Periodic porous silicon thin films with interconnected channels as durable anode materials for lithium ion batteries

• Free-standing porous Si films with interconnected channels have been fabricated.
• These PSi films as anode deliver a high reversible specific capacity over 2500 mAh g−1.
• The special porous structure plays an important role in stabilizing the anodes.

A novel porous Si (PSi) films with interconnected channels and periodic nanostructures are fabricated by a facile electrochemical etching method. The films thus obtained feature highly porous structures with nano-branches connecting pores, possessing periodically varying porosity profiles along the film thickness direction. These periodic porous Si films are found to be promising anode materials for rechargeable lithium ion batteries with a high reversible specific capacity over 2500 mAh g−1 and capacity retention over 83% after 60 cycles, which compares favorably with the conventional Si-based electrodes, including the commercially available Si nanoparticles, sputtered Si thin films, and the normal porous Si films with homogenous porosities. The improved cycling stability achieved on the periodic porous Si film is ascribed to its special nanoporous morphology featuring high surface area, interconnecting nano-branches, and structural periodicity, which helps efficiently accommodate the volume expansion and contraction along both the vertical and the planner directions during lithiation and delithiation.