Ionothermal Synthesis of Li-Based Fluorophosphates Electrodes

Fluoride-based materials have regained interest within the field of Li-ion batteries largely due to the advent of nanosizing which has transformed the insulating insertion compounds into attractive electrode materials. Herein we demonstrate the effectiveness of ionothermal synthesis in the preparation of nanometric LiFePO 4 F and LiTiPO 4 F phases with structures isotopic to tavorite LiFePO 4 (OH) at temperatures of only 260 °C, while temperatures of 600−700 °C are required to obtain coarse powders via the ceramic method. However, the redox-active phases, which are obtained in a high state of division, have lower redox voltages than LiFePO 4 despite the presence of fluorine. Additionally, LiTiPO 4 F shows staircase charge/discharge profiles with Ti 2/3+ and Ti 3/4+ couples. Though quite unusual in lithium intercalation oxides, a hint of a Li-driven Fe 3/4+ transition has been detected in LiFePO 4 F.