3D N-doped mesoporous carbon/SnO2 with polypyrrole coating layer as high-performance anode material for Li-ion batteries

Abstract SnO2/carbon hybrids with porous carbon as the carrier are considered as promising candidates for substituting graphite anode in Li-ion batteries (LIBs). However, in these composites, the active SnO2 particles are usually agglomerated and exposed on the surfaces of carbon matrix, which will lead to weak structure stability of the electrode, insufficient electric contact area between SnO2 and carbon, as well as more side reactions. To overcome these drawbacks, herein, a three-dimensional (3D) N-doped mesoporous carbon (NMC)/SnO2 composite with polypyrrole (PPy) coating layers (NMC/SnO2@PPy) is synthesized through a wet-impregnation and subsequent in situ vapor-phase pyrrole polymerization method, in which ultrafine SnO2 particles with monodisperse morphology are well encapsulated between porous carbon matrix and PPy coating layer. This novel structure can effectively reduce SnO2 aggregation, enhance electrical conductivity and depress excessive side reactions. The NMC/SnO2@PPy anode shows a reversible capacity of 775 mAh g−1 at a current density of 500 mA g−1 after 300 cycles. And a high reversible capacity of 591 mAh g−1 is obtained at a high rate of 1 A g−1 even after 1000 cycles. The successful preparation of NMC/SnO2@PPy anode can provide a rational approach to devise metal oxide-carbon hybrid anodes with 3D porous structures for LIBs development.