Perovskite-type LaFeO₃ has promising applications as a negative-electrode material for Ni/metal-hydride batteries. To further improve electrode performance, a thorough understanding of its charge-transport mechanisms is required. We use hybrid density functional theory to investigate the structural and electronic properties of bulk LaFeO₃, as well as the effect of point defects and polarons on charge transport. Electronic charge localizes in the form of small hole and electron polarons; this self-trapping occurs in the bulk and also in the vicinity of point defects and impurities. We find that oxygen vacancies act as deep donors, while Fe and La vacancies are acceptors with the induced holes trapped as small polarons. Hydrogen interstitials and Ge and Ti impurities, on the other hand, act as donors that can trap small electron polarons. Hydrogen binds strongly to the La and Fe vacancies and hence these defects are detrimental to protonic conduction. We also elucidate how doping with Sr enhances the electrode performance of LaFeO₃:Sr impurities substituting on La sites act as acceptors and enable electronic conductivity through hole polarons, with a hopping barrier of 0.39 eV. In addition, Sr impurities suppress the formation of cation vacancies, thereby enhancing proton conductivity.

中文翻译：

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LaFeO _3中的电子和质子传导

钙钛矿型LaFeO ₃作为镍/金属氢化物电池的负极材料具有广阔的应用前景。为了进一步提高电极性能，需要对其电荷传输机理有透彻的了解。我们使用混合密度泛函理论研究块状LaFeO ₃的结构和电子性质以及点缺陷和极化子对电荷传输的影响。电子电荷以小空穴和电子极化子的形式局域化；这种自陷发生在主体中以及在点缺陷和杂质附近。我们发现，氧空位起着深的供体作用，而铁和镧空位则是受主空穴被诱集为小极化子的受主。另一方面，氢间隙和Ge和Ti杂质是可以俘获小的电子极化子的施主。氢牢固地与La和Fe空位结合，因此这些缺陷不利于质子传导。我们还阐明了Sr掺杂如何增强LaFeO ₃的电极性能：La位置上取代的Sr杂质充当受体，并通过空穴极化子实现电子传导，其跳跃势垒为0.39 eV。另外，Sr杂质抑制了阳离子空位的形成，从而提高了质子传导性。