Epitaxial growth of hexahedral FeO@SnO nano-heterostructure for improved lithium-ion batteries.

FeO is one of the most important lithium storage materials and has attracted increasing interest owing to its good capacity in theory, abundant reserves, and better security. The utilization of FeO materials is hampered by their inferior cycle performance, low rate performance, and restricted composite variety. Herein, the heterostructure of FeO@SnO with hexahedral structure was manufactured by two- step hydrothermal strategy, while the SnO nanopillars were epitaxially grown in six faces, not in the twelve edges of hexahedral FeO cubes, which comes from maximizing lattice matching on the six surfaces of FeO. Furthermore, the experimental results prove that the hexahedral FeO@SnO heterostructure exhibits remarkably enhanced electrochemical reversibility and reaction kinetics and delivers an impressive initial discharge capacity (1742 mA h g at 4 A g), great rate performance (565 mA h g at 5 A g), and stable long-term durability (661 mA h g after 4000 cycles at 4 A g) as an anode for LIBs. The result of the finite element mechanical simulation further indicates that the SnO nanopillars grow on the six surfaces but not on the twelve edges of the hexahedral FeO cube, which would provide great rate performance and long-term stability. This study underlines the merits of the heterostructure and offers a useful design routine for superior electrode materials in LIBs.