Preparation of SnO2-Carbon Composite Hollow Spheres and Their Application In Lithium Batteries
Xiong Wen (David) Lou, Division of Bioengineering, School of Chemical and Biomedical Engineering, Nanyang Technological University, Block N1.3 Level B5-01, 70 Nanyang Avenue, Singapore, 637457, Singapore and Lynden A. Archer, Chemical and Biomolecular Engineering, Cornell University, 120 Olin Hall, Ithaca, NY 14853.
We have developed a simple one-step template-free method for the controlled synthesis of hollow or hollow core/shell-type SnO2 nanostructures with controllable sizes in the range of 200 – 500 nm. This method is based on hydrothermal treatment of stannate in a mixed ethanol-water solvent. An inside-out Ostwald ripening mechanism is proposed to account for the template-free formation of these hollow nanostructures. A shortcoming of the method is that size uniformity of the as-synthesized SnO2 hollow nanoparticles is difficult to achieve. To solve this problem, the hydrothermal method has been extended to synthesize SnO2 hollow nanostructures with controlled sizes using monodisperse silica nanospheres as templates. Remarkably, uniform surface coating can be achieved without any prior surface modification. By repeated hydrothermal deposition or controlling the synthetic conditions, multi-shelled structures can also be prepared. These hollow SnO2 nanostructures may find applications in many important technological fields. Here we study their application as electrodes for lithium ion batteries and report encouraging initial results. We have also designed new nanostructured SnO2/carbon composite anode materials with hollow spherical structure. 3D carbon networks or shells in nanoscale can be effectively integrated with the SnO2 shells by selective infiltration of carbon precursor in solution followed by carbonization. The carbon networks act as both physical buffering cushion for the intrinsic large volume change and electrical conducting path. As a result, the capacity retention of the composite electrode is largely improved.