评估电池正极材料Li$_x$CoO$_2$（$x=0,1$）的磁态及第一性原理Hubbard修正的准确性
Assessing the magnetic states and the accuracy of first-principles Hubbard corrections for the battery cathode Li$_x$CoO$_2$ ($x=0,1$)
- Paul Scherrer Institute（保罗谢勒研究所）
- École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）
- Università degli Studi di Milano-Bicocca（米兰比可卡大学）
- University of Bremen（不来梅大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过第一性原理Hubbard修正和磁态系统探索，评估了LiCoO2和CoO2的结构、电子及电化学性质，发现磁态探索对确定基态至关重要，插层电压与实验偏差仅2%。
AI中文摘要：
Li$_x$CoO$_2$是锂离子电池中典型的层状正极材料，然而，由于自相互作用误差、弱的层间相互作用以及复杂的磁性能量景观，从第一性原理对其准确描述仍具挑战性。在此，我们使用密度泛函理论结合自洽Hubbard修正和长程范德华相互作用，并系统探索可能的磁态，对Li$_x$CoO$_2$（$x=0,1$）的结构、电子、磁性和电化学性质进行了系统研究。Co-$3d$和O-$2p$态的局域相互作用以及Co-O位间相互作用，通过密度泛函微扰理论框架下的线性响应理论从第一性原理确定，其中采用Löwdin正交化原子轨道作为Hubbard投影子。对于LiCoO$_2$，包含Hubbard修正能准确描述结构性质，而电子结构对Hubbard投影子的选择非常敏感。特别是，与局域原子轨道相比，前沿Wannier函数投影子显著改善了占据电子态的描述。对于CoO$_2$，我们证明了系统探索磁性能量景观对于识别能量最低的低自旋基态至关重要。然而，由此得到的Hubbard修正电子结构是绝缘的，与HSE06杂化泛函的预测一致，但与实验观察到的金属行为相反。结构弛豫进一步将系统推向另一种金属解，其电子构型与低自旋Co$^{4+}$特征不符。尽管存在这些局限性，计算得到的插层电压与实验吻合良好，偏差小至2%。
英文摘要：
Li$_x$CoO$_2$ is a prototypical layered cathode material for Li-ion batteries, yet its accurate description from first principles remains challenging because of self-interaction errors, weak interlayer interactions, and a complex magnetic energy landscape. Here, we present a systematic investigation of the structural, electronic, magnetic, and electrochemical properties of Li$_x$CoO$_2$ ($x=0,1$) using density-functional theory augmented with self-consistent Hubbard corrections and long-range van der Waals interactions, together with a systematic exploration of possible magnetic states. The on-site interactions on Co-$3d$ and O-$2p$ states, as well as inter-site Co-O interactions, are determined from first principles using linear-response theory in the framework of density-functional perturbation theory, with Löwdin-orthogonalized atomic orbitals employed as Hubbard projectors. For LiCoO$_2$, the inclusion of Hubbard corrections provides an accurate description of the structural properties, while the electronic structure is very sensitive to the choice of Hubbard projectors. In particular, frontier Wannier-function projectors substantially improve the description of the occupied electronic states compared with localized atomic orbitals. For CoO$_2$, we demonstrate that a systematic exploration of the magnetic energy landscape is essential to identify the lowest-energy low-spin ground state. However, the resulting Hubbard-corrected electronic structure is insulating, consistent with the prediction of the HSE06 hybrid functional, but in contrast to the experimentally observed metallic behavior. Structural relaxation further drives the system toward a different metallic solution with an electronic configuration inconsistent with low-spin Co$^{4+}$ character. Despite these limitations, the calculated intercalation voltages agree well with experiment, with deviations as small as 2%.
