Urchin‐Like Fe3Se4 Hierarchitectures: A Novel Pseudocapacitive Sodium‐Ion Storage Anode with Prominent Rate and Cycling Properties

Abstract Transition metal chalcogenides have received great attention as promising anode candidates for sodium‐ion batteries (SIBs). However, the undesirable cyclic life and inferior rate capability still restrict their practical applications. The design of micro–nano hierarchitectures is considered as a possible strategy to facilitate the electrochemical reaction kinetics and strengthen the electrode structure stability upon repeated Na + insertion/extraction. Herein, urchin‐like Fe 3 Se 4 hierarchitectures are successfully prepared and developed as a novel anode material for SIBs. Impressively, the as‐prepared urchin‐like Fe 3 Se 4 can present an ultrahigh rate capacity of 200.2 mAh g ‐1 at 30 A g ‐1 and a prominent capacity retention of 99.9% over 1000 cycles at 1 A g ‐1 , meanwhile, a respectable initial coulombic efficiency of ≈100% is achieved. Through the conjunct study of in situ X‐ray diffraction, ex situ X‐ray absorption near‐edge structure spectroscopy, as well as cyclic voltammetry curves, it is intriguing to reveal that the phase transformation from monoclinic to amorphous structure accompanied by the pseudocapacitive Na + storage behavior accounts for the superior electrochemical performance. When paired with the Na 3 V 2 (PO 4 ) 3 cathode materials, the assembled full cell enables high energy density and decent cyclic stability, demonstrating potential practical feasibility of the present urchin‐like Fe 3 Se 4 anode.