Ultrahigh Reversibility of SnO 2 in SnO 2 @C Quantum Dots/Graphene Oxide Nanosheets for Lithium Storage

Among promising substitutions for commercial graphite anodes for lithium ion batteries, SnO 2 has a fourfold theoretical capacity of graphite (if the O element is completely reversible), while the oxygen reutilization is seriously hampered by poor conductivity of both the electron and Li + ions. This work proposes a novel ternary architecture of SnO 2 @C quantum dots (QDs, with average diameter of 3.37 nm) grafted on graphene oxides, denoted as SnO 2 @C/G, via a facile and scalable one‐pot hydrothermal method. The SnO 2 @C/G show extraordinary long‐term cycling performance (1080 mAh g −1 at 200 mA g ‐1 after 300 cycles) and rate capability (∼840 mAh g −1 at 2 A g −1 ). If excluding the contribution of carbon, the specific capacity of SnO 2 is 1447 mAh g −1 at 200 mA g ‐1 , 96.9% of its theoretical capacity. The extraordinary performance is ascribed to ultrahigh reversibility of SnO 2 QDs, good structural stability, and much better ionic/electronic diffusions confirmed by XPS, TEM, EIS, respectively.