Nanotubular Heterostructure of Tin Dioxide/Titanium Dioxide as a Binder-Free Anode in Lithium-Ion Batteries

Titanium dioxide (TiO2), tin dioxide (SnO2), and heterostructured TiO2/SnO2 nanotube (NT) arrays have been fabricated by template‐assisted atomic‐layer deposition (ALD) for use as anodes in a lithium‐ion battery (LIB). TiO2 NT arrays with 8 nm thick walls showed higher capacity (≈250 mA h g−1 after the 50th cycle at a rate of C/10) than the typical theoretical capacity of bulk TiO2 and a radically improved capacity retention property upon cycling. SnO2 NT arrays with different wall thicknesses (8, 10, 13, and 20 nm) were also fabricated and their electrochemical performances were measured. All of the SnO2 NT arrays showed substantially higher initial irreversible capacity and higher reversible capacity than those of bulk TiO2. Thinner walls of the SnO2 NTs result in better capacity retention. Heterotubular structures of TiO2 (5 nm)/SnO2 (10 nm)/TiO2 (5 nm) were successfully fabricated, and displayed a sufficiently high capacity (≈300 mA h g−1 after 50 cycles) with exceptionally improved cycling performance up to the 50th cycle. Solid foundations: Arrays of TiO2, SnO2, heterotubular TiO2/SnO2, and TiO2/SnO2/TiO2 as binder‐free anodes in lithium‐ion batteries are successfully synthesized by using template‐assisted atomic‐layer deposition (ALD), which enables not only precise structural control, but also suppression of a large volume change in SnO2.