Tetrahedral Bonding Structure (Ni 3 -Se) Induced by Lattice-Distortion of Ni to Achieve High Catalytic Activity in Na-Se Battery.

Fabrication of transition-metal catalytic materials is regarded as a promising strategy for developing high-performance sodium-selenium (Na-Se) batteries. However, more systematic explorations are further demanded to find out how their bonding interactions and electronic structures can affect the Na storage process. This study finds that lattice-distorted nickel (Ni) structure can form different bonding structures with Na 2 Se 4 , providing high activity to catalyze the electrochemical reactions in Na-Se batteries. Using this Ni structure to prepare electrode (Se@NiSe 2 /Ni/CTs) can realize rapid charge transfer and high cycle stability of the battery. The electrode exhibits high storage performance of Na + ; i.e., 345 mAh g⁻ 1 at 1 C after 400 cycles, and 286.4 mAh g⁻ 1 at 10 C in rate performance test. Further results reveal the existence of a regulated electronic structure with upshifts of the d-band center in the distorted Ni structure. This regulation changes the interaction between Ni and Na 2 Se 4 to form a Ni 3 -Se tetrahedral bonding structure. This bonding structure can provide higher adsorption energy of Ni to Na 2 Se 4 to facilitate the redox reaction of Na 2 Se 4 during the electrochemical process. This study can inspire the design of bonding structure with high performance in conversion-reaction-based batteries.