dc.description.abstract | Anode materials play a pivotal role for high power density lithium ion batteries applications. Graphite was the dominant materials of choice, but still fall short of the goal owing to low rate-capability and specific capacity (372 mAh g-1). Among other electrochemically active materials, Tin monoxide (SnO) appears promising to replace graphite and is widely explored due to its high specific capacity (875 mAh g-1).
However it suffered from pulverization problem and hampered its commercial implementation. In this study we have developed a novel composite anode material that combined two types of lithium ion insertion and exertion mechanisms with the purpose to reduce pulverization, improve rate capability and cycling performance. SnO is alloying/de-alloying system, which possess higher specific capability and electrochemical activity. On the other hand, Li4Ti5O12 (LTO) is an intercalation/de-intercalation system, which shows unique rate-capability and zero-strain ability. Combining the two features of the two materials we are able to stabilize the huge volume change of SnO. Pure SnO and the composite powder with SnO/LTO of 75/25, 50/50 and 25/75 wt% were successfully synthesized by sol-gel method. The decrease of capacity with increasing C-Rate was found to be slower in SnO-LTO (75/25) composite powders, and a high discharge capacity of 466.2 mAh.g-1 at 1Crate was observed, which is higher than that in commercial graphite anode materials. The presence of LTO appears to improve simultaneously the rate capability and cycle life through stabilizing the structure of whole active material. The observed cyclic voltammetry and galvanostatic cycling are reflected as lithium storage mechanism based on alloying-dealloying reaction of Sn in composite of Sn-LTO-Li2O, in which LTO acting as a buffer matrix, thus reducing pulverization. In addition, a flat plateau of LTO (1.55V) observed during charge cycle, but does not appear under discharge cycling of both samples, SnO-LTO (75/25) and SnO-LTO (50/50), represents that LTO could transport Li-ion to SnO from, accelerate alloying-dealloying reaction at higher C-Rate operation, and stabilize the pulverization during such reaction
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