Layered manganese oxide Mn5O8 as a structural matrix for fast lithium and magnesium intercalation

Abstract

Layered Mn5O8 is considered as low-cost and high-voltage electrode materials for storing Na+ ions in aqueous media. Herein we provide the first report on the intercalation of Li+ and Mg2+ ions into layered Mn5O8 in non-aqueous electrolytes. The layered oxide Mn5O8 is simply prepared by a thermal decomposition of freshly precipitated γ-MnOOH at 500 °C for a short heating time. The morphology of Mn5O8 consists of well-crystalized nanoparticles with rod-like shape. The intercalation properties of Mn5O8 are examined galvanostatically in half lithium-ion cells. Two type of electrolytes are utilized: lithium and magnesium electrolytes containing 1 M LiPF6 in EC:DMC and 0.5 M MgTFSI in diglyme. Because of the layered structure, specific morphology and mixed oxidation states of manganese ions, layered Mn5O8 is able to intercalate reversibly and in high-amount both Li+ and Mg2+ ions in lithium and magnesium electrolytes. In lithium electrolyte, Mn5O8 exhibits high specific capacity (about 180 mAh/g at C/20), excellent rate capability (about 120 mAh/g at C1) and good cycling stability (the Coulombic efficiency more than 99% at C1). The mechanism of the electrochemical reaction is discussed on the basis of ex-situ HR-TEM and electron paramagnetic resonance spectroscopy (EPR). The storage capability of Mn5O8 will, most probably, be of significance for understanding the electrochemical behavior of layered Mn-based oxides in non-aqueous electrolyte.