Double core-shell of Si@PANI@TiO2 nanocomposite as anode for lithium-ion batteries with enhanced electrochemical performance

A unique double core-shell structure of Si@PANI@TiO₂ nanocomposite is synthesized by a simple in-situ growth method. The two shells of polyaniline (PANI) and TiO₂, hand in hand, play a key role to improve the electrochemical performance: First, the flexible properties of polyaniline (PANI) effectively accommodate the volume change of Si during the cycling. Second, the good mechanical feature of TiO₂ can maintain the structural integrity and attenuate the volume expansion of Si cores. Finally, both of polyaniline and the lithiated TiO₂ enhance the conductivity of Si, which promotes the electrons transport. Resulting in the Si@PANI@TiO₂ double core-shell nanocomposite exhibits remarkable synergy in large, reversible lithium storage, delivering a reversible capacity as high as 1027 mAh g^?1 after 500 cycles and a superior rate capacity of 640 mAh g^?1, at a current of 500 and 4000 mA g^?1, respectively. This excellent cycling and high-rate capability can be ascribed to the unique and well-designed double core-shell structure with the synergistic effect between polyaniline (PANI) and TiO₂.