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

Abstract: 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°C for 12h). 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., 700W, 4min), 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. [Copyright &y& Elsevier]