Browsing by Author "Zeng, Zhiyuan"

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In situ TEM study of the Li-Au reaction in an electrochemical liquid cell
(2014-01-01)
Zeng, Zhiyuan
;
Liang, Wen-I.
;
Chu, Ying-Hao
;
Zheng, Haimei
;
材料科學與工程學系
We study the lithiation of a Au electrode in an electrochemical liquid cell using transmission electron microscopy (TEM). The commercial liquid electrolyte for lithium ion batteries (1 M lithium hexafluorophosphate LiPF6 dissolved in 1 : 1 (v/v) ethylene carbonate (EC) and diethyl carbonate (DEC)) was used. Three distinct types of morphology change during the reaction, including gradual dissolution, explosive reaction and local expansion/shrinkage, are observed. It is expected that significant stress is generated from lattice expansion during lithium-gold alloy formation. There is vigorous bubble formation from electrolyte decomposition, likely due to the catalytic effect of Au, while the bubble generation is less severe with titanium electrodes. There is an increase of current in response to electron beam irradiation, and electron beam effects on the observed electrochemical reaction are discussed.
Visualization of Electrode-Electrolyte Interfaces in LiPF6/EC/DEC Electrolyte for Lithium Ion Batteries via in Situ TEM
(2014-04-01)
Zeng, Zhiyuan
;
Liang, Wen-I
;
Liao, Hong-Gang
;
Xin, Huolin L.
;
Chu, Yin-Hao
We report direct visualization of electrochemical lithiation and delithiation of Au anodes in a commercial LiPF6/EC/DEC electrolyte for lithium ion batteries using transmission electron microscopy (TEM). The inhomogeneous lithiation, lithium metal dendritic growth, electrolyte decomposition, and solid-electrolyte interface (SEI) formation are observed in situ. These results shed lights on strategies of improving electrode design for reducing short-circuit failure and improving the performance of lithium ion batteries.