Hydrothermally hollow SnO2 microspheres as sodium ion battery anode with high capacity and superior stability

Hollow SnO2 microspheres were synthesised through a hydrothermal process with post-calcination in air. Compared with commercial SnO2 nanoparticles, this organised and hollow SnO2 microspheres show a 3.3-3.6 times higher charge/discharge capacity, a superior cycling stability and a higher Coulomb efficiency when used as an anode material for sodium ion batteries (SIBs). The superior performance of hollow SnO2 microspheres was mainly attributed to the hollow structure with number of smaller nanoparticles. Compared with the disordered commercial SnO2 nanoparticles, the organised and hollow SnO2 microspheres with mesopores and micropores not only can facilitate charge transfer between the electrode and electrolyte, improve electronic and ionic transports, but also can accommodate the volume change to enhance the cycling stability of SnO2-based SIB anodes. This work also demonstrates that the unique hollow structures can be broadly used to construct electrode nanomaterials.