Ultrasmall Sn Nanodots Embedded inside N-Doped Carbon Microcages as High-Performance Lithium and Sodium Ion Battery Anodes
Sn based materials are the promising anodes both in Li-ion batteries and Na-ion batteries for the high theoretical capacities (994 mAh g-1 for LIBs and 847 mAh g-1 for SIBs, respectively). In order to improve the cycle performance, Sn/N-doped carbon microcages composites (Sn/NMC) with Sn nanodots uniformly embedded inside the N-doped carbon microcages are synthesized through a simple spray drying process, followed by thermal treatment. When used as the electrodes, Sn/NMC exhibits an initial reversible capacity of 780 mAh g-1 at 200 mA g-1, and maintains 472 mAh g-1 after 500 cycles in LIBs. For Na-ion batteries, Sn/NMC delivers an initial reversible capacity of 439 mAh g-1 at 50 mA g-1 and maintains 332 mAh g-1 after 300 cycles. The remarkable electrochemical performance is mainly owing to the advanced structure of Sn/NMC, which could be attributed to the pore-forming using NaCl, and the grain size inhibition of Sn using N-doped carbon. Moreover, this preparation method is accessible to scale up and can be extended to fabricate other electrode materials.