Spinel zinc ferrite (ZnFe₂O₄) is a well-known anode material in lithium ion batteries (LIBs) because of its large theoretical capacity. However, the high potentials observed at the initial stage of lithiation cannot be captured using a model of Li⁺ intercalation into the stoichiometric ZnFe₂O₄ bulk. Here, using density functional theory, we report for the first time that the ZnFe₂O₄ surfaces are responsible for the measured initial potentials. Among the three identified stable surfaces, ZnFeO₂-terminated ZnFe₂O₄(1 1 0), O-terminated ZnFe₂O₄(1 1 1), and Zn-terminated ZnFe₂O₄(1 1 1), both (1 1 1) surfaces display higher lithiation potentials than the (1 1 0) surface, and the estimated potentials based on Zn-terminated (1 1 1) fit well with the experimental observations, whereas using the models based on ZnFe₂O₄(1 1 0) and previously ZnFe₂O₄ bulk, the estimated potentials are much lower. In terms of Li⁺ diffusion, the Zn-terminated ZnFe₂O₄(1 1 1) surface is the most active, where the energetically favorable saturation of Li⁺ on the surface is able to facilitate the process. Our results provide a new strategy for the design of LIB materials, via controlling the particle shape and the associated surface characteristics, thus enhancing the discharging performance.

中文翻译：

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尖晶石ZnFe ₂ O ₄表面在锂化过程中的重要作用

尖晶石型铁氧体锌（ZnFe ₂ O ₄）由于其理论容量大，是锂离子电池（LIBs）中众所周知的阳极材料。但是，在锂化初始阶段观察到的高电势不能使用Li ⁺嵌入化学计量的ZnFe ₂ O ₄主体中的模型来捕获。在这里，我们使用密度泛函理论首次报告了ZnFe ₂ O ₄表面负责所测量的初始电势。在三个确定的稳定表面中，ZnFeO ₂终止的ZnFe ₂ O ₄（1 1 0），O终止的ZnFe ₂ O ₄（1 1 1）和以Zn为末端的ZnFe ₂ O ₄（1 1 1），两个（1 1 1）表面均显示出比（1 1 0）表面更高的锂化电位，并且基于Zn终止的（ 1 1 1）与实验结果非常吻合，而使用基于ZnFe ₂ O ₄（1 1 0）和以前的ZnFe ₂ O ₄体积的模型，估计的电势要低得多。就Li ⁺扩散而言，以Zn为末端的ZnFe ₂ O ₄（1 1 1）表面最活跃，其中Li ⁺在能量上有利于饱和表面上能够促进该过程。我们的结果通过控制颗粒形状和相关的表面特性，为LIB材料的设计提供了新的策略，从而提高了放电性能。