Three-dimensional carbon foam supported tin oxide nanocrystallites with tunable size range: Sulfonate anchoring synthesis and high rate lithium storage properties

The development of a free-standing electrode with high rate capability requires the realization of facile electrolyte percolation, fast charge transfer at the electrode-electrolyte interface as well as the intimate electrical wiring to the current collector. Employing a sulfonated high internal phase emulsion polymer (polyHIPE) as the carbon precursor, we developed a free-standing composite of carbon foam encapsulated SnO₂ nanocrystallites, which simultaneously satisfies the aforementioned requirements. When directly evaluated in the pouch cell without using the binder, carbon additive or metallic current collector, the best performing composite exhibits a good rate performance up to 8 A g^-1 and very stable cyclability for 250 cycles. This cycling performance was attributed to the synergistic coupling of hierarchical macro/mesoporous carbon foam and SnO₂ nanocrystals with optimized size range. Postmortem characterizations unveiled the significant influence of subtle size variation of oxides on the electrochemical performance.