Closely packed Si@C and Sn@C nano-particles anchored by reduced graphene oxide sheet boosting anode performance of lithium ion batteries.

[Display omitted] • Si@C/Sn@C/rGO nanocomposite was synthesized via impregnation and hydrogenation reduction. • Si@C/Sn@C/rGO delivers a reversible capacity of 1880 mA h g⁻¹ after 60 cycles and high rate capability. • Double core-shell structure effectively suppresses volume variation of electrodes. • The preparation process is acid-free and environmentally friendly. Both silicon and tin are promising anodes for new generation lithium ion batteries due to high lithium storage capacities (theoretically 4200 mA h g⁻¹ and 992 mA h g^-1, respectively). However, their large volumetric expansions (both are above 300 %) usually lead to poor cycling stability. In this case, we synthesized closely packed Si@C and Sn@C nano-particles anchored by reduced graphene oxide (denoted as Si@C/Sn@C/rGO) by the way of solution impregnation and subsequent hydrogenation reduction. Sn particles with a diameter of 100 nm are coated by carbon and surrounded by Si@C particles around 40 nm in average diameter through the high-resolution transmission electron microscopy. Expansions of Si and Sn are alleviated by carbon shells, and reduced graphene oxide sheets accommodate their volume changes. The prepared Si@C/Sn@C/rGO electrode delivers an enhanced initial coulombic efficiency (78 %), rate capability and greatly improved cycle stability (a high reversible capacity of nearly 1000 mA h g⁻¹ is achieved after 300 cycles at a current density of 1000 mA g⁻¹). It can be believed that packing Sn@C nano-particles with Si@C relieves the volume expansion of both and releases the expansion stresses. Sn@C particles enhance anode process kinetics by reducing charge transfer resistance and increasing lithium ion diffusion coefficient. The present work provides a viable strategy for facilely synthesizing silicon-tin-carbon composite anode with long life. [ABSTRACT FROM AUTHOR]