A hierarchical hybrid design for high performance tin based Li-ion battery anodes

Novel hierarchical hybrids, tin dioxide@carbon hollow spheres with encapsulated tin nanoparticles (SnO₂@HCS@Sn), were fabricated by combining solution and vapor phase techniques. The phase composition, morphological evolution and porosity of the hierarchical hybrids were characterized by x-ray diffraction, energy dispersive x-ray spectroscopy, scanning and transmission electron microscopy, and N₂ adsorption-desorption analysis. The significantly improved electrochemical performance of this functional material is attributed to its heterogeneous architecture which unifies hollow carbon spheres with tin nanoparticles with a diameter of less than 20 nm, which are further conformally covered by ultra-small tin dioxide nanoplates. The ultrathin SnO₂ nanoplates grown on the carbon spheres effectively increase the charge-transfer properties and shorten the transport lengths for both electrons and lithium ions. The mesoporous carbon spheres offer excellent conductivity and abundant void space to buffer the large volume change during cycling. High initial capacity (∼1766 mAh g⁻¹ at 0.1 Ag⁻¹), high initial Coulombic efficiency (56.4%), and long cycle life (100 cycles with ∼710 mAh g⁻¹) have been realized in the hierarchical hybrid tin-based anodes.