Improvement of the sodiation/de-sodiation stability of Sn(C) by electrochemically inactive Na₂Se

Abstract

Tin forms a series of sodium alloys, some with a large change in volume, sufficient to fracture the sodiated/ de-sodiated tin electrodes. In a series of Sn/C and Sn/Se/C electrodes, made similarly by ball milling the elements, the sodiation/de-sodiation cycling stability in the 0.01-1.00 V vs. Na + /Na voltage window, in which the initially formed Na 2 Se is electrochemically inactive, is best at an Sn : Se atomic ratio of 9 : 2. At this ratio the retained capacity is $300 mA h g À1 after 150 cycles at 0.17 A g À1 rate versus only 70 mA h g À1 in the absence of Na 2 Se. The improvement is attributed to prevention of crystallization of the Na-Sn alloys by the Na 2 Se.

Novel Metal Chalcogenide SnSSe as a High‐Capacity Anode for Sodium‐Ion Batteries

“…Here, we have improved a new layered SnSSe material as a high‐performance anode for SIBs. The SnSSe material is synthesized by a simple solid‐state reaction, and the electrodes produced by simple ball‐mill mixing and scraper‐coating techniques exhibit excellent cycling performance and rate capability through different discharge cut‐off voltage regulations of 0.5 and even 0.1 V, and this may be attributed to the following reasons: i) for the layered material, a large interlayer spacing can degrade the volume expansion during the sodiation process, thus ensuring the cyclability; ii) further integration of selenium compounds with better conductivity than sulfur compounds can reduce the inert component and benefit the transport rate of Na + to obtain better battery performance, and the autogenous Na 2 Se can confine the alloying process; iii) the preferred growth along the (001) crystal plane (deduced from the X‐ray diffraction (XRD) data) is favorable to the intercalation of Na + ; iv) suitable discharge cut‐off voltages can ensure a moderate volume change of tin particles and high Coulombic efficiency at the premise of sufficient capacity output; v) partial pseudocapacitive behavior should be responsible for the high current discharge–charge capability; vi) the autogenous nanocrystallization process is favorable to the resistance to structure pulverization, thus leading to the superior cyclability.…”

One-dimensional van der Waals transition metal chalcogenide as an anode material for advanced lithium-ion batteries

“…The superior structural stability can be ascribed to the Se-Se buffer layer and the Se-rich characteristics of the Nb 2 Se 9 phase, providing advantages in maintaining structural integrity. As stated by Dang et al, 45,46 homogenously distributed Na 2 Se around the TM prevents the coalescing of the TM by forming Na 2 Se-TM crystalline interfaces. Moreover, introducing an excess of selenium into the transition metal chalcogenide material leads to excess selenium atoms acting as both a buffer layer and a conductive pathway, effectively mitigating volume expansion.…”

“…5b). As previously mentioned, the growth of metal might have been inhibited by selenide products 45,46 or the formation of the Li 2 Se-Nb-Li 2 Se phase, 47 which resulted from the conversion reaction.…”

FeSe2 micro-nanorods confined in N-doped carbon as an advanced anode for fast sodium ion storage

“…62 Furthermore, a new peak near 61.7 eV at a discharge voltage of 1.2 V is SeO 4 2− , which is assigned to the oxidization of Na 2 Se. 63,64 In the course of charging, the Se 3d peak steadily strengthens, while the Fe 3p peak weakens and returns to its initial position. When charged to 3 V, the SeO 4 2− peak disappears, indicating the transition from Na 2 Se to FeSe 2 and demonstrating the admirable reversibility of the reaction.…”