Direct Physical Imaging and Chemical Probing of LiFePO_4 for Lithium-Ion Batteries

摘要

The control of unexpectedly rapid Li intercalation reactions without structural instability in olivine-type LiFePO_4 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 LiFePO_4 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 LiFePO_4 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 LiFePO_4 nanocrystals with controlled defect structures.