Computational Investigation of Li Insertion in Li3VO4

详细信息    查看全文

• 作者：M. Elena Arroyo-de Dompablo ; Pedro Tartaj ; J. Manuel Amarilla ; Ulises Amador
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：August 23, 2016
• 年：2016
• 卷：28
• 期：16
• 页码：5643-5651
• 全文大小：583K
• 年卷期：0
• ISSN：1520-5002

文摘

Parallel electrochemical reactions in low-voltage anode Li₃VO₄ represent a fundamental barrier for fully reliable mechanistic studies even using the most advanced electrochemical and structural characterization techniques. Aiming to unravel the lithium insertion mechanism in Li₃VO₄ anodes, we have investigated by density functional theory a total of 33 Li_3+xVO₄ configurations (x = 0, 0.5, 1, 1.5, 2, 2.5, 3). The key aspect of the proposed Li insertion mechanism is the structural rearrangement of the host-Li₃VO₄ as larger amounts of Li ions are incorporated, due to ion size and electrostatic effects. We found that for 0 < x < 2 the Li_3+xVO₄ phases are energetically stabilized by the distortion of the initial hexagonal package of the oxygen array (H1 → H2 transformation). Specifically, a very stable intermediate H2-Li₅VO₄ phase is formed after a biphasic region at 0.7 V. The close structural relationship between H1-Li₃VO₄ and H2-Li₅VO₅, with a moderate volume expansion of 4%, supports an insertion reaction as the main mechanism for the reversible cycling of Li_3+xVO₄ anodes in the range 0 < x < 2. Insertion of a third Li ion in Li₃VO₄ would produce a reconstructive phase transformation to an antifluorite-type Li₆VO₄ structure (H2→ C transformation). The low predicted voltage for such a process (0.14 vs Li/Li⁺) and the major structural rearrangements (20% volume variation) make unlikely the reversible insertion of 3 Li ions in Li₃VO₄. The calculated compositional–voltage profile and X-ray diffraction patterns are in agreement with experimental observations.