We report a new facile route to synthesize the ZnO nanotubes by thermal annealing of solid nanorods in ambient NH3. The unique characteristic of this approach allows achievement of ultrathin nanotubes with well-organized hexagonal nanowalls and sealed layouts. On the basis of our experimental observations, we developed a nanotube formation mechanism illustrating the following: (i) energetically active nanorod surfaces could be readily passivated to form a few-atoms-thick Zn3N2 layer and (ii) nanopores generated from the seed layer were extended to the inside of nanorod bottoms and then propagated upward until they reached the tops of the nanorods. On the basis of key features of these tubular structures, we assessed the electrochemical performance of the nanotubes as anode materials in lithium ion batteries, demonstrating significant improvements in cycling performance over counterparts made of solid nanostructures.

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