Layered hollow FeSe2 based on salt template as anode for sodium-ion batteries with advanced electrochemical performance

Iron selenides are considered as potential anode materials for sodium-ion batteries (SIBs) because of its low cost and high theoretical specific capacity. Yet the severe volume expansion leading to capacity degradation has critically hindered its utilization in SIBs. Herein, FeSe2 with layered hollow structure (noted as LH-FeSe2) was designed and synthesized by KCl template method. Hollow nanostructures formed by salt templates alleviate the capacity attenuation caused by volume expansion, and the interlayer structure of LH-FeSe2 also increases the Na+ storage capacity and ion diffusion rate. The as-acquired LH-FeSe2 performs good cycling stability with high retention capacity of 517 mA h g−1 after 500 cycles at 1 A g−1. In addition, LH-FeSe2 with small specific surface area shows extremely high pseudocapacitive behavior, suggesting that it is an intrinsic pseudocapacitive material. This method provides a new horizon for the preparation of high-performance anode materials for SIBs.