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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.

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Three-dimensional porous Sb/Sb2 O3 anode materials are successfully fabricated using a simple electrodeposition method with a polypyrrole nanowire network. The Sb/Sb2 O3 -PPy electrode exhibits excellent cycle performance and outstanding rate capabilities; the charge capacity is sustained at 512.01 mAh g(-1) over 100 cycles, and 56.7% of the charge capacity at a current density of 66 mA g(-1) is retained at 3300 mA g(-1) . The improved electrochemical performance of the Sb/Sb2 O3 -PPy electrode is attributed not only to the use of a highly porous polypyrrole nanowire network as a substrate but also to the buffer effects of the Sb2 O3 matrix on the volume expansion of Sb. Ex situ scanning electron microscopy observation confirms that the Sb/Sb2 O3 -PPy electrode sustains a strong bond between the nanodeposits and polypyrrole nanowires even after 100 cycles, which maintains good electrical contact of Sb/Sb2 O3 with the current collector without loss of the active materials.

The electrochemical properties and sodiation/desodiation mechanism of Sn electrodes prepared by electrodeposition were investigated for Na-ion batteries. The sodiation of the electrodeposited Sn electrodes proceeded via three conjugated reactions in the cutoff voltage range of 0.001–0.65 V, as follows: the β-Sn phase, which contains a small amount of Na, was sodiated into amorphous NaSn, and crystalline Na9Sn4 and Na15Sn4 were then formed sequentially. However, the cycle performance of the electrode was highly dependent on the morphologies and the crystallographic orientations of the electrodeposits. The Sn electrode composed of coarse particles had the poor cycle performance due to the electrical isolation of Sn caused by the large volume changes during cycling. In contrast, the thin-layered Sn electrode exhibited a stable cycle performance in which the charge capacity was maintained at 607.51 mAh g–1 after 40 cycles, which corresponds to 98.21% of its initial charge capacity. The improvement in the cyclability of the layered Sn electrode was attributed not only to reduced structural degradations by restricting the cutoff voltage but also to an improved bond between the Sn electrodeposit and the Cu substrate.