Unusual Conversion-type Lithiation in LiVO3 Electrode for Lithium-Ion Batteries

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• 作者：Jeong Beom Lee ; Janghyuk Moon ; Oh B. Chae ; Jae Gil Lee ; Ji Heon Ryu ; Maenghyo Cho ; Kyeongjae Cho ; Seung M. Oh
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：August 9, 2016
• 年：2016
• 卷：28
• 期：15
• 页码：5314-5320
• 全文大小：455K
• 年卷期：0
• ISSN：1520-5002

文摘

This work finds that LiVO₃ is lithiated by a conversion reaction at 25 °C, which is unusual for the family of vanadium oxides. The spectroscopic studies and first-principle calculations performed on the lithiation mechanism of LiVO₃ consistently propose that a two-phase insertion-type lithiation proceeds in the early stage of lithiation; LiVO₃ transforms into a rock-salt structured Li₂VO₃. The continuing single-phase Li⁺ insertion into the tetrahedral sites in the rock-salt Li₂VO₃ produces a more Li-rich phase (Li_2.5VO₃), which is highly distorted because of the unfavorable Li⁺ insertion into the tetrahedral sites such as to be vulnerable to lattice breakdown. Hence, a two-phase (nucleation/growth type) conversion reaction is followed along with a structural disintegration; the Li_2.5VO₃ phase decomposes into metallic vanadium and Li₂O. To determine the factors facilitating the conversion reaction of LiVO₃, galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) are performed on LiVO₃, the results of which are then compared to those observed with V₂O₅, which is not lithiated by the conversion reaction at 25 °C. The results show that the quasi-equilibrium potential for the conversion reaction is more positive for LiVO₃ (thermodynamically more feasible). Also, the conversion reaction is kinetically more facilitated for LiVO₃ due to faster solid-state diffusion of mobile ionic species during the two-phase growth stage of metallic vanadium and lithium oxide (Li₂O) in the conversion process.