Preparation and electrochemical characteristics of a new Li-Mn-V-O system formed from heat-treatment of a MnO₂, NH₄VO₃ and LiNO₃ mixture

Abstract

New quarternary oxides (Li₂O) _x · MnO₂ · yV₂O₅ (x = 0.125 ∼ 0.25, y = 0.125 ∼ 0.25), formed by heating mixtures of MnO₂, NH₄VO₃ and LiNO₃ at various Li/Mn and V/Mn atomic ratios and at different temperatures (300 ∼ 400 °C in air, have been characterized by X-ray diffraction, X-ray photoelectron spectroscopy (ESCA) and infrared spectroscopy. The quarternary oxide with x = 0.25 and y = 0.25 showed a discharge capacity of 220 A h (kg oxide)⁻¹ and an energy density of ca. 600 W h (kg oxide)⁻¹ at a current density of 0.20 mA cm⁻¹ in 1 m LiClO₄-propylene carbonate at 25 °C. When charge-discharge cycling with the (Li₂O) · MnO₂ · 0.25V₂O₅ electrode was performed at a constant capacity of 30 A h (kg oxide)⁻¹ and at a constant current density of 0.10 0.20 mA cm⁻², the electrode sustained over 100 cycles at a high mean discharge potential of ca. 3 V vs Li/Li⁺.