Overwhelming microwave irradiation assisted synthesis of olivine-structured LiMPO4 (M=Fe, Mn, Co and Ni) for Li-ion batteries

The olivine-structured LiMPO4 (M=Fe, Mn, Co and Ni), particularly LiFePO4, is one of the most viable and promising candidates of cathode material for the sustainable lithium ion batteries (LIBs) as reversible electrochemical energy storage (EES) devices. Usually, LiMPO4 can be synthesized via solid phase thermal (SPT) route, which is considered as a crucial process for improving the crystallinity of LiMPO4. However, in the conventional SPT process, e.g., common calcination, energy is generally transferred through heat convection, heat conduction and heat radiation from the surfaces to inners, which entail prolonged exposure to high calcination temperature (e.g. 700 degrees C for 12 h). Different from the heat treatment route of calcinaiton, microwave irradiation can provide inert and instant heating of LiMPO4 precursors and synthesize even crystallite LiMPO4 cathode materials. This microwave-assisted SPT (MW-SPT) method is not only energy- and time-saving (e.g., 700 W, 4 min), but also exhibits superiority in optimizing physical characters, improving Li-ion diffusion kinetics and enhancing high rate performance. Furthermore, the microwave-assisted liquid phase thermal (MW-LPT) method has been also employed to prepare LiMPO4 cathode materials. Recently, both MW-SPT and MW-LPT routes have led to increased interest in the development of LiMPO4 cathode materials and processing capabilities to enable high electrochemical performance. In this review, we focus on the LiMPO4 cathode materials synthesized by microwave irradiation assisted synthesis (MIAS) route, which conclude mainly two parts, MW-SPT and MW-LPT routes. The major goal is to highlight the reaction mechanism and current developments of LiMPO4 synthesized via MW-SPT and MW-LPT methods. The structural, morphological and electrochemical performance of LiMPO4 cathode materials prepared by MIAS has also been discussed. (C) 2013 Elsevier Ltd. All rights reserved.