WEB Electrochemical performance and crystallinity: SnS as an anode active material for lithium ion batteriesTuesday (22.09.2020) 14:30 - 14:45 F: Functional Materials, Surfaces, and Devices 1 Part of:
SnS is a promising anode active material for lithium ion batteries as it exhibits high theoretical reversible capacity of 755 mAh/g which is two times larger than that of graphite (372 mAh/g). Furthermore, SnS, which can crystallize in various polymorphs, is non-toxic, earth abundant and available at low-cost. During the first discharge cycle vs. Li+/Li, SnS reacts with lithium via the conversion mechanism to produce Li2S and Sn. The Sn particles subsequently alloy with Li on further lithiation to form various LixSny intermetallic phases. However, due to the large volume expansion of the Sn particles on alloy formation, pulverization of the electrode and eventually capacity fade can occur.
It is known that the degree of crystallinity of the electrode active material can affect the uptake of lithium. However, this aspect has not yet been explored for SnS-based electrodes. Therefore, the aim of this work is to investigate the influence of the crystallinity of SnS on the electrochemical performance. In order to synthesize phase pure, nano-SnS with different crystallinities, the hydrothermal and precipitation wet-chemical methods were applied. The difficulties in the synthesis of phase pure SnS which had to be addressed in this work are 1) the ready oxidation of Sn2+ to Sn4+ leading to the presence of SnS2 impurities 2) the formation of Sn hydroxide complexes, and 3) the reaction between Sn2+ and oxygen to form tin(IV)-oxide. Furthermore, the choice of synthesis method and conditions (temperature, pressure, reaction time) also influences the physical, structural and textural features of the materials produced.
The phase composition of obtained products was determined using powder X-ray diffraction (PXRD) and structural parameters were extracted using Rietveld analysis of the measured patterns. Furthermore, sample morphology was characterized by scanning electron microscopy (SEM) and the particle size distributions was determined using laser diffraction. Electrochemical investigations were carried out in coin cells, using SnS from the precipitation and hydrothermal reactions as the active material vs Li+/Li. Furthermore, since anode pre-lithiation is an increasingly attractive technique to compensate for irreversible lithium losses due to SEI formation, chemical lithiation of SnS was performed using n-Butyl lithium in order to compare the structural differences between chemically and electrochemically lithiated SnS.