Construction of N-doped carbon encapsulated hollow FeSe2 nanocubes for enhancing lithium storage performance

FeSe 2 is an attractive anode candidate for lithium-ion batteries (LIBs) owing to its high theoretical capacity based on a unique conversion mechanism and low cost. However, the practical application of FeSe 2 is hindered by the fast capacity attenuation and the poor ion/electron transfer kinetics. Herein, a yolk-shell N-doped graphene-embedded hollow FeSe 2 nanocube/carbon composite (NG/FeSe 2 /C) is designed to address these issues, which exhibits high specific capacity and outstanding rate performance in half cells. The interaction mechanism between FeSe 2 and NG is systematically investigated by combining spectral characterizations, electrochemical measurements, and density functional theory calculations, revealing that NG enhances the electrical conductivity, elongates the Fe-Se bond, and decreases the valence of Fe species in FeSe 2 by delocalizing the charge distribution of Se, which are essential to high initial Coulombic efficiency and fast reaction kinetics. Moreover, the practicality of NG/FeSe 2 /C in a full cell is demonstrated by pairing it with a commercial LiNi 0.5 Mn 0.3 Co 0.2 O 2 cathode, showing high capacity and acceptable electrochemical performance. This work could offer guidance for the design of high-performance conversion-type anode materials for LIBs. N-doping induces delocalized charge distribution in the NG/FeSe 2 /C hetero-interface and enables the yolk-shell NG/FeSe 2 /C nanostructure with decreased Fe valence and elongated Fe-Se bond, demonstrating superior electrochemical performance.