Ultrafine SnO 2 /Sn Nanoparticles Embedded into an In Situ Generated Meso-/Macroporous Carbon Matrix with a Tunable Pore Size.

Ultrafine SnO 2 /Sn nanoparticles encapsulated into an adjustable meso-/macroporous carbon matrix have been successfully fabricated by the in situ SiO x sacrificial strategy. The control over the void space in the carbon matrix effectively improves the accessibility of the SnO 2 /Sn toward an electrolyte solution. More importantly, the void space also provides an efficient means to accommodate the mechanical stress caused by the volume change of the SnO 2 /Sn over cycles. As a result, the enhanced electrolyte accessibility and suppressed mechanical stress improve the electrochemical performance regarding reversible capacity, cyclic stability, and rate capability. A reversible capacity of 1105 mAh g -1 is still retained after 290 cycles at 200 mAg -1 , and the capacity still can keep at 107 mAh g -1 at a high current density of 10 A g -1 .