Evidence of Solid-Solution Reaction upon Lithium Insertion into Cryptomelane K0.25Mn2O4 Material

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• 作者：Wei Kong Pang ; Vanessa K. Peterson ; Neeraj Sharma ; Chaofeng Zhang ; Zaiping Guo
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：February 27, 2014
• 年：2014
• 卷：118
• 期：8
• 页码：3976-3983
• 全文大小：561K
• 年卷期：v.118,no.8(February 27, 2014)
• ISSN：1932-7455

文摘

Cryptomelane-type K_0.25Mn₂O₄ material is prepared via a template-free, one-step hydrothermal method. Cryptomelane K_0.25Mn₂O₄ adopts an I4/m tetragonal structure with a distinct tunnel feature built from MnO₆ units. Its structural stability arises from the inherent stability of the MnO₆ framework which hosts potassium ions, which in turn permits faster ionic diffusion, making the material attractive for application as a cathode in lithium-ion batteries. Despite this potential use, the phase transitions and structural evolution of cryptomelane during lithiation and delithiation remain unclear. The coexistence of Mn³⁺ and Mn⁴⁺ in the compound during lithiation and delithiation processes induces different levels of Jahn鈥揟eller distortion, further complicating the lattice evolution. In this work, the lattice evolution of the cryptomelane K_0.25Mn₂O₄ during its function as a cathode within a lithium-ion battery is measured in a customized coin cell using in situ synchrotron X-ray diffraction. We find that the lithiation鈥揹elithiation of cryptomelane cathode proceeds through a solid-solution reaction, associated with variations of the a and c lattice parameters and a reversible strain effect induced by Jahn鈥揟eller distortion of Mn³⁺. The lattice parameter changes and the strain are quantified in this work, with the results demonstrating that cryptomelane is a relatively good candidate cathode material for lithium-ion battery use.