In situ fabrication of W-doped SnO_2 nanoparticles anchored in ultrathin graphite nanosheets as high performance anode material for lithium ion batteries

摘要

Lithium-ion batteries based on conversion/alloying reactions have high potential applications in various electric energy storage. SnO2-based anode materials for LIBs have been considered as promising choices. However, their development is hindered by inherent large-volume variations and sluggish kinetics during discharge and charge processes. The W-doped SnO2 nanoparticles are evenly embedded in the graphite nanosheets (W-SnO2-C) via a facile ball milling method. The W doping can improve its electronic conductivity and stabilize the structure during cycling. Meanwhile, the ultrathin graphite wrapping effectively buffers the large volumetric variation of the SnO2-based anodes as well as shorten the diffusion path of electron and lithium-ion. The W-SnO2-C exhibits a reversible capacity of 1148.8 mAh g(-1) at 0.2 Ag-1 after 500 cycles, with a high initial coulombic efficiency (ICE) of 76.2%. Furthermore, it shows remarkable rate performance with the capacity of 312.3 mAh g(-1) at 5.0 Ag-1 and long-term cycling stability with a capacity of 1229.5 mAh g(-1) after 800 cycles at 1.0 Ag-1. The first-principles calculations reveal that the final free energy of W-SnO2 is -3413.94 eV, which is much lower than that of SnO2 (-1937.4 eV), indicating the structure of the composite for W doping is more stability than SnO2-based anodes.