Reaction Mechanism of the Sn₂Fe Anode in Lithium-Ion Batteries

Abstract

Sn2Fe anode materials were synthesized by a solvothermal route, and their electrochemical performance and reaction mechanism were evaluated. The structural evolution in the first two lithium cycles was investigated by X-ray absorption spectroscopy (XAS), synchrotron X-ray diffraction (XRD), and magnetic studies. In the first cycle, progressive alloying of Sn with Li accompanied by metallic iron displacement occurs upon lithiation, and the delithiation proceeds by LixSn dealloying and recovery of the Sn2Fe phase. In the second cycle, both XRD and XAS identify Li–Sn alloying at earlier lithiation stages than in the first cycle, with low-Li-content alloys evident in the beginning of the lithiation process. In the fully lithiated state, XAS analysis reveals higher coordination numbers in both the LixSn and Fe phases, which points toward more complete reaction and higher crystallinity of the products. Upon second delithiation, the Sn2Fe phase is generally reformed as evidenced by XRD. However, XAS indicates somewhat reduced Sn–Fe coordination and shorter Fe–Fe distance, which indicates incomplete reconversion and metallic Fe retention, which is also evident in the magnetic studies. Thus, a combination of long-range (XRD, magnetic) and local (XAS) techniques has revealed differences between the first and the second Li cycles relevant to the understanding of the capacity fading mechanisms.

Recent trends in batteries and lubricants for electric vehicles

“…372 mAhÁg 21 ). 29 Different strategies have been employed to overcome these drawbacks, such as mild oxidation of graphite, the fabrication of composites with metal oxides, coatings with polymeric materials, and the use of alternative carbon structures. In the last decades, non-lithium-based anode materials have gained growing interest as substitutes for carbon-based electrodes, with silicon and tin as the most promising alternatives.…”

Effects of Electrolyte Additives and Nanowire Diameter on the Electrochemical Performance of Lithium‐Ion Battery Anodes based on Interconnected Nickel–Tin Nanowire Networks

“…[6][7][8][9] Tin (Sn) is a promising Li-alloying material as the anode in LIB because of its higher volumetric and gravimetric capacities. [5,[10][11][12] Similar to other Li-alloying materials, the major hindrance to use Sn in LIB is the large volumetric change (%260%) [13] it undergoes during (de)lithiation. This volume change has two main effects on the electrochemical performance of Sn-based materials.…”

“…One promising strategy is to downsize the electrode particles to the nanoscale in the form of nanowires, [14][15][16][17] nanoparticles, [18] or nanoporous structures, [11] which help to accommodate stress on the particles during volume change. [10] Another strategy is to use Sn-based materials in the form of oxides, [15,17,19] phosphides, [20,21] sulfides, [22,23] or Sn-M alloys (M ¼ Cu, Fe, Ni, etc.). [24][25][26][27][28][29] In addition to buffering volume change, the introduction of M to form Sn-M alloys enhances the electronic conductivity and avoids Sn particles' aggregation during cycling, improving the rate performance (RP) and capacity retention of the electrode.…”

“…[24][25][26][27][28][29] In addition to buffering volume change, the introduction of M to form Sn-M alloys enhances the electronic conductivity and avoids Sn particles' aggregation during cycling, improving the rate performance (RP) and capacity retention of the electrode. [10,[24][25][26][27][28][29]…”

“…A holistic consideration of practical application of Li-alloying anodes strongly renders Sn-based materials as potential replacements for graphite as anode in LIB, [5,[10][11][12]70] yet there is a dearth of works on comparative studies between the effects of FEC and VC additives for Sn-based materials. As far as we know, only Seo et al [71] have done this comparative study, but there are unresolved questions regarding the RP, the cause of high impedance in cells containing VC-based electrolytes, and the effects of electrode design.…”