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

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 degrees 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.