Direct Physical Imaging and Chemical Probing of LiFePO4 for Lithium-Ion Batteries

The control of unexpectedly rapid Li intercalation reactions without structural instability in olivine-type LiFePO4 nanocrystals is one of the notable scientific advances and new findings attained in materials physics and chemistry during the past decade. A variety of scientific studies and technological investigations have been carried out with LiFePO4 to elucidate the origins of many peculiar physical aspects as well as to develop more effective synthetic processing techniques for better electrochemical performances. Among the several features of LiFePO4 that have attracted much interest, in this article we address four important issues-regarding doping of aliovalent cations, distribution of Fe-rich secondary metallic phases, nanoparticle formation during crystallization, and antisite Li/Fe partitioning-by means of straightforward atomic-scale imaging and chemical probing. The direct observations in the present study provide significant insight into alternative efficient approaches to obtain conductive LiFePO4 nanocrystals with controlled defect structures.