Highly stable SnO2-Fe2O3-C hollow spheres for reversible lithium storage with extremely long cycle life.

SnO2-Fe2O3-C triple-shell hollow nano-spheres are fabricated by combining the template-based sol-gel coating technique and hydrothermal method, and their electrochemical performance as an anode for lithium ion batteries (LIBs) is investigated, particularly focusing on their structural stability and long term cyclability. To accomplish this, same-sized SnO2 solid spheres, Fe2O3 solid spheres, SnO2-Fe2O3 solid spheres, SnO2-Fe2O3-C solid spheres, SnO2 hollow spheres and SnO2-Fe2O3 hollow spheres are prepared in a similar manner and their cyclic performances are compared. It is found that the as-synthesized 80 nm-sized SnO2-Fe2O3-C hollow sphere electrode exhibits an extraordinary reversible capacity (1100 mA h g-1 after 100 cycles at 200 mA g-1) and excellent long cycle stability (475 mA h g-1 after 1000 cycles at 2000 mA g-1), which are attributed to the Fe-enhanced reversibility of the Li2O reduction reaction, high electrical conductivity, high Li+ ion mobility, and structural stability of the carbon-coated triple-shell hollow spheres.