Template-free electrochemical synthesis of Sn nanofibers as high-performance anode materials for Na-ion batteries.

Sn nanofibers with a high aspect ratio are successfully synthesized using a simple electrodeposition process from an aqueous solution without the use of templates. The synthetic approach involves the rapid electrochemical deposition of Sn accompanied by the strong adsorption of Triton X-100, which can function as a growth modifier for the Sn crystallites. Triton X-100 is adsorbed on the {200} crystallographic planes of Sn in an elongated configuration and suppressed the preferential growth of Sn along the [100] direction. Consequently, the Sn electrodeposits are forced to grow anisotropically in a direction normal to the (112) or (1̅12) plane, forming one-dimensional nanofibers. As electrode materials for the Na-ion batteries, the Sn nanofibers exhibit a high reversible capacity and an excellent cycle performance; the charge capacity is maintained at 776.26 mAh g(-1) after 100 cycles, which corresponds to a retention of 95.09% of the initial charge capacity. The superior electrochemical performance of the Sn nanofibers is mainly attributed to the high mechanical stability of the nanofibers, which originate from highly anisotropic expansion during sodiation and the pore volumes existing between the nanofibers.