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首页> 外文期刊>Physica status solidi, B. Basic research >A first‐principles study of bulk and surface Sn‐doped LiFePO 44 : The role of intermediate valence component in the multivalent doping
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A first‐principles study of bulk and surface Sn‐doped LiFePO 44 : The role of intermediate valence component in the multivalent doping

机译：第一原理研究散装和表面Sn-Doped Lifepo 4 4 ：中间价组分在多价掺杂中的作用

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> Doping can be employed to enhance the electrical conductivity and electrochemical performance of LiFePO 4 , a promising material for Li‐ion batteries. However, the microscopic mechanism of doping is not fully understood. In this study, ab initio density functional theory (DFT) with the generalized gradient approximation (GGA) + U calculations was performed on both bulk and surface Sn‐doped LiFePO 4 . Our results indicate that surface doping is preferred over bulk or subsurface doping because it shows a lower doping energy and surface energy. The doping effect appears to be local, and the effect of the Li vacancy (V Li ) distribution was examined. The multivalent Sn doping may facilitate the formation of an Fe 2+ /Fe 3+ complex with the involvement of an effective intermediate Sn 3+ component, which complements the existing charge transfer model for LiFePO 4 . The effective Sn 3+ –Fe 3+ /2V Li complex may exist on the LiFePO 4 surfaces, providing possible surface design schemes to control charge transfer. The results suggest that the Sn dopant could modulate band gap and local charge transfer, and improve the electrochemical performance at the last stage of the charging process with no capacity loss. However, an optimized doping concentration may exist for electrochemically inactive doping with an unfavorable doping energy.
机译： > 掺杂可用于增强LiFePo的电导率和电化学性能 4 是锂离子电池的有希望的材料。然而，掺杂的显微镜机制尚不完全理解。在本研究中，在散装和表面Sn-掺杂的生命佩皮上进行AB Initio密度函数理论（DFT）具有广义梯度近似（GGA）+ U计算 4 。我们的结果表明，表面掺杂优于散装或地下掺杂，因为它显示出较低的掺杂能量和表面能。掺杂效果似乎是局部的，并且LI空缺的效果（v li ）分布被检查。多价Sn掺杂可以有助于形成Fe 2 + / FE. 3 + 复杂的有效中间sn 3 + 组件，它补充了LiFePo的现有电荷转移模型 4 。有效的sn. 3 + -fe. 3 + / 2v. li 在生活中可能存在复杂的 4 表面，提供可能的表面设计方案来控制电荷转移。结果表明，Sn掺杂剂可以调制带隙和局部电荷转移，并在没有容量损失的情况下提高充电过程的最后阶段的电化学性能。然而，可以存在优化的掺杂浓度用于具有不利掺杂能量的电化学无效掺杂。

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