In Situ Synthesis of the Peapod-Like Cu–SnO₂@Copper Foam as Anode with Excellent Cycle Stability and High Area Specific Capacity

The theoretical specific capacity of tin oxide (SnO₂) anode material is more than twice that of graphite material (782 vs 372 mAh g^–1), whereas its potential usage is limited fatally by its huge volume expansion during lithiation. An effective solution is to encapsulate tin oxide into hollow structure such as yolk-shell based on the principle of confinement. However, in light of the restricted space of active substance, this kind of hollow electrode always has the low capacity, severely limiting its commercial value. Herein, a peapod-like Cu-SnO₂@copper foam (CF) as high area specific capacity anode based on the Kirkendall effect, in which the “pod and peas” in the peapod-like structure are composed of SnO₂ and Cu nanoparticles, respectively, is tactfully designed and constructed. Compared to other SnO_x-based electrodes with different hollow structure designs in published reports, the unique peapod-like Cu-SnO₂@CF anode delivers a remarkably high first reversible capacity of 5.80 mAh cm^-2 as well as excellent cycle stability with 66.7% capacity retention and ≈100% coulombic efficiency after 200 cycles at a current density of 1 mA cm^–2, indicative of its quite promising application toward high-performance lithium-ion batteries.