This RUI award in the Analytical and Surface Chemistry Program supports Professor Gan Liang at Sam Houston State University (SHSU) in investigating the origins and mechanism of the enhancement of electronic conductivity in cation-doped lithium iron phosphate (LiFePO4) cathode materials. The first objective is to devise a novel approach to resolve a controversy regarding whether such enhancement is truly due to the intrinsic structural substitution of lithium or iron ions by multivalent metal cations or due to extrinsic impurities formed in the grain-boundary network of the materials. This project is designed to rule out the complicating factors due to grain boundary impurities by (1) synthesizing the cation-doped LiFePO4 in the form of single crystals, which are free of grain boundaries, and (2) synthesizing these materials in the form of very fine and well separated nanowires, for which the continuous grain-boundary network is either broken or cannot be formed. The second objective is to establish a basic understanding of how electrochemical performance and electronic conductivity vary with the size of the nanoparticles of the cation-doped LiFePO4 cathode materials. Such an understanding is currently absent due to the difficulties in making separable nanoparticles with desired sizes. Except material synthesis, the experimental program also includes the study of the transport, electronic structure, and electrochemical/physical properties of the cation-doped LiFePO4 materials. The characterization and property study include electronic conductivity, electrochemical performance (such as cyclic voltammetry, discharge profile, discharge capacity), x-ray absorption spectroscopy, x-ray diffraction, and transmission electron microscopy measurements.
The success of this project will provide a better understanding of the origins of enhancement of the electronic conductivity in cation-doped LiFePO4, which could bring breakthrough in the application of these cathode materials in next generation lithium-ion batteries. The research will be conducted at a predominantly undergraduate institution, SHSU. This project will provide cutting edge research opportunities to undergraduate students at SHSU for their research training in several fields: electrochemistry, nanoscience, crystallography, and condensed matter physics.
