Steric-hindrance effect and self-sacrificing template behavior induced PDA@SnO2-QDs/N-doped carbon hollow nanospheres: Enhanced structural stability and reaction kinetics for long-cyclic Li-ion half/full batteries

A SnO2-QDs/PDA hollow nanosphere assembled by ultrafine SnO2 quantum dots (SnO2-QDs) and nitrogen-doped carbon, containing residual polydopamine (PDA) core was prepared by PDA-assisted hydrothermal methods. PDA polymer acted as a steric hindrance and sacrificed template during the hydrothermal reaction of metal salts to achieve the formation of ultra-small metal oxide particles and hollow spheres. The strong interaction between the ultra-small SnO2-QDs and N-doping carbon layer in the hollow structure could effectively accommodate the volume expansion and maintain structural stability. Furthermore, the residual PDA core inside the hollow sphere further captures the oxygen free radicals in the rechargeable batteries and influences the composition of the SEI layer and interface dynamics which enhances the reversibility of the conversion reaction. This synergistic strategy makes SnO2-QDs/PDA hollow nanosphere obtain a high reversible capacity (∼1200 mAh g−1) and long cycle stability (>3000 cycles). Thus, the SnO2-QDs/PDA||LiFePO4 full cell at 0.3 A g−1 exhibits excellent cycle stability with a good retention rate after 200 cycles. This study provides a new basis for the improvement of the lithium storage performance of metal oxide anode.