Hierarchically structured carbon-coated SnO2-Fe3O4 microparticles with enhanced lithium storage performance

Abstract A facile and scalable strategy was developed to fabricate SnO 2 -Fe 3 O 4 @C micrometer-sized particles as a good lithium-ion battery anode. The obtained materials were constructed by aggregated nanoclusters(100–200 nm) consisting of SnO 2 -Fe 3 O 4 @C nanospheres (20 ∼ 30 nm), in which SnO 2 and Fe 3 O 4 nanoparticles (5 ∼ 8 nm) were homogeneously embedded in a percolating carbonaceous network with an average thickness of about 3 nm. SnO 2 -Fe 3 O 4 @C microparticles were synthesized by a one-pot hydrothermal process followed by annealing under Ar and subsequent chemical vapor transformation (CVT) under vacuum. The peculiar strategy allows to obtain hierarchical structure of micrometer-sized particles including nanospheres, nanoclustersand micro-scale particles, and the combination of SnO 2 and Fe 3 O 4 could promote the synergistic effects to enhance the reversible capacity as well as the structural stability. Meanwhile, the carbon layer, homogeneously covering the nanoparticles does not only accommodate the volume change of active materials to maintain the structural integrity but also forms a conductive network throughout the whole micro-sized structure during charge/discharge processes. As a result, the electrode of SnO 2 -Fe 3 O 4 @C microparticles exhibits good rate performance (1056 mAh g −1 at 0.1 C, 734 mAh g −1 at 0.2 C, 449 mAh g −1 at 0.5 C, 212 mAh g −1 at 1 C and 133 mAh g −1 at 2 C, 1 C = 1 A g −1 ), high reversible capacity and good cycling stability (a high initial charge capacity of 1131.8 mAh g −1 was achieved and the capacity maintained 853.3 mAh g −1 after 50 cycles at 0.1 A g −1 ).