Confined Synthesis of SnO2 Nanoparticles Encapsulated in Carbon Nanotubes for High-Rate and Stable Lithium-Ion Batteries

The use of tin oxide (SnO2) with high theoretical capacity in practical application as the anode material of lithium-ion batteries (LIBs) has been limited due to its large volume expansion and fast capacity decay. To address this problem, we proposed the synthesis of encapsulating SnO2 nanoparticles in the channels of nitrogen-doped carbon nanotubes (SnO2-in-NCNTs) by capillary force. The confined spaces of NCNTs not only restrict the particle size of SnO2, but also effectively buffer the volume change during lithiation/delithiation processes. In addition, the conductive NCNTs also ensure the effective contact of the electrolyte to the electrode surface, facilitating both ion and electron transfer. When applied to LIBs, the SnO2-in-NCNTs possess high reversible capacities of 961.8 mAh g−1 at 0.1 A g−1 and 326.3 mAh g−1 at 10 A g−1. Moreover, they exhibited superior cyclic stability with a capacity retention of 96% at 5 A g−1 after 500 cycles. This work provides a simple and effective strategy for performance improvement of SnO2-based anode materials.