RUI: A Novel Study of the Origin of the Enhancement of Electronic Conductivity and Properties of Cation-doped LiFePO4 Cathode Materials

该RUI分析和表面化学项目奖支持萨姆休斯顿州立大学（SHSU）的甘亮教授研究阳离子掺杂磷酸铁锂（LiFePO 4）阴极材料电子电导率增强的起源和机制。第一个目标是设计一种新的方法来解决这样的增强是否真正是由于多价金属阳离子的锂或铁离子的内在结构取代或由于在材料的晶界网络中形成的外来杂质的争议。该项目旨在排除由于晶界杂质而导致的复杂因素，方法是：（1）以无晶界的单晶形式合成阳离子掺杂的LiFePO 4，以及（2）以非常细且分离良好的纳米线形式合成这些材料，其中连续的晶界网络被破坏或无法形成。第二个目标是建立一个基本的理解，电化学性能和电子电导率如何随着阳离子掺杂的LiFePO 4正极材料的纳米颗粒的大小而变化。由于难以制备具有所需尺寸的可分离纳米颗粒，目前缺乏这种理解。除了材料合成外，实验计划还包括阳离子掺杂LiFePO 4材料的输运，电子结构和电化学/物理性质的研究。表征和性能研究包括电子电导率、电化学性能（如循环伏安法、放电曲线、放电容量）、x射线吸收光谱、x射线衍射和透射电子显微镜测量。该项目的成功将使人们更好地了解阳离子掺杂LiFePO 4电子电导率增强的原因，这可能会为这些正极材料在下一代锂离子电池中的应用带来突破。 这项研究将在一个主要的本科院校SHSU进行。该项目将为SHSU的本科生提供前沿研究机会，以便他们在几个领域进行研究培训：电化学，纳米科学，晶体学和凝聚态物理学。

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.