Sandwich-structured graphene hollow spheres limited Mn₂SnO₄/SnO₂ heterostructures as anode materials for...

Sn-based metal oxides and composites have been widely investigated as candidate anodes for lithium-ion batteries. However, continuous capacity fade caused by serious volumetric expansion and crystal pulverization is often noticed during lithiation and alloying processes. In this study, we design a novel heterogeneous structural composite by constructing sandwich-structured graphene hollow spheres limited Mn₂SnO₄/SnO₂ heterostructures (Mn₂SnO₄/SnO₂@SG), of which infiltration of Mn source promotes the dissolution-redeposition of SnO₂ in hollow-spherical graphene (SnO₂@SG) and their in-situ transformation into Mn₂SnO₄; and the uniform distributed Mn₂SnO₄ and SnO₂ nanoparticles are adjacent each other to form heterostructure within the sandwiched graphene hollow spheres. By comparing with the single metal oxide SnO₂@SG material, the influence of the microstructure, chemical composition, element valence state and electrochemical properties of the heterostructured Mn₂SnO₄/SnO₂@SG is investigated. The results show that the construction of Mn₂SnO₄/SnO₂ heterostructure dramatically improves electronic/ionic transport kinetics and increases lithium storage reversibility, therefore leading to distinctly superior rate capability (823.8 mAh g^-1 at 5 C) and cycling capacity. An ultra-high discharge capacity of 1180.4 mA h g^-1 is maintained up to 100 cycles at 100 mA g^-1. The promising electrochemical performances can be attributed to the sandwiched-structure hollow graphene spherical skeleton and the formation of unique Mn₂SnO₄/SnO₂ heterostructures.