SnO2 quantum dots modified N-doped carbon as high-performance anode for lithium ion batteries by enhanced pseudocapacitance

SnO2 is considered to be a promising candidate as anode material for lithium ion batteries, due to its high theoretical specific capacity (1494 mAh.g(-1)). Nevertheless, SnO2-based anodes suffer from poor electronic conductivity and serious volume variation (300%) during lithiation/delithiation process, leading to fast capacity fading. To solve these problems, SnO2 quantum dots modified N-doped carbon spheres (SnO2 QDs@N-C) are fabricated by facile hydrolysis process of SnCl2, accompanied with the polymerization of polypyrrole (PPy), followed by a calcination method. When used as anodes for lithium ion batteries, SnO2 QDs@N-C exhibits high discharge capacity, superior rate properties as well as good cyclability. The carbon matrix completely encapsulates the SnO2 quantum dots, preventing the aggregation and volume change during cycling. Furthermore, the high N content produces abundant defects in carbon matrix. It is worth noting that SnO2 QDs@N-C shows excellent capacitive contribution properties, which may be due to the ultra-small size of SnO2 and high conductivity of the carbon matrix.