Insights into Changes of Lattice and Electronic Structure Associated with Electrochemistry of Li2CoSiO4 Polymorphs

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• 作者：Caixia Zhang ; Zhenlian Chen ; Yongzhi Zeng ; Zhifeng Zhang ; Jun Li
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：April 10, 2014
• 年：2014
• 卷：118
• 期：14
• 页码：7351-7356
• 全文大小：322K
• 年卷期：v.118,no.14(April 10, 2014)
• ISSN：1932-7455

文摘

First-principles calculations combined with XRD simulations are performed to systematically study crystal structures, bonding characteristics and electronic structures of Li_xCoSiO₄ (x = 2.0, 1.5, 1.0) polymorphs with symmetries Pmn2₁-DP and Pbn2₁. The calculated average voltages by lithium extraction agree well with available experiments. CoO₄ tetrahedron is the key structural unit to track the process of delithiation. The oxidation of CoO₄ tetrahedron results in a special pattern of bonding characteristic, which corresponds to spin ordering and may be observable in XRD spectra according to simulation. We find delithiated phases are intrinsic Mott insulators, electronic band gaps change from Mott鈥揌ubbard-type to charge-transfer-type during lithium removing. The swapping of near-gap states is associated with the contraction of the oxidized CoO₄ units, indicating Peierls distortions that may be the physical origin of capacity degrading of Co鈥搒ilicate chemistry.