Understanding and Modelling the Thermodynamics and Electrochemistry of Lithiation of Tin Sulfide Compounds As Novel Anode Materials for Lithium Ion Batteries

摘要

Due to its theoretical capacity of 960 mAh/g, which is approximately two and a half times that of graphite (372 mAh/g), as well as its natural abundance, Sn is as an interesting anode active material to replace the currently used graphite in lithium ion batteries. However, Sn-based anodes have not been commercialized because they suffer from prohibitively large volume expansions due to the formation of brittle Li_xSn alloys during lithiation (>185% for full lithiation to Li_(17)Sn_4). These volume changes lead to extensive crack formation, loss of electrical contact between particles, pulverization of the electrode during cycling, lithium trapping, and the growth of an unstable SEI. One way to take advantage of the high capacity of Sn and simultaneously overcome its degradation mechanisms is to use Sn-based chalcogenide compounds such as SnS_2 and SnS as anode active materials. During lithiation of these compounds, a composite electrode structure consisting of active Sn particles embedded in an inactive Li_2S buffer matrix is formed, which is expected to accommodate the mechanical stress of the alloying and de-alloying reactions during cycling.