Low temperature aqueous synthesis of LiMnPO4 nano particles for Li ion battery cathodes

Abstract

LiMnPO4 (LMP) is a promising material for improved Li ion batteries. It is, like the already commercially applied LiFePO4 (LFP), an olivine cathode material. The main advantage is its higher potential (4.1V vs. 3.5V for LFP, with respect to Li+/Li). The main drawbacks are the reduced electronic and ionic conductivities, compared to LFP. This results in reduced experimental capacities, especially at elevated (dis)charging rates. This drawback can be circumvented, by reducing particle sizes to nano dimensions, resulting in shorter Li ion diffusion distances. This presentation describes a low temperature (100°C) aqueous precipitation synthesis method based on Delacourt et al.1, yielding nano particles (NP) with typical sizes in the range of 50-200 nm. In this study, a more defined, optimized and reproducible synthesis was obtained, by studying the influence of several parameters (like pH, flow rate, reaction time, temperature, base, …) in this thermodynamically and kinetically fragile system. Results show that phase pure LMP NP are only obtained in a particular small subset of these parameter values. Outside this range, secondary phases are formed, or LMP is even completely absent. Results show that the reaction time can be significantly reduced by changing the base. T. Vranken is a Ph.D. fellow of the Research Foundation – Flanders (FWO) 1. Delacourt, C.; Poizot, P.; Morcrette, M.; Tarascon, J.-M.; Masquelier, C. One-Step Low-Temperature Route for the Preparation of Electrochemically Active LiMnPO4 Powders. Chem. Mater. 2004, 16, 93–99.