Nanopropping effect of residual silicas on reversible lithium storage over highly ordered mesoporous SnO ₂ materials

Highly ordered mesoporous SnO ₂ materials with residual silica species were successfully synthesized from a mesoporous silica template (SBA-15) via nano-replication and simple etching processes. The controlled removal of silica templates using NaOH or HF solutions with different concentrations results in the successful preparation of mesoporous SnO ₂ materials, where the amounts of residual silica species are in the range 0.9-17.4 wt%. The residual silica species induce a nano-propping effect enabling the mesoporous SnO ₂ material (containing 6.0 wt% of silica species) to remain stable up to 973 K without any significant structural collapse. More importantly, the optimum amount of residual silica species (3.9-6.0 wt%) results in a dramatic reduction in capacity fading after prolonged charging-discharging cycles in Li-ion battery. The mesoporous SnO ₂ material with 3.9 wt% of silica species still exhibits a large capacity (about 600 mAh g ^-1) after the 30th cycle, which is probably because the residual silica species act as a physical barrier to suppress the aggregation of Sn clusters formed in the mesoporous SnO ₂ materials during the reversible lithium storage.