Carbon nanotube-assisted growth of single-/multi-layer SnS2 and SnO2 nanoflakes for high-performance lithium storage

Abstract

SnS₂ nanoparticles and SnS₂ nanoflake/CNTs composite are prepared by a low-cost facile hydrothermal method for their use in rechargeable Li-ion batteries. It is found that the presence of multi-walled CNTs during synthesis greatly affects the morphology of as-formed SnS₂ nanostructures, and circinal single-layer and multilayer SnS₂ nanoflakes enwrapped by CNTs are produced. The composite is further oxidized to porous SnO₂ nanoflake/CNTs hybrid by annealing at 500 °C in air. The formation mechanism of SnS₂/CNTs and SnO₂/CNTs composites is examined. All the three materials are used as the anode in Li-ion batteries. The SnS₂/CNTs composite delivers stronger cycling stability than the pure SnS₂ anode. In tests the former exhibits excellent capacity retention of 91.5% at 100 mA g⁻¹ over 50 cycles, while the latter displays 66.8%. The rate capability of SnS₂/CNTs composite is much better than pure SnS₂ as well. Redox reaction characteristics and Li-ion transfer kinetics at the two SnS₂ anodes are studied by differential capacity plots and electrochemical impedance spectroscopy. It is discovered that the SnS₂/CNTs composite with larger surface area allows faster Li-ion transfer kinetics, effective cushion of volume changes, and thus gains the improved Li-ion intercalation behaviours. The capacity of the tin-based anode can be further raised by transformation to a SnO₂/CNTs hybrid that also delivers excellent rate and cycling performances.