Diffusion-controlled evolution of core-shell nanowire arrays into integrated hybrid nanotube arrays for Li-ion batteries.

Controlled integration of multiple semiconducting oxides into each single unit of ordered nanotube arrays is highly desired in scientific research for the realization of more attractive applications. We herein report a diffusion-controlled solid-solid route to evolve simplex Co(CO3)0.5(OH)0.11H2O@TiO2 core-shell nanowire arrays (NWs) into CoO-CoTiO3 integrated hybrid nanotube arrays (NTs) with preserved morphology. During the evolution procedure, the decomposition of Co(CO3)0.5(OH)0.11H2O NWs into chains of CoCO3 nanoparticles initiates the diffusion process and promotes the interfacial solid-solid diffusion reaction even at a low temperature of 450 °C. The resulting CoO-CoTiO3 NTs possess well-defined sealed tubular geometries and a special "inner-outer" hybrid nature, which is suitable for application in Li-ion batteries (LIBs). As a proof-of-concept demonstration of the functions of such hybrid NTs in LIBs, CoO-CoTiO3 NTs are directly tested as LIB anodes, exhibiting both a high capacity (~600 mA h g(-1) still remaining after 250 continuous cycles) and a much better cycling performance (no capacity fading within 250 total cycles) than CoO NWs. Our work presents not only a diffusion route for the formation of integrated hybrid NTs but also a new concept that can be employed as a general strategy to fabricate other oxide-based hybrid NTs for energy storage devices.