Electrochemical Properties of Electrodeposited Sn Anodes for Na-Ion Batteries

Abstract

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.

Template-Free Electrochemical Synthesis of Sn Nanofibers as High-Performance Anode Materials for Na-Ion Batteries

“…As shown in Figure 6(c), the first charge curve for the Sn nanofibers has three distinct plateaus, denoted as I, II and III in order of increasing Na content. On the basis of the results of the previous study, 24 it can be suggested that the electrochemical sodiation/ desodiation of the Sn nanofibers undergoes the following reactions in the voltage range of 0.001 to 0.650 V.…”

“…49,50 However, pure Sn electrodes exhibit poor cyclability on account of the structural failure of Sn that results from a significant volume change (up to approximately 420%) during sodiation/desodiation. 24 Consequently, major challenges remain for improving the cycle stability of the Sn electrodes. One possible strategy for overcoming such a problem is to make a nanostructured or nanoscale electrode for facilitating the relaxation of material stress.…”

“…Despite the low Coulombic efficiency, the excellent retention of the charge capacity indicated that the Sn nanofibers reversibly reacted with Na with a high stability and that abrupt capacity deterioration due to the detachment of Sn was completely suppressed, unlike in the case of a typical pure Sn electrode. 24 The rate capabilities of the Sn nanofibers with varying C rates are shown in Figure 6(b). The Sn nanofibers exhibit a charge capacity of 808.19 mAh g À1 at a rate of 0.1 C and retain a high reversible capacity of 784.53 mAh g À1 at 1 C (only a 2.93% reduction).…”

“…In fact, the phase I formed between plateaus II and III is controversial because the XRD pattern for this phase does not correspond to the pattern reported for the crystalline Na 9 Sn 4 phase. 24,41 According to Ellis et al, 41 the inability of Sn and Na atoms to arrange into complex structures, such as Na 9 Sn 4 , at room temperature may account for the formation of the metastable phase instead of the expected thermodynamically stable phase. Consequently, the formation of the metastable phase of Na 9 Sn 4 was avoided, and Na 15 Sn 4 was directly converted into the amorphous phase of NaSn (IV) after the fifth cycle.…”

Electrochemically Synthesized Sb/Sb2O3 Composites as High-Capacity Anode Materials Utilizing a Reversible Conversion Reaction for Na-Ion Batteries

“…24 The cell consisted of the Sb/Sb 2 O 3 electrode as a working electrode, pure Na(SigmaAldrich) as a counter electrode, and 1 M NaClO 4 (Sigma-Aldrich) dissolved in anhydrous over the potential range of 0.01 ~ 2.50 V vs. Na + /Na at 25 °C. For rate capability testing, the charge and discharge currents were varied from 66 to 3300 mA g -1 and returned to 66 mA g -1 .…”