-ion batteries (SIBs), but it suffers from severe structural degradation and poor electrical conductivity during cycling, leading to rapid capacity decay. Carbon coating is introduced to address these challenges by enhancing electronic conductivity, buffering volume changes, and improving ion diffusion kinetics. The CoSe₂/FeSe₂@C composite with a hollow nanostructure was obtained, which was prepared via co-precipitation, selenization, and carbon coating. Electrochemical measurements reveal that the composite boasts excellent electrochemical performance. It delivers a high reversible capacity of 443.5 mAh·g −1 at 0.1 A·g −1 , with 93.4 % capacity retention after 100 cycles, and 310.3 mAh·g −1 at 2 A·g −1 , maintaining 80.1 % retention after 500 cycles. The carbon coating significantly enhances conductivity, structural stability, and ion diffusion, endowing the material with superior cycling and rate capabilities. Through ex-situ XRD scanning and other characterization verifications, this work highlights the great potential of Prussian blue analogue (PBA)-derived materials as high-performance anodes for sodium-ion batteries.