Hierarchically Porous SnO₂/Cu Composites via Freeze Casting and Selective Cu Reduction

Lamellar SnO₂/Cu foams are created by directional freeze casting of SnO₂/CuO slurries followed by liquid phase sintering and subsequent hydrogen reduction to achieve a two‐phase, interpenetrating SnO₂‐30 vol% Cu lamellar structure. The resulting SnO₂/Cu foams exhibit both lamellar channels (millimeters in length) from the freeze‐casting step and submicron porosity within the Cu phase from the reduction step. This hierarchical microstructure provides increased electronic conductivity relative to unmodified SnO₂. When applied as a negative electrode material for lithium‐ion batteries, the interaction between the mesoporous Cu phase and embedded SnO₂ enables the conversion reaction of the SnO₂ and Li to become reversible, improving the capacity of the electrode. However, the lamellar structure is ultimately unable to accommodate the expansion of the Sn during lithiation, resulting in a breakdown of the architecture during cycling.