论文标题
来自扩展哈伯德功能
Accurate electronic properties and intercalation voltages of olivine-type Li-ion cathode materials from extended Hubbard functionals
论文作者
论文摘要
锂离子电池的新型阴极材料的设计将大大受益于对结构，电子和磁性特性的准确预测，以及包含过渡金属元件的化合物中的互电压。对于此类系统，具有标准（半）本地交换相关功能的密度功能理论（DFT）的使用有限，因为它通常由于强大的自我交互错误而失败，这些错误在部分填充的$ d $ shell中特别相关。 Here, we perform a detailed comparative study of the phospho-olivine cathode materials Li$_x$MnPO$_4$, Li$_x$FePO$_4$, and the mixed transition metal Li$_x$Mn$_{1/2}$Fe$_{1/2}$PO$_4$ ($x=0, 1/4, 1/2, 3/4, 1$) using四种电子结构方法：DFT，DFT+$ U $，DFT+$ U $+$ V $和HSE06。我们表明，DFT+$ U $+$ V $，具有现场$ u $和intersite $ v $ hubbard参数，从第一原理确定，并通过密度官能扰动理论（线性响应）对结构参数进行自我一致，提供了对这些挑战性复合物的电子结构的最准确描述。特别是，我们证明了DFT+$ u+$ v $显示出非常清楚的“数字”变化在所有化合物中过渡金属离子的氧化状态，包括在中间LI浓度下发生的混合价阶段，从而导致与实验的显着一致性的电压。我们表明，包括现场哈伯德相互作用的包含对于准确预测热力学数量至关重要，平衡了由现场$ u $与Interstoite $ v $ v $ orbital杂交诱导的定位驱动器。
The design of novel cathode materials for Li-ion batteries would greatly benefit from accurate first-principles predictions of structural, electronic, and magnetic properties as well as intercalation voltages in compounds containing transition-metal elements. For such systems, density-functional theory (DFT) with standard (semi-)local exchange-correlation functionals is of limited use as it often fails due to strong self-interaction errors that are especially relevant in the partially filled $d$ shells. Here, we perform a detailed comparative study of the phospho-olivine cathode materials Li$_x$MnPO$_4$, Li$_x$FePO$_4$, and the mixed transition metal Li$_x$Mn$_{1/2}$Fe$_{1/2}$PO$_4$ ($x=0, 1/4, 1/2, 3/4, 1$) using four electronic-structure methods: DFT, DFT+$U$, DFT+$U$+$V$, and HSE06. We show that DFT+$U$+$V$, with onsite $U$ and intersite $V$ Hubbard parameters determined from first principles and self-consistently with respect to the structural parameters by means of density-functional perturbation theory (linear response), provides the most accurate description of the electronic structure of these challenging compounds. In particular, we demonstrate that DFT+$U$+$V$ displays very clearly "digital" changes in oxidation states of the transition-metal ions in all compounds, including the mixed-valence phases occurring at intermediate Li concentrations, leading to voltages in remarkable agreement with experiments. We show that the inclusion of intersite Hubbard interactions is essential for the accurate prediction of thermodynamic quantities, balancing the drive for localization induced by the onsite $U$ with intersite $V$ orbital hybridizations.
