Core-shell structured hollow SnO₂-polypyrrole nanocomposite anodes with enhanced cyclic performance for lithium-ion batteries

Core-shell structured hollow SnO₂-polypyrrole (PPy) nanocomposites (SnO₂@PPy) with excellent electrochemical performance were synthesized using a hydrothermal method followed by an in situ chemical-polymerization route. The thickness of the polymerized amorphous PPy coating covering on the hollow SnO₂ microspheres is about 25nm, demonstrated by microscopy images. As an anode in lithium ion batteries, the nanocomposite is capable of retaining a high capacity of 448.4mAhg^-1 after 100 cycles with a coulomb efficiency above 97%. Compared to other reported SnO₂ anodes, the enhanced cycling stability is attributed to the unique core-shell structure and a possible synergistic effect between the PPy coating layer and the hollow SnO₂ spheres. The PPy coating not only prevents the possible pulverization of the hollow SnO₂ spheres, but also prevents the SnO₂/Sn spheres from aggregating. Furthermore, the hollow space within the SnO₂ nanoparticles effectively mitigates the enormous volume change during charge-discharge cycling. Meanwhile, the Li⁺ diffusion coefficient in the hollow SnO₂@PPy (21wt%) core-shell nanocomposite electrode is significantly improved compared to the hollow SnO₂ microspheres electrode. Thus, these benefits from the PPy coating and the hollow SnO₂ spheres are able to provide a robust architecture for lithium-ion battery anodes.