Enhancement of Cycling Stability of LiMnPO₄ at Elevated Temperature by Fe-Mg co-Substitution

摘要

Olivine-type LiMnPO4 has been extensively investigated as a promising cathode material for the nextgeneration high performance Li-ion batteries due to its high working voltage (4.1 V vs Li+/Li) and hightheoretical specific capacity (170 mAh g?1). However, poor cycling performance at elevatedtemperature hinders its practical application. Here carbon coating and Fe-Mg co-substitution ofLiMnPO4 is attempted by a facile solid-state process. To substitute the smaller Fe2+ ions and Mg2+ ionsfor the larger Mn2+ ions strengthens the Mn-O bond, which makes the structure of LiMnPO4 morestable. Hence, Mn dissolution in the electrolyte is retrained. The obtained LiMn0.9Fe0.09Mg0.01PO4/Cmaterial presents a high discharge capacity (160 mAh g?1 at 0.1 C) and excellent cycling performanceat elevated temperature. Even at a high rate of 1 C, it delivers a capacity of about 135 mAh g?1 at 50°C without capacity fade after 120 cycles.