Reversible Li+ Storage in a LiMnTiO4 Spinel and Its Structural Transition Mechanisms

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• 作者：Ruiyong Chen ; Michael Knapp ; Murat Yavuz ; Ralf Heinzmann ; Di Wang ; Shuhua Ren ; Vanessa Trouillet ; Sergei Lebedkin ; Stephen Doyle ; Horst Hahn ; Helmut Ehrenberg ; Sylvio Indris
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：June 19, 2014
• 年：2014
• 卷：118
• 期：24
• 页码：12608-12616
• 全文大小：522K
• 年卷期：v.118,no.24(June 19, 2014)
• ISSN：1932-7455

文摘

In this work, LiMnTiO₄ (a structural analogue of classic spinel LiMn₂O₄) with a disordered cubic spinel structure (Fd3̅m) has been synthesized by a low-temperature sol鈥揼el route. The as-obtained LiMnTiO₄ exhibits excellent cycling stability in a wide voltage range from 1.5 to 4.8 V with high discharge capacities of 290, 250, and 140 mA h g^鈥? at a C/40, C/19, and 1C rate, respectively. Combined long- and short-range structural characterization techniques are used to reveal the correlation between structure and electrochemical behavior. During cycling, the charge/discharge profiles of LiMnTiO₄ evolve from initially two well-separated plateaus into sloping regimes. In the early stage of discharge, LiMnTiO₄ undergoes phase transitions from an initial spinel phase to mixtures of predominant rock-salt (Fm3̅m) and tetragonal (I4₁/amd) structures along with a decrease in crystallite size from 12 nm to 3 to 4 nm. During further cycling, the spinel/rock-salt phase transition was found to be reversible with the cubic framework remaining intact. The presence of the tetragonal phase after the first discharge suggests that the Mn³⁺ Jahn鈥揟eller distortion is partially involved during lithiation from Li_1鈥?i>yMn^3+yTiO₄ to Li_1+xMn^3鈥?i>xTiO₄ and the fraction of such a tetragonal phase remains at about 30鈥?0% during subsequent cycling.