Molenda Janina, Kulka Andrzej, Milewska Anna, Zając Wojciech, Świerczek Konrad
Department of Hydrogen Energy, Faculty of Energy and Fuels, AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Krakow, Poland.
Materials (Basel). 2013 Apr 29;6(5):1656-1687. doi: 10.3390/ma6051656.
LiFePO₄ is considered to be one of the most promising cathode materials for lithium ion batteries for electric vehicle (EV) application. However, there are still a number of unsolved issues regarding the influence of Li and Fe-site substitution on the physicochemical properties of LiFePO₄. This is a review-type article, presenting results of our group, related to the possibility of the chemical modification of phosphoolivine by introduction of cation dopants in Li and Fe sublattices. Along with a synthetic review of previous papers, a large number of new results are included. The possibility of substitution of Li⁺ by Al, Zr, W and its influence on the physicochemical properties of LiFePO₄ was investigated by means of XRD, SEM/EDS, electrical conductivity and Seebeck coefficient measurements. The range of solid solution formation in LiAlFePO₄, LiZrFePO₄ and LiWFePO₄ materials was found to be very narrow. Transport properties of the synthesized materials were found to be rather weakly dependent on the chemical composition. The battery performance of selected olivines was tested by cyclic voltammetry (CV). In the case of LiFeMPO₄ (M = Mn, Co and Ni), solid solution formation was observed over a large range of (0 < ≤ 1). An increase of electrical conductivity for the substitution level = 0.25 was observed. Electrons of 3 metals other than iron do not contribute to the electrical properties of LiFeMPO₄, and substitution level > 0.25 leads to considerably lower values of σ. The activated character of electrical conductivity with a rather weak temperature dependence of the Seebeck coefficient suggests a small polaron-type conduction mechanism. The electrochemical properties of LiFeMPO₄ strongly depend on the Fe substitution level.
磷酸铁锂被认为是用于电动汽车（EV）的锂离子电池中最有前景的正极材料之一。然而，关于锂和铁位点取代对磷酸铁锂物理化学性质的影响，仍存在许多未解决的问题。这是一篇综述型文章，展示了我们团队的研究成果，涉及通过在锂和铁亚晶格中引入阳离子掺杂剂对磷橄榄石进行化学改性的可能性。除了对先前论文的综合综述外，还包含了大量新成果。通过X射线衍射（XRD）、扫描电子显微镜/能谱仪（SEM/EDS）、电导率和塞贝克系数测量，研究了用铝、锆、钨取代Li⁺及其对磷酸铁锂物理化学性质的影响。发现LiAlFePO₄、LiZrFePO₄和LiWFePO₄材料中固溶体形成的范围非常窄。发现合成材料的传输性质对化学成分的依赖性相当弱。通过循环伏安法（CV）测试了所选橄榄石的电池性能。在LiFeMPO₄（M = Mn、Co和Ni）的情况下，在较大的x范围（0 < x ≤ 1）内观察到了固溶体的形成。观察到取代水平x = 0.25时电导率增加。除铁之外的3种金属的电子对LiFeMPO₄的电学性质没有贡献，并且取代水平x > 0.25会导致σ值显著降低。电导率的活化特性以及塞贝克系数对温度的依赖性较弱，表明存在小极化子型传导机制。LiFeMPO₄的电化学性质强烈依赖于铁的取代水平。
