Synergistic encapsulation engineering of N-doped carbon confined Bi2Se3 nanocomposites for stable sodium-ion storage

To solve the volume expansion and slow dynamics of bismuth selenide (Bi₂Se₃) based anodes for sodium ion batteries (SIBs), synergistic encapsulation engineering is proposed to prepare N-doped carbon coated Bi₂Se₃ composites (Bi₂Se₃) by combining pyrolysis and selenization of ZIF-67-coated bismuth nanospheres (Bi NS@ZIF-67). As Bi₂Se₃@NC(Co), Bi₂Se₃ nanoparticles with 60–90 nm are dispersed uniformly in N-doped carbon. When used as anode material for SIBs, Bi₂Se₃@NC(Co) demonstrates excellent sodium storage capacities, exhibiting a reversible capacity of 238 mA h g⁻¹ after 500 cycles at 5.0 A g⁻¹, as well as rate capabilities of 364 and 303 mA h g⁻¹ at 2.0 and 5.0 A g⁻¹, respectively. The high sodium storage capacity is primarily due to the formation of N-doped carbon protective layer on the Bi₂Se₃ nanoparticle surface, which helps mitigate the volume expansion of Bi₂Se₃ during cycling, enhances its electrical conductivity, and increases the number of active sites for sodium storage, thereby boosting the overall storage capacity. These studies offer valuable insights and inspiration for the rational design and development of Bi_xSe_y/C composites, paving the way for their potential practical applications.